<p>Table S1. Experimental values of folding and unfolding rate constants at mid-transition and under the “biologically normal” aqueous conditions for single-domain proteins (or separate domains) without disulfide bonds or covalently bound ligands</p><p>Experimental data PDB code (and the chain region, Protein Number mt if the kinetic # ln k f = w w L short name ln k ln k PDB study uses only a of mt f u L states =lnku part of the 3D structure) 1 β-hairpin (1) 2 12.0 12.0a 12.0a 16 16 1PGB (41–56) 2 Trp-cage (2) 2 13.0 12.5a 11.5a 20 20 1L2Y 3 -helix (3) 2 15.5 15.5a 15.5a 21 — — 4 BBA5 (4) 2 ≈12.5b 11.8a 13.2a 23 23 1T8J 5 Pin WW domain (5) 2 9.1 9.3a 4.2a 36 34 1PIN (6–39) 6 HP36 (6) 2 10.6 –c –c 36 36 1VII 7 FBP28 (7) 2 9.2 10.6 8.6 37 37 1E0L 8 WW prototype (7) 2 7.7 8.9 7.1 38 37 1E0M 9 psbd41 (8) 2 9.8 –c –c 41 41 2PDD 10 YAP65 (7) 2 7.0 8.4 6.7 40 40 1JMQ (5–44) 11 c-Myb (9) 2 3.1 8.7 1.7 55 54 1IDY 12 1prb (10) 2 13.3 –c –c 47 47 1PRB (7–53) E3-binding domain 13 2 8.0 11.2 6.6 47 47 2WAV of BBL (11) 14 LysM domain (12) 2 3.7 7.0 2.3 66 48 1E0G 15 hTRF1 (9) 2 1.6 5.9 1.2 53 53 1BA5 16 POB (13) 2 8.0 12.3 6.3 51 51 1W4J 17 En-HD (9) >2 8.1 10.5 7.6 54 54 1ENH 18 NTL9 (14) 2 1.9 6.6 0.1 56 56 1DIV (1–56) B1 domain of 19 2 -0.4 6.3 -1.7 62 56 1PGB protein G (14) 20 Src SH3 (14) 2 0.4 4.4 -1.3 61 56 1SRM 21 Fyn SH3 (14) 2 -2.0 4.9 -4.3 78 57 1AVZ (chain C) 22 Spectrin SH3 (14) 2 -3.7 1.1 -4.8 62 57 1SHG Pit1 homeodomain 23 >2 7.4 9.7 4.8 63 58 1AU7 (103–160) (15) 24 Abp1 SH3 (14) 2 -2.1 2.5 -2.7 68 58 1JO8 25 hRAP1 (9) 2 3.9 8.2 2.9 60 59 1FEX 26 BdpA (16) 2 5.8 11.7 4.2 58 58 1BDD (2–59) B1 domain of 27 2 -1.4 4.1 -3.3 72 60 2PTL (18–77) protein L (14) 28 Sso7d (17) 2 0.6 7.0 -3.2 64 63 1BF4 29 Ci2 (14) 2 -3.5 5.8 -10.3 64 64 2CI2 30 434 Cro (18) >2 0.3 3.7 -0.5 71 65 2CRO CspB (B. 31 2 0.2 7.2 -0.4 66 66 1C9O caldolyticus) (19) CspB (T. maritima) 32 2 -2.6 6.3 -4.0 66 66 1G6P (19) CspB (B. subtilis) 33 2 2.7 6.5 2.3 67 67 1CSP (19) 34 EC298 (14) 2 6.4 9.1 4.5 89 69 1JYG 35 CspA (20) 2 1.6 5.3 1.4 69 69 1MJC</p><p>1 36 FF domain (21) >2 2.3 7.6 1.4 71 71 1UZC 37 α3D (22) 2 12.4 –c –c 73 73 2A3D 38 Ubiquitin (14) 2 -1.5 7.3 -6.8 76 76 1UBQ 39 GW1 (14) 2 0.1 4.0 -1.7 85 76 1M9S 40 raf RBD (14) 2 -0.2 8.4 -2.8 80 78 1RFA 41 l-repressor (14) 2 5.2 10.4 3.2 80 80 1LMB 42 ADAh2 (14) 2 1.5 6.8 -0.4 81 81 1O6X C-domain of spore 43 2 -8.1 -2.0 -9.3 83 83 1PRS (91–173) coat protein S (23) apocytochrome b 44 5 2 0.1 3.0 -1.4 84 84 1EHB (24) 45 Im7* (14) 2 2.8 7.2 2.3 94 85 1AYI 46 Im9* (14) 2 -1.4 7.3 -1.9 93 85 1IMQ 47 HPr (25) 2 -3.0 2.7 -6.2 85 85 1POH 48 ACBP (Cow) (14) 2 -0.3 7.0 -3.9 86 86 1NTI 49 ACBP (Yeast) (26) >2 -0.4 8.5 6.4 86 86 1ST7 CAfn2 (B. 50 2 -3.8 1.4 -7.0 88 86 1K85 (559–644) circulans) (27) 51 PI3-SH3 (28) 2 -4.8 -1.0 -7.3 90 86 1PNJ 52 HypF-N (29) >2 -0.8 4.4 -6.8 91 88 1GXT 53 Barstar (30) >2 -1.4 3.4 -2.7 89 89 1BTB 54 TNfn3 (31) 2 -4.4 1.1 -7.7 90 89 1TEN 55 TI I27 (32) >2 -6.9 3.6 -7.6 89 89 1TIU N-domain of spore 56 2 -4.6 3.0 -9.4 90 90 1PRS (1–90) coat protein S (23) 1FNF (1326– 57 9FNIII (33) 2 -2.2 -0.9 -2.9 90 90 1415) 1DIV 58 CTL9 (14) 2 -4.4 3.3 -7.9 92 92 (58–149) 59 TWIg18' (34) 2 -5.9 0.4 -8.2 93 93 1WIT 60 hbLBD (35) 2 -4.7 -0.9 -7.8 93 93 1K8M Third PDZ domain 61 >2 -0.2 3.0 -3.4 100 93 1BFE from PSD-95 (36) 62 FNfn10 (37) >2 -0.5 5.5 -8.4 94 94 1TTF PDZ2 domain 63 >2 -1.2 0.8 -2.3 94 94 1GM1 (9–102) from PTP-BL (38) 64 FRB (39) >2 -2.4 6.0 -5.4 97 94 1AUE 65 CD2.D1 (40) >2 -3.5 1.8 -7.6 98 98 1HNG (2–99) 66 L23 (14) 2 -2.4 2.0 -3.9 96 96 1N88 67 U1A (14) 2 -0.4 4.6 -11.7 102 96 1URN 68 suc1(41) >2 -1.0 4.2 -6.1 113 96 1SCE 69 S6 (14) 2 -3.9 6.1 -8.3 101 97 1RIS 70 muscle AcP (14) 2 -7.3d -1.6d -9.0d 99 98 1APS common-type AcP 71 2 -4.4 0.8 -6.5 98 98 2ACY (42) 72 SrcSH2 (14) 2 -1.4 8.7 -3.5 110 103 1SPR 73 Death domain (43) 2 -0.6 6.8 -3.0 107 100 1E41 (93–192) 74 R16 (44) 2 -2.0 4.8 -6.0 116 106 1CUN (7–112) apocytochrome b 75 562 2 -0.1 12.3 -5.0 106 106 256B (45) 1CUN 76 R17 (44) 2 -3.4 3.4 -7.8 116 107 (113–219)</p><p>2 77 FKBP (14) 2 -5.2 1.6 -8.1 110 107 1FKB 78 P13 (46) 2 -8.5 0.0 -11.0 109 109 1QTU (1–109) 79 Barnase (47) >2 -4.3 2.6 -9.1 110 109 1RNB 80 R15 (44) 2 4.0 11.0 0.3 116 110 1U5P 81 Myotrophin (48) >2 -0.3 4.7 -3.2 118 118 2MYO 82 Hisactophilin (49) >2 -6.5 4.0 -9.0 118 118 1HCD 83 Villin 14T (50) >2 -1.6 5.0 -4.1 126 126 2VIL 84 ILBP (51) >2 -2.8 1.3 -4.9 127 127 1EAL 85 CheY (52) >2 -1.3 1.0 -4.4 129 128 3CHY 86 IFABP (53) >2 -2.8 3.4 -4.6 131 131 1IFC 87 CRBPII (53) >2 -5.0 1.4 -9.2 134 133 1OPA 88 CRABPI (53) >2 -6.7 -3.2 -9.8 138 136 1CBI 89 CheW (14) 2 -5.0 7.4 -12.1 151 143 1K0S RNase-H (C. 90 >2 -4 1.9 -14 146 146 3H08 tepidum) (54) Apoflavodoxin (D. 91 >2 -4.0 3.6 -4.8 148 147 3F6R desulfuricans) (55) Staphylococcal 92 >2 -5.3 2.3 -8.4 149 149 1JOO nuclease (56) 93 apoMb (57) >2 -1.4 1.1 -3.8 151 151 1A6N Apical domain of 94 >2 -3.4 -1.5 -5.7 155 155 1AON (191–345) GroEL (58) 95 RNase HI (59) >2 -4.6 0.1 -12.0 155 155 2RN2 96 p16 (60) >2 0.4 3.5 0.2 148 148 2A5E (9–156) 97 p19INK4d (61) >2 -1.9 2.9 -2.3 160 156 1BD8 98 DHFR (62) >2 -5.2 -3.2 -6.1 159 159 1RA9 99 CyPA (63) 2 -3.0 6.6 -10.4 164 164 1LOP 100 T4L (59) >2 -5.7 4.1 -14.0 164 164 2LZM Apoflavodoxin 101 (Anabaena sp.) 2 -0.2 2.8 -2.7 169 168 1FTG (64) 102 N-PGK (65) >2 -1.3 2.3 -4.2 175 175 1PHP (1–175) 103 C-PGK (66) >2 -5.1 -3.9 -10.8 221 219 1PHP (176–394) 104 sIGPS (67) >2 -8.9 -4.6 -13.6 222 222 1IGS (27–248) Carbonic anhydrase 105 >2 -10.6 -4.2 -24.0 260 259 1V9E (68) Trp-synthase α 106 subunit (E. coli) >2 -5.7 -2.5 -8.9 268 267 1QOP (chain A) (69) 107 VlsE (14) 2 -4.7 2.0 -8.5 338 271 1L8W(chain A)</p><p>Description of each protein includes: Column 1: “#”, the protein number. Column 2: “Protein short name” with a reference to the original experimental paper on folding kinetics. Column 3: “Number of states”: “2” means “two-state folding” and “>2” means “multi-state folding”, experimentally observed at the lowest studied denaturant concentration. mt mt Column 4: “ln k f =lnku ”, natural logarithm of the experimentally found mid-transition folding (= unfolding) rate constant measured in s-1. w w Columns 5, 6: “ln k f ”, “ ln ku ” are natural logarithms of experimentally found (see references in Column 2) folding and unfolding rate constants under “biologically normal” aqueous</p><p>3 w conditions. ln k f is either directly measured in the absence of denaturant, or extrapolated to w “normal” aqueous conditions from the region of experimentally measured folding. ln ku is obtained by linear extrapolation to “normal” aqueous conditions from the region of w w experimentally measured unfolding. ln ku  ln k f gives stability of the native state, G/RT. Column 7: “L”, the number of residues in the protein chain. Column 8: “LPDB”, the number of folded residues according to PDB. Column 9: “PDB code”, the protein 3D structure code according to the Protein Data Bank (70). If only a part of the chain was used in experiments on protein folding, this part is designated in the Table.</p><p>Notes: a w w for proteins denatured by temperature, ln k f and ln ku values refer to 25°C. b for protein # 4 (BBA5), the experimental mid-transition folding rate was not determined directly (4), since the 3D fold of this protein is unstable even at low temperatures; we take mt w w ln k f  12.5 as the average of ln k f = 11.8 and ln ku = 13.2 found at 25°C. c the point is not taken into account: the experiment was carried out at high temperatures and extrapolation of experimental results to 25°C inevitably contains a large error. d for protein # 70 (muscle AcP), the values mf  (ln k f ) / M D and mu  (ln ku ) / M D</p><p>(where MD is denaturant concentration) were erroneously interchanged in the original paper (14) (K. W. Plaxco, F. 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