Corinne Sanchez

Full-field XANES analysis of Roman ceramics to estimate firing conditions—A novel probe to study hierarchical heterogeneous materials

Roman black gloss ceramics from two different locations and separated by 50–80 years were investigated by X-ray absorption near edge structure analysis in full field hard X-ray transmission microscopes. These spectro-microscopy measurements were complemented by Raman spectroscopy, and X-ray diffraction spot analyses to gain insights into possible differences in manufacturing technology. Our results indicate that the two vessels underwent significantly different firing protocols, suggesting that there was a surprisingly quick evolution of a complex technological process in response to changing needs and tastes of a burgeoning empire. Furthermore, our results show that the ability of the full field X-ray spectro-microscope to investigate large sample areas (from hundreds of µm2 to as much as 2 mm2) with high spatial resolution (of 300 nm down to 30 nm) together with its ability to correlate sample porosity (derived from tomography) with the distribution of chemical phases makes it an invaluable tool in the investigation of nanoscale processes in hierarchically heterogeneous chemical systems—from Roman ceramics to some of the most advanced technological products of today.

Rotor architecture in the yeast and bovine F1-c-ring complexes of F-ATP synthase.

The F(1)F(O)-ATP synthase is a rotary molecular nanomotor. F(1) is a chemical motor driven by ATP hydrolysis while F(O) is an electrical motor driven by the proton flow. The two stepping motors are mechanically coupled through a common rotary shaft. Up to now, the three available crystal structures of the F(1)c(10) sub-complex of the yeast F(1)F(O)-ATP synthase were isomorphous and then named yF(1)c(10)(I). In this crystal form, significant interactions of the c(10)-ring with the F(1)-head of neighboring molecules affected the overall conformation of the F(1)-c-ring complex. The symmetry axis of the F(1)-head and the inertia axis of the c-ring were tilted near the interface between the F(1)-central stalk and the c-ring rotor, resulting in an unbalanced machine. We have solved a new crystal form of the F(1)c(10) complex, named yF(1)c(10)(II), inhibited by adenylyl-imidodiphosphate (AMP-PNP) and dicyclohexylcarbodiimide (DCCD), at 6.5Å resolution in which the crystal packing has a weaker influence over the conformation of the F(1)-c-ring complex. yF(1)c(10)(II) provides a model of a more efficient generator. yF(1)c(10)(II) and bovine bF(1)c(8) structures share a common rotor architecture with the inertia center of the F(1)-stator close to the rotor axis.

Evolution of terra sigillata technology from Italy to Gaul through a multi-technique approach

To understand how the terra sigillata technology was transferred from Italy to Gaul, a large corpus of samples from various worskshops was studied by using standard laboratory techniques (Raman spectroscopy, SEM, electron microprobe analysis and colorimetry). Based on these results, a few representative samples were selected and investigated by synchrotron radiation at ALS on the 12.3.2 microdiffraction beamline. The beamline is very adapted to the crystallographic study of thin layers and allows us to determine precisely the mineral composition of the sigillata slips. The set of findings revealed significant differences between the Italic and Gallic slips, which suggest a modification in the manufacturing process. The transfer of the sigillata technique to Gaul is associated with an increase of the firing temperatures due to the use of more refractory clay. This change has no significant influence on their esthetic appearance (brilliance and color) but modify their mechanical properties, resulting in a stronger resistance for the Gallic slips. The implication of these results in archeological context is discussed. In particular, we will try to propose assumptions on the reason for the change in the manufacturing process.

Unambiguous structure of atractyloside and carboxyatractyloside

Atractyloside (ATR) was characterized in 1868 and until now structural studies on diterpenic moiety had been done through the characterization of ATR derivatives; while the glycosidic moiety seemed to be a β-D-glucopyranose a recent crystal structure of the mitochondrial ATP/ADP carrier in complex with CATR showed an α-D-glucopyranose. We decided to re-examine the ATR and CATR structures by crystallographic study of ATR.