Fall, the season of colors: Leaves turn red, yellow, and brown. The disappearance of the color green and the simultaneous appearance of these other colors are also signs of ripening fruit. A team led by Bernhard Kräutler at the University of Innsbruck (Austria) has now determined that the breakdown of chlorophyll in ripening apples and pears produces the same decomposition products as those in brightly colored leaves. As the researchers report in the journal Angewandte Chemie, these colorless decomposition products, called nonfluorescing chlorophyll catabolytes (NCC), are highly active antioxidants—making them potentially very healthy.
The beautifully colored leaves of fall are a sign of leaf senescence, the programmed cell death in plants. This process causes the disappearance of chlorophyll, which is what gives leaves their green color. For a long time, no one really knew just what happens to the chlorophyll in this process. In recent years, Kräutler and his team, working with the Zurich botanists Philippe Matile and Stefan Hörtensteiner, have been able to identify the first decomposition products: colorless, polar NCCs that contain four pyrrole rings—like chlorophyll and heme.
Now the Innsbruck researchers have examined the peels of apples and pears. Unripe fruits are green because of their chlorphyll. In ripe fruits, NCCs have replaced the chlorophyll, especially in the peel and the flesh immediately below it. These catabolytes are the same for apples and pears, and are also the same as those found in the leaves of the fruit trees. “There is clearly one biochemical pathway for chlorophyll decomposition in leaf senescence and fruit ripening,” concludes Kräutler.
When chlorophyll is released from its protein complexes in the decomposition process, it has a phototoxic effect: When irradiated with light, it absorbs energy and can transfer it to other substances. For example, it can transform oxygen into a highly reactive, destructive form. As the researchers were able to demonstrate, the NCCs have an opposite effect: They are powerful antioxidants and can thus play an important physiological role for the plant. It then became apparent that NCCs are components of the diets of humans and other higher animals, and that they could thus also play a role in their systems. Other previously identified important antioxidants in the peels of fruits include the flavonoids. Thus, the saying, “an apple a day keeps the doctor away” seems to be true, according to Kräutler.
Author: Bernhard Kräutler, Universität Innsbruck (Austria), http://pc43-c726.uibk.ac.at/oci/people/en_bernhard_kraeutler.html
Title: Colorless Tetrapyrrolic Chlorophyll Catabolites in Ripening Fruit Are Effective Antioxidants
Angewandte Chemie International Edition 2007, 46, No. 45, 8699–8702, doi: 10.1002/anie.200703587
Bernhard Kräutler | Angewandte Chemie
Rainbow colors reveal cell history: Uncovering β-cell heterogeneity
22.09.2017 | DFG-Forschungszentrum für Regenerative Therapien TU Dresden
The pyrenoid is a carbon-fixing liquid droplet
22.09.2017 | Max-Planck-Institut für Biochemie
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!
When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...
For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.
Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
22.09.2017 | Life Sciences
22.09.2017 | Medical Engineering
22.09.2017 | Physics and Astronomy