Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

• Published in: Journal of the American Chemical Society Vol. 126; no. 25; pp. 7981 - 7990
• Main Authors: Demirdöven, Nurettin, Cheatum, Christopher M, Chung, Hoi Sung, Khalil, Munira, Knoester, Jasper, Tokmakoff, Andrei
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 30.06.2004
• Subjects: Amides - chemistry; Biological and medical sciences; Concanavalin A - chemistry; Electronic structure; Fundamental and applied biological sciences. Psychology; Hydrogen Bonding; Molecular biophysics; Muramidase - chemistry; Myoglobin - chemistry; Peptides - chemistry; Polylysine - chemistry; Protein Structure, Secondary; Proteins - chemistry; Ribonuclease, Pancreatic - chemistry; Spectrophotometry, Infrared - methods; Spectroscopy, Fourier Transform Infrared - methods; Structure in molecular biology; Infrared spectrometry; Vibrational transition; Electronic structure; Molecular structure; Electron delocalization; Biological macromolecule; Secondary structure; Aminoacid polymer; Two dimension spectrometry; Conformational transition
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja049811j

We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-l-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-l-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.