Optical rotatory dispersion and infrared studies of β-structures of poly-O-benzyl-L-serine in solution

Beta-structure of polypeptides in non-aqueous solutions. I. Spectral characteristics of the polypeptide backbone

The optical rotatory features of the beta-structure of the polypeptides in non-aqueous solutions and films cast from these solutions have been investigated. The beta-structure of poly-S-benzyl-L-cysteine, poly-S-carbobenzoxy-L-cysteine and poly-S-benzyl-L-cysteine, poly-S-carbobenzoxy-L-cysteine and poly-O-carbo-bands of their films. The optical rotatory dispersion (ORD) and circular dichroism (CD) spectra of these polypeptides are found to be very similar in both film and solution. In solvents promoting the beta-structure, the polypeptides are characterized by CD troughs in the n-pi* transition region of the peptide chromophore. The ORD spectra are found to be positive in sign throughout the visible and accessible ultraviolet regions and are interpreted in terms of the possible existence of a relatively much larger positive pi-pi* CD bands as compared with the negative n-pi* band. The rotatory data obtained in the non-aqueous solution are compared with those obtained for other poly peptides in aqueous solutions, with respect to the type and extent of beta-structure present.

An improved double-beam infrared microspectrometer

The conversion of single-beam monochromators to double-beam microspectrometers is described. The principal advantage of the present system over others used is a great improvement in the long-term stability of the electronics; other advantages include simplicity, compactness, and complete freedom from beats due to mains frequency pickup. The system has been designed for use, in conjunction with a polarizer, for the examination of fibers, small crystals, and small areas of oriented biological macromolecules as well as for microsamples.

The effects of solvent environment on the optical rotatory dispersion parameters of polypeptides. I. Studies on poly-gamma-benzyl-L-glutamate

The constancy of the Moffitt optical rotatory dispersion parameters for polypeptides in different solvents was tested by dispersion measurements on poly-gamma-benzyl-L-glutamate in fifty-five solvents and solvent mixtures. b(0) was not constant but varied linearly with the refractive index of the solvent according to the equation -b(0) = 1701 - 730.3 n(8). This variation could not be explained by changes in configuration of the polypeptide. a(0) also showed a trend with solvent index but the values were widely scattered. lambda(0) did not show a statistically significant dependence on solvent index. The variation in b(0) can be interpreted as an effect of solvent polarizability on the frequencies of optically active transitions.