A new approach for the speciation of metallothioneins (MT) in human brain cytosols is described. The analysis is performed by application of a newly developed coupling of capillary electrophoresis (CE) with inductively coupled plasma-sector field mass spectrometry (ICP-SFMS). Isoforms of metallothioneins are separated from 30-100 microliter sample volumes by CE and the elements Cu, Zn, Cd, and S are detected by use of ICP-SFMS. The extraction of cytosols is the first step in the analytical procedure. Tissue samples from human brain are homogenized in a buffer solution and submitted to ultra-centrifugation. The supernatant is defatted and the cytosol pre-treatment is optimized for CE separation by matrix reduction. The buffer concentration and pH used for capillary electrophoretic separation of metallothionein from rabbit liver were optimized. CE with ICP-MS detection is compared to UV detection. In the electropherograms obtained from the cytosols three peaks can be assigned to MT-1, MT-2, and MT-3. As an additional method, size-exclusion chromatography (SEC) is applied. Fractions from an SEC separation of the cytosol are collected, concentrated, and then injected into the CE. The detection of sulfur by ICP-SFMS (medium resolution mode) and quantification by isotope dilution have also been investigated as a new method for the quantification of MT isoforms. The analytical procedure developed has been used for the first time in comparative studies of the distributions of MT-1, MT-2, and MT-3 in brain samples taken from patients with Alzheimer's disease and from a control group. 相似文献
LbL nano self‐assembly coating of A. vinosum with different polyelectrolyte combinations is presented as an example to investigate substrate uptake in bacteria. The effects of surface charge and the formation of a physical barrier provides new insights in the contact mechanisms between the cell surface and insoluble elemental sulfur. Furthermore, uptake of sulfide by encapsulated cells was investigated. Growth experiments of coated cells showed that surface charge did neither affect sulfide uptake nor the contact formation between the cells and solid sulfur. However, increasing layers slowed or inhibited the uptake of sulfide and elemental sulfur. This work demonstrates how defining surface properties of bacteria has potential for microbiological and biotechnological applications.
Sergeolide , isolated from the French Guyanan Simaroubaceae, Picrolemma pseudocoffea Ducke, is a novel quassinoid possessing the normal C20 basic skeleton with a butenolide function attached to the A ring. Structure was established by interpretation of the 400 MHz 1H-NMR and the 13C-NMR data. It is highly cytotoxic and is active against mouse leukemia P388. The previously known isobruceine B was also isolated. 相似文献
X-ray absorption near-edge spectroscopy (XANES) is used to study the N environment in bulk GaN and in GaNyAs1−y epilayers on GaAs (0 0 1), for y∼5%. Density-functional optimized structures were used to predict XANES via multiple-scattering theory. We obtain striking agreement for pure GaN. An alloy model with nitrogen pairs on Ga accurately predicts the threshold energy, the width of the XANES ‘white line’, and features above threshold, for the given X-ray polarization. The presence of large quantitities of N-pairs may point to a role for molecular N2 in epitaxial growth kinetics. 相似文献