Is the hypothiocyanite anion (OSCN)- the major product in the peroxidase catalyzed oxidation of the thiocyanate anion (SCN)-? A joint experimental and theoretical study.
The hypothiocyanate anion (OSCN)(-) is reported to be a major product of the lactoperoxidase/H(2)O(2)/(SCN)(-) system, and this anion is proposed to have significant antimicrobial properties. The collision induced (CID) negative ion mass spectrum of "(OSCN)(-)" has been reported: there is a pronounced parent anion at m/z 74, together with fragment anions at m/z 58 (SCN)(-) and 26 (CN)(-). These fragment anions are consistent with structure (OSCN)(-). However there is also a lesser peak at m/z 42 (OCN(-) or CNO(-)) in this spectrum which is either formed by rearrangement of (OSCN)(-) or from an isomer of this anion. The current theoretical investigation of (OSCN)(-) and related isomers, together with the study of possible rearrangements of these anions, indicates that ground-state singlet (OSCN)(-) is a stable species and that isomerization is unlikely. The three anions (OSCN)(-), (SCNO)(-), and (SNCO)(-) have been synthesized (in the ion source of a mass spectrometer) by unequivocal routes, and their structures have been confirmed by a consideration of their collision induced (negative ion) and charge reversal (positive ion) mass spectra. The CID mass spectrum of (SCNO)(-) shows formation of m/z 42 (CNO(-)), but the corresponding spectra of (OSCN)(-) or (SNCO)(-) lack peaks at m/z 42. Combined theoretical and experimental data support earlier evidence that the hypothiocyanite anion is a major oxidation product of the H(2)O(2)/(SCN)(-) system. However, the formation of m/z 42 in the reported CID spectrum of "(OSCN)(-)" does not originate from (OSCN)(-) but from another isomer, possibly (SCNO)(-).
Dua
Suresh
S
Department of Chemistry, The University of Adelaide, South Australia, 5005.
Maclean
Micheal J
MJ
Fitzgerald
Mark
M
McAnoy
Andrew M
AM
Bowie
John H
JH
D000890:Anti-Infective Agents / Q000737:chemistry; D002384:Catalysis; D007536:Isomerism; D007784:Lactoperoxidase / Q000737:chemistry*; D013058:Mass Spectrometry; D008954:Models, Biological; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013861:Thiocyanates / Q000138:chemical synthesis / Q000737:chemistry*
D000890:Anti-Infective Agents; D013861:Thiocyanates; C014607:hypothiocyanite ion; D007784:Lactoperoxidase; C031760:thiocyanate