Table 3.

Titration constants from pH dependent changes in the chemical shifts of the ¹³C-enriched carbons of Z-Ala-Ala-Phe-¹³CHO and Z-Ala-Ala-Phe-¹³COCHO when they form complexes with α-chymotrypsin.

Inhibitor	δ1 (ppm)	δ2 (ppm)	δ3 (ppm)	δ2–δ1 (ppm)	δ3–δ2 (ppm)	δ3–δ1 (ppm)	pKa1	pKa2
ZAAF-13CHOa	99.25	100.14		0.89			7.00
ZAAF-13CHOb	95.55	97.66	98.99	2.11	1.33	3.44	6.86	10.65
ZAAF-13COCHOc	100.79	104.00	104.32	3.21	0.32	3.53	5.52	7.89

^aPresent work, fitted values from Fig. 2C.

^bPresent work, fitted values from Fig. 2B.

^cFitted data from [16].