Influence of stigmastanol and stigmastanyl-phosphorylcholine, two plasma cholesterol lowering substances, on synthetic phospholipid membranes : a 2H- and 31P-NMR study

Cholesterol, stigmastanol, and stigmastanyl-phosphorylcholine (ST-PC) were incorporated into model membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). POPC and ST-PC were deuterated at the lipid headgroup, DOPC at the cis-double bonds. The influence of the three sterols on the motion and conformation of the lipid headgroups and the hydrocarbon chains was monitored with 2H- and 31P-NMR. All three sterols were freely miscible with the lipid matrix in concentrations of up to 50 mol% without inducing phase separations or nonbilayer structures. However, the molecules exert quite different effects on the phospholipid bilayer. Cholesterol and stigmastanol are largely buried in the hydrocarbon part of the membrane, distinctly restricting the flexing motions of the fatty acyl chains whereas the conformation of the phospholipid headgroups is little affected. In contrast, ST-PC is anchored with its headgroup in the layer of phospholipid dipoles, preventing an extensive penetration of the sterol ring into the hydrocarbon layer. Hence ST-PC has almost no effect on the hydrocarbon chains but induces a characteristic conformational change of the phospholipid headgroups. The 2H- and 31P-NMR spectra of mixed phospholipid/ST-PC membranes further demonstrate that the PC headgroup of ST-PC has a similar orientation as the surrounding phosphatidylcholine headgroups. For both types of molecules the -P-N+ dipole is essentially parallel to the membrane surface. Addition of ST-PC induces a small rotation of the POPC headgroup towards the water phase

On the behavior of bidirectionally coupled multistable systems

In this work, we study the synchronization states for a specific pair of mutually coupled multistable scroll systems. First, we determine conditions in the coupling scheme, to achieve partial or complete synchronization, under a uniform-coupling strength. Second, it is analyzed how the changes in the coupling strength modify the synchronous state. Our main results show that the nature of the coupling scheme determines the obtained synchronization type, while the coupling strength allows us to have various synchronized state attractors that differ from initial attractors. The analysis of the emergence of stable collective behavior is presented using Lyapunov functions of the different couplings and illustrated by numerical simulations

Os direitos sexuais e o enfrentamento da violência sexual

O artigo tem como temática a problematização acerca da emergência dos direitos sexuais como direitos humanos e dos processos de criminalização contemporâneos que se materializam na violência sexual, colocando em análise suas múltiplas formas de entendimento e delimitações. Busca-se visibilizar produções de saberes - sempre articulados a relações de poder - para pôr em questão processos de subjetivação, a partir da análise do funcionamento do poder biopolítico e seus efeitos na contemporaneidade