Induced chirality upon binding of cis‐parinaric acid to bovine β‐lactoglobulin: spectroscopic characterization of the complex

Abstract

Binding of the polyunsaturated cis-parinaric acid to bovine L L-lactoglobulin (BLG) was studied by circular dichroism (CD), electronic absorption spectroscopy and mass spectrometry methods. Upon protein binding, the UV absorption band of parinaric acid is red shifted by ca. 5 nm, showing hypochromism and reduced vibrational fine structure, suggesting that the ligand binds as a monomer in non-planar geometry. In the CD spectra measured at pH 7.36 and 8.5 a strong, negative Cotton band appears centered at 310 nm (v vO O = 3 325 M 31 cm 31 ) corresponding to the long-wavelength absorption band of cis-parinaric acid. The source of this induced optical activity is the helical distortion of the polyene chromophore caused by the chiral protein environment. From CD spectral data the value of the association constant was calculated to be 4.7U U10 5 M 31 at pH 7.36. CD and mass spectrometry measurements showed that parinaric acid binds weakly to BLG in acidic solution, though small peaks at mass 18559 and 18645 can be obtained in the reconstructed electrospray mass spectrum; these correspond to the binding of parinaric acid in 1:1 stoichiometry to both monomer variants of BLG B and A. The hydrophobic interior cavity of BLG was assigned as the primary binding site of cisparinaric acid. ß 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.

Modulation of the reactivity of the thiol of human serum albumin and its sulfenic derivative by fatty acids

“…The concentration of working solutions was determined from the absorbance at 305 nm (74200 M −1 cm −1 [29] in ethanol). FA-free HSA, either reduced or oxidized to sulfinic acid (10 mM H 2 O 2 , 10 min, 37 ºC), was purified by ion-exchange chromatography as described above.…”

Supramolecular Anchoring of NCN‐Pincer Palladium Complexes into a β‐Barrel Protein Host: Molecular‐Docking and Reactivity Insights

“…The near‐UV circular dichroism spectrum of β‐LG displays a pattern of negative bands between 250 and 310 nm assigned to its aromatic residues . Binding of a chromophore to β‐LG may induce a change of the CD spectrum caused by its presence in the chiral environment of the protein (extrinsic effect) or by perturbation of the environment of the aromatic residues (intrinsic effect) . Unfortunately, no significant change of the near‐UV CD spectrum of the protein was noticed upon addition of ligands 6aa′ – 6ca′ (1 equiv.)…”

Physicochemical characterization and in vitro digestibility of β-lactoglobulin/β-Lg f142-148 complexes

“…The spectrum obtained for b-Lg A (Fig. 3A) shows a typical mass spectrum profile with a major peak at 18,367.4 Da, corresponding to the molecular mass of the protein (Imre, Zsila, & Szabo, 2003;Leonil et al, 1997;Zsila, Imre, Szabo, Bikadi, & Simonyi, 2002). Other minor peaks observed at 18,582 and 18,694 Da are likely due to lactosylated conjugates (Leonil et al, 1997;Zsila et al, 2002).…”