A Tale of two topologies: Woodward-Hoffmann rules at your fingertips!

A simple procedure for determining whether a pericyclic reaction is thermally allowed is described. The focus is on the potential aromaticity of the transition state of the process, which is inferred from the topological features of the interacting orbitals and the number of electrons involved

Fascinating organic transformations. 2. The ubiquitous hydrogen bond

Hydrogen bonds can transform simple molecules into beautiful architectures. This is well illustrated in this article

Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis

Two possibilities exist for the evolution of individual enzymes/proteins from a milieu of amino acids, one based on preference and selectivity and the other on the basis of random events. Logic is overwhelmingly in favour of the former. By protein data base analysis and experiments, we have provided data to show the manifestation of two types of preferences, namely, the choice of the neighbour and its acceptance from the amino end (left) or the carboxyl end (right). The study tends to show that if the 20 proteinous amino acids were made to combine in water, the resulting profile would be nonrandom. Such selectivity could be a factor in protein evolution

One-step transformation of 2-oxa-3-azabicyclo[2.2.1]hept-5-ene and methyl 2,3-diazabicyclo[2.2.1]heptane-2-carboxylate to ion uptake systems

Linker generated duplexes of the title compounds- prepared from cyclopentadiene- with possibility for positioning of four oxygen in the cavity, are shown to be excellent ion uptake systems. Mass spectrometric doping studies with lithium, sodium, potassium and silver ions, show a clear preference for lithium complexation. The lithium salts of the best examples have been prepared and characterized

The crafting of uracils with enhanced stacking potential

Uracils having enhanced stacking profile are of interest from diverse vantages ranging from the chemical simulation of transcription to the design of novel anti viral agents. This objective has been realized by synthetic strategies leading to uracils having,inter alia, pseudo aromatic and hydrophobic rings crafted to the 5-6 location and ionophore and hydrophobic chains affixed at the C-5 and nitrogen atoms. Endeavours to prepare a 5-2' uracil-pyrimidine composite have led to novel uracil arising from 2-O → =CH(COOR)2 transformation and a tethered malonic acid pyrimidine complex

Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis †

Two possibilities exist for the evolution of individual enzymes/proteins from a milieu of amino acids, one based on preference and selectivity and the other on the basis of random events. Logic is overwhelmingly in favour of the former. By protein data base analysis and experiments, we have provided data to show the manifestation of two types of preferences, namely, the choice of the neighbour and its acceptance from the amino end (left) or the carboxyl end (right). The study tends to show that if the 20 proteinous amino acids were made to combine in water, the resulting profile would be nonrandom. Such selectivity could be a factor in protein evolution. [Ranganathan S, Kundu D and Vudayagiri S D 2003 Protein evolution: intrinsic preferences in peptide bond formation: a computational and experimental analysis; J. Biosci. 28 [683][684][685][686][687][688][689][690

Solubilization of silica: synthesis, characterization and study of penta-coordinated pyridine N-oxide silicon complexes

In an effort to design agents that could solubilize silica in water, under ambient conditions and pH, as takes place in nature, novel zwitterionic, penta-oxo-coordinated silicon compounds with siliconate cores have been prepared from 4-substituted pyridine N-oxides (H, OMe, morpholino, NO2) as donor ligands, their structures established by 1H, 13C and MS, and the coordination number of silicon, by 29Si NMR. The formation of complexes from pyridine N-oxides is noteworthy since they arise from interaction with a weakly nucleophilic oxygen centre. The ability of the pyridine N-oxides to enhance the solubilization of silica in water has been experimentally demonstrated. Possible rationalization of this observation on the basis of O → Si coordination via the oxygen atom of pyridine N-oxide is suggested