Table 2 Variations in the concentration (in ppb) of pyrimidine nucleobases and their related analogs in meteorite extracts and the Murchison soil.

Cytosine & its isomers

Cytosine

C₄H₅N₃O

112.0505

4

4

4

5

2

 30

Isocytosine

C₄H₅N₃O

112.0505

0.5

1

1

1

0.2

 0.2

1H-Imidazole-4-carboxamide

C₄H₅N₃O

112.0505

5

3

4

1

6

 n.d.

Uracil & its isomers

Uracil

C₄H₄N₂O₂

113.0346

15

1

7

30

n.d.**

n.d.

19

 <138

2-Imidazole

carboxylic acid

C₄H₄N₂O₂

113.0346

19

9

13

4

14

 n.d.

4-Imidazole

carboxylic acid

C₄H₄N₂O₂

113.0346

90

54

70

19

99

 <20

Methyl cytosine

5-Methylcytosine

C₅H₇N₃O

126.0662

1

1

1

n.d.

1

 n.d.

6-Methylisocytosine

C₅H₇N₃O

126.0662

0.2

0.4

0.3

n.d.

1

 n.d.

5-Methylisocytosine

C₅H₇N₃O

126.0662

0.1

0.1

0.1

n.d.

Thymine & its isomers

Thymine

C₅H₆N₂O₂

127.0502

5

1

3

<2

5

n.d.

≤1

 <19

6-Methyluracil

C₅H₆N₂O₂

127.0502

4

0.5

2

17

0.3

 <12

1-Methyluracil

C₅H₆N₂O₂

127.0502

1

5

3

n.d.

5

1-Methyl-1H-imidazole-5-carboxylic acid

C₅H₆N₂O₂

127.0502

150

75

107

9

100

2-Methyl-1H-imidazole-4-carboxylic acid

C₅H₆N₂O₂

127.0502

21

11

15

9

23

4-Methyl-1H-imidazole-5-carboxylic acid

C₅H₆N₂O₂

127.0502

26

22

24

n.d.

30

Others

4-Hydroxypyrimidine

C₄H₄N₂O

97.0396

6

2

4

10

3

 23

2,4-Diaminopyrimidine

C₄H₆N₄

111.0665

1

n.d.

0.2

n.d.

0.2

 n.d.

5-amino-4-imidazolecarboxamide

C₄H₆N₄O

127.0614*

0.02

***

 n.d.

Dihydrouracil

C₄H₆N₂O₂

115.0502

51

n.d.

25

n.d.

n.d.

 n.d.

Nicotinamide

C₆H₆N₂O

123.0553

10

20

16

5

65

Isonicotinamide

C₆H₆N₂O

123.0553

3

3

3

4

6

Picolinamide

C₆H₆N₂O

123.0553

1

2

1

3

10

Nicotinic acid

C₆H₅NO₂

124.0393

91

264

190

108

626

Isonicotinic acid

C₆H₅NO₂

124.0393

53

216

147

118

307

Total pyrimidines

37

15

24

38

13

Pyrimidines/Purines

0.2

1.4

0.3

4.3

0.4