James Isn't this also related to the speed of sound in the material? I guess measurements are made all made with crystals at room temperature and would be different at 100K. Any info on this for protein crystals?
Speed of sound depends on density and elastic modulus though I guess would rapidly go beyond the elastic limit for a protein crystal. Speed of sound 3152 m/s for ice 1497 m/s for water Colin -----Original Message----- From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of James Holton Sent: 28 July 2009 13:16 To: [email protected] Subject: Re: [ccp4bb] Overall forces in crystals? The google keyword you are looking for is "Vickers hardness" which is mechanical engineering speak for how much "compliance" you get when you poke a sample of interest with a pointed stick. (After you specify the pointiness (tip dimensions), the sample has a flat surface, and you know the hardness of the tip of your stick.) Obviously, the stick must be harder than the crystal, but in this case you can't loose because it looks like lysozyme crystals have the lowest Vickers hardness ever measured: http://dx.doi.org/10.1016/S0022-0248(98)01096-3 http://dx.doi.org/10.1080/14786430410001716791 As with many things in engineering, there is more than one way to measure the "stiffness" of a substance. Perhaps a more elegant method would be Brillouin scattering. By "elegant", of course, I mean more accurate and harder to understand, but it looks like this was done as well: http://dx.doi.org/10.1016/S0022-0248(01)01092-2 This is about as far as I got looking into this at one point. Let me know if you learn anything more! -James Holton MAD Scientist Frank von Delft wrote: > Hi, > > I don't remember ever seeing any references to this, and am also not > quite sure where to start looking -- but the BB readership tends to > dredge up this sort of thing: > > Has anybody published (or just done) estimates of the magnitude of the > forces that hold a crystal together? E.g. how hard would I need to > poke it with a pointed stick to make a hole in it? (Or conversely, > how pointed would the stick need to be.) > > (I thought Alex McPherson's AFM papers might point me there, but they > only say what nominal forces they used, not what forces demolished the > crystals.) > > Cheers > phx -- Scanned by iCritical.
