Lactoperoxidase-catalyzed oxidation of thiocyanate by hydrogen peroxide: a reinvestigation of hypothiocyanite by nuclear magnetic resonance and optical spectroscopy.
In an effort to reconcile conflicting reports regarding the spectra of the human defense factor hypothiocyanite (OSCN(-)), we have synthesized OSCN(-) by three methods and characterized the product spectroscopically. Method I is lactoperoxidase-catalyzed oxidation of SCN(-) by H(2)O(2) at pH 7. Method II is hydrolysis of (SCN)(2) at pH 13. Method III is oxidation of SCN(-) by OX(-) (X = Cl and Br) at pH 13. All three methods produced essentially the same initial UV, (13)C NMR, and (15)N NMR spectra. The UV spectrum reveals a lambda(max) of 376 nm, which is a previously unreported distinguishing feature. The (13)C NMR spectrum (delta = 127.8 ppm at pH 13 vs dioxane at 66.6 ppm) is comparable to those that have been previously reported for OSCN(-) as prepared by methods I and II (although in some cases different assignments have been made). However, the (15)N NMR spectrum we measure (delta = -80.6 ppm at pH 13 vs NO(3)(-) at 0 ppm) contrasts with previous reports. We conclude that all three methods produce the same species, and the spectra are now self-consistent with the formulation OSCN(-).
Nagy
Péter
P
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA.
Alguindigue
Susan S
SS
Ashby
Michael T
MT
D002247:Carbon Isotopes; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D066298:In Vitro Techniques; D007784:Lactoperoxidase / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009587:Nitrogen Isotopes; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D013861:Thiocyanates / Q000737:chemistry / Q000378:metabolism*
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D013861:Thiocyanates; C014607:hypothiocyanite ion; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; C031760:thiocyanate