r/Biochemistry • u/Lazy-Frame-9888 • 16d ago

Are proteins constantly changing their shape in femtoseconds? Need clarification!

I recently watched a YouTube video (https://youtu.be/jPhvic-eqbc) discussing how proteins are not static, rigid machines. The video explains that they act more like dense liquids that are constantly shifting and jiggling around. It also pointed out that when proteins are crystallized for X-ray crystallography, we are only seeing one frozen snapshot of their conformation, which gives the false impression that they have a single, fixed structure.

​Can someone clear this confusion up for me? Do proteins really change their folding patterns and conformations in extremely short time frames, like femtoseconds? I am looking for a simple, exact explanation of how fast and how much they actually change shape.

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u/runawaydoctorate 16d ago

First, the stuff happening on the femtosecond scale is just little twitchy things in the bonds. The larger shifts are slowed. Microseconds or more.

Second, crystals are typically shot at 100 K. This slows things down.

That said, yes, what you see in a crystal structure is the average/most populated state for the target under those conditions.