HNO to NO Conversion Mechanism with Copper Zinc Superoxide Dismutase, Comparison with Heme Protein Mediated Conversions, and the Origin of Questionable Reversibility.

The interconversion of NO and HNO, via copper zinc superoxide dismutase (CuZnSOD), is important in biomedicine and for HNO detection. Many mechanistic questions, including the decades-long debate on reversibility, were resolved in this work. Calculations of various active-site and full-protein models show that the basic mechanism is proton-coupled electron transfer with a computed barrier of 10.

Why copper is preferred over iron for oxygen activation and reduction in haem-copper oxidases.

Haem-copper oxidase (HCO) catalyses the natural reduction of oxygen to water using a haem-copper centre. Despite decades of research on HCOs, the role of non-haem metal and the reason for nature's choice of copper over other metals such as iron remains unclear. Here, we use a biosynthetic model of HCO in myoglobin that selectively binds different non-haem metals to demonstrate 30-fold and 11-fold enhancements in the oxidase activity of Cu- and Fe-bound HCO mimics, respectively, as compared with Zn-bound mimics.

Toward Relatively General and Accurate Quantum Chemical Predictions of Solid-State (17)O NMR Chemical Shifts in Various Biologically Relevant Oxygen-Containing Compounds.

Oxygen is an important element in most biologically significant molecules, and experimental solid-state (17)O NMR studies have provided numerous useful structural probes to study these systems. However, computational predictions of solid-state (17)O NMR chemical shift tensor properties are still challenging in many cases, and in particular, each of the prior computational works is basically limited to one type of oxygen-containing system. This work provides the first systematic study of the effects of geometry refinement, method, and basis sets for metal and nonmetal elements in both geometry optimization and NMR property calculations of some biologically relevant oxygen-containing compounds with a good variety of XO bonding groups (X = H, C, N, P, and metal).

HNO/NO Conversion Mechanisms of Cu-Based HNO Probes with Implications for Cu,Zn-SOD.

HNO has broad biological effects and pharmacological activities. Direct HNO probes for in vivo applications were recently reported, which are Cu-based complexes having fluorescence reporters with reaction to HNO resulting in Cu systems and the release of NO. Their coordination environments are similar to that in Cu,Zn-superoxide dismutase (SOD), which plays a significant role in cellular HNO/NO conversion.