Increased resolution data from a large unit cell crystal collected at a third-generation synchrotron X-ray source

Abstract

A third‐generation synchrotron source was used to collect data from crystals with a very large unit cell. There was an increase in the effective resolution of the data from 5 to 3.5 Å. Data were collected on crystals of HK97 mature empty capsids, space group P21, with unit‐cell parameters a = 580, b = 625, c = 790 Å, β = 90.0°. Like other crystals with very large unit‐cell dimensions, the intensity falls off rapidly as a function of resolution, with a precipitous drop beginning at 9 Å resolution. Synchrotron data from these crystals were previously observed at the CHESS F1 beamline to about 3.5 Å resolution, but the intensities could not be accurately measured beyond 5 Å. In experiments conducted at the Advanced Photon Source (APS) beamline 14‐BM‐C, data from identical crystals could be processed to a resolution of 3.5 Å. The lifetime of the crystals in the beam was increased from one exposure per crystal volume to between four and eight exposures per crystal volume. More than 500 images were collected in two trips, allowing the extension of the resolution of the data set and the structure determination to 3.5 Å resolution. Factors in the increased resolution may include X‐ray flux, beamline geometry and low background scatter. These results suggest that other crystals with large unit cells and pronounced intensity falloff with resolution may benefit from the use of this or similar beamlines.

Topologically Linked Protein Rings in the Bacteriophage HK97 Capsid

“…Determination of the particle orientation and position at 7 A resolution was described (16). The data were subsequently extended to 3.45 A resolution (17), and a total of 22 million reflections (4.8 million unique) were measured on unfrozen crystals. The phasing to 3.6 A resolution is described in Table 1.…”

Beam-size effects in radiation damage in insulin and thaumatin crystals

“…These experiments often require the collection of significantly more than 180 of data in order to obtain a sufficient data redundancy, and they are carried out at long wavelengths where careful flux adjustment is required to compensate for the increase of the photoelectric cross section, which would otherwise entail a higher dose to the crystal thereby causing more rapid sample deterioration for the same incident flux. Another way to reduce radiation damage and improve data quality in mediumresolution data collections, which will not be discussed here, is to focus the beam on the detector, whereby the flux density will be reduced on the sample but maximized on the detector (Wikoff et al, 2000).…”

The mechanism of high-pressure-induced ordering in a macromolecular crystal

“…The size of the beam at the sample position was 600 mm horizontally and 350 mm vertically. This set-up exposes the entire crystal volume and reduces radiation damage, as described by Wikoff et al (2000).…”