Dipankar Roy

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[Structure: see text]. The synthesis and characterization of a series of organochalcogen (Se, Te) compounds derived from benzyl alcohol 13 are described. The synthesis of the key precursor dichalcogenides 15, 22, and 29 was achieved by the ortho-lithiation route. Selenide 18 was obtained by the reaction of the dilithiated derivative 14 with Se(dtc)2.(More)
The side-chains of the residues of glutamine (Q) and asparagine (N) contain amide groups. These can H-bond to each other in patterns similar to those of the backbone amides in α-helices. We show that mutating multiple Q's for alanines (A's) in a polyalanine helix stabilizes the helical structure, while similar mutations with multiple N's do not. We suggest(More)
Intramolecular nonbonding interactions between chalcogen atoms in a series of ortho substituted arylselenides (S/O...Se-Y, with Y = -Me, -CN, -Cl, and -F) are quantified using the coupled cluster CCSD(T)/cc-pVDZ level of theory. A homodesmic reaction method as well as an ortho-para approach are employed in evaluating the strength of intramolecular(More)
Although a large volume of experimental evidence is available on the existence of intramolecular nonbonding interactions between chalcogen atoms in main group organometallic compounds, the primary focus has been on the contact distances involving the chalcogen atoms. The important class of intramolecular Se...X (where X is O, S, N) nonbonding interaction in(More)
We report the synthesis and characterization of a series of imidazolium iodide ionic liquids (ILs) containing monomethoxy-terminated poly(ethylene glycol) (mPEG), and n-alkyl groups. These PEGylated ILs contain 7, 12, or 16 ethylene glycol units in the side chains, and are designed as potential electrolytes for energy conversion and storage devices such as(More)
We compare dispersion and induction interactions for noble gas dimers and for Ne, methane, and 2-butyne with HF and LiF using a variety of functionals (including some specifically parameterized to evaluate dispersion interactions) with ab initio methods including CCSD(T) and MP2. We see that inductive interactions tend to enhance dispersion and may be(More)
The first ab initio and DFT studies on the mechanism of the MBH reaction show that the rate-limiting step involves an intramolecular proton transfer in the zwitterionic intermediate generated by the addition of enolate to electrophile. The activation barrier for the C-C bond-formation is found to be 20.2 kcal/mol lower than the proton-transfer step for the(More)
This paper demonstrates potential applications of two periplasmic receptor proteins from E. coli as sensing elements for biosensors using the surface plasmon resonance (SPR) technique. These molecules, namely the aspartate to cysteine mutant of the leucine-specific receptor (LS-D1C) and the glutamine to cysteine mutant of the D-glucose/D-galactose receptor(More)
We present a new classification of β-turns specific to antiparallel β-sheets based upon the topology of H-bond formation. This classification results from ONIOM calculations using B3LYP/D95** density functional theory and AM1 semiempirical calculations as the high and low levels, respectively. We chose acetyl(Ala)(6)NH(2) as a model system as it is the(More)