The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Laurence D. Barron - One of the best experts on this subject based on the ideXlab platform.
-
The development of biomolecular Raman Optical Activity spectroscopy
Biomedical Spectroscopy and Imaging, 2015Co-Authors: Laurence D. BarronAbstract:Following its first observation over 40 years ago, 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, equivalently, the intensity of a small circularly polarized component in the scattered light using incident light of fixed polarization, has evolved into a powerful chirOptical spectroscopy for studying a large range of biomolecules in aqueous solution. The long and tortuous path leading to the first observations of ROA in biomolecules in 1989, in which the author was closely involved from the very beginning, is documented, followed by a survey of subsequent developments and applications up to the present day. Among other things, ROA provides information about motif and fold, as well as secondary structure, of proteins; solution structure of carbohydrates; polypeptide and carbohydrate structure of intact glycoproteins; new insight into structural elements present in unfolded protein sequences; and protein and nucleic acid structure of intact viruses. Quantum chemical simulations of observed Raman Optical Activity spectra provide the complete three-dimensional structure, together with information about conformational dynamics, of smaller biomolecules. Biomolecular ROA measurements are now routine thanks to a commercial instrument based on a novel design becoming available in 2004.
-
Glycan structure of a high-mannose glycoprotein from Raman Optical Activity.
Angewandte Chemie (International ed. in English), 2011Co-Authors: Christian Johannessen, Lutz Hecht, Robert Pendrill, Göran Widmalm, Laurence D. BarronAbstract:A revealing signature: The glycan structure of intact yeast external invertase, a high-mannose glycoprotein used as biocatalyst, was investigated by using Raman Optical Activity (ROA) spectroscopy. The conformational preferences present in mannose-containing di- and trisaccharides were found to be preserved in the glycan chains, with secondary polpeptide backbone structure suppressed.
-
Raman Optical Activity of Biological Molecules
Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields, 2009Co-Authors: Ewan W. Blanch, Laurence D. BarronAbstract:Now an incisive probe of biomolecular structure, Raman Optical Activity (ROA) measures a small difference in Raman scattering from chiral molecules in right- and left-circularly polarized light. As ROA spectra measure vibrational Optical Activity, they contain highly informative band structures sensitive to the secondary and tertiary structures of proteins, nucleic acids, viruses and carbohydrates as well as the absolute configurations of small molecules. In this review we present a survey of recent studies on biomolecular structure and dynamics using ROA and also a discussion of future applications of this powerful new technique in biomedical research.
-
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.
-
Raman Optical Activity comes of age
Molecular Physics, 2004Co-Authors: Laurence D. Barron, Lutz Hecht, Iain H. Mccoll, Ewan W. BlanchAbstract:The theory 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. Thanks to new developments in instrumentation, ROA may be applied to a wide range of chiral molecular species. 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 great promise for the determination of the three-dimensional structure and conformational distribution in unprecedented detail. The many structure-sensitive bands in the 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 such as helix and sheet. ROA studies ...
Lutz Hecht - One of the best experts on this subject based on the ideXlab platform.
-
Glycan structure of a high-mannose glycoprotein from Raman Optical Activity.
Angewandte Chemie (International ed. in English), 2011Co-Authors: Christian Johannessen, Lutz Hecht, Robert Pendrill, Göran Widmalm, Laurence D. BarronAbstract:A revealing signature: The glycan structure of intact yeast external invertase, a high-mannose glycoprotein used as biocatalyst, was investigated by using Raman Optical Activity (ROA) spectroscopy. The conformational preferences present in mannose-containing di- and trisaccharides were found to be preserved in the glycan chains, with secondary polpeptide backbone structure suppressed.
-
Raman Optical Activity comes of age
Molecular Physics, 2004Co-Authors: Laurence D. Barron, Lutz Hecht, Iain H. Mccoll, Ewan W. BlanchAbstract:The theory 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. Thanks to new developments in instrumentation, ROA may be applied to a wide range of chiral molecular species. 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 great promise for the determination of the three-dimensional structure and conformational distribution in unprecedented detail. The many structure-sensitive bands in the 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 such as helix and sheet. ROA studies ...
-
Vibrational Raman Optical Activity of Polynucleotides
Spectroscopy of Biological Molecules: Modern Trends, 1997Co-Authors: Alasdair F. Bell, Lutz Hecht, Laurence D. BarronAbstract:Vibrational Raman Optical Activity (ROA) is measured in our laboratory as a small intensity difference in Raman scattered light from chiral molecules in right and left circularly polarized incident light.[l, 2] Recently, a series of instrumental advances [3] has opened up the realm of biopolymers, including proteins, polysaccharides and now nucleic acids, to this novel chirOptical technique. For proteins and polysaccharides it has already been demonstrated that ROA can probe key structural elements more incisively than conventional Raman spectroscopy because it can cut through the complexity of the conventional spectra by probing directly the crucial chiral elements of biomolecular structure. In this contribution we focus on some of our recent results on polynucleotides and as an example present the Raman and ROA spectra of poly(rG)•poly(rC) in H2O between 650 and 1750 cm −1 in Figure 1.
-
Vibrational Raman Optical Activity of biopolymers
Journal of Molecular Structure, 1995Co-Authors: Laurence D. Barron, Lutz Hecht, Steven J. Ford, Alasdair F. Bell, Gary A. WilsonAbstract:Abstract Vibrational Raman Optical Activity measurements can now provide a wealth of new information about the structure and conformation of biopolymers in aqueous solution. Typical results are exemplified here for proteins by bovine serum albumin in H 2 O and D 2 O solution, and for polysaccharides by laminarin.
-
Raman Optical Activity of enantiomorphic single crystals
Journal of Raman Spectroscopy, 1995Co-Authors: M. Lindner, B. Schrader, Lutz HechtAbstract:Conventional Raman and incident circular polarization Raman Optical Activity (ROA) spectra are presented for the lattice vibrations of enantiomorphic pairs of Optically active cubic crystals NaBrO3 and NaCIO3 in depolarized right-angle scattering (65-145 cm−1) and unpolarized backscattering (55-200 cm−1). Since enantiomorphic cubic crystals are also piezoelectric owing to the lack of a centre of inversion, the degeneracy of their triply degenerate polar (infrared and Raman active) F phonons is partially lifted because of long-range dipole-dipole interactions. Therefore, non-degenerate longitudinal and doubly degenerate transverse Optical phonons can be separately observed in the ROA spectra.
Ewan W. Blanch - One of the best experts on this subject based on the ideXlab platform.
-
Surface-Enhanced Raman Optical Activity (SEROA)
Encyclopedia of Spectroscopy and Spectrometry, 2017Co-Authors: S. Ostovar Pour, Ewan W. BlanchAbstract:Raman Optical Activity (ROA) provides exquisite sensitivity to molecular stereochemistry and its dynamics, but at the cost of relatively weak signal intensity. Increasing ROA signals through the use of plasmon resonance enhancements has long been seen as a desirable strategy, but unfortunately has not proven to be an easy solution to implement. This review discusses recent developments that can now provide spectroscopists with the ability to combine the structural selectivity of ROA with the quantitative sensitivity of SERS.
-
Distinguishing Epimers Through Raman Optical Activity.
The journal of physical chemistry. A, 2016Co-Authors: Shaun T. Mutter, François Zielinski, Christian Johannessen, Paul L. A. Popelier, Ewan W. BlanchAbstract:The Raman Optical Activity spectra of the epimers β-d-glucose and β-d-galactose, two monosaccharides of biological importance, have been calculated using molecular dynamics combined with a quantum mechanics/molecular mechanics approach. Good agreement between theoretical and experimental spectra is observed for both monosaccharides. Full band assignments have been carried out, which has not previously been possible for carbohydrate epimers. For the regions where the spectral features are opposite in sign, the differences in the vibrational modes have been noted and ascribed to the band sign changes.
-
Raman Optical Activity of Biological Samples
Challenges and Advances in Computational Chemistry and Physics, 2013Co-Authors: Katarzyna Chruszcz-lipska, Ewan W. BlanchAbstract:In this Chapter, the fundamentals and instrumentation of vibrational Raman Optical Activity are briefly presented. Next, we describe selected examples of successful applications of computational approaches to the analysis of ROA spectra of biomolecules showing that such calculations are an important aspect of this incisive structural technique.
-
use of a hydrogel polymer for reproducible surface enhanced Raman Optical Activity seroa
Chemical Communications, 2011Co-Authors: Saeideh Ostovar Pour, Steven E J Bell, Ewan W. BlanchAbstract:We present surface enhanced Raman Optical Activity (SEROA), as well as Raman, SERS and ROA, spectra of D- and L-ribose. By employing a gel forming polyacrylic acid to control colloid aggregation and associated birefringent artefacts we observe the first definitive proof of SEROA through measurement of mirror image bands for the two enantiomers.
-
Raman Optical Activity of Biological Molecules
Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields, 2009Co-Authors: Ewan W. Blanch, Laurence D. BarronAbstract:Now an incisive probe of biomolecular structure, Raman Optical Activity (ROA) measures a small difference in Raman scattering from chiral molecules in right- and left-circularly polarized light. As ROA spectra measure vibrational Optical Activity, they contain highly informative band structures sensitive to the secondary and tertiary structures of proteins, nucleic acids, viruses and carbohydrates as well as the absolute configurations of small molecules. In this review we present a survey of recent studies on biomolecular structure and dynamics using ROA and also a discussion of future applications of this powerful new technique in biomedical research.
Zai Q. Wen - One of the best experts on this subject based on the ideXlab platform.
-
Vibrational Raman Optical Activity of proteins
Laser Study of Macroscopic Biosystems, 1993Co-Authors: Steven J. Ford, Laurence D. Barron, Lutz Hecht, Alan Cooper, Zai Q. WenAbstract:Recent advances in Optical technology have led to the development, at Glasgow, Scotland of a backscattering incident circular polarization (ICP) Raman Optical Activity (ROA) instrument. The higher S/N ratio and the greater control of polarization artifacts has allowed the study of protein samples to become almost routine. The advantage of ROA, over conventional Raman, is the far more prominent stereochemical sensitivity. In the case of the Glasgow instrument ROA is achieved by measuring the small difference between the Raman intensities in incident circularly right polarized and circularly left polarized light. We hope to utilize this chirOptical extension of conventional Raman to gain new insights into protein conformation and dynamics.
-
Vibrational Raman Optical Activity of biological molecules
Laser Study of Macroscopic Biosystems, 1993Co-Authors: Laurence D. Barron, Lutz Hecht, Steven J. Ford, Zai Q. Wen, Alasdair F. BellAbstract:Advances in Raman Optical Activity (ROA) instrumentation based on the employment of a backscattering geometry together with a cooled backthinned CCD detector, a holographic notch filter, and a high-efficiency single-grating spectrograph have now enhanced the sensitivity to the level necessary to provide vibrational ROA spectra of most biological molecules in aqueous solution. Results on peptides and proteins show features originating in coupled C(alpha )-H and N-H deformations of the peptide backbone which appear to be sensitive to the secondary conformation including loop and turn structures. Also carbohydrates show many features characteristic of the central aspects of carbohydrate architecture, with effects from the glycosidic link in oligosaccharides particularly prominent. Preliminary ROA spectra of pyrimidine nucleosides appear to reflect the mutual orientation of the sugar and base rings and the dominant furanose conformations.
-
Vibrational Raman Optical Activity of monosaccharides
Journal of the American Chemical Society, 1993Co-Authors: Zai Q. Wen, Laurence D. Barron, Lutz HechtAbstract:Vibrational Raman Optical Activity (ROA) spectra measured in backscattering covering from 600 to 1600 cm -1 of 15 monosaccharides in aqueous solution are reported which carry signatures from the central features of monosaccharide architecture. Most of the ROA bands in this range appear to be generated by short-range interactions and so reflect local stereochemical details. Three main regions are apparent: ∼750-950 cm -1 , containing information about anomeric configuration ∼950-1200 cm -1 , showing ROA band fingerprints characteristic of the ring structure and the pattern of substituents; and above ∼1200 cm -1 , dominated by CH 2 and C-O-H deformations and reflecting the conformation of an exocyclic hydroxymethyl group
-
Raman Optical Activity of Biological Molecules
1992Co-Authors: Zai Q. WenAbstract:This thesis describes work that has helped to establish Raman Optical Activity (ROA) as a powerful new chirOptical spectroscopic technique for the study of molecular chirality and conformation of biological molecules in aqueous solution. The first chapter describes the background and recent developments of vibrational Optical Activity including both the infrared vibrational circular dichroism (VCD) and Raman Optical Activity approaches. In chapter two, the basic theory of vibrational Raman Optical Activity is briefly reviewed. It comprises the fundamental theory to describe the vibrational Raman Optical Activity phenomenon, the rationale of the choice of the backscattering geometry for ROA instrument set-up and the basis of the more advanced ab initio ROA theory for calculation of ROA spectra. A new ROA instrument based on the backscattering geometry and back thinned CCD (Charge-Coupled Device) light detector is detailed in chapter 3. The new ROA instrument represents the contemporary development of ROA instrumentation and the up-to-date sophisticated Optical and electronic devices used in the ROA spectrometer. A few basic considerations in ROA instrumentation and the performance of the instrument are discussed. The breakthrough of the instrument sensitivity has enabled ROA spectroscopy to be applied to important biological molecules in aqueous solution for the first time. The following three chapters are devoted to the ROA study of a number of biological molecules including small peptides, polypeptides, proteins and carbohydrates. These ROA data constitute the basis of ROA study for more complicated biological molecules in the future. Chapter 4 deals with ROA studies on model peptides and polypeptides. They comprise L-alanine oligomers: di-L-alanine and tri-, tetra-L-alanine, and a tripeptide L-Pro-L-Leu-Gly-amide for model ?-turn structure plus two polyamino acids poly-L-glutamic acid and poly-L-lysine. Di-L-alanine and its enantiomer are investigated in detail in various aqueous solutions and the results suggest that di-L-alanine could be used as a good model peptide for vibrational Optical Activity spectra analysis of peptides and polypeptides. ROA is a very local effect that is related to the intrinsic chirality. The most important ROA bands of peptides are in the extended amide 111 region. In chapter 5, the first ROA spectra of eight globular proteins in aqueous solution are reported and a preliminary empirical analysis presented. These protein ROA data clearly demonstrate that ROA is now able to investigate protein structure in the solution phase. The dominant ROA features of proteins arise mainly from the polypeptide backbone. Proteins containing different secondary structure compositions show characteristic ROA patterns. The most prominent ROA features are concentrated in the extended amide III region and are particularly sensitive to reverse turn structure. The ROA band intensity and A value offer a sensitive probe of the rigidity or flexibility of the globular proteins. In the last chapter 6, the ROA spectra of a range of carbohydrates including fifteen monosaccharides, a disaccharide and a cyclodextrin are investigated. The overwhelming ROA spectral information convincingly demonstrates that carbohydrates are particularly favourable samples for vibrational ROA study. ROA measurements on carbohydrates can yield ample stereochemical information with respect to the glycosidic linkage, anomeric configuration, sugar ring chair conformation and intramolecular interaction between adjacent chiral centres. Of all the information available from carbohydrate ROA spectra, the characteristic ROA couplet of the glycosidic linkage is probably the most valuable, which may be used to probe the conformation of disaccharides, oligosaccharides and polysaccharides.
-
Vibrational Raman Optical Activity of enzymes
Faraday discussions, 1992Co-Authors: Laurence D. Barron, Lutz Hecht, Steven J. Ford, Alan Cooper, Zai Q. WenAbstract:Advances in Raman Optical Activity (ROA) instrumentation, based on the employment of a backscattering geometry together with a back-thinned CCD detector and a single-grating spectrograph with a holographic edge filter, have now enhanced the sensitivity to the level necessary to provide vibrational ROA spectra of proteins in aqueous solution. Early results show at least four separate regions in protein ROA spectra associated with vibrations of the backbone which appear to characterize the α-helix, β-sheet, reverse turn and random-coil secondary conformation content. Side-group ROA features also appear, with tryptophan particularly prominent in lysozyme and α-lactalbumin. ROA should become a sensitive new probe of protein folding and ligand-induced conformational change in aqueous solution.
Laurence A. Nafie - One of the best experts on this subject based on the ideXlab platform.
-
Raman Optical Activity, Theory
Encyclopedia of Spectroscopy and Spectrometry, 2010Co-Authors: Laurence A. NafieAbstract:Raman Optical Activity (ROA) is defined as the difference between Raman scattering intensity of right and left circularly polarized light. Along with Optical rotational and circular dichroism, ROA is a form of natural Optical Activity. It has been applied with a high degree of success to the study of the structure of chiral molecules in solution. Areas of application include proteins, nucleic acids, carbohydrates, natural products, pharmaceuticals and other kinds of molecules of biological or therapeutic significance. This article describes the general theory of ROA together with the far from resonance and single electronic state theories. The various ROA forms are also discussed.
-
Near-infrared excited Raman Optical Activity.
Applied spectroscopy, 2007Co-Authors: Laurence A. Nafie, Bruce E. Brinson, Xiaolin Cao, David Andrew Rice, Omar Mahmoud Rahim, Rina K. Dukor, Naomi J. HalasAbstract:Measurements of near-infrared scattered circular polarization Raman Optical Activity (SCP-ROA) are presented using laser excitation at 780 nm for samples of S-(−)-α-pinene and L-alanyl-L-alanine. These are the first measurements of ROA outside the blue-to-green visible region between 488 and 532 nm. Comparison of Raman and ROA intensities measured with excitation at 532 and 780 nm demonstrate that the expected frequency to the fourth-power dependence for Raman scattering and the corresponding fifth-power dependence for ROA are observed. It can be concluded that, to within this frequency dependence, the same level of efficiency of Raman and ROA measurements using commercial instrumentation with 532 nm excitation is maintained with the change to near-infrared excitation at 780 nm.
-
Resonance and Non-Resonance Raman Optical Activity in Pharmaceutical Analgesic Molecules
Spectroscopy of Biological Molecules: Modern Trends, 1997Co-Authors: Mária Vargek, Teresa B. Freedman, Laurence A. NafieAbstract:Raman Optical Activity (ROA)1, the difference in Raman scattering intensity for right and left circularly polarized incident and/or Raman scattered radiation, has emerged as a technique for investigating the solution structure of chiral molecules, and has been applied to biomolecules in aqueous solution. 1, 2 Resonance Raman spectroscopy is well established as a technique for probing the structure and dynamics of appropriate chromophores in biomolecules. However, resonance Raman Optical Activity (RROA) has not been reported. Recently, the theory of Raman Optical Activity has been extended to the case of strong resonance with a single electronic state.3 The theory predicts that, in this limit, the RROA bands will all have the same sign (opposite in sign to the pure electronic circular dichroism of the resonant electronic transition) and will be proportional in intensity to the parent resonance Raman bands. We provide here evidence for both resonance and non-resonance ROA in the spectra of the analgesics naproxen and ibuprofen in basic and nonaqueous solution.
-
COMPARISON OF FOURIER-TRANSFORM VIBRATIONAL CIRCULAR DICHROISM AND MULTICHANNEL-DETECTED Raman Optical Activity
Progress in Fourier Transform Spectroscopy, 1997Co-Authors: Laurence A. Nafie, Eunah Lee, Teresa B. FreedmanAbstract:Infrared, vibrational circular dichroism, dual circular polarization Raman Optical Activity and Raman spectra have been used in conjunction for investigation of the vibrational modes of trans- and cis-pinane, and α- and β-pinene with a view of evaluating the usefulness of these techniques. It has been concluded that vibrational circular dichroism and Raman Optical Activity provide highly complementary and non-redundant information, of comparable spectral quality.
-
Raman Optical Activity of biological molecules
Vibrational Spectroscopy, 1995Co-Authors: Laurence A. Nafie, Teresa B. FreedmanAbstract:Abstract Recent progress in the use of Raman Optical Activity (ROA) to study the stereochemical properties of biological molecules is described. The basic experimental, theoretical, instrumental and calculational methodology of backscattering ROA is presented together with examples of applications to amino acids and peptides in aqueous solution.
