Alignment and phylogenetic analysis of type II DNA topoisomerases

DNA topoisomerases have been evolved to solve the topological problems of DNA during replication, transcription, recombination and segregation. Discovery of several new enzymes and their characterization has necessitated this compilation. This analysis shows the distinct evolutionary relatedness of type II DNA topoisomerases. A striking feature is the absence of a contiguous stretch of about 160 amino acids in one of the subunits of prokaryotic type II enzymes, which might have important implications to their structure and function

Transcriptional specificity after mycobacteriophage I3 infection

Transcriptional regulation following mycobacteriophage I3 infection has been investigated. For this purpose, RNA polymerase mutants (rif) of host bacterium, Mycobacterium smegmatis have been isolated and characterised. Phage growth inrifs and rifr cells in presence of rifampicin revealed the involvement of host RNA polymerase in phage genome transcription. This was confirmed by studies onin vivo RNA synthesis as well as by direct RNA polymerase assay after phage infection. Significant stimulation in RNA polymerase activity was seen following phage infection. The maximal levels were attained in about 60 min post infection and maintained throughout the phage development period. The stimulation of polymerase activity was most pronounced when the phage DNA was used as the template. RNA polymerases from uninfected and phage-infected Mycobacterium smegmatis have been purified to homogeniety. The enzyme purification was accomplished by a rapid procedure utilising affinity chromatography on rifampicin-Sepharose columns. Subunit structure analysis of the purified RNA polymerase from uninfected and phage-infected cells showed the presence of α ,β , β ' and σ subunits similar to the other prokaryotic RNA polymerases. In addition, a polypeptide of 79, 000 daltons was associated with the enzyme after phage infection. The enzymes differed in their properties with respect to template specificity. Phage 13 DNA was the preferred template for the modified RNA polymerase isolated from infected cells which may account for the transcriptional switch required for phage development

Requirement for calcium ions in mycobacteriophage I3 DNA injection and propagation

Ca2+ ions are absolutely necessary for the propagation of mycobacteriophage I3 in synthetic medium. These ions are required for successful infection of the host and during the entire span of the intracellular development of the phage. A direct assay of the phage DNA injection using 32[p] labelled phage, shows that Ca2+ ions are necessary for the injection process. The injection itself is a slow process and takes 15 min to complete at 37°. The bacteria infected in presence of Ca2+ tend to abort if the ions are subsequently withdrawn from the growth medium. The effect of calcium withdrawal is maximally felt during the early part of the latent period; however, later supplementation of Ca2+ ions salvage phage production and the mature phage progeny appear after a delayed interval, proportional to the time of addition of Ca2+

Gauss Legendre Quadrature Formulae for Tetrahedra

In this paper we consider the Gauss Legendre quadrature method for numerical integration over the standard tetrahedron: {(x, y, z)| 0 ≤ x, y, z ≤ 1, x + y + z ≤ 1} in the Cartesian three-dimensional (x, y, z) space. The mathematical transformation from the (x, y, z) space to (ξ, η, ζ) space is described to map the standard tetrahedron in (x, y, z) space to a standard 2-cube: {(ξ, η, ζ)| − 1 ≤ ξ, η, ζ ≤ 1} in the (ξ, η, ζ) space. This overcomes the difficulties associated with the derivation of new weight co-efficients and sampling points. The effectiveness of the formulae is demonstrated by applying them to the integration of three nonpolynomial and three polynomial functions

Cashew research in India

Cashew, after its introduction from Brazil during the 16th Century, has established very well in India. A total of 40 high-yielding varieties have been released so far by the Directorate of Cashew Research, Puttur, and various Agricultural Universities, for cultivation. Of these, 13 are hybrids and 27 are selections. Research achievements in the area of crop improvement, management, protection and post-harvest technology over the last six decades are reviewed and documented here. As India has been importing raw nuts to the tune of 6.5 lakh tons annually to cater the demand of established processing factories, research priorities have been identified to meet the challenges of enhancing production and productivity of cashew in the country

Structural heterogeneity in DNA gyrases from Gram-positive and Gram-negative bacteria

GyraseA (GyrA) subunit of DNA gyrase from mycobacteria has certain characteristics distinct from that of E. coli. Polyclonal antibodies produced against M. tuberculosis GyrA recognized GyrA from different slow and fast growing mycobacterial species and also from several Gram-positive bacteria. However, these antibodies did not cross-react with E. coli GyrA and the enzyme from other Gram-negative bacteria. The results from the present study together with multiple alignment, pairwise comparison and biochemical properties support the idea of the occurrence of two subclasses of gyrases in the bacterial kingdom, emphasizing the importance of the enzyme as a molecular target for the development of novel therapeutics

Cloning and sequence analysis of DNA gyrase genes from Mycobacterium tuberculosis

Using a heterologous DNA gyrase probe from Streptomyces sphaeroides, we have cloned the gyrA and gyrB genes of Mycobacterium tuberculosis. The M. tuberculosis gyrB gene has been sequenced and compared with the amino acid sequences of GyrB from other bacteria. There is a significant level (60-80%) of amino acid sequence homology between GyrB of M tuberculosis and that of other bacterial species, indicating a high degree of conservation of this essential enzyme

6-(4-Chloro­phen­yl)-2-isobutyl­imidazo[2,1-b][1,3,4]thia­diazole

In the title compound, C14H14ClN3S, the imidazo[2,1-b][1,3,4]thia­diazole system is essentially planar, with a maximum deviation of 0.006 (2) Å. The dihedral angle between the imidazo[2,1-b][1,3,4]thia­diazole and chloro­phenyl rings is 5.07 (8)°. In the crystal, there are no classical hydrogen bonds but stabilization is provided by weak π–π [centroid–centroid distance = 3.5697 (11) Å] and C—H⋯π inter­actions

1-{4-Chloro-2-[2-(2-fluoro­phen­yl)-1,3-dithio­lan-2-yl]phen­yl}-2-methyl-1H-imidazole-5-carbaldehyde

There are two mol­ecules in the asymmetric unit of the title imidazole derivative, C20H16ClFN2OS2. In one mol­ecule, the dithiol­ane ring is disordered over two positions in a 0.849 (9):0.151 (10) ratio. The imidazole ring makes dihedral angles of 79.56 (9) and 18.45 (9)° with the 4-chloro­phenyl and 2-fluoro­phenyl rings, respectively, in one mol­ecule; in the other mol­ecule, the corresponding angles are 82.72 (9) and 17.39 (10)°. In the crystal, mol­ecules are linked by weak C—H⋯O inter­actions and these linked mol­ecules are stacked along the b axis by π–π inter­actions with a centroid–centroid distance of 3.4922 (11) Å. In addition, π–π inter­actions between the imidazole and 2-fluoro­phenyl rings are also observed, with centroid–centroid distances of 3.4867 (11) and 3.4326 (10) Å. The crystal is further consolidated by weak C—H⋯π inter­actions. Cl⋯S [3.5185 (8) Å], C⋯O [3.192 (3) Å] and C⋯C [3.326 (2)–3.393 (3) Å] short contacts are also observed