A p-nitrophenyl alpha-galactoside hydrolase from Pseudomonas atlantica. Localization of the enzyme.

A p-nitrophenyl alpha-galactoside hydrolase is partially released when whole cells of Pseudomonas atlantica are converted to spheroplasts. The p-nitrophenyl alpha-glactoside hydrolase is completely inactivated by treatment of whole cells with diazonaphthalene -- disulfonic acid (NDS), a reagent which does not penetrate the cytoplasmic membrane. Under the conditions used no inactivation of lactic acid dehydrogenase was observed. A specific staining procedure for this enzyme for use in electron microscopy was developed. The results with this technique in conjunction with the results of spheroplasting and NDS localization suggest that p-nitrophenyl alpha-galactoside hydrolase is located in or on the double-track membranes, primarily on the outer double track.     

C-n.m.r. spectroscopic investigation of methylated and charged agarose oligosaccharides and polysaccharides

The ¹³C-n.m.r. signals of agarose oligomers with various substituted repeating units have been assigned. Enzymic hydrolysis of agaroses gave 2¹-O-methylagarobiose, 6²-O-methylagarobiose, the agarobiose biological precursor, agarobiose 4²-sulfate, 2¹-O-methylagarobiose 4²-sulfate, and pyruvylated agarobiose. The chemical shift data of the oligomers and the parent polymers were compared, and indicated the distribution of the substituents in hybrid polymers.     

Enzymatic hydrolysis of agar: purification and characterization of beta-neoagarotetraose hydrolase from Pseudomonas atlantica.

Agarose is degraded by a beta-agarase from Pseudomonas atlantica to neoagarooligosaccharides of degree of polymerization (DP), 4, 6, 8, and 10. A beta-neoagarotetraose hydrolase cleaves the central beta-linkage in neoagarotetraose and the beta-linkage near the nonreducing end in neoagarohexaose and -octaose to yield neoagarobiose. The beta-neoagarotetraose hydrolase was localized on or outside the cytoplasmic membrane, in the cell wall region. The enzyme was activated by NaCl, KCl, CaCl2, MnCl2, and MgSO4, has a Km of 3.4 X 10(-3) M for neoagarotetraose, was free from beta-agarase and alpha-neoagarobiose hydrolase activity, and showed no transglycosidic activity.     

Enzymatic hydrolysis of agar: purification and characterization of neoagarobiose hydrolase and p-nitrophenyl alpha-galactoside hydrolase.

The mixture of polysaccharides in the gelling component of agar (agarose) is hydrolyzed to D-galactose and 3,6-anhydro-L-galactose by a series of hydrolytic enzymes obtained from Pseudomonas atlantica. The final degradative step in the pathway of agarose decomposition is the hydrolysis of the alpha-linkage in the dissaccharide neoagarobiose yielding D-galactose and 3,6-anhydro-L-galactose. Pseudomonas atlantica when grown on agar produces two specific enzymes, p-nitrophenyl alpha-galactose hydrolase and neoagarobiose hydrolase. The purification and partial characterization of both enzymes are presented.     

Perceptions of family medicine and career choice among first year medical students: a cross-sectional survey in a Turkish medical school

Public attitudes to family medicine in Turkey have lagged behind its rapid academic development. The effect of undergraduate training in primary care on medical students' attitudes to family medicine has not been assessed. Objectives of this study were to assess the attitudes of first year medical students at Uludag University School of Medicine in Bursa, Turkey to family medicine and to determine their career aspirations. The study was a survey of the first year medical class in 2003-2004. The response rate was 95% (248/261 students). Students were positive about their choice of medicine as a career but had negative opinions of general practice. Female students were more positive in this respect. Initial preference was for specialization in fields other than general practice with little knowledge of the academic specialty of family medicine. Greater undergraduate exposure to family medicine is needed in order to increase knowledge of the field and influence student career choices.     

Properties of agar: parameters affecting gel-formation and the agarose-iodine reaction

The effects of concentration of agarose, methyl sulphoxide, and substituted agaroses on the mechanism of gel formation have been evaluated with reference to the “Network theory of gel formation”. Factors affecting formation of the agarose gel-iodine color complex were investigated, and the results suggest that the iodine molecules are incorporated between the agarose helices in the Gel II state of agarose.     

Effects of seasons on the chemical structure and gel strength of Gracilaria pseudoverrucosa agar (Gracilariaceae, rhodophyta)

The seasonal effects on the chemical structure and rheological properties of Gracilaria pseudoverrucosa agar have been investigated using a sequential solvent extraction, ¹³C NMR and infrared spectroscopy, and gel strength measurements. The results showed that agar enriched in precursor to the agarobiose repeat unit were obtained from algae collected in summer. In contrast, algae collected in winter contained agar molecules richer in alkali-stable sulfate groups attributed in part to -galactose-4-sulfate. A similar total concentration of 6-O-methylated agarobiose repeat units was present in the agar from both algal samples but the distribution of the methylated disaccharide varied in the fractions. Agar fractions from the summer-collected sample had higher gel strength than those of the winter ones. Alkali treatment markedly improved the gel strength of the agar from the summer harvested seaweed. Different gel strengths were observed for the native and alkali-treated agar fractions extracted from the same algal sample and a gel strength comparable to that obtained for a commercial bacteriological grade agar was obtained from the alkali-treated 40% ethanol extract agar from the summer collected alga. The chemical and rheological variations due to seasonal changes are interpreted as reflecting the ratio of actively-growing (young) to resting (old) tissue in the alga and are proposed to represent a type of ‘secondarization’ of the algal cell-wall.