Corrigenda

Abstract

On p. 624, lines 4 and 5, the J values should be interchanged.

Fluorescent Tautomers and the Apparent Photophysics of Adenine and Guanine

“…1A (Longworth et al, 1966). This does not seem to be the case; the 7-MA phosphorescence peaks are at 372, 392 and 412 nm, whereas the AMP peaks are at 381, 403 and 428 nm (Longworth et al, 1966; we have also found similar values in this laboratory). We conclude that moving the substitution from the 7 to the 9 position does not broaden the phosphorescence, but does broaden the fluorescence.…”

“…The question arises because the AMP phosphorescence is quite structured, at first glance appearing identical to the phosphorescence of 7-MA in Fig. 1A (Longworth et al, 1966). This does not seem to be the case; the 7-MA phosphorescence peaks are at 372, 392 and 412 nm, whereas the AMP peaks are at 381, 403 and 428 nm (Longworth et al, 1966; we have also found similar values in this laboratory).…”

“…(This is because the bases are attached to the phosphate backbone in DNA through a ribose at the 9 position.) In early studies of the luminescence of adenine and guanine (Callis et al, 1964;Longworth et al, 1966), the implicit assumption was made that the observed emission was from the species with the proton at the 9 position ; at the time there was no reason to think otherwise.…”

An Epr Study on the Triplet State of Purine Free Base in Aqueous Glasses at 77 K

“…Excited singlet states can be deactivated by emission of Ruorescence and/or by radiationless transitions. Fluorescence yields have not been reported for the different (Longworth, 1962;Longworth et al, 1966) for PuH and the ionic forms of adenine are low, in the order of lo-'. Thus, the observed difference in the triplet yield for the charged forms of purine which have similar triplet states is interpreted in terms of a higher probability in nonradiative processes from the first excited singlet state of purine in its cationic form than in the other ionic forms or can be due to changes in the electronic state of the excited singlet state.…”

“…purine in ethylene glycol-water (1 : 1) glasses at 77 K. A value of 2.2 s was determined by Aaron and Winefordner (1973) in a methanol-water mixture (1:9) at 77 K. In inert matrices of methane, Ar and sulfurhexafluoride, phosphorescence decay lifetimes of 1.6, 1.9 and 1.9s have been measured by Smith (1977). Longworth (1962) has determined from luminescence studies a phosphorescence-fluorescence yield of 1.9 and a fluorescence yield of 0.02 for purine free base in 50% propane-l,Zdiol, 50% 0.01 M phosphate buffer glass at 77K, thus a phosphorescence yield of 0.04 can be calculated.…”