| Summary: | 碩士 === 國立臺灣大學 === 藥學研究所 === 84 === Valinomycin可促進陽離子通過細胞膜，尤其是促進鉀離子對細胞膜的通
透性。因此，valinomycin吸附在細胞膜上可能是一個很重要的過程，我
們選擇表面極性不同之聚苯乙烯(polystyrene,PS)與聚甲基丙烯酸甲酯(
polymethyl methacrylate,PMMA)乳膠作為評估valinomycin吸附現象的固
體受質。合成方式為無乳化劑聚合法。掃瞄式電子顯微鏡與粒徑分析儀觀
察合成所得乳膠的粒子外形與粒徑及其粒徑分佈，可知所製備的聚合物乳
膠皆為圓球型，表面平坦並有高度單一分散性。每毫升PS與PMMA乳膠粒子
表面積分別為0.5854與1.4375平方公尺；電位與電導度滴定的方法所測得
乳膠粒子的表面電荷密度為每平方公分4.8483微庫侖與0.8917微庫侖。為
了測量valinomycin吸附在聚合物乳膠表面的量，我們發展出一個準確而
且精確性高之定量溶液中valinomycin含量的方法。首先將valinomycin水
解後，再以fluorescamine螢光法分析水解產物中valine的含量，進而推
算出valinomycin的含量。比較以HPLC的方式和fluorescamine螢光法定
量 valine的試驗結果，發現fluorescamine螢光法在低濃度範圍有較高的
靈敏度與準確度，螢光法之最低偵測濃度為每毫升1毫微克，而HPLC法則
為每毫升2微克 。吸附實驗係將固定量的聚合物乳膠與不同濃度的
valinomycin溶液在25度恆溫中振搖20小時，並利用溶液耗損法估算的吸
附量。吸附動態曲線中，可明顯地可以看出valinomycin對PS乳膠吸附達
到平衡所需時間較對PMMA乳膠來的短。類似的結果亦可在溶液中氯化鉀存
在吸附實驗結果觀察到。從吸附等溫曲線之高原期吸附量可以估算出吸附
在乳膠表面之分子於緊密排列時之每分子所佔表面積分別為183與163平方
埃。氯化鉀存在下，對PS及PMMA乳膠之吸附等溫曲線可觀察到有一不連續
之轉折點存在，而且會有較高之高原吸附量。以氯化鈉取代氯化鉀時，所
得吸附等溫曲線仍會有一轉折點，高原吸附量則與無鹽類存在下的結果相
近。吸附等溫曲線上的轉折點為溶液中離子所造成的影響，而於KCl存在
之溶液中，因部份 valinomycin可能與鉀離子形成錯合物，因為此錯合物
帶有部份正電性，因此對帶負電荷的乳膠粒子表面有較大之親和力，而且
由空間填充模型所得 valinomycin錯合物之分子截面積亦小於非錯合物之
分子截面積，因此在吸附等溫曲線上可觀察到valinomycin對二種乳膠皆
有較大之高原吸附量。
Valinomycin acts as acarrier of ions, especially potassium ion,
to transport through the cell membrane. Two different types of
latexes used were polystyrene (PS) and polymethyl methacrylate
(PMMA). The preparation of the PS and PMMA latexes was non -
emulsifier polymerization. The particle shape and diameter of
latexes were determined by the scanning electron microscopy and
the particle analyzer. Surface areas per unit volume of PS and
PM MA latexes were 0.5854 and 1.4375 square meter per
miniliter. The surface charge densities of the two latexes, was
determined by the potentiometric and conductometric titrations.
The quantitative method, in brief, valinomycin was first
hydrolyzed by fumed HCl to give products of valine, lactic acid
and alfa-hydroxyisovaleric acid. A fluorescamine fluorescence
method was applied to determinethe amount of valine in the
hydrolysate. Comparison of the fluorescamine fluorescence
method and the HPLC method indicated that both methods provided
highly accurate and precise assay for valine. Nevertheless, the
fluorescence method seems to be more sensitive and precisely at
a lower concentration range. The adsorption experiments were
carried out by adding a fixed amount of polymer latex into
valinomycin solutions. The equili- brium time of adsorption for
the PS latex was much shorter than that of the PMMA latex. The
areas occupied per valinomycin mole- cule were 183 and 163
square armstrone. In the presence of KCl, the discontinuity on
the isotherm and a greater plateau adsorp- tion amount were
observed for the adsorption isotherms of the two polymer
latexes. It seems that the discontinuity on the iso- therm may
be due to the existence of ions. The greater plateau adsorption
is due to that part of valinomycin existed as complex with
potassium ions.
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