Binding of cupric ions to bovine serum albumin.

The binding of cupric ions to bovine serum albumin was investigated by using a cupric-ion-specific electrode. When using a modified form of the Scatchard equation, it was determined that there are at least two classes of binding sites on bovine serum albumin for cupric ions. One class has three binding sites of relatively strong affinity, with an average binding constant of 3.0 times 10(6). The other class has about 16 binding sites of relatively weak affinity, with an average binding constant of 2.0 times 10(4).     

Binding of [3H]mianserin to bovine serum albumin,human serum albumin and α1-acid glycoprotein

Scatchard plots which were curvilinear with negative slopes were obtained when the binding of [³H]mianserin to bovine serum albumin (BSA), human serum albumin (HSA), defatted human serum albumin (D-HSA) and α₁-acid glycoprotein (α₁-AGP) was studied with equilibrium dialysis with constant protein concentrations and various ligand concentrations. Binding parameters were estimated graphically and with a non-linear least-squares computer program, assuming two classes of independent binding sites. α₁-AGP had the highest binding affinity (K) and binding capacity (nK). The binding parameters, n and K were not independent of protein concentration when the BSA concentration was varied. Linear atypical Scatchard plots with positive slopes were obtained when the protein concentration was varied for BSA, HSA and D-HSA, at a fixed ligand concentration.     

Binding of the organophosphates parathion and paraoxon to bovine and human serum albumin

Binding of parathion and paraoxon to bovine serum albumin (BSA) and human serum albumin (HSA) was studied by using equilibrium dialysis. The concentration of unbound organophosphate was determined from its anticholinesterase activity.Binding of parathion to BSA was shown to be reversible. The organophosphates interact with only one type of binding sites in BSA and HSA. The affinity constants at pH 7.2 and 4° C for the interaction of BSA or HSA and parathion were found to be 2.7×10⁶ and 1.5×10⁶ M^–1, respectively. The affinity constants for the interaction of the serum albumins and paraoxon were considerably lower, 6.0×10³ and 1.6×10⁴ M^–1, respectively. Lowering the pH from 7.2 to 4.8 did not significantly affect the binding parameters. The great difference of affinity of the serum albumins to parathion and paraoxon is discussed with respect to the fate of parathion in the body.     

Binding of some phenoxyalkanoic acids to bovine serum albumin in vitro.

The phenoxyalkanoix acids are bound to bovine serum albumin at a single site of high affinity, where the interaction is most importantly influenced by strong hydrophobic bonding, with ionic bonding being of lesser importance, and also at several sites of lower affinity. The hydrophobic binding site has almost equal affinity for the phenoxy groups of 2,4-dichlorophenoxyacetic acid, 4-(2,4-dichlorophenoxy)butyric acid and 2-(2,4,5-trichlorophenoxy)propionic acid and greater affinity for the phenoxy group of 2,4,5-trichlorophenoxyacetic acid. The properties of the high affinity binding site bear some resemblance to the properties of the amino acid sequence adjoining the tryptophan residue of human serum albumin, and evidence is presented for the presence of tryptophan at the high affinity binding site of bovine serum albumin.     

Binding of formaldehyde to human and rat nasal mucus and bovine serum albumin

The function of the nasal mucociliary apparatus, an important airway defense mechanism, is inhibited by inhaled formaldehyde. Nasal mucus, which contains significant concentrations of glycoprotein and soluble proteins, is an integral component of this system. This investigation addresses some reactions of formaldehyde with human and rat mucus in vitro in comparison with a model protein, bovine serum albumin. [14C]Formaldehyde was incubated with reconstituted preparations of human and rat nasal mucus or bovine serum albumin. Formaldehyde adducts, stabilized by sodium cyanoborohydride reduction to methylamines, were separated by Sepharose 2B gel filtration. [14C]Formaldehyde bound exclusively to one component of nasal mucus which had an elution volume identical to that of albumin. There was no detectable binding to the large molecular weight glycoproteins. The time course of reaction of formaldehyde to free amino groups was then measured using the fluorescamine technique. Formaldehyde binding was characterized by an initial fast phase (less than 2 min) followed by a slower phase which appeared to approach equilibrium (greater than 60 min). The rate of binding to human and rat nasal mucus was similar to albumin. Irreversible binding of formaldehyde to albumin was insignificant within the first 60 min indicating the reversibility of binding during this time. These data indicate that within the first 60 min, formaldehyde reacts rapidly and reversibly with nasal mucus and that it binds primarily to one component of nasal mucus. Gel filtration analysis suggests this component may be albumin although other low molecular weight proteins cannot be ruled out.     

Binding of the membrane active drugs to bovine serum albumin and human erythrocyte membranes.

The binding of 14 non-steroidal anti-inflammatory drugs, 3 beta-adrenolytics and 8 miscellaneous drugs to bovine serum albumin (BSA) and human erythrocyte membranes (HEM) was investigated by using 8-anilino-1-naphthalene sulphonate (ANS) as a fluorescent probe. Anionic drugs which are known to protect proteins against denaturation strongly quench the fluorescence of the ANS-BSA complex, and to a lesser extent the fluorescence of the ANS-HEM complex. None of cationic or nonionic drugs tested so far are able to displace ANS from the ANS-BSA complex but some of them, known as “membrane active” agents, intensify the fluorescence of the ANS—HEM complex. Within the group of nonsteroidal anti-inflammatory drugs only those drugs which are inhibitors of prostaglandin biosynthesis have been found to quench the fluorescence of the complexes of ANS with BSA or HEM. Both anionic and cationic “membrane active” drugs protect erythrocytes against hypotonic hemolysis but the mechanisms of this effect are different.     

Binding of sodium houttuyfonate analogues to bovine serum albumin revealed by fluoresence quenching study

The binding reaction of sodium houttuyfonate analogues (SHAs) to bovine serum albumin (BSA) was studied by fluorescence quenching. Both dynamic and static interactions are involved in the quenching process. SHAs with shorter carbon chains are more likely to undergo a predominantly dynamic quench over a static quench. In contrast, SHAs with longer carbon chains act as static quenchers. Quench efficiency is in the order SHA-C₈ > SHA-C₁₀ > SHA-C₁₂ ≈ SHA-C₁₄ > SHA-C₆. It was also observed that the two tryptophan residues of BSA are accessible to SHAs. Most of the SHAs have two binding sites, except SHA-C₁₂, which has one. Binding of SHAs to BSA is as a result of spontaneous intermolecular interaction at the experimental temperature. We concluded that SHAs bind to and may be transported by BSA.     

Binding of Sudan II and Sudan IV to bovine serum albumin: Comparison studies

In this paper, we report the interaction of Sudan II and Sudan IV to bovine serum albumin (BSA). Structural analysis showed that both Sudan II and Sudan IV interact mainly with BSA at the hydrophobic pocket and via Van der Waals forces. The number of bound Sudan molecule for each protein molecule was approximately 1. The overall binding constants at 293 K (20 °C) estimated for Sudan II and Sudan IV were 1.22 × 10⁴ M⁻¹ and 1.48 × 10⁴ M⁻¹, respectively. BSA backbone structure was damaged by the dyes with more severe phenomenon observed for Sudan IV. For two Sudan dyes with the same concentration, Sudan IV could cause more alterations on CD spectra of BSA with slight decrease of α-helical content and increase of β-sheet content, suggesting a partial protein unfolding.     

Binding of coumarin anticoagulants to human and bovine serum albumin. Circular dichroism studies

The interaction of acenocoumarin, coumachlor, phenprocoumon, and warfarin with human and bovine serum albumin was investigated by ultracentrifugation and circular dichroism measurements. Although all four drugs generate extrinsic Cotton effects when bound to human and bovine serum albumin, large differences in the signs and the intensities of the Cotton effects are observed. The differences in the induced Cotton effects suggest differential molecular binding mechanisms.     

Binding study of sulfonylureas and phenothiazines to bovine serum albumin using difference spectrophotometry.

2-(4'-Hydroxybenzeneazo)benzoic acid is a spectrophotometric probe which shows absorption spectrum changes upon binding to protein. Difference absorption spectra of this probe were used as an indirect measurement of the binding of selected sulfonylurea and phenothiazine drugs to bovine serum albumin. The results obtained using the spectrophotometric probe were similar to data obtained from other methods, especially fluorescent methods. Of the four sulfonylureas studied, tolbutamide showed the highest binding affinity, followed by glyburide, glipizide, and acetohexamide, in that order. The data collected for phenothiazine drugs indicated that chlorpromazine has the highest affinity, followed in order by trifluoperazine, perphenazine, fluphenazine, and promazine. Correlation of these results with chemical composition indicated that the interaction of phenothiazine drugs with bovine serum albumin was of a hydrophobic nature.     

Binding of teicoplanin to human serum albumin

Summary The interaction between the main components of the new glycopeptide antibiotic teicoplanin, A2–2, A2–3, A2–4, A2–5 and A3–1, and human serum albumin has been studied in vitro by equilibrium dialysis (pH 7.4, 37°C).From Scatchard analysis of the data, the calculated association constants (Ka) were: A2–2, 2.47×10⁴, A2–3, 2.86×10⁴, A2–4, 2.95×10⁴ and A2–5, 3.87×10⁴ mol·l^–1. The number of binding sites per albumin molecule ranged between 1.23 to 1.31. A3–1 had a lower affinity with a Ka of about 5×10³ mol·l^–1.Extrapolated to the in vivo situation, the data suggested that about 90–95% of A2 components will be bound to serum albumin, and about 68–72% of A3–1.The in vitro findings were confirmed by a pharmacokinetic study in volunteers given [¹⁴C] teicoplanin i.v., in whom the fraction of teicoplanin bound to serum protein ranged between 87.6 and 90.8%.     

Binding of prostaglandin to human serum albumin

The interaction of tritiated prostaglandin E₁ (³H-PGE₁) with various constituents of human blood was examined by equilibrium dialysis and incubation experiments. Plasma bound ³H-PGE₁ weakly, apparently due to an interaction with serum albumin. Blood cells and plasma globulins did not interact with PG. When albumin and other proteins were precipitated by ethanol, as a preliminary stage of extracting PG from plasma, the recoveries of added PGs were poor. Addition of acid and non-precipitating amounts of ethanol (40–50%) to the plasma allowed quantitative extraction of added PGE, F, and A compounds into chloroform.     

Binding of cefalotin to human serum albumin

Binding of cefalotin to human serum albumin was studied in vitro by equilibrium dialysis and the quantitative measurement of cefalotin was made by fluorimetric assay. The binding rate of cefalotin to human serum albumin found to be 61,1%. The determination of drug binding parameters showed a large number of binding sites (n = 9.36) and a moderate affinity (K = 3898 M-1).     

Binding of propofol to human serum albumin

The binding properties of the short-acting hypnotic agent propofol (CAS 2078-54-8) to human serum albumin were studied in vitro. Using centrifugation through ultrafiltration membranes the ratio of free and bound propofol as a function of the human serum albumin concentration was determined. In addition, a biomathematical approach was tested that allowed the determination of the number of binding sites from the measured binding profile. At a total propofol concentration of 8.81 +/- 0.25 microg/mL the concentration of the free fraction of propofol ranged from 338 +/- 11 ng/mL (mean +/- SE) at an albumin concentration of 0.5% to 15 +/- 2 ng/ mL at an albumin concentration of 8.0%. The corresponding percentage of propofol binding ranged from 96.07 +/- 0.14% to 99.83 +/- 0.02%. From this binding profile the binding site was estimated to be n(0) = 2. The measured influence of the albumin concentration on propofol binding might be of relevance in states of hypo- or hyperalbuminaemia which could result in an altered demand of propofol.