Self-Assembly Science Research Section

概要

Nucleic acids and their nanostructures, such as scaffolded DNA origami, 1 have been used for organ- izing enzyme cascades and shown to enhance the ef- ficiency and rate of sequential reactions. 2 Besides some proof-of-concept experiments, the use of DNA origami for templating the biomass-related enzymes is hampered by their unsatisfactory stability to with- stand the folded structure under application-specific conditions. For example, the origami structures are only stable below the melting temperature of around 50 °C. 3 Also, the origami materials poorly withstand the mechanical forces and break even under the mild forces applied during the structural analysis by force-based methods such as atomic force microsco- py (AFM).4 Further, it requires a significantly high ionic strength of typically 5-20 mM of MgCl2.5 Ionic strengths in physiological conditions where enzymes are often handled are much lower than needed to en- sure origami stability. The typical Mg2+ concentration in cell culture media is 0.04 to 0.8 mM, and that of Na+ and K+ are about 150 and 5.5 mM, respectively, making these environments significantly destabiliz- ing toward DNA origami materials.6
Moreover,the solutions containing enzymes often undergo desalting and buffer exchanging processes and may also be stored in pure water to adapt the optimum conditions suitable for the enzymatic reactions . However, in pure water or low ionic strength buffers, the DNA origami immediately unfolds, and it is not very con- venient to store the templated enzymes under these conditions and carry out multienzyme reactions . Bi- omass often undergoes chemical pretreatments using strong acids or bases to break down the lignin. Also, the biomass product contains several carboxylic acids with a pH of 2 to 2.5 . Though the DNA origami ma- terials were shown to be stable up to a pH of 11 , the low pH values below 4 were found to denature the DNA origami. 5 Thus, it is necessary to develop methods to stabilize the DNA origami nanomaterials for various applications , particularly for handling the enzymes related to biomass energy conversion.

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