Insight into microwave irradiation and enzyme catalysis in enantioselective resolution of dl-(±)-3-phenyllactic acid

Lipase catalyzed kinetic resolution of DL-(±)-3-phenyllactic acid (DL-(±)-3-PLA) was investigated to study the synergistic effect of microwave irradiation and enzyme catalysis. Lipases from different sources were employed for the transesterification of DL-(±)-3-PLA under otherwise similar conditions, among which Novozyme 435 efficiently catalyzed the resolution of DL-(±)-3-PLA to L-(-)-O-acetyl-3-PLA using vinyl acetate as the acyl donor, showing excellent conversion (49?%) and enantiomeric excess (>99?%). The effect of various parameters affecting the initial rate, conversion and enantiomeric excess of the reaction were studied to establish kinetics and mechanism. There is a synergism between enzyme catalysis and microwave irradiation; an increase in initial rates up to 1.8-fold was observed under microwave irradiation than that under conventional heating. The analysis of initial rate data showed that reaction obeys ternary complex (ordered bi-bi) mechanism with inhibition by DL-(±)-3-PLA. The calculated and simulated rates match very well showing the validity of the proposed kinetic model.     

Competition between Folding, Native-State Dimerisation and Amyloid Aggregation in β-Lactoglobulin

We show that a series of peptides corresponding to individual β-strands in native β-lactoglobulin readily form amyloid aggregates and that such aggregates are capable of seeding fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are reduced. By contrast, preformed fibrils corresponding to only one of the β-strands that we considered, βA, were found to promote fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are intact. These results indicate that regions of high intrinsic aggregation propensity do not give rise to aggregation unless at least partial unfolding takes place. Furthermore, we found that the high aggregation propensity of one of the edge strands, βI, promotes dimerisation of the native structure rather than misfolding and aggregation since the structure of βI is stabilised by the presence of a disulfide bond. These findings demonstrate that the interactions that promote folding and native-state oligomerisation can also result in high intrinsic amyloidogenicity. However, we show that the presence of the remainder of the sequence dramatically reduces the net overall aggregation propensity by negative design principles that we suggest are very common in biological systems as a result of evolutionary processes.     

Flux of certain radionuclides in the blood-clam Anadara granosa Linneaus under environmental conditions

The flux of fission product nuclides, caesium-137. cerium-144. and ruthenium-106, in the Bombay harbour ecosystem has been measured over a period of six years (1970–1976). during which the input of controlled low level radioactive waste was gradually reduced by more than 20 times. Of the various pelagic and benthic species studied, the arcid clam Anadara granosa Linn, showed a specific affinity for all three radionuclides; sequence of the degree of bio-accumulation was Ce ? Ru > Cs. Furthermore, the concentration of these nuclides in the tissues varied with the levels in the sedimentary material, which in turn was related to the inputs, maintaining some kind of equilibrium. On reaching maximum accumulation the levels of all three nuclides in the clam population decreased exponentially with time although the radioactivity was still available especially in the sediment. This decrease of radioactivity is defined as an ‘ecological loss rate’. The ecological half-time for cerium-144 and ruthenium-106 was about 3.6 times longer, and that of caesium-137 significantly shorter, than their respective physical half-lives. The ecological half-times of all three radionuclides were predominantly influenced by the environment rather than by the biological half-lives. This indicates that the biological half-lives of these nuclides were much shorter than their respective ecological half-lives. The biological half-time of caesium-137 was biphasic; the short-lived component had a half-time of about three days and the long-lived component had one of about 15 days.The bio-accumulation of an activation product nuclide cobalt-60 in A. granosa increased with the time of exposure and reached a level significantly higher than that of caesium-137, but was independent of the ambient concentrations and temperature. Thus the species was found to maintain the tissue concentration of fission product nuclides, cerium-144, ruthenium-106, and caesium-137 through adjusting physiological flux rates, in equilibrium with the changing levels of radionuclides in the environmental matrices, but not of the activation product nuclide cobalt-60.     

Larvicidal activity of Acacia nilotica extracts and isolation of D-pinitol--a bioactive carbohydrate

A low-molecular-weight, sugar-like compound other than glucose, fructose, sucrose, or myo-inositol showing lipophilic nature was isolated from the EtOH extract of Acacia nilotica. The structure of the compound was determined by spectral methods. This alicyclic polyalcohol was found to be D-pinitol (= 3-O-methyl-D-chiro-inositol; 1). The configuration of the compound was confirmed by single-crystal X-ray analysis. The compound 1 is known from Soybean, Australian mangroves, Fagonia indica, Arachis hypogaea, etc., but we have isolated this compound for the first time from the aerial parts of A. nilotica. Very few references have been cited for compound 1 for its entomological activity, and there are no reports on mosquitoes. Therefore, the crude extracts of A. nilotica were tested for its biological activity against mosquito larvae. Acetone extract at 500-ppm concentration showed chronic toxicity against Aedes aegypti and Culex quinquefasciatus IVth instar mosquito larvae. Such a biological activity has been observed for the first time for this plant. This study could be a stepping stone to a solution for destroying larval species as well as consumption of such a widely grown, problem weed, A. nilotica. This larvicidal agent, since it is derived from plant, is eco-friendly, cost effective, non-hazardous to non-target organisms and would be safe unlike commercially available insecticides.     

Molecular mechanisms of autoimmunity triggered by microbial infection

Autoimmunity can be triggered by microbial infection. In this context, the discovery of Toll-like receptors (TLRs) provides new insights and research perspectives. TLRs induce innate and adaptive antimicrobial immune responses upon exposure to common pathogen-associated molecules, including lipopeptides, lipopolysaccharides, and nucleic acids. They also have the potential, however, to trigger autoimmune disease, as has been revealed by an increasing number of experimental reports. This review summarizes important facts about TLR biology, available data on their role in autoimmunity, and potential consequences for the management of patients with autoimmune disease.     

A blood stage fraction of Plasmodium berghei induces protective and long lasting immune response in BALB/c mice

Incorporation of the parasite's subcellular fractions in subunit vaccines can be a possible approach for formulation of vaccine against malaria. In this study, the immunogenicity and protective efficacy of 10,000 g fraction of blood stage Plasmodium berghei was evaluated in mouse model. This fraction induced higher levels of anti-parasite antibodies and provided complete and long lasting protection as compared to whole parasite antigens. Antiserum raised against it was immunoadsorbed on CNBr activated sepharose-4B to elute antigens from this fraction. Eluted antigens were characterized electrophoretically, and after lyophilization these were designated as ML-I (having 55, 64, 66, and 74 kDa proteins), ML-II (having 51, 64, 66, and 72 kDa proteins) and ML-III (having only 47 kDa protein) sub-fractions. Mice were immunized with these sub-fractions and immune responses induced by various immunization regimens were evaluated and compared with that of 10,000 g fraction. These sub-fractions imparted partial protection except ML-III, which was non-protective. 10,000 g fraction as a whole provided complete protection and generated significantly higher level of IL-2 and IFN-γ in immune mice. ML-I produced significant amount of IL-1 and IL-4 as compared to ML-II. Enhanced level of malaria-specific IgG1 was produced by ML-II, but IgG2a was significantly higher in ML-I immunized mice. Conclusively, this study identifies 10,000 g fraction as a promising blood stage vaccine candidate and suggests that a vaccine based upon multiple antigens may be more efficacious as compared to single antigen based formulations.     

Design and evaluation of deformable talc agglomerates prepared by crystallo-Co-agglomeration technique for generating heterogenous matrix

The crystallo-co-agglomeration technique was used to design directly compressible and deformable agglomerates of talc containing the low-dose drug bromhexine hydrochloride (BXH). The process of agglomeration involved the use of dichloromethane as a good solvent and bridging liquid for BXH, water as a poor solvent, talc as diluent, and Tween 80 to aid dispersion of BXH and diluent into the poor solvent. Hydroxypropyl methylcellulose (50 cps) 4% wt/wt was used to impart the desired mechanical strength and polyethylene glycol 6000 5% wt/wt was used to impart the desired sphericity to the agglomerates. Clarity of the supernatant was considered an endpoint for completion of the agglomeration process. The drug-to-talc ratio in optimized batch 1 (BT1) and batch 2 (BT2) was kept at 1:15.66 and 1:24, respectively. The spherical agglomerates obtained were evaluated for topographic, micromeritic, mechanical, deformation, compressional, and drug release properties. The agglomeration yield and drug entrapment for both batches were above 94% wt/wt. Crushing strength and friability studies showed good handling qualities of agglomerates. Heckel plot studies showed low mean yield pressure and high tensile strength, indicating excellent compressibility and compactibility of agglomerates. Diametral and axial fracture of compacts showed deformation of agglomerates revealing formation of a heterogeneous compact. Drug release was sustained for 9 hours and 5 hours from BT1 and BT2, respectively, in 0.1N HCl. Hence, the crystallo-co-agglomeration technique can be successfully used for obtaining spherical, deformable, and directly compressible agglomerates, generating a heterogeneous matrix system and providing sustained drug release. Published: July 27, 2007