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The structural pathway of spontaneous microtubule nucleation was identified for the first time using recombinant mutant tubulin with a high nucleation rate, rapid flash-negative stain electron microscopy, and kinetic analyses of the size of critical nucleus. The singlestranded tubulin oligomers assembled during the early stage of polymerization had a variety of lengths and curvatures; however, the majority of these oligomers dissociated to tubulin. It was the few straight oligomers exceeding the critical size that underwent lateral interaction, had two-dimensional growth into sheets, and eventually closed into microtubules. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) are a novel class of porous materials composed of metal ions and imidazole linkers. Here we focus on core-shell particles, where ZIF-67 core particles are covered with ZIF-8 shells (ZIF-67@ZIF-8). However, the synthesis of ZIF-67@ZIF-8 is generally difficult because the nucleation rate of ZIF-8 is so high that self-nucleation is unavoidable. In this study, we propose the following two approaches to overcome this challenge: (1) decreasing the nucleation rate by changing the water to methanol ratio used as solvents; and (2) intensifying the mixing during the synthesis by using a microreactor. Our experiments demonstrated that an increase in the water ratio suppresses the self-nucleation of the ZIF-8 particles, whereas surfaces of the resultant ZIF-67@ZIF-8 particles become irregular. The ZIF-67@ZIF-8 particles with uneven surfaces experienced an approximately 14% decrease in the adsorption amount as compared with that of the ZIF-67 particles. In contrast, the microreactor successfully produced ZIF-67@ZIF-8 particles with a smooth surface and high surface area. Our study revealed that intensive mixing is key to obtain uniform core-shell particles. [ABSTRACT FROM AUTHOR]