17 results on '"Patrick G. Isenegger"'
Search Results
2. Precise Probing of Residue Roles by Post-Translational β,γ-C,N Aza-Michael Mutagenesis in Enzyme Active Sites
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Jitka Dadová, Kuan-Jung Wu, Patrick G. Isenegger, James C. Errey, Gonçalo J. L. Bernardes, Justin M. Chalker, Lluís Raich, Carme Rovira, and Benjamin G. Davis
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Chemistry ,QD1-999 - Published
- 2017
- Full Text
- View/download PDF
3. Post-translational insertion of boron in proteins to probe and modulate function
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Lukas Lercher, Shabaz Mohammed, Tim A. Mollner, Benjamin G. Davis, Patrick G. Isenegger, Brian Josephson, Charles J. Buchanan, Daniel Oehlrich, Andrew Baldwin, Véronique Gouverneur, and D. Flemming Hansen
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Mutation ,Proteins ,chemistry.chemical_element ,Cell Biology ,medicine.disease_cause ,Article ,Footprinting ,Residue (chemistry) ,NMR spectroscopy ,chemistry ,Covalent bond ,Intramolecular force ,Biophysics ,medicine ,Target protein ,Chemical tools ,Boron ,Molecular Biology ,Function (biology) ,Chemical modification - Abstract
Boron is absent in proteins, yet is a micronutrient. It possesses unique bonding that could expand biological function including modes of Lewis acidity not available to typical elements of life. Here we show that post-translational Cβ–Bγ bond formation provides mild, direct, site-selective access to the minimally sized residue boronoalanine (Bal) in proteins. Precise anchoring of boron within complex biomolecular systems allows dative bond-mediated, site-dependent protein Lewis acid–base-pairing (LABP) by Bal. Dynamic protein-LABP creates tunable inter- and intramolecular ligand–host interactions, while reactive protein-LABP reveals reactively accessible sites through migratory boron-to-oxygen Cβ–Oγ covalent bond formation. These modes of dative bonding can also generate de novo function, such as control of thermo- and proteolytic stability in a target protein, or observation of transient structural features via chemical exchange. These results indicate that controlled insertion of boron facilitates stability modulation, structure determination, de novo binding activities and redox-responsive ‘mutation’., Post-translational site-selective formation of boronoalanine in proteins enables applications of boron for binding partner capture, footprinting of interactions with reactive oxygen species, proteolytic control and mapping of transient structures.
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- 2021
4. Residue-Selective Protein C-Formylation via Sequential Difluoroalkylation-Hydrolysis
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Véronique Gouverneur, Mateusz Imiołek, Benjamin G. Davis, Aziz Khan, Patrick G. Isenegger, and Wai-Lung Ng
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chemistry.chemical_classification ,Bioconjugation ,010405 organic chemistry ,Stereochemistry ,General Chemical Engineering ,Chemical biology ,Photoredox catalysis ,General Chemistry ,010402 general chemistry ,01 natural sciences ,3. Good health ,0104 chemical sciences ,Amino acid ,Formylation ,Chemistry ,Residue (chemistry) ,chemistry ,Reactivity (chemistry) ,QD1-999 ,Carbonylation ,Research Article - Abstract
The carbonyl group is now a widely useful, nonproteinogenic functional group in chemical biology, yet methods for its generation in proteins have relied upon either cotranslational incorporation of unnatural amino acids bearing carbonyls or oxidative conversion (chemical or enzymatic) of existing natural amino acids. If available, alternative strategies for directly adding the C=O group through C–C bond-forming C-carbonylation, particularly at currently inaccessible amino acid sites, would provide a powerful method for adding valuable reactivity and expanding possible function in proteins. Here, following a survey of methods for HCF2· generation, we show that reductive photoredox catalysis enables mild radical-mediated difluoromethylation-hydrolysis of native protein residues as an effective method for carbonylation. Inherent selectivity of HCF2· allowed preferential modification of Trp residues. The resulting C-2-difluoromethylated Trp undergoes Reimer-Tiemann-type dehalogenation providing highly effective spontaneous hydrolytic collapse in proteins to carbonylated HC(O)-Trp (C-formyl-Trp = CfW) residues. This new, unnatural protein residue CfW not only was found to be effective in bioconjugation, ligation, and labeling reactions but also displayed strong “red-shifting” of its absorption and fluorescent emission maxima, allowing direct use of Trp sites as UV–visualized fluorophores in proteins and even cells. In this way, this method for the effective generation of masked formyl-radical “HC(O)·” equivalents enables first examples of C–C bond-forming carbonylation in proteins, thereby expanding the chemical reactivity and spectroscopic function that may be selectively and post-translationally “edited” into biology., Radical difluoromethylation (→C−CF2H) and subsequent hydrolysis (→C−CHO) allow direct, Trp-selective introduction of protein aldehyde, which acts as both a labeling and minimally sized fluorescent tag on proteins and cells.
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- 2021
5. Synthesis of Fluorinated Alkyl Aryl Ethers by Palladium-Catalyzed C–O Cross-Coupling
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Véronique Gouverneur, David C. Blakemore, Maxime Ghosez, Patrick G. Isenegger, Natan J. W. Straathof, Rosa Cookson, Paul G. Richardson, and Robert Szpera
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chemistry.chemical_classification ,Letter ,010405 organic chemistry ,Aryl ,Organic Chemistry ,chemistry.chemical_element ,010402 general chemistry ,01 natural sciences ,Biochemistry ,3. Good health ,0104 chemical sciences ,Catalysis ,Coupling (electronics) ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Physical and Theoretical Chemistry ,Alkyl ,Palladium - Abstract
Herein, we report a highly effective protocol for the cross-coupling of (hetero)aryl bromides with fluorinated alcohols using the commercially available precatalyst tBuBrettPhos Pd G3 and Cs2CO3 in toluene. This Pd-catalyzed coupling features a short reaction time, excellent functional group tolerance, and compatibility with electron-rich and -poor (hetero)arenes. The method provides access to 18F-labeled trifluoroethyl ethers by cross-coupling with [18F]trifluoroethanol.
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- 2020
6. PET Imaging Using [18F]olaparib in Mouse Models of Malignant Glioma: Considerations for Molecular Imaging and Radionuclide Therapy Targeting PARP
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Patrick G. Isenegger, Gemma M. Dias, Samantha L. Hopkins, Anna Pacelli, Chung Ying Chan, Bart Cornelissen, Véronique Gouverneur, Rebekka Hueting, Julia Baguña Torres, Michael Mosley, Florian Guibbal, Zijun Chen, Doreen Lau, and Thomas C. Wilson
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business.industry ,Poly ADP ribose polymerase ,Pet imaging ,medicine.disease ,Olaparib ,chemistry.chemical_compound ,Text mining ,chemistry ,Glioma ,Radionuclide therapy ,Cancer research ,Medicine ,Molecular imaging ,business - Abstract
PurposeRadiopharmaceuticals targeting poly(ADP-ribose) polymerase (PARP) have emerged as promising agents for cancer diagnosis and therapy. PARP enzymes are expressed in both cancerous and normal tissue. Hence, the injected mass, molar activity and potential pharmacological effects are important considerations for the use of radiolabelled PARP inhibitors for diagnostic and radionuclide therapeutic applications. Here, we performed a systematic evaluation by varying the molar activity of [18F]olaparib and the injected mass of [TotalF]olaparib to investigate the effects on tumour and normal tissue uptake in two subcutaneous human glioblastoma xenograft models.Methods[18F]Olaparib uptake was evaluated in the human glioblastoma models: in vitro on U251MG and U87MG cell lines, and in vivo on tumour xenograft-bearing mice, after administration of [TotalF]olaparib (varying injected mass: 0.04-8.0 µg, and molar activity: 1-320 GBq/μmol).ResultsSelective uptake of [18F]olaparib was demonstrated in both models. Tumour uptake was found to be dependent on the injected mass of [TotalF]olaparib (µg), but not the molar activity per sé. An injected mass of 1 μg resulted in the highest tumour uptake (up to 6.9 ± 1.3%ID/g), independent of the molar activity. In comparison, both the lower and higher injected masses of [TotalF]olaparib resulted in lower relative tumour uptake (%ID/g; PEx vivo analysis of U87MG xenograft sections showed that the heterogeneity in [18F]olaparib intratumoural uptake correlated with PARP1 expression. Substantial upregulation of PARP1-3 expression was observed after administration of [TotalF]olaparib (>0.5 µg).Conclusion Our findings show that the injected mass of [TotalF]olaparib has significant effects on tumour uptake. Moderate injected masses of PARP inhibitor-derived radiopharmaceuticals may lead to improved relative tumour uptake and tumour-to-background ratio for cancer diagnosis and radionuclide therapy.
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- 2021
7. Radiosynthesis of [18F]ArylSCF2H using aryl boronic acids, S-(chlorofluoromethyl)benzenesulfonothioate and [18F]fluoride
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Véronique Gouverneur, Florian Guibbal, Thomas C. Wilson, Jeroen B. I. Sap, Long Lu, Qunchao Zhao, Qilong Shen, and Patrick G. Isenegger
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inorganic chemicals ,chemistry.chemical_compound ,Chemistry ,Reagent ,Aryl ,Radiosynthesis ,Fluorine ,chemistry.chemical_element ,macromolecular substances ,General Chemistry ,18f fluoride ,environment and public health ,Combinatorial chemistry - Abstract
Herein, we report a mild and practical protocol for the copper-catalyzed chlorofluoromethylthiolation of (hetero)aryl boronic acids with the novel reagent PhSO2SCFClH. The resulting products are amenable to halogen exchange 18F-fluorination with cyclotron-produced [18F]fluoride affording [18F]ArSCF2H. This process highlights the combined value of reagent development and (hetero)aryl boron precursors for radiochemistry by adding the [18F]SCF2H group to the list of 18F-motifs within reach for positron emission tomography studies.
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- 2020
8. [18F]AZD2461, an Insight on Difference in PARP Binding Profiles for DNA Damage Response PET Imaging
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Samantha L. Hopkins, Rebekka Hueting, Patrick G. Isenegger, Véronique Gouverneur, Julia Baguña Torres, Michael Mosley, Florian Guibbal, Damien Mahaut, Anna Pacelli, Bart Cornelissen, and Gemma M. Dias
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Fluorine Radioisotopes ,Cancer Research ,DNA damage ,Poly ADP ribose polymerase ,Cell ,Mice, Nude ,Molecular imaging ,Poly(ADP-ribose) Polymerase Inhibitors ,Piperazines ,AZD2461 ,030218 nuclear medicine & medical imaging ,Olaparib ,PARP ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Piperidines ,In vivo ,Cell Line, Tumor ,medicine ,Animals ,Tissue Distribution ,Radiology, Nuclear Medicine and imaging ,Boron ,Cancer ,PARP Inhibitor AZD2461 ,Mice, Inbred BALB C ,Esters ,Xenograft Model Antitumor Assays ,In vitro ,3. Good health ,medicine.anatomical_structure ,PET ,Oncology ,chemistry ,Positron-Emission Tomography ,030220 oncology & carcinogenesis ,PARP inhibitor ,Cancer research ,Phthalazines ,Poly(ADP-ribose) Polymerases ,Copper ,Research Article ,DNA Damage ,Protein Binding - Abstract
Background Poly (ADP-ribose) polymerase (PARP) inhibitors are extensively studied and used as anti-cancer drugs, as single agents or in combination with other therapies. Most radiotracers developed to date have been chosen on the basis of strong PARP1–3 affinity. Herein, we propose to study AZD2461, a PARP inhibitor with lower affinity towards PARP3, and to investigate its potential for PARP targeting in vivo. Methods Using the Cu-mediated 18F-fluorodeboronation of a carefully designed radiolabelling precursor, we accessed the 18F-labelled isotopologue of the PARP inhibitor AZD2461. Cell uptake of [18F]AZD2461 in vitro was assessed in a range of pancreatic cell lines (PSN-1, PANC-1, CFPAC-1 and AsPC-1) to assess PARP expression and in vivo in xenograft-bearing mice. Blocking experiments were performed with both olaparib and AZD2461. Results [18F]AZD2461 was efficiently radiolabelled via both manual and automated procedures (9 % ± 3 % and 3 % ± 1 % activity yields non-decay corrected). [18F]AZD2461 was taken up in vivo in PARP1-expressing tumours, and the highest uptake was observed for PSN-1 cells (7.34 ± 1.16 %ID/g). In vitro blocking experiments showed a lesser ability of olaparib to reduce [18F]AZD2461 binding, indicating a difference in selectivity between olaparib and AZD2461. Conclusion Taken together, we show the importance of screening the PARP selectivity profile of radiolabelled PARP inhibitors for use as PET imaging agents.
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- 2020
9. Manual and automated Cu-mediated radiosynthesis of the PARP inhibitor [18F]olaparib
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Damien Mahaut, Patrick G. Isenegger, Thomas C. Wilson, Véronique Gouverneur, Jeroen B. I. Sap, Rebekka Hueting, Nicholas J. Taylor, Florian Guibbal, Sean Preshlock, Bart Cornelissen, Stefan Verhoog, and Anna Pacelli
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0303 health sciences ,Nuclear imaging ,Radiosynthesis ,Synthetic chemistry methodology ,Automated radiosynthesis ,Combinatorial chemistry ,General Biochemistry, Genetics and Molecular Biology ,Olaparib ,03 medical and health sciences ,chemistry.chemical_compound ,Automation ,0302 clinical medicine ,chemistry ,Positron-Emission Tomography ,PARP inhibitor ,030217 neurology & neurosurgery ,Sensors and probes ,030304 developmental biology ,Chemical modification - Abstract
Positron emission tomography (PET) is a diagnostic nuclear imaging modality that relies on automated protocols to prepare agents labeled with a positron-emitting radionuclide (e.g., 18F). In recent years, new reactions have appeared for the 18F-labeling of agents that are difficult to access by applying traditional radiochemistry, for example those requiring 18F incorporation into unactivated (hetero)arenes. However, automation of these new methods for translation to the clinic has progressed slowly because extensive modification of manual protocols is typically required when implementing novel 18F-labeling methodologies within automated modules. Here, we describe the workflow that led to the automated radiosynthesis of the poly(ADP-ribose) polymerase (PARP) inhibitor [18F]olaparib. First, we established a robust manual protocol to prepare [18F]olaparib from the protected N-[2-(trimethylsilyl)ethoxy]methyl (SEM) arylboronate ester precursor in a 17% ± 5% (n = 15; synthesis time, 135 min) non-decay-corrected (NDC) activity yield, with molar activity (Am) up to 34.6 GBq/µmol. Automation of the process, consisting of copper-mediated 18F-fluorodeboronation followed by deprotection, was achieved on an Eckert & Ziegler Modular-Lab radiosynthesis platform, affording [18F]olaparib in a 6% ± 5% (n = 3; synthesis time, 120 min) NDC activity yield with Am up to 319 GBq/µmol. Automation of new methods for 18F incorporation into unactivated (hetero)arenes for translation to the clinic has progressed slowly. This protocol describes a workflow leading to automated radiosynthesis of the PARP inhibitor [18F]olaparib.
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- 2020
10. 18F-trifluoromethanesulfinate enables direct C–H 18F-trifluoromethylation of native aromatic residues in peptides
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Stefan Verhoog, Thomas C. Wilson, Jane K. Sosabowski, Véronique Gouverneur, Giulia Boscutti, Christophe Plisson, Florian Guibbal, Jan Passchier, Sharon Ashworth, Mateusz Imiołek, Michael J. Tilby, Sven Macholl, Benjamin G. Davis, Choon Wee Kee, Adeline W. J. Poh, Bart Cornelissen, Osman Tack, Juliette Chupin, Michael C. Willis, Patrick G. Isenegger, and Roxana Kashani
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Bioconjugation ,Trifluoromethylation ,Radical ,Communication ,Lysine ,Radiosynthesis ,Tryptophan ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Fluoride ,Cysteine - Abstract
18F labeling strategies for unmodified peptides with [18F]fluoride require 18F-labeled prosthetics for bioconjugation more often with cysteine thiols or lysine amines. Here we explore selective radical chemistry to target aromatic residues applying C-H 18F-trifluoromethylation. We report a one-step route to [18F]CF3SO2NH4 from [18F]fluoride and its application to direct [18F]CF3 incorporation at tryptophan or tyrosine residues using unmodified peptides as complex as recombinant human insulin. The fully automated radiosynthesis of octreotide[Trp(2-CF218F)] enables in vivo positron emission tomography imaging.
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- 2020
11. Manual and automated Cu-mediated radiosynthesis of the PARP inhibitor [
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Florian, Guibbal, Patrick G, Isenegger, Thomas C, Wilson, Anna, Pacelli, Damien, Mahaut, Jeroen B I, Sap, Nicholas J, Taylor, Stefan, Verhoog, Sean, Preshlock, Rebekka, Hueting, Bart, Cornelissen, and Véronique, Gouverneur
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Automation ,Fluorine Radioisotopes ,Radiochemistry ,Positron-Emission Tomography ,Phthalazines ,Chemistry Techniques, Synthetic ,Poly(ADP-ribose) Polymerase Inhibitors ,Radiopharmaceuticals ,Copper ,Piperazines - Abstract
Positron emission tomography (PET) is a diagnostic nuclear imaging modality that relies on automated protocols to prepare agents labeled with a positron-emitting radionuclide (e.g.
- Published
- 2019
12. Concepts of Catalysis in Site-Selective Protein Modifications
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Benjamin G. Davis and Patrick G. Isenegger
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Azides ,Chemistry ,education ,Proteins ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Catalysis ,Ruthenium ,0104 chemical sciences ,3. Good health ,Colloid and Surface Chemistry ,Alkynes ,Site selective ,Biochemical engineering ,Copper ,Palladium - Abstract
[Image: see text] The manipulation and modulation of biomolecules has the potential to herald new modes of Biology and Medicine through chemical “editing”. Key to the success of such processes will be the selectivities, reactivities and efficiencies that may be brought to bear in bond-formation and bond-cleavage in a benign manner. In this Perspective, we use select examples, primarily from our own research, to examine the current opportunities, limitations and the particular potential of metal-mediated processes as exemplars of possible alternative catalytic modes and manifolds to those already found in nature.
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- 2019
13. Imaging of translocator protein upregulation is selective for pro-inflammatory polarized astrocytes and microglia
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Maria Pannell, Thomas C. Wilson, Patrick G. Isenegger, Veerle Kersemans, Vasiliki Economopoulos, Véronique Gouverneur, Sean Smart, James R. Larkin, Stuart Gilchrist, and Nicola R. Sibson
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0301 basic medicine ,Lipopolysaccharides ,Pathology ,medicine.medical_specialty ,Population ,microglia ,03 medical and health sciences ,Cellular and Molecular Neuroscience ,Mice ,0302 clinical medicine ,Downregulation and upregulation ,In vivo ,medicine ,Translocator protein ,Animals ,education ,Neuroinflammation ,Research Articles ,Inflammation ,education.field_of_study ,brain inflammation ,Microglia ,biology ,translocator protein ,Macrophages ,astrocytes ,Disease Models, Animal ,030104 developmental biology ,medicine.anatomical_structure ,PET ,Neurology ,Positron-Emission Tomography ,biology.protein ,Tumor necrosis factor alpha ,Carrier Proteins ,Neuroglia ,030217 neurology & neurosurgery ,Ex vivo ,Research Article - Abstract
Translocator protein (TSPO) expression is increased in activated glia, and has been used as a marker of neuroinflammation in PET imaging. However, the extent to which TSPO upregulation reflects a pro‐ or anti‐inflammatory phenotype remains unclear. Our aim was to determine whether TSPO upregulation in astrocytes and microglia/macrophages is limited to a specific inflammatory phenotype. TSPO upregulation was assessed by flow cytometry in cultured astrocytes, microglia, and macrophages stimulated with lipopolysaccharide (LPS), tumor necrosis factor (TNF), or interleukin‐4 (Il‐4). Subsequently, mice were injected intracerebrally with either a TNF‐inducing adenovirus (AdTNF) or IL‐4. Glial expression of TSPO and pro‐/anti‐inflammatory markers was assessed by immunohistochemistry/fluorescence and flow cytometry. Finally, AdTNF or IL‐4 injected mice underwent PET imaging with injection of the TSPO radioligand 18F‐DPA‐713, followed by ex vivo autoradiography. TSPO expression was significantly increased in pro‐inflammatory microglia/macrophages and astrocytes both in vitro, and in vivo after AdTNF injection (p, Main points TSPO expression is strongly associated with pro‐ but not anti‐inflammatory microglia, macrophages and astrocytes, in vitro and in vivo.PET imaging with TSPO ligand 18F‐DPA‐713 reveals the pro‐inflammatory population of glial cells.
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- 2019
14. Asymmetric Morita-Baylis-Hillman Reaction: Catalyst Development and Mechanistic Insights Based on Mass Spectrometric Back-Reaction Screening
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Andreas Pfaltz, Florian Bächle, and Patrick G. Isenegger
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010405 organic chemistry ,Organic Chemistry ,Enantioselective synthesis ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Aldol reaction ,chemistry ,Organocatalysis ,Organic chemistry ,Baylis–Hillman reaction ,Bifunctional ,Methyl acrylate ,Phosphine - Abstract
An efficient protocol for the evaluation of catalysts for the asymmetric Morita-Baylis-Hillman (MBH) reaction was developed. By mass spectrometric back-reaction screening of quasi-enantiomeric MBH products, an efficient bifunctional phosphine catalyst was identified that outperforms literature-known catalysts in the MBH reaction of methyl acrylate with aldehydes. The close match between the selectivities measured for the forward and back reaction and kinetic measurements provided strong evidence that the aldol step and not the subsequent proton transfer is rate- and enantioselectivity-determining.
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- 2016
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15. Precise Probing of Residue Roles by Post-Translational β,γ-C,N Aza-Michael Mutagenesis in Enzyme Active Sites
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Kuan-Jung Wu, Benjamin G. Davis, Gonçalo J. L. Bernardes, James C. Errey, Carme Rovira, Patrick G. Isenegger, Justin M. Chalker, Lluís Raich, and Jitka Dadová
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0301 basic medicine ,Stereochemistry ,General Chemical Engineering ,medicine.medical_treatment ,010402 general chemistry ,01 natural sciences ,lcsh:Chemistry ,03 medical and health sciences ,Residue (chemistry) ,chemistry.chemical_compound ,Dehydroalanine ,medicine ,Histidine ,chemistry.chemical_classification ,Protease ,Mutagenesis ,Subtilisin ,General Chemistry ,0104 chemical sciences ,3. Good health ,Amino acid ,030104 developmental biology ,Enzyme ,chemistry ,lcsh:QD1-999 ,Research Article - Abstract
Biomimicry valuably allows the understanding of the essential chemical components required to recapitulate biological function, yet direct strategies for evaluating the roles of amino acids in proteins can be limited by access to suitable, subtly-altered unnatural variants. Here we describe a strategy for dissecting the role of histidine residues in enzyme active sites using unprecedented, chemical, post-translational side-chain-β,γ C–N bond formation. Installation of dehydroalanine (as a “tag”) allowed the testing of nitrogen conjugate nucleophiles in “aza-Michael”-1,4-additions (to “modify”). This allowed the creation of a regioisomer of His (iso-His, Hisiso) linked instead through its pros-Nπ atom rather than naturally linked via C4, as well as an aza-altered variant aza-Hisiso. The site-selective generation of these unnatural amino acids was successfully applied to probe the contributing roles (e.g., size, H-bonding) of His residues toward activity in the model enzymes subtilisin protease from Bacillus lentus and Mycobacterium tuberculosis pantothenate synthetase., Chemical mutagenesis can expand genetic methods. Now, chemical, post-translational side-chain-β,γ C−N bond formation probes activities of new histidine regioisomers and analogues (Hisiso, aza-Hisiso).
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- 2017
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16. Mass Spectrometric Back Reaction Screening of Quasi-Enantiomeric Products as a Mechanistic Tool
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Andreas Pfaltz and Patrick G. Isenegger
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010405 organic chemistry ,Chemistry ,General Chemical Engineering ,Reactive intermediate ,Enantioselective synthesis ,General Chemistry ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,0104 chemical sciences ,Catalysis ,Energy profile ,Catalytic cycle ,Aldol reaction ,Organocatalysis ,Materials Chemistry ,Enantiomer - Abstract
In this account, we discuss a mass spectrometric method that enables unambiguous identification of intermediates involved in the enantioselective step of a catalytic cycle. This method, which we originally developed for rapid evaluation of chiral catalysts, is based on monitoring the back reaction of mass-labeled quasi-enantiomeric products by ESI-MS. In this way, the intrinsic enantioselectivity of a chiral catalyst can be determined directly by quantification of catalytically relevant intermediates. By comparing the results from the forward and back reaction, direct evidence for the involvement of a catalytic intermediate in the enantioselective step can be obtained. In addition, insights about the energy profile of the catalytic cycle may be gained. The potential of back reaction screening as a mechanistic tool is demonstrated for organocatalytic aldol reactions, 1,4-additions of aldehydes to nitroolefins, Diels-Alder reactions, Michael additions, and Morita-Baylis-Hillman reactions.
- Published
- 2016
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17. Light-driven post-translational installation of reactive protein side chains
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Jeroen B. I. Sap, Véronique Gouverneur, Charlie Fehl, Shabaz Mohammed, Patrick G. Isenegger, Adeline W. J. Poh, Andrew Baldwin, Oluwatobi Arisa, Richard G. Compton, Benjamin G. Davis, Simon Nadal, Akane Kawamura, Tom H. Wright, Grace Roper, Lifu Chen, Christopher Batchelor-McAuley, Andrew M. Giltrap, Ben J. Bower, and Brian Josephson
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Hydrocarbons, Fluorinated ,Light ,Radical ,010402 general chemistry ,01 natural sciences ,Heterolysis ,chemistry.chemical_compound ,Dehydroalanine ,Side chain ,Humans ,Protein Interaction Domains and Motifs ,Binding site ,Multidisciplinary ,Alanine ,Binding Sites ,010405 organic chemistry ,Chemistry ,Proteins ,Esters ,Photochemical Processes ,Small molecule ,Combinatorial chemistry ,Carbon ,0104 chemical sciences ,Homolysis ,Enzymes ,Indicators and Reagents ,Oxidation-Reduction ,Protein Processing, Post-Translational ,Boronic acid ,HeLa Cells - Abstract
Post-translational modifications (PTMs) greatly expand the structures and functions of proteins in nature1,2. Although synthetic protein functionalization strategies allow mimicry of PTMs3,4, as well as formation of unnatural protein variants with diverse potential functions, including drug carrying5, tracking, imaging6 and partner crosslinking7, the range of functional groups that can be introduced remains limited. Here we describe the visible-light-driven installation of side chains at dehydroalanine residues in proteins through the formation of carbon-centred radicals that allow C-C bond formation in water. Control of the reaction redox allows site-selective modification with good conversions and reduced protein damage. In situ generation of boronic acid catechol ester derivatives generates RH2C• radicals that form the native (β-CH2-γ-CH2) linkage of natural residues and PTMs, whereas in situ potentiation of pyridylsulfonyl derivatives by Fe(II) generates RF2C• radicals that form equivalent β-CH2-γ-CF2 linkages bearing difluoromethylene labels. These reactions are chemically tolerant and incorporate a wide range of functionalities (more than 50 unique residues/side chains) into diverse protein scaffolds and sites. Initiation can be applied chemoselectively in the presence of sensitive groups in the radical precursors, enabling installation of previously incompatible side chains. The resulting protein function and reactivity are used to install radical precursors for homolytic on-protein radical generation; to study enzyme function with natural, unnatural and CF2-labelled post-translationally modified protein substrates via simultaneous sensing of both chemo- and stereoselectivity; and to create generalized 'alkylator proteins' with a spectrum of heterolytic covalent-bond-forming activity (that is, reacting diversely with small molecules at one extreme or selectively with protein targets through good mimicry at the other). Post-translational access to such reactions and chemical groups on proteins could be useful in both revealing and creating protein function.
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