Viedma ripening

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Viedma ripening or attrition-enhanced deracemization is a chiral symmetry breaking phenomenon observed in solid/liquid mixtures of enantiomorphous (racemic conglomerate) crystals that are subjected to comminution. It can be classified in the wider area of spontaneous symmetry breaking phenomena observed in chemistry and physics.

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It was discovered in 2005 by geologist Cristobal Viedma, who used glass beads and a magnetic stirrer to enable particle breakage of a racemic mixture of enantiomorphous sodium chlorate crystals in contact with their saturated solution in water. [1] A sigmoidal (autocatalytic) increase in the solid-phase enantiomeric excess of the mixture was obtained, eventually leading to homochirality, i.e. the complete disappearance of one of the chiral species. Since the original discovery, Viedma ripening has been observed in a variety of intrinsically chiral organic compounds that exhibit conglomerate crystallization and are able to inter-convert in the liquid via racemization reactions. [2] It is also regarded as a potential new technique to separate enantiomers of chiral molecules in the pharmaceutical and fine chemical industries (chiral resolution).

Mechanism

The exact interplay of the mechanisms leading to deracemization in Viedma ripening is a subject of ongoing scientific debate. [3] [4] It is, however, currently believed that for intrinsically chiral molecules, deracemization occurs via a combination of various phenomena:

Two key assumptions often invoked to explain the mechanism is that: a) small fragments generated by breakage for each enantiomeric crystal population can maintain their chirality, even when they are smaller than the critical radius for nucleation (and are thus expected to dissolve) and b) small chiral fragments can undergo enantiospecific aggregation to larger particles of the same chirality. Using these two assumptions, it can be shown mathematically, [6] that any stochastic even immeasurable asymmetry of one enantiomeric crystal population over the other can be amplified to homochirality in a random manner.

Implications for the origin of life

In principle, molecules required for the generation of life, i.e. amino acids that combine to form proteins and sugars that form DNA molecules are all chiral and are thus able to adopt two mirror-image forms (often described as left- and right-handed), which from a chemical perspective are equally likely to exist. However, all biologically-relevant molecules known on earth are of a single handedness, even though their mirror images are also capable of forming similar molecules. The reason of the prevalence of homochirality in living organisms is currently unknown and is often connected to the origin of life itself. Whether homochirality emerged before or after life is currently unknown, but many researchers believe that homochirality could have been a result of amplification of extremely small chiral asymmetries.

Since Viedma ripening has been observed in biologically-relevant molecules, such as chiral amino acids [7] it has been put forward by some as a possible contributing mechanism for chiral amplification in a prebiotic world. [8] [9] [10]

See also

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References

  1. ↑ Viedma, Cristobal (17 February 2005). "Chiral Symmetry Breaking During Crystallization: Complete Chiral Purity Induced by Nonlinear Autocatalysis and Recycling". Physical Review Letters. 94 (6): 065504. arXiv: cond-mat/0407479 . Bibcode:2005PhRvL..94f5504V. doi:10.1103/PhysRevLett.94.065504. PMID   15783745. S2CID   118964653.
  2. ↑ Sögütoglu, Leyla-Cann; Steendam, René R. E.; Meekes, Hugo; Vlieg, Elias; Rutjes, Floris P. J. T. (21 September 2015). "Viedma ripening: a reliable crystallisation method to reach single chirality". Chemical Society Reviews. 44 (19): 6723–6732. doi: 10.1039/C5CS00196J . hdl: 2066/149815 . PMID   26165858.
  3. ↑ Noorduin, Wim L.; van Enckevort, Willem J. P.; Meekes, Hugo; Kaptein, Bernard; Kellogg, Richard M.; Tully, John C.; McBride, J. Michael; Vlieg, Elias (2010). "The Driving Mechanism Behind Attrition-Enhanced Deracemization" (PDF). Angewandte Chemie International Edition. 49 (45): 8435–8438. doi:10.1002/anie.201002036. PMID   20859973. S2CID   5596199.
  4. ↑ Uwaha, Makio; Katsuno, Hiroyasu (10 February 2009). "Mechanism of Chirality Conversion by Grinding Crystals: Ostwald Ripening vs Crystallization of Chiral Clusters". Journal of the Physical Society of Japan. 78 (2): 023601. Bibcode:2009JPSJ...78b3601U. doi:10.1143/JPSJ.78.023601.
  5. ↑ Xiouras, Christos; Fytopoulos, Antonios A.; Ter Horst, Joop H.; Boudouvis, Andreas G.; Van Gerven, Tom; Stefanidis, Georgios D. (2 May 2018). "Particle Breakage Kinetics and Mechanisms in Attrition-Enhanced Deracemization" (PDF). Crystal Growth & Design. 18 (5): 3051–3061. doi:10.1021/acs.cgd.8b00201.
  6. ↑ Iggland, Martin; Mazzotti, Marco (5 October 2011). "A Population Balance Model for Chiral Resolution via Viedma Ripening". Crystal Growth & Design. 11 (10): 4611–4622. doi:10.1021/cg2008599.
  7. ↑ Viedma, Cristobal; Ortiz, José E.; Torres, Trinidad de; Izumi, Toshiko; Blackmond, Donna G. (19 November 2008). "Evolution of Solid Phase Homochirality for a Proteinogenic Amino Acid" (PDF). Journal of the American Chemical Society. 130 (46): 15274–15275. doi:10.1021/ja8074506. PMID   18954052.
  8. ↑ Ribó, Josep M.; Hochberg, David; Crusats, Joaquim; El-Hachemi, Zoubir; Moyano, Albert (31 December 2017). "Spontaneous mirror symmetry breaking and origin of biological homochirality". Journal of the Royal Society Interface. 14 (137): 20170699. doi:10.1098/rsif.2017.0699. PMC   5746574 . PMID   29237824.
  9. ↑ McBride, J. Michael; Tully, John C. (March 2008). "Did life grind to a start?". Nature. 452 (7184): 161–162. doi: 10.1038/452161a . PMID   18337809. S2CID   205036438.
  10. ↑ Blackmond, Donna G. (2010). "The Origin of Biological Homochirality". Cold Spring Harbor Perspectives in Biology. 2 (5): a002147. doi:10.1101/cshperspect.a002147. PMC   2857173 . PMID   20452962.
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