G. Tsoucaris

Making make-up in Ancient Egypt

The extensive use of green, white and black make-up has been known since the earliest periods of Egyptian history,. We have investigated cosmetic powders dating from between 2000 and 1200 BC that were preserved in their original containers. Quantitative crystallographic and chemical analysis of the organic and mineral components of the powders enabled us to identify two natural lead-based compounds: crushed ore of galena (PbS) and cerussite (PbCO3). We also found two unexpected constituents: laurionite (PbOHCl) and phosgenite (Pb2Cl2CO3). Because they are neither natural extracted ores nor products resulting from subsequent ageing or chemical modification, laurionite and phosgenite appear to be synthetic products manufactured by the Egyptians using ‘wet’ chemistry.

Microbeam synchrotron imaging of hairs from ancient Egyptian mummies.

Developments in microfocus synchrotron techniques have led to new results regarding the long-term alteration of archaeological samples of biological origin. Here, ancient hair samples from two Egyptian mummies have been analyzed using a conjunction of structural and elemental synchrotron methods. In this favored context of conservation, structural analysis revealed a remarkable preservation of keratin supramolecular organization at any observed length scale. Bulk keratin structure has therefore not been modified significantly over 2000 years. However, infrared spectroscopy indicated a partial disorganization of keratins close to the hair surface through polypeptide bond breakage. Elemental mapping showed a strongly heterogeneous distribution which can be related to mummification and cosmetic treatments.

Hair Fiber as a Nanoreactor in Controlled Synthesis of Fluorescent Gold Nanoparticles

The synthesis and detailed characterization of gold nanoparticles (AuNPs) inside human hair has been achieved by treatment of hair with HAuCl(4) in alkaline medium. The AuNPs, which show a strong red fluorescence under blue light, are generated inside the fiber and are arranged in the cortex in a remarkably regular pattern of whorls based on concentric circles, like a fingerprint. It opens an area of genuine nanocomposites with novel properties due to AuNPs inside the hair shaft.

Inclusion of spironolactone in cyclomaltoheptaose: A guest affected by the hospitality of the host

Abstract A study of the interaction of spironolactone (SP) and cyclomaltoheptaose (β-cyclodextrin, βCD), using molecular graphics, shows a possible stable 1:2 SP/βCD inclusion complex. The complex was prepared by coprecipitation from an aqueous solution and inclusion was confirmed in the solution and solid state, using the solubility technique, i.r. spectroscopy, and d.s.c. N.m.r. spectroscopy revealed chemical modification (S-deacetylation) of SP due to the environment of the βCD.

A Synchrotron X-ray diffraction study of Egyptian cosmetics

This chapter draws attention to the synchrotron X-ray diffraction study of Egyptian cosmetics. Unguents, creams, powders and eye-paints were commonly used and kept in receptacles with characteristic shapes made of stone (alabaster, hematite, and marble), ceramic, wood, or reed. These receptacles had been placed in tombs as burial artefacts. Previous studies have shown that the make-up was used since the earlier periods (around 4000 EC for the pre-dynastic times) in relation to its aesthetic, hygienic, therapeutic, and religious functions. Their function is respectively to “clean” the gods face and to enable him to “see through Horuss eye.”These documents also describe the symbolic role that the ancient Egyptians attributed to cosmetics in maintaining cosmic order. The analysis of cosmetics as used in Ancient Egypt reveals the great variety of compositions using lead compounds along with chemical synthesis. This shows that 4000 years ago, people already wanted more impact from their use of cosmetics than simply highlighting of the eyes.

Ab initio determination of a crystal structure by means of the Schrödinger equation

It is shown that the use of the Schrödinger equation may lead to the ab initio determination of the positions of the nuclei in a crystal, given a limited number of diffracted-beam intensities. In particular, it is shown that an extremely simplified Schrödinger equation in physical momentum space provides a sufficiently sound theoretical basis to develop an algorithm using diffraction data alone. This algorithm has been tested with a known 41 atom crystalline structure (not including hydrogen atoms) in space group P1. The extracted information is sufficient to determine the positions of all atoms. In addition, theoretical developments relevant to the connection between momentum space in quantum mechanics and diffraction theory have been formulated.

Unveiling the Structure of Ancient Lead Pigments Example of “Lead White”

Although the basic lead carbonate naturally occurs as the rare mineral hydrocerussite, it has been produced artificially since the early historical times and extensively used for artistic and cosmetic purposes (the “lead white”; pigment). Lead white is the most important of all lead pigments and, not overlooking the special uses of lime white in wall painting, it is the most important of all white pigments. During the Antiquity, it is used as a face cream and ancient authors often laughed at its abusive use: “Are you an ape with white lead,or the ghost of some old hag returned form the dark borderlands of death?”; - Aristophanes (455-388 BC), Ecclesiazusae (ed. Eugene O’Neill, Jr.), 1049. It was the only white pigment used in European easel painting until the nineteenth century and it became the major component of white building painting. Its fabrication was forbidden in 1915 but it has been used until the middle of the century. This wide use explains why white lead is still involved in the current public health problem concerning children saturnism.

The crystallographic symmetry test for the correctness of a set of phases

One of the most important problems in the application of direct methods for large structures is to establish reliable consistency criteria for the correctness of a phasing trial. The introduction in the twin variables method [Bethanis, Tzamalis, Hountas, Mishnev & Tsoucaris (2000). Acta Cryst. A56, 105-111] of a new criterion based on the crystallographic symmetry consists of testing the phase extension and refinement algorithm by deliberately sacrificing the space-group-symmetry information in the auxiliary variable set then using its gradual re-appearance as a criterion for correctness. In the present paper, the crystallographic symmetry test has been used in the implementation of the twin algorithm in two different ways: (i) as an overall test throughout the iterations that is likely to reflect the correctness of the phasing procedure for each one of the extension trials in a macromolecular phasing environment; (ii) as a convenient criterion to determine the optimum cycle for freeing the initial phases used by the algorithm for the phase-extension procedure.

Convergence study of a Schrödinger-equation algorithm and structure-factor determination from the wavefunction

The algorithm [Bethanis, Tzamalis, Hountas & Tsoucaris (2002). Acta Cryst. A58, 265-269] which reformulates the quantum-mechanical problem of solving a Schrödinger (S) equation in a crystallographic context has been upgraded and tested for many aspects of convergence. The upgraded algorithm in reciprocal space aims at determining a wavefunction Phi(H) such that (a) Phi(H) fulfils the S equation within certain precision and (b) Phi(H) minimizes by least squares the differences between the calculated structure factors from the wavefunction and the observed ones. Calculations have been made with three molecules (11, 41 and 110 non-H atoms in the asymmetric unit) for different numbers of initially given phases. Three main questions have been addressed: (I) Does the iterative calculation of the wavefunction converge? (II) Do the calculated wavefunctions converge to a unique set of Phi(H) values independent of the initial random set of Phi(H)? (III) Is the calculated Phi(H) set a good approximation of a wavefunction able to produce within certain errors the correct values of the phases of the structure factors? Concerning questions (I) and (II), our results give a strong hint about fast convergence to a unique wavefunction independent of the arbitrary starting wavefunction. This is an essential prerequisite for practical applications. For question (III) in the case closer to the ab initio situation, the final mean phase error, respectively, for the three structures is 3, 26 and 28 degrees. The combination of (a) and (b) in the upgraded algorithm has been proved crucial especially for the results concerning the larger structures.

Is Supramolecular Organisation a Key Factor for Long Term Preservation

The long term alteration of organic archaeological materials often raises difficult questions concerning the preferential points of attack or “weakest points” of the material, and the subsequent chemical reactions leading to its transformation. These transformations are closely related to the archaeological context, and their study can shed new light on the history and significance of ancient objects. The stability of a solid organic material involves multiple attractive interactions between the constituent molecules. These interactions contribute to the internal cohesion of the material and are involved in chemical degradation processes. The branch of Chemistry studying molecular interactions is Supramolecular Chemistry, and we will examine in the present paper general principles applied to keratinised tissues (hair, skin, nail), a particular family of biological materials that often exhibit long-term preservation. A remarkable feature of these organic materials is the existence of precisely organised structures atseven successive length scalesranging from the atomic scale (diameter of a single keratin molecule: one nanometre) to the macroscopic scale (diameter of human hair: several tens of micrometers). In the present lecture we will try to answer the question: can the supramolecular organisation of such a complex material account for its long term preservation?