198 research outputs found
Universal relationship in gene-expression changes for cells in steady-growth state
Cells adapt to different conditions by altering a vast number of components,
which is measurable using transcriptome analysis. Given that a cell undergoing
steady growth is constrained to sustain each of its internal components, the
abundance of all the components in the cell has to be roughly doubled during
each cell division event. From this steady-growth constraint, expression of all
genes is shown to change along a one-parameter curve in the state space in
response to the environmental stress. This leads to a global relationship that
governs the cellular state: By considering a relatively moderate change around
a steady state, logarithmic changes in expression are shown to be proportional
across all genes, upon alteration of stress strength, with the proportionality
coefficient given by the change in the growth rate of the cell. This theory is
confirmed by transcriptome analysis of Escherichia Coli in response to several
stresses.Comment: 7 pages (5 figures) + 2 Supplementary pages (figures
Shape transformations of lipid vesicles by insertion of bulky-head lipids
Lipid vesicles, in particular Giant Unilamellar Vesicles (GUVs), have been increasingly
important as compartments of artificial cells to reconstruct living cell-like systems in a
bottom-up fashion. Here, we report shape transformations of lipid vesicles induced by
polyethylene glycol-lipid conjugate (PEG lipids). Statistical analysis of deformed vesicle
shapes revealed that shapes vesicles tend to deform into depended on the concentration
of the PEG lipids. When compared with theoretically simulated vesicle shapes, those
shapes were found to be more energetically favorable, with lower membrane bending
energies than other shapes. This result suggests that the vesicle shape transformations
can be controlled by externally added membrane molecules, which can serve as a
potential method to control the replications of artificial cells
Liposome-based liquid handling platform featuring addition, mixing, and aliquoting of femtoliter volumes
This paper describes the utilization of giant unilamellar vesicles (GUVs) as a platform for handling chemical and biochemical reagents. GUVs with diameters of 5 to 10 µm and containing chemical/biochemical reagents together with inert polymers were fused with electric pulses (electrofusion). After reagent mixing, the fused GUVs spontaneously deformed to a budding shape, separating the mixed solution into sub-volumes. We utilized a microfluidic channel and optical tweezers to select GUVs of interest, bring them into contact, and fuse them together to mix and aliquot the reaction product. We also show that, by lowering the ambient temperature close to the phase transition temperature Tm of the lipid used, daughter GUVs completely detached (fission). This process performs all the liquid-handing features used in bench-top biochemistry using the GUV, which could be advantageous for the membrane-related biochemical assays
Activities of 20 aminoacyl-tRNA synthetases expressed in a reconstituted translation system in Escherichia coli
AbstractA significant challenge in the field of in vitro synthetic biology is the construction of a self-reproducing cell-free translation system, which reproduces its components, such as translation proteins, through translation and transcription by itself. As a first step for such construction, in this study we expressed and evaluated the activity of 20 aminoacyl-tRNA synthetases (aaRSs), a major component of a translation system, in a reconstituted translation system (PURE system). We found that 19 aaRS with the exception of phenylalanyl-tRNA synthetase (PheRS) are expressed as soluble proteins and their activities are comparable to those expressed in Escherichia coli . This study provides basic information on the properties of aaRSs expressed in the PURE system, which will be helpful for the future reconstitution of a self-reproducing translation system
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