The ADDit™ Additives Screen contains 96 different small molecule and salt solutions that have been found to be effective in aiding the crystallization of biological macromolecules. It comprises a range of crystal growth promoters and nucleation suppressants including detergents, chelators, reducing agents, volatile and non-volatile organics, heavy atoms and salts. The purpose of these solutions is to increase the quality and/or size of initial crystal hits when added to a lead condition. The additives are delivered in a 96 well block containing 1 ml of solution in each well at 10x the recommended final concentration. The block is designed for easy use with a single or multi-channel pipette, the latter allowing for rapid setup of a full 96 formulation optimization screen. Furthermore, the additives are organized in the block according to category in order to facilitate the setup of subsequent refinement screens that lack some of the additive classes.

The preferred use of this screen follows this scheme:

1. Identify a non-perfect hit (i.e. microcrystals, weakly diffracting crystals, shiny precipitate.)
2. Supplement 96 identical crystallization experiments with 10% (v/v) of additive screen component.
3. Inspect and note change in morphology of crystals.
4. Use the improved crystals for diffraction or follow up hits with changed morphology with a one-dimensional fine scree (e.g vary additive component from 0.5, 2, 5, 8, 15 to 20% (v/v)).