Biology Reference
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Figure 7.5 Normal (a) and mutant (b) insulin molecules. In both molecules, the posi-
tions of A- and B-chain amino acids are denoted by circles and triangles, respectively.
Because there is no standard orientation for displaying them, both molecules are ori-
ented so that their long axes are horizontal and the first molecule in the A-chain (A1)
is to the left of the last (A21). The amino-acid substitution in the mutant is at position
B24, producing a pronounced kink in the B chain.
Because the amino acids literally form a chain, it is useful to think of
the form differences in terms of the angles between the chain's links.
At B24, we can think of the angle between these segments as becom-
ing more acute ( Figure 7.5 ) . At the other extreme of the matrix, we see
that the ten largest values involve distances between the A and B
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