C-D modes of deuterated side chain of leucine as structural reporters via dual-frequency two-dimensional infrared spectroscopy

J Phys Chem B. 2009 Apr 9;113(14):4940-6. doi: 10.1021/jp8112446.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anisotropy
  • Computer Simulation
  • Energy Transfer
  • Leucine / chemistry*
  • Models, Chemical
  • Molecular Structure
  • Proteins / chemistry
  • Spectrophotometry, Infrared / methods
  • Time Factors

Substances

  • Proteins
  • Leucine