Showing papers on "Bovine serum albumin published in 1990"

Anti-phospholipid antibodies are directed against a complex antigen that includes a lipid-binding inhibitor of coagulation: beta 2-glycoprotein I (apolipoprotein H).

Abstract: Anti-phospholipid (aPL) antibodies that exhibit binding in cardiolipin (CL) ELISA can be purified to greater than 95% purity by sequential phospholipid affinity and ion-exchange chromatography. However, these highly purified aPL antibodies do not bind to the CL antigen when assayed by a modified CL ELISA in which the blocking agent does not contain bovine serum, nor do they bind to phospholipid affinity columns. Binding to the phospholipid antigen will only occur if normal human plasma, human serum, or bovine serum is present, suggesting that the binding of aPL antibodies to CL requires the presence of a plasma/serum cofactor. Using sequential phospholipid affinity, gel-filtration, and ion-exchange chromatography, we have purified this cofactor to homogeneity and shown that the binding of aPL antibodies to CL requires the presence of this cofactor in a dose-dependent manner. N-terminal region sequence analysis of the molecule has identified the cofactor as beta 2-glycoprotein I (beta 2GPI) (apolipoprotein H), a plasma protein known to bind to anionic phospholipids. These findings indicate that the presence of beta 2GPI is an absolute requirement for antibody-phospholipid interaction, suggesting that bound beta 2GPI forms the antigen to which aPL antibodies are directed. Recent evidence indicates that beta 2GPI exerts multiple inhibitory effects on the coagulation pathway and platelet aggregation. Interference with the function of beta 2GPI by aPL antibodies could explain the thrombotic diathesis seen in association with these antibodies.

A new redox cofactor in eukaryotic enzymes: 6-hydroxydopa at the active site of bovine serum amine oxidase

Abstract: An active site, cofactor-containing peptide has been obtained in high yield from bovine serum amine oxidase. Sequencing of this pentapeptide indicates: Leu-Asn-X-Asp-Tyr. Analysis of the peptide by mass spectrometry, ultraviolet-visible spectroscopy, and proton nuclear magnetic resonance leads to the identification of X as 6-hydroxydopa. This result indicates that, contrary to previous proposals, pyrroloquinoline quinone is not the active site cofactor in mammalian copper amine oxidases. Although 6-hydroxydopa has been implicated in neurotoxicity, the data presented suggest that this compound has a functional role at an enzyme active site.

Preferential interactions determine protein solubility in three-component solutions: the MgCl2 system.

Abstract: The correlation between protein solubility and the preferential interactions of proteins with solvent components was critically examined with aqueous MgCl2 as the solvent system. Preferential interaction and solubility measurements with three proteins, beta-lactoglobulin, bovine serum albumin, and lysozyme, resulted in similar patterns of interaction. At acid pH (pH 2-3) and lower salt concentrations (less than 2 M), the proteins were preferentially hydrated, while at higher salt concentrations, the interaction was either that of preferential salt binding or low salt exclusion. At pH 4.5-5, all three proteins exhibited either very low preferential hydration or preferential binding of MgCl2. These results were analyzed in terms of the balance between salt binding and salt exclusion attributed to the increase in the surface tension of water by salts, which is invariant with conditions. It was shown that the increase in salt binding at high salt concentration is a reflection of mass action, while its decrease at acid pH is due to the electrostatic repulsion between Mg2+ ions and the high net positive charge on the protein. The preferential interaction pattern was paralleled by the variation of protein solubility with solvent conditions. Calculation of the transfer free energies from water to the salt solutions for proteins in solution and in the precipitate showed dependencies on salt concentration. This indicates that the nature of interactions between proteins and solvent components is the same in solution and in the solid state, which implies no change in protein structure during precipitation. Analysis of the transfer free energies and preferential interaction parameter in terms of the salting-in, salting-out, and weak ion binding contributions has led to the conclusions that, when the weak ion binding contribution is small, the predominant protein-salt interaction must be that of preferential salt exclusion most probably caused by the increase of the surface tension of water by addition of the salt. A necessary consequence of this is salting-out of the protein, if the protein structure is to remain unaltered.

Bovine and mouse serum beta inhibitors of influenza A viruses are mannose-binding lectins.

Abstract: Normal bovine and mouse sera contain a component, termed beta inhibitor, that inhibits the infectivity and hemagglutinating activity of influenza A viruses of the H1 and H3 subtypes. To investigate the nature of the interaction of beta inhibitors with influenza A viruses we isolated a mutant of the virus Mem71H-BelN (H3N1) that could grow in the presence of bovine serum. The mutant virus was resistant to hemagglutination inhibition by mouse serum as well as by bovine serum and had undergone changes in the receptor-binding and the antigenic properties of its hemagglutinin (HA) molecule. Sequence analysis of the HA genes of parent and mutant viruses revealed a single nucleotide change in the mutant, resulting in the substitution Thr----Asn at residue 167 of the HA1 chain of HA. This change leads to loss of the potential glycosylation site Asn-165-Val-166-Thr-167 at the tip of the HA spike, which in viruses of the H3 subtype is known to bear a high-mannose (type II) carbohydrate side chain N-linked to Asn-165. The association of beta inhibitor resistance with loss of this carbohydrate side chain suggested that beta inhibitors may be lectins. In support of this hypothesis, treatment of the beta inhibitor-sensitive parent virus Mem71H-BelN with periodate converted it to the resistant state. Furthermore, the inhibitory activity of both bovine and mouse sera for the parental virus was abrogated by D-mannose. We conclude that the beta inhibitors in bovine and mouse sera are mannose-binding lectins that inhibit hemagglutination and neutralize virus infectivity by binding to carbohydrate at the tip of the HA spike, blocking access of cell-surface receptors to the receptor-binding site on HA.

An improved method for determining proteoglycans synthesized by chondrocytes in culture.

Abstract: An improved micro method for measuring sulfated glycosaminoglycans (S-GAG) in chondrocyte cultures using 1,9-Dimethylmethylene Blue (DMB) has been developed. By increasing the protein concentration in the DMB assay a soluble GAG-DMB complex is prolonged. Without bovine serum albumin (BSA) in the phosphate-buffered saline (PBS) medium, the half time for loss of absorbance was 18 min; with 1% BSA-PBS there was no loss of absorbance over this time period. The limit of detection in a 96 well microtiter plate assay was 2 micrograms/ml; for a cuvette assay it was 1 microgram/ml. Collagen, DNA and RNA did not interfere with this assay. Hyaluronate caused an increase in absorbance at 530 nm that was lost by preincubating with Streptomyces hyaluronidase. The increase in absorbance was due to a turbidity change because there was no color shift from 600 to 530 nm but rather a uniform increase in absorbance between 400 to 700 nm. To validate the assay, the S-GAG was measured in conditioned medium from primary bovine articular chondrocyte monolayer cultures. A protein synthesis inhibitor, cycloheximide, blocked proteoglycan synthesis by greater than 90%. A cytokine, Interleukin-1 alpha, caused a dose-dependent decrease in proteoglycan accumulation. Chondroitinase ABC digestion of the chondrocyte conditioned medium completely prevented reactivity with the DMB. By preincubating samples with specific enzymes, different types of S-GAG can be measured with this assay. This assay can be used to measure changes in proteoglycans synthesized by chondrocytes.

Structural and biological characterization of bovine insulin-like growth factor binding protein-3.

Abstract: Insulin-like growth factor binding protein-3 (IGFBP-3) purified from bovine serum shares 19 of 25 amino-terminal amino acid residues with IGFBP-3 purified from human, rat, and porcine sources. A newly characterized bovine fibroblast model was used to investigate the biological effects of purified bovine IGFBP-3 (bIGFBP-3). Coincubation of insulin-like growth factor I (IGF-I) with increasing concentrations of bIGFBP-3 produced a dose-dependent inhibition of IGF-I-stimulated [3H]aminoisobutyric acid (AIB) uptake in cultured bovine fibroblasts. Inhibition was complete at equimolar concentrations of IGF-I and bIGFBP-3. Inhibition of IGF-I-stimulated [3H]AIB uptake paralleled the ability of bIGFBP-3 to prevent [125I]IGF-I cell surface binding. In contrast, preincubation with bIGFBP-3 resulted in a dose-dependent enhancement of IGF-I-stimulated [3H]AIB uptake; a 32-86% increase in IGF-I bioactivity was seen after a 24 h preexposure to 10 nM bIGFBP-3, and a 2- to 6-fold potentiation was seen after a 72 h preincubation. Preincubation with bIGFBP-3 increased both the sensitivity and maximal responsiveness of the cells to IGF-I. The potentiating effects of bIGFBP-3 were associated with increased [125I]IGF-I binding to cultured bovine fibroblasts. Affinity cross-linking experiments indicated that the increase in IGF-I binding was due to increased membrane-associated bIGFBP-3 rather than to a bIGFBP-3-induced increase in type I IGF receptors. bIGFBP-3 had no effect on insulin stimulation of [3H]AIB uptake under either experimental condition. These data suggest that soluble bIGFBP-3 inhibits IGF-I action by sequestering and preventing IGF-I receptor binding, whereas surface-associated bIGFBP-3 enhances the growth-promoting effects of IGF-I in bovine fibroblasts. We propose that IGFBP-3 serves a dual function in modulating IGF action in vivo.

Kinetic analysis of oligodeoxyribonucleotide-directed triple-helix formation on DNA.

Abstract: Pyrimidine oligonucleotides recognize extended purine sequences in the major groove of double-helical DNA by triple-helix formation. The resulting local triple helices are relatively stable and can block DNA recognition by sequence-specific DNA binding proteins such as restriction endonucleases. Association and dissociation kinetics for the oligodeoxyribonucleotide 5'-CTCTTTCCTCTCTTTTTCCCC (bold C's indicate 5-methylcytosine residues) are now measured with a restriction endonuclease protection assay. When oligonucleotides are present in greater than 10-fold excess over the DNA target site, the binding reaction kinetics are pseudo first order in oligonucleotide concentration. Under our standard conditions (37 degrees C, 25 mM Tris-acetate, pH 6.8, 70 mM sodium chloride, 20 mM magnesium chloride, 0.4 mM spermine tetrahydrochloride, 10 mM beta-mercaptoethanol, 0.1 mg/mL bovine serum albumin) the value of the observed pseudo-first-order association rate constant, k_(2obs), is 1.8 x 10^3 +± 1.9 x 10^2 L.(mol of oligomer^-1·s^-1. Measurement of the dissociation rate constant yields an equilibrium dissociation constant of approximately 10 nM. Increasing sodium ion concentration slightly decreased the association rate, substantially increased the dissociation rate, and thereby reduced the equilibrium binding constant. This effect was reversible by increasing multivalent cation concentration, confirming the significant role of multivalent cations in oligonucleotide-directed triple-helix formation under these conditions. Finally, a small reduction in association rate, a large increase in dissociation rate, and a resulting reduction in the equilibrium binding constant were observed upon increasing the pH between 6.8 and 7.2.

Binding of progesterone to nerve cell membranes of rat brain using progesterone conjugated to 125I-bovine serum albumin as a ligand.

Abstract: Radioiodinated bovine serum albumin conjugated to progesterone was used as a probe to examine binding parameters of steroids to membrane preparations from rat brain tissue. The binding of 11 alpha-hydroxyprogesterone-11-hemisuccinate-125I-bovine serum albumin conjugate reached saturation after 30 min of incubation at 5 degrees C. Several bovine serum albumin-conjugated steroids were then tested for competition displacement studies. Among these steroid conjugates, the bovine serum albumin conjugate at position 3 of progesterone had the highest affinity, with an estimated inhibition constant of 28.5 +/- 2.1 nM (n = 3), whereas bovine serum albumin itself and the 17 beta-estradiol 6-(O-carboxy-methyl)oxime-bovine serum albumin conjugate showed no specific displacement. In addition, the binding sites were localized in an axolemma-enriched fraction of rat brainstem. Specific binding was obtained in tissues from cerebral cortex, brainstem, cerebellum, corpus striatum, and hypothalamus, but little or no binding occurred in uterus, ovary, liver, and spleen. The present data indicate that progesterone-125I-bovine serum albumin conjugate can be used as a ligand to study progesterone-membrane receptor interactions.

The adsorption of bovine serum albumin on positively and negatively charged polystyrene latices

Abstract: The present study deals with the electrostatic aspects of the interaction between monomeric bovine serum albumin (BSA) and polystyrene latex particles. Adsorption and electrophoresis experiments have been performed as a function of pH, using both negatively and positively charged latices with different surface charge densities. The adsorption isotherms develop well-defined plateaus. These plateaus vary with pH, showing a maximum at the isoelectric point of the protein-covered polystyrene particles, rather than that of the isoelectric point of the protein itself. Co-adsorption of low-molecular-weight ions is shown to be an important parallel process. Studying it helps to discriminate between electrical and chemical contributions to the binding affinity.

Serum Albumin and Globulin

Abstract: Hundreds of proteins are dissolved in the plasma. By measuring the concentration of these proteins, the clinician can obtain information regarding disease states in different organ systems. The measurement of protein is done on serum, which is the fluid that remains after plasma has clotted, thus removing fibrinogen and most of the clotting factors. Total protein content provides some information regarding a patient's general status; more clinically useful data are obtained from fractionating the total protein. The normal serum protein level is 6 to 8 g/dl. Albumin makes up 3.5 to 5.0 g/dl, and the remainder is the total globulins. These values may vary according to the individual laboratory.

Surface‐enhanced Raman spectroscopy of biomolecules. Part I.—water‐soluble proteins, dipeptides and amino acids

Abstract: Surface-enhanced Raman (SER) spectra of water-soluble proteins (lysozyme and bovine serum albumin), dipeptides and amino acids were analysed. Chemisorption is a necessary condition for the appearance of SER spectra on silver electrodes and hydrosols for these compounds. The Raman cross-section enhancement per molecule may reach a factor of 105–106, depending closely on the frequency of the vibration band considered. The mechanism of enhancement has a short-range character and is attributed to the π-electron complexes of the aromatic amino acids side-chains and σ-complexes of the molecular groups containing unshared electron pairs with the metal. The effect of induced optical activity in the visible region for aromatic amino adsorbed by silver hydrosols has been elucidated.

Serum albumin as a modulator on growth of the human breast cancer cell line, MCF-7.

Abstract: The growth of the estrogen responsive human breast cancer cell line, MCF-7, is inhibited by high serum concentrations, and this growth inhibition can be abolished by estradiol (E2). To investigate this inhibitory phenomenon further, we decided to purify the inhibitory factor from newborn calf serum (NCS). After the use of various fractionation methods, we found that inhibitory activity in NCS was exclusively expressed by albumin containing fractions. The inhibitory potential of several commercial bovine serum albumin (BSA) preparations and one human serum albumin preparation were analysed. They all exerted inhibitory activity comparable to that of NCS, and BSA inhibited MCF-7 cell proliferation in a concentration-dependent manner similar to that of NCS. Albumin itself or a contaminating factor in the albumin preparations seemed to be responsible for the growth inhibition. It could be excluded that the growth inhibitor TGF-beta, known to be present in serum, was the factor which inhibited MCF-7 cell proliferation. We separated contaminating proteins from albumin by gel filtration of a BSA preparation, revealing that neither low mol.wt nor high mol.wt proteins in the preparation exerted any significant growth inhibitory activity. NCS and BSA affected the secretion of specific proteins from MCF-7 cells similarly, when grown with or without E2. In conclusion, we assume that albumin is the factor in serum exerting a growth inhibition which can be reversed by E2. Our results indicate that albumin may affect cell proliferation by modulating the activities of autocrine growth regulatory factors.

Protein adsorption in asymmetric ultrafiltration membranes with highly constricted pores

Abstract: Although protein adsorption can have profound effects on membrane transport, accurate measurements of protein uptake in asymmetric ultrafiltration membranes with highly constricted pores are currently unavailable. We have evaluated bovine serum albumin adsorption of Filtron NOVA and OMEGA polyethersulfone membranes with molecular weight cutoffs ranging from 30,000 to 1,000,000 using both 125 I-radiolabeled albumin and direct measurement of unlabeled protein uptake by mass. Data indicate that the radiolabeled proteins proteins adsorb preferentially compared to the unlabeled protein in both the ultrathin skin and substructure, but not in the membrane matrix due to differences in polymer properties. Protein uptake was evaluated in each region of the membrane using data for the isolated matrix, the substructure and matrix in combination, and the full asymmetric membrane. Albumin uptake in the substructure and matrix attained monolayer levels in all of the membranes. Monolayer adsorption was also found in the ulthrathin skin of membranes with molecular weight cutoffs of 300,000 or greater, even though the pores in these membranes are only twice the size of an albumin molecule. Albumin adsorption in the ultrathin skin of the 100,000 molecular weight cutoff membrane was substantially reduced compared to monolayer levels, and protein uptake in the skin of the 50,000 molecular weight cutoff membrane was negligible. Measurements of the membrane hydraulic permeability before and after protein adsorption indicate that the effective pore radius in the larger molecular weight cutoff membranes was reduced by approximately 60 A, which is in good agreement with calculations based on monolayer adsorption.

Glycosphingolipid receptors for Pseudomonas aeruginosa.

Abstract: The binding of Pseudomonas aeruginosa to glycosphingolipids and to buccal and bronchial epithelial cells was analyzed. Three independently expressed specificities were found by bacterial binding to glycosphingolipids separated by thin-layer chromatography. All strains bound gangliotria- and gangliotetrasylceramide. All but one of the strains bound sialic acid-containing glycosphingolipids and lactosylceramide. The latter two specificities could be separated in that the lactosylceramide binding was retained and the sialic acid binding was suppressed when bovine serum albumin was used as a blocking agent in the thin-layer chromatography assay. The attachment to buccal epithelial cells, like the binding to sialylated compounds and lactosylceramide, was abolished by Formalin treatment of the bacteria, suggesting the importance of these specificities for cell adherence. In contrast, the binding to gangliotria- and gangliotetraosylceramide was retained by nonattaching Formalin-treated bacteria. Images

Tumor necrosis factor-alpha augments pulmonary arterial transendothelial albumin flux in vitro.

Abstract: Tumor necrosis factor-alpha (TNF alpha) has been implicated as a mediator of pulmonary vascular endothelial injury. We studied the effect of human recombinant TNF alpha (rTNF alpha) on transfer of 14C-labeled bovine serum albumin (BSA) across cultured bovine pulmonary arterial endothelial cell monolayers. rTNF alpha induced a dose-, time-, and temperature-dependent increment in transendothelial [14C]BSA flux. Only after an incubation time of greater than or equal to 4 h did rTNF alpha significantly (P less than 0.005) increase transendothelial albumin flux. rTNF alpha exposure times as brief as 5 min induced significantly (P less than 0.005) increased albumin transfer at 6 h. Although this initial rTNF alpha-endothelial interaction was not temperature dependent, the subsequent barrier dysfunction could only be generated at 37 degrees C. The rTNF alpha-induced changes could not be ascribed to endothelial cell cytotoxicity and was not blocked by protein synthesis inhibition. The effects of rTNF alpha on endothelial permeability were reversible and not specific for albumin transfer. Therefore, rTNF alpha may influence the movement of macromolecules across the pulmonary vascular endothelial barrier.

Production of monoclonal antibodies for the determination of s‐triazines with enzyme immunoassays

Abstract: Two triazine derivatives, ametryn sulphoxide (2‐ethylamino‐4‐isopropylamino‐6‐methyl‐sulphoxide‐1,3,5‐triazine) and dichloroatrazine (2,6‐dichloro‐4‐isopropylamino‐1,3,5‐triazine) were conjugated to bovine serum albumin (BSA) and used for the immunization of BALB/c mice. Hybridomas were produced by cell fusion of immune spleen and mouse myeloma cells (PAI‐B3AG8.I). After screening with a competitive enzyme‐linked immunosorbent assay (ELISA), four anti‐triazine monoclonal antibodies from permanent hybridoma cell lines were selected for further characterization. Cross‐reaction studies with the antibodies developed against the ametryn sulphoxide conjugate showed strong affinities to terbutryn and prometryn. ELISAs with antibodies from clone AS‐K1F4 reached a detection limit of approximately 0.1 μg/l for terbutryn, and with AS‐K1A11 antibodies a limit of 0.3 μg/l for prometryn was attained. Cell lines from mice immunized with the dichloroatrazine‐conjugate produced antibodies with the highest affinities to az...