PapC ushers are outer-membrane proteins enabling assembly and secretion of P pili in uropathogenic E. coli. Their translocation domain is a large β-barrel occluded by a plug domain, which is displaced to allow the translocation of pilus subunits across the membrane. Previous studies suggested that this gating mechanism is controlled by a β-hairpin and an α-helix. To investigate the role of thes...

Three mutants of the antibiotic nisin Z, in which the Val32 residue was replaced by a Glu, Lys or Trp residue, were produced and characterized for the purpose of establishing the role of charge differences in the C-terminal part of nisin on antimicrobial activity and signaling properties. 1H-NMR analyses showed that all three mutants harbor an unmodified serine residue at position 33, instead o...

in order to study the residues of phosphorous insecticides in mazandaran district of iran, ethion, azinphosmethyl, diazinon and malathion four most used pesticides were chosen and river water samples were collected in april to sept. 2000, throughout the mazandaran state. thin layer chromatography was used, since it was the best applicable method in area with reasonably high level of sensitivity...

viAcknowledgments, vAppendices, 51AppendixTable of Minimum Weights, 52Bibliography, 56Dedication, iv

The pseudo-oligosaccharides, validamycins, showed potent inhibitory activity against trehalase of Rhizoctonia solani while no significant inhibition was exhibited against cellulase, pectinase, chitinase, alpha-amylase, alpha- and beta-glucosidases. In particular, validoxylamine A strongly inhibited trehalase in a competitive manner with a Ki value of 1.9 X 10(-9) M. The uptake of the antibiotic...

Because dihydrostreptomycin can remain as a slowly removed antibiotic residue in dairy animals and because of the need for more sensitive procedures with which to provide information concerning antibiotic residues in food products, procedures were developed in more sensitive assays of dihydrostreptomycin in milk and some representative dairy products. The cleanup procedures that aided these imp...

Rising resistance to current clinical antibacterial agents is an imminent threat to global public health and highlights the demand for new lead compounds for drug discovery. One such potential lead compound, the peptide antibiotic teixobactin, was recently isolated from an uncultured bacterial source, and demonstrates remarkably high potency against a wide range of resistant pathogens without a...

Antibiotics are used by veterinarians and producers to treat disease and improve animal production. The federal government, to ensure the safety of the food supply, establishes antibiotic residue tolerances in edible animal tissues and determines the target tissues (e.g., muscle) for residue monitoring. However, when muscle is selected as the target tissue, the federal government does not speci...

Analysis of rhesus macaque leukocytes disclosed the presence of an 18-residue macrocyclic, tridisulfide antibiotic peptide in granules of neutrophils and monocytes. The peptide, termed rhesus theta defensin-1 (RTD-1), is microbicidal for bacteria and fungi at low micromolar concentrations. Antibacterial activity of the cyclic peptide was threefold greater than that of an open-chain analog, and ...

In the present study Aflatoxin M (AFM ) and various Antibiotic Residue (AbR) including 1 1 oxytetracyclin, streptomycin, gentamicin, neomycin and penicillin were comparatively evaluated through Thin-Layer Chromatographic (TLC) technique in various types of milk samples i.e. fresh, boiled and pasteurized milk samples. AFM contamination was recorded in 20% of the total fresh milk and 15% of the b...