Skip to content
Login Register

#pH gradient

2 public questions tagged with this topic.

Electrophoresis

Which buffer component creates the pH gradient in stacking gel?

Discontinuous electrophoresis depends on Tris-glycine discontinuous buffer system to create transient isotachophoretic stacking. Chloride ions from Tris-HCl serve as highly mobile leading ions. Glycine is amphoteric with pKa2 near 9.6; at stacking gel pH 6.8 it exists predominantly as zwitterion with very low electrophoretic mobility, acting as trailing ion, while proteins possess intermediate mobility. Resulting Kohlrausch boundary generates steep voltage gradient that focuses proteins into micrometer-thin zones. APS and TEMED drive radical polymerization, and acrylamide forms sieving matrix;

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details
Electrophoresis

Which method uses ampholytes for creating a pH gradient?

Isoelectric focusing requires a stable, continuous pH gradient along electrophoretic path for proteins to focus precisely at their pI. Carrier ampholytes are complex mixtures of low-molecular-weight polycarboxylic polyamino amphoteric compounds possessing varied pI values between 3 and 10. Under electric field, they migrate and buffer locally to establish a smooth pH gradient from anode to cathode. SDS-PAGE, capillary zone electrophoresis and second dimension of 2D gels use uniform buffer pH, not gradient. Ampholytes or immobilines are thus central to creating the field for charge-based focusi

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details