Table 1 Optimization of modification conditionsa

From: Chemoselective and photocleavable cysteine modification of peptides and proteins using isoxazoliniums

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Entry

2a (equiv.)

AgNO3 (mol%)

pH values

Temp. (° C)

Conversions (%)b

1

1

1

7.4

25

79

2

1

2.5

7.4

25

86

3

1

5

7.4

25

96

4

1

10

7.4

25

68

5

2

10

7.4

25

91c

6

3

15

7.4

25

87c

7

4

20

7.4

25

84c

8

5

25

7.4

25

77c

9

1

5

5.3

25

88

10

1

5

6.3

25

91

11

1

5

8.0

25

98

12

1

5

9.0

25

99

13

1

5

7.4

37

99

14

1

5

7.4

4

39

15

0

0

7.4

25

0

16

1d

0

7.4

25

0

  1. aConditions of the modifications: treatment of STSSSCNLSK 1a (0.1 mM) with isoxazolinium reagent 2a (different amounts with different loadings of AgNO3) in 50 mM PBS buffer/CH3CN (19:1) with different pH values for 2 h. bConversion of the modification was determined by LC-MS analysis. cNearly complete conversion (≥99%) was achieved after 24 h. dReagent was prepared without addition of AgNO3
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