76
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Schwab KS, Heine A, Weimann T, Kristiansen G, Brossart P. Development of Hemolytic Anemia in a Nivolumab-Treated Patient with Refractory Metastatic Squamous Cell Skin Cancer and Chronic Lymphatic Leukemia. Case Rep Oncol 2016; 9:373-8. [PMID: 27462240 PMCID: PMC4939691 DOI: 10.1159/000447508] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 06/08/2016] [Indexed: 11/19/2022] Open
Abstract
Management of patients with metastatic squamous cell skin cancer, refractory to initial therapy with standard chemotherapy and radiation protocols, remains difficult with poor overall prognosis and limited therapeutic options. Recently, promising response rates with nivolumab, a programmed death receptor-1-blocking antibody, in squamous cancer of the head and neck have been demonstrated. Considering the similar histological patterns of squamous cell cancer of the skin and squamous cell cancer of the head and neck, we assumed that nivolumab could also be effective in our patients with refractory metastatic squamous cell cancer of the skin. So far, there have been no clinical data on the therapeutic efficacy of nivolumab in squamous cell skin cancer. We here present a case of a patient with metastatic squamous cell skin cancer refractory to previous therapies, who showed a good response to nivolumab over a period of 5 months, but developed a serious hemolytic crisis under nivolumab treatment after eight applications.
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77
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Hinkes S, Wuttke A, Saupe SM, Ivanova T, Wagner S, Knörlein A, Heine A, Klebe G, Steinmetzer T. Optimization of Cyclic Plasmin Inhibitors: From Benzamidines to Benzylamines. J Med Chem 2016; 59:6370-86. [DOI: 10.1021/acs.jmedchem.6b00606] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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78
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Schiebel J, Radeva N, Krimmer SG, Wang X, Stieler M, Ehrmann FR, Fu K, Metz A, Huschmann FU, Weiss MS, Mueller U, Heine A, Klebe G. Six Biophysical Screening Methods Miss a Large Proportion of Crystallographically Discovered Fragment Hits: A Case Study. ACS Chem Biol 2016; 11:1693-701. [PMID: 27028906 DOI: 10.1021/acschembio.5b01034] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fragment-based lead discovery (FBLD) has become a pillar in drug development. Typical applications of this method comprise at least two biophysical screens as prefilter and a follow-up crystallographic experiment on a subset of fragments. Clearly, structural information is pivotal in FBLD, but a key question is whether such a screening cascade strategy will retrieve the majority of fragment-bound structures. We therefore set out to screen 361 fragments for binding to endothiapepsin, a representative of the challenging group of aspartic proteases, employing six screening techniques and crystallography in parallel. Crystallography resulted in the very high number of 71 structures. Yet alarmingly, 44% of these hits were not detected by any biophysical screening approach. Moreover, any screening cascade, building on the results from two or more screening methods, would have failed to predict at least 73% of these hits. We thus conclude that, at least in the present case, the frequently applied biophysical prescreening filters deteriorate the number of possible X-ray hits while only the immediate use of crystallography enables exhaustive retrieval of a maximum of fragment structures, which represent a rich source guiding hit-to-lead-to-drug evolution.
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79
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Rudolph J, Heine A, Quast T, Kolanus W, Trebicka J, Brossart P, Wolf D. The JAK inhibitor ruxolitinib impairs dendritic cell migration via off-target inhibition of ROCK. Leukemia 2016; 30:2119-2123. [DOI: 10.1038/leu.2016.155] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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80
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Maiwald A, Hammami M, Wagner S, Heine A, Klebe G, Steinmetzer T. Changing the selectivity profile – from substrate analog inhibitors of thrombin and factor Xa to potent matriptase inhibitors. J Enzyme Inhib Med Chem 2016; 31:89-97. [DOI: 10.3109/14756366.2016.1172574] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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81
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Huschmann FU, Linnik J, Sparta K, Ühlein M, Wang X, Metz A, Schiebel J, Heine A, Klebe G, Weiss MS, Mueller U. Structures of endothiapepsin-fragment complexes from crystallographic fragment screening using a novel, diverse and affordable 96-compound fragment library. Acta Crystallogr F Struct Biol Commun 2016; 72:346-55. [PMID: 27139825 PMCID: PMC4854561 DOI: 10.1107/s2053230x16004623] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 03/16/2016] [Indexed: 11/10/2022] Open
Abstract
Crystallographic screening of the binding of small organic compounds (termed fragments) to proteins is increasingly important for medicinal chemistry-oriented drug discovery. To enable such experiments in a widespread manner, an affordable 96-compound library has been assembled for fragment screening in both academia and industry. The library is selected from already existing protein-ligand structures and is characterized by a broad ligand diversity, including buffer ingredients, carbohydrates, nucleotides, amino acids, peptide-like fragments and various drug-like organic compounds. When applied to the model protease endothiapepsin in a crystallographic screening experiment, a hit rate of nearly 10% was obtained. In comparison to other fragment libraries and considering that no pre-screening was performed, this hit rate is remarkably high. This demonstrates the general suitability of the selected compounds for an initial fragment-screening campaign. The library composition, experimental considerations and time requirements for a complete crystallographic fragment-screening campaign are discussed as well as the nine fully refined obtained endothiapepsin-fragment structures. While most of the fragments bind close to the catalytic centre of endothiapepsin in poses that have been observed previously, two fragments address new sites on the protein surface. ITC measurements show that the fragments bind to endothiapepsin with millimolar affinity.
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82
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Rühmann EH, Rupp M, Betz M, Heine A, Klebe G. Boosting Affinity by Correct Ligand Preorganization for the S2 Pocket of Thrombin: A Study by Isothermal Titration Calorimetry, Molecular Dynamics, and High-Resolution Crystal Structures. ChemMedChem 2016; 11:309-19. [PMID: 26762840 DOI: 10.1002/cmdc.201500531] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Revised: 12/14/2015] [Indexed: 01/19/2023]
Abstract
Structural preorganization to fix bioactive conformations at protein binding sites is a popular strategy to enhance binding affinity during late-stage optimization. The rationale for this enhancement relates to entropic advantages assigned to rigidified versus flexible ligands. We analyzed a narrow series of peptidomimetics binding to thrombin. The individual ligands exhibit at P2 a conformationally flexible glycine, more restricted alanine, N-methylglycine, N-methylhomoalanine, and largely rigidified proline moiety. Overall, affinity was found to increase by a factor of 1000, explained partly by an entropic advantage. All ligands adopt the same binding mode with small deviations. The residual mobility of the bound ligands is decreased across the series, and a protein side chain differs in its order/disorder behavior along with changes in the surface-water network pattern established across the newly generated protein-ligand surfaces. The enthalpy/entropy inventory displays a rather complex picture and emphasizes that thermodynamics can only be compared in terms of relative differences within a structurally similar ligand series.
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83
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Gaspari R, Rechlin C, Heine A, Bottegoni G, Rocchia W, Schwarz D, Bomke J, Gerber HD, Klebe G, Cavalli A. Kinetic and Structural Insights into the Mechanism of Binding of Sulfonamides to Human Carbonic Anhydrase by Computational and Experimental Studies. J Med Chem 2016; 59:4245-56. [PMID: 26700575 DOI: 10.1021/acs.jmedchem.5b01643] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The binding of sulfonamides to human carbonic anhydrase II (hCAII) is a complex and long-debated example of protein-ligand recognition and interaction. In this study, we investigate the para-substituted n-alkyl and hydroxyethylene-benzenesulfonamides, providing a complete reconstruction of their binding pathway to hCAII by means of large-scale molecular dynamics simulations, density functional calculations, surface plasmon resonance (SPR) measurements, and X-ray crystallography experiments. Our analysis shows that the protein-ligand association rate (kon) dramatically increases with the ligand's hydrophobicity, pointing to the existence of a prebinding stage largely stabilized by a favorable packing of the ligand's apolar moieties with the hCAII "hydrophobic wall". The characterization of the binding pathway allows an unprecedented understanding of the structure-kinetic relationship in hCAII/benzenesulfonamide complexes, depicting a paradigmatic scenario for the multistep binding process in protein-ligand systems.
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84
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Rühmann E, Betz M, Heine A, Klebe G. Fragment Binding Can Be Either More Enthalpy-Driven or Entropy-Driven: Crystal Structures and Residual Hydration Patterns Suggest Why. J Med Chem 2015; 58:6960-71. [PMID: 26270568 DOI: 10.1021/acs.jmedchem.5b00812] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In lead optimization, small, enthalpically advantaged fragments have been suggested to be superior, as an entropic component will be added inevitably during late-stage optimization. Determination of thermodynamic signatures of weak-binding fragments is essential to support the decision-making process, to decide which fragment to take to further optimization. High-resolution crystal structures of six fragments binding to the S1 pocket of thrombin were determined and analyzed with respect to their thermodynamic profile. The two most potent fragments exhibiting an amidine-type scaffold are not the most enthalpic binders; instead a chloro-thiophene fragment binds more enthalpically. Two chemically very similar chloro-aromatic fragments differ strongly in their potency (430 μM vs 10 mM); their binding modes are related, but the surrounding residual water network differs. The more potent one recruits a water molecule and involves Glu192 in binding, thus succeeding in firmly capping the S1 pocket. Fragments exhibiting a rather perfect solvation pattern in their binding mode also experience the highest potency.
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85
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Heine A, Schiebel J, Radeva N, Metz A, Huschmann FU, Ühlein M, Sparta K, Weiss MS, Mueller U, Klebe G. Crystallographic fragment screening: challenges, opportunities and lessons learned. Acta Crystallogr A Found Adv 2015. [DOI: 10.1107/s2053273315095996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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86
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Huschmann FU, Gerlach M, Foerster R, Heine A, Hellmig M, Klebe G, Linnik J, Malecki PH, Metz A, Radeva N, Schiebel J, Sparta K, Steffien M, Uehlein M, Wilk P, Weiss MS, Mueller U. Crystallographic fragment-screening – results from the HZB-Marburg collaboration. Acta Crystallogr A Found Adv 2015. [DOI: 10.1107/s2053273315099386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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87
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Sparta KM, Mueller U, Weiss MS, Ühlein M, Huschmann F, Schiebel J, Heine A, Klebe G. Automated solutions for fragment screening at the HZB MX beamlines. Acta Crystallogr A Found Adv 2015. [DOI: 10.1107/s2053273315099660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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88
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Schiebel J, Radeva N, Köster H, Metz A, Krotzky T, Kuhnert M, Diederich WE, Heine A, Neumann L, Atmanene C, Roecklin D, Vivat-Hannah V, Renaud JP, Meinecke R, Schlinck N, Sitte A, Popp F, Zeeb M, Klebe G. One Question, Multiple Answers: Biochemical and Biophysical Screening Methods Retrieve Deviating Fragment Hit Lists. ChemMedChem 2015; 10:1511-21. [DOI: 10.1002/cmdc.201500267] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Indexed: 12/12/2022]
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89
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Stefek M, Soltesova Prnova M, Majekova M, Rechlin C, Heine A, Klebe G. Identification of novel aldose reductase inhibitors based on carboxymethylated mercaptotriazinoindole scaffold. J Med Chem 2015; 58:2649-57. [PMID: 25695864 DOI: 10.1021/jm5015814] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Fifteen compounds, sharing an indole-1-acetic acid moiety as a common fragment, were selected from commercial databases for testing aldose reductase inhibition. 3-Mercapto-5H-1,2,4-triazino[5,6-b]indole-5-acetic acid (13) was the most promising inhibitor, with an IC50 in the submicromolar range and high selectivity, relative to aldehyde reductase. The crystal structure of aldose reductase complexed with 13 revealed an interaction pattern explaining its high affinity. Physicochemical parameters underline the excellent "leadlikeness" of 13 as a promising candidate for further structure optimizations.
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90
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Kuhnert M, Köster H, Bartholomäus R, Park AY, Shahim A, Heine A, Steuber H, Klebe G, Diederich WE. Chamäleon-artige Bindungsmodi in der Leitstrukturoptimierung: wechselnde Bindungsgeometrien bei Aspartylprotease-Inhibitoren. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201411206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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91
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Kuhnert M, Köster H, Bartholomäus R, Park AY, Shahim A, Heine A, Steuber H, Klebe G, Diederich WE. Tracing binding modes in hit-to-lead optimization: chameleon-like poses of aspartic protease inhibitors. Angew Chem Int Ed Engl 2015; 54:2849-53. [PMID: 25630461 DOI: 10.1002/anie.201411206] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2014] [Indexed: 12/28/2022]
Abstract
Successful lead optimization in structure-based drug discovery depends on the correct deduction and interpretation of the underlying structure-activity relationships (SAR) to facilitate efficient decision-making on the next candidates to be synthesized. Consequently, the question arises, how frequently a binding mode (re)-validation is required, to ensure not to be misled by invalid assumptions on the binding geometry. We present an example in which minor chemical modifications within one inhibitor series lead to surprisingly different binding modes. X-ray structure determination of eight inhibitors derived from one core scaffold resulted in four different binding modes in the aspartic protease endothiapepsin, a well-established surrogate for e.g. renin and β-secretase. In addition, we suggest an empirical metrics that might serve as an indicator during lead optimization to qualify compounds as candidates for structural revalidation.
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92
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Barandun LJ, Ehrmann FR, Zimmerli D, Immekus F, Giroud M, Grünenfelder C, Schweizer WB, Bernet B, Betz M, Heine A, Klebe G, Diederich F. Frontispiece: Replacement of Water Molecules in a Phosphate Binding Site by Furanoside-Appended lin-Benzoguanine Ligands of tRNA-Guanine Transglycosylase (TGT). Chemistry 2015. [DOI: 10.1002/chem.201580162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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93
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Barandun LJ, Ehrmann FR, Zimmerli D, Immekus F, Giroud M, Grünenfelder C, Schweizer WB, Bernet B, Betz M, Heine A, Klebe G, Diederich F. Replacement of Water Molecules in a Phosphate Binding Site by Furanoside-Appendedlin-Benzoguanine Ligands of tRNA-Guanine Transglycosylase (TGT). Chemistry 2014; 21:126-35. [DOI: 10.1002/chem.201405764] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Indexed: 11/09/2022]
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94
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Heine A, Radeva N, Schiebel J, Park A, Köster H, Ühlein M, Sparta K, Weiss M, Mueller U, Klebe G. Crystallographic fragment screening: challenges, opportunities, lessons learned. Acta Crystallogr A Found Adv 2014. [DOI: 10.1107/s2053273314092936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Fragment-based approaches are now routinely applied for lead development in pharmaceutical drug research. Usually, a small but well selected library of low molecular weight compounds is pre-screened by biochemical or biophysical methods such as surface plasmon resonance (SPR), nuclear magnetic resonance (NMR) or thermal shift assay; often followed for promising hit candidates by X-ray crystallography. We designed a small fragment library consisting of 364 compounds that is not strictly compliant to the otherwise often followed Astex rule of three for fragment library composition.[1] Thereafter, our library was validated on the pepsin-like aspartyl protease endothiapepsin, which serves as a model system for proteins that are involved in serious diseases such as malaria (plasmepsins), hypertension (renin) and Alzheimer's disease (ß-secretase) and therefore, is a valid target for further drug development. Due to the small size of fragments, they frequently exhibit only low affinity to the applied target protein and thus are often hard to detect in any screening approach, reflected in little overlap between different screening methods. After initial screening, we decided to validate the entire library by X-ray crystallography, which requires a steady supply of crystals, reproducible soaking conditions and a reliable setup at a synchrotron source, such as HZB BESSY II BL14.1 [2], preferably with some automation in initial data processing and refinement. A total hit rate greater than 10% was obtained, which will be compared to results from other screening methods. The resulting crystal structures will be discussed and provide an ideal basis for further lead development.
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95
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Mueller U, Ühlein M, Linnik J, Heine A, Klebe G, Weiss M. Fragment-screening at the BESSY II MX-beamlines of the Helmholtz-Zentrum Berlin. Acta Crystallogr A Found Adv 2014. [DOI: 10.1107/s2053273314092882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
"Within the last decade, the fragment-based screening approach has been matured to a reliable and powerful instrument of pharmaceutical drug discovery. The success of fragment screening strongly depends on the quality of the chosen fragment library (100-200 Da), the quality of the target protein diffraction as well as the possibility to use high throughput methods for the screen application. A thorough crystallographic analysis of many protein-fragment complex structures and their binding modes has the perspective to result in the development of new potential lead structures and to map the interaction landscape of protein surfaces. Recently we started the development of a dedicated experimental facility for high throughput fragment screening at the BESSY II storage ring. The in house data processing pipeline ""XDSAPP"" [1] has been developed to speed up the data evaluation of large amounts of diffraction data. We have assembled a fragment library of 96 compounds and have validated this library against two target proteins. These first results suggest that our library is capable of identifying binding partners at a hit rate of close to 10%. This library together with a fully automated beam line [2] will be made accessible to users, thus enabling fragment-screening experiments on a much broader basis. "
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96
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Neeb M, Betz M, Heine A, Barandun LJ, Hohn C, Diederich F, Klebe G. Beyond Affinity: Enthalpy–Entropy Factorization Unravels Complexity of a Flat Structure–Activity Relationship for Inhibition of a tRNA-Modifying Enzyme. J Med Chem 2014; 57:5566-78. [DOI: 10.1021/jm5006868] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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97
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Neeb M, Czodrowski P, Heine A, Barandun LJ, Hohn C, Diederich F, Klebe G. Chasing protons: how isothermal titration calorimetry, mutagenesis, and pKa calculations trace the locus of charge in ligand binding to a tRNA-binding enzyme. J Med Chem 2014; 57:5554-65. [PMID: 24955548 DOI: 10.1021/jm500401x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Drug molecules should remain uncharged while traveling through the body and crossing membranes and should only adopt charged state upon protein binding, particularly if charge-assisted interactions can be established in deeply buried binding pockets. Such strategy requires careful pKa design and methods to elucidate whether and where protonation-state changes occur. We investigated the protonation inventory in a series of lin-benzoguanines binding to tRNA-guanine transglycosylase, showing pronounced buffer dependency during ITC measurements. Chemical modifications of the parent scaffold along with ITC measurements, pKa calculations, and site-directed mutagenesis allow elucidating the protonation site. The parent scaffold exhibits two guanidine-type portions, both likely candidates for proton uptake. Even mutually compensating effects resulting from proton release of the protein and simultaneous uptake by the ligand can be excluded. Two adjacent aspartates induce a strong pKa shift at the ligand site, resulting in protonation-state transition. Furthermore, an array of two parallel H-bonds avoiding secondary repulsive effects contributes to the high-affinity binding of the lin-benzoguanines.
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98
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Habben CD, Heine A, Sheldrick GM, Stalke D. Synthese und Kristallstruktur von l,3-Di-tert-butyl-4,4-di-methyl-2-pentafluorphenyl-4,2-stannabora-cyclobutan / Synthesis and Crystal Structure of 1,3-Di-tert-butyl-4,4-di-methyl-2-pentafluorophenyl-4,2-stannabora-cyclobutane. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-1992-1005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The synthesis and crystal structure of 1,3-di-tert-butyl-4,4-dimethyl-2-pentafluorophenyl-1,3,4,2-diazastannoboracyclobutane are reported.
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99
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Hasselbring R, Roesky HW, Heine A, Stalke D, Sheldrick GM. Neue Cyclophosphazene mit Metallen der III. Hauptgruppe als Ringbausteine / New Cyclophosphazenes with Metals of Main Group III as Building Blocks. ACTA ACUST UNITED AC 2014. [DOI: 10.1515/znb-1994-0110] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Acylic silylated phosphazenes of the type HN(PR2NSiMe3)2 (1) react quantitatively with molecules MMe3 (M = Al, Ga, In) under ring formation and CH4 evolution. The ring compounds N(PPh2NSiMe3)2AlMe2 (2 a) and N(PPh2NSiMe3)2InMe2 (4 a) have been investiga ted by X-ray structure determination. 2a and 4a crystallize in the space groups P 1̄ and P 31, respectively; they show different conformations regarding the cyclohexane framework. NMR spectroscopy of the nuclei in the chelating phosphazene ligand indicates decreasing Lewis acidity of the metal containing fragments in the series AlMe2 ≥ GaMe2 > InMe2.
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100
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Krimmer SG, Betz M, Heine A, Klebe G. Corrigendum: Methyl, Ethyl, Propyl, Butyl: Futile But Not for Water, as the Correlation of Structure and Thermodynamic Signature Shows in a Congeneric Series of Thermolysin Inhibitors. ChemMedChem 2014. [DOI: 10.1002/cmdc.201400087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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