Elucidating the mechanism of a light-driven sodium pump

Researchers at the Paul Scherrer Institute PSI have succeeded for the first time in recording a light-driven sodium pump from bacterial cells in action. The findings promise progress in the development of new methods in neurobiology. ...

It takes a neutron beam to find a proton

Understanding the behavior of proteins and enzymes is key to unlocking the secrets of biological processes. The atomic structures of proteins are generally investigated using X-ray crystallography; however, the precise information ...

Scientists discover new features of molecular elevator

Biophysicists from the Moscow Institute of Physics and Technology and the University of Groningen in the Netherlands have visualized a nearly complete transport cycle of the mammalian glutamate transporter homologue from ...

Researchers use snake venom to solve structure of muscle protein

Researchers at UT Southwestern Medical Center have uncovered the detailed shape of a key protein involved in muscle contraction. The report, published today in Neuron, may lead to improved understanding of muscle-weakening ...

Cell membrane proteins imaged in 3-D

A team of scientists including researchers at the National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility at DOE's Brookhaven National Laboratory—have demonstrated ...

Blocking iron transport could stop tuberculosis

One of the most devastating pathogens that lives inside human cells is Mycobacterium tuberculosis, the bacillus that causes tuberculosis. According to the World Health Organization, 1.5 million people died in 2019 from this ...

Shaping the social networks of neurons

The three proteins teneurin, latrophilin and FLRT hold together and bring neighboring neurons into close contact, enabling the formation of synapses and the exchange of information between the cells. In the early phase of ...

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Crystallography

Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.

Before the development of X-ray diffraction crystallography (see below), the study of crystals was based on their geometry. This involves measuring the angles of crystal faces relative to theoretical reference axes (crystallographic axes), and establishing the symmetry of the crystal in question. The former is carried out using a goniometer. The position in 3D space of each crystal face is plotted on a stereographic net, e.g. Wulff net or Lambert net. In fact, the pole to each face is plotted on the net. Each point is labelled with its Miller index. The final plot allows the symmetry of the crystal to be established.

Crystallographic methods now depend on the analysis of the diffraction patterns of a sample targeted by a beam of some type. Although X-rays are most commonly used, the beam is not always electromagnetic radiation. For some purposes electrons or neutrons are used. This is facilitated by the wave properties of the particles. Crystallographers often explicitly state the type of illumination used when referring to a method, as with the terms X-ray diffraction, neutron diffraction and electron diffraction.

These three types of radiation interact with the specimen in different ways. X-rays interact with the spatial distribution of the valence electrons, while electrons are charged particles and therefore feel the total charge distribution of both the atomic nuclei and the surrounding electrons. Neutrons are scattered by the atomic nuclei through the strong nuclear forces, but in addition, the magnetic moment of neutrons is non-zero. They are therefore also scattered by magnetic fields. When neutrons are scattered from hydrogen-containing materials, they produce diffraction patterns with high noise levels. However, the material can sometimes be treated to substitute hydrogen for deuterium. Because of these different forms of interaction, the three types of radiation are suitable for different crystallographic studies.

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