Table 1.
Illustrated is the method employed in estimating the average diameter, in Ångströms, of the twenty standard amino acids. The method entails (1) estimating the nanometers diameter of each non-alanine amino acid relative to the known diameter of alanine, 0.69 nanometer, using the formula, amino acid molar mass/alanine molar mass ×0.69 nanometer(s); (2) multiplying each estimated amino acid diameter times 10 in order to convert each amino acid diameter from nanometers to Ångströms; (3) summing the Ångströms diameters and dividing by 20 to yield an average amino acid diameter per amino acid equal to 10.6 Ångströms.
| Estimation of average amino acid diameter | ||||
|---|---|---|---|---|
| Molar mass | Amino acids | Nanometer diameter | Diameter in Ångströms | |
| 89.1 | A | Alanine | 0.6** | 6.9 |
| 132.1 | N | Asparagine | 1.02 | 10.2 |
| 133.1 | D | Aspartic acid | 1.03 | 10.3 |
| 121.6 | C | Cysteine | 0.94 | 9.4 |
| 147.1 | E | Glutamic acid | 1.14 | 11.4 |
| 146.1 | Q | Glutamine | 1.13 | 11.3 |
| 75.1 | G | Glycine | 0.58 | 5.8 |
| 115.1 | P | Proline | 0.89 | 8.9 |
| 105.1 | S | Serine | 0.81 | 8.1 |
| 181.2 | Y | Tyrosine | 1.40 | 14.0 |
| 174.2 | R | Arginine | 1.35 | 13.5 |
| 155.2 | H | Histidine | 1.20 | 12.0 |
| 131.2 | I | Isoleucine | 1.02 | 10.2 |
| 131.2 | L | Leucine | 1.02 | 10.2 |
| 146.2 | K | Lysine | 1.13 | 11.3 |
| 149.2 | M | Methionine | 1.16 | 11.6 |
| 165.2 | F | Phenylalanine | 1.28 | 12.8 |
| 119.1 | T | Threonine | 0.92 | 9.2 |
| 204.2 | W | Tryptophan | 1.58 | 15.8 |
| 117.5 | V | Valine | 0.91 | 9.1 |
|
| ||||
| Average Ångströms diameter per amino acid → | 10.6 | |||
**[14].