Hi Xiao, I have observed this phenomenon with two proteins I worked with: rubber-like crystals which you can bend without breaking. As others mentioned: if you have this rubber-like crystals it must be protein, since salt crystals behave very differently. Also I could not think of any reason why salt crystals would refuse to dissolve. Fresh crystals did not suffer from this phenomenon, so I suspect it is due to some (slow) crosslinking. I did not try myself, but you could consider adding reducing agents (glutathion, TCEP, DTT) to your crystallization setup to see if this helps.
Also try the freshest crystals you have for Xray diffraction since in my hands this “rubber-transition” led to a dramatic reduction in resolution of the data. Good luck! Herman Von: CCP4 bulletin board [mailto:[email protected]] Im Auftrag von Xiao Xiao Gesendet: Freitag, 26. September 2014 01:53 An: [email protected] Betreff: [ccp4bb] off-topic;Crystal cannot dissolved in buffer Hi everyone, Sorry for an off-topic question. I got a problem with crystal dissolving. Basically I got crystals of my protein in various conditions, most conditions contain PEGs but different salts. These crystals has very similar shape, so it should not be salt. Now I am trying to dissolve the crystal to make sure it is my protein, by SDS-PAGE and N-term sequencing. I washed the crystals in its original crystallization buffer few times then transfered them into regular buffer (500mM NaCl, 50mM HEPES 7.5) with or without 10mM DTT, however the crystal didn't dissolve. I then tried to heat it then add SDS loading buffer to run a gel, I did see very small amount of protein on the gel, at the correct position, but it's not enough for N-term sequencing. Is it normal for a protein crystal? And does anyone have any suggestion for dissolving such crystals?
