Table 2. Comparison of quantum yields for trans-to-cis (t → c) and cis-to-trans (c → t) isomerisation in vacuo, in solution, and in the RNA environment. The values in vacuo and in solution are taken from ref. 32; the experimental results are taken from ref. 54, referring to irradiation at 334 nm.

Environment	Φ t→c	Φ c→t
In vacuo	0.21	0.54
Methanol	0.24	0.57
Ethylene glycol	0.24	0.67
Azo–RNA1	0.10	0.50
Azo–RNA2	0.14	0.52
Experiment (methanol)	0.155	0.39