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Query: UMLS:C0393754 (HSA)
 2,996 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Classical model system: Poly-L-glutamic acid (Poly-Glu) was investigated in a disordered coil state (at pH-7.0) and in helix state (at pH 2.0) by Rayleigh scattering of Moessbauer radiation technique. Consider that the coil state of poly-Glu models unfolded (random coil) state and alpha-helix state models the fluctuating secondary structure (during consequent folding of protein) comparative analysis of dynamical properties of poly-Glu in different states with dynamical properties of different proteins in native state (alpha-helical myoglobin and HSA, partially beta-sheet lysozyme) and in intermediate (molten globule) state (alpha-lactalbumin) was performed. This comparison bring some surprising results: native alpha-helical proteins behave itself close to random coil, native partially beta-sheet protein behaves close to fluctuating secondary structure (alpha-helix) and the dynamic behaviour of molten globule state (partially beta-sheet alpha-lactalbumin) is not different from those behaviour of lysozyme and much more rigid than native alpha-helical proteins. As a result one cannot exclude the possibility that folding process and dynamical properties at different steps of the folding are very different for alpha-helical and beta-sheet proteins.
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PMID:[Comparison of dynamic properties of various globular proteins and polyglutamic acid in alpha-helical and coil states. Rayleigh scattering of Mossbauer radiation data]. 918

Kinetics of NO dissociation were characterized for three five-coordinate systems, heme-NO, HSA-heme-NO (human serum albumin), GC-NO (soluble guanylate cyclase), and for the six-coordinate system, Im-heme-NO. Nitrosyl myoglobin was redetermined for comparison. Previously known, six-coordinate R and T state nitrosyl hemoglobins are also included in the comparison. The data indicate that NO dissociates more than 1000 times faster from five-coordinate model heme than it does from the six-coordinate analog. Such a negative trans-effect between NO and a proximal base is in sharp contrast to carboxy heme derivatives, in which ligand dissociation rates are greatly slowed in when a trans base is present. As a result of opposite trans-effects, six-coordinate carboxy and nitrosyl derivatives have comparable dissociation rates, even though the five-coordinate species are very different. In proteins, five- and six-coordinate forms do not show a large difference in dissociation rates. Part of the reason may be due to different probabilities for geminate recombination in the different proteins, but this cannot explain all the facts. There must also be influences of the protein structure on bond-breaking rate constants themselves. With the exception of hemoglobin in the T state, nitrosyl guanylate cyclase shows the highest NO dissociation rate constant, k(obs) = 6 x 10(-4) s(-1). This would yield a half-life of about 2 min at 37 degrees C for dissociation of NO from GC-NO, a number that has implications for the mechanism of regulation of the activity of this key heme enzyme.
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PMID:Kinetics of nitric oxide dissociation from five- and six-coordinate nitrosyl hemes and heme proteins, including soluble guanylate cyclase. 918 64

2-[8-{N-(2-Methylimidazolyl)}octanoyloxymethyl]-5,10,15, 20-tetrakis(o-pivalamido)phenylporphinatoiron(II)s (FePs) were incorporated into hydrophobic cavities of recombinant human serum albumin (rHSA), providing a totally synthetic O(2)-carrying hemoprotein (rHSA-FeP). An rHSA host absorbs maximally eight FeP molecules. Solution properties of the obtained albumin hybrid [[rHSA] = 5 wt %; FeP/HSA = 1-8 (mol/mol)] are almost identical to those of the rHSA itself; the specific gravity is 1.013 and the viscosity is 1.1 cP. Circular dichroism spectroscopy and isoelectric focusing measurement revealed that the second-order structure and surface charge distribution of rHSA were always constant independent of the binding numbers of FeP. Hydrophobic interaction is probably a major molecular force of the incorporation of this synthetic heme. rHSA-FeP can bind and release dioxygen reversibly under physiological conditions (in aqueous media, pH 7.3, 37 degrees C) like hemoglobin and myoglobin. Its O(2)-coordination structure was evaluated by resonance Raman spectroscopy. The O(2) rebinding after the laser flash photolysis showed three-phases decay, which were analyzed by triple-exponential kinetics. The O(2)-binding affinity and O(2)-association and -dissociation rate constants of rHSA-FeP satisfy the initial clinical requirements for O(2) infusion as a red cell substitute.
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PMID:Human serum albumin incorporating Tetrakis(o-pivalamido) phenylporphinatoiron(II) derivative as a totally synthetic O2-carrying hemoprotein. 1050 45

A novel quantitative method for the determination of proteins in aqueous solutions has been based on the quenching of the resonance scattering light of colloidal silver chloride in the presence of proteins. The detection limits for eight kinds of proteins (BSA, HSA, egg albumin, human gamma-IgG,alpha-chymotrypsin, E. Coli. alpsase, myoglobin, alpha-casein) were at about 8 ng/mL; the linear ranges of the calibration curves were 10-400 ng/mL under optimal conditions,except for human gamma-IgG (20-400 ng/mL), myoglobin (10-300 ng/mL), and alpha-casein (10-300 ng/mL). Three wavelengths (398 nm, 475 nm, 499 nm) were all suitable for the determination and any acidity from pH 3.0 to pH 9.0 could be chosen. A few non-protein substances at high concentration levels interfered with this method, but this problem could simply be overcome by diluting the samples before the assay. Mechanism studies showed that the quenching effect of proteins on the scattering light of colloidal silver chloride was mainly due to the coagulation of AgCl particles retarded by protein. The method was employed for the determination of total protein in human serum with satisfactory results.
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PMID:Determination of proteins at nanogram levels by their quenching effect on large particle scattering of colloidal silver chloride. 1122 23

The first competitive fluorescence polarization immunoassay using ruthenium metal-ligand complexes (5-MC and 55-DC) as labels is described. These were newly synthesized and characterized in terms of their spectra, their covalent linkage to proteins, and their use in both homogeneous and competitive immunoassays. Linkage to proteins was achieved by the N-hydroxysuccinimide ester method, which was demonstrated for the systems HSA-anti-HSA and myoglobin-anti-myoglobin. The values of the fundamental polarization are 0.18 for 5-MC and 0.33 for 55-DC. Polarization immunoassays with labeled HSA and myoglobin were performed in the homogeneous format and resulted in an increase of the fluorescence polarization of up to 100%. In the competitive assay, a decrease in polarization of >90% was detectable. When the competitive HSA immunoassay was validated against an independent test both methods gave almost the same results.
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PMID:Polarization immunoassays using reactive ruthenium metal-ligand complexes as luminescent labels. 1194 39

The size and charge-selective properties of the glomerular barrier are partly controversial. Glomerular sieving coefficients (theta) for proteins have rarely been determined noninvasively before in vivo. Therefore, theta was assessed vs. glomerular filtration rate (GFR; (51)Cr-EDTA clearance) in intact rats for radiolabeled myoglobin, kappa-dimer, neutral horseradish peroxidase (nHRP), neutral human serum albumin (nHSA), and native albumin (HSA). To obtain theta, glomerular tracer clearance, assessed from the 7- to 8-min kidney uptake of protein, was divided by the GFR. The data were fitted with a two-pore model of glomerular permeability, where the small-pore radius was 37.35 +/- 1.11 (SE) A, and the "unrestricted pore area over diffusion path length" (A(0)/DeltaX) 1.84 +/- 0.43 x 10(6) cm. Although seemingly horizontal for nHRP and nHSA, the log theta vs. GFR curves showed slightly negative slopes for the proteins investigated in the GFR interval of 2-4.5 ml/min. Strong negative (linear) correlations between (log) theta and GFR were obtained for myoglobin (P = 0.002) and HSA (P = 0.006), whereas they were relatively weak for nHRP and nHSA and nonsignificant for kappa-dimer. Theta for nHSA was markedly higher than that for HSA. In conclusion, there were no indications of increases in theta vs. GFR, as indicative of concentration polarization, for the proteins investigated at high GFRs. Furthermore, the glomerular small-pore radius assessed from endogenous (neutral) protein sieving data was found to be smaller than previously determined using dextran or Ficoll as test molecules.
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PMID:Glomerular filtration rate dependence of sieving of albumin and some neutral proteins in rat kidneys. 1262 Sep 29

The recombinant human serum albumin (rHSA) dimer, which was cross-linked by a thiol group of Cys-34 with 1,6-bis(maleimido)hexane, has been physicochemically characterized. Reduction of the inert mixed-disulfide of Cys-34 beforehand improved the efficiency of the cross-linking reaction. The purified dimer showed a double mass and absorption coefficient, but unaltered molar ellipticity, isoelectric point (pI: 4.8) and denaturing temperature (65 degrees C). The concentration dependence of the colloid osmotic pressure (COP) demonstrated that the 8.5 g dL(-1) dimer solution has the same COP with the physiological 5 g dL(-1) rHSA. The antigenic epitopes of the albumin units are preserved after bridging the Cys-34, and the circulation lifetime of the 125I-labeled variant in rat was 18 h. A total of 16 molecules of the tetrakis[(1-methylcyclohexanamido)phenyl]porphinatoiron(II) derivative (FecycP) is incorporated into the hydrophobic cavities of the HSA dimer, giving an albumin-heme hybrid in dimeric form. It can reversibly bind and release O2 under physiological conditions (37 degrees C, pH 7.3) like hemoglobin or myoglobin. Magnetic circular dichroism (CD) revealed the formation of an O2-adduct complex and laser flash photolysis experiments showed the three-component kinetics of the O2-recombination reaction. The O2-binding affinity and the O2-association and -dissociation rate constants of this synthetic hemoprotein have also been evaluated.
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PMID:Physicochemical characterization of cross-linked human serum albumin dimer and its synthetic heme hybrid as an oxygen carrier. 1553 64

Thin-film myoglobin molecularly imprinted polymers have been fabricated using a micro-contact approach. By initially selecting the cross-linker on the basis of it having a minimal recognition for the template and using this as a starting point for functional monomer selection, we have produced myoglobin imprinted polymers with exceptionally high selectivities. The affinity of the polymers, for myoglobin, when prepared with a variety of different cross-linkers and no functional monomer was evaluated. Of these, tetraethylene glycol dimethacrylate (TEGDMA) exhibited the lowest affinity for the template species. Methyl methacrylate (MMA) was chosen as the functional monomer as when it was used in conjunction with TEGDMA, it exhibited maximum selectivity for the template compared to polymers made with other functional monomers. With a MMA to TEGDMA ratio of 1 to 3, the myoglobin molecularly imprinted polymer adsorbed 15.03+/-0.89 x 10(-11)mole/cm(2) of template from a 5.68 x 10(-7)M myoglobin solution, compared to 2.58+/-0.02 x 10(-11)mole/cm(2) for a polymer of similar composition, but formed in the absence of a template. Various washing conditions, using alkaline media to remove the template, were investigated. An extraction solvent comprising 2 wt.% SDS and 0.6 wt.% NaOH used at 80 degrees C for 30 min was shown to give the highest imprinting factor i.e. 5.83 with 72.82% myoglobin removal. The saturation kinetics of template binding to the thin-film MIP were examined and found to display a simple two-phase profile typical of non-cooperative binding. A Scatchard binding plot showed the dissociation constant (K(d)) for the specific binding phase to be 3.4 x 10(-7)M and the binding site capacity to be 7.24 x 10(-11)mole/cm(2). For the non-specific binding phase, K(d) was found to be 1.355 x 10(-5)M and the binding site capacity was determined as 9.62 x 10(-10)mole/cm(2). Selectivity experiments were carried out in both single protein and binary protein systems all using a total protein concentration of 5.68 x 10(-7)M. The molar ratio of adsorbed myoglobin to IgG, HSA and hemoglobin was found to 115.5, 230.9 and 2.5, respectively. While, in binary competition systems, myoglobin selectivity to IgG, HSA and hemoglobin was, respectively, 94.18, 98.21 and 61.09%. Rebinding in natural biological matrices, i.e. human serum or urine, showed the imprinted films to have significantly greater uptake than non-imprinted films. Re-binding in undiluted urine was found to be a facile process, with the imprinting factor, i.e. the ratio of MIP to NIP binding, being determined as 37.4.
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PMID:Optimizing the formulation of a myoglobin molecularly imprinted thin-film polymer--formed using a micro-contact imprinting method. 1722 34

Complexing an iron protoporphyrin IX into a genetically engineered heme pocket of recombinant human serum albumin (rHSA) generates an artificial hemoprotein, which can bind O2 in much the same way as hemoglobin (Hb). We previously demonstrated a pair of mutations that are required to enable the prosthetic heme group to bind O2 reversibly: (i) Ile-142-->His, which is axially coordinated to the central Fe2+ ion of the heme, and (ii) Tyr-161-->Phe or Leu, which makes the sixth coordinate position available for ligand interactions [I142H/Y161F (HF) or I142H/Y161L (HL)]. Here we describe additional new mutations designed to manipulate the architecture of the heme pocket in rHSA-heme complexes by specifically altering distal amino acids. We show that introduction of a third mutation on the distal side of the heme (at position Leu-185, Leu-182, or Arg-186) can modulate the O2 binding equilibrium. The coordination structures and ligand (O2 and CO) binding properties of nine rHSA(triple mutant)-heme complexes have been physicochemically and kinetically characterized. Several substitutions were severely detrimental to O2 binding: for example, Gln-185, His-185, and His-182 all generated a weak six-coordinate heme, while the rHSA(HF/R186H)-heme complex possessed a typical bis-histidyl hemochrome that was immediately autoxidized by O2. In marked contrast, HSA(HL/L185N)-heme showed very high O2 binding affinity (P1/2O2 1 Torr, 22 degrees C), which is 18-fold greater than that of the original double mutant rHSA(HL)-heme and very close to the affinities exhibited by myoglobin and the high-affinity form of Hb. Introduction of Asn at position 185 enhances O2 binding primarily by reducing the O2 dissociation rate constant. Replacement of polar Arg-186 with Leu or Phe increased the hydrophobicity of the distal environment, yielded a complex with reduced O2 binding affinity (P1/2O2 9-10 Torr, 22 degrees C), which nevertheless is almost the same as that of human red blood cells and therefore better tuned to a role in O2 transport.
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PMID:Genetic engineering of the heme pocket in human serum albumin: modulation of O2 binding of iron protoporphyrin IX by variation of distal amino acids. 1770 94

Myeloperoxidase, released by activated phagocytes, forms reactive oxidants by catalysing the reaction of halide and pseudo-halide ions with H(2)O(2). These oxidants have been linked to tissue damage in a range of inflammatory diseases. With physiological levels of halide and pseudo-halide ions, similar amounts of HOCl (hypochlorous acid) and HOSCN (hypothiocyanous acid) are produced by myeloperoxidase. Although the importance of HOSCN in initiating cellular damage via thiol oxidation is becoming increasingly recognized, there are limited data on the reactions of HOSCN with other targets. In the present study, the products of the reaction of HOSCN with proteins has been studied. With albumin, thiols are oxidized preferentially forming unstable sulfenyl thiocyanate derivatives, as evidenced by the reversible incorporation of (14)C from HOS(14)CN. On consumption of the HSA (human serum albumin) free thiol group, the formation of stable (14)C-containing products and oxidation of tryptophan residues are observed. Oxidation of tryptophan residues is observed on reaction of HOSCN with other proteins (including myoglobin, lysozyme and trypsin inhibitor), but not free tryptophan, or tryptophan-containing peptides. Peptide mass mapping studies with HOSCN-treated myoglobin, showed the addition of two oxygen atoms on either Trp(7) or Trp(14) with equimolar or less oxidant, and the addition of a further two oxygen atoms to the other tryptophan with higher oxidant concentrations (> or = 2-fold). Tryptophan oxidation was observed on treating myoglobin with HOSCN in the presence of glutathione and ascorbate. Thus tryptophan residues are likely to be favourable targets for the reaction in biological systems, and the oxidation products formed may be useful biomarkers of HOSCN-mediated protein oxidation.
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PMID:Tryptophan residues are targets in hypothiocyanous acid-mediated protein oxidation. 1865 72


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