RESUMO
RATIONALE: The thiosuccinimide linker is widely used in the synthesis of bioconjugates. However, it is susceptible to hydrolysis and is transformed into its hydrolyzed and/or the isobaric thiazine forms, the latter of which is a fairly common product in a conjugate that contains a cysteinyl peptide. Matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) and matrix-assisted laser desorption/ionization-tandem mass spectrometry (MALDI-MS/MS) are useful for differentiating these isobaric species. METHODS: Four cross-linked peptides with thiosuccinimide linkers were synthesized. Analogs with linkers that were transformed into thiazine and/or the hydrolyzed thiosuccinimide linkers were then synthesized by incubating the samples at neutral or basic pH. All the cross-linked peptides were purified using RP-HPLC (reversed-phase high-performance liquid chromatography) and differentiated using MALDI-MS, MALDI-MS/MS, and ultraviolet photodissociation. RESULTS: A cysteinyl peptide-containing conjugate, the thiosuccinimide form, was largely transformed into the hydrolyzed or thiazine forms after incubation at neutral or basic pH. MALDI-MS allowed the three forms to be differentiated: the thiosuccinimide and its hydrolysis product yielded two constituent peptides after reductive cleavage between the Cys and succinimide moieties; no fragment ions were produced from the thiazine form. In addition, MALDI-MS/MS of the thiosuccinimide form yielded two pairs of complementary fragment ions via 1,4-elimination: Cys-SH and maleimide, and dehydro-alanine and thiosuccinimide, which are different from those produced via reductive cleavage in MALDI-MS. The thiazine form yielded fragment ions resulting from the cleavage of the newly formed amide bond in the linker that resulted from thiazine formation. CONCLUSIONS: The thiosuccinimide (but not thiazine) form of the cross-linked peptide yielded individual constituent peptides using MALDI-MS and MALDI-MS/MS, showing specific 1,4-elimination for the thiosuccinimide form and cleavage at the newly formed peptide bond via transcyclization for the thiazine form.
Assuntos
Espectrometria de Massas em Tandem , Tiazinas , Espectrometria de Massas em Tandem/métodos , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz/métodos , Peptídeos/química , Íons , MaleimidasRESUMO
The reaction between L-cysteine (Cys) and 6-maleimidohexanoic acid (Mhx) in an aqueous medium at different levels of pH was analyzed via RP-HPLC, finding the presence of two reaction products throughout the evaluated pH range. By means of solid-phase extraction (SPE), it was possible to separate the products and obtain isolated profiles enriched up to 80%. The products were analyzed individually through mass spectrometry, DAD-HPLC, NMR 1H, 13C, and two-dimensional evidence of isomerization between the hydrogen atoms of the α-amino and the thiol group present in the cysteine. Thus, it was concluded that the products obtained corresponded to a mixture of the isomer Cys-S-Mhx, where the adduct is formed by a thioether bond, and the isomer Cys-NH-Mhx, in which the union is driven by the amino group. We consider that the phenomenon of isomerization is an important finding, since it has not previously been reported for this reaction.
Assuntos
Cisteína , Compostos de Sulfidrila , Cromatografia Líquida de Alta Pressão , Cisteína/química , Isomerismo , Maleimidas/química , Compostos de Sulfidrila/químicaRESUMO
The first total synthesis of the marine alkaloid aqabamycin G is disclosed. The synthetic sequence involved the stepwise addition to maleimide of an indole motif and a substituted diazo-benzenoid unit derived from acetaminophen. An alternative strategy using a protected phenol is also reported.
Assuntos
Alcaloides , Antineoplásicos , Vibrio , Acetaminofen , Maleimidas , Indóis , Fenóis , Alcaloides IndólicosRESUMO
A transition metal-free protocol for the preparation of fluorescent and non-fluoresent 3-methylthio-4-arylmaleimides in a single step through a new rearrangement from thiazolidine-2,4-diones is described. By employing the optimized reaction conditions, a broad scope of derivatives was prepared in ≤97% yield. The reaction tolerated several substituted aryl groups, including the challenging preparation of pyridyl-containing derivatives. A series of control experiments strongly suggested that the new rearrangement involves a key isocyanate intermediate and a further reaction with in situ-generated methylthiomethyl acetate. The photophysical properties of some of the synthesized derivatives as well as their use in live cell imaging were also investigated, revealing that some of the substituted maleimides are capable of selectively staining different regions of the cells.
Assuntos
MaleimidasRESUMO
OBJECTIVE: To evaluate laboratory indices in patients with hereditary spherocytosis, with positive and borderline flow cytometry eosin-5-melamide (EMA)-bound red blood cells screening test. STUDY DESIGN: We compared laboratory indices of 151 samples obtained from 139 different individual patients with negative, borderline, or positive EMA-test results. We also compared the clinical data of the patients in each EMA test results group. RESULTS: Borderline EMA-test results were obtained for 13 patients and were associated with more severe anemia, and lower reticulocyte count and reticulocyte production index compared with samples with positive EMA-test results. A receiving operator characteristic analysis identified mean corpuscular hemoglobin concentration of <32.5 g/dL as a cut-off, between positive/borderline and negative test results with 100% sensitivity. A higher prevalence of clinical markers typical of hereditary spherocytosis was found in patients with borderline or positive compared with negative EMA test samples. CONCLUSIONS: Based on laboratory data, borderline EMA-test results may be an indication of a more severe form of hereditary spherocytosis. Using mean corpuscular hemoglobin concentration as a cut-off may help predict and reduce negative EMA tests without compromising sensitivity. This finding needs to be further validated in other flow cytometry laboratories with a large EMA test sample pool.
Assuntos
Laboratórios , Esferocitose Hereditária , Amarelo de Eosina-(YS)/análise , Citometria de Fluxo/métodos , Humanos , Maleimidas , Esferocitose Hereditária/diagnósticoRESUMO
Herein we present the evaluation of 11C-labeled-maleimides as radiotracers for positron emission tomography imaging of GSK-3 associated with Alzheimer's disease (AD). 3-Acetyl-4-(1-[11C]-methyl-1H-indol-3-yl)[1H]pyrrole-2,5-dione ([11C]-2) was obtained by direct methylation using [11C]-CH3I and Cs2CO3 in DMF with a 31 ± 4% radiochemical yield and a radiochemical purity of 97.7 ± 0.8%. [11C]-2 was stable both in its final formulation and in human plasma for 120 min and had a plasma protein binding of 70 ± 1% and a LogD7.4 value of 1.84 ± 0.04. [11C]-2 ex vivo biodistributions in healthy animals demonstrated significant brain uptake and retention, showing its ability to penetrate the intact blood-brain barrier. In vivo PET imaging in mice bearing AD showed, with respect to normal animals, significant differences in uptake in the hypothalamus, the striatum, and the amygdala and a significant increase in amygdala uptake in later stages of the pathology. These results are very promising, and further studies are being performed for a complete validation of this compound as novel tracer for AD.
Assuntos
Doença de Alzheimer/tratamento farmacológico , Encéfalo/efeitos dos fármacos , Radioisótopos de Carbono/metabolismo , Quinase 3 da Glicogênio Sintase/antagonistas & inibidores , Maleimidas/química , Tomografia por Emissão de Pósitrons/métodos , Inibidores de Proteínas Quinases/farmacologia , Doença de Alzheimer/diagnóstico por imagem , Animais , Encéfalo/metabolismo , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Estudo de Prova de Conceito , Radioquímica , Compostos Radiofarmacêuticos/farmacologiaRESUMO
SLK (STE20-like kinase) and STK10 (serine/threonine kinase 10) are closely related kinases whose enzymatic activity is linked to the regulation of ezrin, radixin, and moesin function and to the regulation of lymphocyte migration and the cell cycle. We identified a series of 3-anilino-4-arylmaleimides as dual inhibitors of SLK and STK10 with good kinome-wide selectivity. Optimization of this series led to multiple SLK/STK10 inhibitors with nanomolar potency. Crystal structures of exemplar inhibitors bound to SLK and STK10 demonstrated the binding mode of the inhibitors and rationalized their selectivity. Cellular target engagement assays demonstrated the binding of the inhibitors to SLK and STK10 in cells. Further selectivity analyses, including analysis of activity of the reported inhibitors against off-targets in cells, identified compound 31 as the most potent and selective inhibitor of SLK and STK10 yet reported.
Assuntos
Compostos de Anilina/farmacologia , Maleimidas/farmacologia , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Compostos de Anilina/química , Compostos de Anilina/metabolismo , Sítios de Ligação , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Células HEK293 , Humanos , Maleimidas/química , Maleimidas/metabolismo , Proteínas dos Microfilamentos/metabolismo , Simulação de Acoplamento Molecular , Estrutura Molecular , Fosforilação/efeitos dos fármacos , Ligação Proteica , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/química , Proteínas Serina-Treonina Quinases/metabolismo , Relação Estrutura-AtividadeRESUMO
Allatotropin is a pleiotropic peptide originally characterized in insects. The existence of AT neuropeptide signaling was proposed in other invertebrates. In fact, we previously proposed the presence of an AT-like system regulating feeding behavior in Hydra sp. Even in insects, the information about the AT signaling pathway is incomplete. The aim of this study is to analyze the signaling cascade activated by AT in Hydra plagiodesmica using a pharmacological approach. The results show the involvement of Ca2+ and IP3 signaling in the transduction pathway of the peptide. Furthermore, we confirm the existence of a GPCR system involved in this pathway, that would be coupled to a Gq subfamily of Gα protein, which activates a PLC, inducing an increase in IP3 and cytosolic Ca2+. To the best of our knowledge, this work represents the first in vivo approach to study the overall signaling pathway and intracellular events involved in the myoregulatory effect of AT in Hydra sp.
Assuntos
Sinalização do Cálcio , Hydra/metabolismo , Hormônios de Inseto/metabolismo , Neuropeptídeos/metabolismo , Orexinas/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Animais , Cálcio/metabolismo , Sinalização do Cálcio/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Estrenos/farmacologia , Proteínas de Ligação ao GTP/metabolismo , Indóis/farmacologia , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Maleimidas/farmacologia , Meliteno/farmacologia , Proteína Quinase C/antagonistas & inibidores , Proteína Quinase C/metabolismo , Pirrolidinonas/farmacologia , Fosfolipases Tipo C/antagonistas & inibidores , Fosfolipases Tipo C/metabolismoRESUMO
N-aryl maleimides can undergo a 1,4-Michael-type addition reaction with reduced glutathione (GSH), leading to a decreased concentration of GSH and an increased concentration of free radicals (FRs) in cells. GSH is a critical scavenging molecule responsible for protecting cells from oxidation and for maintaining redox homeostasis. N-aryl maleimides disturb redox homeostasis in cells because they scavenge thiol-containing molecules, especially GSH. This study aimed at measuring the concentrations of GSH and FRs by electronic paramagnetic resonance (EPR), in the brain and liver tissue of male Wistar rats (ex vivo) at different ages and after treatment with 3,5-dimaleimylbenzoic acid (3,5-DMB). Our results showed a relationship between age and the concentrations of GSH and FRs in cells. In young rats, the concentration of GSH was higher than in old rats, while the concentration of FRs was higher in adult rats than in young rats, suggesting an inverse relationship between GSH and FRs. On the other hand, the reaction of 3,5-DMB (an electrophilic maleimide) with cellular GSH increased the FR content. The results of this study contribute to the awareness that the process of aging implies not only a loss of tissue function but also essential changes in the molecular contents of cells, especially the concentrations of FRs and GSH.
Assuntos
Envelhecimento , Radicais Livres/metabolismo , Glutationa/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Glutationa/química , Fígado/efeitos dos fármacos , Fígado/metabolismo , Masculino , Maleimidas/farmacologia , Modelos Biológicos , Oxirredução , Ratos , Ratos WistarRESUMO
Rhodopsin is the photoreceptor protein involved in visual excitation in retinal rods. The functionality of bovine rhodopsin was determined following treatment with sulfosuccinimidyl 4-(N maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC), a bifunctional reagent capable of forming covalent cross-links between suitable placed lysines and cysteines. Denaturing polyacrylamide gel electrophoresis showed that rhodopsin incubated with sulfo-SMCC generated intermolecular dimers, trimers, and higher oligomers, although most of the sulfo-SMCC-treated protein remained as a monomer. Minor alterations on the absorption spectrum of light-activated sulfo-SMCC-treated rhodopsin were observed. However, only â¼2% stimulation of the guanine nucleotide binding activity of transducin was measured in the presence of sulfo-SMCC-cross-linked photolyzed rhodopsin. Moreover, rhodopsin kinase was not able of phosphorylating sulfo-SMCC-cross-linked rhodopsin after illumination. Rhodopsin was purified in the presence of either 0.1% or 1% n-dodecyl ß-d-maltoside, to obtain dimeric and monomeric forms of the protein, respectively. Interestingly, no generation of the regular F1 and F2 thermolytic fragments was perceived with sulfo-SMCC-cross-linked rhodopsin either in the dimeric or monomeric state, implying the formation of intramolecular connections in the protein that might thwart the light-induced conformational changes required for interaction with transducin and rhodopsin kinase. Structural analysis of the rhodopsin three-dimensional structure suggested that the following lysine and cysteine pairs: Lys66/Lys67 and Cys316, Cys140 and Lys141, Cys140 and Lys248, Lys311 and Cys316, and/or Cys316 and Lys325 are potential candidates to generate intramolecular cross-links in the protein. Yet, the lack of fragmentation of sulfo-SMCC-treated Rho with thermolysin is consistent with the formation of cross-linking bridges between Lys66/Lys67 and Cys316, and/or Cys140 and Lys248.