Table 2.

Comparison of excited-state lifetime values of native and alternative nucleobases in aqueous solution.^[a]

Nucleobase	Excited-state lifetimes (τ, ps)	Reference
Uncharged bases (neutral pH 6.8–7.3)
Hypoxathine	0.13 ± 0.3	[29]
Adenine	0.18 ± 0.3	[34]
Guanine(as Guanosine)	0.16[b]	[35]
Xanthine	0.28–0.50[c]	[29]
Cytosine	1.0 ± 0.2, 2.9, 12	[36]
Uracil	1.9 ± 0.1, 24 ± 0.2	[36b]
Thymine	2.8 ± 0.1, 30 ± 13	[36b]
5-Methylcytosine	7.2 ± 0.4	[36a]
N4-Acetylcytosine	280 ± 30	[36a]
2,4-Diaminopyrimidine	10–1000[a] (gas)	[37]
5-Hydroxyuracil	1800[a]	[38]
2,6-Diaminopurine	6300 ± 400[a] (gas)	[37]
2-Aminopurine	11800	[39]
Cation charged bases (pH 0–2) via protonatation
Guanine	191 ± 4[b]	[40]
Hypoxanthine	<0.2	[35]
5-Methylcytosine	2.57 ± 0.22	[36a]
Anion charged bases (pH 13)
Hypoxanthine (pH 10)	19	[35]
Cytosine	13.3 ± 0.4	[36a]
5-Methylcytosine	250 ± 30	[36a]

^[a]Gas-phase experimental studies.

^[b]Due to solubility problems with guanine, the community has relied on the value obtained from deoxyguanosine and guanosine to model/approximate nucleobase values.

^[c]Expected value range based on the derivatives used in the study.