Minh-Hai Tran

Nonspecific cleavage of proteins using graphene oxide

In this article, we report the intrinsic catalytic activity of graphene oxide (GO) for the nonspecific cleavage of proteins. We used bovine serum albumin (BSA) and a recombinant esterase (rEstKp) from the cold-adapted bacterium Pseudomonas mandelii as test proteins. Cleavage of BSA and rEstKp was nonspecific regarding amino acid sequence, but it exhibited dependence on temperature, time, and the amount of GO. However, cleavage of the proteins did not result in complete hydrolysis into their constituent amino acids. GO also invoked hydrolysis of p-nitrophenyl esters at moderate temperatures lower than those required for peptide hydrolysis regardless of chain length of the fatty acyl esters. Based on the results, the functional groups of GO, including alcohols, phenols, and carboxylates, can be considered as crucial roles in the GO-mediated hydrolysis of peptides and esters via general acid-base catalysis. Our findings provide novel insights into the role of GO as a carbocatalyst with nonspecific endopeptidase activity in biochemical reactions.

Improved dispersion of graphite derivatives by solution plasma

Solution plasma is applied to graphite and thermally reduced graphite oxide in ambient conditions in order to improve their dispersion. Changes in morphology, oxygen functional groups, defects, decomposition temperatures, oxygen to carbon atomic ratio, conductivity, stability, and degree of dispersion are systematically investigated by using scanning electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, Thermogravimetric analysis, X-ray photoelectron spectroscopy, Zeta potential analyzers, and ultraviolet–visible spectrophotometry. Dramatic enhancement of the dispersion after the simple plasma treatment is introduced without evident change of conductivities. This simple, easy, economical, and eco-friendly plasma method could functionalize and reform material efficiently in many application fields.