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Formation of a highly dense tetra-rhenium cluster in a protein crystal and its implications in medical imaging

DOI: 10.1107/S2052252519006651 DOI Help

Authors: Alice Brink (University of the Free State; University of Manchester) , John Helliwell (University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Iucrj , VOL 6

State: Published (Approved)
Published: July 2019

Open Access Open Access

Abstract: The fact that a protein crystal can serve as a chemical reaction vessel is intrinsically fascinating. That it can produce an electron-dense tetranuclear rhenium cluster compound from a rhenium tri­carbonyl tri­bromo starting compound adds to the fascination. Such a cluster has been synthesized previously in vitro, where it formed under basic conditions. Therefore, its synthesis in a protein crystal grown at pH 4.5 is even more unexpected. The X-ray crystal structures presented here are for the protein hen egg-white lysozyme incubated with a rhenium tri­carbonyl tri­bromo compound for periods of one and two years. These reveal a completed, very well resolved, tetra-rhenium cluster after two years and an intermediate state, where the carbonyl ligands to the rhenium cluster are not yet clearly resolved, after one year. A dense tetranuclear rhenium cluster, and its technetium form, offer enhanced contrast in medical imaging. Stimulated by these crystallography results, the unusual formation of such a species directly in an in vivo situation has been considered. It offers a new option for medical imaging compounds, particularly when considering the application of the pre-formed tetranuclear cluster, suggesting that it may be suitable for medical diagnosis because of its stability, preference of formation and biological compatibility.

Journal Keywords: rhenium tetranuclear clusters; thera­nostics; time-resolved protein crystallography; chemical crystallography; medical imaging

Subject Areas: Biology and Bio-materials, Medicine

Instruments: I04-Macromolecular Crystallography