Model peptide studies of Ag+ binding sites from the silver resistance protein SilE.

Using model peptides, each of the nine MX2H or HXnM (n = 1, 2) motifs of the silver resistance protein SilE has been shown to coordinate to one Ag+ ion by its histidine and methionine residues with Kd in the µM range. This suggests an Ag+ buffering role for SilE in the case of high Ag+ overload.

Synthesis, characterization, antibacterial activity and cytotoxicity of hollow TiO2-coated CeO2 nanocontainers encapsulating silver nanoparticles for controlled silver release.

Biomaterials as implants are being applied more extensively in medicine due to their on-going development and associated improvements, and the increase in human life expectancy. Nonetheless, biomaterial-related infections, as well as propagating bacterial resistance, remain significant issues. Therefore, there is a growing interest for silver-based drugs because of their efficient and broad-range antimicrobial activity and low toxicity to humans. Most newly-developed silver-based drugs have an extremely fast silver-ion release, increasing adverse biological impact to the surrounding tissue and achieving only short-term antimicrobial activity. Nanoencapsulation of these drugs is hypothesized as beneficial for controlling silver release, and thus is the aim of the present study. Initially, an amorphous or crystalline (anatase) titania (TiO2) coating was synthesized around silver nanoparticle-containing (AgNP) ceria (CeO2) nanocontainers using a sonication method forming AgNP/CeO2/TiO2 nanocontainers. These nanocontainers were characterized by high-resolution transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, gas sorption experiments and energy-dispersive X-ray spectroscopy. Silver release, monitored by using inductively coupled plasma optical emission spectroscopy, showed that these containers prevented silver release in water at neutral pH, and released the silver in concentrated nitric acid solution (pH = 1.1). The AgNP/CeO2/TiO2 nanocontainers showed an antibacterial activity against E. coli, however a concentration-dependent cytotoxicity towards a model epithelial barrier cell type (A549 cells) was observed. These nanocontainers offer the concept of potentially controlling silver delivery for the prevention of implant-associated infections.

4-Hydroxy-1-naphthaldehydes: proton transfer or deprotonation.

A series of naphthaldehydes, including a Mannich base, have been investigated by UV-Vis spectroscopy, NMR and theoretical methods to explore their potential tautomerism. In the case of 4-hydroxy-1-naphthaldehyde concentration dependent deprotonation has been detected in methanol and acetonitrile. For 4-hydroxy-3-(piperidin-1-ylmethyl)-1-naphthaldehyde (a Mannich base) an intramolecular proton transfer involving the OH group and the piperidine nitrogen occurs. In acetonitrile the equilibrium is predominantly at the OH-form, whereas in methanol the proton transferred tautomer is the preferred form. In chloroform and toluene, the OH form is completely dominant. Both 4-hydroxy-1-naphthaldehyde and 4-methoxy-1-naphthaldehyde (fixed enol form) show dimerization in the investigated solvents and the crystallographic data, obtained for the latter, confirm the existence of a cyclic dimer.

Integrating silver compounds and nanoparticles into ceria nanocontainers for antimicrobial applications.

Silver compounds and nanoparticles (NPs) are gaining increasing interest in medical applications, specifically in the treatment and prevention of biomaterial-related infections. However, the silver release from these materials, resulting in a limited antimicrobial activity, is often difficult to control. In this paper, ceria nanocontainers were synthesized by a template-assisted method and were then used to encapsulate silver nitrate (AgNO3/CeO2 nanocontainers). Over the first 30 days, a significant level of silver was released, as determined using inductively coupled plasma optical emission spectroscopy (ICP-OES). A novel type of ceria container containing silver NPs (AgNP/CeO2 containers) was also developed using two different template removal methods. The presence of AgNPs was confirmed both on the surface and in the interior of the ceria containers by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Upon removal of the template by calcination, the silver was released over a period exceeding three months (>90 days). However, when the template was removed by dissolution, the silver release was shortened to ≤14 days. The antimicrobial activity of the silver-containing CeO2 containers was observed and the minimum bactericidal concentration (MBC) was determined using the broth dilution method. Investigation on human cells, using a model epithelial barrier cell type (A549 cells), highlighted that all three samples induced a heightened cytotoxicity leading to cell death when exposed to all containers in their raw form. This was attributed to the surface roughness of the CeO2 nanocontainers and the kinetics of the silver release from the AgNO3/CeO2 and AgNP/CeO2 nanocontainers. In conclusion, despite the need for further emphasis on their biocompatibility, the concept of the AgNP/CeO2 nanocontainers offers a potentially alternative long-term antibactericidal strategy for implant materials.

7-[(Morpholin-4-yl)(phen-yl)meth-yl]quinolin-8-ol.

In the title compound, C20H20N2O2, the quinoline ring system makes dihedral angles of 81.05 (4) and 61.16 (5)° with the mean planes of the benzene and morpholine rings, respectively; the mean planes of the latter two rings make a dihedral angle of 83.59 (4)°. In the crystal, pairs of O-H⋯N hydrogen bonds link neighbouring mol-ecules related by a twofold rotation axis, generating R2(2)(10) motifs.

Combating implant infections. Remarks by a women's team.

Research on implant infections requires cooperative efforts and integration between basic and clinical expertises. An international group of women scientists is acting together in this field. The main research topics of the participants of this group are described. Formation of bacterial biofilms, antibiotic resistance and production of virulence factors like adhesins and toxins are investigated. New biomaterials, coatings and drugs designed to inhibit microbial adhesion are evaluated, and infection-resistant biomaterials are under study, such as a novel heparinizable polycarbonate-urethane (Bionate) or incorporation of diamino-diamide-diol (PIME) to reduce bacterial attachment. The correlation between biofilm production and the accessory-gene-regulator (agr) is investigated in Staphylococcus aureus. The ability to form biofilm has also been shown to be one of the important virulence factors of Enterococcus faecalis, favouring colonization of inert and biological surfaces. The study of quorum sensing has led to the discovery of a quorum sensing inhibitor termed RIP that suppresses staphylococcal biofilm and infections. The immune response and the local defence mechanisms of the host against implant-associated infections, activation and infiltration of immunocompetent cells into the sites of infection have been studied in patients with implant-associated osteomyelitis. Production of monoclonal antibodies (mAbs) as possible vaccines against the staphylococcal collagen-binding MSCRAMMs is in progress.

Electron transfer through bridging molecular structures.

Pairs of reducible pentakis(thiophenyl)benzene subunits are linked by different molecular structures as model compounds for reducible molecular-wire-type synthons showing varying electron-transfer ability as a function of the bridging structures, consisting of either para-divinylbenzene, bis-hydrazone, or diacetylene. Their electron-transfer ability from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods. In the case of the bis-hydrazone bridge and the diacetylene bridge, the solid-state structures support the experimental findings. While the para-divinylbenzene bridge completely isolates the reducible subunits (class I system) the diacetylene bridge electronically connects the two reducible structures (class III system), demonstrating its potential application as a "molecular wire." The bis-hydrazone linked dimer displays electronic communication only to a small extend, which was only observed in the spectroelectrochemical investigation. The diacetylene connection as active electron-transfer linker together with poly(thiophenyl)benzene as reducible subunits was used to design more complex molecular architectures. Linear rodlike structures did allow adjustment of the length of these type of molecular wires and investigation of the extent of electron mobility. Cyclic structures addressed the possibility of moving electrons on a bent molecular wire.

A logical concept of structure prediction derived from supramolecular polymers of alkaline Earth metal halides formed by hydrogen bonding and complexation of the metal ion.

Several different dimensional polymers derived from alkaline earth metal iodides are obtained as a result of supramolecular noncovalent bonding modes of the metal ion, namely complexation and hydrogen bonding. These polymers consist of complex cations linked to the halide ions by hydrogen bonds of the water ligands coordinated to the metal. They are built up in a logical way, depending on the ratio of complexing ligands to complexing and hydrogen-bonding ligands so that their dimensionality and, to a certain extent, their structure can be predicted.

Electron transfer through molecular bridges between reducible pentakis(thiophenyl)benzene subunits.

"Dimers" 3, 4 and 7, which consist of two reducible pentakis(thiophenyl)benzene subunits linked by different molecular structures, have been synthesised as model compounds for reducible molecular-wire-type synthons to represent differences in the electron-transfer ability as a function of the bridging structure. The bridging units consist of para-divinylbenzene in 3, bis-hydrazone in 4 and diacetylene in 7. Their ability to transfer electrons from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods and, in the case of 4 and 7, the solid-state structures support the experimental findings. The para-divinylbenzene bridge in 3 was found to completely isolate the reducible structures (Class I system). In contrast, the diacetylene bridge in 7 electronically connects the two reducible structures (Class III system) and, thus, demonstrates its potential application as a "molecular wire". The bis-hydrazone-linked compound 4 displayed only a low level of electronic connection between the subunits and was only observed in the spectroelectrochemical investigation.

Positive and negative psychosocial sequelae of bone marrow transplantation: implications for quality of life assessment.

Life-threatening disease can trigger positive effects such as greater appreciation for life and enhanced interpersonal relationships. Little research has examined these salutary effects or their association with quality of life (QOL). Adult bone marrow transplantation (BMT) survivors (n = 90) were interviewed regarding psychosocial sequelae of BMT and completed indices of QOL and psychological adjustment. Thematic analysis was used to code interview responses into discrete categories of negative and positive sequelae. Multiple regression analyses indicated POSTOTAL scores were inversely associated with time post-BMT and positively associated with negative prognostic factors at BMT. Scores on indices of QOL and psychological adjustment were significantly correlated with reports of negative post-BMT sequelae but unrelated to positive sequelae. It was concluded that life-threatening disease can trigger positive sequelae that can contribute to QOL. However, standard QOL indices may not measure this positive QOL dimension, thus yielding a potentially incomplete picture of current QOL.