UVP Life Science - Manual (Page 126)

LS Software User Guide
112
Molecular Weight
Perform Molecular Weight Calibrations
Overview
Molecules in an electric field migrate through a gel matrix at rates inversely proportional to the log10 of
the number of base pairs. Large molecules migrate more slowly due to large frictional force from the pore
of the matrix while small molecules migrate faster due to less frictional force.
There are many experimental conditions affecting the migration rate: gel concentration; conformation of
the DNA; applied voltage; direction of electric field; base composition and temperature; presence of
intercalating dyes; and electrophoresis buffer. It is therefore desirable to use a known molecular weight
standard as a reference to unknown samples. This marker is used to calibrate the resulting molecular
weight for each unknown bands.
Using a molecular weight (MW) marker results in a band encompassing the whole gel horizontally. This
band can be thought of as the distance traveled of a band relative to its front (Retardation factor - Rf) or
starting position. This Rf line exists for each band in the molecular weight standard. Any bands in the
unknown samples that migrate to any of these Rf lines are then compared to the Rf lines.
Note: Rf line functions are only required if there are less than two calibrated lanes
Next Steps:
• Applying a Molecular Weight Standard to a Lane
• Molecular Weight Calibration: Add, Edit, Remove, Copy Functions
• Retardation factor Rf Lines