title: A strategy for the study of the interactions between metal-dyes and proteins with QM/MM approaches: the case of iron-gall dye.
abstract: Historical textiles dyed with tannins usually show more extended degradation than fabrics dyed with other coloring materials. In order to shed light on this phenomenon we investigated the molecular interactions between tannin dyes and protein-based textiles using quantum-mechanical tools. In particular, we focused on the iron-gall complex with a fragment of α-helix wool keratin. We developed a step by step protocol which moves from the simplest ternary complexes with free amino acids (all treated quantum mechanically) to the more realistic system of the polypeptide fragment (treated at QM/MM level), passing through an intermediate model of interacting sites to evaluate the local environmental effects. The analysis of the interactions between the iron-gall complexes and free amino acids allowed us to identify possible coordination modes as well as determining their relative geometries. However, we also showed that only with the addition of the proteic environment a detailed picture of the interaction sites and binding modes can be achieved. An important role is in fact played by the microenvironment which can favor specific coordinations with respect to others due to both structural and electronic changes in the possible interaction sites.
authors.affiliation: Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, Pisa 56126, Italy. s.jurinovich@studenti.unipi.it
authors.forename: Sandro
authors.initials: S
authors.lastname: Jurinovich
authors.forename: Ilaria
authors.initials: I
authors.lastname: Degano
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mennucci
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D011506:Proteins / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D004396:Coloring Agents; D011506:Proteins; D007501:Iron