Cristobal Viedma Talks About Deracemization of Racemic Crystals

Fast Moving Front Commentary, January 2011

Cristobal Viedma

Article: Chiral symmetry breaking during crystallization: Complete chiral purity induced by nonlinear autocatalysis and recycling

Authors: Viedma, C
Journal: PHYS REV LETT, 94 (6): art. no.-065504, FEB 18, 2005
Addresses: Univ Complutense, Fac Geol, Dept Cristalog & Mineral, E-28040 Madrid, Spain.
(Commentary for September 2010 [late entry])

Cristobal Viedma talks with and answers a few questions his Fast Moving Fronts paper in the field of Physics from September 2010.

SW: Why do you think your paper is highly cited?

My paper shows counterintuitive results that are of interest for many aspects concerning chirality. I have put the theoretical and experimental bases for a new method to obtain pure enantiomers from a previously racemic medium: "the grinding method." As Professor Michael McBride says in the News & Views section of Nature (452 [7184]: 161-2, 2008), this grinding method is "the first original method for isolating single-handed crystals from a mixture of mirror-image forms since Pasteur used tweezers to effect such a separation in 1848."

SW: Does it describe a new discovery, methodology, or synthesis of knowledge?

Yes, it describes a new methodology for deracemization of racemic crystals based on the discovery of a new physicochemical phenomenon that has been called "Viedma Ripening."

SW: Would you summarize the significance of your paper in layman's terms?

Many organic molecules are chiral, i.e., they can occur in right-handed and left-handed forms that are non-superimposable mirror images of each other. The mirror symmetry of chiral molecules and their crystals implies that most chemical-physical properties, like melting point, density, and solubility are identical. Under normal conditions, chemical synthesis will therefore produce equal amounts of left- and right-handed molecules, a racemic mixture.

"The origin of life in general or the origin of homochirality in particular requires multidisciplary research involving all areas of science as biology, geology or chemistry."

Life, however, has somehow chosen a single handedness, with amino acids being left-handed and sugars right-handed. This fact has spurred many theories on the origin of homochirality in life and has very practical consequences for the response of living organisms to the different enantiomers of a chiral molecule: the active components of most medicines must be of single chirality.

In my paper I show how two populations of chiral crystals (left-handed and right-handed) cannot coexist in the same mixture: one of the populations disappears in a self-catalytic process to benefit the other. The existence of only one type of crystal, crystals of only one chirality, seems to be an inexorable destiny in our system, ruled by a simple dissolution-growth process.

SW: How did you become involved in this research, and how would you describe the particular challenges, setbacks, and successes that you've encountered along the way?

I believe that challenging problems require interdisciplinary approach for innovative answers to old questions. The origin of life in general, or the origin of homochirality in particular, requires multidisciplinary research involving all areas of science as biology, geology, or chemistry.

My paper shows counterintuitive results and in fact many researchers in the field could hardly believe the results. In fact my paper had problems to be accepted. Now the novel process that was described in the paper has become firmly established and has implications beyond what I expected initially.

SW: Where do you see your research leading in the future?

I would like to stress that if my initial paper has been widely recognized, it is due to the impressive work carried out by the teams of Professor Donna Blackmond and Professor Elias Vlieg.

I am interested in amino acids, the building block of proteins, we are working with this novel grinding method in the realm of amino acids with very good initial results (J. Am. Chem. Soc. 130 [46]: 15274-+, 2008).

At the same time we are looking for new systems with prebiotic significance with similar behavior: it seems that sublimation-condensation system is a good candidate (Chem. Commun. 2011 DOI: 10.1039/c0cc04271d). Practical applications to pharmaceutical processing of this research should not be distant.

SW: Do you foresee any social or political implications for your research?

One of the important and unsolved mysteries of science is the origin of homochirality in the biosphere. On the other hand, if the active components of most new medicines must be of single chirality, the efficient production of enantiomerically pure compounds has become a key issue in the pharmaceutical industry. I believe that my research touches both problems: the intriguing conundrum of the origin of biological chirality as well as the manufacture of chiral substances.

Dr. Cristóbal Viedma
Profesor Titular de Universidad
Departamento de Cristalografía y Mineralogía
Facultad de Geología, Universidad Complutense
Madrid, Spain




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