[Standard structures in protein molecules. I. Alpha-beta hairpins].

Structures formed by consecutive alpha-helices and beta-strands which are packed approximately antiparallel into alpha-beta-hairpins are considered. It is shown that there is a limited number of standard conformations for the alpha-beta-hairpins having not more than six peptide units in connecting regions. The features of the amino acid sequences encoding the alpha-beta-hairpins are analyzed. It is shown that each standard alpha-beta-hairpin has a strictly definite order of hydrophobic, hydrophilic and glycine residues in the sequence.