The document summarizes the development of cryo-electron microscopy (cryo-EM) which allows researchers to generate 3D images of biomolecules like proteins at atomic resolution. Richard Henderson, Joachim Frank, and Jacques Dubochet made key contributions to cryo-EM's development. Henderson produced the first high resolution cryo-EM image in 1990. Frank developed methods to process 2D cryo-EM images into 3D models. Dubochet invented a vitrification technique to rapidly freeze samples without damaging them. Together, their work has revolutionized structural biology by enabling atomic level views of biomolecules and their functions.
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Nobel Prize in Chemistry 2017
Joachim Frank
Cryo-Electron Microscopy
5. Electron spectroscopy for surface analysis.
Applications of scanning electron microscope Applications of Transmission electron Microscope Brief history of electron microscopy Coherency and stability on the electron beam Different kinds of electron microscopes Different parts of electron microscope Effect of Brightness Electron Microscopy Electron Sources Field emission Interaction of electrons with Matter Limitations of Transmission electron Microscope Magnification contrast etc Material Characterization techniques Resolution Scanning electron microscope Scattering of electrons Specimen preparation of Transmission electron Microscope Thermionic Emission Various sources of electron beams and Detectors
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
Nobel Prize in Chemistry 2017
Joachim Frank
Cryo-Electron Microscopy
5. Electron spectroscopy for surface analysis.
Applications of scanning electron microscope Applications of Transmission electron Microscope Brief history of electron microscopy Coherency and stability on the electron beam Different kinds of electron microscopes Different parts of electron microscope Effect of Brightness Electron Microscopy Electron Sources Field emission Interaction of electrons with Matter Limitations of Transmission electron Microscope Magnification contrast etc Material Characterization techniques Resolution Scanning electron microscope Scattering of electrons Specimen preparation of Transmission electron Microscope Thermionic Emission Various sources of electron beams and Detectors
Introduction
The applications of microscopy in the forensic sciences are almost limitless. This is due in large measure to the ability of
microscopes to detect, resolve and image the smallest items of evidence, often without alteration or destruction. As a
result, microscopes have become nearly indispensable in all forensic disciplines involving the natural sciences. Thus, a
firearms examiner comparing a bullet, a trace evidence specialist identifying and comparing fibers, hairs, soils or dust, a
document examiner studying ink line crossings or paper fibers, and a serologist scrutinizing a bloodstain, all rely on
microscopes, in spite of the fact that each may use them in different ways and for different purposes.
The principal purpose of any microscope is to form an enlarged image of a small object. As the image is more greatly
magnified, the concern then becomes resolution; the ability to see increasingly fine details as the magnification is
increased. For most observers, the ability to see fine details of an item of evidence at a convenient magnification, is
sufficient. For many items, such as ink lines, bloodstains or bullets, no treatment is required and the evidence may
typically be studied directly under the appropriate microscope without any form of sample preparation. For other types of
evidence, particularly traces of particulate matter, sample preparation before the microscopical examination begins is
often essential. Types of Microscopes Used in the Forensic Sciences
A variety of microscopes are used in any modern forensic science laboratory. Most of these are light microscopes which
use photons to form images, but electron microscopes, particularly the scanning electron microscope (SEM), are finding
applications in larger, full service laboratories because of their wide range of magnification, high resolving power and
ability to perform elemental analyses when equipped with an energy or wavelength dispersive X-ray spectrometer.
In light microscopy, illuminating light is passed through the sample as uniformly as possible over the field of view. For thicker samples, where the objective lens does not have sufficient depth of focus, light from sample planes above and below the focal plane will also be detected. The out of focus light will add blur to the image reducing the resolution. In fluorescence microscopy, any dye molecules in the field of view will be stimulated, including those in out-of-focus planes. Confocal microscopy provides a means of rejecting the out-of-focus light from the detector such that it does not contribute blur to the images being collected. This technique allows for high-resolution imaging in thick tissues.
In a confocal microscope, the illumination and detection optics are focused on the same diffraction limited spot in the sample, which is the only spot imaged by the detector during a confocal scan. To generate a complete image, the spot must be moved over the sample and data collected point by point.
A significant advantage of the confocal microscope is the optical sectioning provided, which allows for 3D reconstruction of a sample from high-resolution stacks of images. The primary functions of a confocal microscope are to produce a point source of light and reject out-of-focus light, which provides the ability to image deep into tissues with high resolution, and optical sectioning for 3D reconstructions of imaged samples. The basic principle include illumination and detection optics are focused on the same diffraction-limited spot, which is moved over the sample to build the complete image on the detector. The entire field of view is illuminated during confocal imaging, anything outside the focal plane contributes little to the image, lessening the haze observed in standard light microscopy with thick and highly-scattering samples, and providing optical sectioning.
A presentation on microscopes- its evolution, history, uses, types, etc. beneficial for pathology students. impart knowledge about types of lens, parts of microscope ands their use.
Beam of electrons is transmitted through an ultra thin specimen,
An image is formed from the interaction of the electrons transmitted through the specimen,
The image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera
Introduction
The applications of microscopy in the forensic sciences are almost limitless. This is due in large measure to the ability of
microscopes to detect, resolve and image the smallest items of evidence, often without alteration or destruction. As a
result, microscopes have become nearly indispensable in all forensic disciplines involving the natural sciences. Thus, a
firearms examiner comparing a bullet, a trace evidence specialist identifying and comparing fibers, hairs, soils or dust, a
document examiner studying ink line crossings or paper fibers, and a serologist scrutinizing a bloodstain, all rely on
microscopes, in spite of the fact that each may use them in different ways and for different purposes.
The principal purpose of any microscope is to form an enlarged image of a small object. As the image is more greatly
magnified, the concern then becomes resolution; the ability to see increasingly fine details as the magnification is
increased. For most observers, the ability to see fine details of an item of evidence at a convenient magnification, is
sufficient. For many items, such as ink lines, bloodstains or bullets, no treatment is required and the evidence may
typically be studied directly under the appropriate microscope without any form of sample preparation. For other types of
evidence, particularly traces of particulate matter, sample preparation before the microscopical examination begins is
often essential. Types of Microscopes Used in the Forensic Sciences
A variety of microscopes are used in any modern forensic science laboratory. Most of these are light microscopes which
use photons to form images, but electron microscopes, particularly the scanning electron microscope (SEM), are finding
applications in larger, full service laboratories because of their wide range of magnification, high resolving power and
ability to perform elemental analyses when equipped with an energy or wavelength dispersive X-ray spectrometer.
In light microscopy, illuminating light is passed through the sample as uniformly as possible over the field of view. For thicker samples, where the objective lens does not have sufficient depth of focus, light from sample planes above and below the focal plane will also be detected. The out of focus light will add blur to the image reducing the resolution. In fluorescence microscopy, any dye molecules in the field of view will be stimulated, including those in out-of-focus planes. Confocal microscopy provides a means of rejecting the out-of-focus light from the detector such that it does not contribute blur to the images being collected. This technique allows for high-resolution imaging in thick tissues.
In a confocal microscope, the illumination and detection optics are focused on the same diffraction limited spot in the sample, which is the only spot imaged by the detector during a confocal scan. To generate a complete image, the spot must be moved over the sample and data collected point by point.
A significant advantage of the confocal microscope is the optical sectioning provided, which allows for 3D reconstruction of a sample from high-resolution stacks of images. The primary functions of a confocal microscope are to produce a point source of light and reject out-of-focus light, which provides the ability to image deep into tissues with high resolution, and optical sectioning for 3D reconstructions of imaged samples. The basic principle include illumination and detection optics are focused on the same diffraction-limited spot, which is moved over the sample to build the complete image on the detector. The entire field of view is illuminated during confocal imaging, anything outside the focal plane contributes little to the image, lessening the haze observed in standard light microscopy with thick and highly-scattering samples, and providing optical sectioning.
A presentation on microscopes- its evolution, history, uses, types, etc. beneficial for pathology students. impart knowledge about types of lens, parts of microscope ands their use.
Beam of electrons is transmitted through an ultra thin specimen,
An image is formed from the interaction of the electrons transmitted through the specimen,
The image is magnified and focused onto an imaging device, such as a fluorescent screen, on a layer of photographic film, or to be detected by a sensor such as a CCD camera
DEVELOPING CRYO-ELECTRON MICROSCOPY OF BIOMOLECULES IN WATERGuttiPavan
Cryo-electron microscopy (Cryo-EM) is a type of transmission electron microscopy that allows for the specimen of interest to be viewed at cryogenic temperatures (-150°C)
Following years of improvement, the cryo-electron microscope has become a valuable tool for viewing and studying the 3D structures of various biological molecules in water.
Electron Microscope. This booklet is a primer on electron and ion beam microscopy and is intended for students and others interested in learning more about the history, technology, and instruments behind this fascinating field of
scientific inquiry.
x ray spectroscopy has leading role in defining the internal structure of substances , e.g. crystal structure of compounds , elemental composition, fluorescent compounds and many more.
Overview Of Nanotechnology Historical Perspective Of Integration Of Biology ...academicbiotech
Explore the evolution of nanotechnology in this presentation, tracing its historical roots and emphasizing the fusion of biology, chemistry, and material science. Delve into the interdisciplinary nature of nanotechnology, highlighting key contributions from each field and showcasing pivotal milestones that shaped the convergence of these sciences, revolutionizing technology and research.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
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Monitor common gases, weather parameters, particulates.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.
THE NOBEL PRIZE IN CHEMISTRY 2017
1. THE NOBEL PRIZE IN CHEMISTRY 2017
POPUL AR SCIENCE BACKGROUND
NobelPrize®isaregisteredtrademarkoftheNobelFoundation.
They captured life in atomic detail
Jacques Dubochet, Joachim Frank and Richard Henderson are awarded the Nobel Prize in Chemistry
2017 for their development of an effective method for generating three-dimensional images of the
molecules of life. Using cryo-electron microscopy, researchers can now freeze biomolecules mid-
movement and portray them at atomic resolution. This technology has taken biochemistry into a new era.
Over the last few years, numerous astonishing structures of life’s molecular machinery have filled
the scientific literature (figure 1): Salmonella’s injection needle for attacking cells; proteins that
confer resistance to chemotherapy and antibiotics; molecular complexes that govern circadian
rhythms; light-capturing reaction complexes for photosynthesis and a pressure sensor of the type
that allows us to hear. These are just a few examples of the hundreds of biomolecules that have now
been imaged using cryo-electron microscopy (cryo-EM).
When researchers began to suspect that the Zika virus was causing the epidemic of brain-damaged
newborns in Brazil, they turned to cryo-EM to visualise the virus. Over a few months, three-
dimensional (3D) images of the virus at atomic resolution were generated and researchers could start
searching for potential targets for pharmaceuticals.
Jacques Dubochet, Joachim Frank and Richard Henderson have made ground-breaking discoveries
that have enabled the development of cryo-EM. The method has taken biochemistry into a new era,
making it easier than ever before to capture images of biomolecules.
Pictures – an important key to knowledge
In the first half of the twentieth century, biomolecules – proteins, DNA and RNA – were terra
incognita on the map of biochemistry. Scientists knew they played fundamental roles in the cell,
but had no idea what they looked like. It was only in the 1950s, when researchers at Cambridge
began to expose protein crystals to X-ray beams, that it was first possible to visualise their wavy
and spiralling structures.
Figure 1. Over the last few years, researchers have published atomic structures of numerous complicated protein complexes.
a. A protein complex that governs the circadian rhythm. b. A sensor of the type that reads pressure changes in the ear and allows us
to hear. c. The Zika virus.
2. 2(7) THE NOBEL PRIZE IN CHEMISTRY 2017 THE ROYAL SWEDISH ACADEMY OF SCIENCES WWW.KVA.SE
In the early 1980s, the use of X-ray crystallography was supplemented with the use of nuclear
magnetic resonance (NMR) spectroscopy for studying proteins in solid state and in solution. This
technique not only reveals their structure, but also how they move and interact with other molecules.
Thanks to these two methods, there are now databases containing thousands of models of bio-
molecules that are used in everything from basic research to pharmaceutical development. However,
both methods suffer from fundamental limitations. NMR in solution only works for relatively small
proteins. X-ray crystallography requires that the molecules form well-organised crystals, such as
when water freezes to ice. The images are like black and white portraits from early cameras – their
rigid pose reveals very little about the protein’s dynamics.
Also, many molecules fail to arrange themselves in crystals, which caused Richard Henderson to abandon
X-ray crystallography in the 1970s – and this is where the story of 2017’s Nobel Prize in Chemistry begins.
Problems with crystals made Henderson change track
Richard Henderson received his PhD from the bastion of X-ray crystallography, Cambridge, UK. He
used the method for imaging proteins, but setbacks arose when he attempted to crystallise a protein
that was naturally embedded in the membrane surrounding the cell.
Membrane proteins are difficult to manage. When they are removed from their natural environment
– the membrane – they often clump up into a useless mass. The first membrane protein that Richard
Henderson worked with was difficult to produce in adequate amounts; the second failed to crystallise.
After years of disappointment, he turned to the only available alternative: the electron microscope.
It is open to discussion whether electron microscopy really was an option at this time. Transmission
electron microscopy, as the technique is called, works more or less like ordinary microscopy, but a beam
of electrons is sent through the sample instead of light. The electrons’ wavelength is much shorter than
that of light, so the electron microscope can make very small structures visible – even the position of
individual atoms.
In theory, the resolution of the electron microscope was thus more than adequate for Henderson to obtain
the atomic structure of a membrane protein, but in practice the project was almost impossible. When the
electron microscope was invented in the 1930s, scientists thought that it was only suitable for studying
dead matter. The intense electron beam necessary for obtaining high resolution images incinerates bio-
logical material and, if the beam is weakened, the image loses its contrast and becomes fuzzy.
In addition, electron microscopy requires a vacuum, a condition in which biomolecules deteriorate
because the surrounding water evaporates. When biomolecules dry out, they collapse and lose their
natural structure, making the images useless.
Almost everything indicated that Richard Henderson would fail, but the project was saved by the
special protein that he had chosen to study: bacteriorhodopsin.
The best so far was not good enough for Henderson
Bacteriorhodopsin is a purple-coloured protein that is embedded in the membrane of a photosynthesising
organism, where it captures the energy from the sun’s rays. Instead of removing the sensitive protein
from the membrane, as Richard Henderson had previously tried to do, he and his colleague took the
complete purple membrane and put it under the electron microscope. When the protein remained
3. 3(7)THE NOBEL PRIZE IN CHEMISTRY 2017 THE ROYAL SWEDISH ACADEMY OF SCIENCES WWW.KVA.SE
surrounded by the membrane it retained its structure; they covered the sample’s surface with a glucose
solution that protected it from drying out in the vacuum.
The harsh electron beam was a major problem, but the researchers
made use of how the bacteriorhodopsin molecules are packed in the
organism’s membrane. Instead of blasting it with a full dose of electrons,
they had a weaker beam flow through the sample. The image’s contrast
was poor and they could not see the individual molecules, but they
used the fact that the proteins were regularly packed and oriented in
the same direction. When all the proteins diffract the electron beams
in an almost identical manner, they were able to calculate a more
detailed image based on the diffraction pattern – they used a similar
mathematical approach to that used in X-ray crystallography.
At the next stage, the researchers turned the membrane under the
electron microscope, taking pictures from many different angles.
This way, in 1975 it was possible to produce a rough 3D model of
bacteriorhodopsin’s structure (figure 2), which showed how the protein
chain wiggled through the membrane seven times.
It was the best picture of a protein ever generated using an electron microscope. Many people
were impressed by the resolution, which was 7 Ångström (0.0000007 millimetres), but this was not
enough for Richard Henderson. His goal was to achieve the same resolution as that provided by
X-ray crystallography, about 3 Ångström, and he was convinced that electron microscopy had more
to give.
Henderson produces the first image at atomic resolution
Over the following years, electron microscopy gradually
improved. The lenses got better and cryotechnology developed
(we will return to this), in which the samples were cooled with
liquid nitrogen during the measurements, protecting them
from being damaged by the electron beam.
Richard Henderson gradually added more details to the model
of bacteriorhodopsin. To get the sharpest images he travelled
to the best electron microscopes in the world. They all had
their weaknesses, but complemented each other. Finally, in
1990, 15 years after he had published the first model, Henderson
achieved his goal and was able to present a structure of bacterio-
rhodopsin at atomic resolution (figure 3).
He thereby proved that cryo-EM could provide images as detailed as those generated using X-ray
crystallography, which was a crucial milestone. However, this progress was built upon an exception:
how the protein naturally packed itself regularly in the membrane. Few other proteins spontaneously
order themselves in this way. The question was whether the method could be generalised: would
it be possible to use an electron microscope to generate high-resolution 3D images of proteins that
were randomly scattered in the sample and oriented in different directions? Richard Henderson
believed it would be, while others thought this was a utopia.
Figure 2. The first rough model of
bacteriorhodopsin, published in
1975. Image from Nature 257: 28-32
Figure 3. In 1990, Henderson presented
a bacteriorhodopsin structure at atomic
resolution.
4. 4(7) THE NOBEL PRIZE IN CHEMISTRY 2017 THE ROYAL SWEDISH ACADEMY OF SCIENCES WWW.KVA.SE
On the other side of the Atlantic, at the New York
State Department of Health, Joachim Frank had
long worked to find a solution to just that problem.
In 1975, he presented a theoretical strategy where
the apparently minimal information found in the
electron microscope’s two-dimensional images
could be merged to generate a high-resolution,
three-dimensional whole. It took him over a
decade to realise this idea.
Frank refines image analysis
Joachim Frank’s strategy (figure 4) built upon
having a computer discriminate between the
traces of randomly positioned proteins and their
background in a fuzzy electron microscope image.
He developed a mathematical method that allo-
wed the computer to identify different recurring
patterns in the image. The computer then sorted
similar patterns into the same group and merged
the information in these images to generate an
averaged, sharper image. In this way he obtained
a number of high-resolution, two-dimensional
images that showed the same protein but from
different angles. The algorithms for the software
were complete in 1981.
The next step was to mathematically determine
how the different two-dimensional images were
related to each other and, based on this, to create
a 3D image. Frank published this part of the
image analysis method in the mid-1980s and
used it to generate a model of the surface of a
ribosome, the gigantic molecular machinery that
builds proteins inside the cell.
Joachim Frank’s image processing method was
fundamental to the development of cryo-EM. Now
we’ll jump a few years back in time – in 1978, at
the same time as Frank was perfecting his computer programs, Jacques Dubochet was recruited to the
European Molecular Biology Laboratory in Heidelberg to solve another of the electron microscope’s
basic problems: how biological samples dry out and are damaged when exposed to a vacuum.
Dubochet makes glass from water
In 1975, Henderson used a glucose solution to protect his membrane from dehydrating, but this
method did not work for water-soluble biomolecules. Other researchers had tried freezing the samples
because ice evaporates more slowly than water, but the ice crystals disrupted the electron beams so
much that the images were useless.
The computer
calculates how the
different 2D images
relate to each other
and generates a
high-resolution
structure in 3D.
4
4. FRANK’S IMAGE ANALYSIS
FOR 3D STRUCTURES
Randomly oriented proteins are
hit by the electron beam, leaving a
trace on the image.
The computer discriminates
between the traces and the
fuzzy background, placing
similar ones in the same group.
Using thousands of
similar traces, the
computer generates
a high-resolution
2D image
1
2
3
5. 5(7)THE NOBEL PRIZE IN CHEMISTRY 2017 THE ROYAL SWEDISH ACADEMY OF SCIENCES WWW.KVA.SE
The vaporising water was a major dilemma. How-
ever, Jacques Dubochet saw a potential solution:
cooling the water so rapidly that it solidified in
its liquid form to form a glass instead of crystals.
A glass appears to be a solid material, but is actu-
ally a fluid because it has disordered molecules.
Dubochet realised that if he could get water to
form glass – also known as vitrified water – the
electron beam would diffract evenly and provide
a uniform background.
Initially, the research group attempted to vitrify
tiny drops of water in liquid nitrogen at –196°C,
but were successful only when they replaced the
nitrogen with ethane that had, in turn, been
cooled by liquid nitrogen. Under the microscope
they saw a drop that was like nothing they had
seen before. They first assumed it was ethane, but
when the drop warmed slightly the molecules sud-
denly rearranged themselves and formed the fami-
liar structure of an ice crystal. It was a triumph
– particularly as some researchers had claimed
it was impossible to vitrify water drops. We now
believe that vitrified water is the most common
form of water in the universe.
A simple technique for contrast
After the breakthrough in 1982, Dubochet’s
research group rapidly developed the basis of the
technique that is still used in cryo-EM (figure 5).
They dissolved their biological samples – initially
different forms of viruses – in water. The solution
was then spread across a fine metal mesh as a thin
film. Using a bow-like construction they shot the
net into the liquid ethane so that the thin film of
water vitrified.
In 1984, Jacques Dubochet published the first images
of a number of different viruses, round and hexa-
gonal, that are shown in sharp contrast against the
background of vitrified water. Biological material
could now be relatively easily prepared for electron
microscopy, and researchers were soon knocking on
Dubochet’s door to learn the new technique.
From blobology to revolution
The most important pieces of cryo-EM were thus in place, but the images still had poor resolution. In
1991, when Joachim Frank prepared ribosomes using Dubochet’s vitrification method and analysed
1
2
3
The sample is
transferred to a metal
mesh and excess
material removed.
ETHANE
-196°
LIQUID
NITROGEN
5. DUBOCHET’S
VITRIFICATION METHOD
The sample forms a thin
film across the holes in the
mesh when it is shot into
ethane at about -190°C.
The water vitrifies
around the sample,
which then is cooled by
liquid nitrogen during
the measurements in
the electron microscope.
Dubochet generated the first images of viruses surrounded
by vitrified water in 1984. Image from Nature 308: 32-36.
6. 6(7) THE NOBEL PRIZE IN CHEMISTRY 2017 THE ROYAL SWEDISH ACADEMY OF SCIENCES WWW.KVA.SE
the images with his own software, he obtained a 3D structure that had a resolution of 40 Å. It was
an amazing step forward for electron microscopy, but the image only showed the ribosome’s conto-
urs. Frankly, it looked like a blob and the image did not even come close to the atomic resolution of
X-ray crystallography.
Because cryo-EM could rarely visualise anything other than an uneven surface, the method was
sometimes called “blobology”. However, every nut and bolt of the electron microscope has gradually
been optimised, greatly due to Richard Henderson stubbornly maintaining his vision that electron
microscopy would one day routinely provide images that show individual atoms. Resolution has
improved, Ångström by Ångström, and the final technical hurdle was overcome in 2013, when a new
type of electron detector came into use (figure 6).
Every hidden corner of a cell can be explored
Now the dream is reality, and we are facing an explosive development within biochemistry. There
are a number of benefits that make cryo-EM so revolutionary: Dubochet’s vitrification method is
relatively easy to use and requires a minimal sample size. Due to the rapid cooling process, biomolecules
can be frozen mid-action and researchers can take image series that capture different parts of a process.
This way, they produce ‘films’ that reveal how proteins move and interact with other molecules.
Using cryo-EM, it is also easier than ever before to depict membrane proteins, which often function as
targets for pharmaceuticals, and large molecular complexes. However, small proteins cannot be studied
with electron microscopy, but they can be visualised using NMR spectroscopy or X-ray crystallography.
After Joachim Frank presented the strategy for his general image processing method in 1975, a
researcher wrote: “If such methods were to be perfected, then, in the words of one scientist, the sky
would be the limit.”
Now we are there – the sky is the limit. Jacques Dubochet, Joachim Frank and Richard Henderson
have, through their research, brought “the greatest benefit to mankind.” Each corner of the cell can
be captured in atomic detail and biochemistry is all set for an exciting future.
Figure 6. The electron microscope’s resolution has radically improved in the last few years, from mostly showing shapeless blobs to
now being able to visualise proteins at atomic resolution. Image: Martin Högbom.