Synthetic ligands capable of recognizing the specific DNA sequences inside human mitochondria and modulating gene transcription are in increasing demand because of the surge in evidence linking mitochondrial genome and diseases. In the work described herein, we created a new type of mitochondria-specific synthetic ligand, termed MITO-PIPs, by conjugating a mitochondria-penetrating peptide with pyrrole-imidazole polyamides (PIPs). The designed MITO-PIPs showed specific localization inside mitochondria in HeLa cells and recognized the target DNA in a sequence-specific manner. Furthermore, MITO-PIPs that inhibit the binding of mitochondrial transcription factor A to the light-strand promoter (LSP) also triggered targeted transcriptional suppression. The tunability of PIPs' properties suggests the potential of the MITO-PIPs as potent modulators of not only mitochondrial gene transcription but also its DNA mutations.

Liquid-ordered (Lo)-phase domains, a cholesterol-rich area on lipid bilayers, have attracted significant attention recently because of their relevance to lipid rafts, the formation/collapse of which is associated with various kinds of information exchange through the plasma membrane. Here, we demonstrate that the formation/collapse of Lophase domains in cell-sized liposomes, that is, giant unilamellar vesicles (GUVs), can be controlled with bioactive plasmonic nanoparticles and light. The nanoparticles were prepared by surface modification of gold nanorods (AuNRs) using a cationized mutant of high-density lipoprotein (HDL), which is a natural cholesterol transporter. Upon the addition of surface-engineered AuNRs to GUVs with the mixed domains of Lo and liquid-disorder (Ld) phases, the Lo domains collapsed and solid-ordered (So)-phase domains were formed. The reverse phase transition was achieved photothermally, with the AuNRs loaded with cholesterol. During these transitions, the AuNRs appeared to be selectively localized on the less fluidic domain (Lo or So) in the phase-mixed GUVs. These results indicate that the phase transitions occur through the membrane binding of the AuNRs followed by spontaneous/photothermal transfer of cholesterol between the AuNRs and GUVs. Our strategy to develop bioactive AuNRs potentially enables spatiotemporal control of the formation/collapse of lipid rafts in living cells.

No abstract

Considering the importance of surface chemistry in the colloidal stabilization of gold nanorods (AuNRs), we designed AuNRs in two physiologically relevant, salt and salt‐free aqueous solutions to validate its role in colloidal stability. Here, we show that AuNRs coated with cationic lipid/lipid‐binding protein composite materials is stable in both phosphate‐buffered saline (PBS) and sucrose solution (200 mM), but not in deionized water. Salting‐in effects of proteins explain the relatively better stability of AuNRs in PBS than in deionized water. Sucrose‐assisted stabilization of the AuNRs was associated with a decrease in their zeta potential and tended to diminish without the cationic lipid, which would be attributed to an electrostatic interaction between sucrose and the cationic lipid. Given that sucrose solution is often used for cell‐sized liposome studies, our finding will enable nanomaterial‐membrane interaction analyses in live cell and cell‐free systems with identical nanomaterials.

Liquid–liquid phase-separated (LLPS) droplets play key roles in regulating protein behaviors, such as enzyme compart-mentalization, stress response, and disease pathogenesis, in living cells. The manipulation of the droplet for-mation/deformation dynamics is the next target of nano-biotechnology, although the required nanodevices for controlling the dynamics of liquid–liquid phase separation, LLPS, have not been invented. Here, we propose a butterfly-shaped gold nanobutterfly (GNB) as a nanodevice for manipulating the droplet-formation/deformation dynamics of LLPS. GNBs are moderate, symmetrical gold nanomaterials (average diameter = ~30 nm) bearing two concaves and resembling a butter-fly. Their growth process is analyzed via their time-lapse electroscopic images and time-lapse ultraviolet/visible/near-infrared (NIR) spectroscopy, as well as the application of solution additives in protein science. These nanomaterials are synthesized via the seed-mediated method with an efficiency of ~70%. Interestingly, the GNBs stabilized the LLPS droplet of adenosine triphosphate (ATP)/poly-L-lysine, whereas other two gold nanoparticles with different shapes (spherical and rod-shaped) did not, indicating that the concave of the GNBs interacts with the precursor of the droplets. The NIR-laser irradiation of the GNBs facilitates the on-demand deformation of the droplets via the localized-heat effect. This but-terfly-shaped nanodevice represents a future strategy for manipulating the dynamics of LLPS.