過去的研究已經發現心臟毒蛋白A3會進入H9C2心肌細胞，最終其路徑會進入到粒線體中，並且發現過程會受到膽固醇及溫度的影響(王佳蕙，2005，博士論文)。因此本論文利用Rhodamine螢光標定不同心臟毒蛋白，以共軛焦顯微鏡觀察，研究其它心臟毒蛋白是否會有與A3相同的機制表現。結果顯示心臟毒素A2與A3進入到細胞中的量幾乎差不多，並且遠大於心臟毒素A1和A6，顯示的第一指環區(loop 1)可能會影響心臟毒蛋白進入到細胞的量。而在溫度影響方面，所有心臟毒蛋白皆在低溫下受到抑制完全不進入到細胞中，顯示進入的路徑是跟溫度有很大的關係。膽固醇含量不同的結果則顯示心臟毒素A2和A3有著很明顯完全相反的結果差異，表示出第二指環區(loop 2)對於細胞上膽固醇含量的影響似乎有很大的關係。以上研究結果發現不同的心臟毒蛋白進入到細胞的量是不一致的，但是卻都會受到溫度與膽固醇的影響，由結構序列則可以發現似乎是與心臟毒素上的第一、第二指環區有很大的關係。然而也發現到不同心臟毒蛋白進入到細胞中的路徑也似乎並非一致，不過此部分還需要更進一步的實驗去探討。

It has recently been shown that CTX A3 internalizes into H9C2 cell and targets at mitochondria. It is a temperature-dependent and cholesterol-sensitive process. In order to understand the structure-function correlation of CTX internalization, I employed confocal microscopy to study the internalization of different rhodamine-labeled CTX homologues. My results showed that the amount of internalized CTXs have the tendency of A2 ~ A3 > A1 ~A6. It suggests the ability of CTX internalization may correlate with the loop 1 structure.
In addition, CTX treatments under low temperature impaired their internalization, which implies the possible temperature-sensitive pathway involved.
Finally, the effect of cholesterol content on their internalization is different for CTX A2 and A3, which suggests the loop 2 structure might play important role.
In summary, different cardiotoxins exhibit different behavior as distinguished by either internalized amount or cholesterol sensitivity. Comparison of their primary sequences suggests the loop 1 and loop 2 regions play role in CTX internalization, and the different effects are contributed by their structural diversity.

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