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What is the fastest way of finding a randomly hidden target? Experimental observations reveal that the search behavior of foraging animals is generally intermittent: active search phases randomly alternate with phases of fast ballistic motion. Here, we study the efficiency of this two state search strategy by calculating analytically the mean first passage(More)
Gene regulation relies on transcription factors (TFs) exploring the nucleus searching their targets. So far, most studies have focused on how fast TFs diffuse, underestimating the role of nuclear architecture. We implemented a single-molecule tracking assay to determine TFs dynamics. We found that c-Myc is a global explorer of the nucleus. In contrast, the(More)
It has long been appreciated that the transport properties of molecules can control reaction kinetics. This effect can be characterized by the time it takes a diffusing molecule to reach a target-the first-passage time (FPT). Determining the FPT distribution in realistic confined geometries has until now, however, seemed intractable. Here, we calculate this(More)
Many cellular processes require a polarization axis which generally initially emerges as an inhomogeneous distribution of molecular markers in the cell. We present a simple analytical model of a general mechanism of cell polarization taking into account the positive feedback due to the coupled dynamics of molecular markers and cytoskeleton filaments. We(More)
OBJECTIVE The Osteoarthritis Initiative (OAI) is targeted at identifying sensitive biomarkers and risk factors of symptomatic knee osteoarthritis (OA) onset and progression. Quantitative cartilage imaging in the OAI relies on validated fast low angle shot (FLASH) sequences that suffer from relatively long acquisition times, and on a near-isotropic double(More)
How long does it take a random walker to reach a given target point? This quantity, known as a first-passage time (FPT), has led to a growing number of theoretical investigations over the past decade. The importance of FPTs originates from the crucial role played by first encounter properties in various real situations, including transport in disordered(More)
We present a model of cell motility generated by actomyosin contraction of the cell cortex. We identify, analytically, dynamical instabilities of the cortex and show that they yield steady-state cortical flows, which, in turn, can induce cell migration in three-dimensional environments. This mechanism relies on the regulation of contractility by myosin,(More)
It is widely recognized that the cleaving rate of a restriction enzyme on target DNA sequences is several orders-of-magnitude faster than the maximal one calculated from the diffusion-limited theory. It was therefore commonly assumed that the target site interaction of a restriction enzyme with DNA has to occur via two steps: one-dimensional diffusion along(More)
Albers-Schönberg disease, or autosomal dominant osteopetrosis, type II (ADO II), is the most common form of osteopetrosis, a group of conditions characterized by an increased skeletal mass due to impaired bone and cartilage resorption. Following the assignment of the gene causing ADO II to chromosome 16p13.3, we now report seven different mutations in the(More)
The restriction endonuclease EcoRV can rapidly locate a short recognition site within long non-cognate DNA using 'facilitated diffusion'. This process has long been attributed to a sliding mechanism, in which the enzyme first binds to the DNA via nonspecific interaction and then moves along the DNA by 1D diffusion. Recent studies, however, provided evidence(More)