Fluctuations and transport in cells and the information that can be extracted from optical experiments

SILVINA PONCE DAWSON

San Pablo

Congreso; School on Physics Applications in Biology,; 2016

Cells are permanently interacting with their environment. Thisinteraction usually involves the binding of molecules to receptorsthat are located on the plasma membrane inducing changes in a seriesof intracellular components that eventually generate an endresponse. Both the arrival of the external molecules and the cascadeof events that the initial binding induces involve the transport ofsubstances. Most often this transport includes the diffusion ofrelevant species that, on their way, also interact with various cellcomponents. All these processes occur in a very fluctuatingrealm. Fluctuations set limits to the accuracy with which endogenousprocesses can occur. The physical principles that rule these limitsalso affect the experimental quantification of biophysical parametersin situ. The characterization of fluctuations, on the other hand,provides a way to quantify biophysical parameters. In this talk Iwill discuss the behavior of transport and fluctuations in cells andhow the latter can be used to quantify certain parameters. Tothis end I will consider a simple system of reacting and diffusingspecies. I will introduce the idea of effective diffusioncoefficients and will analyze what information is provided in such acase by optical experiments that are currently used to quantifiedconcentrations and transport rates. I will finally discuss how theseideas can be extended to understand the time it takes for endogenousmechanisms to ``read'' concentration changes.