Table 2.

Comparison of PCA-derived enriched sequences and NGS read frequency for the 2nd round library.

PCA dimension	PCA-derived motif	Most frequent match	Frequency ranking
1	ZMHKKRHZ	ZMHKKRHZ	1
2	ZEYGEQZ	ZEYGEQZ	2
3	ZRYGTZ	ZRYGTZ	3
4	ZGERQZ	ZGERQZ	4
	ZGEZ
5	ZGVYGGFZ	ZGVYGGFZ	7
	ZGVYZ	ZGVYZ	8
6	ZAKERHZ	ZAKERHZ	5
	GVY	ZGVYZ	8
	ZE(V/K/R)XZ	ZEKERHZ	108
7	ZAKEXH	ZAKERHZ	5
	Z(A/G)YVZ	ZGYVZ	6
8	ZEEVHZ	ZEEVHZ	9
9	Z(A/W)(E/Y)EHRZ	ZWEGRQZ	10
	ZWEGR(Q)Z	ZAYEHRZ	12
	VEGRQ
10	VXZ
	Z(A/G)Y(Y/E)HRZ	ZGVYZ	8
	ZGY(Y)Z	ZAYEHRZ	12
	ZGAYEHRZ

Motifs were reconstructed for the first 10 PCA dimensions and used to search the NGS results for the ranking of the highest enriched sequences (highest Z-scores). Because the second round post-selection library was significantly smaller and heavily biased, correlation between PCA and NGS frequency is very good. Some sequence variation and small motifs can still be seen.