01417nas a2200169 4500008004100000245008600041210006900127260000800196300001400204490000600218520074400224653009300968100002101061700002001082700003001102856011501132 2007 eng d00aControlled aggregation of gold nanoparticle networks induced by alkali metal ions0 aControlled aggregation of gold nanoparticle networks induced by  cAUG a2683-26890 v73 a

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.

10aAggregation; Alkali Metal Ions; Au Nanoparticles; Crown Ether; Surface Plasmon Resonance1 aTamang, Sudarsan1 aHotha, Srinivas1 aPrasad, Bhagavatula L. V. uhttps://library.ncl.res.in/content/controlled-aggregation-gold-nanoparticle-networks-induced-alkali-metal-ions01623nas a2200193 4500008004100000022001400041245014900055210006900204260011000273300001400383490000700397520078300404100002301187700001901210700002001229700002201249700003001271856012801301 2010 eng d a1144-054600aClicking molecular hooks on silica nanoparticles to immobilize catalytically important metal complexes: the case of gold catalyst immobilization0 aClicking molecular hooks on silica nanoparticles to immobilize c aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcAUG a2662-26700 v343 a

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 ``click chemistry''. 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.

1 aGanai, Anal, Kumar1 aBhardwaj, Rima1 aHotha, Srinivas1 aGupta, Sayam, Sen1 aPrasad, Bhagavatula L. V. uhttps://library.ncl.res.in/content/clicking-molecular-hooks-silica-nanoparticles-immobilize-catalytically-important-metal-002126nas a2200217 4500008004100000022001400041245009900055210006900154260007100223300001400294490000700308520131800315100001801633700002201651700001601673700002601689700002101715700002001736700002201756856013001778 2012 eng d a1525-779700aControlled synthesis of O-glycopolypeptide polymers and their molecular recognition by lectins0 aControlled synthesis of Oglycopolypeptide polymers and their mol a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAY a1287-12950 v133 a

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.

1 aPati, Debasis1 aShaikh, Ashif, Y.1 aDas, Soumen1 aNareddy, Pavan, Kumar1 aSwamy, Musti, J.1 aHotha, Srinivas1 aGupta, Sayam, Sen uhttps://library.ncl.res.in/content/controlled-synthesis-o-glycopolypeptide-polymers-and-their-molecular-recognition-lectins-002237nas a2200205 4500008004100000022001400041245012400055210006900179260007100248300001400319490000700333520144600340100002201786700001601808700001801824700002001842700002201862700002001884856012701904 2014 eng d a1525-779700aCationic charged helical glycopolypeptide using ring opening polymerization of 6-deoxy-6-azido-glyco-N-carboxyanhydride0 aCationic charged helical glycopolypeptide using ring opening pol a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT a3679-36860 v153 a

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.

1 aShaikh, Ashif, Y.1 aDas, Soumen1 aPati, Debasis1 aDhaware, Vinita1 aGupta, Sayam, Sen1 aHotha, Srinivas uhttps://library.ncl.res.in/content/cationic-charged-helical-glycopolypeptide-using-ring-opening-polymerization-6-deoxy-6-0