UV Transition Moments of Tyrosine
Artikel i vetenskaplig tidskrift, 2014

To assist polarized-light spectroscopy for protein-structure analysis, the UV spectrum of p-cresol, the chromophore of tyrosine, was studied with respect to transition moment directions and perturbation by solvent environment. From linear dichroism (LD) spectra of p-cresol aligned in stretched matrices of poly(vinyl alcohol) and polyethylene, the lowest pi-pi* transition (L-b) is found to have pure polarization over its entire absorption (250-300 nm) with a transition moment perpendicular to the symmetry axis (C-1-C-4), both in polar and nonpolar environments. For the second transition (L-a), polarized parallel with the symmetry axis, a certain admixture of intensity with orthogonal polarization is noticed, depending on the environment. While the L-b spectrum in cydohexane shows a pronounced vibrational structure, it is blurred in methanol, which can be modeled as due to many microscopic polar environments. With the use of quantum mechanical (QM) calculations, the transition moments and solvent effects were analyzed with the B3LYP and omega B97X-D functionals in cyclohexane, water, and methanol using a combination of implicit and explicit solvent models. The blurred L-b band is explained by solvent hydrogen bonds, where both accepting and donating a hydrogen causes energy shifts. The inhomogeneous solvent-shift sensitivity in combination with robust polarization can be exploited for analyzing tyrosine orientation distributions in protein complexes using LD spectroscopy.

p-cresol

spectra

protein-structure

optical-properties

circular-dichroism

rad51 filament

aromatic-amino-acids

hydrogen-bonds

linear dichroism spectroscopy

raman-spectroscopy

Författare

Louise Fornander

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Bobo Feng

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Tamas Beke-Somfai

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Bengt Nordén

Chalmers, Kemi- och bioteknik, Fysikalisk kemi

Journal of Physical Chemistry B

1520-6106 (ISSN) 1520-5207 (eISSN)

Vol. 118 31 9247-9257

Ämneskategorier

Fysikalisk kemi

DOI

10.1021/jp5065352