Biochemists solve the structure of cell's DNA gatekeeper
Caltech scientists have produced the most detailed map yet of the massive protein machine that controls access to the DNA-containing heart of the cell.
Caltech scientists have produced the most detailed map yet of the massive protein machine that controls access to the DNA-containing heart of the cell.
Biochemistry
Apr 15, 2016
0
2157
Sunday, November 8 marks the 120th anniversary of one of the greatest moments in the history of science: an obscure German physics professor's discovery of the X-ray. His name was Wilhelm Roentgen, and in the six weeks that ...
General Physics
Nov 6, 2015
0
13138
Atoms are the building blocks of all matter on Earth, and the patterns in which they are arranged dictate how strong, conductive or flexible a material will be. Now, scientists at UCLA have used a powerful microscope to image ...
Nanophysics
Sep 21, 2015
1
314
(Phys.org)—Researchers at the University of California have succeeded in stretching a carbon monoxide molecule bond to a record length. In their paper published in the journal Nature Chemistry, the team describes how they ...
(PhysOrg.com) -- Scientists at the University of Glasgow have imaged the self-assembly of nano-particles, unveiling the blueprint for building designer molecular machines atom-by-atom.
Nanophysics
Jan 4, 2010
0
0
(Phys.org)—Creating 3D visualizations of hydrogen atoms in proteins is especially challenging, often requiring their locations to be inferred from those of nearby carbon, nitrogen, oxygen or sulfur atoms stored in protein ...
A wide variety of fruits and vegetables contain oxalate. But humans and most other animals lack the ability to metabolize this molecule—that is, to break it down while digesting it. And so for some people, a buildup of ...
Biochemistry
Dec 29, 2015
4
948
A new study published in PeerJ uses modern methods to understand the preservation of unique ichthyosaur fossils. Two new ichthyosaur specimens—one complete animal and one tail—are the first to preserve outer body shape ...
Paleontology & Fossils
Apr 7, 2022
0
1457
Chemists at Carnegie Mellon University have demonstrated that synthetic nanoparticles can achieve the same level of structural complexity, hierarchy and accuracy as their natural counterparts - biomolecules. The study, published ...
Bio & Medicine
Jan 23, 2017
1
1565
(Phys.org)—Biological systems are characterized by a form of molecular recycling – and proteins do not escape this fate. In particular, unneeded or damaged proteins biochemically marked for destruction undergo controlled ...
X-ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X-rays strikes a crystal and diffracts into many specific directions. From the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder and various other information.
Since many materials can form crystals — such as salts, metals, minerals, semiconductors, as well as various inorganic, organic and biological molecules — X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among various materials, especially minerals and alloys. The method also revealed the structure and functioning of many biological molecules, including vitamins, drugs, proteins and nucleic acids such as DNA. X-ray crystallography is still the chief method for characterizing the atomic structure of new materials and in discerning materials that appear similar by other experiments. X-ray crystal structures can also account for unusual electronic or elastic properties of a material, shed light on chemical interactions and processes, or serve as the basis for designing pharmaceuticals against diseases.
In an X-ray diffraction measurement, a crystal is mounted on a goniometer and gradually rotated while being bombarded with X-rays, producing a diffraction pattern of regularly spaced spots known as reflections. The two-dimensional images taken at different rotations are converted into a three-dimensional model of the density of electrons within the crystal using the mathematical method of Fourier transforms, combined with chemical data known for the sample. Poor resolution (fuzziness) or even errors may result if the crystals are too small, or not uniform enough in their internal makeup.
X-ray crystallography is related to several other methods for determining atomic structures. Similar diffraction patterns can be produced by scattering electrons or neutrons, which are likewise interpreted as a Fourier transform. If single crystals of sufficient size cannot be obtained, various other X-ray methods can be applied to obtain less detailed information; such methods include fiber diffraction, powder diffraction and small-angle X-ray scattering (SAXS). In all these methods, the scattering is elastic; the scattered X-rays have the same wavelength as the incoming X-ray. By contrast, inelastic X-ray scattering methods are useful in studying excitations of the sample, rather than the distribution of its atoms.
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