Reaction rate, activation energy, and detection limit for the reaction of 5-furoylquinoline-3-carboxaldehyde with neurotransmitters in artificial cerebrospinal fluid

The fluorogenic reagent 5-furoylquinoline-3-carboxaldehyde (FQ) has proven valuable in the analysis of proteins and small neurotransmitters. We monito red the reaction rate between this reagent and five neurotransmitters at 40 degrees and 65 degrees C in artificial cerebrospinal fluid. The reactions followed pseudo-first order kinetics. The activation energy for the reactio n of FQ was 10.6, 10.7, 22.0, 31.4, and 34.4 kJ mol(-1) for alanine, taurin e, gamma-aminobutyric acid (GABA), glutamine, and glutamic -3 acid, respect ively. At 65 degrees C, the reaction rate was quite similar for alanine, ta urine, glutamine, and glutamic acid (1.8X10(-3) s(-1)) but was twice as fas t for GABA. A reaction time of nearly 1 h was required to quantitatively co nvert these neurotransmitters to their fluorescent products at 65 degrees C . Detection limits for the labeled neurotransmitters were 10(-9)-10(-8) M, which corresponded to 0.3-7 amol injected onto the capillary. (C) 2000 Else vier Science BN. All rights reserved.