Further simplification of the general analysis of the intercalative drug-DNA interaction

The application of McGhee and von Hippel's general equation [J. Mol. Biol., 86 (1974), 469-489, Eq. (15)] to the analysis of the interaction of intercalative drugs with DNA has been further simplified. The value of n can now be determined mathematically, using a simple function, and without any approximation. It is also established that the summation of squared deviation of (( (nu/c), nu)) points would be minimum for and only for the true set of (K,n,omega) of the interaction system. The method incorporating the simplification has been applied to determine the binding parameters of adriamycin-DNA interaction according to the above general equation.     

Xylonucleic acid: synthesis,structure, and orthogonal pairing properties

There is a common interest for studying xeno-nucleic acid systems in the fields of synthetic biology and the origin of life, in particular, those with an engineered backbone and possessing novel properties. Along this line, we have investigated xylonucleic acid (XyloNA) containing a potentially prebiotic xylose sugar (a 3′-epimer of ribose) in its backbone. Herein, we report for the first time the synthesis of four XyloNA nucleotide building blocks and the assembly of XyloNA oligonucleotides containing all the natural nucleobases. A detailed investigation of pairing and structural properties of XyloNAs in comparison to DNA/RNA has been performed by thermal UV-melting, CD, and solution state NMR spectroscopic studies. XyloNA has been shown to be an orthogonal self-pairing system which adopts a slightly right-handed extended helical geometry. Our study on one hand, provides understanding for superior structure-function (-pairing) properties of DNA/RNA over XyloNA for selection as an informational polymer in the prebiotic context, while on the other hand, finds potential of XyloNA as an orthogonal genetic system for application in synthetic biology.     

Zinc oxide nanoparticle inhibits the biofilm formation of <Emphasis Type="Italic">Streptococcus pneumoniae</Emphasis>

Biofilms are structured consortia of microbial cells that grow on living and non living surfaces and surround themselves with secreted polymers. Infections with bacterial biofilms have emerged as a foremost public health concern because biofilm growing cells can be highly resistant to both antibiotics and host immune defenses. Zinc oxide nanoparticles have been reported as a potential antimicrobial agent, thus, in the current study, we have evaluated the antimicrobial as well as antibiofilm activity of zinc oxide nanoparticles against the bacterium Streptococcus pneumoniae which is a significant cause of disease. Zinc oxide nanoparticles showed strong antimicrobial activity against S. pneumoniae, with an MIC value of 40 μg/ml. Biofilm inhibition of S. pneumoniae was also evaluated by performing a series of experiments such as crystal violet assay, microscopic observation, protein count, EPS secretion etc. using sub-MIC concentrations (3, 6 and 12 µg/ml) of zinc oxide nanoparticles. The results showed that the sub-MIC doses of zinc oxide nanoparticles exhibited significant anti-biofilm activity against S. pneumoniae, with maximum biofilm attenuation found at 12 μg/ml. Taken together, the results indicate that zinc oxide nanoparticles can be considered as a potential agent for the inhibition of microbial biofilms.     

Optimization,purification, and characterization of L-asparaginase from Actinomycetales bacterium BkSoiiA

Actinobacteria are promising source of a wide range of important enzymes, some of which are produced in industrial scale, with others yet to be harnessed. L-Asparaginase is used as an antineoplastic agent. The present work deals with the production and optimization of L-asparaginase from Actinomycetales bacterium BkSoiiA using submerged fermentation in M9 medium. Production optimization resulted in a modified M9 medium with yeast extract and fructose as carbon and nitrogen sources, respectively, at pH 8.0, incubated for 120 hr at 30 ± 2°C. The crude enzyme was purified to near homogeneity by ammonium sulfate precipitation following dialysis, ion-exchange column chromatography, and finally gel filtration. The sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) revealed an apparent molecular weight of 57 kD. The enzyme was purified 95.06-fold and showed a final specific activity of 204.37 U/mg with 3.49% yield. The purified enzyme showed maximum activity at a pH 10.0 and was stable at pH 7.0 to 9.0. The enzyme was activated by Mn²⁺ and strongly inhibited by Ba²⁺. All these preliminary characterization suggests that the L-asparaginase from the source may be a tool useful to pharmaceutical industries after further research.     

Expression of Multiple Virus-derived Resistance Determinants in Transgenic Plants Does Not Lead to Additive Resistance Properties

Plants can be protected against infection by potyviruses by expressing different portions of potyviral genomes as transgenes. This strategy has proven effective with several potyvirus genes, including the Nla, Nlb, and coat protein coding regions. Given the effectiveness of separate potyvirus coding regions as determinants of resistance, we tested the hypothesis that combinations of potyvirus coding regions would provide additively greater protection of plants against potyviruses. For this, we compared transgenic plant lines that expressed either the coat protein (CP) or the Nla+Nlb+coat protein (NNC) coding regions from tobacco vein mottling virus (TVMV). We found that plants that carry the NNC gene combination were invariably less resistant to TVMV than were lines that contain a CP gene alone. Additionally, we found that NNC lines displayed virtually no resistance to tobacco etch virus (TEV), in contrast to the CP lines. We conclude that combining more than one virus-derived resistance determinant in a single construct is detrimental to the production of virus-resistant plants.     

Quinone and oxyradical scavenging properties of N-acetylcysteine prevent dopamine mediated inhibition of Na+, K+-ATPase and mitochondrial electron transport chain activity in rat brain: implications in the neuroprotective therapy of Parkinson's disease

Dopamine oxidation products such as H2O2 and reactive quinones have been held responsible for various toxic actions of dopamine, which have implications in the aetiopathogenesis of Parkinson's disease. This study has shown that N-acetylcysteine (0.25-1 mm) is a potent scavenger of both H2O2 and toxic quinones derived from dopamine and it further prevents dopamine mediated inhibition of Na+,K+-ATPase activity and mitochondrial respiratory chain function. The quinone scavenging ability of N-acetylcysteine is presumably related to its protective effect against dopamine mediated inhibition of mitochondrial respiratory chain activity. However, both H2O2 scavenging and quinone scavenging properties of N-acetylcysteine probably account for its protective effect against Na+,K+-ATPase inhibition induced by dopamine. The results have important implications in the neuroprotective therapy of sporadic Parkinson's disease since inactivation of mitochondrial respiratory activity and Na+,K+-ATPase may trigger intracellular damage pathways leading to the death of nigral dopaminergic neurons.