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Kenji Monde - One of the best experts on this subject based on the ideXlab platform.
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Studying the stereostructures of biomolecules and their analogs by Vibrational Circular Dichroism
Polymer Journal, 2016Co-Authors: Tohru Taniguchi, Takahiro Hongen, Kenji MondeAbstract:The functions of biomacromolecules are largely governed by their stereostructure (i.e., configuration and conformation). Therefore, detailed understanding of their structural properties should help in regulating the functions of artificial macromolecules. However, studying the stereostructure of a molecule in the solution state is typically difficult due to the lack of suitable analytical techniques. Vibrational Circular Dichroism (VCD) spectroscopy, which measures Circular Dichroism in the infrared region, exhibits high sensitivity toward molecular stereostructures. In this paper, we first discuss a method for the elucidation of the stereostructures of small to large molecules based on theoretical calculations of VCD. The rest of the paper is dedicated to the applications of a VCD exciton chirality method, a novel approach recently developed by the authors to interpret VCD data by observing a VCD couplet in the C=O stretching region, to various biomolecules such as peptides, carbohydrates, polyesters and lipids. Vibrational Circular Dichroism (VCD) is effective for analyzing the configuration and conformation of various bio(macro)molecules. In addition to a conventional VCD approach using theoretical calculations, this review explains how the use of an exciton-type VCD couplet can be employed to elucidate the structures of bio(macro)molecules, such as carbohydrates, glycerophospholipids, proteins and polyesters.
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Studying the stereostructures of biomolecules and their analogs by Vibrational Circular Dichroism
Polymer Journal, 2016Co-Authors: Tohru Taniguchi, Takahiro Hongen, Kenji MondeAbstract:Vibrational Circular Dichroism (VCD) is effective for analyzing the configuration and conformation of various bio(macro)molecules. In addition to a conventional VCD approach using theoretical calculations, this review explains how the use of an exciton-type VCD couplet can be employed to elucidate the structures of bio(macro)molecules, such as carbohydrates, glycerophospholipids, proteins and polyesters.
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Stereochemical Study of Sphingosine by Vibrational Circular Dichroism.
Organic letters, 2016Co-Authors: Atsufumi Nakahashi, Ananda Kumar C. Siddegowda, Mostafa A. S. Hammam, Siddabasave Gowda B. Gowda, Yuta Murai, Kenji MondeAbstract:Vibrational Circular Dichroism (VCD) was first applied to the stereochemical analysis of sphingosine. VCD patterns derived from the C═C stretch as well as other mid-infrared (IR) regions were practical markers to discriminate all the stereoisomers of intact sphingosine. Glutaraldehyde was found as an excellent derivatizing reagent for sphingosine which improves its solubility in VCD-friendly nonpolar solvents such as chloroform and enhances the VCD intensities by forming a rigid cyclized structure.
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Stereochemical analysis of glycerophospholipids by Vibrational Circular Dichroism.
Journal of the American Chemical Society, 2015Co-Authors: Tohru Taniguchi, Daisuke Manai, Masataka Shibata, Yutaka Itabashi, Kenji MondeAbstract:The stereochemistry of glycerophospholipids (GPLs) has been of interest for its roles in the evolution of life and in their biological activity. However, because of their structural complexity, no convenient method to determine their configuration has been reported. In this work, through the first systematic application of Vibrational Circular Dichroism (VCD) spectroscopy to various diacylated GPLs, we have revealed that their chirality can be assigned by the sign of a VCD exciton couplet generated by the interaction of two carbonyl groups. This paper also presents spectroscopic evidence for the stereochemistry of GPLs isolated from bacteria, eukaryotes, and mitochondria.
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exciton chirality method in Vibrational Circular Dichroism
Journal of the American Chemical Society, 2012Co-Authors: Tohru Taniguchi, Kenji MondeAbstract:The interaction of two IR chromophores yields a strong Vibrational Circular Dichroism couplet whose sign reflects the absolute configuration of the molecule. We present a method to determine absolute configuration of a chiral molecule based on this couplet without need of theoretical calculation. Not only can this method analyze various molecules whose absolute configuration is difficult to determine by other spectroscopic methods, but also it can significantly enhance VCD signals.
Timothy A. Keiderling - One of the best experts on this subject based on the ideXlab platform.
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Vibrational Circular Dichroism spectra of unblocked proline oligomers
International journal of peptide and protein research, 2009Co-Authors: Rina K. Dukor, Timothy A. Keiderling, Vladimír GutAbstract:Vibrational Circular Dichroism (VCD) spectra of unblocked l-proline oligopeptides, (Pro)n n = 3 to 7, dissolved in D2O are reported. For these oligomers, the VCD spectra can be attributed to a conformational dominance of the trans amide conformation with subunits interrelated by a left-handed twist, particularly for the longer oligomers. As a function of oligomer length, formation of this conformation starts at n = 3; and by n = 5 a spectrum closely resembling that of the poly-l-proline II helix in shape and magnitude is seen. The VCD data are compared with previous (Pro)n results using IR, CD, Raman and NMR spectroscopies, and reasons for the variations in interpretation are discussed.
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protein and peptide secondary structure and conformational determination with Vibrational Circular Dichroism
Current Opinion in Chemical Biology, 2002Co-Authors: Timothy A. KeiderlingAbstract:Abstract Vibrational Circular Dichroism (VCD) provides alternative views of protein and peptide conformation with advantages over electronic (UV) CD (ECD) or IR spectroscopy. VCD is sensitive to short-range order, allowing it to discriminate β-sheet and various helices as well as disordered structure. Quantitative secondary structure analyses use protein VCD bandshapes, but are best combined with ECD and IR for balance. Much recent work has focused on empirical and theoretical VCD analyses of peptides, with detailed prediction of helix, sheet and hairpin spectra and site-specific application of isotopic substitution for structure and folding.
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Measurement of Amide III Vibrational Circular Dichroism of Proteins
Spectroscopy of Biological Molecules: Modern Trends, 1997Co-Authors: Bernoli I. Baello, Petr Pancoska, Timothy A. KeiderlingAbstract:Empirical correlations have been made between protein Vibrational Circular Dichroism (VCD) spectra for amide I and II modes and the fractions of secondary structure found in analyses of their X-ray crystal structure [1]. We have now studied protein VCD in another region, the amide III (primarily C-N stretch). Its measurement has proven difficult in the infrared due to its low overall absorbance intensity and to its mixing with other non-amide modes lying in the general region near 1300cm−1 [2].
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Vibrational Circular Dichroism of Proteins in H2O Solution
Journal of the American Chemical Society, 1993Co-Authors: Vladimír Baumruk, Timothy A. KeiderlingAbstract:Spectroscopic studies have historically been important for estimation of the average secondary structure of proteins. Vibrational Circular Dichroism (VCD) is a hybrid of the more established electronic CD and infrared spectroscopies that combines the advantages of both (relatively high spectral resolution in IR region with high conformational sensitivity of CD methods). 1 For proteins the most valuable transition to study has proven to be the amide I band (assigned primarily to the C=O stretching of the amide group). Due to interference by water absorption band, all aqueous-phase VCD studies of the amide I have been done in D2O solution (termed as the amide I’). But the extent of deuteration is a poorly controlled parameter which leads to an ambiguity in interpretation of the data.
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Rotational Zeeman effect in carbon monoxide as determined by magnetic Vibrational Circular Dichroism
The Journal of Chemical Physics, 1993Co-Authors: Baoliang Wang, Timothy A. KeiderlingAbstract:The magnetic Vibrational Circular Dichroism (MVCD) of carbon monoxide has been measured by use of a Fourier transform infrared Vibrational Circular Dichroism spectrometer with an 8 T magnet. At 0.5 cm−1 resolution, the spectra are rotationally resolved, and both the sign and the magnitude of the g‐factor for the rotational Zeeman effect in C≡O can be determined using moment analysis to deconvolve the MVCD band shape. A rotational g value of −0.262 was obtained with an estimated error in accuracy of ±0.026 and a precision of ±0.011. Averaging individual gJ determinations for more than 30 transitions in the R‐ and P‐branches showed a much higher precision in the measurement. That this value agrees with the results of earlier, more precise, microwave‐based measurements as well as theoretical determinations of gJ confirms that MVCD can be used as an alternate method to determine molecular Zeeman g factors.
Tohru Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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Studying the stereostructures of biomolecules and their analogs by Vibrational Circular Dichroism
Polymer Journal, 2016Co-Authors: Tohru Taniguchi, Takahiro Hongen, Kenji MondeAbstract:The functions of biomacromolecules are largely governed by their stereostructure (i.e., configuration and conformation). Therefore, detailed understanding of their structural properties should help in regulating the functions of artificial macromolecules. However, studying the stereostructure of a molecule in the solution state is typically difficult due to the lack of suitable analytical techniques. Vibrational Circular Dichroism (VCD) spectroscopy, which measures Circular Dichroism in the infrared region, exhibits high sensitivity toward molecular stereostructures. In this paper, we first discuss a method for the elucidation of the stereostructures of small to large molecules based on theoretical calculations of VCD. The rest of the paper is dedicated to the applications of a VCD exciton chirality method, a novel approach recently developed by the authors to interpret VCD data by observing a VCD couplet in the C=O stretching region, to various biomolecules such as peptides, carbohydrates, polyesters and lipids. Vibrational Circular Dichroism (VCD) is effective for analyzing the configuration and conformation of various bio(macro)molecules. In addition to a conventional VCD approach using theoretical calculations, this review explains how the use of an exciton-type VCD couplet can be employed to elucidate the structures of bio(macro)molecules, such as carbohydrates, glycerophospholipids, proteins and polyesters.
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Studying the stereostructures of biomolecules and their analogs by Vibrational Circular Dichroism
Polymer Journal, 2016Co-Authors: Tohru Taniguchi, Takahiro Hongen, Kenji MondeAbstract:Vibrational Circular Dichroism (VCD) is effective for analyzing the configuration and conformation of various bio(macro)molecules. In addition to a conventional VCD approach using theoretical calculations, this review explains how the use of an exciton-type VCD couplet can be employed to elucidate the structures of bio(macro)molecules, such as carbohydrates, glycerophospholipids, proteins and polyesters.
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Stereochemical analysis of glycerophospholipids by Vibrational Circular Dichroism.
Journal of the American Chemical Society, 2015Co-Authors: Tohru Taniguchi, Daisuke Manai, Masataka Shibata, Yutaka Itabashi, Kenji MondeAbstract:The stereochemistry of glycerophospholipids (GPLs) has been of interest for its roles in the evolution of life and in their biological activity. However, because of their structural complexity, no convenient method to determine their configuration has been reported. In this work, through the first systematic application of Vibrational Circular Dichroism (VCD) spectroscopy to various diacylated GPLs, we have revealed that their chirality can be assigned by the sign of a VCD exciton couplet generated by the interaction of two carbonyl groups. This paper also presents spectroscopic evidence for the stereochemistry of GPLs isolated from bacteria, eukaryotes, and mitochondria.
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exciton chirality method in Vibrational Circular Dichroism
Journal of the American Chemical Society, 2012Co-Authors: Tohru Taniguchi, Kenji MondeAbstract:The interaction of two IR chromophores yields a strong Vibrational Circular Dichroism couplet whose sign reflects the absolute configuration of the molecule. We present a method to determine absolute configuration of a chiral molecule based on this couplet without need of theoretical calculation. Not only can this method analyze various molecules whose absolute configuration is difficult to determine by other spectroscopic methods, but also it can significantly enhance VCD signals.
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Absolute configurations of endoperoxides determined by Vibrational Circular Dichroism (VCD)
Tetrahedron Letters, 2006Co-Authors: Kenji Monde, Tohru Taniguchi, Nobuaki Miura, Charles Santhanaraju Vairappan, Minoru SuzukiAbstract:Abstract Diastereomeric mixture on the peroxide portion of an endoperoxide acetylmajapolene A (1) was efficiently separated by HPLC on a chiral column, submitting to Vibrational Circular Dichroism (VCD) investigation. The ab initio theoretical VCD and IR calculations of 1a and 1b were performed by density functional theory (DFT) using the B3PW91/6-31G(d,p) level of theory. Focusing on an isolated characteristic peroxide Vibrational band, absolute configurations of 1a and 1b were unambiguously determined as (1R,4R,7S,10S) and (1S,4S,7S,10S), respectively. This is the first VCD application to endoperoxides which exist abundantly in nature.
Giovanna Longhi - One of the best experts on this subject based on the ideXlab platform.
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Electronic and Vibrational Circular Dichroism spectra of (R)-(−)-apomorphine
Chemical Physics, 2012Co-Authors: Sergio Abbate, Giovanna Longhi, Matteo TommasiniAbstract:Abstract Apomorphine is a chiral drug molecule; notwithstanding its extraordinary importance, little attention has been paid to the characterization of its chiroptical properties. Here we report on its electronic Circular Dichroism (ECD) spectra, recorded in methanol and water, and Vibrational Circular Dichroism (VCD) in methanol and dimethyl sulfoxide (DMSO) solutions. Density functional theory (DFT) calculations have allowed us to interpret the spectra and to evaluate the role of possible conformations, charge-states and interactions with counter ions.
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NIR-VCD, Vibrational Circular Dichroism in the near-infrared: experiments, theory and calculations.
Chirality, 2009Co-Authors: Sergio Abbate, Ettore Castiglioni, Fabrizio Gangemi, Roberto Gangemi, Giovanna LonghiAbstract:The first well documented experiments of Near Infrared Vibrational Circular Dichroism (NIR-VCD) were performed around 1975. We review the thirty year history of NIR-VCD, encompassing both instrumental development and theoretical/computational methods that allow interpretation of experimental spectra, harvesting useful structural information therefrom. We hope to stimulate interest in this still scarcely explored spectroscopy of chiral molecules.
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nir vcd Vibrational Circular Dichroism in the near infrared experiments theory and calculations
Chirality, 2009Co-Authors: Sergio Abbate, Ettore Castiglioni, Fabrizio Gangemi, Roberto Gangemi, Giovanna LonghiAbstract:The first well documented experiments of Near Infrared Vibrational Circular Dichroism (NIR-VCD) were performed around 1975. We review the thirty year history of NIR-VCD, encompassing both instrumental development and theoretical/computational methods that allow interpretation of experimental spectra, harvesting useful structural information therefrom. We hope to stimulate interest in this still scarcely explored spectroscopy of chiral molecules. Chirality 21:E242–E252, 2009. © 2009 Wiley-Liss, Inc.
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Vibrational Circular Dichroism in the near infrared: instrumental developments and applications.
Enantiomer, 2002Co-Authors: Ettore Castiglioni, Giovanna Longhi, Sergio AbbateAbstract:Near infrared Vibrational Circular Dichroism spectra in the region of 1300 to 800 nm were recorded for 12 enantiomeric pairs of molecules with a home-made dispersive apparatus. With respect to earlier measurements, a better signal-to-noise ratio was obtained, thus allowing a more precise determination of molecular parameters. A detailed examination of the spectra between 1300 and 1100 nm allowed us to correlate the data of the different molecules, based on local properties of given molecular moieties. The relevance of this correlation in configurational and/or conformational studies is discussed.
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Observation of Vibrational Circular Dichroism for Overtone Transitions with Commercially Available CD Spectrometers
Applied Spectroscopy, 1996Co-Authors: Sergio Abbate, Giovanna Longhi, John W. Givens, Stefan E. Boiadjiev, David A. Lightner, Albert MoscowitzAbstract:It is demonstrated that some commercially available Circular Dichroism spectrometers can be used to gather Vibrational Circular Dichroism data associated with overtone transitions. By way of specific example, the Circular Dichroism spectra of neat S-(–)-limonene and R-(+)-limonene are measured in the region 800–600 nm. The observed spectral features correspond to the overtone bands Δv = 5 and 6 for CH-stretching motions. A discussion of the data is also given.
Laurence A. Nafie - One of the best experts on this subject based on the ideXlab platform.
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A Vibrational Circular Dichroism Microsampling Accessory: Mapping Enhanced Vibrational Circular Dichroism in Amyloid Fibril Films.
Applied Spectroscopy, 2017Co-Authors: Xuefang Lu, Jordan W. Nafie, Tomáš Pazderka, Markéta Pazderková, Rina K. Dukor, Honggang Li, Laurence A. NafieAbstract:We report the first Vibrational Circular Dichroism (VCD) measurement of spatial heterogeneity in a sample using infrared (IR) microsampling. Vibrational Circular Dichroism spectra are typically mea...
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A Vibrational Circular Dichroism Microsampling Accessory: Mapping Enhanced Vibrational Circular Dichroism in Amyloid Fibril Films.
Applied spectroscopy, 2017Co-Authors: Jordan W. Nafie, Tomáš Pazderka, Markéta Pazderková, Rina K. Dukor, Laurence A. NafieAbstract:We report the first Vibrational Circular Dichroism (VCD) measurement of spatial heterogeneity in a sample using infrared (IR) microsampling. Vibrational Circular Dichroism spectra are typically measured using a standard IR cell with an IR beam diameter of 10 mm or greater making it impossible to investigate the spatial heterogeneity of a solid film sample. We have constructed a VCD sampling assembly with either 3 mm or 1 mm spatial resolution. An XY-translation stage was used to measure spectra at different spatial locations producing IR and VCD maps of the sample. In addition, a rotating sample stage was employed using a dual photoelastic modulator (PEM) setup to suppress artifacts due to linear birefringence in solid-phase or film samples. Infrared and VCD mapping of an insulin fibril film has been carried out at both 3 and 1 mm spatial resolution, and lysozyme films were mapped at 1 mm resolution. The IR spectra of different spots vary in intensity due primarily to sample thickness. The changes in the VCD intensity across the map largely correlate to corresponding changes in the IR map. Closer inspection of the insulin map revealed changes in the relative intensities of the VCD spectra not present in the parent IR spectra, which indicated differences in the degree of supramolecular chirality of the fibrils in the various spatial regions. For lysozyme films, in addition to different degrees of supramolecular chirality, reversal of the net fibril chirality was observed. The large signal-to-noise ratio observed at 1 mm resolution implies the feasibility of further increasing the spatial resolution by one or two orders of magnitude for protein fibril film samples.
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8.25 Spectroscopic Analysis: Vibrational Circular Dichroism
Comprehensive Chirality, 2012Co-Authors: Laurence A. NafieAbstract:Vibrational Circular Dichroism (VCD) is the extension of electronic CD into infrared and near-infrared regions where Vibrational transitions occur. VCD is one of the two principal areas of Vibrational optical activity, the other being Vibrational Raman optical activity. Experimental and theoretical methodologies are presented as a basis for measuring and calculating VCD spectra. Instrumentation and computational advances are explained as a guide for carrying out applications of VCD, these being absolute configuration determination, enantiomeric excess determinations, reaction monitor of multiple chiral species, conformational analysis of biological molecules including amyloid fibrils and VCD of solids with extensions for raw-material identification, and formulated drug analysis in the pharmaceutical industry. With these current and projected applications, VCD is realizing its potential as a powerful new stereochemical tool for chiral structure elucidation.
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Fourier transform Vibrational Circular Dichroism of small pharmaceutical molecules
1998Co-Authors: Fujin Long, Teresa B. Freedman, Laurence A. NafieAbstract:Fourier transform Vibrational Circular Dichroism (FT-VCD) spectra of the small pharmaceutical molecules propanolol, ibuprofen and naproxen have been measured in the hydrogen stretching and mid-infrared regions to obtain information on solution conformation and to identify markers for absolute configuration determination. Ab initio molecular orbital calculations of low energy conformations, Vibrational frequencies and VCD intensities for fragments of the drugs were utilized in interpreting the spectra. Features characteristic of five conformers of propranolol were identified. The weak positive CH stretching VCD signal in ibuprofen and naproxen is characteristic of the S-configuration of the chiral center common to these two analgesics.
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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.