constant pulling velocity in SMD

From: Jiao, Dian NMN (-EXP) (
Date: Wed Apr 25 2012 - 14:41:06 CDT

Hi, I was trying to pull this metal ion through an ion channel along Z-axis in SMD simulation. SMDvel was set at 0.0001, which means it will travel around 10 A in 1ns. However, my ion travels a whole lot faster. It is first placed near the top of the channel (extracellular surface), it goes from 15.233 to 7.753 (z direction) in merely 50 fs. It doesn't slow down until it hits this spot where the binding between the ion and the lumen facing residues (5 Glu) is very strong. This position is fairly close to the bottom of the channel (intracellular surface). The ion seems to be stablized there and never gets past this position throughout 5ps simulation. Isn't SMDvel supposed to control the speed of the ion moving? Why is it still going so fast? What do I do to make it easy for the ion to escape the binding of that glutamic ring and keeps going down? Thanks in advance.

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