Quebec influence: Molecular structure controls the strange quantum effect
For the first time, experts have directly measured how a molecule’s control affects the spin of an electron. This mysterious CISS effect may have played a role in the origin of life.
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Unfortunately, this DNA avatar is completely wrong: it shows DNA upside down in a mirror. But why life’s molecules almost always use one hand is a mystery. The Quebec effect is said to be able to explain the mystery.
The mysterious effect is said to improve quantum computers and help solve the biggest mystery about the origin of life. But until now, experts have found it extremely difficult to decipher the details of chirality-induced spin selectivity (CISS), which was discovered about 25 years ago. In this quantum effect, the “handedness” of a molecule controls the direction of spin of the electrons flowing through that molecule – that is, the macroscopic structure of matter is closely linked to its quantum mechanical properties. Now this phenomenon has been observed directly in molecules for the first time.
A team led by Hannah J. Ekvall from Northwestern University in Evanston Use the properties of liquid crystals to make CISS’s strange effect measurable. To do this, the group built a chiral molecule—of which there are two mirror-image versions—between two other parts of the molecule, between which an electron can flow. The resulting rod-shaped molecule aligns precisely into crystal-like structures. This allows you to use the magnetic field to align the spin of the electrons relative to the molecules. This is the only way to monitor the effect.
Because with the CISS effect, only electrons with a certain spin direction can pass through a molecule using either hand. On the other hand, the mirror image version of the molecule allows only electrons with opposite spin to pass through. Ekvall’s team has now measured this phenomenon directly thanks to a sophisticated experiment. As reported in “Science” magazine.. In the experiment, the working group irradiated the molecule with laser light so that an electron in one part of the molecule was excited. This then flows through the chiral molecule in the middle to the other part of the molecule – but only if its rotation is properly aligned with handedness due to the magnetic field.
Until now, the CISS effect has only been measured indirectly for molecules in contact with electrodes. The new experiment shows that this close connection between large-scale molecular structure and the quantum properties of individual electrons is actually a fundamental property of chiral molecules. This allows these molecules to act as “spin rectifiers” and may play a role in spin-based quantum computers in the future.
In particular, the researchers suspect that CISS could solve a central puzzle in the origin of life: why biomolecules always have a certain advantage. Proteins, genetic material molecules, and sugar building blocks all contain molecular parts of which there is a mirror image – but organisms do not use them. This handedness was already present when life arose, but why this happened and why these molecules are used instead of their mirror images is quite a mystery. Some experts suspect that CISS once played a crucial role in selecting these molecules.
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