- 2877 - X-RAYS - from microscopes to telescopes. - Let’s look at a protein’s atom. A three-dimensional arrangement of atoms within a protein helps us to understand how it can perform its functions. The electron cryo-microscopy (cryo-EM) has developed as a structural biology technique in X-ray crystallography and has been the only technique able to visualize individual atoms.
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--------------------------- 2877 - X-RAYS - from microscopes to telescopes.
- Scientists have been able to resolve individual protein atoms for the first time in a three-dimensional cryo-EM image. These scientists have achieved the highest resolution using the best available technology seemed to have reached a limit at around 2.5 Ångströms (Å).
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- Atomic resolution is usually reported in Ångströms, a unit of length that is one ten-billionth of a meter, or 0.1 nanometers, or 10^-10 meters. The Angstrom refers to the smallest distance between which two objects can be seen to be separate.
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- The length of a typical carbon-carbon bond is 1.5 Å; other bonds in proteins are a bit shorter. Thus, as the resolution gets down to 1.2 Å, it becomes possible to see individual atoms within a protein, achieving true atomic resolution.
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- Scientists are able to obtain a 1.22 Å resolution of the apoferritin structure, beating the previous 1.53 Å record to be the highest resolution single-particle cryo-EM structure yet obtained. This resolution enabled visualization of individual hydrogen atoms, even on water molecules inside the protein structure.
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- The visualization of hydrogen bonding networks inside protein structures and in drug binding pockets allows researchers to better understand how they work. These higher-resolution reconstructions will allow a better understanding of how proteins work and facilitate design of more specific drugs that could impact on treatments for a huge range of diseases.
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- Observing individual atoms in a protein structure provide insights that make it easier to understand how proteins do their work or cause diseases in the living cell. The technique can also be used in the future to develop new drugs.
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- Since the outbreak of the COVID-19 pandemic, scientists around the world have been solving 3-D structures of important key proteins of the novel coronavirus. Their common goal is to find docking sites for an active compound which can combat the pathogen effectively.
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- Cryo electron microscopy (cryo-EM) can be used to make three-dimensional structures of biomolecules visible. To capture the fuzzy molecules without damaging them, they are cooled down extremely quickly, or shock-frozen so to speak.
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- The frozen samples are bombarded with electrons, and the resulting images are recorded. The three-dimensional structure of the molecules can then be calculated.
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- Using the new microscope, the scientists have taken more than one million images of the protein apoferritin to map the molecular structure with a resolution of 1.25 angstroms.
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- Remember, one angstrom is equivalent to a ten millionth of a millimeter.
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- This technique will be the basis for structure-based drug design by being able to study a protein structure with such unprecedented atomic resolution? Proteins which are the nanomachines of living cells.
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- To get an idea how they carry out their tasks, one has to know the exact position of all atoms of the protein. Such detailed insights are also relevant for structure-based drug design. Compounds for drugs are customized in a way that they bind to viral proteins, for example, and block their function.
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- X-rays have wavelengths of 1 Angstrom which is 10^-10 meters. Lightwaves are 3500 to 7000 ^10-10 meters.
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- X-Rays not only work in microscopes they work in telescopes too. The X-ray photons passing through magnetized plasma could help astronomers search for axion-like particles. If axions do exist they could explain cold-dark matter. Cold dark matter could explain what is holding spinning galaxies together.
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- If photons coming from around galaxy “NGC 1275’s” central black hole convert into axions as they pass through the cluster’s magnetized gas, the gas will in a sense absorb the light in a complex and energy-dependent way. Thus, if axions exist, the light spectrum of NGC 1275’s center would show a tell-tale set of anomalous dips at various X-ray energies.
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- Axion-like particles turn into photons. X-ray photons are passing through hot gas. The spectrum of X-ray photons emanating from around the galaxy's black hole would change.
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- Chandra telescope was never designed to stare directly at a bright source like the center of NGC 1275. A faint-object machine, Chandra’s CCD chip catches light for three seconds at a time, expecting at most one photon per pixel.
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- When researchers in the past slewed Chandra toward the centers of galaxies like NGC 1275, their spectra were ruined by photon pileup, the equivalent of saturation in a normal camera.
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- To get around this, the team flipped one of Chandra’s diffraction grating arrays,, normally used to provide detailed information about the photons’ X-ray energies, into the path of the light. This switch smeared out the X-rays into a whole line, from which the team could extract a high-resolution spectrum.
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- Axions are strong dark matter candidates, and may even explain why there is far more matter than antimatter in the universe. Many theories that go beyond the Standard Model of particle physics, most notably string theory, predict low-mass axions.
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- Discovering these exotic particles would help propel particle physics into a new era of understanding. The power of astrophysical observations is helping us to understand properties of elementary particles and in testing new models in particle physics.
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- See also Review 1687 about X-ray telescopes.
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- October 26, 2020 2877
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