CrysAlis^Pro Tip

One Bad Reflection

Here is a short video from Lee Daniels to show you how to find, validate and remove that one bad reflection ruining your otherwise great structure.

Lee Daniels addresses how to troubleshoot a problematic reflection in an integrated crystallographic dataset using Olex2, SHELX, and CrysAlis^Pro software. The example focuses on a dataset that appears high quality based on standard indicators such as I/σ(I), R_int, and the absence of significant peaks in the difference map, yet exhibits an unusually high R-value and a poor goodness-of-fit.

To diagnose the issue, Lee examines the “bad reflections” list in Olex2 and identifies a single large outlier flagged in red. The discrepancy is traced to a reflection that has an extremely high F_obs value compared to F_calc. Using CrysAlis^Pro, he locates this reflection in the frame data and discovers that it aligns with two hot pixels on the detector.

The tutorial emphasizes the value of inspecting individual reflections when standard refinement metrics suggest hidden issues and illustrates the practical use of software tools to resolve such anomalies