Studeo
10th June 2010, 17:25
X-Ray Diffraction Microscope Reveals 3-D Internal Structure of Whole Cell
http://www.sciencedaily.com/releases/2010/06/100607101808.htm
ScienceDaily (June 9, 2010) — Three-dimensional imaging is
dramatically expanding the ability of researchers to examine
biological specimens, enabling a peek into their internal structures.
And recent advances in X-ray diffraction methods have helped extend
the limit of this approach.
While significant progress has been made in optical microscopy to
break the diffraction barrier, such techniques rely on fluorescent
labeling technologies, which prohibit the quantitative 3-D imaging of
the entire contents of cells. Cryo-electron microscopy can image
structures at a resolution of 3 to 5 nanometers, but this only works
with thin or sectioned specimens.
And although X-ray protein crystallography is currently the primary
method used for determining the 3-D structure of protein molecules,
many biological specimens -- such as whole cells, cellular organelles,
some viruses and many important protein molecules -- are difficult or
impossible to crystallize, making their structures inaccessible.
Overcoming these limitations requires the employment of different
techniques.
Now, in a paper published May 31 in Proceedings of National Academy of
Sciences, UCLA researchers and their collaborators demonstrate the use
of a unique X-ray diffraction microscope that enabled them to reveal
the internal structure of yeast spores. The team reports the
quantitative 3-D imaging of a whole, unstained cell at a resolution of
50 to 60 nanometers using X-ray diffraction microscopy, also known as
lensless imaging.
Researchers identified the 3-D morphology and structure of cellular
organelles, including the cell wall, vacuole, endoplasmic reticulum,
mitrochondria, granules and nucleolus. The work may open a door to
identifying the individual protein molecules inside whole cells using
labeling technologies.
The lead authors on the paper are Huaidong Jiang, a UCLA assistant
researcher in physics and astronomy, and John Miao, a UCLA professor
of physics and astronomy. The work is a culmination of a collaboration
started three years ago with Fuyu Tamanoi, UCLA professor of
microbiology, immunology and molecular genetics. Miao and Tamanoi are
both researchers at UCLA's California NanoSystems Institute. Other
collaborators include teams at Riken Spring 8 in Japan and the
Institute of Physics, Academia Sinica, in Taiwan.
"This is the first time that people have been able to peek into the
3-D internal structure of a biological specimen, without cutting it
into sections, using X-ray diffraction microscopy," Miao said.
"By avoiding use of X-ray lenses, the resolution of X-ray diffraction
microscopy is ultimately limited by radiation damage to biological
specimens. Using cryogenic technologies, 3-D imaging of whole
biological cells at a resolution of 5 to 10 nanometers should be
achievable," Miao said. "Our work hence paves a way for quantitative
3-D imaging of a wide range of biological specimens at nanometer-scale
resolutions that are too thick for electron microscopy."
Tamanoi prepared the yeast spore samples analyzed in this study.
Spores are specialized cells that are formed when they are placed
under nutrient-starved conditions. Cells use this survival strategy to
cope with harsh conditions.
"Biologists wanted to examine internal structures of the spore, but
previous microscopic studies provided information on only the surface
features. We are very excited to be able to view the spore in 3-D,"
Tamanoi said. "We can now look into the structure of other spores,
such as Anthrax spores and many other fungal spores. It is also
important to point out that yeast spores are of similar size to many
intracellular organelles in human cells. These can be examined in the
future."
Since its first experimental demonstration by Miao and collaborators
in 1999, coherent diffraction microscopy has been applied to imaging a
wide range of materials science and biological specimens, such as
nanoparticles, nanocrystals, biomaterials, cells, cellular organelles,
viruses and carbon nanotubes using X-ray, electron and laser
facilities worldwide. Until now, however, the radiation-damage problem
and the difficulty of acquiring high-quality 3-D diffraction patterns
from individual whole cells have prevented the successful
high-resolution 3-D imaging of biological cells by X-ray diffraction.
Story Source:
The above story is reprinted (with editorial adaptations by
ScienceDaily staff) from materials provided by University of
California - Los Angeles. The original article was written by Jennifer
Marcus.
http://www.sciencedaily.com/releases/2010/06/100607101808.htm
ScienceDaily (June 9, 2010) — Three-dimensional imaging is
dramatically expanding the ability of researchers to examine
biological specimens, enabling a peek into their internal structures.
And recent advances in X-ray diffraction methods have helped extend
the limit of this approach.
While significant progress has been made in optical microscopy to
break the diffraction barrier, such techniques rely on fluorescent
labeling technologies, which prohibit the quantitative 3-D imaging of
the entire contents of cells. Cryo-electron microscopy can image
structures at a resolution of 3 to 5 nanometers, but this only works
with thin or sectioned specimens.
And although X-ray protein crystallography is currently the primary
method used for determining the 3-D structure of protein molecules,
many biological specimens -- such as whole cells, cellular organelles,
some viruses and many important protein molecules -- are difficult or
impossible to crystallize, making their structures inaccessible.
Overcoming these limitations requires the employment of different
techniques.
Now, in a paper published May 31 in Proceedings of National Academy of
Sciences, UCLA researchers and their collaborators demonstrate the use
of a unique X-ray diffraction microscope that enabled them to reveal
the internal structure of yeast spores. The team reports the
quantitative 3-D imaging of a whole, unstained cell at a resolution of
50 to 60 nanometers using X-ray diffraction microscopy, also known as
lensless imaging.
Researchers identified the 3-D morphology and structure of cellular
organelles, including the cell wall, vacuole, endoplasmic reticulum,
mitrochondria, granules and nucleolus. The work may open a door to
identifying the individual protein molecules inside whole cells using
labeling technologies.
The lead authors on the paper are Huaidong Jiang, a UCLA assistant
researcher in physics and astronomy, and John Miao, a UCLA professor
of physics and astronomy. The work is a culmination of a collaboration
started three years ago with Fuyu Tamanoi, UCLA professor of
microbiology, immunology and molecular genetics. Miao and Tamanoi are
both researchers at UCLA's California NanoSystems Institute. Other
collaborators include teams at Riken Spring 8 in Japan and the
Institute of Physics, Academia Sinica, in Taiwan.
"This is the first time that people have been able to peek into the
3-D internal structure of a biological specimen, without cutting it
into sections, using X-ray diffraction microscopy," Miao said.
"By avoiding use of X-ray lenses, the resolution of X-ray diffraction
microscopy is ultimately limited by radiation damage to biological
specimens. Using cryogenic technologies, 3-D imaging of whole
biological cells at a resolution of 5 to 10 nanometers should be
achievable," Miao said. "Our work hence paves a way for quantitative
3-D imaging of a wide range of biological specimens at nanometer-scale
resolutions that are too thick for electron microscopy."
Tamanoi prepared the yeast spore samples analyzed in this study.
Spores are specialized cells that are formed when they are placed
under nutrient-starved conditions. Cells use this survival strategy to
cope with harsh conditions.
"Biologists wanted to examine internal structures of the spore, but
previous microscopic studies provided information on only the surface
features. We are very excited to be able to view the spore in 3-D,"
Tamanoi said. "We can now look into the structure of other spores,
such as Anthrax spores and many other fungal spores. It is also
important to point out that yeast spores are of similar size to many
intracellular organelles in human cells. These can be examined in the
future."
Since its first experimental demonstration by Miao and collaborators
in 1999, coherent diffraction microscopy has been applied to imaging a
wide range of materials science and biological specimens, such as
nanoparticles, nanocrystals, biomaterials, cells, cellular organelles,
viruses and carbon nanotubes using X-ray, electron and laser
facilities worldwide. Until now, however, the radiation-damage problem
and the difficulty of acquiring high-quality 3-D diffraction patterns
from individual whole cells have prevented the successful
high-resolution 3-D imaging of biological cells by X-ray diffraction.
Story Source:
The above story is reprinted (with editorial adaptations by
ScienceDaily staff) from materials provided by University of
California - Los Angeles. The original article was written by Jennifer
Marcus.