| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 92 === Abstract
The major purposes of this study are to modify the surfaces of the colloidal gold nanoparticles by mercapto-aliphatic acids of various lengths (C2 to C16), to study the effects of aliphatic chain length on the adsorption of Human serum albumin (HSA) and Bacillus amyloliquefaciens α-amylase (BAA), and to elucidate conformational changes of these two proteins upon adsorption to the modified surfaces.
Thiolated aliphatic acids of different concentrations were added into solutions containing Au nanoparticle, it is found that the binding capacity of mercaptoundecanoic acid (MUA) on Au nanoparticle is the highest and the resulting modified Au particles has the highest stability in salt. It is suggested that the salt endurability of these modified Au particles is affected by both the coverage of thiolated aliphatic acids as well as the chain length.
We also found that the amount of HSA adsorption was much higher than that of BAA. And it was found that the amounts of HSA adsorption was roughly followed the order of the degree of surface thiolation, but that of BAA basically increases as the degree of thiolation decreases. After HSA adsorption, the stability in salt of these particles was dramatically increased, especially for the MAA-modified one. The MAA-modified nanogold was the least stable one among all the modified particles under study, and became the the most stable one after HSA adsorption. This phenomenon might be attributed to its high protein adsorption.
The structural alteration of proteins after adsorption was defined by the fluorescent emission intensities ratio of 350 nm to 305 nm (I350/I305). By comparing the ratios prior to and after adsorption, conformational changes of HSA and BAA on different Au surfaces were analyzed. It was found that the value of I350/I305 after HSA adsorption was smaller than that before adsorption. We also found that the adsorbed HSA exhibited blue shift in its fluorescent emission spectra. It indicated that HSA adsorbed on various Au nanoparticles undergoes a certain degree of structural changes. On the contrary, we did not find any indication of conformational changes of adsorbed BAA.
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