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Transport of dust across the Solar System: Constraints on the spatial origin of individual micrometeorites from cosmic-ray exposure. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2024; 382:20230197. [PMID: 38736334 DOI: 10.1098/rsta.2023.0197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Accepted: 01/11/2024] [Indexed: 05/14/2024]
Abstract
The origin of micrometeorites (MMs) from asteroids and comets is well-established, but the relative contribution from these two classes remains poorly resolved. Likewise, determining the precise origin of individual MMs is an open challenge. Here, cosmic-ray exposure ages are used to resolve the spatial origins of 12 MMs collected from urban areas and Antarctica. Their 26Al and 10Be concentration, produced during cosmic-ray irradiation in space, were measured by accelerator mass spectrometry. These data are compared to results from a model simulating the transport and irradiation of the MM precursors in space. This model, for the first time, considers a variety of orbits, precursor particle sizes, compositions and densities and incorporates non-isotropic solar and galactic cosmic-ray flux profiles, depth-dependent production rates, as well as spherical evaporation during atmospheric entry. While the origin for six MMs remains ambiguous, two MMs show a preferential tendency towards an origin in the Inner Solar System (Near Earth Objects to the Asteroid Belt) and four towards an origin in the Outer Solar System (Jupiter Family Comets to the Kuiper Belt). These findings challenge the notion that dust originating from the Outer Solar System is unlikely to survive long-term transport and delivery to the terrestrial planets. This article is part of the theme issue 'Dust in the Solar System and beyond'.
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A large meteoritic event over Antarctica ca. 430 ka ago inferred from chondritic spherules from the Sør Rondane Mountains. SCIENCE ADVANCES 2021; 7:eabc1008. [PMID: 33789890 PMCID: PMC8011977 DOI: 10.1126/sciadv.abc1008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Accepted: 02/12/2021] [Indexed: 06/12/2023]
Abstract
Large airbursts, the most frequent hazardous impact events, are estimated to occur orders of magnitude more frequently than crater-forming impacts. However, finding traces of these events is impeded by the difficulty of identifying them in the recent geological record. Here, we describe condensation spherules found on top of Walnumfjellet in the Sør Rondane Mountains, Antarctica. Affinities with similar spherules found in EPICA Dome C and Dome Fuji ice cores suggest that these particles were produced during a single-asteroid impact ca. 430 thousand years (ka) ago. The lack of a confirmed crater on the Antarctic ice sheet and geochemical and 18O-poor oxygen isotope signatures allow us to hypothesize that the impact particles result from a touchdown event, in which a projectile vapor jet interacts with the Antarctic ice sheet. Numerical models support a touchdown scenario. This study has implications for the identification and inventory of large cosmic events on Earth.
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MD simulations of charged binary mixtures reveal a generic relation between high- and low-temperature behavior. J Chem Phys 2021; 154:024501. [PMID: 33445919 DOI: 10.1063/5.0031417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Experimental studies of the glassy slowdown in molecular liquids indicate that the high-temperature activation energy E∞ of glass-forming liquids is directly related to their glass transition temperature Tg. To further investigate such a possible relation between high- and low-temperature dynamics in glass-forming liquids, we analyze the glassy dynamics of binary mixtures using molecular dynamics simulations. We consider a binary mixture of charged Lennard-Jones particles and vary the partial charges of the particles and, thus, the high-temperature activation energy and the glass transition temperature of the system. Based on previous results, we introduce a phenomenological model describing relaxation times over the whole temperature regime from high temperatures to temperatures well inside the supercooled regime. By investigating the dynamics of both particle species on molecular and diffusive length scales along isochoric and isobaric pathways, we find a quadratic charge dependence of both E∞ and Tg, resulting in an approximately constant ratio of both quantities independent of the underlying observable, the thermodynamic ensemble, and the particle species, and this result is robust against the actual definition of Tg. This generic relation between the activation energy and the glass transition temperature indicates that high-temperature dynamics and the glassy slowdown are related phenomena, and the knowledge of E∞ may allow us to approximately predict Tg.
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Efficacy of DiaLife, an education program for relatives of adult patients with diabetes - study protocol of a cluster randomized controlled trial. Trials 2019; 20:523. [PMID: 31439049 PMCID: PMC6704511 DOI: 10.1186/s13063-019-3600-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 07/18/2019] [Indexed: 11/11/2022] Open
Abstract
Background The global prevalence of diabetes mellitus (DM) has been increasing over recent decades. In Germany, the prevalence for DM type 1 and type 2 in adults is estimated at about 7.7%. Hence, diabetes has to be classified as a serious public health concern. Being diagnosed with DM and facing possible sequelae might have a negative impact on patients’ mental and physical well-being. However, diabetes not only affects patients themselves, but also their close relatives. To improve the quality of life for patients and relatives alike, the German Association of Diabetes Nurses and Education experts (VDBD) elaborated the first education program tailor-made for relatives of diabetes patients. This article describes the concept and design of the trial evaluating the efficacy of this education program called “DiaLife—Living Together with Diabetes”. Methods This evaluation study is a cluster randomized controlled trial, in which the study centers will be randomly assigned either to the intervention group or the control group. Study centers will recruit relatives of and patients with DM type 1 and type 2. Members of the intervention group will participate in the education program DiaLife, whereas participants randomized in the control group will act as waiting-list controls. The study will assess the efficacy of DiaLife by comparing diabetes-related knowledge between the intervention and control groups as the primary outcome for participants. As the primary outcome in patients, the Hba1c value will be assessed. In addition, diabetes-related distress, family interaction, and other secondary endpoints will be considered as secondary outcomes. Long-term efficacy will be assessed 6 and 12 months after intervention. Hierarchical regression models will be used to analyze effects over time. Discussion While there is scientific evidence for the efficacy of education programs addressed to (diabetes) patients, there is a research gap with regard to intervention studies evaluating the efficacy of education programs designed for patients’ relatives. The study results will provide information on the efficacy of the DiaLife education program. In addition, factors that might hinder a successful implementation of an education program for relatives will be identified. Trial registration German Clinical Trials Register, DRKS00015157. Registered on 24 August 2018. Electronic supplementary material The online version of this article (10.1186/s13063-019-3600-4) contains supplementary material, which is available to authorized users.
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Evaluation des diabetesrelevanten Fachwissens von examinierten Gesundheits- und Krankenpflegern im klinischen Setting. DIABETOL STOFFWECHS 2015. [DOI: 10.1055/s-0035-1549650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Existiert ein Zusammenhang zwischen Hyperglykämie und Verweildauer bei Patienten mit Diabetes im stationären Setting? Ein systematisches Review. DIABETOL STOFFWECHS 2013. [DOI: 10.1055/s-0033-1341890] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Attentional Selection of Simple and Complex Objects. J Vis 2012. [DOI: 10.1167/12.9.923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Awareness of Attentional System and Spatial Judgments. J Vis 2012. [DOI: 10.1167/12.9.667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Scale of attention influences figure-ground assignment. J Vis 2010. [DOI: 10.1167/9.8.934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Intramuskuläre Applikation von Depotmedikamenten. Rechtsmedizin (Berl) 2010. [DOI: 10.1007/s00194-010-0698-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Temporal extension of figures: Evidence from the attentional blink. J Vis 2010. [DOI: 10.1167/10.7.286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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Effekte einer CPAP-Therapie auf Marker der Insulinresistenz und des Glukosestoffwechsels bei Patienten mit obstruktivem Schlafapnoesyndrom. Ein systematischer Review mit Metaanalyse. DIABETOL STOFFWECHS 2010. [DOI: 10.1055/s-0030-1253819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Prävalenz schlafbezogener Atemstörungen bei Patienten mit insulinpflichtigem Diabetes mellitus. DIABETOL STOFFWECHS 2008. [DOI: 10.1055/s-2008-1076380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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Abstract
Adenomatoid tumor with intra-testicular localization is rare. Although most reported cases arise from the epididymis, rare cases have been reported in the testicular tunica, spermatic cord, ejaculatory ducts, prostate and suprarenal recess. Adenomatoid tumors occur in both sexes and are also found in the uterus, ovary and fallopian tubes of the female genital tract. Adenomatoid tumors are benign proliferations of mesothelial origin. We report the case of a 50-year-old male with an adenomatoid tumor of the left testis. Because of its rarity, the clinical, diagnostic and therapeutic aspects as well as the possibilities of testicular preservation are discussed.
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Modeling life satisfaction among the aged: a comparison of Chinese and Americans. J Cross Cult Gerontol 2004; 15:289-305. [PMID: 14617996 DOI: 10.1023/a:1006793304508] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This paper reports on a survey conducted among elderly Chinese in Taiwan and Americans in eastern Oregon. The focus is on health status and selected social network characteristics (such as range, density, and percentage of relatives) as they relate to life satisfaction. In addition to examining differences among these and other variables in the two national samples, two hypotheses are tested using hierarchical regression analysis. The first hypothesis relates higher values of range and density to greater life satisfaction. The second is a test of the stress-buffering hypothesis. We then examine the data controlling for gender and conclude with a discussion and interpretation of both the national and gender differences yielded by this analysis.
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alpha.-Helix and associated loop signatures in vibrational Raman optical activity spectra of proteins. J Am Chem Soc 2002. [DOI: 10.1021/ja00081a003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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The Tissue Viability Society. Nurs Stand 2001; 16:48. [PMID: 11977724 DOI: 10.7748/ns.16.6.48.s52] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Tryptophan absolute stereochemistry in viral coat proteins from raman optical activity. J Am Chem Soc 2001; 123:4863-4. [PMID: 11457308 DOI: 10.1021/ja015615q] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
Raman optical activity (ROA) spectra have been measured for the proteins hen phosvitin, yeast invertase, bovine alpha-casein, soybean Bowman-Birk protease inhibitor, and rabbit Cd(7)-metallothionein, all of which have irregular folds in the native state. The results show that ROA is able to distinguish between two types of disorder. Specifically, invertase, alpha-casein, the Bowman-Birk inhibitor, and metallothionein appear to possess a "static" type of disorder similar to that in disordered states of poly(L-lysine) and poly(L-glutamic acid); whereas phosvitin appears to possess a more "dynamic" type of disorder similar to that in reduced (unfolded) lysozyme and ribonuclease A and also in molten globule protein states. In the delimiting cases, static disorder corresponds to that found in loops and turns within native proteins with well-defined tertiary folds that contain sequences of residues with fixed but nonrepetitive phi,psi angles; and dynamic disorder corresponds to that envisaged for the model random coil in which there is a distribution of Ramachandran phi,psi angles for each amino acid residue, giving rise to an ensemble of interconverting conformers. In both cases there is a propensity for the phi,psi angles to correspond to the alpha, beta and poly(L-proline) II (PPII) regions of the Ramachandran surface, as in native proteins with well-defined tertiary folds. Our results suggest that, with the exception of invertase and metallothionein, an important conformational element present in the polypeptide and protein states supporting the static type of disorder is that of the PPII helix. Long sequences of relatively unconstrained PPII helix, as in alpha-casein, may impart a plastic (rheomorphic) character to the structure.
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Raman optical activity characterization of native and molten globule states of equine lysozyme: comparison with hen lysozyme and bovine alpha-lactalbumin. Biopolymers 2000; 57:235-48. [PMID: 10861388 DOI: 10.1002/1097-0282(2000)57:4<235::aid-bip5>3.0.co;2-h] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Vibrational Raman optical activity (ROA) spectra of the calcium-binding lysozyme from equine milk in native and nonnative states are measured and compared with those of the homologous proteins hen egg white lysozyme and bovine alpha-lactalbumin. The ROA spectrum of holo equine lysozyme at pH 4.6 and 22 degrees C closely resembles that of hen lysozyme in regions sensitive to backbone and side chain conformations, indicating similarity of the overall secondary and tertiary structures. However, the intensity of a strong positive ROA band at approximately 1340 cm(-1), which is assigned to a hydrated form of alpha helix, is more similar to that in the ROA spectrum of bovine alpha-lactalbumin than hen lysozyme and may be associated with the greater flexibility and calcium-binding ability of equine lysozyme and bovine alpha-lactalbumin compared with hen lysozyme. In place of a strong sharp positive ROA band at approximately 1300 cm(-1) in hen lysozyme that is assigned to an alpha helix in a more hydrophobic environment, equine lysozyme shows a broader band centered at approximately 1305 cm(-1), which may reflect greater heterogeneity in some alpha-helical sequences. The ROA spectrum of apo equine lysozyme at pH 4.6 and 22 degrees C is almost identical to that of the holo protein, which indicates that loss of calcium has little influence on the backbone and side chain conformations, including the calcium-binding loop. From the similarity of their ROA spectra, the A state at pH 1.9 and both 2 and 22 degrees C and the apo form at pH 4.5 and 48 degrees C, which are partially folded denatured (molten globule or state A) forms of equine lysozyme, have similar structures that the ROA suggests contain much hydrated alpha helix. The A state of equine lysozyme is shown by these results to be more highly ordered than that of bovine alpha-lactalbumin, the ROA spectrum of which has more features characteristic of disordered states. A positive tryptophan ROA band at approximately 1551 cm(-1) in the native holo protein disappears in the A state, which is probably due to the presence of nonnative conformations of the tryptophans associated with a previously identified cluster of hydrophobic residues.
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Is polyproline II helix the killer conformation? A Raman optical activity study of the amyloidogenic prefibrillar intermediate of human lysozyme. J Mol Biol 2000; 301:553-63. [PMID: 10926527 DOI: 10.1006/jmbi.2000.3981] [Citation(s) in RCA: 185] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The amyloidogenic prefibrillar partially denatured intermediate of human lysozyme, prepared by heating the native protein to 57 degrees C at pH 2.0, was studied using Raman optical activity (ROA). A positive band in the room temperature ROA spectrum of the native protein at approximately 1345 cm(-1), assigned to a hydrated form of alpha-helix, is not present in that of the prefibrillar intermediate, where a new strong positive band at approximately 1318 cm(-1) appears instead that is assigned to the poly(l-proline) II (PPII)-helical conformation. A sharp negative band at approximately 1241 cm(-1) in the native protein, assigned to beta-strand, shows little change in the ROA spectrum of the prefibrillar intermediate. The disappearance of a positive ROA band at approximately 1551 cm(-1) assigned to vibrations of tryptophan side-chains indicates that major conformational changes have occurred among the five tryptophan residues present in human lysozyme, four of which are located in the alpha-domain. The various ROA data suggest that a substantial loss of tertiary structure has occurred in the prefibrillar intermediate and that this is located more in the alpha-domain than in the beta-domain. There is no evidence for any increase in beta-structure. The ROA spectrum of hen lysozyme, which does not form amyloid fibrils so readily, remains much more native-like on heating to 57 degrees C at pH 2.0. The thermal behaviour of the alanine-rich alpha-helical peptide AK21 in aqueous solution was found to be similar to that of human lysozyme. Hydrated alpha-helix therefore appears to readily undergo a conformational change to PPII structure on heating, which may be a key step in the conversion of alpha-helix into beta-sheet in the formation of amyloid fibrils in human lysozyme. Since it is extended, flexible, lacks intrachain hydrogen bonds and is fully hydrated in aqueous solution, PPII helix has the appropriate characteristics to be implicated as a critical conformational element in many conformational diseases. Disorder of the PPII type may be a sine qua non for the formation of regular fibrils; whereas the more dynamic disorder of the random coil may lead only to amorphous aggregates.
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Solution structure and dynamics of biomolecules from Raman optical activity. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2000; 73:1-49. [PMID: 10781828 DOI: 10.1016/s0079-6107(99)00017-6] [Citation(s) in RCA: 164] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Raman optical activity (ROA) measures vibrational optical activity by means of a small difference in the intensity of Raman scattering from chiral molecules in right and left circularly polarized incident laser light. The ROA spectra of a wide range of biomolecules in aqueous solution can now be measured routinely. Because of its sensitivity to the chiral elements of biomolecular structure, ROA provides new information about solution structure and dynamics complementary to that supplied by conventional spectroscopic techniques. This article provides a brief introduction to the theory and practice of ROA spectroscopy followed by a review of recent ROA results on polypeptides, proteins, carbohydrates, nucleic acids and viruses which illustrate how new insight into current problems of structure, folding and function may be obtained from ROA studies.
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Abstract
We report the first observations of vibrational Raman optical activity (ROA) on intact viruses. Specifically, ROA spectra of the filamentous bacteriophages Pf1, M13 and IKe in aqueous solution were measured in the range approximately 600-1800 cm-1. On account of its ability to probe directly the chiral elements of biomolecular structure, ROA has provided a new perspective on the solution structures of these well-studied systems. The ROA spectra of all three are dominated by signatures of helical elements in the major coat proteins, as expected from pre-existing data. The helical elements generate strong sharp positive ROA bands at approximately 1300 and 1342 cm-1in H2O solution, but in2H2O solution the approximately 1342 cm-1bands disappear completely. The spectra are similar to those of polypeptides under conditions that produce alpha-helical conformations. Our present results, together with results from other studies, suggest that the positive approximately 1342 cm-1ROA bands are generated by a highly hydrated form of alpha-helix, and that the positive approximately 1300 cm-1bands originate in alpha-helix in a more hydrophobic environment. The presence of significant amounts of highly hydrated helical sequences accords with the known flexibility of these viruses. Differences of spectral detail for Pf1, M13 and IKe demonstrate that ROA is sensitive to subtle variations of conformation and hydration within the major coat proteins, with M13 and IKe possibly containing more non-helical structure than Pf1. The ROA spectra of Pf1 at temperatures above and below that at which a structural transition is known to occur (approximately 10 degrees C) reveal little difference in the protein conformation between the two forms, but there are indications of changes in DNA structure.
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New insight into the pH-dependent conformational changes in bovine beta-lactoglobulin from Raman optical activity. Protein Sci 1999; 8:1362-7. [PMID: 10386887 PMCID: PMC2144349 DOI: 10.1110/ps.8.6.1362] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
We have studied the conformation of beta-lactoglobulin in aqueous solution at room temperature over the pH range approximately 2.0-9.0 using vibrational Raman optical activity (ROA). The ROA spectra clearly show that the basic up and down beta-barrel core is preserved over the entire pH range, in agreement with other studies. However, from the shift of a sharp positive ROA band at approximately 1268 to approximately 1294 cm(-1) on going from pH values below that of the Tanford transition, which is centered at pH approximately 7.5, to values above, the Tanford transition appears to be associated with changes in the local conformations of residues in loop sequences possibly corresponding to a migration into the alpha-helical region of the Ramachandran surface from a nearby region. These changes may be related to those detected in X-ray crystal structures which revealed that the Tanford transition is associated with conformational changes in loops which form a doorway to the interior of the protein. The results illustrate how the ability of ROA to detect loop and turn structure separately from secondary structure is useful for studying conformational plasticity in proteins.
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Raman optical activity: an incisive new probe of the structure and dynamics of biomolecules. Sci Prog 1998; 81 ( Pt 1):17-34. [PMID: 9567775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Determination of the solution structure and function of biomolecules such as proteins, carbohydrates and nucleic acids remains at the forefront of biomedical research. Thanks to recent developments in instrumentation, biomolecules can now be studied using Raman optical activity (ROA), a novel technique which measures vibrational optical activity in chiral molecules by means of a small difference in the intensity of Raman scattering in right- and left-circularly polarized incident laser light. This article reviews recent progress in the application of ROA to the determination of the solution structure and dynamics of proteins, carbohydrates and nucleic acids.
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Evidence for global mobility in the premelting of a polynucleotide from temperature-dependent Raman optical activity. BIOSPECTROSCOPY 1998; 4:107-11. [PMID: 9557905 DOI: 10.1002/(sici)1520-6343(1998)4:2<107::aid-bspy3>3.0.co;2-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The backscattered Raman and Raman optical activity (ROA) spectra of poly(rA)-poly(rU) at 20 degrees C and 45 degrees C in buffered aqueous solution between 650 and 1750 cm(-1) are reported. Although the intensity of the majority of the Raman bands increase by varying amounts as the temperature is raised in accordance with the well-known hypochromic effect, the reverse effect is found for the ROA signals which we attribute to thermal accessibility of a greater number of distinct conformations leading to cancellation of ROA signals. The difference ROA spectrum obtained by subtracting the spectrum recorded at 45 degrees C from that recorded at 20 degrees C displays a very similar sign pattern to those at both 20 degrees C and 45 degrees C throughout the spectral region examined. This indicates that the same average structure is maintained in this temperature range and that the thermal fluctuations are correlated through the bases, the glycosidic link, the sugar ring, and the phosphate backbone of both strands. These results indicate that ROA may be a useful new probe of the dynamics of nucleic acid in solution.
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The lubricant of life: a proposal that solvent water promotes extremely fast conformational fluctuations in mobile heteropolypeptide structure. Biochemistry 1997; 36:13143-7. [PMID: 9376374 DOI: 10.1021/bi971323j] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent observations using the novel technique of Raman optical activity suggest that individual residues in unfolded proteins and in disordered loop regions of molten globule-like states cluster in the alpha-helix, beta-structure, and PPII-helix regions of the Ramachandran surface and that they "flicker" between these regions at rates approximately 10(12) s-1 at room temperature. It is proposed that these rapid motions, which occur on the same picosecond time scale as rearrangements of the hydrogen bond network in bulk water, are promoted by solvent water molecules via a repertoire of transient hydrated reverse turn conformations. Some implications of this proposal for protein folding and function are discussed.
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Constraints on the origin of zonation of the granite complexes in the Fichtelgebirge (Germany and Czech Republic): evidence from a gravity and geochemical study. ACTA ACUST UNITED AC 1997. [DOI: 10.1007/pl00014669] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Because of its ability to probe directly the chiral elements of the peptide backbone, together with the very short time scale of the scattering process, vibrational Raman optical activity (ROA) can provide new information on structure in non-native states of proteins. Here we report ROA studies of hen egg white lysozyme and bovine ribonuclease A in unfolded denatured states, prepared by reducing all the disulfide bonds. ROA spectra of unfolded lysozyme at 45, 20, and 2 degrees C, and of unfolded ribonuclease A at 35 and 20 degrees C, are presented and discussed. At 45 and 20 degrees C, unfolded lysozyme appears to contain very little extended secondary structure, but at 2 degrees C there could be roughly 20% of the native amount of alpha-helix present but little beta-sheet. Unfolded ribonuclease A, on the other hand, appears to contain roughly 50% of its native-like secondary structure, including both alpha-helix and beta-sheet, at 20 degrees C; similar secondary structure persists at 35 degrees C, but the amount is reduced. The most striking result is the observation of three sharp ROA bands in the extended amide III region, originating in coupled C alpha-H and N-H deformations, which might monitor directly the dominant intrinsic propensities for residues to adopt particular phi, psi angles, averaged over the different amino acids in the mobile heteropolypeptide. Specifically, positive bands at approximately 1300 and 1314 cm-1 appear to monitor propensities for alpha-helix and beta-structure, respectively, and a negative band at approximately 1237 cm-1 appears to monitor that for the poly(L-proline) II helix. These signals are generated by individual residues clustering in the most favorable regions of the Ramachandran plot and are present even in the absence of signals from the corresponding extended secondary structures. At 45 degrees C, the 1300 and 1314 cm-1 ROA bands of unfolded lysozyme coalesce into a single sharp band from which an analysis similar to that used for exchange effects in NMR suggests a rate of approximately 2.6 x 10(12) s-1 for interconversion between the individual residue conformations at this temperature.
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The native-like tertiary fold in molten globule alpha-lactalbumin appears to be controlled by a continuous phase transition. J Mol Biol 1996; 261:341-7. [PMID: 8780777 DOI: 10.1006/jmbi.1996.0467] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
On account of its ability to discriminate between secondary, loop and sidegroup structure and its special sensitivity to conformational mobility, vibrational Raman optical activity (ROA) has provided new insights into the complexity of order within the molten globule state from measurements on alpha-lactalbumin at pH 2.0 over the temperature range 2 to 45 degrees C. Thus while much of the secondary structure present in the native protein persists with only a small gradual decrease with increasing temperature, the tertiary backbone fold changes dramatically, being almost complete and native-like at 2 degrees C and almost completely disordered at 35 degrees C. The change of the tertiary fold with temperature is cooperative but has no latent heat, and so has the approximate characteristics of a continuous phase transition, being of the order-disorder type since it involves the interconversion of rigid, locally-ordered loop structure with disordered mobile backbone structure. This has implications for protein folding because the long-range correlations that exist in the critical region of a continuous (but not in a first-order) phase transition could resolve, in principle, the problem of how the protein finds its native-like folding pattern at the molten globule stage.
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Solution-Phase Conformations of N-Acetyl-N‘-methyl-l-alaninamide from Vibrational Raman Optical Activity. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp951865f] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Vibrational Raman optical activity of alpha-lactalbumin: comparison with lysozyme, and evidence for native tertiary folds in molten globule states. J Mol Biol 1995; 254:747-60. [PMID: 7500347 DOI: 10.1006/jmbi.1995.0652] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Proteins in aqueous solution are now accessible to Raman optical activity (ROA) measurements, which provide an incisive new probe of secondary and tertiary structure illustrated here by a study of bovine alpha-lactalbumin. The room-temperature ROA spectrum of native bovine alpha-lactalbumin is similar to that of native hen egg-white lysozyme except for features attributable to differences in the loop regions: in particular, a positive ROA band at approximately 1338 cm-1 assigned to conformationally homogeneous loop structure, possibly with local order corresponding to 3(10)-helix, has more than double the intensity in alpha-lactalbumin compared with lysozyme. This is consistent with the two proteins having similar secondary structure but different local details in the tertiary fold. ROA measurements on alpha-lactalbumin at pH 2.0 over a range of temperatures have provided a new perspective on the molten globule state. Thus at 35 degrees C ROA reveals the presence of some secondary structure but an almost complete loss of the tertiary loop structure; whereas at 2 degrees C the ROA spectrum is almost identical with that of the native protein, which is strong evidence that virtually all of the secondary structure and the tertiary backbone fold persist, albeit within a looser framework associated with increased solvent exposure and change of environment of many of the side-chains as evidenced by an increase in noise and bandwidth of some of the ROA signals together with aromatic fluorescence and near-UV circular dichroism signals characteristic of the molten globule state. Our sample of acid alpha-lactalbumin at 2 degrees C therefore appears to be an archetypal example of Ptitsyn's "native-like" molten globule, having a fixed native-like tertiary fold but with loss of tight packing of the side-chains; whereas at 35 degrees C it is a "disordered" molten globule. At 20 degrees C the acid molten globule appears to retain highly native-like secondary structure but with most of the tertiary fold already lost. A calcium-free sample of alpha-lactalbumin at neutral pH displayed a broad cooperative transition between native and molten globule states at approximately 15 degrees C, with the latter state showing similar but somewhat degraded tertiary loop ROA signatures to the native protein. In both the acid and apo molten globule states the ROA signatures of the secondary structure and the tertiary loops showed a gradual change with temperature.
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Perseverance pays off: health care providers' impact on HIV testing decisions by adolescent females. Pediatrics 1994; 94:878-82. [PMID: 7971005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND AND OBJECTIVE Although HIV counseling and testing of adolescents has increased rapidly in recent years due to increasing HIV seroprevalence rates, little is known about adolescents' use of HIV testing services. The aims of this study were to determine what proportion of high risk adolescent girls would use confidential HIV testing services linked to primary care and to explore the characteristics, beliefs, and experiences that distinguish those teenage girls who obtain HIV testing in this setting from those who do not. DESIGN Prospective cohort study. SETTING General pediatrics clinic with adolescent-specific appointments at a large urban HMO. PARTICIPANTS Convenience sample of 124 adolescent girls engaging in risky behaviors identified by chart review before regularly scheduled clinic appointments. INTERVENTION Subjects completed a self-report questionnaire assessing HIV-related knowledge, attitudes, beliefs, and behaviors before the medical visit. During their provider visit, teens were counseled about their risk behaviors and the availability of HIV testing services at the clinic. Subjects were also given the opportunity to view an educational video about HIV testing designed for adolescents. MAIN OUTCOME MEASURES Use of HIV counseling and testing services at the clinic and HIV test results. RESULTS Forty-one percent of these adolescent girls obtained HIV testing at the clinic on the day of their scheduled appointment. Univariate analysis revealed that adolescents who obtained testing had initiated sexual intercourse at a younger age (mean age 13.8 vs 14.4 years, P = .02) and were more likely to have had a prior discussion about HIV testing with a health care provider [RR = 2.02, 95% CIs (1.22, 3.36)]. Those who did not view the video were less likely to test [RR = 0.20, 95% CIs (0.07, 0.58)]. Multiple logistic regression modeling revealed that a prior discussion with a health care provider was the only independent predictor of obtaining an HIV test [OR = 3.47 95% CIs (1.26, 9.52)]. CONCLUSIONS A significant proportion of adolescent girls engaging in risky behaviors will use confidential HIV counseling and testing services that are linked to primary care. Health care providers play an important role in helping teens address their risk for and concerns about HIV infection by engaging adolescents in repeated discussions about HIV testing.
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Abstract
This paper reports the first vibrational Raman optical activity (ROA) spectrum of a glycoprotein. The sample, orosomucoid (alpha 1-acid glycoprotein), shows ROA bands characteristic of a high beta-sheet content together with new bands which could be specific for the carbohydrate and its association with the protein. Our results suggest that ROA spectra of intact glycoproteins may contain information about both protein and carbohydrate conformation and the mutual influence on each other's stability and conformation.
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Beta-sheet and associated turn signatures in vibrational Raman optical activity spectra of proteins. Protein Sci 1994; 3:435-9. [PMID: 7912598 PMCID: PMC2142703 DOI: 10.1002/pro.5560030308] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
We have measured the aqueous solution vibrational Raman optical activity (ROA) spectra of concanavalin A, alpha-chymotrypsin, and beta-lactoglobulin, all of which are rich in beta-sheet, together with that of the model beta-turn peptide L-pro-L-leu-gly-NH2. Possible ROA signatures of antiparallel beta-sheet include a strong sharp positive band at approximately 1,313 cm-1 associated with backbone amide III C alpha H and NH deformations, and an amide I couplet, negative at low wavenumber and positive at high, centered at approximately 1,658 cm-1. Negative ROA bands in the range approximately 1,340-1,380 cm-1, which might originate in glycine CH2 deformations, appear to be characteristic of beta-turns. Our results provide further evidence that ROA is a more incisive probe of protein conformation than conventional vibrational spectroscopy, infrared, or Raman, because only those few vibrational coordinates within a given normal mode that sample the skeletal chirality directly contribute to the corresponding ROA band intensity.
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Methyl torsion Raman optical activity in trans-2,3-dimethyloxirane and trans-2,3-dimethylthiirane. ACTA ACUST UNITED AC 1992. [DOI: 10.1016/0584-8539(92)80133-h] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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