Table 1.

Structure and IC₅₀ values of all R2 sequence derived peptides. For a full overview of compound structures and IC₅₀ values see supplemental Table 2.

Peptide[a]	Sequence/mutation[b]	Cyclization	IC50 [nM]
1	676 680   688 FITC‐PEG‐KLLSSSETKRAARRPYKPIALRQSQA‐NH2	–	—
2	Ac‐KLLSSSETKRAARRPYKPIALRQSQA‐NH2	–	13.4±3.0
3	Ac‐ETKRAARRPYKPIA‐NH2	–	2621±786
4	Ac‐ETKRAARRPYKPKA‐NH2	amide	47.7±12.5
5	Ac‐ETKREARRPYKPKA‐NH2	amide	125.6±32.3
6	Ac‐CTKRAARRPYKPCA‐NH2	ortho xylene	77.4±6.5
7	Ac‐CTKRAARRPYKPCA‐NH2	meta xylene	18.7±4.1
8	Ac‐CTKRAARRPYKPCA‐NH2	para xylene	15.1±5.4
9	Ac‐CTKRAARRPYKPCA‐NH2	meta pyridine	34.9±14.0
10	Ac‐ETKRCARRPYKPCA‐NH2	ortho xylene	321.7±56.8
11	Ac‐ETKRCARRPYKPCA‐NH2	meta xylene	388.0±69.8
12	Ac‐ETKRCARRPYKPCA‐NH2	para xylene	2342±363
13	Ac‐ETKRCARRPYKPCA‐NH2	meta pyridine	146.8±10.7
33	Ac‐CTKRCARRPYKPCA‐NH2	mesitylene	12.3±2.0
36 (R2 scrambled)	Ac‐CPRACRYKTAPRCK‐NH2	mesitylene	>10 000
37	Ac‐CAKRCARRPYKPCA‐NH2	mesitylene	12.4±3.2
38	Ac‐CTARCARRPYKPCA‐NH2	mesitylene	262.9±42.7
39	Ac‐CTKACARRPYKPCA‐NH2	mesitylene	77.4±9.6
40	Ac‐CTKRCAARPYKPCA‐NH2	mesitylene	4319±974
41	Ac‐CTKRCARAPYKPCA‐NH2	mesitylene	24.6±3.9
42	Ac‐CTKRCARRAYKPCA‐NH2	mesitylene	131.3±15.3
43	Ac‐CTKRCARRPAKPCA‐NH2	mesitylene	38.3±1.9
44	Ac‐CTKRCARRPYAPCA‐NH2	mesitylene	19.8±3.6
45	Ac‐CTKRCARRPYKACA‐NH2	mesitylene	15.6±2.2
46	Ac‐CTKRCARRPYKPC‐NH2	mesitylene	20.5±1.4
47	N3‐PEG‐CTKRCARRPYKPCA‐NH2	mesitylene	13.9±5.6
48 (R2 scrambled)	N3‐PEG‐CPRACRYKTAPRCK‐NH2	mesitylene	>10 000
49 (Tat‐modified)	H‐GRKKRRQRRRPQGCTKRCARRPYKPCA‐NH2	mesitylene	4.4±1.4
50	H‐GRKKRRQRRRPQ‐NH2	–	1239±358

[a] All sequences are derived from the MTA1‐R2 sequence unless otherwise indicated. [b] Residues used for cyclization are highlighted in blue. Mutated residues are highlighted in red.