Carbohydrate binding specificity of the B-cell maturation mitogen from Artocarpus integrifolia seeds

Artocarpin, a mannose-specific lectin, is a homotetrameric protein (M(r) 65,000) devoid of covalently attached carbohydrates and consists of four isolectins with pI in the range 5-6.5. Investigations of its carbohydrate binding specificity reveal that among monosaccharides, mannose is preferred over glucose. Among mannooligosaccharides, mannotriose (Man alpha 1-3[Man alpha 1-6]Man) and mannopentaose are the strongest ligands followed by Man alpha 1-3Man. Extension of these ligands by GlcNAc at the reducing ends of mannooligosaccharides tested remarkably improves their inhibitory potencies, while substitution of both the alpha 1-3 and alpha 1-6 mannosyl residues of mannotriose and the core pentasaccharide of N-linked glycans (Man alpha 1-3[Man alpha 1-6]Man beta 1-4GlcNAc beta 1-4GlcNAc) by GlcNAc or N-acetyllactosamine in beta 1-2 linkage diminishes their inhibitory potencies. Sialylated oligosaccharides are non-inhibitory. Moreover, the substitution of either alpha 1-3 or alpha 1-6 linked mannosyl residues of M5Gn or both by mannose in alpha 1-2 linkage leads to a considerable reduction of their inhibitory power. Addition of a xylose residue in beta 1-2 linkage to the core pentasaccharide improves the inhibitory activity. Considering the fact that artocarpin has the strongest affinity for the xylose containing hepasaccharide from horseradish peroxidase, which differs significantly from all the mannose/glucose-specific lectins, it should prove a useful tool for the isolation and characterization of glycoproteins displaying such structure.

Carbohydrate binding specificity of the basic lectin from winged bean (Psophocarpus tetragonolobus)

The carbohydrate binding specificity of the basic lectin from winged bean (Psophocarpus tetragonolobus) was investigated by quantitative precipitin analysis using blood group A, B, H, Le and I substances and by precipitation inhibition with various mono- and oligosaccharides. The lectin precipitated best with A1 substances and moderately with B and A2 substances, but not with H or Le substances. Inhibition assays of lectin-blood group A1 precipitation demonstration that A substance-derived oligosaccharides having the common structure: d-Ga1NAcα(1 → 3)d-Gal-(β1 → Image ) to a d-Glc, were the best inhibitors and about 8 and 4 times more active than d-Ga1NAc and d-Ga1NAcα(1 → 3)d-Ga1, respectively. A difucosyl A-specific oligosaccharide (A-penta), a monofucosyl (A-tetra) and a non-fucosyl containing (A5 II) oligosaccharide, d-Ga1NAcα(1 → 3)d-Ga1β(1 → 3)d-G1cNAc, had almost the same reactivity, suggesting that the fucose linked to the sub-terminal d-Ga1 or to the third sugar, d-GlcNAc, from the non-reducing end made no contribution to the carbohydrate binding. Although a terminal non-reducing d-Ga1NAc or d-Ga1 residue was indispensible for binding, the lectin bound not only to these terminal non-reducing galactopyranosyl residues, but also showed increased binding to oligosaccharides in which it was bonded to a sub-terminal d-Ga1 joined to a d-GlcNAc residue, as in blood group A or B substances. This defines the site, thus far, as complementary to a disaccharide plus the β linkage to the third sugar (d-Glc or d-GlcNAc) from the non-reducing end. The role of the β(1 → 3) or β(1 → 4) linkage of the sub-terminal non-reducing d-Gal to the d-GlcNAc requires further study.

The specificity of the colour reaction between ammonia and 3-phenyl-2-thiohydantoin

The colour reaction between 3-phenyl-2-thiohydantoin and ammonia is studied quantitatively. Determinations of 0.1–0.6 μmoles of 3-phenyl-2-thiohydantoin are possible with a precision close to 2%. In analyses of amino acid mixtures for glycine after conversion to 3-phenyl-2-thiohydantoin, only derivatives of serine and threonine interfere to a slight extent. The specificity of the primary colour reaction with ammonia, and the structural requirements for it are discussed; a structure for the pigment species is proposed.

Alkaline and acid phosphatases of the silkworm, Bombyx mori L.

The variations in the activities of the alkaline and acid phosphatases of the silkworm, Bombyx mori, were studied in all stages of the life cycle. From hatching until the spinning stage a steady increase was recorded in the activity of both the enzymes followed with a conspicuous decrease at each moult. During the pupal stage the alkaline phosphatase was almost absent, whereas the acid phosphatase maintained a high and constant value. Increase or decrease of the activity of the enzymes during larval development was reflected in a decrease or increase in the acid-soluble phosphorus content. Acid phosphatase activity slowly increased from laying of the eggs to hatching of the larvae with a concomitant decrease in the acid-soluble phosphorus. Tissue analysis showed a high concentration of the alkaline enzyme in the intestines, but the haemolymph was almost free of both enzymes. Feeding of inorganic phosphate increased the alkaline enzyme in the intestines, whereas glucose had no effect on either of the enzymes in the intestines.

Fatty acid specificity for the esterification of vitamin A and cholesterol by intestinal and pancreatic enzymes in rats

VITAMIN A and cholesterol esters have been shown to undergo extensive hydrolysis in the lumen of the small intestine during the process of absorption; they are re-esterified to appear in the lymph mostly as esters1,2. However, the vitamin A esters of the lymph, blood and liver of the rat are formed by long-chain fatty acids3 and in the normal rat liver, probably as palmitates4. On the other hand, cholesterol esters are usually made up of poly-unsaturated fatty acids in the lymph and blood of rats5. For the absorption of the two lipid materials, the enzymes of the pancreas have been largely implicated, while not much attention has been paid to the possible role of the mucosal enzymes. From the behaviour of the mucosal enzymes, as presented here, it appears that probably these enzymes play a more important part in the re-esterification of the two lipid materials during their absorption.

Dual-Drug Delivery System Based on In Situ Gel-Forming Nanosuspension of Forskolin to Enhance Antiglaucoma Efficacy

The present study was designed to improve the bioavailability of forskolin by the influence of precorneal residence time and dissolution characteristics. Nanosizing is an advanced approach to overcome the issue of poor aqueous solubility of active pharmaceutical ingredients. Forskolin nanocrystals have been successfully manufactured and stabilized by poloxamer 407. These nanocrystals have been characterized in terms of particle size by scanning electron microscopy and dynamic light scattering. By formulating Noveon AA-1 polycarbophil/poloxamer 407 platforms, at specific concentrations, it was possible to obtain a pH and thermoreversible gel with a pH(gel)/T-gel close to eye pH/temperature. The addition of forskolin nanocrystals did not alter the gelation properties of Noveon AA-1 polycarbophil/poloxamer 407 and nanocrystal properties of forskolin. The formulation was stable over a period of 6 months at room temperature. In vitro release experiments indicated that the optimized platform was able to prolong and control forskolin release for more than 5 h. The in vivo studies on dexamethasone-induced glaucomatous rabbits indicated that the intraocular pressure lowering efficacy for nanosuspension/hydrogel systems was 31% and lasted for 12 h, which is significantly better than the effect of traditional eye suspension (18%, 4-6 h). Hence, our investigations successfully prove that the pH and thermoreversible polymeric in situ gel-forming nanosuspension with ability of controlled drug release exhibits a greater potential for glaucoma therapy.

On the specificity of activation of mitochondrial succinate dehydrogenase by ubiquinol

Activation of succinate dehydrogenase on preincubation with mitochondria is not specific for ubiquinol-10. Other homologues of ubiquinol, plastoquinol, o-, m- and p-quinols, 2-nitro-, 4-nitro- and 2,4-dinitro- phenols showed different degrees of activation. The lipid quinols, however, showed activation greater than succinate, hitherto considered to give maximum activation.

Characterization of human symptomatic rotavirus isolates MP409 and MP480 having ‘long’ RNA electropherotype and subgroup I specificity, highly related to the P6[1],G8 type bovine rotavirus A5, from Mysore, India

In an epidemiological study of symptomatic human rotaviruses in Mysore, India during 1993 and 1994, isolates MP409 and MP480 were isolated from two children suffering from severe, acute dehydrating diarrhea. Both isolates exhibited 'long' RNA pattern and subgroup I specificity suggesting the likelihood of their animal origin. Both isolates did not react with monoclonal antibodies (MAbs) specific for serotypes G1 to G6 as well as CIO. To determine the genetic origin of these isolates, complete nucleotide sequences of genes encoding the outer capsid proteins VP4 and VP7, nonstructural proteins NSP1 and NSP3 and viral enterotoxin protein NSP4 from MP409 and partial sequences of genes from MP480 were determined. Comparison of the 5' and 3' terminal sequences of 250 nucleotides revealed complete identity of the gene sequences in both strains suggesting that MP409 and MP480 are two different isolates of a single strain. Comparison of the nucleotide and deduced amino acid sequences of VP4, VP7, NSP1 and NSP3 of MP409 with published sequences of strains belonging to different serotypes revealed that both outer capsid proteins VP4 and VP7 and NSP1 are highly related to the respective proteins from the P6[1], G8 type bovine rotavirus A5 isolated from a calf with diarrhoea in Thailand and that the NSP3 is highly homologous to that of bovine rotaviruses. The NSP 1 protein showed greatest sequence identity with NSP4s belonging to the KUN genetic group to which NSP4s from human G2 type strains and bovine rotaviruses belong. MP409 and MP480 likely signify interspecies transmission of P6[1], G8 type strains from cattle to humans and represent the first P6[1] type rotaviruses isolated in humans. These and our previous studies on the asymptomatic neonatal strain I321 are of evolutionary and epidemiological significance in the context of close association of majority of the Indian population with cattle.

High Rate Capability of a Dual-Porosity LiFePO4/C Composite

Mesoporous intercalation compounds consisting of two differentdistributions of pores represent a potentially attractive material for high-rate cathodes. A mesoporous LiFePO4/C composite with two sizes of pores is prepared for the first time via a solution-based polymer templating technique. The precursor of the LiFePO4/C composite is heated at different temperatures in the range from 600 to 800 degrees C to study the effect of crystallinity, porosity, and morphology on the electrochemical performance. The composite is found to attain reduction in the surface area, carbon content, and porosity upon increasing temperature. Nonetheless, the composite prepared at 700 degrees C with pore-size distributions of around 4 and 50 nm exhibits a high rate capability and stable capacity retention upon cycling.

Plasticity in the primary binding site of galactose/N-acetylgalactosamine-specific lectins - Implication of the C-H center dot center dot center dot O hydrogen bond at the specificity-determining C-4 locus of the saccharide in 4-methoxygalactose recognition by jacalin and winged bean (basic) agglutinin I

It is currently believed that an unsubstituted axial hydroxyl at the specificity-determining C-4 locus of galactose is indispensable for recognition by galactose/N-acetylgalactosamine-specific lectins. Titration calorimetry demonstrates that 4-methoxygalactose retains binding allegiance to the Moraceae lectin jacalin and the Leguminosae lectin, winged bean (basic) agglutinin (WBA I). The binding reactions were driven by dominant favorable enthalpic contributions and exhibited significant enthalpy-entropy compensation. Proton NMR titration of C-methoxygalactose with jacalin and WBA I resulted in broadening of the sugar resonances without any change in chemical shift. The alpha-and beta-anomers of 4-methoxygalactose were found to be in slow exchange with free and lectin-bound states. Both the anomers experience magnetically equivalent environments at the respective binding sites. The binding constants derived from the dependence of NMR line widths on 4-methoxygalactose concentration agreed well with those obtained from titration calorimetry. The results unequivocally demonstrate that the loci corresponding to the axially oriented C-4 hydroxyl group of galactose within the primary binding site of these lectins exhibit plasticity. These analyses suggest, for the first time, the existence of C-H ... O-type hydrogen-bond(s) in protein-carbohydrate interactions in general and between the C-4 locus of galactose derivative and the lectins jacalin and WBA I in particular.

Sequence specificity in spermine-induced structural changes in CG-oligomers

The role of spermine in inducing A-DNA conformation in deoxyoligonucleotides has been studied using CCGG and GGCC as model sequences. It has been found that while CCGG adopts an alternating B-DNA conformation in low salt solution at low temperature, addition of spermine to this medium induces a B --greater than A transition. In contrast, the A-DNA-like structure of GGCC in low salt solution at low temperature does not change under the influence of spermine. This suggests a sequence-dependent behaviour of spermine. Further these results suggest that the A-DNA conformation observed in the crystals of d(iCCGG) and d(GGCC)2 might have been due to the presence of spermine in the crystallization cocktail.