If we compare the right side with the left side, we see that they are mirror images – that is, as symmetrical shapes seen in a mirror – and they cannot overlap. This property is chirality (A new mechanism for the transfer of chirality), a component of matter that plays into the symmetry of biological structures at various scales, from the DNA molecule to the heart muscle tissue.
Today, a new article published in the journal Nature Communications reveals a new mechanism for the transfer of chirality between molecules in the nanoscale, according to a study led by UB lecturer Josep Puigmartí-Luis of the Faculty of Chemistry and the Institute of Theoretical and Computational Chemistry (IQTC) at UB.
Chirality: from basic particles to biomolecules
Chirality is an intrinsic property of matter that determines the biological activity of biomolecules. “Nature is not symmetrical, has left and right and can distinguish between them. The biomolecules that make up living matter – amino acids, sugars and lipids – are chiral: they consist of the same chemical molecules, which are mirror images (enantiomers), a component that provides different properties as active compounds (optical activity, pharmacological action, etc.). ), ”Said Josep Puigmartí-Luis, an ICREA researcher and member of the Department of Materials Science and Physical Chemistry.
“The enantiomers are chemically similar until they are located in the chiral environment that separates them (as the right shoe ‘recognizes’ the right foot). and react differently to enantiomeric species, and can easily control the chiral trait of biochemical processes that cause stereospecific changes.
How chiral molecules are extracted by chemical reactions
Chirality control is key in the production of drugs, pesticides, odors, flavors and other chemical compounds (new mechanism for the transfer of chirality between molecules in the nanoscale) Each enantiomer (molecule with symmetry) has a specific activity that is different from other similar chemical compounds (its reflection). In many cases, the pharmacological activity of the enantiomer may be minimal, and in the worst case, it may be toxic. “That’s why chemists need to be able to make compounds as an enantiomer, which is called asymmetric synthesis,” says Puigmartí-Luis.
There are many strategies to manage the character of chirality in chemical processes. For example, the use of natural enantiomerically pure compounds known as chiral pools (e.g. Chiral resolution is another option that allows the separation of enantiomers using an enantiomerically pure solvent and the recovery of the compounds of interest as pure enantiomers. The use of chiral auxiliaries which help the substrate to react in a diastereoselective manner is another effective method to obtain an enantiomerically pure product. Finally, asymmetric catalysis – based on the use of asymmetric catalysts – is the highest method for achieving asymmetric synthesis (new mechanism for the transfer of chirality between molecules in the nanoscale).
Photo: rom left to right, the experts Josep Puigmartí-Luis and Alessandro Sorrenti, from the Faculty of Chemistry and the Institute of Theoretical and Computational Chemistry (IQTC) of the UB. Courtesy: University of Barcelona.
“Each of the methods described above has its advantages and disadvantages,” said Alessandro Sorrenti, a member of the Organic Chemistry Section at the University of Barcelona and a study partner. “For example, chiral resolution – the most common method for the industrial production of enantiomerically pure products – is limited to 50% yield. The chiral pool is the most abundant source of enantiomerically pure compounds, but normally only one enantiomer is present. The chiral auxiliary method offers a high enantiomeric excess, but requires additional synthetic steps to add and remove the auxiliary compound, such as purification steps. Finally, chiral catalysts can be effective and used only in small amounts, but are only good for a relatively small number of reactions.
“All of the above methods use enantiomerically pure compounds – in the form of solvents, auxiliaries or ligands for metal catalysts – which are ultimately obtained directly or indirectly from natural sources. In other words, nature is the ultimate form of asymmetry.” Management of signs of chirality by smooth dynamics
The new paper describes how modulation of helical reactor geometry at the macroscopic level can suppress the signal of chirality in the process at the nanometric scale, which is not yet discovered in the scientific literature.
Chirality is also transmitted from top to bottom, manipulating the spiral tube to the molecular level, through the interaction of hydrodynamics in asymmetric secondary streams and spatiotemporal control of reagent concentration gradients.
For this to work, we need to understand and identify the transport events that take place in the reactor, that is, fluid dynamics and mass transport, which determine reagent concentration formation and reaction zone settings in areas of specific chirality, ”said Puigmartí-Luis.
In a spiral channel, the flow is more complicated than in a straight path, because the curved walls generate centrifugal forces, which lead to the formation of secondary plane currents that are vertical in the direction of the fluid (main flow). These secondary currents (vortices) have a dual function: they are areas of antichirality and create the necessary chiral environment for enantioselection. In addition, advection within the device and for the development of reagent concentration gradients.
By modulating the geometry of the spiral reactor at the macroscopic level, “it is possible to control the asymmetry of the secondary streams in such a way that the reaction zone, – the area where the reagents meet at the appropriate concentration for the reaction.” revealed exclusively one of the two faiths, and thus a specific chirality. This chirality transport mechanism, based on the rational control of fluid flow and mass transport, is ultimately able to control enantioselection depending on the macroscopic chirality of the spiral reactor, where the helix handling determines the importance of enantioselection, ”said Puigmartí-Luis.
The findings shed light on new frontiers to achieve enantioselection at the molecular level – without the use of enantiomerically pure compounds – simply by combining the geometry and operating conditions of liquid reactors. “Again, our study provides a new basic understanding of the mechanisms underlying the transmission of chirality and shows that this intrinsic property of living matter is based on the interaction of physical and chemical inhibitions at work. Synergically on multiple length scales,” concluded teacher Josep Puigmartí-Luis. .
