Title: Interaction of Biological Molecules with Clay Minerals: A Combined Spectroscopic and Sorption Study of Lysozyme on Saponite
Authors: Johnston, Cliff T ×
Premachandra, Gnanasiri S
Szabo, Tamas
Lok, Joyce
Schoonheydt, Robert #
Issue Date: 2012
Publisher: American Chemical Society
Series Title: Langmuir vol:28 issue:1 pages:611-619
Abstract: The interaction of hen egg white lysozyme (HEWL) with Na-and Cs-exchanged saponite was investigated using sorption, structural, and spectroscopic methods as a model system to study clay_protein interactions. HEWL sorption to Na- and Cs-saponite was determined using the bicinchoninic acid (BCA) assay, thermogravimetric analysis, and C and N analysis. For Na-saponite, the TGA and elemental analysis-derived sorption maximum was 600 mg/g corresponding to a surface coverage of 0.85 ng/mm2 with HEWL occupying 526 m2/g based on a cross-sectional area of 13.5 nm2/molecule. HEWL sorption on Na-saponite was accompanied by the release of 9.5 Na+ ions for every molecule of HEWL sorbed consistent with an ion exchange mechanism between the positively charged HEWL (IEP 11) and the negatively charged saponite surface. The d-spacing of the
HEWL_Na-saponite complex increased to a value of 4.4 nm consistent with the crystallographic dimensions of HEWL of 3 _ 3 _ 4.5 nm. In the case of Cs-saponite, there was no evidence of interlayer sorption; however, sorption of HEWL to the “external” surface of Cs-saponite showed a high affinity isotherm. FTIR and Raman
analysis of the amide I region of the HEWL_saponite films prepared from water and D2O showed little perturbation to the secondary structure of the protein. The overall hydrophilic nature of the HEWL_Na-saponite complex was determined by water vapor sorption measurements. The clay retained its hydrophilic character with a water content of 18% at high humidity corresponding to 240 H2O molecules per molecule of HEWL.
ISSN: 0743-7463
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
× corresponding author
# (joint) last author

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