4(R/S)-Amino/Guanidino-substituted Proline Peptides: Design, Synthesis and DNA Transfection Properties

Abstract

Collagen is a major structural protein found in the connective tissues of higher organisms and mammals and its biomechanical properties are related to the high thermal stability of its triple helical structure. The primary structure of collagen is composed of the repeating tripeptide motif of Pro-Hyp-Gly, where Hyp is 4 R -hydroxy proline. Cationic collagen mimetics consisting of [Pro(X)-Pro(Y)-Gly](6) where Pro(X) and Pro(Y) are 4(R/S)-amino/guanidine proline have been synthesized and shown to form triplexes more stable than the unmodified collagen peptide [Pro-Hyp-Gly](6). The origin of hyperstability is due to conformational pre-organization of proline pucker arising from the electronegativity of the cationic group. These cationic collagen peptides are shown to be effective cell penetrating and plasmid DNA transfecting agents. The results have potential for design of new collagen mimetics for biomaterial applications and efficient cell penetrating agents for drug delivery applications.

Spiegelmeric 4R/S‐hydroxy/amino‐L/D‐prolyl collagen peptides: conformation and morphology of self‐assembled structures

“…The protected monomer 4 R‐ O 4 (tButyl)‐N1(Fmoc)‐ L Hyp ( 1 ) is commercially available and 4 R‐ N 4 H(Boc)‐N1(Fmoc)‐ L Amp ( 3 ) needed for assembling collagen L‐peptides P1 and P3 was synthesized starting from the commercial 4 R ‐hydroxy‐L‐proline using reaction protocols as described in earlier literature . The protected monomers 4 S‐ O 4 (tButyl)‐N1(Fmoc)‐ D Hyp ( 2 ) and 4 S‐ N 4 H(Boc)‐N1(Fmoc)‐ D Amp ( 4 ) necessary for synthesis of corresponding enantiomeric D‐OH/NH 2 collagen peptides ( P2 and P4 , Figure ) were synthesized as shown in Scheme .…”

“…4 R ‐(OH)‐D‐proline 6 was synthesized from commercially available 4 R ‐(OH)‐L‐proline according to literature procedure . 4 R / S ‐O 4 (t‐Bu)‐N1‐(Fmoc)‐D‐proline ( 1 , 2 ) and 4 R / S ‐N 4 (Boc)‐N1‐(Fmoc)‐D‐proline ( 3 , 4 ) were synthesized from 4 R ‐hydroxy‐L‐proline by sequential transformation of functional groups, protection/ deprotection strategies as described previously …”

“…All peptides were synthesized manually in sintered glass vessel equipped with stopcock using standard protocols . Rink amide resin with loading value 0.6 mmol/g was used using standard Fmoc chemistry.…”

Orchestration of Structural, Stereoelectronic, and Hydrogen-Bonding Effects in Stabilizing Triplexes from Engineered Chimeric Collagen Peptides (ProX-ProY-Gly)6 Incorporating 4(R/S)-Aminoproline

“…The amino group being a chemically reactive functionality, the results would be useful in design of chimeric hyperstable collagen peptides with potential to hybridize with natural collagens and cross-link further to form fibrils. Such supramolecular composites may have implications for creating new functional materials for biomedical applications, drug/gene delivery, and tissue engineering …”