Reengineering a Type II b -Turn as a Potential Helix Nucleator-NMR Characterization of Boc-Ala-Val-Pro-(D) Asp-Leu-Leu-NHMe
E.B. Raju 1 , M. Dhanasekaran 1 , S. Durani 1 , S. Srivastava 2,*
1. Department o f Chemistry &
Biotechnology Centre, Indian Institute of Technology, Bombay,
India 400 076 (India)
2. National Facility for High Field
NMR, Tata Institute of Fundamental Research, Homi Bhabha Road,
Navy Nagar, Mumbai -400005 (India)
Manuscript received: May 3, 1999; revised: July 29, 1999.
Accepted for publication: September 10, 1999.
Abstract
A stereochemically constrained type II b -turn is reengineered over two steps into a potential helix nucleator. NMR studies in DMSO establish that the hexapeptide Boc-Ala1-Val2-Pro3-(D)Asp4-Leu5-Leu6-NHMe is a type II b -turn at Pro3-(D)Asp4 with a conformation nucleating H-bond between Asp4 carboxylate and Leu6 NH, to which is attributable a type I/III b -turn at Leu5-Leu6- NHMe potentially capable of serving as a helix template.
KEYWORDS: Type II b -turn, D-amino acid, Peptide, NMR, Helix.
Abbreviations
NMM-N-Methyl Morpholine, IBCF-Isobutyl chloroformate, DCC - Dicyclohexyl carbodiimide, HOBt - Hydroxy benzotriazole, TFA-Trifluoroacetic Acid, COSY-Correlation spectroscopy, TOCSY-Total Correlation spectroscopy, ROESY-Rotating frame nuclear Overhauser enhancement spectroscopy, NOE- Nuclear Overhauser effect.