Structure & Properties of Antibodies Flashcards

Question

In an electropheresis pattern, why is the peak of the homogeneous protein albumin narrow compared to the broad peak of the Immunoglobulin?

Answer 1

Because Antibodies are very heterogeneous - they can bind many different Antigens. When Antibodies are present in antiserum, they are heterogeneous. The heterogeneity of Antibodies poses a problem for further understanding of the structure of an Antibody.

Answer 2

A tumor of plasma cells that generally secretes a single species of Immunoglobulin, otherwise known as _homogeneous_ Antibodies or _Myeloma Proteins_. The electrophoresis pattern of normal human serum shows polyclonal/heterogeneous Immunoglobulins, which represent the product of many different plasma cells (low, broad peak). The electrophoresis pattern of Multiple Myeloma serum shows proliferation of a homogeneous Immunoglobulin or a _single_ clone of cells (high, sharp peak). It is a significant finding because it allowed for further understanding of the structure of Antibodies.

Answer 3

_Homogeneus Antibodies_ that are produced by malignant plasma cells; plasma cells are Antibody-producing factories.

Answer 4

Monoclonal/homogenous L chains in patients with Multiple Myeloma. People with Multiple Myeloma make more L chains than H chains. L chains are small, so they are filtered out by the kidneys. The urine from people with Multiple Myeloma can be filtered to isolate large quantities of _homogeneous_ L chains for further analysis and understanding of the structure of Antibodies. Bence-Jones proteins have an unusualy property - If heated until a certain temperature, they precipitate. But if continue heating, the proteins willl go back into solution (normal proteins never go back into solution).

Answer 5

1. 2 categories of Light chains: kappa & lambda

Answer 6

There are 2 categories of Light chains: kappa and lambda.

Answer 7

Investigators used Bence-Jones proteins (homogeneous Light chains) from 2 different people with Multiple Myeloma (and therefore from different plasma cells) and produced proteolytic fragments from these different Light chains. They analyzed the fragments by 2D peptide mapping, in which the fragments are separated by chromatography (solubility) in 1 dimension and electrophoresis (charge) in the other. RESULT: They found that 1/2 of the cleavage products are identical between the 2 chains, while the other half differ. (Shaded spots indicate peptides shared by the 2 kappa or lambda chains.) CONCLUSION: Light chains have a Variable region and a Constant region. All kappa Light chains had the same Constant region, while all lambda had the same Constant region (although kappa and lambda Constant region differ from each other.)

Answer 8

EXP: They used protein sequencing, which required large quantities of homogeneous protein, and sequenced both Light and Heavy chains. CONCLUSION: The Variable region of both Light and Heavy chains were at the amino terminus (front) while the Constant region was at the carboxy terminus (tail).

Answer 9

The Variable regions had relatively conserved regions and **hypervariable** regions.

Answer 10

An investigator proposed a Metric of Variability, in which the number of different amino acids in a particular position is divided by the frequency of the most common amino acid. If there is only 1 amino acid present at the particular position, then the variability is 1 (100%, relatlively constant). If all amino acids are the same frequency, then the variability is 400 (20 amino acids/5% = 400, very high variability = hypervariable region). CONCLUSION: He was able to identify hypervariable regions and conserved regions of the Variable region of Light chains.

Answer 11

He hypothesized that the Hypervariable regions were responsible for the different binding specificities. These Hypervariable regions were called "Complementarity Determining Regions" (CDRs), and predicted that this part of the Antibody could contact the Antigen and determine the binding specificity.

Answer 12

EXP: **X-Ray Crystallography** The crystal structure of a Light chain shows that CDRs of the Variable region are present on loops at the end of proteins. The conserved regions of Light chains are called "**framework**" amino acids because they keep the hypervariable loops/CDRs in the proper orientation.