Professor Caulkins published the paper below in January 2022:
Holmes, J. B.; Liu, V.; Caulkins, B. G.; Hilario, E.; Ghosh, R. K.; Drago, V. N.; Young, R. P.; Romero, J. A.; Gill, A. D.; Bogie, P. M.; Paulino, J.; Wang, X.; Riviere, G.; Bosken, Y. K.; Struppe, J.; Hassan, A.; Guidoulianov, J.; Perrone, B.; Menink-Vigier, F.; Chang, C. A.; Long, J. R.; Hooley, R. J.; Mueser, T. C.; Dunn, M. F.; Mueller, L. J. Imaging Active Site Chemistry and Protonation States: NMR Crystallography of the Tryptophan Synthase α-Aminoacrylate Intermediate Proc. Natl. Acad. Sci. 2022, 119, DOI: 10.1073/pnas.2109235119.