Table 2 Reaction conditions and detection results of the products from the reaction of Pro with other amino acids and P3m.

From: Prebiotic formation of cyclic dipeptides under potentially early Earth conditions

P3m + Pro + AAsa

Initial reaction conditions

Relative abundance based on the total three proline-containing peptidesb

Initial pH

Temp. (°C)

Time (days)

Cyclo-Pro-AAs

Linear-Pro-AAs

Cyclo-Pro-Pro

Ser

10.7

35

7

45.8%

×c

54.2%

Ala

10.7

35

7

32.5%

×

67.5%

Glu

10.7

35

7

18.4%

×

81.6%

Gly

10.7

35

7

16.5%

×

83.5%

Arg

10.7

35

7

15.4%

×

84.6%

Asp

10.7

35

7

12.8%

×

87.2%

Lys

10.7

35

7

6.2%

×

93.8%

Phe

10.7

35

7

2.2%

92.4%

5.4%

Met

10.7

35

7

1.9%

74.3%

23.8%

Tyr

10.7

35

7

1.7%

64.3%

34.0%

Trp

10.7

35

7

0.6%

80.7%

18.6%

His

10.7

35

7

×

×

×

  1. aAAs: amino acids. bThe relative abundance were calculated by the integral area at 210 nm. As the Fig. 1 showed that linear-Pro-Pro was easy to form cyclo-Pro-Pro, so the linear-Pro-Pro was not included in the proline-containing products; c×The corresponding product was not detected by HPLC-MS.
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