Size estimate. The relative electrophoretic mobilities of a...

Size estimate. The relative electrophoretic mobilities of a 30 -kDa protein and a 92 -kDa protein used as standards on an SDS-polyacrylamide gel are 0.80 and $0.41,$ respectively. What is the apparent mass of a protein having a mobility of 0.62 on this gel?

Key Concepts

SDS-PAGE

SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) is a fundamental technique used in biochemistry to separate proteins primarily based on their molecular weight. SDS disrupts the native conformation of proteins and uniformly coats them with a negative charge, ensuring that the migration through the gel is mainly determined by size.

Electrophoretic Mobility

Electrophoretic mobility refers to the rate at which a molecule moves under the influence of an electric field. In an SDS-PAGE setup, the mobility of a protein is inversely related to its molecular weight: smaller proteins move faster, while larger proteins move more slowly through the polyacrylamide gel.

Molecular Weight Estimation Using Protein Standards

Estimating the molecular weight of an unknown protein involves comparing its electrophoretic mobility to that of standard proteins with known molecular weights. By using these standards to generate a calibration curve, typically through plotting the logarithm of the molecular weight against the relative mobility, the apparent molecular weight of the unknown protein can be interpolated.

Logarithmic Relationship in Protein Separation

There is often a logarithmic relationship between the molecular weight of proteins and their mobility in SDS-PAGE. This relationship is utilized to create a standard curve which allows researchers to determine an unknown protein's molecular weight by fitting its mobility to the logarithmic trend established by the standards.

Transcript

Please give Ace some feedback