Amino Acids, Proteins and Porphyrins
Structure of Antibodies is composed of
|A||Single peptide chain|
|B||Two peptide chain|
|C||Non sulphur amino acid|
|D||2 long & 2 short peptide chain|
a. Immunoglobulins (antibodies) contain a minimum of two identical Light (L) chains (23 kDa) and twoidentifiable heavy (H) chains (53-73 kDa), held together as a tetramer (L2H2) by disulfide bonds.
b. The half of the light (L) chain toward the carboxyl terminal is referred to as the constant region (CL) while aminoterminal half is variable region of light chain (VL)
c. Approximately one quarter of the heavy (H) chain at the amino-terminals is referred to as its variable region (VH), and the other three quarters of H-chain are referred to as the constant regions (CH1, CH2, CH3, of that H- chain.
d. Variable regions (if both VH and VL) - bind specific antigen.
e. Antigenic determinant or Epitope →the site on the antigen to which an antibody (Ig) binds
f. All Light chains are either Kappa (κ) or lambda (λ) in type - never mixture of κ and. λ
g. The five types of Heavy chain determine immunoglobulin class.
h. No two variable regions are identical.
i. Hinge region - the region between CH1 and CH2 domains → confers flexibility ‘Q’
j. The constant regions determine class-specific effector functions.
k. Hybridomas provide long term sources of highly useful monoclonal antibodies. ‘Q’
- Antibody Diversity:
1. depends on Gene Rearrangements
2. depends upon a number of factors:
a. the existence of multiple gene segments (V,C, J, and D segments), their recombinations, the combinations of different L and H chains, a high frequency of somatic mutations in Ig genes and Junctional diversity.
b. Junctional diversity reflects the addition or deletion of a random number of nucleotides when certain gene segments are jointed together, and introduces an additional degree of diversity.