Peroxidase-like Catalytic Activity of Copper-Mediated Protein–Inorganic Hybrid Nanoflowers and Nanofibers of β-Lactoglobulin and α-Lactalbumin: Synthesis, Spectral Characterization, Microscopic Features, and Catalytic Activity

Abstract

A free Cys-SH-containing protein, β-lactoglobulin (β-LG), and another protein not possessing the same, viz., apo-α-lactoglobulin (apo-α-LA), were used in studies to demonstrate the role of this amino acid, along with its secondary structure, in the formation of a protein dimer and a protein-inorganic hybrid nanoflower and in the creation of the peroxidase-like activity of the nanomaterials produced when the proteins were treated with varying Cu(2+) concentration under different pH conditions. An increase in the pH as well as the Cu(2+) mole ratio results in increasing dimer formation in case of β-LG due to the presence of free Cys121-SH, while the dimer is not formed in case of apo-α-LA under the same conditions. The role of Cys in the dimer formation has been demonstrated both by MALDI and sodium dodecyl sulfate-polyacrylamide gel electrophoresis studies. Both of the proteins exhibited changes in their secondary structures to different extents as a function of pH, and the structures were stabilized by Cu(2+) interactions, as studied by CD and fluorescence spectroscopy. The small and spherical nanoparticles formed at pH 7 with lower equivalents of Cu(2+) join together to form larger aggregates at higher equivalents of Cu(2+). For the same concentration at pH 9, both the aggregates and the nanoflowers were noticed. However, at pH 12, the Cu(2+) binding induces the formation of fibers along with the flowers. Both the nanoflowers and nanofibers exhibited peroxidase-like activity in a catalytic manner. Nanoflowers were also shown to detect phenol in the concentration range from 10 to 200 μM. The copper-induced nanobiomaterial obtained in the case of apo-α-LA also exhibited peroxidase-like activity. Thus, this paper deals with the green synthesis of copper-induced protein (β-LG/apo-α-LA)-inorganic hybrid nanomaterials that are important due to their applications as nanobiomaterials.

Synthesis of RGO/Cu8S5/PPy Composite Nanosheets with Enhanced Peroxidase-Like Activity for Sensitive Colorimetric Detection of H2O2and Phenol

“…The catalytic measurements were conducted by monitoring the absorbance changes in spectrum mode after 10 min of the catalytic reaction in natural daylight. The absorbance of the resulting solution was measured at 500 nm, corresponding to the formation of quinone–imine complex …”

“…The absorbance of the resulting solution was measured at 500 nm, corresponding to the formation of quinone-imine complex. [53] Characterization: A TEM (JEOL JEM-1200 EX) was used to observe morphology and structure of the samples at 100 kV. HRTEM images and EDX analysis were investigated by a FEI Tecnai G2 F20 high-resolution transmission electron microscope.…”

Interactions of Whey Proteins with Metal Ions

“…An interesting study by Thawari et al [120] on β-LG and apo-α-LA was reported on the effect of copper (II) ions on the formation of protein dimers and the catalytic activity of the formed nanobiomaterials, which were inorganic hybrid nanomaterials in its nature. Nanostructures in the form of nanoflowers and nanofibers combined with copper-LG and copper-LA with Cu as the inorganic part exhibited peroxidase-like catalytic activity.…”

Synthesis of organic-inorganic hybrid nanoflowers using Trigonella foenum-graecum seed extract and investigation of their anti-microbial activity

“…They created novel hybrid nanoflowers (hNFs) with much greater enzymatic activity and stability than those obtained with free enzymes. Some researchers have prepared various kinds of organicinorganic nNFs and used them for different applications (Sun et al, 2014;Liang et al, 2015;Huang et al, 2015;Somturk et al, 2015;Altinkaynak et al 2016a;Altinkaynak et al, 2016b;Ariza-Avidad et al, 2016;Thawari et al, 2016;Zhang et al, 2016).…”