Factors affecting the properties of insolubilized anitbodies.

IgG separated from an antiserum to estradiol was coupled under various experimental conditions to Sepharose activated either with CNBr or by conversion into a long-armed derivative (the N-hydroxysuccinimide ester). The conjugates were characterized by measurement of the binding parameters, in order to evaluate separately the loss of sites and the loss of affinity. The cross-reactivity with estriol and estrone was measured to obtain information on the occurrence of structural alterations of the antibody site. The results show that the loss of immunoreactivity varies in extent (from 95% to less than 10%) and in nature (loss of sites or of affinity or a combination of both effects) depending on the coupling conditions. The use of a hydrocarbon extension to keep the protein distant from the matrix does not prevent the loss of active sites but is effective in safeguarding the affinity of the residual sites. The loss of sites can be substantially reduced by coupling at a pH value around neutrality and by keeping the protein/matrix mass ratio low. At a coupling pH of 6.4 and at a mass ratio of 0.1-0.2 nmol IgG/mg of Sepharose, the antibodies were insolubilized with a negligible loss of sites and affinity; on increasing the mass ratio (up to 10 nmol IgG/mg Sepharose) there is a progressive loss of sites accompanied by a substantial lowering of the affinity of the residual sites. On the basis of the above-mentioned findings, the nature of the effects occurring when antibodies are transferred from solution onto a solid matrix is discussed.     

Use of epoxysepharose for protein immobilisation

Epoxy Sepharose, an activated affinity matrix which has been used for immobilisation of carbohydrates has been tried for immobilisation of proteins. Under normal conditions of coupling at neutral or alkaline pH proteins do not couple to epoxy Sepharose. However, a very high salt concentration during coupling allows the binding of proteins to epoxy Sepharose at a pH as low as 8.5. Increasing ionic strength and/or pH facilitates the binding. The bioactivity of the proteins is not destroyed by the immobilisation. This matrix, unlike cyanogen bromide-Sepharose, retains its ability to bind albumin by 80–90% even after 60 days of storage in aqueous suspension at 4°C. Its capacity to bind proteins is comparable to that of cyanogen bromide-Sepharose.     

Rapid isolation of human plasma anti-alpha-galactoside antibody using sugar-specific binding to guar galactomannan or agarose.

A method of purifying the naturally occurring antibody to alpha-galactoside moiety (anti-alpha-Gal) in human plasma by a single-step affinity chromatography on cross-linked guar galactomannan (CLGG) or agarose (Sepharose 4B) is described. IgG nature of the two preparations, as revealed by agar gel diffusion, as well as their preference for alpha-anomer of galactose, as revealed in inhibition of their agglutination of trypsinized rabbit erythrocytes by sugars, identified them with anti-alpha-Gal. The antibody binding capacity of Sepharose 4B was only a third of that of CLGG. Both gels showed similar dependence on ionic strength for binding. The pH optimum for binding of anti-alpha-Gal to CLGG was 8.0. Significantly anti-alpha-Gal binding to Sepharose was unaffected by CNBr activation and ligand coupling to the gel, thus warning that contaminating plasma could introduce artifacts in agarose-based chromatography of human tissue biomolecules.     

Analysis of histidine-containing dipeptides, polyamines, and related amino acids by high-performance liquid chromatography: application to guinea pig brain.

A procedure is described for coupling wheat germ agglutinin to cyanogen bromide-activated Sepharose to yield a lectin affinity column of high capacity. Covalent linkage of the lectin to the insoluble matrix is carried out in the presence of a mixture of β-1,4-linked N-acetylglucosamine oligosaccharides prepared from chitin. The lectin-affinity column specifically recognizes glycoproteins containing N-acetylglucosamine residues with the capacity of binding 0.6–1.0 mg of ovomucoid per milliliter of gel. The affinity column is stable (as determined by ovomucoid binding) and shows little loss in binding capacity or specificity after repeated usage. Important characteristics for the use of this column to purify glycoproteins are described.     

Amino Acid Sequence of αkSubstance,a Mating Pheromone of Saccharomyces kluyveri

A fraction containing IgA (IgA-rich fraction) was prepared from bovine colostrum by anion exchange chromatography using DEAE-Sephadex A-50 and gel filtration on Sephadex G-200. A large amount of IgG1-dimer was found in this fraction, which could not be separated from IgA by repeated gel filtration.

The Fc fragment of bovine colostral IgG (IgG-Fc) was prepared from papain digestion mixtures. IgG-Fc was found to be heterogeneous on DEAE-cellulose column chromatography. Two IgG-Fc fractions were obtained, but no antigenic difference was found between them. Anti-IgG-Fc antibodies raised in rabbits by injection of these Fc preparations reacted only with IgG1 and IgG2. An immunoadsorbent (anti-IgG-Fc-Sepharose) was prepared by coupling these anti-IgG-Fc antibodies to CNBr-activated Sepharose 4B.

IgA was purified from the IgA-rich fraction by affinity chromatography on anti-IgG-Fc-Sepharose adsorbent. IgG1-dimer was effectively removed by this treatment. The purified sample gave only one precipitin arc characteristic of IgA on immunoelectrophoresis with multiple anti-bovine colostral whey antiserum. A small amount of IgA was found to be adsorbed to the affinity column nonspecifically.

When a rabbit was immunized with the purified IgA, besides anti-IgA antibodies, antibodies against the secretory component (SC) were found in the antiserum. This finding leads us to expect that the purified IgA is secretory IgA containing SC.     

Interaction between immobilized antibodies and the antigen-enzyme complex]

The interaction between immobilized antibodies against human immunoglobulin G (IgG) and the immunoenzyme complex IgG-peroxidase (IgG-P) was studied. The complex was obtained by covalent binding of IgG to peroxidase modified by sodium periodate. Study of the IgG-P binding kinetics and dissociation of the antibody-(IgG-P) complex showed that the antibodies immobilized on Sepharose reversibly interacted with IgG-P, similar to the antigen-antibody reaction in solution. The efficient values of the binding constants for the antibodies binding to Sepharose covalently and through the antigen-antibody bond are (2,2+/-0,5) 10(8) M-1 and (4,2+/-0,2) 10(8) M-1, respectively. The nature of a carrier and the immobilization method used do not significantly affect the rate of the complex binding to the antibodies. The activation energy of the reaction of IgG-P binding to the antibodies immobilized on Sepharose covalently and through the antigen-antibody bond is 7,3 and 4,1 kcal/mole, respectively. A procedure of titration of immobilized antibodies active sites with the antigen-enzyme complex is discussed.     

金黄色葡萄球菌蛋白A (SpA) Z结构域串联体的克隆、表达和筛选

筛选一种高效重组金黄色葡萄球菌蛋白A(SpA)用于制备抗体纯化亲和介质。首先通过基因操作获得金黄色葡萄球菌蛋白A(SpA)的Z结构域单体、二串体、三串体、四串体和五串体基因,将目的基因分别克隆至pET-22b表达载体并转化至大肠杆菌BL21(DE3)感受态细胞,获得不同串联个数的Z结构域基因工程菌,经诱导表达和Ni2+亲和层析纯化得到Z结构域单体和二-五串体蛋白。纯化后的目的蛋白偶联至琼脂糖凝胶作为亲和层析介质,对人免疫球蛋白G(IgG)进行分离纯化。分析比较Z结构域串联体蛋白产量及其偶联的亲和介质对抗体吸附载量的差异。结果表明,构建的Z结构域单体、二串体、三串体、四串体和五串体基因工程菌能有效表达目的蛋白,制备的凝胶亲和介质可特异性吸附人IgG。增加Z结构域串联数,重组蛋白产量和单位摩尔数多聚体蛋白吸附载量获得提高,其中,重组四串体蛋白产量大(160 mg/10 g湿菌体),对抗体的吸附载量高(34.4 mg人IgG/mL胶),更适合作为配基用于亲和层析介质的制备。     

Adsorption equilibrium in immunoaffnity chromatography with antibodies to synthetic peptides

The effects of charged residues in peptide antigens on the binding characteristics of polyclonal antipeptide antibodies were studied using immunoadsorbents prepared by coupling the antibodies to CNBr-activated Sepharose 4B. Among the antipeptide antibodies, an antibody to the peptide without charged residues showed the most stable interaction with the peptide to the changes in pH. Conversely, the binding affinity of antibodies to the pep-tides with histidine residues having a unique pKa value of 6.0 decreased steeply with pH at around 6.0. The binding affinity of an antibody to the peptide with many charged residues decreased steeply with an increase in the ionic strength (adjusted by NaCl). Since circular dichroism (CD) spectrum measurements indicate that these peptides show disordered structures in the pH range of adsorption measurement, the dependence of peptide-antibody interaction on environmental conditions is attributed to the characteristics of side chains of the peptides. These results indicate that the dependence of the binding affinity of antipeptide antibodies on pH and the ionic strength is dominantly affected by the number and the pKa values of charged residues in the peptides.     

Isolation and characterization of a thermolabile beta-2 macroglycoprotein ('thermolabile substance' or 'Hakata antigen') detected by precipitating (auto) antibody in sera of patients with systemic lupus erythematosus.

A novel thermolabile beta-2 macroglycoprotein ('thermolabile substance' (TLS) or 'Hakata antigen' (HA], which was detected by the precipitating (auto) antibodies of patients with systemic lupus erythematosus, was isolated and characterized. The purification procedure entailed the following steps: isoelectric precipitation in the range between pH 5.2-6.1, hydroxyapatite absorption chromatography, 35% saturated ammonium sulfate precipitation, Sephadex G-200 gel filtration, Pevikon block electrophoresis, lentil lectin affinity chromatography and immobilized rabbit anti-human whole serum IgG column chromatography. Utilizing these procedures, 0.1 mg of HA was purified from 3 1 of pooled human serum. The molecular mass of HA was determined as 650 kDa by Sepharose 4B gel filtration. On SDS-PAGE analysis, HA showed a single band at 35 kDa under reduced conditions and numerous ladder bands between 35 kDa to more than 300 kDa under nonreduced conditions. On analytical ultracentrifugation, HA gave a molecular mass of 520 kDa with a single meniscus and a sedimentation constant of 12.0. The amino acid and carbohydrate analysis of reduced and S-pyridylethylated HA revealed that it contained five residues of hydroxyproline and an N-linked type sugar chain.     

IgG Subclass and Heavy Chain Domains Contribute to Binding and Protection by mAbs to the Poly γ-D-glutamic Acid Capsular Antigen of Bacillus anthracis

Bacterial capsules are common targets for antibody-mediated immunity. The capsule of Bacillus anthracis is unusual among capsules because it is composed of a polymer of poly-γ-d-glutamic acid (γdPGA). We previously generated murine IgG3 monoclonal antibodies (mAbs) to γdPGA that were protective in a murine model of pulmonary anthrax. IgG3 antibodies are characteristic of the murine response to polysaccharide antigens. The goal of the present study was to produce subclass switch variants of the γdPGA mAbs (IgG3→IgG1→IgG2b→IgG2a) and assess the contribution of subclass to antibody affinity and protection. Subclass switch antibodies had identical variable regions but differed in their heavy chains. The results showed that a switch from the protective IgG3 to IgG1, IgG2b or IgG2a was accompanied by i) a loss of protective activity ii) a change in mAb binding to the capsular matrix, and iii) a loss of affinity. These results identify a role for the heavy chain constant region in mAb binding. Hybrid mAbs were constructed in which the CH1, CH2 or CH3 heavy chain constant domains from a non-protective, low binding IgG2b mAb were swapped into the protective IgG3 mAb. The IgG3 mAb that contained the CH1 domain from IgG2b showed no loss of affinity or protection. In contrast, swapping the CH2 or CH3 domains from IgG2b into IgG3 produced a reduction in affinity and a loss of protection. These studies identify a role for the constant region of IgG heavy chains in affinity and protection against an encapsulated bacterial pathogen.     

An affinity column for ecdysone binding proteins

Under basic conditions β-ecdysone can be covalently linked to the oxirane residue of epoxy-activated Sepharose 6B. Such an ecdysone-modified column matrix retards antibodies to β-ecdysone while permitting, however, the free passage of other antibodies in rabbit antiserum. The bound anti-ecdysone antibodies can subsequently be eluted by a low pH (3.8), high salt (0.5 m) buffer. The utility of such an affinity column for the isolation of ecdysone receptors is discussed.     

Improved methods for prepurification and detection of staphylococcal enterotoxin B from cell-free culture filtrate

An improved ELISA method for the detection of Staphylococcal Enterotoxin B (SEB) in protein A preparations is presented. Fab fragments were obtained by digestion with papain of anti-SEB IgG bound to SEB immobilized on Sepharose 4B. Anti-SEB and peroxidase-labeled Fab fragments from secondary antibodies were successfully used in a modified ELISA of SEB in protein A preparations. SEB-Sepharose was used repeatedly for the production of anti-SEB Fab fragments by papain digestion without loss of affinity. In addition, for the purification of SEB from crude culture filtrates, an initial step utilizing a combined heat and pH treatment for the removal of significant amounts of contaminating proteins without losses of toxin activity is presented. This pretreatment step yielded positive effects in further downstream processing considering both shortened time and an increase in total recovery.     

The presence of natural human antibodies reactive against pharmacologically active pectic polysaccharides from herbal medicines

Direct ELISA was performed using normal human sera and human colostrum, to analyse the presence of antibodies which react with pharmacologically active pectic polysaccharides isolated from plants used in traditional Japanese herbal (Kampo) medicine. All sera and colostrum were shown to contain IgM, IgG, IgA and secretory IgA class antibodies which react with the active pectic polysaccharides to different degrees. The reacting IgG antibody in normal human serum recognized the ramified regions (rhamnogalacturonan core with carbohydrate side-chains) of the pharmacologically active pectic polysaccharides as the active sites for complement-activating activity. Correlation analysis indicated that a significant and positive correlation was observed between reactivity with the reacting antibody of IgG class and the degree of complement-activating activity of the active polysaccharides.The reacting IgG class antibody, which was purified from normal human serum by affinity chromatography on bupleuran 2IIc (a pharmacologically active pectic polysaccharide from the roots of Bupleurum falcatum)-immobilized Sepharose, showed cross-reactivity not only with some other pharmacologically active pectic polysaccharides from other medicinal herbs but also with autoantigens such as single-strand DNA, myosin and tublin from mammals.     

Preparation and characterization of polyclonal and monoclonal antibodies against human aromatase cytochrome P-450 (P-450AROM), and their use in its purification

Aromatase cytochrome P-450 (P-450AROM) was partially purified from human placental microsomes by hydrophobic affinity chromatography using Phenyl-Sepharose and ion-exchange chromatography on DEAE-cellulose. The resulting preparation had a specific activity of 2 nmol/mg protein with respect to cytochrome P-450 content and displayed a type I difference spectrum upon addition of the substrate androstenedione. When the cytochrome P-450-enriched fractions were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and stained with Coomassie blue, there was an enrichment of two proteins having apparent molecular weights of 50,000 and 55,000. The bands containing these proteins were removed from unstained polyacrylamide gels and injected separately or together into three rabbits. An aliquot of the serum or an immunoglobulin (IgG) fraction prepared from the serum of the rabbit injected with the 55-kDa band or with both the 50- and 55-kDa bands inhibited aromatase activity of human placental microsomes by 80%; this IgG had no effect on 17 alpha-hydroxylase or 21-hydroxylase activities of human fetal adrenal microsomes. In contrast, the serum of the rabbit injected with the 50-kDa band had little capacity to inhibit placental aromatase activity. By immunoblot analysis, it was found that the IgG from the serum of the rabbit immunized with the 55-kDa protein bound specifically to a protein of 55 kDa in human placental microsomes. Monoclonal antibodies were prepared from a hybridoma cell line derived from the spleen cells of mice immunized against the 55-kDa protein. The monoclonal IgG was covalently linked to a Sepharose 4B column and was used for immunoaffinity chromatography of cytochrome P-450AROM. The finding that cytochrome P-450 and the 55-kDa protein were selectively retained by the affinity column and eluted with NaCl (2 M) and glycine (0.2 M, pH 3.0) and that this fraction contained aromatase activity upon reconstitution with purified NADPH-cytochrome P-450 reductase and phospholipid, is indicative that the 55-kDa protein is indeed cytochrome P-450AROM. These findings are also indicative that both the monoclonal and polyclonal IgGs are specific for human cytochrome P-450AROM.     

Isolation of antibodies to steroid hormones by affinity chromatography on antigen-linked sepharose: An efficient electrophoretic elution procedure

An electrophoretic elution procedure of antibodies retained on affinity columns is described. It afforded a 60% recovery of the binding activity of a high affinity (Ka ～ 10¹⁰ M^?1) antiserum to 5α-dihydrotestosterone retained on antigen-linked Sepharose 4B affinity columns. These purified unbound antibodies, (Ka ～ 10¹⁰ M^?1) when applied again on identical antigen-linked affinity columns, were all retained and totally recovered after a new electrophoretic elution. Comparable results were obtained by elution with 1M NH₄OH.The residual 40% binding activity remaining on the antigen-linked Sepharose gel after electrophoretic elution was totally recovered by elution with an excess of 5α-dihydrotestosterone. It corresponded to antibodies of higher affinity (Ka ～ 10¹¹ M^?1). On the other hand the residual 40% fraction of antibodies resistant to NH₄OH elution was denaturated.     

Separation of immunoglobulin G from human serum by pseudobioaffinity chromatography using immobilized l-histidine in hollow fibre membranes

l-Histidine, intended as a pseudobiospecific ligand, was immobilized on poly(ethylenevinyl alcohol) hollow fibre membranes after their activation with epichlorohydrin or butanediol diglycidyl ether. The affinity membranes obtained allowed the one-step separation of immunoglobulin G (IgG) from untreated human serum. Elution was possible under mild conditions with discontinuous pH or salt gradients. IgM was also adsorbed to a certain extent and partially separated from IgG by pH gradient elution. The bound IgG fractions showed pI values between 8 and 9.5 and contained IgG₁ and IgG₃. The dissociation constants for IgG on the bisoxirane- and epichlorohydrin-activated membranes coupled with histidine were determined by equilibrium binding analysis to be 2.5·10⁻⁵ and 2.0·10⁻⁵ M, respectively. The maximum binding capacity of the affinity hollow fibre membranes was 80 and 70 mg of IgG per gram of support, respectively. With a cartridge of surface area 1 m² (about 19 g of fibres), during a 60-min run, theoretically up to 1.5 g of IgG can be removed from human serum. The histidine affinity membranes are very stable owing to the simple nature of the ligand and the coupling via an ether linkage. Reproducible results were obtained over more than 1 year even with untreated human serum being used regularly.     

Estrogen synthetase (aromatase) Affinity purification of antibody against the cytochrome P450 component

To procure an affinity gel capable of purifying antibody against the cytochrome P450 component of estrogen synthetase (P450ES), we coupled purified P450ES to agarose supports. OUr purpose was to compare two differently-activated agarose gels (Affi-Gel 15 and Tresyl-activated Sepharose) with the same P450ES preparation to compare the efficiency of coupling and the yield of purified antibody. Using supplier-directed protocols to covalently attach P450ES to each of the supports, and identical procedures to bind and elute anti-P450ES, we reached the following conclusions. Tresyl-activated Sepharose bound greater amounts of antigen than Affi-Gel 15 based on the amount of residual antigen after the coupling procedure and the amount of bound antigen detected by an ELISA-type method. However, both ligand-coupled supports yielded comparable amounts of purified anti-P450ES at a 48-fold purification relative to the starting IgG preparation.     

Ca2+ binding to chromaffin vesicle matrix proteins: effect of pH, Mg2+, and ionic strength

Recently we found that Ca2+ within chromaffin vesicles is largely bound [Bulenda, D., & Gratzl, M. (1985) Biochemistry 24, 7760-7765]. In order to explore the nature of these bonds, we analyzed the binding of Ca2+ to the vesicle matrix proteins as well as to ATP, the main nucleotide present in these vesicles. The dissociation constant at pH 7 is 50 microM (number of binding sites, n = 180 nmol/mg of protein) for Ca2+-protein bonds and 15 microM (n = 0.8 mumol/mumol) for Ca2+-ATP bonds. When the pH is decreased to more physiological values (pH 6), the number of binding sites remains the same. However, the affinity of Ca2+ for the proteins decreases much less than its affinity for ATP (dissociation constant of 90 vs. 70 microM). At pH 6 monovalent cations (30-50 mM) as well as Mg2+ (0.1-0.5 mM), which are also present within chromaffin vesicles, do not affect the number of binding sites for Ca2+ but cause a decrease in the affinity of Ca2+ for both proteins and ATP. For Ca2+ binding to ATP in the presence of 0.5 mM Mg2+ we found a dissociation constant of 340 microM and after addition of 35 mM K+ a dissociation constant of 170 microM. Ca2+ binding to the chromaffin vesicle matrix proteins in the presence of 0.5 mM Mg2+ is characterized by a Kd of 240 microM and after addition of 15 mM Na+ by a Kd of 340 microM.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation and immunochemical characterization of immunoglobulin-binding factor from bovine peripheral blood lymphocytes

The shedding of immunoglobulin-binding factor (IBF) has been studied in peripheral blood lymphocytes during 1 h incubation at 37 degrees C. IBF was detectable in the incubating medium on the basis of their ability to bind immunoglobulin G (IgG) specifically. IBF was affinity purified on Sepharose beads coated with bovine IgG, fluoresceinated and identified by their biological activities, i.e., for binding immunoglobulin-binding factor labeled with fluoresceinizothiocyanate (FITC-IBF) to erythrocytes coated with purified antibodies (EAIgG) by fluorometric binding assay. The effect of various pH, temperatures and proteolytic enzymes on the binding properties of FITC-IBF to EAIgG was also studied. We showed that IBF are sensitive to pronase E, higher temperature and pH.     

Quantitative recovery, selective removal and one-step purification of human parotid and leukemic lysozymes by immunoadsorption

Immunoadsorption affinity chromatography was used to isolate and purify human lysozyme. The immunoadsorbent was prepared by coupling sheep anti-(human leukemic lysozyme) IgG to epoxy-activated Sepharose 6B. Lyophilized parotid saliva (21) was resuspended in distilled water (325 ml, 50 mg/ml, w/v) and applied to a column which had a capacity to bind 4.25 mg human enzyme. Non-adsorbed material did not contain lysozyme, as determined by enzymatic and immunological analyses. All lysozyme activity present in the applied sample (1.97 mg) bound to and was desorbed from the column by elution with 0.2 M sodium acetate HCl buffer, pH 1.8. The isolated material was homogeneous as determined by cationic and sodium dodecyl sulfate/polyacrylamide gel electrophoresis, ultracentrifugation, amino acid and amino-terminal analyses, and immunoelectrophoretic analysis. The one-step purification procedure yielded a 1370-fold increase in specific activity. Human lysozyme was also selectively purified by this method from an ammonium sulfate precipitate of the urine of a patient with chronic monocytic leukemia. Amino acid and polyacrylamide gel electrophoretic analyses indicated that the purified enzyme was identical to human lysozyme isolated from leukemic urine by classical biochemical techniques.