Diagonal plot

Another useful type of representation for protein structures is the diagonal plot. It is a matrix with the amino acid sequence number along both axes, in which either distance between the respective a-carbons or contact between the respective residues is plotted for each possible pair of residues (see Fig. 10). The diagonal plot is probably the most successful method yet devised of quantitatively mapping the... 

Self-diagonal plots for finding repeated motifs Sechon 7.3.3... 

Figure 7.15. A Self-Diagonal Plot For the TATA-Box-Binding Protein From the YXant Arabidopsis. Self-diagonal plots are used to search for amino acid sequence repeats within a protein. The central diagonal is the sequence aligned with itself Red dots indicating a correspondence of amino acids appear where two or more amino acids in a row match. Lines of dots, highlighted in pink, parallel to the central diagonal suggest an internal repeat.

Explain the use of a self-diagonal plot. Most proteins would show no evidence of internal repeats. 

Find a representation of the heavy chain of immunoglobin G (IgG) in Chapter 34 of your textbook. What would a self-diagonal plot of this protein look like ... 

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