. 2002 Nov 27;99(25):16052–16057. doi: 10.1073/pnas.252340199

Table 1.

Designed sequences and self-assembly behavior as a function of the molecule net charge

Sequence	Net charge of the molecule
Sequence	+1	Neutral	−1	>1
No. 1 KTVIIE	Ac—K⁺TVIIE—Am	Ac—K⁺TVIIE⁻—am	Ac—KTVIIE⁻—Am	N⁺—K⁺TVIIE—C
	pH 2.6, 98%; β	pH 7.4, 100%; β	pH 12.5, 100%; rc + β	pH 2.6, 92%, +2; rc
No. 3 STVIIE	N⁺—STVIIE—C	Ac—STVIIE—Am	Ac—STVIIE⁻—am
	pH 2.6, 92%; β	pH 2.6, 98%; rc	pH 7.4, 100%; rc + β
No. 4 KTVIIT	Ac—K⁺TVIIT—Am	Ac—KTVIIT—Am	N—KTVIIT—C⁻	N⁺—K⁺TVIIT—C
	pH 2.6, 100%; rc	pH 12.5, 100%; rc	pH 12.5, 100%; rc	pH 2.6, 97%, +2; rc
No. 5 STVIIT	N⁺—STVIIT—C	Ac—STVIIT—Am	Ac—STVIIT—C⁻
	pH 2.6, 97%; β	pH 2.6, 100%; β	pH 7.4, 100%; rc + β
		N⁺—STVIIT—C⁻
		pH 6.0, 96%; β
No. 6 KTVLIE	Ac—K⁺TVLIE—Am	Ac—K⁺TVLIE⁻—Am	Ac—KTVLIE⁻—Am	N⁺—K⁺TVLIE—C
	pH 2.6, 98%; rc	pH 7.4, 100%; β	pH 12.5, 100%; rc	pH 2.6, 92%, +2; rc
No. 7 KTVIVE	Ac—K⁺TVIVE—Am	Ac—K⁺TVIVE⁻—Am	Ac—KTVIVE⁻—Am	N⁺—K⁺TVIVE—C
	pH 2.6, 98%; rc	pH 7.4, 100%; β	pH 12.5, 100%; rc	pH 2.6, 92%, +2; rc
No. 8 KTVIYE	Ac—K⁺TVIYE—Am	Ac—K⁺TVIYE⁻—Am	Ac—KTVIYE⁻—Am	N⁺—K⁺TVIYE⁻—C
	pH 2.6, 98%; rc	pH 7.4, 100%; rc	pH 12.5, 100%; rc	pH 2.6, 92%, +2; rc
No. 9 STVIYE	N⁺—STVIYE—C	Ac—STVIYE—Am	Ac—STVIYE⁻—Am
	pH 2.6, 92%; rc + β	pH 2.6, 98%; rc	pH 7.4, 100%; rc + β

rc and β annotations refer to the CD signature of the peptide at the pH given. “rc” indicates random coil CD spectrum, “β” stands for β-sheet CD spectrum, and “rc + β” indicates the presence of both β-structure and unfolded conformations in solution. Bold annotations correspond to sequences and conditions that showed amyloid fibril formation as indicated by EM and x-ray diffraction data.

Sequences are given using the one-letter code for amino acid residues. Amino acids modelled for the six-residue β-strands of the six-stranded polymeric β-sheet are: at positions 1 and 6, K, E, T, and S; at positions 2 and 5, K, E, T, S, V, I, L, Y and W; and at positions 3 and 4, V, I, L, Y and W. The predicted sequence stability is No. 1 > 3 > 6 > 7 > 8 > 9 > 5 > 4.

^†

Superscripts “+” and “−” stand for a formal positive and negative charge, respectively. “Ac” stands for an N terminus protected with an acetyl group, “Am” for a C terminus protected with an amide group, “N” for a free N terminus, and “C” for a free C terminus. pH and percentage of molecules with a given net charge at that pH are given below each peptide sequence. This percentage has been calculated by using the Arrhenius equation (pH = pK + log([acceptor]/[donor])) and the following pKa values (31): free N terminus, pK_a(S) = 7.34; pK_a(K) = 7.10. Free C terminus, pK_a(T) = 4.07; pK_a(E) = 3.65. Charged side chains, pK_a(K) = 10.60; pK_a(E) = 4.25.