Etray: a program for efficient design and recording of crystallization trials

Determination of conditions suitable for crystallizing macromolecules often involves many iterative trials. The current standard procedure of manual d esign of experiments (including manual calculation of volumes of reagents) and recording observations by hand, is tedious, susceptible to errors, make s organization of records and searches for patterns difficult, and is not s uited to automation. We have therefore written Etray, an open-source progra m that is freely obtainable over the Web, Elkin, C., Hogle, J., http://sbwe b.med.harvard.edu/similar to hogle/etray (2000), to automate record keeping , most aspects of experimental planning, and to facilitate computational an alyses of these results. Etray displays an image of a standard 24 well crys tal tray and allows the user to add reagents in appropriate concentrations to the wells, either individually or using tools for grid searches and inco mplete factorial design. Etray automatically calculates volumes of stock so lutions necessary to achieve the specified concentration, and contains tool s for sketching, commenting and scoring the well contents. Speech recogniti on features allow the observations to be spoken out loud while the investig ator looks into the microscope. An example of the use of Etray to design an d analyze an incomplete factorial crystallization experiment is presented. (C) 2001 Elsevier Science B.V. All rights reserved.