In this article, plain woven, rib knitted and sequentially stacked rib knitted/plain woven, flax fabric reinforced epoxy composites are investigated for their flexural and impact properties. The effect of lay-up angle and the number of preform layers on the above-mentioned properties are also studied. The composite laminates were processed by hand lay-up technique using 2 and 4 mm thick spacers and cured under pressure of 3 bar for 2 h at 50 C, followed by curing in an oven at 120 C for 1 h. Specimen preparation and testing were carried out as per ASTM standards. The results indicate that the woven preform reinforced laminates perform better in both flexural and impact properties for all the lay-up angles and thicknesses investigated in this study. Among the sequentially stacked knitted/woven preform reinforced laminates, specimen with knitted preform as the skin layers exhibited better flexural and impact properties. The data obtained show a tendency of lower flexural and impact values with increase in number of preform layers for all lay-up angles with the exception of lay-up angle [0 / + 45 /À45 /0 ]. At low fibre volume fraction, the sequentially stacked knitted/woven preform reinforced laminates were found comparable to woven preform laminates.

Enolases are generally thought of as cytoplasmic enzymes involved in glycolysis and gluconeogenesis. However, several bacteria have active forms of enolase associated with the cell surface and these proteins are utilized for functions other than central metabolism. Recently, a surface-associated protein produced by Lactobacillus gasseri ATCC 33323 with homology to enolase was found to inhibit the adherence of the sexually transmitted pathogen, Neisseria gonorrhoeae, to epithelial cells in culture. Here, we show that the protein is an active enolase in vitro. A recombinantly expressed, C-terminal His-tagged version of the protein, His6-Eno3, inhibited gonococcal adherence. Assays utilizing inhibitors of enolase enzymatic activity showed that this inhibitory activity required the substrate-binding site to be in an open conformation; however, the enolase enzymatic activity of the protein was not necessary for inhibition of gonococcal adherence. An L. gasseri strain carrying an insertional mutation in eno3 was viable, indicating that eno3 is not an essential gene in L. gasseri 33323. This observation, along with the results of the enzyme assays, is consistent with reports that this strain encodes more than one enolase. Here we show that the three L. gasseri genes annotated as encoding an enolase are expressed. The L. gasseri eno3 mutant exhibited reduced, but not abolished, inhibition of gonococcal adherence, which supports the hypothesis that L. gasseri inhibition of gonococcal adherence is a multifactorial process.

Protein crystallization screens frequently yield salt crystals as well as protein crystals. A simple method for determining whether a crystal is composed of salt or macromolecules is suggested. A drop containing one or more crystals is transferred to a glass cover slip and the cover slip is then passed through the flame of a Bunsen burner. Macromolecule crystals are destroyed by this treatment, while salt crystals generally remain. The test can be performed after other commonly used tests such as crushing and staining.

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