Characterization of Color Production in Xalla´s Palace Complex, Teotihuacan

A multi-analytical approach was used to characterize color remains from Xalla, a Teotihuacan palace complex (project Teotihuacan, Elite and Government. Excavations in Xalla led by Linda R. Manzanilla). Color samples were obtained from polished lithic instruments and pigment ores. Those samples were analyzed combining microscopic and spectroscopic techniques. Our results coincide with previous studies in Teotihuacan, with the chromatic palette displaying a predominance of iron oxides such as hematite, yellow ochre and natural earths, as well as malachite, celadonite and glauconite. We have enlarged the corpus of raw materials with the characterization of jarosite and bone white and mica as aggregate. The identification of raw materials crossed with functional analysis of polished lithic artefacts suggests a production and application process for the pigmenting materials that were divided in four phases, from the crushing of the raw material to the application and finishing of the painted surfaces

Reorganization Energy for Internal Electron Transfer in Multicopper Oxidases.

We have calculated the reorganization energy for the intramolecular electron transfer between the reduced type 1 copper site and the peroxy intermediate of the trinuclear cluster in the multicopper oxidase CueO. The calculations are performed at the combined quantum mechanics and molecular mechanics (QM/MM) level, based on molecular dynamics simulations with tailored potentials for the two copper sites. We obtain a reorganization energy of 91-133 kJ/mol, depending on the theoretical treatment. The two Cu sites contribute by 12 and 22 kJ/mol to this energy, whereas the solvent contribution is 34 kJ/mol. The rest comes from the protein, involving small contributions from many residues. We have also estimated the energy difference between the two electron-transfer states and show that the reduction of the peroxy intermediate is exergonic by 43-87 kJ/mol, depending on the theoretical method. Both the solvent and the protein contribute to this energy difference, especially charged residues close to the two Cu sites. We compare these estimates with energies obtained from QM/MM optimizations and QM calculations in a vacuum and discuss differences between the results obtained at various levels of theory