DNA replication, repair, and recombination in the cell play a significant role in the regulation of the inheritance, maintenance, and transfer of genetic information. To elucidate the biomolecular mechanism in the cell, some molecular models of DNA replication, repair, and recombination have been proposed. These biological studies have been conducted using bulk assays, such as gel electrophoresis. Because in bulk assays, several millions of biomolecules are subjected to analysis, the results of the biological analysis only reveal the average behavior of a large number of biomolecules. Therefore, revealing the elementary biological processes of a protein acting on DNA (e.g., the binding of protein to DNA, DNA synthesis, the pause of DNA synthesis, and the release of protein from DNA) is difficult. Single-molecule imaging allows the analysis of the dynamic behaviors of individual biomolecules that are hidden during bulk experiments. Thus, the methods for single-molecule imaging have provided new insights into almost all of the aspects of the elementary processes of DNA replication, repair, and recombination. However, in an aqueous solution, DNA molecules are in a randomly coiled state. Thus, the manipulation of the physical form of the single DNA molecules is important. In this review, we provide an overview of the unique studies on DNA manipulation and single-molecule imaging to analyze the dynamic interaction between DNA and protein.

Continued advancement of protein array, bioelectrode, and biosensor technologies is necessary to develop methods for higher amount and highly oriented immobilization activity of proteins. In pursuit of these goals, we developed a new immobilization method by combining electrostatic transport and subsequent molecular diffusion of protein molecules. Our developed immobilization method is based on a model that transports proteins toward the substrate surface due to steep concentration gradient generated by low-frequency AC electric field. The immobilization of the maximum amounts can be obtained by the application of the AC voltage of 80 Vpp, 20 Hz both for His-tagged Green Fluorescent Protein (GFP) and Discosoma sp. Red Fluorescent Protein (DsRed), used as model proteins. The amounts of the immobilized His-tagged GFP and DsRed were approximately seven-fold higher than that in the absence of the application of low-frequency AC electric field. Furthermore, the positively and negatively charged His-tagged GFP at acidic and alkaline pH were immobilized by applying of low-frequency AC electric field, whereas the non-charged His-tagged GFP at the pH corresponding to its isoelectric point (pI) was not immobilized. Therefore, unless the pH is equal to pI, the immobilization of electrically charged proteins was strongly enhanced through electrostatic transport and subsequent molecular diffusion.

Circular DNA immobilization via triplex formation onto streptavidin surfaces creates orientation-controlled templates. These templates yield approximately 4.6 times more protein than linear DNA in cell-free synthesis and can be reused on-chip.

We synthesized a new silyl porphyrin derivative conjugated with 6-deoxy-6-sulfo-α-d-glucopyranose (SGlc). Conjugation with SGlc improved A549 cellular uptake without significant changes in the photophysical and photochemical properties and subcellular localization. This improved cellular uptake led to enhanced photodynamic activity. Furthermore, conjugation with SGlc suppressed dark toxicity. These advantages were not observed for a conjugate with a glucose molecule. These results indicated that the conjugation with SGlc is a promising strategy for enhancing photodynamic efficacy.

真核生物のDNAポリメラーゼ阻害剤として単離した含硫糖脂質Sulfoquinovosyl-acylglycerol（SQAG）の構造を改変したSulfoquinovosyl-acylpropanediol（SQAP、薬剤名：レブリチン）は、株式会社エム・ティー・スリーが2023年9月15日に農林水産省より動物用医薬品製造販売承認を得た化合物である。SQAPは単剤でも抗癌活性はあったものの、単剤では投与量が多くなり実用化が困難であった。しかし、単剤では抗癌活性のない量を投与していた動物サンプルに対し放射線を照射したところ、強い抗癌効果を示したことから放射性増感剤としての開発が始まった。