The effects of biliverdin on pressure-induced unfolding of apomyoglobin: The specific role of Zn2+ ions

Apomyoglobin (apoMb), a model protein in biochemistry, exhibits a strong propensity to bind various ligands, which makes it a good candidate as a carrier of bioactive hydrophobic drugs. The stability of its hydrophobic pocket determines its potential as a carrier of bioactive compounds. High pressure (HP) is a potent tool for studying protein stability, revealing the specific role of hydrophobic cavities in unfolding. We probed the effects of biliverdin (BV) binding and its complex with Zn 2+ ions on the structure and HP stability of apoMb. CD spectroscopy and SAXS measurements revealed that BV and BV-Zn 2+ complexes make the apoMb structure more compact with higher α-helical content. We performed in-situ HP measurements of apoMb intrinsic fluorescence to demonstrate the ability of BV to stabilise apoMb structure at HP conditions. Furthermore, the presence of Zn 2+ within the apoMb-BV complex significantly enhances the BV stabilisation effect. In-situ visible absorption study of BV chromophore confirmed the ability of Zn 2+ to increase the stability of apoMb-BV complex under HP: the onset of complex dissociation is shifted by ~100 MPa in the presence of Zn 2+. By combining HPfluorescence and HP-visible absorption spectroscopy, our strategy highlights the crucial role of tetrapyrrole-metal complexes in stabilising apoMb hydrophobic pocket

Assessing the potential of para-donor and para-acceptor substituted 5-benzylidenebarbituric acid derivatives as push-pull electronic systems: Experimental and quantum chemical study

Electronic interactions in donor-pi-linker-acceptor systems with barbituric acid as an electron acceptor and possible electron donor were investigated to screen promising candidates with a push-pull character based on experimental and quantum chemical studies. The tautomeric properties of 5-benzylidenebarbituric acid derivatives were studied with NMR spectra, spectrophotometric determination of the pKa values, and quantum chemical calculations. Linear solvation energy relationships (LSER) and linear free energy relationships (LFER) were applied to the spectral data - UV frequencies and C-13 NMR chemical shifts. The experimental studies of the nature of the ground and excited state of investigated compounds were successfully interpreted using a computational chemistry approach including ab initio MP2 geometry optimization and time-dependent DFT calculations of excited states. Quantification of the push-pull character of barbituric acid derivatives was performed by the (CNMR)-C-13 chemical shift differences, Mayer pi bond order analysis, hole-electron distribution analysis, and calculations of intramolecular charge transfer (ICT) indices. The results obtained show, that when coupled with a strong electron-donor, barbituric acid can act as the electron-acceptor in push-pull systems, and when coupled with a strong electron-acceptor, barbituric acid can act as the weak electron-donor

Noncovalent interactions of bovine α-lactalbumin with green tea polyphenol, epigalocatechin-3-gallate

Bovine alpha-lactalbumin (ALA) is an important Ca-binding protein of milk. Epigallocatechin-3-gallate (EGCG) is the major and the most biologically active catechin of green tea, which has the highest binding affinity to whey proteins due to galloyl functional group. In this study experimental and computational methods were used to investigate noncovalent interactions of EGCG and ALA. Binding affinity of EGCG for ALA, determined by fluorescence quenching analysis, was in the range described for complexes of EGCG and other dietary proteins, and lower than affinity of some phenolic compounds to ALA. Based on circular dichroism and Fourier transform infrared spectroscopy spectra, binding of EGCG change ALA conformation inducing alpha-helix to beta-structures transition. The isothermal titration calorimetry results suggest that the binding of EGCG to ALA is enthalpically favorable. The docking analysis shows that EGCG binds in the hydrophobic pocket at the entrance of cleft between alpha-helical and beta-sheetrich domains and includes residues of aromatic cluster II. Uptake of ALA by monocytes proceeds at a slower rate in the presence of EGCG suggesting that EGCG binding may impair uptake of ALA by antigen-presenting cells. ALA, being of low cost and widely available protein, can serve as suitable delivery system for EGCG, as well as for food fortification with this bioactive catechin. (C) 2016 Elsevier Ltd. All rights reserved.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3585

(A) Temperature dependence of 0.5 μM HSA ellipticity at 222 nm in the presence and absence of 0.5 μM PCB; (B) Temperature dependence of 1 μM HSA fluorescence at 340 nm in the presence and absence of 1 μM PCB (λ_EX = 280 nm); (C) SDS-PAGE profile after trypsin digestion of 3.8 μM HSA in the presence and absence of 3.8 μM PCB.

<p>Lane K: HSA without trypsin; lane M: MW markers; lanes 1–6 correspond to digestion times 0.5, 2, 5, 10, 30, and 60 min without PCB, respectively; lanes 7–12 correspond to digestion times 0.5, 2, 5, 10, 30 and 60 min with PCB, respectively.</p

Calculated RMSF values (Å) from molecular dynamics simulation of free HSA, HSA-PCB(IB), and HSA-PCB(IIA).

<p>RMSF values along whole protein sequence (A), sum of RMSF values of each HSA domain (B), and difference of RMSF values between PCB-HSA complexes and free HSA, with marked amino acid (aa) residues involved in PCB binding for site IB (C), and for site IIA (D).</p

A) PCB chemical structure with labeled (A-D) pyrolle rings (oxygen atoms are in red and nitrogen in blue); B) Schematic of HSA structure with domains and ligand binding sites labeled; Radius of gyration (Rg) values (C) and 2D RMDS plots for free HSA (D), HSA-PCB(IIA) (E), and HSA-PCB(IB) (F) during 300 ns molecular dynamic simulation.

<p>A) PCB chemical structure with labeled (A-D) pyrolle rings (oxygen atoms are in red and nitrogen in blue); B) Schematic of HSA structure with domains and ligand binding sites labeled; Radius of gyration (Rg) values (C) and 2D RMDS plots for free HSA (D), HSA-PCB(IIA) (E), and HSA-PCB(IB) (F) during 300 ns molecular dynamic simulation.</p

Covalent binding of food-derived blue pigment phycocyanobilin to bovine β-lactoglobulin under physiological conditions

In this study, we investigated structural aspects of covalent binding of food derived blue pigment phycocyanobilin (PCB) to bovine beta-lactoglobulin (BLG), major whey protein, by spectroscopic, electrophoretic, mass spectrometry and computational methods. At physiological pH (7.2), we found that covalent pigment binding via free cysteine residue is slow (k(a)=0.065 min(-1)), of moderate affinity (K-a=4x10(4) M-1), and stereo-selective. Binding also occurs at a broad pH range and under simulated gastrointestinal conditions. Adduct formation rises with pH, and in concentrated urea (k(a)=0.101 min(-1)). The BLG-PCB adduct has slightly altered secondary and tertiary protein structure, and bound PCB has higher fluorescence and more stretched conformation than free chromophore. Combination of steered molecular dynamic for disulfide exchange, non-covalent and covalent docking, favours Cys119 residue in protein calyx as target for covalent BLG-PCB adduct formation. Our results suggest that this adduct can serve as delivery system of bioactive PCB

Catalogue Maison Bigot [titres “Viens dans ma nacelle” => “Bazeilles”]

Catalogue Maison Bigot, 157 rue du Temple [Paris] : “Romances et chansons nouvelles” (verso “Sommes nous prêts ?”) ; titres : “Viens dans ma nacelle => “Bazeilles” ; quatre colonnes par deux foix (titres, auteurs, compositeurs, genres) ; interprètes crédités dans la colonne “genre” : Marius Richard, Mercadier, Amiati, Debailleul, Paulus, B. Delahaye, Gibert, Garnier [Léon Garnier], d’Aubreuil [Daubreuil ?], Antony [Antony Lassaigne], Duhem [Émile Duhem], Canon [Fernande Canon], Bourgès, Bonnet, E. Faure [Elise Faure], Dlle (Mlle?) Derly, Libert, Caudieux, Leduc, Judith, G. Lange [Gabrielle Lange], Mme Barnoll, Kaiser [Augustine Kaïser], Limat [Louis Limat], Farville, Réval [Jules Réval], Velly [Louis Velly], Plessis [Henri Plessis] ; datation par analyse des titres 1886 (hypothèse à confirmer)

Conformational stability of digestion-resistant peptides of peanut conglutins reveals the molecular basis of their allergenicity

Conglutins represent the major peanut allergens and are renowned for their resistance to gastrointestinal digestion. Our aim was to characterize the digestion-resistant peptides (DRPs) of conglutins by biochemical and biophysical methods followed by a molecular dynamics simulation in order to better understand the molecular basis of food protein allergenicity. We have mapped proteolysis sites at the N- and C-termini and at a limited internal segment, while other potential proteolysis sites remained unaffected. Molecular dynamics simulation showed that proteolysis only occurred in the vibrant regions of the proteins. DRPs appeared to be conformationally stable as intact conglutins. Also, the overall secondary structure and IgE-binding potency of DRPs was comparable to that of intact conglutins. The stability of conglutins toward gastro-intestinal digestion, combined with the conformational stability of the resulting DRPs provide conditions for optimal exposure to the intestinal immune system, providing an explanation for the extraordinary allergenicity of peanut conglutins