| 1. |
- Araújo, Ana Catarina, et al.
(författare)
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A general route to xyloglucan-peptide conjugates for the activation of cellulose surfaces
- 2012
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 354, s. 116-120
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose is an attractive supporting matrix for diverse biotechnological applications, including chromatography, diagnostics, and tissue replacement/scaffolding, due to its renewable resource status, low cost, and low non-specific interaction with biomolecules. In an effort to expand the biofunctionality of cellulose materials, we present here a versatile method for the synthesis of xyloglucan-peptide conjugates that harness the strong xyloglucan-cellulose binding interaction for gentle surface modification. Xylogluco-oligosaccharide aminoalditols (XGO-NH2) were coupled to both linear and cyclic peptides, which contained the endothelial cell epitope Arg-Gly-Asp, in a facile two-step approach employing diethyl squarate cross-linking. Subsequent xyloglucan endo-transglycosylase-mediated coupling of the resulting XGO-GRGDS (Gly-Arg-Gly-Asp-Ser) and XGO-c[RGDfK]-PEG-PEG (cyclo[Arg-Gly-Asp-(D-Phe)-Lys]-PEG-PEG; where PEG is 8-amino-3,6-dioxaoctanoic acid) conjugates into high molecular mass xyloglucan yielded xyloglucan-RGD peptide conjugates suitable for cellulose surface activation. Notably, use of XGO-squaramate as a readily accessible, versatile intermediate overcomes previous limitations of solid-phase synthetic approaches to XGO-peptide conjugates, and furthermore allows the method to be generalized to a wide variety of polypeptides and proteins, as well as diverse primary amino compounds.
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| 2. |
- Larsbrink, Johan, et al.
(författare)
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Structural and enzymatic characterization of a glycoside hydrolase family 31 alpha-xylosidase from Cellvibrio japonicus involved in xyloglucan saccharification
- 2011
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 436, s. 567-580
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Tidskriftsartikel (refereegranskat)abstract
- The desire for improved methods of biomass conversion into fuels and feedstocks has re-awakened interest in the enzymology of plant cell wall degradation. The complex polysaccharide xyloglucan is abundant in plant matter, where it may account for up to 20% of the total primary cell wall carbohydrates. Despite this, few studies have focused on xyloglucan saccharification, which requires a consortium of enzymes including endo-xyloglucanases, alpha-xylosidases, beta-galactosidases and alpha-L-fucosidases, among others. In the present paper, we show the characterization of Xy131A, a key alpha-xylosidase in xyloglucan utilization by the model Gram-negative soil saprophyte Cellvibrio japonicus. CjXy131A exhibits high regiospecificity for the hydrolysis of XGOs (xylogluco-oligosaccharides), with a particular preference for longer substrates. Crystallographic structures of both the apo enzyme and the trapped covalent 5-fluoro-beta-xylosyl-enzyme intermediate, together with docking studies with the XXXG heptasaccharide, revealed, for the first time in GH31 (glycoside hydrolase family 31), the importance of PA14 domain insert in the recognition of longer oligosaccharides by extension of the active-site pocket. The observation that CjXy131A was localized to the outer membrane provided support for a biological model of xyloglucan utilization by C. japonicas, in which XGOs generated by the action of a secreted endo-xyloglucanase are ultimately degraded in close proximity to the cell surface. Moreover, the present study diversifies the toolbox of glycosidases for the specific modification and saccharification of cell wall polymers for biotechnological applications.
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| 3. |
- Nakhai, Azadeh, et al.
(författare)
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Synthesis of Benzotriazine and Aryltriazene Derivatives Starting from 2-Azidobenzonitrile Derivatives
- 2010
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Ingår i: European Journal of Organic Chemistry. - : Wiley. - 1434-193X .- 1099-0690. ; :34, s. 6588-6599
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Tidskriftsartikel (refereegranskat)abstract
- 3-Substituted 3,4-dihydro-4-imino-1,2,3-benzotriazine derivatives 7 were formed from 2-azidobenzonitriles 4 as starting materials on treatment with Grignard or lithium organic reagents. In some cases these procedures gave aryltriazenes 10 and 11 as products. All compounds were identified by NMR spectroscopy and the structures of three products, namely 7a, 10a and 11i, were corroborated by X-ray crystallography.
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| 4. |
- Nakhai, Azadeh
(författare)
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Synthetic studies of nitrogen containing heterocycles, particularly pyrazole and benzotriazine derivatives
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis will mainly focus on the chemistry of nitrogen containing heterocyclic compounds, particularly pyrazole and benzotriazine and related ring systems to these compounds. The first part includes a short introduction to biologically important compounds as well as a description of reactivity and chemistry of benzo[c]pyrazole (indazole) and its derivatives. The second part features the synthesis of 3-substituted tetrahydroindazoles and hexahydroindazoles using α,β-unsaturated ketones and hydrazine derivatives. Dehydrogenation of 3-substituted hexahydroindazoles and tetrahydroindazoles using different equivalents DDQ and p-chloranil is also discussed. The third part describes synthesis of a hitherto unknown spirocyclic dihydropyrazolone, namely 4-cyano-1-cyanoacetyl-2-(cyclohexen-1-yl)-1,2-diazaspiro[4.5]decan-3-one, whose structure was confirmed by an X-ray analysis. Mild hydrolysis of this compound resulted in isolation of a des-cyanoacetylated product. In addition, prolonged reflux time during hydrolysis delivered a fully hydrolysed product, namely 4-cyano-1,2- diazaspiro[4.5]decan-3-one, whose structure also was established by X-ray crystallography. The fourth part of this thesis deals with the syntheses of 3,3'-biindolyl and 3,3'- biindazolyl derivatives. A new method for the preparation of 3,3'-biindolyl derivatives via oxidative coupling induced by tellurium tetrachloride was successfully developed. Attempts to achieve 3,3'-biindazolyl derivatives using the same reaction conditions failed. However isolation of 3,3'-biindazolyl derivatives using palladium-catalyzed Stille cross-coupling reaction on SEM-protected derivatives (SEM=2- (trimethylsilyl)ethoxymethyl) is described. Upon preparation of 3,3'-biindazolyl, inconsistencies between the previously reported data promoted further investigations. Hence, the molecule was subjected to an X-ray analysis which gave conclusive evidence for the SEM-protected 3,3'-biindazolyl structure. The last part describes attempts to synthesize 3-substituted indazoles. The anticipated transformation involved treatment of o-azidobenzonitriles with Grignard or lithium reagents, which surprisingly delivered an unexpected product, namely benzotriazines, in good yields. It has also been clarified that substituents on 2-azidobenzonitriles have a clear impact on the formation of products and yields. Furthermore, when aryl Grignard or lithium reagents were used, the only isolable products were aryl-triazene derivatives.
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| 5. |
- Qin, Liena, et al.
(författare)
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Diversity-Oriented Synthesis of Libraries Based on Benzofuran and 2,3-Dihydrobenzofuran Scaffolds
- 2017
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Ingår i: ACS Combinatorial Science. - : American Chemical Society (ACS). - 2156-8952 .- 2156-8944. ; 19:6, s. 370-376
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Tidskriftsartikel (refereegranskat)abstract
- Benzofuran and 2,3-dihydrobenzofuran scaffolds are core components in a large number of biologically active natural and synthetic compounds including approved drugs. Herein, we report efficient synthetic protocols for preparation of libraries based on 3-carboxy 2-aryl benzofuran and 3-carboxy 2-aryl trans-2,3-dihydrobenzofuran scaffolds using commercially available salicylaldehydes, aryl boronic acids or halides and primary or secondary amines. The building blocks were selected to achieve variation in physicochemical properties and statistical molecular design and subsequent synthesis resulted in 54 lead-like compounds with molecular weights of 299-421 and calculated octanol/water partition coefficients of 1.9-4.7.
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| 6. |
- Xu, Chunlin, et al.
(författare)
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Chemo-enzymatic Assembly of Clickable Cellulose Surfaces via Multivalent Polysaccharides
- 2012
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Ingår i: ChemSusChem. - : Wiley. - 1864-5631. ; 5:4, s. 661-665
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Tidskriftsartikel (refereegranskat)abstract
- The chemist′s guide to the galactosyl unit: A chemo-enzymatic process is developed for the multivalent functionalization of cellulose surfaces via regioselective oxidation of heteropolysaccharides with galactose 6-oxidase. Reductive amination, surface sorption, and click chemistry enable the assembly of (bio)chemically active cellulose surfaces for applications ranging from functional biocomposites to in vitro diagnostics.
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| 7. |
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