THE FLUORESCENCE DECAY OF REDUCED NICOTINAMIDES IN AQUEOUS SOLUTION AFTER EXCITATION WITH A UV‐MODE LOCKED Ar ION LASER

Abstract

The fluorescence decay kinetics of the reduced nicotinamides NMNH, NADH and NADPH in aqueous solution were investigated using an Ar ion laser, mode locked in the UV, as source of excitation and single photon counting electronics in the detection system allowing for a time resolution in the picosecond range. Analysis of the experimental fluorescence decay showed that the dinucleotides did not follow a single exponential decay law. Good fitting was accomplished with a sum of two exponentials. The mononucleotide fluorescence decay was a single exponential for at least 95% of its amplitude.The heterogeneity in lifetimes of the fluorescence of the dinucleotides was interpreted in terms of an exciplex mechanism. INTRODUaIONThe fluorescence decay kinetics of the reduced nicotinamide nucleotides NMNH (reduced b-nicotinamide mononucleotide), NADH (reduced b-nicotinamide adenine dinucleotide) and NADPH (reduced p-nicotinamide adenine dinucleotide phosphate) have received

Nanosecond time-resolved circular polarization of fluorescence: study of NADH bound to horse liver alcohol dehydrogenase.

“…4 presents the CD spectra of NADH in the binary complex with LADH and in the ternary LADH-NADH-IBA complex. In contrast to the steady-state CPL signals mentioned above, the CD spectra of these two complexes are practically identical, in agreement with previous reports (5,16), and the anisotropy factor calculated from the CD and (17)(18)(19). These increases are due to unstacking of the adenine and nicotinamide rings of the coenzyme and to shielding of the fluorophore from aqueous solvent as shown by crystallographic studies (20).…”

“…These increases are due to unstacking of the adenine and nicotinamide rings of the coenzyme and to shielding of the fluorophore from aqueous solvent as shown by crystallographic studies (20). The increased fluorescence of the ternary complex apparently reflects its higher rigidity (5,18,19,21). The fluorescence of NADH, both free and LADH-bound, has previously been found to decay nonexponentially, an observation that was explained in terms of either ground-state heterogeneity (18) or excited-state interaction of the nicotinamide ring (19).…”

“…The increased fluorescence of the ternary complex apparently reflects its higher rigidity (5,18,19,21). The fluorescence of NADH, both free and LADH-bound, has previously been found to decay nonexponentially, an observation that was explained in terms of either ground-state heterogeneity (18) or excited-state interaction of the nicotinamide ring (19). Our data (not shown) confirms the nonexponentiality of the fluorescence decay of both binary and ternary complexes, which can be fit well by three and two exponentials, respectively.…”

Excited-State Dynamics of NADH and 1-N-Propyl-1,4Dihydronicotinamide

“…max at 460 nm and has been used for in ~ assays of NADH. The photophysics of NADH has been .extensively studied (1)(2)(3)(4)(5)(6)(7)(8)(9). In room temperature aqueous solution, the fluorescence quantum yield is 0.…”

“…02 and the llf.etime -0·. 40 ns (3)(4)(5) • Recently, biphotonic induced electron ejection by NADH has been reported (9]. NADH reportedly exists in aqueous solution:in two conformations--extended and folded (3,5, 101 • The present study reports time-resolved emission and transient absorption studies on the disodium salt of NADH and on a simple analog, 1-Npropyl-1,4-dihydronicotinamide (~NH), (shown below) in several solvents.…”