Gene activity is described by the time-series of discrete, stochastic mRNA production events. This transcriptional time-series exhibits intermittent, bursty behavior. One consequence of this temporal intricacy is that gene expression can be tuned by varying different features of the time-series. What schemes for varying the transcriptional time-series are observed in the cell? Are the observed properties of these time-series optimized for cellular function? To address these questions, we characterize mRNA copy-number statistics at single-molecule resolution from multiple Escherichia coli promoters. We find that the degree of burstiness depends only on the gene expression level, while being independent of the details of gene regulation. The observed behavior is explained by the underlying variation in the duration of bursting events. Using information theory, we find that the properties of the transcriptional time series allow the cell to efficiently map the extracellular concentration of inducer molecules to intracellular levels of mRNA and proteins.
Bacterial lysogeny serves as a simple paradigm for cell differentiation.We characterize the activity of the fate-determining genes, cI and cro, with single-molecule resolution.Stability of the lysogenic state is found to depend in a simple manner on the frequency of activity bursts from cI.
We report a measurement of the modification of the effective precession frequency of polarized 3 He atoms in response to a dressing field in a room temperature cell. The 3 He atoms were polarized using the metastability spin-exchange method. An oscillating dressing field is then applied perpendicular to the constant magnetic field. Modification of the 3 He effective precession frequency was observed over a broad range of the amplitude and frequency of the dressing field. The observed effects are compared with calculations based on quantum optics formalism.Key words: dressed spin; polarized 3 He; neutron EDM PACS: 11.30.Er,, 13.40.Em,, 21.10.Dk A non-zero neutron electric dipole moment(EDM) is direct evidence for violations of both parity (P ) and time-reversal (T ) symmetries [1,2]. Assuming CP T invariance, T violation also implies CP -violation [3]. Observation of a non-zero neutron EDM would provide qualitatively new information on the origin of CP -violation, since no CP violation has ever been found for a baryon or a hadron containing light quarks only, like a neutron.The most sensitive neutron EDM measurement was carried out at the ILL (Institut Laue Langevin) using bottled ultracold neutrons (UCNs) and an upper limit of |d n | < 2.9 × 10 −26 e cm (90% C.L.) was obtained [4]. A non-zero
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