1
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Sofferman DL, Konar A, Mastron JN, Spears KG, Cisneros C, Smith AC, Tapavicza E, Sension RJ. Probing the Formation and Conformational Relaxation of Previtamin D 3 and Analogues in Solution and in Lipid Bilayers. J Phys Chem B 2021; 125:10085-10096. [PMID: 34473504 DOI: 10.1021/acs.jpcb.1c04376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The photosynthesis of vitamin D3 in mammalian skin results from UV-B irradiation of provitamin D3 (7-dehydrocholesterol, DHC) at ca. 290 nm. Upon return to the ground state, the hexatriene product, previtamin D3, undergoes a conformational equilibration between helical gZg and more planar tZg and tZt forms. The helical gZg forms provide a pathway for the formation of vitamin D3 via a [1,7]-sigmatropic hydrogen shift. Steady state photolysis and UV transient absorption spectroscopy are combined to explore the conformational relaxation of previtamin D3 formed from DHC in isotropic solution and confined to lipid bilayers chosen to model the biological cell membrane. The results are compared with measurements for two analogues: previtamin D2 formed from ergosterol (provitamin D2) and previtamin D3 acetate formed from DHC acetate. The resulting spectral dynamics are interpreted in the context of simulations of optical excitation energy and oscillator strength as a function of conformation. In solution, the relaxation dynamics and steady state product distributions of the three compounds are nearly identical, favoring tZg forms. When confined to lipid bilayers, the heterogeneity and packing forces alter the conformational distributions and enhance the population of a gZg conformer capable of vitamin D formation.
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Affiliation(s)
- Danielle L Sofferman
- Program in Applied Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Joseph N Mastron
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.,Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kenneth G Spears
- Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Cecilia Cisneros
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States
| | - Adam C Smith
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States
| | - Enrico Tapavicza
- Department of Chemistry and Biochemistry, California State University, Long Beach, 1250 Bellflower Boulevard, Long Beach, California 90840-9507, United States
| | - Roseanne J Sension
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.,Department of Chemistry, University of Michigan, 930 N. University Avenue, Ann Arbor, Michigan 48109-1055, United States
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2
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Sofferman DL, Konar A, Spears KG, Sension RJ. Ultrafast excited state dynamics of provitamin D 3 and analogs in solution and in lipid bilayers. J Chem Phys 2021; 154:094309. [PMID: 33685160 DOI: 10.1063/5.0041375] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The photochemical ring-opening reaction of 7-dehydrocholesterol (DHC, provitamin D3) is responsible for the light-initiated formation of vitamin D3 in mammalian skin membranes. Visible transient absorption spectroscopy was used to explore the excited state dynamics of DHC and two analogs: ergosterol (provitamin D2) and DHC acetate free in solution and confined to lipid bilayers chosen to model the biological cell membrane. In solution, the excited state dynamics of the three compounds are nearly identical. However, when confined to lipid bilayers, the heterogeneity of the lipid membrane and packing forces imposed on the molecule by the lipid alter the excited state dynamics of these compounds. When confined to lipid bilayers in liposomes formed using DPPC, two solvation environments are identified. The excited state dynamics for DHC and analogs in fluid-like regions of the liposome membrane undergo internal conversion and ring-opening on 1 ps-2 ps time scales, similar to those observed in isotropic solution. In contrast, the excited state lifetime of a subpopulation in regions of lower fluidity is 7 ps-12 ps. The long decay component is unique to these liposomes and results from the structural properties of the lipid bilayer. Additional measurements in liposomes prepared with lipids having slightly longer or shorter alkane tails support this conclusion. In the lipid environments studied, the longest lifetimes are observed for DHC. The unsaturated sterol tail of ergosterol and the acetate group of DHC acetate disrupt the packing around the molecule and permit faster internal conversion and relaxation back to the ground state.
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Affiliation(s)
- Danielle L Sofferman
- Program in Applied Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, USA
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, USA
| | - Kenneth G Spears
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
| | - Roseanne J Sension
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, USA
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3
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Miller NA, Kaneshiro AK, Konar A, Alonso-Mori R, Britz A, Deb A, Glownia JM, Koralek JD, Mallik L, Meadows JH, Michocki LB, van Driel TB, Koutmos M, Padmanabhan S, Elías-Arnanz M, Kubarych KJ, Marsh ENG, Penner-Hahn JE, Sension RJ. The Photoactive Excited State of the B 12-Based Photoreceptor CarH. J Phys Chem B 2020; 124:10732-10738. [PMID: 33174757 DOI: 10.1021/acs.jpcb.0c09428] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have used transient absorption spectroscopy in the UV-visible and X-ray regions to characterize the excited state of CarH, a protein photoreceptor that uses a form of B12, adenosylcobalamin (AdoCbl), to sense light. With visible excitation, a nanosecond-lifetime photoactive excited state is formed with unit quantum yield. The time-resolved X-ray absorption near edge structure difference spectrum of this state demonstrates that the excited state of AdoCbl in CarH undergoes only modest structural expansion around the central cobalt, a behavior similar to that observed for methylcobalamin rather than for AdoCbl free in solution. We propose a new mechanism for CarH photoreactivity involving formation of a triplet excited state. This allows the sensor to operate with high quantum efficiency and without formation of potentially dangerous side products. By stabilizing the excited electronic state, CarH controls reactivity of AdoCbl and enables slow reactions that yield nonreactive products and bypass bond homolysis and reactive radical species formation.
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Affiliation(s)
- Nicholas A Miller
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - April K Kaneshiro
- Department of Biological Chemistry, University of Michigan, 1150 W. Medical Center Dr., Ann Arbor, Michigan 48109-0600, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Alexander Britz
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States.,Stanford PULSE Institute, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Aniruddha Deb
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - James M Glownia
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Jake D Koralek
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Leena Mallik
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Joseph H Meadows
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Lindsay B Michocki
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Tim B van Driel
- Linac Coherent Light Source, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States
| | - Markos Koutmos
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - S Padmanabhan
- Instituto de Química Física "Rocasolano", Consejo Superior de Investigaciones Científicas, Madrid 28006, Spain
| | - Montserrat Elías-Arnanz
- Departamento de Genética y Microbiología, Área de Genética (Unidad Asociada al Instituto de Química Física "Rocasolano", Consejo Superior de Investigaciones Científicas), Facultad de Biología, Universidad de Murcia, Murcia 30100, Spain
| | - Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - E Neil G Marsh
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - James E Penner-Hahn
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Roseanne J Sension
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.,Department of Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
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4
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Salerno EV, Miller NA, Konar A, Li Y, Kieninger C, Kräutler B, Sension RJ. Ultrafast Excited State Dynamics and Fluorescence from Vitamin B 12 and Organometallic [Co]-C≡C-R Cobalamins. J Phys Chem B 2020; 124:6651-6656. [PMID: 32692181 PMCID: PMC7397374 DOI: 10.1021/acs.jpcb.0c04886] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
![]()
Cobalamins are cobalt-centered
cyclic tetrapyrrole ring-based molecules
that provide cofactors for exceptional biological processes and possess
unique and synthetically tunable photochemistry. Typical cobalamins
are characterized by a visible absorption spectrum consisting of peaks
labeled α, β, and sh. The physical basis of these peaks
as having electronic origin or as a vibronic progression is ambiguous
despite much investigation. Here, for the first time, cobalamin fluorescence
is identified in several derivatives. The fluorescence lifetime is
ca. 100–200 fs with quantum yields on the order of 10–6–10–5 because of rapid population of “dark”
excited states. The results are compared with the fluorescent analogue
with zinc replacing the cobalt in the corrin ring. Analysis of the
breadth of the emission spectrum provides evidence that a vibrational
progression in a single excited electronic state makes the dominant
contribution to the visible absorption band.
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Affiliation(s)
- Elvin V Salerno
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Nicholas A Miller
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Yan Li
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Christoph Kieninger
- Institute of Organic Chemistry & Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Bernhard Kräutler
- Institute of Organic Chemistry & Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Roseanne J Sension
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, United States.,Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
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5
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Salerno EV, Miller NA, Konar A, Salchner R, Kieninger C, Wurst K, Spears KG, Kräutler B, Sension RJ. Exceptional Photochemical Stability of the Co-C Bond of Alkynyl Cobalamins, Potential Antivitamins B 12 and Core Elements of B 12-Based Biological Vectors. Inorg Chem 2020; 59:6422-6431. [PMID: 32311266 PMCID: PMC7201400 DOI: 10.1021/acs.inorgchem.0c00453] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
![]()
Alkynylcorrinoids
are a class of organometallic B12 derivatives,
recently rediscovered for use as antivitamins B12 and as
core components of B12-based biological vectors. They feature
exceptional photochemical and thermal stability of their characteristic
extra-short Co–C bond. We describe here the synthesis and structure
of 3-hydroxypropynylcobalamin (HOPryCbl) and photochemical experiments
with HOPryCbl, as well as of the related alkynylcobalamins: phenylethynylcobalamin
and difluoro-phenylethynylcobalamin. Ultrafast spectroscopic studies
of the excited state dynamics and mechanism for ground state recovery
demonstrate that the Co–C bond of alkynylcobalamins is stable,
with the Co–N bond and ring deformations mediating internal
conversion and ground state recovery within 100 ps. These studies
provide insights required for the rational design of photostable or
photolabile B12-based cellular vectors. Most alkylcobalamins are photolabile; in contrast, alkynylcobalamins
are photostable. Through time-resolved measurements, we demonstrate
for three alkynylcobalamins that the Co−C bond is stable (i.e.
“locked”), while expansion of the Co−N axial
bond (which is “unlocked”) and ring deformations mediate
internal conversion and ground state recovery within 100 ps. The barrier
for ground state recovery is independent of the R group on the alkynyl
ligand.
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Affiliation(s)
- Elvin V Salerno
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Nicholas A Miller
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Robert Salchner
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Christoph Kieninger
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Klaus Wurst
- Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Kenneth G Spears
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
| | - Bernhard Kräutler
- Institute of Organic Chemistry and Center for Molecular Biosciences, University of Innsbruck, Innrain 80/82, A-6020 Innsbruck, Austria
| | - Roseanne J Sension
- Department of Chemistry, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States.,Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States.,Biophysics, University of Michigan, 930 N University Ave. Ann Arbor, Michigan 48109-1055, United States
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6
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Miller NA, Michocki LB, Konar A, Alonso-Mori R, Deb A, Glownia JM, Sofferman DL, Song S, Kozlowski PM, Kubarych KJ, Penner-Hahn JE, Sension RJ. Ultrafast XANES Monitors Femtosecond Sequential Structural Evolution in Photoexcited Coenzyme B 12. J Phys Chem B 2020; 124:199-209. [PMID: 31850761 DOI: 10.1021/acs.jpcb.9b09286] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Polarized X-ray absorption near-edge structure (XANES) at the Co K-edge and broadband UV-vis transient absorption are used to monitor the sequential evolution of the excited-state structure of coenzyme B12 (adenosylcobalamin) over the first picosecond following excitation. The initial state is characterized by sub-100 fs sequential changes around the central cobalt. These are polarized first in the y-direction orthogonal to the transition dipole and 50 fs later in the x-direction along the transition dipole. Expansion of the axial bonds follows on a ca. 200 fs time scale as the molecule moves out of the Franck-Condon active region of the potential energy surface. On the same 200 fs time scale there are electronic changes that result in the loss of stimulated emission and the appearance of a strong absorption at 340 nm. These measurements provide a cobalt-centered movie of the excited molecule as it evolves to the local excited-state minimum.
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Affiliation(s)
- Nicholas A Miller
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
| | - Lindsay B Michocki
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
| | - Arkaprabha Konar
- Department of Physics , University of Michigan , 450 Church Street , Ann Arbor , Michigan 48109-1040 , United States
| | - Roberto Alonso-Mori
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Aniruddha Deb
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States.,Department of Biophysics , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
| | - James M Glownia
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Danielle L Sofferman
- Program in Applied Physics , University of Michigan , 450 Church Street , Ann Arbor , Michigan 48109-1040 , United States
| | - Sanghoon Song
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Pawel M Kozlowski
- Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States
| | - Kevin J Kubarych
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States.,Department of Biophysics , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
| | - James E Penner-Hahn
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States.,Department of Biophysics , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
| | - Roseanne J Sension
- Department of Chemistry , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States.,Department of Physics , University of Michigan , 450 Church Street , Ann Arbor , Michigan 48109-1040 , United States.,Department of Biophysics , University of Michigan , 930 N. University Ave. , Ann Arbor , Michigan 48109-1055 , United States
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7
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Michocki LB, Miller NA, Alonso-Mori R, Britz A, Deb A, Glownia JM, Kaneshiro AK, Konar A, Koralek J, Meadows JH, Sofferman DL, Song S, Toda MJ, van Driel TB, Kozlowski PM, Kubarych KJ, Penner-Hahn JE, Sension RJ. Probing the Excited State of Methylcobalamin Using Polarized Time-Resolved X-ray Absorption Spectroscopy. J Phys Chem B 2019; 123:6042-6048. [PMID: 31290669 DOI: 10.1021/acs.jpcb.9b05854] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We use picosecond time-resolved polarized X-ray absorption near-edge structure (XANES) measurements to probe the structure of the long-lived photoexcited state of methylcobalamin (MeCbl) and the cob(II)alamin photoproduct formed following photoexcitation of adenosylcobalamin (AdoCbl, coenzyme B12). For MeCbl, we used 520 nm excitation and a time delay of 100 ps to avoid the formation of cob(II)alamin. We find only small spectral changes in the equatorial and axial directions, which we interpret as arising from small (<∼0.05 Å) changes in both the equatorial and axial distances. This confirms expectations based on prior UV-visible transient absorption measurements and theoretical simulations. We do not find evidence for the significant elongation of the Co-C bond reported by Subramanian [ J. Phys. Chem. Lett. 2018 , 9 , 1542 - 1546 ] following 400 nm excitation. For AdoCbl, we resolve the difference XANES contributions along three unique molecular axes by exciting with both 540 and 365 nm light, demonstrating that the spectral changes are predominantly polarized along the axial direction, consistent with the loss of axial ligation. These data suggest that the microsecond "recombination product" identified by Subramanian et al. is actually the cob(II)alamin photoproduct that is produced following bond homolysis of MeCbl with 400 nm excitation. Our results highlight the pronounced advantage of using polarization-selective transient X-ray absorption for isolating structural dynamics in systems undergoing atomic displacements that are strongly correlated to the exciting optical polarization.
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Affiliation(s)
| | | | - Roberto Alonso-Mori
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Alexander Britz
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | | | - James M Glownia
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - April K Kaneshiro
- Department of Biological Chemistry , University of Michigan , 1150 W. Medical Center Dr. , Ann Arbor , Michigan 48109-0600 , United States
| | | | - Jake Koralek
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | | | | | - Sanghoon Song
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Megan J Toda
- Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States
| | - Tim B van Driel
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Pawel M Kozlowski
- Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States
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8
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Song Y, Konar A, Sechrist R, Roy VP, Duan R, Dziurgot J, Policht V, Matutes YA, Kubarych KJ, Ogilvie JP. Multispectral multidimensional spectrometer spanning the ultraviolet to the mid-infrared. Rev Sci Instrum 2019; 90:013108. [PMID: 30709236 DOI: 10.1063/1.5055244] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 11/29/2018] [Indexed: 06/09/2023]
Abstract
Multidimensional spectroscopy is the optical analog to nuclear magnetic resonance, probing dynamical processes with ultrafast time resolution. At optical frequencies, the technical challenges of multidimensional spectroscopy have hindered its progress until recently, where advances in laser sources and pulse-shaping have removed many obstacles to its implementation. Multidimensional spectroscopy in the visible and infrared (IR) regimes has already enabled respective advances in our understanding of photosynthesis and the structural rearrangements of liquid water. A frontier of ultrafast spectroscopy is to extend and combine multidimensional techniques and frequency ranges, which have been largely restricted to operating in the distinct visible or IR regimes. By employing two independent amplifiers seeded by a single oscillator, it is straightforward to span a wide range of time scales (femtoseconds to seconds), all of which are often relevant to the most important energy conversion and catalysis problems in chemistry, physics, and materials science. Complex condensed phase systems have optical transitions spanning the ultraviolet (UV) to the IR and exhibit dynamics relevant to function on time scales of femtoseconds to seconds and beyond. We describe the development of the Multispectral Multidimensional Nonlinear Spectrometer (MMDS) to enable studies of dynamical processes in atomic, molecular, and material systems spanning femtoseconds to seconds, from the UV to the IR regimes. The MMDS employs pulse-shaping methods to provide an easy-to-use instrument with an unprecedented spectral range that enables unique combination spectroscopies. We demonstrate the multispectral capabilities of the MMDS on several model systems.
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Affiliation(s)
- Yin Song
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Riley Sechrist
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Ved Prakash Roy
- Department of Chemistry, University of Michigan, 930 N University Ave., Ann Arbor, Michigan 48109, USA
| | - Rong Duan
- Department of Chemistry, University of Michigan, 930 N University Ave., Ann Arbor, Michigan 48109, USA
| | - Jared Dziurgot
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Veronica Policht
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Yassel Acosta Matutes
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Kevin J Kubarych
- Department of Chemistry, University of Michigan, 930 N University Ave., Ann Arbor, Michigan 48109, USA
| | - Jennifer P Ogilvie
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
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9
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Konar A, Sechrist R, Song Y, Policht VR, Laible PD, Bocian DF, Holten D, Kirmaier C, Ogilvie JP. Electronic Interactions in the Bacterial Reaction Center Revealed by Two-Color 2D Electronic Spectroscopy. J Phys Chem Lett 2018; 9:5219-5225. [PMID: 30136848 DOI: 10.1021/acs.jpclett.8b02394] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The bacterial reaction center (BRC) serves as an important model system for understanding the charge separation processes in photosynthesis. Knowledge of the electronic structure of the BRC is critical for understanding its charge separation mechanism. While it is well-accepted that the "special pair" pigments are strongly coupled, the degree of coupling among other BRC pigments has been thought to be relatively weak. Here we study the W(M250)V mutant BRC by two-color two-dimensional electronic spectroscopy to correlate changes in the Q x region with excitation of the Q y transitions. The resulting Q y-Q x cross-peaks provide a sensitive measure of the electronic interactions throughout the BRC pigment network and complement one-color 2D studies in which such interactions are often obscured by energy transfer and excited-state absorption signals. Our observations should motivate the refinement of electronic structure models of the BRC to facilitate improved understanding of the charge separation mechanism.
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Affiliation(s)
- Arkaprabha Konar
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Riley Sechrist
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Yin Song
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Veronica R Policht
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
| | - Philip D Laible
- Biosciences Division , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - David F Bocian
- Department of Chemistry , University of California , Riverside , California 92521 , United States
| | - Dewey Holten
- Department of Chemistry , Washington University , St. Louis , Missouri 63130 , United States
| | - Christine Kirmaier
- Department of Chemistry , Washington University , St. Louis , Missouri 63130 , United States
| | - Jennifer P Ogilvie
- Department of Physics , University of Michigan , Ann Arbor , Michigan 49109-1040 , United States
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Wiley TE, Konar A, Miller NA, Spears KG, Sension RJ. Primed for Efficient Motion: Ultrafast Excited State Dynamics and Optical Manipulation of a Four Stage Rotary Molecular Motor. J Phys Chem A 2018; 122:7548-7558. [DOI: 10.1021/acs.jpca.8b06472] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Theodore E. Wiley
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Arkaprabha Konar
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
| | - Nicholas A. Miller
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kenneth G. Spears
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Roseanne J. Sension
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
- Department of Physics, University of Michigan, 450 Church Street, Ann Arbor, Michigan 48109-1040, United States
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11
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Tiwari V, Matutes YA, Konar A, Yu Z, Ptaszek M, Bocian DF, Holten D, Kirmaier C, Ogilvie JP. Strongly coupled bacteriochlorin dyad studied using phase-modulated fluorescence-detected two-dimensional electronic spectroscopy. Opt Express 2018; 26:22327-22341. [PMID: 30130927 DOI: 10.1364/oe.26.022327] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Accepted: 07/30/2018] [Indexed: 05/27/2023]
Abstract
Fluorescence-detected two-dimensional electronic spectroscopy (F-2DES) projects the third-order non-linear polarization in a system as an excited electronic state population which is incoherently detected as fluorescence. Multiple variants of F-2DES have been developed. Here, we report phase-modulated F-2DES measurements on a strongly coupled symmetric bacteriochlorin dyad, a relevant 'toy' model for photosynthetic energy and charge transfer. Coherence map analysis shows that the strongest frequency observed in the dyad is well-separated from the excited state electronic energy gap, and is consistent with a vibrational frequency readily observed in bacteriochlorin monomers. Kinetic rate maps show a picosecond relaxation timescale between the excited states of the dyad. To our knowledge this is the first demonstration of coherence and kinetic analysis using the phase-modulation approach to F-2DES.
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Miller NA, Deb A, Alonso-Mori R, Glownia JM, Kiefer LM, Konar A, Michocki LB, Sikorski M, Sofferman DL, Song S, Toda MJ, Wiley TE, Zhu D, Kozlowski PM, Kubarych KJ, Penner-Hahn JE, Sension RJ. Ultrafast X-ray Absorption Near Edge Structure Reveals Ballistic Excited State Structural Dynamics. J Phys Chem A 2018; 122:4963-4971. [PMID: 29799204 DOI: 10.1021/acs.jpca.8b04223] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Polarized ultrafast time-resolved X-ray absorption near edge structure (XANES) allows characterization of excited state dynamics following excitation. Excitation of vitamin B12, cyanocobalamin (CNCbl), in the αβ-band at 550 nm and the γ-band at 365 nm was used to uniquely resolve axial and equatorial contributions to the excited state dynamics. The structural evolution of the excited molecule is best described by a coherent ballistic trajectory on the excited state potential energy surface. Prompt expansion of the Co cavity by ca. 0.03 Å is followed by significant elongation of the axial bonds (>0.25 Å) over the first 190 fs. Subsequent contraction of the Co cavity in both axial and equatorial directions results in the relaxed S1 excited state structure within 500 fs of excitation.
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Affiliation(s)
| | | | - Roberto Alonso-Mori
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - James M Glownia
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | | | | | | | - Marcin Sikorski
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | | | - Sanghoon Song
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Megan J Toda
- Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States
| | | | - Diling Zhu
- Linac Coherent Light Source , SLAC National Accelerator Laboratory , 2575 Sand Hill Road , Menlo Park , California 94025 , United States
| | - Pawel M Kozlowski
- Department of Chemistry , University of Louisville , 2320 South Brook Street , Louisville , Kentucky 40292 , United States
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Khasnobish A, Datta S, Bose R, Tibarewala DN, Konar A. Analyzing text recognition from tactually evoked EEG. Cogn Neurodyn 2017; 11:501-513. [PMID: 29147143 DOI: 10.1007/s11571-017-9452-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 08/12/2017] [Accepted: 08/23/2017] [Indexed: 10/18/2022] Open
Abstract
Tactual exploration of objects produce specific patterns in the human brain and hence objects can be recognized by analyzing brain signals during tactile exploration. The present work aims at analyzing EEG signals online for recognition of embossed texts by tactual exploration. EEG signals are acquired from the parietal region over the somatosensory cortex of blindfolded healthy subjects while they tactually explored embossed texts, including symbols, numbers, and alphabets. Classifiers based on the principle of supervised learning are trained on the extracted EEG feature space, comprising three features, namely, adaptive autoregressive parameters, Hurst exponents, and power spectral density, to recognize the respective texts. The pre-trained classifiers are used to classify the EEG data to identify the texts online and the recognized text is displayed on the computer screen for communication. Online classifications of two, four, and six classes of embossed texts are achieved with overall average recognition rates of 76.62, 72.31, and 67.62% respectively and the computational time is less than 2 s in each case. The maximum information transfer rate and utility of the system performance over all experiments are 0.7187 and 2.0529 bits/s respectively. This work presents a study that shows the possibility to classify 3D letters using tactually evoked EEG. In future, it will help the BCI community to design stimuli for better tactile augmentation n also opens new directions of research to facilitate 3D letters for visually impaired persons. Further, 3D maps can be generated for aiding tactual BCI in teleoperation.
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Affiliation(s)
- A Khasnobish
- TCS Innovation Labs, New Town, Kolkata, 700156 India
| | - S Datta
- TCS Innovation Labs, New Town, Kolkata, 700156 India
| | - R Bose
- Electrical Engineering Department, Calcutta Institute of Engineering and Management, 24/1A, Chandi Ghosh Road, Kolkata, 700040 India
| | - D N Tibarewala
- School of Bioscience and Engineering, Jadavpur University, Kolkata, 700032 India
| | - A Konar
- Department of Electronics and Telecommunication Engineering, Jadavpur University, Kolkata, 700032 India
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Khanum BNMK, Guha R, Sur VP, Nandi S, Basak SK, Konar A, Hazra S. Pirfenidone inhibits post-traumatic proliferative vitreoretinopathy. Eye (Lond) 2017; 31:1317-1328. [PMID: 28304388 DOI: 10.1038/eye.2017.21] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 01/09/2017] [Indexed: 12/13/2022] Open
Abstract
PurposeThe purpose of the study was to evaluate the efficacy and safety of intravitreal pirfenidone for inhibition of proliferative vitreoretinopathy (PVR) in a model of penetrating ocular injury.Patients and methodsPenetrating trauma was induced on the retina of rabbit and treated either with 0.1 ml of phosphate-buffered saline (PBS) or 0.1 ml of 0.5% pirfenidone, and development of PVR was evaluated clinically and graded after 1 month. Histopathology and immunohistochemistry with transforming growth factor beta (TGFβ), alpha smooth muscle actin (αSMA), and collagen-1 were performed to assess the fibrotic changes. Expression of cytokines in the vitro-retinal tissues at different time points following pirfenidone and PBS injection was examined by RT-PCR. Availability of pirfenidone in the vitreous of rabbit at various time points was determined by high-performance liquid chromatography following injection of 0.1 ml of 0.5% pirfenidone. In normal rabbit eye, 0.1 ml of 0.5% pirfenidone was injected to evaluate any toxic effect.ResultsClinical assessment and grading revealed prevention of PVR formation in pirfenidone-treated animals, gross histology, and histopathology confirmed the observation. Immunohistochemistry showed prevention in the expression of collagen-I, αSMA, and TGFβ in the pirfenidone-treated eyes compared to the PBS-treated eyes. Pirfenidone inhibited increased gene expression of cytokines observed in control eyes. Pirfenidone could be detected up to 48 h in the vitreous of rabbit eye following single intravitreal injection. Pirfenidone did not show any adverse effect following intravitreal injection; eyes were devoid of any abnormal clinical sign, intraocular pressure, and electroretinography did not show any significant change and histology of retina remained unchanged.ConclusionThis animal study shows that pirfenidone might be a potential therapy for PVR. Further clinical study will be useful to evaluate the clinical application of pirfenidone.
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Affiliation(s)
- B N M K Khanum
- Department of Veterinary Surgery &Radiology, West Bengal University of Animal &Fishery Sciences, Kolkata, India
| | - R Guha
- CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - V P Sur
- CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - S Nandi
- CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | - A Konar
- CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - S Hazra
- Department of Veterinary Surgery &Radiology, West Bengal University of Animal &Fishery Sciences, Kolkata, India
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Konar S, Guha R, Kundu B, Nandi S, Ghosh TK, Kundu SC, Konar A, Hazra S. Silk fibroin hydrogel as physical barrier for prevention of post hernia adhesion. Hernia 2016; 21:125-137. [DOI: 10.1007/s10029-016-1484-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 03/16/2016] [Indexed: 12/25/2022]
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16
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Nairat M, Konar A, Lozovoy VV, Beck WF, Blanchard GJ, Dantus M. Controlling S2 Population in Cyanine Dyes Using Shaped Femtosecond Pulses. J Phys Chem A 2016; 120:1876-85. [PMID: 26935762 DOI: 10.1021/acs.jpca.6b01835] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fast population transfer from higher to lower excited states occurs via internal conversion (IC) and is the basis of Kasha's rule, which states that spontaneous emission takes place from the lowest excited state of the same multiplicity. Photonic control over IC is of interest because it would allow direct influence over intramolecular nonradiative decay processes occurring in condensed phase. Here we tracked the S2 and S1 fluorescence yield for different cyanine dyes in solution as a function of linear chirp. For the cyanine dyes with polar solvation response IR144 and meso-piperidine substituted IR806, increased S2 emission was observed when using transform limited pulses, whereas chirped pulses led to increased S1 emission. The nonpolar solvated cyanine IR806, on the other hand, did not show S2 emission. A theoretical model, based on a nonperturbative solution of the equation of motion for the density matrix, is offered to explain and simulate the anomalous chirp dependence. Our findings, which depend on pulse properties beyond peak intensity, offer a photonic method to control S2 population thereby opening the door for the exploration of photochemical processes initiated from higher excited states.
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Affiliation(s)
- Muath Nairat
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Arkaprabha Konar
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Vadim V Lozovoy
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Warren F Beck
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - G J Blanchard
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States.,Department of Physics and Astronomy, Michigan State University , East Lansing, Michigan 48824, United States
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Affiliation(s)
- Arkaprabha Konar
- Department of Chemistry and ‡Department of
Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Vadim V. Lozovoy
- Department of Chemistry and ‡Department of
Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- Department of Chemistry and ‡Department of
Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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Patel L, Konar A, Sarkar A. Field evaluation of various treatment-schedules for the control of epilachna beetle, Henosepilachna vigintioctopunctata(Fab.), on Brinjal. Appl Biol Res 2016. [DOI: 10.5958/0974-4517.2016.00022.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Nairat M, Konar A, Kaniecki M, Lozovoy VV, Dantus M. Investigating the role of human serum albumin protein pocket on the excited state dynamics of indocyanine green using shaped femtosecond laser pulses. Phys Chem Chem Phys 2015; 17:5872-7. [DOI: 10.1039/c4cp04984e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
When indocyanine green (ICG) is confined inside the pocket of human serum albumin its triplet state formation is mitigated and coherent vibrational motion becomes more observable.
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Affiliation(s)
- Muath Nairat
- Department of Chemistry
- Michigan State University
- East Lansing
- USA
| | | | - Marie Kaniecki
- Department of Chemistry
- Michigan State University
- East Lansing
- USA
| | | | - Marcos Dantus
- Department of Chemistry
- Michigan State University
- East Lansing
- USA
- Department of Physics and Astronomy
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Jati A, Singh G, Koley S, Konar A, Ray AK, Chakraborty C. A novel segmentation approach for noisy medical images using intuitionistic fuzzy divergence with neighbourhood-based membership function. J Microsc 2014; 257:187-200. [PMID: 25458042 DOI: 10.1111/jmi.12200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Accepted: 10/24/2014] [Indexed: 11/26/2022]
Abstract
Medical image segmentation demands higher segmentation accuracy especially when the images are affected by noise. This paper proposes a novel technique to segment medical images efficiently using an intuitionistic fuzzy divergence-based thresholding. A neighbourhood-based membership function is defined here. The intuitionistic fuzzy divergence-based image thresholding technique using the neighbourhood-based membership functions yield lesser degradation of segmentation performance in noisy environment. Its ability in handling noisy images has been validated. The algorithm is independent of any parameter selection. Moreover, it provides robustness to both additive and multiplicative noise. The proposed scheme has been applied on three types of medical image datasets in order to establish its novelty and generality. The performance of the proposed algorithm has been compared with other standard algorithms viz. Otsu's method, fuzzy C-means clustering, and fuzzy divergence-based thresholding with respect to (1) noise-free images and (2) ground truth images labelled by experts/clinicians. Experiments show that the proposed methodology is effective, more accurate and efficient for segmenting noisy images.
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Affiliation(s)
- A Jati
- Department of Electronics & Telecommunication Engineering, Jadavpur University, Kolkata, India
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21
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Abstract
Interaction of intense laser pulses with atoms and molecules is at the forefront of atomic, molecular, and optical physics. It is the gateway to powerful new tools that include above threshold ionization, high harmonic generation, electron diffraction, molecular tomography, and attosecond pulse generation. Intense laser pulses are ideal for probing and manipulating chemical bonding. Though the behavior of atoms in strong fields has been well studied, molecules under intense fields are not as well understood and current models have failed in certain important aspects. Molecules, as opposed to atoms, present confounding possibilities of nuclear and electronic motion upon excitation. The dynamics and fragmentation patterns in response to the laser field are structure sensitive; therefore, a molecule cannot simply be treated as a "bag of atoms" during field induced ionization. In this article we present a set of experiments and theoretical calculations exploring the behavior of a large collection of aryl alkyl ketones when irradiated with intense femtosecond pulses. Specifically, we consider to what extent molecules retain their molecular identity and properties under strong laser fields. Using time-of-flight mass spectrometry in conjunction with pump-probe techniques we study the dynamical behavior of these molecules, monitoring ion yield modulation caused by intramolecular motions post ionization. The set of molecules studied is further divided into smaller sets, sorted by type and position of functional groups. The pump-probe time-delay scans show that among positional isomers the variations in relative energies, which amount to only a few hundred millielectronvolts, influence the dynamical behavior of the molecules despite their having experienced such high fields (V/Å). High level ab initio quantum chemical calculations were performed to predict molecular dynamics along with single and multiphoton resonances in the neutral and ionic states. We propose the following model of strong-field ionization and subsequent fragmentation for polyatomic molecules: Single electron ionization occurs on a suboptical cycle time scale, and the electron carries away essentially all of the energy, leaving behind little internal energy in the cation. Subsequent fragmentation of the cation takes place as a result of further photon absorption modulated by one- and two-photon resonances, which provide sufficient energy to overcome the dissociation energy. The proposed hypothesis implies the loss of a photoelectron at a rate that is faster than intramolecular vibrational relaxation and is consistent with the observation of nonergodic photofragmentation of polyatomic molecules as well as experimental results from many other research groups on different molecules and with different pulse durations and wavelengths.
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Affiliation(s)
- Arkaprabha Konar
- Department of Chemistry and ‡Department of Physics and Astronomy, Michigan State University , East Lansing, Michigan 48824, United States
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Paul B, Biswas P, Sarkar D, Konar A, Sur K. Neutrophil count and its correlation with short term morbidity and mortality in patients with acute coronary syndrome. Indian Heart J 2014. [DOI: 10.1016/j.ihj.2014.10.100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
The spectroscopy of large organic molecules and biomolecules in solution has been investigated using various time-resolved and frequency-resolved techniques. Of particular interest is the early response of the molecule and the solvent, which is difficult to study due to the ambiguity in assigning and differentiating inter- and intramolecular contributions to the electronic and vibrational populations and coherence. Our measurements compare the yield of fluorescence and stimulated emission for two laser dyes IR144 and IR125 as a function of chirp. While negatively chirped pulses are insensitive to solvent viscosity, positively chirped pulses are found to be uniquely sensitive probes of solvent viscosity. The fluorescence maximum for IR125 is observed near transform-limited pulses; however, for IR144, it is observed for positively chirped pulses once the pulses have been stretched to hundreds of femtoseconds. We conclude that chirped pulse spectroscopy is a simple one-beam method that is sensitive to early solvation dynamics.
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Affiliation(s)
- Arkaprabha Konar
- †Department of Chemistry and ‡Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Vadim V Lozovoy
- †Department of Chemistry and ‡Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- †Department of Chemistry and ‡Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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Affiliation(s)
- Mohsin Ahmad Bhat
- Department of Chemistry; University of Pune; Ganeshkhind Pune 411007 India
- Department of Chemistry; University of Kashmir; Srinagar 190006 India
| | - Arkaprabha Konar
- Department of Chemistry; University of Pune; Ganeshkhind Pune 411007 India
| | - Pravin P. Ingole
- Physical Chemistry and Electrochemistry; Technical University of Dresden; Bergstrasse 66b 01062 Dresden Germany
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Konar A, Shah JD, Lozovoy VV, Dantus M. Optical response of fluorescent molecules studied by synthetic femtosecond laser pulses. EPJ Web of Conferences 2013. [DOI: 10.1051/epjconf/20134107017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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26
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Abstract
The early optical dynamic response, resulting population, and electronic coherence are investigated experimentally and modeled theoretically for IR144 in solution. The fluorescence and stimulated emission response are studied systematically as a function of chirp. The magnitude of the chirp effect on fluorescence and stimulated emission is found to depend quadratically on pulse energy, even where excitation probabilities range from 0.02 to 5%, in the so-called "linear excitation regime". Interestingly, the shape of the chirp dependence on fluorescence and stimulated emission is found to be independent of pulse energy. The chirp dependence reveals dynamics related to solvent rearrangement following excitation and also depends on electronic relaxation of the chromophore. The experimental results are successfully simulated using a four-level model in the presence of inhomogeneous broadening of the electronic transitions.
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Affiliation(s)
- Arkaprabha Konar
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Vadim V Lozovoy
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
- ‡Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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Abstract
The optical response of the fluorescent molecule IR144 in solution is probed by pairs of collinear pulses with intensity just above the linear dependence using two different pulse shaping methods. The first approach mimics a Michelson interferometer, while the second approach, known as multiple independent comb shaping (MICS), eliminates spectral interference. The comparison of interfering and non-interfering pulses reveals that linear interference between the pulses leads to the loss of experimental information at early delay times. In both cases, the delay between the pulses is controlled with attosecond resolution and the sample fluorescence and stimulated emission are monitored simultaneously. An out-of-phase behavior is observed for fluorescence and stimulated emission, with the fluorescence signal having a minimum at zero time delay. Experimental findings are modeled using a two-level system with relaxation that closely matches the phase difference between fluorescence and stimulated emission and the relative intensities of the measured effects.
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Affiliation(s)
- Arkaprabha Konar
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Jay D Shah
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Vadim V Lozovoy
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Marcos Dantus
- †Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
- ‡Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
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Bhowmik P, Das S, Konar A, Nandi D, Chakraborty A. Emotion clustering from stimulated electroencephalographic signals using a Duffing oscillator. ACTA ACUST UNITED AC 2010. [DOI: 10.1504/ijcih.2010.034131] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Chakraborty A, Konar A, Chakraborty U, Chatterjee A. Emotion Recognition From Facial Expressions and Its Control Using Fuzzy Logic. ACTA ACUST UNITED AC 2009. [DOI: 10.1109/tsmca.2009.2014645] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Das S, Dasgupta S, Biswas A, Abraham A, Konar A. On Stability of the Chemotactic Dynamics in Bacterial-Foraging Optimization Algorithm. ACTA ACUST UNITED AC 2009. [DOI: 10.1109/tsmca.2008.2011474] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Abstract
Sarcoma-like mural nodule is a very rare occurrence in a mucinous tumour of the ovary. Two such nodules having morphologically benign features with osteoclastic giant cells, in the wall of mucinous cystadenoma are described. In addition, these nodules exhibited reactive vascular proliferations. The sarcoma-like nodules are associated with a favourable outcome and must be distinguished from other malignant nodules composed of sarcoma or anaplastic carcinoma that may also occur in the wall of mucinous ovarian tumours.
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Affiliation(s)
- S Chakrabarti
- Department of Pathology, NRS Medical College and Midnapur Medical College, Midnapur, Kolkata, India.
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34
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Chakrabarti S, Konar A, Biswas S, Das S. Sarcoma-like mural nodules in ovarian mucinous cystadenomas--a report of two cases. Indian J Med Sci 2005; 59:499-502. [PMID: 16340150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Sarcoma-like mural nodule is a very rare occurrence in a mucinous tumour of the ovary. Two such nodules having morphologically benign features with osteoclastic giant cells, in the wall of mucinous cystadenoma are described. In addition, these nodules exhibited reactive vascular proliferations. The sarcoma-like nodules are associated with a favourable outcome and must be distinguished from other malignant nodules composed of sarcoma or anaplastic carcinoma that may also occur in the wall of mucinous ovarian tumours.
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Affiliation(s)
- S Chakrabarti
- Department of Pathology, NRS Medical College and Midnapur Medical College, Midnapur, Kolkata, India.
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De K, Ghosh G, Datta M, Konar A, Bandyopadhyay J, Bandyopadhyay D, Bhattacharya S, Bandyopadhyay A. Analysis of differentially expressed genes in hyperthyroid-induced hypertrophied heart by cDNA microarray. J Endocrinol 2004; 182:303-14. [PMID: 15283691 DOI: 10.1677/joe.0.1820303] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Experiments were carried out to identify the altered genes in hyperthyroid rat heart and their influence on the functions of cardiac myocytes. Chronic treatment of rats with 3,5,3' triiodo-L-thyronine (T3) resulted in a prominent increase in the size of the left ventricle with increased wall thickness and reduced chamber volume leading to concentric cardiac hypertrophy. The heart weight to body weight ratio (HW/BW) in hyperthyroid rats was increased by about 58% over that of normal rats. Using cDNA microarray comprising 588 genes, we compared the differences in mRNA expression of hyperthyroid and normal rat heart. Based on a threshold of greater than 10% change, about 37 genes were found to be regulated by T3. Further analyses by Western blotting, Northern blotting and real-time quantitative RT-PCR of some of the genes confirmed the microarray results. The T3-altered genes encode various types of proteins related to metabolism, matrix and cytoskeletal structures, growth factors, transcription factors, Ca(2+)-channels etc. The physiological significance of one of these altered proteins in hyperthyroid heart, insulin-responsive glucose transporter (GLUT) type 4 (GLUT4), was studied in detail. The expression of GLUT4 was drastically reduced in the ventricular tissues of hyperthyroid heart. Insulin-induced glucose uptake in hyperthyroid cardiomyocytes was reduced significantly, indicating the impaired glucose transport in cardiac cells. Interestingly, a few genes such as GLUT4, cytochrome P450 isoforms, superoxide dismutase (SOD), collagens, matrix metalloproteinases (MMP), tissue inhibitors of matrix metalloproteinases etc. which had not been reported earlier were found to be altered in hyperthyroid heart. Our results show some new aspects of hyperthyroid heart which will be important in assessing the pathophysiology of hypertrophied cardiomyocytes.
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Affiliation(s)
- K De
- Indian Institute of Chemical Biology, 4 Raja S. C. Mullick Road, Kolkata 700032, India
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Gleiter R, Kobayashi M, Spanget-Larsen J, Gronowitz S, Konar A, Farnier M. Electronic structure of sulfur compounds. 24. Electronic effects of the heteroatom in five-membered heterocycles. Photoelectron spectra of selenolo and pyrrolo analogs of thieno[2,3-b]thiophene and thieno[3,2-b]thiophene. J Org Chem 2002. [DOI: 10.1021/jo00433a008] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dhar A, Konar A, Sengupta D. Transcatheter therapy of intravisceral bleeding. J Invasive Cardiol 2001; 13:126-8. [PMID: 11176023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Intravisceral bleeding is a life-threatening situation demanding fast and active steps to control, unless it stops spontaneously as in a few lucky patients. A surgical approach is a major intervention with its associated procedural risks when the site is in organs other than the spleen. The transcatheter approach helps in precise location and embolization of the bleeding site; it is a more practical approach that has been known for the past 2 decades to be effective and provide good long-term results. However, the transcatheter approach has been reported in fewer than 200 cases in the literature. Our small series of 43 cases shows initial success of 95% and a fatal early recurrence of only 2.4%. Non-hemorrhagic etiology (sepsis, head injury, etc.) was the major cause of early death (14.6%) among the successfully embolized cases. Long-term follow-up shows recurrence (4.8%) only in the group of chronic etiology. Transcatheter embolization of intravisceral bleeding with Gel-Foam and/or poly-vinyl alcohol particles is a swift, effective and precise method of treatment without major operational hazards.
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Affiliation(s)
- A Dhar
- Department of Cardiology and Gastroenterology, Peerless Hospital, and BK Roy Research Center, Calcutta, India
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Mazumder DG, Chaudhuri S, Konar A, Santra A, Pal B, Sarkar S. Response to low-dose interferon in chronic liver disease due to hepatitis B virus infection. Indian J Gastroenterol 1998; 17:97-9. [PMID: 9695390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND Interferon is at present the only effective therapy for chronic hepatitis B virus (HBV) infection. Data regarding its efficacy in India are scant. The present study was undertaken to assess the efficacy of low-dose interferon in chronic liver disease due to HBV infection. METHODS Twenty four patients with histologic evidence of chronic hepatitis with or without cirrhosis, and persistent elevation of serum aminotransferases and persistent positivity for HBsAg and HBeAg for more than six months, were included. Fourteen patients were treated with interferon alpha-2b, 3 million units thrice weekly for 16 weeks; ten patients who could not afford the drug were followed up as controls without specific therapy. Patients were examined weekly for the first 4 weeks, followed by two weekly for 12 weeks and then every two months. Blood tests for viral markers and liver biochemistry were done at 0, 4, 8, 12, 16 weeks and then at two-month intervals for at least one year after therapy. Patients who cleared HBeAg were followed up for 2.2 (1-4) years for HBsAg clearance. RESULTS HBeAg clearance occurred in 9 patients (64%) in the interferon group, and in one control patient (p < 0.01). HBsAg clearance occurred in only one patient in the treatment group during follow up of mean 2.4 years. No patient in the control group cleared HBsAg. Patients having high ALT level at the beginning of treatment had significantly higher HBeAg clearance rate (7 of 7) than patients with low ALT levels (2 of 7; p < 0.05). CONCLUSION Low-dose interferon therapy is effective in attaining HBeAg, but not HBsAg, clearance in chronic HBV infection.
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Affiliation(s)
- D G Mazumder
- Department of Gastroenterology, Institute of Post Graduate Medical Education and Research, Calcutta
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Konar A, Das AS, De PK, Roy A, Mazumder DN. Natural history of severe duodenal ulcer disease. Indian J Gastroenterol 1998; 17:48-50. [PMID: 9563218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND A subset of patients with chronic duodenal ulcer has severe ulcer diathesis in the form of frequent relapses and complications like perforation and hemorrhage. We observed the effect of drug treatment on the natural history of this subset. METHODS Of 526 patients diagnosed to have chronic duodenal ulcer by endoscopy, 23 patients with severe diathesis were available for long follow-up (mean period 36 months). Each patient was assessed clinically and endoscopically every 2 months for at least 12 months and then every 3 months or when symptomatic. Helicobacter pylori status was assessed during endoscopy. The effect of antisecretory drugs and anti-H. pylori therapy on natural history was determined. RESULTS Thirteen of 23 patients (56%) had refractory ulcers; six responded to double dose of H2-receptor antagonists (H2RA) for 8 weeks and six to omeprazole 40 mg daily for 4-8 weeks. Of 20 patients (87%) who were H. pylori-positive, 15 completed triple-drug therapy; of these, 10 patients eradicated H. pylori. These 10 patients were followed up for 24 months; there were no ulcer relapses within the first 12 months but 8 of them relapsed between 12 and 24 months (total number of relapses 8). Reinfection with H. pylori occurred in 3 patients. In the other 10 patients who remained H. pylori-positive, there were 19 episodes of ulcer relapse in 7 patients over 24 months, in spite of maintenance therapy with H2RA (p < 0.05). CONCLUSIONS Refractoriness in patients with severe ulcer disease is usually episodic and amenable to larger doses of omeprazole or H2RA. Anti-H. pylori therapy improves the natural history but its effect in preventing ulcer relapse is short lasting (less than 12 months). Recurrence of infection is a problem in our population.
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Affiliation(s)
- A Konar
- Department of Gastroenterology, Institute of Post Graduate Medical Education and Research, Calcutta
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Abstract
The paper presents a new model for cognitive reasoning using fuzzy neural nets. The analysis of the proposed model yields guaranteed stability of the temporal fuzzy inferences, derived from the network and conditional stability of the structure of the cognitive map, framed by the arcs of the network. The results arrived at in the paper have been illustrated with reference to a typical weather forecast system.
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Affiliation(s)
- S Pal
- Dept. of Comput. Services, Garden Reach Shipbuilders & Eng. Ltd., Calcutta
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Ghose AK, Dasgupta J, Konar A, Raha K, Basu PK, Mazumder DN. Collision tumor of gastrointestinal tract. Indian J Gastroenterol 1994; 13:29-30. [PMID: 8119747] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A rare combination of multiple adenomatous polyps of the colon and carcinoid tumor of the ileum in a 54-year-old man is reported.
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Affiliation(s)
- A K Ghose
- Department of Gastroenterology, Institute of Post-Graduate Medical Education and Research, Calcutta
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Konar A, Mazumder DN. Hepatitis C virus and autoimmune chronic active hepatitis. Indian J Gastroenterol 1993; 12:158-9. [PMID: 8270301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- A Konar
- Department of Medicine and Gastroenterology, Post-Graduate Institute of Medical Education and Research, Calcutta
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Konar A, Mazumder DN. Interferon therapy for chronic NANB hepatitis. Indian J Gastroenterol 1992; 11:103-4. [PMID: 1428028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- A Konar
- Department of Gastroenterology, Institute of Post Graduate Medical Education & Research, Calcutta
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Konar A, Ivie GW. Fate of [14C]coumaphos after dermal application to lactating goats as a pour-on formulation. Am J Vet Res 1988; 49:488-92. [PMID: 3377307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Two lactating Nubian goats were dermally treated with [14C]coumaphos (O-[3-chloro-4-methyl-2-oxo-2H-benzopyran-7-yl] O,O-diethyl phosphorothioate) as a 4% active ingredient pour-on formulation. Doses were administered, along the dorsal midline from withers to sacrum, at a rate equivalent to 14 mg of coumaphos/kg of body weight. During the 7 days after treatment, an average of less than 0.1, 4.7, and 1% of the administered dose was eliminated in the milk, urine, and feces, respectively. When goats were killed after 7 days, about 45% of the administered radiocarbon remained on the hair and skin, and this consisted almost entirely of intact coumaphos. Residues in selected tissues collected after 7 days were, in every case, less than 1 mg of coumaphos equivalent/kg of tissue, with highest residues in adipose tissue, followed by residues in kidney and liver. In milk, residue amounts plateaued after about 2 days and remained relatively constant at about 0.1 mg of coumaphos equivalent/kg of milk. Residues in adipose tissue and in milk consisted mainly of unmetabolized coumaphos. In urine, most radiocarbon was present as metabolites of coumaphos, but in feces, most radiocarbon was present as the intact parent compound. Coumaphos was absorbed slowly and at a constant rate after dermal application to lactating goats as a pour-on formulation.
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Affiliation(s)
- A Konar
- Agricultural Research Service, USDA, College Station, Texas 77841
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Abstract
We describe a patient who presented with oedema and hypoproteinaemia which was proved to be due to protein-losing enteropathy. Extensive gastrointestinal investigations failed to discover any definitive cause. He subsequently developed tuberculous inguinal lymphadenopathy but although treated for tuberculosis the protein-losing state persisted. Later on he developed renal failure due to obstructive nephropathy. Laparotomy was carried out and it disclosed the diagnosis of non-Hodgkin's lymphoma, treatment of which cured the protein-losing state.
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Gronowitz S, Konar A, Abronin IA, Litvinov VP. 1H,13C, and77Se NMR spectra of compounds of the selenopheno[2,3-c]thiophene series. Russ Chem Bull 1981. [DOI: 10.1007/bf00950284] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Gronowitz S, Konar A, Hörnfeldt AB. 77Se n.m.r. studies of organoselenium compounds: III—substituent effects in 4,4′-disubstituted diphenyl selenides and 4,4′-disubstituted diphenylmethanes studied by1H,13C and77Se spectroscopy. ACTA ACUST UNITED AC 1977. [DOI: 10.1002/mrc.1270090408] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Konar A, Thomas PC. The effect of dehydration and intravenous infusion of vasopressin on milk secretion in the goat. Br Vet J 1970; 126:Suppl:25-8. [PMID: 5529171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Konar NR, Datta SK, Nag A, Konar A. Murmur over liver in cases of severe anaemia. Br Med J 1967; 4:154. [PMID: 6053982 PMCID: PMC1750053 DOI: 10.1136/bmj.4.5572.154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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