The Circular Dichroism Spectrum Andstructure of Unordered Polypeptides Andproteins

Theoretical calculation of the circular dichroism of unordered polypeptide chains.

Synopsis A calculation has been done of the circular dichroism (CD) spectrum of an unordered polypeptide chain. This has been based on a Boltzmann averaging over a dipeptide conformational CD map. This is shown to be valid by comparing the CD spectra of 28-mer oligopeptides with those generated by summing dipeptide CD spectra. The calculated CD spectrum of an unordered polypeptide chain is foun...

The calculated circular dichroism of polyproline II in the polarizability approximation.

The circular dichroism (CD) spectrum of polyproline I1 (PPII) has heretofore been moderately well calculated from exciton theory only at the expense of assuming unreasonable chain conformations and accepting a conservative spectrum in the 180250-nm region (which is not observed). We have incorporated far uv transitions in the polarisability approximation and, together with the r2r* transition, ...

Single peptide bonds exhibit poly(pro)II ("random coil") circular dichroism spectra.

The far-UV circular dichroism spectra of a series of amino acid derivatives containing single peptide bonds have been measured. The N-acetyl-alanine displays a polyproline (PP) II-like spectrum, but alaninamide shows a very weak positive signal. Similarly Gly-Ala shows a PPII spectrum, but Ala-Gly does not. On heating, the spectrum shows a two-state transition also shown by long PPII polypeptid...

Conformation analysis of the polypeptides in the thylakoid membrane.

The ultraviolet circular dichroism spectrum of a chloroplast fraction of Antirrhinum ma jus has recently been published The fraction was obtained from stroma-freed chloroplasts by ultrasonic treatment and fractioning centrifugation2-3. The spectrum shows extrema of ellipticity at 194 ( + ) , 208 ( ) and 222 ( —) nm. Thus it is similar to a protein with a considerable a-helix content. G R E E N ...

Effect of temperature on the circular dichroism spectra of polypeptides in the extended state.