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At least 235 records · Page 13Linked to original sources
PubMed1983

A comparison of dye binding methods for albumin determination: the effects of abnormal sera, reaction times, acute phase reactants and albumin standards.

Four bromcresol green methods were evaluated, three of which were used with a reaction time of 15 seconds. An immunonephelometric assay and a bromcresol purple method were used as comparison methods. The bromcresol purple method agreed well with the more specific immunonephelometric procedure. Forty-seven human sera, thirty with low albumin concentrations and seventeen with high albumin concentrations were used in each assessment. The best bromcresol green methods were those using low dye and surfactant (Brij-35) concentrations and the shortest possible reaction times. Except in one bromcresol green method with a long reaction time of 10 minutes, there was no significant difference in values overall between sera having a low albumin concentration with either raised or normal acute phase reactants. Comparable results were obtained using standards of human and bovine albumin preparations in bromcresol green methods but not in the bromcresol purple method.

Bromcresol Green↗
PubMed2002

Bilirubin binding properties of pigeon serum albumin and its comparison with human serum albumin.

Binding of bilirubin (BR) to pigeon serum albumin (PgSA) was studied by absorption, fluorescence and CD spectroscopy and results were compared with those obtained with human serum albumin (HSA). PgSA was found to be structurally similar to HSA as judged by near- and far-UV CD spectra. However, PgSA lacks tryptophan. Binding of BR to PgSA showed relatively weaker interaction compared to HSA in terms of binding affinity, induced red shift in the absorption spectrum of BR and CD spectral characteristics of BR-albumin complexes. Photoirradiation results of BR-albumin complexes also showed PgSA-bound BR more labile compared to HSA-bound BR.

Animals↗
PubMed1992

Localization of the binding site for streptococcal protein G on human serum albumin. Identification of a 5.5-kilodalton protein G binding albumin fragment.

Protein G is a streptococcal cell wall protein with separate and repetitively arranged binding domains for immunoglobulin G (IgG) and human serum albumin (HSA). In this work, the binding of protein G to HSA was studied. The results suggest that a single binding site is present on HSA: the apparent size of the HSA-protein G complex (230 kDa) corresponded to two or three HSA molecules bound to one protein G molecule, and Ouchterlony immunodiffusion did not yield any precipitate between protein G and HSA. HSA was cleaved by pepsin and CNBr into several fragments which were identified by SDS-PAGE and N-terminal amino acid sequencing, and the binding of protein G to the fragments was studied in Western blot experiments. The results indicated that the binding area was located in disulfide loops 6-8, involving both the second (loop 6) and the third (loops 7 and 8) domain of HSA. One of the protein G binding pepsin fragments, with an apparent molecular mass of 5.5 kDa, located in loops 7 and 8, was isolated and found to completely inhibit the binding between protein G and the intact HSA, again suggesting a single protein G binding site on serum albumin. Reducing the disulfide bonds of HSA, and subsequent alkylation of the half-cystine residues, significantly decreased the affinity for protein G. Protein G bound to albumin from baboon, cat, guinea pig, hamster, hen, horse, man, mouse, and rat, but not to albumin from cow, dog, goat, pig, rabbit, sheep, snake, or turkey.

Amino Acid Sequence↗
PubMed2002

Probing the cysteine-34 position of endogenous serum albumin with thiol-binding doxorubicin derivatives. Improved efficacy of an acid-sensitive doxorubicin derivative with specific albumin-binding properties compared to that of the parent compound.

We have recently proposed a macromolecular prodrug strategy for improved cancer chemotherapy based on two features (Kratz, F.; et al. J. Med. Chem 2000, 43, 1253-1256.): (a) rapid and selective binding of thiol-reactive prodrugs to the cysteine-34 position of endogenous albumin after intravenous administration and (b) release of the albumin-bound drug in the acidic environment at the tumor site due to the incorporation of an acid-sensitive bond between the drug and the carrier. To investigate this therapeutic strategy in greater depth, four (maleinimidoalkanoyl)hydrazone derivatives of doxorubicin were synthesized differing in the length of the aliphatic spacer (1, -(CH(2))(2)-; 2, -(CH(2))(3)-; 3, -(CH(2))(5)-; 4, -(CH(2))(7)-). The albumin-binding doxorubicin prodrugs, especially the (6-maleimidocaproyl)hydrazone derivative of doxorubicin (3), are rapidly and selectively bound to the cysteine-34 position of endogenous albumin. 3 was distinctly superior to the parent compound doxorubicin in three animal tumor models (RENCA, MDA-MB 435, and MCF-7) with respect to antitumor efficacy and toxicity.

Animals↗
PubMed1976

Isolation of albumin from whole human plasma and fractionation of albumin-depleted plasma.

The dye Cibacron Blue F-3-GA was conjugated to Sepharose to provide an affinity column for serum albumin. Passage of whole human plasma through a column of Cibacron Blue-Sepharose results in the removal of approx. 98% of the albumin. The latter can be quantitatively recovered by desorption with NaSCN. Albumin-depleted plasma can be readily resolved into discrete fractions by a combination of conventional biochemical techniques. In particular, the resolution of plasma proteins with properties similar to those of native human plasma albumin can readily be accomplished by ion-exchange chromatography of the Sepharose-dye-treated plasma on DEAE-cellulose.

Ammonium Sulfate↗
PubMed1982

Effect of post-ischaemic recovery on albumin synthesis and relative amount of translatable albumin messenger RNA in rat liver.

In liver cells recovering from reversible ischaemia, total protein synthesis by postmitochondrial supernatant and membrane-bound and free polyribosomes is not different from that in sham-operated controls. However, the relative proportion of specific proteins is changed, since the incorporation of [3H]leucine in vivo into liver albumin, relative to incorporation into total protein, as determined by precipitation of labelled albumin with the specific antibody, decreases by 40-50% in post-ischaemic livers. Cell-free synthesis by membrane-bound polyribosomes and poly(A)-enriched RNA isolated from unfractionated liver homogenate shows that the decrease in albumin synthesis in liver of rats recovering from ischaemia is due to the relative decrease in translatable albumin mRNA.

Animals↗
PubMed2003

Albumin is a substrate of human chymase. Prediction by combinatorial peptide screening and development of a selective inhibitor based on the albumin cleavage site.

Human chymase is a chymotryptic serine peptidase stored and secreted by mast cells. Compared with other chymotryptic enzymes, such as cathepsin G and chymotrypsin, it is much more slowly inhibited by serum serpins. Although chymase hydrolyzes several peptides and proteins in vitro, its target repertoire is limited compared with chymotrypsin because of selective interactions in an extended substrate-binding site. The best-known natural substrate, angiotensin I, is cleaved to generate vasoactive angiotensin II. Selectivity of angiotensin cleavage depends in major part on interactions involving substrate residues on the carboxyl-terminal (P1'-P2') side of the cleaved bond. To identify new targets based on interactions with residues on the aminoterminal (P4-P1) side of the site of hydrolysis, we profiled substrate preferences of recombinant human chymase using a combinatorial, fluorogenic peptide substrate library. Data base queries using the peptide (Arg-Glu-Thr-Tyr-X) generated from the most preferred amino acid at each subsite identify albumin as the sole, soluble, human extracellular protein containing this sequence. We validate the prediction that this site is chymase-susceptible by showing that chymase hydrolyzes albumin uniquely at the predicted location, with the resulting fragments remaining disulfide-linked. The site of hydrolysis is highly conserved in vertebrate albumins and is near predicted sites of metal cation binding, but nicking by chymase does not alter binding of Cu2+ or Zn2+. A synthetic peptidic inhibitor, diphenyl N alpha-benzoxycarbonyl-l-Arg-Glu-Thr-PheP-phosphonate, was designed from the preferred P4-P1 substrate sequence. This inhibitor is highly potent (IC50 3.8 nM) and 2,700- and 1,300-fold selective for chymase over cathepsin G and chymotrypsin, respectively. In summary, these findings reveal albumin to be a substrate for chymase and identify a potentially useful new chymase inhibitor.

Albumins↗
PubMed1985

Bleeding disorder associated with albumin-dependent partial deficiency in platelet thromboxane production. Effect of albumin on arachidonate metabolism in platelets.

The authors describe a patient with a longstanding bleeding disorder associated with impaired platelet aggregation and secretion despite normal granule contents. Thrombin-induced platelet thromboxane A2 production, measured using a radioimmunoassay for thromboxane B2, was markedly decreased or undetectable in platelet-rich plasma and whole blood serum. However, significant amounts of thromboxane B2 were detected on thrombin stimulation of platelets suspended in albumin-free salt medium. Malondialdehyde and 14C-hydroxyheptadecatrienoic acid production was undetectable in the patient's platelets. Liberation of free 14C-arachidonic acid from phospholipids during stimulation of prelabeled platelets was normal, indicating normal phospholipase activity. These observations indicate an albumin-dependent partial deficiency in thromboxane production resulting from a defect either in cyclooxygenase or thromboxane synthetase. Further, the authors studied the effect of albumin on arachidonic acid metabolism in normal platelets. These studies indicate that albumin enhances liberation of arachidonic acid from phospholipids but has an overall inhibitory effect on thromboxane synthesis.

Adult↗
PubMed1982

Elimination of monomeric, dimeric and polymeric human albumin from the plasma of inbred mice and dissociation of natural albumin polymers.

Covalently linked albumin dimers and polymers had plasma half-lives (t 1/2s) in mice which were not significantly different from that of native albumin. The elimination of a chemically treated albumin monomer was also not appreciably different from that of the native protein, but it was significantly faster than covalently linked albumin dimers and polymers. Essentially similar results were obtained when natural monomers, dimers and trimers were compared, although precise t 1/2 data may have been affected by the dissociation of natural polymers into appreciable amounts of monomer in vivo.

Animals↗
PubMed1995

A genetic variant of albumin (albumin Asola; Tyr140-->Cys) with no free -SH group but with an additional disulfide bridge.

A slow migrating variant of human serum albumin, present in lower amount than the normal protein, has been detected by routine clinical electrophoresis at pH 8.6 in two members of a family living in Asola (Lombardia, Italy). Ion-exchange chromatography of serum samples failed to separate the normal protein from the variant. Analysis of the albumin peak by SDS/PAGE revealed that the variant had a lower apparent molecular mass than its normal counterpart. However, the abnormal band was not detectable when the separation was performed under reducing conditions or when both albumins were carboxymethylated. Isoelectric-focusing analysis of CNBr fragments localized the mutation to fragment CNBr 3 (residues 124-298). This fragment was isolated on a preparative scale and subjected to tryptic digestion. Sequence determination of the abnormal tryptic peptide revealed that the variant arises from a Tyr140--> Cys substitution. This result was confirmed by DNA sequence analysis, which showed a single transition of TAT-->TGT at nucleotide position 5074. Despite the presence of an additional cysteine residue, several lines of evidence indicated that albumin Asola has no free -SH group; therefore, we propose the formation of a new S-S bond between Cys140 and Cys34, the only free sulphydryl group present in the normal protein. The relatively low level of the variant in serum and its abnormal mobility on cellulose acetate electrophoresis and SDS/PAGE are probably caused by a gross conformational change of the molecule induced by the new S-S bridge.

Amino Acid Sequence↗
PubMed1966

Albumin Naskapi: a new variant of serum albumin.

An apparently new Variant of human serum albumin, albumin Naskapi, has been found in high frequency in the Naskapi Indians of Quebec and, in lower frequency,in other North American Indians. The family and population data of the albumin are consistent with its inheritance as a simple autosomal trait Controlled by a gene designated Al Naskapi. This gene is allelic with the gene Al(A) which controls the common albumin.Both homozygotes and heterozygotes have been distinguished. This is the first report of a homozygote for an albumin Variant.

Blood Protein Electrophoresis↗
PubMed1983

Bleomycin-induced changes in pulmonary microvascular albumin permeability and extravascular albumin space.

Pulmonary microvascular permeability to serum albumin and the extravascular albumin space (EAS) were measured in rat lungs 5 days after intratracheal instillation of bleomycin. The albumin permeability-surface area product (PS) was measured using a new method: lungs were removed and perfused with Ringer's solution; they were then perfused for 3 min with Ringer's containing [125I]albumin, followed by 3 min with plain Ringer's to clear the vascular space. The PS was calculated from the 125I activity in perfusate and homogenized lung tissue. In separate experiments the EAS was measured using standard methods. Compared with control rats, the injected animals showed a slight, but significant, increase in PS, and a doubling of the EAS. In previous work, using other techniques, the EAS increase was interpreted as an increased PS. Our new method for PS measurement is easy and more accurate than those previously used, and shows that the acute pulmonary response to intratracheally administered bleomycin involves significant interstitial changes with little alteration in the microvascular endothelium.

Animals↗
PubMed1983

Bromocresol purple and the measurement of albumin. Falsely high plasma albumin concentrations eliminated by increased reagent ionic strength.

This study was undertaken to investigate the extent of the reported discrepancy between serum and plasma albumin concentrations measured by the bromocresol purple (BCP) method. We have shown that plasma albumin concentrations are falsely increased by turbidity due to the precipitation of fibrinogen when plasma is diluted into the BCP reagent. Modification of the BCP buffer (to 0.1M acetate containing 0.15M NaCl, pH 5.5) eliminates the turbidity and thus permits the measurement of albumin in either serum or plasma. Plasma albumin concentrations measured with the modified BCP reagent show excellent correlation with results by an immunoturbidimetric method.

Bromcresol Purple↗
PubMed2005

Phase I comparability of recombinant human albumin and human serum albumin.

Recombinant human albumin (rHA) is a highly purified animal-, virus-, and prion-free product developed as an alternative to human serum albumin (HSA), to which it is structurally equivalent. The present investigation compared the safety, tolerability, and pharmacokinetics/pharmacodynamics of rHA with HSA. Two double-blind, randomized trials were performed in healthy volunteers using intramuscular (IM) and intravenous (IV) administration. The IM trial included 500 volunteers, each receiving 5 repeat doses of 5 mg (100 subjects), 15 mg (100 subjects), or 65 mg (300 subjects) of rHA or HSA. Thirty volunteers participated in the IV trial, each receiving ascending doses (10 g, 20 g, and 50 g) of either rHA or HSA. In both trials, all adverse events were recorded and conventionally classified; potential allergic responses were also monitored. Blood samples were taken in both studies to test for IgG or IgE antibodies against test products and potential impurities. For the IV study, pharmacokinetic/pharmacodynamic assessments were performed, including measurement of serum albumin, colloid osmotic pressure, and hematocrit pre- and postinfusion. Nine subjects in the IM study (4 recipients of rHA and 5 of HSA) reported drug-related, potentially allergic events; all but 2 of these were skin related. No serious or potentially allergic events were reported with either product in the IV study. There was no immunological response to either product, and dose level did not influence the study outcomes. Serum albumin, colloid osmotic pressure changes, and hematocrit ratio were as expected, with no differences between rHA and HSA. rHA and HSA exhibited similar safety, tolerability, and pharmacokinetic/pharmacodynamic profiles, with no evidence of any immunological response.

Adolescent↗
PubMed1978

Measurement of bilirubin-albumin binding. I. Comparative analysis of four methods and four human serum albumin preparations.

Four methods for the measurement of bilirubin-albumin binding have been compared. Three of these, the fluorescent dye binding (Direct Yellow 7), Sephadex G-25 column chromatography, and the 2-(4-hydroxyazobenzene)benzoic acid (HBABA) dye binding methods demonstrate significant correlations of measured binding capacities for bilirubin over a range of bilirubin/albumin molar ratios. All three methods concurred in the demonstration that fresh adult human sera had a higher molar albumin binding capacity for bilirubin than the purified human serum albumin preparations. The fluorescent dye binding and Sephadex column methods agreed most closely in defining presumed deficiency in binding capacity. The HBABA dye binding method was less consistent and appeared to measure non-bilirubin binding sites on albumin in addition to bilirubin binding sites. The fourth method, the saturation index, yielded highly variable results as compared with the other methods because of an inherent excessive risk of laboratory error.

Adult↗
PubMed1978

The modification of the lone tryptophan residue in human serum albumin by 2-hydroxy-5-nitrobenzyl bromide. Characterization of the modified protein and the binding of L-tryptophan and benzodiazepines to the tryptophan-modified albumin.

The possible function of the lone tryptophan residue of human serum albumin in the stereospecific binding site for indole and benzodiazepine compounds was investigated by chemical modification. This residue can be selectively modified with 2-hydroxy-5-nitrobenzyl bromide. The modification alters the conformation of the albumin only slightly, as revealed by circular dichroism, fluorescence, and ultraviolet absorption measurements. A decrease in the association constants of L-tryptophan and diazepam of about 30 - 50% and a decrease in the extrinsic Cotton effects of four benzodiazepine derivatives of about 10 - 15% were found as specific effects of the tryptophan modification. The tryptophan modification itself did not change the number of binding sites of diazepam and L-tryptophan. It is suggested that the lone tryptophan residue of human serum albumin is not directly involved in the specific binding site for indole and benzodiazepine compounds. However, the modification alters the properties of the binding site either by an incomplete refolding of the albumin after urea treatment, or a more selective allosteric effect of the modified tryptophan residue.

2-Hydroxy-5-nitrobenzyl Bromide↗
PubMedDate not supplied

Early glycated albumin, but not advanced glycated albumin, methylglyoxal, or 3-deoxyglucosone increases the expression of PAI-1 in human peritoneal mesothelial cells.

OBJECTIVE: The continuous contact of glucose-containing peritoneal dialysis (PD) fluids with the peritoneum results in the intraperitoneal formation of early and advanced glycation end-products. This nonenzymatic glycation of proteins may cause morphological and functional alterations to the peritoneum, which may contribute to patient dropout from PD therapy. Because fibrinolytic system components have been demonstrated to play an important role in the balance of intraperitoneal generation and degradation of fibrin, we studied the effect of early and advanced glycated human serum albumin, methylglyoxal, and 3-deoxyglucosone on the synthesis of tissue-type plasminogen activator (tPA), as well as its specific inhibitor (PAI-1), in human peritoneal mesothelial cells (HPMC). METHODS: Antigen concentrations in the supernatants of cultured HPMC were measured by ELISA. Northern blot analysis was conducted for mRNA expression. Electrophoretic mobility shift assays were applied to demonstrate the involvement of the transcription factors nuclear factor kappa B (NF-kappaB) and activator protein-1 (AP-1) in signal transduction. RESULTS: Incubation of HPMC with early glycated albumin (GHSA) resulted in a time- and concentration-dependent increase in PAI-1 mRNA expression and antigen secretion. In contrast, no changes in PAI-1 synthesis occurred after stimulation with either the 1,2-dicarbonyl compounds methylglyoxal and 3-deoxyglucosone, or with late advanced glycation end-products. tPA synthesis was not affected by any of the tested components. Furthermore, HPMC exposed to GHSA induced NF-kappaB and AP-1 DNA binding activity, suggesting that GHSA-induced overexpression of PAI-1 is transcriptionally regulated by both transcription factors. CONCLUSIONS: We conclude that Amadori modified glycated albumin upregulates PAI-1 synthesis in HPMC, possibly mediated through the activation of the transcription factors NF-kappaB and AP-1. The present data support the clinical relevance of the formation of glycated proteins and their involvement in pathological processes in PD patients. Thus, glycated albumin may contribute to an imbalance between intraperitoneal formation and degradation of fibrin that causes peritoneal structural alterations, with subsequent membrane failure.

Albumins↗
PubMed1990

The distribution of oleic acid between chylomicron-like emulsions, phospholipid bilayers, and serum albumin. A model for fatty acid distribution between lipoproteins, membranes, and albumin.

In the process of lipoprotein lipolysis, masses of fatty acid are generated at the surface of the lipoprotein. The newly generated fatty acid may at least partly redistribute from the site of lipolysis to phospholipid-rich membranes and to albumin. We have studied the distribution of [1-13C]oleic acid in model systems consisting of chylomicron-like triacylglycerol-rich emulsions, unilamellar phosphatidylcholine vesicles, and bovine serum albumin. By using high resolution 13C NMR spectroscopy it was possible to distinguish fatty acid in each compartment (emulsion, vesicle, albumin) and quantitate the fatty acid distribution under various conditions of lipid compartment concentration and aqueous pH. When emulsions and vesicles were present in equivalent mass amounts, fatty acid exhibited a profound preference for the lipid bilayers. The release of oleic acid to phospholipid bilayers was presumably also a function of its high molar stoichiometry (5:1) with the albumin present. More equitable distributions of fatty acid between vesicles and emulsions were seen when higher concentrations of emulsion were used. The distribution of fatty acid between compartments was in good agreement with predictions made using the apparent ionization constant, expressed as pKapp, of 7.5 and the surface to core (phospholipid to triacylglycerol) distribution coefficient of 7.0, measured for unionized oleic acid in chylomicron particles (Spooner, P. J. R., Bennett Clark, S., Gantz, D. L., Hamilton, J. A., and Small, D. M. (1988) J. Biol. Chem. 263, 1444-1455). These results indicate that the affinities of fatty acid for phospholipid bilayer and chylomicron-like emulsion surfaces are equivalent. Redistribution of lipolytically generated fatty acid from chylomicron surface to cell membrane may simply be driven by the predominant quantity of the cell membrane surfaces.

Cell Membrane↗