Concentrating rotaviruses from water samples using monolithic chromatographic supports

Rotaviruses are the leading cause of diarrhoea in infants around the globe and, under certain conditions they can be present in drinking water sources and systems. Ingestion of 10–100 viral particles is enough to cause disease, emphasizing the need for sensitive diagnostic methods. In this study we have optimized the concentration of rotavirus particles using methacrylate monolithic chromatographic supports. Different surface chemistries and mobile phases were tested. A strong anion exchanger and phosphate buffer (pH 7) resulted in the highest recoveries after elution of the bound virus with 1 M NaCl. Using this approach, rotavirus particles spiked in 1 l volumes of tap or river water were efficiently concentrated. The developed concentration method in combination with a real time quantitative polymerase chain reaction assay detected rotavirus concentrations as low as 100 rotavirus particles/ml.     

The effects of eluent mixing on TLS detection in gradient elution HPLC

The effects of changing solvent composition on the LOD of TLS detection in gradient elution HPLC have been studied from the perspective of thermo-optical properties of the solvent. Hyphenated gradient high-performance liquid chromatography (HPLC)-thermal lens spectrometry (TLS), was used to separate and detect 13 carotenoid compounds and two chlorophylls. Utilization of mixing coils into the system reduces the inhomogeneities during eluent changes and therefore enables the application of thermal lens detection in the gradient HPLC method. For gradient chromatographic conditions in which the thermo-optical properties and related enhancement factor change as much as 50% over 10 min, the LODs for the TLS detector were enhanced by as much as three times in comparison with UV-Vis detection. For the isocratic part of the chromatogram, up to a tenfold improvement of LODs was achieved with TLS detection.     

TEAD–YAP Interaction Inhibitors and MDM2 Binders from DNA-Encoded Indole-Focused Ugi Peptidomimetics

DNA-encoded combinatorial synthesis provides efficient and dense coverage of chemical space around privileged molecular structures. The indole side chain of tryptophan plays a prominent role in key, or “hot spot”, regions of protein–protein interactions. A DNA-encoded combinatorial peptoid library was designed based on the Ugi four-component reaction by employing tryptophan-mimetic indole side chains to probe the surface of target proteins. Several peptoids were synthesized on a chemically stable hexathymidine adapter oligonucleotide “hexT”, encoded by DNA sequences, and substituted by azide-alkyne cycloaddition to yield a library of 8112 molecules. Selection experiments for the tumor-relevant proteins MDM2 and TEAD4 yielded MDM2 binders and a novel class of TEAD-YAP interaction inhibitors that perturbed the expression of a gene under the control of these Hippo pathway effectors.     

Dipole moment and self-association of cyclohexylsulfamic acid in 1,4-dioxane solution at 298.15?K

Abstract  

The density, refractive index, and electrical permittivity of cyclohexylsulfamic acid in 1,4-dioxane solutions were measured at 298.15 K. The limiting apparent specific volume, refraction, and polarization were calculated from the experimental data. The electrical dipole moment of cyclohexylsulfamic acid was estimated using the Debye, Onsager, and Kirkwood equations. The dipole association of cyclohexylsulfamic acid was treated with the assumption that the dipole moment of dimeric species is zero. The dimerization constant and dipole moment of monomeric species were evaluated.     

Membrane switch hypothesis. 1. Cell density influences lateral domain structure of tumor cell membranes

The domain structure of human cancer cells membranes was investigated by electron paramagnetic resonance (EPR) in different phases of cell growth, and the results were compared to those obtained for nonmalignant cells. On the basis of computer simulation of the EPR spectra using a newly developed GHOST condensation routine it was suggested that plasma membranes of cancer cells have less lateral lipid domain types at confluent conditions than in the exponential growing phase, while in nonmalignant cells the domain structure does not change significantly during cell growth. In accordance to our experimental data we propose a membrane switch hypothesis: disappearance of certain membrane domain types might act as a switch promoting the clustering of membrane constituents into the active units in a common lipid membrane domain and thus influencing the physiology of cells.     

Search for 8+ strength in 16O via the 12C(α, α2)12C1(7.66 MeV) reaction

Closely spaced angular distributions have been measured for the ${}^{12}\text{C}\text{(α, α}{}_2\text{)}{}^{12}\text{C}\text{1(7.66}\text{MeV}\text{)}$ reaction between E_α = 17.39 and 20.5 MeV in a search for 8⁺ strength in ¹⁶O. No evidence of 8⁺ strength is found, but evidence is found for a narrow 7^? resonance at 21.52 MeV excitation.     

Synthesis of alkyl‐modified poly(sodium glutamate)s for preparation of polymer‐protein nanoparticles in combination with N,N,N‐trimethyl chitosan

The negatively charged, water‐soluble, hydrophobically modified poly(sodium glutamate)s containing different amounts of alkyl grafts were synthesized. First, poly(γ‐benzyl‐L‐glutamate) was prepared by ring‐opening polymerization of the corresponding N‐carboxyanhydride, which was in the next step aminolysed with octylamine. After removal of the remaining benzyl protective groups, the alkyl‐modified poly(sodium glutamate)s [P(Glu‐oa)] were obtained and, together with the oppositely charged N,N,N‐trimethyl chitosan (TMC), used for the preparation of nanoparticles (NPs) of a recombinant granulocyte colony‐stimulating factor (GCSF) protein by polyelectrolyte complexation method. It is observed that, beside electrostatic interaction, the hydrophobic grafts on poly(sodium glutamate)s significantly contribute to association efficiency (AE) with GCSF protein. The addition of TMC solution to the dispersion of GCSF/P(Glu‐oa) complexes results in formation of much more defined NPs with high AE and final protein loading. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2976–2985     

Improved broad-spectrum antibiotics against Gram-negative pathogens via darobactin biosynthetic pathway engineering

The development of new antibiotics is imperative to fight increasing mortality rates connected to infections caused by multidrug-resistant (MDR) bacteria. In this context, Gram-negative pathogens listed in the WHO priority list are particularly problematic. Darobactin is a ribosomally produced and post-translationally modified bicyclic heptapeptide antibiotic selectively killing Gram-negative bacteria by targeting the outer membrane protein BamA. The native darobactin A producer Photorhabdus khanii HGB1456 shows very limited production under laboratory cultivation conditions. Herein, we present the design and heterologous expression of a synthetically engineered darobactin biosynthetic gene cluster (BGC) in Escherichia coli to reach an average darobactin A production titre of 13.4 mg L⁻¹. Rational design of darA variants, encoding the darobactin precursor peptide with altered core sequences, resulted in the production of 13 new ‘non-natural’ darobactin derivatives and 4 previously hypothetical natural darobactins. One of the non-natural compounds, darobactin 9, was more potent than darobactin A, and showed significantly improved activity especially against Pseudomonas aeruginosa (0.125 μg mL⁻¹) and Acinetobacter baumannii (1–2 μg mL⁻¹). Importantly, it also displayed superior activity against MDR clinical isolates of E. coli (1–2 μg mL⁻¹) and Klebsiella pneumoniae (1–4 μg mL⁻¹). Independent deletions of genes from the darobactin BGC showed that only darA and darE, encoding a radical forming S-adenosyl-l-methionine-dependent enzyme, are required for darobactin formation. Co-expression of two additional genes associated with the BGCs in hypothetical producer strains identified a proteolytic detoxification mechanism as a potential self-resistance strategy in native producers. Taken together, we describe a versatile heterologous darobactin platform allowing the production of unprecedented active derivatives in good yields, and we provide first experimental evidence for darobactin biosynthesis processes.

Heterologous expression of a synthetically engineered darobactin gene cluster in E. coli yields new darobactin derivatives with improved anti-Gram-negative activity. Targeted gene deletions provide first insights into biosynthetic steps.     

Zero product determined Jordan algebras,I

We show that the Jordan algebra 𝒮 of symmetric matrices with respect to either transpose or symplectic involution is zero product determined. This means that if a bilinear map {.,?.} from 𝒮?×?𝒮 into a vector space X satisfies {x, y}?=?0 whenever x?○?y?=?0, then there exists a linear map T : 𝒮?→?X such that {x,?y}?=?T(x?○?y) for all x, y?∈?𝒮 (here, x?○?y?=?xy?+?yx).