Simulação de espectros de ressonância paramagnética eletrônica (RPE) através do programa NLSL

EPR users often face the problem of extracting information from frequently low-resolution and complex EPR spectra. Simulation programs that provide a series of parameters, characteristic of the investigated system, have been used to achieve this goal. This work describes the general aspects of one of those programs, the NLSL program, used to fit EPR spectra applying a nonlinear least squares method. Several motion regimes of the probes are included in this computational tool, covering a broad range of spectral changes. The meanings of the different parameters and rotational diffusion models are discussed. The anisotropic case is also treated by including an orienting potential and order parameters. Some examples are presented in order to show its applicability in different systems.

Efeito da floretina na hidratação de vesículas neutras de agregados anfifílicos de DMPC

The effect of phloretin in the structure and hydration of dimiristoyl phosphatidylcholine vesicles (DMPC) was investigated by electron paramagnetic resonance technique (EPR) at the bilayer core of membrane, using 14-PCSL spin label derivative of phosphatidylcoline. The spectra obtained by pure DMPC vesicles and with addition of phloretin were simulated using the Nonlinear Least-Square program, at the tempearature between 15 oC to 50 oC. Through these simulations it was possible to analyse the membrane hydration and bilayer order, to understand the interaction between DMPC aggregates and phloretin. The results show that the phloretin decreases the membrane hydration in both gel and fluid phases. This reduction of water molecules is accompanied by increasing of the bilayer order at this micro-region