PULSE CHASE EXPERIMENT

Preliminary concept:Radio-active chemical elements emit

radiation and this can be detected experimentally

Adding or substituting radio-active elements or atom-types (also called 'isotopes') into the reactant-molecules in an experiment can be very useful to follow or 'trace' the various details of what happens to certain molecules involved in a chemical and sequential reaction. Such methods can demonstrate the fate of a single atom in a specific reaction sequence.

Definition of "Pulse-chase" technique:Researchers often use the "PULSE-CHASE" technique in labeling experiments.  In this protocol, a cell sample is exposed to a radio-labeled compound for only a brief period of time (this is called the 'pulse'),...then it is washed with a buffer solution to remove the isotope, and finally incubated with a non-labeled form of compound (this called the 'chase' part).

The length of exposure time can be shown to be a function of the quantity of resultant labeling that can occur.  Pulse-Chase experiments are useful for following the intra-cellular location of proteins or the transformation of a metabolite into others over a period of biochemical reaction-time.  Therefore these types of techniques are important for the elucidation of biochemical and metabolic pathways in biotechnology and medical science.

HISTORY:In 1955 scientist george palade and his

colleagues used a pulse chase experiment to determine the role of rough endoplasmic reticulum and golgi apparatus in the protein synthesis and secretion

They studied pancreatic cells which are specialized in producing and secreting digestive enzymes

Steps in the experiment:Allow normal protein synthesisAdd large dose of radioactive atoms/ molecule for the

pulse phaseTrack the position of radioactivity by fixing the sample

at different time intervalCells are prepared for microscopy and overlaid with the

photographic imulsion, and samples are developedRadioactive protein produces black spots against gray

background revealing the location of the proteinIf the reserachers fixes a sample a few minutes after

the pulse begins the radioactivity will be found in in endoplasmic reticulum

Add the large dose of the nonradioactive molecules of leucine for chase phase

This experiment helped researcher to understand the path of protein synthesis and its secretion

A Pulse-Chase Experiment.swf