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Table 1 Comparison for relative hydrophilicity and hydrophobicity of amino acids for the real data sets.

From: Artificial neural network models for prediction of intestinal permeability of oligopeptides

    

Hydrophobicity*

 

Amino acid

Hominga

Randomb

Ratioc

Calculatedd

Side-chain analoguese

Amino acidsf

N-acetyl amidesg

Hydrophilicity*

Alanine

6.85

6.50

1.05

-0.39

-0.87

-0.50

-0.31

-0.45

Glycine

4.02

2.20

1.83

0.00

0.00

0.00

0.00

0.00

Isoleucine

1.56

2.10

0.74

-1.82

-3.98

-1.80

-1.80

-0.24

Leucine

7.19

9.60

0.75

-1.82

-3.98

-1.80

-1.70

-0.11

Valine

1.98

1.90

1.04

-1.30

-3.10

-1.50

-1.22

-0.40

Methionine

2.69

3.30

0.82

-0.96

-1.41

-1.30

-1.23

-3.87

Phenylalanine

1.56

2.10

0.74

-2.27

-2.04

-2.50

-1.79

-3.15

Tryptophan

0.66

1.90

0.35

-2.13

-1.39

-3.40

-2.25

-8.27

Proline

11.41

10.70

1.07

-0.99

-

-1.40

-0.72

-

Cysteine

0.02

0.00

-

-0.99

-0.34

-1.00

-1.54

-3.63

Serine

13.42

8.60

1.56

1.24

4.34

0.30

0.04

-7.45

Threonine

10.72

13.10

0.82

1.00

3.51

-0.40

-0.26

-7.27

Tyrosine

1.95

2.40

0.81

-1.47

1.08

-2.30

-0.96

-8.50

Asparagine

6.22

6.40

0.97

1.91

7.58

0.20

0.60

-12.07

Glutamine

7.56

7.10

1.06

1.30

6.48

0.20

0.22

-11.77

Histidine

6.74

6.90

0.98

0.64

5.60

-0.50

-0.13

-12.66

Lysine

5.33

3.80

1.40

2.77

6.49

3.00

0.99

-11.91

Arginine

4.89

4.30

1.14

3.95

15.86

3.00

1.01

-22.31

Aspartic acid

3.06

4.10

0.75

3.81

9.66

2.50

0.77

-13.34

Glutamic acid

2.18

3.10

0.70

2.91

7.75

2.50

0.64

-12.63

Correlation Coefficienth

0.17

0.21

0.40

0.50

0.03

  1. a Observed frequency of each amino acid in the tissue-homing heptapeptide set obtained from peroral phage display
  2. b Observed frequency of each amino acid in the phage library (Ph. D-C7Câ„¢ library)
  3. c Relative ratio of amino acid frequency in homing peptidea to amino acid frequency in phage libraryb
  4. d Calculated from hydrophobicities of the individual groups that make up each side chain, using data for the partition coefficient between water and octanol of many model compounds.
  5. e Hydrophilicity was measured by the partition coefficient K D of the model for each side chain from vapor → water; hydrophobicity for water → cyclohexane. For ionizing side chains, the values were corrected for the fraction of each side chain that is ionized at pH 7. Both scales were normalized to zero for the value of Gly.
  6. f Some values were measured from the relative solubilities of the amino acid in water and ethanol or dioxane.
  7. g Measured from the partition coefficient between water and octanol of the N-acetyl amino acid amides.
  8. h Correlation coefficients between relative ratioc and each hydrophobicity/hydrophilicity.
  9. *Reference [26].