| Summary: | 碩士 === 國立臺灣師範大學 === 化學系 === 99 === Sulfonation and phosphorylation are important post-translational modifications (PTMs) of protein function in cells and occur frequently in oligosaccharides. The glycosaminoglycans (GAGs), which are characterized by a variably sulfated repeating disaccharide unit, bind with cell surface proteoglycans. For example, heparin/haparan sulfates influence numerous biological processes which include anticoagulation, cellular physiology, ionic strength regulation, cancer, viral invasion, bacteria invasion and genetic diseases. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is one of the tools for the structure analysis of proteins and oligosaccharides. However, the low abundance and low stoichiometry of post-translationally modified oligosaccharides and peptides in organisms make isolation and concentration of the compound indispensable prior to MS analysis. In this study, we utilize polyarginine-coated nanodiamond as a high affinity nanoprobe for sulfopeptides and phosphopeptides. We compared the affinity of there two post-translationally modified peptides toward the nanoparticle and found preferential adsorption of sulfopeptide in their mixture. With this technique, we are able to selectively extract heparin disaccharides in high abundant sucrose solution. Additionally, we found that adding 1,1,3,3-tetramethylguanidine (TMG) to 3-aminoquanoline (3-AQ) matrix not only reduces the sulfate fragmentation of heparin disaccharides but also enhances the signal of the protonated ions of MALDI-TOF MS analysis. We conclude that MALDI MS combined with this nanodiamond–based solid phase extraction is a useful technique. It can facilitate our understanding of viral invasion through interaction with sulfate saccharides on cell membrane surface in the future.
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