Table 4.

Interplay of hydrophobicity and salt bridges.^[a]

Entry	template	FM	# of salt bridge[b]	Ka (×105 M−1)	Krel	−ΔG (kcal/mol)
1	WNW	none	0	35.7 ± 5.1		8.94
2	WNW	2	1	59.1 ± 5.9	1.7	9.24
3	WWW	none	0	123.5 ± 9.9		9.67
4	WWW	2	1	159.6 ± 6.5	1.3	9.83
5	WDW	none	0	15.7 ± 1.4		8.45
6	WDW	2	2	80.8 ± 7.2	5.1	9.42
7	WEW	none	0	16.2 ± 1.5		8.47
8	WEW	2	2	92.7 ± 9.2	5.7	9.50

^[a]The K_a values were determined by fluorescence titrations in Millipore water. When FM 2 was used, the FM/carboxylate ratio was kept 1.5:1 in all cases. K_rel is the binding constant of the MINP with the thiouronium FM relative to that without.

^[b]The salt bridge refers to the hydrogen bond-reinforced thiouronium–carboxylate salt bridge.