Computational investigations of HNO in biology

Abstract

HNO (nitroxyl) has been found to have many physiological effects in numerous biological processes. Computational investigations have been employed to help understand the structural properties of HNO complexes and HNO reactivities in some interesting biologically relevant systems. The following computational aspects were reviewed in this work: 1) structural and energetic properties of HNO isomers; 2) interactions between HNO and non-metal molecules; 3) structural and spectroscopic properties of HNO metal complexes; 4) HNO reactions with biologically important non-metal systems; 5) involvement of HNO in reactions of metal complexes and metalloproteins. Results indicate that computational investigations are very helpful to elucidate interesting experimental phenomena and provide new insights into unique structural, spectroscopic, and mechanistic properties of HNO involvement in biology.

Acidity and Hydrogen Exchange Dynamics of Iron(II)‐Bound Nitroxyl in Aqueous Solution

“…In general, the computed NMR chemical shifts for [Fe II (CN) 5 (HNO)] 3À are in reasonable agreement with our experimental data. In addition, our computational results are also consistent with those reported by Zhang and co-workers [26] on 1 H and 15 N chemical shifts. As mentioned earlier, since [Fe(CN) 5 (HNO)] 3À is too unstable at pH values greater than 11, we were unable to obtain 15 N and 17 O chemical shifts for [Fe II (CN) 5 (NO)] 4À .…”

“…As mentioned earlier, since [Fe(CN) 5 (HNO)] 3À is too unstable at pH values greater than 11, we were unable to obtain 15 N and 17 O chemical shifts for [Fe II (CN) 5 (NO)] 4À . However, two recent reports on analogous Fe II -NO À complexes suggest that the 15 N chemical shift for the deprotonated Fe II -bound nitroxyl is about d = 1100-1200 ppm (relative to liquid [26] the computed NMR chemical shifts shown in Table 1 are reasonable. The exceedingly large reduction in both 15 N and 17 O chemical shifts, upon coordination of HNO to Fe II , is entirely consistent with the observation in C-nitroso compounds and can be largely attributed to the paramagnetic shielding contributions resulting from magnetic-field induced mixing between occupied and unoccupied MOs.…”

Solvation and Proton-Coupled Electron Transfer Reduction Potential of 2NO• to 1HNO in Aqueous Solution: A Theoretical Investigation

“…Computational chemistry calculations have assisted the understanding of several structural, spectroscopic, and mechanistic properties related to the chemistry and biochemistry of HNO and NO . However, despite the size of the system, the proton-coupled electron transfer reduction of NO to 1 HNO in aqueous solution, as far as we know, has not yet been addressed by these calculations.…”

Photolytic mechanisms of hydroxylamine

“…17 HNO is a reactive radical with a rather long lifetime (0.1 s), 18 and it has been studied extensively both experimentally and theoretically. 8 Although computational studies have suggested the formation of triplet HNO ( 3 HNO), the bent structure in the singlet state ( 1 HNO) was concluded to be the most stable, 19 with a singlet-triplet energy gap of 77 kJ mol À1 . 20 Using thermodynamic data, the threshold wavelength (l thres ) for the formation of HNO and H 2 aer excitation of NH 2 OH by 193 nm-UV radiation was predicted to be 891 nm (1.39 eV).…”