SB_ Pretzel and the puppies_ Rough_ RiverPhan (2024)
AFFINITY chromatography.pptx
1.
2. What is Affinity Chromatography?
Chromatographic technique for selective separation/purification of
a molecule from a biochemical mixture.
PRINCIPLE
Separation of mixture of protein/nucleic acids/enzymes take place by specific
and reversible interaction of these molecules with a component – Ligand,
which is immobilized on an inert support, and packed in a column
When a mixture of, say, proteins passes through the column, one of the proteins
binds to the ligand based on its specificity and high affinity
• The protein and the ligand fit together like a lock and key
Other proteins in the mixture pass through the column since these are unable
to bind to the ligand
3. Components of Affinity Matrix
Matrix
Spacer
Target protein
Affinity Matrix
Highly selective
Ligand
4. Matrix or Affinity Supports
Inert support to which ligand is directly or indirectly bound
Chemically and mechanically stable
Uniform particle and pore size
Low non specific adsorption
Examples: Cellulose, agarose, silica, polystyene, sepharose
(All these are available commercially)
5. Ligand
Selection based on specific and reversible binding with the target molecule
Carries a group which can couple to matrix without losing binding activity
Stable in different binding and elution conditions
Ligand can be bound to matrix by
Covalent bonding
Non-covalent bonding
Adsorption
Biospecific interaction
6. Commonly used Ligands
Ligand Specificity
Blue B Kinases, dehydrogenases, nucleic acid binding
proteins
Orange A Lactate dehydrogenase
Lysine Plasminogen, rRNA, dsDNA
Protein A Fc regions of many IgG subtypes; species
dependent weak interactions with IgA, IgM, IgD
Biotin Streptavidin, avidin
Gelatin Fibronectin
Lectins Glycoproteins, polysaccharides, glycolipids
Direct binding of ligand to matrix may lead to stearic hindrance resulting
in inefficient binding of target to ligand.
Solution: Spacer
7. Spacer
Overlap between target
molecule and bead leads to
inefficient binding ,i.e., stearic
hindrance
Spacer covalently
bound to matrix
• Allows complete access
of target molecule to
ligand.
• Should be hydrophillic
• Should be of optimum
length
Matrix
8. Steps Involved in Affinity Chromatography
Matrix beads + Buffer: Beads swell
Couple the ligand (and spacer, if required) with the matrix
Filter: Affinity matrix
Pack in a glass column
Equilibrate the column with buffer
Load the sample
Wash the column to remove unbound molecules
Elute bound molecules
Analyze the eluent
9. 1.Binding 2. Washing 3. Elution
Ligand Other proteins
Target protein
Steps Involved in Affinity Chromatography
10. Elution
Specific Elution
- Competing free ligand
- Competing binding substance
Competitive
ligand in solution
+
Example: Elution of enzymes from Blue Sepharose by free NADH
Competitive binding
substance
+
Example: Elution of Antigens from antibody columns with specific peptides
Competitive soluble ligands or binding substances can elute the bound target specifically
Gentler than general methods
Expensive (like specific peptides for antigen elution)
11. Applications
Purification of substances from biological mixtures.
Separation of native form of protein from
denatured form.
Purification and concentration of enzymes in
solution.
13. Liquid chromatography
PRINCIPLE: Separates molecules in solution by their “effective size” in
solution. Hence, also called size exclusion chromatography.
Separation is achieved by the differential exclusion or inclusion of solutes as
they pass through porous stationary phase consisting of cross linked
polymeric gel beads.
Gel Chromatography
Also known as gel filtration/gel permeation/size exclusion chromatogaphy
(GFC) (GPC) (SEC)
14.
15. Gel Chromatography
Stationary Phase
Semi permeable, porous polymer gel beads.
Properties of gel beads
• Chemically inert
• Mechanically stable
• Uniform particle and pore size
Examples
• Dextran gel
• Agarose gel
• Polyacrylamide gel
16. Advantages
Short analysis time
No sample loss
Less consumption of mobile phase
Disadvantage
Molecules with closely related molecular mass show broad peak