title: C-D modes of deuterated side chain of leucine as structural reporters via dual-frequency two-dimensional infrared spectroscopy.
abstract: Perdeuteration of the side chains of amino acids such as leucine results in appearance of reasonably strong absorption peaks around 2050-2220 cm(-1) that belong to the CD stretching modes and exhibit extinction coefficients of up to 120 M(-1) cm(-1). The properties of the CD stretching transitions in leucine-d(10) as structural labels are studied via the methods of two-dimensional infrared (2DIR) spectroscopy. The cross peaks caused by interactions of the CD stretching modes with amide I (Am-I), CO, and amide II (Am-II) modes are obtained by the dual-frequency 2DIR method. The CD stretching peaks in leucine-d(10) are characterized using DFT computational modeling as well as relaxation-assisted 2DIR (RA 2DIR) measurements. The RA 2DIR measurements showed different enhancements and different energy transport times (arrival times) for different CD/Am-II and CD/CO cross peaks; a correlation between the intermode distance, the arrival time, and the amplification factor is reported. We demonstrated that the CD transitions of leucine-d(10) amino acid can serve as convenient structural reporters via the dual-frequency 2DIR methods and discussed the potential of leucine-d(10) and other amino acids with deuterium-labeled side chains as probes of protein structure and dynamics.
authors.affiliation: Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, USA.
authors.forename: Sri Ram G
authors.initials: SR
authors.lastname: Naraharisetty
authors.forename: Valeriy M
authors.initials: VM
authors.lastname: Kasyanenko
authors.forename: Jörg
authors.initials: J
authors.lastname: Zimmermann
authors.forename: Megan C
authors.initials: MC
authors.lastname: Thielges
authors.forename: Floyd E
authors.initials: FE
authors.lastname: Romesberg
authors.forename: Igor V
authors.initials: IV
authors.lastname: Rubtsov
mesh_terms: D016880:Anisotropy; D003198:Computer Simulation; D004735:Energy Transfer; D007930:Leucine / Q000737:chemistry*; D008956:Models, Chemical; D015394:Molecular Structure; D011506:Proteins / Q000737:chemistry; D013055:Spectrophotometry, Infrared / Q000379:methods; D013997:Time Factors
chemical_list: D011506:Proteins; D007930:Leucine