RECENT STRUCTURAL STUDIES OF PEPTIDES IN JAPAN

Recent x-ray structure analyses of peptides in Japan were reviewed. A series of peptides containing an aminoisobutyric acid (Aib) residue wa s analyzed and their helical types were investigated. Two convenient m ethods to determine helical types were obtained. One method was obtain ed by calculating averaged helical parameters and the other was obtain ed by investigating meridional intensity distributions. The conformati ons of some peptides, such as aureobasidin E, ascidiacyclamide, synthe tic analogues of heat-stable enterotoxin, were studied by an x-ray dif fraction method, and in some cases, with help of nmr spectroscopy and molecular mechanics calculations. Since these peptides have physiologi cally important activities, the structure-activity relationships of th ese peptides were discussed. Several other peptide structures and the polymorphism of amino acids are also reported. (C) 1996 John Wiley & S ons, Inc.