Work

2D IR Spectroscopy of Histidine: Probing Side-Chain Structure and Dynamics via Backbone Amide Vibrations

Year: 2014

Type: article

Abstract: It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain. However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult. Herein we show, using a histidine dipeptide as a model, that it is possible to probe the tautomer and protonation status of a histidine residue by measuring the two-dimensional infrared (2D IR) spectrum of its amide I vibrational transition. Specifically, for the histidine dipeptide studied, the amide unit of the histidine gives rise to three spectrally resolvable amide I features at approximately 1630, 1644, and 1656 cm(-1), respectively, which, based on measurements at different pH values and frequency calculations, are assigned to a τ tautomer (1630 cm(-1) component) and a π tautomer with a hydrated (1644 cm(-1) component) or dehydrated (1656 cm(-1) component) amide. Because of the intrinsic ultrafast time resolution of 2D IR spectroscopy, we believe that the current approach, when combined with the isotope editing techniques, will be useful in revealing the structural dynamics of key histidine residues in proteins that are important for function.

Source: The Journal of Physical Chemistry B

DOI: 10.1021/jp411901m

Authors: Ayanjeet Ghosh, Matthew J. Tucker, Feng Gai

Institutions: University of Pennsylvania, University of Nevada, Reno

Language: English

Topic: Spectroscopy and Quantum Chemical Studies

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid

Funders: National Institutes of Health, National Institute of General Medical Sciences

Awards: Ultrafast Processes In Proteins And Other Assemblies, G2020095017, ULTRAFAST PROCESSES IN PROTEINS AND OTHER ASSEMBLIES, ULTRAFAST OPTICAL PROCESSES LABORATORY