Those wanting to study the movement of atoms have to be fast: required is a high-speed camera with “shutter speeds” in the femtosecond range, which is one millionth of one billionth of a second (10-15 s). Researchers have now succeeded in generating electron pulses of just 28 femtoseconds in duration – six times shorter than was previously possible. When these ultrashort pulses meet a biomolecule crystal they are dispersed on it. A characteristic diffraction image like the one shown here is generated for each molecule. In future, physicists want to use these new possibilities to observe particle movements during a reaction. To do this, they excite the molecule with the help of an optical laser pulse and follow this with an electron pulse to capture the momentary structure. An extremely large number of such snapshots in series result in a film of the atomic dynamics.
Albert Einstein postulated the existence of gravitational waves in his General Theory of Relativity more than 100 years ago. On September 14, 2015 scientists were able to directly measure them for the first time. In the universe, these tiny distortions in spacetime occur practically all the time. However, even with the most sensitive detectors they are measurable only when very large masses move very quickly – for example when two black holes or two neutron stars collide. Even then, the signals that arrive at Earth are very, very faint. In order to be able to identify them in the vast volumes of detector data, physicists study events in which strong gravitational waves are generated by means of numerical simulations. The picture shows a simulation of exactly that collision of two black holes measured in September 2015.
White blood corpuscles play an important role in our immune system. Among these cells, the neutrophil granulocytes – generally referred to as the neutrophils – form the first line of defence. They literally devour bacteria by surrounding the pathogen and digesting it in their cell interior. The neutrophils (shown here in orange) also have another ingenious trick up their sleeves: they can cast fibrous net-like structures (yellowish green), trap bacteria in them and thereby kill them outside the cell. This image shows Shigella bacteria (blue) being caught in a net cast by neutrophils.
All living organisms are made of proteins. The basic structure of these macromolecules - from which, for example, skin, hair or muscles are built - are long chains composed of 23 different amino acids. Their sequence is determined in the genetic material in each and every cell. Chemically, two forms of each amino acid exist, which differ only in their optical rotation. In nature, however, normally only one of these forms can be found, the so-called L-shape. By using LC-PolScope technology, researchers hope to discover why this is the case, and what molecular recognition processes lead to this preference. The growth direction and the optical activity of individual grains in a thin polycrystalline amino acid-polymer hybrid film can be identified through the assignment of different colours. Grains of the same colour have the same growth direction.
The giant asteroid Vesta is a relic from the stormy youth of our solar system. At that time, more than four billion years ago, there were no major planets yet. Small pieces of debris clumped together and formed into protoplanets, which in turn grew into planets. Vesta, which is about 525 km in diameter, appears to be such a protoplanet, perhaps the last example of its kind. This interpretation is also supported by the measurements of Nasa's Dawn spacecraft. The false-colour image helps us to engage in geological field research. The topographic map was constructed from more than 17,000 individual images taken by the framing camera of Dawn, whose camera eyes were equipped with varying filters. The different colours indicate different highs and lows: purple denotes 22.5 kilometres below the surface; white 19.5 kilometres above the surface. Vesta's densely cratered landscape - evidence of earlier collisions with other celestial bodies – also features high mountains and is surprisingly heterogeneous. It looks more like a terrestrial planet than a primitive asteroid.
Researchers hope for higher efficiency in future solar cells. To achieve this, they form the silicon for photovoltaic elements not into today's conventionally smooth layers, but into 'carpets' of nanowires which absorb a lot more light. Since the wires are just 100 nanometres thick and two micrometres long, they resemble tiny towers. Max Planck researchers produce these structures by initially coating a thin layer of silicon with polystyrene spheres. They then remove the silicon, which is not protected by the beads, by etching it with plasma, i.e. strongly ionized gas. Normally, the silicon towers stand close together. Here, researchers have left gaps between the polystyrene spheres to be able to inspect the wires from the side as well. The electron microscope, with which the picture was taken, distinguishes between different materials because it uses two different detectors. It shows polystyrene in red and silicon in green.
For agriculture, the thale cress (Arabidopsis thaliana) has virtually no significance. And yet it is one of the most famous plants in the world: the small, annual weed is the most important model organism in plant research. It is unpretentious, grows quickly and forms large amounts of seed. Above all, it has already been thoroughly investigated, and its genome, consisting of exactly 25,498 genes - which is rather small for a plant - has been completely sequenced. This image shows an Arabidopsis seedling, which scientists use to investigate the transport of proteins between cells and tissues. The picture shows the first two leaves of the plant; the empty seed coat is lying on the bottom left. The plantlet produces a red fluorescent protein in its epidermal cells; the chloroplasts and plastids are illuminated in blue. In the experiment, the examined protein can only be found in the epidermal cells, which means it will probably not be transported into the cells below.
It forms clouds, causes storms – and presents considerable challenges for climate researchers: turbulence forms in the atmosphere when warm and cold air come together. For example, if a city heats up considerably more than its surroundings in summer, the warm air rises rapidly, like in a chimney. Along the edges, it mixes with the colder ambient air in numerous large and small vortices. Particularly interesting situations arise when the rising plumes of heat from two or more sources of heat interact. The likelihood then increases that they will churn up the atmospheric layering of an entire region and eventually influence the climate. Scientists use computer simulations to vary the magnitude of the heat sources and their distance from each other.
Spherical lenses are widely used in research, for example as front lenses in microscope objectives. A special kind of such lenses are solid immersion lenses (SIL), hemispherical lenses made of material with a particularly high refractive index. These lenses play an important role in many areas of physics, biology and medicine today, as very high spatial resolution can be attained with their help. The image shows an SIL, the surface of which is being measured in a Twyman-Green interferometer for the purpose of quality assessment. The lens consists of gallium phosphide (GaP), a material that is transparent for light of certain wavelengths and has a very high refractive index. By this means, the light focusing required for high-resolution tests can be attained.
The SIL in the photograph appears to hover in the air as a sphere; however, this impression is misleading: the hemispherical lens and the objective of the interferometer are reflected in the object slide, a metal mirror, on which the lens is placed.
Whether corals, worms or mussels: Many marine invertebrates begin their lives as part of the plankton. This is also the case with the annelid or ragworm Platynereis dumerilii, which has become an important model organism in evolutionary developmental biology in recent years. The larva controls its movement with the help of a prominent, regularly beating belt consisting of thousands of tiny hairs or cilia. But how does it find a place that can offer the adult worm ideal conditions for its rather stationary existence? A simple organ at the head end of the larva, known as the apical organ, plays a crucial role. Neurons located here perceive environmental stimuli and produce a neuropeptide in response, which alters the beat of the cilia. The larvae start to sink, and then crawl along, surveying the sea floor. They can presumably detect food in this way, and thereby find a suitable habitat.
Methane is over 20 times stronger in its effect as a greenhouse gas than carbon dioxide. It is formed when certain bacteria from the Archaea group decompose organic material under the exclusion of air – for example, in rice fields, bogs and cows’ stomachs. The enzyme Frh, a hydrogenase, plays a key role in the process: it splits hydrogen, which can then react with carbon dioxide to form the methane. The Frh protein consists of a total of twelve trimers, each of which has three subunits, here in blue green and purple. It contains several iron-sulphur clusters – shown as yellow structures in the image – and nickel and iron in the active centres, where the reaction takes place. The structure and function of this enzyme are not only of interest to climate researchers: the molecule could provide a model for the development of catalysts for hydrogen production.
Although humans and zebra fish appear to have little in common at a first glance, an astonishing number of parallels can be observed in their development and the structure of their organs. For example, the retina of the eyes in both species is structured very similarly. For this reason, the small fish is a popular model organism for studying the development of our visual organ. The image shows a cross-section of the retina of a three-day-old zebrafish embryo. The researchers made different cell types visible using fluorescent proteins. This enables them to trace the way in which the cells rearrange themselves while the initially simple tissue layer develops into a multi-layered structure. Part of the cell skeleton can be seen here in green, and the cell walls of the photoreceptors and the optic nerve, which conveys information to the brain, are bright pink.
What is 17 multiplied by 146? Or 111 plus 97? Complex cognitive skills such as calculation wouldn't be possible without complicated connections of neuronal circuits in various brain regions. With the help of diffusion-weighted magnetic resonance imaging (MRI), neuroscientists are able to uncover how these nerve fibre bundles connect different regions of the brain. To this end, the scientists use the natural magnetism of the particles in the brain in order to measure the diffusion movement of water molecules in the tissue. This enables them to draw conclusions on the pathways and signal orientation of the large nerve fibre bundles. The researchers translate the measured diffusion gradients into bright colour patterns, with the colours corresponding to the direction of the fibres (red: left-right; green: front-back; blue: top-bottom).
One day, magnetic vortex structures, like the one shown here, could help to process data particularly quickly. These structures arise in magnetic wafers of one micrometre in diameter and just a few nanometres thick. Unlike in a standard permanent magnet, the individual magnetic moments, which can be imagined as tiny rod magnets, order themselves in these wafers: their magnetic field forms needles which project from the front (red) or back (blue) of the disk and can thus store the zero or one of a data bit. Short magnetic pulses flip the needles from one direction to the other with lightening speed. The simulation shows the transition with the needles to the front (red) and back (blue). The magnetic moments in the orange and green areas only project slightly from the image plane.
Chaos often arises when non-linear processes unfold. The minutest changes can have major impacts, as in the case of the climate, for example. In this simulation, however, a non-linear interaction has a more ordering effect: a very intensive flash of ultraviolet light lasting just 100 femtoseconds – one femtosecond corresponds to the millionth of a billionth of a second – runs from left to right through the noble gas xenon. After a time a soliton – a type of super light pulse that is stabilised by non-linear processes – splits from the light pulse, which can be seen in yellow on the left-hand edge of the image. Unlike normal light or water waves, solitons do not dissolve. The merely 15-femtosecond soliton can be identified as the sharp line, the most intensive areas of which are red.
Learning and memory are based on the constant modification, dismantling and re-establishment of the connections between cells in the brain. Simplified models are needed to enable scientists to study and understand these complex processes. Researchers at the Max Planck Institute for Brain Research grow neurons in fine microchannels on plates with a photolithographic structure. In this way, the complex three-dimensional network of neurons in the brain is reduced to two dimensions in the cell culture. The researchers can thus analyse how the synapses between the cells form or dissolve, and examine the role played by substances like neurotransmitters in these processes. This cell culture technology is also of great interest for the development of new active pharmaceutical substances.
Precious feathers were much prized in Pre-Columbian Central America; they played an important role as tribute, as cult offerings and as part of rulers' regalia. The feather mosaics of early colonial Mexico link this tradition with European figurative culture. Made of the finest feather fragments, they represent Christian motifs derived from European prints imported for missionary purposes. In turn, the feather icons were brought back to Europe as diplomatic gifts – shimmering testimonies of the early encounter between the arts of the Old and New Worlds. Here exotic humming bird feathers are used to represent heaven in a picture of the Evangelist John. The poor conservation is also evident: insect damage threatens the iridescent colours.
Detail of a feather mosaic, Saint John the Evangelist, 16th/17th century, Colección Daniel Liebsohn, Mexico City
This flower of the thale cress (Arabidopsis thaliana) shows its stamens clearly visible - scientists at the Max Planck Institute for Plant Breeding Research lightened the tissue using a solvent. The pollen grains appear bright blue under the fluorescence microscope. The photograph was produced as part of a project on the effect of copper deficiency on plants. Copper is important for, among other things, the formation of lignin, which guarantees both the stability and functioning of the vascular bundles in plants and the release of the pollen when the flower opens. A lack of copper in agriculture, for example in cultivation on sandy soils, causes considerable reductions in yields.
The zebra fish (Danio rerio), a striped fish around five centimetres long, has similar heart genes to those of human beings. The signalling pathways that control the organ’s formation also match to a large extent. This small animal is thus a popular model organism. Scientists suppress the formation of specific signalling proteins and observe the effects on organ development. The image shows a normally developed heart of a 48-hour-old zebra fish embryo, dyed using fluorescent proteins. At this point, the heart measures only half a millimetre and – as in all fish – consists of an atrium and a ventricle. The heart muscle cells are highlighted in green, and the cell nuclei in red. The atrial myosin – a protein that only exists in the atrium – glows blue.
Turbulent currents play an important role in climate events, for example in cloud formation or – as calculated and visualised here – in the exchange processes that occur on the surface of water bodies. When the water on the boundary with the air cools down, through convection and uplift, a typical cell-like pattern of the heat distribution in the water arises in the layer underneath. The dark zones in the image are relatively warm areas, which move upwards while cooler areas, often just a few millimetres wide, move down – the light-coloured edges of the “cells” here. Tiny whirlpools arise at the network nodes, sometimes even double vortices with opposite directions of rotation.
Numerous proteins interact with the cell envelope. They fulfil a wide range of tasks - from signal processing to cell division. Due to the extreme complexity of these processes, scientists at the Max Planck Institute of Biochemistry use an approach known as minimal systems. In these minute, synthetically generated systems, they can observe selected cell components and their functions under controlled laboratory conditions – like the lipid membrane shown here with accumulated proteins. Because these proteins move and organise themselves independently in the membrane, they form movement patterns that look like a wave carpet. The researchers observe these structures as an interplay of purple shapes and forms.
Neutron stars unite about one and a half solar masses in a sphere whose radius of ten to twelve kilometres is no bigger than that of a small town. This results in extremely high densities and gravitational forces. When two neutron stars collide and melt into a black hole, gravitational waves arise – tiny distortions in spacetime. Albert Einstein’s General Theory of Relativity postulated the existence of gravitational waves more than 100 years ago. However, they were directly measured for the first time on September 14, 2015. Physicists learn more about the signals from gravitational waves with the help of numerical simulations. This enables them to identify gravitational waves more easily in the vast volumes of detector data. The image shows a simulation of a neutron star collision.
Although it was already in use in ancient China, cast iron is to this day a popular subject of current basic research. As an alloy with spheroidal graphite, it is as malleable as steel, but significantly less complicated and less expensive to produce. Also known as spheroidal iron, it is used for the production of pipes, in the automotive industry or in reactor technology, for example. The image shows the microstructure of the alloy: the spherical nodules of carbon appear as round islets; the fine network of lines indicates where different grains of materials collide. Max Planck researchers are studying the effect of this microstructure on material properties. They would like to be able to tailor the structure and thus the properties of the material to different applications.
The flow of liquids or gases plays a very important role in many technical processes, also economically, for example, in the development of vehicles with lower fuel consumption. To describe the characteristics of a flow, researchers analyse the movement of the individual particles. An important feature here is the so-called streak line, which arises from a multitude of particles that are introduced successively into the flow from the same location. This process is easy to research in the laboratory using smoke, which is blown continually from a nozzle and moves with the flow. To date, it has not been very easy to simulate this in a computer-based visualisation. However, thanks to a new mathematical approach, it is now possible to describe streak lines by means of standard differential equations and compute their characteristics much faster. The streak lines in this image were calculated in less than one minute using the new process; it would take over two hours using the classical algorithm.
Solar cells provide a climate-friendly energy supply. To ensure that solar cells increase their efficiency in converting sunlight into electricity and require smaller amounts of silicon in the future, scientists are researching photovoltaic elements that do not consist of a closed silicon layer, but a thin 'carpet' of nanowires. Usually, the silicon wires are very close together. On the one hand, the light is trapped between the columns, hall-of-mirrors style; on the other hand, the nanowires have special optical properties that allow them to absorb more light than a smooth layer. Aesthetically, however, isolated nanowires are far more pleasing - especially when they are scanned with an electron beam that is captured by three diodes which show the scattered electrons in red, green or blue, respectively. This colour display is created when one or two of the diodes are in the shade, cast by the electron beam on a nanowire.
Standing on a shell, the sea god Neptune steers a team of horses through the waters. This scene is captured in an extraordinary mosaic in the Fonte Doria in Genoa. The artificial grotto – which was constructed by the architect Galeazzo Alessi in the mid-16th century – has several fountains and is decorated with coral, shells, majolica tiles and crystals. Due to its extremely poor conservation status, the Fonte Doria is no longer accessible to the public. The mosaics were surveyed and documented as part of a photographic campaign by the photo library of the Kunsthistorisches Institut in Florenz. Each year, the KHI photo campaign produces around 3,000 digital images of the interiors of Florentine palaces and villas – which are still relatively poorly researched – and of the art and architecture in smaller centres in Tuscany.
A ramified vein winds its way through the spinal cord of a rat. The blood stream transports vital nutrients to the neurons and removes waste substances. Normally, the cell wall of the blood vessel forms a barrier that protects the sensitive neuronal tissue against pathogens. However, in diseases such as multiple sclerosis, cells from the body’s own immune system penetrate this protective barrier: aggressive T cells – shown here in red – adhere to the blood vessel wall and move along it. They eventually force their way through the wall and penetrate into the spinal cord, where their contact with scavenger cells or macrophages triggers the invasion of more T cells. Inflammation arises as a result and damages the neurons.
Plasma at several thousand degrees rises from the Sun's interior, cools and sinks back down to the depths. Wherever strong magnetic fields restrain the plasma, dark sunspots are generated. In the edges of the spot shown, thread-like structures are visible. The fields in these regions should actually be strong enough to prevent currents; they should therefore appear darker. However, scientists at the Max Planck Institute for Solar System Research have been able to prove that the magnetic fields here have loosened in some places. In these regions, elongated bright structures form, in which high-energy plasma can reach the surface despite high field strengths. In a chronological sequence of high-resolution images, these structures seem to rotate around their own axis.
In modern layered semiconductors, the electrons in the interface area between two neighboring semiconductor layers are almost unrestricted in their movement. An externally applied magnetic field focuses electrons escaping from a point contact onto a second point contact (lower half of the simulation). If impurity atoms, for example phosphorous atoms, are introduced into the semiconductor to increase conductivity, the extremely weak electrical fields of these doping atoms already generate random minimal deflections of the electrons. This results in the formation of additional focusing lines, which give rise to a highly characteristic ramification of the current density (upper half of simulation). Very similar mechanisms in oceans can result in monster waves that appear to come ‘out of nowhere’.
The zebrafish (Danio rerio) is a popular model organism in developmental biology. It grows from a fertilised egg to a sexually mature animal within a period of three months. The image shows two-day-old larvae, in which the mouth opening can already be clearly identified. However, at first glance, the apertures which look like eyes surrounded by eyelashes are, in fact, the organisms’ future olfactory organs. The scientists at the Max Planck Institute for Developmental Biology study tissue and organ development in zebrafish embryos. A genetic defect in the embryo on the left causes problems in the development of the skin.
Max Planck Institute for Developmental Biology, Tübingen / Jürgen Berger, Mahendra Sonawane
At the Root of a Plant Hair
In order to thrive, plants require sufficient nitrogen. If nitrogen is lacking, they must cut back on photosynthesis and growth. To deal with this, plants have developed various strategies, for example the increased formation of the red leaf dye anthocyanin, which protects against excess light irradiation. Scientists suspect that the mechanisms that regulate anthocyanin also regulate the formation of the leaf hairs, which protect the plant against dehydration. Therefore, as part of studies on the effect of nitrogen deficiency, the size and number of leaf hairs were examined. The image shows just such a leaf hair from the thale cress plant (Arabidopsis thaliana).
Dark matter is not visible, it does not emit any kind of radiation, yet it exists – as its gravitation attracts other, standard matter. This computer simulation makes dark matter visible; it shows a virtual cosmic network of dark matter that connects individual, brightly shining galaxies in the universe with each other. The colourful image is part of the Millennium Simulation Project and demonstrates the enormous variety and complexity that arises from the gravitational dynamics of the dark matter particles. Differences in brightness represent the local density, and the colours represent the different speeds of the matter.
What looks like an exotic flower at first glance, is, in fact, the human immune system in action: a white blood corpuscle (shown here in red) is in the process of disarming tuberculosis bacteria (yellow). The pathogens are encircled by the scavenger cell membrane, pulled into the interior of the cell and locked in there – ideally forever. However, Mycobacterium tuberculosis is an extremely tough customer: thanks to a particularly resistant membrane, the bacteria can survive for many years inside the scavenger cells and may be released again if the host immune system is weakened, for example through diseases like AIDS or the effects of ageing.
Tiny cones of silica gel grow in an ordered arrangement on a glass surface. Inside, they consist of nanometre-sized silica gel tubes that wrap themselves in a spiral around an axis – like liquorice spirals. The central symmetrical axis already exists in the seed of the cone and is responsible for the subsequent appearance and characteristics of the silica forms. The tubes contain ordered organic molecules. Therefore, the entire arrangement has a hierarchical structure. Up to now, hierarchical structures were mainly known from nature, for example from bone development.
Powdery mildew (Golovinomyces orontii), a plant pest from the sac fungi group, forms a thread-like mass or mycelium on the leaves of the thale cress (Arabidopsis thaliana). The sporophores which protrude from the mycelium develop stacks of asexual spores at their tips which are spread by the wind. This way, the fungus can infest other plants. Scientists use the interaction between powdery mildew and the thale cress as a model system for studying how plants react to fungal infestations and how the fungi deal with the plant’s defence mechanisms.
Fusion power plants are supposed to harness energy from the fusion of atomic nuclei, in a similar way to the sun. The fusion fuel, an ultra-thin hydrogen plasma, has an ignition temperature of over 100 million degrees Celsius. Even the vessel walls reach temperatures of a few hundred degrees. Researchers therefore have to develop heat-resistant materials for the construction of such plants. The sample shows a wolfram alloy, into which silicon and chrome have been incorporated to make the material oxidation-resistant. Under the microscope, stress cracks can be seen. These are caused by the different rates of thermal expansion - an effect that should be avoided during subsequent application..
Scientists use photoelectron and photoion spectroscopy to study the electronic properties of solids and gaseous samples: energy-rich light can knock electrons out of matter. Scientist can then draw conclusions about the electronic structure of matter from the flight path and speed of the electrons. The sample in the image, which is being hit by the light beam from a free electron laser (FEL), is located in the brightly shining centre of the ball. Sensors on the walls of the ball, known as time-of-flight spectrometers, trap the electrons. The entire system is cooled using liquid nitrogen, which is trickled onto the middle of the array from above and escapes below it in a cloud.
The Neisseria bacteria shown here are just one thousandth of a millimetre in size. These pathogens, which are also known as gonococci, cause the sexually transmitted disease gonorrhoea. In the early stages of an infection, they accumulate in sets of two and four at the cells of human mucous membranes. This detailed image clearly shows how the bacteria succeed in being absorbed by the mucous membrane cells: the cell membrane has already closed around some of the gonococci. This marks the beginning of the infection, which can result in inflammation and copious pus discharge.
With its deep turquoise shimmer, this object could easily be mistaken for a real crystal. It is, in fact, a colloidal crystal. Colloidal crystals like this one can form when a watery synthetic dispersion dries out. In polymer chemistry, all emulsions or dispersions, that is mixtures of a solid or liquid polymer, in a liquid are referred to as latex – a name derived from the milky sap of the rubber tree. The colloidal crystal shown here formed from such latex: the elongated “crystalline” grains arise along the flow direction of the polymer.
Pharmaceutical substances are most effective and cause fewest side effects when they are released directly in the diseased area of the body. Max Planck scientists are working on the development of a drug delivery system that only releases drugs when it recognises the target cells: microcapsules with special recognition molecules dock directly onto diseased cells, e.g. cancer cells. The drugs can escape through the capsule walls as a result of changes in the temperature, pH value or salt content. The image shows different types of such capsules that were exposed to different temperatures: some shrivelled to form solid balls (yellow) and others melted to form bigger capsules (green), which collapsed when they dried out.
Spirals arise in a wide variety of contexts in nature, for example snail shells, galaxies and low-pressure vortices. And yet they have one thing in common: they are always coiled in one direction. However, this computer simulation of a twisted spiral, in which the internal and external parts wind in opposite directions, shows that this is not always necessarily the case. This kind of spiral can arise when oscillators distributed in space interact: if a frequency that differs to their natural frequency is forced on the oscillators through a periodic external disturbance, they may organise in the form of an inverted spiral.
Small missteps can have major consequences. This also applies to electrons - as demonstrated by this simulation - which spread in all directions from a point-shaped source in a two-dimensional electron gas. The process takes place in a layer of particular semiconductor components, which are just a few millionths of a millimetre thick. This image depicts electron density – the darker the area, the more electrons it contains. Weak faults – small “irregularities” in the conducting layer – cause the electrons to go astray and result in the pronounced ramification of the particle stream. An effect that must be taken into account in the development of future semiconductor components.
Chlamydia tracomatis is one of the most common sexually transmitted pathogens– 90 million new infections arise throughout the world each year. The bacteria cause diseases of the urogenital tract. Chlamydia, which measure just 0.5 micrometres and are among the smallest bacteria that exist, can only reproduce inside cells. They survive in so-called inclusion bodies (green) and exploit the host cell's metabolism. The invaded cell eventually bursts and releases hundreds of new infectious particles. Researchers are aiming to track down the pathogen’s virulence mechanisms with the help of molecular-biological techniques.
This zebra fish hair sensory cell looks like a candle flickering in the wind. Hair sensory cells transmit mechanical stimuli to the nervous system. Such mechanical stimuli can be triggered by movement or sound, for example. Hair sensory cells consist of bundles of up to 300 stereocilia, long hair-like extensions that vary in height. The stereocilia connect with each other through fine filaments. The areas that specialise in the transmission of mechanical stimuli are located at the tip of the stereocilia bundles.
This electron microscope image of small drops of salt embedded in gel-like structures is reminiscent of a painting by Vincent van Gogh. Max Planck scientists study crystallisation processes in liquid films. In this case, they mixed a solution of DL-lysine monohydrochloride and polyacrylic acid with ethanol and painted it onto a glass plate. The thin film, which unlike traditional gels consists of two phases, quickly spreads over the entire surface. Due to the vaporisation of the ethanol, isolated yellow crystals – around 20 micrometres in diameter – arise, conjuring up associations with the stars in Van Gogh’s “Starry Night”.
It is unusual for the mineral barium sulphate to have a fibrous structure – it usually crystallises to form small plates. The formation of this surprising fibre-like structure is due to the addition of polyacrylic acid during crystallisation. Polyacrylic acid belongs to the class of polymers: chemical compounds consisting of long or strongly branched molecule chains. Polymers change the properties of almost all modern materials and also influence the growth of crystals. Nature has long exploited this phenomenon producing composite materials like bones, teeth and pearls through biomineralisation.
The rotation of this biological rotor provides energy for the formation of the molecule ATP and thus the fuel required for the energy supply to all living cells. It was found in the cell membrane of the bacterium Ilyobacter tartaricus. The rotor’s ring diameter is around five nanometres. Scientists were able to generate a three-dimensional structural model of the rotor which is composed of eight identical protein sub-units. To do this, they crystallised the insulated ring of carbon subunits with lipids. The electron microscope images of the crystal were evaluated by computer and then converted into an electron density map.
A special characteristic of the bacterium Magnetospirillum gryphiswaldense is its ability to orient itself on the basis of the earth’s magnetic field. This is made possible by special structures in the bacterium’s cell, the magnetosomes. These contain minute iron oxide crystals (magnetites) which orient themselves to the magnetic field. The tomogram provides a view of the cell interior: the magnetites (coloured red) are surrounded by membranes (yellow) that enclose them as vesicles and thus separate them from each other. The filamentous structures are coloured green and the bacterial cell membrane blue. This image clearly demonstrates how the magnetosomes are lined up on a kind of string, and orient the bacterium like a compass needle.
The galactic double star system SS 433 consists of a high-mass, young giant star, which is presumably encircled by a black hole. The latter devours gas that flows out of the giant star. The energy released in the process spews a very small proportion of the overflowing gas into space in the form of two bundled rays known as jets. The spatial direction of the jets changes at regular intervals due to the effect of tidal forces. This causes the formation of a spiral structure like this computer simulation of one of the two jets.
Leaf hairs fulfil different functions for plants. For example, they provide protection against transpiration: a leaf with hairs loses far less moisture than one without. In addition, they can contain substances that prevent attacks from herbivores – as in the case of nettles – or substances that provide protection against parasites and fungi. Genetic mutations can influence leaf development in plants – including the shape and distribution of the fine leaf hairs. Leaf hairs are thus a good indicator for biologists, enabling them to discover more about the function of genes through the effects of mutations.
The image shows an isolated rat cardiac cell, magnified by a factor of 7000. When cardiac cells are kept outside their natural environment in cell cultures, their shape changes: the initially cylindrical structure becomes flat and outstretched in form. New sarcomeres – the smallest functional units in cardiac muscle cells – are formed. The proteins in the cardiac cell shown here were marked immunocytochemically to make the changes visible. In this cell, which has been in a cell culture for twelve days, the green myosin staining shows how the formation of the new sarcomeres arises from the centre of the cell.