@article {42683, title = {Controlled aggregation of gold nanoparticle networks induced by alkali metal ions}, journal = {Journal of Nanoscience and Nanotechnology}, volume = {7}, year = {2007}, month = {AUG}, pages = {2683-2689}, type = {Article}, abstract = {

Gold nanoparticle networks were obtained by linking them with cysteine modified triethyleneglycols. The oligo-ether linker molecule initially having a linear structure probably adopts a crown ether type structure upon complexation with alkali metal ions that leads to a controlled aggregation of the network. The extent of aggregation depends on the degree of conformational change in the molecule upon complexation with the metal ion, which in turn is governed by the metal ion radius leading to a dependence of red shift of the surface plasmon resonance on the metal ion radius. Since this network is present in the organic solvent they also act as phase transferring agent for the alkali metal ions from aqueous to organic media.

}, keywords = {Aggregation; Alkali Metal Ions; Au Nanoparticles; Crown Ether; Surface Plasmon Resonance}, doi = {10.1166/jnn.2007.612}, author = {Tamang, Sudarsan and Hotha, Srinivas and Bhagavatula L. V. Prasad} } @article { ISI:000283495200040, title = {Clicking molecular hooks on silica nanoparticles to immobilize catalytically important metal complexes: the case of gold catalyst immobilization}, journal = {New Journal of Chemistry}, volume = {34}, number = {11}, year = {2010}, month = {AUG}, pages = {2662-2670}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Gold mediated reactions have emerged as one of the best choices for affecting a variety of chemical transformations with a wide range of functional group tolerance. Application of such transformations to industrial processes necessitates immobilization of the Au ions into a matrix for easy separation of the catalyst after reaction. We report the synthesis and characterization of silica nanoparticles in which Au(III) has been immobilized through a 1,2,3-triazole linkage using an alkynalated picolinic acid exploiting {\textquoteleft}{\textquoteleft}click chemistry{\textquoteright}{\textquoteright}. The Au( III) immobilized silica nanoparticle has been thoroughly characterized using FT-IR, C-13 CP MAS NMR and XPS. The utility of these particles as an easily separable catalyst for the Hashmi phenol synthesis is also reported.

}, issn = {1144-0546}, doi = {10.1039/c0nj00292e}, author = {Ganai, Anal Kumar and Bhardwaj, Rima and Hotha, Srinivas and Sen Gupta, Sayam and Bhagavatula L. V. Prasad} } @article { ISI:000303951600008, title = {Controlled synthesis of O-glycopolypeptide polymers and their molecular recognition by lectins}, journal = {Biomacromolecules}, volume = {13}, number = {5}, year = {2012}, month = {MAY}, pages = {1287-1295}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

The facile synthesis of high molecular weight water-soluble O-glycopolypeptide polymers by the ring-opening polymerization of their corresponding N-carboxyanhydride (NCA) in very high yield (overall yield \> 70\%) is reported. The per-acetylated-O-glycosylated lysine-NCA monomers, synthesized using stable glycosyl donors and a commercially available protected amino acid in very high yield, was polymerized using commercially available amine initiators. The synthesized water-soluble glycopolypeptides were found to be alpha-helical in aqueous solution. However, we were able to control the secondary conformation of the glycopolypeptides (alpha-helix vs nonhelical structures) by polymerizing raceznic amino acid glyco NCAs. We have also investigated the binding of the glycopolypeptide poly(alpha-manno-O-lys) with the lectin Con-A using precipitation and hemagglutination assays as well as by isothermal titration calorimetry (ITC). The ITC results clearly show that the binding process is enthalpy driven for both alpha-helical and nonhelical structures, with negative entropic contribution. Binding stoichiometry for the glycopolypeptide poly(alpha-manno-O-lys) having a nonhelical structure was slightly higher as compared to the corresponding polypeptide which adopted an alpha-helical structure.

}, issn = {1525-7797}, doi = {10.1021/bm201813s}, author = {Pati, Debasis and Shaikh, Ashif Y. and Das, Soumen and Nareddy, Pavan Kumar and Swamy, Musti J. and Hotha, Srinivas and Sen Gupta, Sayam} } @article { ISI:000343026600023, title = {Cationic charged helical glycopolypeptide using ring opening polymerization of 6-deoxy-6-azido-glyco-N-carboxyanhydride}, journal = {Biomacromolecules}, volume = {15}, number = {10}, year = {2014}, month = {OCT}, pages = {3679-3686}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Glycopolypeptides with a defined secondary structure are of significance in understanding biological phenomena. Synthetic glycopolypeptides, or polypeptides featuring pendant carbohydrate moieties, have been of particular interest in the field of tissue engineering and drug delivery. In this work, we have synthesized charged water-soluble glycopolypeptides that adopt a helical conformation in water. This was carried out by the synthesis of a glyco-N-carboxyanhydride (glyco-NCA) containing an azide group at the sixth position of the carbohydrate ring. Subsequently, the NCA was polymerized to obtain azide-containing glycopolypeptides having good control over molecular weight and polydispersity index (PDI) in high yields. We were also able to control the incorporation of the azide group by synthesizing random co-glycopolypeptide containing 6-deoxy-6-azido and regular 6-OAc functionalized glucose. This azide functionality allows for the easy attachment of a bioactive group, which could potentially enhance the biological activity of the glycopolypeptide. We were able to obtain water-soluble charged glycopolypeptides by both reducing the azide groups into amines and using CuAAC with propargylamine. These charged glycopolypeptides were shown to have a helical conformation in water. Preliminary studies showed that these charged glycopolypeptides showed good biocompatibility and were efficiently taken up by HepG2 cells.

}, issn = {1525-7797}, doi = {10.1021/bm5009537}, author = {Shaikh, Ashif Y. and Das, Soumen and Pati, Debasis and Dhaware, Vinita and Sen Gupta, Sayam and Hotha, Srinivas} }