Drug-antiserum molecular interactions: a Raman spectroscopic study

Abstract

The binding of the phenytoin (5,5-diphenyl-2,4-imidazolidinedione) antiserum with its specific antigen and other chemicals with very low cross-reactivity coefficients was studied by means of Raman spectroscopy. The experimental results indicate that the predominant secondary structure of this antiserum is the bsheet conformation and that the interaction with the ligands is able to modify the overall structure of the protein. The antiserum-antigen binding causes a slight decrease in the random conformation in all systems, whereas the changes in the b-sheet and a-helix content depend on the nature of the ligands. Ligands with a high cross-reactivity coefficient increase the a-helix percentage, whereas the opposite effect is observed with low cross-reactivity ligands. The stereochemical properties of the substituents in the 5-position of the heterocyclic ring, relative to the rest of the molecule, are an important factor in determining the crossreactivity and the kind of interaction with the antiserum. If in this position only one phenyl group is present, the antiserum-ligand affinity is low and the a-helix percentage decreases, but when in this position two phenyl groups are present, the affinity is high and the a-helix percentage increases. As regards the tertiary structure of the antiserum protein, alkyl side-chains and Trp residues contribute to the stability of the antiserum-specific antigen complex by means of hydrophobic interactions. The spectral features of alkyl side-chains and Trp do not change in the presence of ligands with low affinity.

The Reductive Desulfurization of Met and Cys Residues in Bovine RNase A Is Associated with trans Lipids Formation in a Mimetic Model of Biological Membranes

“…To probe the extent of the conformational changes induced by the radical attack, the analysis of the amide I band was performed by curve fitting (Figure B). All the components were assigned to a particular secondary structure on the basis of previous reports, – and the conformational contents were calculated from the integrated intensities of the individual assigned bands. Although this method does not yield the absolute content of the secondary structures (since the effective intensities of the bands corresponding to different structure elements are not completely equivalent), it may be used to demonstrate protein conformational changes induced by external factor interaction, such as radical attack.…”

Thermomyces lanuginosus lipase in the liquid-crystalline phases of aqueous phytantriol: X-ray diffraction and vibrational spectroscopic studies

“…on the parameters of amide group vibrations [39]. The spectral region below 1630 cm -1 was fitted by 5-6 relatively narrow, with full width at half maximum (FWHM) of 5-12 cm -1 , components representing vibrations of Trp, Phe, and Tyr residues, while amide vibrational contour (1630-1720 cm -1 ) was fitted by five component bands assigned to α-helix (1652-1655 cm -1 ), organized β-sheet (1669-1672 cm -1 ), strongly hydrogen bonded disordered (1630-1645 cm -1 ), and two non-hydrogen bonded disordered (1680-1693 and 1696-1702 cm -1 ) secondary structures [39][40][41][42][43][44]. The high frequency disordered structure components might incorporate vibrations of loose β-strands and polyproline II (PPII) structural elements [39], while the low frequency disordered structure component might have the contribution from the vibronic coupling modes [39,45].…”

Probing of Lipase Activity at Air/Water Interface by Sum-Frequency Generation Spectroscopy

“…This feature falls into the frequency region (1610−1695 cm -1 ) characteristic for a particular vibration of protein amide linkages called amide I mode . The main contribution for amide I vibration comes from the backbone CO stretching motion (83%) coupled with an out-of-phase C−N stretching and C−C−N deformation, therefore frequency of this mode is sensitive to the secondary structure of polypeptide chains. − TLL is a 269 amino acid residue enzyme and according to X-ray diffraction data it consists of a single spherical domain with the central sheet composed of eight predominantly parallel β-pleated sheets with five interconnecting α-helixes . The contents of α-helixes, β-sheets and turns, and 3 10 -helixes determined by X-ray crystallography were found to be 26, 26, and 7% of the overall amide bonds, respectively .…”