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Various Sugars (various + sugar)
Selected AbstractsEffects of Various Sugars Added to Growth and Drying Media upon Thermotolerance and Survival throughout Storage of Freeze-Dried lactobacillus delbrueckii ssp. bulgaricusBIOTECHNOLOGY PROGRESS, Issue 1 2004Ana S. Carvalho The aim of this research effort was to investigate the role of various sugar substrates in the growth medium upon thermotolerance and upon survival during storage after freeze-drying of Lactobacillus bulgaricus. Addition of the sugars tested to the growth medium, and of these and sorbitol to the drying medium (skim milk) was investigated so as to determine whether a relationship exists between growth and drying media, in terms of protection of freeze-dried cells throughout storage. The lowest decrease in viability of L. bulgaricuscells after freeze-drying was obtained when that organism was grown in the presence of mannose. However, L. bulgaricusclearly survived better during storage when cells had been grown in the presence of fructose, lactose or mannose rather than glucose (the standard sugar in the growth medium). A similar effect could not be observed in terms of thermotolerance; in this case, the growth medium supplemented with lactose was found to yield cells bearing the highest heat resistance. Supplementation of the drying medium with glucose, fructose, lactose, mannose or sorbitol led in most cases to enhancement of protection during storage, to a degree that was growth medium-dependent. [source] Molecular recognition of sugars by lanthanide (III) complexes of a conjugate of N, N -bis[2-[bis[2-(1, 1-dimethylethoxy)-2-oxoethyl]amino]ethyl]glycine and phenylboronic acidCONTRAST MEDIA & MOLECULAR IMAGING, Issue 4 2007Elisa Battistini Abstract A novel conjugate of phenylboronic acid and an Ln(DTPA) derivative, in which the central acetate pendant arm was replaced by the methylamide of L -lysine, was synthesized and characterized. The results of a fit of variable 17O NMR data and a 1H NMRD profile show that the water residence lifetime of the Gd(III) complex (150,ns) is shorter than that of the parent compound Gd(DTPA)2, (303,ns). Furthermore, the data suggest that several water molecules in the second coordination sphere of Gd(III) contribute to the relaxivity of the conjugate. The Ln(III) complexes of this conjugate are highly suitable for molecular recognition of sugars. The interaction with various sugars was investigated by 11B NMR spectroscopy. Thanks to the thiourea function that links the phenylboronic acid targeting vector with the DTPA derivative, the interactions are stronger than that of phenylboronic acid itself. In particular, the interaction with N -propylfructosamine, a model for the glucose residue in glycated human serum albumin (HSA), is very strong. Unfortunately, the complex also shows a rather strong interaction with hexose-free HSA (KA,=,705,±,300). Copyright © 2007 John Wiley & Sons, Ltd. [source] Adenylyl cyclase encoded by AC78C participates in sugar perception in Drosophila melanogasterEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2008Kohei Ueno Abstract In gustatory receptor neurons (GRNs) in Drosophila melanogaster, Gr5a and one of the Gr64s encode sugar receptors with seven transmembrane domains. Previously, we have shown that the responses to various sugars are depressed in DGs, mutant flies (Ueno et al., 2006). Because DGs, is a homolog of Gs, we hypothesized that the sugar receptors are coupled to adenylyl cyclase (AC) in Drosophila. The aim of this study was to identify the AC that participates in sugar perception. Here, we found that an AC inhibitor, MDL-12330A, depressed the response in GRNs to trehalose as well as sucrose; that an AC gene, AC78C, was expressed in the sugar-sensitive GRNs; that RNAi against AC78C depressed the electrical response in GRNs to sucrose; and that the sugar response in GRNs, as well as sugar intake in a behavioral assay in an AC78C mutant, was depressed at low sugar concentrations. We conclude that AC78C, via cAMP, participates in the sugar-taste signaling pathway at the low concentration range. [source] Improving thermostability and catalytic activity of pyranose 2-oxidase from Trametes multicolor by rational and semi-rational designFEBS JOURNAL, Issue 3 2009Oliver Spadiut The fungal homotetrameric flavoprotein pyranose 2-oxidase (P2Ox; EC 1.1.3.10) catalyses the oxidation of various sugars at position C2, while, concomitantly, electrons are transferred to oxygen as well as to alternative electron acceptors (e.g. oxidized ferrocenes). These properties make P2Ox an interesting enzyme for various biotechnological applications. Random mutagenesis has previously been used to identify variant E542K, which shows increased thermostability. In the present study, we selected position Leu537 for saturation mutagenesis, and identified variants L537G and L537W, which are characterized by a higher stability and improved catalytic properties. We report detailed studies on both thermodynamic and kinetic stability, as well as the kinetic properties of the mutational variants E542K, E542R, L537G and L537W, and the respective double mutants (L537G/E542K, L537G/E542R, L537W/E542K and L537W/E542R). The selected substitutions at positions Leu537 and Glu542 increase the melting temperature by approximately 10 and 14 °C, respectively, relative to the wild-type enzyme. Although both wild-type and single mutants showed first-order inactivation kinetics, thermal unfolding and inactivation was more complex for the double mutants, showing two distinct phases, as revealed by microcalorimetry and CD spectroscopy. Structural information on the variants does not provide a definitive answer with respect to the stabilizing effects or the alteration of the unfolding process. Distinct differences, however, are observed for the P2Ox Leu537 variants at the interfaces between the subunits, which results in tighter association. [source] The Kluyver effect revisitedFEMS YEAST RESEARCH, Issue 4 2003Hiroshi Fukuhara Abstract Yeast species can grow on various sugars. However, in many cases the growth on certain sugars (especially oligosaccharides) occurs only under aerobic conditions, and not in anaerobiosis or in the absence of respiration. Fermentation is blocked under these conditions. This apparent dependence of sugar utilization on the respiration has been called Kluyver effect, and such ,respiration-dependent' species are called Kluyver effect positive. A yeast may be Kluyver effect positive for some sugars and not for others. The physiological meaning and the molecular basis of the phenomenon are not clear. It has recently been reported that Kluyveromyces lactis, which is Kluyver effect positive for galactose and a few other sugars, could be converted into a Kluyver effect-negative form by introduction of relevant sugar transporter genes. Such results offer for the first time a direct support to the hypothesis that the immediate cause of the Kluyver effect may be the low level of sugar transporter activities which is not sufficient to sustain the high substrate flow necessary for fermentative growth, whereas the energy-efficient respiratory growth does not require a high rate of sugar uptake. We examined to what extent this sugar transporter theory of the Kluyver effect can be generalized. [source] Structure of a bovine secretory signalling glycoprotein (SPC-40) at 2.1,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2006Janesh Kumar A recently discovered new class of 40,kDa glycoproteins forms a major component of the secretory proteins in the dry secretions of non-lactating animals. These proteins are implicated as protective signalling factors that determine which cells are to survive during the processes of drastic tissue remodelling. In order to understand its role in the remodelling of mammary glands, the detailed three-dimensional structure of the bovine signalling glycoprotein (SPC-40) has been determined using X-ray crystallography. SPC-40 was purified from bovine dry secretions and crystallized using the hanging-drop vapour-diffusion method. The crystals belong to the orthorhombic space group P212121, with unit-cell parameters a = 62.6, b = 67.4, c = 106.9,Å. The protein was also cloned in order to determine its complete amino-acid sequence. Its three-dimensional structure has been determined using data to 2.1,Å resolution. The amino-acid sequence determination of SPC-40 reveals two potential N-glycosylation sites at Asn39 and Asn345, but electron density for a glycan chain was only present at Asn39. The protein adopts a conformation with the classical (,/,)8 -barrel fold of triosephosphate isomerase (TIM barrel; residues 1,237 and 310,360) with the insertion of a small ,+, domain (residues 240,307) similar to that observed in chitinases. However, the substitution of Leu for Glu in the consensus catalytic sequence in SPC-40 caused a loss of chitinase activity. Furthermore, the chitin-binding groove in SPC-40 is considerably distorted owing to unfavourable conformations of several residues, including Trp78, Tyr120, Asp186 and Arg242. Three surface loops, His188,His197, Phe202,Arg212 and Tyr244,Pro260, have exceptionally high B factors, suggesting large-scale flexibility. Fluorescence studies indicate that various sugars bind to SPC-40 with low affinities. [source] | |||||||||||||