arXiv subjects

Ayako Yamada

Publications and source records attributed to Ayako Yamada.

3 recordsLinked to original sources

arXiv2006

Micro-Bioreactor Mimicking a Cellular Environment

We report that a cell-sized water droplet (CWD) with a diameter of several tens of microns can serve as a micro-biochemical reactor. Since the droplet inner surface is covered by a phospholipid layer, it provides an environment similar to that in living cells. The CWD is manipulated with laser tweezers and we monitor the time-development of biochemical reactions in a single CWD by fusing two droplets which contain a substrate and an enzyme, respectively. As actual examples of enzymatic reactions, we present results on the reaction of calcein with esterase and on the expression reaction of green fluorescent protein.

physics.bio-ph↗

arXiv2006

Transporting of a Cell-Sized Phospholipid Vesicle Across Water/Oil Interface

When a cell-sized water droplet, with a diameter of several tens of micro meter, is placed in oil containing phospholipids, a stable cell-sized vesicle is spontaneously formed as a water-in-oil phospholipid emulsion (W/O CE) with a phospholipid monolayer. We transferred the lipid vesicle thus formed in the oil phase to the water phase across the water/oil interface by micromanipulation, which suggests that the vesicle is transformed from a phospholipid monolayer as W/O CE into a bilayer. The lipid vesicle can then be transported back into the oil phase. This novel experimental procedure may be a useful tool for creating a model cellular system, which, together with a microreactor, is applicable as a micrometer-scale biochemical reaction field.

physics.chem-ph↗

arXiv2004

All-or-none switching of transcriptional activity on single DNA molecules caused by a discrete conformational transition

Recently, it has been confirmed that long duplex DNA molecules with sizes larger than several tens of kilo-base pairs (kbp), exhibit a discrete conformational transition from an elongated coil state to a compact globule state upon the addition of various kinds of chemical species that usually induce DNA condensation. In this study, we performed a single-molecule observation on a large DNA, Lambda ZAP II DNA (ca. 41 kbp), in a solution containing RNA polymerase and substrates along with spermine, a tetravalent cation, at different concentrations, by use of fluorescence staining of both DNA and RNA. We found that transcription, or RNA production, is completely inhibited in the compact state, but is actively performed in the unfolded coil state. Such an all-or-none effect on transcriptional activity induced by the discrete conformational transition of single DNA molecules is discussed in relation to the mechanism of the regulation of large-scale genetic activity.

q-bio.BM↗