New Microscopy Techniques Reveals Inner Workings of Cells As Never Before [I]

 Microscopy  

Researchers have developed a suite of new optical techniques that smash through the diffraction barrier in microscopy and allow us to see, in detail, the inner workings of cells. New fluorescent tags are also used that light up structures within the dense darkness inside cells. These new optical approaches are making what was once an invisible part of ourselves, visible.

New super-resolution microscopy techniques are challenging what many scientists think about cells, and according to some, the major breakthroughs they will bring about are only at the knee of the curve.

Inside a single cell there may be more than 10,000 different proteins; thousands of the energy factories called mitochondria; and half a billion actin molecules, which are used to construct the scaffolding that supports cells, help it move and change shape.

Nerve cells that send electrical signals are coated in a protective sheath of myelin (like the insulation surrounding electrical wires), without which the elaborate, efficient nervous system of vertebrates might never have evolved. Precisely how myelin sheaths form is still a mystery, and one that scientists would desperately like to solve, since faulty myelin has been implicated in several neurological diseases including multiple sclerosis. This glial cell will extend to wrap a nerve in myelin, a task likely dependent on the actin skeleton (green) and the associated actin proteins (red). Image Source: B. Zuchero and A. Olson, Barres Lab/Stanford

Up until recently, the internal machinery of cells  has remained largely hidden from sight. Viewed through microscopes similar to the person who first discovered and named cells, 'cells,'  Robert Hooke, most cells are see-through and colorless.

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This transparency is mainly due to diffraction, the bending of light, objects smaller than about 250 nanometers — the size of the smallest bacteria — are very blurry when viewed through an optical microscope, if they can be seen at all. 

On top of that, most proteins are merely a few nanometers across. This diffraction barrier, explicitly defined by German physicist Ernst Abbe in 1873, has made it virtually impossible to clearly see what actually happens in and on an individual cell.

In the last few decades the diffraction barrier has begun to be broken down.

At the top of this page, as an example, scientists are expanding their view of mitochondria, long known for their energy-producing role in the cell.  Blurred by conventional techniques (left), mitochondria’s details are revealed through super-resolution microscopy (shown color-coded by depth, center, and in cross section at right). (Image Source: Zhuang Lab/Harvard/HHMI).

Scientists have developed a suite of new optical techniques that circumvent the diffraction barrier and allow us to peer into the inner workings of nature. New fluorescent tags that light up structures in the dense darkness inside a cell are among the  new optical approaches produce detailed images of what was once invisible.

The tiny diameter and high density of actin filaments are visible in the sheetlike protrusions at this monkey kidney cell’s edge (color-coded by depth, red farthest away). Scientists are still trying to figure out precisely how these sheets form and connect to the cell’s interior so they can understand more about how cells travel. Image Source: K. Xu, H.P. Babcock and X. Zhuang/Nature Methods 2012

By capturing the inner workings of a cell and interactions between cellular neighbors, scientists can now connect knowledge acquired from genetic experiments to actual structures and activities they can see. Discoveries will lead to new hypotheses and experiments that will further our understanding of animal development and function, and what can go wrong.

But for now, we can all enjoy stunning, unprecedented views of the cellular world.

Next, examine the new techniques that are bringing about the revolution in super-resolution microscopy.


SOURCE  Science News

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