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instead promotes high concentration of La, Gd and Yb in solution (Figure 8). Thus, these alkaline fluids may be the key to transporting both F and REE in sufficient concentration to explain the common association of F and REE in nature, demonstrated both by the high amounts of fluorite observed in hydrothermal veins and the formation of the main REE ore minerals such as bastnaesite, a fluoro- carbonate (REECO3F).

These findings not only provide important information about the mechanisms that enable the hydrothermal concentration of REE in nature but may have further industrial applications, as they define a new alkaline route to extract REEs without recourse to destructive acids and potentially separate more valuable HREE from LREE.

PRINCIPAL PUBLICATION AND AUTHORS

Carbonate complexation enhances hydrothermal transport of rare earth elements in alkaline fluids, M. Louvel (a), B. Etschmann (b), Q. Guan (b), D. Testemale (c), J. Brugger (b), Nat. Commun. 13, 1456 (2022); https:/doi.org/10.1038/s41467-022-28943-z (a) Institute for Mineralogy, WWU Münster, Münster (Germany) (b) School of Earth, Atmosphere & Environment, Monash University, Clayton (Australia) (c) University Grenoble Alpes, CNRS, Grenoble INP, Institute Néel, Grenoble (France)

REFERENCES

[1] A. Migdisov et al., Chem. Geol. 439, 13-42 (2016). [2] D. Testemale et al., Rev. Sci. Instr. 76, 043905 (2005). [3] M. Louvel et al., Chem. Geol. 417, 228-237 (2015). [4] Q. Guan et al., Geochim. Cosmochim. Acta 330, 27-46 (2022).

solubility in acidic Cl-bearing fluids [4], suggesting a new mechanism to fractionate light REE (LREE: La to Eu) from the more valuable heavy REE (HREE: Gd to Lu, +Y).

Extended X-ray absorption fine structure (EXAFS) analysis, supported by quantum mechanical calculations, demonstrate that large polynuclear carbonate complexes of the form [REE3(CO3)2(OH)4]+ (Figure 9) are behind the enhanced solubility of Gd and Yb in carbonate-bearing fluids. Similar structures are expected for LREE as La, but are yet to be investigated.

Unexpectedly, the in-situ XAS measurements also reveal that the addition of fluorine to carbonate solutions does not result in the precipitation of REE fluoride phases but

The excited states of the oncogene Ras protein revealed by high hydrostatic pressure crystallography

High hydrostatic pressure macromolecular crystallography has been used to characterise the excited states of the Ras oncogene protein involved in many cancers. Putting Ras crystals under high pressure induces a phase transition within the crystal. Beyond this transition, segments that switch from one conformational state to another have been precisely localised in Ras structures at different pressures.

Proteins in solution are in equilibrium between several conformational states of slightly different free energies associated to different populations. The structures of their dominant ground states can be determined at atomic resolution using standard macromolecular crystallography, but it is much more difficult to get precise information about the low populated excited states. And yet, proteins interact with their different partners when they are in these excited states. It is therefore challenging to rationally design inhibitors specifically targeting these low- populated conformational states. High hydrostatic pressure crystallography (HPMX) is an ideal tool for determining the structure of these excited states with high precision. Pressure allows to populate the excited states, thus modifying the distribution of the populations of the various states.

Fig. 9: Proposed transport mechanism for REE in carbonate-rich alkaline fluids derived from the EXAFS analysis of Gd in 0.7m Na2CO3 solution (spectra collected at 200°C and 800 bars in the transparent autoclave at the BM30-FAME beamline). Photo: S. Ansermet, Bastnäsite-(Ce) from Mt Malosa, Malawi; sample MGL093126, Musée Cantonal de Géologie, Lausanne, Switzerland.