Browsing by Author "Liu, MC"

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Cytosolic sulfotransferases and environmental estrogenic chemicals
(2005)
Suiko, M
;
Sakakibara, Y
;
Liu, MY
;
Yang, YS
;
Liu, MC
Over the past three decades, a substantial body of evidence has accumulated on the estrogenic activities of numerous environmental compounds. These "environmental estrogens," consisting of pesticides and a variety of industrial chemicals and their by-products, are becoming ubiquitous in the environment and are making their way into the food chain. An important issue is whether vertebrate animals are equipped with mechanisms for the inactivation and/or disposal of environmental estrogens. This review attempts to summarize the currently available data concerning the sulfation of environmental estrogenic compounds by the cytosolic sulfotransferases in vertebrate animals. (c) Pesticide Science Society of Japan.
Fluorometric assay for alcohol sulfotransferase
(2005-04-01)
Chen, WT
;
Liu, MC
;
Yang, YS
;
生物科技學系
;
Department of Biological Science and Technology
A sensitive fluorometric assay was developed for alcohol sulfotransferase (AST). This was the first continuous fluorometric assay reported for AST. It used 3 '-phosphoadenosine 5 '-phosphosulfate regenerated from 3-phosphoadenosine 5 '-phosphate by a recombinant phenol sulfotransferase (PST) using 4-methylumbelliferyl sulfate as the sulfuryl group donor. The recombinant PST did not use the alcohol substrate under the designed condition, and the sensitivity for AST activity was found to be comparable to that of radioactive assay as reported in the literature. The change of fluorescence intensity of 4-methylumbelliferone corresponded directly to the amount of active AST and was sensitive enough to measure nanogram or picomole amounts of the enzyme activity. This fluorometric assay was used to determine the activities of AST as purified form and in crude extracts of pig liver, rat liver, and Escherichia coli. Some properties of human dehydroepiandrosterone sulfotransferase were determined by this method and were found to be comparable to published data. Under similar assay conditions, the contaminated activities of arylsulfatase in crude extracts were also determined. This method not only is useful for the routine and detailed kinetic study of this important class of enzymes but also has the potential for the development of a high-throughput procedure using microplate reader. (c) 2004 Elsevier Inc. All rights reserved.
From motion verb to linking element: Discourse explanations for the grammaticalization of jiu in Mandarin Chinese
(1997-06-01)
Liu, MC
;
交大名義發表
;
National Chiao Tung University
Lexical information and beyond: Meaning coercion and constructional inference of the Mandarin verb GAN
(2005-06-01)
Liu, MC
;
交大名義發表
;
National Chiao Tung University
This paper argues for the inclusion of constructional inferences in semantic representation of verbs. By examining the transitive pattern of the Mandarin verb GAN (sic) 'rush', it is found that verbal semantics can only be adequately represented if constructionally coerced information is taken into consideration. The construction [GAN + NP] renders specific interpretations that cannot be directly derived from the lexical meaning of either the verb or the object NP. The construction itself carries salient information for the appropriate interpretation. The 'ellipsed' eventive information is analyzed from the perspective of Construction Grammar (Goldberg 1995). Moreover, a compositional framework based on Qualia Structure (Pustejovsky 1995) is utilized to resolve the potential ambiguity arising from the construction-triggered meaning. By combining the two complementary approaches, this paper attempts to account for and represent contextualized information as well as varied meaning facets associated with a partially-filled construction.
Synthesis and characterization of segmented copolymers of aromatic polyether sulfone and thermotropic liquid crystalline poly(oxy-1,4-phenylenecarbonyl-co-oxy-2,6-naphthaloyl)
(1996-03-01)
Chang, YM
;
Hsu, CS
;
Liu, MC
;
應用化學系
;
Department of Applied Chemistry
The synthesis of segmented copolymers of aromatic polyether sulfone and thermotropic liquid crystalline poly(oxy-1,4-phenylenecarbonyl-co-oxy-2,6-naphthaloyl) is presented. The segmented copolymers were prepared by solution polycondensation of hydroxy-terminated polyether sulfone with 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid in a mixture of triphenylphosphine, pyridine and hexachloroethane. The obtained polymers were fractionated to isolate the pure segmented copolymers. All of the segmented copolymers reveal two glass transitions. The first glass transition at about 75 degrees C belongs to the segmental motions of liquid crystalline polyester blocks. The second glass transition at about 140 degrees C belongs to the segmental motions of polyether sulfone blocks. Optical polarizing microscopy and X-ray diffraction measurements verify the presence of a nematic liquid crystalline phase for the segment copolymers. The experimental results indicate that the segmental copolymers have a microphase-separated morphology, i.e., both amorphous and liquid crystalline properties are shown by the polyether sulfone and liquid crystalline polyester segments, respectively.