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Blinc A, Planinšič G, Keber D, Jarh O, Lahajnar G, Zidansěk A, Demsar F. Dependence of Blood Clot Lysis on the Mode of Transport of Urokinase into the Clot - A Magnetic Resonance Imaging Study in Vitro. Thromb Haemost 2018. [DOI: 10.1055/s-0038-1648188] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
SummaryMagnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3 .7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 ± 2.4 × 10−2 ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p <0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.
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Affiliation(s)
- A Blinc
- The Trnovo Hospital of Internal Medicine, University Clinical Center of Ljubljana, Ljubljana, Yugoslavia
| | - G Planinšič
- The Department of Physics, Faculty of Natural and Technical Sciences, Univeriiity of Ljubljana, Yugoslavia
| | - D Keber
- The Trnovo Hospital of Internal Medicine, University Clinical Center of Ljubljana, Ljubljana, Yugoslavia
| | - O Jarh
- The J. Stefan Institute, University of Ljubljana, Ljubljana, Yugoslavia
| | - G Lahajnar
- The J. Stefan Institute, University of Ljubljana, Ljubljana, Yugoslavia
| | - A Zidansěk
- The J. Stefan Institute, University of Ljubljana, Ljubljana, Yugoslavia
| | - F Demsar
- The J. Stefan Institute, University of Ljubljana, Ljubljana, Yugoslavia
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Blinc A, Keber D, Lahajnar G, Stegnar M, Zidanšek A, Demsar F. Lysing Patterns of Retracted Blood Clots with Diffusion or Bulk Flow Transport of Plasma with Urokinase into Clots – a Magnetic Resonance Imaging Study In Vitro. Thromb Haemost 2018. [DOI: 10.1055/s-0038-1646341] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
SummaryFresh retracted clots are known to be poorly lysable by fibrinolytic agents. We have studied whether lysis of retracted clots could be enhanced by bulk transport in comparison to pure diffusion of plasma containing urokinase (400 IU/ml) into the clots. Cylindrical retracted blood clots were occlusively glued by a polyester into plastic tubes and put in contact with plasma through the clot bases. One group of clots (perfused clots, n = 10) was placed under a pressure difference of 6 kPa (60 cm H20) which resulted in an average plasma flow of 0.97 ± 0.34 µl/min through the clot during the first hour. Another group of clots (non-perfused clots, n = 10) was incubated in the lytic plasma without a pressure difference. Clot sizes were measured during lysis by magnetic resonance imaging (MRI). Channels representing lysed areas penetrated into perfused clots with a velocity of 5.4 ± 1.6 mm/h (n = 10), whereas the boundaries of non-perfused clots subsided with a velocity of less than 0.1 mm/h. Eight of the 10 perfused clots were recanalized after 8 h and the sizes of the perfused group were reduced to 64.0 ± 10.7% of the initial values. The relative sizes of non-perfused clots after 8 h remained significantly higher: 95.0 ± 1.3%, p <0.005. In a separate experiment good agreement was obtained between the measured clot sizes by MRI and the residual radioactivity of 125I-fibrin in the clot. The strong dependence of lysis on the transport mechanism of plasma with urokinase into retracted clots suggests that local hemodynamic conditions in vivo are likely to influence the lysis of thrombi.
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Affiliation(s)
- A Blinc
- The University Clinical Centre, Trnovo Hospital of Internal Medicine, Ljubljana, Slovenia
| | - D Keber
- The University Clinical Centre, Trnovo Hospital of Internal Medicine, Ljubljana, Slovenia
| | - G Lahajnar
- The Institute J. Stefan, University of Ljubljana, Slovenia
| | - M Stegnar
- The University Clinical Centre, Trnovo Hospital of Internal Medicine, Ljubljana, Slovenia
| | - A Zidanšek
- The Institute J. Stefan, University of Ljubljana, Slovenia
| | - F Demsar
- The Institute J. Stefan, University of Ljubljana, Slovenia
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Lahajnar G, Sobotič B, Sepe A, Jazbinšek V, Peča S. Influence of sodium nitroprusside on human erythrocyte membrane water permeability: an NMR study. Gen Physiol Biophys 2010; 29:373-80. [DOI: 10.4149/gpb_2010_04_373] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [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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Vuk-pavlović S, Benko B, Maricić S, Lahajnar G, Kuranova IP, Vainshtein BK. The haem-accessibility in leghaemoglobin of Lupinus luteus as observed by proton magnetic relaxation. Int J Pept Protein Res 2009; 8:427-34. [PMID: 965150 DOI: 10.1111/j.1399-3011.1976.tb02522.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Using the solvent-protons' longitudinal magnetic relaxation rates (p.m.r.) for Lupinus luteus leghaemoglobin derivatives the accessibility of the haem has been evaluated by our "stereo-chemical p.m.r. titration" method with nonexchangeable protons of aliphatic lower alcohols in otherwise deuterated solutions. The haem in leghaemoglobin is more accessible and its protein environment more flexible compared with vertebrate haemoglobins. The correlation time in aquometleghaemglobin aqueous solution has been determined by measuring the frequency dispersion of the p.m.r. rates between 6.1 and 93 MHZ. Taking into account the measured value of tauc = (7.7 +/- 0.5 x 10(-10) s the iron-to-proton inter-spin distances have been calculated. The significance of these distances as well as the electronic g-factor anisotrophy for elucidation of fine structural details of the haem-environment are discussed.
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Lahajnar G, Benko B, Rutar V, Zupancic I. Proton magnetic relaxation dispersion in human fluoromethaemoglobin solutions. Int J Pept Protein Res 2009; 8:317-22. [PMID: 1279086 DOI: 10.1111/j.1399-3011.1976.tb02509.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The solvent proton spin-lattice relaxation time of high spin Fe3+ (S=5/2) human A fluoromethaemoglobin aqueous solutions was measured at 14 Larmor frequencies in the range from 2.2 to 96 MHz. The observed paramagnetic relaxation rates are analysed in terms of the Solomon-Bloembergen theory, with the g-tensor value of 2 based on the consideration of the protein tertiary structure. From the H2O (pH 6) haemoprotein solution relaxation data, tau(c) =(9.3+/-0.3) X 10(-10) sec. If the total relaxation rates are corrected for the "outer-sphere" paramagnetic contribution, tau(c)=(6.5+/-0.4) X 10(-10) sec. The latter correction is obtained from the p.m.r. of the non-exchangeable aliphatic protons of C2H4(OD)2 added to the D2O-solution of fluoromethaemoglobin. Assuming that single proton transfer is taking place through the protein channel along the axis normal to the haem (g=2), the protein "binding" site is at a distance of 3.93 to 3.98 A from the haem Fe3+ ion.
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Vilfan M, Apih T, Sebastião PJ, Lahajnar G, Zumer S. Liquid crystal 8CB in random porous glass: NMR relaxometry study of molecular diffusion and director fluctuations. Phys Rev E Stat Nonlin Soft Matter Phys 2007; 76:051708. [PMID: 18233674 DOI: 10.1103/physreve.76.051708] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Indexed: 05/25/2023]
Abstract
We present the measurements of the proton spin-lattice relaxation time T1 of liquid crystal 4-n-octyl-4'-cyanobiphenyl (8CB) confined into randomly oriented approximately 15 nm pores of untreated porous glass. In the low kilohertz range the spin-lattice relaxation rate in the nanoconfined 8CB is about ten times larger than in the bulk. We show that the increase is mainly due to molecular reorientations mediated by translational displacements (RMTD). In the paranematic phase the power law describing the RMTD dispersion, (T1(-1))RMTD proportional, omega(-p), is well characterized by the exponent p=0.5+/-0.06 and suggests an equipartition of diffusion modes with different wavelengths. The largest distance related to the decay of the orientational correlation function is about twice the diameter of the cavity. The situation is different in the nematic phase, where the orientational correlation is eventually lost at approximately 60 nm in the direction along the pore, a distance corresponding roughly to the length of a pore segment in the glassy matrix. The exponent p is between 0.65 and 0.9, depending on the temperature, which implies that in the nematic phase long wavelength modes are relatively more important--a consequence of the uniform director field along the pore. These observations are in agreement with the model of mutually independent pores with nematic director parallel to the pore axis in each segment. We point out that in strongly confined liquid crystals the proton NMR relaxometry does not provide the evidence of director fluctuations correlated over micrometer distances as was suggested earlier. The local translational diffusion of molecules within the cavities is found about as fast as in bulk.
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Affiliation(s)
- M Vilfan
- Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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Sebastião PJ, Sousa D, Ribeiro AC, Vilfan M, Lahajnar G, Seliger J, Zumer S. Field-cycling NMR relaxometry of a liquid crystal above in mesoscopic confinement. Phys Rev E Stat Nonlin Soft Matter Phys 2005; 72:061702. [PMID: 16485959 DOI: 10.1103/physreve.72.061702] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Indexed: 05/06/2023]
Abstract
We measured the proton spin-lattice relaxation times in the isotropic phase of liquid crystal 4-n-pentyl-4-cyanobiphenyl (5CB) confined into porous glass (CPG) with the average pore diameter approximately 72 nm. The analysis of T1(-1) frequency dispersions, spanning over four decades, shows that the main relaxation mechanism induced by the ordered surface layer are molecular reorientations mediated by translational displacements (RMTD). The RMTD contribution to T1(-1) is proportional to the inverse square root of Larmor frequency, a consequence of the equipartition of diffusion modes along the surface. Low and high frequency cutoffs of the RMTD mechanism clearly reveal that the surface alignment of liquid crystal is random planar with the size of uniformly oriented patches approximately 5 nm, depending on the treatment of the CPG matrix. According to the size of the uniformly oriented patches varies also the thickness of the ordered surface layer and its temperature behavior. The surface-induced order parameter is found to be temperature independent and determined by the local short range surface interactions.
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Affiliation(s)
- P J Sebastião
- Centro de Física da Matéria Condensada, Av. Prof. Gama Pinto 2, 1649-003 Lisbon, Portugal.
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Abstract
Using proton NMR relaxometry in the kilohertz frequency range, we study dynamics of 5CB liquid crystal molecules dispersed in the form of spherical microdroplets in a PDLC material. The focus of the study is the spin-lattice relaxation in the rotating frame, T1rho(-1), measured above the nematic-isotropic transition TNI. We show that the relaxation rate T1rho(-1)--when induced by uniform molecular translational diffusion in a spherical cavity--depends on the strength of the rotating magnetic field as T1rho(-1) proportional to omega1(-alpha) where alpha varies between 0.7 and 1, depending on the thickness of the ordered surface layer. This relaxation mechanism governs mainly the transverse spin relaxation, whereas the measurements of the frequency and temperature dependence of T1rho(-1) indicate a strong effect of slowing-down of molecular translational diffusion in contact with the polymer surface and yield the average dwell-time of molecules at the surface of the order 10(-5) s.
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Affiliation(s)
- M Vilfan
- Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia.
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Vilfan M, Apih T, Gregorovic A, Zalar B, Lahajnar G, Zumer S, Hinze G, Böhmer R, Althoff G. Surface-induced order and diffusion in 5CB liquid crystal confined to porous glass. Magn Reson Imaging 2001; 19:433-8. [PMID: 11445325 DOI: 10.1016/s0730-725x(01)00262-4] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [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: 11/23/2022]
Abstract
Liquid crystals confined into small cavities are known to have a weak orientational order even above the nematic-isotropic transition temperature. The surface-induced order and molecular dynamics in this temperature range are studied with the aid of deuteron NMR spectra, spin relaxation times T(1) and T(2,) proton dipolar-correlation effect, and direct measurements of the effective diffusion coefficient for the liquid crystal 5CB confined to controlled-pore glasses. Our results show that an arrangement of molecules parallel to the wall is induced by local molecular interactions between the liquid crystal and solid, resulting in a weak and temperature independent surface order parameter, S(0) approximately 0.02 +/- 0.01. There is no indication of a significant slowing-down of molecular diffusion at the wall, neither rotational nor translational. In cavities of nanometer size, where the nematic order evolves gradually upon cooling, a broadening of the NMR linewidths due to dynamic effects should be taken into account.
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Affiliation(s)
- M Vilfan
- J. Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia.
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Abstract
The inhibitory effect of a series of neutral lipophilic solutes (methanol, ethanol, n-propanol, iso-propanol, n-butanol, iso-amylalcohol, n-hexanol, diethylether, nitrobenzene, and pyridine) on the diffusional water permeability (Pd, tot) of bovine erythrocyte membrane at 25 degrees C was studied in comparison to that of p-chloromercuri benzoate (pCMB). Permeability data were obtained by measuring the transmembrane diffusional water exchange time tau(exch) using an 1H-T2 NMR technique. Maximal inhibition by approximately 50% of Pd, tot was produced by 2 mM pCMB which completely blocked the membrane water channels in 20 min, hence suggesting the channel-to-lipid diffusional water permeability ratio of about 1:1. Furthermore, the maximal inhibitory effect of pCMB in combination with the lipophilic solutes was lower than that of pCMB alone. As pCMB does not interfere with the lipid bilayer, and provided that it blocks the water channels in solute presence as well, this confirms that the solutes induce an increase in the lipid-mediated background water permeability contribution (Pd, lipid) by the formation of aqueous leaks in the membrane hydrophobic barrier. However, faster but less efficient in permeability inhibition than pCMB (either alone or combined with solutes) were the lipophilic solutes alone. Taken together, the results indicate that the lipophilic solutes suppress the membrane total permeability Pd, tot by two opposing effects: a reduction of its channel-mediated part (Pd, channel) to the extent exceeding that of a simultaneous Pd, lipid increase. The inhibitory potency of the solutes tested appears to be correlated with their solubility in the membrane medium.
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Affiliation(s)
- G Lahajnar
- Jozef Stefan Institute, Ljubljana, Slovenia.
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Kralj S, Zidansek A, Lahajnar G, Zumer S, Blinc R. Influence of surface treatment on the smectic ordering within porous glass. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 62:718-725. [PMID: 11088509 DOI: 10.1103/physreve.62.718] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2000] [Indexed: 05/23/2023]
Abstract
The influence of the surface treatment on the Sm-A-N phase transition of the 8CB (octylcyanobiphenyl) liquid crystal confined to controlled pore glass (CPG) matrices is studied. The characteristic linear size of voids in the chosen CPG matrix is 0.2 &mgr;m. The voids' surface was either nontreated or silane treated enforcing tangential or homeotropic anchoring, respectively. In both cases the x-ray measurements reveal a qualitative change of the temperature dependence of the smectic order-parameter correlation length in comparison to the bulk sample. In addition, the apparent smectic pretransitional ordering is observed for the silane-treated sample. A theoretical description based on the Landau-de Gennes type approach is developed to explain the experimental data. The surface positional anchoring strength of the silane-treated sample is estimated to be of the order of 10(-4) J/m(2) and at least 100 times weaker for the nontreated case.
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Affiliation(s)
- S Kralj
- J. Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia and Department of Physics, Faculty of Education, University of Maribor, Koroska 160, 2000 Maribor, Slovenia
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Sepcić K, Musevic I, Lahajnar G, Turk T, Macek P. AFM imaging of surface adsorbed polymeric 3-alkylpyridinium salts from the marine sponge Reniera sarai. Int J Biol Macromol 1999; 26:353-6. [PMID: 10628537 DOI: 10.1016/s0141-8130(99)00106-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [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: 10/18/2022]
Abstract
Bioactive 3-alkylpyridinium polymers (poly-APS) have recently been isolated from the marine sponge Reniera sarai. Previous results have shown that these molecules in aqueous solutions form supramolecular aggregates with an average hydrodynamic radius of 23 +/- 2 nm. To obtain additional evidences about the shape and the dimensions of poly-APS aggregates, we used atomic force microscopy (AFM) operating in tapping mode. The images clearly showed adsorbed aggregates with a lateral dimension of approximately 40 nm and a thickness of the order of approximately 1 nm. The distribution of volumes of the adsorbed aggregates is very similar to the distribution of hydrodynamic radii as obtained from the dynamic light scattering experiments. The volume distribution of these aggregates shows a maximum at 1750 nm3, which corresponds to a sphere with a radius of 7.5 nm.
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Affiliation(s)
- K Sepcić
- Department of Biology, Biotechnical Faculty, University of Ljubliana, Slovenia.
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Zrimec A, Jerman I, Lahajnar G. Low frequency alternating electric fields inhibit lactose uptake in Kluyveromyces marxianus. Bioelectrochem Bioenerg 1999; 48:481-4. [PMID: 10379572 DOI: 10.1016/s0302-4598(99)00025-2] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Frequency-dependent lactose uptake via the H+/lactose symporter in an externally applied low-intensity alternating electric field was demonstrated, using tracer flux experiments. The uptake of radiolabeled lactose was significantly inhibited with the electric field-strength of 30 V/cm and at frequencies below 10 Hz.
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Affiliation(s)
- A Zrimec
- Bion, Institute for Bioelectromagnetics and New Biology, Ljubljana, Slovenia.
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Kralj S, Zidansek A, Lahajnar G, Musevic I, Zumer S, Blinc R, Pintar MM. Nematic ordering in porous glasses: A deuterium NMR study. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 53:3629-3638. [PMID: 9964673 DOI: 10.1103/physreve.53.3629] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Vilfan M, Lahajnar G, Zupančič I, Žumer S, Blinc R, Crawford GP, Doane JW. Dynamics of a nematic liquid crystal constrained by a polymer network: A proton NMR study. J Chem Phys 1995. [DOI: 10.1063/1.470129] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Abstract
One-dimensional modeling of fibrinolysis (Senf, 1979; Zidansek and Blinc, 1991; Diamond and Anand, 1993) has accounted for the dissolution velocity, but the shape of the lysing patterns can be explained only by two- or three- drug-induced blood clot dissolution patterns obtained by proton nuclear magnetic resonance imaging, which can be described by the enzyme transport-limited system of fibrinolytic chemical equations with diffusion and perfusion terms (Zidansek and Blinc, 1991) in the reaction time approximation if the random character of gel porosity is taken into account. A two-dimensional calculation based on the Hele-Shaw random walk models (Kadanoff, 1985; Liang, 1986) leads to fractal lysing patterns as, indeed, is observed. The fractal dimension of the experimental lysing patterns changes from 1.2 at the beginning of the experiments to a maximum of approximately 1.3 in the middle and then decreases toward one when the clot is recanalized.
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Affiliation(s)
- A Zidansek
- J. Stefan Institute, University of Ljubljana, Slovenia
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Lahajnar G, Macek P, Smid P, Zupancic I. Ethanol- and acetonitrile-induced inhibition of water diffusional permeability across bovine red blood cell membrane. Biochim Biophys Acta 1995; 1235:437-42. [PMID: 7538790 DOI: 10.1016/0005-2736(95)80033-c] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of 0-3% (v/v) ethanol and acetonitrile on water diffusional permeability of bovine and chicken red blood cells (RBCs) was studied using a pulse 1H-T2 NMR technique. Transmembrane water diffusional exchange times, tau exch, of 9.2 +/- 0.46 ms and 18.3 +/- 1.0 ms were determined for bovine and chicken erythrocytes at 27.5 degrees C, respectively. Arrhenius activation energies Ea of water diffusion were 20.4 and 35.8 kJ mol-1. Ethanol, and acetonitrile being 2-fold more effective, markedly increased both tau exch and Ea in bovine RBC as compared to the well-known mercurial inhibitor of water channels, p-chloromercuribenzene sulfonate. Chicken RBCs that have no protein water channels, were found to be completely insensitive for either agent. It was suggested that ethanol and acetonitrile partitioning into the lipid phase of bovine RBC membrane affects the permeability of CHIP28 water channel but not the lipid confined water diffusion. The results suggest that the inhibition of transmembrane movement of water via CHIP28 channels might be involved in the anti-hemolytic action of anaesthetics such as ethanol.
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Affiliation(s)
- G Lahajnar
- J. Stefan Institute, Ljubljana, Slovenia
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Zidansek A, Kralj S, Lahajnar G, Blinc R. Deuteron NMR study of liquid crystals confined in aerogel matrices. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1995; 51:3332-3340. [PMID: 9963011 DOI: 10.1103/physreve.51.3332] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Lahajnar G, Zupančič I, Blinc R, Zidanšek A, Kind R, Ehrensperger M. NMR self-diffusion study of organic glasses: COANP, MBANP, PNP, NPP. ACTA ACUST UNITED AC 1994. [DOI: 10.1007/bf01312197] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Abstract
Highly oriented calf-thymus MgDNA fibers, prepared by a wet spinning method, were studied with a simple mechanochemical set-up. The relative fiber length, L/Lo, was measured with the fibers submerged in ethanol-water solutions. In one type of experiment L/Lo was measured as a function of ethanol concentration at room temperature. No substantial decrease in L/Lo with increasing ethanol concentration was observed, indicating that MgDNA fibers stay in the B form even when the water activity is very low. For low ethanol concentrations the fiber structure is stable and does not dissolve even at very high water activities. In a second type of experiment, the heat-induced helix-coil transition was manifested by a marked contraction of the fibers. The transition temperature decreases linearly with increasing ethanol concentration between 52 and 68% ethanol. At higher ethanol concentrations the helix-coil transition temperature increases due to strong aggregation within the DNA fibers, and above 77% ethanol the fibers do not contract at all, not even at the upper temperature limit of the experiments, approximately 80 degrees C. This behavior is discussed with reference to dried DNA and the P form of DNA. The helix-coil transition temperature of the MgDNA fibers in 70% ethanol does not show any dependence on the MgCl2 concentration. It is shown that the Poisson-Boltzmann cylindrical cell model can account qualitatively for this lack of salt dependence.
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Affiliation(s)
- J Schultz
- Division of Physical Chemistry, Arrhenius Laboratory, University of Stockholm, Sweden
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Kralj S, Lahajnar G, Zidansek A, Vrbancic-Kopac N, Vilfan M, Blinc R, Kosec M. Deuterium NMR of a pentylcyanobiphenyl liquid crystal confined in a silica aerogel matrix. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1993; 48:340-349. [PMID: 9960597 DOI: 10.1103/physreve.48.340] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Zidanšek A, Blinc A, Lahajnar G, Keber D, Blinc R. Lysing patterns of blood clots: a nuclear magnetic resonance imaging study in vitro and mathematical modelling of the lysing pattern kinetics. J Mol Struct 1993. [DOI: 10.1016/0022-2860(93)80370-b] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Blinc A, Keber D, Lahajnar G, Stegnar M, Zidansek A, Demsar F. Lysing patterns of retracted blood clots with diffusion or bulk flow transport of plasma with urokinase into clots--a magnetic resonance imaging study in vitro. Thromb Haemost 1992; 68:667-71. [PMID: 1287880] [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: 12/26/2022]
Abstract
Fresh retracted clots are known to be poorly lysable by fibrinolytic agents. We have studied whether lysis of retracted clots could be enhanced by bulk transport in comparison to pure diffusion of plasma containing urokinase (400 IU/ml) into the clots. Cylindrical retracted blood clots were occlusively glued by a polyester into plastic tubes and put in contact with plasma through the clot bases. One group of clots (perfused clots, n = 10) was placed under a pressure difference of 6 kPa (60 cm H2O) which resulted in an average plasma flow of 0.97 +/- 0.34 microliters/min through the clot during the first hour. Another group of clots (non-perfused clots, n = 10) was incubated in the lytic plasma without a pressure difference. Clot sizes were measured during lysis by magnetic resonance imaging (MRI). Channels representing lysed areas penetrated into perfused clots with a velocity of 5.4 +/- 1.6 mm/h (n = 10), whereas the boundaries of non-perfused clots subsided with a velocity of less than 0.1 mm/h. Eight of the 10 perfused clots were recanalized after 8 h and the sizes of the perfused group were reduced to 64.0 +/- 10.7% of the initial values. The relative sizes of non-perfused clots after 8 h remained significantly higher: 95.0 +/- 1.3%, p < 0.005. In a separate experiment good agreement was obtained between the measured clot sizes by MRI and the residual radioactivity of 125I-fibrin in the clot.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A Blinc
- University Clinical Centre, Trnovo Hospital of Internal Medicine, Ljubljana, Slovenia
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Blinc A, Keber D, Lahajnar G, Zupancic I, Zorec-Karlovsek M, Demsar F. Magnetic resonance imaging of retracted and nonretracted blood clots during fibrinolysis in vitro. Haemostasis 1992; 22:195-201. [PMID: 1468722 DOI: 10.1159/000216319] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Magnetic resonance imaging (MRI) of retracted blood clots embedded in nonretracted clots was used to follow their lysis with urokinase in a plasma milieu in vitro. The two types of clots that were imaged in the same plane differed in signal intensity on T2-weighted spin echo MR images throughout the 20-hour observation period. It was thus possible to delineate the contours of both clot types and measure their relative sizes by digital image processing. Lysis of retracted clots proceeded significantly slower than lysis of nonretracted clots. Our in vitro results suggest that MRI might prove useful in detecting thrombus retraction in vivo and in predicting the outcome of thrombolytic therapy.
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Affiliation(s)
- A Blinc
- Trnovo Hospital of Internal Medicine, University Medical Center, Ljubljana
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Blinc A, Planinsic G, Keber D, Jarh O, Lahajnar G, Zidansĕk A, Demsar F. Dependence of blood clot lysis on the mode of transport of urokinase into the clot--a magnetic resonance imaging study in vitro. Thromb Haemost 1991; 65:549-52. [PMID: 1871717] [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: 12/29/2022]
Abstract
Magnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3.7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 +/- 2.4 x 10(-2) ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p less than 0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.
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Affiliation(s)
- A Blinc
- Trnovo Hospital of Internal Medicine, University Clinical Center of Ljubljana, Yugoslavia
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Desando M, Lahajnar G, Zupančič I, Reeves L. A pulsed field gradient spin-echo nuclear magnetic resonance study of self-diffusion in isotropic micellar solutions containing potassium n-alkanoates and tetramethylsilane. J Mol Liq 1990. [DOI: 10.1016/0167-7322(90)80074-t] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Abstract
A proton NMR relaxation and pulsed field gradient self-diffusion study of water in fibrin gels, plasma, and blood clots has been performed with special emphasis on the effect of the sol-gel and shrinkage transitions. Deuteron NMR in fibrin gels was also studied to supplement the proton data. It is shown that a measurement of the water proton or deuteron T1/T2 ratio allows for a determination of the bound water fraction in all these systems. The change in the T1/T2 ratio at the shrinkage transition further allows for a determination of the surface fractal dimension of the gel if the change in the volume of the gel is known. The self-diffusion coefficient of water in these systems, which determines the transport properties of the gel, is found to be proportional to the free water fraction in both the nonshrunken and shrunken state.
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Affiliation(s)
- A Blinc
- University Institute of Gerontology, Trnovo Internal Clinic, Ljubjana, Yugoslavia
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Rutar V, Kovac M, Lahajnar G. Nondestructive study of liquids in single fir seeds using nuclear magnetic resonance and magic angle sample spinning. J AM OIL CHEM SOC 1989. [DOI: 10.1007/bf02682617] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- V. Rutar
- ; Department of Chemistry; Iowa State University; Ames 50011 IA
| | - M. Kovac
- ; lnstitute of Biology; University of Ljubljana; Yugoslavia
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Abstract
The NMR relaxation times T'2, T2, and T1 were measured in isolated rat lungs as functions of external magnetic field B0, temperature, and lung inflation. The observed linear dependence on B0 of the tissue-induced free induction decay rate (T'2)-1 provides independent confirmation of the air/water interface model of the lung. Furthermore, measurements of the Larmor frequency dependence of T1 are consistent with a spin-lattice relaxation rate of the form 1/T1 = A omega -1/2 + B as expected for the case in which the relaxation arises from water-biopolymer cross-relaxation, which should be proportional to the surface area of the lung. This prediction was verified by observations of an approximately linear dependence of 1/T1 on transpulmonary pressure and thus on the lung surface area.
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Affiliation(s)
- M Kveder
- J. Stefan Institute, E. Kardelj University of Ljubljana, Yugoslavia
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Blinc R, Lahajnar G, Zumer S, Pintar MM. NMR study of the time evolution of the fractal geometry of cement gels. Phys Rev B Condens Matter 1988; 38:2873-2875. [PMID: 9946612 DOI: 10.1103/physrevb.38.2873] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Vilfan M, Rutar V, Žumer S, Lahajnar G, Blinc R, Doane JW, Golemme A. Proton spin–lattice relaxation in nematic microdroplets. J Chem Phys 1988. [DOI: 10.1063/1.455451] [Citation(s) in RCA: 40] [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: 11/14/2022] Open
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Abstract
Pulsed field gradient NMR measurements of rat lung tissue have shown that the apparent water self-diffusion coefficient is nearly an order of magnitude smaller than that of free water and moreover is not constant but varies as the inverse square root of the diffusion time. The mean square displacement of water molecules is similarly proportional to the square root of the diffusion time. Possible origins of this non-Brownian behavior are discussed.
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Affiliation(s)
- M Kveder
- J. Stefan Institute, E. Kardelj University of Ljubljana, Yugoslavia
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Abstract
A sample of highly oriented Na-hyaluronate was prepared with a wet--spinning method and equilibrated to 75% relative humidity. Its proton NMR spectrum was recorded as a function of the angle theta between the hyaluronate helix axis and the external magnetic field. It appeared as a singlet with an angle-dependent line width expressed by delta v o + A(1-3cos2 theta)2. This reveals a residual intramolecular dipolar interaction of anisotropically rotating water molecules. The merging of the expected doublet into a single line is assumed to be caused by proton exchange between water molecules. The result indicates a hydration similar to that of many other fibrous biopolymers at comparable relative humidities.
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MacTavish JC, Miljković L, Schreiner LJ, Pintar MM, Blinc R, Lahajnar G. A Study of Portland Cement Hydration by Paramagnetic Iron Suppression of Proton Magnetic Resonance. ACTA ACUST UNITED AC 1985. [DOI: 10.1515/zna-1985-0107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The dynamics of the hydration of a white cement with negligible iron content and of Portland cement with a considerable amount of iron has been studied by proton magnetic resonance. The presence of iron in Portland cement results in the protons close to the free electron spins of iron being out of resonance and their signal being suppressed. The evolution in time of the percentage of protons out of resonance in a Portland cement and the growth of the solid component have been determined as a function of hydration time.
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Affiliation(s)
- J. C. MacTavish
- 1Guelph-Waterloo Program for Graduate Work in Physics, Waterloo Campus, University of Waterloo, Waterloo. Ontario, Canada N2L 3G1
| | - L. Miljković
- 1Guelph-Waterloo Program for Graduate Work in Physics, Waterloo Campus, University of Waterloo, Waterloo. Ontario, Canada N2L 3G1
| | - L. J. Schreiner
- 1Guelph-Waterloo Program for Graduate Work in Physics, Waterloo Campus, University of Waterloo, Waterloo. Ontario, Canada N2L 3G1
| | - M. M. Pintar
- 1Guelph-Waterloo Program for Graduate Work in Physics, Waterloo Campus, University of Waterloo, Waterloo. Ontario, Canada N2L 3G1
| | - R. Blinc
- 2Institute J. Stefan. University E. Kardelj, Ljubljana, Yugoslavia
| | - G. Lahajnar
- 2Institute J. Stefan. University E. Kardelj, Ljubljana, Yugoslavia
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Vilfan M, Blinc R, Dolinšek J, Ipavec M, Lahajnar G, Žumer S. Dispersion of proton spin-lattice relaxation in a cholesteric liquid crystal. ACTA ACUST UNITED AC 1983. [DOI: 10.1051/jphys:0198300440100117900] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Affiliation(s)
- M. Vilfan
- J. Stefan Institute, E. Kardelj University of Ljubljana, Ljubljana, Yugoslavia
| | - G. Lahajnar
- J. Stefan Institute, E. Kardelj University of Ljubljana, Ljubljana, Yugoslavia
| | - V. Rutar
- J. Stefan Institute, E. Kardelj University of Ljubljana, Ljubljana, Yugoslavia
| | - R. Blinc
- J. Stefan Institute, E. Kardelj University of Ljubljana, Ljubljana, Yugoslavia
| | - B. Topic̆
- J. Stefan Institute, E. Kardelj University of Ljubljana, Ljubljana, Yugoslavia
| | - A. Zann
- Laboratoire Central de Recherches Thomson‐CSF, 91401 Orsay, France
| | - J. C. Dubois
- Laboratoire Central de Recherches Thomson‐CSF, 91401 Orsay, France
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Kind R, Pleško S, Arend H, Blinc R, Žekš B, Seliger J, Ložar B, Slak J, Levstik A, Filipič C, Žagar V, Lahajnar G, Milia F, Chapuis G. Erratum: Dynamics of the n‐decylammonium chains in the perovskite‐type layer structure compound (C 10H 21NH 3) 2CdCl 4) [J. Chem. Phys. 71, 2118 (1979)]. J Chem Phys 1980. [DOI: 10.1063/1.440763] [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: 11/14/2022] Open
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Blinc R, Zupančič I, Lahajnar G, Slak J, Rutar V, Verbec M, Žumer S. 31P chemical shift and relaxation study of the pseudo‐one‐dimensional ferroelectric transition in CsD2PO4. J Chem Phys 1980. [DOI: 10.1063/1.439623] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Kind R, Pleko S, Arend H, Blinc R, Seliger J, Loar B, Slak J, Levstik A, Filipi C, Lahajnar G, Milia F, Chapuis G. Dynamics of the n-decylammonium chains in the perovskite-type layer structure compound (C10H21NH3)2CdCl4. J Chem Phys 1979. [DOI: 10.1063/1.438584] [Citation(s) in RCA: 173] [Impact Index Per Article: 3.8] [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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Milia F, Lahajnar G, Rožmarin M, Slak J, Blinc R. Proton magnetic resonance study of molecular motion in (NH4)2HAsO4 and (NH4)2HPO4. ACTA ACUST UNITED AC 1977. [DOI: 10.1002/pssa.2210420135] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Lahajnar G, Zupancic I, Blinc R, Pifat G, Maricić S. Frequency dependence of the proton magnetic relaxation in aqueous solutions iof haemoproteins. Biopolymers 1974; 13:1187-93. [PMID: 4852094 DOI: 10.1002/bip.1974.360130610] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Pumpernik D, Lahajnar G, Hadži D, Ažman A. NMR relaxation study of a hydrogen bonded complex. Chem Phys Lett 1974. [DOI: 10.1016/0009-2614(74)89081-0] [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: 10/18/2022]
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Blinc R, Jamšek‐Vilfan M, Lahajnar G, Hajduković G. NMR Study of the Ferroelectric Transitions in Diglycine Nitrate and Trissarcosine Calcium Chloride. J Chem Phys 1970. [DOI: 10.1063/1.1672956] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.8] [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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Blinc R, Dimic V, Kolar D, Lahajnar G, Stepišnik J, Žumer S, Vene N, Hadži D. High‐Temperature Phase Transition in KH2PO4. J Chem Phys 1968. [DOI: 10.1063/1.1669990] [Citation(s) in RCA: 72] [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] [Indexed: 11/14/2022] Open
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