Microtubules as Platforms for Assaying Actin Polymerization In Vivo

The actin cytoskeleton is continuously remodeled through cycles of actin filament assembly and disassembly. Filaments are born through nucleation and shaped into supramolecular structures with various essential functions. These range from contractile and protrusive assemblies in muscle and non-muscle cells to actin filament comets propelling vesicles or pathogens through the cytosol. Although nucleation has been extensively studied using purified proteins in vitro, dissection of the process in cells is complicated by the abundance and molecular complexity of actin filament arrays. We here describe the ectopic nucleation of actin filaments on the surface of microtubules, free of endogenous actin and interfering membrane or lipid. All major mechanisms of actin filament nucleation were recapitulated, including filament assembly induced by Arp2/3 complex, formin and Spir. This novel approach allows systematic dissection of actin nucleation in the cytosol of live cells, its genetic re-engineering as well as screening for new modifiers of the process

Synthetic and Computational Evaluation of Regiodivergent Epoxide Opening for Diol and Polyol Synthesis

In a combined synthetic and computational study, the factors governing the selectivity of the titanocene(III)‐catalyzed regiodivergent epoxide opening (REO) with Kagan’s complex via electron transfer leading to derivatives of 1,2‐, 1,3‐, and 1,4‐diols were investigated. In this manner, valuable building blocks for the synthesis of 1,3‐ and 1,4‐diols were identified. The computational study provides crucial structural features and energies of the transition states of ring opening that are important for the design of more selective catalysts