1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 0.00000 0.00000 0.00000 Zhang, J.Y. Hong, M. http://mmcif.pdb.org/dictionaries/ascii/mmcif_pdbx.dic C2 H4 O 44.053 ACETYL GROUP non-polymer C5 H10 N2 O3 146.144 y GLUTAMINE L-peptide linking C6 H10 N3 O2 1 156.162 y HISTIDINE L-peptide linking C6 H13 N O2 131.173 y ISOLEUCINE L-peptide linking C6 H13 N O2 131.173 y LEUCINE L-peptide linking H2 N 16.023 AMINO GROUP non-polymer C5 H11 N O2 117.146 y VALINE L-peptide linking N 1 N C N 2 N O N 3 N C N 4 N H N 5 N H N 6 N H N 7 N H N 8 N N N 9 S C N 10 N C N 11 N O N 12 N C N 13 N C N 14 N C N 15 N O N 16 N N N 17 N O N 18 N H N 19 N H N 20 N H N 21 N H N 22 N H N 23 N H N 24 N H N 25 N H N 26 N H N 27 N H N 28 N N N 29 S C N 30 N C N 31 N O N 32 N C Y 33 N C Y 34 N N Y 35 N C Y 36 N C Y 37 N N N 38 N O N 39 N H N 40 N H N 41 N H N 42 N H N 43 N H N 44 N H N 45 N H N 46 N H N 47 N H N 48 N H N 49 N N N 50 S C N 51 N C N 52 N O N 53 S C N 54 N C N 55 N C N 56 N C N 57 N O N 58 N H N 59 N H N 60 N H N 61 N H N 62 N H N 63 N H N 64 N H N 65 N H N 66 N H N 67 N H N 68 N H N 69 N H N 70 N H N 71 N N N 72 S C N 73 N C N 74 N O N 75 N C N 76 N C N 77 N C N 78 N C N 79 N O N 80 N H N 81 N H N 82 N H N 83 N H N 84 N H N 85 N H N 86 N H N 87 N H N 88 N H N 89 N H N 90 N H N 91 N H N 92 N H N 93 N N N 94 N H N 95 N H N 96 N N N 97 S C N 98 N C N 99 N O N 100 N C N 101 N C N 102 N C N 103 N O N 104 N H N 105 N H N 106 N H N 107 N H N 108 N H N 109 N H N 110 N H N 111 N H N 112 N H N 113 N H N 114 N H N 1 N doub N 2 N sing N 3 N sing N 4 N sing N 5 N sing N 6 N sing N 7 N sing N 8 N sing N 9 N sing N 10 N sing N 11 N sing N 12 N sing N 13 N doub N 14 N sing N 15 N sing N 16 N sing N 17 N sing N 18 N sing N 19 N sing N 20 N sing N 21 N doub N 22 N sing N 23 N sing N 24 N sing N 25 N sing N 26 N sing N 27 N sing N 28 N sing N 29 N sing N 30 N sing N 31 N sing N 32 N doub N 33 N sing N 34 N sing N 35 N sing N 36 N sing Y 37 N sing Y 38 N doub Y 39 N doub N 40 N sing Y 41 N sing N 42 N sing Y 43 N sing N 44 N sing N 45 N sing N 46 N sing N 47 N sing N 48 N sing N 49 N sing N 50 N sing N 51 N sing N 52 N sing N 53 N doub N 54 N sing N 55 N sing N 56 N sing N 57 N sing N 58 N sing N 59 N sing N 60 N sing N 61 N sing N 62 N sing N 63 N sing N 64 N sing N 65 N sing N 66 N sing N 67 N sing N 68 N sing N 69 N sing N 70 N sing N 71 N sing N 72 N sing N 73 N sing N 74 N doub N 75 N sing N 76 N sing N 77 N sing N 78 N sing N 79 N sing N 80 N sing N 81 N sing N 82 N sing N 83 N sing N 84 N sing N 85 N sing N 86 N sing N 87 N sing N 88 N sing N 89 N sing N 90 N sing N 91 N sing N 92 N sing N 93 N sing N 94 N sing N 95 N sing N 96 N sing N 97 N doub N 98 N sing N 99 N sing N 100 N sing N 101 N sing N 102 N sing N 103 N sing N 104 N sing N 105 N sing N 106 N sing N 107 N sing N 108 N sing US Proc.Natl.Acad.Sci.USA PNASA6 0040 1091-6490 123 e2618039123 e2618039123 10.1073/pnas.2618039123 42696554 Peptides adopt stable omega-loop structures in concentrated sulfuric acid. 2026 0000-0002-1921-4848 0000-0002-6892-6948 0000-0001-5255-5858 10.2210/pdb12uf/pdb pdb_000012uf 10.13018/BMR31302 885.087 HHQ peptide 1 syn polymer no yes (ACE)IHVHLQI(NH2) XIHVHLQIX A polypeptide(L) n n n n n n n n n repository Initial release 1 0 2026-09-16 United States Other private G-2023-20929 meihong@mit.edu 0000-0001-5255-5858 Mei Hong principal investigator/group leader HHQ peptide structure in 98% H2SO4 N RCSB Y RCSB 2026-04-19 REL REL 32630 synthetic construct sample 1 9 N Y A ACE 0 Terminal acetylation A ACE 1 A ILE 1 ILE A ILE 2 1_555 ACE 3 1_555 None A NH2 8 Terminal amidation A NH2 9 A ILE 7 ILE A ILE 8 1_555 NH2 3 1_555 None structures with the lowest energy 1000 20 isotropic 1 2D 1H-1H NOESY isotropic 1 2D 1H-13C HMQC isotropic 1 2D 1H-15N HSQC isotropic 1 3D HNHA 20 mg/mL natural abundance 98 % w/w natural abundance 1 mg/mL natural abundance 18.4 M condition_1 0 pH 1 atm 293 K na 1 lowest energy 20 mg/mL HHQ peptide, 98 % w/w H2SO4, 1 mg/mL Dimethyl sulfone, 98% H2SO4/2% H2O NA_HHQ 98% H2SO4/2% H2O solution CCPN chemical shift assignment CcpNmr Analysis Schwieters, Kuszewski, Tjandra and Clore structure calculation X-PLOR NIH 800 Bruker AVANCE III ACE 0 n 1 ACE 0 A ILE 1 n 2 ILE 1 A HIS 2 n 3 HIS 2 A VAL 3 n 4 VAL 3 A HIS 4 n 5 HIS 4 A LEU 5 n 6 LEU 5 A GLN 6 n 7 GLN 6 A ILE 7 n 8 ILE 7 A NH2 8 n 9 NH2 8 A author_and_software_defined_assembly 1 monomeric not applicable NMR Distance Restraints 1.0 0.0 0.0 0.0 1.0 0.0 0.0 0.0 1.0 1_555 x,y,z identity operation 0.0 0.0 0.0 1 A VAL 3 -167.84 93.87 1 A LEU 5 -160.05 -36.68 1 A GLN 6 -137.30 -57.86 2 A VAL 3 -167.61 94.16 2 A LEU 5 -159.83 -36.55 2 A GLN 6 -139.04 -57.72 3 A VAL 3 -167.48 94.30 3 A LEU 5 -159.80 -35.70 3 A GLN 6 -140.16 -58.38 4 A VAL 3 -166.83 92.30 4 A LEU 5 -159.47 -35.61 4 A GLN 6 -142.36 -56.74 5 A VAL 3 -167.08 92.93 5 A LEU 5 -159.94 -36.90 5 A GLN 6 -136.45 -57.73 6 A VAL 3 -166.80 92.26 6 A LEU 5 -159.75 -37.44 6 A GLN 6 -136.05 -57.92 7 A VAL 3 -166.94 92.92 7 A LEU 5 -159.92 -37.79 7 A GLN 6 -135.63 -57.73 8 A VAL 3 -167.26 93.69 8 A LEU 5 -159.75 -36.52 8 A GLN 6 -136.73 -57.93 9 A VAL 3 -167.45 94.74 9 A LEU 5 -159.65 -35.49 9 A GLN 6 -140.90 -57.29 10 A VAL 3 -167.69 100.36 10 A HIS 4 36.39 56.86 10 A LEU 5 -158.74 -39.17 10 A GLN 6 -136.54 -48.51 11 A VAL 3 -166.36 92.21 11 A LEU 5 -160.08 -31.78 11 A GLN 6 -145.61 -57.18 12 A VAL 3 -167.78 92.66 12 A LEU 5 -159.26 -37.44 12 A GLN 6 -133.05 -64.87 13 A VAL 3 -166.74 92.81 13 A LEU 5 -159.89 -35.00 13 A GLN 6 -141.11 -56.35 14 A VAL 3 -167.63 94.10 14 A LEU 5 -160.09 -36.67 14 A GLN 6 -135.86 -58.26 15 A VAL 3 -167.00 100.80 15 A HIS 4 35.88 57.63 15 A LEU 5 -159.00 -40.17 15 A GLN 6 -134.69 -50.34 16 A LEU 5 -157.80 -64.25 17 A VAL 3 -167.61 92.02 17 A LEU 5 -159.01 -37.48 17 A GLN 6 -133.11 -65.28 18 A VAL 3 -167.63 102.59 18 A HIS 4 36.21 56.72 18 A LEU 5 -159.14 -33.71 18 A GLN 6 -142.59 -52.40 19 A VAL 3 -167.05 100.05 19 A HIS 4 36.78 57.76 19 A LEU 5 -158.73 -35.18 19 A GLN 6 -143.12 -57.03 20 A VAL 3 -167.23 100.22 20 A HIS 4 36.73 57.82 20 A LEU 5 -158.78 -35.18 20 A GLN 6 -143.06 -57.16 N NMR structure of HHQ peptide in 98% H2SO4 1 N N covale 1.330 both A ACE 0 A C ACE 1 1_555 A ILE 1 A N ILE 2 1_555 covale 1.327 both A ILE 7 A C ILE 8 1_555 A NH2 8 A N NH2 9 1_555 DE NOVO PROTEIN protein folding, concentrated sulfuric acid, exoplanet, Venus cloud, DE NOVO PROTEIN 12UF PDB 1 1 12UF 0 8 12UF 0 8 12UF A 1 1 9