title: A vibrational spectral maker for probing the hydrogen-bonding status of protonated Asp and Glu residues.
abstract: Hydrogen bonding is a fundamental element in protein structure and function. Breaking a single hydrogen bond may impair the stability of a protein. We report an infrared vibrational spectral marker for probing the hydrogen-bond number for buried, protonated Asp or Glu residues in proteins. Ab initio computational studies were performed on hydrogen-bonding interactions of a COOH group with a variety of side-chain model compounds of polar and charged amino acids in vacuum using density function theory. For hydrogen-bonding interactions with polar side-chain groups, our results show a strong correlation between the C=O stretching frequency and the hydrogen bond number of a COOH group: approximately 1759-1776 cm(-1) for zero, approximately 1733-1749 cm(-1) for one, and 1703-1710 cm(-1) for two hydrogen bonds. Experimental evidence for this correlation will be discussed. In addition, we show an approximate linear correlation between the C=O stretching frequency and the hydrogen-bond strength. We propose that a two-dimensional infrared spectroscopy, C=O stretching versus O-H stretching, may be employed to identify the specific type of hydrogen-bonding interaction. This vibrational spectral marker for hydrogen-bonding interaction is expected to enhance the power of time-resolved Fourier transform infrared spectroscopy for structural characterization of functionally important intermediates of proteins.
authors.affiliation: Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
authors.forename: Beining
authors.initials: B
authors.lastname: Nie
authors.forename: Jerrod
authors.initials: J
authors.lastname: Stutzman
authors.forename: Aihua
authors.initials: A
authors.lastname: Xie
mesh_terms: D001224:Aspartic Acid / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D001703:Biophysics / Q000379:methods*; D002244:Carbon / Q000737:chemistry; D018360:Crystallography, X-Ray; D018698:Glutamic Acid / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D020283:Photoreceptors, Microbial / Q000737:chemistry; D011487:Protein Conformation; D011522:Protons; D013053:Spectrophotometry / Q000379:methods*; D013055:Spectrophotometry, Infrared; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation / Q000379:methods*; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014732:Vibration
chemical_list: D001426:Bacterial Proteins; D020283:Photoreceptors, Microbial; D011522:Protons; C050162:photoactive yellow protein, Bacteria; D001224:Aspartic Acid; D018698:Glutamic Acid; D002244:Carbon; D006859:Hydrogen; D010100:Oxygen