#isoelectric focusing

Electrophoresis

In isoelectric focusing, separation is based on:

Isoelectric focusing separates macromolecules based on differences in isoelectric point rather than solely molecular weight or total charge at fixed pH. A stable pH gradient is created using carrier ampholytes or immobilines immobilized in gel matrix. Proteins migrate under electric field until reaching zone where local pH equals pI, resulting in zero net charge and cessation of movement. This focusing concentrates proteins into extremely narrow bands at characteristic pH values. Distinction from SDS-PAGE which separates by size, or ion-exchange which separates by constant charge, underlies it

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.

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Electrophoresis

In IEF, where will a protein stop migrating?

In isoelectric focusing, a stable pH gradient is established using carrier ampholytes or immobilized buffers spanning acidic to basic range. Proteins introduced into gradient acquire positive charge below their pI and negative charge above, causing migration in electric field. As movement proceeds, net charge diminishes upon approaching pH equal to isoelectric point, where protein becomes electrically neutral. Loss of electrophoretic driving force halts further migration, while diffusion is counteracted by focusing effect, concentrating proteins into sharp zones at characteristic positions. Fo

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.

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Electrophoresis

Which synthetic ampholyte is commonly used?

Commercial carrier ampholytes are synthetic mixtures of amphoteric molecules produced by copolymerization of polyamines with unsaturated carboxylic acids like acrylic acid, yielding intricate polyamino-polycarboxylic structures with aliphatic backbones containing numerous isomeric species with closely spaced pI values. Their excellent buffering capacity and conductivity across pH 2-11 allow generation of continuous linear gradients upon application of electric field, essential for high-resolution isoelectric focusing. Histones are basic proteins, phosphopeptides are modified peptides, and beta

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.

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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.

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Electrophoresis

What separates molecules in the first dimension of 2D electrophoresis?

Two-dimensional electrophoresis couples orthogonal separation principles to resolve highly complex proteomes containing thousands of polypeptides. First dimension is isoelectric focusing in immobilized pH gradient strips or carrier ampholyte tubes where proteins migrate under electric field until net charge becomes zero at their isoelectric point, effectively focusing at pI independent of size. This separates isoforms differing by charged modifications. Second dimension is SDS-PAGE where focused proteins are further separated by molecular mass. Charge alone or solubility does not define 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