Temperature dependence of water interactions with the amide carbonyls of α-helices.
Hydration is a key determinant of the folding, dynamics, and function of proteins. In this study, temperature-dependent Fourier transform infrared (FTIR) spectroscopy combined with singular value decomposition (SVD) and global fitting were used to investigate both the interaction of water with α-helical proteins and the cooperative thermal unfolding of these proteins. This methodology has been applied to an isolated α-helix (Fs peptide) and to globular α-helical proteins including the helical subdomain and full-length villin headpiece (HP36 and HP67). The results suggest a unique IR signature for the interaction of water with the helical amide carbonyl groups of the peptide backbone. The IR spectra indicate a weakening of the net hydrogen bond strength of water to the backbone carbonyls with increasing temperature. This weakening of the backbone solvation occurs as a discrete transition near the maximum of the temperature-dependent hydrophobic effect, not a continuous change with increasing temperature. Possible molecular origins of this effect are discussed with respect to previous molecular dynamics simulations of the temperature-dependent solvation of the helix backbone.
Department of Chemistry, Franklin & Marshall College, Lancaster, PA 17604-3003, USA.
Scott H
SH
Brewer
Yuefeng
Y
Tang
Dung M
DM
Vu
S
S
Gnanakaran
Daniel P
DP
Raleigh
R Brian
RB
Dyer
D000577:Amides / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D014867:Water / Q000737:chemistry*
D000577:Amides; D010455:Peptides; D014867:Water