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1.
Methods Mol Biol ; 2370: 237-264, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34611873

RESUMO

Carbohydrates are an essential class of biomolecule and carbohydrate active enzymes (CAZys) catalyze their synthesis, refinement, and degradation, hence contributing an overall regulatory capacity to their underpinning physiological roles. Here we survey recent accomplishments for accessing defined carbohydrate structures, suitably equipped with FRET probe capability, followed by their utilization in studying particular classes of CAZy.

2.
Molecules ; 26(16)2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34443344

RESUMO

Surface modification of electrodes with glycans was investigated as a strategy for modulating the development of electrocatalytic biofilms for microbial fuel cell applications. Covalent attachment of phenyl-mannoside and phenyl-lactoside adlayers on graphite rod electrodes was achieved via electrochemically assisted grafting of aryldiazonium cations from solution. To test the effects of the specific bio-functionalities, modified and unmodified graphite rods were used as anodes in two-chamber microbial fuel cell devices. Devices were set up with wastewater as inoculum and acetate as nutrient and their performance, in terms of output potential (open circuit and 1 kΩ load) and peak power output, was monitored over two months. The presence of glycans was found to lead to significant differences in startup times and peak power outputs. Lactosides were found to inhibit the development of biofilms when compared to bare graphite. Mannosides were found, instead, to promote exoelectrogenic biofilm adhesion and anode colonization, a finding that is supported by quartz crystal microbalance experiments in inoculum media. These differences were observed despite both adlayers possessing thickness in the nm range and similar hydrophilic character. This suggests that specific glycan-mediated bioaffinity interactions can be leveraged to direct the development of biotic electrocatalysts in bioelectrochemical systems and microbial fuel cell devices.


Assuntos
Fontes de Energia Bioelétrica , Polissacarídeos/química , Adesividade , Biofilmes , Eletrodos , Interações Hidrofóbicas e Hidrofílicas
3.
Chem Soc Rev ; 50(19): 10857-10894, 2021 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-34397045

RESUMO

Nature harnesses the unique properties of cysteinyl radical intermediates for a diverse range of essential biological transformations including DNA biosynthesis and repair, metabolism, and biological photochemistry. In parallel, the synthetic accessibility and redox chemistry of cysteinyl radicals renders them versatile reactive intermediates for use in a vast array of synthetic applications such as lipidation, glycosylation and fluorescent labelling of proteins, peptide macrocyclization and stapling, desulfurisation of peptides and proteins, and development of novel therapeutics. This review provides the reader with an overview of the role of cysteinyl radical intermediates in both chemical synthesis and biological systems, with a critical focus on mechanistic details. Direct insights from biological systems, where applied to chemical synthesis, are highlighted and potential avenues from nature which are yet to be explored synthetically are presented.

4.
Nat Commun ; 12(1): 4254, 2021 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-34253723

RESUMO

Lipoproteins serve diverse functions in the bacterial cell and some are essential for survival. Some lipoproteins are adjuvants eliciting responses from the innate immune system of the host. The growing list of membrane enzymes responsible for lipoprotein synthesis includes the recently discovered lipoprotein intramolecular transacylase, Lit. Lit creates a lipoprotein that is less immunogenic, possibly enabling the bacteria to gain a foothold in the host by stealth. Here, we report the crystal structure of the Lit enzyme from Bacillus cereus and describe its mechanism of action. Lit consists of four transmembrane helices with an extracellular cap. Conserved residues map to the cap-membrane interface. They include two catalytic histidines that function to effect unimolecular transacylation. The reaction involves acyl transfer from the sn-2 position of the glyceryl moiety to the amino group on the N-terminal cysteine of the substrate via an 8-membered ring intermediate. Transacylation takes place in a confined aromatic residue-rich environment that likely evolved to bring distant moieties on the substrate into proximity and proper orientation for catalysis.


Assuntos
Aciltransferases/química , Aciltransferases/metabolismo , Membrana Celular/metabolismo , Lipoproteínas/biossíntese , Acilação , Sequência de Aminoácidos , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Sequência Conservada , Cisteína/metabolismo , Análise Mutacional de DNA , Processamento de Proteína Pós-Traducional , Relação Estrutura-Atividade , Especificidade por Substrato
5.
Front Chem ; 8: 583272, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33282831

RESUMO

Radical thiol-ene chemistry has been demonstrated for a range of applications in peptide science, including macrocyclization, glycosylation and lipidation amongst a myriad of others. The thiol-ene reaction offers a number of advantages in this area, primarily those characteristic of "click" reactions. This provides a chemical approach to peptide modification that is compatible with aqueous conditions with high orthogonality and functional group tolerance. Additionally, the use of a chemical approach for peptide modification affords homogeneous peptides, compared to heterogeneous mixtures often obtained through biological methods. In addition to peptide modification, thiol-ene chemistry has been applied in novel approaches to biological studies through synthesis of mimetics and use in development of probes. This review will cover the range of applications of the radical-mediated thiol-ene reaction in peptide and protein science.

6.
ACS Chem Biol ; 15(9): 2415-2421, 2020 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-32786261

RESUMO

Macrophages are key immune cells for combatting Mycobacterium tuberculosis. However, M. tuberculosis possesses means to evade macrophage bactericidal responses by, for instance, secretion of the immunomodulatory para-hydroxybenzoic acid derivatives (pHBADs). While these molecules have been implicated in inhibiting macrophage responses in an acute context, little is known about their ability to reprogram macrophages via induction of long-term innate memory. Since innate memory has been highlighted as a promising strategy to augment bactericidal immune responses against M. tuberculosis, investigating corresponding immune evasion mechanisms is highly relevant. Our results reveal for the first time that pHBAD I and related molecules (unmethylated pHBAD I and the hexose l-rhamnose) reduce macrophage bactericidal mechanisms in both the short- and the long-term. Moreover, we demonstrate how methyl-p-anisate hinders bactericidal responses soon after exposure yet results in enhanced pro-inflammatory responses in the long-term. This work highlights new roles for these compounds in M. tuberculosis pathogenesis.


Assuntos
Imunidade Inata/efeitos dos fármacos , Fatores Imunológicos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Parabenos/farmacologia , Animais , Benzoatos/farmacologia , Interleucina-10/metabolismo , Camundongos , Óxido Nítrico/metabolismo , Óxido Nítrico Sintase Tipo II/metabolismo , Ramnose/farmacologia , Fator de Necrose Tumoral alfa/metabolismo
7.
Bioelectrochemistry ; 136: 107621, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32791485

RESUMO

Grafting of aryldiazonium cations bearing a p-mannoside functionality over microbial fuel cell (MFC) anode materials was performed to investigate the ability of aryl-glycoside layers to regulate colonisation by biocatalytic biofilms. Covalent attachment was achieved via spontaneous reactions and via electrochemically-assisted grafting using potential step experiments. The effect of different functionalisation protocols on MFC performance is discussed in terms of changes in wettability, roughness and electrochemical response of modified electrodes. Water contact angle measurements (WCA) show that aryl-mannoside grafting yields a significant increase in hydrophilic character. Surface roughness determinations via atomic force microscopy (AFM) suggest a more disordered glycan adlayer when electrografting is used to facilitate chemisorption. MFCs were used as living sensors to successfully test the coated electrodes: the response of the MFCs in terms of start-up time was accelerated when compared to that of MFC equipped with non-modified electrodes, this suggests a faster development of a mature biofilm community resulting from aryldiazonium modifications, as confirmed by cyclic voltammetry of MFC anodes. These results therefore indicate that modification with glycans offers a bioinspired route to accelerating biofilm colonisation without any adverse effects on final MFC outputs.


Assuntos
Bactérias/metabolismo , Fontes de Energia Bioelétrica , Eletrodos , Microbiota , Biofilmes , Eletricidade , Glicosilação , Propriedades de Superfície
8.
Molecules ; 25(13)2020 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-32646036

RESUMO

Sulfur centered radicals are widely employed in chemical synthesis, in particular for alkene and alkyne hydrothiolation towards thioether bioconjugates. The steadfast radical chain process that enables efficient hydrothiolation has been explored in the context of cascade reactions to furnish complex molecular architectures. The use of thiyl radicals offers a much cheaper and less toxic alternative to the archetypal organotin-based radical methods. This review outlines the development of thiyl radicals as reactive intermediates for initiating carbocyclization cascades. Key developments in cascade cyclization methodology are presented and applications for natural product synthesis are discussed. The review provides a chronological account of the field, beginning in the early seventies up to very recent examples; a span of almost 50 years.


Assuntos
Radicais Livres/química , Compostos de Sulfidrila/química , Compostos de Sulfidrila/síntese química , Ciclização
9.
Chemistry ; 26(68): 15804-15810, 2020 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-32584428

RESUMO

A mild, metal-free, atmospheric oxygen-mediated radical hydrothiolation of alkenes (and alkyne) is reported. A variety of sulfur containing motifs including alkanethiols, thiophenols and thioacids undergo an atmospheric oxygen-mediated radical hydrothiolation reaction with a plethora of alkenes in good yield with excellent functional group compatibility, typically with short reaction times to furnish a range of functionalized products. Biomolecules proved tolerant to the conditions and the procedure is robust and easily executable requiring no specialized equipment. Concise mechanistic studies confirm the process proceeds through radical intermediates in a thiol-ene reaction manifold. The methodology offers an efficient "green" approach for thiol-ene mediated "click" ligation and a milder alternative to thermally initiated hydrothiolation processes.

10.
Org Biomol Chem ; 18(18): 3475-3480, 2020 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-32329760

RESUMO

An investigation into the self-assembly of two 4-amino- and a 4-bromo-1,8-naphthalimide (Nap) based structures (1-3) possessing an appended glycan unit, from protic polar media, is presented. The results demonstrate the formation of complex hierarchical luminescent aggregates, wherein the morphologies, sizes and spherical structures were highly dependent on both the media and the Nap structure. Upon cleaving the native glycosidic bond, using an enzyme, the structure/morphology of the self-assembly of 3 in buffered solution was significantly transformed.

11.
Nat Commun ; 11(1): 140, 2020 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-31919415

RESUMO

Antimicrobial resistance is a major global threat that calls for new antibiotics. Globomycin and myxovirescin are two natural antibiotics that target the lipoprotein-processing enzyme, LspA, thereby compromising the integrity of the bacterial cell envelope. As part of a project aimed at understanding their mechanism of action and for drug development, we provide high-resolution crystal structures of the enzyme from the human pathogen methicillin-resistant Staphylococcus aureus (MRSA) complexed with globomycin and with myxovirescin. Our results reveal an instance of convergent evolution. The two antibiotics possess different molecular structures. Yet, they appear to inhibit identically as non-cleavable tetrahedral intermediate analogs. Remarkably, the two antibiotics superpose along nineteen contiguous atoms that interact similarly with LspA. This 19-atom motif recapitulates a part of the substrate lipoprotein in its proposed binding mode. Incorporating this motif into a scaffold with suitable pharmacokinetic properties should enable the development of effective antibiotics with built-in resistance hardiness.


Assuntos
Ácido Aspártico Endopeptidases/metabolismo , Proteínas de Bactérias/metabolismo , Macrolídeos/metabolismo , Staphylococcus aureus Resistente à Meticilina/enzimologia , Peptídeos/metabolismo , Sítios de Ligação/fisiologia , Membrana Celular/efeitos dos fármacos , Cristalografia por Raios X , Farmacorresistência Bacteriana/genética , Farmacorresistência Bacteriana/fisiologia , Macrolídeos/farmacologia , Peptídeos/farmacologia , Ligação Proteica/fisiologia , Estrutura Terciária de Proteína
12.
Org Biomol Chem ; 17(35): 8094-8105, 2019 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-31380542

RESUMO

Nine modified nucleosides, incorporating zinc-binding pharmacophores, have been synthesised and evaluated as inhibitors of the DNA repair nuclease SNM1A. The series included oxyamides, hydroxamic acids, hydroxamates, a hydrazide, a squarate ester and a squaramide. A hydroxamic acid-derived nucleoside inhibited the enzyme, offering a novel approach for potential therapeutic development through the use of rationally designed nucleoside derived inhibitors.


Assuntos
Proteínas de Ciclo Celular/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Exodesoxirribonucleases/antagonistas & inibidores , Ácidos Hidroxâmicos/farmacologia , Proteínas de Ciclo Celular/metabolismo , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/química , Exodesoxirribonucleases/metabolismo , Humanos , Ácidos Hidroxâmicos/síntese química , Ácidos Hidroxâmicos/química , Estrutura Molecular , Relação Estrutura-Atividade
13.
Org Lett ; 21(9): 3281-3285, 2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-31017793

RESUMO

Dehydroalanine (ΔAla) is a highly electrophilic residue that can react efficiently with sulfur nucleophiles to furnish cysteinyl analogues. Herein, we report an efficient synthesis of N-terminal cysteinyl thioesters, suitable for S, N-acyl transfer, based on ß,γ-C,S thiol-Michael addition. Both ionic and radical-based methodologies were found to be efficient for this process.

14.
Org Lett ; 21(9): 3460-3464, 2019 05 03.
Artigo em Inglês | MEDLINE | ID: mdl-31013100

RESUMO

A novel strategy for the synthesis of δ-thiolactones from inexpensive and readily available γ-unsaturated esters has been developed. This strategy incorporates a radical acyl thiol-ene reaction as the key C-S bond forming step. Cyclization is achieved via a Steglich-type thiolactonization of 5-mercaptopentanoic acids. We report the facile and scalable synthesis of δ-thiolactones in moderate to good yield under mild reaction conditions with tolerance for a range of functional groups.

15.
Org Biomol Chem ; 17(8): 2287, 2019 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-30702731

RESUMO

Correction for 'Glycosylated naphthalimides and naphthalimide Tröger's bases as fluorescent aggregation probes for Con A' by Elena Calatrava-Pérez et al., Org. Biomol. Chem., 2019, DOI: 10.1039/c8ob02980f.

16.
Org Biomol Chem ; 17(8): 2116-2125, 2019 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-30629076

RESUMO

Herein we report the synthesis of fluorescent, glycosylated 4-amino-1,8-naphthalimide (Nap) 1, and the related 1,8-naphthalimides Tröger's bases (TBNap) 2 and 3, from 1,8-naphthalic anhydride precursors, the α-mannosides being introduced through the use of CuAAC mediated 'click' chemistry. We investigate the photophysical properties of these probes in buffered solution and demonstrate their ability to function as fluorescent probes for Concanavalin A (Con A) lectin. We show that both the Nap and TBNap structures self-assemble in solution. The formation of the resulting supramolecular structures is driven by head-to-tail π-π stacking and extended hydrogen bonding interactions of the Nap and the triazole moieties. These interactions give rise to spherical nano-structures (ca. 260 nm and 100 nm, for 1 and 3, respectively), which interact with the Con-A protein, the interaction being probed by using both luminescent and Scanning Electron Microscopy imaging as well as dynamic light scattering measurements. Finally, we show that these supramolecular assembles can be used as luminescent imaging agents, through confocal fluorescence imaging of HeLa cells of the per-acetylated version 2.

17.
Org Lett ; 20(10): 2948-2951, 2018 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-29717872

RESUMO

A new synthetic approach to thiolactones that employs an efficient acyl thiol-ene (ATE) or acyl thiol-yne (ATY) cyclization to convert unsaturated thiocarboxylic acid derivatives into thiolactones under very mild conditions is described. The high overall yields, fast kinetics, high diastereoselectivity, excellent regiocontrol, and broad substrate scope of these reaction processes render this a very useful approach for diversity-oriented synthesis and drug discovery efforts. A detailed computational rationale is provided for the observed regiocontrol.

18.
Molecules ; 23(4)2018 04 13.
Artigo em Inglês | MEDLINE | ID: mdl-29652812

RESUMO

Thiolactones have attracted considerable attention in recent years as bioactive natural products, lead compounds for drug discovery, molecular probes, and reagents for polymerisation. We have investigated radical-mediated C-C bond forming reactions as a strategy for thiolactone synthesis. Cyclisation of an α-bromo aluminium thioacetal was investigated under radical conditions. It was found that at low temperature, a radical fragmentation and rearrangement process occurs. A putative reaction mechanism involving a previously unreported aluminium templated thiol-ene step for the rearrangement process is presented. Cyclisation reactions of α-bromo thioesters and α-xanthate thioesters under radical mediated conditions furnished the desired thiolactones in moderate yields.


Assuntos
Alumínio/química , Compostos de Sulfidrila/síntese química , Ciclização , Estrutura Molecular , Compostos de Sulfidrila/química
19.
Biochem Pharmacol ; 146: 23-41, 2017 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-28893617

RESUMO

It is well established for a broad range of disease states, including cancer and Mycobacterium tuberculosis infection, that pathogenesis is bolstered by polarisation of macrophages towards an anti-inflammatory phenotype, known as M2. As these innate immune cells are relatively long-lived, their re-polarisation to pro-inflammatory, phagocytic and bactericidal "classically activated" M1 macrophages is an attractive therapeutic approach. On the other hand, there are scenarios where the resolving inflammation, wound healing and tissue remodelling properties of M2 macrophages are beneficial - for example the successful introduction of biomedical implants. Although there are numerous endogenous and exogenous factors that have an impact on the macrophage polarisation spectrum, this review will focus specifically on prominent macrophage-modulating carbohydrate motifs with a view towards highlighting structure-function relationships and therapeutic potential.


Assuntos
Carboidratos/química , Carboidratos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Anti-Inflamatórios/química , Anti-Inflamatórios/farmacologia , Humanos , Imunossupressão , Inflamação
20.
ACS Chem Biol ; 12(8): 1969-1979, 2017 08 18.
Artigo em Inglês | MEDLINE | ID: mdl-28692249

RESUMO

Tuberculosis is the leading infectious cause of mortality worldwide. The global epidemic, caused by Mycobacterium tuberculosis, has prompted renewed interest in the development of novel vaccines for disease prevention and control. The cell envelope of M. tuberculosis is decorated with an assortment of glycan structures, including glycolipids, that are involved in disease pathogenesis. Phenolic glycolipids and the structurally related para-hydroxybenzoic acid derivatives display potent immunomodulatory activities and have particular relevance for both understanding the interaction of the bacterium with the host immune system and also in the design of new vaccine and therapeutic candidates. Interest in glycobiology has grown exponentially over the past decade, with advancements paving the way for effective carbohydrate based vaccines. This review highlights recent advances in our understanding of phenolic glycans, including their biosynthesis and role as virulence factors in M. tuberculosis. Recent chemical synthesis approaches and biochemical analysis of synthetic glycans and their conjugates have led to fundamental insights into their roles in host-pathogen interactions. The applications of these synthetic glycans as potential vaccine candidates are discussed.


Assuntos
Mycobacterium tuberculosis/fisiologia , Polissacarídeos/metabolismo , Tuberculose/microbiologia , Fatores de Virulência/metabolismo , Cápsulas Bacterianas/química , Parede Celular/química , Interações Hospedeiro-Patógeno/fisiologia , Humanos , Fenóis/química , Fenóis/metabolismo , Polissacarídeos/química , Fatores de Virulência/química
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