Advances in automation have facilitated the widespread adoption of highthroughput vapour-diffusion methods for initial crystallization screening. However, for many proteins, screening thousands of crystallization conditions fails to yield crystals of sufficient quality for structural characterization. Here, the rates of crystal identification for thaumatin, catalase and myoglobin using microfluidic Crystal Former devices and sitting-drop vapour-diffusion plates are compared. It is shown that the Crystal Former results in a greater number of identified initial crystallization conditions compared with vapour diffusion. Furthermore, crystals of thaumatin and lysozyme obtained in the Crystal Former were used directly for structure determination both in situ and upon harvesting and cryocooling. On the basis of these results, a crystallization strategy is proposed that uses multiple methods with distinct kinetic trajectories through the protein phase diagram to increase the output of crystallization pipelines.
The high-frequency characteristics of AlGaN/GaN high-electron-mobility transistors (HEMTs) and metal-insulator-semiconductor HEMTs (MIS-HEMTs) are investigated under ultraviolet (UV) radiation with 365 nm wavelength. When HEMTs and MIS-HEMTs are illuminated with an UV source, their drain currents increase apparently owing to the generated photocurrent. Nevertheless, they show different high-frequency response to the UV light. For HEMTs, the peak cutoff frequency (fT) and maximum oscillation frequency (fmax) of illuminated devices are 20% and 10% higher than those in dark condition, respectively, owing to the increased transconductance. For MIS-HEMTs, however, their high-frequency performances are degraded when transistors are subject to light exposure. The degradations of peak fT and fmax are around 3.7% and 18%, respectively. The small-signal model parameters relevant to the high-frequency characteristics were extracted to explain these phenomena. Additional trapped charges in the SiN gate dielectric induced by UV light would be responsible for the degraded high-frequency parameters in illuminated MIS-HEMTs. These experimental results are important for designing a suitable GaN-based HEMT for optoelectronic applications.
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