The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Petr Bouř - One of the best experts on this subject based on the ideXlab platform.
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recent trends in chirOptical spectroscopy theory and applications of vibrational circular dichroism and raman Optical Activity
ChemPlusChem, 2020Co-Authors: Monika Krupova, Jiři Kessler, Petr BouřAbstract:ChirOptical spectroscopy exploring the interaction of matter with polarized light provides many tools for molecular structure and interaction studies. Here, some recent discoveries are reviewed, primarily in the field of vibrational Optical Activity. Technological advances results in the development of more sensitive vibrational circular dichroism (VCD), Raman Optical Activity (ROA) or circular polarized luminescence (CPL) spectrometers. Significant contributions to the field also come from the light scattering and electronic structure theories, and their implementation in computer systems. Finally, new chirOptical phenomena have been observed, such as enhanced circular dichroism of biopolymers (protein fibrils, nucleic acids), plasmonic and resonance chirality-transfer ROA experiments. Some of them are not yet understood or attributed to instrumental artifacts so far. Nevertheless, these unknown territories also indicate the vast potential of the chirOptical spectroscopy, and their investigation is even more challenging.
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binding of lanthanide complexes to histidine containing peptides probed by raman Optical Activity spectroscopy
Chemistry: A European Journal, 2018Co-Authors: Eva Brichtova, Jaroslav Šebestík, Jana Hudecova, Nikola Vrskova, Petr BouřAbstract:Lanthanide complexes are used as convenient spectroscopic probes for many biomolecules. Their binding to proteins is believed to be enhanced by the presence of histidine, but the strength of the interaction significantly varies across different systems. To understand the role of peptide length and sequence, short histidine-containing peptides have been synthesized (His-Gly, His-Gly-Gly, His-Gly-Gly-Gly, Gly-His, Gly-His-Gly, His-His, and Gly-Gly-His) and circularly polarized luminescence (CPL) induced at the [Eu(dpa)3 ]3- complex has been measured by means of a Raman Optical Activity (ROA) spectrometer. The obtained data indicate relatively weak binding of the histidine residue to the complex, with a strong participation of other parts of the peptide. Longer peptides, low pH, and a histidine residue close to the N-peptide terminus favor the binding. The binding strengths are approximately proportional to the CPL intensity and roughly correlate with predictions based on molecular dynamics (MD) simulations. The specificity of lanthanide binding to the peptide structure and its intense luminescence and high Optical Activity make the ROA/CPL technique suitable for probing secondary and tertiary structures of peptides and proteins.
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first principles predictions of vibrational raman Optical Activity of globular proteins
Journal of Physical Chemistry Letters, 2015Co-Authors: Jiři Kessler, Josef Kapitán, Petr BouřAbstract:Computational methods based on the Schrodinger equation have been traditionally confined to rather small molecules. Using an automatic computational methodology, however, we obtained a stunning agreement between experimental and theoretical vibrational spectra of large globular proteins containing thousands of atoms as well. Principle atomic properties are obtained from small molecular fragments and combined with a minimal accuracy loss. This “first-principles” interpretation of the data reveals a wealth of information, such as nature of localized molecular motions as well as collective vibrational modes describing folding of larger protein parts. A new insight is provided to the origin of the chirOptical effects, and the theory lends the used spectroscopic techniques, unpolarized Raman scattering and vibrational Raman Optical Activity, immense potential to structural studies of biological systems.
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transition polarizability model of induced resonance raman Optical Activity
Journal of Computational Chemistry, 2013Co-Authors: Shigeki Yamamoto, Petr BouřAbstract:Induced resonance Raman Optical Activity (IRROA) proved to be a very sensitive method to detect molecular chirality. It is exhibited, for example, by complexes of lanthanides with chiral alcohols or ketones. So far, the phenomenon has not been understood at a quantitative level. To elucidate its mechanisms and to correctly relate the spectra to the structure, a transition polarizability model (TPM) is developed and applied to a camphor-europium complex. The model well reproduces the high ROA/Raman intensity ratio of the IRROA observed experimentally. The results additionally indicate a fundamental role of the nonchiral fod ligand in the Eu(fod)3 compound for the chirality enhancement. The TPM model thus serves as a guidance for both experimental and theoretical studies to come. © 2013 Wiley Periodicals, Inc.
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Ramachandran Plot for Alanine Dipeptide as Determined from Raman Optical Activity
The journal of physical chemistry letters, 2013Co-Authors: Václav Parchaňský, Josef Kapitán, Jakub Kaminský, Jaroslav Šebestík, Petr BouřAbstract:Accessible values of the φ and ψ torsional angles determining peptide main chain conformation are traditionally displayed in the form of Ramachandran plots. The number of experimental methods making it possible to determine such conformational distribution is limited. In the present study, Raman Optical Activity (ROA) spectra of Ac-Ala-NHMe were measured and fit by theoretical curves. This revealed the most favored conformers and a large part of the potential energy surface (PES) of this model dipeptide. Such experimental PES compares well to quantum chemical computations, whereas molecular dynamics (MD) modeling reproduces it less faithfully. The surface shape is consistent with the temperature dependence of the spectra, as observed experimentally and predicted by MD. Despite errors associated with spectral modeling and the measurement, the results are likely to facilitate future applications of ROA spectroscopy.
Laurence D. Barron - One of the best experts on this subject based on the ideXlab platform.
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vibrational Optical Activity
Chemical Physics Letters, 2010Co-Authors: Laurence D. Barron, David A BuckinghamAbstract:Although Optical Activity in chiral molecules was discovered almost two centuries ago, it was not until the early 1970s that Optical Activity in vibrational spectra was observed. Thanks to progress in experiment, theory and computation, powerful chirOptical spectroscopies based on vibrational Optical Activity measurements have evolved rapidly. We review the basic theory and recent applications of the Raman and infrared approaches, emphasising the impact ab initio calculations are making on simulation of vibrational Optical Activity spectra to extract detailed structures, including the absolute configuration and conformer populations, of chiral molecular and biomolecular species, and discuss many new features that are emerging.
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raman Optical Activity an incisive probe of molecular chirality and biomolecular structure
Journal of Molecular Structure, 2007Co-Authors: Laurence D. Barron, Lutz Hecht, Fujiang Zhu, George E Tranter, Neil W IsaacsAbstract:The theory, instrumentation and applications of Raman Optical Activity (ROA), which 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 light or, equivalently, a small circularly polarized component in the scattered light, are briefly reviewed. As well as providing the absolute configuration of small chiral molecules, ab initio simulations of observed ROA spectra provide the three-dimensional structure and conformational distribution. The rich ROA spectra of biomolecules in aqueous solution provide detailed structural information including, in the case of proteins, the tertiary fold in addition to secondary structure elements. The many structure-sensitive bands in protein ROA spectra makes them ideal for the application of multivariate analysis methods such as nonlinear mapping to determine structural relationships between different proteins. ROA studies of unfolded and partially folded proteins provide insight into the residual structure in denatured proteins and the aberrant behaviour of proteins responsible for misfolding diseases. It is even possible to measure the ROA spectra of intact viruses, from which information about the fold of the major coat proteins and the structure of the nucleic acid core may be obtained.
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raman Optical Activity an incisive probe of chirality and of biomolecular structure and behaviour
Vibrational Spectroscopy, 2006Co-Authors: Laurence D. Barron, Fujiang Zhu, Lutz HechtAbstract:The theory, instrumentation and applications of Raman Optical Activity (ROA), which 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 light or, equivalently, a small circularly polarized component in the scattered light, are briefly reviewed. As well as providing the absolute configuration of small chiral molecules, the application of ab initio methods to the analysis of experimental ROA spectra holds promise for the determination of the three-dimensional structure and conformational distribution in unprecedented detail. The rich ROA spectra of aqueous solutions of biomolecules provide detailed structural information including, in the case of proteins, the tertiary fold in addition to secondary structure elements. ROA studies of unfolded and partially folded proteins provide new insight into the residual structure in denatured proteins and the aberrant behaviour of proteins responsible for misfolding diseases. It is even possible to measure the ROA spectra of intact viruses, from which information about the fold of the major coat proteins and the structure of the nucleic acid core may be obtained.
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structure and behaviour of biomolecules from raman Optical Activity
Current Opinion in Structural Biology, 2006Co-Authors: Laurence D. BarronAbstract:Raman Optical Activity, which can be measured as a small circularly polarized component in Raman-scattered light from chiral molecules, holds much promise for studying a large range of biomolecules in aqueous solution. Among other things, it provides information about motif and fold, as well as secondary structure, of proteins; the solution structure of carbohydrates; and the structure of the polypeptide and carbohydrate components of intact glycoproteins. In addition, new insights into the structural elements present in unfolded protein sequences, and the structure of the protein and nucleic acid components of intact viruses can be obtained. Ab initio quantum-chemical simulations of observed Raman Optical Activity spectra provide the complete three-dimensional structure of small biomolecules. Raman Optical Activity measurements are now routine thanks to the availability of a commercial instrument based on a novel design.
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raman Optical Activity of proteins carbohydrates and glycoproteins
Chirality, 2006Co-Authors: Fujiang Zhu, Lutz Hecht, George E Tranter, Neil W Isaacs, Laurence D. BarronAbstract:On account of its sensitivity to chirality, Raman Optical Activity (ROA), which may be measured as a small difference in the intensity of vibrational Raman scattering from chiral molecules in right- and left-circularly polarized incident light, or as the intensity of a small circularly polarized component in the scattered light, is a powerful probe of the structure of biomolecules. Protein ROA spectra provide information on secondary and tertiary structures of polypeptide backbones, backbone hydration and side-chain conformations, and on structural elements present in unfolded states. Carbohydrate ROA spectra provide information on the central features of carbohydrate stereochemistry, especially that of the glycosidic link. Glycoprotein ROA spectra provide information on both the polypeptide and carbohydrate components. This article describes the ROA technique and presents and discusses the ROA spectra of a selection of proteins, carbohydrates, and a glycoprotein. The many structure-sensitive bands in protein ROA spectra are favorable for applying pattern recognition techniques, illustrated here using nonlinear mapping, to determine structural relationships between different proteins.
Lutz Hecht - One of the best experts on this subject based on the ideXlab platform.
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raman Optical Activity an incisive probe of molecular chirality and biomolecular structure
Journal of Molecular Structure, 2007Co-Authors: Laurence D. Barron, Lutz Hecht, Fujiang Zhu, George E Tranter, Neil W IsaacsAbstract:The theory, instrumentation and applications of Raman Optical Activity (ROA), which 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 light or, equivalently, a small circularly polarized component in the scattered light, are briefly reviewed. As well as providing the absolute configuration of small chiral molecules, ab initio simulations of observed ROA spectra provide the three-dimensional structure and conformational distribution. The rich ROA spectra of biomolecules in aqueous solution provide detailed structural information including, in the case of proteins, the tertiary fold in addition to secondary structure elements. The many structure-sensitive bands in protein ROA spectra makes them ideal for the application of multivariate analysis methods such as nonlinear mapping to determine structural relationships between different proteins. ROA studies of unfolded and partially folded proteins provide insight into the residual structure in denatured proteins and the aberrant behaviour of proteins responsible for misfolding diseases. It is even possible to measure the ROA spectra of intact viruses, from which information about the fold of the major coat proteins and the structure of the nucleic acid core may be obtained.
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raman Optical Activity an incisive probe of chirality and of biomolecular structure and behaviour
Vibrational Spectroscopy, 2006Co-Authors: Laurence D. Barron, Fujiang Zhu, Lutz HechtAbstract:The theory, instrumentation and applications of Raman Optical Activity (ROA), which 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 light or, equivalently, a small circularly polarized component in the scattered light, are briefly reviewed. As well as providing the absolute configuration of small chiral molecules, the application of ab initio methods to the analysis of experimental ROA spectra holds promise for the determination of the three-dimensional structure and conformational distribution in unprecedented detail. The rich ROA spectra of aqueous solutions of biomolecules provide detailed structural information including, in the case of proteins, the tertiary fold in addition to secondary structure elements. ROA studies of unfolded and partially folded proteins provide new insight into the residual structure in denatured proteins and the aberrant behaviour of proteins responsible for misfolding diseases. It is even possible to measure the ROA spectra of intact viruses, from which information about the fold of the major coat proteins and the structure of the nucleic acid core may be obtained.
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raman Optical Activity of proteins carbohydrates and glycoproteins
Chirality, 2006Co-Authors: Fujiang Zhu, Lutz Hecht, George E Tranter, Neil W Isaacs, Laurence D. BarronAbstract:On account of its sensitivity to chirality, Raman Optical Activity (ROA), which may be measured as a small difference in the intensity of vibrational Raman scattering from chiral molecules in right- and left-circularly polarized incident light, or as the intensity of a small circularly polarized component in the scattered light, is a powerful probe of the structure of biomolecules. Protein ROA spectra provide information on secondary and tertiary structures of polypeptide backbones, backbone hydration and side-chain conformations, and on structural elements present in unfolded states. Carbohydrate ROA spectra provide information on the central features of carbohydrate stereochemistry, especially that of the glycosidic link. Glycoprotein ROA spectra provide information on both the polypeptide and carbohydrate components. This article describes the ROA technique and presents and discusses the ROA spectra of a selection of proteins, carbohydrates, and a glycoprotein. The many structure-sensitive bands in protein ROA spectra are favorable for applying pattern recognition techniques, illustrated here using nonlinear mapping, to determine structural relationships between different proteins.
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raman Optical Activity a tool for protein structure analysis
Structure, 2005Co-Authors: Fujiang Zhu, Lutz Hecht, Neil W Isaacs, Laurence D. BarronAbstract:On account of its sensitivity to chirality, Raman Optical Activity (ROA), measured here as the intensity of a small, circularly polarized component in the scattered light using unpolarized incident light, is a powerful probe of protein structure and behavior. Protein ROA spectra provide information on secondary and tertiary structures of polypeptide backbones, backbone hydration, and side chain conformations, and on structural elements present in unfolded states. This article describes the ROA technique and presents ROA spectra, recorded with a commercial instrument of novel design, of a selection of proteins to demonstrate how ROA may be used to readily distinguish between the main classes of protein structure. A principal component analysis illustrates how the many structure-sensitive bands in protein ROA spectra are favorable for applying pattern recognition techniques to determine structural relationships between different proteins.
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unfolded proteins studied by raman Optical Activity
Advances in Protein Chemistry, 2002Co-Authors: Laurence D. Barron, Ewan W. Blanch, Lutz HechtAbstract:Publisher Summary To understand the behavior of unfolded proteins it is necessary to employ experimental techniques able to discriminate between the dynamic true random coil state and more static types of disorder, including situations in which some ordered secondary structure might be present. One such technique is a novel chirOptical spectroscopy called Raman Optical Activity (ROA). This chapter reviews the application of ROA to studies of unfolded proteins. Because many discrete structure-sensitive bands are present in protein ROA spectra, the technique provides a fresh perspective on the structure and behavior of unfolded proteins and of unfolded sequences in proteins such as A-gliadin and prions that contain distinct structured and unstructured domains. It also provides new insight into the complexity of order in molten globule and reduced protein states and of the more mobile sequences in fully folded proteins such as β-lactoglobulin. The power of ROA in this area derives from the fact that, like the complementary technique of vibrational circular dichroism (VCD), it is a form of vibrational Optical Activity and so is sensitive to chirality associated with all the 3N−6 fundamental molecular vibrational transitions, where N is the number of atoms.
C M Soukoulis - One of the best experts on this subject based on the ideXlab platform.
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terahertz chiral metamaterials with giant and dynamically tunable Optical Activity
Physical Review B, 2012Co-Authors: Jiangfeng Zhou, Dibakar Roy Chowdhury, Rongkuo Zhao, Abul Kalam Azad, Houtong Chen, C M Soukoulis, Antoinette J Taylor, John F OharaAbstract:We demonstrated giant Optical Activity using a chiral metamaterial composed of an array of conjugated bilayer metal structures. The chiral metamaterials were further integrated with photoactive inclusions to accomplish a wide tuning range of the Optical Activity through illumination with near-infrared light. The strong chirality observed in our metamaterials results in a negative refractive index, which can also be well controlled by the near-infrared Optical excitation.
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conjugated gammadion chiral metamaterial with uniaxial Optical Activity and negative refractive index
Physical Review B, 2011Co-Authors: Jiangfeng Zhou, Rongkuo Zhao, C M Soukoulis, Lei Zhang, Th KoschnyAbstract:We demonstrate numerically and experimentally a conjugated gammadion chiral metamaterial that uniaxially exhibits huge Optical Activity and circular dichroism, and gives a negative refractive index. This chiral design provides smaller unit cell size and larger chirality compared with other published planar designs. Experiments are performed at GHz frequencies (around 6 GHz) and are in good agreement with the numerical simulations.
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twisted split ring resonator photonic metamaterial with huge Optical Activity
arXiv: Optics, 2010Co-Authors: Manuel Decker, Rongkuo Zhao, C M Soukoulis, Stefan Linden, Martin WegenerAbstract:Coupled split-ring-resonator metamaterials have previously been shown to exhibit large coupling effects, which are a prerequisite for obtaining large effective Optical Activity. By a suitable lateral arrangement of these building blocks, we completely eliminate linear birefringence and obtain pure Optical Activity and connected circular Optical dichroism. Experiments at around 100-THz frequency and corresponding modeling are in good agreement. Rotation angles of about 30 degrees for 205nm sample thickness are derived.
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strong Optical Activity from twisted cross photonic metamaterials
Optics Letters, 2009Co-Authors: Manuel Decker, C M Soukoulis, Stefan Linden, Matthias Ruther, C E Kriegler, J Zhou, Martin WegenerAbstract:Following a recent theoretical suggestion and microwave experiments, we fabricate photonic metamaterials composed of pairs of twisted gold crosses using two successive electron-beam-lithography steps and intermediate planarization via a spin-on dielectric. The resulting two effective resonances of the coupled system lie in the 1-2 microm wavelength regime and exhibit pronounced circular dichroism, while the circular polarization conversion is very small. In between the two resonances, we find a fairly broad spectral regime with strong Optical Activity, i.e., with a pure rotation of incident linear polarization. The measured Optical transmittance spectra agree well with theory.
Laurence A Nafie - One of the best experts on this subject based on the ideXlab platform.
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simultaneous resonance raman Optical Activity involving two electronic states
Journal of Physical Chemistry A, 2012Co-Authors: Christian Merten, Laurence A NafieAbstract:In the present work, the first observation of strong resonance Raman Optical Activity (RROA) involving more that one resonant electronic state is reported. The chiral transition metal complex bis-(trifluoroacetylcamphorato) copper(II), abbreviated Cu(tfc)(2), exhibits both resonance Raman (RR) and RROA spectra with laser excitation at 532 nm. Vibrational assignments for this complex were carried out by comparing the non-RR spectra of Cu(tfc)(2) excited at 1024 nm to density functional theory (DFT) calculations. The theory of the single-electronic-state (SES) RROA is extended to the next simplest level of theory involving two resonant electronic states (TES) without interstate vibronic coupling as an aide to the interpretation of the observed TES-RROA spectra. Based on measured UV-vis electronic absorbance spectra and corresponding TD-DFT calculations, the most likely two states associated with the RROA spectra are identified.
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a confidence level algorithm for the determination of absolute configuration using vibrational circular dichroism or raman Optical Activity
ChemPhysChem, 2011Co-Authors: Elke Debie, Ewoud De Gussem, Rina K Dukor, Wouter A Herrebout, Laurence A Nafie, Patrick BultinckAbstract:Spectral comparison is an important part of the assignment of the absolute configuration (AC) by vibrational circular dichroism (VCD), or equally by Raman Optical Activity (ROA). In order to avoid bias caused by personal interpretation, numerical methods have been developed to compare measured and calculated spectra. Using a neighbourhood similarity measure, the agreement between a computed and measured VCD or ROA spectrum is expressed numerically to introduce a novel confidence level measure. This allows users of vibrational Optical Activity (VOA) techniques (VCD and ROA) to assess the reliability of their assignment of the AC of a compound. To that end, a database of successful AC determinations is compiled along with neighbourhood similarity values between the experimental spectrum and computed spectra for both enantiomers. For any new AC determination, the neighbourhood similarities between the experimental spectrum and the computed spectra for both enantiomers are projected on the database allowing an interpretation of the reliability of their assignment.
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infrared and raman vibrational Optical Activity theoretical and experimental aspects
Annual Review of Physical Chemistry, 1997Co-Authors: Laurence A NafieAbstract:▪ Abstract Advances in the field of vibrational Optical Activity (VOA) are reviewed over the past decade. Topics are surveyed with an emphasis on the theoretical and instrumental progress in both vibrational circular dichroism (VCD) and Raman Optical Activity (ROA). Applications of VOA to stereochemical and biological problems are reviewed, with a bias toward new kinds of experiments made possible by theoretical and instrumental advances. In the field of VCD, the most notable advances have taken place in the quality and size of ab initio calculations of VOA intensities and in the quality of step-scan Fourier transform instrumentation. For ROA, the most dramatic progress has occurred in the areas of theoretical formulation and high-throughput instrumentation. Applications of VOA now include all major classes of biological and pharmaceutical molecules. VOA's importance as a diagnostic tool will likely grow as the control of molecular chirality increases in research and industrial areas.
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dual and incident circular polarization raman Optical Activity backscattering of trans pinane
Chemical Physics Letters, 1991Co-Authors: Diping Che, Lutz Hecht, Laurence A NafieAbstract:Abstract We report the first measurement of dual circular polarization (DCP) Raman Optical Activity (ROA). DCP ROA was predicted recently to be a new form of ROA in which the incident and scattered light beams are synchronously modulated between right and left circular polarization states. Using a new backscattering apparatus and (—)-trans-pinane, we confirm the theoretical predictions and compare our results to the conventional incident circular polarization (ICP) form of ROA.
