Water-Dispersible Carbon Nano-Test Tubes as a Container for Concentrated DNA Molecules.

Water-dispersible carbon nano-test tubes (CNTTs) with an inner and outer diameter of about 25 and 35 nm, respectively, were prepared by the template technique and then their inner carbon surface was selectively oxidized to introduce carboxy groups. The adsorption behavior of DNA molecules on the oxidized CNTTs (Ox-CNTTs) was examined in the presence of Ca2+ cations. Many DNA molecules are attracted to the inner space of Ox-CNTTs based on the Ca2+ -mediated electrostatic interaction between DNA phosphate groups and carboxylate anions on the inner carbon surface. Moreover, the total net charge of the DNA adsorbed was found to be equal to the total charge of the carboxylate anions. This selective adsorption into the interior of Ox-CNTTs can be explained from the fact that the electrostatic interaction onto the inner concave surface is much stronger than that on the outer convex surface. On the other hand, the desorption of DNA easily occurs whenever Ca2+ cations are removed by washing with deionized water. Thus, each of Ox-CNTTs works well as a nano-container for a large amount of DNA molecules, thereby resulting in the occurrence of DNA enrichment in the nanospace.

Water-Dispersible Carbon Nano-Test Tubes as a Container for Concentrated DNA Molecules.

Invited for the cover of this issue are Takashi Kyotani, Tetsuji Itoh and co-workers at Tohoku University, Gunma University and AIST. The image depicts the synthesis of water-dispersible carbon nano-test tubes by using a template technique and the selective adsorption of DNA into the inner space of these test tubes. Read the full text of the article at 10.1002/chem.202301422.

Orientation Control of Trametes Laccases on a Carbon Electrode Surface to Understand the Orientation Effect on the Electrocatalytic Activity.

By using a carbon-coated anodic aluminum oxide (CAAO) film as a monolithic porous electrode for the immobilization of Trametes laccases (LACs), an attempt is made to control the orientation of LAC molecules toward the electrode surface simply by applying an electric potential to the CAAO film. Because the resulting film is characterized by a myriad of open, simple, and straight nanochannels with diameters as large as 40 nm, the O2 diffusion problem in pores is minimized, thereby making it possible to highlight the effect of such orientation on the electrocatalytic activity as a biocathode. It has been evidenced that LAC molecules are favorably oriented for a smooth electron transfer from the electrode when the LACs are immobilized with applying a positive voltage to the electrode, and such favorable orientation exhibits 3.7-times higher electrocatalytic activity than unfavorable orientation. Furthermore, the orientation mechanism has been rationally explained in terms of local surface chemistry on a LAC molecule.