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The interaction between apo-human serum transferrin (Apo-hTf) and alprazolam was investigated using various spectroscopic techniques. The drug quenched the fluorescence intensity of Apo-hTf and the mechanism behind the quenching was static. The thermodynamic parameters (ΔG, ΔH, and ΔS) that obtained from tryptophan fluorescence study revealed that the interactions between alprazolam and Apo-hTf were spontaneous. Collectively, hydrophobic interactions and hydrogen bonding most likely played major roles in Apo-hTf/alprazolam interactions. Also, the absorption spectra of Apo-hTf increased in the presence of increasing concentration of alprazolam, reflecting Apo-hTf structural alteration after drug’s binding. The CD results demonstrated that the Apo-hTf/alprazolam interaction does not affect the protein secondary and tertiary structure significantly until the molar ratios (alprazolam/Apo-hTf) of 10, but the conformational changes become visible at higher molar ratios. The DSC results suggested that alprazolam stabilized the Apo-hTf at alprazolam/Apo-hTf molar ratio of 20. Based on the achieved results, this potentially therapeutic agent can significantly bind to Apo-hTf which also further confirmed by molecular docking study. This study on the interaction of the drug with Apo-hTf should be helpful for understanding the transportation and distribution of drugs in vivo , as well as the action mechanism and dynamics of a drug at the molecular level. [ABSTRACT FROM AUTHOR]

β-Lactoglobulin (β-LG) is a member of lipocalin superfamily of transporters for small hydrophobic molecules. β-LG is also one of the major allergens in milk. Despite a lot of researches on decreasing of cow's milk allergenicity, the effects of the mutation of β-LG on its recognition by IgE from cow's milk allergy (CMA) patients have not been investigated. We described here the expression in the yeast Pichia pastoris of a mutant β-LG, in which Alanine 86 was changed into Glutamine (Ala86Gln; a mutation on one of the major epitopes of the protein). The purity and native like folded structure of the recombinant Ala86Gln have been demonstrated using circular dichroism, HPLC, SDS-PAGE and mass spectrometry. The effect of the mutation on the binding of IgE from CMA patients to mutant protein was evaluated by ELISA methods and the results showed that the mutation of Ala-86 was associated with weaker binding of IgE from CMA patients to Ala86Gln mutant protein. Subsequently, the binding of various ligands such as retinol, palmitic acid, resveratrol and serotonin, with native, recombinant wild type and Ala86Gln mutant β-LGs were investigated by fluorescence spectroscopy and an improvement on the binding affinity of the mutated protein to various ligands was observed. [ABSTRACT FROM AUTHOR]

Abstract: Bovine β-lactoglobulin (β-LG) present in milks has been found “in vivo” in complexes with lipids such as butyric and oleic acids. To elucidate the still unknown structure–function relationship in this protein, the structural changes of β-lactoglobulin variant A (β-LG A) in the presence of cationic surfactant such as dodecyltrimethyl ammonium bromide (DTAB) have been investigated using various experimental techniques such as UV–vis spectrophotometry, fluorimetry, isothermal titration calorimetry (ITC) and circular dichroism (CD). Subsequently, the retinol binding by β-LG has been investigated in the presence of various amounts of this surfactant as its extrinsic functional binding fluorophore. Comparison of the results allowed to determine the binding of retinol by β-LG in the presence of DTAB. The results of UV–vis and fluorescence studies showed a red shift in wavelength and an increase in absorbance and enhancement in the intensity of the quantum yield of protein during its interaction with DTAB. The results of UV–vis also showed two distinct conformational changes corresponding first to precipitation and second to solubilization of the precipitated β-LG at pH 6.7 and 8.0. The results indicate the cooperative character of binding at pH 2.0. The results of fluorescence studies showed that the binding strength of β-LG/DTAB complex increases with the increase of the pH. CD results showed the shifts in positions of the major minima and change in magnitude of ellipticity and subsequently signified two significant changes in structure of β-LG between 10–30 and 50–100 molar ratio of [DTAB]/[β-LG]. ITC measurements indicated the endothermic nature of β-LG/DTAB interactions at pH 6.7 and the exothermic nature of β-LG/DTAB interactions at pH 8.0. The analysis of the binding data demonstrates the absence of significant changes in retinol-binding properties of β-LG in the presence of various amounts of this surfactant. This implies that surfactant binding does not change the conformation of β-LG in the regions defining retinol-binding site nor interferes with retinol binding by a competition for the same binding site(s). [Copyright &y& Elsevier]

This study describes HSA binding properties of two cyclometalated platinum (II) complexes with non-leaving lipophilic ligands; deprotonated 2-phenylpyridine (ppy): C 1 and deprotonated benzo [h]quinolone (bhq): C 2 , using UV–vis, fluorescence and circular dichroism (CD) spectroscopy. The absorption spectra of HSA decreased in the presence of increasing concentration of these complexes, reflecting HSA structural alteration after drug׳s binding. Also the thermodynamic parameters (Δ G , Δ H and Δ S ) that obtained from Trp fluorescence study revealed that the interaction between these complexes and HSA were spontaneous. In addition, C 1 with flexible chemical structure indicated significantly higher fluorescence quenching and binding affinity to HSA than C 2 which possesses a higher structural rigidity. The ANS fluorescence results also indicated that two Pt (II) complexes were competing for binding to the hydrophobic regions of HSA. Moreover, CD results demonstrated that C 2 complex induced alteration of HSA conformation to more significant extent compared to C 1 . The molecular docking results revealed the involvement of π – π stacking and hydrophobic interaction between these complexes and the protein. Overall, this study may highlight the significance of structural flexibility in designing of future anticancer Pt (II) complexes with improved binding affinity for HSA. [ABSTRACT FROM AUTHOR]

Highlights: [•] The novel PFH derivatives (L 1 –L 4 ) efficiently interacted with β-LG due to a ground state complex formation. [•] The ligands and β-LG form a single complex (1:1) and L 4 proved to have highest affinity towards β-LG. [•] The nature of interactions was proved to be hydrophobic, hydrogen bonding and vander Waals forces. [•] No structural alteration was induced in the secondary structures of β-LG due to the complexation with ligands. [ABSTRACT FROM AUTHOR]

• Binding of the EA to HSA was studied by spectroscopic and computational methods. • The negative amount of ΔG° revealed that HSA interaction with EA is spontaneous. • Hydrogen bonding and Van der Waals forces are major forces in the complex. • EA is docked in the HSA secondary structure. • The RMSD findings revealed that HSA is very stable due to binding EA on HSA. • The RMSF data indicated the HSA structure's flexibility has diminished. • The EA quenched the fluorescence of HSA via a static quenching mechanism. Elaidic acid (EA) is an unsaturated trans-fatty acid and one of the most important fatty acids obtained from solidifying vegetable oils. The increase in the consumption of EA is associated with rise and decline of LDL-cholesterol and HDL-cholesterol levels, respectively. It activates pro-inflammatory markers in the body and increases heart stroke and cardiovascular diseases. In this study, to understand the impact of EA in humans, we investigated the molecular interaction between EA and human serum albumin (HSA) and its binding affinity using spectroscopic, molecular dynamics (MD), and molecular docking techniques. According to fluorescence quenching experiments, EA could quench the inherent fluorescence of HSA via a static quenching mechanism. The thermodynamic characteristics of EA binding on HSA demonstrated hydrogen bonds and Van der Waals forces within the interaction, which matched molecular docking results. Further, the negative amount of ΔG° indicated the spontaneous binding of HSA to EA. Based on Förster's resonance energy transfer, the spatial distance between EA and HSA was 3.493 nm. The far-UV circular dichroism spectrum showed the decrease in the contents of the β-sheet and α-helix in the HSA structure. According to the RMSF data, the HSA structure's flexibility was diminished. The molecular dynamic simulation and spectroscopic studies also indicated that the binding interactions altered the milieu of the Trp chromophore and HSA structures. All experimental data could be matched with molecular dynamics simulation. [Display omitted] [ABSTRACT FROM AUTHOR]