抄録
Electronic structures of polypeptide chains are theoretically studied.To extract the electronic tendency and/or electronic functions of individualamino acids, twelve kinds of homopolypeptide chains, which are formed bya single kind of amino acids, are considered, and their electronic structuresare investigated by the first-principle band calculation. Polypeptide chains have the potential to be a semiconductor havinga wide band gap of 3 -- 5 eV. Their band-edge states are basically theπ electronic states and can delocalize along the peptide backbone. Thedegree of the delocalization depends on the kind of constituent amino acidsand also the orientation of the amino acid side chains against the peptidebackbone. We also investigate how the random alignment of amino acids affectsthe band-edge electronic structures by using the coherent potential approximationapproach. In accordance with the kind of aligned amino acids, the aperiodicityin the alignment produces amalgamated electronic states so as to annihilatethe individual amino acid's electronic identity, or produces persistentstates in order to maintain their electronic characteristics.
