Polyurethane (PU) microcapsules containing hexamethylene diisocyanate (HDI) as core materials are facilely manufactured via interfacial polymerization reaction of commercial methylene diphenyl diisocyanate (MDI) prepolymer and 1,4-butanediol in an oil-in-water emulsion. The resultant capsules have diameters of 5-350 mm and shell thickness of 1-15 mm, both linearly related to the agitation rate in the double logarithm coordinates. The typical core fraction of microcapsules and the yield of synthesis are around 60 wt% and 70 wt%, respectively, while varying with reaction conditions. The effects of parameters including reaction duration and temperature, surfactant concentration, agitation rate, and environmental factors on the formation of microcapsules were systematically investigated and optimized. Quality assessments of each batch of microcapsules were performed using thermogravimetric analysis and scanning electron microscopy. Anticorrosion coatings mixed with synthesized microcapsules were prepared on a steel substrate. Preliminary results indicated significant corrosion retardancy happened in the self-healing coatings under an accelerated corrosion process, showing the great potential of this facile microencapsulation technique in development of catalyst-free, one-part self-healing coatings for corrosion control.

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Properties of the metal ion binding sites of Zn-transcription factor IIIA (TFIIIA) were investigated to understand the potential of this type of zinc finger to undergo reactions that remove Zn 2+ from the protein. Zn-TFIIIA was purified from E. coli containing the cloned sequence for Xenopus laevis oocyte TFIIIA and its stoichiometry of bound Zn 2+ was shown to depend on the details of the isolation process. The average dissociation constant of Zn 2+ in Zn-TFIIIIA was 10 −7 . The dissociation constant for Zn-F3, the third finger from the N-terminus of TFIIIA, was 1.0 × 10 −8 . The reactivity of Zn-TFIIIA with a series of metal binding ligands, including 2-carboxy-2′-hydroxy-5′-sulfoformazylbenzene (zincon), 4-(2-pyridylazo)-resorcinol (PAR), and 3-ethoxy-2-oxo-butyraldehyde-bis-(N 4 -dimethylthiosemicarbazone) (H 2 KTSM 2 ) revealed similar kinetics. The reactivity of PAR with Zn-TFIIIA declined substantially when the protein was bound to the internal control region (ICR) of the 5S ribosomal DNA. Both Cd 2+ and Pb 2+ disrupt TFIIIA binding to its cognate DNA sequence. The Pb 2+ dissociation constant of Pb-F3 was measured as 2.5 × 10 −8 . According to NMR spectroscopy, F3 does not fold into a regular conformation in the presence of Pb 2+ .

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