Distributed entanglement induced by dissipative bosonic media

We describe a scheme with analytic result that allows to generate steady-state entanglement for two atoms over a dissipative bosonic medium. The resonant coupling between the mediating bosonic mode and cavity modes produces three collective atomic decay channels. This dissipative dynamics, together with the unitary process induced by classical microwave fields, drives the two atoms to the symmetric or asymmetric entangled steady state conditional upon the choice of the phases of the microwave fields. The effects on the steady-state entanglement of off-resonance mediating bosonic modes are analyzed. The entanglement can be obtained with high fidelity regardless of the initial state and there is a linear relation in the scaling of the fidelity with the cooperativity parameter. The fidelity is insensitive to the fluctuation of the Rabi frequencies of the classical driving fields.Comment: to appear in Europhysics Letter

Reactions of biologically important thiols with nitroxyl (HNO) and development of a HNO marker

Biologically active nitroxyl (HNO) is one of the least understood nitrogen oxides. It may play a distinct role from NO in protecting the cardiovascular system, and thiols are suspected to be a major nitroxyl target. The major low-molecular-mass intracellular antioxidant, glutathione (GSH), is an important regulator of cellular homeostasis, and is the most likely biological target of HNO. Cysteine (Cys) and HCys (HCys) are naturally occurring thiol-containing amino acids with antioxidant properties and their levels have been linked to many diseases. Reactions of these thiols with Angeli's salt (AS), a HNO donor, were investigated here. N -acetyl-glutathione and N -acetyl-homocysteine were used in this study but are unavailable commercially. An efficient and simple method was developed to prepare N -acetylated low-mass thiols from the corresponding disulfides (e.g., GSSG, homocystine) in aqueous buffer using sulfosuccinimidyl acetate (NHSA) followed by disulfide reduction by immobilized tris (2-carboxyethyl)phosphine (TCEP). The pK a values of the low-mass thiols used here were determined by pH titration in 0.15 M KCl using the GLpKa instrument. GSH was incubated with AS for 30 min and room temperature, and the products were analyzed by ESI-MS. The sulfinamide (GSONH 2 ) and disulfide (GSSG) were formed at pH>5 but GSSG was the dominant product at higher pHs and GSH concentrations. Disulfides only were detected in the incubations of AS with Cys, N -AcCys, HCys, and penicillamine at pH>5. N -acetylation of penicillamine decreased its reactivity with HNO and led to sulfoxide disulfide (RSOSR) formation. Control experiments with NaNO 2 revealed that the products formed in the AS incubates are due to reaction with HNO at pH>5 but with HNO 2 at pH<4, which yields S -nitrosothiols. The results provide the first comparative study of HNO reactivity with biologically important low-mass RSHs. Furthermore, the efficient conversion of GSH to stable GSONH 2 and GSSG products is consistent with the reported depletion of intracellular GSH by HNO. At present, HNO is detected mainly by monitoring its dimerization product, N 2 O. Since N 2 O can arise from other reactions, a specific method of HNO detection is desirable. The high reactivity of thiols with HNO to form sulfinamide was examined as a method of HNO detection. The CysGlu and CysAsp dipeptides, with two negative charges at the C-terminus, exhibited high sulfinamide yields at pH {598}7.4, and are good candidates for the further development of a HNO marker