Dear Careina, I usually see such kind of "Quasi-crystal" when the folding force was not properly adjusted. Of course, you need to verify they are protein ppt before any further modifications.
For these melon-seed-like crystals, the sharp-end indicated that some crystallization occurred. However, the condition needs to be further modified. 1. For buffer, you need to try different buffers within the similar pH range 7.0 ~ 7.8. For Tris, the temperature is important. Different buffer salts could give you crystals with different morphologies. In general, sulphate salt is harder. Sodium salt or other cations from buffer salts should also be counted for the total Sodium/cation concentration. PEG usually could bring down the pH value. 2. For NaCl, you may try NH4 salts, Li Salts, Na salts, K salts with different anion combinations, including Cl, NO3, SO4. 3. For PEG3350, you may try PEG with different molecular weights, 1K -6K. In your case, I will expect better crystallization with lower MW PEG, since higher MW may introduce more hydrophobic factors resulting in oil-like effects. Anyway, you need to try both for comparison. Different polymers have different pH values, like MME 1.5K, PVP 1.5K, PAS 5.1K. For PAS 5.1K, the pH value is 7.0, and I obtained nice crystals of my target which I could only get quasi-xtals under PEG 3k. 4. Try 5mM ZnCl2, which may work too. Well, there must be a lot of modification strategies ahead. All of my suggestions here are to fine tune the ionic strength in the conditions since you are very close to get xals. Good luck ! Kevin. PS. You may try Coca or Pepsi + PEG 3K too. I got a hit for DEAD-Box complex before. On Wed, Nov 8, 2023 at 7:18 AM stephen.c...@rc-harwell.ac.uk < 00008f3604def7f0-dmarc-requ...@jiscmail.ac.uk> wrote: > Hi Careina, > > Without knowing what's in your protein buffer or crystallisation condition > it's hard to comment. > > Best wishes, > Steve > > Dr Stephen Carr > Research Complex at Harwell (RCaH) > Rutherford Appleton Laboratory > Harwell Oxford > Didcot > Oxon OX11 0FA > United Kingdom > Email stephen.c...@rc-harwell.ac.uk > tel 01235 567717 > ------------------------------ > *From:* CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of > careinaedgo...@yahoo.com <000002531c126adf-dmarc-requ...@jiscmail.ac.uk> > *Sent:* 08 November 2023 15:00 > *To:* ccp4bb <ccp4bb@jiscmail.ac.uk> > *Subject:* [ccp4bb] What could these crystals be? > > Hi all > We have been trying with no success to crystalize a protein. Recently we > got these strange shape "crystals". They are hard and flat but they do not > diffract at all. Any ideas as to what could cause this? > Careina > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > > This email and any attachments may contain confidential, copyrightand or > privileged material, and are for the use of the intended addressee only. If > you are not the intended addressee or an authorized recipient of the > addressee, please notify us of receipt by returning the e-mail and do not > use, copy, retain, distribute or disclose the information in or attached to > this email. > > > > Any views or opinions presented are solely those of the author and do not > necessarily represent those of the Research Complex at Harwell. > > > > There is no guarantee that this email or any attachments are free from > viruses and we cannot accept liability for any damage which you may sustain > as a result of software viruses which may be transmitted in or with the > message. > > > > We use an electronic filing system. Please send electronic versions of > documents, unless paper is specifically requested. > > > > This email may have a protective marking, for an explanation, please see: > > > http://www.mrc.ac.uk/About/informationandstandards/documentmarking/index.htm > . > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/WA-JISC.exe?SUBED1=CCP4BB&A=1 This message was issued to members of www.jiscmail.ac.uk/CCP4BB, a mailing list hosted by www.jiscmail.ac.uk, terms & conditions are available at https://www.jiscmail.ac.uk/policyandsecurity/
