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Azo dicarboxylates are not conjugated: X-ray crystal structure and theoretical calculations on di-t-butylazodicarboxylate. J Mol Struct 2015. [DOI: 10.1016/j.molstruc.2015.06.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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2
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Klamt A, Eckert F, Diedenhofen M, Beck ME. First Principles Calculations of Aqueous pKa Values for Organic and Inorganic Acids Using COSMO-RS Reveal an Inconsistency in the Slope of the pKa Scale. J Phys Chem A 2015; 107:9380-6. [PMID: 26313337 DOI: 10.1021/jp034688o] [Citation(s) in RCA: 214] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The COSMO-RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for more realistic solvation (RS) simulations, has been used for the direct prediction of pKa constants of a large variety of 64 organic and inorganic acids. A highly significant correlation of r(2) = 0.984 with a standard deviation of only 0.49 between the calculated values of the free energies of dissociation and the experimental pKa values was found, without any special adjustment of the method. Thus, we have a theoretical a priori prediction method for pKa, which has the regression constant and the slope as only adjusted parameters. Such a method can be of great value in many areas of physical chemistry, especially in pharmaceutical and agrochemical industry. To our surprise, the slope of pKa vs ΔGdiss is only 58% of the theoretically expected value of 1/RTln(10). A careful analysis with respect to different contributions as well as a comparison with the work of other authors excludes the possibility that the discrepancy is due to weaknesses of the calculation method. Hence, we must conclude that the experimental pKa scale depends differently on the free energy of dissociation than generally assumed.
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Affiliation(s)
- Andreas Klamt
- COSMOlogic GmbH&COKG, Burscheider Str. 515, 51381 Leverkusen, Germany.,Bayer Cropscience, BCS-R-SCLA, Alfred-Nobel-Str. 50, 40789 Monheim, Germany
| | - Frank Eckert
- COSMOlogic GmbH&COKG, Burscheider Str. 515, 51381 Leverkusen, Germany.,Bayer Cropscience, BCS-R-SCLA, Alfred-Nobel-Str. 50, 40789 Monheim, Germany
| | - Michael Diedenhofen
- COSMOlogic GmbH&COKG, Burscheider Str. 515, 51381 Leverkusen, Germany.,Bayer Cropscience, BCS-R-SCLA, Alfred-Nobel-Str. 50, 40789 Monheim, Germany
| | - Michael E Beck
- COSMOlogic GmbH&COKG, Burscheider Str. 515, 51381 Leverkusen, Germany.,Bayer Cropscience, BCS-R-SCLA, Alfred-Nobel-Str. 50, 40789 Monheim, Germany
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Khrenova M, Savitsky AP, Topol IA, Nemukhin AV. Exploration of the zinc finger motif in controlling activity of matrix metalloproteinases. J Phys Chem B 2014; 118:13505-12. [PMID: 25375834 PMCID: PMC4254000 DOI: 10.1021/jp5088702] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 11/05/2014] [Indexed: 12/19/2022]
Abstract
Discovering ways to control the activity of matrix metalloproteinases (MMPs), zinc-dependent enzymes capable of degrading extracellular matrix proteins, is an important field of cancer research. We report here a novel strategy for assembling MMP inhibitors on the basis of oligopeptide ligands by exploring the pattern known as the zinc finger motif. Advanced molecular modeling tools were used to characterize the structural binding motifs of experimentally tested MMP inhibitors, as well as those of newly proposed peptidomimetics, in their zinc-containing active sites. The results of simulations based on the quantum mechanics/molecular mechanics (QM/MM) approach and Car-Parrinello molecular dynamics with QM/MM potentials demonstrate that, upon binding of Regasepin1, a known MMP-9 inhibitor, the Zn(2+)(His3) structural element is rearranged to the Zn(2+)(Cys2His2) zinc finger motif, in which two Cys residues are borrowed from the ligand. Following consideration of the crystal structure of MMP-2 with its inhibitor, the oligopeptide APP-IP, we proposed a new peptidomimetic with two replacements in the substrate, Tyr3Cys and Asp6Cys. Simulations show that this peptide variant blocks an enzyme active site by the Zn(2+)(Cys2His2) zinc finger construct. Similarly, a natural substrate of MMP-2, Ace-Gln-Gly ∼ Ile-Ala-Gly-Nme, can be converted to an inhibiting compound by two replacements, Ile by Cys and Gly by the d isomer of Cys, favoring formation of the zinc finger motif.
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Affiliation(s)
- Maria
G. Khrenova
- A.N. Bach Institute
of Biochemistry of the Russian Academy of Science, Leninsky Prospect, 33, Moscow 119071, Russian Federation
- Chemistry
Department, M.V. Lomonosov Moscow State
University, Leninskie
Gory 1/3, Moscow, 119991, Russian Federation
| | - Alexander P. Savitsky
- A.N. Bach Institute
of Biochemistry of the Russian Academy of Science, Leninsky Prospect, 33, Moscow 119071, Russian Federation
| | - Igor A. Topol
- Advanced
Biomedical Computing Center, Information Systems Program, Leidos Biomedical
Research Inc., Frederick National Laboratory
for Cancer Research, Frederick, Maryland 21702, United States
| | - Alexander V. Nemukhin
- Chemistry
Department, M.V. Lomonosov Moscow State
University, Leninskie
Gory 1/3, Moscow, 119991, Russian Federation
- N.M.
Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygina 4, Moscow, 119334, Russian Federation
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Vibrational Analysis and Intermolecular Hydrogen Bonding of Azodicarbonamide in the Pentamer Cluster. B KOREAN CHEM SOC 2008. [DOI: 10.5012/bkcs.2008.29.10.1951] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Turpin JA, Schito ML, Jenkins LMM, Inman JK, Appella E. Topical microbicides: a promising approach for controlling the AIDS pandemic via retroviral zinc finger inhibitors. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2008; 56:229-56. [PMID: 18086414 DOI: 10.1016/s1054-3589(07)56008-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Affiliation(s)
- Jim A Turpin
- Preventions Sciences Program, Division of AIDS, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA
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Miller Jenkins LM, Hara T, Durell SR, Hayashi R, Inman JK, Piquemal JP, Gresh N, Appella E. Specificity of acyl transfer from 2-mercaptobenzamide thioesters to the HIV-1 nucleocapsid protein. J Am Chem Soc 2007; 129:11067-78. [PMID: 17705474 DOI: 10.1021/ja071254o] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The HIV-1 nucleocapsid protein (NCp7) is a small, highly conserved protein with two zinc-binding domains that are essential for the protein's function. Molecules that bind to and inactivate NCp7 are currently being evaluated as new antiviral drugs. In particular, derivatives based on a 2-mercaptobenzamide thioester template have been shown to specifically eject zinc from the C-terminal zinc-binding domain (ZD2) of NCp7 via acyl transfer from the thioester to a cysteine sulfur. In this study, mutational analysis of the NCp7 amino acid sequence has been used to investigate the specificity of the interaction between ZD2 and a 2-mercaptobenzamide thioester compound using UV-vis spectroscopy and mass spectrometry to monitor the rate of metal ejection from NCp7 mutant peptides and sites of acylation, respectively. We were able to extend the previously reported mechanism of action of these thioester compounds to include a secondary S to N intramolecular acyl transfer that occurs after the primary acyl transfer from the thioester to a cysteine side chain in the protein. Structural models of the thioester/ZD2 complex were then examined to identify the most likely binding orientation. We determined that position x+1 (where x is Cys36) needs to be an aromatic residue for reactivity and a hydrogen-bond donor in position x+9 is important for optimal reactivity. A basic residue (lysine or arginine) is required at position x+2 for the correct fold, while a lysine residue is needed for reactivity involving S to N acyl transfer. We report highly specific interactions between 2-mercaptobenzamide thioester compounds and NCp7 that offer a structural basis for refining and designing new antiretroviral therapeutics, directed toward a target that is resistant to viral mutation.
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Affiliation(s)
- Lisa M Miller Jenkins
- Laboratory of Cell Biology, NCI, and Laboratory of Immunology, NIAID, National Institutes of Health, Bethesda, Maryland 20892, USA
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Jensen JH, Li H, Robertson AD, Molina PA. Prediction and rationalization of protein pKa values using QM and QM/MM methods. J Phys Chem A 2007; 109:6634-43. [PMID: 16834015 DOI: 10.1021/jp051922x] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We describe the development and application of a computational method for the prediction and rationalization of pKa values of ionizable residues in proteins, based on ab initio quantum mechanics (QM) and the effective fragment potential (EFPs) method (a hybrid QM/MM method). The theoretical developments include (1) a covalent boundary method based on frozen localized orbitals, (2) divide-and-conquer methods for the ab initio computation of protein EFPs consisting of multipoles up to octupoles and dipole polarizability tensors, (3) a method for computing vibrational free energies for a localized molecular region, and (4) solutions of the polarized continuum model of bulk solvation equations for protein-sized systems. The QM-based pKa prediction method is one of the most accurate methods currently available and can be used in cases where other pKa prediction methods fail. Preliminary analysis of the computed results indicate that many pKa values (1) are primarily determined by hydrogen bonds rather than long-range charge-charge interactions and (2) are relatively insensitive to large-scale dynamical fluctuations of the protein structure.
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Affiliation(s)
- Jan H Jensen
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, USA.
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Jenkins LMM, Durell SR, Maynard AT, Stahl SJ, Inman JK, Appella E, Legault P, Omichinski JG. Comparison of the Specificity of Interaction of Cellular and Viral Zinc-Binding Domains with 2-Mercaptobenzamide Thioesters. J Am Chem Soc 2006; 128:11964-76. [PMID: 16953638 DOI: 10.1021/ja063329e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interactions of two 2-mercaptobenzamide thioester compounds with six diverse zinc-binding domains (ZBDs) have been analyzed by UV/visible spectroscopy, NMR spectroscopy, and nucleic acid binding assays. These thioester compounds serve as useful tools for probing the intrinsic chemical stability of ZBDs that exist within a variety of cellular and viral proteins. In our studies, the classical (Cys(2)His(2)) zinc finger ZBDs, the interleaved RING like ZBDs of protein kinase C delta (Cys(2)HisCys and HisCys(3)), and the carboxyl-terminal (Cys(2)HisCys) ZBD of Mouse Mammary Tumor Virus nucleocapsid protein (MMTV NCp10) were resistant to reaction with the thioester compounds. In contrast, the thioester compounds were able to efficiently eject zinc from the amino-terminal (Cys(2)HisCys) ZBD of MMTV NCp10, a Cys(2)HisCys ZBD from Friend of GATA-1 (FOG-1), and from both Cys(4) ZBDs of GATA-1. In all cases, zinc ejection led to a loss of protein structure. Interestingly, GATA-1 was resistant to reaction with the thioester compounds when bound to its target DNA sequence. The electronic and steric screening was calculated for select ZBDs to further explore their reactivity. Based on these results, it appears that both first and second zinc-coordination shell interactions within ZBDs, as well as nucleic acid binding, play important roles in determining the chemical stability and reactivity of ZBDs. These studies not only provide information regarding the relative reactivity of cysteine residues within structural ZBDs but also are crucial for the design of future therapeutic agents that selectively target ZBDs, such as those that occur in the HIV-1 nucleocapsid protein.
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Affiliation(s)
- Lisa M Miller Jenkins
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, USA
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Abstract
The COSMO-RS method, a combination of the quantum chemical dielectric continuum solvation model COSMO with a statistical thermodynamics treatment for realistic solvation simulations, has been used for the prediction of base pK(a) constants. For a variety of 43 organic bases the directly calculated values of the free energies of dissociation in water showed a very good correlation with experimental base pK(a) values (r2 = 0.98), corresponding to a standard deviation of 0.56 pK(a) units. Thus, we have an a priori prediction method for base pK(a) with the regression constant and the slope as only adjusted parameters. In accord with recent findings for pK(a) acidity predictions, the slope of pK(a) vs. DeltaG(diss) was significantly smaller than the theoretically expected value of 1/RTln(10). The predictivity of the presented method is general and not restricted to certain compound classes, but systematic corrections of 1 and 2 pKa units for secondary and tertiary aliphatic amines are required, respectively. The pK(a) prediction method was validated on a set of 58 complex multifunctional drug-like compounds, yielding an RMS accuracy of 0.66 pK(a) units.
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Affiliation(s)
- Frank Eckert
- COSMOlogic GmbH & Co KG, Burscheider Str. 515, D-51381 Leverkusen, Germany.
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Li H, Robertson AD, Jensen JH. The determinants of carboxyl pKa values in turkey ovomucoid third domain. Proteins 2004; 55:689-704. [PMID: 15103631 DOI: 10.1002/prot.20032] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A computational methodology for protein pK(a) predictions, based on ab initio quantum mechanical treatment of part of the protein and linear Poisson-Boltzmann equation treatment of the bulk solvent, is presented. The method is used to predict and interpret the pK(a) values of the five carboxyl residues (Asp7, Glu10, Glu19, Asp27, and Glu43) in the serine protease inhibitor turkey ovomucoid third domain. All the predicted pK(a) values are within 0.5 pH units of experiment, with a root-mean-square deviation of 0.31 pH units. We show that the decreased pK(a) values observed for some of the residues are primarily due to hydrogen bonds to the carboxyl oxygens. Hydrogen bonds involving amide protons are shown to be particularly important, and the effect of hydrogen bonding is shown to be nonadditive. Hydrophobic effects are also shown to be important in raising the pK(a). Interactions with charged residues are shown to have relatively little effect on the carboxyl pK(a) values in this protein, in general agreement with experiment.
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Affiliation(s)
- Hui Li
- Department of Chemistry, The University of Iowa, Iowa City 52242, USA
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Khandogin J, Musier-Forsyth K, York DM. Insights into the regioselectivity and RNA-binding affinity of HIV-1 nucleocapsid protein from linear-scaling quantum methods. J Mol Biol 2003; 330:993-1004. [PMID: 12860122 DOI: 10.1016/s0022-2836(03)00658-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein (NC) plays several important roles in the viral life-cycle and presents an attractive target for rational drug design. Here, the macromolecular reactivity of NC and its binding to RNA is characterized through determination of electrostatic and chemical descriptors derived from linear-scaling quantum calculations in solution. The computational results offer a rationale for the experimentally observed susceptibility of the Cys49 thiolate toward small-molecule electrophilic agents, and support the recently proposed stepwise protonation mechanism of the C-terminal Zn-coordination complex. The distinctive binding mode of NC to SL2 and SL3 stem-loops of the HIV-1 genomic RNA packaging signal is studied on the basis of protein side-chain contributions to the electrostatic binding energies. These results indicate the importance of several basic residues in the 3(10) helical region and the N-terminal zinc finger, and rationalize the presence of several evolutionarily conserved residues in NC. The combined reactivity and RNA-binding study provides new insights that may contribute toward the structure-based design of anti-HIV therapies.
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Affiliation(s)
- Jana Khandogin
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
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Abstract
In zinc proteins, the Zn2+ cation frequently binds with a tetrahedral coordination to cysteine and histidine side chains, for example, in many DNA-binding proteins, where it plays primarily a structural role. We examine the possibility of thiolate protonation in Cys(x)His(y)-Zn2+ groups, both in proteins and in solution, through a combination of theoretical calculations and database analysis. Seventy-five percent of the thiolate-coordinated zincs in the Cambridge Structural Database are tetrahedral, while di-alkanethiol coordination always involves five or more ligands. Ab initio quantum calculations are performed on (ethanethiol/thiolate)(3)imidazole-Zn2+ complexes in vacuum, yielding geometries and gas phase basicities. Protonating one (respectively two) thiolates increases the Zn-S(thiol) distance by 0.4 A (respectively 0.3 A), providing a structural marker for protonation. The stabilities of the complexes in solution are compared by combining the gas phase basicities with continuum dielectric solvation calculations. In a continuum solvent with permittivity epsilon = 4, 20, or 80, one of three thiolates is predicted to be protonated at neutral pH. By extension, Cys4-Zn2+ groups are expected to be protonated in the same conditions. In contrast, most Cys3His and Cys4 geometries in the Protein Data Bank (PDB) appear consistent with all-thiolate Zn2+ coordination. This apparent discrepancy is resolved by two recent surveys of zinc protein structures, which suggest that these all-thiolate sites are stabilized by charged and polar groups nearby in the protein, thus overcoming their intrinsic instability. However, the experimental resolution is not sufficient in all the PDB structures to rule out a thiol/thiolate mixture, and protonated thiolates may occur in some proteins not solved at high resolution or not represented in the PDB, as suggested by recent mass spectrometry experiments; this possibility should be allowed for in X-ray structure refinement.
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Affiliation(s)
- Thomas Simonson
- Department of Structural Biology and Genomics, Institut de Génétique et Biologie Moléculaire et Cellulaire (C.N.R.S.), Strasbourg-Illkirch, France.
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Li H, Hains AW, Everts JE, Robertson AD, Jensen JH. The Prediction of Protein pKa's Using QM/MM: The pKa of Lysine 55 in Turkey Ovomucoid Third Domain. J Phys Chem B 2002. [DOI: 10.1021/jp013995w] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hui Li
- Department of Chemistry and Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Alexander W. Hains
- Department of Chemistry and Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Joshua E. Everts
- Department of Chemistry and Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Andrew D. Robertson
- Department of Chemistry and Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
| | - Jan H. Jensen
- Department of Chemistry and Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242
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