A Protein‐Based Encapsulation System with Calcium‐Controlled Cargo Loading and Detachment

Protein‐based encapsulation systems have a wide spectrum of applications in targeted delivery of cargo molecules and for chemical transformations in confined spaces. By engineering affinity between cargo and container proteins it has been possible to enable the efficient and specific encapsulation of target molecules. Missing in current approaches is the ability to turn off the interaction after encapsulation to enable the cargo to freely diffuse in the lumen of the container. Separation between cargo and container is desirable in drug delivery applications and in the use of capsids as catalytic nanoparticles. We describe an encapsulation system based on the hepatitis B virus capsid in which an engineered high‐affinity interaction between cargo and capsid proteins can be modulated by Ca²⁺. Cargo proteins are loaded into capsids in the presence of Ca²⁺, while ligand removal triggers unbinding inside the container. We observe that confinement leads to hindered rotation of cargo inside the capsid. Application of the designed container for catalysis was also demonstrated by encapsulation of an enzyme with β‐glucosidase activity.     

Insight into Signal Response of Protein Ions in Native ESI-MS from the Analysis of Model Mixtures of Covalently Linked Protein Oligomers

Native ESI-MS is increasingly used for quantitative analysis of biomolecular interactions. In such analyses, peak intensity ratios measured in mass spectra are treated as abundance ratios of the respective molecules in solution. While signal intensities of similar-size analytes, such as a protein and its complex with a small molecule, can be directly compared, significant distortions of the peak ratio due to unequal signal response of analytes impede the application of this approach for large oligomeric biomolecular complexes. We use a model system based on concatenated maltose binding protein units (MBPn, n = 1, 2, 3) to systematically study the behavior of protein mixtures in ESI-MS. The MBP concatamers differ from each other only by their mass while the chemical composition and other properties remain identical. We used native ESI-MS to analyze model mixtures of MBP oligomers, including equimolar mixtures of two proteins, as well as binary mixtures containing different fractions of the individual components. Pronounced deviation from a linear dependence of the signal intensity with concentration was observed for all binary mixtures investigated. While equimolar mixtures showed linear signal dependence at low concentrations, distinct ion suppression was observed above 20 μM. We systematically studied factors that are most often used in the literature to explain the origin of suppression effects. Implications of this effect for quantifying protein–protein binding affinity by native ESI-MS are discussed in general and demonstrated for an example of an anti-MBP antibody with its ligand, MBP.

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Analysis of isotopic signals in the Danube River water at Tulln,Austria, based on daily grab samples in 2012

Results of stable isotope measurements (δ²H, δ¹⁸O) of daily grab samples, taken from the Danube River at Tulln (river km 1963) during 2012, show seasonal and short-term variations depending on the climatic/hydrological conditions and changes in the catchment area (temperature changes, heavy rains and snow melt processes). Isotope ratios in river water clearly reflect the isotopic composition of precipitation water in the catchment area since evaporation influences play a minor role. Average δ²H and δ¹⁸O values in 2012 are?78‰ and?11.0‰, respectively, deuterium excess averages 10‰. The entire variation amounts to 1.8‰ in δ¹⁸O and 15‰ in δ²H. Quick changes of the isotopic composition within a few days emphasise the necessity of daily sampling for the investigation of hydrological events, while monthly grab sampling seems sufficient for the investigation of long-term hydro-climatic trends. ³H results show peaks (half-width 1–2 days, up to about 150 TU) exceeding the regional environmental level of about 9 TU, probably due to releases from nuclear power plants.     

Pyrolysis study of poplar biomass by tunable synchrotron vacuum ultraviolet photoionization mass spectrometry

Pyrolysis is one of the most important methods to convert biomass into biofuel, which is a potential substitute for fossil fuel. The pyrolysis process of poplar biomass, a potential biofuel feedstock, has been studied with tunable synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry (PIMS). The mass spectra at different photon energies, temperatures, and time-evolved profiles of selected species during poplar pyrolysis process were measured. Our results reveal that poplar is typical of hardwood according to its relative contents of three lignin monomeric precursors. As temperature increases from 300 to 700 °C, the overall intensities of pyrolysis products decrease due to the gas-phase cracking. Observed intensities of syringyl and guaiacyl subunits of lignin in poplar at low temperature present different trends: the intensities of syringyl subunits of lignin undergo an increase firstly and then a decrease, whereas those of guaiacyl subunits of lignin show decrease continuously. Time-dependent data demonstrate that hemicellulose pyrolysis is faster than lignin in poplar. This work reports a new application of SVUV PIMS in biomass pyrolysis, which performs very well in products analysis.     

Synthesis of styrene–butadiene rubber latex via miniemulsion copolymerization

High-butadiene-level styrene–butadiene rubber latexes up to high solid-contents are synthesized using the miniemulsion process. It is shown that the miniemulsion polymerization approach offers an efficient heterophase route synthesizing styrene–butadiene copolymer latexes with flexible copolymer composition and narrow size distribution of the resulting latex particles. Secondary nucleation was successfully prevented by using a hydrophobic initiator. Due to the nanoreactor situation, even at high conversions, a low crosslinking degree and, therefore, low gel contents are obtained. The microstructure of the polymers obtained in miniemulsion is independent of the synthesis parameters, especially the temperature. The molecular weight can be easily adjusted by the application of transfer agents while the insoluble gel content is substantially reduced. An up-scaling of the procedure is easily possible.     

Concomitant crystallization of two polymorphs-a ring and a helix: concentration effect on supramolecular isomerism

For the first time in Ag coordination chemistry, two supramolecular isomers, a ring and a helix, are isolated from the same mother liquor as a result of concentration effects.     

Determination of tenuazonic acid in human urine by means of a stable isotope dilution assay

The content of tenuazonic acid in human urine was determined by a stable isotope dilution assay (SIDA) that was recently developed for the analysis of food commodities and extensively re-validated for urine matrix in this study. Linearity of the response curve was proven between molar ratios n(labeled standard)/n(analyte) of 0.02–100. The limits of detection and determination were 0.2 and 0.6 μg/L, respectively. The mean recovery of the stable isotope dilution assay was 102?±?3 % in the range between 1.0 and 100 μg/L. Interassay precision was 6.7 % (relative standard deviation of three triplicate analyses of a human urine sample during 3 weeks). The method was applied to two studies dealing with urinary excretion of tenuazonic acid: In the first study, tenuazonic acid was quantified in the 24-h urine of six volunteers from Germany (three female, three male) in a concentration range of 1.3–17.3 μg/L or 2.3–10.3 ng/mg^?1 creatinine, respectively. In the second study, two volunteers (one female, one male) ingested 30 μg tenuazonic acid by consumption of naturally contaminated whole meal sorghum infant cereals and tomato juice, respectively. The urinary excretion of the ingested tenuazonic acid was 54–81 % after 6 h, depending on matrix and volunteer. After 24 h, 87–93 % of the ingested amount of tenuazonic acid was excreted, but the fate of the remaining about 10 % is open. Thus, it is not possible to exclude potential health hazards for the consumer, completely.