Mmj. Oosthuizen et al., THE EFFECT OF PH ON CHEMILUMINESCENCE OF DIFFERENT PROBES EXPOSED TO SUPEROXIDE AND SINGLET OXYGEN GENERATORS, Journal of bioluminescence and chemiluminescence, 12(6), 1997, pp. 277-284
The compromised optima for high intensity chemiluminescence (CL), usin
g superoxide generators, were all above pH 9.0 for the CL probes lumin
ol and lucigenin. With luminol the optima were at pH 9.0 and 9.4 for t
he generators KO2 and hypoxanthine/xanthine oxidase (HX/XO), respectiv
ely. Lucigenin, with the same generators, produced optima at pH 9.5 an
d 10.0, respectively. The probe methyl-Cypridina-luciferin analogue (M
CLA) produced optima closer to neutral pH, which is preferred for phys
iological assessments. MCLA had optima at pH 6.0, 8.7 and 9.5 with KO2
and with HX/XO optima at pH 4.8, 6.0, 7.0 and 8.7. When CL was assess
ed at physiological pH, MCLA observed superoxide radicals with a sensi
tivity of 100- and 330-fold more than luminol or luicigenin respective
ly. For singlet oxygen, the sensitivity of MCLA at this pH was 45- and
5465-fold more than for the said probes respectively. H2O2 did not el
icit CL between pH 4 and 9.5 with any of the probes and did not influe
nce the production of superoxide or singlet oxygen when co-assessed. T
herefore CL could only be obtained when enzymes were used as converter
s. The optima for the enzyme-conversion system horseradish peroxidase
(HRP)/H2O2, and luminol, were at pH 8.0 and 9.2. Lucigenin and HRP/H2O
2 also had a biphasic CL profile with optima at pH 7.4 and 9.6. MCLA a
nd HRP/H2O2 had five optima, with the major ones at pH 6.1 and beyond
10. The optima for the myeloperoxidase/H2O system were at 8.6 and beyo
nd 10.0 when luminol and 0.15 mol/L NaBr were used. (C) 1997 John Wile
y & Sons, Ltd.