S.Pakalnis, V.Sitas, H.Schneckenburger, R.Rotomskis
Picosecond absorption spectroscopy of biologically active pigments NADH, FMN and fluorescence marker Rhodamine-123

In summary, to our knowledge we have performed the first measurements of the excited state dynamics of Rh-123, NADH, and FMN in aqueous solution by picosecond transient spectroscopy. According to our investigations, rapid formation of transient species occurs immediately after excitation of the biologically active pigments NADH, FMN in aqueous solution. The
excited state lifetime of the fluorescence marker Rh-123 in the aqueous solution is about 3.7 ns. FMN exhibits biexponential transient absorption relaxation kinetics with relaxation lifetimes t1 around 170 ps and t2 around 4.7 ns. The short relaxation lifetime of transient absorption might be related to intermediate states appearing during formation of the long-lived photoproduct. Further experiments are needed to characterize this photoproduct and its intermediate states. For more precise measurements of energy relaxation in aqueous solution of NADH, photostability of NADH has either to be studied in detail, or experimental conditions have to be established at which NADH is sufficiently stable.


We wish to express our gratitude to Dr V.Vaicaitis for his assistance in making preliminary experiments on picosecond laser spectroscopy. Financial support by the Lithuanian State Science and Studies Foundation is gratefully acknowledged.

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