Although Hampton Research does offer specifically formulated Additive Screen and GRAS Additive, here is a tip when one already has a sparse matrix screen or two laying about the lab. When screening additives, try adding 50 microliters of each Crystal Screen reagent to 950 microliters of the "best" crystallization conditions thus far in order to see if any of the reagents in Crystal Screen might serve as good additives. Crystal Screen 2 is an especially good kit for this technique since Crystal Screen 2 contains numerous divalent cations, Jeffamine® Reagent, and a few other "novel" agents.

James R. Birtley and Stephen Curry. Crystallization of foot-and-mouth disease virus 3C protease: surface mutagenesis and a novel crystal-optimization strategy. Acta Crystallographica Section D, Volume 61, Part 5, Pages 646-650, May 2005. https://doi.org/10.1107/S0907444905007924

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