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Researchers use DNA to take pictures of cells, Cell

To observe a cell, the standard approach is to use a microscope. Now researchers (Joshua Weinstein of the Broad Institute of in Cambridge, Massachusetts, and colleagues) have developed a new optic-free technique-DNA microscopy-that can take a snapshot of a cell by copying the DNA in the cell and observing their interactions.
 
To start with, the DNA versions of the RNA molecules in a cell were created. Some other short pieces of DNA were attached to the DNA duplicates as tags. Then chemicals were added to the system to duplicate the DNA with tags and thus a huge amount of such DNA was produced. The DNA duplicates would start to drift away from their original location as the number increased. Some of the DNA would run into each other as they diffuse and link up to form a unique DNA label. After the process was done, researchers grinded up the cell and analyzed the DNA labels created by such encounters. A computer algorithm was used to infer the position of the original DNA molecule based on the data.
 
In short, the original DNA molecules copied from the RNA molecules acted as radio towers that generate radio signals in the form of duplicated DNA molecules with tags. The communication between the towers took the form of DNA linkage and left unique DNA labels. These labels were then studied by researchers to determine the original position of the radio towers.
 
Researchers tested the accuracy of this method with cells that carry genes for either green or red proteins, and DNA microscopy successfully distinguished the genetically distinct red and green cells (as shown in the picture above). According to Weinstein, DNA microscopy can potentially be used to distinguish among cells with DNA differences, such as tumor cells with specific mutations or immune cells, which cannot be done by optical microscopy. The method sounds very cool, but it is still very immature. Researchers still need to determine the technique’s full capabilities.

A new way to measure pressure

Last month, the new definition of four basic units-the ampere, the kilogram, the kelvin, and the mole-took effect. Now researchers focused on the next target of the metrology evolution: pressure. Conventionally, pressure is defined as force per unit area and has unit newton per meter squared. For nearly 400 years, the value of pressure was measured by mercury-based instruments called manometers. But now, researchers from NIST (the US National Institute of Standards and Technology) developed a new and high precise method of measuring pressure by treating pressure as energy density, which is an equivalent physical description to force per unit area because it is derived from the same combination of the SI base units.
 
NIST’s new pressure sensor, called a fixed-length optical cavity (FLOC), compares the speed of a laser traveling through a gas-filled cavity with that of an identical beam in a vacuum. The speed of light varies with the density of the gas in a way that quantum chemists can calculate based on the properties of atoms. For a steady-temperature system, metrologists can combine these density measurements — effectively the number of particles in the cavity — with the Boltzmann constant, which relates temperature to kinetic energy. This calculates the gas’s ‘energy density’, which is equivalent to pressure.
 
This new method not only can help us get rid of mercury but also provides a way to measure pressure directly, using a fundamental constant of nature, without relying on previous measurements of other quantities, such as the density of the mercury in conventional manometers. In theory, it could also allow anyone to measure pressure from first principles without “the tedious work of” a chain of calibrations to a primary standard that is currently required, says Bo Gao, a Chinese metrologist.

How goats protect their teeth against dirt in their food, Mammalian Biology

 
Despite the fact that goats chew a large amount of sand and dust in their dishes, their teeth never seem to wear down. To investigate this phenomenon, scientists fed 28 goats diets with different amounts of grit for 6 months. Then they took CT scans of the stomach of the goats and, after slaughtering them, analyzed the contents of their digestive tracts.
 
Like cows and other ruminants, goats have a four-compartment stomach: large pieces of food go into the upper compartment, where they are regurgitated for chewing, and small pieces of food go straight to one of the lower stomachs for digestion. The study shows that sand and dirt sink directly to the lower stomach and are never brought up for chewing. That means the upper stomach helps “wash” grasses and plants free of grit, just like we wash our greens, saving ruminant teeth from wear.
Watch artificial intelligence predict Conan O’Brien’s gestures just from the sound of his voice
ISP Sci. Rev. 24 (2019)
Editor: Rossoneri
Integrated Science Program
Northwestern University






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