Graphene oxide (GO) has a large surface-to-volume ratio and hydrophobic hexagonal rings that can interact with biomolecules. Single-stranded DNA adsorbs strongly to the surface of GO via hydrophobic interactions. GO has been used in optical biosensors and biomedical platforms for the detection of DNA, proteins, and small molecules. This study was designed to measure the adsorption of double-stranded DNA (dsDNA) onto GO according to DNA length, salt concentration, and pH of the reaction. Results showed that dsDNA molecules were adsorbed progressively as the pH changed from 6.0 to 4.0. At high pH, dsDNA adsorption was enhanced by the presence of MgCl2 rather than NaCl. Desorption of DNA from GO, with triton X-100 led to the rapid release of DNA from GO in the presence of MgCl2.

Recent studies have shown that single-stranded DNA adsorbed onto graphene oxide is protected from DNase I cleavage. However, double-stranded DNA bound to graphene oxide and could be digested by DNase I. To elucidate whether single-stranded DNA is protect from DNase I in the presence of graphene oxide, this study conducted DNase I digestion using single-stranded DNA and single-stranded DNA containing the duplex region in the presence of graphene oxide. Addition of DNase I resulted in restoration of the fluorescence emission that had been quenched when DNA was adsorbed to graphene oxide. It indicates that DNase I cleaved the adsorbed single-stranded DNA onto graphene oxide, which was sufficient for the detection of DNase I activity.

DNA polymerase plays an important role in the proliferation and survival of all forms of life and the variety of biotechnological applications. In this study, DNA‐templated copper nanoclusters were utilized to detect Klenow fragment exo‐ (KF‐) activity and monitor its inhibition in the presence of 5‐fluorouracil by measurement of fluorescence intensities. This study showed that the fluorescence intensities increased continuously for KF‐ concentrations ranging from 0 to 5 U/mL. In addition, inhibition of KF‐ activity was measured at 5‐fluorouracil concentrations ranging from 0 to 150 μM. Using nonlinear regression, the corresponding IC50 was determined to be 6.23 μM in the presence of 5.0 U/mL KF‐.

Bacteriocin was maximally produced by Pediococcus pentosaceus KC-007 in the late exponential phase in MRS broth. The activity of bacteriocin was completely inactivated by proteinase K, trypsin, chymotrypsin, pepsin, and subtilisin A, but not by catalase, lysozyme, lipase, ribonuclease A, and alpha-amylase. Furthermore, its activity was not affected by pH changes ranging from 2 to 8 and heat treatment at 100 o C for 60 min or autoclaving. The activity of bacteriocin remained after treatment of organic solvents or detergent such as acetone, chloroform, ethanol, hexane, isopropanol, methanol, SDS, or Tween 20. Therefore, the bacteriocin isolated in this study could be used for a food preservative due to its growth inhibition against Bacillus cereus, Escherichia coli O157-H7, and Listeria monocytogenes.

In this study, the G-quadruplex structure was used to detect the enzymatic activity and inhibition of the Klenow fragment exo−(KF−) in the presence ofN-methylmesoporphyrin IX (NMM) which binds specifically to the G-quadruplex.