Advent Calendar 2021

Lanceolate, elliptical, uni or multipinnate  ̶  in nature there is an immense variety of leaf shapes. Even closely related species can have very different leaves, because leaf shape is also an adaptation to the environment. Scientists at the Max Planck Institute for Plant Breeding Research are looking for genes that control leaf growth. They use the hairy bittercress, a filigree white-flowered plant with pinnate leaves, as a model. In this way, they have succeeded in identifying the so-called RCO gene, which plays a key role during leaf development. The picture of a leaf bud shows in pink those cells in which the gene is active. They sit at regular intervals along the leaf margin and can no longer divide as a result of the gene activity. The surrounding tissue, on the other hand, continues to grow. This is how indentations and bulges develop, which gradually grow into leaflets.
Read more: Diversity in the leafy forest

Fluorescence microscopy

The smallest one is found in the middle ear, the most powerful in the buttocks - in the human body, about 400 skeletal muscles provide movement. They consist of individual muscle fibres, which in turn are composed of parallel fibrils ̶ the sarcomeres. Inside the sarcomeres, the interaction of the proteins actin and myosin ensures contraction and relaxation of the muscle. Max Planck researchers have succeeded for the first time in producing a 3D image of a sarcomere in almost atomic resolution. To do this, they shock-froze isolated muscle tissue from a mouse at -175°C and milled out a wafer-thin lamella with an ion beam. In the electron microscope, they created a series of images while the sample was tilted gradually along an axis. By combining the individual images, they created this three-dimensional image, which appears almost textile-like. For the first time, it shows the smallest details of muscle movement, such as how two heads of the same myosin bind to an actin strand.
Read more: Zooming in on muscle cells

3D reconstruction from electron microscopy images

The Basilica di Santa Maria di Campagna in Piacenza houses one of the most venerable statues of the Madonna in northern Italy. The small, in itself rather inconspicuous statue is attributed with the God-given ability to to perform miracles. In order to preserve and strengthen the veneration of the cult object, it was spectacularly staged in the basilica. The central dome overlooking the Madonna was decorated in the 16th century by Giovanni Antonio da Pordenone with a sweeping trompe l'oeil vision of the heavenly realm. The figures in the frescoes, with fervent gestures downwards as well as upwards, create a link between the world of the viewer and God the Father, who is depicted in the lantern of the dome. In its entirety, the dome, lavishly decorated with a variety of motifs (only the upper part can be seen here), represents a celebration of the exuberant abundance of nature, which here serves to glorify the famous Madonna of Piacenza. At the KHI in Florence, Jason di Resta investigates the impact of miraculous artefacts on the production of religious painting as well as on the self-representation of artists in the early modern period.

Pordenone, central cupola, 1530–1532, Fresco. Piacenza, Santa Maria di Campagna.

Photography

The universe is teeming with planets. Almost 5,000 of these celestial bodies, which orbit distant stars like the Earth orbits our Sun, have been detected so far. Most of them can only be detected indirectly. All the more astonishing is the feat that a team with the participation of the Max Planck Institute for Astronomy has achieved: with ALMA, the Atacama Large Millimetre/Submillimetre Array, the researchers have not only directly imaged the exoplanet PDS 70c at a distance of around 400 light years, but for the first time also a dust disk that surrounds it. This circumplanetary disk - seen as a small washed-out patch to the right of centre - is about the same diameter as the distance from the Sun to Earth and has enough mass to form up to three natural satellites the size of our Moon. The mother sun PDS 70 is also surrounded by dust. This matter appears here as a central cloud, but more importantly as a large circumstellar disk that resembles a ring in the photo.

Read more: The birth of exomoons

Telescope image

 

Artificial organs from the lab are one of the great visions of the future in medicine. But in order to create functional tissue, it must also be possible to grow vessels in it. This is the only way to ensure the supply of organs. Max Planck researchers have now succeeded in creating functioning vascular systems in an artificial hydrogel. To do this, they prick two parallel channels into the gel with an acupuncture needle. In one channel, they seed endothelial cells, which also line the blood vessels in natural tissues. After about a day, these cells form a functional vessel. Through the second channel, the scientists deliver a cocktail of growth factors that induce the endothelial cells (recognisable here by their pink-stained cell nuclei) to migrate into the surrounding gel. There they form new vessels, which were perfused with a liquid containing yellow fluorescent bead in the experiment.

Read more: Synthetic tissue modell

Photocatalysts use the energy of light to catalyse various chemical reactions. For example, they make it possible to split water into oxygen and hydrogen with the help of sunlight. To develop sustainable catalysts, researchers rely on organic instead of metal-based starting materials for their synthesis. The final structure of such a material is generally less defined than that of metals or metal oxides and contains more defects and dislocations. This can be seen here in the photocatalyst sodium poly(heptazinimide), or NaPHI. Transmission electron microscopy makes it possible to examine the material structure on the nanoscale down to the level of individual atoms. The image reveals a layered structure, whereby the layers are not stacked perfectly on top of each other, but are rotated at different angles. This gives the impression of a knitted snowflake.

Transmission electron microscopy

Proteins are the tools of our cells - they carry out all vital tasks. However, they can only do this if they fold correctly and adopt their very specific 3D structure. To ensure that nothing goes wrong, this process is strictly monitored in the cell. The far-reaching consequences of faulty quality control can be seen in neurodegenerative diseases such as Alzheimer's, in which incorrectly folded proteins are deposited in the brain. This image shows cells that partially reproduce Alzheimer's disease and can thus serve as a model for scientists. The typical Alzheimer's deposits of misfolded proteins can be seen in purple. The cell nuclei are stained blue. In order to be able to study the disease in detail, the researchers have developed a special sensor that indicates when the quality control of a cell is overloaded and the cell cannot dispose of all the misfolded proteins. Then the sensor protein clumps together and is clearly visible in the microscope image in the form of green dots.

 Fluorescence microscopy

Instead of ox and donkey, there are alpacas in the stable at the Max Planck Institute for Biophysical Chemistry in Göttingen – and not only at Christmas. What makes them so intriguing for science (and, in the future, also for medicine) is a special property of their blood. If an alpaca comes into contact with foreign proteins, e.g. pathogens, antibodies against this protein are formed in its blood. So far, so ordinary. But alpacas can do even more: they form a second type of antibodies, which are much smaller and simpler. And which can be simplified even further in the laboratory, into so-called “nanobodies”. These have all the properties of the original antibodies desired by the researchers, but are much simpler, faster and can also be used with better results, e.g. in labelling cancer cells. Most importantly, once established, nanobodies can be produced in large quantities using bacteria. So the alpacas are only needed for a vaccination and a blood donation ­ everything else happens in the lab. As has recently been shown, alpaca nanobodies are also very promising as a drug against Covid-19.  

Read more: Alpaca Nanobodies stop SARS-CoV-2 
 
Photography

Various mechanisms of movement have evolved in nature, including propulsion by tiny hair-like structures. These so-called cilia and flagella perform whip-like movements to enable locomotion. Arrays of ciliated cells with cilia on their surface work together to expel pollutants from our airways, for example. Last but not least, the regular beating pattern of cilia and flagella also propels sperm or microorganisms such as the green alga Chlamydomonas reinhardtii. The picture shows experimental forms of a flagellum isolated from C. reinhardtii and reactivated with ATP, the universal storage form for energy in cells. The isolated flagellum, which is about one hundredth of a millimetre in size, begins to oscillate and rotates counterclockwise in the field of view.

More here in this YouTube video.

The first glance is misleading, because contrary to what you might expect, this picture has no connection to astronomy, nor does it show any New Year's Eve fireworks. Instead, it depicts the dazzling variety of aerosol particles that are created and emitted in the respiratory tract when humming "Happy birthday to you". These particles were collected and shine here in different colours and different level of brightness under the dark-field microscope depending on their size and scattering power. Scientists from the Max Planck Institute for Chemistry, together with a team at the Max Planck Institute for Dynamics and Self-Organization, have investigated the structure and chemical composition of individual aerosol particles in the sub-micrometer range. Technically, X-ray microscopes with synchrotron radiation were used. In this way, the scientists are gaining fundamental insights that will help to understand the aerogenic spread of pathogens such as SARS-CoV-2 and improve measures to protect against infection. 
Read more: Synchrotrons accelerate corona research

Dark-field microscopy

Bringing space into the laboratory - the ultracold storage ring CSR has gone some way towards doing just that. The globally unique machine at the Max Planck Institute for Nuclear Physics in Heidelberg is used to store beams of atomic or molecular ions and cool them down to extremely low temperatures of less than -263°C. Researchers can use it to simulate realistic space conditions, for example to study how organic molecules are formed in the universe. One of the instruments in the storage ring is the low-temperature reaction microscope CSR-REMI, which was specially developed for the CSR and designed and manufactured at the Heidelberg Institute. It enables fundamental investigations of quantum dynamics through collisions of the stored ions with atoms, molecules or electrons. The picture shows the connection field for the cables of the CSR reaction microscope.

Digital photography

Implants in medicine are often made of titanium. But even with this very biocompatible material, fatigue fractures are commonly observed under stress. The reason is often tiny impurities that are deposited along so-called grain boundaries - i.e. where areas of different crystal orientation meet. The image shows a luminous band of iron atoms deposited along such a grain boundary in titanium. Scientists at the Max-Planck-Institut für Eisenforschung investigate the atomic structure of grain boundaries in different metals under the transmission electron microscope. By comparing their observations with the respective material properties, they can explain why grain boundaries fail in certain materials. The goal is to develop stronger and safer materials for medical implants.

Transmission electron microscopy

 

Leonardo da Vinci, born in 1452 in Tuscany, is considered a universal genius. He made a name for himself not only as a painter and sculptor, but also as an architect, anatomist, scientist and engineer. These diverse talents also found expression in an almost unbridled thirst for knowledge - and so he also called an extensive library with almost 200 books his own. Today, there is only one book left  that possibly belonged to Leonardo. But with the help of numerous notes and manuscripts by Leonardo himself, in which he often refers to books in his possession, scientists have been able to reconstruct his library. And not only that: in an exhibition, numerous contemporary editions of the books were brought together. Together with reproductions of codices, works of art and objects, they give visitors an insight into "Leonardo's intellectual cosmos".

More: online-exhibition 

Photography
 

Immediately after the universe came into being 13.8 billion years ago, a 'soup' of atomic particles sloshed through space and time. For several hundred million years, the universe lay in deep darkness. But then the - literally - lights went on: the first stars and galaxies were born. Their intense UV radiation transformed neutral hydrogen gas that wafted between the Milky Way systems into a highly ionised plasma. Although this cosmic reionisation is very closely related to galaxy formation, the two processes have usually been studied separately until now. Using computer simulations, a team led by the Max Planck Institute for Astrophysics has now recreated the baby phase of the cosmos. In doing so, the researchers have taken various specific physical properties into account. For example, the image in a section of the main simulation of this project, called Thesan, shows six different variables: Density, temperature, metal content, dust, gas and radiation (from top left, clockwise).

Computer simulation

Read more: Galaxy formation meets Reionization

 

In a way, this simulation opens a window into another world. Researchers at the Max Planck Institute for the Physics of Complex Systems have calculated how a spin liquid could be detected. In spin liquids, the spins that give each atom a magnetic moment interact strongly with each other, as in a ferromagnet. However, they do not form a fixed order, but move constantly. According to theoretical considerations, spin fluids should slosh through some materials, but they have not yet been clearly demonstrated experimentally. The Max Planck team has simulated what signature a certain type of spin fluid would leave in neutron scattering. This method can be used to elucidate the magnetic structure of a material. In simulating the scattering pattern, the researchers used a model that is mathematically related to the theory of fundamental forces such as electromagnetism. However, their model only applies to spin fluids in our world. In another universe with different physical laws, however, it could describe the effect of the fundamental forces. In this respect, spin liquids provide insights into the physics of possible other worlds.

Computer simulation

Many solids are crystals whose atoms or molecules form regular lattices. However, especially in metals, there are often areas where the crystal lattices have different orientations. This affects the electrical and mechanical properties. Materials researchers therefore grow special single crystals in which the crystal planes are oriented the same everywhere. This picture shows a section through such a vanadium single crystal. The different colours show areas in which all atoms lie in one plane. However, the differences in height are minimal: the step height is about 0.2 nanometres. The stripes on the coloured terraces are caused by oxygen atoms that migrate to the surface when the crystal is purified. They form a so-called superstructure, which has many defects. Researchers are making a virtue out of necessity: they are investigating precisely such defects, because some of these interact with the vanadium substrate. By comparing these interactions in normal and superconducting substrates, the scientists gain important insights for the development of new superconductors.

Scanning tunnelling microscopy

About 95 per cent of the universe literally lies in darkness. Only the meagre remainder consists of matter, as it is in stars, planets and also in us humans. A space telescope is now to illuminate the darkness: The European observatory Euclid, named after a Greek mathematician, will be launched at the end of 2022 to study the dark side of space. On board are an optical telescope with a diameter of 1.2 metres, an infrared spectrometer (VIS) and an infrared photometer (NISP). Over the six-year mission, VIS will observe the shape of galaxies in the sky in visible light; NISP, whose optics were lead-developed and built at the Max Planck Institute for Extraterrestrial Physics, will measure the distance of Milky Way systems. All this information can then be used to draw conclusions about dark matter and dark energy. Incidentally, the lenses for NISP, with diameters of about 20 centimetres (picture), are the largest and by far the most precise optics ever used in a civilian satellite to explore the cosmos.

Read more: Sharp eyes for EUCLID 

Photography

The late Gothic Palazzo Chiaramonte in Palermo, also called Lo Steri (Fortress Palace) since 1446, has a turbulent history. In the 17th and 18th centuries, it was the site of the Tribunal of the Holy Office of the Inquisition and its prisons. People of the most diverse religions and origins were imprisoned there. The walls of the cells are almost entirely covered in drawings, sometimes in several layers. In addition to religious depictions, there are also maps and inscriptions in many languages, including Italian, Sicilian, Hebrew, Latin and English. Our image shows the iconography - still very significant today, especially in the Eastern Church - of Christ's descent into the underworld: Christ rescues the souls of the righteous, embodied here by the patriarchs of the Old Testament, from the jaws of Leviathan, the biblical monster that devours sinners. KHI's Graffiti Art in Prison (GAP) project looks at both historical and contemporary prison graffiti and murals, and makes references to other sites of detainment, spaces characterised by deprivation and censorship, such as concentration camps or even psychiatric hospitals. 
 
Photography