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求助！！头都想爆了

求助！！头都想爆了# Biology - 生物学

e*02012-05-28 07:05

1 楼

知道这里的牛人多，明天PROPOSAL就DUE了，但是现在还很纠结一个问题，想到头都爆
了，而且没机会和别人讨论（我讨厌节日！），所以想来请教下。
我的proposal研究如何建立一个模型来研究膜转运蛋白P-gp和代谢酶CYP3A4关系。里面
涉及到一个关于partition coefficient的问题，：如果在单个细胞里，大概画多久的
时间，几秒，几分，几小时，还是几天，可以要hydrophobic的substrate reach
equilibrium （细胞外，细胞膜，细胞内，还是细胞内的其他膜都达到平衡状态）?假
设所有的transporter, enzyme, protein binding等等的因素都可以忽略。
先谢谢了！

y*n2012-05-28 07:05

2 楼

我会告诉你你的问题没讲清楚么？

x*22012-05-28 07:05

3 楼

http://www.madsci.org/posts/archives/2002-04/1018464369.Cb.r.ht
The average distance that each type of molecule travels from
its starting point is proportional to the square root of the time involved:
that is, if it takes a particular molecule 1 second on average to go 1 um,
it will go 2 um in 4 seconds, 10 um in 100 seconds, and so on. Diffusion is
therefore an efficient way for molecules to move limited distances but an
inefficient way for molecules to move long distances.
Experiments performed by injecting fluorescent dyes and other labeled
molecules into cells show that the diffusion of small molecules through the
cytoplasm is nearly as rapid as it is in water. A molecule the size of ATP,
for example, requires only about 0.2 second to diffuse an average distance
of 10 um - the diameter of a small animal cell. Large macromolecules,
however, move much more slowly. Not only is their diffusion rate
intrinsically slower, but their movement is retarded by frequent collisions
with many other macromolecules that are held in place by molecular
associations in the cytoplasm (Figure 3-8).
Hope it helps.