Archive | Molecular Biology

Although it is clear how a particular secondary, ter­tiary, and quaternary structure is maintained, how such a specific arrangement is initially achieved is not fully understood. Cells appear not to possess tem­plates or special enzymes that function in molding a particular three-dimensional shape. Instead, most polypeptides spontaneously assume their biologically active shape from among the many different alterna­tes that exist. [...]

Homologous and Variable Domains: Among the immunoglobulin's, certain domains of both H and L chains are homologous or constant (i.e., essentially the same from one immunoglobulin to an­other) and certain domains are variable (i.e., they are the basis of the differences among the immunoglobulin's). Each L chain has one variable and one constant domain; each H chain has one variable [...]

Proteins are composed of one or more chains of amino acids called polypeptides. The neighboring amino ac­ids in the chain are linked together by peptide bonds; these bonds are formed, in effect, by the elimination of one molecule of water from the two amino acids linked by the bond, such that the a-carboxyl carbon atom of one amino acid is [...]