4.2.1. Quasi-mirror antisymmetry  



Antisymmetric amino acids, which are located on both sides of the plane I, we call quasi-mirror plane. They form pairs, which have similar physical characteristics but different chain length or weight. They are connected by the transformation, which we designate by the letter alpha (a). To the right of a plane I there were shorter or lighter side chains (they are shown on light green background), and at the left - longer or more heavy (dark-green background).  To see this in more detail, the side chains are represented separately from the dodecahedron on the left and right sides of the central band.






















































Our analysis will be carried out from top to bottom. At the top left and right side chains of serine (Ser - right) and threonine (Thr - left) are situated, both have the C-OH group, but a threonine has also methyl group.


A little closer to the center cysteine ​​(Cys - left) and methionine (Met - right) are situated. Cysteine is a lighter sulfur-containing side chain, methionine - heavier, in which a methyl group, linked to a sulfur atom, prevents the appearance of weak acid properties characteristic of cysteine.


At the vertices of a dodecahedron, connected by an edge with serine and threonine are lower aspartic (Asp - right) and glutamic (Glu - left) acids. Their side chains contain at the end the О=С-ОН groups, which have acidic properties. Glutamic acid is by one СН2- group longer than aspartic acid.


Even lower, closer to the center, settles down the pair of nonpolar side chains - valine (Val - right) and isoleucine (Ile - left). The last is by one methyl group longer than valine.

At the vertices connected by edges with cysteine ​​and methionine, settle down asparagine (Asn - right) and glutamine (Gln - left). These are the neutral side chains capable of forming of hydrogen bonds. They have the same O=C-NH2 group, but the chain of glutamine is longer by one СН2 group.


Vertices occupied by aspartic and glutamic acids, connected with the vertices, in which the side chains of arginine (Arg - right) and lysine (Lys - left) are located. Both amino acids exhibit alkaline properties. Lysine has the longer side chain.


Below the vertices of arginine and lysine are connected with vertices occupied by the side chains of histidine (His - right) and tryptophan (Trp - left). Each of them contains the five-membered cycle. Tryptophan has a four-piece fragment attached to its five-membered cycle forming thus an additional six-membered cycle. Possess weakly alkaline properties.


Closer to the center at the bottom settles down a pair of cyclic side chains having six-membered cycles - phenylalanine (Phe-right) and tyrosine (Tyr - left). Thus tyrosine is by one oxygen atom longer than phenylalanine. Possess a weakly acid properties.




























































Thus, we were convinced that the distribution of side chains pairs in the plane I is in exact conformity with the given principle of a quasi-mirror antisymmetry: on the right settle down the lighter side chains, on the left - heavier, and their physical properties are similar in pairs.


For further acquaintance with the antisymmetries of amino acids, which are identified by the use of our model, go to the sections 4.2.2., 4.2.3., 4.2.4. or return to section 4.


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