Increasing Access to Natural Areas: Connecting Physical and Social Dimensions

Report of the 2015 Berkley Workshop Held at the Asticou Inn, Northeast Harbor, Maine - July 201

Improving Human Health by Increasing Access to Natural Areas: Linking Research to Action at Scale

Report of the 2014 Berkley Workshop Held at the Wingspread Conference Center, Johnson Foundation, Racine, Wisconsin - June 201

Characterisation of the metal-ion-GDP complex at the active sites of transforming and nontransforming p21 proteins by observation of the ¹⁷O-Mn superhyperfine coupling and by kinetic methods

Kinetic studies on the interaction of three Ha-ras-encoded p21 proteins with GDP and MgGDP have yielded values for the association (10(6)-10(7) M-1 s-1) and dissociation (10(-3)-10(-5) s-1) rate constants at 0 degrees C. Dramatic differences in the rate constants were not observed for the three proteins. Under non-physiological conditions (absence of Mg2+), the rate constant for GDP release was an order of magnitude faster for the viral protein p21v than for the cellular form p21c or the T24 mutant p21t, but this was reduced to a factor of about 3 in the presence of Mg2+. In all cases, there was an increase of about one order of magnitude in the rate of GDP release on removing magnesium. The binding affinities ranged from 5.7 X 10(10) M-1 for p21c to 1.3 X 10(11) M-1 for p21v. Electron paramagnetic resonance (EPR) measurements on Mn2+ bound together with stereospecifically 17O-labelled GDP showed direct coordination of a beta-phosphate oxygen to the metal ion with a superhyperfine coupling constant of 0.16-0.22 mT, but no interaction with the alpha-phosphate oxygens at the active site of all three proteins. The association constant of Mn(II) to p21 proteins in the absence of nucleotides was estimated to be greater than 10(5) M-1. In agreement with the EPR results, experiments on the metal ion dependence of the binding of thiophosphate analogs of GDP provided further evidence for the absence of direct coordination of the metal ion to the alpha-phosphate group. These results have been used to construct a model for the interactions of Mg X GDP with the active site of p21 proteins

Functionalization of C(sp2)–H Bonds of Arenes and Heteroarenes Assisted by Photoredox Catalysts for the C–C Bond Formation

International audienceThe formation of C–C bonds from arenes and heteroarenes through transition metal-catalyzed C–H bond functionalizations is one of the major achievements of these last decades. It is now possible to perform such transformations under mild reaction conditions with the help of visible light photocatalysis leading to eco-friendly and safer process to build organic molecules or materials. This chapter will focus on photoredox catalysis which involves a C(sp2)–H bond functionalization step for the formation of C(sp2)–C bonds [i.e., direct arylations and (perfluoro)alkylations] and will show how this hot topic contributes to the development of green chemistry