In this paper, a novel nanocomposite based on magnetic
nanoparticles decorated by dopamine were reported. Three modified
magnetic nanocomposites by dopamine were offered with different type of
linkers. The mentioned magnetic nanocomposites were applied to separate
α-amylase protein from fresh bovine milk. All of the magnetic
nanocomposites were characterized and investigated by using
Fourier-transform infrared spectroscopy, energy-dispersive X-ray
spectroscopy, field-emission scanning microscope, X-ray diffraction
pattern, and vibrating-sample magnetometer analyses. To investigate the
purifying application, sodium dodecyl sulfate polyacrylamide gel
electrophoresis, one-dimensional isoelectric focusing gel
electrophoresis, and alpha-amylase activity assay were employed. With
paying attention to factors such as yield of purification and
concentration of separated protein by each of magnetic nanocomposite, it
could be concluded that the length of linkers played an important role
in α-amylase protein separation. According to the results, the best
separation and purification of α-amylase protein with 49.83% recovery
and 40.11-fold purification efficiency was related to longest length
linker, 1,4-butanediol diglycidyl ether, because of considerable
conjugation with nanocomposite. Also, docking calculation has shown that
the binding energy is - 1.697 kcal/mol and ΔG = - 6.844 kcal/mol which
result that the interaction process between dopamine and α-amylase
protein is spontaneous.