. Author manuscript; available in PMC: 2008 Dec 8.

Published in final edited form as: J Am Chem Soc. 2006 Feb 15;128(6):1859–1867. doi: 10.1021/ja056423o

Table 2.

Dissociation kinetic parameters of 33-mer peptide 1 as well as analogues 4 and 5 at pH 5.5 and pH 7.3 and 37 °C in the presence of 20 µM competing DQ2 strong binding peptide AAIAAVKEEAF.

Peptide	pH 5.5					pH 7.3
Peptide	T_50% (h)^a	A_f (%)^b	k_f (h⁻¹)	A_s (%)^c	k_s (h⁻¹)	k_off (h⁻¹)	T_1/2 (h)
1	15±3	54±8	7±1	46±8	0.022±0.002	0.019±0.003	36.5
5	25±5	30±1	3.3±0.3	70±1	0.011±0.004	0.012±0.002	57.8
4	0.8±0.1	69±3	2.1±0.4	31±3	0.10±0.06	0.020±0.002	34.6

The dissociation kinetics at pH 5.5 were fit to an exponential double decay function: Y=A_f×exp(−k_fx)+A_s×exp(−k_sx) using Kaleidagraph 3.5.

T_50% is defined as the apparent half life when 50% of overall fluorescent DQ2 signal has disappeared, i.e. x=T_50% | Y=0.5×(A_f+A_s).

A_f(%) is a measure of the fraction of ligand that dissociates in the fast phase of the dissociation curve. A_f(%)=A_f/(A_f+A_s) ×100

A_s(%) is defined as the fraction of ligand dissociating in the slow phase of the dissociation curve. A_s(%)=A_s/(A_f+A_s) ×100.

The dissociation kinetics at pH 7.3 follows a monophasic exponential decay function Y=A×exp(−k_offx). Half life T_1/2 was calculated as ln(2)/k_off.