Synthesis of two sequential polypeptides by dispersion in benzene and their circular dichroism spectra in aqueous solution: Poly(L-glu-L-lys-L-ala-gly) and poly(L-ala-D-glu-L-lys-D-ala-gly)

Synthesis and wettability characteristics of model adhesive protein sequences inspired by a marine mussel

Three adhesive polyoctapeptides (X/Y-Gly-Tyr-Ser-Ala-Gly-Tyr-Lys)n (X, Thr and Ala: Y, Thr:Ala = 3:2), which are the C-terminal octapeptide sequences shared by all those consensus motifs of a ribbed mussel Geukensia demissa adhesive protein (RMAP), have been synthesized by the polycondensation of the active esters. The correlation between wettability and adhesion with the alternative substitution by hydrophobic Ala and hydrophilic Thr in the synthetic RMAPs in aqueous solution and as films on high and low surface free energy (sfe) surfaces has been investigated by surface chemical approaches. The side chain moieties of RMAPs arrange their local conformation to adapt to the inherent surface character, and they orientate on high and low sfe surfaces. On a high sfe glass the hydrophilic side chains of the RMAP molecules face toward the surface, and on a low sfe polyethylene (HDPE) the hydrophobic side chains face toward the surface. The bonding strengths of synthetic RMAPs on glass and HDPE with and without enzymatic oxidation have been examined. Increased starting concentration exhibited the strongest adhesive capability (7.5 kgf/cm2) on alumina due to the increased cohesion among RMAP molecules. As another factor to increase adhesive ability, the intermolecular cross-linking among RMAP molecules by tyrosinase increases their adhesive capability by about 20% on HDPE, glass, and alumina except iron.

Antibody levels to bacterial peptidoglycan in human sera during the time course of endocarditis and bacteremic infections caused by Staphylococcus aureus

Sera from patients with endocarditis and bacteremia due to Staphylococcus aureus were compared for peptidoglycan-binding capacity with those from normal blood donors. Those patients treated with beta-lactam antibiotics had higher antigen-binding levels than normal donors and patients treated exclusively with vancomycin (P less than 0.01). The factor responsible for this activity was purified by affinity chromatography from a normal donor and shown to be an immunoglobulin. Specificity studies indicated that the immunodominant determinant was a peptide sequence found in peptidoglycan precursors. Since soluble peptidoglycan molecules having the precursor peptide sequence are known to be secreted by some gram-positive bacteria like Micrococcus luteus when grown in the presence of beta-lactam antibiotics, these soluble molecules may constitute the "natural" immunogen. Such a hypothesis is consistent with the study of the peptidoglycan-binding capacities in the sera of these patients during the course of treatment. For most of the responding patients studied (four of four with bacteremia and seven of nine with endocarditis), a significant increase in peptidoglycan-binding capacity was observed in sera taken 1 to 5 weeks after the initiation of beta-lactam antibiotic therapy (compared with the initial serum studied). No such increase in the peptidoglycan-binding capacity over a similar time span was noted in the sera of people not receiving beta-lactam antibiotics (none of seven).

Immune responses of inbred guinea pigs and mice to helical sequential polymers of amino acids

The immune responses against the sequential polypeptides; (T-G-A-Gly)n, (T-A-G-Gly)n, (Phe-G-A-Gly)n and (Phe-A-G-Gly)n were studied in inbred guinea pigs and mice. Strain 13 guinea pigs responded to (Phe-G-A-Gly)n and (T-G-A-Gly)n whereas strain 2 guinea pigs responded to (T-A-G-GLY)n and (Phe-A-G-Gly)n. These responses which are linked to MHC, are only against the helical form of the polymers which have conformational determinants. Significant cross reactions at the humoral and T cell levels (PELS) are exhibited with the following reciprocal combinations: (Phe-G-A-Gly)n and (T-G-A-Gly)n; (T-A-G-Gly)n and (Phe-A-G-Gly)n. With mice, the polymers were shown to be T dependent with the following response patterns: mice of H-2b haplotype respond against (T-G-A-Gly)n; those of H-2b, f and r haplotypes respond against (T-A-G-Gly)n. There are no responders against (Phe-G-A-Gly)n and only mice of H-2f respond against (Phe-A-G-Gly)n. "Nonresponders" respond against the MBSA aggregates of all of these polymers. The Ir gene(s) controlling these T cell dependent H-linked responses mapped to the IA subregion. Antibody responses against (T-G-A-Gly) and (T-A-G-Gly) were quite variable, and were most marked in, F1 mice of (responder and nonresponder) and in backcross populations of (F1 x R) and (F1 x NR). However, the T cell proliferative responses performed with nylon wool purified T cells gave clear cut and predictable distinctions between "responders" and nonresponders and linkage with responding haplotype. Hypotheses advanced to explain these findings relate to the poor immunogenicity (antibody) of these polymers, which have a restricted number of repeating determinants, the B cell mitogenic properties of these polymers and the possible involvement of suppressor cells. The specificities of the humoral responses, i.e. cross reactions, were similar to those found in guinea pigs. However, in contrast to the guinea pig studies cross stimulation with structurally related polymers occurred only in those situations where the immunizing and "crossreacting" polymers were both immunogenic in mice of the same haplotype, i.e., (T-A-G-Gly)n and (Phe-A-G-Gly)n in mice of H-2f haplotypes.