If you have an ACS member number, please enter it here so we can link this account to your membership. (optional)

ACS values your privacy. By submitting your information, you are gaining access to C&EN and subscribing to our weekly newsletter. We use the information you provide to make your reading experience better, and we will never sell your data to third party members.


Analytical Chemistry

Telltale Signatures Identify Emerging Flu Viruses

Analytical Chemistry: Raman spectroscopy can identify the surface proteins on different strains of influenza virus

by Jyoti Madhusoodanan
December 2, 2015

CORRECTION: This story was updated on Dec. 16, 2015, to correct Kwang-il Lim’s affiliation.

Every few years, new variants of the influenza virus emerge to join the common seasonal strains that circulate during flu season. Identifying these new strains quickly is crucial to combating them with improved, targeted flu shots. Researchers have now found a way to spot new flu virus strains easily using surface-enhanced Raman spectroscopy (SERS) (Anal. Chem. 2015, DOI: 10.1021/acs.analchem.5b02661).

Credit: Anal. Chem.
Gold nanoparticles hold a flu viral particle in place for surface-enhanced Raman spectroscopy (SERS). SERS detects proteins on the virus surface, producing unique spectra for different viral strains.
Schematic of a flu virus held by gold nanoparticles for analysis by surface enhanced Raman spectroscopy.
Credit: Anal. Chem.
Gold nanoparticles hold a flu viral particle in place for surface-enhanced Raman spectroscopy (SERS). SERS detects proteins on the virus surface, producing unique spectra for different viral strains.

One way scientists identify new viruses is using immunoassays such as ELISA, which requires having antibodies to a virus. Another is the polymerase chain reaction, which requires knowing something of its DNA sequence, notes Marc D. Porter of the University of Utah, who was not involved with the new work. To identify viral strains where DNA sequences and proteins may be unknown, Kwang-il Lim of Sookmyung Women’s University, Yeonho Choi of Korea University, and their colleagues, turned to SERS. In SERS, the material of interest is coupled to a metal surface—in this case, gold nanoparticles—and excited with laser light. The gold nanoparticles enhance the spectral signals the molecules emit. In the new study, researchers used copper sulfate to clump gold particles closer, creating a surface well-tuned to amplify emitted spectra from proteins on the outsides of viruses bound to the particles.

Working with noninfective forms of viruses to avoid infection risks, the team first demonstrated that influenza could be distinguished from a non-flu virus, vesicular stomatitis virus, by its spectrum. Then the team looked at different strains of flu.

Two surface proteins on flu viruses, hemagglutinin and neuraminidase, are typically used to identify subtypes and name them H1N1, H5N1, and so on. Analyzing tens of signals from H1N1 and a variant that emerged in 2009, the researchers identified specific peaks that corresponded to small differences in the amino acid sequences of these two proteins from the H1N1 and variant strains. These differences could serve as a signature of each strain’s surface H and N proteins, demonstrating that strains could be distinguished using SERS.

Then, they shuffled the genomes of the two H1N1 strains together to produce a novel flu strain, which had a unique spectrum combining peaks traceable to the two parent strains. “Our work shows that influenza viruses with genome re-assortment can produce unique Raman signals,” Choi says, so the method has the potential to identify newly emerging strains without needing immunoassays.

“To me, the most interesting part of the paper is the way the measurements themselves can be used to identify or recognize viral strains that you don’t know yet,” Porter says. But so far the method has only been tested with previously characterized viruses, he adds. Extending the technique to identify completely novel strains will require further work.

In future work, the researchers aim to sharpen the signals from viral proteins by improving the substrate surfaces. With additional experiments, this method could help identify Raman peaks characteristic of other influenza surface proteins such as H5, N3, and others, according to Choi.


This article has been sent to the following recipient:

Chemistry matters. Join us to get the news you need.