RESUMO
Self-assembling systems in nature display remarkable complexity with assemblies of different sub-units to generate functional species. Synthetic analogues of such systems are a challenge, often requiring the ability to bias distributions that are under thermodynamic assembly control. Using lantern-type MOCs (metal-organic cages) as a prototypical self-assembling system, herein we explore the role that steric bulk plays in controlling the exchange rate of ligands in paddlewheel-based assemblies, and thus the stability of cages, in competitive self-assembling scenarios. The effective lifetime of the lantern-type MOCs varies over an order of magnitude depending on the steric bulk proximal to the metal nodes with lifetimes of the cages ranging from tens of minutes to several hours. The bulk of the coordinating solvents likewise reduces the rate of ligand exchange, and thus yields longer-lived species. Understanding this subtle effect has implications for controlling the stability of complex assemblies in competitive environments with implications for guest release and application.
RESUMO
The ability of an octanuclear cubic coordination cage to catalyse a nucleophilic aromatic substitution reaction on a cavity-bound guest was studied with 2,4-dinitrofluorobenzene (DNFB) as the guest/substrate. It was found that DNFB undergoes a catalysed reaction with hydroxide ions within the cavity of the cubic cage (in aqueous buffer solution, pHâ 8.6). The rate enhancement of kcat/kuncat was determined to be 22, with cavity binding of the guest being required for catalysis to occur. The product, 2,4-dinitrophenolate (DNP), remained bound within the cavity due to electrostatic stabilisation and exerts two apparently contradictory effects: it initially auto-catalyses the reaction when present at low concentrations, but at higher concentrations inhibits catalysis when a pair of DNP guests block the cavity. When encapsulated, the UV/Vis absorption spectrum of DNP is red-shifted when compared to the spectrum of free DNP in aqueous solution. Further investigations using other aromatic guests determined that a similar red-shift on cavity binding also occurred for 4-nitrophenolate (4NP) at pHâ 8.6. The red-shift was used to determine the stoichiometry of guest binding of DNP and 4NP within the cage cavity, which was confirmed by structural analysis with X-ray crystallography; and was also used to perform catalytic kinetic studies in the solution-state.
RESUMO
Surfactants provide detergency, foaming, and texture in personal care formulations, yet the micellization of typical industrial primary and cosurfactants is not well understood, particularly in light of the polydisperse nature of commercial surfactants. Synergistic interactions are hypothesized to drive the formation of elongated wormlike self-assemblies in these mixed surfactant systems. Small-angle neutron scattering, rheology, and pendant drop tensiometry are used to examine surface adsorption, viscoelasticity, and self-assembly structure for wormlike micellar formulations comprising cocoamidopropyl betaine, and its two major components laurylamidopropyl betaine and oleylamidopropyl betaine, with sodium alkyl ethoxy sulfates. The tail length of sodium alkyl ethoxy sulfates was related to their ability to form wormlike micelles in electrolyte solutions, indicating that a tail length greater than 10 carbons is required to form wormlike micelles in NaCl solutions, with the decyl homologue unable to form elongated micelles and maintaining a low viscosity even at 20 wt % surfactant loading with 4 wt % NaCl present. For these systems, the incorporation of a disperse ethoxylate linker does not enable shorter chain surfactants to elongate into wormlike micelles for single-component systems; however, it could increase the interactions between surfactants in mixed surfactant systems. For synergy in surfactant mixing, the nonideal regular solution theory is used to study the sulfate/betaine mixtures. Tail mismatch appears to drive lower critical micelle concentrations, although tail matching improves synergy with larger relative reductions in critical micelle concentrations and greater micelle elongation, as seen by both tensiometric and scattering measurements.
RESUMO
Two dipyridyl ligands, L3,3 and L3,4, have been used in combination with palladium(II) in the construction of metallosupramolecular species that show anion-dependent behavior in solution. A rare example of a low-symmetry (C2h) lantern-type cage is formed in one instance, [Pd2(L3,3)4]4+, while the isomeric ligand yields a larger double-walled square complex, [Pd4(L3,4)8]8+. [Pd2(L3,3)4](NO3)4 was isolated in crystalline form revealing two anions within the interior of the C2h-symmetry cage. The cage itself is held together by hydrogen bonding between "head-to-tail" pairs of ligands that reinforces the symmetry generated by the ditopic ligands. In solution, the cage with NO3- has sharp 1H nuclear magnetic resonance (NMR) signals at room temperature, while the BF4- analogue has broad signals that sharpen at higher temperatures or upon addition of (Bu4N)(NO3), highlighting the importance of the anion in templating or otherwise influencing self-assembly in solution. Altering the substitution position of one of the pyridyl rings yields a more "open" complex, with [Pd4(L3,4)8](NO3)8 being isolated as a crystalline solid. The double-walled square complex has a greater Pd···Pd separation due to the increased angle that the pyridyl groups subtend at the core of the ligand. NMR spectroscopy and mass spectrometry studies suggest a single species in the presence of nitrate but multiple species with tetrafluoroborate.
RESUMO
It is well known that hydrogen peroxide (H2O2) is a signaling molecule essential for vital physiological reactions in mammalian cells, such as cell survival, intercellular communication, and cancer metabolism. However, to fully understand the function of H2O2, it is critical to monitor its intracellular and/or extracellular concentrations. Current techniques implemented to address this need require large sample volumes, expensive instrumentation, and long sample preparation and analysis times, inapplicable to inline or online monitoring. In this paper, a new integrated microfluidic device capable of overcoming these limitations is demonstrated for the colorimetric detection of extracellular hydrogen peroxide H2O2. The device contains an optical waveguide to determine absorbance changes and micromixers to enable complete mixing of reagents using a passive approach. This novel H2O2-sensing device has allowed the detection of H2O2 in the range of 0.5-60 µM with a detection limit of 167 ± 5.8 nM and a sensitivity of 13.5 ± 0.1 AU/mM. Proof of concept of the device was demonstrated by quantifying H2O2 release from benign prostatic epithelial (BPH-1) cells upon stimulation with phorbol 12-myristate 13-acetate (PMA). Results show that this integrated device can be potentially utilized to continuously monitor cell-released metabolites autonomously without constant human supervision during the process. Furthermore, this can be achieved without interfering with the cell culture conditions, as only a very small volume of conditioned media (less than 0.4 µL), and not the cells, is required.
Assuntos
Colorimetria , Peróxido de Hidrogênio , Animais , Humanos , Peróxido de Hidrogênio/análise , Dispositivos Lab-On-A-Chip , Acetato de TetradecanoilforbolRESUMO
Azobenzene-containing surfactants (azo-surfactants) have garnered significant attention for their use in generating photoresponsive foams, interfaces, and colloidal systems. The photoresponsive behavior of azo-surfactants is driven by the conformational and electronic changes that occur when the azobenzene chromophore undergoes light-induced trans â cis isomerization. Effective design of surfactants and targeting of their properties requires a robust understanding of how the azobenzene functionality interacts with surfactant structure and influences overall surfactant behavior. Herein, a library of tail substituted azo-surfactants were synthesized and studied to better understand how surfactant structure can be tailored to exploit the azobenzene photoswitch. This work shows that tail group structure (length and branching) has a profound influence on the critical micelle concentration of azo-surfactants and their properties once adsorbed to an air-water interface. Neutron scattering studies revealed the unique role that intermolecular π-π azobenzene interactions have on the self-assembly of azo-surfactants, and how the influence of these interactions can be tuned using tail group structure to target specific aqueous aggregate morphologies.
RESUMO
Because of their unique photochemical and photophysical properties, luminescent lanthanide-based complexes have long captivated chemists. In recent years, the number of reports of luminescent lanthanide complex-based probes for monitoring of biological and environmental processes has dramatically increased, namely, because of their selectivity for particular analytes, lower limits of detection, and the fact that they allow monitoring of analytes in real time. Lanthanide-based probes need to be paired with an appropriate antenna/sensitizer to allow maximum energy transfer, with the antenna typically covalently attached to the stable lanthanide chelate. We have recently investigated "dark" lanthanide-based probes where the sensitizer is not covalently linked to the lanthanide chelate. Herein we report the use of a luminescent lanthanide-based probe system for the detection of Zn2+ ions based on the formation of a ternary complex between a "dark" terbium complex, lumazine, and Zn2+. The terbium(III)-based probe incorporates a 1,4,7,10-tetraazacyclododecane-1,4,7,10-triacetic acid macrocyclic chelator covalently attached to a cyclen moiety, which is the Zn2+ ion binding group. In the presence of Zn2+ ions and lumazine (a strongly UV-absorbing sensitizer), a 1:1:1 ternary complex forms. The resulting complex is highly luminescent and selective for Zn2+ ions over other cations of environmental significance. Furthermore, with a limit of detection of 1.2 µM, this probe can detect the level of chronic zinc(II) concentrations denoted by the U.S. Environmental Protection Agency.
RESUMO
Structural modifications of the neuronal calcium channel blocker MONIRO-1, including constraining the phenoxyaniline portion of the molecule and replacing the guanidinium functionality with tertiary amines, led to compounds with significantly improved affinities for the endogenously expressed CaV2.2 channel in the SH-SY5Y neuroblastoma cell line. These analogues also showed promising activity towards the CaV3.2 channel, recombinantly expressed in HEK293T cells. Both of these ion channels have received attention as likely targets for the treatment of neuropathic pain. The dibenzoazepine and dihydrobenzodiazepine derivatives prepared in this study show an encouraging combination of neuronal calcium ion channel inhibitory potency, plasma stability and potential to cross the blood-brain-barrier.
Assuntos
Anilidas/síntese química , Antineoplásicos/síntese química , Benzodiazepinas/química , Bloqueadores dos Canais de Cálcio/síntese química , Canais de Cálcio/metabolismo , Neuralgia/tratamento farmacológico , Proteínas Recombinantes/metabolismo , Anilidas/metabolismo , Animais , Antineoplásicos/metabolismo , Antineoplásicos/farmacologia , Barreira Hematoencefálica/metabolismo , Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/metabolismo , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/genética , Linhagem Celular Tumoral , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Modelos Moleculares , Neurônios/metabolismo , Ratos Sprague-Dawley , Proteínas Recombinantes/genética , Transdução de Sinais , Relação Estrutura-AtividadeRESUMO
An in-depth study of the interaction of a trinuclear terbium(III)-dizinc(II) complex with an array of nucleotides differing in the type of nucleobase and number of phosphate groups, as well as cyclic versus acyclic variants, is presented. The study examined the nature of the interaction and the efficiency at which guanine was able to sensitize terbium(III) luminescence. Competitive binding and titration studies were performed to help establish the nature/mode of the interactions. These established that (1) interaction occurs by the coordination of phosphate groups to zinc(II) (in addition to uridine in the case of uridine monophosphate), (2) acyclic nucleotides bind more strongly than cyclic counterparts because of their higher negative charge, (3) guanine-containing nucleotides are able to sensitize terbium(III) luminescence with the efficiency of sensitization following the order guanosine monophosphate (GMP) > guanosine diphosphate > guanosine triphosphate because of the mode of binding, and (4) nucleoside monophosphates bind to a single zinc(II) ion, whereas di- and triphosphates appear to bind in a bridging mode between two host molecules. Furthermore, it has been shown that guanine is a sensitizer of terbium(III) luminescence. On the basis of the ability of GMP to effectively sensitize terbium(III)-based luminescence while cyclic GMP (cGMP) does not, the complex has been utilized to monitor the catalytic conversion of cGMP to GMP by a phosphodiesterase enzyme in real time using time-gated luminescence on a benchtop fluorimeter. The complex has the potential to find broad application in monitoring the activity of enzymes that process nucleotides (co)substrates, including high-throughput drug-screening programs.
Assuntos
Complexos de Coordenação/química , Guanosina Monofosfato/química , Diester Fosfórico Hidrolases/análise , Térbio/química , Zinco/química , Complexos de Coordenação/síntese química , Complexos de Coordenação/efeitos da radiação , GMP Cíclico/química , Ensaios Enzimáticos , Luz , Luminescência , Espectrofotometria , Água/químicaRESUMO
Lab-on-a-chip sensing technologies have changed how cell biology research is conducted. This review summarises the progress in the lab-on-a-chip devices implemented for the detection of cellular metabolites. The review is divided into two subsections according to the methods used for the metabolite detection. Each section includes a table which summarises the relevant literature and also elaborates the advantages of, and the challenges faced with that particular method. The review continues with a section discussing the achievements attained due to using lab-on-a-chip devices within the specific context. Finally, a concluding section summarises what is to be resolved and discusses the future perspectives.
Assuntos
Bactérias/citologia , Bactérias/metabolismo , Dispositivos Lab-On-A-Chip/tendências , Mamíferos/metabolismo , Metaboloma , Pesquisa , Animais , Técnicas Eletroquímicas , HumanosRESUMO
Both N- and T-type calcium ion channels have been implicated in pain transmission and the N-type channel is a well-validated target for the treatment of neuropathic pain. An SAR investigation of a series of substituted aminobenzothiazoles identified a subset of five compounds with comparable activity to the positive control Z160 in a FLIPR-based intracellular calcium response assay measuring potency at both CaV2.2 and CaV3.2 channels. These compounds may form the basis for the development of drug leads and tool compounds for assessing in vivo effects of variable modulation of CaV2.2 and CaV3.2 channels.
Assuntos
Benzimidazóis/síntese química , Benzotiazóis/síntese química , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/química , Canais de Cálcio Tipo T/química , Ciclopropanos/síntese química , Naftalenos/síntese química , Piperidinas/síntese química , Benzimidazóis/química , Benzimidazóis/farmacologia , Benzotiazóis/química , Benzotiazóis/farmacologia , Bloqueadores dos Canais de Cálcio/síntese química , Bloqueadores dos Canais de Cálcio/química , Canais de Cálcio Tipo N/efeitos dos fármacos , Canais de Cálcio Tipo T/efeitos dos fármacos , Ciclopropanos/química , Ciclopropanos/farmacologia , Estrutura Molecular , Naftalenos/química , Naftalenos/farmacologia , Piperazinas/síntese química , Piperazinas/química , Piperazinas/farmacologia , Piperidinas/química , Piperidinas/farmacologia , Relação Estrutura-AtividadeRESUMO
Two new bifunctional macrocyclic chelate ligands that form luminescent terbium(III) complexes featuring an alkyne group for conjugation to (bio)molecules via the Cu(I)-catalyzed "click" reaction were synthesized. Upon ligation, the complexes exhibit a significant luminescent enhancement when excited at the λ(max) of the "clicked" products. To demonstrate the utility of the complexes for luminescent labeling, they were conjugated in vitro to E. coli aspartate/glutamate-binding protein incorporating a genetically encoded p-azido-L-phenylalanine or p-(azidomethyl)-L-phenylalanine residue. The complexes may prove useful for time-gated assay applications.
Assuntos
Alcinos/química , Proteínas/química , Térbio/química , LuminescênciaRESUMO
A new bifunctional macrocyclic chelator featuring a conjugatable alkynyl-naphthalimide fluorophore pendant group has been prepared and its Gd(III) complex coupled to a cell-penetrating lipidated azido-Tat peptide derivative using Cu(I)-catalysed "click" chemistry. The resulting fluorescent conjugate is able to enter CAL-33 tongue squamous carcinoma cells, as revealed by confocal microscopy, producing a very modest anti-proliferative effect (IC50 = 93 µM). Due to the photo-reactivity of the naphthalimide moiety, however, the conjugate's cytotoxicity is significantly enhanced (IC50 = 16 µM) upon brief low-power UV-A irradiation.
Assuntos
Antineoplásicos/metabolismo , Complexos de Coordenação/metabolismo , Naftalimidas/metabolismo , Fármacos Fotossensibilizantes/metabolismo , Antineoplásicos/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Quelantes/metabolismo , Quelantes/farmacologia , Química Click , Complexos de Coordenação/farmacologia , Gadolínio/química , Compostos Heterocíclicos com 1 Anel/química , Humanos , Naftalimidas/farmacologia , Fármacos Fotossensibilizantes/farmacologia , Produtos do Gene tat do Vírus da Imunodeficiência Humana/químicaRESUMO
Macrophages accumulate in blood vessels during hypertension. However, their contribution to vessel remodeling is unknown. In the present study, we examined the polarization state of macrophages (M1/M2) in aortas of mice during hypertension and investigated whether antagonism of chemokine receptors involved in macrophage accumulation reduces vessel remodeling and blood pressure (BP). Mice treated with ANG II (0.7 mg·kg(-1)·day(-1), 14 days) had elevated systolic BP (158 ± 3 mmHg) compared with saline-treated animals (122 ± 3 mmHg). Flow cytometry revealed that ANG II infusion increased numbers of CD45(+)CD11b(+)Ly6C(hi) monocytes and CD45(+)CD11b(+)F4/80(+) macrophages by 10- and 2-fold, respectively. The majority of macrophages were positive for the M2 marker CD206 but negative for the M1 marker inducible nitric oxide synthase. Expression of other M2 genes (arginase-1, Fc receptor-like S scavenger receptor, and receptor-1) was elevated in aortas from ANG II-treated mice, whereas M1 genes [TNF and chemokine (C-X-C motif) ligand 2] were unaltered. A PCR array to identify chemokine receptor targets for intervention revealed chemokine (C-C motif) receptor 2 (CCR2) to be upregulated in aortas from ANG II-treated mice, while flow cytometry identified Ly6C(hi) monocytes as the main CCR2-expressing cell type. Intervention with a CCR2 antagonist (INCB3344; 30 mg·kg(-1)·day(-1)), 7 days after the commencement of ANG II infusion, reduced aortic macrophage numbers. INCB334 also reduced aortic collagen deposition, elastin loss, and BP in ANG II-treated mice. Thus, ANG II-dependent hypertension in mice is associated with Ly6C(hi) monocyte and M2 macrophage accumulation in the aorta. Inhibition of macrophage accumulation with a CCR2 antagonist prevents ANG II-induced vessel fibrosis and elevated BP, highlighting this as a promising approach for the future treatment of vessel remodeling/stiffening in hypertension.
Assuntos
Aorta/patologia , Pressão Sanguínea , Elastina/metabolismo , Hipertensão/patologia , Macrófagos/metabolismo , Angiotensina II/toxicidade , Animais , Antígenos CD/genética , Antígenos CD/metabolismo , Antígenos Ly/genética , Antígenos Ly/metabolismo , Aorta/efeitos dos fármacos , Aorta/metabolismo , Arginase/genética , Arginase/metabolismo , Colágeno/genética , Colágeno/metabolismo , Elastina/genética , Fibrose/metabolismo , Fibrose/patologia , Hipertensão/etiologia , Hipertensão/metabolismo , Macrófagos/classificação , Macrófagos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Receptores CCR2/genética , Receptores CCR2/metabolismoRESUMO
Pseudocontact shifts (PCS) induced by paramagnetic lanthanide ions provide unique long-range structural information in nuclear magnetic resonance (NMR) spectra, but the site-specific attachment of lanthanide tags to proteins remains a challenge. Here we incorporated p-azido-phenylalanine (AzF) site-specifically into the proteins ubiquitin and GB1, and ligated the AzF residue with alkyne derivatives of small nitrilotriacetic acid and iminodiacetic acid tags using the Cu(I) -catalysed "click" reaction. These tags form lanthanide complexes with no or only a small net charge and produced sizeable PCSs with paramagnetic lanthanide ions in all mutants tested. The PCSs were readily fitted by single magnetic susceptibility anisotropy tensors. Protein precipitation during the click reaction was greatly alleviated by the presence of 150â mM NaCl.
Assuntos
Iminoácidos/química , Elementos da Série dos Lantanídeos/química , Ácido Nitrilotriacético/química , Proteínas/química , Química Click , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Conformação ProteicaRESUMO
A set of fluorophenoxyanilides, designed to be simplified analogues of previously reported ω-conotoxin GVIA mimetics, were prepared and tested for N-type calcium channel inhibition in a SH-SY5Y neuroblastoma FLIPR assay. N-type or Cav2.2 channel is a validated target for the treatment of refractory chronic pain. Despite being significantly less complex than the originally designed mimetics, up to a seven-fold improvement in activity was observed.
Assuntos
Analgésicos não Narcóticos/farmacologia , Anilidas/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/metabolismo , Desenho de Fármacos , Proteínas do Tecido Nervoso/antagonistas & inibidores , Neurônios/efeitos dos fármacos , Analgésicos não Narcóticos/síntese química , Analgésicos não Narcóticos/química , Analgésicos não Narcóticos/metabolismo , Anilidas/síntese química , Anilidas/química , Anilidas/metabolismo , Ligação Competitiva , Bloqueadores dos Canais de Cálcio/síntese química , Bloqueadores dos Canais de Cálcio/química , Bloqueadores dos Canais de Cálcio/metabolismo , Canais de Cálcio Tipo N/química , Sinalização do Cálcio/efeitos dos fármacos , Linhagem Celular Tumoral , Fluorbenzenos/síntese química , Fluorbenzenos/química , Fluorbenzenos/metabolismo , Fluorbenzenos/farmacologia , Ensaios de Triagem em Larga Escala , Humanos , Estrutura Molecular , Terapia de Alvo Molecular , Proteínas do Tecido Nervoso/metabolismo , Neuralgia/tratamento farmacológico , Neuralgia/metabolismo , Neurônios/metabolismo , Neurotoxinas/química , Dor Intratável/tratamento farmacológico , Dor Intratável/metabolismo , Relação Estrutura-Atividade , ômega-Conotoxina GVIA/química , ômega-Conotoxina GVIA/metabolismo , ômega-Conotoxina GVIA/farmacologiaRESUMO
BACKGROUND: The community-associated methicillin-resistant S. aureus (CA-MRSA) ST93 clone is becoming dominant in Australia and is clinically highly virulent. In addition, sepsis and skin infection models demonstrate that ST93 CA-MRSA is the most virulent global clone of S. aureus tested to date. While the determinants of virulence have been studied in other clones of CA-MRSA, the basis for hypervirulence in ST93 CA-MRSA has not been defined. RESULTS: Here, using a geographically and temporally dispersed collection of ST93 isolates we demonstrate that the ST93 population hyperexpresses key CA-MRSA exotoxins, in particular α-hemolysin, in comparison to other global clones. Gene deletion and complementation studies, and virulence comparisons in a murine skin infection model, showed unequivocally that increased expression of α-hemolysin is the key staphylococcal virulence determinant for this clone. Genome sequencing and comparative genomics of strains with divergent exotoxin profiles demonstrated that, like other S. aureus clones, the quorum sensing agr system is the master regulator of toxin expression and virulence in ST93 CA-MRSA. However, we also identified a previously uncharacterized AraC/XylS family regulator (AryK) that potentiates toxin expression and virulence in S. aureus. CONCLUSIONS: These data demonstrate that hyperexpression of α-hemolysin mediates enhanced virulence in ST93 CA-MRSA, and additional control of exotoxin production, in particular α-hemolysin, mediated by regulatory systems other than agr have the potential to fine-tune virulence in CA-MRSA.
Assuntos
Infecções Comunitárias Adquiridas/microbiologia , Infecções Comunitárias Adquiridas/patologia , Expressão Gênica , Proteínas Hemolisinas/biossíntese , Staphylococcus aureus Resistente à Meticilina/patogenicidade , Infecções Cutâneas Estafilocócicas/microbiologia , Infecções Cutâneas Estafilocócicas/patologia , Animais , Austrália , Toxinas Bacterianas/biossíntese , Toxinas Bacterianas/genética , Modelos Animais de Doenças , Feminino , Deleção de Genes , Regulação Bacteriana da Expressão Gênica , Teste de Complementação Genética , Genoma Bacteriano , Proteínas Hemolisinas/genética , Humanos , Staphylococcus aureus Resistente à Meticilina/isolamento & purificação , Camundongos , Camundongos Endogâmicos BALB C , Análise de Sequência de DNARESUMO
The first enantioselective total syntheses of the proposed structures of the natural product prevezol B are reported. The reported syntheses complement the previously-reported syntheses of the proposed structures of prevezol C, a stereoisomer of prevezol B. It was previously shown that the structure of the naturally occurring prevezol C had been incorrectly assigned. This work has led us to conclude that the proposed structures of prevezol B are also incorrect and major revision of both of the structures of the prevezols B and C is required. Cytotoxicity studies on the human cervical cancer cell line HeLa revealed that the synthesized prevezol B and C compounds were not active even at the highest concentration used (100 µM). However, one of the synthetic precursors was shown to have modest potency against HeLa cells (IC50 = 23.5 ± 1.8 µM).
Assuntos
Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Diterpenos/farmacologia , Antineoplásicos/química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Proliferação de Células/efeitos dos fármacos , Diterpenos/síntese química , Diterpenos/química , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Células HeLa , Humanos , Conformação Molecular , Estrutura Molecular , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Tercyclic scaffolds, designed to have improved synthetic accessibility and aqueous solubility, were evaluated as structural α-helix mimetics by using an iterative in silico approach. The synthesis of these tercyclic scaffolds was accomplished using a modular synthetic approach by employing functionalised methoxyphenyl units which were readily manipulated to allow the introduction of various nitrogen-based heterocycles. The ability of these scaffolds to mimic the key i, i + 3 and i + 7 residues of a polyalanine α-helix was ratified by in silico studies, X-ray crystallographic and NOESY analysis, and their aqueous solubility was measured by a kinetic turbidimetric method.
Assuntos
Simulação por Computador , Peptídeos/síntese química , Modelos Moleculares , Conformação Molecular , Peptídeos/química , Estrutura Secundária de Proteína , Solubilidade , Termodinâmica , ÁguaRESUMO
The occurrence of mutations in methicillin-resistant Staphylococcus aureus (MRSA) during persistent infection leads to antimicrobial resistance but may also impact host-pathogen interactions. Here, we investigate the host-pathogen consequences of 2 mutations arising in clinical MRSA during persistent infection: RpoB H481Y, which is linked to rifampicin resistance, and RelA F128Y, which is associated with an active stringent response. Allelic exchange experiments showed that both mutations cause global transcriptional changes, leading to upregulation of capsule production, with attenuated virulence in a murine bacteremia model and reduced susceptibility to both antimicrobial peptides and whole-blood killing. Disruption of capsule biosynthesis reversed these impacts on innate immune function. These data clearly link MRSA persistence and reduced virulence to the same mechanisms that alter antimicrobial susceptibility. Our study highlights the wider consequences of suboptimal antimicrobial use, where drug resistance and immune escape mechanisms coevolve, thus increasing the likelihood of treatment failure.