Synthesis of zirconium diboride–zirconium nitride composite powders by self-propagating high-temperature synthesis

Formation of zirconium diboride–zirconium nitride composite powders by self propagating high temperature reaction of zirconium, boron and hexagonal boron nitride powders was investigated. Zirconium diboride–zirconium nitride powder mixtures with varying proportions were produced by changing the amount of boron nitride in the reactants. Products were subjected to powder X-ray diffraction analysis; and grain size and morphology was examined by scanning electron microscope. It was seen that the velocity of the wave front, adiabatic temperature of the reaction and grain size of the products decreased by increasing the boron nitride amount in the reactants. It was deduced from the scanning electron microscope examinations and crystal size calculations performed from the broadening of the peaks on the X-ray diffractions patterns that zirconium nitride grains were much finer than zirconium diboride grains.     

An Engineered ClyA Nanopore Detects Folded Target Proteins by Selective External Association and Pore Entry

Nanopores have been used in label-free single-molecule studies, including investigations of chemical reactions, nucleic acid analysis, and applications in sensing. Biological nanopores generally perform better than artificial nanopores as sensors, but they have disadvantages including a fixed diameter. Here we introduce a biological nanopore ClyA that is wide enough to sample and distinguish large analyte proteins, which enter the pore lumen. Remarkably, human and bovine thrombins, despite 86% sequence identity, elicit characteristic ionic current blockades, which at -50 mV differ in their main current levels by 26 ± 1 pA. The use of DNA aptamers or hirudin as ligands further distinguished the protein analytes. Finally, we constructed ClyA nanopores decorated with covalently attached aptamers. These nanopores selectively captured and internalized cognate protein analytes but excluded noncognate analytes, in a process that resembles transport by nuclear pores.