碩士 / 國立臺灣海洋大學 / 生物科技研究所 / 93 / Pentavalence arsenic and trivalence arsenic chemical compounds are toxicant in the environment and methylation of arsenic species is a detoxification pathway in some organisms. Experimental analysis by HG-GCT-AAS(Hydride Generation-Gamma Cold Trap-Atomic Absorption Spectrophotometer)showed that marine alga Tetraselmis chuii cultrued with 0.133mM arsenate for 7 days generated monomethyl arsenic species (MMA) and dimethyl arsenic species (DMA), but freshwater alga Chlorella pyrenoidosa showed no methylating activity under the same condition. For producing an alga species capable of methylating arsenic in freshwater, a 1011-bp cDNA carrying the complete open reading frame of mouse arsenic methyltransferase(cyt 19) was cloned into the expression vector pBIN19 under the control of a Pnos promotor and cyt19 ORF was transformed into Chlorella via infection with Agrobacterium tumefaciens. The cyt19 cDNA was detected by PCR in several colonies of transformed Chlorella after 2-day infection and no cyt19 cDNA could be found in all nontransformed Chlorella colonies. Whether arsenic methylating activity can be produced in transformed Chlorella awaits further investigation. Northern blot analysis of total RNA of T. chuii using cyt19 ORF as the probe detected a hybridization signal and the signal intensity increased to 142% of control after culturing T. chuii in the medium containing arsenate for 4 days and returned to normal levels 6 days later. Although three arsenate-induced polypeptides were detected by 2-D gel electrophoresis of crude extract proteins of T. chuii cultured in the presence or absence of arsenate, no induction of cyt19-like proteins was found, suggesting that the expression of arsenic methyltrnsferase in T. chuii was not regulated by arsenate.
| Identifer | oai:union.ndltd.org:TW/093NTOU5111008 |
| Date | January 2005 |
| Creators | Shi-Hua Gi, 紀熙華 |
| Contributors | Todd Hsu, 許濤 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 75 |
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