Mesocellular Silica Foams (MCFs) with Tunable Pore Size as a Support for Lysozyme Immobilization: Adsorption Equilibrium and Kinetics, Biocomposite Properties
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Authors: Chrzanowska, Agnieszka; Derylo-Marczewska, Anna; Wasilewska, Malgorzata
Abstract
The effect of the porous structure of mesocellular silica foams (MCFs) on the lysozyme (LYS) adsorption capacity, as well as the rate, was studied to design the effective sorbent for potential applications as the carriers of biomolecules. The structural (N(2)adsorption/desorption isotherms), textural (SEM, TEM), acid-base (potentiometric titration), adsorption properties, and thermal characteristics of the obtained lysozyme/silica composites were studied. The protein adsorption equilibrium and kinetics showed significant dependence on silica pore size. For instance, LYS adsorption uptake on MCF-6.4 support (pore diameter 6.4 nm) was about 0.29 g/g. The equilibrium loading amount of LYS on MCF-14.5 material (pore size 14.5 nm) increased to 0.55 g/g. However, when the pore diameter was larger than 14.5 nm, the LYS adsorption value systematically decreased with increasing pore size (e.g., for MCF-30.1 was only 0.27 g/g). The electrostatic attractive interactions between the positively charged lysozyme (at pH = 7.4) and the negatively charged silica played a significant role in the immobilization process. The differences in protein adsorption and surface morphology for the biocomposites of various pore sizes were found. The thermal behavior of the studied bio/systems was conducted by TG/DSC/FTIR/MS coupled method. It was found that the thermal degradation of lysozyme/silica composites was a double-stage process in the temperature range 165-420-830 degrees C.
PolyTag: A peptide tag that affords scaffold-less covalent protein assembly catalyzed by microbial transglutaminase
ANALYTICAL BIOCHEMISTRY
Authors: Sato, R.; Minamihata, K.; Wakabayashi, R.; Goto, M.; Kamiya, N.
Abstract
Assembling proteins in close vicinity to each other provides an opportunity to gain unique function because collaborative and even synergistic functionalities can be expected in an assembled form. There have been a variety of strategies to synthesize functional protein assemblies but site-specific covalent assembly of monomeric protein units without impairing their intrinsic function remains challenging. Herein we report a powerful strategy to design protein assemblies by using microbial transglutaminase (MTG). A serendipitous discovery of self-crosslinking of enhanced green fluorescent protein (EGFP) fused with StrepTag I at the C-terminus revealed that EGFP was assembled through the crosslinking of the Lys (K) residue in the C-terminus of EGFP and the Gln (Q) residue in StrepTag I (AWRHPQFGG). Site-directed mutagenesis of the residues next to the K and Q yielded EGFP assemblies with higher molecular weights. An optimized peptide tag comprised of both K and Q residues (HKRWRHYQRGG) enabled the assembly of different types of proteins of interest (POI) when it was fused to either the N- or C-terminus. The peptide tag that enabled the self-polymerization of the functional POI without a scaffold was designated as a 'PolyTag'.