Cobalt-Catalyzed Asymmetric Hydrogenation:Substrate Specificity and Mechanistic Variability

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area

Cobalt-Catalyzed Asymmetric Hydrogenation:Substrate Specificity and Mechanistic Variability

Asymmetric hydrogenation finds widespread application in academia and industry. And indeed, a number of processes have been implemented for the production of pharma and agro intermediates as well as flavors & fragrances. Although these processes are all based on the use of late transition metals as catalysts, there is an increasing interest in the use of base metal catalysis in view of their lower cost and the expected different substrate scope. Catalysts based on cobalt have already shown their potential in enantioselective hydrogenation chemistry. This review outlines the impressive progress made in recent years on cobalt-catalyzed asymmetric hydrogenation of different unsaturated substrates. We also illustrate the ligand dependent substrate specificity as well as the mechanistic variability in detail. This may well guide further catalyst development in this research area

Gaugino mass non-universality in an SO(10) supersymmetric Grand Unified Theory: low-energy spectra and collider signals

We derive the non-universal gaugino mass ratios in a supergravity (SUGRA) framework where the Higgs superfields belong to the non-singlet representations {\bf 54} and {\bf 770} in a SO(10) Grand Unified Theory (GUT). We evaluate the ratios for the phenomenologically viable intermediate breaking chain $SU(4)_C \times SU(2)_L \times SU(2)_R (G_{422})$. After a full calculation of the gaugino mass ratios, noting some errors in the earlier calculation for {\bf 54}, we obtain, using the renormalisation group equations (RGE), interesting low scale phenomenology of such breaking patterns. Here, we assume the breaking of the SO(10) GUT group to the intermediate gauge group and that to the Standard Model (SM) take place at the GUT scale itself. We also study the collider signatures in multilepton channels at the Large Hadron Collider (LHC) for some selected benchmark points allowed by the cold dark matter relic density constraint provided by the WMAP data and compare these results with the minimal supergravity (mSUGRA) framework with similar gluino masses indicating their distinguishability in this regard.Comment: 35 pages, 5 figures, 9 tables. Part of the calculations modifie

Extracellular vesicle-mediated transfer of processed and functional RNY5 RNA

Extracellular vesicles (EVs) have been proposed as a means to promote intercellular communication. We show that when human primary cells are exposed to cancer cell EVs, rapid cell death of the primary cells is observed, while cancer cells treated with primary or cancer cell EVs do not display this response. The active agents that trigger cell death are 29- to 31-nucleotide (nt) or 22- to 23-nt processed fragments of an 83-nt primary transcript of the human RNY5 gene that are highly likely to be formed within the EVs. Primary cells treated with either cancer cell EVs, deproteinized total RNA from either primary or cancer cell EVs, or synthetic versions of 31- and 23-nt fragments trigger rapid cell death in a dose-dependent manner. The transfer of processed RNY5 fragments through EVs may reflect a novel strategy used by cancer cells toward the establishment of a favorable microenvironment for their proliferation and invasion

Resonant Leptogenesis with nonholomorphic R-Parity violation and LHC Phenomenology

In R-parity violating supersymmetric models both leptogenesis and the correct neutrino masses are hard to achieve together. The presence of certain soft nonholomorphic R-parity violating terms helps to resolve this problem. We consider a scenario where the lightest and the second-lightest neutralino are nearly degenerate in mass and enough CP-asymmetry can be produced through resonant leptogenesis. In this model, the lighter chargino and the lightest neutralino are highly degenerate. We have relatively lighter gauginos which can be produced at the LHC leading to heavily ionizing charged tracks. At the same time this model can also generate the correct neutrino mass scale. Thus our scenario is phenomenologically rich and testable at colliders.Comment: 17 pages, 7 figures, Numerical results are improved and new plots are added, Journal version. arXiv admin note: text overlap with arXiv:hep-ph/0006173 by other author

Patchy Amphiphilic Dendrimers Bind Adenovirus and Control Its Host Interactions and in Vivo Distribution

The surface of proteins is heterogeneous with sophisticated but precise hydrophobic and hydrophilic patches, which is essential for their diverse biological functions. To emulate such distinct surface patterns on macromolecules, we used rigid spherical synthetic dendrimers (polyphenylene dendrimers) to provide controlled amphiphilic surface patches with molecular precision. We identified an,. I optimal spatial arrangement of these patches on certain dendrimers that enabled their interaction with human adenovirus 5 (Ads). Patchy dendrimers bound to the surface of Ads formed a synthetic polymer corona that greatly altered various host interactions of Ads as well as in vivo distribution. The dendrimer corona (1) improved the ability of Ad5-derived gene transfer vectors to transduce cells deficient for the primary Ad5 cell membrane receptor and (2) modulated the binding of Ads to blood coagulation factor X, one of the most critical virus host interactions in the bloodstream. It significantly enhanced the transduction efficiency of Ad5 while also protecting it from neutralization by natural antibodies and the complement system in human whole blood. Ads with a synthetic dendrimer corona revealed profoundly altered in vivo distribution, improved transduction of heart, and dampened vector sequestration by liver and spleen. We propose the design of bioactive polymers that bind protein surfaces solely based on their amphiphilic surface patches and protect against a naturally occurring protein corona, which is highly attractive to improve Ad5-based in vivo gene therapy applications