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1.
Nat Commun ; 11(1): 4692, 2020 09 17.
Artigo em Inglês | MEDLINE | ID: mdl-32943624

RESUMO

Hemicelluloses, a family of heterogeneous polysaccharides with complex molecular structures, constitute a fundamental component of lignocellulosic biomass. However, the contribution of each hemicellulose type to the mechanical properties of secondary plant cell walls remains elusive. Here we homogeneously incorporate different combinations of extracted and purified hemicelluloses (xylans and glucomannans) from softwood and hardwood species into self-assembled networks during cellulose biosynthesis in a bacterial model, without altering the morphology and the crystallinity of the cellulose bundles. These composite hydrogels can be therefore envisioned as models of secondary plant cell walls prior to lignification. The incorporated hemicelluloses exhibit both a rigid phase having close interactions with cellulose, together with a flexible phase contributing to the multiscale architecture of the bacterial cellulose hydrogels. The wood hemicelluloses exhibit distinct biomechanical contributions, with glucomannans increasing the elastic modulus in compression, and xylans contributing to a dramatic increase of the elongation at break under tension. These diverging effects cannot be explained solely from the nature of their direct interactions with cellulose, but can be related to the distinct molecular structure of wood xylans and mannans, the multiphase architecture of the hydrogels and the aggregative effects amongst hemicellulose-coated fibrils. Our study contributes to understanding the specific roles of wood xylans and glucomannans in the biomechanical integrity of secondary cell walls in tension and compression and has significance for the development of lignocellulosic materials with controlled assembly and tailored mechanical properties.


Assuntos
Parede Celular/química , Celulose/química , Extratos Vegetais/química , Plantas/química , Polissacarídeos/química , Madeira/química , Configuração de Carboidratos , Sequência de Carboidratos , Catárticos/química , Citoesqueleto/química , Hidrogéis/química , Mananas , Xilanos/química
2.
Nat Commun ; 11(1): 2664, 2020 05 29.
Artigo em Inglês | MEDLINE | ID: mdl-32471982

RESUMO

Controlling the chemical glycosylation reaction remains the major challenge in the synthesis of oligosaccharides. Though 1,2-trans glycosidic linkages can be installed using neighboring group participation, the construction of 1,2-cis linkages is difficult and has no general solution. Long-range participation (LRP) by distal acyl groups may steer the stereoselectivity, but contradictory results have been reported on the role and strength of this stereoelectronic effect. It has been exceedingly difficult to study the bridging dioxolenium ion intermediates because of their high reactivity and fleeting nature. Here we report an integrated approach, using infrared ion spectroscopy, DFT computations, and a systematic series of glycosylation reactions to probe these ions in detail. Our study reveals how distal acyl groups can play a decisive role in shaping the stereochemical outcome of a glycosylation reaction, and opens new avenues to exploit these species in the assembly of oligosaccharides and glycoconjugates to fuel biological research.


Assuntos
Química Computacional/métodos , Oligossacarídeos/síntese química , Compostos de Selênio/química , Configuração de Carboidratos , Galactose/química , Glucose/química , Glicosilação , Manose/química , Espectrofotometria Infravermelho
3.
Nucleic Acids Res ; 48(9): 4643-4657, 2020 05 21.
Artigo em Inglês | MEDLINE | ID: mdl-32282904

RESUMO

We report on the synthesis of siRNAs containing both 2'-5'- and 3'-5'-internucleotide linkages and their effects on siRNA structure, function, and interaction with RNAi proteins. Screening of these siRNAs against their corresponding mRNA targets showed that 2'-5' linkages were well tolerated in the sense strand, but only at a few positions in the antisense strand. Extensive modification of the antisense strand minimally affected 5'-phosphorylation of the siRNA by kinases, however, it negatively affected siRNA loading into human AGO2. Modelling and molecular dynamics simulations were fully consistent with these findings. Furthermore, our studies indicated that the presence of a single 5'p-rN1-(2'-5')-N2 unit in the antisense strand does not alter the 'clover leaf' bend and sugar puckers that are critical for anchoring the 5'-phosphate to Ago 2 MID domain. Importantly, 2'-5'-linkages had the added benefit of abrogating immune-stimulatory activity of siRNAs. Together, these results demonstrate that 2'-5'/3'-5'-modified siRNAs, when properly designed, can offer an efficient new class of siRNAs with diminished immune-stimulatory responses.


Assuntos
Interferência de RNA , RNA Interferente Pequeno/química , Proteínas Argonauta/metabolismo , Configuração de Carboidratos , Células HeLa , Humanos , Luciferases de Vaga-Lume/genética , Simulação de Dinâmica Molecular , Conformação de Ácido Nucleico , RNA Interferente Pequeno/síntese química , RNA Interferente Pequeno/imunologia , Proteína Supressora de Tumor p53/genética
4.
Org Biomol Chem ; 18(7): 1462-1475, 2020 02 19.
Artigo em Inglês | MEDLINE | ID: mdl-32025679

RESUMO

Selective glycosylation of the C-6 fluorinated galactofuranosyl acceptor 2 was studied with four galactofuranosyl donors. It was highlighted that this electron-withdrawing atom strongly impacted the behavior of the acceptor, thus leading to unprecedented glycosylation pathways. Competition between expected glycosylation of 2, ring expansion of this acceptor and furanosylation, and intermolecular aglycon transfer was observed. Further investigation of the fluorinated synthetic compounds showed that the presence of fluorine atom contributed to increase the inhibition of the growth of Leishmania tarentolae, a non-pathogenic strain of Leishmania.


Assuntos
Antiprotozoários/farmacologia , Furanos/farmacologia , Galactosídeos/farmacologia , Leishmania/efeitos dos fármacos , Antiprotozoários/síntese química , Antiprotozoários/química , Configuração de Carboidratos , Furanos/síntese química , Furanos/química , Galactosídeos/síntese química , Galactosídeos/química , Glicosilação , Testes de Sensibilidade Parasitária , Estereoisomerismo
5.
Biochemistry (Mosc) ; 85(2): 241-247, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32093600

RESUMO

Capsular polysaccharide (CPS), isolated from Acinetobacter baumannii LUH5549 carrying the KL32 capsule biosynthesis gene cluster, was studied by sugar analysis, Smith degradation, and one- and two-dimensional 1H and 13C NMR spectroscopy. The K32 CPS was found to be composed of branched pentasaccharide repeats (K units) containing two residues of ß-D-GalpNAc and one residue of ß-D-GlcpA (ß-D-glucuronic acid) in the main chain and one residue each of ß-D-Glcp and α-D-GlcpNAc in the disaccharide side chain. Consistent with the established CPS structure, the KL32 gene cluster includes genes for a UDP-glucose 6-dehydrogenase (Ugd3) responsible for D-GlcA synthesis and four glycosyltransferases that were assigned to specific linkages. Genes encoding an acetyltransferase and an unknown protein product were not involved in CPS biosynthesis. Whilst the KL32 gene cluster has previously been found in the global clone 2 (GC2) lineage, LUH5549 belongs to the sequence type ST354, thus demonstrating horizontal gene transfer between these lineages.


Assuntos
Acinetobacter baumannii/genética , Família Multigênica/genética , Polissacarídeos Bacterianos/química , Polissacarídeos Bacterianos/metabolismo , Cápsulas Bacterianas/química , Cápsulas Bacterianas/genética , Cápsulas Bacterianas/metabolismo , Configuração de Carboidratos , Biologia Computacional , Polissacarídeos Bacterianos/isolamento & purificação
6.
Biochem Biophys Res Commun ; 523(3): 573-579, 2020 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-31932036

RESUMO

The applications of dextran depend not only on the molecular weight but also on the types and number of branches. In this study, dextran generated from Leuconostoc mesenteroides (L.M.CICC-20724) was characterized by fourier-transform infrared spectrum and nuclear magnetic resonance spectroscopy. Our analyses showed that dextran was a polysaccharide composed of d-glucose units with predominantly α(1 â†’ 6) linkages in the main chain and few α(1 â†’ 3) linkages in the branch. Periodate oxidation, a classic chemical method, was usually combined with Smith degradation and gas chromatography to analyze glycosidic linkages in polysaccharide quantitatively. In this study, we calculated the exact straight-chain/branched-chain ratio in the dextran using periodate oxidation only. The ratios obtained by periodate oxidation only were compared to the ratios obtained by nuclear magnetic resonance. The results showed that the ratios of the two groups were nearly equal, and the average relative error between the two groups was 0.83%. This method was evaluated and found to be accurate and stable. This technique provided a convenient and straightforward chemical method for the quantitative analysis of the straight-chains and branched-chains in polysaccharides which had a similar structure. The ratios during the enzymatic synthesis process of dextran were analyzed by this method and were found to be stable with a high level of approximately 95% on average.


Assuntos
Dextranos/química , Leuconostoc mesenteroides/química , Biocatálise , Configuração de Carboidratos , Dextranos/metabolismo , Leuconostoc mesenteroides/metabolismo , Oxirredução , Ácido Periódico/química , Espectroscopia de Prótons por Ressonância Magnética , Espectroscopia de Infravermelho com Transformada de Fourier
7.
Carbohydr Polym ; 232: 115780, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31952589

RESUMO

Paenibacillus polymyxa 92, isolated from wheat roots, produced large amounts (38.4 g L-1) of exopolysaccharide (EPS) in a liquid nutrient medium containing 10 % (w/v) sucrose. The EPS was precipitated from the culture broth with cold acetone and was purified by gel filtration and anion-exchange chromatography. The molecular mass of the EPS was 2.29-1.10 × 105 Da. Diffuse reflectance infrared Fourier transform and nuclear magnetic resonance spectra showed that the EPS was a linear ß-(2→6)-linked fructan (levan). Aqueous EPS solutions showed pseudoplastic behavior when shear stress was applied at different temperatures. By using the Ostwald-de Waele model, the rheological characteristics of the EPS solution were ascertained. The sorption capacity of the EPS for Zn(II), Cd(II), Pb(II), and Cu(II) was investigated. Sorption was maximal (q = 481 mg g-1) for Cu(II) ions. In model experiments, treatment of wheat seeds with EPS solution significantly increased the length of seedling roots and shoots.


Assuntos
Biotecnologia , Paenibacillus polymyxa/química , Polissacarídeos Bacterianos/isolamento & purificação , Adsorção , Configuração de Carboidratos , Metais Pesados/química , Polissacarídeos Bacterianos/química , Reologia , Triticum/microbiologia
8.
Carbohydr Polym ; 232: 115804, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31952602

RESUMO

In this present study, the structure and immunomodulatory activity of a novel polysaccharide (WSRP-1b) from Kushui rose (Rosa setate x Rosa rugosa) waste were investigated. Structure characterization demonstrated that WSRP-1b had a weight-average molecular weight of 1.11 × 104 Da and consisted of glucose (42.6 %), mannose (21.4 %), arabinose (9.9 %), xylose (2.2 %), and galactose (23.9 %). Its backbone was composed of 1, 4-linked α-Glcp, 1, 4-linked ß-Glcp, and 1, 4-linked ß-Manp, with branches of 1, 4-linked α-Glcp and 1, 4-linked ß-Manp substituted at C-6 by 1, 6-linked ß-Galp. The branches mainly contained 1, 5-linked Araf, terminal arabinose and terminal glucose. Bioactivity assays showed that WSRP-1b had immunomodulatory activity by enhancing phagocytosis of macrophages, increasing production of ROS, NO, cytokines (IL-6, TNF-α), and activating NF-κB signaling pathway. These results suggested that it could be developed as a potential and safe immunomodulatory agent in fields of pharmacological or functional foods.


Assuntos
Fatores Imunológicos/farmacologia , Macrófagos/efeitos dos fármacos , Polissacarídeos/farmacologia , Rosa/química , Configuração de Carboidratos , Citocinas/biossíntese , Humanos , Fatores Imunológicos/química , Macrófagos/metabolismo , NF-kappa B/imunologia , Óxido Nítrico/biossíntese , Polissacarídeos/química , Espécies Reativas de Oxigênio/metabolismo
9.
Carbohydr Polym ; 232: 115805, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31952603

RESUMO

Cancer is increasingly becoming a serious threat to human life and health. Therefore, the development of safe and effective therapeutic agents against the disease is of crucial significance. Cyclodextrins (CDs) are cyclic oligosaccharides obtained by the enzymatic hydrolysis of starch, and constitute a class of cyclic oligosaccharides with external hydrophilic and internal hydrophobic properties and have been used widely in cancer therapy. Cyclodextrin has been extensively applied in nanomedicine therapy, gene therapy, cell therapy, immunotherapy, and chemotherapy. In this review, we summarize chemotherapy drugs for cancer treatment, classify various CD-based drug delivery systems, and describe their chemotherapy release and cancer treatment performance. In addition, current challenges and new opportunities for CD-based chemotherapeutic agents delivery systems are discussed.


Assuntos
Antineoplásicos/uso terapêutico , Ciclodextrinas/química , Sistemas de Liberação de Medicamentos , Neoplasias/tratamento farmacológico , Animais , Antineoplásicos/química , Configuração de Carboidratos , Ciclodextrinas/síntese química , Portadores de Fármacos/química , Humanos , Interações Hidrofóbicas e Hidrofílicas
10.
Carbohydr Polym ; 232: 115822, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31952617

RESUMO

Chondroitin sulfate is a linear glycosaminoglycan widely distributed as an important extracellular matrix component of mammalian cells. It participates in numerous pathological processes, however, illustration of its diverse biological roles is hampered by the unavailability of structurally defined chondroitin polymers and their derivatives. Herein, we report a novel homogeneous chondroitin polymers synthetic strategy which combines stepwise oligosaccharides synthesis with one-pot homogeneous chondroitin chain polymerization. Exogenous trisaccharide was proved to be the necessary acceptor for PmCS-catalyzed homogeneous chondroitin polymers synthetic reactions. The strategy exhibited a well-controlled relationship between the final sugar chain length and the molar ratios of reaction substrates that could synthesize homogenous chondroitin polymers with unprecedented narrow molecular weight distribution. More importantly, the strategy was further expanded to synthesis of unnatural zwitterionic and N-sulfonated chondroitin polymers by incorporation of sugar nucleotide derivatives into the synthetic approach.


Assuntos
Condroitina/biossíntese , N-Acetilgalactosaminiltransferases/metabolismo , Polímeros/metabolismo , Configuração de Carboidratos , Condroitina/análogos & derivados , Condroitina/química , Pasteurella multocida/enzimologia , Polimerização , Polímeros/química
11.
J Chromatogr A ; 1612: 460658, 2020 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-31703890

RESUMO

Fucoidans represent an intriguing class of fucose-containing sulfated polysaccharides. The biological activities of these polysaccharides are related to their compositional and structural parameters, whereby their degree of sulfation, as well as molecular weight (MW) distribution and chain conformation play important roles. Modern NMR and mass spectrometry techniques allow elucidating details of the glycan structure, but not the structure of the whole molecules in their native state. Accordingly, the knowledge about the latter of the fucoidans is currently still limited. Contrary to traditional MW determination by SEC with column calibration, SEC with triple detection provides not only the absolute Mw, but can also give information on additional molecule characteristics. In the present study, we used this method to compare six fucoidans extracted from Fucus vesiculosus (FV), F. serratus (FS), F. evanescens (FE), Dictyosiphon foeniculaceus (DF), Laminaria digitata (LD), and Saccharina latissima (SL) concerning their molar mass (Mw, Mn, Mp, dispersity) and size (rms radius, Rh) characteristics and distribution as well as their chain conformation in solution. The tested fucoidans displayed considerable structural diversity including large differences in their MW profiles and showed to be heterogeneously composed. Fuc-FV and Fuc-SL showed the broadest MW distributions, those from Fuc-FE and Fuc-DF the narrowest ones. Most of the fucoidan fractions (except for Fuc-DF) turned out to exist as expanded flexible chains in PBS solution. The conformation data suggest branched structures with partly long side chains. The knowledge obtained by this study is useful for further fractionation and structural characterization as well as the interpretation of the bioactivity differences between the various fucoidans.


Assuntos
Feófitas/química , Polissacarídeos/química , Configuração de Carboidratos , Cromatografia em Gel , Fucus/química , Peso Molecular
12.
Biochem Mol Biol Educ ; 48(1): 8-20, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31532889

RESUMO

Carbohydrates, or in strictly chemical terms, polyhydroxy-aldehydes or ketones represent enormous structural diversity in terms of the arrangement of atoms in space, resulting in hundreds of stereoisomers. Although the chemical properties of most stereoisomers may not be very different, their metabolic fate and utilization in biological systems is significantly different and known to influence the overall carbohydrate metabolism. This dictates the importance of understanding the structures of various stereochemical structures for a biochemist. At graduate level teaching, it is really a challenging task to correlate, connect, and recall all the structures. Conventional teaching methods and standard textbook illustrations seldom enable the learners and instructors to sustain the information for a prolonged period. We, in this article, present a unique approach and introduce sigma notation rules for the correlation of stereochemistry of carbohydrates in order to enhance the understanding of stereochemical structures. © 2019 International Union of Biochemistry and Molecular Biology, 48(1):8-20, 2020.


Assuntos
Educação de Pós-Graduação/métodos , Hexoses/química , Biologia Molecular/educação , Ensino/educação , Configuração de Carboidratos , Metabolismo dos Carboidratos , Hexoses/metabolismo , Humanos , Estereoisomerismo , Estudantes
13.
Biochim Biophys Acta Proteins Proteom ; 1868(2): 140301, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31678194

RESUMO

Heparin is a naturally occurring glycosaminoglycan isolated from animal tissues and is medically used as an anticoagulant drug. Adulteration attempts of isolated heparin with chondroitin sulfate in the past resulted in great safety concerns. Also, increasing demands on batch-to-batch homogeneity for better evaluation and control of its pharmacodynamic and pharmacokinetic properties kindled the development of synthetic routes for the production of heparin and its derivatives. The discovery of enzymes involved in glycosaminoglycan biosynthesis and their application in chemoenzymatic synthesis makes it feasible to generate low molecular weight heparins (LMWHs) and ultra-low molecular weight heparins (ULMWHs). Understanding the scope and limitations of these enzymes currently used in the production of synthetic heparins will help to achieve more defined heparins with controlled medicative properties. Here, we summarized the recent advances in the chemoenzymatic synthesis of LMW/ULMW heparins.


Assuntos
Heparina de Baixo Peso Molecular/biossíntese , Animais , Configuração de Carboidratos , Dissacarídeos/química , Dissacarídeos/metabolismo , Glucosiltransferases/metabolismo , Heparina de Baixo Peso Molecular/química , Oligossacarídeos/metabolismo , Racemases e Epimerases/metabolismo , Sulfotransferases/metabolismo
14.
Chem Commun (Camb) ; 56(6): 908-911, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31850411

RESUMO

Poly(glycerol methacrylate) chitosan nanospheres were facilely one-pot synthesized. For the first time, poly(glycerol methacrylate) with a highly flexible density of hydrophilic molecules grafted on the surface of chitosan was applied to highly specific enrichment of glycopeptides.


Assuntos
Quitosana/química , Glicopeptídeos/análise , Metacrilatos/química , Configuração de Carboidratos , Quitosana/síntese química , Interações Hidrofóbicas e Hidrofílicas , Metacrilatos/síntese química , Nanosferas/química , Tamanho da Partícula , Propriedades de Superfície
15.
Biomater Sci ; 8(2): 577-585, 2020 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-31872195

RESUMO

Hypersialylation is the aberrant expression of sialic acid in cell surface glycans and is pervasive in cancer cells. Recent studies have shown that hypersialylation provides a microenvironment conducive to cancer progression, mediated by the interaction between sialic acid and sialic acid-binding receptors. Therefore, a technique to block the interaction between the overexpressed sialic acid on cancer cell surfaces and its receptors is a promising approach to develop new cancer therapies. We focused on hydrogels as an artificial barrier to block this interaction and present here the development of a novel technique for selectively covalently binding a thin hydrogel barrier on sialic acid residues on cancer cell surfaces. This technique effectively inhibited cancer cell adhesion, motility and growth, caused cancer cell death in vitro, and completely suppressed tumor growth in vivo, thereby clearly demonstrating a potent antitumor effect.


Assuntos
Antineoplásicos/farmacologia , Membrana Celular/química , Hidrogéis/farmacologia , Ácido N-Acetilneuramínico/farmacologia , Antineoplásicos/química , Configuração de Carboidratos , Adesão Celular/efeitos dos fármacos , Morte Celular/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Hidrogéis/química , Células MCF-7 , Ácido N-Acetilneuramínico/química
16.
Nat Struct Mol Biol ; 26(12): 1151-1157, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31792450

RESUMO

The Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe and often lethal respiratory illness in humans, and no vaccines or specific treatments are available. Infections are initiated via binding of the MERS-CoV spike (S) glycoprotein to sialosides and dipeptidyl-peptidase 4 (the attachment and entry receptors, respectively). To understand MERS-CoV engagement of sialylated receptors, we determined the cryo-EM structures of S in complex with 5-N-acetyl neuraminic acid, 5-N-glycolyl neuraminic acid, sialyl-LewisX, α2,3-sialyl-N-acetyl-lactosamine and α2,6-sialyl-N-acetyl-lactosamine at 2.7-3.0 Å resolution. We show that recognition occurs via a conserved groove that is essential for MERS-CoV S-mediated attachment to sialosides and entry into human airway epithelial cells. Our data illuminate MERS-CoV S sialoside specificity and suggest that selectivity for α2,3-linked over α2,6-linked receptors results from enhanced interactions with the former class of oligosaccharides. This study provides a structural framework explaining MERS-CoV attachment to sialoside receptors and identifies a site of potential vulnerability to inhibitors of viral entry.


Assuntos
Coronavírus da Síndrome Respiratória do Oriente Médio/química , Ácidos Siálicos/metabolismo , Glicoproteína da Espícula de Coronavírus/química , Sítios de Ligação , Configuração de Carboidratos , Microscopia Crioeletrônica , Dipeptidil Peptidase 4/química , Dipeptidil Peptidase 4/metabolismo , Dipeptidil Peptidase 4/ultraestrutura , Hemaglutinação por Vírus , Humanos , Modelos Moleculares , Ligação Proteica , Conformação Proteica , Domínios Proteicos , Mapeamento de Interação de Proteínas , Ácidos Siálicos/química , Glicoproteína da Espícula de Coronavírus/metabolismo , Glicoproteína da Espícula de Coronavírus/ultraestrutura , Relação Estrutura-Atividade
17.
Acta Neurobiol Exp (Wars) ; 79(4): 338-351, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31885391

RESUMO

Over the last twenty years chondroitin sulfate (CS) has become a focus of interest of neuroscience due to its indubitable role in shaping axonal growth, synaptic plasticity and glial scar forming. Various patterns of sulfation give rise to various CS molecules with different properties that are capable of interactions with a plethora of molecules, including growth factors, receptors and guidance molecules. The involvement of CS chains has been implicated in visual critical period regulation, memory formation, spinal cord regeneration. As part of proteoglycan molecules, they are widely expressed in the central nervous system, however, little is known about the enzymatic machinery responsible for CS synthesis and degradation. In this review we attempt to extract and collect the available information concerning the expression and function of enzymes of CS metabolism in the brain.


Assuntos
Encéfalo/metabolismo , Sulfatos de Condroitina/metabolismo , Animais , Encéfalo/enzimologia , Configuração de Carboidratos , Retículo Endoplasmático/metabolismo , Matriz Extracelular/metabolismo , Glicosiltransferases/metabolismo , Humanos , Redes e Vias Metabólicas , Proteínas do Tecido Nervoso/metabolismo , Plasticidade Neuronal , Proteoglicanas/metabolismo , Xilose/metabolismo
18.
Biomolecules ; 9(12)2019 12 17.
Artigo em Inglês | MEDLINE | ID: mdl-31861084

RESUMO

The chemical and physical properties of extracellular rhamnolipid synthesized by a nonfluorescent Pseudomonas species soil isolate, identified as DYNA270, is described, along with characteristics of rhamnolipid production under varying growth conditions and substrates. The biosurfactant is determined to be an anionic, extracellular glycolipid consisting of two major components, the rhamnopyranoside ß-1-3-hydroxydecanoyl-3-hydroxydecanoic acid (GU-6) and rhamnopyranosyl ß→ß2-rhamnopyranoside-ß1-3-hydroxydecanoyl-3-hydroxydecanoic acid (GL-2), of molecular weight 504 and 649 daltons, respectively. These glycolipids are produced in a stoichiometric ratio of 1:3, respectively. The purified rhamnolipid mixture exhibits a critical micelle concentration of 20 mg/L, minimum surface (air/water interface) tension of 22 mN/m, and minimum interfacial tension values of 0.005 mN/m (against hexane). The pH optimum, critical micelle concentration, and effective alkane carbon number were established for Pseudomonas species DYNA270 and compared to those of rhamnolipid produced by Pseudomonas aeruginosa PG201. Significant differences are documented in the physical properties of extracellular rhamnolipids derived from these two microorganisms. The surface properties of this rhamnolipid are unique in that ultra-low surface and interfacial tension values are present in both purified rhamnolipid and culture broth containing the rhamnolipid complex (GU6 and GL2). We are not aware of prior studies reporting surface activity values this low for rhamnolipids. An exception is noted for an extracellular trehalose glycolipid produced by Rhodococcus species H13-A, which measured 0.00005 mN/m in the presence of the co-agent pentanol (Singer et al. 1990). Similar CMC values of 20 mg/L have been reported for rhamnolipids, a few being recorded as 5-10 mg/L for Pseudomonas species DSM2874 (Lang et al. 1984).


Assuntos
Glicolipídeos/química , Pseudomonas/química , Tensoativos/química , Configuração de Carboidratos , Glicolipídeos/isolamento & purificação , Pseudomonas/citologia , Propriedades de Superfície , Tensoativos/isolamento & purificação
19.
J Agric Food Chem ; 67(45): 12520-12527, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31634426

RESUMO

Water-soluble ß-d-glucan was obtained from wild Cordyceps sinensis by alkali solution and ethanol precipitation. The structure characteristics were determined using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD), methylation combined with gas chromatography-mass spectrometry, and one-/two-dimensional nuclear magnetic resonance spectroscopy. Results showed that ß-d-glucan had a structure of every seven (1→3)-ß-d-Glcp backbone residues with two (1→6)-ß-d-Glcp branches. Additionally, conformation properties in different solvents were investigated by static light scattering, dynamic light scattering, and HPSEC with multiple detectors. It was found that ß-d-glucan in 0.5 M NaOH had a narrow unimodal distribution of hydrodynamic radius displaying a spherical coil conformation, whereas it formed severe aggregation in dimethyl sulfoxide. In 0.1 M NaNO3, ß-d-glucan mainly existed as a rod-like conformation corresponding to a helical structure together with small aggregates (10%). This work added more information to the understanding of C. sinensis polysaccharides.


Assuntos
Cordyceps/química , Extratos Vegetais/química , beta-Glucanas/química , Configuração de Carboidratos , Cromatografia Gasosa-Espectrometria de Massas , Espectroscopia de Ressonância Magnética , Extratos Vegetais/isolamento & purificação , Água/química , beta-Glucanas/isolamento & purificação
20.
Molecules ; 24(20)2019 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-31635397

RESUMO

A practical synthesis of the very rare sugar d-idose and the stable building blocks for d-idose, d-iduronic, and d-idonic acids from ido-heptonic acid requires only isopropylidene protection, Shing silica gel-supported periodate cleavage of the C6-C7 bond of the heptonic acid, and selective reduction of C1 and/or C6. d-Idose is the most unstable of all the aldohexoses and a stable precursor which be stored and then converted under very mild conditions into d-idose is easily prepared.


Assuntos
Hexoses/síntese química , Ácido Idurônico/síntese química , Açúcares Ácidos/síntese química , Configuração de Carboidratos , Glucose/química , Heptoses/química , Hexoses/química , Ácido Idurônico/química , Estrutura Molecular , Açúcares Ácidos/química
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