Related Experiment Video
Updated: Jun 12, 2026

Quantifying X-Ray Fluorescence Data Using MAPS
Published on: February 17, 2018
Quantifying instrument errors in macromolecular X-ray data sets
1University of Konstanz, Faculty of Biology, M647, D-78457 Konstanz, Germany. kay.diederichs@uni-konstanz.de
Abstract:
An indicator which is calculated after the data reduction of a test data set may be used to estimate the (systematic) instrument error at a macromolecular X-ray source. The numerical value of the indicator is the highest signal-to-noise [I/sigma(I)] value that the experimental setup can produce and its reciprocal is related to the lower limit of the merging R factor. In the context of this study, the stability of the experimental setup is influenced and characterized by the properties of the X-ray beam, shutter, goniometer, cryostream and detector, and also by the exposure time and spindle speed. Typical values of the indicator are given for data sets from the JCSG archive. Some sources of error are explored with the help of test calculations using SIM_MX [Diederichs (2009), Acta Cryst. D65, 535-542]. One conclusion is that the accuracy of data at low resolution is usually limited by the experimental setup rather than by the crystal. It is also shown that the influence of vibrations and fluctuations may be mitigated by a reduction in spindle speed accompanied by stronger attenuation.
Related Concept Videos
Systematic Error: Methodological and Sampling Errors
Sampling errors originate from improper sampling methods or the wrong sample population. These errors can be minimized by refining the sampling strategy. Defective instruments or faulty calibrations are the sources of instrumental...
NMR Spectrometers: Resolution and Error Correction
Statistical Analysis: Overview
One of the most commonly used statistical quantifiers is the mean, which is the ratio between the sum of the numerical values of all results and the...
Uncertainty in Measurement: Accuracy and Precision
Random and Systematic Errors
X-ray Diffraction of Biological Samples
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are scattered by the electron clouds around the sample atoms. The X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal crystal...

