Spectroscopy circular dichroism

In practical terms, transition (a) is observed as a 190 nm absorption band with a shoulder at 208 nm. Transition (b) is observed only at lower wavelengths with good optical equipment. UV-visible tt tt transitions involving either /i-sheets or less regular structures (known broadly as random coil) are not subject to extensive chromophore perturbation effects and hence UV-visible spectroscopy is unable to identify the presence of either secondary structural elements directly. 

Turning to nucleic acids, the potential of UV-visible spectroscopy for nucleic acid structural analysis has always been considered high in principle. The reason for this is the sheer number of base chromophores available in nucleic acids and their potential for electronic interactions. Given the high degree of structural uniformity in nucleic acids, the total absorbance A(A.) of a given sample of nucleic acids may be given by 

Circular dichroism (CD) spectroscopy is in many ways a more sophisticated version of UV-visible spectroscopy and is able to give substantially more structural information than may be obtained by routine UV-visible spectroscopy. Unfortunately, CD spectroscopy gives 

The most basic CD spectrum is then generated by plotting AA(A.) as a function of k. CD spectra may be rendered in at least two other ways. The first uses the Beer-Lambert law  

In the same way as for AA(X) and Ae X) plots, only 6 (A.) plots should be used if combinations of more than one optically active molecule are under investigation in the same sample, since molarity forms part of the dimensions of [6 (A.)], which once again is difficult to define if more than one optically active type of molecule is involved in the sample. 

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Xie X and Simon J D 1989 Picosecond time-resolved circular dichroism spectroscopy experimental details and applications Rev. Sol. Instrum. 60 2614-27... 

Xie X L and Simon J D 1990 Picosecond magnetic circular dichroism spectroscopy J. Rhys. Chem. 94 8014-16... 

K. Nakanishi and N. Harada, Circular Dichroism Spectroscopy Exciton Coupling in Organic Stereochemistry, University Science Books, Mill Vallqr, California, 1983 D. N. Kirk, Tetrahedron 42 777 (1986). 

Peculiar DNA architecture was demonstrated in 25% aqueous ethanol when DNA was complexed with series of cationic detergents in the presence of poly(glutamic acid) [124]. Electron microscopy and x-ray scattering demonstrated that DNA can pack cetyltrimethylammonium bromide molecules into rodlike micelles, which form a hexagonal lattice. Interestingly, circular dichroism spectroscopy revealed that in these complexes DNA adopts left-handed conformation. 

The protein-containing colloidal solutions of water-in-organic solvents are optically transparent. Hence, absorption spectroscopy, circular dichroism spectroscopy and fluorescence spectroscopy are found to be convenient for studying biocatalysis [53]. The reversed micelles are interesting models for studying bioconversion, since the majority of the enzymes in vivo act inside or on the surface of biological membranes. 

Zsila, F., Z. Bikadi, Z. Keresztes, J. Deli, and M. Simonyi. 2001b. Investigation of the self-organization of lutein diacetate by electronic absorption, circular dichroism spectroscopy, and atomic force microscopy. J. Phys. Chem. B 105 9413-9421. 

Wallace, B. A., and Janes, R. W. (2001). Synchrotron radiation circular dichroism spectroscopy of proteins Secondary structure, fold recognition and structural genomics. Curr. Opin. Chem. Biol. 5, 567-571. 

Zaiss, K. and R. Jaenicke. 1999. Thermodynamic study of phosphoglycerate kinase from Thermotoga maritima and its isolated domains reversible thermal unfolding monitored by differential scanning calorimetry and circular dichroism spectroscopy. Biochemistry 38 4633 -639. 

In order to obtain more information about the interactions between AmB and lipids at the molecular level, we chose to use spectroscopic measurements electronic absorption and circular dichroism (19). The particular structure of the AmB molecule, with several conjugated double bonds in the hydrophobic stretch, means that these techniques can be used to study its aggregation state under different conditions. Of the two, circular dichroism spectroscopy is the more sensitive way of detecting the aggregated forms of AmB. 

A convenient method to demonstrate guest binding in mPE systems is circular dichroism spectroscopy (CD). CD is a method which allows the determination of chiral excess in a system [56]. In the absence of a chiral influence, the mPE helix exists as a racemic mixture of both M and P helices and displays no CD signal. Upon the addition of a chiral guest, diastereomeric complexes are... 

Optical Spectroscopy General principles and overview, 246, 13 absorption and circular dichroism spectroscopy of nucleic acid duplexes and triplexes, 246, 19 circular dichroism, 246, 34 bioinorganic spectroscopy, 246, 71 magnetic circular dichroism, 246, 110 low-temperature spectroscopy, 246, 131 rapid-scanning ultraviolet/visible spectroscopy applied in stopped-flow studies, 246, 168 transient absorption spectroscopy in the study of processes and dynamics in biology, 246, 201 hole burning spectroscopy and physics of proteins, 246, 226 ultraviolet/visible spectroelectrochemistry of redox proteins, 246, 701 diode array detection in liquid chromatography, 246, 749. 

Several direct methods are available to analyze the tertiary structure of ODNs like nuclear magnetic resonance (NMR) and X-ray crystallographic (XRC) techniques, which needs a sophisticated setup and infrastructure. An alternative but indirect method to study the structure and conformations of nucleic acids is circular dichroism spectroscopy (CD spectroscopy) (25, 26), where circular dichroism refers to the differential absorption of left and right circularly polarized light (27). 

Among the most intensively investigated of all the chalcone Diels Alder adducts are a group obtained solely from Morus species in which the diene component of the reaction is a dehydroprenylflavanone. The structures of several such compounds published prior to 1992 have now been revised on the basis of new spectroscopic and chemical data. Among the most important of the techniques used were two-dimensional NMR and circular dichroism spectroscopy. The revised structures listed in Table 16.5 are those of sanggenons C (210), D (211), E (212), and O (213). In these compounds, the flavanones show the common feature... 

Berchemia zeyheri (Rhamnaceae), a tree native to southern Africa which is prized for its beautiful wood, known as pink ivory or red ivory. The complexity of the phenolic compounds present in heartwood extracts prompted their analysis as permethylated derivatives. Stereochemical features were determined by using both NMR and circular dichroism spectroscopy of the parent compounds and their degradation products. These methods were used successfully to obtain a full stereochemical description of the zeyherin epimers 374 and 375, ° which were first isolated in 1971 but not fully characterized at that time. Subsequent work has led to the discovery of further auronol dimers and novel heterodimers with flavanone or isoflavanone constituents as summarized in Table 16.15. ° ° °... 

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