Exploring the potential of 3'-O-carboxy esters of thymidine as inhibitors of ribonuclease A and angiogenin

In this study, compounds with a carboxy ester in lieu of the phosphate ester at the 3'-position have been employed to inhibit the ribonucleolytic activity of ribonuclease A (RNase A). Phosphates at the 3'-position of pyrimidine bases are well-known inhibitors of the protein. We have investigated the inhibition of RNase A by 3'-O-carboxy esters of thymidine. The compounds behave as competitive inhibitors with inhibition constants ranging from 42 to 95 microM. The mode of inhibition has also been confirmed by (1)H NMR studies of the active site histidines of RNase A. Docking studies have further substantiated the experimental results. The compounds are also found to inhibit the ribonucleolytic activity of angiogenin, a homologous protein and potent inducer of blood vessel formation.     

Interface of apoptotic protein complexes has distinct properties

Apoptosis is a programmed mechanism of cell death that is a normal component of development and health of multi-cellular organisms. In this study, we ask if interface properties of apoptotic protein complexes are different from protein complexes in general. We find that although in apoptotic protein complexes the overall distribution of interface size, surface complementarity, hydrogen bonding, hydrophobicity are similar to general interface properties, apoptotic complexes tend to have more fragmented interfaces and different secondary structural preferences. The statistics on the number of interfaces where specific amino acid(s) occur with significantly enhanced frequency suggest that Arg, Met and Asp are most important functional residues. The role of Met is believed to be unique, as evidenced from the existing data on hot spot potential of residues. These findings together provide insight into the possible role of various physico-chemical attributes at the protein interface in regulation of the apoptosis process.     

Effect of Ayurvedic mercury preparation Makaradhwaja on geriatric canine--a preliminary study

Makaradhwaja, an alchemical Ayurvedic mercury preparation is used as stimulant and vitalizer. Towards veterinary practices, the acceptability, tolerability and toxicity studies were undertaken in geriatric pet dogs aged more than 10 years irrespective of breed and sex for future use. Makaradhwaja (2.5 mg/kg) was used with honey once daily for 30 days. Before and after treatment, blood was collected for hematological studies as well as liver, kidney function and anti-oxidant activity. In control group, honey itself showed no appreciable change whereas, Makaradhwaja lowered neutrophil and total leucocyte count. Serum cholesterol, urea, glucose, alanine amino transferase, aspartate amino transferase, sodium, phosphorus and calcium were decreased. Haemoglobin and serum creatinine were significantly increased. There was appreciable physical, behavioral and body weight change including quality of life. The dose was used in replication of human dose (125 mg/50 kg). Anti-oxidant study showed significant increase of lipid per oxidation in experimental group while the values of ABTS radical cation decolorisation assay although decreased but did not show any significant changes. Decrease of serum urea and increase of serum creatinine could not be explained on single dose response. Different dose study could only explain the optimum dose to be required in canine practices.     

Lipotropes promote immunobiochemical plasticity and protect fish against low-dose pesticide-induced oxidative stress

An experiment was conducted to evaluate the role of different lipotropes in modulating immunity and biochemical plasticity under conditions of sublethal low-dose pesticide-induced stress in fish. Labeo rohita fish fingerlings were divided in two sets with one set of fish continuously exposed to low-dose endosulfan (1/10th of 96-h LC₅₀) for 21 days, the other was unexposed, and both sets of fish were fed with practical diets supplemented with either 2 % lecithin, 0.5 % betaine, or 0.1 % choline and compared against unsupplemented diet. Low-dose endosulfan exposure had adverse effects (P < 0.05/P < 0.01) on hematological profile (erythrocyte count, hemoglobin, and hematocrit), serum protein (total protein, albumin, and globulin) and lipid profile (cholesterol and triglyceride), anti-oxidative status (ascorbic acid content of muscle, liver, brain, and kidney and activity of anti-oxidative enzymes: catalase and superoxide dismutase), neurotransmission (acetylcholinesterase activity in muscle and brain), immunological attributes (WBC count, albumin to globulin ratio, phagocytic activity, and serum cortisol), and metabolic plasticity as revealed from enzyme activities (muscle lactate dehydrogenase, liver and kidney glucose-6-phosphatase dehydrogenase-G6PDH activity). Dietary lipotropes prevented these effects completely or partially and the effects were lipotrope dependent. Kinetics (maximum velocity value V_max, catalytic efficiency and Michaelis constant K_m) of G6PDH enzyme from crude extracts of liver and kidney indicated inhibition due to endosulfan but lipotropes could protect enzyme and showed a stabilizing effect. The supplements also helped maintain integrity of histoarchitecture of the hepatocytes in endosulfan-exposed fish to a great extent. Feeding lipotropes to fish reared in endosulfan-free water also improved hematological and serum protein and lipid profiles and were immunostimulatory. In conclusion, dietary lipotropes, especially betaine and lecithin at the levels used, improve erythropoiesis, serum protein and lipid profile, anti-oxidant status, immunocompetence, neurotransmission, and protect the livers of L. rohita fingerlings even when continuously exposed to low-dose endosulfan.     

QSAR study on some pyridoacridine ascididemin analogues as anti-tumor agents

Pyridoacridine ascididemin analogues have been reported as anticancer agents for their interesting antitumor activity against human cancer cells. A quantitative structure–activity relationship (QSAR) analysis of ascididemin analogues was attempted using the physicochemical parameters and the electrotopological state atom (ETSA) indices. This study indicates that the electron withdrawing substituents with higher MR (molar refractivity) value at R₁ position favor the anti-tumor activity and the presence of NHR (R is hydrogen or alkyl group) at the R₃ position has contribution to the anti-tumor activity. ETSA indices have been incorporated as independent variable in the QSAR model with physicochemical parameters. It clearly suggests the importance of atoms 2, 3, 4, 5, 6 and 7 to the anti-tumor activity.     

Crystal Structures of HIV-1 gp120 Envelope Glycoprotein in Complex with NBD Analogues That Target the CD4-Binding Site

Efforts to develop therapeutic agents that inhibit HIV-1 entry have led to the identification of several small molecule leads. One of the most promising is the NBD series, which binds within a conserved gp120 cavity and possesses para-halogen substituted aromatic rings, a central oxalamide linker, and a tetramethylpiperidine moiety. In this study, we characterized structurally the interactions of four NBD analogues containing meta-fluoro substitution on the aromatic ring and various heterocyclic ring replacements of the tetramethylpiperidine group. The addition of a meta-fluorine to the aromatic ring improved surface complementarity and did not alter the position of the analogue relative to gp120. By contrast, heterocyclic ring replacements of the tetramethylpiperidine moiety exhibited diverse positioning and interactions with the vestibule of the gp120 cavity. Overall, the biological profile of NBD-congeners was modulated by ligand interactions with the gp120-cavity vestibule. Herein, six co-crystal structures of NBD-analogues with gp120 provide a structural framework for continued small molecule-entry inhibitor optimization.     

Modulation of physiological responses with TiO<Subscript>2</Subscript> nano-particle in <Emphasis Type="Italic">Azolla pinnata</Emphasis> R.Br. under 2,4-D toxicity

The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO₂ nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO₂-NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO₂-NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO₂-NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid–nitrate pool, but no changes with glutamine synthase activity with TiO₂-NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO₂-NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO₂ supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO₂-NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation.     

不同耕作措施对冬小麦-夏玉米复种连作系统土壤有机碳和水分利用效率的影响

在连续8年田间定位试验的基础上,分析了关中平原冬小麦 夏玉米复种连作系统2008—2009年连续两个生长季期间不同耕作措施(结合秸秆还田和不还田)对土壤有机碳和水分利用率的影响.结果表明: 相对于传统耕作,保护性耕作有利于土壤有机碳、水分利用效率和作物产量的提高,其中在“深松+秸秆还田”耕作模式下的增幅最高,土壤有机碳含量在0～30 cm土层增幅达到19.5%,水分利用效率和作物产量提高了16.9%和20.5%,而免耕模式则有效提高了0～10 cm土层有机碳含量.在该地区土壤和气候条件下,深松结合秸秆粉碎还田是最理想的耕作模式,最有利于土壤有机碳累积,并提高水分利用效率和作物产量.     

Interaction with a kinesin-2 tail propels choline acetyltransferase flow towards synapse

Bulk flow constitutes a substantial part of the slow transport of soluble proteins in axons. Though the underlying mechanism is unclear, evidences indicate that intermittent, kinesin-based movement of large protein-aggregates aids this process. Choline acetyltransferase (ChAT), a soluble enzyme catalyzing acetylcholine synthesis, propagates toward the synapse at an intermediate, slow rate. The presynaptic enrichment of ChAT requires heterotrimeric kinesin-2, comprising KLP64D, KLP68D and DmKAP, in Drosophila. Here, we show that the bulk flow of a recombinant Green Fluorescent Protein-tagged ChAT (GFP::ChAT), in Drosophila axons, lacks particulate features. It occurs for a brief period during the larval stages. In addition, both the endogenous ChAT and GFP::ChAT directly bind to the KLP64D tail, which is essential for the GFP::ChAT entry and anterograde flow in axon. These evidences suggest that a direct interaction with motor proteins could regulate the bulk flow of soluble proteins, and thus establish their asymmetric distribution.     

Interactions of berberine with poly(A) and tRNA.

The interaction of berberine chloride with poly(A) and tRNA has been studied by various spectroscopic techniques. Binding parameters determined from spectrophotometric and spectrofluorimetric measurements by Scatchard analysis indicate a very high effective binding capacity of berberine to poly(A) as compared to DNA or tRNA. The circular dichroism studies show that binding of berberine to poly(A) causes a significant change in the circular dichroic spectrum of poly(A) itself, as manifested by (i) a decrease of both positive and negative bands and (ii) appearance of a conservative type of extrinsic circular dichroic spectrum in the wavelength range of 300-400 nm, while it does not cause any significant alteration to the A form structure of tRNA. It is concluded that berberine interacts stronger with poly(A) than DNA or tRNA. The results are interpreted in terms of its reported biological activities.