Vibrational circular dichroism spectra of proteins in the amide III region: measurement and correlation of bandshape to secondary structure.
Vibrational circular dichroism (VCD) spectra have been measured for 23 globular proteins dissolved in H2O/phosphate buffer over the 1400 to 1100 cm(-1) region which encompasses the amide III mode. Spectral responses characteristic of the dominant secondary structure type were found as broad features at approximately 1300 cm(-1), with the extreme forms having positive VCD for highly helical proteins and negative VCD for highly sheet-containing proteins. Quantitative correlation with secondary structure was carried out using previously developed factor analysis and restricted multiple regression (FA/RMR) techniques. Since the absorbance intensity of the amide III mode is difficult to determine due to overlap with other transitions, an alternative, absolute intensity-independent, simple structural analysis method was used. A linear regression was developed between the fractional components of secondary structure for the protein set and the overlap integrals of the normalized spectra from the set with that of a selected protein. The results of this simple method are quite comparable to those of the FA/ RMR approach for analysis with amide III VCD. On the other hand, test calculations with the new method when used with electronic CD spectra are not as good as FA/RMR due to its more intensity-dependent relationship with secondary structure.
Baello
B I
BI
Department of Chemistry, University of Illinois at Chicago, 60607-7061, USA.
Pancoska
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P
Keiderling
T A
TA
D002942:Circular Dichroism; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D013223:Statistics as Topic
D011506:Proteins