N-Acetyl-Cysteine Regenerates Albumin Cys34 by a Thiol-Disulfide Breaking Mechanism: An Explanation of Its Extracellular Antioxidant Activity

In the present paper, the extracellular antioxidant activity of N-acetyl-cysteine (NAC) is explained by considering its ability to regenerate the free form of albumin Cys34 by breaking the disulfide bond of the cysteinylated form (HSA-Cys). NAC’s capability to regenerate albumin Cys34 (HSA-SH) was studied by MS intact protein analysis in human plasma and in a concentration range of NAC easily achievable after oral and i.v. administration (5–50 µg/mL). NAC dose-dependently broke the HSA-Cys bond to form the dimer NAC-Cys thus regenerating Cys34, whose reduced state was maintained for at least 120 min. Cys was faster in restoring Cys34, according to the reaction constant determined with the glutathione disulfide (GSSG) reaction, but after 60 min the mixed disulfide HSA-Cys turned back due to the reaction of the dimer Cys-Cys with Cys34. The explanation for the different rate exchanges between Cys-Cys and Cys-NAC with Cys34 was given by molecular modeling studies. Finally, the Cys34 regenerating effect of NAC was related to its ability to improve the total antioxidant capacity of plasma (TRAP assay). The results well indicate that NAC greatly increases the plasma antioxidant activity and this effect is not reached by a direct effect but through the regenerating effect of Cys34.

The PANDORA project: an experimental setup for measuring in-plasma β-decays of astrophysical interest

Experiments performed on Storage Rings have shown that lifetimes of beta-radionuclides can change dramatically as a function of theionization state. PANDORA (Plasmas for Astrophysics, Nuclear Decay Observation and Radiation for Archaeometry) aims at measuring, for the first time, nuclear β-decay rates in stellar-like conditions, especially for radionuclides involved in nuclear-astrophysics processes (BBN, s- processing, CosmoChronometers, Early Solar System formation). Compact magnetic plasma traps, where plasmas reach density ne~10n-1014 cm-3, and temperature Te~0.1-30 keV, are suitable for such studies. The decay rates can be measured as a function of the charge state distribution of the inplasma ions. The collaboration is now designing the plasma trap able to reach the needed plasma densities, temperatures and charge states distributions. A first list of radioisotopes, including tens of physics cases of potential interest is now available. Possible physics cases include, among the others, 2°4Tl, 63Ni, 6°Co, 171Tm, 147Pm, 85Kr, 176Lu and the pairs 187Re-187Os and 87Sr-87Rb, which play a crucial role as cosmo-clock. Physics cases are now under evaluation in terms of lifetime measurements feasibility in a plasma trap.

A two-dimensional hybrid model of an open plasma trap

Представлена гибридная математическая модель осесимметричной плазменной ловушки, основанная на кинетическом описании для ионной компоненты плазмы и приближении МГД для электронной компоненты. На основе гибридной модели разработан двумерный алгоритм для изучения динамики разлета инжектируемых частиц в поле ловушки. Движение ионной компоненты рассчитывается по методу частиц в ячейках, для расчета магнитного поля и электронной компоненты плазмы используются конечно-разностные схемы. На основе разработанного алгоритма создан комплекс программ для исследования механизмов формирования самосогласованной структуры магнитного поля ловушки. A hybrid mathematical model of an axisymmetric plasma trap based on the kinetic description for the ion component of the plasma and the MHD approximation for the electronic component is presented. On the basis of the hybrid model, a two-dimensional algorithm is developed to study the dynamics of injected particles in the trap field. The motion of the ion component is calculated by the particle-in-cell method. Finite-difference schemes are used to calculate the magnetic field and the electron component of the plasma. On the basis of the developed algorithm, a program code is created to study the mechanisms of the self-consistent magnetic field structure formation.