Zobrazení zdroje stránky Sheridancohen9140

Metal-organic framework (MOF) membranes have enormous potential in separation applications. There are several MOF membranes grown on polymer substrates aimed for scale-up, but their brittleness hampers any industrial application. Herein, intergrown continuous polypropylene (PP)-supported ZIF-8 membranes have been successfully synthesized via fast current-driven synthesis (FCDS) within 1 h. The PP-supported ZIF-8 membranes exhibit a promising separation factor of 122 ± 13 for binary C3H6-C3H8 mixtures combined with excellent flexibility behavior. The C3H6/C3H8 separation performance of the PP-supported ZIF-8 membrane was found to be constant after bending the supported ZIF-8 film with a curvature of 92 m-1. This outstanding mechanical property is crucial for practical applications. Moreover, we further synthesized ZIF-8 membranes on various polymer substrates and even polymer hollow fibers to demonstrate the production scalability.The streptavidin-based enrichment of biotin-tagged molecules is a common methodology that is routinely used across multiple disciplines in biomedical research. Numerous and varied formats of immobilized streptavidin and related proteins are available, but predicting which product is most apt for a given application is complicated by the fact that there are numerous technical considerations and no universal reporting standards for describing the binding capacity of the beads. Here, we define criteria that should be considered when performing a fit-for-purpose evaluation of streptavidin beads. We also describe a colorimetric competitive displacement assay, the streptAVIdin binDing capacITY (AVIDITY) assay, a fast, easy, and inexpensive absorbance-based method to measure the binding capacity of streptavidin beads, which can be used to compare different products and evaluate variation among many of the same product. We expect that the fit-for-purpose criteria and the AVIDITY assay will benefit users across disciplines to make informed decisions regarding the most apt streptavidin bead products for their own experiments.Decoding the structural information contained in the interfacial vibrational spectrum of water requires understanding how the spectral signatures of individual water molecules respond to their local hydrogen bonding environments. In this study, we isolated the contributions for the five classes of sites that differ according to the number of donor (D) and acceptor (A) hydrogen bonds that characterize each site. These patterns were measured by exploiting the unique properties of the water cluster cage structures formed in the gas phase upon hydration of a series of cations M+·(H2O) n (M = Li, Na, Cs, NH4, CH3NH3, H3O, and n = 5, 20-22). This selection of ions was chosen to systematically express the A, AD, AAD, ADD, and AADD hydrogen bonding motifs. The spectral signatures of each site were measured using two-color, IR-IR isotopomer-selective photofragmentation vibrational spectroscopy of the cryogenically cooled, mass selected cluster ions in which a single intact H2O is introduced without isotopic scrambling, an important advantage afforded by the cluster regime. The resulting patterns provide an unprecedented picture of the intrinsic line shapes and spectral complexities associated with excitation of the individual OH groups, as well as the correlation between the frequencies of the two OH groups on the same water molecule, as a function of network site. The properties of the surrounding water network that govern this frequency map are evaluated by dissecting electronic structure calculations that explore how changes in the nearby network structures, both within and beyond the first hydration shell, affect the local frequency of an OH oscillator. The qualitative trends are recovered with a simple model that correlates the OH frequency with the network-modulated local electron density in the center of the OH bond.Previously, vacuum matrix-assisted ionization (vMAI) was employed with matrix/analyte sample introduction into the vacuum of a mass spectrometer on a probe sample introduction device. Low attomole detection was achieved, while no carryover was observed even for concentrated samples. Here, we report a new vacuum ionization source designed to duplicate the sensitivity and robustness of probe device while providing fast multisample introduction to vacuum and rapid sequential ionization. Exposure of a sample to the vacuum of the mass spectrometer provides spontaneous ionization of volatile as well as nonvolatile analytes without the need for external energy input. However, the novel source design described herein, in addition to vMAI, can employ a laser to obtain vacuum matrix-assisted laser desorption/ionization (vMALDI). [https://www.selleckchem.com/products/lw-6.html LW 6 research buy] In particular, ionization by vMAI or vMALDI is achieved by using the appropriate matrix. Switching between ionization modes is accomplished in a few seconds. We present results demonstrating the utility of the two ionization methods in combination to improve the molecular analyses of sample composition. In both ionization modes, multiple samples can be sequentially and rapidly acquired to increase throughput in MS. With the prototype source, samples were acquired in as little as 1 s per sample. Exchanging multisample plates can be accomplished in as little as 2 s, suggesting low-cost high-throughput automation when properly developed.Despite experimental efforts spanning more than 80 years, there has been no direct observation of free ethylidene (CH3CH), the simplest alkyl-substituted carbene. Here, we report that ethylidene is indefinitely stable in the absence of collisions if produced in the triplet ground state at energies below the threshold for intersystem crossing. Near-UV photolysis of gaseous methylketene, or propenal (followed by isomerization to methylketene), leads to CO loss producing triplet ethylidene, which is detected by photoionization mass spectrometry. Electronically excited singlet ethylidene is also produced, rapidly undergoing isomerization by a 1,2-hydrogen atom shift, producing highly vibrationally excited ethylene. The measured product translational energy distributions verify the theoretically calculated enthalpy of formation of triplet ethylidene and are consistent with a singlet-triplet energy gap of approximately 12.5 kJ/mol.