Collagen-based structures containing the peptoid residue N-isobutylglycine (Nleu): synthesis and biophysical studies of Gly-Nleu-Pro sequences by circular dichroism and optical rotation.
Single-chain peptide-peptoid structures, Ac-(Gly-Nleu-Pro)n-NH2 (n = 3, 6, and 10) and (Gly-Nleu-Pro)n-NH2 (n = 1 and 9), and template-assembled collagen analogs, KTA-[Gly-(Gly-Nleu-Pro)n-NH2]3 (n = 3 and 6; KTA represents cis,cis-1,3,5-trimethylcyclohexane-1,3, 5-tricarboxylic acid, also known as the Kemp triacid; Nleu denotes N-isobutylglycine), were prepared by solid-phase peptide synthesis methods. Biophysical studies using circular dichroism (CD) and optical rotation measurements show that these collagen analogs form triple-helical conformations when the chain is longer than a critical length. Unlike collagen-based structures composed of Gly-Pro-Hyp and Gly-Pro-Nleu sequences, results reveal that the presence of a positive CD peak between 220 and 225 nm is indicative of triple-helical conformations for these collagen-based structures composed of Gly-Nleu-Pro sequences. Results also indicate that the Gly-Nleu-Pro sequence possesses a higher triple-helical propensity than the Gly-Pro-Nleu sequence as demonstrated by the higher melting temperatures, the faster triple-helix folding, and the lower minimum concentration necessary to detect triple-helicity for the single-chain structures. Therefore, we conclude that the Nleu residue in the second position of the trimeric repeat is more effective in inducing triple-helix formation than Pro in the same position.
Feng
Y
Y
Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0343, USA.
Melacini
G
G
Goodman
M
M
D000595:Amino Acid Sequence; D002942:Circular Dichroism; D003094:Collagen / Q000031:analogs & derivatives*; D019855:Ethylene Glycol; D005026:Ethylene Glycols; D013058:Mass Spectrometry; D008956:Models, Chemical; D009904:Optical Rotation; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D034444:Peptoids; D017433:Protein Structure, Secondary; D012996:Solutions
D005026:Ethylene Glycols; D010455:Peptides; D034444:Peptoids; D012996:Solutions; D003094:Collagen; D019855:Ethylene Glycol