Preparation of affinity adsorbents with toyopearl gels

Polyacrylate adsorbents for the selective adsorption of cholesterol-rich lipoproteins from plasma or blood

Polyacrylate (PAA) adsorbents selectively bind low density lipoproteins (LDL) from human plasma and blood, whereas very low density lipoproteins (VLDL) are only minimally adsorbed. The adsorption of cholesterol-rich lipoproteins to PAA adsorbents is related to the molecular weight (mw) of the polyanion ligand. Ca(++) and Mg(++) inhibit the binding of LDL to PAA adsorbents. The chemical composition of the organic hardgels of the adsorbents does not have an influence on adsorption. The selective adsorption of LDL to PAA adsorbents can be explained to result from their low negative surface charge density and the specific colloid-chemical properties of the surface-bound PAA, which do not prevent LDL from binding to charge-like domains of the ligand. By contrast, VLDL and high density lipoproteins (HDL) are repelled from the adsorbents due to their higher negative surface charge density.

Arraying glycomics: a novel bi-functional spacer for one-step microscale derivatization of free reducing glycans

Glycan array development is limited by the complexity of efficiently generating derivatives of free reducing glycans with primary amines or other functional groups. A novel bi-functional spacer with selective reactivity toward the free glycan and a second functionality, a primary amine, was synthesized. We demonstrated an efficient one-step derivatization of various glycans including naturally isolated N-glycans, O-glycans, milk oligosaccharides, and bacterial polysaccharides in microgram scale. No protecting group manipulations or activation of the anomeric center was required. To demonstrate its utility for glycan microarray fabrication, we compared glycans with different amine-spacers for incorporation onto an amine-reactive glass surface. Our study results revealed that glycans conjugated with this bi-functional linker were effectively printed and detected with various lectins and antibodies.

Solid-phase chemical tools for glycobiology

Techniques involving solid supports have played crucial roles in the development of genomics, proteomics, and in molecular biology in general. Similarly, methods for immobilization or attachment to surfaces and resins have become ubiquitous in sequencing, synthesis, analysis, and screening of oligonucleotides, peptides, and proteins. However, solid-phase tools have been employed to a much lesser extent in glycobiology and glycomics. This review provides a comprehensive overview of solid-phase chemical tools for glycobiology including methodologies and applications. We provide a broad perspective of different approaches, including some well-established ones, such as immobilization in microtiter plates and to cross-linked polymers. Emerging areas such as glycan microarrays and glycan sequencing, quantum dots, and gold nanoparticles for nanobioscience applications are also discussed. The applications reviewed here include enzymology, immunology, elucidation of biosynthesis, and systems biology, as well as first steps toward solid-supported sequencing. From these methods and applications emerge a general vision for the use of solid-phase chemical tools in glycobiology.

Immobilization of pectin fragments on solid supports: novel coupling by thiazolidine formation

As a prerequisite to solid-phase and sequence analyses and for the study of the fine structure of pectin, we have developed oriented and chemoselective methodologies to couple model pectin fragments onto a solid support. Polyethylene glycol polyacrylamide (PEGA) resins were selected due to their excellent swelling properties in a wide range of solvents, including water, and their easy accessibility to enzymes. Following appropriate derivatization of amino-terminated PEGA resins, oligomers of alpha-D-galacturonic acid (GalA), up to the trimer, were anchored to the support through their reducing end. In addition to reductive amination, the strategies included the formation of an oxime bond, a glycosyl hydrazide, and a pyroglutamyl ring. Further, we developed a new immobilization approach based on the formation of a thiazolidine ring. All methods proved efficient and did not require modification of the GalA oligomers prior to coupling. In addition, very mild conditions and few steps for derivatization of the support were required. Immobilization by thiazolidine ring and oxime bond formation were the preferred methods, given the stability of the linkages formed, their compatibility with aqueous solvents, the few number of steps required, and their potential for application to larger pectin fragments. Thiazolidine and pyroglutamyl anchoring were developed further by the insertion of a disulfide bond which allowed release of the saccharides under mild, selective conditions.

Three novel high performance affinity chromatographic media for the separation of antithrombin III from human plasma

Novel monodisperse, non-porous, cross-linked poly (glycidyl methacrylate) beads (PGMA) were employed as the support for high performance affinity chromatography. Heparin was covalently attached to PGMA beads by three different coupling methods. Heparin-PGMA-I was prepared by directly coupling amino-groups of heparin with PGMA. Heparin-PGMA-II and III were prepared by the coupling of heparin to amino-PGMA, which was obtained by amination of PGMA. Heparin-PGMA-II was prepared by coupling the carboxyl groups of heparin to amino-PGMA by using water-soluble carbodiimide as coupling reagent, and heparin-PGMA-III was prepared by the reductive amination of heparin and amino-PGMA with sodium cyanoborohydride. The heparin contents of heparin-PGMA-I, II and III were 1.6, 10.2 and 1.0 mg/g beads, respectively. Their affinity capacities for antithrombin III were investigated. Their binding activity to antithrombin III was not proportional to the content of heparin immobilized, and heparin-PGMA-I was the most efficient affinity medium for antithrombin III. The resultant affinity media presented minimal non-specific interaction with other proteins and can be used in a wide pH range. All the three heparin-PGMA beads were exploited for the separation of antithrombin III from human plasma. The purity of antithrombin III obtained was higher than 90%, which was confirmed by high performance size exclusion chromatography.

Improved removal of anti-A and anti-B antibodies from plasma using blood-group-active haptens

Highly efficient anti-blood group A and B immunoadsorbents for extracorporeal treatment were developed by immobilizing A and B trisaccharide and A tetrasaccharide haptens on Sepharose 4FF and Fractogel TSK using three different methods. The adsorption of the IgG and IgM anti-A antibodies was essentially the same regardless of the A hapten used or the method of oligosaccharide coupling. The adsorption of IgM anti-A was found to be more sensitive than IgG anti-A to changes in column flow rate. The binding of both the IgM and IgG antibodies was slightly lower at 37 degrees C than at 22 degrees C. An anti-A/anti-B adsorbent column potentially suitable for treatment of patients was prepared. A column switching system resulted in a more efficient adsorption of antibodies. Hapten leakage from the column was very low. No nonspecific adsorption of plasma proteins to the column (other than traces of albumin) could be detected.

Preparation of ferric adsorbent paper and its interaction with phosphate-containing biomolecules

A procedure for the synthesis of a selective adsorbent for phosphate-containing biomolecules is described. The sorbent is based on Whatman chromatography paper, which is activated with epichlorohydrine, followed by the coupling of iminodiacetic acid to the active surface of the sorbent. The immobilized complex-forming chelating groups are saturated with ferric ions. The synthesized adsorbent is a counterpart to Chelating Sepharose and makes it possible to extend the use of immobilized ferric chelating groups for analytical purposes. It displays a high affinity towards compounds containing free terminal phosphate groups (phosphopeptides, nucleotides). The results of the binding experiments are compared to the corresponding data obtained with Chelating Sepharose gels.

Immobilization of protein ligands with methyl vinyl ether-maleic anhydride copolymer

Methyl vinyl ether-maleic anhydride copolymer (MMAC) is a water-insoluble polymer with an acid anhydride group which reacts with amino groups of ligands to form stable amide bonds. MMAC was used to immobilize protein ligands on two kinds of supports, the wells of plastic microtitre plates for enzyme-linked immunosorbent assay and related methods, and gels for affinity adsorbents. The wells were first coated with MMAC and then allowed to react with proteins. The immobilization of proteins by this method was efficient and occurred in a dose-dependent manner. Shodex Et123, a gel having amino groups, was incubated with MMAC, and then the activated Shodex was used to immobilize high concentrations of proteins. Concanavalin A-Shodex thus obtained had high affinities and was successfully used for the high-performance liquid affinity chromatography of sugar derivatives on a short column.

Chiral copper-chelate complexes alter selectivities in metal affinity protein partitioning

Proteins can be distinguished by exploiting complementarity between a histidine's microenvironment and a metal-chelate ligand in metal-affinity separations. The partitioning behavior of three myoglobins was investigated in aqueous two-phase polyethylene glycol-dextran systems containing polyethylene glycol derivatized with Cu(II) complexes of the L- and D-isomers of methionine and aspartate. TSK chromatographic supports derivatized with the methionine complexes were used to study retention of these proteins in metal-affinity chromatography. In the partitioning studies, the amino acid metal chelates exhibit selectivities for the myoglobins that are different from that of Cu(II)-iminodiacetate. Significant differences in selectivity based on the chiral nature of the amino acid complexes were also observed. The chromatographic selectivities of the chelating ligands exhibit little variation, however, suggesting that interactions occurring in solution but not on a surface play an important role in protein binding to the Cu(II)-amino acid-PEG complexes. In solution, the Cu(II)-amino acid complexes are sensitive probes of the microenvironments of surface histidines. The choice of the metal chelate affinity ligand offers a powerful means by which the selectivity of metal-affinity separations can be altered.

Purification of acetyl-CoA: 17-O-deacetylvindoline 17-O-acetyltransferase from Catharanthus roseus leaves

The enzyme acetyl-CoA: 17-O-deacetylvindoline 17-O-acetyltransferase which terminates vindoline biosynthesis has been isolated from Catharanthus roseus leaves, further characterized and purified to homogeneity by three step column chromatography and subsequent preparative isoelectric focusing. Kinetic properties concerning the enzyme reaction are discussed. Five multiple forms of the acetyl-transferase could be observed, each consisting of two subunits. This enzyme is now the best characterized of the enzymes involved in vindoline biosynthesis.

Improved method for the immobilization of heparin

The optimal conditions for immobilizing heparin through its terminal formyl group were investigated. When Amino Sepharose (1 g) was suspended in 1 ml of phosphate buffer (pH 7) containing 30 mg of heparin and 3 mg of sodium cyanoborohydride, with shaking at room temperature, the maximum immobilization of heparin (10 mg of heparin per gram of wet gel) was reached within 2 days. The Heparin Sepharose thus obtained was stable: no significant loss of the heparin content was observed after storage for 4 months at 4 degrees C. Heparin was also immobilized by the same method with Amino TSK gel G5000PW instead of Amino Sepharose 4B and was successfully applied to the high-performance liquid affinity chromatography of fibronectin and thrombin.

High-performance affinity chromatography of plasmin and plasminogen on a hydrophilic vinyl-polymer gel coupled with p-aminobenzamidine

p-Aminobenzamidine was covalently attached via a spacer moiety to a microparticulate hydrophilic vinyl-polymer gel (Toyopearl HW65S) and this affinity adsorbent was used for the separation of plasmin and plasminogen by high-performance affinity chromatography. Toyopearl HW65S was alkylated with chloroacetylglycylglycine in dimethyl sulphoxide using methylsulphinyl carbanion as a catalyst, then p-aminobenzamidine was coupled to the carboxyl group of glycylglycine to form an acid amide bond. A column packed with the adsorbent retained both plasmin and plasminogen. Plasminogen was eluted with 6-aminohexanoic acid, a haptenic compound for the lysine-binding sites of plasminogen. For the elution of plasmin, the coexistence of 6-aminohexanoic acid and leupeptin (a competitive inhibitor for plasmin) was necessary. The results indicate a two-site interaction of plasmin with the immobilized ligand, i.e., at the lysine-binding sites and the catalytic site. Fluorometric detection of eluted protein and on-line assay of plasmin activity using a fluorogenic substrate, peptidylmethylcoumarylamide, revealed that effective chromatographic separation of the enzyme could be achieved with high sensitivity (10 micrograms) within 1 h.