Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 116
Filtrar
1.
Chem Pharm Bull (Tokyo) ; 69(11): 1097-1103, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34719592

RESUMO

The structure of an ornithine (Orn)-free Gramicidin S (GS) analogue, cyclo(Val-Nle-Leu-D-Phe-Pro)2 (NGS), was studied. Its circular dichroism (CD) spectrum showed that NGS has a structure similar to GS, though the value of [θ] indicated smaller ß-turn and sheet populations. This is probably because the Nle side chain could not form intramolecular hydrogen bonds stabilizing the sheet structure. The chemical shift perturbation of αH and JNH-αH were similar in GS and NGS. Three independent NGS molecules formed intramolecular ß-sheet structures in crystal. The turn structures of D-Phe-Pro moieties were classed as type II' ß-turns, but one part was unclassed. The molecules were arranged in a twisting manner, which resulted in the formation of a helical sheet. Similar structural characteristics were observed previously in a Leu-type, Orn-free GS analogue and in GS trifluoroacetic acid salt.


Assuntos
Gramicidina/química , Norleucina/química , Ornitina/química , Sequência de Aminoácidos , Cristalização , Ligação de Hidrogênio , Modelos Moleculares , Conformação Proteica em Folha beta , Ácido Trifluoracético/química
2.
Int J Biol Macromol ; 193(Pt B): 2165-2172, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34774865

RESUMO

Methylglyoxal (MG) is a highly reactive α-dicarbonyl compound which reacts with proteins to form advanced glycation end products (AGEs). MG-induced AGE (MAGE) formation is particularly significant in diabetic condition. In the current study, we have undertaken a time-dependant characterization of MG-modified myoglobin following incubation of the heme protein with the α-dicarbonyl compound for different time periods. Interestingly, mass spectrometric studies indicated modifications at two specific lysine residues, Lys-87 and Lys-133. The AGE adducts identified at Lys-87 were carboxymethyllysine and carboxyethyllysine, while those detected at Lys-133 included pyrraline-carboxymethyllysine and carboxyethyllysine, respectively. Far-UV CD studies revealed a decrease in the native α-helical content of the heme protein gradually with increasing time of MG incubation. In addition, MG modification was found to induce changes in tertiary structure as well as surface hydrophobicity of the heme protein. MG-derived AGE adducts thus appear to alter the structure of Mb considerably. Considering the increased level of MG in diabetic condition, the current study appears physiologically relevant in terms of understanding AGE-mediated protein modification and subsequent structural changes.


Assuntos
Produtos Finais de Glicação Avançada/química , Mioglobina/química , Aldeído Pirúvico/química , Heme/química , Interações Hidrofóbicas e Hidrofílicas , Lisina/análogos & derivados , Lisina/química , Espectrometria de Massas/métodos , Norleucina/análogos & derivados , Norleucina/química , Conformação Proteica em alfa-Hélice , Estrutura Terciária de Proteína , Pirróis/química
3.
Org Biomol Chem ; 20(1): 98-105, 2021 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-34596204

RESUMO

A new vobasine-tryptamine-based monoterpene indole alkaloid pseudodimer was isolated from the stem bark of Voacanga africana. As a minor constituent occurring in a thoroughly investigated plant, this molecule was targeted based on a molecular networking strategy and a rational MS2-guided phytochemical investigation led to its isolation. Its structure was formally established based on HRMS, 1D/2D NMR data, and the application of the tool Small Molecule Accurate Recognition Technology (SMART 2.0). Its absolute configuration was assigned by the exciton chirality method and TD-DFT ECD calculations. Besides featuring an unprecedented intermonomeric linkage in the small group of vobasine/tryptamine hybrids, pyrrovobasine also represents the first pyrraline-containing representative in the whole monoterpene indole alkaloids group. Biosynthetic hypotheses possibly underpinning these structural oddities are proposed here.


Assuntos
Alcaloides Indólicos/química , Aprendizado de Máquina , Monoterpenos/química , Norleucina/análogos & derivados , Pirróis/química , Alquilação , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Norleucina/química , Voacanga/química
4.
Cell Biol Int ; 45(3): 518-527, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32068315

RESUMO

Arginine-deprivation therapy is a rapidly developing metabolic anticancer approach. To overcome the resistance of some cancer cells to this monotherapy, rationally designed combination modalities are needed. In this report, we evaluated for the first time indospicine, an arginine analogue of Indigofera plant genus origin, as potential enhancer compound for the metabolic therapy that utilizes recombinant human arginase I. We demonstrate that indospicine at low micromolar concentrations is selectively toxic for human colorectal cancer cells only in the absence of arginine. In arginine-deprived cancer cells indospicine deregulates some prosurvival pathways (PI3K-Akt and MAPK) and activates mammalian target of rapamycin, exacerbates endoplasmic reticulum stress and triggers caspase-dependent apoptosis, which is reversed by the exposure to translation inhibitors. Simultaneously, indospicine is not degraded by recombinant human arginase I and does not inhibit this arginine-degrading enzyme at its effective dose. The obtained results emphasize the potential of arginine structural analogues as efficient components for combinatorial metabolic targeting of malignant cells.


Assuntos
Apoptose/efeitos dos fármacos , Arginina/deficiência , Neoplasias/patologia , Norleucina/análogos & derivados , Arginase/metabolismo , Arginina/química , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Humanos , Norleucina/química , Norleucina/farmacologia , Biossíntese de Proteínas/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Especificidade por Substrato/efeitos dos fármacos
5.
Theranostics ; 10(24): 11324-11338, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33042285

RESUMO

Rationale: Cell therapy for myocardial infarction is promising but largely unsuccessful in part due to a lack of mechanistic understanding. Techniques enabling identification of stem cell-specific proteomes in situ in the injured heart may shed light on how the administered cells respond to the injured microenvironment and exert reparative effects. Objective: To identify the proteomes of the transplanted mesenchymal stem cells (MSCs) in the infarcted myocardium, we sought to target a mutant methionyl-tRNA synthetase (MetRSL274G) in MSCs, which charges azidonorleucine (ANL), a methionine analogue and non-canonical amino acid, to tRNA and subsequently to nascent proteins, permitting isolation of ANL-labeled MSC proteomes from ischemic hearts by ANL-alkyne based click reaction. Methods and Results: Murine MSCs were transduced with lentivirus MetRSL274G and supplemented with ANL; the ANL-tagged nascent proteins were visualized by bio-orthogonal non-canonical amino-acid tagging, spanning all molecular weights and by fluorescent non-canonical amino-acid tagging, displaying strong fluorescent signal. Then, the MetRSL274G-transduced MSCs were administered to the infarcted or Sham heart in mice receiving ANL treatment. The MSC proteomes were isolated from the left ventricular protein lysates by click reaction at days 1, 3, and 7 after cell administration, identified by LC/MS. Among all identified proteins (in Sham and MI hearts, three time-points each), 648 were shared by all 6 groups, accounting for 82±5% of total proteins in each group, and enriched under mitochondrion, extracellular exosomes, oxidation-reduction process and poly(A) RNA binding. Notably, 26, 110 and 65 proteins were significantly up-regulated and 11, 28 and 19 proteins were down-regulated in the infarcted vs. Sham heart at the three time-points, respectively; these proteins are pronounced in the GO terms of extracellular matrix organization, response to stress and regulation of apoptotic process and in the KEGG pathways of complements and coagulation cascades, apoptosis, and regulators of actin cytoskeleton. Conclusions: MetRSL274G expression allows successful identification of MSC-specific nascent proteins in the infarcted hearts, which reflect the functional states, adaptive response, and reparative effects of MSCs that may be leveraged to improve cardiac repair.


Assuntos
Transplante de Células-Tronco Mesenquimais , Células-Tronco Mesenquimais/metabolismo , Metionina tRNA Ligase/análise , Infarto do Miocárdio/terapia , Miocárdio/patologia , Animais , Azidas/química , Células Cultivadas , Química Click , Biologia Computacional , Modelos Animais de Doenças , Humanos , Metionina tRNA Ligase/química , Metionina tRNA Ligase/genética , Metionina tRNA Ligase/metabolismo , Camundongos , Infarto do Miocárdio/patologia , Norleucina/análogos & derivados , Norleucina/química , Proteômica/métodos , Transdução Genética
6.
Food Chem ; 317: 126458, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32109656

RESUMO

A kinetic model for Maillard reaction (MR) model system of d-glucose and l-lysine was established; activation energy (Ea) of each step was calculated. Potential generation pathways of furosine and pyrraline were a combination of either 3-deoxyglucosone (3-DG) or methylglyoxal (MG) with l-lysine. Ea value for furosine generated through 3-DG pathway was 81.70 ± 14.01 kJ mol-1, which was significantly higher than that through MG pathway (52.08 ± 4.48 kJ mol-1). As for pyrraline, Ea for the 3-DG pathway (53.45 ± 4.02 kJ mol-1) was significantly lower than that through the MG pathway (110.22 ± 18.77 kJ mol-1). Results of the kinetic study indicated that furosine was preferred to be generated through the MG pathway since MG is more likely to react with each other and form a furan ring as a precursor of furosine. Pyrraline was more easily to be generated from the 3-DG pathway through cyclization of 1,4-dicarbonyl compounds to pyrrole.


Assuntos
Glucose/química , Lisina/análogos & derivados , Lisina/química , Reação de Maillard , Norleucina/análogos & derivados , Pirróis/química , Desoxiglucose/análogos & derivados , Desoxiglucose/química , Cinética , Norleucina/química , Aldeído Pirúvico/química
7.
PLoS Comput Biol ; 16(1): e1007600, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31917825

RESUMO

Designed enzymes are of fundamental and technological interest. Experimental directed evolution still has significant limitations, and computational approaches are a complementary route. A designed enzyme should satisfy multiple criteria: stability, substrate binding, transition state binding. Such multi-objective design is computationally challenging. Two recent studies used adaptive importance sampling Monte Carlo to redesign proteins for ligand binding. By first flattening the energy landscape of the apo protein, they obtained positive design for the bound state and negative design for the unbound. We have now extended the method to design an enzyme for specific transition state binding, i.e., for its catalytic power. We considered methionyl-tRNA synthetase (MetRS), which attaches methionine (Met) to its cognate tRNA, establishing codon identity. Previously, MetRS and other synthetases have been redesigned by experimental directed evolution to accept noncanonical amino acids as substrates, leading to genetic code expansion. Here, we have redesigned MetRS computationally to bind several ligands: the Met analog azidonorleucine, methionyl-adenylate (MetAMP), and the activated ligands that form the transition state for MetAMP production. Enzyme mutants known to have azidonorleucine activity were recovered by the design calculations, and 17 mutants predicted to bind MetAMP were characterized experimentally and all found to be active. Mutants predicted to have low activation free energies for MetAMP production were found to be active and the predicted reaction rates agreed well with the experimental values. We suggest the present method should become the paradigm for computational enzyme design.


Assuntos
Enzimas , Método de Monte Carlo , Ligação Proteica/genética , Engenharia de Proteínas/métodos , Especificidade por Substrato/genética , Monofosfato de Adenosina/análogos & derivados , Monofosfato de Adenosina/química , Monofosfato de Adenosina/metabolismo , Azidas/química , Azidas/metabolismo , Sítios de Ligação/genética , Catálise , Enzimas/química , Enzimas/genética , Enzimas/metabolismo , Metionina/análogos & derivados , Metionina/química , Metionina/metabolismo , Metionina tRNA Ligase/química , Metionina tRNA Ligase/genética , Metionina tRNA Ligase/metabolismo , Mutação/genética , Norleucina/análogos & derivados , Norleucina/química , Norleucina/metabolismo
8.
Biomacromolecules ; 21(1): 126-132, 2020 01 13.
Artigo em Inglês | MEDLINE | ID: mdl-31482703

RESUMO

The preparation and characterization of a new epoxide containing polypeptide, poly(5,6-epoxy-l-norleucine), via postpolymerization modification of poly(l-homoallylglycine) is described. Addition of thiols to the epoxide groups in poly(5,6-epoxy-l-norleucine) was studied as a means to prepare side-chain functional polypeptides. The solution properties of the derivatized polypeptides were studied in water and compared to similar thioether containing functional polypeptides prepared via different routes. Subtle differences in side-chain linkage chemistry were found to influence polypeptide solubility, chain conformation in solution, and thermoresponsive behavior. Poly(5,6-epoxy-l-norleucine) was found to be useful as a readily prepared intermediate that can be reacted with thiols to give a variety of functional polypeptides.


Assuntos
Norleucina/química , Peptídeos/química , Dicroísmo Circular , Compostos de Epóxi/química , Glicina/química , Espectroscopia de Ressonância Magnética , Peptídeos/síntese química , Conformação Proteica , Solubilidade , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
9.
Biomolecules ; 9(11)2019 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-31717655

RESUMO

Advanced glycation end products (AGEs), which are present in heat-processed foods, have been associated with several chronic diseases. Sodium chloride (NaCl) modulates the formation of furfurals and acrylamide in the Maillard reaction; however, the effects of NaCl on AGE formation are inconsistent. In this study, we investigated the effects of NaCl on pyrraline formation using glucose-lysine model systems. NaCl, especially at 0.50%, promoted Maillard browning and pyrraline formation, with a simultaneous increase in the 3-deoxyglucosone concentration. To reduce the rate of pyrraline formation, NaCl coated with different gums and starches were used. The results showed that NaCl encapsulation is an effective approach to mitigate pyrraline and 3-deoxyglucosone formation. The content of NaCl in the microparticles were 284 ± 12, 269 ± 6, 258 ± 8, 247 ± 10, 273 ± 16, and 288 ± 15 mg/g (coated with waxy maize starch, normal maize starch, HYLON VII high amylose maize starch, gelatinized resistant starch, xanthan gum, and gum arabic, respectively). The heat resistance of the coating material was negatively correlated with the pyrraline and 3-deoxyglucosone formation, whereas the solubility of the coating material had the opposite results. Coating the material with gum had little effects on the reduction of pyrraline and 3-deoxyglucosone.


Assuntos
Glucose/genética , Produtos Finais de Glicação Avançada/genética , Norleucina/análogos & derivados , Pirróis/química , Cloreto de Sódio/química , Amilose/química , Amilose/genética , Desoxiglucose/análogos & derivados , Desoxiglucose/química , Desoxiglucose/genética , Glucose/química , Produtos Finais de Glicação Avançada/química , Temperatura Alta , Lisina/química , Lisina/genética , Reação de Maillard , Norleucina/química , Norleucina/metabolismo , Pirróis/metabolismo , Cloreto de Sódio/metabolismo , Zea mays/genética
10.
Acta Crystallogr B Struct Sci Cryst Eng Mater ; 75(Pt 3): 393-405, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32830661

RESUMO

The diffraction patterns of DL-norleucine (SR-2-aminohexanoic acid, DL-Nle) crystals may show obvious diffuse scattering, usually described as `streaking', between the Bragg peaks. This phenomenon is obviously related to the non-ideal behaviour of the crystal. The normal interpretation is disorder in the stacking of weakly interacting 2D layers, known also for a number of other racemates of amino acids with linear hydrophobic side chains, as well as 1:1 complexes between different L- and D-enantiomers (quasi-racemates). Presented here is the first attempt to extract the information hidden in the diffuse scattering for this group of compounds by applying Monte Carlo simulations to the site distributions of two polymorphs in a block of 48 × 48 × 48 unit cells (four sites in each unit cell, 442 368 in total). The results demonstrate that it is indeed possible to model the diffuse scattering and relate it to processes expected to take place during phase transitions, characterized by slipping of molecular bilayers (or parts of them) relative to their neighbours. The understanding of the (intermediate) mixed phases in terms of domain size and defect density is consequently brought to a new level.


Assuntos
Norleucina/química , Cristalização , Cristalografia por Raios X , Modelos Moleculares , Método de Monte Carlo , Estereoisomerismo
11.
Org Biomol Chem ; 16(43): 8030-8033, 2018 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-30334043

RESUMO

A three-step one-pot biocatalytic cascade was designed for the enantioselective formal α-amination of hexanoic acid to l-norleucine. Regioselective hydroxylation by P450CLA peroxygenase to 2-hydroxyhexanoic acid was followed by oxidation to the ketoacid by two stereocomplementary dehydrogenases. Combination with final stereoselective reductive amination by amino acid dehydrogenase furnished l-norleucine in >97% ee.


Assuntos
Biocatálise , Caproatos/química , Sistema Enzimático do Citocromo P-450/metabolismo , Norleucina/química , Aminação , Bactérias/enzimologia , Estereoisomerismo , Especificidade por Substrato
12.
Toxins (Basel) ; 10(9)2018 09 03.
Artigo em Inglês | MEDLINE | ID: mdl-30177604

RESUMO

Indospicine, a hepatotoxic arginine analog, occurs in leguminous plants of the Indigofera genus and accumulates in the tissues of grazing animals that consume these plants. Furthermore, indospicine has caused toxicity in dogs following consumption of indospicine-contaminated meat; however, the potential impact on human health is unknown. The present study was designed to determine the effect of simulated human gastrointestinal digestion on the release and degradation of indospicine from contaminated camel meat following microwave cooking. Results showed no significant (p > 0.05) indospicine degradation during cooking or in vitro digestion. However, approximately 70% indospicine was released from the meat matrix into the liquid digesta during the gastric phase (in the presence of pepsin) and increased to >90% in the intestinal phase (with pancreatic enzymes). Following human consumption of contaminated meat, this soluble and more bioaccessible fraction of intact indospicine could be readily available for absorption by the small intestine, potentially circulating indospicine throughout the human body to tissues where it could accumulate and cause detrimental toxic effects.


Assuntos
Camelus , Culinária , Contaminação de Alimentos , Carne , Norleucina/análogos & derivados , Toxinas Biológicas/química , Animais , Bile/química , Digestão , Temperatura Alta , Humanos , Concentração de Íons de Hidrogênio , Norleucina/química , Pancreatina/química , Pepsina A/química
13.
Org Biomol Chem ; 16(34): 6306-6315, 2018 08 29.
Artigo em Inglês | MEDLINE | ID: mdl-30117511

RESUMO

The development of γ-thionorleucine (ThioNle) as a handle for native chemical ligation-desulfurization is reported here. ThioNle is a new addition to the expanding thiolated amino acid toolbox and serves as a methionine substitute in NCL with the advantage that it lacks the undesirable oxidation-prone thioether moiety. Its usefulness for N-terminal ubiquitination is demonstrated by efficient preparation of fully synthetic linear diubiquitin with preserved protein folding compared to the expressed material. Interestingly, gel-based deubiquitinating assays revealed that the methionine to norleucine substitution did affect diubiquitin cleavage, which may indicate a more profound role for methionine in the interaction between ubiquitin and the deubiquitinating enzymes than has been known so far.


Assuntos
Metionina/química , Norleucina/química , Ubiquitinas/química , Ubiquitinas/metabolismo
14.
PLoS One ; 13(5): e0197082, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29742153

RESUMO

WHSC1 is a histone methyltransferase that is responsible for mono- and dimethylation of lysine 36 on histone H3 and has been implicated as a driver in a variety of hematological and solid tumors. Currently, there is a complete lack of validated chemical matter for this important drug discovery target. Herein we report on the first fully validated WHSC1 inhibitor, PTD2, a norleucine-containing peptide derived from the histone H4 sequence. This peptide exhibits micromolar affinity towards WHSC1 in biochemical and biophysical assays. Furthermore, a crystal structure was solved with the peptide in complex with SAM and the SET domain of WHSC1L1. This inhibitor is an important first step in creating potent, selective WHSC1 tool compounds for the purposes of understanding the complex biology in relation to human disease.


Assuntos
Inibidores Enzimáticos/química , Histona-Lisina N-Metiltransferase/antagonistas & inibidores , Neoplasias/tratamento farmacológico , Peptídeos/química , Proteínas Repressoras/antagonistas & inibidores , Cristalografia por Raios X , Inibidores Enzimáticos/farmacologia , Histona-Lisina N-Metiltransferase/química , Histona-Lisina N-Metiltransferase/genética , Histonas/química , Histonas/genética , Humanos , Lisina/química , Neoplasias/enzimologia , Norleucina/análogos & derivados , Norleucina/química , Norleucina/farmacologia , Domínios PR-SET/genética , Peptídeos/genética , Conformação Proteica/efeitos dos fármacos , Proteínas Repressoras/química , Proteínas Repressoras/genética
15.
Methods Mol Biol ; 1728: 137-145, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29404995

RESUMO

The incorporation of noncanonical amino acids has given protein chemists access to an expanded repertoire of amino acids. This methodology has significantly broadened the scope of protein engineering allowing introduction of amino acids with non-native functionalities, such as bioorthogonal reactive handles (azides and alkynes) and hydrophobic fluorinated side chains. Here, we describe the efficient residue-specific replacement of methionine by azidonorleucine in an engineered green fluorescent protein using a bacterial expression system to introduce a single reactive site for the strain-promoted azide-alkyne cycloaddition.


Assuntos
Aminoácidos/genética , Biossíntese de Proteínas , Engenharia de Proteínas , Proteínas/genética , Sequência de Aminoácidos , Aminoácidos/química , Aminoacil-tRNA Sintetases/química , Aminoacil-tRNA Sintetases/metabolismo , Azidas/química , Cromatografia de Afinidade , Expressão Gênica , Genes Reporter , Modelos Moleculares , Norleucina/análogos & derivados , Norleucina/química , Norleucina/genética , Conformação Proteica , Proteínas/química , Proteínas/isolamento & purificação , Proteínas/metabolismo
16.
J Sci Food Agric ; 98(9): 3225-3233, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29280151

RESUMO

Pyrraline and pentosidine are advanced Maillard reaction products derived from the reaction of glucose with the lysine amino group on proteins. They have been implicated in uremia, diabetes, and related complications, including inflammation, retinopathy, and nephropathy. This review focuses on the formation mechanism, human potential risks, and detections of pentosidine and pyrraline and lays the foundation for further study of pentosidine and pyrraline. © 2017 Society of Chemical Industry.


Assuntos
Arginina/análogos & derivados , Análise de Alimentos , Lisina/análogos & derivados , Norleucina/análogos & derivados , Pirróis/efeitos adversos , Pirróis/análise , Arginina/efeitos adversos , Arginina/análise , Arginina/química , Reagentes de Ligações Cruzadas , Complicações do Diabetes/induzido quimicamente , Diabetes Mellitus/induzido quimicamente , Glucose/química , Produtos Finais de Glicação Avançada , Humanos , Inflamação/induzido quimicamente , Lisina/efeitos adversos , Lisina/análise , Lisina/química , Estrutura Molecular , Norleucina/efeitos adversos , Norleucina/análise , Norleucina/química , Pirróis/química , Fatores de Risco , Uremia/induzido quimicamente
17.
J Agric Food Chem ; 65(34): 7528-7534, 2017 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-28787565

RESUMO

The known accumulation of the hepatotoxin indospicine in tissues of camels and cattle grazing Indigofera pasture plants is unusual in that free amino acids would normally be expected to be degraded during the fermentation processes in these foregut fermenters. In this study, in vitro experiments were carried out to examine the degradability of indospicine of Indigofera spicata by camel and cattle foregut microbiota. In the first experiment, a 48 h in vitro incubation was carried out using foregut fluid samples that were collected from 15 feral camels and also a fistulated cow. Degradability of indospicine ranged between 97% and 99%, with the higher value of 99% for camels. A pooled sample of foregut fluids from three camels that were on a roughage diet was used in a second experiment to examine the time-dependent degradation of indospicine present in the plant materials. Results indicated that camels' foregut fluids have the ability to biodegrade ∼99% of the indospicine in I. spicata within 48 h of incubation and produced 2-aminopimelamic acid and 2-aminopimelic acid. The time-dependent degradation analysis showed rapid indospicine degradation (65 nmol/h) during the first 8-18 h of incubation followed by a slower degradation rate (12 nmol/h) between 18 and 48 h. Indospicine degradation products were also degraded toward the end of the experiment. The results of these in vitro degradation studies suggest that dietary indospicine may undergo extensive degradation in the foregut of the camel, resulting in trace levels after 48 h. The retention time for plant material in the camel foregut varies depending on feed quality, and the results of this study together with the observed accumulation of indospicine in camel tissues suggest that, although indospicine can be degraded by foregut fermentation, this degradation is not complete before the passage of the digesta into the intestine.


Assuntos
Ração Animal/análise , Camelus/metabolismo , Bovinos/metabolismo , Sistema Digestório/metabolismo , Indigofera/metabolismo , Norleucina/análogos & derivados , Ração Animal/toxicidade , Animais , Indigofera/química , Indigofera/toxicidade , Modelos Biológicos , Norleucina/química , Norleucina/metabolismo , Norleucina/toxicidade , Rúmen/metabolismo
18.
Eur Phys J E Soft Matter ; 40(2): 21, 2017 02.
Artigo em Inglês | MEDLINE | ID: mdl-28236111

RESUMO

The side chain effect on transport in ionic aqueous salt solutions was investigated for [Formula: see text]-amino acids glycine, alanine, [Formula: see text]-amino butyric acid, norvaline, and norleucine --that together define a chemical homologous series based on the length of the characteristic side chain which increases from zero to four carbons, respectively. Binary mutual diffusion coefficients at infinitesimal concentration in aqueous solutions of NaCl (0.15 mol kg -1) are measured by means of Taylor dispersion technique for this series and significant differences were found against previous published results for identical systems in pure water. In this way, NaCl effect on the transport of each amino acid is thus assessed and discussed in terms of salting-out effects. Also, solvated Stokes hydrodynamic radii were computed for the series showing comparable results in water and NaCl solution. The new information should prove useful in the design and characterization of transport-controlled systems in physiological and pharmacological studies.


Assuntos
Alanina/química , Glicina/química , Norleucina/química , Valina/análogos & derivados , Ácido Butírico/química , Difusão , Interações Hidrofóbicas e Hidrofílicas , Concentração Osmolar , Valina/química
19.
J Pept Sci ; 23(1): 38-44, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-28054429

RESUMO

Radiolabelled peptides with high specificity and affinity towards receptors that are overexpressed by tumour cells are used in nuclear medicine for the diagnosis (imaging) and therapy of cancer. In some cases, the sequences of peptides under investigations contain methionine (Met), an amino acid prone to oxidation during radiolabelling procedures. The formation of oxidative side products can affect the purity of the final radiopharmaceutical product and/or impair its specificity and affinity towards the corresponding receptor. The replacement of Met with oxidation resistant amino acid analogues, for example, norleucine (Nle), can provide a solution. While this approach has been applied successfully to different radiolabelled peptides, a Met → Nle switch only preserves the length of the amino acid side chain important for hydrophobic interactions but not its hydrogen-bonding properties. We report here the use of methoxinine (Mox), a non-canonical amino acid that resembles more closely the electronic properties of Met in comparison to Nle. Specifically, we replaced Met15 by Mox15 and Nle15 in the binding sequence of a radiometal-labelled human gastrin derivative [d-Glu10 ]HG(10-17), named MG11 (d-Glu-Ala-Tyr-Gly-Trp-Met-Asp-Phe-NH2 ). A comparison of the physicochemical properties of 177 Lu-DOTA[X15 ]MG11 (X = Met, Nle, Mox) in vitro (cell internalization/externalization properties, receptor affinity (IC50 ), blood plasma stability and logD) showed that Mox indeed represents a suitable, oxidation-stable amino acid substitute of Met in radiolabelled peptide conjugates. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.


Assuntos
Gastrinas/síntese química , Compostos Heterocíclicos com 1 Anel/química , Homosserina/análogos & derivados , Lutécio/química , Oligopeptídeos/síntese química , Radioisótopos/química , Compostos Radiofarmacêuticos/síntese química , Substituição de Aminoácidos , Linhagem Celular Tumoral , Células Epiteliais/citologia , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Gastrinas/metabolismo , Gastrinas/farmacologia , Compostos Heterocíclicos com 1 Anel/metabolismo , Compostos Heterocíclicos com 1 Anel/farmacologia , Homosserina/química , Humanos , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Marcação por Isótopo , Metionina/química , Norleucina/química , Oligopeptídeos/metabolismo , Oligopeptídeos/farmacologia , Oxirredução , Compostos Radiofarmacêuticos/metabolismo , Compostos Radiofarmacêuticos/farmacologia , Glândula Tireoide/citologia , Glândula Tireoide/efeitos dos fármacos , Glândula Tireoide/metabolismo
20.
J Agric Food Chem ; 64(44): 8447-8453, 2016 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-27737547

RESUMO

Ingestion of indospicine-contaminated camel and horse meat has caused fatal liver injury to dogs in Australia, and it is currently not known if such contaminated meat may pose a human health risk upon dietary exposure. To date, indospicine-related research has tended to focus on analytical aspects, with little information on post-harvest management of indospicine-contaminated meat. In this study, indospicine degradation was investigated in both aqueous solution and also contaminated meat, under a range of conditions. Aqueous solutions of indospicine and indospicine-contaminated camel meat were microwaved (180 °C) or autoclaved (121 °C) with the addition of food-grade additives [0.05% (v/v) acetic acid or 0.05% (w/v) sodium bicarbonate] for 0, 15, 30, and 60 min. An aqueous sodium bicarbonate solution demonstrated the greatest efficacy in degrading indospicine, with complete degradation after 15 min of heating in a microwave or autoclave; concomitant formation of indospicine degradation products, namely, 2-aminopimelamic and 2-aminopimelic acids, was observed. Similar treatment of indospicine-contaminated camel meat with aqueous sodium bicarbonate resulted in 50% degradation after 15 min of heating in an autoclave and 100% degradation after 15 min of heating in a microwave. The results suggest that thermo-alkaline aqueous treatment has potential as a pragmatic post-harvest handling technique in reducing indospicine levels in indospicine-contaminated meat.


Assuntos
Camelus , Contaminação de Alimentos , Carne , Norleucina/análogos & derivados , Aminoácidos Neutros/análise , Animais , Cromatografia Líquida/métodos , Hidrólise , Espectrometria de Massas/métodos , Norleucina/análise , Norleucina/química , Ácidos Pimélicos/análise , Bicarbonato de Sódio/química
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...