Hi Fairolniza, There is little detail to go on here - I'd double check everything including the processing. All things being equal, even with reduced acceleration, you should have the same crystal form.
That said, if there is a difference, I suspect it has little to do with any reduced acceleration directly on the growth process - Brownian motion probably dominates at this scale. Not having many details to go on and assuming the growth geometry used on the ground was similar to that on the flight I'd look to temperature as a possible culprit. Temperature control in a reduced acceleration environment is difficult (greatly reduced convection) and requires power (limited on a space vehicle). If I remember correctly Lipase has a pH dependent structural change between an open and closed state. I'd check your buffer dependance on temperature, the conditions recorded on the ground and in the flight, and check if the growth has occurred at the same pH in both. If not match the ground crystal experiment to that of the on orbit one (probably negatively biasing the ground). I assume you'd tried molecular replacement and know if there are any major structural changes between the two samples? Another possibility, although I'm not sure why it should cause a difference in the number of molecules per asymmetric unit, might be the presence of Marangoni convection. In vapor diffusion this is masked on the ground (unless you have volatile organic components) but present with reduced acceleration. For a shameless plug check out Macromolecular Crystallization in Microgravity, Snell and Helliwell, Reports in Progress in Physics, 68, 799-853 (2005) (http://iopscience.iop.org/0034-4885/68/4/R02). This has extensive details of the work in this field and some of the points above. Cheers, Eddie Edward Snell Ph.D. Assistant Prof. Department of Structural Biology, SUNY Buffalo, Senior Scientist, Hauptman-Woodward Medical Research Institute 700 Ellicott Street, Buffalo, NY 14203-1102 Phone: (716) 898 8631 Fax: (716) 898 8660 Skype: eddie.snell Email: esn...@hwi.buffalo.edu Telepathy: 42.2 GHz Heisenberg was probably here! ______________________________________ From: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] On Behalf Of ferrol shariff [ferrol2...@gmail.com] Sent: Sunday, July 10, 2011 4:10 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Same protein, different molecule numbers per ASU Hello and good day to everyone! :) I have some general questions on crystallography work. I hope you don't mind giving me some ideas. I have solved my lipase protein both ground-grown crystals and space-grown crystals with good resolutions (1.4A and 2.2A). They are the same protein from the same source, same purification methods, and produced crystals from the same crystallization conditions (except the gravity part). >From the data, it shows that both of them belong to the same space group >P212121. But they have different number of molecule per asymmetric unit. >Ground crystal= 1 molecule/ASU, Space crystal= 2 molecules/ASU. At the moment >i have problem explaining this issue. Is it normal to have such results? Same >protein with different number of molecule/ASU? I've been trying to get some references on this matter but so far i don't really get anything that can directly explain it. Furthermore, do i need to relate this with the gravity effect? I hope you don't mind sharing some experiences on crystallography especially regarding this matter. Thank you very much -- FAIROLNIZA "The advantage of the emotions is that they lead us astray, and the advantage of science is that it is not emotional" -Oscar Wilde, The Picture of Dorian Gray, 1891
