Sir

In an effort to condense Letters to Nature in the printed version of the journal, there is a risk that some of the critical information necessary for an independent judgement of the quality of biological structural information may be omitted, appearing only in the Supplementary Information available in the online version.

These indicators are: the resolution of the structure determination; the 'free R factor' (an unbiased metric of agreement between the experimental X-ray diffraction data and the derived molecular model); and the Ramachandran analysis (the only independent measure of a model's stereochemical reasonableness).

In some cases, this critical information — which takes little space — is excluded, whereas non-essential information, such as the location of the synchrotron beamlines where the diffraction data were collected and the names of standard programs used to determine the structure, is included in the printed version. It is often inconvenient to have to access the Internet while reading a paper in print, in order to obtain these essential quality indicators.

The crystallographic community has had a welcome change of heart on agreement about validation criteria for structural models — critical use of the indicators I have mentioned above — and on data availability via deposition in publicly available databases. Given that Nature has fully supported this shift, should the journal not also enforce minimal, accessible reporting of a structure's quality indicators in the printed versions of papers, rather than allowing authors to deposit all this information in the online-only format of Supplementary Information?