Mechanic Studies Of Helical Supramolecular Structures Of Polysaccharides By AFM

The force has been taken as one of core research interests in the natural scientific studies. In life science, it weights more and more among the entire research topics since it covers nearly all the biological processes. As one of fundamental materials, polysaccharides are playing a key role during the life processes. Similar to the genetic material, DNA molecules, and major functional material, proteins, the polysaccharides express their functions based on their supramolecular structures. Comparing to the mechanic studies of their prime structure, the research interests of supramolecular structures are based on more topics of biological activities. In my thesis, we individually analyzed the mechanical helical structures of one kind of polysaccharides by AFM-based single-molecular spectroscopy.In my second chapter, we introduced curdlan, aB-1,3 linked D-glucose and analyzed its mechanics by AFM. Our results showed that in a low concentration of NaOH aqueous solution that was lower than the transitional concentration of helical structure, curdlan mainly maintained its triplex structure; while in far higher concentration of NaOH than transitional concentration, the random coil was the more favorite conformational structures to curdlan molecules; during the conformational change that was in the 0.19M-0.24M NaOH solution, curdlanmolecules adopted the duplex structure. The results indicated that the whole triplex helical structure, which was the structure bases of the bioactivities of curdlan, was destroyed with the increase of the NaOH concentration from triplexes via duplexes to the random coils. While the themo-experiment showed in the high-set curdlan gel, the hydrophobic interaction was formed within the supramolecular structures that increased the transitional force of the secondary structure.