Buy article online - an online subscription or single-article purchase is required to access this article.
Download citation
Download citation
link to html
Frozen crystals of proteins, nucleic acids or other biological macromolecules often have mosaic spreads comparable to the maximum useful oscillation angles. It is, therefore, necessary to develop scaling methods that are independent of the exclusive use of full reflections. The Hamilton, Rollett and Sparks [Acta Cryst (1965), 18, 129-130] procedure for scaling frames of X-ray area-detector data has been generalized to utilize partial reflections by adding intensities of partial reflections from consecutive frames (method 1) or by correcting intensities of partial reflections, using a model to calculate the reflection partiality (method 2). Both methods have been applied to scaling and averaging of data-sets collected on crystals of biological macromolecules. The agreement factors of the scaled data are better when using method 1, although it often fails when there are rotation gaps between successive images or when the data redundancy is low. Method 2 is more stable and versatile, allowing scaling of data-sets with incompletely measured reflections and low redundancy. The major drawback of method 2 is its sensitivity to inaccuracy in calculated partiality. The actual values of the scale factors obtained with the two methods are within 5%. However, when the true value of the scale factor changes dramatically between consecutive frames (e.g. due to beam dumps and refills at a synchrotron source), the results of the two methods can differ by as much as 15% because method 1 produces physically wrong results. The scaling algorithm implemented in the commercially available program SCALEPACK is vulnerable to the same problems as method 1.

Subscribe to Journal of Applied Crystallography

The full text of this article is available to subscribers to the journal.

If you have already registered and are using a computer listed in your registration details, please email support@iucr.org for assistance.

Buy online

You may purchase this article in PDF and/or HTML formats. For purchasers in the European Community who do not have a VAT number, VAT will be added at the local rate. Payments to the IUCr are handled by WorldPay, who will accept payment by credit card in several currencies. To purchase the article, please complete the form below (fields marked * are required), and then click on `Continue'.
E-mail address* 
Repeat e-mail address* 
(for error checking) 

Format*   PDF (US $40)
   HTML (US $40)
   PDF+HTML (US $50)
In order for VAT to be shown for your country javascript needs to be enabled.

VAT number 
(non-UK EC countries only) 
Country* 
 

Terms and conditions of use
Contact us

Follow J. Appl. Cryst.
Sign up for e-alerts
Follow J. Appl. Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds