Browsing by Author "Chen, Yi-Yun"

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Catalytic function of a newly purified exo-beta-D-glucosaminidase from the entomopathogenic fungus Paecilomyces lilacinus
(2013-04-02)
Chao, Cheng-Fu
;
Chen, Yi-Yun
;
Cheng, Chih-Yu
;
Li, Yaw-Kuen
;
應用化學系
An entomopathogenic fungus, Paecilomyces lilacinus, was found to grow on chitosanase-detecting plates. Besides an endo-chitosanase, an exo-beta-D-glucosaminidase was purified by cation-exchange chromatography from this microorganism cultivated in M9 minimal media containing 0.5% chitosan as the sole carbon source. The molecular weight of the enzyme is 95 kDa; the optimum pH and temperature for activity are 6.0 and 45 degrees C, respectively. The purified exo-beta-D-GlcNase promotes the hydrolysis of 95% deacetylated chitosan from its non-reducing end and liberates 2-amino-2-deoxy-D-glucopyranose (GlcN) as the sole product; however, 2-acetamido-2-deoxy-D-glucopyranose (GlcNAc) was not detected when chitin was used as the substrate. The cleavage pattern confirmed using real-time mass spectrometry shows that exo-beta-D-glucosaminidase cleaves the glycosidic bonds between GlcN-GlcN and GlcN-GlcNAc but not between GlcNAc-GlcN or GlcNAc-GlcNAc. In the presence of a 10% solution of various alcohols, many alkyl-beta-D-glucosaminides were obtained, indicating that exo-beta-D-glucosaminidase is a retaining enzyme. (c) 2012 Elsevier Ltd. All rights reserved.
Very small photoluminescent gold nanoparticles for multimodality biomedical imaging
(2013-05-01)
Lai, Sheng-Feng
;
Chien, Chia-Chi
;
Chen, Wen-Chang
;
Chen, Hsiang-Hsin
;
Chen, Yi-Yun
An original synthesis method based on X-ray irradiation produced gold nanoparticles (AuNPs) with two important properties for biomedical research: intense visible photoluminescence and very high accumulation in cancer cells. The nanoparticles, coated with MUA (11-mercaptoundecanoid acid), are very small (1.4 nm diameter); the above two properties are not present for even slightly larger sizes. The small MUA-AuNPs are non-cytotoxic (except for very high concentrations) and do not interfere with cancer cell proliferation. Multimodality imaging using visible light fluorescence and X-ray microscopy is demonstrated by tracing the nanoparticle-loaded tumor cells. (C) 2012 Elsevier Inc. All rights reserved.