Affinity chromatography of serum haemopexin

The Lipopeptide, Pam3Cys-Ser-(Lys)4: An Alternative Adjuvant to Freund's Adjuvant for the Immunisation of Chicken to Produce Egg Yolk Antibodies

This study describes an alternative adjuvant for the immunisation of chicken. The lipopeptide, Pam3Cys-Ser-(Lys)4 (PCSL), has been demonstrated to be a very potent adjuvant, by immunisation with the hapten methyl phosphonic acid paraaminophenyl 1,2,2-trimethylpropyl diester, with coronavirus, with rotavirus and with the Escherichia coli K99 pilus antigen. The antibody titres in chickens that received PCSL were compared with those in animals that received Freund's complete adjuvant/Freund's incomplete adjuvant (FCA/FIA). Antigen-dependent differences in antibody titres could be shown. The optimal dosage for PCSL was 250μg per injection. Whereas injection of FCA/FIA resulted in chronic inflammatory alterations, mostly accompanied with granulomatous reactions, no long-term tissue damage could be found with PCSL. When PCSL was used as the adjuvant, the total immunoglobulin Y (IgY) levels in chicken sera were constant during the immunisation period (20.2mg/ml, SD ± 1.3), and were significantly different (p < 0.0001) from those in chickens given FCA as adjuvant (26.6mg7ml, SD ± 4.9). IgY concentrations in the egg yolks showed no significant differences in both groups (PCSL — 13.7mg/ml, SD ± 3.7; FCA — 13.5mg/ml, SD ± 4.2), and were significantly lower (p < 0.0001) than the IgY serum levels.

An alternative view of the proposed alternative activities of hemopexin

Hemopexin is a plasma protein that plays a well-established biological role in sequestering heme that is released into the plasma from hemoglobin and myoglobin as the result of intravascular or extravascular hemolysis as well as from skeletal muscle trauma or neuromuscular disease. In recent years, a variety of additional biological activities have been attributed to hemopexin, for example, hyaluronidase activity, serine protease activity, pro-inflammatory and anti-inflammatory activity as well as suppression of lymphocyte necrosis, inhibition of cellular adhesion, and binding of divalent metal ions. This review examines the challenges involved in the purification of hemopexin from plasma and in the recombinant expression of hemopexin and evaluates the questions that these challenges and the characteristics of hemopexin raise concerning the validity of many of the new activities proposed for this protein. As well, an homology model of the three-dimensional structure of human hemopexin is used to reveal that the protein lacks the catalytic triad that is characteristic of many serine proteases but that hemopexin possesses two highly exposed Arg-Gly-Glu sequences that may promote interaction with cell surfaces.

A novel approach for identifying the heme-binding proteins from mouse tissues

Heme is a key cofactor in aerobic life, both in eukaryotes and prokaryotes. Because of the high reactivity of ferrous protoporphyrin IX, the reactions of heme in cells are often carried out through heme-protein complexes. Traditionally studies of heme-binding proteins have been approached on a case by case basis, thus there is a limited global view of the distribution of heme-binding proteins in different cells or tissues. The procedure described here is aimed at profiling heme-binding proteins in mouse tissues sequentially by 1) purification of heme-binding proteins by heme-agarose, an affinity chromatographic resin; 2) isolation of heme-binding proteins by SDS-PAGE or two-dimensional electrophoresis; 3) identification of heme-binding proteins by mass spectrometry. In five mouse tissues, over 600 protein spots were visualized on 2DE gel stained by Commassie blue and 154 proteins were identified by MALDI-TOF, in which most proteins belong to heme related. This methodology makes it possible to globally characterize the heme-binding proteins in a biological system.

Chromatographic methods to study protein-protein interactions

Proteins and enzymes are now generally thought to be organized within the cell to form clusters in a dynamic and versatile way, and heterologous protein-protein interactions are believed to be involved in virtually all cellular events. Therefore we need appropriate tools to detect and study such interactions. Chromatographic techniques prove to be well suited for this kind of investigation. Real complexes formed between proteins can be studied by classic gel filtration. When enzymes are studied, active enzyme gel chromatography is a useful alternative. A variant of classic gel filtration is gel filtration equilibrium analysis, which is similar to equilibrium dialysis. When the association formed is only dynamic and equilibrates very rapidly, either the Hummel-Dryer method of equilibrium gel filtration or large-zone equilibrium filtration sometimes allows the interactions to be analyzed, both qualitatively and quantitatively. Very often, however, interactions between enzymes and proteins can only be evidenced in vitro in media that mimic the intracellular situation. Immobilized proteins are excellent tools for this type of research. Several examples are indeed known where the immobilization of an enzyme on a solid support does not affect its real properties, but rather changes its environment in such a way that the diffusion becomes limiting. Affinity chromatography using immobilized proteins allows the analysis of heterologous protein-protein interactions, both qualitatively and quantitatively. A useful alternative appears to be affinity electrophoresis. The latter technique, however, is exclusively qualitative. All these techniques are described and illustrated with examples taken from the literature.

The specificity and affinity of polyclonal antibodies raised in rabbits against a hapten conjugated to rabbit serum albumin

In this study, rabbit antisera to hapten-rabbit serum albumin conjugates were investigated regarding antibody titer, affinity, specificity, and affinity distribution. Methyl phosphonic acid p-amino-phenyl 1,2,2-trimethylpropyldiester (MATP) served as model hapten. Four MATP-rabbit serum albumin conjugates with various hapten densities (with and without spacer) were synthesized and used for immunization of rabbits. Antisera were collected over a 130 day-period and characterized with different ELISA methods. We found that immunogens with rabbit serum albumin gave antisera with lower titers, but similar affinity as compared to polyclonal or monoclonal antibodies obtained with non-rabbit protein as carrier protein. Immunogens with a low hapten density led to higher final titers without affecting antibody affinity or specificity. Immunogens containing a bridging group resulted in higher antibody affinity with a changed specificity. The pattern of antibody affinity distribution differed considerably among individual rabbits and showed a non-Gaussian subpopulation distribution.

Association of polyacrylamide beads to polyethylene terephthalate prostheses

A method for the coupling of polyacrylamide beads to polyethylene terephthalate (PET) vascular prostheses is described. The reactional procedure used is performed along several steps; acrylic acid grafting on PET textile fibres, in order to introduce reactive carboxylic groups, introduction of terminal primary amine groups onto the beads, and then, attachment method which consists in coupling carboxylic groups of prostheses with amine groups of modified beads. The relative weight increase of the samples before and after the coupling reaction and, microscopic observations of beads distribution onto the prostheses surface demonstrate the binding feasibility of polyacrylamide matrices to PET prostheses. In the near future, authors expect to replace these beads by microcapsules with polyacrylamide wall and containing active compounds to improve the vascular prostheses biocompatibility.

Influence of various adjuvants on the synthesis of specific antibodies of chicken, sheep and rabbit following immunization with an hapten

In order to obtain high amounts of specific antibodies against the hapten methylphosphoric acid, para-aminophenyl-1,2,2-trimethyl-propyldiester (MATP) different animals were immunized with MATP coupled to the carrier protein human serum albumin (MATP12-HSA) using several adjuvants. The best specific immune response in sheep, rabbit and chicken was reached with Freund's complete adjuvant with animal specific differences being tested by an ELISA. The adjuvants aluminium hydroxide (5% and 10%) and diphosphoryl lipid A showed no significant difference compared to the control group (NaCl with MATP12-HSA). In rabbits and chickens MATP12-HSA can be used to reach an immune response without the help of an adjuvant.

Development of an ELISA for detection of an organophosphorus compound using monoclonal antibodies

This paper describes a specific and highly sensitive ELISA system using monoclonal antibodies in order to assay an organophosphorus compound. The soman derivative methyl phosphonic acid, p-aminophenyl 1,2,2,-trimethyl-propyl diester (MATP) served as model substance. In order to obtain antibody-producing hybridomas BALB/c mice were immunized with MATP linked onto human serum albumin (HSA). The spleen cells of immunized mice were fused with syngenic plasmacytomas of the non-producer-line X63Ag8.653 with the aid of polyethylene glycol. To eliminate undesirable cross-reaction, common screening procedures were modified by directly coating the ELISA plates with hapten. Five out of 15 positive cell-lines were cloned by limiting dilution and further propagated. The respective immunoglobulin class and subclass of the obtained monoclonal antibodies was determined. Four of which were identified as IgG1, the other as IgG2a. After enrichment of antibodies in ascites and their isolation by protein A-sepharose, the affinity of various monoclonal antibodies was estimated in competitive inhibition enzyme immunoassay (CIEIA) by measuring the IC50 rates of free MATP. The rates were found to lie between 2.5 x 10(-6) mol/l and 4.3 x 10(-4) mol/l MATP. The IC10 rate for detectable MATP concentration was 5.4 x 10(-7) mol/l MATP. Test duration was 280 min. The reactivity of the monoclonal antibodies with structurally related substances was used to check their specificity. Cross-reaction turned out to be negative. In order to develop a direct competitive ELISA, MATP was linked to horse radish peroxidase (HRPO) by adding a spacer. This helped to reduce total duration to 40 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Confirmation of a ping-pong mechanism for S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat by an exchange reaction

An exchange reaction between unlabeled S-adenosyl-L-methionine and radiolabeled S-adenosyl-L-homocysteine has been used to confirm the occurrence of a ping-pong mechanism in S-adenosyl-L-methionine:magnesium protoporphyrin methyltransferase of etiolated wheat. The enzyme, S-adenosyl-L-homocysteine hydrolase, has been used to prepare radiolabeled S-adenosyl-L-homocysteine from labeled adenosine and DL-homocysteine. The exchange reaction was accomplished with a methyltransferase preparation purified by affinity chromatography on hemin-linked Sepharose 4B, and radioactivity was exchanged into unlabeled S-adenosyl-L-methionine to an extent of 70% of the theoretical maximum value.

Purification of pig serum haemopexin by haemin-Sepharose affinity chromatography

Haemopexin was isolated from pig serum in pure form by affinity chromatography and ion-exchange chromatography. The affinity gel synthesized contained about 0.3 mumol/ml haemin covalently linked to AH-Sepharose 4B. The molecular weight of the protein was measured by polyacrylamide gel electrophoresis in the presence of SDS followed by sensitive silver staining. This procedure and also immunoelectrophoretic studies indicated purity. The mobility of haemopexin in polyacrylamide gels changed following reduction with dithiothreitol.

Isolation of human haemopexin by bioaffinity chromatography on haeme-sepharose

A preparative procedure was developed for the isolation of human apohaemopexin from Cohn fraction IV or blood serum, based on bioaffinity chromatography on haeme-Sepharose. The isolation is carried out in the pH range 4-8; hence the possibility of degradation of the carbohydrate moiety of the glycoprotein in the acidic media used in other isolation procedures is decreased. Owing to the conditions of the separation and the good stability of the affinity support, the column can be used repeatedly for long periods without a significant loss of binding capacity. The reversibility of the conformational changes that haemopexin undergoes in acidic media was examined by hydrophobic chromatography. The original hydrophobic characteristics were restored only approximately 48 h after haemopexin had been brought into a neutral medium.

Human serum hemopexin: direct evidence for change of its isoelectric point upon heme binding. A new serum protein fractionation

Human serum was submitted to a one step displacement-ligand exchange chromatography. Displacement removed serum albumin and part of gamma-globulins. Ligand exchange furnished an enriched heme-hemopexin fraction. An original, non denaturing human heme-hemopexin preparation is proposed.