Insights into Structural and Dynamical Changes Experienced by Human RNase 6 upon Ligand Binding.

Ribonuclease 6 (RNase 6) is one of eight catalytically active human pancreatic-type RNases that belong to a superfamily of rapidly evolving enzymes. Like some of its human homologues, RNase 6 exhibits host defense properties such as antiviral and antibacterial activities. Recently solved crystal structures of this enzyme in its nucleotide-free form show the conservation of the prototypical kidney-shaped fold preserved among vertebrate RNases, in addition to revealing the presence of a unique secondary active site. In this study, we determine the structural and conformational properties experienced by RNase 6 upon binding to substrate and product analogues. We present the first crystal structures of RNase 6 bound to a nucleotide ligand (adenosine 5'-monophosphate), in addition to RNase 6 bound to phosphate ions. While the enzyme preserves B2 subsite ligand preferences, our results show a lack of typical B2 subsite interactions normally observed in homologous ligand-bound RNases. A comparison of the dynamical properties of RNase 6 in its apo-, substrate-, and product-bound states highlight the unique dynamical properties experienced on time scales ranging from nano- to milliseconds. Overall, our results confirm the specific evolutionary adaptation of RNase 6 relative to its unique catalytic and biological activities.

Antibacterial properties of the pituitary adenylate cyclase-activating polypeptide: A new human antimicrobial peptide.

The Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP), a polycationic, amphiphilic and helical neuropeptide, is well known for its neuroprotective actions and cell penetrating properties. In the present study, we evaluated the potent antibacterial property of PACAP38 and related analogs against various bacterial strains. Interestingly, PACAP38 and related analogs can inhibit the growth of various bacteria including Escherichia coli (JM109), Bacillus subtilis (PY79), and the pathogenic Burkholderia cenocepacia (J2315). Investigation of the mechanism of action suggested that a PACAP metabolite, identified as PACAP(9-38), might indeed be responsible for the observed PACAP38 antibacterial action. Surprisingly, PACAP(9-38), which does not induce haemolysis, exhibits an increased specificity toward Burkholderia cenocepacia J2315 compared to other tested bacteria. Finally, the predisposition of PACAP(9-38) to adopt a π-helix conformation rather than an α-helical conformation like PACAP38 could explain this gain in specificity. Overall, this study has revealed a new function for PACAP38 and related derivatives that can be added to its pleiotropic biological activities. This innovative study could therefore pave the way toward the development of new therapeutic agents against multiresistant bacteria, and more specifically the Burkholderia cenocepacia complex.

Ag Nanoencapsulation for Antimicrobial Applications.

Biomaterial-related infections remain a significant challenge in medicine. Antimicrobial materials on the basis of Ag nanoparticles represent a promising solution for this issue. Therefore several Ag-containing nanocontainers and nanorattles have been synthesized and characterized that exhibit remarkable control over the release of Ag+ as antimicrobial active species. Their biological evaluation against prokaryotic as well as eukaryotic cells reveals that they fulfill the prerequisites for applications as antimicrobial implant coatings.

Directing the Viedma ripening of ethylenediammonium sulfate using "Tailor-made" chiral additives.

Both enantiomers of trans-cyclohexane-1,2-diammonium sulfate and trans-1,2-diphenylethylenediammonium sulfate were used as "tailor-made" additives to direct the mirror-symmetry breaking in the attrition-enhanced deracemization (i.e. Viedma ripening) of conglomerate crystals of ethylenediammonium sulfate (EDS). Isothermal titration calorimetry (ITC) shows chiral recognition of (1R,2R)- and (1S,2S)-1,2-diphenylethylenediamine to EDS crystals where the enthalpy of adsorption of the (1R,2R)-isomer on l-EDS crystals is higher in comparison to that on d-EDS crystals. These results are consistent with a "rule of reversal" mechanism driving the chiral outcome of the Viedma ripening of EDS.

Ambient surface analysis of organic monolayers using direct analysis in real time Orbitrap mass spectrometry.

A better characterization of nanometer-thick organic layers (monolayers) as used for engineering surface properties, biosensing, nanomedicine, and smart materials will widen their application. The aim of this study was to develop direct analysis in real time high-resolution mass spectrometry (DART-HRMS) into a new and complementary analytical tool for characterizing organic monolayers. To assess the scope and formulate general interpretation rules, DART-HRMS was used to analyze a diverse set of monolayers having different chemistries (amides, esters, amines, acids, alcohols, alkanes, ethers, thioethers, polymers, sugars) on five different substrates (Si, Si3N4, glass, Al2O3, Au). The substrate did not play a major role except in the case of gold, for which breaking of the weak Au-S bond that tethers the monolayer to the surface, was observed. For monolayers with stronger covalent interfacial bonds, fragmentation around terminal groups was found. For ester and amide-terminated monolayers, in situ hydrolysis during DART resulted in the detection of ions characteristic of the terminal groups (alcohol, amine, carboxylic acid). For ether and thioether-terminated layers, scission of C-O or C-S bonds also led to the release of the terminal part of the monolayer in a predictable manner. Only the spectra of alkane monolayers could not be interpreted. DART-HRMS allowed for the analysis of and distinction between monolayers containing biologically relevant mono or disaccharides. Overall, DART-HRMS is a promising surface analysis technique that combines detailed structural information on nanomaterials and ultrathin films with fast analyses under ambient conditions.

Complete asymmetric amplification of ethylenediammonium sulfate using an abrasion/grinding technique.

Complete asymmetric amplification of ethylenediammonium sulfate was achieved under continuous dissolution/crystallization conditions using an abrasion/grinding method.

Selective irrigation of the sinuses in the management of chronic rhinosinusitis refractory to medical therapy: a promising start.

BACKGROUND: Although endoscopic sinus surgery has been widely used for the treatment of chronic rhinosinusitis, some patients fail to derive clinical benefit from this procedure. We evaluated the efficacy of a treatment regimen consisting of selective irrigation of diseased sinus mucosa with topical antibiotics and steroids in conjunction with oral antibiotics and steroids. METHODS: Twenty patients suffering from chronic rhinosinusitis and resistant to medical treatment (mean duration 3.4 years) underwent intubations of the affected maxillary and/or ethmoid sinuses for irrigation for a duration of 21 to 30 days. A computed tomographic (CT) scan of the paranasal sinus was taken both pre- and post-treatment and staged according to the Lund-MacKay system. Clinical symptoms were scored for rhinorrhea, facial pain, nasal congestion, and smell at least 2 months prior to treatment and approximately 18 months after the follow-up. RESULTS: The clinical experience with the technique of intubation and irrigation was well tolerated by all patients. We found an improvement in all symptom scores, including rhinorrhea, nasal congestion, smell (n = 20; p < .001), and facial pain (n = 20; p < .01). Similar improvements were seen on the CT scans, with reduced staging from 14.6 +/- 1.1 to 5.6 +/- 1.1 (p < .001). Only three patients did not respond to selective irrigation of the sinuses and needed further surgery. CONCLUSION: These results suggest that sinus irrigation could provide a reasonable and effective alternative to ethmoidectomy with drainage procedures and offer promise for the treatment of patients with chronic rhinosinusitis who are resistant to medical treatment.