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1.
Emerg Infect Dis ; 30(4): 711-720, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38526123

RESUMO

To examine the risk associated with bus riding and identify transmission chains, we investigated a COVID-19 outbreak in Germany in 2021 that involved index case-patients among bus-riding students. We used routine surveillance data, performed laboratory analyses, interviewed case-patients, and conducted a cohort study. We identified 191 case-patients, 65 (34%) of whom were elementary schoolchildren. A phylogenetically unique strain and epidemiologic analyses provided a link between air travelers and cases among bus company staff, schoolchildren, other bus passengers, and their respective household members. The attack rate among bus-riding children at 1 school was ≈4 times higher than among children not taking a bus to that school. The outbreak exemplifies how an airborne agent may be transmitted effectively through (multiple) short (<20 minutes) public transport journeys and may rapidly affect many persons.


Assuntos
COVID-19 , SARS-CoV-2 , Criança , Humanos , COVID-19/epidemiologia , Estudos de Coortes , Surtos de Doenças , Alemanha/epidemiologia
2.
J Am Chem Soc ; 140(21): 6710-6717, 2018 05 30.
Artigo em Inglês | MEDLINE | ID: mdl-29750514

RESUMO

Vinylcyclopropanes (VCPs) are known to generate 1,3-dipoles with a palladium catalyst that initially serve as nucleophiles to undergo [3 + 2] cycloadditions with electron-deficient olefins. In this report, we reverse this reactivity and drive the 1,3-dipoles to serve as electrophiles by employing 3-alkylated indoles as nucleophiles. This represents the first use of VCPs for the completely atom-economic functionalization of 3-substituted 1 H-indoles and tryptophan derivatives via a Pd-catalyzed asymmetric allylic alkylation (Pd-AAA). Excellent yields and high chemo-, regio-, and enantioselectivities have been realized, providing various indolenine and indoline products. The method is amenable to gram scale and works efficiently with tryptophan derivatives that contain a diketopiperazine or diketomorpholine ring, allowing us to synthesize mollenine A in a rapid and ligand-controlled fashion. The obtained indolenine products bear an imine, an internal olefin, and a malonate motif, giving multiple sites with diverse reactivities for product diversification. Complicated polycyclic skeletons can be conveniently constructed by leveraging this unique juxtaposition of functional groups.


Assuntos
Compostos Alílicos/síntese química , Ciclopropanos/química , Indóis/química , Paládio/química , Triptofano/química , Alquilação , Compostos Alílicos/química , Catálise , Reação de Cicloadição , Estrutura Molecular
3.
J Am Chem Soc ; 140(49): 17316-17326, 2018 12 12.
Artigo em Inglês | MEDLINE | ID: mdl-30457857

RESUMO

The synthesis of des-epoxy-amphidinolide N was achieved in 22 longest linear and 33 total steps. Three generations of synthetic endeavors are reported herein. During the first generation, our key stitching strategy that highlighted an intramolecular Ru-catalyzed alkene-alkyne (Ru AA) coupling and a late-stage epoxidation proved successful, but the installation of the α,α'-dihydroxyl ketone motif employing a dihydroxylation method was problematic. Our second generation of synthetic efforts addressed the scalability problem of the southern fragment synthesis and significantly improved the efficiency of the atom-economical Ru AA coupling, but suffered from several protecting group-based issues that proved insurmountable. Finally, relying on a judicious protecting group strategy together with concise fragment preparation, des-epoxy-amphidinolide N was achieved in a convergent fashion. Calculations disclose a hydrogen-bonding bridge within amphidinolide N. Comparisons of 13C NMR chemical shift differences using our synthetic des-epoxy-amphidinolide N suggest that amphidinolide N and carbenolide I are probably identical.


Assuntos
Macrolídeos/síntese química , Alcenos/química , Alcinos/química , Catálise , Ciclização , Esterificação , Ligação de Hidrogênio , Conformação Molecular , Oxirredução , Rutênio/química , Estereoisomerismo
4.
Angew Chem Int Ed Engl ; 57(39): 12916-12920, 2018 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-30073727

RESUMO

A protocol for the asymmetric synthesis of highly substituted chiral allenes with control of point and axial chirality has been developed. A palladium-catalyzed [3+2] cycloaddition using readily available racemic allenes gives access to densely functionalized chiral allenes with excellent yields and functional group tolerance. The catalytic asymmetric protocol utilizes a broad range of allenyl TMM (trimethylenemethane) donors to form cyclopentanes, pyrrolidines, and spirocycles with very good control of regio-, enantio-, and diastereoselectivity. The chiral allene moiety is shown to be a valuable functional group for rapid elaboration towards complex targets.

5.
Angew Chem Int Ed Engl ; 57(32): 10085-10090, 2018 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-29927035

RESUMO

The enzyme tRNA-guanine transglycosylase, a target to fight Shigellosis, recognizes tRNA only as a homodimer and performs full nucleobase exchange at the wobble position. Active-site inhibitors block the enzyme function by competitively replacing tRNA. In solution, the wild-type homodimer dissociates only marginally, whereas mutated variants show substantial monomerization in solution. Surprisingly, one inhibitor transforms the protein into a twisted state, whereby one monomer unit rotates by approximately 130°. In this altered geometry, the enzyme is no longer capable of binding and processing tRNA. Three sugar-type inhibitors have been designed and synthesized, which bind to the protein in either the functionally competent or twisted inactive state. They crystallize with the enzyme side-by-side under identical conditions from the same crystallization well. Possibly, the twisted inactive form corresponds to a resting state of the enzyme, important for its functional regulation.


Assuntos
Pentosiltransferases/metabolismo , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Modelos Moleculares , Estrutura Molecular , Pentosiltransferases/antagonistas & inibidores , Pentosiltransferases/química
6.
Chemistry ; 22(20): 6750-4, 2016 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-26991861

RESUMO

Shigellosis is one of the most severe diarrheal diseases worldwide without any efficient treatment so far. The enzyme tRNA-guanine transglycosylase (TGT) has been identified as a promising target for small-molecule drug design. Herein, we report a transition-state analogue, a small, immucillin-derived inhibitor, as a new lead structure with a novel mode of action. The complex inhibitor synthesis was accomplished in 18 steps with an overall yield of 3 %. A co-crystal structure of the inhibitor bound to Z. mobilis TGT confirmed the predicted conformation of the immucillin derivative in the enzyme active site.


Assuntos
Proteínas de Bactérias/antagonistas & inibidores , Pentosiltransferases/antagonistas & inibidores , Pirimidinas/química , Pirróis/química , Pirrolidinas/química , Zymomonas/enzimologia , Cristalografia por Raios X , Modelos Moleculares , Conformação Molecular , Pentosiltransferases/química , Pirimidinas/síntese química , Pirróis/síntese química , Pirrolidinas/síntese química , Estereoisomerismo
7.
Bioorg Med Chem ; 24(20): 4900-4910, 2016 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-27501913

RESUMO

Small-molecule ligands binding with partial disorder or enhanced residual mobility are usually assumed as unfavorable with respect to their binding properties. Considering thermodynamics, disorder or residual mobility is entropically favorable and contributes to the Gibbs energy of binding. In the present study, we analyzed a series of congeneric ligands inhibiting the tRNA-modifying enzyme TGT. Attached to the parent lin-benzoguanine scaffold, substituents in position 2 accommodate in a flat solvent-exposed pocket and exhibit varying degree of residual mobility. This is indicated in the crystal structures by enhanced B-factors, reduced occupancies, or distributions over split conformers. MD simulations of the complexes suggest an even larger scatter over several conformational families. Introduction of a terminal acidic group fixes the substituent by a salt-bridge to an Arg residue. Overall, all substituted derivatives show the same affinity underpinning that neither order nor disorder is a determinant factor for binding affinity. The additional salt bridge remains strongly solvent-exposed and thus does not contribute to affinity. MD suggests temporary fluctuation of this contact.


Assuntos
Glicosiltransferases/metabolismo , RNA de Transferência/metabolismo , Sítios de Ligação , Glicosiltransferases/química , Ligantes , Simulação de Dinâmica Molecular , Estrutura Molecular , RNA de Transferência/química
8.
Biochim Biophys Acta ; 1840(9): 2843-50, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24792574

RESUMO

BACKGROUND: The thermodynamic characterization of protein-ligand interactions by isothermal titration calorimetry (ITC) is a powerful tool in drug design, giving valuable insight into the interaction driving forces. ITC is thought to require protein and ligand solutions of high quality, meaning both the absence of contaminants as well as accurately determined concentrations. METHODS: Ligands synthesized to deviating purity and protein of different pureness were titrated by ITC. Data curation was attempted also considering information from analytical techniques to correct stoichiometry. RESULTS AND CONCLUSIONS: We used trypsin and tRNA-guanine transglycosylase (TGT), together with high affinity ligands to investigate the effect of errors in protein concentration as well as the impact of ligand impurities on the apparent thermodynamics. We found that errors in protein concentration did not change the thermodynamic properties obtained significantly. However, most ligand impurities led to pronounced changes in binding enthalpy. If protein binding of the respective impurity is not expected, the actual ligand concentration was corrected for and the thus revised data compared to thermodynamic properties obtained with the respective pure ligand. Even in these cases, we observed differences in binding enthalpy of about 4kJ⋅mol(-1), which is considered significant. GENERAL SIGNIFICANCE: Our results indicate that ligand purity is the critical parameter to monitor if accurate thermodynamic data of a protein-ligand complex are to be recorded. Furthermore, artificially changing fitting parameters to obtain a sound interaction stoichiometry in the presence of uncharacterized ligand impurities may lead to thermodynamic parameters significantly deviating from the accurate thermodynamic signature.


Assuntos
Ligantes , Pentosiltransferases/química , Termodinâmica , Tripsina/química , Animais , Calorimetria/instrumentação , Bovinos
9.
Nat Chem ; 12(7): 629-637, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32483385

RESUMO

Polyketide natural products are an important class of biologically active compounds. Although substantial progress has been made on the synthesis of repetitive polyketide motifs through the iterative application of a single reaction type, synthetic access to more diverse motifs that require more than one type of carbon-carbon bond connection remains a challenge. Here we describe a catalytic, multicomponent method for the synthesis of the privileged polyketide 1,3-dienyl-6-oxy motif. The method allows for the formation of two new carbon-carbon bonds and two stereodefined olefins. It generates products that contain up to three contiguous sp3 stereocentres with a high stereoselectivity in a single operation and can be used to generate chiral products. The successful development of this methodology relies on the remarkable efficiency of the ruthenium-catalysed alkene-alkyne coupling reaction between readily available vinyl boronic acids and alkynes to provide unsymmetrical 3-boryl-1,4-diene reagents. In the presence of carbonyl compounds, these reagents undergo highly diastereoselective allylations to afford the desired 1,3-dienyl-6-oxy motif and enable complex polyketide synthesis in a rapid and asymmetric fashion.

10.
J Med Chem ; 63(13): 6802-6820, 2020 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-32515955

RESUMO

Fragment-based lead discovery was applied to tRNA-guanine transglycosylase, an enzyme modifying post-transcriptionally tRNAs in Shigella, the causative agent of shigellosis. TGT inhibition prevents translation of Shigella's virulence factor VirF, hence reducing pathogenicity. One discovered fragment opens a transient subpocket in the preQ1-recognition site by pushing back an aspartate residue. This step is associated with reorganization of further amino acids structurally transforming a loop adjacent to the recognition site by duplicating the volume of the preQ1-recognition pocket. We synthesized 6-carboxamido-, 6-hydrazido-, and 4-guanidino-benzimidazoles to target the opened pocket, including a dihydro-imidazoquinazoline with a propyn-1-yl exit vector pointing into the transient pocket and displacing a conserved water network. MD simulations and hydration-site analysis suggest water displacement to contribute favorably to ligand binding. A cysteine residue, exclusively present in bacterial TGTs, serves as gatekeeper of the transient subpocket. It becomes accessible upon pocket opening for selective covalent attachment of electrophilic ligands in eubacterial TGTs.


Assuntos
Pentosiltransferases/metabolismo , Benzimidazóis/farmacologia , Sítios de Ligação , Desenho de Fármacos , Avaliação Pré-Clínica de Medicamentos , Ligantes , Modelos Moleculares , Pentosiltransferases/química , Conformação Proteica , Shigella/enzimologia
11.
J Med Chem ; 57(13): 5566-78, 2014 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-24960372

RESUMO

Lead optimization focuses on binding-affinity improvement. If a flat structure-activity relationship is detected, usually optimization strategies are abolished as unattractive. Nonetheless, as affinity is composed of an enthalpic and entropic contribution, factorization of both can unravel the complexity of a flat, on first sight tedious SAR. In such cases, the binding free energy of different ligands can be rather similar, but it can factorize into enthalpy and entropy distinctly. We investigated the thermodynamic signature of two classes of lin-benzopurines binding to tRNA-guanine transglycosylase. While the differences are hardly visible in the free energy, they involve striking enthalpic and entropic changes. Analyzing thermodynamics along with structural features revealed that one ligand set binds to the protein without inducing significant changes compared to the apo structure; however, the second series provokes complex adaptation, leading to a conformation similar to the substrate-bound state. In the latter state, a cross-talk between two pockets is suggested.


Assuntos
Benzimidazóis/química , Entropia , Pentosiltransferases/antagonistas & inibidores , Pentosiltransferases/química , Quinazolinonas/química , Termodinâmica , Sítios de Ligação , Cristalização , Cristalografia por Raios X , Ligantes , Modelos Moleculares , Conformação Molecular , Pentosiltransferases/metabolismo , Ligação Proteica , Conformação Proteica , RNA de Transferência/metabolismo , Relação Estrutura-Atividade
12.
J Med Chem ; 57(13): 5554-65, 2014 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-24955548

RESUMO

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.


Assuntos
Benzimidazóis/química , Pentosiltransferases/metabolismo , Ligação Proteica , Prótons , Quinazolinonas/química , Ácido Aspártico/química , Ácido Aspártico/metabolismo , Sítios de Ligação , Calorimetria , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Cinética , Ligantes , Modelos Moleculares , Mutagênese , Pentosiltransferases/antagonistas & inibidores , Pentosiltransferases/genética , RNA de Transferência/metabolismo , Termodinâmica
13.
Shock ; 34(1): 46-54, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19997050

RESUMO

Statins are established in the prevention and therapy of chronic cardiovascular diseases because of inhibition of HMG-CoA (3-hydroxy-3-methylglutaryl-coenzyme A), thus lowering blood cholesterol levels. However, their cholesterol-independent effects include regulation of Rho/Rho-kinases (ROCK) and eNOS, proteins centrally involved in various models of acute inflammation. Therefore, we tested the hypothesis that simvastatin confers protection after rat hemorrhage/resuscitation (H/R) and wanted to elucidate the mechanisms involved. Fifty-two female Lewis rats (180-250 g) were pretreated with simvastatin 5 mg/kg per day or vehicle for 6 days (i.p.). Then, rats were hemorrhaged to a mean arterial pressure of 30 +/- 2 mmHg for 60 min and resuscitated. Control group underwent surgical procedures without H/R. Two hours after resuscitation, tissues were harvested. Mortality was assessed 72 h after H/R. Simvastatin pretreatment increased survival after H/R from 20% to 80%. Serum alanine aminotransferase after H/R increased 2.2-fold in vehicle as compared with simvastatin-treated rats. Histopathological analysis revealed decreased hepatic necrosis in simvastatin-treated rats after H/R. Hepatic oxidative (4-hydroxynonenal) and nitrosative (3-nitrotyrosine) stress, inflammatory markers (serum IL-6 and hepatic infiltration with polymorphonuclear leukocytes), and actin cytoskeleton rearrangements were decreased after simvastatin pretreatment compared with vehicle-treated rats after H/R. Simvastatin increased eNOS and heme oxygenase 1 expression and eNOS activation. Expression of Rho/Rho-kinase and myosin phosphatase targeting subunit, Thr-MYPT1, a marker for Rho-kinase activity, decreased after simvastatin treatment compared with vehicle-treated rats after H/R. Simvastatin pretreatment exerts beneficial effects in this model of acute inflammation by supporting protective mechanisms that are important for hepatic microcirculation after H/R.


Assuntos
Hemorragia/tratamento farmacológico , Hemorragia/mortalidade , Fígado/efeitos dos fármacos , Fígado/patologia , Ressuscitação/efeitos adversos , Sinvastatina/uso terapêutico , Actinas/metabolismo , Aldeídos , Animais , Apoptose/efeitos dos fármacos , Citoesqueleto/efeitos dos fármacos , Citoesqueleto/metabolismo , Fragmentação do DNA/efeitos dos fármacos , Hemodinâmica/efeitos dos fármacos , Hemorragia/sangue , Hemorragia/patologia , Inibidores de Hidroximetilglutaril-CoA Redutases/uso terapêutico , Interleucina-6/sangue , Peroxidação de Lipídeos/efeitos dos fármacos , Fígado/imunologia , Masculino , Neutrófilos/citologia , Óxido Nítrico Sintase Tipo III/metabolismo , Ratos , Tirosina/análogos & derivados
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