Solid phase peptide synthesis on epoxy-bearing methacrylate monoliths

Monoliths based on a copolymer of glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) can be used directly as sorbents for affinity chromatography after solid phase peptide synthesis. The quality of the synthesized products, the amount of grown peptides on a support and the reproducibility of the process must be considered. A determination of the quantity of the introducing beta-Ala (and, consequently, the total amount of synthesized peptide) was carried out. Three peptides complementary to recombinant tissue plasminogen activator (t-PA) have been synthesized using Fmoc-chemistry on GMA-EDMA disks. The peptidyl ligands were analysed by amino acid analysis, ES-MS and HPLC methods. The affinity binding parameters were obtained from frontal elution data. The results were compared with those established for GMA-EDMA affinity sorbents formed by the immobilization of the same but separately synthesized and purified ligands. The immobilization on GMA-EDMA disks was realized using a one-step reaction between the amino groups of the synthetic ligand and the original epoxy groups of monolithic material. The affinity constants found for two kinds of sorbent did not vary significantly. Finally, the directly obtained affinity sorbents were tested for t-PA separation from a cellular supernatant.

Cloning and expression of gene fragment IgA-binding protein of group B streptococci

Different fragments of the bac gene coding for the IgA-binding protein were cloned, sequenced and expressed in E. coli. Cloning was accomplished after amplification of different parts of the gene by PCR. The 1.5-kb fragment of the gene was cloned using plasmid pBluescript. This fragment coded for the 45-kDa protein with the stable expression of IgA binding. In order to verify the exact location of the IgA-binding domain two smaller plasmids were constructed. Both plasmids were prepared using pQE30 (31, 32) expression vectors from Qiagen. The plasmids carried 245 and 123 bp bac gene fragments encoding 14- and 7-kDa proteins. These proteins together with the 20-amino-acid oligopeptide ITNEDKDSMLKKIEDINRQA were tested for IgA binding. Only the 14-kDa protein was able to bind IgA. This protein was used for rabbit immunization and found to be immunogenic. The data obtained lead to the conclusion that there is a lower limit in the size of recombinant IgA-binding proteins that can be utilized for anti-GBS vaccination.