Showing papers on "Serum albumin published in 1999"
TL;DR: Serum albumin concentration is a relatively low-cost test that should be used more frequently as a prognostic tool to detect malnutrition and risk of adverse surgical outcomes, particularly in populations in whom comorbid conditions are relatively frequent.
Abstract: Objective: To improve the precision and reliability of estimates of the association between preoperative serum albumin concentration and surgical outcomes. Design: Prospective observational study. Patients were followed up for 30 days postoperatively. Multiple logistic regression models were developed to evaluate serum albumin level as a predictor of operative mortality and morbidity in relation to 61 other preoperative patient risk variables.
896 citations
TL;DR: It is proposed that rapid plasma elimination of polycation/DNA complexes results from their binding serum albumin and other proteins, perhaps due to aggregation and phagocytic capture or accumulation of the ternary complexes in fine capillary beds.
Abstract: Self-assembling polycation/DNA complexes represent a promising synthetic vector for gene delivery. However, despite considerable versatility and transfectional activity in vitro, such materials are quickly eliminated from the bloodstream following intravenous injection (plasma α half-life typically less than 5 min). For targeted systemic delivery a more prolonged plasma circulation of the vector is essential. Here we have examined factors contributing to rapid elimination of poly(L-lysine) (pLL)/DNA complexes from the bloodstream, and implicate the binding of proteins to the polyelectrolyte complexes as a likely cause for their blood clearance. pLL/DNA complexes reisolated from serum associate with several proteins, depending on their net charge, although the major band on SDS-PAGE co-migrates with albumin. Serum albumin binds to pLL/DNA complexes in vitro, forming a ternary pLL/DNA/albumin complex which regains some ethidium bromide fluorescence and fails to move during agarose electrophoresis. Albumin also causes increased turbidity of complexes, and reduces their zeta potential to the same level (−16 mV) as is measured in serum. We propose that rapid plasma elimination of polycation/DNA complexes results from their binding serum albumin and other proteins, perhaps due to aggregation and phagocytic capture or accumulation of the ternary complexes in fine capillary beds.
396 citations
TL;DR: Low-molecular-weight molecules in serum induce hyphal differentiation in C. albicans through a Ras-mediated signal transduction pathway, and strains expressing the dominant active Ras1(V13) allele manifest enhanced hyphal growth, whereas those expressing a dominant negative RAS1(A16) allele show reduced hyphalgrowth.
Abstract: Serum induces Candida albicans to make a rapid morphological change from the yeast cell form to hyphae. Contrary to the previous reports, we found that serum albumin does not play a critical role in this morphological change. Instead, a filtrate (molecular mass, <1 kDa) devoid of serum albumin induces hyphae. To study genes controlling this response, we have isolated the RAS1 gene from C. albicans by complementation. The Candida Ras1 protein, like Ras1 and Ras2 of Saccharomyces cerevisiae, has a long C-terminal extension. Although RAS1 appears to be the only RAS gene present in the C. albicans genome, strains homozygous for a deletion of RAS1 (ras1-2/ras1-3) are viable. The Candida ras1-2/ras1-3 mutant fails to form germ tubes and hyphae in response to serum or to a serum filtrate but does form pseudohyphae. Moreover, strains expressing the dominant active RAS1V13 allele manifest enhanced hyphal growth, whereas those expressing a dominant negative RAS1A16 allele show reduced hyphal growth. These data show that low-molecular-weight molecules in serum induce hyphal differentiation in C. albicans through a Ras-mediated signal transduction pathway.
349 citations
TL;DR: In well-dialyzed patients who were iron replete, the acute-phase response was the most important predictor of EPO resistance, and EPO/Hct was independent of PTH and aluminum levels, PCRn, and Kt/V.
302 citations
TL;DR: It is proposed that, considering the poor glucose control found in diabetics as well as the key role of oxidative stress in vascular complications, glycation‐mediated and free radical‐induced impairment of the antioxidant properties of albumin might be important parameters in vascular complication encountered in diabetes.
Abstract: Epidemiological data consistently show that reduced levels of serum albumin, which is the most abundant protein in plasma, are associated with an increased mortality risk. Various biological properties evidenced by direct effects of the albumin molecule may explain its beneficial effects. The present work aimed to investigate in vitro whether glycation or free radicals or both factors would affect the antioxidant properties of bovine serum albumin (BSA). Glycation was performed by long-term incubations (60 days) of BSA with increasing concentrations of glucose (up to 500 mmol/l) at 37°C. Minimally oxidized BSA was obtained after controlled incubations of dialyzed BSA samples with a water-soluble free radical generator [2,2′ azo-bis(2-amidinopropane) HCl]. The glycation-mediated modifications and the free radical-induced conformational changes of BSA were monitored using intrinsic fluorescence measurements of the tryptophan residues and acrylamide as a quenching agent. Thiol groups, Amadori glycophore cont...
301 citations
TL;DR: CRP is a significant predictor of death in chronic dialysis patients, independent of serum albumin and other possible confounders, and Dialysis patients with high CRP levels should be carefully evaluated and monitored regardless of serumalbumin concentrations in the normal range.
Abstract: Background. The prognosis of chronic dialysis patients is poor, in part due to the high incidence of cardiovascular disease. Malnutrition, such as hypoalbuminaemia, has been shown to be a predictor of death in this group of patients, while serum C-reactive protein (CRP) is a predictor of myocardial infarction and sudden death. Thus, the aim of the present study was to determine of the relationship between CRP and serum albumin concentration, and the value of baseline CRP data in the prediction of death. Methods. In one of the dialysis units in Okinawa, Japan, baseline CRP data was available (n=163, 95 men and 68 women) in January 1991. These patients were divided into two groups according to their baseline CRP levels, with group 1 consisting of CRP<10 mg/l (n=128) and group 2 of CRP≥10 mg/l (n=35), and then followed up until the end of 1997. Survival curves were calculated using the Kaplan-Meier method. The statistical significance of the relationship between CRP levels and the risk of death was evaluated by multiple logistic analysis with covariables such as age, sex, diabetes mellitus, serum albumin, and blood pressure. Results. The mean (SD) level of serum albumin was 38 (3) g/l in group 1 and 36 (3) g/l in group 2 (P<0.00001). The 5-year survival rate was significantly poorer in group 2 (44.4%) than in group 1 (82.5%) (P<0.0001). Furthermore, the risk of death was significantly higher in group 2 (relative risk 3.48 (95% confidence interval 1.76-6.89), P<0.0003) by multivariate Cox proportional hazard analysis. Conclusions. CRP is a significant predictor of death in chronic dialysis patients, independent of serum albumin and other possible confounders. Dialysis patients with high CRP levels should be carefully evaluated and monitored regardless of serum albumin concentrations in the normal range.
299 citations
TL;DR: In this article, photolysis using ultraviolet light and graft polymerization of hydrophilic monomers onto the membrane surface was used to create more hyrophilic and lower fouling membrane surfaces.
273 citations
TL;DR: Steadystate and dynamic fluorescence measurements were used to investigate the interactions and structures of complexes formed between bovine serum albumin (BSA) and anionic, cationic, and nonioni as discussed by the authors.
Abstract: Steady-state and dynamic fluorescence measurements were used to investigate the interactions and structures of complexes formed between bovine serum albumin (BSA) and anionic, cationic, and nonioni ...
258 citations
TL;DR: The strong cross-sectional associations found between levels of these proteins with each other and with concentrations of serum amyloid A protein suggest that some underlying process related to inflammation is likely to be of relevance to the causation of disease.
Abstract: AIMS: Circulating levels of C-reactive protein and serum amyloid A protein increase markedly, and albumin levels fall, during the acute-phase response to tissue injury, infection and inflammation. Some acute-phase proteins have been associated with increased risks of coronary heart disease in long-term prospective studies. The aim of the present study was to determine whether circulating concentrations of C-reactive protein, albumin and serum amyloid A protein are correlated with one another, standard vascular risk factors, markers of persistent infection, or indicators of socio-economic status. METHODS AND RESULTS: We report a cross-sectional study of 704 individuals without a history of coronary heart disease from five general practices in Bedfordshire, U.K. Plasma levels of C-reactive protein and serum amyloid A protein were strongly associated with each other (2 P<0.00001) and inversely related to levels of serum albumin (2 P<0.00001). There were highly significant associations of plasma C-reactive protein concentrations with cigarette smoking and obesity (2 P<0.00001 for each). Serum albumin levels were strongly associated with blood pressure (2 P<0.0001) and plasma lipids (2 P<0.001), and concentrations of serum amyloid A protein were strongly correlated with obesity (2 P<0.0001). CONCLUSION: Previously reported long-term prospective studies have found an increased risk of coronary heart disease of about 50% in people with raised baseline levels of plasma C-reactive protein or low albumin. The strong cross-sectional associations we have found between levels of these proteins with each other and with concentrations of serum amyloid A protein suggest that some underlying process related to inflammation is likely to be of relevance to the causation of disease. Further studies are needed to determine if the strong associations of plasma levels of C-reactive protein with cigarette smoking and obesity indicate that this particular protein can mediate some of the effects of those risk factors on coronary heart disease.
252 citations
TL;DR: It is reported that E2-BSA conjugate preparations, but not unconjugated E2, activate extracellular signal-regulated protein kinases (ERK1 and ERK2) in the SK-N-SH neuroblastoma cell line, raising concerns regarding the use of these reagents as E2 mimics.
Abstract: The steroid 17beta-estradiol (E2) acts to modulate transcription through classical nuclear estrogen receptors (ER-alpha and ER-beta). However, E2 also induces a number of rapid responses (<10 min) within cells, including cells devoid of classical ERs, consistent with the presence of a membrane receptor for E2. Membrane impermeable steroids, typically bovine serum albumin (BSA) conjugates, are commonly used to characterize these non-genomic actions of E2 to exclude the involvement of nuclear ERs. Here we report that E2-BSA conjugate preparations, but not unconjugated E2, activate extracellular signal-regulated protein kinases (ERK1 and ERK2) in the SK-N-SH neuroblastoma cell line, raising concerns regarding the use of these reagents as E2 mimics. Freshly prepared solutions of E2-BSA were found to contain free immunoassayable E2 (iE2), which could be removed by filtration. E2-BSA solutions devoid of free iE2 failed to compete for binding of 125I16alpha-iodo-E2 to ER-alpha or ER-beta. Furthermore, in contrast to E2, E2-BSA conjugates did not bind to ER-alpha or ER-beta as assessed by electrophoretic mobility shift analyses. Protein analysis demonstrated that certain E2-BSA preparations were of very high molecular weight, suggesting extreme protein cross-linking. These findings suggest that E2-BSA does not mimic E2 and is not an appropriate ligand for investigating estrogen receptors. This underscores the need to design stable, cell impermeable analogs of estrogen for the characterization of membrane estrogen receptors.
199 citations
TL;DR: It is demonstrated that M6P‐modified bovine serum albumin (BSA) accumulates in slices of normal and cirrhotic human livers and can be applied as a selective drug carrier for HSC.
TL;DR: Under physiologic conditions, the predominant mechanism of cellular FFA uptake is facilitated transport of FA-; at much higher, non-physiologic FFA concentrations, passive flip-flop of FAH predominates.
Abstract: Cells take up long chain free fatty acids (FFA) in vivo from the non-protein bound ligand pools in extracellular fluid and plasma, which contain ∼100 and 600 μM albumin, respectively. The physiologic range of unbound FFA concentrations in such fluids has traditionally been calculated at 10 sec, and thus comparable to the rates of non-saturable uptake we determined. Thus, under physiologic conditions, the predominant mechanism of cellular FFA uptake is facilitated transport of FA-; at much higher, non-physiologic FFA concentrations, passive flip-flop of FAH predominates. Several plasma membrane proteins have been identified as potential mediators of facilitated FFA transport. Studies in animal models of obesity and non-insulin dependent diabetes mellitus demonstrate that tissue-specific regulation of facilitated FFA transport has important pathophysiologic consequences. (Mol Cell Biochem 192: 17–31, 1999)
TL;DR: In this article, the binding properties of propofol to erythrocytes, to human serum, and to isolated serum proteins were investigated using a co-binding technique with dextran coated charcoal.
Abstract: Aims Propofol is a widely used iv anaesthetic agent However, its binding properties to blood components have not been fully studied
Methods We studied the binding of propofol to erythrocytes, to human serum and to isolated serum proteins Because propofol bound to ultrafiltration and equilibrium dialysis membranes, we used a co-binding technique with dextran coated charcoal and with erythrocytes
Results Propofol free fraction in blood was 12–17% at total concentrations ranging from 280 to 179 μm (05 to 32 μg ml−1 ) Fifty percent was bound to erythrocytes and 48% to serum proteins, almost exclusively to human serum albumin In the clinical range of concentrations (05–16 μg ml−1 ) 40% of the molecules bound to erythrocytes are on the red blood cells membranes No binding to lipoproteins occurred and binding to α1-acid glycoprotein was less than 15%
Conclusions We conclude that hypoalbuminaemia may increase propofol free fraction particularly during prolonged administration Since propofol is non-restrictively cleared, no change in clearance is expected to occur, and the increase in free fraction will not be compensated by a parallel increase in clearance It is also noted that many in vitro studies used concentrations 50 to 500 times the concentration expected to be encountered in the immediate cellular environment
TL;DR: The results are consistent with a proposed pathophysiological role of Amadori albumin in microvascular complications of type 1 diabetic patients.
Abstract: Nonenzymatic glycation is increased in diabetes. Most studies so far have focused on the role of advanced glycation end products (AGEs) in vascular complications, whereas the role of early glycation Amadori-modified proteins, which is the predominant form of glycated proteins, has not been systemically investigated in humans. We developed an antiserum against glycated human serum albumin (HSA) and used this to study the role of early glycation products in vascular complications in type 1 diabetic patients. Amadori albumin was determined to be the recognition epitope of the antiserum. The antibody recognized a specific glucose adduct and a conformational component specific for human albumin in Amadori albumin, with no recognition of AGEs. Plasma Amadori albumin levels were significantly higher in type 1 diabetic patients (n = 55) than in healthy control subjects (n = 60) (39.2+/-9.9 vs. 20.9+/-4.0 U/ml, P < 0.0005). Amadori albumin correlated with levels of plasma markers of endothelial function von Willebrand factor (r = 0.29, P < 0.05) and vascular cell adhesion molecule-1 (r = 0.41, P < 0.005), but not soluble E-selectin. In addition, Amadori albumin immunoreactivity was detected in the capillaries of retinas of diabetic patients. Plasma levels of Amadori albumin were determined in a second group of type 1 diabetic patients with long-standing diabetes with (n = 199) or without (n = 192) diabetic nephropathy. Patients with nephropathy had higher Amadori albumin levels than did those without it (50.9+/-9.5 vs. 45.1+/-6.3 U/ml, P < 0.0005). Age-, sex-, and diabetes duration-adjusted analyses showed that nephropathy was significantly associated with Amadori albumin with an odds ratio (OR [95% CI]) of 1.11 [1.08-1.15] per U/ml increase. After additional adjustment for levels of creatinine, glycated hemoglobin, cholesterol, triglycerides, blood pressure, preexistent retinopathy, and cardiovascular disease, Amadori albumin continued to be significantly associated with nephropathy (OR 1.06 [1.01-1.11]) per U/ml increase. Our results are consistent with a proposed pathophysiological role of Amadori albumin in microvascular complications of type 1 diabetic patients.
TL;DR: Plasma contains at least 300 times more amyloid inhibitory activity than cerebrospinal fluid, which may provide one explanation as to why beta-amyloid deposits are not found in peripheral tissues but are only found in the central nervous system.
TL;DR: An automated assay for Hp utilising SB-7 was developed for production as a biochemical assay kit and was evaluated for use in veterinary diagnosis and has negligible interference from albumin.
Abstract: Measurement of the acute phase serum protein, haptoglobin (Hp), is performed by biochemical methods based on haemoglobin binding, in many veterinary diagnostic laboratories. During attempts to develop a robust biochemical assay for serum Hp it was discovered that serum albumin interfered with the assay system increasing results by as much as 0.28 mg/ml, which could affect interpretation of results especially in species with low normal Hp concentrations. A reagent cocktail (SB-7) was devised which inhibited the interfering effect of albumin. An automated assay for Hp utilising SB-7 was developed for production as a biochemical assay kit and was evaluated for use in veterinary diagnosis. The intra-assay coefficients of variation were of 0.9%, 0.9% and 1.3% for Hp concentrations of 2.0, 1.0 and 0.23 mg/ml, respectively and interassay coefficients of variation of 1.7% and 4.5% for Hp of 2.08 mg/ml and 0.24 mg/ml, respectively. The lower limit of detection of was 0.02 mg/ml, linearity extended to 8 mg/ml and recovery was 101±7% (mean ±SD). The assay had correlation coefficients (R2) of 0.96 and 0.90 when compared with immunodiffusion assays of canine Hp and bovine Hp, respectively. Lipaemia and bilirubinaemia caused no interference. Haemolysis did not affect measurement of low levels of Hp, but at serum Hp concentrations of 0.4 and 1.8 mg/ml the apparent Hp concentration was decreased. Elevated concentrations of Hp were measured in cattle with mastitis, dogs with polyarthritis and rats experimentally infected withBordetella pertussis. The automated assay is precise and has negligible interference from albumin.
TL;DR: It is suggested that lower serum Zn in depression may be secondary to sequestration of metallothionein in the liver, which may be related to increased production of interleukin-6.
TL;DR: In all age groups, serum calcium levels were higher in men with a history of myocardial infarction than in those without, and the difference was significant in a linear regression analysis adjusted for age.
Abstract: Total serum calcium levels were measured in 12 865 men and 14 293 women, between the ages of 25 and 97 years, in the Tromso Study during 1994 and 1995. With the use of a sex-specific multiple linear regression model with age, calcium, body mass index, cholesterol, HDL cholesterol, triglycerides, systolic and diastolic blood pressure, and pulse as possible covariates, serum calcium was significantly (P<0.001) and positively associated with systolic and diastolic blood pressure, serum cholesterol, and HDL cholesterol in both sexes. A similar but weaker association was observed between serum calcium and triglycerides in men (P<0.01). In all age groups, serum calcium levels were higher in men with a history of myocardial infarction than in those without, and the difference was significant (P<0.0001) in a linear regression analysis adjusted for age. When all the other variables were also included in a logistic regression model, serum calcium was a highly significant (P<0.0001) predictor of myocardial infarction in men, with an odds ratio of 1.2 per 0.1 mmol/L increase in serum calcium. In women, a nonsignificant trend was again seen. Because the free or ionized form of calcium is the physiologically important form and serum calcium was not corrected for serum albumin in our study, the results must be interpreted with caution. However, it appears likely that serum calcium is a predictor of cardiovascular disease in men.
TL;DR: It is proposed that embryo culture media should contain both serum albumin and hyaluronan, while the transfer medium need only contain hyalonsonan, as the highest cell numbers and hatching rates obtained in this study occurred when both serum Albumin and Hyaluronans were present in the same medium.
Abstract: The effect of macromolecules on mouse embryo development and viability after culture in sequential media was investigated. It was found that high rates of viable blastocysts could be obtained in the absence of any macromolecule. Blastocyst cell numbers were increased when bovine serum albumin was present in the culture medium, although this benefit was not manifest after blastocyst transfer. Rather, the highest rates of implantation and fetal development after blastocyst transfer were observed when hyaluronan was the macromolecule in the culture media. Subsequent analysis revealed that the beneficial effects of hyaluronan were due to its presence in the transfer medium. As the highest cell numbers and hatching rates obtained in this study occurred when both serum albumin and hyaluronan were present in the same medium, it is proposed that embryo culture media should contain both serum albumin and hyaluronan, while the transfer medium need only contain hyaluronan.
TL;DR: The analytical procedure could be successfully applied to the analysis of albumin samples from Iranian victims of the Iran-Iraq war and allowed a detection limit for in vitro exposure of human blood of 10 nM, which is 1 order of magnitude lower than that obtained by means of modified Edman degradation.
Abstract: To develop a mass spectrometric assay for the detection of sulfur mustard adducts with human serum albumin, the following steps were performed: quantitation of the binding of the agent to the protein by using [14C] sulfur mustard and analysis of acidic and tryptic digests of albumin from blood after exposure to sulfur mustard for identification of alkylation sites in the protein. The T5 fragment containing an alkylated cysteine could be detected in the tryptic digest with micro-LC/tandem MS analysis. Attempts to decrease the detection limit for in vitro exposure of human blood by analysis of the alkylated T5 fragment were not successful. After Pronase treatment of albumin, S-[2-[(hydroxyethyl)thio]ethyl]Cys-Pro-Phe was analyzed by means of micro-LC/tandem MS, allowing a detection limit for in vitro exposure of human blood of 10 nM, which is 1 order of magnitude lower than that obtained by means of modified Edman degradation. The analytical procedure could be successfully applied to the analysis of albumin samples from Iranian victims of the Iran-Iraq war.
TL;DR: The data suggest that the hemin-LDL complex may exist in vivo and that its oxidative potential should be considered pro-atherogenic.
TL;DR: Evidence of ligand-induced (oleic acid) structural changes in serum albumin are shown in both time-resolved and steady-state fluorescence quenching and anisotropy measurements of tryptophan 214 (Trp214), suggesting an oleate-dependent structural transformation.
Patent•
15 Jun 1999
TL;DR: Erythropoietin analog-human serum albumin (EPOa-hSA) fusion protein and methods of making and using the fusion protein were discussed in this article.
Abstract: Erythropoietin analog-human serum albumin (EPOa-hSA) fusion protein and methods of making and using the fusion protein.
TL;DR: IL‐6 may be vitally involved in fibrotic changes and maintenance of serum albumin levels, partly by modulating intrahepatic expression of these cytokines.
Abstract: Chronic intermittent injection of car- bon tetrachloride (CCl4) for more than 10 weeks induced liver fibrosis in mice, as evidenced by positive Azan staining and increased intrahepatic collagen content. Preceding the onset of liver fibrosis, interleukin-6 (IL-6) gene expression was enhanced in liver and immunoreactive IL-6 was detected in infiltrating inflammatory cells. To delin- eate the role of IL-6 in this process, we treated IL-6-deficient mice with CCl4 in a similar manner for 12 weeks, after which fibrotic changes were less evident and serum albumin levels were lower in IL-6-deficient than wild-type mice. Moreover, CCl4- induced expression of transforming growth factor b1 and hepatocyte growth factor genes in liver was significantly reduced in IL-6-deficient mice. Thus, IL-6 may be vitally involved in fibrotic changes and maintenance of serum albumin levels, partly by modulating intrahepatic expression of these cyto- kines. J. Leukoc. Biol. 66: 601-608; 1999.
TL;DR: Subsequent reactions of the Amadori and Heyns rearrangement products, cross-linking, development of Maillard fluorescence, oxidation, and fragmentation, indicated that the alpha-hydroxy carbonyl group of Amador i products is more reactive than the aldehydo group of Heyni products.
Abstract: Glycation of bovine serum albumin by d-glucose and d-fructose under dry-heating conditions was studied. The reactivities of d-glucose and d-fructose, with respect to their ability to utilize primary amino groups of proteins, to cross-link proteins, to develop Maillard fluorescence, and to reduce protein solubility in the presence and absence of air (molecular oxygen) were investigated. d-Glucose showed a higher initial rate of utilization of primary amino groups than d-fructose, both in the presence and in the absence of oxygen. Subsequent reactions of the Amadori and Heyns rearrangement products, cross-linking, development of Maillard fluorescence, oxidation, and fragmentation, indicated that the α-hydroxy carbonyl group of Amadori products is more reactive than the aldehydo group of Heyns products. d-Fructose showed a greater sensitivity than d-glucose toward the presence of oxygen at the initial stages of the Maillard reaction. The presence or absence of oxygen in the glycation mixture did not seem to ...
TL;DR: The degree of acidosis observed in hemodialysis patients does not seem to have a deleterious effect on the nutritional status of these patients because correlation of serum total carbon dioxide level with nutritional parameters, such as serum creatinine and serum albumin levels, was either negative or not statistically significant.
TL;DR: The high-capacity retrieval pathway for albumin is most likely associated with transtubular cell transport and it is apparent that most albuminuric states could be accounted for by the malfunctioning of this pathway without resorting to any change in glomerular permselectivity.
TL;DR: The plasma proteins hemopexin (Hx) and albumin (Alb) are known to bind heme with high and medium affinity, respectively as discussed by the authors, and this binding modifies heme catalytic reactivity, the effects of Hx, human serum Alb, and bovine serum Alb on the peroxidase-and catalaselike activities of hemin were investigated.
TL;DR: The hypothesis that mannose-BSA, but not progesterone, activates T-type Ca2+ channels in human spermatozoa for the following reasons is supported: the ability of these neoglycoproteins to rapidly increase intracellular free calcium ([Ca2+]i) accounts for the known ability ofThese compounds to induce the acrosome reaction in human semen.
Abstract: The neoglycoproteins alpha-D-mannose-bovine serum albumin (mannose-BSA) and N-acetyl-alpha-D-glucosamine-BSA (glucNAc-BSA) were shown to rapidly increase intracellular free calcium ([Ca2+]i) in human spermatozoa. The increase in [Ca2+]i induced by these neoglycoproteins accounts for the known ability of these compounds to induce the acrosome reaction in human spermatozoa. Our data support the hypothesis that mannose-BSA, but not progesterone, activates T-type Ca2+ channels in human spermatozoa for the following reasons: (i) the capacity of mannose-BSA to increase [Ca2+]i was inhibited by the specific T-type Ca2+ channel blocker mibefradil (IC50 = 10(-6) mol/l) while progesterone was not inhibited by 10(-5) M mibefradil; (ii) the effect of mannose-BSA to elevate [Ca2+]i was inhibited more potently by Ni2+ (IC50 = 0.1 mmol/l) than Cd2+ (IC50 = 0.5 mmol/l), whereas the effect of progesterone to elevate [Ca2+]i was inhibited equally by Ni2+ and Cd2+ (IC50 = 0.25 mmol/l); (iii) the effects of mannose-BSA and progesterone to increase [Ca2+]i were greater than additive. These data support the idea that mannose-BSA and progesterone were activating distinct Ca2+ channels, one of which was a T-type Ca2+ channel activated by mannose-BSA whereas the Ca2+ channel that was activated by progesterone has yet to be defined at the molecular level.
TL;DR: In this paper, the binding of quercetin to Bovine serum albumin (BSA) was quantitatively investigated by fluorescence spectroscopy, and it was shown that a significant fraction of queretin adopts a pyrylium-like structure in the complex.
Abstract: Quercetin (3,3′,4′,5,7-pentahydroxyflavone) and quercetin derivatives (3-methylquercetin, isoquercitrin, rutin) are strong polyphenolic antioxidants abundant in plants and in the human diet. Recent investigations have shown that significant concentrations of albumin-bound quercetin conjugates are present in the plasma of humans fed a quercetin-rich diet.In this work, binding of quercetin and quercetin glycosides to bovine serum albumin (BSA) is quantitatively investigated by fluorescence spectroscopy. The strong fluorescence enhancement of quercetin upon binding points to the fact that a significant fraction of quercetin adopts a pyrylium-like structure in the complex. On the other hand, the observation of a very efficient quenching of tryptophan fluorescence by quercetin is consistent with a binding occurring in the IIA domain.Flavonoid-derived quinones may be formed upon quenching of reactive oxygen species by flavonoids (antioxidant activity). In this work, the quinones are conveniently formed upon periodate oxidation of the selected flavonoids in methanol and in aqueous buffers with and without BSA. A kinetic investigation by UV–visible spectroscopy shows that albumin-bound flavonoids are oxidized as quickly as free flavonoids. Interestingly, the quercetin quinone, which is merely detectable in the absence of BSA because of fast solvent addition, is efficiently stabilized in the complex by charge transfer interactions (pH 9). No evidence for quercetin–BSA conjugates could be found, thus showing that water addition (and subsequent degradation) remains the sole significant pathway of quinone transformation in the complex.