Deamination solid state

Dealkylation ligands, 432 Deamination solid state anation, 469... 

Racemizations in the crystalline state have a long history. It is known that L-a-amino acids slowly racemize in the solid state [62]. As this also happens in solid proteins the implications are manifold, not only in pure chemistry but also in biochemistry, nutrition, food technology, and geology. Therefore, techniques have been developed to determine the dl ratio of amino acids down to 0.1% and inversion rate constants have been determined under acid hydrolysis conditions [63]. One could think of very slow deamination and readdition of the amine or an enolization mechanism. However, such reactions can also be induced by photolysis or radiolysis from natural sources [64]. 

The assessment of stability in biotechnology-derived products such as peptides for preformulation is similar to that of the small-molecule drug. Degradation subjected to hydrolysis, oxidation, and deamination influenced by pH, temperature, and buffer species may be studied in the same manner. Protein in solution is not inherently stable. As chemical reactions are retarded in the solid state, a freeze-dried formulation is more suitable for protein product. 

The next example of comparatively simplicity, this time nonaqueous, is the crystalline alanine. There are several products of irradiation of that solid crystalline amino acid. In this state it occurs as zwitterion as NMR shows, i.e. the amine group is protonated -N+H3. Single ionization spurs, of a low energy, cause deamination which leads to detachment of ammonia and formation of a free radical. Pulse radiolysis of single crystals of L-alanine shows, that the alanine derived radical CH3-C H-C02-, which shows the spectrum with maximum at 348 nm [9], stabilizes during 5 milliseconds [10], It is usually observed not spectroscopically but by the EPR method [11] it shows extreme stability, being applied as reference dosimeter. 

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