02972nas a2200253   4500008004100000022001400041245012000055210006900175260011000244300001400354490000600368520200200374100001602376700002202392700001802414700002102432700002202453700002002475700002002495700002102515700003202536700002202568856012802590       2012                        eng d  a1744-683X00aCompetition between gelation and crystallisation of a peculiar multicomponent liquid system based on ammonium salts0 aCompetition between gelation and crystallisation of a peculiar m  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcFEB  a3446-34560 v83 a<p>An exemplar competition between gelation and crystallisation phenomena was examined with an unusual synergistic multicomponent (organo) gelator solution (MGS), which consists of a well-defined methanolic solution of (1R, 2R)-1,2-diaminocyclohexane L-tartrate containing 2.4 equiv. of concentrated hydrochloric acid. The optimal composition of the MGS was determined through meticulous solubility, gelation and structural studies, which support a transient gelation mechanism based on the kinetic self-assembly of the tartrate salt driven by hydrogen-bonding interactions, involving ammonium nitrogen donors and hydroxyl oxygen acceptors, and electrostatic interactions. The hydrochloric acid is involved in the solubilisation of the salt through an ionic dissociation-exchange process, which ends up with the formation-precipitation of (1R, 2R)-1,2-diaminocyclohexane dihydrochloride. As a consequence, an irreversible destruction of the gel takes place, which indicates the metastable nature of this phase that cannot be accessed from the thermodynamically equilibrated state. Gelation of a variety of oxygenated and nitrogenated solvents with moderate polarity occurred efficiently using extremely low MGS concentrations at low temperatures, and the gel phase was confirmed by dynamic rheological measurements. Several features make the described MGS unique: (1) it is a multicomponent solution where each component and its stoichiometry play a key role in the reproducible formation and stabilization of the gels; (2) it is formed by simple, small, and commercially available chiral building blocks (dissolved in a well-defined solvent system), which are easily amenable for further modifications; (3) the gelation phenomenon takes place efficiently at low temperature upon warming up the isotropic solution, conversely to the typical gel preparation protocol; and (4) the formed organogels are not thermoreversible despite the non-covalent interactions that characterize the 3D-network.</p>1 aKapoor, Iti1 aSchoen, Eva-Maria1 aBachl, Jurgen1 aKuehbeck, Dennis1 aCativiela, Carlos1 aSaha, Subhadeep1 aBanerjee, Rahul1 aRoelens, Stefano1 aMarrero-Tellado, Jose, Juan1 aDiaz, David, Diaz  uhttps://library.ncl.res.in/content/competition-between-gelation-and-crystallisation-peculiar-multicomponent-liquid-system-001838nas a2200265   4500008004100000022001400041245007400055210006900129260008600198300001400284490000600298520092700304653001701231653003301248653001201281653001901293653001201312100002101324700002401345700002201369700002201391700002901413700002201442856010801464       2013                        eng d  a1860-539700aC-C Bond formation catalyzed by natural gelatin and collagen proteins0 aCC Bond formation catalyzed by natural gelatin and collagen prot  aTRAKEHNER STRASSE 7-9, FRANKFURT AM MAIN, 60487, GERMANYbBEILSTEIN-INSTITUTcJUN  a1111-11180 v93 a<p>The activity of gelatin and collagen proteins towards C-C bond formation via Henry (nitroaldol) reaction between aldehydes and nitroalkanes is demonstrated for the first time. Among other variables, protein source, physical state and chemical modification influence product yield and kinetics, affording the nitroaldol products in both aqueous and organic media under mild conditions. Significantly, the scale-up of the process between 4-nitrobenzaldehyde and nitromethane is successfully achieved at 1 g scale and in good yield. A comparative kinetic study with other biocatalysts shows an increase of the first-order rate constant in the order chitosan &lt; gelatin &lt; bovine serum albumin (BSA) &lt; collagen. The results of this study indicate that simple edible gelatin can promote C-C bond forming reactions under physiological conditions, which may have important implications from a metabolic perspective.</p>10abiocatalysis10acarbon-carbon bond formation10agelatin10aHenry reaction10aprotein1 aKuehbeck, Dennis1 aDhar, Basab, Bijayi1 aSchoen, Eva-Maria1 aCativiela, Carlos1 aGotor-Fernandez, Vicente1 aDiaz, David, Diaz  uhttps://library.ncl.res.in/content/c-c-bond-formation-catalyzed-natural-gelatin-and-collagen-proteins-0