Poliovirus, pathogenesis of poliomyelitis, and apoptosis.

Poliovirus (PV) is the causal agent of paralytic poliomyelitis, an acute disease of the central nervous system (CNS) resulting in flaccid paralysis. The development of new animal and cell models has allowed the key steps of the pathogenesis of poliomyelitis to be investigated at the molecular level. In particular, it has been shown that PV-induced apoptosis is an important component of the tissue injury in the CNS of infected mice, which leads to paralysis. In this review the molecular biology of PV and the pathogenesis of poliomyelitis are briefly described, and then several models of PV-induced apoptosis are considered; the role of the cellular receptor of PV, CD155, in the modulation of apoptosis is also addressed

Organic Lewis Pairs Based on Phosphine and Electrophilic Silane for the Direct and Controlled Polymerization of Methyl Methacrylate: Experimental and Theoretical Investigations

Fully organic Lewis pairs, combining a phosphine such as tri-n-butylphosphine (PnBu3), tritert-butylphosphine (PtBu3) or tris(2,4,6-trimethoxyphenyl) phosphine (TTMPP) as a Lewis base, and N-(trimethylsilyl)bis(trifluoromethane sulfonyl)imide (Me3SiNTf2) as a Lewis acid, are shown to directly initiate the polymerization of methyl methacrylate (MMA) at room temperature in toluene. A dual reaction mechanism involving an optimal TTMPP:Me3SiNTf2 ratio of 1:2 accounts for the control of the polymerization. Molar masses of poly(methyl methacrylate)’s (PMMA’s) can be varied by the initial [MMA]0/[TTMPP]0 molar ratio. Chain extension experiments confirm that a majority of chains of a TTMPP/Me3SiNTf2-derived PMMA can be reactivated. Both density functional theory (DFT) calculations and stoichiometric studies reveal that TTMPP and Me3SiNTf2 form a P-silyl phosphonium intermediate that is in equilibrium with the corresponding frustrated Lewis pair (FLP). This FLP could correspond to the active form of the initiation step. Both computational and experimental data support the existence of a cooperative mechanism during the TTMPP/Me3SiNTf2 Lewis pair-mediated polymerization of MMA.POLYMERISATIONS ORGANOCATALYSEES PAR LES CARBENES : VERS UNE PLATEFORME CATALYTIQUE MULTI-TACH