ScienceDaily (May 4, 2010) — UCLA researchers report in the April 30 edition of the journal Cell that they have imaged a virus structure at a resolution high enough to effectively "see" atoms, the first published instance of imaging biological complexes at such a resolution.
Cover of the journal Cell showing an artistic representation of a Cryo-EM 3-D reconstruction of an aquareovirus, the colors are added to show contrast between various structures in the virus. (Credit: Image courtesy of UCLA)
The research team, led by Hong Zhou, UCLA professor of microbiology, immunology and molecular genetics, used cryo-electron microscopy to image the structure at 3.3 angstroms. An angstrom is the smallest recognized division of a chemical element and is about the distance between the two hydrogen atoms in a water molecule.
The study, the researchers say, demonstrates the great potential of cryo-electron microscopy, or Cryo-EM, for producing extremely high-resolution images of biological samples in their native environment.
"This is the first study to determine an atomic resolution structure through Cryo-EM alone," said Xing Zhang, a postdoctoral candidate in Zhou's group and lead author of the Cell paper. "By proving the effectiveness of this microscopy technique, we have opened the door to a wide variety of biological studies."
With traditional light microscopy, a magnified image of a sample is viewed through a lens. Some samples, however, are too small to diffract visible light (in the 500 to 800 nm range, or 5,000 to 8,000 angstroms) and therefore cannot be seen. To image objects at the sub-500 nm scale, scientists must turn to other tools, such as atomic force microscopes, which use an atomically thin tip to generate an image by probing a surface, in much the same way a blind person reads by touching Braille lettering.
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Volume 141, Issue 3, 30 April 2010, Pages 472-482
3.3 Å Cryo-EM Structure of a Nonenveloped Virus Reveals a Priming Mechanism for Cell Entry
Xing Zhang1, Lei Jin1, Qin Fang2, Wong H. Hui3 and Z. Hong Zhou1, 3, ,
1 Department of Microbiology, Immunology & Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095-7364, USA
2 State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China
3 California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095-7364, USA
Received 8 December 2009;
revised 22 January 2010;
accepted 29 March 2010.
Published online: April 15, 2010.
Available online 15 April 2010.
Summary
To achieve cell entry, many nonenveloped viruses must transform from a dormant to a primed state. In contrast to the membrane fusion mechanism of enveloped viruses (e.g., influenza virus), this membrane penetration mechanism is poorly understood. Here, using single-particle cryo-electron microscopy, we report a 3.3 Å structure of the primed, infectious subvirion particle of aquareovirus. The density map reveals side-chain densities of all types of amino acids (except glycine), enabling construction of a full-atom model of the viral particle. Our structure and biochemical results show that priming involves autocleavage of the membrane penetration protein and suggest that Lys84 and Glu76 may facilitate this autocleavage in a nucleophilic attack. We observe a myristoyl group, covalently linked to the N terminus of the penetration protein and embedded in a hydrophobic pocket. These results suggest a well-orchestrated process of nonenveloped virus entry involving autocleavage of the penetration protein prior to exposure of its membrane-insertion finger.
Graphical Abstract
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Highlights
► A 3.3Å structure of a primed nonenveloped virus is obtained by cryo-EM ► Atomic models are built from the cryo-EM density alone for six protein conformers ► Autocleavage occurs in the membrane penetration protein during priming ► A membrane-insertion “finger” is buried in a hydrophobic pocket during priming
Author Keywords: HUMDISEASE; PROTEINS
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NOTA INQUIETANTE DESTE BLOGGER:
Quem hoje teria melhores condições de ter a maior ideia que toda a humanidade já teve -- a evolução através da seleção natural, se utilizando do microscópio de Darwin ou este aqui que enxerga até a alma [cruz, credo, cometi um assassinato epistemológico] do átomo?
Fui, nem sei por que, pensando que a maior ideia que toda a humanidade já teve não é corroborada através de microscópios que enxergam átomos. Alguém precisa avisar a estes pesquisadores de que nada em biologia faz sentido a não ser à luz da evolução. Razão? Gente, eles não mencionaram o fundamento teórico de toda a biologia: como enxergar a evolução desses átomos através da seleção natural. Uma tremenda injustiça contra Darwin...
