Search results for "Kinetic"
showing 10 items of 3064 documents
Conformational transitions of gramicidin A in phospholipid model membranes. A high-performance liquid chromatography assessment.
1991
We have investigated the conformation of gramicidin A reconstituted in different phospholipid environments, small unilamellar vesicles, extensive bilayers, and micelles by exploiting a recently proposed experimental approach based on high-performance liquid chromatography [Bano et al. (1988) J. Chromatogr. 458, 105; Bano et al. (1989) FEBS Lett. 250, 67]. The method allows the separation of conformational species of the peptide namely, antiparallel double-stranded (APDS) dimers and β 6.3 -helical monomers, and quantitation of their proportions in the lipid environment. Various experimental parameters (e.g., nature of organic solvent, time of incubation in organic solvent, lipid-to-peptide m…
Core Histones Are Glutaminyl Substrates for Tissue Transglutaminase
1996
Chicken erythrocyte core histones are glutaminyl substrates in the transglutaminase (TGase) reaction with monodansylcadaverine (DNC) as donor amine. The modification is very fast when compared with that of many native substrates of TGase. Out of the 18 glutamines of the four histones, nine (namely glutamine 95 of H2B; glutamines 5, 19, and 125 of H3; glutamines 27 and 93 of H4; and glutamines 24, 104, and 112 of H2A) are the amine acceptors in free histones. The use of Gln112 of H2A requires a temperature-dependent partial unfolding of the histone, showing that structural determinants are decisive for the glutamine specificity. The structures of H2A and H2B do not appreciably change upon mo…
Influence of pH on the benzodiazepine-human serum albumin complex. Circular dichroism studies.
1974
The influence of pH on the binding of benzodiazepine derivatives to HSA was studied by circular dichroism measurements and by gel filtration. The binding of nearly all benzodiazepines is increased by rising the pH from 6.60 to 8.20. For flurazepam, clonazepam, and nitrazepam this increase in binding is due to an increase of the affinities, while for the other substances the affinity remains constant and the number of binding sites is increased from one to two. The changes in binding of the benzodiazepines by rising the pH are explained by a cationic amino acid residue near or at the benzodiazepine binding site of the HSA molecule. This second binding site is not detectable by circular dichr…
A semi-empirical approach for the simulation of circular dichroism spectra of gramicidin A in a model membrane
1992
In an extension of our previous work (Bañó, M. C., Braco, L., and Abad, C. 1991. Biochemistry. 30:886-94), the kinetics of dissociation of gramicidin A double-stranded dimers into beta 6.3-helical monomers in small unilamellar vesicles prepared following different protocols, were investigated using in combination circular dichroism (CD) and high-performance liquid chromatography (HPLC). The analysis of the data from both techniques according to a two-component model strongly supports that any given CD pattern of gramicidin incorporated in the phospholipid bilayer can be deconvoluted essentially as a linear combination of the reference subspectra calculated for the double-stranded dimer and …
Bovine Serum Albumin protofibril-like aggregates formation: Solo but not simple mechanism
2011
We report an experimental study on the model protein Bovine Serum Albumin (BSA), with the aim of elucidating the mechanisms by which a fully folded globular protein undergoes different aggregation pathways leading to the formation of amyloid fibrils or amorphous aggregates. We observe thermally induced formation of fibrillar structures at pH far from the protein isoelectric point. The increase of electrostatic repulsion results in protein destabilization and in modifications of inter and intra-molecular interactions leading to the growth of fibril-like aggregates stabilized by inter-molecular-β sheets. The aggregation kinetics is studied by means of fluorescence techniques, light scattering…
Thermal aggregation and ion-induced cold-gelation of bovine serum albumin
2009
Protein cold-gelation has recently received particular attention for its relevance in bio and food technology. In this work, we report a study on bovine serum albumin cold-gelation induced by copper or zinc ions. Metal-induced cold-gelation of proteins requires two steps: during the first one, the heat treatment causes protein partial unfolding and aggregation; then, after cooling the solution to room temperature, gels are formed upon the addition of metal ions. The thermally induced behaviour has been mainly investigated through different techniques: Fourier transform infrared (FTIR) spectroscopy, circular dichroism, dynamic light scattering (DLS) and rheology. Data have shown that the agg…
Ferricytochrome c encapsulated in silica nanoparticles: structural stability and functional properties.
2004
Using a modified sol-gel technique, we have succeeded in encapsulating ferric cytochrome c in silica nanoparticles obtained from hydrolysis and polycondensation of tetramethylorthosilicate. Particles dimensions have been determined with dynamic light scattering; this technique yields an hydrodynamic radius of about 100 nm, each nanoparticle containing about 10(2)-10(3) proteins. If stored in the cold at low ionic strength, nanoparticles are stable for more than one week, even if a slow radius increase with time is observed. CD measurements show that encapsulated proteins exhibit substantially increased stability against guanidinium hydrochloride induced denaturation. Reduction kinetics of e…
Biosensor-based kinetic and thermodynamic characterization of opioids interaction with human μ-opioid receptor.
2019
Development of opioid analgesics with minimal side effects requires substantial knowledge on structure-kinetic and -thermodynamic relationship of opioid-receptor interactions. Here, combined kinetics and thermodynamics of opioid agonist binding to human μ-opioid receptor (h-μOR) was investigated using real-time label-free surface plasmon resonance (SPR)-based method. The N-terminal end truncated and C-terminal 6His-tagged h-μOR was constructed and expressed in E. coli. Receptor was purified, detergent-solubilized and characterized by circular dichroism. The uniform immobilization of h-μOR on Ni-NTA chips was achieved using hybrid capture-coupling approach followed by reconstitution in lipid…
Absolute Configurations of Three Naturally Occurring Acetylenic Spiroacetal Enol Ethers
1993
The absolute configurations of three 6,7-oxygenated acetylenic spiroacetal enol ethers were determined by using the kinetic method of Horeau. The results were confirmed by the circular dichroism of the compounds in correlation with the corresponding 6,7-epoxide.
Bone-Targeted Cisplatin-Complexed Poly(γ-benzyl-L-glutamate)-Poly(glutamic acid) Block Polymer Nanoparticles: An Electrochemical Approach
2015
The voltammetric response of different osteotropic multifunctional nanoparticles based on cisplatin-complexed poly(γ-benzyl-L-glutamate)–poly(glutamic acid) block polymer (CDDP-PBLG-b-PGlu) copolymer, with or without poly(γ-benzyl-L-glutamate)–poly(ethylene glycol) block polymer (PBLG-b-PEG), and having bone-targeting properties is studied at biologically relevant pH. Significant differences in the cisplatin-centered voltammetric signals allow monitoring of the association of cisplatin to nanoparticles as well as release kinetics from them, in agreement with atomic absorption spectroscopy data. Electrochemical studies reveal that the cisplatin association is significant only if the proporti…