Isotope effects and symmetry of hydrogen bonds in solution: Single- and double-well potential

Isotope Effects in Chemistry and Biology

Volumn , Issue , 2005, Pages 231-252

  Lau, Jonathan S ^a   Perrin, Charles L ^a  

^a UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 78650487394     PISSN: None     EISSN: None     Source Type: Book    
DOI: 10.1201/9781420028027     Document Type: Chapter

References (114)

1. Perrin, C. L. and Nielson, J. B., “Strong” hydrogen bonds in chemistry and biology, Annu. Rev. Phys. Chem., 48, 511-544, 1997.
2. Frey, P. A. and Cleland, W. W., Are there strong hydrogen bonds in aqueous solutions? Bioorg. Chem., 26, 175-192, 1998.
3. Northrop, D. B., Follow the protons: a low-barrier hydrogen bond unifies the mechanisms of the aspartic proteases, Acc. Chem. Res., 34, 790-797, 2001.
4. Kim, K. S., Kim, D., Lee, J. Y., Tarakeshwar, P., and Oh, K. S., Catalytic mechanism of enzymes: preorganization, short strong hydrogen bond, and charge buffering, Biochemistry, 41, 5300-5306, 2002.
5. Gilli, P., Bertolasi, V., Ferretti, V., and Gilli, G., Evidence for resonance-assisted hydrogen bonding. 4. Covalent nature of the strong homonuclear hydrogen bond. Study of the O-H• • •O system by crystal structure correlation methods, J. Am. Chem. Soc., 116, 909-915, 1994.
6. Gilli, G. and Gilli, P., Towards an unified hydrogen-bond theory, J. Mol. Struct., 552, 1-15, 2000.
7. Schiøtt, B., Iversen, B. B., Madsen, G. K. H., Larsen, F. K., and Bruice, T. C., On the electronic nature of low-barrier hydrogen bonds in enzymatic reactions, Proc. Natl Acad. Sci. USA, 95, 12799-12802, 1998.
8. Gilli, P., Bertolasi, V., Pretto, L., Lycka, A., and Gilli, G., The nature of solid-state N-H• • •O/O-H• • •N tautomeric competition in resonant systems intramolecular proton transfer in low-barrier hydrogen bonds formed by the • • •OvC-CvN-NH• • •/• • •HO-CvC-NvN• • • ketohydrazone-azoenol system. A variable-temperature x-ray crystallographic and DFT computational study, J. Am. Chem. Soc., 124, 13554-13567, 2002.
9. Novoa, J. J., Nobeli, I., Grepioni, F., and Braga, D., Are all short O-H• • •O contacts hydrogen bonds? A quantitative look at the nature of O-H• • •O intermolecular hydrogen bonds, New J. Chem., 24, 5-8, 2000.
10. Kato, Y., Toledo, L. M., and Rebek, J. Jr., Energetics of a low barrier hydrogen bond in nonpolar solvents, J. Am. Chem. Soc., 118, 8575-8579, 1996.
11. Cassidy, C. S., Lin, J., Tobin, J. B., and Frey, P. A., Low-barrier hydrogen bonding in aqueous and aprotic solutions of dicarboxylic acids: spectroscopic characterization, Bioorg. Chem., 26, 213-219, 1998.
12. Filarowski, A., Koll, A., and Glowiak, T., Low barrier hydrogen bonds in sterically modified Schiff bases, J. Chem. Soc. Perkin Trans., 2, 835-842, 2002.
13. Eberson, L. and Forsen, S., Proton magnetic resonance studies on intramolecular hydrogen bonding in mono-anions of sterically hindered succinic acids, J. Phys. Chem., 64, 767-769, 1960.
14. Morawetz, H., A new look at the ionization equilibrium of dicarboxylic acids, Gazz. Chim. Ital., 116, 693-695, 1986.
15. Kent, D. R. IV, Petterson, K. A., Gregoire, F., Snyder-Frey, E., Hanely, L. J., Muller, R. P., Goddard, W. A. III, and Roberts, J. D., An NMR and quantum-mechanical investigation of tetrahydrofuran solvent effects on the conformational equilibria of 1,4-butanedioic acid and its salts, J. Am. Chem. Soc., 124, 4481-4486, 2002.
16. Hammes-Schiffer, S. and Tully, J. C., Vibrationally enhanced proton transfer, J. Phys. Chem., 99, 5793-5797, 1995.
17. Basilevsky, M. V., and Vener, M. V., Theoretical investigations of proton and hydrogen atom transfer in the condensed phase, Russ. Chem. Rev., 72, 1-33, 2003.
18. Smallwood, C. J. and McAllister, M. A., Characterization of low-barrier hydrogen bonds 7. Relationship between strength and geometry of short-strong hydrogen bonds. The formic acid-formate anion model system. An ab initio and DFT investigation, J. Am. Chem. Soc., 119, 11277-11281, 1997.
19. Adalsteinsson, H., Maulitz, A. H., and Bruice, T. C., Calculation of the potential energy surface for intermolecular amide hydrogen bonds using semiempirical and ab initio methods, J. Am. Chem. Soc., 118, 7689-7693, 1996.
20. Garcia-Viloca, M., Gonzalez-Lafont, A., and Llúch, J. M., Theoretical study of the low-barrier hydrogen bond in the hydrogen maleate anion in the gas phase comparison with normal hydrogen bonds, J. Am. Chem. Soc., 119, 1081-1086, 1997.
21. Kovacs, A., Izvekov, V., Zauer, K., and Ohta, K., Strong intramolecular hydrogen bonding and molecular vibrations of 9-hydroxyphenalen-1-one, J. Phys. Chem. A, 105, 5000-5009, 2001.
22. Dannenberg, J. J. and Rios, R., Theoretical study of the enolic forms of acetylacetone. How strong is the hydrogen bond? J. Phys. Chem., 98, 6714-6718, 1994.
23. Hibbert, F. and Emsley, J., Hydrogen bonding and chemical reactivity, Adv. Phys. Org. Chem., 26, 255-379, 1990.
24. Buemi, G., Evaluation of hydrogen-bonding strength in 3-(40-biphenyl)pentane-2,4-dione-an AM1 study, J. Mol. Struct. (THEOCHEM), 201, 193-198, 1989.
25. Buemi, G., Zuccarello, F., and Gandolfo, C., Effect of 3-substitution on the intramolecular hydrogen-bonding of pentane-2,4-dione-a theoretical-study, Gazz. Chim. Ital., 123, 215-221, 1993.
26. McAllister, M. A., Characterization of low-barrier hydrogen bonds 3. Hydrogen maleate. An ab initio and DFT investigation, Can. J. Chem., 75, 1195-1202, 1997.
27. Pan, Y. and McAllister, M. A., Characterization of low-barrier hydrogen bonds 6. Cavity polarity effects on the formic acid-formate anion model system. An ab Initio and DFT investigation, J. Am. Chem. Soc., 120, 166-169, 1998.
28. Garcia-Viloca, M., González-Lafont, À., and Lluch, J. M., Asymmetry of the hydrogen bond of hydrogen phthalate anion in solution. A QM/MM study, J. Am. Chem. Soc., 121, 9198-9207, 1999.
29. Bach, R. D., Dmitrenko, O., and Glukhovtsev, M. N., A theoretical study of the effect of a tetraalkylammonium counterion on the hydrogen bond strength in Z-hydrogen maleate, J. Am. Chem. Soc., 123, 7134-7145, 2001.
30. Schwartz, B. and Drueckhammer, D. G., A simple method for determining the relative strengths of normal and low-barrier hydrogen bonds in solution: implications to enzyme catalysis, J. Am. Chem. Soc., 117, 11902-11905, 1995.
31. Mock, W. L. and Morsch, L. A., Low barrier hydrogen bonds within salicylate mono-anions, Tetrahedron, 57, 2957-2964, 2001.
32. Shan, S., Loh, S., and Herschlag, D., The energetics of hydrogen bonds in model systems: implications for enzymatic catalysis, Science, 272, 97-101, 1996.
33. 22, J. Am. Chem. Soc., 102(10), 3315-3322, 1980.
34. 2, J. Am. Chem. Soc., 99(15), 5207-5209, 1977.
35. Ventura, K. M., Greene, S. N., Halkides, C. J., and Messina, M., A mixed quantum-classical approach for computing effects of intramolecular motion on the low-barrier hydrogen bond, Struct. Chem., 12, 23-31, 2001.
36. Cleland, W. W., Low-barrier hydrogen bonds and low fractionation factor bases in enzymic reactions, Biochemistry, 31, 317-319, 1992.
37. Garcia-Viloca, M., Gelabert, R., González-Lafont, A., Moreno, M., and Lluch, J. M., Is an extremely low-field proton signal in the NMR spectrum conclusive evidence for a low-barrier hydrogen bond? J. Phys. Chem. A, 101, 8727-8733, 1997.
38. Brück, A., McCoy, L. L., and Kilway, K. V., Hydrogen bonds in carboxylic acid-carboxylate systems in solution 1. In anhydrous, aprotic media, Org. Lett., 2, 2007-2009, 2000.
39. Bruck, A. and Kilway, K. V., Dynamic behavior of hydrogen bonding in hydrogen 5,6- acenaphthenedicarboxylate, Tetrahedron, 57, 7263-7268, 2001.
40. Batiz-Hernandez, H. and Bernheim, R. A., Isotope shift, Prog. Nucl. Magn. Reson. Spectrosc., 3, 63-85, 1967.
41. Hansen, P. E., Isotope effects in nuclear shielding, Prog. Nucl. Magn. Reson. Spectrosc., 20, 207-255, 1988.
42. Saunders, M., Telkowski, L., and Kates, M. R., Isotopic perturbation of degeneracy. Carbon-13 NMR spectra of dimethylcyclopentyl and dimethylnorbornyl cations, J. Am. Chem. Soc., 99, 8070-8071, 1977.
43. Siehl, H.-U., Isotope effects on NMR spectra of equilibrating systems, Adv. Phys. Org. Chem., 23, 63-163, 1987.
44. Levine, I. N., Quantum Chemistry, 2nd ed., Allyn & Bacon, Boston, 1974, 289ff.
45. Dziembowska, T. and Razwadowski, Z., Application of the deuterium isotope effect on NMR chemical shift to study proton transfer equilibrium, Curr. Org. Chem., 5, 289-313, 2001.
46. Altman, L. J., Laungani, D., Gunnarsson, G., Wennerstrom, H., and Forsen, S., Proton, deuterium and tritium nuclear magnetic resonance of intramolecular hydrogen bonds. Isotope effects and the shape of the potential energy function, J. Am. Chem. Soc., 100, 8264-8266, 1978.
47. Bolvig, S., Hansen, P. E., Morimoto, H., Wemmer, D., and Williams, P., Primary tritium and deuterium isotope effects on chemical shifts of compounds having an intramolecular hydrogen bond, Magn. Reson. Chem., 38, 525-535, 2000.
48. Vener, M. V., Model study of the primary H/D isotope effects on the NMR chemical shift in strong hydrogen-bonded system, Chem. Phys., 166, 311-316, 1992.
49. Schah-Mohammedi, P., Shenderovich, I. G., Detering, C., Limbach, H. H., Tolstoy, P. M., Smirnov, S. M., Denisov, G. S., and Golubev, N. S., Hydrogen/deuterium-isotope effects on NMR chemical shifts and symmetry of homoconjugated hydrogen-bonded ions in polar solution, J. Am. Chem. Soc., 122, 12878-12879, 2000.
50. 15N NMR spectroscopy, Ber. Bunsen-Ges. Phys. Chem., 102, 414-418, 1998.
51. +N hydrogen bonds: can coupling constants provide reliable estimates of N -N distances in biomolecules? Magn. Reson. Chem., 39, S109-S119, 2001.
52. Benedict, H., Shenderovich, I. G., Malkina, O. L., Malkin, V. G., Denisov, G. S., Golubev, N. S., and Limbach, H. H., Nuclear scalar spin-spin couplings and geometries of hydrogen bonds, J. Am. Chem. Soc., 122, 1979-1988, 2000.
53. Barczynski, P., Kowalczyk, I., Grundwald-Wyspianska, M., and Szafran, M., Comparison of low-barrier hydrogen bonds in acid salts of carboxylic acids and basic salts of betaines-FTIR study, J. Mol. Struct., 484, 117-124, 1999.
54. Marimanikkuppam, S. S., Lee, I. S. H., Binder, D. A., Young, V. G., and Kreevoy, M. M., The effect of ordered water on a short, strong (Speakman-Hadzi) hydrogen bond, Croat. Chem. Acta, 69, 1661-1674, 1996.
55. Kreevoy, M. M. and Young, V. G., Geometric isotope effects in crystalline sodium hydrogen bis(4-nitrophenoxide) dihydrate, Can. J. Chem., 77, 733-737, 1999.
56. Dega-Szafran, Z., Katrusiak, A., Szafran, M., and Sokolowska, E., Hydrogen bonds and proton location in 1:1 and 2:1 complexes of N-methylmorpholine betaine with picric acid, J. Mol. Struct., 615, 73-81, 2002.
57. Bohner, U. and Zundel, G., Proton potentials and proton polarizability in carboxylic acid-trimethylamine oxide hydrogen bonds as a function of the donor and acceptor properties: IR investigations, J. Phys. Chem., 90, 964-973, 1986.
58. Henn, F. E. G., Cassanas, G. M., Giuntini, J. C., and Zanchetta, J. V., Studies of the H-bonds in sodium hydrogen malate by IR and NMR spectroscopy, and by proton conductivity measurements, Spectrochim. Acta, 50A, 841-849, 1994.
59. Wojciechowski, G., Ratajczak-Sitarz, M., Katrusiak, A., and Brzezinski, B., Shape of the proton potential in an intramolecular hydrogen-bonded system. Part II, J. Mol. Struct., 612, 59-64, 2002.
60. 1H CP MAS and IR description of low barrier hydrogen bonds, J. Mol. Struct., 606, 123-137, 2002.
61. Fillaux, F., Leygue, N., Tomkinson, J., Cousson, A., and Paulus, W., Structure and dynamics of the symmetric hydrogen bond in potassium hydrogen maleate: a neutron scattering study, Chem. Phys., 244, 387-403, 1999.
62. Wojciechowski, G., Ratajczak-Sitarz, M., Katrusiak, A., and Brzezinski, B., Shape of the proton potential in an intramolecular hydrogen-bonded system. Part II, J. Mol. Struct., 612, 59-64, 2002.
63. 1H CP MAS and IR description of low barrier hydrogen bonds, J. Mol. Struct., 606, 123-137, 2002.
64. Harris, T. K., Zhao, Q., and Mildvan, A. S., NMR studies of strong hydrogen bonds in enzymes and in a model compound, J. Mol. Struct., 552, 97-109, 2000.
65. Ubbelohde, A. R. and Woodward, I., Structure and thermal properties associated with some hydrogen bonds in crystals. IV. Isotope effects in some acid phosphates, Proc. R. Soc. London A, 179, 399-407, 1941.
66. 15N NMR and theoretical studies of primary and secondary geometric H/D isotope effects on low-barrier NHN hydrogen bonds, J. Am. Chem. Soc., 120, 2939-2950, 1998.
67. Gilli, G., Bellucci, F., Ferretti, V., and Bertolasi, V., Evidence for resonance-assisted hydrogen bonding from crystal-structure correlations on the enol form of the b-diketone fragments, J. Am. Chem. Soc., 111, 1023-1028, 1989.
68. Bertolasi, V., Gilli, P., Ferretti, V., and Gilli, G., Evidence for resonance-assisted hydrogen bonding. 2. Intercorrelation between crystal structure and spectroscopic parameters in eight intramolecularly hydrogen bonded 1,3-diaryl-1,3-propanedione enols, J. Am. Chem. Soc., 113, 4917-4925, 1991.
69. Gilli, G., Bellucci, F., Ferretti, V., and Bertolasi, V., Evidence for resonance-assisted hydrogen bonding from crystal-structure correlations on the enol form of the b-diketone fragment, J. Am. Chem. Soc., 111, 1023-1028, 1989.
70. Perrin, C. L., Nielson, J. B., and Kim, Y. J., Symmetry of hydrogen bonds in solution, an overview, Ber. Bunsen-Ges. Phys. Chem., 102, 403-409, 1998.
71. Perrin, C. L. and Kim, Y. J., Symmetry of the hydrogen bond in malonaldehyde enol in solution, J. Am. Chem. Soc., 120, 12641-12645, 1998.
72. Perrin, C. L. and Kim, Y.-J., Symmetry of metal chelates, Inorg. Chem., 39, 3902-3910, 2000.
73. Tkadlecova, M., Havlicek, J., Fahnrich, J., Kral, V., and Volka, K., Spectroscopic study of phenyl- and 4-pyridylmalondialdehydes, J. Mol. Struct., 563, 497-501, 2001.
74. Perrin, C. L. and Ohta, B. K., Symmetry of OHO and NHN hydrogen bonds in 6-hydroxy-2- formylfulvene and 6-aminofulvene-2-aldimines, Bioorg. Chem., 30, 3-15, 2002.
75. 13C NMR spectroscopic investigation of the enol-enethiol tautomerism of β-thioxoketones. Isotope effects due to deuteron chelation, J. Mol. Struct., 552, 45-62, 2000.
76. Staab, H. A. and Saupe, T., Proton sponges and the geometry of hydrogen-bonds: aromatic nitrogen bases with exceptional basicities, Angew. Chem. Int. Ed., 27, 865-879, 1988.
77. +, Chem. Phys. Lett., 175, 282-288, 1990.
78. Llamas-Saiz, A. L., Foces-Foces, C., and Elguero, J., Proton sponges, J. Mol. Struct., 328, 297-323, 1994.
79. 1H chemical shifts of proton sponges, J. Mol. Struct., 615, 121-140, 2002.
80. Bienko, A. J., Latajka, Z., Sawka-Dobrowolska, W., and Sobczyk, L., Low barrier hydrogen bond in protonated proton sponge. X-ray diffraction, infrared, and theoretical ab initio and density functional theory studies, J. Chem. Phys., 119, 4313-4319, 2003.
81. +, J. Am. Chem. Soc., 123, 6520-6526, 2001.
82. Perrin, C. L. and Ohta, B. K., Symmetry of NHN hydrogen bonds in solution, J. Mol. Struct., 644, 1-12, 2003.
83. James, M. N. H. and Matsushima, M., Accurate dimensions of maleate mono-anion in a symmetric environment not dictated by crystallographic symmetry: imidazolium maleate, Acta Crystallogr. B, 32, 1708-1713, 1976.
84. Ellison, R. D. and Levy, H. A., A centered hydrogen bond in potassium hydrogen chloromaleate: a neutron-diffraction structure determination, Acta Crystallogr., 19, 260-268, 1965.
85. Lin, J. and Frey, P. A., Strong hydrogen bonds in aqueous and aqueous-acetone solutions of dicarboxylic acids: activation energies for exchange and deuterium fractionation factors, J. Am. Chem. Soc., 122, 11258-11259, 2000.
86. Markley, J. L. and Westler, W. M., Protonation-state dependence of hydrogen-bond strengths and exchange rates in a serine protease catalytic triad: bovine chymotrypsinogen A, Biochemistry, 35, 11092-11097, 1996.
87. Perrin, C. L. and Nielson, J. B., Asymmetry of hydrogen bonds in solutions of monoanions of dicarboxylic acids, J. Am. Chem. Soc., 119, 12734-12741, 1997.
88. Perrin, C. L. and Thoburn, J. D., Symmetries of hydrogen bonds in monoanions of dicarboxylic acids, J. Am. Chem. Soc., 114, 8559-8565, 1992.
89. Perrin, C. L., Symmetries of hydrogen bonds in solution, Science, 266, 1665-1668, 1994.
90. 18O equilibrium isotope effects and fractionation factors, Can. J. Chem., 77, 967-977, 1999.
91. Küppers, H., Kvick, A., and Olovsson, I., Hydrogen-bond studies. 142. Neutron-diffraction study of the 2 very short hydrogen-bonds in lithium hydrogen-phthalate-methanol, Acta Crystallogr. B, 37, 1203-1207, 1981.
92. Adiwidjaja, G. and Küppers, H., Lithium hydrogen phthalate-methanol, Acta Crystallogr. B, 34, 2003-2005, 1978.
93. Gonschorek, W., and Küppers, H., Crystal-structure of lithium hydrogen phthalate dihydrate, containing a very short hydrogen-bond, Acta Crystallogr. B, 31, 1068-1072, 1975.
94. Johnson, A. E. and Myers, A. B., Solvent effects in the Raman spectra of the triiodide ion: observation of dynamic symmetry breaking and solvent degrees of freedom, J. Phys. Chem., 100, 7778-7788, 1996.
95. Waterland, M. R. and Kelley, A. M., Far-ultraviolet resonance Raman spectroscopy of nitrate ion in solution, J. Chem. Phys., 113, 6760-6773, 2000.
96. Hansen, P. E., Sitkowski, J., Stefaniak, L., Rozwadowski, Z., and Dziembowska, T., One-bond deuterium isotope effects on N-15 chemical shifts in Schiff bases, Ber. Bunsen-Ges. Phys. Chem., 102, 410-413, 1998.
97. 13C chemical shifts of intramolecularly hydrogen-bonded Schiff bases, J. Chem. Soc. Perkin Trans., 2, 2809-2817, 1999.
98. 15N, Magn. Reson. Chem., 39, S67-S80, 2001.
99. Song, X. J. and McDermott, A. E., Proton transfer dynamics and NH bond lengthening in NHN model systems: a solid-state NMR study, Magn. Reson. Chem., 39, S37-S43, 2001.
100. Dega-Szafran, Z., Dulewicz, E., and Szafran, M., Interaction of 2,6-dimethylpyridine with chloroacetic acid in some aprotic solvents: problem of stoichiometry, J. Mol. Struct., 177, 317-325, 1988.
101. Barczynski, P., Dega-Szafran, Z., and Szafran, M., Interaction of 2,4,6-trimethylpyridine with some halogenocarboxylic acids in benzene and dichloromethane problem of stoichiometry, J. Chem. Soc. Perkin Trans., 2, 901-906, 1987.
102. Smirnov, S. N., Benedict, H., Golubev, N. S., Denisov, G. S., Kreevoy, M. M., Schowen, R. L., and Limbach, H. H., Exploring zero-point energies and hydrogen bond geometries along proton transfer pathways by low-temperature NMR, Can. J. Chem., 77, 943-949, 1999.
103. Smirnov, S. N., Golubev, N. S., Denisov, G. S., Benedict, H., Schah-Mohammedi, P., and Limbach, H. H., Hydrogen/deuterium isotope effects on the NMR chemical shifts and geometries of intermolecular low-barrier hydrogenbonded complexes, J. Am. Chem. Soc., 118, 4094-4101, 1996.
104. 2H coupling and hydrogen bond geometry correlations in a novel series of hydrogen-bonded acid-base complexes of collidine with carboxylic acids, Magn. Reson. Chem., 39, S18-S29, 2001.
105. 2solution, Magn. Reson. Chem., 39, S91-S99, 2001.
106. Golubev, N. S., Shenderovich, I. G., Smirnov, S. N., Denisov, G. S., and Limbach, H. H., Nuclear scalar spin-spin coupling reveals novel properties of low-barrier hydrogen bonds in a polar environment, Chem. Eur. J., 5, 492-497, 1999.
107. Shenderovich, I. G., Tolstoy, P. M., Golubev, N. S., Smirnov, S. N., Denisov, G. S., and Limbach, H. H., Low-temperature NMR studies of the structure and dynamics of a novel series of acid-base complexes of HF with collidine exhibiting scalar couplings across hydrogen bonds, J. Am. Chem. Soc., 125, 11710-11720, 2003.
108. 1J(F, H) in the hydrogen-bonded FH-collidine complex, Magn. Reson. Chem., 40, 767-771, 2002.
109. Perrin, C. L., Lau, J. S., and Ohta, B. K., Low-barrier hydrogen bonds in pyridine-dichloroacetic acid complexes, Pol. J. Chem., 77, 1693-1702, 2003.
110. Cassidy, C. S., Reinhardt, L. A., Cleland, W. W., and Frey, P. A., Hydrogen bonding in complexes of carboxylic acids with 1-alkylimidazoles: steric and isotopic effects on low barrier hydrogen bonding, J. Chem. Soc. Perkin Trans., 2, 635-641, 1999.
111. Reinhardt, L. A., Sacksteder, K. A., and Cleland, W. W., Enthalpic studies of complex formation between carboxylic acids and 1-alkylimidazoles, J. Am. Chem. Soc., 120, 13366-13369, 1998.
112. Mildvan, A. S., Massiah, M. A., Harris, T. K., Marks, G. T., Harrison, D. H. T., Viragh, C., Reddy, P. M., and Kovach, I. M., Short, strong hydrogen bonds on enzymes: NMR and mechanistic studies, J. Mol. Struct., 615, 163-175, 2002.
113. Poi, M. J., Tomaszewski, J. W., Yuan, C., Dunlap, C. A., Andersen, N. H., Gelb, M. H., and Tsai, M. D., A low-barrier hydrogen bond between histidine of secreted phospholipase A2 and a transition state analog inhibitor, J. Mol. Biol., 329, 997-1009, 2003.
114. Westler, W. M., Frey, P. A., Lin, J., Wemmer, D. E., Morimoto, H., Williams, P. G., and Markley, J. L., Evidence for a strong hydrogen bond in the catalytic dyad of transition-state analogue inhibitor complexes of chymotrypsin from proton-triton NMR isotope shifts, J. Am. Chem. Soc., 124, 4196-4197, 2002.