Clonal populations of cells exhibit substantial phenotypic variation. Such heterogeneity can
be essential for many biological processes and is conjectured to arise from stochasticity, or
noise, in gene expression. We constructed strains of Escherichia coli that enable detection …

Networks of interacting biomolecules carry out many essential functions in living cells 1, but
the 'design principles' underlying the functioning of such intracellular networks remain poorly
understood, despite intensive efforts including quantitative analysis of relatively simple …

Gene expression is a stochastic, or “noisy,” process. This noise comes about in two ways.
The inherent stochasticity of biochemical processes such as transcription and translation
generates “intrinsic” noise. In addition, fluctuations in the amounts or states of other cellular …

The quantitative relation between transcription factor concentrations and the rate of protein
production from downstream genes is central to the function of genetic networks. Here we
show that this relation, which we call the gene regulation function (GRF), fluctuates …

The genetic circuits that regulate cellular functions are subject to stochastic fluctuations, or
'noise', in the levels of their components. Noise, far from just a nuisance, has begun to be
appreciated for its essential role in key cellular activities. Noise functions in both microbial …

The tumor suppressor p53, one of the most intensely investigated proteins 1, 2, 3, 4, 5, is
usually studied by experiments that are averaged over cell populations, potentially masking
the dynamic behavior in individual cells. We present a system for following, in individual …

The rate of protein diffusion in bacterial cytoplasm may constrain a variety of cellular
functions and limit the rates of many biochemical reactions in vivo. In this paper, we report
noninvasive measurements of the apparent diffusion coefficient of green fluorescent protein …

Certain types of cellular differentiation are probabilistic and transient 1, 2, 3. In such systems
individual cells can switch to an alternative state and, after some time, switch back again. In
Bacillus subtilis, competence is an example of such a transiently differentiated state …

Cells regulate gene expression using networks of transcription interactions; it is of interest to
discover the principles that govern the dynamical behavior of such networks. An important
characteristic of these systems is the rise-time: the delay from the initiation of production until …

A central problem in biology is determining how genes interact as parts of functional
networks. Creation and analysis of synthetic networks, composed of well-characterized
genetic elements, provide a framework for theoretical modeling. Here, with the use of a …