Methods and protocolsJul 24, 2026

An Easy Way to Measure the Length of mRNA Tail Sequences

mRNA Technology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Jul 25, 2026

Abstract

An accelerated method can instantly determine the average length of the poly(A) tail in synthetic mRNA.

The poly(A) tail is crucial for optimal stability and translation of mRNA in vaccines and drugs.
Current methods for measuring poly(A) tail length are complex and require specialized technologies.
The new method utilizes a fluorescent oligonucleotide that indicates poly(A) sequence availability.
Fluorescence signal correlates with the amount of poly(A) present, allowing for rapid assessment.
This technique is applicable in various laboratory settings for mRNA analysis in research and clinical trials.

Simplified

Synthetic mRNA produced by in vitro transcription is the active pharmaceutical ingredient of approved vaccines and of many drugs under development. It typically contains a 3' poly(A) tail required for optimal stabilization and translation of the mRNA. The average length of the poly(A) tail in the produced mRNA cannot be precisely predicted and consequently must be measured using complicated technologies such as reverse transcription and sequencing or cleavage of the poly(A) tail and analysis by capillary electrophoresis or mass spectrometry. We report an accelerated method to evaluate the average poly(A) tail length in synthetic mRNA, which benefits from the fact that thiazole orange is fluorescent only when in close proximity of nucleic acid. An oligo(dT)₁₂ oligonucleotide having thiazole orange at its extremities emits a fluorescence signal proportional to the amount of poly(A) sequence available. Using a titration curve made with known amounts of poly(A) RNA oligonucleotide, the thiazole orange oligo(dT)₁₂ oligonucleotide can instantly indicate the average length of the poly(A) tail in an mRNA sample. This fast and easy method can be used in any laboratory to determine the size of the poly(A) tail in in vitro-transcribed mRNA produced for research, pre-clinical studies and clinical trials.

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An Easy Way to Measure the Length of mRNA Tail Sequences

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