Tyrosine Raman Signatures of the Filamentous Virus Ff Are Diagnostic of Non-Hydrogen-Bonded Phenoxyls:  Demonstration by Raman and Infrared Spectroscopy of p-Cresol Vapor^,

Abstract

p-Cresol is a simple molecular model for the para phenolic side chain of tyrosine. Previously, Siamwiza and co-workers [(1975) Biochemistry 14, 4870-4876] investigated p-cresol solutions to identify Raman spectroscopic signatures for different hydrogen-bonding states of the tyrosine phenoxyl group in proteins. They found that the phenolic moiety exhibits an intense Raman doublet in the spectral interval 820-860 cm(-1) and that the doublet intensity ratio (I2/I1, where I2 and I1 are Raman peak intensities of the higher- and lower-wavenumber members of the doublet) is diagnostic of specific donor and acceptor roles of the phenoxyl OH group. The range of the doublet intensity ratio in proteins (0.30 < I2/I1 < 2.5) was shown to be governed by Fermi coupling between the phenolic ring-stretching fundamental nu1 and the first overtone of the phenolic ring-deformation mode nu(16a), such that when the tyrosine phenoxyl proton is a strong hydrogen-bond donor, I2/I1 = 0.30, and when the tyrosine phenoxyl oxygen is a strong hydrogen-bond acceptor, I2/I1 = 2.5. Here, we interpret the Raman and infrared spectra of p-cresol vapor and extend the previous correlation to the non-hydrogen-bonded state of the tyrosine phenoxyl group. In the absence of hydrogen bonding, the Raman intensity of the higher-wavenumber component of the canonical Fermi doublet is greatly enhanced such that I2/I1 = 6.7. Thus, for the non-hydrogen-bonded phenoxyl, the lower-wavenumber member of the Fermi doublet loses most of its Raman intensity. This finding provides a basis for understanding the anomalous Raman singlet signature (approximately 854 cm(-1)) observed for tyrosine in coat protein subunits of filamentous viruses Ff and Pf1 [Overman, S. A., et al. (1994) Biochemistry 33, 1037-1042; Wen, Z. Q., et al. (1999) Biochemistry 38, 3148-3156]. The implications of the present results for Raman analysis of tyrosine hydrogen-bonding states in other proteins are considered.

Consistent assignment of the vibrations of symmetric and asymmetric para-disubstituted benzene molecules

“…The values in Table 5 for p-cresol predominantly come from the gas-phase IR results of Arp et al [54] with one value coming from the gas phase IR spectrum of Jakobsen [55] while in the cases where values were not available, the liquid-phase IR and then Raman values were employed, with the preference in that order from the same work; a couple of the values are taken from the liquid phase…”

The structure of 4-methylphenol and its water cluster revealed by rotationally resolved UV spectroscopy using a genetic algorithm approach

“…5 4-methylphenol has found considerable interest as a chromophore and simple molecular model of the aromatic amino acid tyrosine. 6 Proton transfer, electron transfer, and hydrogen transfer are important processes in clusters of tyrosine. E.g., in the water oxidizing complex of photosystem II, tyrosine is oxidized and reduced by hydrogen atom transfer involving tyrosine, water, and histidine in the active center.…”

UV Raman Markers for Structural Analysis of Aromatic Side Chains in Proteins

“…43 The doublet was reported to become a singlet when the phenol ring is not hydrogen bonded in a strongly hydrophobic environment or in vacuo. 44,45 This observation raises the possibility that the Fermi resonance may also be affected by intermolecular interactions other than hydrogen bonding. In UV Raman spectra, the intensity ratio I850/I830 slightly deviates from the values found with visible light excitation.…”