Solution structure and conformational dynamics of deoxyxylonucleic acids (dXNA): an orthogonal nucleic acid candidate

Orthogonal nucleic acids are chemically modified nucleic acid polymers that are unable to transfer information with natural nucleic acids and thus can be used in synthetic biology to store and transfer genetic information independently. Recently, it was proposed that xylose-DNA (dXNA) can be considered to be a potential candidate for an orthogonal system. Herein, we present the structure in solution and conformational analysis of two self-complementary, fully modified dXNA oligonucleotides, as determined by CD and NMR spectroscopy. These studies are the initial experimental proof of the structural orthogonality of dXNAs. In aqueous solution, dXNA duplexes predominantly form a linear ladderlike (type-1) structure. This is the first example of a furanose nucleic acid that adopts a ladderlike structure. In the presence of salt, an equilibrium exists between two types of duplex form. The corresponding nucleoside triphosphates (dXNTPs) were synthesized and evaluated for their ability to be incorporated into a growing DNA chain by using several natural and mutant DNA polymerases. Despite the structural orthogonality of dXNA, DNA polymerase β mutant is able to incorporate the dXNTPs, showing DNA-dependent dXNA polymerase activity.     

Modified TTA method for the determination of plutonium

The spent fuel from Fast Breeder Test Reactor of various burnups from 25 to 155?GWd/te is being reprocessed in CORAL (COmpact Reprocessing of Advanced fuels in Lead shielded cell) using a modified PUREX (Plutonium Uranium Recovery by EXtraction) process. Total plutonium (Pu^{238, 239, 240, 241 & 242}) concentration in the sample is analysed by HTTA (Thenoyl Trifluoro Acetone) extraction method wherever interference from other alpha emitting nuclides (Raffinate) and bulk natural uranium (uranium products) are present "as reported by Milyukov et al. (Analytical chemistry of plutonium, 1967) and Natarajan and Subba Rao (BARC, pp. 38?C43, 2007)". This method requires the addition of corrosive reagents such as NH₂OH.HCl which is a problem in waste disposal for reduction. A salt-free reagent such as Hydroxyurea is studied as a reducing agent which has the ability to reduce both Pu(VI) and Pu(IV) to Pu(III) "as reported by Zhaowu (260(3):601?C606, 2004) and Zhaowu (262(3):707?C711, 2004)". Pu(III) thus formed can be easily oxidised to Pu(IV) by NaNO₂ for the extraction of Pu by HTTA.     

Apical functionalization of chiral heterohelicenes

We describe a synthetic protocol to selectively functionalize chiral bridged triarylamines at the apical position using regioselective copper-catalyzed amination reaction. This protocol allows the coupling of diphenylamines with a sterically hindered but electronically activated aryl-Br bond in the presence of a sterically unhindered but electronically unactivated aryl-Br bond. The unactivated aryl-Br bond was utilized further to synthesize a chiral heterohelicene homodimer using Stille coupling.     

Issues in the statistical mechanics of steady sedimentation

A critical review is presented of recent experimental and theoretical work on the steady sedimentation of particulate suspensions in viscous fluids. The point of view is that of a practitioner of non-equilibrium statistical physics rather than classical fluid mechanics.     

Linker dependent bond rupture force measurements in single-molecule junctions

We use a modified conducting atomic force microscope to simultaneously probe the conductance of a single-molecule junction and the force required to rupture the junction formed by alkanes terminated with four different chemical link groups which vary in binding strength and mechanism to the gold electrodes. Molecular junctions with amine, methylsulfide, and diphenylphosphine terminated molecules show clear conductance signatures and rupture at a force that is significantly smaller than the measured 1.4 nN force required to rupture the single-atomic gold contact. In contrast, measurements with a thiol terminated alkane which can bind covalently to the gold electrode show conductance and force features unlike those of the other molecules studied. Specifically, the strong Au-S bond can cause structural rearrangements in the electrodes, which are accompanied by substantial conductance changes. Despite the strong Au-S bond and the evidence for disruption of the Au structure, the experiments show that on average these junctions also rupture at a smaller force than that measured for pristine single-atom gold contacts.     

Extracellular biosynthesis of functionalized silver nanoparticles by strains of Cladosporium cladosporioides fungus

In the present investigation, we report the extracellular biosynthesis of silver nanoparticles (AgNP) employing the fungus Cladosporium cladosporioides. The extracellular solution of C. cladosporioides was used for the reduction of AgNO(3) solution to AgNP. The present study includes time dependent formation of AgNP employing UV-vis spectrophotometer, size and morphology by employing TEM (transmission electron microscopy), structure from powder X-ray diffraction (XRD) technique and understanding of protein-AgNP interaction from Fourier transform infrared (FT-IR) spectroscopy. The AgNP were 10-100nm in dimensions as measured by TEM images.     

Synchronization of coupled stochastic oscillators: The effect of topology

We study sets of genetic networks having stochastic oscillatory dynamics. Depending on the coupling topology we find regimes of phase synchronization of the dynamical variables. We consider the effect of time-delay in the interaction and show that for suitable choices of delay parameter, either in-phase or anti-phase synchronization can occur.      

Rainbow Connection Number of Graph Power and Graph Products

Rainbow connection number, rc(G), of a connected graph G is the minimum number of colors needed to color its edges so that every pair of vertices is connected by at least one path in which no two edges are colored the same (note that the coloring need not be proper). In this paper we study the rainbow connection number with respect to three important graph product operations (namely the Cartesian product, the lexicographic product and the strong product) and the operation of taking the power of a graph. In this direction, we show that if G is a graph obtained by applying any of the operations mentioned above on non-trivial graphs, then rc(G) ≤ 2r(G) + c, where r(G) denotes the radius of G and \({c \in \{0, 1, 2\}}\) . In general the rainbow connection number of a bridgeless graph can be as high as the square of its radius [1]. This is an attempt to identify some graph classes which have rainbow connection number very close to the obvious lower bound of diameter (and thus the radius). The bounds reported are tight up to additive constants. The proofs are constructive and hence yield polynomial time \({(2 + \frac{2}{r(G)})}\) -factor approximation algorithms.     

Limit theorems on a linear explosive stochastic model for time series with moving average error

Summary LetX(t) be a linear autoregressively generated explosive time series, with autoregressive coefficientsb ₁,…,b_q, and a constant termb ₀, and an error term ; a₀=1. Where ε(t),t≧1 are independent, Eε(t)=0, and Eε ²(t)=σ² is positive and finite. In this paper two categories of -consisent and asymptotically singularly normal estimators are proposed for (b ₁,…,b_q, b₀) thus settling an open problem since the publication of the paper (Venkataraman [5]). Based on these estimators several additional limit theorems based on estimated error residuals are proved. The parameter-free limit theorems of Spectral and Quenouille types of this paper serve as asymptotic goodness of fit tests for the model generatingX(t).     

Co(II) Complexes of4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzenesulphonamide and 4-((pyridin-2-ylmethylene)amino)-N-(thiazol-2-tl)benzenesulfonamide: Synthesis,Fluorescence Properties and Anticancer Activity

Two new Co(II) complexes of 4-((3-ethoxy-2-hydroxybenzylidene)amino)-N-(thiazol-2-yl)benzenesulphonamide and 4-((pyridin-2-ylmethylene)amino)-N-(thiazol-2-yl)benzene sulfonamide were synthesised. The structure of the complexes was identified by elemental analysis, FT-IR, electronic, EI mass, Powder XRD spectra and magnetic moment. The TG and DTA patterns of the complexes were supported the structures. The fluorescence quenching of these complexes with alizarin dye were premeditated and the free energy change (?G_et) for electron transfer process was designed by Rehm-Weller equation. The [Co(L₁-H)₂(H₂O)₂] and [Co(L₂)₂(H₂O)₂].2H₂O were submitted for in vitro cytotoxicity studies in human breast cancer cell line (MCF 7).