  Data curation presents a challenge to all scientific disciplines to ensure
public availability and reproducibility of experimental data. Standards for
data preservation and exchange are central to addressing this challenge: the
Investigation-Study-Assay Tabular (ISA-Tab) project has developed a widely used
template for such standards in biological research. This paper describes the
application of ISA-Tab to protein titration data. Despite the importance of
titration experiments for understanding protein structure, stability, and
function and for testing computational approaches to protein electrostatics, no
such mechanism currently exists for sharing and preserving biomolecular
titration data. We have adapted the ISA-Tab template to provide a structured
means of supporting experimental structural chemistry data with a particular
emphasis on the calculation and measurement of pKa values. This activity has
been performed as part of the broader pKa Cooperative effort, leveraging data
that has been collected and curated by the Cooperative members. In this
article, we present the details of this specification and its application to a
broad range of pKa and electrostatics data obtained for multiple protein
systems. The resulting curated data is publicly available at
http://pkacoop.org.
