Udai P. Singh

Bio: Udai P. Singh is an academic researcher from Indian Institute of Technology Roorkee. The author has contributed to research in topics: Ligand & Hydrogen bond. The author has an hindex of 21, co-authored 155 publications receiving 1764 citations. Previous affiliations of Udai P. Singh include Indian Institutes of Technology.

Nuclease activity via self-activation and anticancer activity of a mononuclear copper(II) complex: novel role of the tertiary butyl group in the ligand frame.

Abstract: The copper complex [Cu(tBuPhimp)(Cl)] (1) derived from tridentate ligand tBuPhimpH having N2O donors was synthesized, and its molecular structure was determined. A phenoxyl radical complex was generated in solution at room temperature using Ce(IV). The nuclease and anticancer activities of 1 were investigated. The roles of the tert-butyl group and singlet oxygen in the DNA cleavage activity were also discussed.

Thiocyanate selective sensor based on tripodal zinc complex for direct determination of thiocyanate in biological samples

Abstract: A potentiometric thiocyanate-selective sensor based on the use of zinc-tris( N - tert -butyl-2-thioimidazolyl)hydroborate complex [Tt t -Bu –Zn] as a neutral carrier for a thiocyanate-selective electrode is reported. Effect of various plasticizers viz ., o -nitrophenyloctyl ether ( o -NPOE), dioctylphthalate (DOP), dibutylphthalate (DBP), benzylacetate (BA), and anion excluder, hexadecyltrimethylammonium bromide (HTAB), with Tt t -Bu –Zn complex in poly (vinyl chloride) (PVC) were studied. The best performance was obtained with a membrane composition of DOP:PVC:Tt t -Bu –Zn:HTAB percent ratio (w/w) of 60:33:5:2. The sensor exhibits significantly enhanced selectivity toward thiocyanate ions over the concentration range 6.3 × 10 −7 to 1.0 × 10 −2 M with a lower detection limit of 3.16 × 10 −7 M and a Nernstian slope of 59.4 ± 1.1 mV decade −1 . Influences of the membrane composition, pH, and possible interfering anions were investigated on the response properties of the electrode. Fast and stable response, good reproducibility, long-term stability, applicability over a wide pH range (3.5–9.0) are demonstrated. The sensor has a response time of 14 s and can be used for at least 45 days without any considerable divergence in their potential response. The proposed electrode shows fairly good discrimination of thiocyanate from several inorganic and organic anions. It was successfully applied to direct determination of thiocyanate within physiological fluids and environmental samples.

Cell biology and molecular basis of denitrification.

Abstract: Denitrification is a distinct means of energy conservation, making use of N oxides as terminal electron acceptors for cellular bioenergetics under anaerobic, microaerophilic, and occasionally aerobic conditions. The process is an essential branch of the global N cycle, reversing dinitrogen fixation, and is associated with chemolithotrophic, phototrophic, diazotrophic, or organotrophic metabolism but generally not with obligately anaerobic life. Discovered more than a century ago and believed to be exclusively a bacterial trait, denitrification has now been found in halophilic and hyperthermophilic archaea and in the mitochondria of fungi, raising evolutionarily intriguing vistas. Important advances in the biochemical characterization of denitrification and the underlying genetics have been achieved with Pseudomonas stutzeri, Pseudomonas aeruginosa, Paracoccus denitrificans, Ralstonia eutropha, and Rhodobacter sphaeroides. Pseudomonads represent one of the largest assemblies of the denitrifying bacteria within a single genus, favoring their use as model organisms. Around 50 genes are required within a single bacterium to encode the core structures of the denitrification apparatus. Much of the denitrification process of gram-negative bacteria has been found confined to the periplasm, whereas the topology and enzymology of the gram-positive bacteria are less well established. The activation and enzymatic transformation of N oxides is based on the redox chemistry of Fe, Cu, and Mo. Biochemical breakthroughs have included the X-ray structures of the two types of respiratory nitrite reductases and the isolation of the novel enzymes nitric oxide reductase and nitrous oxide reductase, as well as their structural characterization by indirect spectroscopic means. This revealed unexpected relationships among denitrification enzymes and respiratory oxygen reductases. Denitrification is intimately related to fundamental cellular processes that include primary and secondary transport, protein translocation, cytochrome c biogenesis, anaerobic gene regulation, metalloprotein assembly, and the biosynthesis of the cofactors molybdopterin and heme D1. An important class of regulators for the anaerobic expression of the denitrification apparatus are transcription factors of the greater FNR family. Nitrate and nitric oxide, in addition to being respiratory substrates, have been identified as signaling molecules for the induction of distinct N oxide-metabolizing enzymes.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg