Effect of temperature on the spectral properties of coenzyme F sub(420) and related compounds

The uv-visible spectra of 7,8-didemethyl-8-hydroxy-5-deazaflavin-5'-phosphoryllactyl glutamate (coenzyme F sub(420)), a naturally occurring 5-deazaflavin derivative, in three different buffers changed with a rise in temperature; the effect on the extinction coefficient at 420 nm ( epsilon sub(420)) was as follows: In phosphate-buffered solutions at pH < 7.5, the epsilon sub(420) increased (at pH 5.0 for a temperature shift from 15 to 60 degree C, Delta epsilon sub(420) was +87%), but between pH 7.5 and 8, epsilon sub(420) changed very little.