Question

Match the terms with the descriptions. (a) Assay (b) Molecular exclusion chromatography (c) Ion-exchange chromatography (d) Affinity chromatography (e) High-pressure liquid chromatography (HPLC) (f) Isoelectric focusing (g) Sedimentation coefficient (h) Antigenic determinant (epitope) (i) Monoclonal antibodies (j) Western blotting 1\. Separating proteins on the basis of size differences 2\. Allows high resolution and rapid separation 3\. Produced by hybridoma cells 4\. An immunoassay technique preceded by gel electrophoresis 5\. A measure of the rate of movement due to centrifugal force 6\. Separating proteins on the basis of net charge 7\. Specific site recognized by an antibody 8\. Based on the fact that proteins have a \(\mathrm{pH}\) at which the net charge is zero 9\. Based on attraction to a specific chemical group or molecule 10\. A means of identifying a protein based on a unique property of the protein

Short answer

(b)-1, (e)-2, (i)-3, (j)-4, (g)-5, (c)-6, (h)-7, (f)-8, (d)-9, (a)-10

Step-by-step solution

Match size-based separation

(b) Molecular exclusion chromatography is matched with description 1, as it separates proteins based on size differences.

Match high resolution and rapid separation

(e) High-pressure liquid chromatography (HPLC) is matched with description 2, due to its features allowing high resolution and rapid separation.

Match production by hybridoma cells

(i) Monoclonal antibodies are matched with description 3, because they are produced by hybridoma cells.

Match immunoassay technique preceded by gel electrophoresis

(j) Western blotting is matched with description 4, as it is an immunoassay technique used after gel electrophoresis.

Match rate of movement due to centrifugal force

(g) Sedimentation coefficient is matched with description 5, as it measures the rate of movement due to centrifugal force.

Match separation based on net charge

(c) Ion-exchange chromatography is matched with description 6, since it separates proteins based on their net charge.

Match specific site recognized by an antibody

(h) Antigenic determinant (epitope) is matched with description 7, as it refers to the specific site recognized by an antibody.

Match net charge of zero at certain pH

(f) Isoelectric focusing is matched with description 8, because it is based on the principle that proteins have a specific pH where their net charge is zero.

Match attraction to specific chemical group or molecule

(d) Affinity chromatography is matched with description 9, based on the fact that it separates proteins due to their attraction to a specific chemical group or molecule.

Match identifying protein by unique property

(a) Assay is matched with description 10, as it is a means of identifying a protein based on a unique property of the protein.

Key concepts

Molecular Exclusion Chromatography

Molecular exclusion chromatography, also known as size-exclusion chromatography, is a technique used to separate proteins and other macromolecules based on their size. In this method, a column is packed with porous beads. As the mixture flows through the column, smaller molecules enter the pores and thus take longer to elute, while larger molecules bypass the beads and elute faster.
This method is particularly useful when you want to analyze and purify proteins or polymers. Its strength lies in its simplicity and the fact that it does not involve any chemical interactions with the sample.

• Effective for separating molecules that differ significantly in size.
• Non-destructive to the sample, preserving its original form.
• Commonly used in biochemistry and molecular biology labs.

Ion-exchange Chromatography

Ion-exchange chromatography separates proteins and other charged molecules based on their charge properties. This is achieved using a charged resin, which interacts with oppositely charged molecules from the sample. Depending on the charge of the resin, you have two types:

• Cation-exchange: The resin is negatively charged, attracting positively charged ions or molecules.
• Anion-exchange: The resin is positively charged, attracting negatively charged ions or molecules.

Through careful adjustment of the pH or ionic strength of the buffer, molecules can be selectively eluted from the column. This technique is useful for separating complex mixtures of proteins, nucleic acids, and other charged biomolecules.

Affinity Chromatography

Affinity chromatography is a powerful technique that separates proteins based on specific interactions between a protein and a ligand tethered to the column matrix. This method exploits the unique biochemical properties of the protein, such as binding to a specific substrate or antibody.

• Highly selective, often used for purifying enzymes, receptors, and antibodies.
• Can utilize biological interactions like antigen-antibody, enzyme-substrate, or receptor-ligand bindings.
• After binding, proteins can be eluted with a buffer that disrupts the specific interaction, such as a change in pH or ionic strength.

This technique is extremely efficient for obtaining pure and concentrated forms of a protein, making it indispensable in research and industrial applications.

Sedimentation Coefficient

The sedimentation coefficient is a measure of how fast a particle, like a protein, sediments in a centrifugal field. It is often used to describe the size and shape of macromolecules.
The coefficient is usually expressed in Svedberg units (S), where larger values indicate faster sedimentation, typically reflecting larger or more compact particles.

• Affected by the mass, shape, and density of the molecule.
• Used in ultracentrifugation as a metric to differentiate proteins and nucleic acids based on their sedimentation rates.
• Helps in understanding the molecular weight and conformation of biomolecules.

Monoclonal Antibodies

Monoclonal antibodies are uniform, laboratory-produced molecules engineered to serve specific immunological functions. They are produced using hybridoma technology, which involves fusing an immune cell with a cancer cell, resulting in a cell line that can be both immortal and produce the desired antibody.
These antibodies recognize specific epitopes or antigenic determinants, making them vital tools in diagnostics, therapeutics, and research.

• Provide consistency in usage since they arise from a single clone.
• Used extensively in modern medicine for diseases like cancer and autoimmune disorders.
• Have revolutionized the field of immunoassays, serving as key reagents in the detection and quantification of specific molecules.