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Lignin characterization by acetylation procedures

Cateto, C.A.; Naceur, M.N.; Rodrigues, A.E.; Barreiro, M.F.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
357.7696%
The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis.

FTIR and NMR studies on lignin acetylation

Cateto, C.A.; Barreiro, M.F.; Rodrigues, A.E.; Brochier-Salon, M.C.; Thielemans, W.; Belgacem, M.N.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
355.10332%
In this work, a comparative study of an acetylation procedure, using four different lignin samples was performed. The chosen lignin samples, Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27-11P (Borregaard LignoTech) and Sarkanda (Granit SA), represent both the guaiacyl and guaiacyl-syringyl type, and were obtained from different pulp processes (kraft and organosolv). Lignin was acetylated using an acetic anhydride-pyridine mixture and the final sample was recovered by precipitation. Final samples, with different reaction times (1 and 2 hours), were characterized by FTIR and 13C NMR analysis, and the obtained spectra were compared with the corresponding ones for non-acetylated samples. Within the used experimental conditions and samples, an incomplete acetylation yield appeared to be common. Total hydroxyl content, determined independently by titration and based on the 13C NMR results, was found to be in close agreement.

Lignin characterization by acetylation procedures

Cateto, C.A.; Barreiro, M.F.; Rodrigues, A.E.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
357.7696%
The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis.

Lignin characterization by acetylation procedures

Cateto, C.A.; Belgacem, M.N.; Rodrigues, A.E.; Barreiro, M.F.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
357.7696%
The amount of the total hydroxyl content of lignin is of great importance in the formulation of a lignin based polyurethane system since it allows the quantity of the polyisocyanate counterpart within the right stoichiometry. In this work, the reliability of an acetylation procedure, regarding the determination of total hydroxyl content of a commercial kraft lignin, was studied. Lignin was acetylated using acetic anhydride reagent in solution in pyridine and the recovered acetylated samples were analysed by FTIR using KBr pellets. The experimental variables investigated were: reaction time, reaction temperature, composition of the acetylation reagent, presence of a catalyst and drying process of the acetylated samples. Within this work, the obtained results indicate that acetylation was incomplete for all the studied conditions, resulting in an unreliable total hydroxyl determination and shows the limitation of this technique. This observation is in accordance with recent published works (see, for example, Gosselink et al., 2004) and could justify the lack of agreement among some published experimental results concerning interlaboratory analysis.

FTIR and NMR studies on lignin acetylation

Cateto, C.A.; Barreiro, M.F.; Rodrigues, A.E.; Brochier-Salon, M.C.; Thielemans, W.; Belgacem, M.N.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
355.10332%
In this work, a comparative study of an acetylation procedure, using four different lignin samples was performed. The chosen lignin samples, Indulin AT (Meadwestvaco), Alcell (Repap), Curan 27-11P (Borregaard LignoTech) and Sarkanda (Granit SA), represent both the guaiacyl and guaiacyl-syringyl type, and were obtained from different pulp processes (kraft and organosolv). Lignin was acetylated using an acetic anhydride-pyridine mixture and the final sample was recovered by precipitation. Final samples, with different reaction times (1 and 2 hours), were characterized by FTIR and 13C NMR analysis, and the obtained spectra were compared with the corresponding ones for non-acetylated samples. Within the used experimental conditions and samples, an incomplete acetylation yield appeared to be common. Total hydroxyl content, determined independently by titration and based on the 13C NMR results, was found to be in close agreement.

Estudos físico-químicos de N-acetilação de quitosanas em meio homogêneo; Physicochemical studies of N-acetylation chitosan in homogeneous

Veiga, Sara Cristina Pereira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 12/08/2011 PT
Relevância na Pesquisa
364.58832%
As principais propriedades físico-químicas da quitosana dependem da massa molar média, grau médio de acetilação (GA) e do parâmetro de acetilação (PA) que expressa o padrão de distribuição das unidades 2-acetamido-2-desoxi-D-glucopiranose (GlcNAc) e 2-amino-2-desoxi-D-glucopiranose ( GlcN) ao longo de suas cadeias. A distribuição alternada, randômica ou em blocos das unidades GlcN e GlcNAc ao longo das cadeias poliméricas está diretamente relacionada com as condições de preparação da quitosana, sendo que as reações executadas em condições homogêneas geram quitosanas em cujas cadeias há o predomínio da distribuição randômica, enquanto que nas quitosanas produzidas em condições heterogêneas a distribuição em blocos predomina. Neste trabalho β-quitina extraída de gládios de lulas (Loligo sp) foi submetida a 3 etapas consecutivas do processo de desacetilação assistida por irradiação de ultrassom de alta intensidade (processo DAIUS), resultando em quitosana extensivamente desacetilada (GA ≈ 2%) e de elevada massa molar média viscosimétrica (Mv ≈ 354000 g/mol) comparada a quitosanas obtidas por outros métodos. Essa amostra...

Thermal behavior of cellulose acetate produced from homogeneous acetylation of bacterial cellulose

Barud, Hernane S.; de Araujo Junior, Adalberto M.; Santos, Daniele B.; de Assuncao, Rosana M. N.; Meireles, Carla S.; Cerqueira, Daniel A.; Rodrigues Filho, Guimes; Ribeiro, Clovis A.; Messaddeq, Younes; Ribeiro, Sidney J. L.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 61-69
ENG
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362.2907%
Cellulose acetate (CA) is one of the most important cellulose derivatives and its main applications are its use in membranes, films, fibers, plastics and filters. CAs are produced from cellulose sources such as: cotton, sugar cane bagasse, wood and others. One promissory source of cellulose is bacterial cellulose (BC). In this work, CA was produced from the homogeneous acetylation reaction of bacterial cellulose. Degree of substitution (DS) values can be controlled by the acetylation time. The characterization of CA samples showed the formation of a heterogeneous structure for CA samples submitted to a short acetylation time. A more homogeneous structure was produced for samples prepared with a long acetylation time. This fact changes the thermal behavior of the CA samples. Thermal characterization revealed that samples submitted to longer acetylation times display higher crystallinity and thermal stability than samples submitted to a short acetylation time. The observation of these characteristics is important for the production of cellulose acetate from this alternative source. (C) 2008 Elsevier B.V. All rights reserved.

Molecular Sieves Mediated Green Per-O-Acetylation of Carbohydrate Templates and Lipase Catalyzed Regioselective Alcoholysis of 2,3,5-Tri-O-Acetyl-D-Ribonolactone

Cardozo,Herbert M.; Ribeiro,Thaís F.; Sá,Marcus M.; Sebrão,Damianni; Nascimento,Maria G.; Silveira,Gustavo P.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2015 EN
Relevância na Pesquisa
355.10332%
The per-O-acetylation of D-ribono-1,4-lactone and representative carbohydrates through the combination of acetic anhydride and molecular sieves under solvent-free conditions is demonstrated. The use of 13X/KCl molecular sieves as the heterogeneous catalyst was found to be more efficient than the excess of pyridine normally employed in the conventional method, giving high yields of the expected peracetylated product after 3 h at 25 ºC or 1 h at 50 ºC. The transformation can be carried out in gram scale and in an open flask. Additionally, the catalyst is readily separated from the reaction medium and can be reutilized without significant loss of activity. This green procedure for acetylation was extended to D-ribonolactone derivatives and natural carbohydrates. To demonstrate the synthetic utility of the method, 2,3,5-tri-O-acetyl-D-ribonolactone was selected as the substrate for the regioselective alcoholysis of acetyl group catalyzed by Candida antarctica lipase B in EtOH to selectively produce 2,3-di-O-acetyl-D-ribonolactone in gram scale.

Identification of acetylation-dependent regulatory mechanisms that govern the oncogenic functions of Skp2

Wang, Zhiwei; Inuzuka, Hiroyuki; Zhong, Jiateng; Liu, Pengda; Sarkar, Fazlul H.; Sun, Yi; Wei, Wenyi
Fonte: Impact Journals LLC Publicador: Impact Journals LLC
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
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The Skp2 (S-phase kinase associated protein 2) oncoprotein is often highly expressed in various types of human cancers. However, the mechanistic basis of its oncogenic function, as well as the upstream regulatory pathway(s) that control Skp2 activities remains not fully understood. Recently, we reported that p300 acetylates Skp2 at two conserved lysine residues K68 and K71 within its NLS (Nuclear localization signal). This modification leads to increased Skp2 stability and cytoplasmic translocation, thus contributing to elevated Skp2 oncogenic potential. Moreover, we found that the SIRT3 tumor suppressor serves as the physiological deacetylase that antagonizes p300-mediated Skp2 acetylation. Furthermore, we showed that Skp2 governs E-cadherin ubiquitination and degradation in the cytosol. Consistent with this, we observed an inverse correlation between Skp2 and E-cadherin expression in clinical breast tumor samples. Therefore, our work elucidates a novel acetylation-dependent regulatory mechanism for Skp2 oncogenic functions.

Influência de diferentes níveis de acetilação nas propriedades físico-mecânicas de aglomerados e painéis madeira-cimento; Influence of different degrees of acetylation in the physical and mechanical properties of particleboards and wood-cement composites

Fonte: UFLA - Universidade Federal de Lavras Publicador: UFLA - Universidade Federal de Lavras
Tipo: Artigo de Revista Científica Formato: text/html
PT
Relevância na Pesquisa
359.69527%
Chemical modified wood particles used to particleboards manufacture may, at the same time, improve the dimensional stability and damage the internal bond. The aim of this research was find the optimal point of acetylation for particleboards. Pinus taeda particles with different degrees of acetylation, 8, 15 and 20% of weight percentage gain (WGP), were used in the production of particleboards with urea-formaldehyde resin and wood-cement composites produced by mechanical and vibratory compaction. It was evaluated the water absorption, thickness swelling and internal bind of the particleboards according to the European standards EN 317 and EN 319. Particleboards produced with 15 WPG showed the lowest water absorption and thickness swelling values. However, the use of chemically modified wood had a negative influence in the internal bind of the boards. This phenomenon can be explain due to the similar behavior between resin and water, that way, the high degree acetylation stops the adhesive and adherent bind. In the case of wood-cement composites, the internal bind improves as the acetylation degrees get higher. Nevertheless the inhibition of acetylated wood particles to the cement hydration got higher when the WPG was higher than 8%.; O uso de partículas de madeira...

Rescue of NatB acetylation failure in Schizosaccharomyces pombe

Grunwald, Rebecca
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 740530 bytes; application/pdf
EN
Relevância na Pesquisa
357.7696%
N alpha-terminal acetylation (NAA) is a cotranslational protein modification whose role in the cell is not well understood. NAA is performed by N-terminal acetyltransferases (NATs) which are conserved in all eukaryotes. In fission yeast, Schizosaccharomyces pombe, NAA is catalyzed by NatA, NatB and NatC. Cdc8, arp2 and prp18 are putative substrates of the NatB complex which has specificity for proteins with N-terminal Met-Asp- or Met-Glu- sequence motifs. Disrupting the arm1 gene, an auxiliary subunit required for NatB acetylation, results in the loss of Arm1 function. Failure of proper NatB complex function results in a pleiotropic phenotype characterized by malformed septa, temperature sensitivity, cell elongation, and a disrupted actin cytoskeleton. In budding yeast, Saccharomyces cerevisiae, it is believed that modifying the N-terminus of a protein to Met-His- may restore function in non-acetylated NatB substrates. Plasmids expressing pREP41:cdc8, pREP41:arp2 and pREP41:prp18 with a Met-His- modification were successfully integrated into the fission yeast genome. For cdc8 (tropomyosin) a phenotypic analysis showed that a Met-His- modification was able to restore the pleiotropic phenotype of the cell, in both repressed and derepressed conditions. Expression of arp2 with a Met-His- modification in a cdc8MH-int. background was not observed to further rescue the arm1 mutant phenotype. The expression of prp18 with a Met-His- modification in a cdc8MH-int. background provided additional rescue of the loss of function arm1 phenotype.

Role of CREB-binding protein on histone acetylation and cocaine-associated behaviors

MHILLAJ, EMANUELA
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
361.15125%
Evidence shows that cocaine exposure triggers altered gene expression within the nucleus accumbens, contributing to the development and persistence of drug addiction. Chromatin modification is emerging as a major molecular mechanism involved in the regulation of gene expression critical for long lasting forms of synaptic plasticity, memory processes, and drug-induced neural and behavioral change. Cocaine induces specific chromatin modifications, such as histone acetylation, that modulate histone-DNA interactions and the recruitment of transcriptional regulatory complexes, leading to changes in transcription that may underlie aspects of cocaine addiction. Although changes in histone acetylation in response to cocaine have been documented, relatively little is known about the specific histone acetylation enzymes involved in cocaine-induced plasticity. The enzymes that regulate levels of histone acetylation are histone acetyltransferases (HATs) and histone deacetylases (HDACs), which generally promote or silence gene expression, respectively. Studies have demonstrated that HDACs may negatively regulate cocaine-induced behaviors, but very little is known about the role of specific HATs in long-lasting drug induced plasticity. The histone acetyltransferase CREB-binding protein (CBP) mediates transcriptional activation by recruiting basal transcription machinery and acetylating histones. CBP is a critically important chromatin modifying enzyme involved in regulating gene expression required for long-term plasticity and memory. However...

Acetylation of histone H3 at lysine 64 regulates nucleosome dynamics and facilitates transcription

Di Cerbo, Vincenzo; Mohn, Fabio; Ryan, Daniel P; Montellier, Emilie; Kacem, Salim; Tropberger, Philipp; Kallis, Eleni; Holzner, Monika; Hoerner, Leslie; Feldmann, Angelika; Richter, Florian Martin; Bannister, Andrew J; Mittler, Gerhard; Michaelis, Jens; K
Fonte: eLife Sciences Publications Publicador: eLife Sciences Publications
Tipo: Artigo de Revista Científica Formato: 23 pages
Relevância na Pesquisa
355.10332%
Post-translational modifications of proteins have emerged as a major mechanism for regulating gene expression. However, our understanding of how histone modifications directly affect chromatin function remains limited. In this study, we investigate acetylation of histone H3 at lysine 64 (H3K64ac), a previously uncharacterized acetylation on the lateral surface of the histone octamer. We show that H3K64ac regulates nucleosome stability and facilitates nucleosome eviction and hence gene expression in vivo. In line with this, we demonstrate that H3K64ac is enriched in vivo at the transcriptional start sites of active genes and it defines transcriptionally active chromatin. Moreover, we find that the p300 co-activator acetylates H3K64, and consistent with a transcriptional activation function, H3K64ac opposes its repressive counterpart H3K64me3. Our findings reveal an important role for a histone modification within the nucleosome core as a regulator of chromatin function and they demonstrate that lateral surface modifications can define functionally opposing chromatin states.; Funding was provided by these organisations to the following authors. Deutsche Forschungs Gemeinschaft, grant SFB 746, Fondation pour la Recherche Medicale grant...

Centromere-specific acetylation of histone H4 in barley detected through three-dimensional microscopy

Wako, Toshiyuki; Houben, Andreas; Furushima-Shimogawara, Rieko; Belyaev, Nikolai D.; Fukui, Kiichi
Fonte: Kluwer Publicador: Kluwer
Tipo: Artigo de Revista Científica
Publicado em //2003 EN
Relevância na Pesquisa
361.15125%
Histone acetylation affects chromatin conformation and transcriptional activity. However, the structural role of histone acetylation at specific chromosomal regions, such as the centromere, is poorly understood. In this study, histone H4 acetylation and its localization in barley interphase nuclei are revealed by three-dimensional microscopy. The centromeres form a ring-like allocation near the nuclear membrane in barley. Immunofluorescence studies on non-fixed, interphase nuclei treatment revealed ring-like distribution of the highly acetylated histone H4, located near the nuclear membrane at one pole of the nucleus. This fluorescent structure was similar to the centromere cluster and referred to as hyperacetylated region (HAR). The distribution pattern of the acetylated histone H4 was similar to each of the K5, K8, K12 and K16 lysine residues, although H4 acetylated at K5, K8 and K12 residues was found in almost all nuclei, whereas H4 acetylated at K16 was weakly observed in only half of the nuclei. Each HAR consists of two strongly acetylated cores and a halo-like, less acetylated surrounding area. Fluorescence signals from centromere-specific repetitive sequences of barley, detected through three-dimensional fluorescence in situ hybridization (3D-FISH)...

The acetylation patterns of histones H3 and H4 along Vicia faba chromosomes are different

Belyaev, Nikolai D.; Houben, Andreas; Baranczewski, Pawel; Schubert, Ingo
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Artigo de Revista Científica
Publicado em //1998 EN
Relevância na Pesquisa
362.2907%
The acetylation pattern of H3 was studied on field bean chromosomes by means of indirect immunofluorescence using polyclonal antibodies recognizing H3 isoforms acetylated at lysine positions 9/18, 14 and 23. H3 was found to be hypoacetylated at lysine residues 9/18 and 14 within the heterochromatic regions composed of tandem repetitive Fok-I elements. Hyperacetylation of these residues was observed at the nucleolar organizing region (NOR) and in heterochromatic regions composed of repeats other than Fok-I elements. In contrast, H4 was underacetylated (H4.Ac5, 8, 12) or uniformly acetylated (H4.Ac16) at all heterochromatic regions, and acetylated above the average at all four lysines only within the NOR. Acetylation of lysine-23 of H3 was uniform, except for the NOR that showed no fluorescence. Inhibition of deacetylase during and after replication of heterochromatin by trichostatin A had no influence on the acetylation status of H3 but mediated an increase in acetylation of lysines 5, 12 and 16 of H4 above the average in the field bean heterochromatin. Thus, the chromosomal acetylation patterns of H4 and H3 of this species revealed common and divergent features. Whereas the acetylation level of H4 correlates well with the potential transcriptional activity and inversely with the time of replication of defined chromatin domains of Vicia faba...

Effect of acetylation on the properties of corn starch.

Ayucitra, Aning
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2007
Relevância na Pesquisa
355.10332%
In this study, a corn starch was acetylated with acetic anhydride under alkaline conditions to produce different degrees of substitution. Experimental analyses were performed to investigate the effect of acetylation on a range of starch properties and compare them with those of native corn starch and a commercially available acetylated corn starch. The data obtained, and the observations made in this study will be of value to other researchers in this field, and to food manufacturers wishing to modify corn starch-based foods by acetylation.; Thesis (M.Eng.Sc.) -- University of Adelaide, School of Chemical Engineering, 2007; Title page, summary and table of contents only. The complete thesis in print form is available from the University of Adelaide Library.

Patterns of histone acetylation as targets for novel therapeutic approaches in neurological diseases; Muster der Histon-Azetylierung als Ziele für neue therapeutische Ansätze bei neurologischen Erkrankungen

Ebrahimi, Azadeh
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
359.69527%
Neurological diseases, in particular brain tumors and neurodegenerative disorders, cause significant socio-economic burdens on societies. Exploring epigenetic mechanisms in neurological disorders in recent decades has been an emerging tool for describing the pathogenesis of neurological diseases as well as developing new therapeutics. Global histone acetylation is an epigenetic entity whose alternating patterns in various neurological diseases have recently raised special attention concerning its potency for therapeutic development. I investigated patterns of global histone 3 lysine 9 acetylation (H3K9Ac) in various brain tumors and neurodegenerative animal models, such as APPPS1-21 mice model of Alzheimer’s disease (AD), in order to find out the relevance of this target to clinical outcome of the disease and it potency as a target for therapeutic development. I also tried to find out whether natural products with promising neuroprotective effects in preclinical studies affect H3K9Ac status of the nuclei in the studied models. In the present study, it was shown that H3K9Ac levels change variably in different brain diseases including benign and malignant tumors as well as neurodegenerative conditions such as AD. In brain tumors...

Human 14-3-3 Paralogs Differences Uncovered by CrossTalk of Phosphorylation and Lysine Acetylation

Uhart, Marina; Bustos, Diego Martin
Fonte: Public Library Science Publicador: Public Library Science
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
Relevância na Pesquisa
355.10332%
The 14-3-3 protein family interacts with more than 700 different proteins in mammals, in part as a result of its specific phospho-serine/phospho-threonine binding activity. Upon binding to 14-3-3, the stability, subcellular localization and/or catalytic activity of the ligands are modified. Seven paralogs are strictly conserved in mammalian species. Although initially thought as redundant, the number of studies showing specialization is growing. We created a protein-protein interaction network for 14-3-3, kinases and their substrates signaling in human cells. We included information of phosphorylation, acetylation and other PTM sites, obtaining a complete representation of the 14-3-3 binding partners and their modifications. Using a computational system approach we found that networks of each 14-3-3 isoform are statistically different. It was remarkable to find that Tyr was the most phosphorylatable amino acid in domains of 14-3-3 epsilon partners. This, together with the over-representation of SH3 and Tyr_Kinase domains, suggest that epsilon could be involved in growth factors receptors signaling pathways particularly. We also found that within zeta´s network, the number of acetylated partners (and the number of modify lysines) is significantly higher compared with each of the other isoforms. Our results imply previously unreported hidden differences of the 14-3-3 isoforms interaction networks. The phosphoproteome and lysine acetylome within each network revealed post-transcriptional regulation intertwining phosphorylation and lysine acetylation. A global understanding of these networks will contribute to predict what could occur when regulatory circuits become dysfunctional or are modified in response to external stimuli.; Fil: Uhart...

The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a two-fold helical screw in the secondary plant cell wall of Arabidopsis thaliana.

Busse-Wicher, Marta; Gomes, Thiago C. F.; Tryfona, Theodora; Nikolovski, Nino; Stott, Katherine; Grantham, Nicholas J.; Bolam, David N.; Skaf, Munir S.; Dupree, Paul D.
Fonte: Wiley Publicador: Wiley
Tipo: Article; accepted version
EN
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357.7696%
This is the accepted version of the following article: "Busse-Wicher, M; Gomes, T.C.F; Tryfona, T; Nikolovski, N; Stott, K; Grantham, N.J; Bolam, D.N; Skaf, M.S; Dupree, P. (2014) "The pattern of xylan acetylation suggests xylan may interact with cellulose microfibrils as a two-fold helical screw in the secondary plant cell wall of Arabidopsis thaliana." The Plant Journal. Accepted article [electronic] 10.1111/tpj.12575", which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/tpj.12575/abstract; The interaction between xylan and cellulose microfibrils is important for secondary cell wall properties in vascular plants. However, the molecular arrangement of xylan in the cell wall and the nature of the molecular bonding between the polysaccharides are unknown. In dicots, the xylan backbone of ?-(1,4)-linked xylosyl residues is decorated by occasional glucuronic acid and approximately one half of the xylosyl residues are O-acetylated at C-2 or C-3. We recently proposed that the even periodic spacing of GlcA residues in the major domain of dicot xylan might allow the xylan backbone to fold as a 2-fold helical screw to facilitate alignment along, and stable interaction with, cellulose fibrils (Bromley et al. 2013). However...

An Alternative Approach for Acetylation of Amine Terminated Polyamidoamine (PAMAM) Dendrimer

Gautam,Surya Prakash; Keservani,Raj K.; Gautam,Tapsya; Gupta,Arun K.; Sharma,Anil Kumar
Fonte: Ars Pharmaceutica (Internet) Publicador: Ars Pharmaceutica (Internet)
Tipo: info:eu-repo/semantics/article; journal article; info:eu-repo/semantics/publishedVersion Formato: text/html; application/pdf
Publicado em 01/09/2015 ENG
Relevância na Pesquisa
362.2907%
Aim: Polyamidoamine (PAMAM) dendrimers inherent properties have made it the nanocarrier of choice in the current era of innovation. Dendrimer based products are growing and mushrooming like anything in the current time. Although it suffer from hemolytic toxicity which could be reduced by protecting free amino group. Methods: In the present work alternate acetylated method for PAMAM dendrimers was discussed. 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide Linker was used for acetylation. The acetylated conjugate was evaluated for color reaction, Ultraviolet-visible spectroscopy, Fourier Transform infrared spectroscopy, Differential scanning calorimetric, Nuclear magnetic resonance spectra studies. Results: The PAMAM dendrimers were synthesized using divergent approach and further acetylated. Change in λmax values from 282.0 to 282.5 nm was observed for acetylated dendrimers. Characteristic peak of N-H stretch of primary amine at 3284.16 cm-1 was disappeared due to conversion of primary amine to secondary amine. A new peak of -(CO)-NH stretch was obtained at 1640.28 cm-1 (medium) which shows attachment of acetic acid surface group. The changes in Endothermic peak from 120.56 to 110.40ºC were observed which shows the PAMAM dendrimers surface modifications The peak of -NH2 at 2.99 ppm was replaced by (-NHCOCH3) at 2.42 ppm further supports the proof of acetylation. Conclusions: The spectral data clearly revealed that this approach for acetylation gives considerable amount of acetylation in less time duration with elimination of organic solvent. This method could be employed for regular acetylation of amine terminated nanocarriers. EDC linker mediated capping of amine groups opened a new avenue for acetylation of amine terminated protein/peptides.