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#molecular separation

4 public questions tagged with this topic.

Electrophoresis

Which parameter affects the migration rate of molecules in gel electrophoresis?

Migration velocity in gel electrophoresis is described by electrophoretic mobility balanced against frictional drag. Factors include net charge, molecular size, buffer ionic strength, voltage gradient, and gel matrix friction. The gel matrix provides molecular sieving; larger molecules experience greater obstruction and lower mobility. Gel color or sample volume does not fundamentally alter mobility per molecule, though excessive volume broadens bands. Voltage polarity determines direction, not rate magnitude. Therefore, friction from gel matrix, proportional to gel concentration and crosslink

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 type of support matrix is used in zone electrophoresis?

Zone electrophoresis separates molecules into discrete zones or bands on a stabilizing support to minimize convection and diffusion. Early methods employed filter paper or cellulose acetate strips saturated with buffer, providing a solid anticonvective medium. Samples migrate as discrete zones under applied voltage. Glass and plastic are not porous supports for zone stabilization. Modern zone electrophoresis uses agarose or polyacrylamide gels as improved supports, but historically and categorically, paper represents the classic support matrix distinguishing zone electrophoresis from moving-bo

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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Chromatography

Ion-exchange separates by:

Ion exchange chromatography exploits differences in net electric charge of analytes. Stationary phase functionalized with charged groups interacts electrostatically with oppositely charged solutes. Elution is controlled by pH influencing ionization and ionic strength providing competing counter-ions. Proteins with different pI values exhibit distinct charge at a given pH, causing differential affinity to matrix. Hydrophobicity governs reversed-phase and HIC, mass governs size exclusion, color is irrelevant. Selectivity can be modulated by gradient elution. This mechanism is central to purifica

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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Chromatography

What is the exclusion limit of Sephadex G-50?

Sephadex is cross-linked dextran gel classified by G-value indicating degree of cross-linking and porosity. G-50 denotes moderate cross-linking with fractionation range for globular proteins approximately 1,500 to 30,000 daltons. Molecules larger than 30,000 daltons are excluded, eluting at void volume; smaller molecules penetrate and are retarded. Exclusion limit defines upper molecular weight threshold. Different grades like G-25, G-75, G-100 offer varying ranges. Knowledge of exclusion limits guides selection for desalting, buffer exchange, or separation of peptides from proteins, ensuring

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