Raman scattering investigation of selenomethionine replacement in protein SOUL crystals

Abstract

The vibrational properties of both wild-type and selenomethionine (SeMet)-substituted protein SOUL crystals have been investigated here by Raman spectroscopy. Several Raman peaks observed in the spectra of methionine and SeMet were identified as specific markers. The unambiguous assignment of these peaks has been inferred by comparing the experimental Raman spectra of the pure amino acids, recorded in solid state and in aqueous solution, and the Raman intensities computed using quantum chemical calculations. Moreover, a quantitative evaluation of the relative amount of SeMet replacement in the crystals of protein SOUL labelled with SeMet has been estimated through the ratio between the Raman intensities of marker peaks. These results offer evidence of the potential of Raman microscopy as a reliable and non-invasive tool for novel in-depth structural investigations in biocrystallography.

Using Raman spectroscopy to understand the origin of the phase transition observed in the crystalline sulfur based amino acid l-methionine

“…To the best of our knowledge, very few Raman studies have been reported to date for the solid crystalline form of l-methionine. Using unpolarized light, one compared the solid-state spectra at 273 and 323 K [14], and the other the spectra observed from solid-states samples and water solutions to theoretical spectra of the single-molecules obtained by quantum chemical calculations [15]. Combining IR and Raman spectroscopy to semi-empirical MNDO conformational analysis [14], it was shown that the phase transition observed by means of calorimetric measurements [16,17] on powder samples at about 307 K is related to the existence of a slightly modified H-bonded double layer giving rise to similar lattice vibrations in both phases.…”

Rapid and Quantitative Determination of S-Adenosyl-L-Methionine in the Fermentation Process by Surface-Enhanced Raman Scattering

“…There is no obvious visible distortion in the optimized curve either. The prominent Raman peaks of SAM at about 677, 729, 1041, 1324, 1405, 1510, and 2920 cm −1 were assigned to ν (CS), ν s (CN), ω (CH2), ν (CC), ν as (CN), and ν (CH 3 ), respectively [22, 23]. The radius of RCF, as a key parameter, was analyzed to achieve the optimal results.…”

Monitoring Preparation of Derivative Protein Crystals via Raman Microscopy

“…This spectral feature can be confidently assigned to the C-Se stretching, in agreement with previous Raman studies on selenium-containing organic compounds (Hamada & Morishima, 1977;Paetzold et al, 1967), and on the selenomethionine aminoacid (Zainal & Wolf, 1995;Lopez et al, 1981). Using these assignments, SeMet Raman peaks have been observed also in the SeMet derivative of protein SOUL (Rossi et al, 2009). In these crystals, a quantitative evaluation of the relative amount of SeMet replacement was also achieved by comparative analysis.…”