Metal-ion-responsive transcriptional regulators within the MerR family effectively discriminate between mono- and divalent metal ions. Herein we address the origin of the specificity of the CueR protein for monovalent metal ions. Several spectroscopic techniques were employed to study Ag(I) , Zn(II) , and Hg(II) binding to model systems encompassing the metal-ion-binding loop of CueR from E. coli and V. cholerae. In the presence of Ag(I) , a conserved cysteine residue displays a pKa  value for deprotonation of the thiol that is close to the physiological pH value. This property is only observed with the monovalent metal ion. Quantum chemically optimized structures of the CueR metal site with Cys 112 protonated demonstrate that the conserved Ser 77 backbone carbonyl oxygen atom from the other monomer of the homodimer is "pulled" towards the metal site. A common allosteric mechanism of the metalloregulatory members of the MerR family is proposed. For CueR, the mechanism relies on the protonation of Cys 112.

Metal ion responsive transcriptional regulators within the MerR family effectively discriminate between mono-and divalent metal ions. In this work we address the origin of the specificity of the CueR protein for monovalent metal ions. Several spectroscopic techniques were employed to study Ag I , Zn II , and Hg II binding to model systems encompassing the metal ion binding loop of CueR from E. coli and V. cholerae. In the presence of Ag I a conserved cysteine displays a pKa for deprotonation of the thiol close to physiological pH. This is unique to the monovalent metal ion. Quantum chemically optimized structures of the CueR metal site with Cys112 protonated demonstrate that the Ser77 backbone carbonyl oxygen is "pulled" towards the metal site. A common allosteric mechanism of the metalloregulatory members of the MerR family is proposed. For CueR the mechanism relies on a protonation switch of Cys112.

Cys-Tyr-(YY), targeting Cd(II) ion sensing, was synthesized on various solid supports including two resins, as well as glass and quartz surfaces. The synthesis was based on the Fmoc (9-fluorenylmethoxycarbonyl) and the APTES (3-aminopropyltriethoxysilane) methodologies on the resin and silica supports, respectively. The immobilized ligand, except when coupled to a hydrophobic benzhydrylamine resin, showed a remarkably efficient, pHdependent Cd(II) capturing ability with a maximum binding capacity around neutral pH. The effect of contact time and metal ion concentration was also studied with a hydrophilic resin supported peptide (YY-NTG). The interaction of YY-NTG with Cd(II) was investigated by pH-potentiometric titrations in aqueous samples containing the resin beads and Cd(II). These studies, together with metal ion capturing experiments under buffer-controlled pH, prove that each immobilized peptide can bind one Cd(II) ion at pH=7.0 in the presence of one equivalent metal ion or metal ion excess. For Cd(II) binding to YY-NTG a notably high, K=1.310 10 apparent stability constant was determined (1:1 metal-to-ligand ratio, pH=7.0). Analytical results suggests that the concentration of Cd(II) can be measured below 200 nM with this silica-supported peptide. The usefulness of the probe was demonstrated by fluorescence spectroscopy.

This work demonstrates the preparation, structural characterization, and the kinetics of the drug release of hyaluronic acid (HyA)-based colloidal drug delivery systems which contain hydrophobic ketoprofen (KP) as model molecule. Because of the highly hydrophilic character of HyA the cross-linked derivatives at different cross-linking ratio have been synthesized. The hydrophobized variants of HyA have also been produced by modifying the polymer chains with cetyltrimethylammonium bromide (CTAB) at various HyA/CTAB ratios. Due to modifications the coherent structure of HyA changes into an incoherent colloidal system that were verified by rheological investigations. Nearly 70% of the encapsulated KP dissolve from the totally cross-linked HyA carrier but the release rate of KP is about 20% (after 8 h) from the CTAB-modified colloidal system at HyA monomer/CTAB 1:0.8 mass ratio. It has been verified that the modified HyA may be a potential candidate for controlled drug release of hydrophobic KP molecules.