Reaction of the radical pair NO2* and CO3*- with 2-[6-(4'-amino)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF).
The fluorogenic indicator 2-[6-(4'-amino)phenoxy-3H-xanthen-3-on-9-yl]benzoic acid (APF) is used widely to detect and measure reactive nitrogen and oxygen species such as peroxynitrite, ONOO-, both in vivo and in vitro. We present in this work the results of a combined computational and experimental study to provide insights into the mechanism of the reaction of APF with the radical products of ONOO- reaction with CO2, namely NO2* and CO3*-. The experimental study on the inhibition of APF oxidation by HCO3- suggests that a direct reaction of APF with nitrosoperoxycarbonate, ONOOCO2-, is unlikely. The mechanism of APF action on NO2* and CO3*- was investigated using gas-phase and solvent modeled calculations at the MPW1K/6-311+G(d)//MPW1K/6-31G(d) level of theory. Our computational results suggest that two-electron oxidation of APF takes place in two rapid one-electron oxidation steps, the first being a proton-coupled electron transfer (PCET) between APF and NO2*, followed by addition of CO3*- and subsequent decomposition of the adduct to yield fluorescein.
Mak
Adrian Matthew
AM
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
Whiteman
Matthew
M
Wong
Ming Wah
MW
D001565:Benzoates / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D008958:Models, Molecular; D009585:Nitrogen Dioxide / Q000737:chemistry*
D001565:Benzoates; D002244:Carbon; D009585:Nitrogen Dioxide