. Author manuscript; available in PMC: 2011 Oct 28.

Published in final edited form as: J Phys Chem B. 2010 Oct 28;114(42):13536–13544. doi: 10.1021/jp106406p

Table 1.

Catalytic parameters for RNase variants (measured at 0.4 μM) determined by the method of initial rates of cyclic cytidine monophosphate hydrolysis, monitored by UV-Vis spectroscopy⁴⁹. Also shown are the distances from the nitrile nitrogen to the nearest heavy atom of the imidazole ring of the catalytic His 12. Wild-type refers to intact RNase A.

	Wild-Type	pCN-RNase ^a	mCN-RNase ^a	SCN-RNase ^a
k_cat (s⁻¹)	3.0	1.7	1.5	2.5
K_m (mM)	1.8	1.1	4.0	1.7
distance (Å)	--	5	8 or 4^b	8

pCN and mCN are at position 8; -SCN is at position 13

mCN has two alternative conformations (see text and Fig 2); both distances are given.