Circular dichroism wavelength range

Enantiomers can be distinguished by their rotation of plane-polarized light at a specific wavelength, or over a range of wavelengths (optical rotatory dispersion, ORD), as well as by the difference in absorption of right and left circularly polarized light (circular dichroism. Cotton effect, CD). 

In fact Schulz and co-workers (131,134), and Klabunovskii, Shvartsman and Petrov (55) report that the O. R. D. curves of poly-menthyl-acrylate, poly-bornyl-acrylate and poly-2-methyl-butyl-methacrylate show a maximum at about 300 mp, the wavelength corresponding to the maximum being related to the method of preparation of the polymer. Circular dichroism measurements seem advisable in order to confirm the existence of a Cotton effect postulated by the above authors in that wavelength range. 

Discussions of chiroptical properties of corresponding compounds in this series of The Chemistry of Functional Groups generally refer to the spectral range 589-190 nm, i.e. the emphasis is on optical (molar) rotations [O] J in the transparent region (optical rotatory dispersion, ORD) and rotations [0]J measured at the wavelength of the sodium-D-line (X = 589 nm) as well as electronic circular dichroism A e (CD) in the near ultraviolet region (X 190 nm) ... 

Circular birefringence , - and circular dichroism e, - Cr can both be measured as a function of the wavelength A or the wave number v. The two quantities are not mutually independent. If /Il(A) - /Ir(A) is known for A = 0 up to A = , values of f,.(A) - Er(A) for A = 0 up to A = < can be derived through a mathematical transformation, and vice versa. In spite of the fact that in practice it is not necessary to have values for the complete infinite interval of A, measurements over a sufficiently large range of values are in general quite difficult, so the transformation is not always possible. 

OL-nj, the "circular birefringence", which is proportional to the angle of rotation a. When the wavelength dependence of a is measured in the range of an absorption band, the left and right circularly polarized wave will not only propagate with different speeds, but will also be absorbed to different extents. The difference, Ae = El-Er/ is the "circular dichroism" (CD). 

The absorption and circular dichroism spectra of the blue colour produced by tri-iodide ions in amylose have been characterized. Four fundamental Raman lines were observed for bound to amyloses which were not dependent on the DP in the range 20-100 or the excitation wavelength. Concanavalin A does not react with amylose but does react with the amylose-iodine complex although the complex can be dispersed by shaking. The complex is non-specific as it cannot be displaced by concanavalin A-specific sugars. 

Circular dichroism spectrum (CD spectrum) An absorption spectrum obtained using circularly polarized hght it gives the circular dichroism of the substance over a range of wavelengths. 

Specialized instruments measuring circular dichroism are also available and have a wavelength range of 185-600 nm. Recently composite CD/ORD measuring instruments have also become available and offer a wavelength ran of 185-800 nm. 

Circular dichroism (CD) measurements were carried out with an Ohs 17 DSM a Cary 17 monochromater was used with a spectral output of 184—260 nm. CD spectra were measured at protein concentrations of 0.5 mg/mL using a cell with 0.090 mm light path in the wavelength range of 190-260 nm, with a bandwidth of 2.00 nm and with number of increments of 50 with an integration time of 20 s at 20°C. CD spectra were expressed in terms of mean residue eUipticity (deg cm dmol ). The depicted data represent an average of five scans. 

The circular dichroism (CD) spectra of H-PAs that were synthesized in the (R)-N -LC phase show an absorption of 450-800 nm, corresponding to the PA chain K-K transitions and a positive cotton effect and vice versa. This suggests that the PA chain itself is twisted in one direction. It should be noted that the cotton effect is not due to the binaphthyl derivatives, which only show a cotton effect in the short wavelength range of 240-340 nm, which is different from the absorption region of... 

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