Sun-Gu Lee

Shape memory polyurethane containing mesogenic moiety

The mechanical and thermal properties, in particular the shape memory effect, of TPUs synthesized from diol-terminated poly(caprolactone) (PCL diol), 4,4′-diphenylmethane diisocyanate (MDI), and mesogenic chain extenders, 4,4′-bis-(2-hydroxyethoxy)biphenyl (BEBP) or 4,4′-bis-(6-hydroxyhexoxy)biphenyl (BHBP) were examined and compared with results for PCL diol/MDI/1,4-butanediol (BD) based TPUs in a previous study. Some results related to the rigid structure of BEBP or BHBP were observed in the thermomechanical properties. Shape fixity was related to the crystallization of the PCL phase.

Purification of His-tagged proteins using Ni2+–poly(2-acetamidoacrylic acid) hydrogel

In this study, a new matrix for immobilized metal affinity chromatography (IMAC) using poly(2-acetamidoacrylic acid) (PAAA) hydrogels complexed with Ni(2+) was developed for the purification of the recombinant histidine-tagged green fluorescence protein (His6-GFP). The Ni(2+)-complexed PAAA hydrogel was prepared by polymerizing 2-acetamidoacrylic acid (AAA) and 2,2-[(1,4-dioxo-1,4-butanediyl)diamino] bis(2-propenoic acid) (DBDBPA) with potassium persulfate in DMSO, followed by Ni(2+) complexation. Confocal laser scanning microscopy was used to determine the binding of His6-GFP to the Ni(2+)-PAAA hydrogel in three-dimensional space. Photoluminescence spectroscopy revealed an 81% binding efficiency of His6-GFP to the Ni(2+)-PAAA hydrogel yielded with a recovery of 59%. The specificity of His6-GFP binding to Ni(2+)-PAAA hydrogel was compared with that of the PAAA hydrogel without Ni(2+). His6-GFP was purified directly from the cell lysate with Ni(2+)-PAAA hydrogel matrix but the PAAA hydrogel without Ni(2+) had no effect. The major advantage of the Ni(2+)-PAAA hydrogel system over current methods, such as Ni-nitrilotriacetic acid (NTA) agarose beads, was the simple and low-cost procedure for preparing the matrix.