. Author manuscript; available in PMC: 2012 Feb 8.

Published in final edited form as: Biochemistry. 2011 Jan 11;50(5):882–890. doi: 10.1021/bi101813h

Table 2.

Base pair opening rates of B-form CG-10 and CGX-10 duplexes at 10°C^a


Base	k_o (s⁻¹)^b		k_slope (s⁻¹ M⁻¹)^c
Base	CG-10	CGX-10	CG-10	CGX-10
T2	260 ± 100^d	150 ± 30^d	-^e	-^e
G4	6.7 ± 0.3	4.1 ± 3.5	124 ± 3.0	196 ± 17
G6	4.2 ± 0.2	0.2 ± 0.1	58 ± 2.1	4.6 ± 0.3
T8	10 ± 4	11 ± 6	-^e	-^e

The DNA sequence is indicated as well as the position of the crosslinked base in red. The guanine base opposite to the crosslinked cytosine is indicated in bold. The terminal base pair G10 was not observed due to rapid exchange with water at pH 9.2.

The observed exchange rate at zero concentration ammonia catalyst (see eq 2).

The initial slope of the hyperbolic curve of eq 2, corresponding to the apparent second-order rate constant for general base catalysis of exchange by ammonia k_slope = (k_op/k_cl) × k_b.

Determined by linewidth measurement using eq 2 and a R₂^dip value of 19.0 Hz. derived from the narrowest imino linewidth of the CGX-10 spectra minus its k_o as determined by imino exchange experiments.

Exchange broadened beyond detectable limits.