Evolutionary heat maps describing the amino acid and dipeptide compositions of FF domain structures of different age.

<p>A. Frequency of amino acids in FFs. The color array of 29,480 cells (1,475 rows×20 columns) describes the amino acid composition of 1,475 FFs along the evolutionary timeline. Columns represent the 20 standard amino acids ordered (from left to right) according to average amino acid frequency and rows represent FFs ordered (from top to bottom) according to domain age (<i>nd</i>_FF = 0 ∼ 1). B. Frequency of dipeptides in FFs. The color array of 589,600 cells (1,475 rows×400 columns) describes the 400-dipeptide composition of FFs along the timeline. Columns represent dipeptide types ordered (from left to right) according to average frequency (from LL to WW) and rows represent FFs ordered according to age. The heat maps confirm the existence of non-random patterns of amino acid and dipeptide compositions along the evolutionary timeline of FFs and reveal unique signatures of amino acid and dipeptide use in FFs. Amino acids are described with single-letter codes.