PubMed · 4301985
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K Burton. 1965. Sequence determination in nucleic acids.. https://pubmed.ncbi.nlm.nih.gov/4301985/
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The antibacterial effectiveness of an ultraviolet-irradiated nylon 6, 6 film was investigated for potential use as a food-packaging material to reduce the surface microbial contamination of foods. The film-surface analyses showed that UV irradiation induced conversion of surface amide groups to amines. Irradiation also increased the dimensional scale of the film surface topography (depth of valleys) approximately 5-fold on the scale of nanometers. The irradiated nylon demonstrated antagonistic activity against Staphylococcus aureus 25923 and Escherichia coli TV1058 with 4.5 and 6 log reductions, respectively, of an initial population of 10(6) cfu mL(-1). The irradiated nylon was ineffective against Pseudomonas fluorescens 13525 and Enterococcus faecalis 19433 under similar conditions. The film demonstrated increased antimicrobial activity against S. aureus 25923 with increasing temperatures up to 45 degrees C, the highest temperature tested. Protein and salt inhibited the antibacterial nature of the irradiated film. Amines in solution (4.31 x 10(-8) M; the calculated equivalent of amines on the film) killed at least 1 x 10(4) cfu mL(-1) E. coli TV1058, and 4. 31 x 10(-7) M amines killed up to 1 x 10(7) cfu mL(-1) E. coli TV1058. The amines in solution required similar exposure time to the bacteria for population reduction as was observed with the irradiated film.
In the present study, unilamellar liposomes coated with the crystalline bacterial cell surface layer (S-layer) protein of Bacillus stearothermophilus PV72/p2 were used as matrix for defined binding of functional molecules via the avidin- or streptavidin-biotin bridge. The liposomes were composed of dipalmitoyl phosphatidylcholine, cholesterol and hexadecylamine in a molar ratio of 10:5:4 and they had an average size of 180 nm. For introducing specific functions into the S-layer lattice without affecting substances encapsulated within the liposomes, crosslinking and activation reagents had to be identified which did not penetrate the liposomal membrane. Among different reagents, a hydrophilic dialdehyde generated by periodate cleavage of raffinose and a sulfo-succinimide activated dicarboxylic acid were found to be impermeable for the liposomal membrane. Both reagents completely crosslinked the S-layer lattice without interfering with its regular structure. Biotinylation of S-layer-coated liposomes was achieved by coupling p-diazobenzoyl biocytin which preferably reacts with the phenolic residue of tyrosine or with the imidazole ring of histidine. By applying this method, two biotin residues accessible for subsequent avidin binding were introduced per S-layer subunit. As visualized by labeling with biotinylated ferritin, an ordered monomolecular layer of streptavidin was formed on the surface of the S-layer-coated liposomes. As a second model system, biotinylated anti-human IgG was attached via the streptavidin bridge to the biotinylated S-layer-coated liposomes. The biological activity of the bound anti-human IgG was confirmed by ELISA.
In mammals, leukotriene A(4) hydrolase is a bifunctional zinc metalloenzyme that catalyzes hydrolysis of leukotriene A(4) into the proinflammatory leukotriene B(4) and also possesses an arginyl aminopeptidase activity. We have cloned, expressed, and characterized a protein from Saccharomyces cerevisiae that is 42% identical to human leukotriene A(4) hydrolase. The purified protein is an anion-activated leucyl aminopeptidase, as assessed by p-nitroanilide substrates, and does not hydrolyze leukotriene A(4) into detectable amounts of leukotriene B(4). However, the S. cerevisiae enzyme can utilize leukotriene A(4) as substrate to produce a compound identified as 5S,6S-dihydroxy-7,9-trans-11, 14-cis-eicosatetraenoic acid. Both catalytic activities are inhibited by 3-(4-benzyloxyphenyl)-2-(R)-amino-1-propanethiol (thioamine), a competitive inhibitor of human leukotriene A(4) hydrolase. Furthermore, the peptide cleaving activity of the S. cerevisiae enzyme was stimulated approximately 10-fold by leukotriene A(4) with kinetics indicating the presence of a lipid binding site. Nonenzymatic hydrolysis products of leukotriene A(4), leukotriene B(4), arachidonic acid, or phosphatidylcholine were without effect. Moreover, leukotriene A(4) could displace the inhibitor thioamine and restore maximal aminopeptidase activity, indicating that the leukotriene A(4) binding site is located at the active center of the enzyme. Hence, the S. cerevisiae leukotriene A(4) hydrolase is a bifunctional enzyme and appears to be an early ancestor to mammalian leukotriene A(4) hydrolases.