Objective:

To assess whether Raman spectroscopy with spectral barcoding can distinguish RNA from SARS-CoV-2 variants and subvariants.

Approach:

• Samples: Researchers analyzed extracted RNA from the original Japanese isolate and 19 variants or subvariants, including 12 Omicron subvariants.
• Measurement: A confocal Raman spectrometer with a 532-nm laser collected spectra across 400–1,800 cm⁻¹; 10 measurements from different locations were averaged for each sample.
• Analysis: The team computationally deconvolved overlapping spectral bands and converted selected features into barcodes, then compared results with predicted RNA secondary structures.

Key Findings:

• Raman barcodes differed across all 20 samples, while principal component analysis distinguished only some strains.
• Spectral differences were associated with RNA backbone conformation, phosphate bonds, base pairing, and secondary structure.
• Signals near 432 and 1,460 cm⁻¹ were associated with structural features including hairpin-loop number and stem length.
• The method detects structural effects of sequence variation; it does not sequence RNA or identify individual nucleotide substitutions.

Interpretation:

The authors presented Raman analysis as a potential complement to next-generation sequencing for studying viral RNA structure, not as a replacement.

Limitations:

• The proof-of-concept study used a finite set of purified RNA samples from cell-culture supernatants.
• Recognition of previously unseen variants or strains differing by only a few mutations remains unknown.
• Performance with clinical specimens containing host material and variable viral RNA concentrations has not been tested.

Sources:

• Article context provided by the user