Microstructure evolution mechanisms of undercooled Ni_(80)Cu_(20) alloys were systematically studied, and two types of grain refinement were observed in the as-solidified microstructures. The first type of grain refinement appeared in a low undercooling range (i.e., 50 K ≤ ?T≤ 90 K). The remelting of primary dendrites during or after rapid solidification was due to liquid/solid interfacial tension and chemical superheating. The second type of grain refinement occurred in a high undercooling range (i.e., ?T≥ 165 K), in which the liquid phase pressure drop due to solidification contraction induced the flow of liquid in the inter-dendrite region and produced stress accumulation in the dendrites. At the slow solidification stage, i.e., post-recalescence period, recrystallization was observed. In addition, highly undercooled Ni_(80)Cu_(20)) alloy melts were quenched before rapid solidification by Ga-In liquid alloy, and partially recrystal-lizcd microstructures were obtained. Using electron back-scattering diffraction and transmission electron microscopy techniques, the occurrence of recrystallization was verified experimentally.
Dhandhukia Jugal P.;Brill Dab A.;Kouhi Aida;Pastuszka Martha K.;MacKay J. Andrew
来源期刊：Protein science :
年/卷/期：2017 / 26 / 9
Abstract Elastin‐Like Polypeptides (ELPs) reversibly phase separate in response to changes in temperature, pressure, concentration, pH, and ionic species. While powerful triggers, biological microenvironments present a multitude of more specific biological cues, such as antibodies, cytokines, and cell‐surface receptors. To develop better biosensors and bioresponsive drug carriers, rational strategies are required to sense and respond to these target proteins. We recently reported that noncovalent association of two ELP fusion proteins to a “chemical inducer of dimerization” small molecule (1.5 kDa) induces phase separation at physiological temperatures. Having detected a small molecule, here we present the first evidence that ELP multimerization can also detect a much larger (60 kDa) protein target. To demonstrate this strategy, ELPs were biotinylated at their amino terminus and mixed with tetrameric streptavidin. At a stoichiometric ratio of [4:1], two to three biotin‐ELPs associate with streptavidin into multimeric complexes with an apparent K d of 5 nM. The increased ELP density around a streptavidin core strongly promotes isothermal phase separation, which was tuned to occur at physiological temperature. This phase separation reverses upon saturation with excess streptavidin, which only favors [1:1] complexes. Together, these findings suggest that ELP association with multimeric biomolecules is a viable strategy to deliberately engineer ELPs that respond to multimeric protein substrates.