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Lynseyann wrote:cells don't "live" forever - they all meet a death at some point
I hope this link helps?
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Pharyngula wrote:Here's the central problem: molecules don't behave that way. What is portrayed is wonderfully precise movement; it looks like the molecules are all directed, purposeful, and smooth. Take for instance the behavior of kinesin, that stalk-like molecule seen marching in a stately way down a tubule, with two "feet" in alternating step, towing a large vesicle. That's not how it moves! We have experiments in which kinesin is tagged — it's towing a fluorescent sphere — and far from a steady march, what it does is take one step forward, two steps forward, one step back, two steps forward, one back, one forward … it jitters. On average it progresses in one direction, but moment by moment it's a shivery little dance.
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Paralith wrote:I'm sure the authors had good reason for doing what they did, but for the purposes of accuracy I think it's good to at least be made aware of the stochasticity of molecular behavior so you can keep it in mind while you watch the video. That's why I like to post that link, not because I don't like the video.
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Paralith wrote:Pharyngula wrote:Take for instance the behavior of kinesin, that stalk-like molecule seen marching in a stately way down a tubule, with two "feet" in alternating step, towing a large vesicle. That's not how it moves! We have experiments in which kinesin is tagged — it's towing a fluorescent sphere — and far from a steady march, what it does is take one step forward, two steps forward, one step back, two steps forward, one back, one forward … it jitters. On average it progresses in one direction, but moment by moment it's a shivery little dance.
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MrMistery wrote:i would say kinesin-1 doesn't jitter, because it is a processive motor. How it works is that it never lets go of the tubulin protofilament it's walking on, and can only move forward (by hydrolyzing ATP) or stand still (if it's not hydrolyzing ATP). Now I don't pretend to be an expert on motor proteins nor do I have time to dissect the problem in detail now, but in this figure it seems to me that this is what happens - it does go back sometimes, but very rarely, and this could be accounted by the rare situations when the kinesin lets go of the microtubule, which of course will inevitably happen. The figure is from Grigoriev et al. 2007, Dev Cell 13(2) - figure 3 in the article.
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genemachine wrote:I thought this video of a walking myosin-5 mollecule might belong here.
"Atomic Force Microscopy Shows Myosin Walking On Actin"
http://kambiz.wordpress.com/2010/11/10/ ... -on-actin/
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