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In this paper, we propose a green route to prepare insoluble poly(vinyl alcohol) (PVOH) cast films with potential application as antimicrobial packaging. First PVOH films were cast from different aqueous solutions and analyzed by Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) to determine their physical properties under two storage conditions. In order to obtain insoluble films, PVOH was then crosslinked by citric acid (CTR) as confirmed by Nuclear Magnetic Resonance (NMR) analyses. The crosslinking reaction parameters (curing time, crosslinker content) were studied by comparing the characteristics of PVOH/CTR films, such as free COOH content and glass transition temperature (Tg) value, as well as the impact of the crosslinking reaction on mechanical properties. It was found that for 40 and 10 wt% CTR contents, 120 and 40 min of crosslinking times were necessary to bind all CTR respectively. Brittle films were obtained for 40 wt% CTR whereas 10 wt% CTR content led to ductile films. Finally, films containing hydroxypropyl-β- cyclodextrin (HPβCD), chosen as a potential vector of antimicrobial agent, were prepared. The obtained results show that the incorporation of HPβCD in the PVOH matrix does not mainly influence the physical and mechanical properties of the films. [ABSTRACT FROM AUTHOR]

New crystallographic structures of the response regulator CheY in association with CheA124–257, its binding domain in the kinase CheA, have been determined. In all crystal forms, the molecular interactions at the heterodimer interface are identical. Soaking experiments have been performed on the crystals using acetyl phosphate as phosphodonor to CheY. No phosphoryl group attached to Asp57 of CheY is visible from the electron density, but the response regulator in the CheY- CheA124–257 complex may have undergone a phosphorylation- dephosphorylation process. The distribution of water mole- cules and the geometry of the active site have changed and are now similar to those of isolated CheY. In a second soaking experiment, imido-diphosphate, an inhibitor of the phosphorylation reaction, was used. This compound binds in the vicinity of the active site, close to the N-terminal part of the first α-helix. Together, these results suggest that the binding of CheY to CheA124–257 generates a geometry of the active site that favours phosphorylation and that imido- diphosphate interferes with phosphorylation by precluding structural changes in this region. [ABSTRACT FROM AUTHOR]