Serotonin-dependent kinetics of feeding bursts underlie a graded response to food availability in C. elegans.

Animals integrate physiological and environmental signals to modulate their food uptake. The nematode C. elegans, whose food uptake consists of pumping bacteria from the environment into the gut, provides excellent opportunities for discovering principles of conserved regulatory mechanisms.

Durable spatiotemporal surveillance of Caenorhabditis elegans response to environmental cues.

Animal response to changes in environmental cues is a complex dynamical process that occurs at diverse molecular and cellular levels. To gain a quantitative understanding of such processes, it is desirable to observe many individuals, subjected to repeatable and well defined environmental cues over long time periods. Here we present WormSpa, a microfluidic system where worms are individually confined in optimized chambers.

Nucleocytoplasmic transport: a thermodynamic mechanism.

The nuclear pore supports molecular communication between cytoplasm and nucleus in eukaryotic cells. Selective transport of proteins is mediated by soluble receptors, whose regulation by the small GTPase Ran leads to cargo accumulation in, or depletion from, the nucleus, i.e.

Protein dynamics in individual human cells: experiment and theory.

A current challenge in biology is to understand the dynamics of protein circuits in living human cells. Can one define and test equations for the dynamics and variability of a protein over time? Here, we address this experimentally and theoretically, by means of accurate time-resolved measurements of endogenously tagged proteins in individual human cells. As a model system, we choose three stable proteins displaying cell-cycle-dependant dynamics.

Diffusion of anionic and neutral GFP derivatives through plasmodesmata in epidermal cells of Nicotiana benthamiana.

Plasmodesmata (Pd) are trans-wall membrane channels that permit cell-to-cell transport of metabolites and other small molecules, proteins, RNAs, and signaling molecules. The transport of cytoplasmic soluble macromolecules is a function of the electrochemical gradient between adjacent cells, the number of Pd per interface between adjacent cells, Stokes radius (R(S)), area of the cytoplasmic annulus, and channel length. The size of the largest molecule that can pass through Pd defines the Pd size exclusion limit.

Reversibility in nucleocytoplasmic transport.

Nucleocytoplasmic exchange of proteins and RNAs is mediated by receptors that usher their cargo through the nuclear pores. Peptide localization signals on each cargo determine the receptors with which it will interact. Those interactions are normally regulated by the small GTPase Ran.

CD8 kinetically promotes ligand binding to the T-cell antigen receptor.

The mechanism of CD8 cooperation with the TCR in antigen recognition was studied on live T cells. Fluorescence correlation measurements yielded evidence of the presence of two TCR and CD8 subpopulations with different lateral diffusion rate constants. Independently, evidence for two subpopulations was derived from the experimentally observed two distinct association phases of cognate peptide bound to class I MHC (pMHC) tetramers and the T cells.