Human Serum Albumin Nanotubes with Esterase Activity

Authors

  • Prof. Dr. Teruyuki Komatsu,

    Corresponding author
    1. Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1–13–27 Kasuga, Bunkyo-ku, Tokyo 113–8551 (Japan), Fax: (+81) 3-3817-1910
    • Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1–13–27 Kasuga, Bunkyo-ku, Tokyo 113–8551 (Japan), Fax: (+81) 3-3817-1910

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  • Dr. Takaaki Sato,

    1. International Young Researcher Empowerment Center, Shinshu University, 3-15-1 Tokita, Ueda-shi, Nagano 386-8567 (Japan)
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  • Dr. Christoph Boettcher

    1. Research Center of Electron Microscopy, Institute of Chemistry and Biochemistry, Freie Universität Berlin, Febeckstrasse 36a, 14195 Berlin (Germany)
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Abstract

A nanocylindrical wall structure was obtained by layer-by-layer (LbL) assembly of poly-L-arginine (PLA) and human serum albumin (HSA) and characterized by scanning electron microscopy (SEM), scanning force microscopy (SFM), and cryogenic transmission electron microscopy (cryo-TEM). SEM and SFM measurements of a lyophilized powder of (PLA/HSA)3 nanotubes yielded images of round, chimney-like architectures with approximately 100 nm wall thickness. Cryo-TEM images of the hydrated sample revealed that the tube walls are composed of densely packed HSA molecules. Moreover, when small-angle X-ray scattering was used to characterize the individual PLA and HSA components in aqueous solutions, maximum diameters of approximately 28 nm and 8 nm were obtained, respectively. These values indicate the minimum thickness of wall layers consisting of PLA and HSA. It can also be concluded from SEM as well as from cryo-TEM images that the protein cylinders are considerably swollen in the presence of water. Furthermore, HSA retains esterase activity if assembled in nanotubes, as indicated by measurements of para-nitrophenyl acetate hydrolysis under semi-physiological conditions (pH 7.4, 22 °C). The enzyme activity parameters (Michaelis constant, Km, and catalytic constant, kcat) were comparable to those of free HSA.

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