Using atomic-force microscopy, vision researchers have taken pictures of some of the eyes photon receptors in their natural state, and have analyzed their packing arrangement. Their findings, published in the Jan. 9 issue of Nature, offer insight on how light signaling might be controlled in the retinas outer edge.
THE WELL-ORGANIZED EYE: This close up, high-magnification image of the disc membrane on a rod from the retina shows protrusions lined up in neat, double rows like eggs in a carton. The protrusions are a paracrystal form of rhodopsin, a light absorbing chemical.
The retina receives light through rods and cones. Rods, which are most heavily concentrated on the retinas outer edge, are sensitive to dim light and to movement, but not to color. Rods, like cones, face away from incoming light. Within rods, light causes a chemical reaction with rhodopsin. This begins a chain of stimulation along the visual pathway, which sends information to the brain for interpretation. The brain can detect one photon of light, the smallest unit of energy, when it is absorbed by a photoreceptor.
The outer segment of a rod looks roughly like a stack of microscopic coins inside a wrapping. The segment is made up of discs covered by a membrane. Scientists studying the retina knew that the outer-segment disc membranes of rods are densely packed with rhodopsin molecules. This bunching together allows for optimum absorption of dim light and for subsequent amplification of the faint signal by the visual pathway. However, how rhodopsin molecules are physically arranged to increase the probability of being activated by a photon was not known.
Leila Gray | EurekAlert!
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...
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