Table 2 Modification of a peptide library XSKFR using 2-EBA 2da.

From: N-Terminal selective modification of peptides and proteins using 2-ethynylbenzaldehydes

Entry

Peptide

Conversion (%)b

N-terminal selectivity of mono-modified peptided

Efficiency of N-terminal modificatione

Mono-modifiedc

Di-modified

Total

N-terminus

Lysine

1f

CSKFR

73

–

0

73

>99:1

1.0

2

ASKFR

84

–

3

87

>99:1

0.97

3

YSKFR

56

–

2

58

>99:1

0.97

4

GSKFR

50

–

2

52

>99:1

0.96

5

HSKFR

70

–

4

74

>99:1

0.95

6

DSKFR

39

–

3

42

>99:1

0.93

7

ESKFR

32

–

3

35

>99:1

0.91

8

NSKFR

62

–

6

68

>99:1

0.91

9

SSKFR

42

–

6

48

>99:1

0.88

10

QSKFR

79

–

15

94

>99:1

0.84

11

KSKFR

54

–

13

67

>99:1

0.81

12

LSKFR

51

1

3

55

98:2

0.93

13

ISKFR

59

1

10

70

98:2

0.84

14

WSKFR

38

1

1

40

97:3

0.95

15

FSKFR

58

2

7

67

96:4

0.87

16

VSKFR

61

3

2

66

95:5

0.92

17

MSKFR

60

4

2

66

94:6

0.91

18

TSKFR

51

6

7

64

90:10

0.80

19

RSKFR

56

9

5

70

86:14

0.80

20

PSKFR

10

12

1

23

46:54

0.43

  1. aConditions: XSKFR 1a (0.1 mM) and reagent 2d (2 mM) in 50 mM PBS (pH 6.5)/DMSO (9:1) solution (100 μL), 37 °C, 16 h.
  2. bDetermined by total ion count (TIC) of LC–MS analysis.
  3. cConversion of N-terminal modified peptide (or lysine-modified peptide) is determined by the conversion of mono-modified peptide and N-terminal selectivity of mono-modified peptide.
  4. dN-terminal selectivity is obtained by ratio of mono-modified peptide at N-terminal α-amino group to lysine ε-amino group as determined by extracted ion chromatogram (EIC) of LC–MS analysis.
  5. eEfficiency of N-terminal modification is equal to the conversion of N-terminal modified peptide over the total conversion.
  6. fTris(2-carboxyethyl)phosphine (TCEP, 0.5 mM) was added to prevent the formation of disulfide linkage.
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