The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
Giovanna Longhi - One of the best experts on this subject based on the ideXlab platform.
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experimental methods for measuring Optical Rotatory Dispersion survey and outlook
Chirality, 2011Co-Authors: Ettore Castiglioni, Sergio Abbate, Giovanna LonghiAbstract:The measurement of Optical rotation (OR) and Optical Rotatory Dispersion has been finding renewed interest for some years, because of advancement in computational methods and in the performance of new experiments. Here, we shortly review the traditional and most-used experimental methods. We define and discuss the two main types of approaches in measuring OR: the intensity method and the Optical null method. We report on some new results obtained by redesigning experiments based on the first approach, by adapting nonsophisticated hardware to current circular dichroism instrumentation. Chirality, 2011. © 2011 Wiley-Liss, Inc.
Jen Tsi Yang - One of the best experts on this subject based on the ideXlab platform.
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Optical Rotatory Dispersion AND CIRCULAR DICHROISM
A Laboratory Manual of Analytical Methods of Protein Chemistry, 2015Co-Authors: Jen Tsi YangAbstract:Publisher Summary This chapter discusses the Optical Rotatory Dispersion and circular dichroism. A linearly polarized light can be regarded to be made up of two equal, but opposite, circularly polarized components, one left-handed (lcp) and one right-handed (rep). On passing through an Optically inactive medium, the speeds of both components are equally affected, so the plane of polarization remains unchanged upon recombination. But in an Optically active medium, the speeds of the two components are unequally influenced, so the emergent light rotates through an angle with the plane of polarization of the incident light. The presence or absence of circular dichroism (CD) can also be studied with linearly polarized light. If the left and right circularly polarized components of a linearly polarized beam are absorbed equally, the emergent light remains linearly polarized. If, however, the two components are absorbed unequally, the resultant field no longer oscillates along a single line, and the head of the recombined components traces an ellipse.
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Optical Rotatory Dispersion of polypeptides and proteins
Tetrahedron, 2001Co-Authors: Jen Tsi YangAbstract:“THE invention in 1866 of the Bunsen burner inhibited the more laborious study of Rotatory Dispersion by making it almost too easy to work with the nearly monochromatic light of the sodium flame, and in this way brought to an end the fertile era which Biot had inaugurated half a century before.” Thus wrote Lowry in his classical study of Optical Rotatory power. l As a matter of fact, during the time of Biot and his famous pupil, Pasteur, nearly all studies of Optical activity were associated with measurements of Optical Rotatory Dispersion. It was indeed most unfortunate that much valuable information was lost in later years through the extensive use of the sodium lamp by almost all the workers in this field. Within the last five years, however, we have witnessed an increasing interest in the Optical Rotatory power, both theoretically and experimentally. With the availability of commercial spectropolarimeters, the Optical Rotatory Dispersion studies have experienced a rebirth, and have already yielded many fruitful findings as a result of new developments. On the one hand, this technique has been extensively applied to the structural studies of organic compounds, as evidenced by the beautiful work of Djerassi et al. * Of equal importance are the applications of Optical Rotatory Dispersion to the study of polypeptide and protein conformations. It is at the latter aspect that the present paper will be aimed. Already the vast interest in this field has resulted in the appearance of several excellent reviews.3-6 A monograph on synthetic polypeptides has also been published which describes in detail the work of the English school. 7 Therefore (and taking into consideration the limits of time and space imposed upon me) it seems superfluous to discuss recently publishd work; nor is it necessary to describe the work of some of the distinguished participants present at this symposium. Rather, we will limit our brief review to some of our early work, which I, myself, had the good fortune to observe closely. Some of the older proposals and interpretations will also be re-examined in view of later developments.
Antonio Balbin Villaverde - One of the best experts on this subject based on the ideXlab platform.
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Magneto-Optical Rotatory Dispersion of some non-linear crystals
Journal of Physics: Condensed Matter, 1991Co-Authors: Egberto Munin, Antonio Balbin VillaverdeAbstract:The authors measured the magneto-Optical Rotatory Dispersion (MORD) of eight non-linear KDP-type crystals: RDA, KDA, CDA, ADA, DRDA, DCDA, KDP and RDP. From the data they proceed to calculate the magneto-optic anomaly gamma -factor for each crystal. They also calculate the energy gap by fitting the data to the BHL and KLN formulae, respectively. Finally, they make a comparison between the values of Eg obtained by the MORD method with those calculated from Optical Dispersion data. The effect on the gamma -values and on Eg due to the substitution of cations and/or anions, as well as the deuteration of the samples, is discussed.
Ettore Castiglioni - One of the best experts on this subject based on the ideXlab platform.
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experimental methods for measuring Optical Rotatory Dispersion survey and outlook
Chirality, 2011Co-Authors: Ettore Castiglioni, Sergio Abbate, Giovanna LonghiAbstract:The measurement of Optical rotation (OR) and Optical Rotatory Dispersion has been finding renewed interest for some years, because of advancement in computational methods and in the performance of new experiments. Here, we shortly review the traditional and most-used experimental methods. We define and discuss the two main types of approaches in measuring OR: the intensity method and the Optical null method. We report on some new results obtained by redesigning experiments based on the first approach, by adapting nonsophisticated hardware to current circular dichroism instrumentation. Chirality, 2011. © 2011 Wiley-Liss, Inc.
Prasad L Polavarapu - One of the best experts on this subject based on the ideXlab platform.
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absolute configuration of c76 from Optical Rotatory Dispersion
ChemPhysChem, 2005Co-Authors: Prasad L Polavarapu, Jiangtao He, Jeanne Crassous, Kenneth RuudAbstract:The absolute configuration of C 1 6 has been determined as (+) 5 8 9 -(C)-C 7 6 , for the first time, by comparing the experimental and predicted Optical Rotatory Dispersion (ORD) patterns. The experimental ORD pattern was derived from the experimental electron-ic circular dichroism (ECD) spectrum using the Kramers-(KK) transform. The theoretical ORD spectra were calculated in the resonant region using linear response theory, and also using the KK transform of the theoretical ECD spectrum, at -different theoretical levels, namely BHLYP/6-31G*, B3LYP/6-31G*, BLYP/6-31G*, and HF/6-31G*. Good agreement noted between experimental and predicted spectra allows for an unambiguous determination of the absolute configuration.
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kramers kronig transformation for Optical Rotatory Dispersion studies
Journal of Physical Chemistry A, 2005Co-Authors: Prasad L PolavarapuAbstract:The Kramers−Kronig (KK) transform method for deriving Optical Rotatory Dispersion (ORD) from electronic circular dichroism (ECD) has been analyzed. Three different numerical integration methods for the KK transform have been evaluated, and the method proposed by Ohta and Ishida has been used for further calculations. Using this method, the quantum mechanical predictions of electronic circular dichroism (ECD) have been converted to corresponding ORD and compared with that derived from the linear response method. For three molecules exhibiting monosignate ORD in the nonresonant long wavelength region, the KK transform of ECD associated with the lowest energy electronic transition is found to give ORD values close to those obtained with the linear response method. For molecules exhibiting bisignate ORD in the nonresonant long wavelength region, the KK transform method may not provide the correct results. In the resonant region, the KK transform method provides a computationally economical alternative for pre...
