TY - JOUR
T1 - FTIR spectra of solid poly-l-lysine in the stretching NH mode range
AU - Rozenberg, M.
AU - Shoham, G.
PY - 2007/1
Y1 - 2007/1
N2 - Three bands at 3270 cm- 1, 3200 cm- 1 and 3030 cm- 1 are found in the IR stretching proton (ν1) mode spectral range in spectra of solid poly-l-lysine (PLL). Strong quantitative changes of these bands are observed in samples dried from water solutions with different pH. The narrow band at 3270 cm- 1, which is strong in the spectrum of PLL precipitated from pH = 12 alkaline medium, is assigned to the ν1 peptide proton mode of NH-CO (amide A) of the β-sheet structure type. The band at 3200 cm- 1, which is intensified in PLL precipitated from pH = 1 acidic medium, relates to the ν1 peptide mode in the random coil structure. The band at 3030 cm- 1, whose peak intensity increases two-fold in going from alkaline to acidic medium, is assigned to the ν1 modes of protonated NH3+ side chain groups. The frequencies of all bands were used for estimating H-bond energy relying on an empirical correlation between this property and the red shift of the ν1 band. The enthalpy of the secondary structure transition from β-sheet to the random coil, which is observed in PLL at the change of pH from 11 to 1 amounts to 4.7 kJ mol- 1.
AB - Three bands at 3270 cm- 1, 3200 cm- 1 and 3030 cm- 1 are found in the IR stretching proton (ν1) mode spectral range in spectra of solid poly-l-lysine (PLL). Strong quantitative changes of these bands are observed in samples dried from water solutions with different pH. The narrow band at 3270 cm- 1, which is strong in the spectrum of PLL precipitated from pH = 12 alkaline medium, is assigned to the ν1 peptide proton mode of NH-CO (amide A) of the β-sheet structure type. The band at 3200 cm- 1, which is intensified in PLL precipitated from pH = 1 acidic medium, relates to the ν1 peptide mode in the random coil structure. The band at 3030 cm- 1, whose peak intensity increases two-fold in going from alkaline to acidic medium, is assigned to the ν1 modes of protonated NH3+ side chain groups. The frequencies of all bands were used for estimating H-bond energy relying on an empirical correlation between this property and the red shift of the ν1 band. The enthalpy of the secondary structure transition from β-sheet to the random coil, which is observed in PLL at the change of pH from 11 to 1 amounts to 4.7 kJ mol- 1.
KW - FTIR
KW - Hydrogen bonding
KW - Poly-l-lysine secondary structure
UR - http://www.scopus.com/inward/record.url?scp=33750741900&partnerID=8YFLogxK
U2 - 10.1016/j.bpc.2006.07.008
DO - 10.1016/j.bpc.2006.07.008
M3 - Article
C2 - 16919385
AN - SCOPUS:33750741900
SN - 0301-4622
VL - 125
SP - 166
EP - 171
JO - Biophysical Chemistry
JF - Biophysical Chemistry
IS - 1
ER -