One issue is whether the extra data for the 80% solvent volume consists of independent measurements. The references below suggest that the required "oversampling " of intensities is given when one has a 50% solvent volume.
J. Miao, D. Sayre, and H. N. Chapman, "Phase retrieval from the magnitude of the Fourier transforms of nonperiodic objects," J. Opt. Soc. Am. A 15, 1662-1669 (1998) Or Q. Shen<http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Shen%2C%20Q%2E>, I. Bazarov<http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Bazarov%2C%20I%2E> and P. Thibault<http://scripts.iucr.org/cgi-bin/citedin?search_on=name&author_name=Thibault%2C%20P%2E> Diffractive imaging of nonperiodic materials with future coherent X-ray sources J. Synchrotron Rad. (2004). 11, 432-438 Of course the above assumes everything is ideal. Colin From: CCP4 bulletin board [mailto:[email protected]] On Behalf Of Guangyu Zhu Sent: 15 March 2013 00:28 To: ccp4bb Subject: [ccp4bb] Resolution and data/parameter ratio, which one is more important? I have this question. For exmaple, a protein could be crystallized in two crystal forms. Two crystal form have same space group, and 1 molecule/asymm. One crystal form diffracts to 3A with 50% solvent; and the other diffracts to 3.6A with 80% solvent. The cell volume of 3.6A crystal must be 5/2=2.5 times larger because of higher solvent content. If both data collecte to same completeness (say 100%), 3.6A data actually have higher data/parameter ratio, 5/2/(3.6/3)**3= 1.45 times to 3A data. For refinement, better data/parameter should give more accurate structure, ie. 3.6A data is better. But higher resolution should give a better resolved electron density map. So which crystal form really give a better (more reliable and accurate) protein structure? -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised 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 the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail 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. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom
