Adsorption and enzyme activity of asparaginase at lipid Langmuir and Langmuir-Blodgett films
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2017
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da Rocha Junior, Carlos [UNIFESP]
Caseli, Luciano [UNIFESP]
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In this present work, the surface activity of the enzyme asparaginase was investigated at the air-water interface, presenting surface activity in high ionic strengths. Asparaginase was incorporated in Langmuir monolayers of the phospholipid dipaltnitoylphosphatidylcholine (DPPC), forming a mixed film, which was characterized with surface pressure-area isotherms, surface potential-area isotherms, polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The adsorption of the enzyme at the air-water interface condensed the lipid monolayer and increased the film compressibility at high surface pressures. Amide bands in the PM-IRRAS spectra were identified, with the C - N and C = 0 dipole moments lying parallel to monolayer plane, revealing the structuring of the enzyme into alpha-helices and beta-sheets. The floating monolayers were transferred to solid supports as Langmuir-Blodgett (LB) films and characterized with fluorescence spectroscopy and atomic force microscopy. Catalytic activities of the films were measured and compared to the homogenous medium. The enzyme accommodated in the LB films preserved more than 78% of the enzyme activity after 30 days, in contrast for the homogeneous medium, which preserved less than 13%. The method presented in this work not only allows for an enhanced catalytic activity, but also can help explain why certain film architectures exhibit better performance. (C) 2016 Elsevier B.V. All rights reserved.
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Materials Science & Engineering C-Materials For Biological Applications. Amsterdam, v. 73, p. 579-584, 2017.