Exploring the inhibitory activity of Withaferin-A against Pteridine reductase-1 of L. donovani

Withaferin A is an abundant withanolide present in Withania somnifera leaves and to some extent in roots. It has been known for its profound anti-cancer properties, but its role in counteracting the Leishmania donovani infection has to be explored. Pteridine reductase 1 (PTR1) is involved in pteridine salvage and an important enzyme for the parasite growth, which could be targeted for the development of an efficient antileishmanial drug. We employed molecular docking studies to identify the binding mode of withaferin A with PTR1 in silico. We further cloned, expressed, and purified PTR1 of L. donovani and performed the enzyme kinetics using the Michaelis–Menten equation and enzyme inhibition studies with withaferin A by plotting the Lineweaver–Burk graph, which followed an uncompetitive mode of inhibition. We also showed the inhibition of the enzyme in the crude lysate of treated parasites. Thus, our study contributes towards understanding the mode of action of withaferin A against L. donovani parasite.     

A re-examination of the crystal structure of A-DNA using fiber diffraction data

Classical A-DNA helices with h = 0.25 nm may represent the greatest mass per unit length attainable by polynucleotide duplexes. The X-ray diffraction pattern from polycrystalline and well-oriented fibers of calf thymus DNA in its A-form has been carefully re-examined. Indexing on the basis of a C-face-centered monoclinic unit cell of dimensions a = 2.170 nm, b = 3.990 nm, c = 2.803 nm and beta = 96.82 degrees is superior to alternatives that have been proposed. Two right-handed. Watson-Crick base-paired, helical DNA chains with 2 X 11 nucleotides per 2.803 nm pitch, each carrying C3'-endo furanose rings, pass through the unit cell. The crystallography requires the two chains in the duplex to be antiparallel and conformationally identical but the 11 nucleotides in each pitch may be distinct. However, a secondary structure with a mononucleotide asymmetric unit provides as good an X-ray agreement as one with 11 distinct nucleotides. This relative lack of variability is quite different from what is observed in fibrous B-DNAs.     

Sequence of a cDNA for mouse thymidylate synthase reveals striking similarity with the prokaryotic enzyme

We report the nucleotide sequence of a cloned cDNA, pMTS-3, that contains a 1-kb insert corresponding to mouse thymidylate synthase (E.C. 2.1.1.45). The open reading frame of 921 nucleotides from the first AUG to the termination codon specifies a protein with a molecular mass of 34,962 daltons. The predicted amino acid sequence is 90% identical with that of the human enzyme. The mouse sequence also has an extremely high degree of similarity (as much as 55% identity) with prokaryotic thymidylate synthase sequences, indicating that thymidylate synthase is among the most highly conserved proteins studied to date. The similarity is especially pronounced (as much as 80% identity) in the 44-amino-acid region encompassing the binding site for deoxyuridylic acid. The cDNA sequence also suggests that mouse thymidylate synthase mRNA lacks a 3' untranslated region, since the termination codon, UAA, is followed immediately by a poly(A) segment.      

ISOLATION AND CHARACTERIZATION OF GLYCOSAMINOGLYCANS FROM BRAIN OF CHILDREN WITH PROTEIN-CALORIE MALNUTRITION

Abstract— The uronic acid containing glycosaminoglycans (GAGs) were isolated from the brains of 1-year-old and 4-year-old kwashiorkor children and characterised by constituent analyses. A marked reduction is the total GAG concentration of brain was noticed in both cases of kwashiorkor. In the 1-year-old kwashiorkor brain, hyaluronic acid is the most predominant GAG (73.5 per cent) whereas heparan sulphate, chondroitin sulphates and low sulphated chondroitin sulphate constituted less than 10 per cent. In the 4-year-old kwashiorkor brain, the proportion of hyaluronic acid was 27.5 per cent, low sulphated chondroitin sulphate 31.2 per cent, chondroitin sulphates 28.3 per cent and heparan sulphate 10 per cent. This marked reduction in the concentration as well as qualitative changes in GAG in protein-calorie malnutrition as compared to the normal is discussed in relation to brain function.     

Stopped-flow kinetic, 1H, and 31P NMR analysis of the intercalation of ethidium with poly d(G-C) X d(G-C)

In a low salt buffer (0.011 M Na+) stopped-flow kinetic results for the SDS driven dissociation of an ethidium-Poly d(G-C) X d(G-C) complex are 8.7, 23, and 58.5 s-1 at 20, 30, and 40 degrees C, respectively. These results predict that in NMR experiments at high field strengths, ethidium should be in slow exchange among polymer binding sites. This has been found to be the case for both 31P (109 MHz) and 1H (imino proton spectra in H2O at 270 MHz) experiments. At higher salt, and/or higher temperature, and/or lower field, the bound and free peaks are no longer resolved in the NMR spectra. Good agreement is obtained between the stopped-flow kinetic results and the coalescence temperature observed in NMR experiments. Imino protons in base pairs on both sides of the intercalated ethidium are shifted approximately one ppm upfield while only the phosphate groups at the intercalation site experience large chemical shifts.     

Role of infection in the pathogenesis of rheumatic diseases

Advanced immunological technology has revealed immunological abnormalities not only in some chronic and autoimmune connective tissue disorders but also in conditions like infective arthritis where infection apparently seems to play the only role. On the other hand role of infection in the pathogenesis of some connective tissue disorders has recently gained much importance from the observation of clinical, pathological and immunological similarities between these diseases and certain infectious diseases occurring in animal models. Meanwhile, knowledge gained into human leucocyte-A system and its association with certain diseases opens another angle in etiopathogenesis of certain rheumatic diseases. It has been postulated that adaptive mechanism of a microbe or the binding between the human leucocyte-A molecule and carbohydrate moiety of a microbe may set up an autoimmune reaction and in the presence of some triggering factors in the environment may lead on to disease manifestations. An attempt has been made to discuss the role of infection in the outcome of rheumatic diseases such as septic arthritis, polyarteritis nodosa, rheumatic fever, enteropathic arthritis, ankylosing spondylitis, rheumatoid arthritis and systemic lupus erythematoses in genetically susceptible individuals producing immunological abnormalities.     

Effect of Dietary Supplementation of Novel Probiotic Bacteria Bacillus vireti 01 on Antioxidant Defence System of Freshwater Prawn Challenged with Pseudomonas aeruginosa

Probiotics and Antimicrobial Proteins - The aim of the present work was to isolate probiotic bacteria from the intestinal tract of healthy freshwater prawn Macrobrachium rosenbergii and to examine...