Circular dichro ism

This ionic selectivity observed in solution is directly related with the ability to form gels [48]. From circular dichro ism it is shown that stronger interaction exists with calcium compared with sodium counterions [41,48]. 

Abstract Protoberberine alkaloids and related compounds represent an important class of molecules and have attracted recent attention for their various pharmacological activities. This chapter deals with the physicochemical properties of several isoquinoline alkaloids (berberine, palmatine and coralyne) and many of their derivatives under various environmental conditions. The interaction of these compounds with polymorphic DNA structures (B-form, Z-form, H -form, protonated form, triple helical form and quadruplex form) and polymorphic RNA structures (A-form, protonated form, triple helical form and quadruplex form) reported by several research groups, employing various analytical techniques such as spectrophotometry, spectrofluorimetry, circular dichro-ism, NMR spectroscopy, viscometry as well as molecular modelling and thermodynamic analysis to elucidate their mode and mechanism of action for structure-activity relationships, are also presented. 

Binding of berberine caused changes in the circular dichroic spectrum of all B-DNAs with an increase of molar ellipticity of the 270 nm band the molar ellipticity value at saturation depended strongly on the base composition of DNA being larger for the AT-rich DNA than the GC-rich DNA. However, the generation of berberine-associated extrinsic circular dichro-ism bands was not dependent on the base composition or sequence of base pairs. 

The photochemical formation and the analysis of the absorption and magnetic circular dichro-ism spectra of the anion radical of zinc phthalocyanine were carried out. A complete assignment of the optical spectrum of the anion radical was proposed.834 Similarly, spectroelectrochemical cells have been used to record absorption and magnetic circular dichroism spectra of zinc phthalocyanines and a band assignment scheme proposed.835... 

By contrast, in the CD spectrum of the p derivative (39), no bands were observed even at —80°C, as shown in Figure 4.19b. This is because the Cotton band of the p derivative is canceled by an oppositely signed CD band originating in an equivalent proportion of opposite screw sense helical segments (which may be referred to as masked helicity or masked circular dichro-ism ). The difference between the helical conformations of m and p derivatives may be due to the degree of steric hindrance of (S>2-methylbutoxyphenyl rings, since the p derivative may have enough space to freely rotate the... 

Figure 14 shows the circular dichroism spectra for the LB films of p-CDNH C12-H25 including Naph-SOsNa molecules under the initial surface pressure of 30 mN/m. Different induced circular dichro-isms are clearly observed at1 Bbband of naphthalene, depending on the substituted position the negative and positive Cotton effects occur for 1 - and 2-Naph-SOaNa included in the cavity of the CD... 

Wallace, B. A. (2000). Conformational changes by synchrotron radiation circular dichro-ism spectroscopy. Nat. Struct. Biol. 7, 708-709. 

Kuwajima K., Yamaya H., Miwa S., Sugai S. and Nagamura T. Rapid formation of secondary structure framework in protein folding studied by stopped-flow circular dichro-ism. FEBS Lett. (1987) 221(1) 115-118. 

Structures of the two proteins were characterized using circular dichro-ism (Table 1) [35]. Both proteins were a-helical coiled coils. Although... 

I think it is possible to excite either a clockwise or an anticlockwise pseudorotation state by using a circularly polarized beam and also to probe with a circularly polarized beam to detect the circular dichro-ism induced by the pump beam. 

Sensors for the detection of enantiomers are of great interest, as so far the on-line monitoring of production processes and medical diagnostics using standard chemical analytical methods is not possible. Quite often only one enantiomer of a chiral compound is actually a bioactive therapeutic. Therefore a proper analysis of the final product is essential. Currently, this involves separation techniques like liquid chromatography, GC and capillary electrophoresis, and determination of enantiomeric purity with circular dichro-ism and specific rotation. These are all off-line procedures and therefore no real-time analysis can be performed. Sensing devices for the distinction of different enantiomers would be a much cheaper, faster and easier-to-use alternative for this task, amenable to automation. 

Polarimetry coupled to a liquid chromatograph has been used to determine the optical purity of drugs [113-121]. The advantages of this approach for determining optical purity is that the enantiomers do not need to be resolved and only eluates which give rise to optical rotation or circular dichro-ism are detected. This advantage makes on-line polarimetry inherently more accurate than conventional polarimetry because minor interfering compo-... 

France LL, Piatti PG, Newman JFE, Toth I, Gibbons WA, Brown F (1994) Circular dichro-ism, molecular modeling, and serology indicate that the structural basis of antigenic variation in foot-and-mouth disease virus is a-helix formation. Proc Natl Acad Sci U S A 91(18) 8442-8446... 

HRP. The existence of conformational changes was confirmed by circular dichro-ism studies, and the enhanced thermostability of modified HRP was attributed to side chain reorientations of aromatic residues [66]. 

Kuball HG, Hofer T (2000) In Berova N, Nakanishi K, Woody RW (eds) Circular dichro-ism principles and applications, chap 5. VCH, New York, pp 133-158... 

H2TPPS and [Ru(phen)3]2+. Interaction is indicated by variation in the absorption spectra (Fig. 22) and, especially, by the appearance of an induced circular dichro-ism (Fig. 23) band in the absorption region of the achiral porphyrin. The relationship between chirality of the cationic metal complex and that transferred to the anionic porphyrins is straightforward because interactions of H2TPPS with the A- and A-[Ru(phen)3]2+ lead to mirror-image ICD signals (Fig. 23) [51]. 

Because an unfolded or partly folded protein consists of a conformational ensemble containing a wide range of different structures, it is impossible to obtain meaningful results from crystal structures even if the molecule will form crystals, the resulting structure will not be representative of the ensemble in solution. It is necessary to obtain information on unfolded proteins in solution. Spectroscopic methods are therefore employed to give information on conformational preferences within the ensemble. These include circular dichro-ism, fluorescence, Raman and NMR spectroscopy. NMR gives a great deal of site-specific information, and is preferred when NMR spectra are possible. 

Wu Y, Huang HW, Olah GA. Method of oriented circular dichro-ism. Biophys. J. 1990 57 797-806. 

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