Structural characteristics and spectral behaviours of the preferred conformation of a cyclic pentapeptide, cycloaspeptide G from Cordycepscolonising fungus Isoria farinose
Abstract
The density functional theory (DFT) is exploited to search the stable conformations of a cyclic pentapeptide called cycloaspeptide G from Cordycepscolonising fungus Isoria farinose. Its timedependent version is employed to describe the profiles of electronic circular dichroism (ECD) of the preferred conformation, where the solvent effect in methanol is taken into account on the basis of the polarisable continuum model computation. Four stable conformers are optimised, and the results of the harmonically vibrational frequency calculations illustrate that they are the true minima. In the vibrational CD spectrum at the B3LYP/631G* level, the negative peak at 3334 cm^{1} has its origin of the NH stretches of the peptide ring. In the ECD spectrum at the B3LYP/631G* level, three strong bands are negative, positive, and negative. Since the ECD spectrum at the B3LYP/631G* level is remarkably different from that at the B3LYP/631G level, it is necessary for the expended functions to be added to the 631G basis set.
 Publication:

Molecular Physics
 Pub Date:
 January 2015
 DOI:
 10.1080/00268976.2014.945503
 Bibcode:
 2015MolPh.113..104M
 Keywords:

 cyclic peptide;
 electronic circular dichroism;
 vibrational circular dichroism;
 density functional calculations;
 timedependent density functional calculations