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Electronic Circular Dichroism (electronic + circular_dichroism)
Selected AbstractsDetermination of the Absolute Configurations of Natural Products via Density Functional Theory Calculations of Vibrational Circular Dichroism, Electronic Circular Dichroism, and Optical Rotation: The Iridoids Plumericin and Isoplumericin.CHEMINFORM, Issue 37 2007P. J. Stephens Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Circular dichroism spectroscopic study of non-covalent interactions of poly- L -glutamic acid with a porphyrin derivative in aqueous solutionsJOURNAL OF PEPTIDE SCIENCE, Issue 9 2005Palivec Abstract The interactions of poly- L -glutamic acid and a cationic porphyrin derivative in aqueous solutions were studied by the combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopies. It was found that non-covalent interactions between both agents influence the structure of the polymeric matrix and the guest porphyrins and vice versa, but the physico-chemical properties of the solutions, especially the pH and the relative permittivity of the solvent, play a key role in the structure of the polypeptide part of the formed complexes. It was shown that the interaction with porphyrins prevents the precipitation of poly- L -glutamic acid in aqueous solution at acidic pH. In special conditions, the porphyrins attached to the polypeptide probably possess face-to-face interaction as demonstrated by the enhancement of the characteristic ECD signal and the appearance of sidebands on its short and long wavelength sides. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd. [source] Renaissance in chiroptical spectroscopic methods for molecular structure determinationTHE CHEMICAL RECORD, Issue 2 2007Prasad L. Polavarapu Abstract Two of the chiroptical spectroscopic methods, namely optical rotatory dispersion (ORD) and electronic circular dichroism (ECD), have been around for several decades. But their use in determining the absolute configuration and predominant conformation is gaining renewed interest with the availability of quantum mechanical methods for predicting ORD and ECD. Two other methods, namely vibrational circular dichroism (VCD) and vibrational Raman optical activity (VROA), are relatively new and offer convenient approaches for deducing the structural information in chiral molecules. With the availability of quantum mechanical programs for predicting VCD and VROA, these methods have attracted numerous new researchers to this area. This review summarizes the latest developments in these four areas and provides examples where more than one method has been used to confirm the information obtained from individual methods. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 125,136; 2007: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20117 [source] Circular Dichroism of Designed Peptide Helices and ,-Hairpins: Analysis of Trp- and Tyr-Rich PeptidesCHEMBIOCHEM, Issue 12 2005Radhakrishnan Mahalakshmi VCD versus ECD spectroscopy. Peptides rich in aromatic residues yield anomalous far-UV electronic circular dichroism (ECD) spectra that preclude secondary structure assignment. The utility of vibrational circular dichroism (VCD) in conformation analysis is demonstrated by using a set of well-defined peptide helices and hairpins containing proximal aromatic residues. [source] Spectroscopic rationalization of the separation abilities of decaproline chiral selector in dichloromethane,isopropanol solvent mixtureCHIRALITY, Issue 2 2007Peng Zhang Abstract A chiral column, with decaproline as the chiral selector, has broad chiral selectivity. To understand the separation mechanism of this chiral column, multiple spectroscopic techniques, including optical rotation, electronic circular dichroism, infrared absorption and vibrational circular dichroism, have been used here to study the conformation of the decaproline oligomer in isopropanol(IPA)/dichloromethane(DCM) mixtures. These studies indicate that decaproline oligomer adopts polyproline II conformation in IPA/DCM solvent system (0% IPA , 100% IPA). Hydrogen bonding interactions between CO groups of decaproline and IPA molecules increase as the content of IPA in the solvent mixture increases up to 60% and become less significant from then onwards. These spectroscopic observations are found to have a good correlation with the enantiomeric separation of racemic 2,2,2-trifluoro-1-[10-(2,2,2-trifluoro-1-hydroxy-ethyl-anthracen-9-yl]-ethanol by the decaproline column. Chirality 2006. © 2006 Wiley-Liss, Inc. [source] Chirality of camphor derivatives by density functional theory,CHIRALITY, Issue 10 2006Hayato E. Morita Abstract Infrared (IR) and vibrational circular dichroism (VCD) spectra of chiral camphor, camphorquinone and camphor-10-sulfonic acid (CSA), known as standard compounds for electronic circular dichroism (ECD) spectroscopy, are measured and their vibrational frequencies, infrared intensities, and rotational strengths are calculated using density functional theory (DFT). The observed IR and VCD spectra of chiral camphor and camphorquinone in carbon tetrachloride solution are reproduced by the DFT calculations, but those of CSA are not. DFT calculations of hydration models, where an anionic CSA specifically binds a few water molecules, are carried out. The average of the simulated VCD spectra in the hydration models is more consistent with the observed spectra. In addition, the wavelengths and dipole and rotational strengths for chiral camphor, camphorquinone, anionic CSA, and the hydration models were calculated by time-dependent DFT. In the region of 280,300 nm, the calculated wavelengths of the ECD bands for chiral camphor and camphorquinone coincide with the observed wavelengths that have been reported, and the calculated wavelengths for the hydration models are closer to the observed wavelengths reported than are those calculated for chiral anionic CSA. Consequently, the analysis combined with VCD and ECD spectroscopy using DFT calculations can elucidate the chirality of optically active molecules, even in an aqueous solution. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||