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This work describes the adsorption of pyrene molecules on a Ag(111) surface. We first demonstrate that despite its high vapor pressure, pyrene molecules can form ordered films under ultrahigh vacuum conditions, presenting a well-contrasted diffraction pattern. Studies using high-resolution electron energy loss spectroscopy and ultraviolet photoelectron spectroscopy provide compelling evidence of a physisorbed system where the molecules only weakly interact with the substrate underneath. Comparisons with theoretical calculations, as well as with data obtained from optical spectroscopies, clearly demonstrate that the vibrational and electronic properties of the adsorbed molecules are similar to the expected ones for pristine pyrene. Finally, we used temperature-programmed X-rays photoelectron spectroscopy to study the desorption process of pyrene on the Ag(111) surface and estimate its activation energy to desorption.

Carbon nanotube electrodes were modified with ferrocene and laccase using two different click reactions strategies and taking advantage of bifunctional dendrimers and cyclopeptides. Using diazonium functionalization and the efficiency of oxime ligation, the combination of both multiwalled carbon nanotube surfaces and modified dendrimers or cyclopeptides allows the access to a high surface coverage of ferrocene in the order of 50 nmol cm–2, a 50-fold increase compared to a classic click reaction without oxime ligation of these highly branched macromolecules. Furthermore, this original immobilization strategy allows the immobilization of mono- and bi-functionalized active multicopper enzymes, laccases, viacopper(I)-catalyzed azide–alkyne cycloaddition. Electrochemical studies underline the high efficiency of the oxime-ligated dendrimers or cyclopeptides for the immobilization of redox entities on surfaces while being detrimental to electron tunneling with enzyme active sites despite controlled orientation.

Mercury(II) is an unphysiological soft ion with high binding affinity for thiolate ligands. Its toxicity lies in the interactions with low molecular weight thiols including glutathione and cysteine-containing proteins that disrupt the thiol balance and alter vital functions. However, mercury can also be detoxified via interactions with Hg(II)-responsive regulatory proteins such as MerR, which coordinates Hg(II) with three cysteine residues in a trigonal planar fashion (HgS3coordination). The model cyclodecapeptide P3C, c(GCTCSGCSRP) was designed to promote Hg(II) chelation in a HgS3coordination environment through the parallel orientation of three cysteine side chains. The binding motif is derived from the dicysteine P2Ccyclodecapeptide validated previously as a model for d10metal transporters containing the binding sequence CxxC. The formation of the mononuclear HgP3Ccomplex with a HgS3coordination is demonstrated using electrospray ionization mass spectrometry, UV absorption, and 199Hg NMR. Hg LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy indicates that the Hg(II) coordination environment is T-shaped with two short Hg–S distances at 2.45 Å and one longer distance at 2.60 Å. The solution structure of the HgP3Ccomplex was refined based on 1H–1H NMR constraints and EXAFS results. The cyclic peptide scaffold has a rectangular shape with the three binding cysteine side chains pointing toward Hg(II). The HgP3CH complex has a pKaof 4.3, indicating that the HgS3coordination mode is stable over a large range of pH. This low pKavalue suggests that the preorientation of the three cysteine groups is particularly well-achieved for Hg(II) trithiolate coordination in P3C.

Background: Ethionamide is one of the most widely used drugs for the treatment of multidrug-resistant tuberculosis (MDR-TB). Like isoniazid, and pyrazinamide, ethionamide is a prodrug that needs to be activated by a mycobacterial enzyme. Activation pathways of prodrugs are generally problematic to uncover as they produce intermediates potentially difficult to characterize, to purify and that might prove unstable outside of their cellular context.Objectives and methods: We have used high resolution magic angle spinning-NMR (HRMAS-NMR) to follow ethionamide activation directly within living mycobacterial cells.Results: Data indicated that the intracellular metabolization of ethionamide strictly depends on the presence of the monooxygenase EthA and that EthA-dependent activation of ethionamide is coupled to a precise molecular sorting mechanism of the ethionamide metabolites. We found that the previously identified ethionamide metabolite 2-ethyl-4-hydroxymethylpyridine is produced in substantial amounts by the ethionamide-treated mycobacteria and that it is present exclusively outside of the bacteria. In contrast, the still unidentified ethionamide metabolite ETH* is the only ethionamide derivative detected within the bacterial cell. Moreover, ETH* appears to be unable to cross the bacterial envelope and consequently accumulates within the cytoplasm of the ethionamide-treated mycobacteria.Conclusions: These results strongly suggest that ETH* is the active antimycobacterial ethionamide derivative and open new perspectives for the understanding of the mode of action of prodrugs.

In this paper HRMAS NMR was used to investigate whether peptides on a peptidyl resin swollen in aqueous solution can adopt an intramolecular β-sheet structure. A model peptide YQNPDGSQA, that was previously shown to adopt such a secondary structure in solution, (Blanco et al., J. Am. Chem. Soc., 1993) was grafted onto three different solid supports that swell in aqueous solution to examine the influence of the resin on the structure. Both parameters of resin loading and pH inside the swollen peptidyl resin proved to be important for the physicochemical behaviour of the peptide on the support. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.

In this paper HRMAS NMR was used to investigate whether peptides on a peptidyl resin swollen in aqueous solution can adopt an intramolecular β‐sheet structure. A model peptide YQNPDGSQA, that was previously shown to adopt such a secondary structure in solution, (Blanco et al., J. Am. Chem. Soc., 1993) was grafted onto three different solid supports that swell in aqueous solution to examine the influence of the resin on the structure. Both parameters of resin loading and pH inside the swollen peptidyl resin proved to be important for the physicochemical behaviour of the peptide on the support. Copyright © 2003 European Peptide Society and John Wiley & Sons, Ltd.

We have investigated the extent to which rotor synchronization of radiofrequency pulses leads to spectral improvement in high-resolution magic angle spinning NMR experiments. Several pulse sequences were tested, and the effect was found to be maximal in homonuclear TOCSY spectra. The physicochemical nature of the sample plays a role in the phenomenon, as rotor synchronization allows the refocusing of residual anisotropic interactions. However, even in a liquid sample the effects were visible. Radial inhomogeneities of the radiofrequency field were identified as an important source of the problem.

The WW domain of the human PIN1 and p13 SUC1, a subunit of the cyclin-dependent kinase complex, were previously shown to be involved in the regulation of the cyclin-dependent kinase complex activity at the entry into mitosis, by an unresolved molecular mechanism. We report here experimental evidence for the direct interaction of p13 SUC1with a model CDC25 peptide, dependent on the phosphorylation state of its threonine. Chemical shift perturbation of backbone1HN, 15N, and13Cα resonances during NMR titration experiments allows accurate identification of the binding site, primarily localized around the anion-binding site, occupied in the crystal structure of the homologous p9 CKSHs2by a sulfate molecule. The epitope recognized by p13 SUC1includes the proline at position +1 of the phosphothreonine, as was shown by the decrease in affinity for a mutated CDC25 phosphopeptide, containing an alanine/proline substitution. No direct interaction between the PIN1 WW domain or its catalytic proline cis/trans-isomerase domain and p13 SUC1was detected, but our study showed that in vitrothe WW domain of the human PIN1 antagonizes the binding of the p13 SUC1to the CDC25 phosphopeptide, by binding to the same phosphoepitope. We thus propose that the full cyclin-dependent kinase complex stimulates the phosphorylation of CDC25 through binding of its p13 SUC1module to the phosphoepitope of the substrate and that the reported WW antagonism of p13 SUC1-stimulated CDC25 phosphorylation is caused by competitive binding of both protein modules to the same phosphoepitope.