Conformational behavior of ionic self-complementary peptides

Several de novo designed ionic peptides that are able to undergo conformati onal change under the influence of temperature and pH were studied. These p eptides have two distinct surfaces with regular repeats of alternating hydr ophilic and hydrophobic side chains. This permits extensive ionic and hydro phobic interactions resulting in the formation of stable beta-sheet assembl ies. The other defining characteristic of this type of peptide is a cluster of negatively charged aspartic or glutamic acid residues located toward th e N-terminus and positively charged arginine or lysine residues located tow ard the C-terminus. This arrangement of charge balances the alpha-helical d ipole moment (C --> N), resulting in a strong tendency to form stable alpha -helices as well. Therefore, these peptides can form both stable alpha-heli ces and beta-sheets. They are also able to undergo abrupt structural transf ormations between these structures induced by temperature and pH changes. T he amino acid sequence of these peptides permits both stable beta-sheet and alpha-helix formation, resulting in a balance between these two forms as g overned by the environment. Some segments in proteins may also undergo conf ormational changes in response to environmental changes. Analyzing the plas ticity and dynamics of this type of peptide may provide insight into amyloi d formation. Since these peptides have dynamic secondary structure, they wi ll serve to refine our general understanding of protein structure.