W. Shalongo et al., ANALYSIS OF THE THERMAL TRANSITIONS OF A MODEL HELICAL PEPTIDE USING C-13 NMR, Journal of the American Chemical Society, 116(6), 1994, pp. 2500-2507
The thermal dependence of the C-13 reonances of individual residues in
the model peptide, acetylW(EAAAR)3-Aamide, was analyzed in terms of a
two-state transition. The correlation of the effects of temperature,
pH, and salt concentration on C-13 NMR and circular dichroic measureme
nts of this peptide suggest that both measurements observe a common tw
o-state helix/coil transition. The thermodynamic parameters which char
acterize the thermal transition of each residue suggest that the helic
al conformation of the peptide is stabilized by hydrogen bonds and by
burial of apolar surfaces and that the helical conformation melts as a
largely cooperative unit. The terminal regions of the helix appear le
ss frayed than expected from the Lifson-Roig statistical mechanical mo
del for a peptide helix/coil transition, indicating contributions from
stabilizing noncovalent interactions in addition to backbone hydrogen
bonds.