Ft-Ir spectroscopy and microspectroscopy of ancient egyptian embalmed heads from the Museum of Anthropology and Ethnography of the University of Turin

Fourier Transform Infrared (FT-IR) spectroscopy and microspectroscopy were used to gain insight into the state of preservation of the skin of two Egyptian dynastic embalmed heads (VI-XI Dynasty) and one Predynastic mummy. The mummies came from the necropoles of Asiut and Gebelein (Upper Egypt), and are curated at the Museum of Anthropology and Ethnography of the University of Turin. The state of preservation was inferred from the biochemical composition of the skin, in particular from the secondary structure of the proteins. The secondary structure of the skin protein was investigated by studying the position and shape of the Amide I band, analyzed by means of self-deconvolution techniques. The increase in the b-sheet relative amount in the protein conformation of the mummified tissues with respect to the modern skin, was correlated with aging processes of collagen and keratins, the most abundant proteins in the skin. The steps of the degradation processes are hypothesized and described, and the differences in the recorded state of degradation were ascribed to the diverse mummification procedures undergone by the studied human remains. Other non-skin-derived features in the IR micro spectra of the embalmed specimens were detected and identified either as embalming materials or microbial attack traces

Hydration structure analysis of lysozyme amyloid fibrils by Thermally Stimulated Depolarization Currents (TSDC) technique

Thermally stimulated depolarization currents technique has been employed to investigate the conformation of hen egg white lysozyme in native and amyloid form, in the state of powder at very low hydration level. The technique, able to detect the current generated by thermally activated reorientation of water dipoles previously oriented by an electric field, exploits H2O dipoles, belonging to the solvation shell, as a probe to gain information on the protein conformation. Large differences are detected between the TSDC spectra related to the two different protein conformations, for what concerns the number and position of the main peaks, the native form displaying two peaks, at TM = 175 K and at TM = 297 K, and the amyloid one, only one at intermediate temperature (TM = 235 K). The spectra have been compared with those monitored for poly-L-lysine (MW 80400), as received and prepared in different ways, i.e. α-helix, β-sheet, and coil conformation, respectively. The poly-L-lysine spectra show specific features that can be attributed to water texture around the secondary structure adopted by the macromolecule: the results stress how TSDC technique is a tool of great potential value in the conformational analysis of proteins

Theoretical analysis of the adsorption of metal ions to the surface of melanin particles

We have re-examined the problem of the interaction of melanins with metal ions. Metal ions are normal constituents of the pigment, but in some cases they can be related to pathologies, mainly at the level of the skin (Cu2+ and Fe3+) and of the central nervous system (Fe2+ and Mn2+). Our approach has been based on the mechanisms of adsorption on the particle surface, by the use of theoretical adsorption isotherms and kinetic models. Although this analysis doesn’t give detailed information on the specific sites involved, it is useful to better characterize the surface behaviour of the colloidal melanin. The results obtained demonstrate that the affinity of melanin for metal ions is very high, comparable to the most efficient materials employed in decontamination and recovery techniques. Moreover, our results demonstrate that three-parameters models, such as Langmuir-Freundlich, Redlich-Peterson and Tóth equations, fit the experimental data with great accuracy and that the adsorption follows pseudo-second-order kinetics

Binding of chemicals to melanins re-examined: Adsorption ofsome drugs to the surface of melanin particles

This work presents a first attempt to study the interaction of some drugs with melanins, realistically considered as solid aggregates of primary particles. This situation appears similar to the adsorption of organic molecules onto the surface of colloidal absorbers, as active carbon, zeolites or titanium dioxide. We have applied some of the most popular theoretical models used in technological applications with the aim to give a more realistic picture of the melanin–drug interaction responsible for some observed side effects in vivo. Moreover, this approach can simplify the problem of the search of the physical parameters dominating the binding processes, by reducing the phenomenon to a simple physisorption/chemisorption, at least in a first approximation. We have studied the binding to melanin of gentamicin, methotrexate and chlorpromazine, molecules with different physico-chemical and structural characteristics. Our study demonstrates the possibility to fit experimental adsorption data with Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich equations. In such a way we obtain binding parameters useful to characterize the drug–surface interaction in terms of energy and of mean affinity. D 2005 Elsevier B.V. All rights reserved. Keywords: Melanin; Drugs; Adsorption isotherms; Sorption kinetics; Surface interaction; Chemisorptio