Table 2.

Predicted contributions to the m-value/RT or μ₂₃/RT for exposure of 1,000 Å² of protein surface

	Process						Surface of native protein‡
Surface type, i	Globular protein unfolding*			α-helix melting†
	∆ASA	Urea§	GB§	∆ASA	Urea§	GB§	ASA	Urea§	GB§
Amide O	120	−0.10	0.34	480	−0.42	1.34	100	−0.09	0.28
Carboxylate O	40	−0.02	0.12	100	−0.04	0.29	160	−0.06	0.46
Hydroxyl O	30	−0.01	0.0	0	0	0	20	−0.01	0.0
Amide N	50	−0.02	−0.10	90	−0.03	−0.18	40	−0.01	−0.08
Cationic N	40	0.01	−0.05	0	0	0	130	0.02	−0.16
Aliphatic C	650	−0.07	0.20	330	−0.04	0.10	530	−0.06	0.16
Aromatic C	70	−0.06	−0.16	0	0	0	20	−0.02	−0.05
Predicted m-value/RT or μ23/RT per 1,000 Å2 of surface:		−0.27	0.35		−0.53	1.55		−0.22	0.61
Experimentally derived value:		−0.31	0.34		−1.01	ND		−0.21	1.31

^*Globular protein m- value/RT are from the average of the Hong et al. protein dataset (13) with the addition of trp cage (30) for urea, and from lacDBD (15) for GB. Both are scaled to 1,000 Å².

^†Average observed α-helix unfolding m-value/RT for urea is calculated by multiplying the average residue urea m-value/RT of (AEAAKA)_n peptides [-0.039 M^-1; (19)] by 26, the number of residues needed to expose approximately 1,000 Å² of surface in unfolding this α-helix.

^‡Modeled using urea- and GB-BSA interaction data and BSA surface composition from refs. 4 and 18, scaled to 1,000 Å² of surface.

^§Contribution to unfolding m-value/RT or urea-native protein μ₂₃/RT from each surface type (i), calculated from (α_i values from Table 1) × ΔASA_i.