Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0393754 (HSA)
 2,996 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to characterize the isomerization of serumalbumin in the acidic pH-range equilibrium and kinetic measurements of the intrinsic fluorescence of bovine serumalbumin and human serumalbumin were performed. Additional experiments with modified bovine serumalbumin made use of substituted 1.9 benzoxanthene dyes as SH-specific extrinsic fluorophores. The intrinsic fluorescence (lambda exc = 275 nm) shows a pH-dependent shift of the maximum of fluorescence emissions which correlates with the N in equilibrium F isomerization. This and the acid expansion at pH less than 3.5 is indicated by the pH-dependence of the fluorescence intensity at 350 nm. While tyrosine fluorescence is increased in all steps of the transition, tryptophane fluorescence is decreased in a different way for BSA (2 trp/molecule) and HSA (1 trp/molecule), the latter showing the N in equilibrium F transition only. Combining the tryptophan fluorescence data with the results from the SH-specific modification of BSA the conclusion may be drawn that the tryptophan residues in BSA and the SH-group belong to different domains of the molecule. Stopped-flow experiments prove the N in equilibrium F' and the F' in equilibrium F transitions to be separable along the time axis, the relaxation times being in the range between 40-50 and 300-600 msec respectively. For the "expansion" the kinetic constants critically depend on the initial pH conditions of the solutions. The backward reaction F leads to N seems to be a multistep isomerization process which is characterized by relaxation times greater than 1 sec.
 ...
PMID:Fluorescence and stopped-flow studies on the N in equilibrium F transition of serumalbumin. 24 Apr 54

The reaction of the radical anion -(SCN)2-, produced during pulse radilysis of aqueous KCNS solutions, have been used to study the binding of a range of alkyl sulphates to bovine (BSA) and human (HSA) serum albumin. At neutral pH, -(SCN)2- reacts chiefly with trytophan residues. Approximately ten high-affinity binding sites are detectable for compounds of chain length greater than C7. The results are interpreted in terms of a model in which one hydrophobic region in the protein, containing the tryptophan residues, can accommodate the ten ligand molecules. Electrostatic interactions with positively-charged groups surrounding the hydrophobic area are also involved in binding.
 ...
PMID:Investigation of the interaction of alkyl sulphates with serum albumin using the thiocyanate radical ion (SCN)2. 108 85

The binding of radiolabelled tryptophan enantiomers to human serum albumin was investigated by ultrafiltration and by the microparticle technique. L-Trp was found to exhibit a high degree of secondary binding. D-Trp showed increased degree of binding when the HSA concentration was decreased. Stereoselective binding has also been detected in stereoselectively labelled racemic mixtures. Both L- and D-Trp were found to compete for the primary binding site with specific benzodiazepine markers. All the experiments indicate that stereoselectivity of binding is much lower than generally believed.
 ...
PMID:Investigation on the binding of tryptophan enantiomers to human serum albumin. 309 25

The variable aggregation of porphyrins such as Hp and Hpd introduces uncertainties and errors into attempts to measure their binding to proteins. Methods such as dialysis, ultrafiltration and gel chromatography, so frequently used, proved to be unreliable when applied to the binding of Hp to serum albumin. Quenching of tryptophan fluorescence will only occur at porphyrin binding sites which are closely situated to the tryptophan residue (1.7 nm). Porphyrin bound to more distant sites may not be included in this analytical procedure which must therefore be applied with reserve. In the present work, photofrin II (PII) was shown to consist of large aggregates greater than 20 000-30 000 Mr, solutions of which did not disaggregate on dilution down to 1 mumol/1. Addition of albumin resulted in a change in the absorption spectrum of PII. Thus, it was assumed that measurements of differential absorption gave the proportion of free-to-bound PII when serum albumin was added in graded amounts to its solution. By applying suitable calculations to the data, an association constant of 0.3 1/mumol +/- 30% was deducted. Hill plots of the binding data were linear with slopes close to unity. Experimentally determined uptake of PII by NHIK 3025 cells from solutions containing different amounts of HSA showed that the amount bound to the cells was proportional to the free PII. The kinetics of quenching of tryptophan fluorescence in HSA by PII indicates that there is one main porphyrin-binding site affecting this fluorescence. This binding site seems to have a slightly higher affinity for PII than the remaining sites. Up to 8 porphyrin rings of PII can be bound to an HSA molecule.
 ...
PMID:The binding of dihematoporphyrin ether (photofrin II) to human serum albumin. 315 6

Pigment-protein complexes of chlorin e6 (Chl e6) with human (HSA) and bovine serum albumines (BSA) have been investigated by spectral-luminescent methods. Fluorescence quenching of tryptophan residues caused by the inductive-resonance energy transfer to pigment molecules and the rise of the polarization degree of Chl e6 emission were observed upon incorporation of Chl e6 in the protein globula. The obtained data on spectral-energetic parameters of protein tryptophanyls and Chl e6 permitted us to calculate the energy transfer critical distances R0 in complexes of Chl e6 with HSA (R0 = 32 A) and BSA (R0 = 35A). The binding constants (K) and the number of binding sites (N) of Chl e6 with HSA and BSA have been obtained from the experiments on tryptophanyl fluorescence quenching of the investigated proteins and polarization measurements of pigment emission (KHSA = 1.2.10(6) mole-1, KBSA = 3.6.10(6) mole-1, NHSA = NBSA = 1). On the basis of the measured values of electronic excitation energy transfer efficiency (phi greater than or equal to 99%) the average distances between the protein chromophores and the incorporated Chl e6 molecules have been calculated (RHSA = 15-17 A, RBSA = 16.5-18 A). The questions connected with pigment localization sites in the protein globula and specific features of pigment-protein interaction are discussed.
 ...
PMID:[Characteristics of complex-formation of chlorine e6 with human and bovine serum albumins]. 318 37

The binding of hemin to human alpha-fetoprotein has been estimated by means of fluorescence and spectrophotometric titration. Spectrophotometric titration discloses one strong binding site for hemin with an association constant of 1.5 X 10(7) M-1. The binding causes a shift of the absorption maximum to a higher wavelength and a rise in the molar absorption coefficient. Fluorescence reveals that the binding of hemin to human AFP quenches the protein fluorescence, which changes in character from a tryptophan type to a tyrosine type. As postulated by our results, the binding of hemin to human AFP is similar to the binding of hemin to HSA.
 ...
PMID:A spectroscopic study of the hemin-human-alpha-fetoprotein system. 620 48

Glucosylated human serum albumin (G-HSA) obtained under incubation with glucose at 37 degrees C for 8 days showed a new fluorescence with a maximum at 430 nm, resulting in quenching of the fluorescence of only one tryptophan residue on HSA. The quantum yield of new fluorescence is 0.024 at 25 degrees C. The analysis of the excitation spectra allowed us to conclude the absence of energy transfer. In G-HSA, non-disulfide cross-linking hexamer was confirmed by SDS-PAGE.
 ...
PMID:New fluorescence of nonenzymatically glucosylated human serum albumin. 648 18

Ten uraemic metabolites, alone or in combination, have been investigated by equilibrium dialysis for their effect on the binding of methyl red, methyl orange, 2-(4'-hydroxybenzeneazo)benzoic acid (HABA), phenytoin and L-tryptophan to human albumin (HSA). Indoxyl sulphate emerges as a substance likely to inhibit binding in vivo while the other metabolites were unlikely to be implicated in the binding defect of uraemic plasma. The effects of indoxyl sulphate, on the binding of HABA and methyl red, studied by equilibrium dialysis and spectroscopy respectively, indicated competitive inhibition. The results suggest that indoxyl sulphate and indole carboxylic acids may contribute to the binding defect of uraemic plasma.
 ...
PMID:Decreased drug binding in uraemia: effect of indoxyl sulphate and other endogenous substances on the binding of drugs and dyes to human albumin. 680 8

The binding of keto- and hydroxy bile salts to human serum albumin, the identity of the bile salts binding sites and the identification of the amino acids present in these sites were studied. The keto bile salts cholanate-3-one (C3), cholanate-3,6-dione (C3-6) and cholanate-3-hydroxy-6-one (KHC) were found to quench the native fluorescence emission of albumin. This suggested that the tryptophan residue of human albumin (residue 214) is accessible to the keto bile salts and not to the hydroxy parent compounds. The binding of the keto bile salts was characterized by a simple population of binding sites with Ka ranging from 22 x 10(4) M-1 for the mono keto bile salt (C3) down to 4 x 10(4) M-1 for the hydroxy-keto bile salt (KHC). The substitution of an oxo group at carbon C3 in C3-6 molecule for a hydroxy group (KHC) produce a significant decreasing of the interaction, suggesting that the hybridization state of the carbon at C3 in the steroid ring of the bile salt molecule is also an essential requirement for bile salts binding. It was found that bile salts are bound to the benzodiazepine binding site on human albumin (site II), producing a perturbation on site I, fatty acids and bilirubin binding site. The presence of only one substituent at C3 (oxo or OH) produce an important perturbation on the fatty acid binding sites, decreasing the polarity of the its microenvironment, while a little effect was observed for the dihydroxy and di-oxo-substituted BS, suggesting that the hydroxy substituents at C6, C7 and C12 do not interact in a significant manner with the fatty acid binding sites on HSA. The participation of specific amino acids in albumin-bile salt binding sites depends on the polar groups on the bile salt molecules as exemplified by the quantitatively different role of lysyl residues like those interacting with KHC, C3 and C3-6, and tyrosyl residue interacting with KHC. The following amino acids in human albumin were found to play a role in the bile salts-albumin interaction: lysyl 195 and 225, several arginyls, histidyl 146 and tyrosyl 411.
 ...
PMID:Structural features of the hydroxy- and keto-disubstituted bile salts: human serum albumin binding. 754 67

Saturable binding of various inhaled anesthetics to serum albumin has been shown with a variety of approaches. In order to determine the location of halothane binding sites in serum albumin, both human and bovine serum albumins (HSA and BSA) were photolabeled with [14C]halothane, and subjected to proteolysis and microsequencing. BSA was found to have a higher affinity for halothane than HSA, and it contained two specifically labeled sites. One site was characterized by diffuse labeling from Trp212-Leu217, and the other by a more discrete and higher affinity labeling at Trp134-Gly135. HSA contained only a single labeled site, and although lower affinity, was determined to be analogous to BSA Trp212. The position 130-140 region of HSA, having a leucine instead of tryptophan at position 134, was not labeled. These results demonstrate specific and discrete binding of an inhaled anesthetic to a mammalian-soluble protein, and further suggest the importance of aromatic residues as one feature of inhaled anesthetic binding sites.
 ...
PMID:Amino acid resolution of halothane binding sites in serum albumin. 866 64


1 2 3 4 5 6 7 Next >>