Dichroism and Optical Rotatory Dispersion

A. Circular Dichroism and Optical Rotatory Dispersion Spectra. 236... 

Bohren, C. F., 1977. Circular dichroism and optical rotatory dispersion spectra of arbitrarily shaped optically active particles, J. Theor. Biol., 65, 755-767. 

Optical rotation, circular dichroism and optical rotatory dispersion of chiral thiophenes... 

Reynolds and Schlesinger (53, 67) have determined values of the intrinsic viscosity at different temperatures and pH. These data show that the enzyme is compact down to a pH of 4.0 but appears to be a random coil at pH 2.0 and also in 6 M guanidine hydrochloride. This is in agreement with results obtained from circular dichroism and optical rotatory dispersion studies (48, 53). 

Table III. (Also continued on next page) Predicted and observed n - t Cotton effects for steroid ketones from circular dichroism and optical rotatory dispersion spectroscopy"... 

The physical processes of absorption, refraction, circular dichroism and optical rotatory dispersion are closely inter-related, such that mechanistic discussions of the latter two require adequate consideration of the former two. Accordingly, this presentation begins with consideration of basic elements and terminologies of absorption and refraction, and then treats circular dichroism and optical rotatory dispersion, and in so doing provides prosthetic group examples of excitation resonance interaction and of the dispersion force interactions giving rise to hyper- and... 

Optical rotation is a general term which is used to include both circular dichroism and optical rotatory dispersion. These are closely related phenomena in the same way that absorption and ordinary dispersion (refractive index) are related. They can be interconverted by mathematical transforms. Whereas the common element in absorption and ordinary dispersion is the dipole strength of the transition, the common quantity in circular dichroism and optical rotatory dispersion is rotational strength. And, as will be seen below, the rotational strength of a transition may be obtained from either measurement. 

At this stage the relationship between circular dichroism and optical rotatory dispersion becomes of particular interest. As shown in Figure 15 for an isolated band. 

Circular dichroism and optical rotatory dispersion are related phenomena [20], and correspond respectively to the imaginary and real parts of the dielectric susceptibility. Their form for a positive CD effect is shown in Figure 8. 

Chiroptic Referring to the optical properties of chiral substances, such as optical rotation, circular dichroism, and optical rotatory dispersion. 

Baiasubeamanian D and Kumar C (1976) Recent studies of the circular dichroism and optical rotatory dispersion ofbiopolymers. Appl Spectr Rev 11 223-286. 

The modification of all four tyrosine residues (Tyr-399, 408,449, and 494) of fragment 377-571 by nitration with tetranitromethane yielded a homogeneous derivative which, by circular dichroism and optical rotatory dispersion measurements, had suffered no conformational alterations. Disulfide availability studies, however, indicated a slight increase in the reducibility of its disulfide bonds. The nitrated derivative behaved in an identical manner to unmodified peptide 377-571 in precipitin reactions with antisera to 377-571, and was also equally as effective in inhibiting the precipitin reaction of BSA with antisera to BSA. Also, with each of the antisera tested in immunoadsorbent studies, the derivative... 

Snatzke, G. Circular Dichroism and Optical Rotatory Dispersion - Principles and Application to the Investigation of the Stereochemistry of Natural Products. Angew. Chem. Intemat. Edit., 7, 14 (1968). 

We will now discuss the theory behind circular dichroism and optical rotatory dispersion individual (as we will see in subsequent pages, optical rotatory dispersion and circuW dichroism are mathematically commutable so that one can be known from the value of other it is only for the sake of understanding that they are being discussed Independently). 

Figure 9.3(B) depicts the absorption, circular dichroism and optical rotatory dispersion spectra of the mirror image of the hypothetical molecule considered in Figure 9.3(A). Note that vdille the absorption spectra in both cases are identical, the circular dichroism and optical rotatory dispersion spectra have changed signs. If a racemic mixture of this hypothetical compound is subjected to the above experiment, the absorption spectrum would still be identical but the circular dichroism and optical rotatory dispersion spectra would cancel out.

Crystallographic analyses of nucleosides and their derivatives have revealed that the values of Q)CN for the vast majority of these compounds correspond to the anti conformation The exceptions observed to date which possess the syn conformation are 3, 5 -cyclic guanosine (when it is in a crystalline complex with 5-bromo-2 -deoxy-cytidine), the nucleoside antibiotic formycin , 8-bromoguanosine and 8-bromoadenosine Solution measurements, based on NMR, circular dichroism and optical rotatory dispersion are generally in agreement with the X-ray data, (see paper of Ts o et al and literature cited thereii however, studies using Nuclear Overhauser NMR suggest that AMP may also prefer the syn conformation. 

Ultraviolet Spectra, Circular Dichroism, and Optical Rotatory Dispersion.—... 

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