Synthesis, Structure, and Biological Properties of Sequential Polypeptides

Spontaneous and Selective Peptide Elongation in Water Driven by Aminoacyl Phosphate Esters and Phase Changes

“…37−43 Some of the strategies involve the use of amino acids which are appended at the C-terminus with various activated ester moieties. 44 Aminolytic reactions then achieve sequence elongation in organic media but often encounter challenges associated with the formation of stable species, such as cyclic dipeptides (diketopiperazines). 38 Aqueous peptide bond formation has been demonstrated using N-carboxy anhydrides (NCAs).…”

“…Outside of biology, chemical reactions yielding peptide bonds have gained significant interest too. − Some of the strategies involve the use of amino acids which are appended at the C-terminus with various activated ester moieties . Aminolytic reactions then achieve sequence elongation in organic media but often encounter challenges associated with the formation of stable species, such as cyclic dipeptides (diketopiperazines) .…”

Sequence Specific Liquid Crystallinity in Thick Films of Model Collagen-like Polyhexapeptides

“…The triple helix is stabilized by a large proportion of the imino acids proline and hydroxyproline in the collagen triple helical sequence domains. Correlations between primary sequence, local conformation, supercoiling of the triple helix, and physical properties have been demonstrated. − The presence of amino, rather than imino acids, in the second position of the sequence (Gly-X-Y) results in a conformational change as the helix twists to accommodate hydrogen bonding between the amino acid and the environ ment. − ,,, With a hydrophilic or weakly hydrophobic amino acid in this position, the triple helical conformation can be destabilized. This can also occur with substitution of any amino acid for the glycine in the Gly-X-Y pattern. − ,,, Changes in the triple helical conformation and in supercoiling are observed as shifts in the infrared amide A band (3290−3400 cm -1 ) position. ,,,, The existing research into sequence, conformation, and thermal behavior in model collagens provides a firm basis from which to address aspects of the formation of supermolecular ordered structures, such as liquid crystals and helicoid solids.…”

Synthesis and Hydrogen Bonding Capabilities of Biphenyl-Based Amino Acids Designed To Nucleate β-Sheet Structure

“…The mechanisms of β-sheet folding are under investigation in several laboratories using a variety of approaches. − While β-sheet structure is commonly observed in proteins, our understanding of this structural motif is poor relative to what is known about α-helical secondary structure. This is due, in part, to the difficulties inherent in creating a well-defined peptide model system for the study of β-sheet formation in aqueous solution. − Although studies on the conformational propensities of amino acid homopolymers and sequential copolymers have enhanced our understanding of β-sheet structure, the approach is limited because of competitive intra- and intermolecular folding which leads to heterogeneous aggregated β-sheet structures. − Small hydrophobic or amphiphilic peptides are also poor model systems as they too usually form self-associated β-sheet structures. ,,− The ability to prepare a monomeric β-hairpin structure, where a β-turn reverses the polypeptide chain direction allowing two strands to interact with one another in an antiparallel orientation, would be advantageous. In principle, this could be accomplished using a consensus β-turn sequence combined with flanking strand sequences that have a high β-sheet propensity.…”