Scientific reports (2022). DOI: 10.1038 / s41598-022-11405-3 “width =” 685 “height =” 530 “/>

Negative staining method. (a) Virions are attached to a carbon support film. (b) A solution containing heavy metals (negative staining reagent) is digged onto the film. (c) Excess solution is removed and the sample is dried. (d) transmission electron microscopy (TEM) of heavy metal-coated virions gives (e) an inverse contrast image of the virus. Author: Koichi Sahiro et al, Scientific reports (2022). DOI: 10.1038 / s41598-022-11405-3

To see is to believe, or, for scientists, the beginning of understanding. Researchers can visualize atomically small details using transmission electron microscopy (TEM), exchanging electrons through a sample and recording their interactions to form an image. But such tiny samples can dodge electrons, so they need to be specially treated with heavy metals to ensure interaction. For example, in order to see viruses, the current standard is to pour a sample of the virus with a solution containing a radioactive, tightly controlled substance called uranyl acetate.


The images are clear, but the process of acquiring and storing the necessary radioactive solution of heavy metals can be a difficult barrier for researchers, said Masahira Sadakane, a professor of applied chemistry at Hiroshima University’s School of Advanced Science and Technology. Sadakan and his team recently discovered that non-radioactive treatment can produce the same clear, detailed images without the bureaucratic fuss of uranium acetate.

They published their findings on May 12 Scientific reports.

“Observing the morphology of the virus is very important virologyfor which TEM is the most widely used method because it allows direct visualization at the nanometer scale, but currently requires negative staining reagents containing heavy elements, “said Sadakan, author of the article. non-radioactive compounds for simple, fast and clear observations using traditional TEM are needed worldwide ”.

Currently, a commercially available alternative to radioactive uranyl acetate is a material known as phosphotungstic acid type “Kegin”. The molecule consists of a central unit of one phosphate and four oxygen, densely surrounded by tungsten and more oxygen. While the molecule is not radioactive, it is very acidic and must be neutralized before use, according to Sadakan. He also noted that the images he produces are less clear than those made with uranyl acetate. However, despite these shortcomings, the reagent belongs to a large family of similar – and perhaps the best – compounds.

We have studied phosphotungrate compounds and previously reported that the “Preisler type” can be used as a negative color reagent observe the fine structure of the bacteria, ”Sadakan said.

“Preisler-type molecules also include tungsten, oxygen and phosphate, but they are structurally arranged around an encapsulated positively charged ion, such as sodium or calcium. They have a different structure from Kegin-type compounds, resulting in a much more stable molecule produced as potassium. ».

Researchers used Preisler-type phosphotungrates to stain and image three types of bacterial viruses (phages) that infect bacteria. Morphological structures of them phages already well documented and provide a reliable link to verify the clarity of the images obtained during their study.

“Our results show that Preisler-type phosphotungrates are good negative staining reagents for virus surveillance,” Sadakan said. “They are easy to use as they are not radioactive and do not need to adjust the pH level and also provide clear images.”

The researchers plan to build on their findings to develop a series of non-radioactive negative staining reagents to monitor other viruses, as well as small organic particles such as proteins and more, Sadakan said.


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Additional information:
Koichi Sahiro et al, Preyssler-type phosphotungrate is a new family of negative staining reagents for TEM virus surveillance. Scientific reports (2022). DOI: 10.1038 / s41598-022-11405-3

Citation: New non-radioactive neutral reagent detects viruses in detail (2022, May 26), obtained on May 26, 2022 from https://phys.org/news/2022-05-non-radioactive-neutral-reagent-reveals-viruses . html

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