RESUMO
Ipomoeassin F is a potent natural cytotoxin that inhibits growth of many tumor cell lines with single-digit nanomolar potency. However, its biological and pharmacological properties have remained largely unexplored. Building upon our earlier achievements in total synthesis and medicinal chemistry, we used chemical proteomics to identify Sec61α (protein transport protein Sec61 subunit alpha isoform 1), the pore-forming subunit of the Sec61 protein translocon, as a direct binding partner of ipomoeassin F in living cells. The interaction is specific and strong enough to survive lysis conditions, enabling a biotin analogue of ipomoeassin F to pull down Sec61α from live cells, yet it is also reversible, as judged by several experiments including fluorescent streptavidin staining, delayed competition in affinity pulldown, and inhibition of TNF biogenesis after washout. Sec61α forms the central subunit of the ER protein translocation complex, and the binding of ipomoeassin F results in a substantial, yet selective, inhibition of protein translocation in vitro and a broad ranging inhibition of protein secretion in live cells. Lastly, the unique resistance profile demonstrated by specific amino acid single-point mutations in Sec61α provides compelling evidence that Sec61α is the primary molecular target of ipomoeassin F and strongly suggests that the binding of this natural product to Sec61α is distinctive. Therefore, ipomoeassin F represents the first plant-derived, carbohydrate-based member of a novel structural class that offers new opportunities to explore Sec61α function and to further investigate its potential as a therapeutic target for drug discovery.
Assuntos
Glicoconjugados/farmacologia , Canais de Translocação SEC/antagonistas & inibidores , Sítios de Ligação/efeitos dos fármacos , Glicoconjugados/química , Humanos , Estrutura Molecular , Transporte Proteico/efeitos dos fármacos , Canais de Translocação SEC/metabolismoRESUMO
Convergent total synthesis of bryostatinâ 8 has been accomplished by an organosilane-based strategy. The Câ ring is constructed stereoselectively through a geminal bis(silane)-based [1,5]-Brook rearrangement, and the Bâ ring through geminal bis(silane)-based Prins cyclization, thus efficiently joining the northern and southern parts of the molecule.
RESUMO
A remarkable α-effect of silicon has been discovered that results in soft nucleophilicity at the Cγ of 3,3-bis(silyl) allyloxy lithium 1. The addition of 1 to α,ß-unsaturated carbonyl compounds, including enals, proceeds in a 1,4- over 1,2-manner with medium to good regioselectivity, whereas the parent allyloxy lithium 4 undergoes complete 1,2-addition. The results from DFT calculations of HMPAcomplexed 1 and 4 provide the rationale to explain this different regioselectivity.
Assuntos
Cetonas/química , Lítio/química , Silício/química , Ânions , Cromatografia , Modelos Moleculares , Espectroscopia de Prótons por Ressonância Magnética , EstereoisomerismoRESUMO
The pathogenesis of Parkinson's disease (PD) is characterized by progressive deposition of alpha-synuclein (α-syn) aggregates in dopaminergic neurons and neuroinflammation. Noninvasive in vivo imaging of α-syn aggregate accumulation and neuroinflammation can elicit the underlying mechanisms involved in disease progression and facilitate the development of effective treatment as well as disease diagnosis and prognosis. Here we present a novel approach to simultaneously profile α-syn aggregation and reactive microgliosis in vivo, by targeting oligomeric α-syn in cerebrospinal fluid with nanoparticle bearing a magnetic resonance imaging (MRI), contrast payload. In this proof-of-concept report we demonstrate, in vitro, that microglia and neuroblastoma cell lines internalize agglomerates formed by cross-linking the nanoparticles with oligomeric α-syn. Delayed in vivo MRI scans following intravenous administration of the nanoparticles in the M83 α-syn transgenic mouse line show statistically significant MR signal enhancement in test mice versus controls. The in vivo data were validated by ex-vivo immunohistochemical analysis which show strong correlation between in vivo MRI signal enhancement, Lewy pathology distribution, and microglia activity in the treated brain tissue. Furthermore, neuronal and microglial cells in brain tissue from treated mice display strong cytosolic signal originating from the nanoparticles, attributed to in vivo cell uptake of nanoparticle/oligomeric α-syn agglomerates.
RESUMO
Cr2O3 scale growth and volatilization are the main cause of the performance degradation of solid oxide fuel cells (SOFCs) with an Fe-based ferritic stainless steel (FSS) interconnect. In this work, an amorphous Ti(Nb)-Si-C coating is prepared on the pre-oxidized SUS430 with D.C. magnetron sputtering as the protective coating. The amorphous Ti(Nb)-Si-C coated alloy exhibits significantly enhanced oxidation resistance, and the oxidation kinetics obey the parabolic law with a low parabolic rate of 9.36 × 10-15 g2·cm-4·s-1. A dual-layer oxide scale is formed composed of an inner layer rich in Cr2O3 and an outer layer rich in rutile TiO2 and amorphous SiO2. MnCr2O4 appears at the interface between the inner and outer oxide layers. Meanwhile, the amorphous Ti(Nb)-Si-C coating also effectively blocks the outward diffusion of Cr. In addition, the coated steel presents good electrical properties with an area-specific resistance (ASR) of 13.57 mΩ·cm2 at 800 °C after oxidation at 800 °C in air for 500 h.
RESUMO
A [1,4]-S- to O-silyl migration has been exploited to chemoselectively transform esters into ketones by using organolithium reagents, allowing multicomponent synthesis of α-thioketones. Mechanistic studies reveal that this migration proceeds in an intramolecular manner and is more favorable than the corresponding [1,5]-S- to O- and [1,3]-C- to O-silyl migrations. The resulting α-thioketones are valuable building blocks for the synthesis of cyclic or multifunctionalized organosulfur compounds.
Assuntos
Cetonas/química , Lítio/química , Compostos Organometálicos/química , Ésteres , Cetonas/síntese química , Oxigênio/química , Silício/química , Enxofre/químicaRESUMO
The first line of treatment for most solid tumors is surgical resection of the primary tumor with adequate negative margins. Incomplete tumor resections with positive margins account for over 75% of local recurrences and the development of distant metastases. In cases of oral cavity squamous cell carcinoma (OSCC), the rate of successful tumor removal with adequate margins is just 50-75%. Advanced real-time imaging methods that improve the detection of tumor margins can help improve success rates,overall safety, and reduce the cost. Fluorescence imaging in the second near-infrared (NIR-II) window has the potential to revolutionize the field due to its high spatial resolution, low background signal, and deep tissue penetration properties, but NIR-II dyes with adequate in vivo performance and safety profiles are scarce. A novel NIR-II fluorophore, XW-03-66, with a fluorescence quantum yield (QY) of 6.0% in aqueous media is reported. XW-03-66 self-assembles into nanoparticles (≈80 nm) and has a systemic circulation half-life (t1/2 ) of 11.3 h. In mouse models of human papillomavirus (HPV)+ and HPV- OSCC, XW-03-66 outperformed indocyanine green (ICG), a clinically available NIR dye, and enabled intraoperative NIR-II image-guided resection of the tumor and adjacent draining lymph node with negative margins. In vitro and in vivo toxicity assessments revealed minimal safety concerns for in vivo applications.
Assuntos
Neoplasias Bucais , Infecções por Papillomavirus , Camundongos , Animais , Humanos , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Verde de Indocianina , Corantes Fluorescentes/química , Neoplasias Bucais/diagnóstico por imagem , Neoplasias Bucais/cirurgiaRESUMO
The development of imaging agents for inâ vivo detection of alpha-synuclein (α-syn) pathologies faces several challenges. A major gap in the field is the lack of diverse molecular scaffolds with high affinity and selectivity to α-syn fibrils for inâ vitro screening assays. Better inâ vitro scaffolds can instruct the discovery of better inâ vivo agents. We report the rational design, synthesis, and inâ vitro evaluation of a series of novel 1-indanone and 1,3-indandione derivatives from a Structure-Activity Relationship (SAR) study centered on some existing α-syn fibril binding ligands. Our results from fibril saturation binding experiments show that two of the lead candidates compounds 8 and 32 bind α-syn fibrils with binding constants (Kd ) of 9.0 and 18.8â nM, respectively, and selectivity of greater than 10× for α-syn fibrils compared with amyloid-ß (Aß) and tau fibrils. Our results demonstrate that the lead ligands avidly label all forms of α-syn on PD brain tissue sections, but only the dense core of senile plaques in AD brain tissue, respectively. These results are corroborated by ligand-antibody colocalization data from Syn211, which shows immunoreactivity toward all forms of α-syn aggregates, and Syn303, which displays preferential reactivity toward mature Lewy pathology. Our results reveal that 1-indanone derivatives have desirable properties for the biological evaluation of α-synucleinopathies.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Indanos/farmacologia , Fármacos Neuroprotetores/farmacologia , alfa-Sinucleína/antagonistas & inibidores , Doença de Alzheimer/metabolismo , Doença de Alzheimer/patologia , Relação Dose-Resposta a Droga , Desenho de Fármacos , Humanos , Indanos/síntese química , Indanos/química , Ligantes , Estrutura Molecular , Fármacos Neuroprotetores/síntese química , Fármacos Neuroprotetores/química , Agregados Proteicos/efeitos dos fármacos , Dobramento de Proteína/efeitos dos fármacos , Relação Estrutura-Atividade , alfa-Sinucleína/metabolismoRESUMO
The abnormal phosphorylation of tau is a necessary precursor to the formation of tau fibrils, a marker of Alzheimer's disease. We hypothesize that hyperphosphorylative conditions may result in unique cell surface markers. We identify and demonstrate the utility of such surrogate markers to identify the hyperphosphorylative state. Methods: Cell SELEX was used to identify novel thioaptamers specifically binding hyperphosphorylative cells. Cell surface vimentin was identified as a potential binding target of the aptamer. Novel molecular magnetic resonance imaging (M-MRI) probes using these aptamers and a small molecule ligand to vimentin were used for in vivo detection of this pre-pathological state. Results: In a mouse model of pathological tau, we demonstrated in vivo visualization of the hyperphosphorylative state by M-MRI, enabling the identification at a pre-pathological stage of mice that develop frank tau pathology several months later. In vivo visualization of the hyperphosphorylative state by M-MRI was further validated in a second mouse model (APP/PS1) of Alzheimer's disease again identifying the mutants at a pre-pathological stage. Conclusions: M-MRI of the hyperphosphorylative state identifies future tau pathology and could enable extremely early-stage diagnosis of Alzheimer's disease, at a pre-patholgical stage.
Assuntos
Doença de Alzheimer , Doença de Alzheimer/patologia , Animais , Biomarcadores , Modelos Animais de Doenças , Imageamento por Ressonância Magnética , Camundongos , Camundongos Transgênicos , Vimentina , Proteínas tau/metabolismoRESUMO
Ipomoeassin F, a plant-derived macrolide, exhibited single-digit nanomolar growth inhibition activity against many cancer cell lines. In this report, a series of 5-oxa/aza analogues was prepared and screened for cytotoxicity. Replacement of 5-CH2 with O/NH simplified the synthesis and led to only a small activity loss. N-methylation almost completely restored the potency. Further studies with additional 5-oxa analogues suggested, for the first time, that size and flexibility of the ring also significantly influence the bioactivity of ipomoeassin F.
Assuntos
Antineoplásicos/farmacologia , Compostos Aza/farmacologia , Glicoconjugados/farmacologia , Antineoplásicos/síntese química , Antineoplásicos/química , Compostos Aza/química , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Glicoconjugados/síntese química , Glicoconjugados/química , Humanos , Estrutura Molecular , Relação Estrutura-AtividadeRESUMO
A TMSBr/InBr3-promoted Prins cyclization/homobromination reaction of dienyl alcohol with aldehyde has been developed to construct a unique cis-E THP shown as the A ring in (-)-exiguolide and the B ring in bryostatins.
Assuntos
Álcoois/química , Aldeídos/química , Bromo/química , Piranos/química , CiclizaçãoRESUMO
An intramolecular [1,4]-S- to O-silyl migration has been used to form silyl enol ethers with Z-configurational control. The silyl migration also creates a new anion center at sulfur, which can subsequently react with electrophiles to generate Z-silyl enol ethers with diverse thioether linkages. The synthetic utility of this pathway was demonstrated by modifying the Z-silyl enol ethers with aldehydes via a Mukaiyama aldol reaction or Prins cyclization to generate functionalized organosulfur compounds.
Assuntos
Ânions/química , Silanos/química , Silanos/síntese química , Sulfetos/química , Sulfetos/síntese química , Enxofre/química , Catálise , Ciclização , Estrutura Molecular , EstereoisomerismoRESUMO
A [1,5]-anion relay has been achieved in 3,3-bis(silyl) benzyl enol ether. Deprotonation at the sterically more accessible benzyl position triggers an intramolecular proton transfer to generate the thermodynamically more stable 3,3-bis(silyl) allyloxy lithium. This endo-oriented allyl anion is stable at -78 °C and undergoes diastereoselective syn-addition at the γ-position with aldehydes and ketones to give monobenzyl-substituted 1,2-diols.
Assuntos
Aldeídos/química , Cetonas/química , Lítio/química , Compostos Organometálicos/síntese química , Prótons , Silanos/síntese química , Ânions/química , Éteres/química , Estrutura Molecular , Compostos Organometálicos/química , Silanos/química , EstereoisomerismoRESUMO
Geminal bis(silyl) enal 2a is shown to be a useful scaffold for anion relay chemistry (ARC) aimed at the stereoselective synthesis of C(3),O(1)-disilylated allylic alcohols. The ARC reaction is initiated by the addition of an alkyllithium to the aldehyde and features a CuCN-promoted C(sp2)-to-O 1,4-silyl migration to generate a vinylcuprate that reacts with activated electrophiles.
Assuntos
Propanóis/síntese química , Silanos/química , Silanos/síntese química , Aldeídos/química , Técnicas de Química Combinatória , Estrutura Molecular , Propanóis/química , EstereoisomerismoRESUMO
The [1,5]-anion relay/[2,3]-Wittig rearrangement of 3,3-bis(silyl) enol allyl ethers has been developed. This reaction provides an efficient method to synthesize versatile vinyl bissilanes, which can be transformed into trisubstituted vinylsilanes through a [1,4]-Brook rearrangement/alkylation protocol using a wide range of electrophiles.
Assuntos
Éteres/química , Silanos/síntese química , Compostos de Vinila/síntese química , Ânions/química , Ciclização , Estrutura MolecularRESUMO
A highly stereoselective approach to novel tetrasubstituted (Z)-ß-hydroxy-α-TMS silyl enol ethers is described. The reaction proceeds via a sequential addition/[1,2]-Brook rearrangement/epoxide-opening process of TMS-substituted oxiranyl anions with acylsilanes.