Table 1.

Frequency of cation-π interactions within proteins

Amino acid	Total number*	Interacting pairs†	Cation-π interactions‡	Amino acid pair	Cation-π interactions‡	Percent§
K	13,446	5,881	1,006	KF	285	14.5
R	10,919	8,149	1,988	KY	438	14.7
F	9,162	4,969	915	KW	283	30.2
Y	8,309	6,615	1,187	RF	630	21.0
W	3,412	2,446	892	RY	749	20.6
				RW	609	40.4

^*The total number of times a particular amino acid appears in the dataset of 593 proteins. 

^†The number of times a particular amino acid occurs in an interacting pair. 

^‡The number of times a particular amino acid or pair of amino acids occurs in a cation-π interaction. 

^§Percent of interacting pairs that are energetically significant cation-π interactions.