The Origin of Life and the Crystallization of Aspartic Acid in Water

Abstract

The unusual molecular complexation of the enantiomers of aspartic acid in water was discovered and proven by a solubility test, solution freezing point, crystallization kinetics, and the incubation time change. The transformation of a "conglomerate solution" (CS) to a "racemic compound solution" (RCS) was dependent on both temperature and time. The CS was the solution phase which produced conglomerate crystals, and the RCS was the solution phase which gave a racemic compound. Fourier transformed infrared spectroscopy and powder X-ray diffraction were used to characterize aspartic acid solids crystallized from those complex solution phases and to distinguish conglomerate crystals from a racemic compound. We found that it took more than 36 h at 25 °C and 5 h at 45 °C just to complete the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid. However, the presence of an equimolar of succinic acid could hinder the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid for up to at least 8 h at 60 °C. This leeway of hours had provided an opportunity for the thermodynamically stable racemic aspartic acid to convert into the metastable conglomerate in water first by either a rapid acid-base reaction or the addition of an antisolvent with the temperature drop, without being concerned by its back conversion later to a racemic compound thermodynamically for quite some time. As a result, enantioseparation of aspartic acid by preferential crystallization in a large scale would have been very common and easy to occur on the primitive earth.

Molecular Chirality in Meteorites and Interstellar Ices, and the Chirality Experiment on Board the ESA Cometary Rosetta Mission

“…Later, this phenomenon was determined to be a result of secondary nucleation enhanced by agitation under far-fromequilibrium conditions. [65] The choice of aspartic acid was by no means a coincidence, as it is one of two proteinogenic amino acids that meets all necessary requirements for "Viedma ripening", that is, 1) the formation of conglomerate crystals and 2) fast racemization of the enantiomers in solution. A single chiral solid state was formed under "near-equilibrium" conditions, under which no new crystals nucleate.…”

Propagation of Biochirality: Crossovers and Nonclassical Crystallization Kinetics of Aspartic Acid in Water

“…A standard 6‐h, 40°C vacuum oven drying protocol was used to evaporate water and to generate solids from all aqueous solutions. The characteristic IR assignments and the PXRD diffraction peaks (i.e., 2θ = 11.8º, 25.5º, and 28.2º for racemic conglomerate aspartic acid, and 2θ = 13.2 o and 19.5º for racemic compound aspartic acid) were used to distinguish racemic conglomerates from racemic compounds. However, from the previous literature, IR spectra have shown discriminative peaks for the functional groups, such as ‐COO ‐ (in‐plane bending), ‐COOH (in‐plane bending), ‐CH 2 (rocking), ‐CN (stretching), ‐CH 2 (twisting) for aspartic acid, and ‐NH 2 (scissoring), ‐NH 2 (puckering) for alanine.…”

“…Although the gravimetric method appeared to have an inherent inaccuracy of about ±10%, its advantages were its robustness, simplicity, without the need of performing any calibration, and without the concern of any hydrate formation and any racemic conglomerate‐racemic compound transformation. All measurements were repeated at least three times …”

Aspartic acid interaction with cobalt(II) in dilute aqueous solution: A 57Co emission Mössbauer spectroscopic study

“…Aspartic acid (Asp; HOOC-CH(NH 2 )-CH 2 -COOH), an amino acid commonly present as a constituent in proteins [7], is also found, among other free amino acids, in plant root exudates [8]. K-Mg aspartate is a well-known medicine widely used in adjuvant therapy of heart diseases [9].…”