Inhibition of the Quorum Sensing System,Elastase Production and Biofilm Formation in Pseudomonas aeruginosa by Psammaplin A and Bisaprasin

Natural products derived from marine sponges have exhibited bioactivity and, in some cases, serve as potent quorum sensing inhibitory agents that prevent biofilm formation and attenuate virulence factor expression by pathogenic microorganisms. In this study, the inhibitory activity of the psammaplin-type compounds, psammaplin A (1) and bisaprasin (2), isolated from the marine sponge, Aplysinella rhax, are evaluated in quorum sensing inhibitory assays based on the Pseudomonas aeruginosa PAO1 lasB-gfp(ASV) and rhlA-gfp(ASV) biosensor strains. The results indicate that psammaplin A (1) showed moderate inhibition on lasB-gfp expression, but significantly inhibited the QS-gene promoter, rhlA-gfp, with IC₅₀ values at 14.02 μM and 4.99 μM, respectively. In contrast, bisaprasin (2) displayed significant florescence inhibition in both biosensors, PAO1 lasB-gfp and rhlA-gfp, with IC₅₀ values at 3.53 μM and 2.41 μM, respectively. Preliminary analysis suggested the importance of the bromotyrosine and oxime functionalities for QSI activity in these molecules. In addition, psammaplin A and bisaprasin downregulated elastase expression as determined by the standard enzymatic elastase assay, although greater reduction in elastase production was observed with 1 at 50 μM and 100 μM. Furthermore, the study revealed that bisaprasin (2) reduced biofilm formation in P. aeruginosa.     

New types of self-organizing interfacial alginate membranes

In this publication we describe a new self-association process, which leads to the formation of ultra-thin alginate layers at the interface between oil and water. The water phase contains a highly dilute solution of sodium alginate. These macromolecules are negatively charged and they are not surface active. The oil phase contains a small concentration of positively charged surfactants. At the interface between oil and water, the cationic surfactants tend to form complexes with the negatively charged alginate polyelectrolytes in the aqueous solutions. This leads to striking adsorption processes of the solved polysaccharide molecules at the oil-water interface. Upon the addition of calcium ions, a cross-linking process sets in and one obtains the thin viscoelastic membranes, which are anchored at the interface between oil and water. The thickness of these membranes is of the order of 0.2 mm. Similar structures can also be formed by solving positively charged Gemini surfactants in the oil phase. In this case, the cationic surfactant molecules induce the adsorption processes of alginate macromolecules, and they also act as cross-linking compounds. In a series of experiments, we measured the surface rheological properties of these ultra-thin alginate membranes. The results of these investigations point to the presence of electrostatically stabilized membranes. Special interest was given to the influence of the guluronate content of the alginates, which is important for the cross-linking mechanism according to the egg-box model. Finally, this article finishes with the discussion of the proposed building mechanisms of these membranes.     

Analytical approaches for the determination of PCB metabolites in blood: a review

Polychlorinated biphenyls (PCBs) are among the most ubiquitous pollutants in the environment, and their metabolism leads to the formation of hydroxylated PCBs (OH-PCBs) and methyl sulfone PCBs (MeSO₂-PCBs). These metabolites are generally more hydrophilic than the parent compound, and therefore are more easily eliminated from the body. However, some congeners have been shown to be strongly retained in human blood, binding to transthyretin with an affinity that is, in general, greater than that of the natural ligand thyroxin itself, which could result in toxicological effects, particularly on the thyroid system. Currently available analytical methods require, in general, extensive sample preparation, which includes a series of time-consuming and low-throughput liquid–liquid and back extractions, evaporations, several cleanup steps, and in some cases, derivatization prior to analysis by gas chromatography (GC) or liquid chromatography (LC) coupled with mass spectrometry (MS). Recent developments in the use of LC coupled with tandem MS (MS/MS) have brought some improvements in terms of sample preparation for the determination of PCB metabolites in blood, although there are still possibilities for continued development. The selected literature has evidenced few studies of LC–MS/MS-based methods, a lack of analytical standards, nonassessment of lower-chlorinated OH-PCBs, and scarce attention to MeSO₂-PCBs in blood. This review aims to evaluate critically the currently available analytical methods for determination of OH-PCBs and MeSO₂-PCBs in blood.     

A candidate reference measurement procedure for Cyclosporine A in whole blood

Monitoring of Cyclosporine A (CsA) concentrations in whole blood is widely performed due to the narrow therapeutic index of the drug. Required standardisation for routine analysis of CsA is still missing. The candidate reference measurement procedure presented here is designated for the assignment of CsA values in hemolysed blood associated with expanded measurement uncertainty. Separate stock solutions for calibration and control materials were prepared by spiking hemolysed blood with CsA under gravimetric control. The essential sample pretreatment step was protein precipitation. Analysis was performed using isotope dilution LC-MS/MS with online solid phase extraction. Interference by matrix components was investigated. Using [²H₄]-CsA as the internal standard, no interference from the investigated matrices were detected. Measurement repeatability using three pools of whole blood as samples revealed coefficients of variation (CV) ranging from 1.0 % to 1.6 %. Intermediate measurement precision was determined by repeated analysis of self-prepared control materials taken from different stock solutions of pooled whole blood. CVs were between 0.8 % and 2.4 %. Measurement accuracy was checked using three control materials prepared from three different stock solutions. The recoveries of the mean of mean values obtained on four measurement days ranged from 99.4 % to 101.3 %. The combined expanded uncertainty of measurement based on 5 days of measurement and was evaluated according to the GUM as U = 2.0 % (k = 2).     

Enrichment and desalting of tryptic protein digests and the protein depletion using boron nitride

Sample preparation still remains a great challenge in modern bioanalysis and the interest in new efficient solid phase extraction (SPE) materials still remains high. In this work, hexagonal boron nitride (h-BN) is introduced as a new SPE material for the isolation and enrichment of peptides. The h-BN is isoelectronic and structurally similar to graphite. It has remarkable properties including good thermal conductivity, excellent thermal and chemical stability and a better oxidation resistance than graphite. BN attracts increasing interest because of its wide range of applicability. In the present work, the great potential of h-BN, as a new SPE-material, on the enrichment, preconcentration and desalting of tryptic digest of model proteins is demonstrated. A special attention was dedicated to the efficient enrichment of hydrophilic phosphopeptides. Two elution protocols were developed for the enrichment of peptides compatible for subsequent MALDI-MS and ESI-MS analysis. In addition, the recoveries of 5 peptides and 3 phosphopeptides with wide range of pI values utilizing h-BN materials with different surface areas were investigated. 84–106% recovery rate could be achieved using h-BN materials. The results were compared with those obtained using graphite and silica C18 under the same elution conditions, and lower recoveries were obtained. In addition, h-BN was found to have a capability of protein depletion, which is requisite for the peptide profiling.     

Protein Interactions with Polymer Coatings and Biomaterials

Protein adsorption is considered to be the most important factor of the interaction between polymeric biomaterials and body fluids or tissues. Water‐mediated hydrophobic and hydration forces as well as electrostatic interactions are believed to be the major factors of protein adsorption. A systematic analysis of various monolayer systems has resulted in general guidelines, the so‐called “Whitesides rules”. These concepts have been successfully applied for designing various protein‐resistant surfaces and are being studied to expand the understanding of protein–material interactions beyond existing limitations. Theories on the mechanisms of protein adsorption are constantly being improved due to the fast‐developing analytical technologies. This Review is aimed at improving these empirical guidelines with regard to present theoretical and analytical advances. Current analytical methods to test mechanistic hypotheses and theories of protein–surface interactions will be discussed. Special focus will be given to state‐of‐the‐art bioinert and biospecific coatings and their applications in biomedicine.     

Substituierte 5-Hydroxypyrimidine und ihre O,O-Diethylphosphorsäure-, O,O-Diethylthiophosphorsäure-und N,N-Dimethylcarbamidsäureester

4-Alkyl (or aryl)-6-chloro-5-hydroxy-2-methylpyrimidines5a–5e, 4-alkyl (or aryl)-5-hydroxy-2-methyl-1H-pyrimidin-6-ones5g–5k and 6-alkyl (or aryl)-5-hydroxy-1H,3H-pyrimidin-2,4-diones5l–5n were prepared and converted into O,O-diethylphosphoric acid esters7a–7e, O,O-diethylphosphorothioic acid esters7f–7i and N,N-dimethylcarbamic acid esters8.

     

ERETIC implemented in diffusion-ordered NMR as a diffusion reference

The ERETIC (Electronic Reference To access In vivo Concentrations) technique generates an electronic signal in the NMR spectrometer which is detected simultaneously to the sample FID during the acquisition. The implementation of the ERETIC sequence in any 2D DOSY experimental scheme enables one to generate directly into the raw 2D DOSY spectrum a reference signal with an attenuation simulated to describe a well-defined diffusion behavior. This simulated intensity attenuation can be used to evaluate the output generated by any DOSY data treatment algorithm, in a single as well as multichannel approach and provide insight into their precision, accuracy, scope and limitations. The ERETIC sequence implemented in the standard bipolar pulsed field gradient longitudinal eddy current delay (LED) sequence is illustrated on various algorithms presented previously in the literature for the analysis of the generated ERETIC-DOSY spectra of simulated model systems representing discrete and continuous diffusion profiles in mono- and bi-Gaussian diffusion regimes.     

Quaternary indides LaTIn3Mg (T = Rh and Ir) and CeIrIn3Mg with LaCoAl4 type structure

The quaternary indides LaTIn₃Mg (T = Rh and Ir) and CeIrIn₃Mg were prepared from the elements in sealed tantalum ampoules in an induction furnace. The samples were characterized by X-ray powder and single crystal data: LaCoAl₄ type, Pmma, Z = 2, a = 830.5(1), b = 436.1(1), c = 745.1(1) pm, wR2 = 0.038, 467 F ² values for LaRhIn_3.075Mg_0.925, a = 832.9(1), b = 436.5(1), c = 746.9(1) pm, wR2 = 0.077, 471 F ² values for LaIrIn_3.091Mg_0.909, and a = 832.2(1), b = 434.1(1), c = 743.9(1) pm, wR2 = 0.066, 465 F ² values for CeIrIn_3.07Mg_0.93 with 25 variables for each refinement. The transition metal, indium, and magnesium atoms build up three-dimensional [TIn₃Mg] networks which leave pentagonal prismatic voids for the lanthanum and cerium atoms. The transition metal atoms have tricapped trigonal prismatic coordination and the magnesium atoms fill distorted square prisms. All three crystals revealed a small degree of Mg/In mixing on the latter site.     

Structure and properties of Ce3Pd3Bi4, CePdBi, and CePd2Zn3

The intermetallic cerium compounds Ce₃-Pd₃Bi₄, CePdBi, and CePd₂Zn₃ were synthesized from the elements in sealed tantalum ampoules in an induction furnace. The compounds were characterized by X-ray powder and single crystal diffraction: CeCo₃B₂ type (ordered version of CaCu₅), P6/mmm, a = 538.4(4), c = 427.7(4) pm, wR2 = 0.0540, 115 F ² values, 9 variables for CePd₂Zn₃ and Y₃Au₃Sb₄ type, I [`4]{\bar 4} 3d, a = 1005.2(2) pm, w R2 = 0.0402, 264 F ² values, 9 variables for Ce₃Pd₃Bi₄, and MgAgAs type, a = 681.8(1) pm for CePdBi. The bismuthide structures are build up from three-dimensional networks of corner-sharing PdBi₄ tetrahedra with Pd–Bi distances of 281 (Ce₃Pd₃Bi₄) and 296 pm (CePdBi), respectively. The cerium atoms are located in larger voids of coordination number 12 (Ce₃Pd₃Bi₄) and 10 (CePdBi). In CePd₂Zn₃ the cerium atoms fill larger channels within the three-dimensional [Pd₂Zn₃] network with 18 (6 Pd + 12 Zn) nearest neighbors. The three compounds contain stable trivalent cerium with experimental magnetic moments of μ_eff = 2.70(2), 2.48(1), and 2.49(1) μ_B/Ce atom for CePd₂Zn₃, Ce₃Pd₃Bi₄, and CePdBi, respectively. Susceptibility and specific heat data gave no hint for magnetic ordering down to 2.1 K.