Investigation of the mechanism of photochemically-induced lysozyme crystallization

• Dimer that have the same alignment as the two adjacent molecules in a crystal exhibit as templates.
• Dimers that can become templates are formed between Tyr residues.
• The template is formed by the combination of Tyr53–Tyr53 residues.

This work examined the mechanism involved in photoinduced crystallization of a lysozyme, focusing on the structure of the photoproducts that lead to crystal growth. It was determined that dimers formed via linking of tryptophan (Trp) residues are preferentially produced when applying a high-excitation photon fluence. However, these dimers do not lead to crystal growth. A low fluence forms dimers via the combination of tyrosine (Tyr) residues, generating six types of Tyr–Tyr dimers. The dimer that originates from the linking of Tyr53 and Tyr53 has a configuration similar to that of the two adjacent, yet non-linked, lysozyme molecules in the crystal unit cell. The Tyr53–Tyr53 dimer hence acts as a template for lysozyme crystal nucleation.

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