title: Amino acid propensities revisited.
abstract: Statistical analysis of amino acid patterns in approximately 160,000 alpha-helices in experimentally determined structures revealed di-, tri-, and tetrapeptides, whose frequencies deviate most from the statistical model. Importantly, some sequences were never found in alpha- helices. This fact was detected initially with tripeptides, where nearly 1% of the possible sequences were never seen in the helical segments. For tetrapeptides, this effect is very strong and significant; almost 43% of the possible sequences never appear in alpha-helices. It is possible that there are some steric and energetic restrictions that do not allow these tetrameric amino acid sequences to form alpha-helical structure.
authors.affiliation: Computational and Structural Biochemistry and Bioinformatics, Department of Nutrition and Biochemistry, School of Sciences, Pontificia Universidad Javeriana, Carlos Ortiz Building, Rm. 107, Carrera 7a #43-82, Bogotá, Colombia.
authors.forename: Orlando E
authors.initials: OE
authors.lastname: Acevedo
authors.forename: Leonardo R
authors.initials: LR
authors.lastname: Lareo
mesh_terms: D000596:Amino Acids / Q000737:chemistry*
chemical_list: D000596:Amino Acids