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EC50
鎖定
- 中文名
- 半最大效應濃度
- 外文名
- concentration for 50% of maximal effect
- 所屬學科
- 藥理學
- 簡 稱
- EC50
- 內 涵
- 能引起50%最大效應的濃度
- 屬 性
- 藥物安全性指標
- 另一含義
- 引起50%個體有效的劑量
EC50基本介紹
The term half maximal effective concentration (EC50) refers to the concentration of a drug, antibody or toxicant which induces a response halfway between the baseline and maximum after a specified exposure time. It is commonly used as a measure of a drug's potency.
The EC50 of a graded dose-response curve, therefore, represents the concentration of a compound where 50% of its maximal effect is observed. The EC50 of a quantal dose-response curve represents the concentration of a compound where 50% of the population exhibit a response, after a specified exposure duration.
It is also related to IC50 which is a measure of a compound's inhibition (50% inhibition). For competition binding assays and functional antagonist assays IC50 is the most common summary measure of the dose-response curve. For agonist/stimulator assays the most common summary measure is the EC50.
In biological systems, small changes in ligand concentration typically result in rapid changes in response, following a sigmoidal function. The inflection point at which the increase in response with increasing ligand concentration begins to slow is the EC50. This can be determined mathematically by derivation of the best-fit line. While relying on a graph for estimation is more convenient, this method yields less precise and less accurate results.
它也與IC50有關,IC50是衡量一個化合物的抑制作用(50%的抑制作用)。對於競爭性結合試驗和功能性拮抗劑試驗,IC50是最常見的劑量-反應曲線的總結措施。對於激動劑/刺激劑試驗,最常見的總結措施是EC50。
在生物系統中,配體濃度的微小變化通常會導致反應的快速變化,遵循一個sigmoidal函數。隨着配體濃度的增加,反應的增加開始減緩的拐點是EC50。這可以通過推導最佳擬合線以數學方式確定。雖然依靠圖形來估計比較方便,但這種方法產生的結果不太精確,也不太準確。
EC50有許多種表達式,其中之一如圖《EC50表達式及簡圖》所示:
EC50EC50的求法
通常在用菌落直徑法求EC50時需要作一條迴歸方程。
[1]
測真菌測得的數據以濃度取10的對數為橫座標,通過查生物統計機率值換算表,以抑制率對應的幾率值作為縱座標,求出每個試驗濃度的迴歸方程和相關係數R,以抑制率為50%時對應的幾率值求出EC50的值以及其95%的置信區間。
機率值就是幾率的單位,共分為1-40,其實質就是正態分佈的平均數加減標準誤所得的數值範圍,投射在肩線常態等差點上各個常態等差,就代表不同的死亡率,這樣就可以把死亡率的累計曲線用常態等差來計算,從而化成直線。