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Platzer G, Okon M, McIntosh LP. pH-dependent random coil (1)H, (13)C, and (15)N chemical shifts of the ionizable amino acids: a guide for protein pK a measurements. JOURNAL OF BIOMOLECULAR NMR 2014; 60:109-129. [PMID: 25239571 DOI: 10.1007/s10858-014-9862-y] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/09/2014] [Indexed: 06/03/2023]
Abstract
The pK a values and charge states of ionizable residues in polypeptides and proteins are frequently determined via NMR-monitored pH titrations. To aid the interpretation of the resulting titration data, we have measured the pH-dependent chemical shifts of nearly all the (1)H, (13)C, and (15)N nuclei in the seven common ionizable amino acids (X = Asp, Glu, His, Cys, Tyr, Lys, and Arg) within the context of a blocked tripeptide, acetyl-Gly-X-Gly-amide. Alanine amide and N-acetyl alanine were used as models of the N- and C-termini, respectively. Together, this study provides an essentially complete set of pH-dependent intra-residue and nearest-neighbor reference chemical shifts to help guide protein pK a measurements. These data should also facilitate pH-dependent corrections in algorithms used to predict the chemical shifts of random coil polypeptides. In parallel, deuterium isotope shifts for the side chain (15)N nuclei of His, Lys, and Arg in their positively-charged and neutral states were also measured. Along with previously published results for Asp, Glu, Cys, and Tyr, these deuterium isotope shifts can provide complementary experimental evidence for defining the ionization states of protein residues.
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Affiliation(s)
- Gerald Platzer
- Department of Biochemistry and Molecular Biology, Life Sciences Centre, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
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2
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Gasymov OK, Abduragimov AR, Glasgow BJ. Cation-π interactions in lipocalins: structural and functional implications. Biochemistry 2012; 51:2991-3002. [PMID: 22439821 DOI: 10.1021/bi3002902] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cation-π interaction impacts protein folding, structural stability, specificity, and molecular recognition. Cation-π interactions have been overlooked in the lipocalin family. To fill this gap, these interactions were analyzed in the 113 crystal and solution structures from the lipocalin family. The cation-π interactions link previously identified structurally conserved regions and reveal new motifs, which are beyond the reach of a sequence alignment algorithm. Functional and structural significance of the interactions were tested experimentally in human tear lipocalin (TL). TL, a prominent and promiscuous lipocalin, has a key role in lipid binding at the ocular surface. Ligand binding modulation through the loop AB at the "open" end of the barrel has been erroneously attributed solely to electrostatic interactions. Data revealed that the interloop cation-π interaction in the pair Phe28-Lys108 contributes significantly to stabilize the holo-conformation of the loop AB. Numerous energetically significant and conserved cation-π interactions were uncovered in TL and throughout the lipocalin family. Cation-π interactions, such as the highly conserved Trp17-Arg118 pair in TL, were educed in low temperature experiments of mutants with Trp to Tyr substitutions.
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Affiliation(s)
- Oktay K Gasymov
- Department of Pathology and Jules Stein Eye Institute, University California at Los Angeles, California 90095, USA.
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Binst GV, Biesemans M, Barel AO. Comparative Carbon-13 Nuclear Magnetic Resonance Study at 67.9 MHz on Lysozyme (Human and Egg-White) and α-Lactalbumin (Human and Bovine) in Their Native and Denatured State. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/bscb.19750840101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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4
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Gasymov OK, Abduragimov AR, Glasgow BJ. pH-Dependent conformational changes in tear lipocalin by site-directed tryptophan fluorescence. Biochemistry 2010; 49:582-90. [PMID: 20025287 DOI: 10.1021/bi901435q] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Tear lipocalin (TL), a major protein of human tears, binds a broad array of endogenous ligands. pH-dependent ligand binding in TL may have functional implications in tears. Previously, conformational selections of the AB and GH loops have been implicated in ligand binding by site-directed tryptophan fluorescence (SDTF). In this study, SDTF was applied to the AB and GH loops to investigate pH-driven conformational changes relevant to ligand binding. Both loops demonstrate significant but distinct conformational rearrangements over a wide pH range. In the low-pH transition, from 7.3 to 3.0, residues of the GH loop exhibit decreased solvent accessibilities. In acrylamide quenching experiments, the average quenching rate constant (k(q), accessibility parameter) of the residues in the GH loop is decreased approximately 38%, from 2.1 x 10(9) to 1.3 x 10(9) M(-1) s(-1). However, despite the significant changes in accessibilities for some residues in the AB loop, the average accessibility per residue remained unchanged (average k(q) = 1.2 M(-1) s(-1)). Accordingly, the low-pH transition induces conformational changes that reshuffle the accessibility profiles of the residues in the AB loop. A significant difference in the titration curves between the holo and apo forms of the W28 mutant suggests that the protonation states of the residues around position 28 modulate conformational switches of the AB loop relevant to ligand binding.
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Affiliation(s)
- Oktay K Gasymov
- Department of Pathology, UCLA School of Medicine, Jules Stein Eye Institute, 100 Stein Plaza, Los Angeles, California 90095, USA
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Matzen L, Engesgaard A, Ebert B, Didriksen M, Frølund B, Krogsgaard-Larsen P, Jaroszewski JW. AMPA receptor agonists: synthesis, protolytic properties, and pharmacology of 3-isothiazolol bioisosteres of glutamic acid. J Med Chem 1997; 40:520-7. [PMID: 9046343 DOI: 10.1021/jm9607212] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A number of 3-isothiazolol bioisosteres of glutamic acid (1) and analogs of the AMPA receptor agonist, (RS)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl)propionic acid (AMPA, 2a), including (RS)-2-amino-3-(3-hydroxy-5-methylisothiazol-4-yl)propionic acid (thio-AMPA, 2b), were synthesized. Comparative in vitro pharmacological studies on this series of 3-isothiazolol and the corresponding 3-isoxazolol amino acids were performed using a series of receptor binding assays (IC50 values) and the electrophysiological rat cortical slice model (EC50 values). Whereas 2a (IC50 = 0.04 +/- 0.005 microM, EC50 = 3.5 +/- 0.2 microM) is markedly more potent than the tert-butyl analog ATPA (3a) (IC50 = 2.1 +/- 0.16 microM, EC50 = 34 +/- 2.4 microM) in [3H]AMPA binding and electrophysiological studies, 2b (IC50 = 1.8 +/- 0.13 microM, EC50 = 15.0 +/- 2.4 microM) was approximately equipotent with thio-ATPA (3b) (IC50 = 0.63 +/- 0.07 microM, EC50 = 14 +/- 1.3 microM). (RS)-2-Amino-3-(3-hydroxyisoxazol-5-yl)propionic acid (HIBO, 4a) was approximately equipotent with its thio analog 4b, whereas 4-Br-HIBO (5a) (IC50 = 0.65 +/- 0.12 microM, EC50 = 22 +/- 0.6 microM) turned out to be much more potent than the corresponding 3-isothiazolol 5b (IC50 = 17 +/- 2.2 microM, EC50 = 500 +/- 23 microM). 2b (ED50 = 130 mumol/kg) was more potent than 2a (220 mumol/kg) as a convulsant after subcutaneous administration in mice. The protolytic properties of 2a,b-4a,b were determined using 13C NMR spectroscopy. For each pair of compounds, the alpha-amino acid groups showed similar protolytic properties, whereas the 3-isoxazolol moieties typically showed pKa values 2 units lower than those of the 3-isothiazolols. Accordingly, calculations of ionic species distributions revealed pronounced differences between 3-isoxazolol and 3-isothiazolol amino acids. No simple correlation between activity as AMPA agonists in vitro and pKa values of these compounds was apparent. On the other hand, the relative potencies of AMPA (2a) and thio-AMPA (2b) in vitro and in vivo may reflect that these compounds predominantly penetrate the blood-brain barrier as net uncharged diprotonated ionic species.
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Affiliation(s)
- L Matzen
- Department of Medicinal Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
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6
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Pesek JJ, Schneider JF. The detection of mercury, lead, and methylmercury binding sites on lysozyme by carbon-13 NMR chemical shifts of the carboxylate groups. J Inorg Biochem 1988; 32:233-8. [PMID: 3379392 DOI: 10.1016/0162-0134(88)85002-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The chemical shift changes observed in the carbon-13 NMR spectra of the carboxylate region in conjunction with previous fluorescence data indicate that mercury and lead bind to both disulfide bridge 64-80 and to Asp-52 in hen egg-white lysozyme. Methylmercury appears to bind primarily to the disulfide linkage. The carbon-13 NMR results support previous investigations by halide ion NMR and x-ray crystallography. The combined information from all of these techniques is useful for providing a clearer description of heavy metal binding to proteins.
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Affiliation(s)
- J J Pesek
- Department of Chemistry, San Jose State University, CA 95192
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7
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Laussac JP, Cung MT, Pasdeloup M, Haran R, Marraud M, Lefrancier P, Dardenne M, Bach JF. NMR study of thymulin, a lymphocyte differentiating thymic nonapeptide. Conformational states of free peptide in solution. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)57469-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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8
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Santoro J, Rico M, Bermejo F, Nieto J, Herranz J, Gallego E. 13C NMR spectral assignment of ribonuclease S-peptide. Some new structural information about its low-temperature folding. J Mol Struct 1986. [DOI: 10.1016/0022-2860(86)80329-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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9
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Laussac JP, Sarkar B. Isolation, purification and 13C- and 1H-n.m.r. assignments of peptide [1-24] of human serum albumin. INTERNATIONAL JOURNAL OF PEPTIDE AND PROTEIN RESEARCH 1985; 26:425-38. [PMID: 3841092 DOI: 10.1111/j.1399-3011.1985.tb01009.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Isolation, purification and 360 MHz 1H- and 13C-n.m.r. spectra of the residue corresponding to the NH2-terminal peptide fragment [1-24] of human serum albumin are reported. The various resonances have been assigned to individual amino acid residues and their spatial microenvironment has been determined in a straightforward manner on the basis of (i) pH dependent chemical shifts; (ii) combined use of multiple and selective proton-decoupled 1H- and 13C-n.m.r. spectra; (iii) the characteristic pK values exhibited by protons adjacent to sites of ionization in the molecule; and (iv) comparison of the spectra with the NH2-terminal tripeptide segment of human albumin. The pK values of different ionizable groups all fall in the normal range expected for each titrating sites and support a model of peptide fragment [1-24] in which there is no special structure-forming strong associations. These results are in agreement with those obtained by CD spectroscopy.
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10
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Luthra N, Costello R, Odom J, Dunlap R. Demonstration of the feasibility of observing nuclear magnetic resonance signals of 77Se covalently attached to proteins. J Biol Chem 1982. [DOI: 10.1016/s0021-9258(19)68164-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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11
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Odani A, Yamauchi O. Ternary α-Amino Acid-Palladium(II) Complexes with Ligand-Ligand Hydrogen Bonding. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 1981. [DOI: 10.1246/bcsj.54.3773] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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12
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Halle J, Simonnin M. Proton transfer in histidine hydrochloride induced by a dipolar aprotic solvent. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68881-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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13
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14
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Deuterium isotope effects on carbon-13 chemical shifts in selected amino acids as function of pH. ACTA ACUST UNITED AC 1979. [DOI: 10.1016/0022-2364(79)90172-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Bonora GM, Ferrara L, Paolillo L, Toniolo C, Trivellone E. 13C Nuclear magnetic resonance of protamines. The three main components of clupeine. EUROPEAN JOURNAL OF BIOCHEMISTRY 1979; 93:13-21. [PMID: 571331 DOI: 10.1111/j.1432-1033.1979.tb12789.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The three main components (called YI, YII and Z) of clupeine a protamine from herring have been isolated and characterized by 13C nuclear magnetic resonance. Resonance belonging to the many different amino acid carbon atoms are observable and assigned. The effect of urea on the clupeine fractions points to the molecules being essentially in extended form in 2H2O solutions. Unusual properties of clupeine fractions can be observed in the presence of phosphate. Two of the fractions, i.e. YI and Z, show that a partial folding occurs in some well-defined whereas fraction YII remains essentially unaltered.
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16
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Santoro J, Juretschke HP, Rüterjans H. 13C NMR investigations on Npi-[13C1]carboxymethyl-histidine-119 ribonuclease. BIOCHIMICA ET BIOPHYSICA ACTA 1978; 537:304-9. [PMID: 31923 DOI: 10.1016/0005-2795(78)90513-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The ribonuclease A derivative Npi-[13C1]carboxymethyl-histine-119 ribonuclease prepared by using [13C1]bromoacetate as alkylating reagent has been investigated with high resolution 13C NMR spectroscopy. In the 13C NMR spectra two carbon resonances of relatively high intensity appear which can be assigned to carboxyl groups attached to His-119 and Met-30, their intensity ratio being 10 : 1. The pH dependence of the carbon resonance of the carboxy-methyl group bound to the Npi of His-119 differs in the absence and presence of Cyd-2'-P, thus indicating that the catalytically inactive derivative does bind nucleotides. A mechanism of the alkylation reaction at pH 5.6 is proposed in which the epsilon-amino group of Lys-41 acts as the binding site for the carboxyl group of bromoacetate pushing the bromomethylene group towards the Npi of His-119 or the Ntau of His-12.
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17
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Sperling R, Furie B, Blumenstein M, Keyt B, Furie B. Metal binding properties of gamma-carboxyglutamic acid. Implications for the vitamin K-dependent blood coagulation proteins. J Biol Chem 1978. [DOI: 10.1016/s0021-9258(17)34775-0] [Citation(s) in RCA: 82] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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18
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Chapman BE, Moore WJ. Conformation of myelin basic protein in aqueous solution from nuclear magnetic resonance spectroscopy. Biochem Biophys Res Commun 1976; 73:758-66. [PMID: 1008885 DOI: 10.1016/0006-291x(76)90874-3] [Citation(s) in RCA: 38] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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19
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Norton RS, Bradbury JH. Kinetics of hydrogen-deuterium exchange of tryptophan and tryptophan peptides in deutero-trifluoroacetic acid using proton magenetic resonance spectroscopy. Mol Cell Biochem 1976; 12:103-11. [PMID: 958213 DOI: 10.1007/bf01731556] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The methods which have been used for the observation and assignment of resonances in the NMR spectra of proteins are reviewed. One such method, the selective deuteration of the aromatic protons of tryptophyl residues, is studied by NMR spectroscopy in model compounds in this paper, and in proteins in the following paper. On the basis of a reassignment of the PMR spectrum of the aromatic protons of L-tryptophan, the relative rates of H-D exchange in deutero-trifluoracetic acid (d-TFA) are H-2 greater than H-5 greater than H-6 greater than H-4 approximately H-7. The energies of activation for the first order exchange of both the H-2 and H-5 protons is 12 k.cal.mol-1. The rate constant for exchange of the H-2 protons of tryptophyl residues in peptides is much greater than in the amino acid itself and 5-10 times that for exchange of the H-5 protons. This suggests that the method can be used to label tryptophyl residues in proteins rapidly and specifically.
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20
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13C NMR spectroscopy of labeled pyridoxal 5'-phosphate. Model studies, D-serine dehydratase, and L-glutamate decarboxylase. J Biol Chem 1976. [DOI: 10.1016/s0021-9258(17)33579-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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21
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13C Nmr Spectroscopy in Macromolecular Systems of Biochemical Interest. ADVANCES IN PHYSICAL ORGANIC CHEMISTRY 1976. [DOI: 10.1016/s0065-3160(08)60215-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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22
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Studies of individual carbon sites of proteins in solution by natural abundance carbon 13 nuclear magnetic resonance spectroscopy. Strategies for assignments. J Biol Chem 1975. [DOI: 10.1016/s0021-9258(19)41077-6] [Citation(s) in RCA: 92] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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23
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Wasylishen RE, Tomlinson G. pH-dependence of 13C chemical shifts and 13C,H coupling constants in imidazole and L-histidine. Biochem J 1975; 147:605-7. [PMID: 241331 PMCID: PMC1165488 DOI: 10.1042/bj1470605] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The pH-dependence of selected 13C chemical shifts reflects the state of ionization of the imidazole ring in both imidazole and L-histidine. Titration of the amino and carboxyl groups of histidine also perturbs the shifts. The coupling constants 1J (13C(2),H) and 1J (13C(5),H) for both compounds also vary with pH, but in L-histidine these constants are relatively insensitive to the titration of groups outside the imidazole ring.
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24
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Clark VM, Lilley DM, Howarth OW, Richards BM, Pardon JF. The structure and properties of histone F2a comprising the heterologous group F2a1 and F2a2 studied by 13C nuclear magnetic resonance. Nucleic Acids Res 1974; 1:865-80. [PMID: 10793719 PMCID: PMC343390 DOI: 10.1093/nar/1.7.865] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
(13)C n.m.r. spectra have been obtained for aqueous solutions of histones F2a(1) and F2a(2), for the group F2a, for the appropriate amino acid mixturesand for the corresponding hydrolysates. These, when compared with computer simulated spectra give good agreement for secondary structure with that calculated from the known primary structure of the proteins. Evidence based on the spectra obtained at various salt concentrations leads to the conclusion that F2a is not a simple mixture but an interacting heterologous group of histones F2a(1) and F2a(2).
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25
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Feeney J, Partington P, Roberts G. The assignment of carbon-13 resonances from carbonyl groups in peptides. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/0022-2364(74)90021-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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26
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Grathwohl C, Wüthrich K. Carbon-13 NNIR of the protected tetrapeptides TFA-Gly-Gly-L-X-L-Ala-OCH3, where X stands for the 20 common amino acids. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/0022-2364(74)90008-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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27
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Deslauriers R, Walter R, Smith IC. Long-range, pH-dependent effects on the carbon-13 nuclear magnetic resonance spectra of oxytocin. Proc Natl Acad Sci U S A 1974; 71:265-8. [PMID: 4521798 PMCID: PMC387983 DOI: 10.1073/pnas.71.2.265] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The effects of hydrogen ion concentrations on the carbon-13 nuclear magnetic resonance spectra of oxytocin were investigated. The starting pD of 3.0 was increased stepwise to 8.4. A change of the state of protonation of the N-terminal amino group of oxytocin is accompanied by changes in chemical shifts of carbon-13 nuclei of amino-acid residues located in the 20-membered ring of the hormone. The resonance positions of the acyclic peptide portion, Pro-Leu-Gly-NH(2), remain constant. The pD-induced chemical-shift changes of carbons up to five bonds removed from the site of protonation are interpreted in terms of "through-bond" and "through-space" mechanisms. Chemical-shift changes of carbons more than five bonds removed are proposed to have a conformational origin. It is suggested that a change in the charge density of the amino group perturbs the dihedral angle of the -CH(2)-S-S-CH(2)- moiety of oxytocin, which in turn significantly affects the overall conformation of the 20-membered ring of the hormone.
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Rattle HW. Nuclear magnetic resonance in the study of biopolymers. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1974; 28:1-40. [PMID: 4617245 DOI: 10.1016/0079-6107(74)90015-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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30
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Allerhand A, Childers RF, Oldfield E. Carbon-13 Fourier transform NMR studies in 20 mm sample tubes: observation of individual carbon sites in proteins. Ann N Y Acad Sci 1973; 222:764-77. [PMID: 4361880 DOI: 10.1111/j.1749-6632.1973.tb15303.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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31
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Bradbury JH, Norton RS. Carbon-13 NMR spectra of tryptophan, tryptophan peptides and of native and denatured proteins. BIOCHIMICA ET BIOPHYSICA ACTA 1973; 328:10-9. [PMID: 4796925 DOI: 10.1016/0005-2795(73)90324-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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32
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Gray GA. Applications of 13 C nuclear magnetic resonance in biochemistry. CRC CRITICAL REVIEWS IN BIOCHEMISTRY 1973; 1:247-304. [PMID: 4609688 DOI: 10.3109/10409237309102548] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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