Thaumatin

This example illustrates data collection with the PlateMate configured on a Rigaku MicroMax-007 HF X-ray generator equipped with a AFC11-chi goniometer and a Saturn 944 HG CCD detector. A 200 µm thaumatin crystal, located in well A10 of a Greiner low-profile plate, was centered in the X-ray beam. 50° of data were then collected at room temperature using an exposure time of 30 seconds per 0.25°. The total data collection time for the data set was 1 hour 40 minutes.




Thaumatin crystal used for data collection


Example of diffraction image obtained with an
exposure time of 30 seconds for 0.25°.



Detector distance Δω Osc. range # img Exp time Total exposure time
80 mm 0.25° -30° < ω < 20° 200 30 sec 1 hr 40 min

Data collection parameters



Space group P41212
Unit cell a = 58.70 Å
c = 151.59 Å
Resolution 2.6 Å
Mosaicity 0.38 - 0.40°
Total reflections 26735
Unique reflections 8802
Rejected reflections 17 = 0.06%
Completeness 68.6% (42.8%)
Redundancy 4.4 (2.9)
I/σ(I) 30.2 (6.8)
Linear Rmerge4.9%
χ² 1.193 (0.7173)

Crystal parameters and scaling statistics obtained in HKL-3000R
Numbers in () are for last shell.




Plots of χ² and R-factor vs. resolution.
Orange: χ² merged; Blue: χ² anomalous;
Green: R-factor merged; Red: R-factor anomalous


Plots of I/σ(I) vs. resolution.
Blue: I/σ(I) merged; Red: I/σ(I) anomalous


The thaumatin structure was solved using molecular replacement methods in HKL-3000R. HKL-3000R used the program MOLREP and PDB ID ‘1RQW’ as a starting model, from which ligands and waters were removed. Using data to 3.0 Å, MOLREP readily found a solution.

The model was then subjected to 5 cycles of rigid body refinement using REFMAC and data to 3.0 Å, followed by 10 cycles of restrained atomic refinement using data to 2.6 Å. The Rfac and Rfree values, without the localized waters or correcting for bulk solvent contribution, were 17.8% and 22.2%, respectively.



2Fo-Fc maps contoured at 1.5σ