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TopDimensions Of Protein Molecules
Amino acids are chemical compounds that simultaneously include a carboxyl group COO- and an amine group H3N+. These groups are covalently linked to a carbon atom (α - carbon), to which a hydrogen atom H and a side chain R are also covalently attached (Koolman & Roehm, 2013). Amino acids have two enantiomorphic forms L and D, which are Fischer planar views shown in Figure 1. From Figure 1 it can be seen that the two enantiomorphic forms are related by mirror image relative to the line passing through the amine and carboxyl groups.
Figure 1. Enantiomorphic forms of the amino acid molecule a) L - amino acid, b) D - amino acid
The side chains in Figure 1 have 20 variants in classic amino acids (Koolman & Roehm, 2013). They determine the properties of the corresponding amino acids. Fisher's projections do not reflect the spatial structure of amino acids, although it is clear that these are spatial objects. Spatial images of enantiomorphic amino acids (Zhizhin, 2016) are presented in Figure 2.
Figure 2. Spatial images of amino acids
In Figure 2, covalent bonds are indicated in red. The rest of the segments define the spatial shape of the molecule, they are marked in black.
From Figure 2 it follows that the amino acid molecule is a tetrahedron with a center. The dimension of such a polyhedron can be determined by the Euler-Poincaré (Poincaré, 1895)
(1) in (1)
is the number of elements of a polytope
P of dimension
n having dimension
i.