The chemical tricks of our blood – ScienceDaily

In order to understand the subtle tips of these complex molecules, it is useful to look for similar but simpler structures in the laboratory. In the framework of a cooperation between TU Wien (Vienna) and Trieste research groups, phthalocyanines were studied. Their molecular ring structure is very similar to the crucial sections of hemoglobin or chlorophyll. It has turned out that the center of these ring structures can be tilted into different states with the help of green light, which affects their chemical behavior.

This not only helps to understand biological processes, but also opens up new possibilities for using the artifices of nature in the laboratory for other purposes – a strategy called "biomimetics" that is becoming increasingly important worldwide.

Rings with metal atoms in the center

"The phthalocyanines we are studying are colorful dyes with a characteristic ring structure," says Professor Günther Rupprechter of the Institute of Materials Chemistry at the Vienna University of Technology. "What is crucial for this ring structure, is that it can contain an iron atom at its center – just like the heme, the red dyes in the form of a ring. Hemoglobin, chlorophyll, on the other hand, has a similar ring that captures magnesium atoms. "

Unlike more complex natural molecules, custom-made phthalocyanine-based dyes can be routinely placed side by side on a surface, such as tiles on the bathroom wall. "The rings were placed on a layer of graphene in a regular pattern, so as to create a two-dimensional crystal of dye rings," said Matteo Roiaz, who conducted the experiments with Christoph Rameshan. "It has the advantage of being able to examine several molecules at the same time, which gives us much more powerful measurement signals," explains Christoph Rameshan.

The carbon monoxide molecules have served as probes to study these cycles: a molecule can be attached to the iron atom, which is at the center of the cycle. The vibration of the carbon monoxide molecule makes it possible to obtain information on the state of the iron atom.

To study vibration, the molecule was irradiated with laser light – using a combination of green and infrared light. This measurement gave a result that seemed very counterintuitive at first: "We did not just measure a vibrational frequency of carbon monoxide, we found four different frequencies.Nobody expected it" says Günther Rupprechter. "The iron atoms are all identical, so the CO molecules attached to them should have exactly the same behavior."

It turned out that the green light of the laser was responsible for a remarkable effect: initially all the iron atoms were identical, but the interaction with the green light can tilt them to different states. "It also changes the oscillation frequency of the CO molecule on the iron atom, which shows how sensitive these structures are to minimal changes," says Günther Rupprechter. "This is also the reason why the biomolecules of our body have such a complex structure: the largely branched protein components have minimal impact on the states of the metal atom, but this minimal impact may have very important implications. "

Measurement at room temperature and at atmospheric pressure

Until now, similar effects could only be studied at extremely low temperatures and under ultra-high vacuum. "In the laboratory, we now have two methods to measure such biologically relevant phenomena at room temperature and at atmospheric pressure, with and without green light," says Rupprechter. This opens new possibilities for a better understanding of the chemical behavior of biological substances; this could also offer the opportunity to adapt new molecules in order to optimize them for specific chemical purposes to nature.

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