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Influence of one- and two-dimensional gel electrophoresis procedure on metal-protein bindings examined by electrospray ionization mass spectrometry, inductively coupled plasma mass spectrometry, and ultrafiltration

Three independent methods, (i) electrospray ionization mass spectrometry (ESI-MS), (ii) carrying out the complete protein preparation procedure required for protein gel electrophoresis (GE) including extraction, precipitation, washing, and desalting with subsequent microwave digestion of the produced protein fractions for metal content quantification, and (iii) ultrafiltration for separating protein-bound and unbound metal fractions, were employed to elucidate the influences of protein sample preparation and GE running conditions on metal-protein bindings. A treatment of the protein solution with acetone instead of trichloroacetic acid or ammonium sulfate for precipitate formation led to a strongly enhanced metal binding capacity. The desalting step of the resolubilized protein sample caused a metal loss between 10 and 35%. The omission of some extraction buffer additives led to a diminished metal binding capacity of protein fractions obtained from the sample preparation procedure for GE, whereas a tenside addition to the protein solution inhibited metal-protein bindings. The binding stoichiometry of Cu and Zn-protein complexes determined by ESI-MS was influenced by the type of the metal salt which was applied to the protein solution. A higher pH value of the sample solution promoted the metal ion complexation by the proteins. Ultrafiltration experiments revealed a higher Cu- and Zn-binding capacity of the model protein lysozyme in both resolubilization buffers for 1D- and 2D-GE compared to the protein extraction buffer. Strongly diminished metal binding capacities of lysozyme were recorded in the running buffer of 1D-GE and in the gel staining solutions.     

Bovine serum albumin (BSA) plays a role in the size of SDS micelle-like aggregates at the saturation binding: the ionic strength effect

The influence of ionic strength on the complexes formed by natural bovine serum albumin (BSA), pH 5.4 (near the isoelectric point), and sodium dodecyl sulfate (SDS) in aqueous buffered (sodium acetate) solution was investigated by using surface tension, fluorescence and small angle X-ray scattering (SAXS) techniques. Ionic strength was varied by changing sodium acetate buffer concentration from 0.020 to 0.5 M. Surface tension revealed that SDS:BSA saturation binding occurs at psp = 42 +/- 2 mM, independent of the solution ionic strength. Further, SAXS curves are consistent with the necklace and bead model, where micelle-like aggregates are randomly distributed along the partial unfolded protein. Micelle-like aggregates grow from small spheres at 10 mM SDS to small ellipsoids (upsilon = 1.3 , ratio between the largest and the shortest axes) near psp, in good agreement with micellar aggregation numbers obtained by fluorescence, independent of salt concentration. Protein-bound micelles stop growing above psp and further SDS addition induces free-micelle formation.     

Osteoarthritis subjects have differentiated lower extremity thermal skin response after the concurrent acute training session

Journal of Thermal Analysis and Calorimetry - This study investigated the thermal skin (Tsk) response of lower limbs in older adults with or without osteoarthritis before and after a concurrent...     

Sedimentary process inferences from Humic substances analysis and deposition rates (Western Ross Sea,Antarctica)

The first 40?cm of sediment of three basins in the Ross Sea were sampled using a box corer. Site Y1 was located close to the coast in Terra Nova Bay; the sediment of site Y3 was collected in a more distal basin in the central sector of the Ross Sea; finally site Y5 was sampled in the deepest zone of the Joides Basin.

Sediment cores were sliced and analysed with a depth resolution of 2–4.5?cm. The distribution of humic substances and their structural features along the cores were determined and related to the pattern of Total Organic Carbon (TOC) and sedimentological data. The grain size distribution and the ²¹⁰Pb inventories allow the sediment of the study sites to be characterised.

The humic substance content in the sediment decreases, with a change in slope between 23 and 26?cm at Y1, between 12 and 15?cm at Y3 and constant values with further depth. At Y5 the depth profile of humic substance content shows constant values in the upper 17?cm and values decrease with further depth. The pattern of humic substance yield is similar to that found for TOC. The analysis of the elemental composition of the humic acids extracted from different sediment depths shows an increasing C/N atomic ratio at sites Y1 and Y3 and constant values along the Y5 core. The depth profile of the C/N atomic ratio is confirmed by the changes observed in the structural characterisation and indicates a shift from the freshly deposited organic matter on the sediment surface to more humified material (humin). The results obtained highlight a different sedimentation rate at the three sites as deduced from sedimentological analysis.