Several protein processing events that involve related chemical mechanisms have been observed in nature. Now, new methods have been developed, based on the same chemical reactions, that permit proteins to be modified in ways that were not previously possible. 相似文献
Electrospinning has been exploited for almost one century to process polymers and related materials into nanofibers with controllable compositions, diameters, porosities, and porous structures for a variety of applications. Owing to its high porosity and large surface area, a non‐woven mat of electrospun nanofibers can serve as an ideal scaffold to mimic the extracellular matrix for cell attachment and nutrient transportation. The nanofiber itself can also be functionalized through encapsulation or attachment of bioactive species such as extracellular matrix proteins, enzymes, and growth factors. In addition, the nanofibers can be further assembled into a variety of arrays or architectures by manipulating their alignment, stacking, or folding. All these attributes make electrospinning a powerful tool for generating nanostructured materials for a range of biomedical applications that include controlled release, drug delivery, and tissue engineering.
The determination of Zn, Sr, Ba, and Pb in solid samples has been achieved by laser ablation inductively coupled plasma isotope dilution mass spectrometry using a spinning platform. The fast rotation of a sample and an isotopically enriched spike placed close together on a sample holder allowed performing the isotope dilution directly inside the ablation cell. The proportion of spike versus sample of the aerosol mixture obtained has been determined online by isotope dilution in order to correct for differences in ablation rate although both materials were placed on the axis of rotation of the motor. Homogeneous, time-stable, and reusable samples were prepared by lithium borate fusion. A unique isotopically enriched spike glass was used to analyze four Standard Reference Materials of different matrix (after a simple polishing): two sediments Standard Reference Material (SRM) 1944 and SRM 2702 and two soils SRM 2586 and SRM 2711a. The proposed method yielded mass fractions with a deviation from the certified value usually lower than 12 % and a precision of less than 9 % RSD (except for Zn in SRM 2586 and 2711a). Although direct spiking of the solid before fusion could presumably provide better isotopic mixing, the presented methodology allows the reuse of the spike glass (thus, decreasing drastically the cost of the analysis) and is relatively faster because the spike does not need to be weighted, added, and evaporated each time. These results demonstrate the potential of this newly developed method for fast analysis of solid samples using isotope dilution at a low cost. 相似文献
