@phdthesis{Issaree2008, author = {Issaree, Arisara}, title = {Synthesis of Hetero-chitooligosaccharides}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-17069}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Chitooligosaccharides are composed of linear β-(1→4)-linked 2-acetamido-2-deoxy-β-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-β-D-glucopyranose (GlcN). They are of interest due to their remarkable biological properties including antibacterial, antitumor, antifungal and elicitor activities. They can be obtained from the aminoglucan chitosan by chemical or enzymatic degradation which obviously affords rather heterogenous mixtures. On the other hand, chemical synthesis provides pure compounds with defined sequences of GlcNAc and GlcN monomers. The synthesis of homo- and hetero-chitobioses and hetero-chitotetraoses is described in this thesis. Dimethylmaleoyl and phthaloyl groups were used for protection of the amines. The donor was activated as the trichloroacetimidate in order to form the β-linkages. Glycosylation in the presence of trimethylsilyl trifluoromethanesulfonate, followed by N- and O-deprotection furnished chitobioses and chitotetraoses in good yields.}, language = {en} } @phdthesis{Vijayakrishnan2008, author = {Vijayakrishnan, Balakumar}, title = {Solution and solid phase synthesis of N,N'-diacetyl chitotetraoses}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-18830}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {The three major biopolymers, proteins, nucleic acids and glycoconjugates are mainly responsible for the information transfer, which is a fundamental process of life. The biological importance of proteins and nucleic acids are well explored and oligosaccharides in the form of glycoconjugates have gained importance recently. The β-(1→4) linked N-acetylglucosamine (GlcNAc) moiety is a frequently occurring structural unit in various naturally and biologically important oligosaccharides and related conjugates. Chitin which is the most abundant polymer of GlcNAc is widely distributed in nature whereas the related polysaccharide chitosan (polymer of GlcN and GlcNAc) occurs in certain fungi. Chitooligosaccharides of mixed acetylation patterns are of interest for the determination of the substrate specificities and mechanism of chitinases. In this report, we describe the chemical synthesis of three chitotetraoses namely GlcNAc-GlcN-GlcNAc-GlcN, GlcN-GlcNAc-GlcNAc-GlcN and GlcN-GlcN-GlcNAc-GlcNAc. Benzyloxycarbonyl (Z) and p-nitrobenzyloxycarbonyl (PNZ) were used for the amino functionality due to their ability to form the β-linkage during the glycosylation reactions through neighboring group participation and the trichloroacetimidate approach was utilized for the donor. Monomeric, dimeric acceptors and donors have been prepared by utilizing the Z and PNZ groups and coupling between the appropriate donor and acceptors in the presence of Lewis acid yielded the protected tetrasaccharides. Finally cleavage of PNZ followed by reacetylation and the deblocking of other protecting groups afforded the N,N'-diacetyl chitotetraoses in good yield. Successful syntheses for the protected diacetyl chitotetraoses by solid phase synthesis have also been described.}, language = {en} } @article{EinarssonBahrkeSigurdssonetal.2013, author = {Einarsson, Jon M. and Bahrke, Sven and Sigurdsson, Bjarni Thor and Ng, Chuen-How and Petersen, Petur Henry and Sigurjonsson, Olafur E. and Jonsson, Halldor and Gislason, Johannes and Thormodsson, Finnbogi R. and Peter, Martin G.}, title = {Partially acetylated chitooligosaccharides bind to YKL-40 and stimulate growth of human osteoarthritic chondrocytes}, series = {Biochemical and biophysical research communications}, volume = {434}, journal = {Biochemical and biophysical research communications}, number = {2}, publisher = {Elsevier}, address = {San Diego}, issn = {0006-291X}, doi = {10.1016/j.bbrc.2013.02.122}, pages = {298 -- 304}, year = {2013}, abstract = {Recent evidences indicating that cellular kinase signaling cascades are triggered by oligomers of N-acetylglucosamine (ChOS) and that condrocytes of human osteoarthritic cartilage secrete the inflammation associated chitolectin YKL-40, prompted us to study the binding affinity of partially acetylated ChOS to YKL-40 and their effect on primary chondrocytes in culture. Extensive chitinase digestion and filtration of partially deacetylated chitin yielded a mixture of ChOS (Oligomin(TM)) and further ultrafiltration produced T-ChOS(TM), with substantially smaller fraction of the smallest sugars. YKL-40 binding affinity was determined for the different sized homologues, revealing micromolar affinities of the larger homologues to YKL-40. The response of osteoarthritic chondrocytes to Oligomin(TM) and T-ChOS(TM) was determined, revealing 2- to 3-fold increases in cell number. About 500 mu g/ml was needed for Oligomin(TM) and around five times lower concentration for T-ChOS(TM), higher concentrations abolished this effect for both products. Addition of chitotriose inhibited cellular responses mediated by larger oligosaccharides. These results, and the fact that the partially acetylated T-ChOS(TM) homologues should resist hydrolysis, point towards a new therapeutic concept for treating inflammatory joint diseases.}, language = {en} } @phdthesis{Bahrke2008, author = {Bahrke, Sven}, title = {Mass spectrometric analysis of chitooligosaccharides and their interaction with proteins}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-20179}, school = {Universit{\"a}t Potsdam}, year = {2008}, abstract = {Chitooligosaccharides are composed of glycosamin and N-acetylglycisamin residues. Gel permeations chromatography is employed for the separation of oligomers, cation exchange chromatography is used for the separation of homologes and isomers. Trideuterioacetylation of the chitooligosaccharides followed by MALDI-TOF mass spectrometry allowes for the quantitation of mixtures of homologes. vMALDI LTQ multiple-stage MS is employed for quantitative sequencing of complex mixtures of heterochitooligosaccharides. Pure homologes and isomers are applied to biological assays. Chitooligosaccahrides form high-affinity non-covalent complexes with HC gp-39 (human cartilage glycoprotein of 39 kDa). The affinity of the chitooligosaccharides depends on DP, FA and the sequence of glycosamin and N-acetylglycosamin moieties. (+)nanoESI Q TOF MS/MS is used for identification of a high-affinity binding chitooligosaccharide of a non-covalent chitinase B - chitooligosaccharide complex. DADAA is identified as the heterochitoisomer binding with highest affinity and biostability to HC gp-39. Fluorescence based enzyme assays confirm the results.}, language = {en} } @article{MengibarGananMirallesetal.2011, author = {Mengibar, M. and Ganan, M. and Miralles, B. and Carrascosa, A. V. and Martinez-Rodriguez, Adolfo J. and Peter, Martin G. and Heras, A.}, title = {Antibacterial activity of products of depolymerization of chitosans with lysozyme and chitosanase against Campylobacter jejuni}, series = {Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides}, volume = {84}, journal = {Carbohydrate polymers : an international journal devoted to scientific and technological aspects of industrially important polysaccharides}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0144-8617}, doi = {10.1016/j.carbpol.2010.04.042}, pages = {844 -- 848}, year = {2011}, abstract = {Chitosan has several biological properties useful for the food industry, but the most attractive is its potential use as a food preservative of natural origin due to its antimicrobial activity against a wide range of food-borne microorganisms. Among food-borne pathogens, Campylobacter jejuni and related species are recognised as the most common causes of bacterial food-borne diarrhoeal disease throughout the world. Recently, it has been demonstrated that campylobacters are highly sensitive to chitosan. Even though chitosan is known to have important functional activities, poor solubility makes them difficult to use in food and biomedical applications. Unlike chitosan, the low viscosity and good solubility of chitosan oligosaccharides (COS) make them especially attractive in an important number of useful applications. In the present work, the effect of different COS on C. jejuni was investigated. Variables such as the physicochemical characteristics of chitosan and the enzyme used in COS preparation were studied. The COS had been fractioned using ultrafiltration membranes and each fraction was characterized regarding its FA and molecular weight distribution. It has been demonstrated that the biological properties of COS on Campylobacter depend on the composition of the fraction analysed. COS prepared by enzymatic hydrolysis with chitosanase were more active against Campylobacter that lysozyme-derived COS, and this behaviour seems to be related with the acetylation of the chains. On the other hand. the 10-30 kDa fraction was the most active COS fraction, independently of the enzyme used for the hydrolysis. These results have shown that COS could be useful as antimicrobial in the control of C. jejuni.}, language = {en} }