Utilization of some monosaccharides by two species of Colletotrichum

Summary Utilization of 8 monosaccharides, viz., glucose, fructose, galactose, mannose, sorbose, arabinose, xylose and rhamnose, by some plant pathogenic isolates ofColletotrichum gloeosphorioides andC. dematium has been studied with the help of paper chromatography. Among hexoses, the rate of utilization of glucose, fructose and mannose was fast, whereas, that of galactose was comparatively slow. The rate of assimilation of sorbose was very slow at early stages of incubation, although at later stages this rate showed marked enhancement. The pentoses were utilized readily. The dry weight of mycelial mats showed an increase up to the end of final incubation period (15 days), on sugars which were slowly assimilated. In cases where the sugars were consumed up rapidly, the dry weight at later stages of incubation either became nearly stationary or recorded slight fall.     

The utilization of the mixtures of monosaccharides by some mucorales

Summary The utilization of mixtures of monosaccharides byBlakeslea trispora Thaxter,Choanephora circinans (Naganish &Kawakami)Hesseltine &Benjamin,Gilbertella persicaria var.indica Mehrotra &Mehrotra andHelicostylum piriforme Bainier was studied. The effect of sorbose on the utilization of other sugars present in the mixtures was also studied. It was found that all the mixtures of sugars in combination with asparagine or ammonium chloride were valueless for all the organisms exceptHelicostylum piriforme. Growth ofHelicostylum piriforme on the mixtures with asparagine as the nitrogen source was better than on the mixtures with ammonium chloride as the source of nitrogen. Asparagine being a favourable source counteractecd sorbose inhibition, while ammonium chloride failed to do so. On the other hand, both of the nitrogen sources failed to counteract sorbose inhibition in the rest of the organisms. None of the organisms could finish sorbose and rhamnose from any of the mixtures within the specified period.     

Complex formation of human thrombospondin with osteonectin

Human thrombospondin, a 450-kDa glycoprotein isolated from platelets and endothelial cells, specifically interacts with osteonectin, a protein of 30 kDa isolated from bovine bones and human platelets. Using ELISA, purified osteonectin binds to solid-phase-adsorbed thrombospondin with a dissociation constant (Kd) of 0.7 nM. Binding of thrombospondin to solid-phase-adsorbed osteonectin was also observed (Kd = 0.86 nM). The interaction of thrombospondin with solid-phase-adsorbed osteonectin was significantly decreased (81% inhibition) when using an excess of fluid-phase osteonectin. Thrombospondin-osteonectin complex formation was calcium-dependent as shown by a 50-80% inhibition in the presence of EDTA. None of the proteins known to interact with thrombospondin (fibrinogen, fibronectin, collagen, plasminogen) had a significant inhibitory effect on thrombospondin-osteonectin complex formation. This selective interaction was confirmed by affinity chromatography. Iodinated osteonectin, previously incubated with purified thrombospondin, specifically bound to an anti-thrombospondin monoclonal antibody (P10) linked to protein-A--Sepharose 4B. Elution of the anti-thrombospondin antibody from protein A allowed the recovery of the thrombospondin-osteonectin complex in the eluate, as judged by SDS/polyacrylamide gel electrophoresis and autoradiography. Blotting of purified thrombospondin to osteonectin adsorbed onto nitrocellulose further confirmed complex formation. In addition, when released from thrombin-stimulated platelets, thrombospondin and osteonectin bound to anti-thrombospondin IgG-coated plates indicating that osteonectin was complexed to thrombospondin once the platelet-release reaction has occurred.     

Biological evaluation of fluorinated p-boronophenylalanine derivatives as a boron carrier

Boron neutron capture therapy (BNCT) and magnetic resonance imaging (MRI) are quite attractive techniques for treatment and diagnosis of cancer, respectively. In order to develop practical materials utilizing both for BNCT and MRI, fluorinated p-boronophenylalanines and their alcohol derivatives had already been designed and synthesized. In the present paper the cytotoxicity, the incorporated amount into cancer cells, and the tumor cell killing effects of these compounds were elucidated to evaluate their usefulness as a boron carrier.     

Application of square-wave adsorptive stripping voltammetry to the study of cysteine and its interaction with some monosaccharides

The square-wave adsorptive stripping voltammetric behaviour of cysteine at the physiological pH (7.40) has been optimised with respect to accumulation time, accumulation potential, scan rate and drop size. This study describes the application of voltammetry to studies on the interaction of cysteine with monosaccharides.     

Complex formation of protein with different water-soluble synthetic polymers

The formation of protein-polymer complexes was studied in an aqueous system using dynamic light scattering (DLS) and static light scattering (SLS) as the main experimental tools. Human serum albumin (HSA) was used as a protein and complexed with four representative water-soluble polymers: poly(N-isopropylacrylamide) (PNIPA), poly(ethylene glycol) (PEG), poly(vinyl pyrrolidone) (PVP), and poly(vinyl alcohol) (PVA). The first three molecular weights were within 420,000-540,000 and the last one was 270,000. The complexation was performed at 25 degrees C in 0.01 M NaCl solution adjusted to pH 3 with HCl as a function of mixing ratio (rm; molar ratio of polymer to HSA). From SLS experiments, we determined the molecular weight of the resulting complexes, from the value of which the number (nb) of bound proteins per polymer was estimated. It was found that each polymer forms an intrapolymer complex over a wide range of rm (1.2 > or = rm > or = 0.01). Then, a marked decrease in nb with increasing rm was found. Over the whole rm range, the HSA-PNIPA complex exhibited a large nb value, as compared with the other three complexes whose nb values at the same rm were close to one another. Both the hydrodynamic radius (Rh) by DLS and the radius of gyration (Rg) by SLS for the complexes of PNIPA, PVP, and PVA decreased and then reached a constant value as nb decreased with increasing rm. In the PEG system, however, there were a few changes in Rh and Rg with nb. The Rg/Rh ratio, as an indication of chain expansion, was found to increase with decreasing nb in the PNIPA system. The complexes of PVA and PVP displayed a similar tendency, although the magnitude of the increasing trend was smaller than that of the PNIPA complex. In contrast, the Rg/Rh ratio of the PEG complex hardly varied depending on nb. These results were discussed in connection with the differences of physicochemical properties among four water-soluble polymers.     

The interaction of areneboronic acids with monosaccharides

The interaction of benzeneboronic acid, 4-methoxybenzeneboronic acid, and 3-nitrobenzeneboronic acid with d-glucose, d-mannose, and d-fructose at various pH values has been investigated by means of optical rotation methods. The effects of (a) various molar ratios of sugar and acid and (b) overall concentration on the extent of complex formation are reported.     

Effects of monosaccharides and disaccharides on the formation of food mutagens in model systems

The formation of the mutagenic imidazoquinoxalines (MeIQx, DiMeIQx) was studied using a modification of a previous model system. Creatine or creatinine (0.9 mmole) was heated together with glycine (0.9 mmole) and various sugars (0.45 mmole) dissolved in diethylene glycol and water (3 ml, 5 : 1) for up to 15 min at 180°C. This system produced the same amount of mutagenicity after 10 min at 180°C as a previous one during 2 h of reflux boiling at 12dgC. MeIQx (4 nmole/mmole creatin(in)e was the major mutagen produced together with minor amounts of DiMeIQx, both 4,8- and 7,8-DiMeIQx according to HPLC-MS. A few other mutagenic peaks were also separated on HPLC, but they were not identified. Varying the concentration (0–2.4 mmole) and type of monosaccharides and disaccharides greatly affected the yields of all the mutagenic compounds. Sugar in molar amounts lower than the creatin(in)e concentration increased the yield until an optimum was reached. In higher concentrations the formation of all the mutagens was markedly reduced. The same was found for glucose, fructose, sucrose, and lactose, though the monosaccharides showed the most pronounced inhibitory effects.

The inhibition of the formation of the mutagenic compounds by an excess of sugars is proposed to be an effect of Maillard reaction products, which may block the formation of imidazoquinoxalines by attacking creatine. Support for this mechanism is given by data showing a lower recovery of unreacted creatine with increasing concentration of glucose and also by an inhibitory effect on the formation of these mutagens after adding a typical Maillard reaction product, 5-hydroxymethyl-2-furfural.     

The interaction of yeast Complex III with some respiratory inhibitors

We have examined the effects of eight inhibitors of the bovine-heart mitochondrial Complex III on the catalytic activity of the analogous complex from yeast mitochondria. All eight compounds were inhibitory, with potent inhibition being obtained with antimycin, myxothiazol and UHDBT (5-N-undecyl-6-hydroxy-4,7-dioxobenzothiazole). These three inhibitors, and also funiculosin, have been further studied by characterizing their effects on the visible absorbance, magnetic circular dichroism and EPR spectra of the complex and also on the potentiometric properties of the individual metal centers present in the complex. All four inhibitors had little or no effect on either the absorbance or magnetic circular dichroism spectra. Funiculosin produced a change in the EPR lineshape of the iron-sulfur cluster; EPR spectra recorded at 12 K also revealed complete reduction of cytochrome b-562 by ascorbate. UHDBT also changed the lineshape of the iron-sulfur cluster and this change could be partially reversed by myxothiazol. Neither antimycin nor myxothiazol affected the iron-sulfur cluster and produced only small changes in the EPR absorption envelope of the b cytochromes. Both funiculosin and UHDBT raised the midpoint potential of the iron-sulfur cluster, by about 150 and 70 mV, respectively. Only UHDBT changed the potential of c1, lowering it by about 30 mV. Funiculosin raised the potential of b-562 by about 30 mV, while myxothiazol had no effect; the other two compounds produced only small changes. All four compounds had only small effects on the midpoint potential of b-566. The relative contributions of the two b cytochromes to the magnetic circular dichroism amplitudes could be changed by the addition of inhibitors, even though the absolute magnetic circular dichroism spectra of oxidized and reduced complex were unaffected.