Water-induced switching of β-structure to polyproline II conformation in the 4S-aminoproline polypeptide via H-bond rearrangement.
4S-Aminoproline polypeptide 2 forms unusual β-structure in trifluoroethanol that switches to the polyproline II (PPII) form in aqueous medium, while 4R-aminoproline peptide 1 retains PPII form in both solvents. This first instance of a polyproline derivative showing a β-structure is attributed to competitive pH-dependent (4-NH(3)(+)/NH(2)) stereoelectronic effect (4R vs 4S) and the overriding importance of stereospecific intra/intermolecular H-bonding in (2,4)-cis-4S-aminoproline in contrast to (2,4)-trans-4R-aminoproline oligomers.
Division of Organic Chemistry, National Chemical Laboratory, Dr Homi Bhabha Road, Pune 411008, India.
Mahesh V
MV
Sonar
Krishna N
KN
Ganesh
D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000737:chemistry*; D011392:Proline / Q000031:analogs & derivatives* / Q000737:chemistry; D017433:Protein Structure, Secondary; D013237:Stereoisomerism; D014867:Water / Q000737:chemistry*
D010455:Peptides; C467925:aminoproline; D014867:Water; C011083:polyproline; D011392:Proline