Controlling the Direction of S-Nitrosation versus Denitrosation: Reversible Cleavage and Formation of an S–N Bond within a Dicopper Center

Abstract

Iron and copper enzymes are known to promote reversible S-nitrosation/denitrosation in biology. However, it is unclear how the direction of S–N bond formation/scission is controlled. Herein, we demonstrate the interconversion of metal-S-nitrosothiol adduct M­(RSNO) and metal nitrosyl thiolate complex M­(NO)­(SR), which may regulate the direction of reversible S-(de)­nitrosation. Treatment of a dicopper­(I,I) complex with RSNO leads to a mixture of two structural isomers: dicopper­(I,I) S-nitrosothiol [CuICuI(RSNO)]2+ and dicopper­(II,II) nitrosyl thiolate [CuIICuII(NO)­(SR)]2+. The K eq between these two structural isomers is sensitive to temperature, the solvent coordination ability, and counterions. Our study illustrates how copper centers can modulate the direction of RS–NO bond formation and cleavage through a minor perturbation of the local environment.

Two-State Hydrogen Atom Transfer Reactivity of Unsymmetric [Cu2(O)(NO)]2+ Complexes

“…In our previous studies, we prepared the symmetric [ H L Cu 2 (O)­(NO)] 2+ species (Figure C) by activating nitrite or NO at the dicopper center. , This complex exhibits HAT, C–H hydroxylation, and S -nitrosation reactivity. , We initially assigned [ H L Cu 2 (O)­(NO)] 2+ as an S = 1/2 species based on the S = 1/2 EPR signal around 300 mT and the NO – stretch at 1554 cm –1 . However, a recent computational study by Yoshizawa and Shiota proposed an alternative S = 3/2 state for the [ H L Cu 2 (O)­(NO)] 2+ complex …”

Reductive NO Coupling at Dicopper Center via a [Cu2(NO)2]2+ Diamond-Core Intermediate

“…Given the ability of 2 to release N 2 O, we hypothesized that it might be either a dicopper hyponitrite or a dicopper nitrosyl species. Due to thermal sensitivity, only a few copper hyponitrite − ,, and copper nitrosyl complexes have been characterized. ,,− Considering literature precedence, we proposed several possible binding modes of NO: (i) dicopper (II,II) trans -hyponitrite, (ii) dicopper (II,II) cis -hyponitrite, (iii) dicopper bis-μ-NO [Cu 2 (NO) 2 ] 2+ , or (iv) dicopper mono-μ-NO [Cu 2 NO] 2+ (Scheme ).…”

“…The reactivity studies of 2 provided complementary information on the stoichiometry of Cu/NO in 2 . Considering the weak binding affinity of NO at 1 , we sought to quantify the NO released from 2 by trapping the evolved gas with cobalt­(II) porphyrin (TPP)­Co­(II) (TPP = tetraphenylporphyrin) (Figure A). ,, The resulting {CoNO} 8 product can be quantified with ultraviolet–visible (UV–vis) and 1 H NMR spectroscopy. Complex 2 was first generated in situ by treating 1 with NO at −95 °C.…”

“…Recently, our group characterized the dicopper intermediate before the formation of nitrite as a dicopper μ-oxo μ-nitrosyl species. − Reaction of three equivalents of NO with dicopper­(I) Py 4 DMB complex (Py 4 DMB = 1,2-bis­(di­(pyridin-2-yl)­methoxy)­benzene, L ) affords N 2 O (98% yield) and [ L Cu II Cu III (μ-O)­(μ-NO – )] 2+ (Scheme ). The Cu­(II), Cu­(III), O 2– , and NO – formula is based on the NO stretching frequency at 1554 cm –1 and the four-line pattern of S = 1/2 EPR signal.…”

Roles and current applications of S-nitrosoglutathione in anti-infective biomaterials

“…Therefore, Cu nanoparticles (Cu-NPs) provide an excellent option for the ion catalysis of GSNO. It is worth noting that Cu-NPs not only benefits GSNO decomposition and resultant NO production, but also interacts with other endogenous RSNOs in the blood [ 117 ] and exhibits intrinsic antimicrobial activity [ 118 , 119 ]. When using Cu-NPs to modify NO release from GSNO coated on polyvinyl chloride (PVC) (tubing for extracorporeal circulation) ( Fig.…”