Ion-Pair Reversed-Phase Liquid Chromatography Method for Analysis of mRNA Poly(A) Tail Heterogeneity

Significance of the Topic

The poly(A) tail at the 3′ end of messenger RNA plays a pivotal role in transcript stability and translational efficiency. In emerging mRNA-based therapeutics and vaccines, precise characterization of poly(A) tail length distribution is critical for ensuring product consistency and performance.

Goals and Overview

This study aimed to establish a robust ion-pair reversed-phase liquid chromatography (IP RP LC) with ultraviolet detection method to resolve and quantify heterogeneity in mRNA poly(A) tails. Key objectives included liberation of the poly(A) region via enzymatic digestion, high-resolution separation of length variants up to ~150 nucleotides, and length assignment through calibrated retention times.

Methodology and Instrumentation

Messenger RNA samples were digested with RNase T1 to cleave after guanine residues, releasing the intact poly(A) tail. A subsequent phosphatase treatment removed terminal phosphates. Clean-up was performed using Oasis HLB µElution plates. Separation was achieved on a Waters ACQUITY Premier UPLC system equipped with SM-FTN and QSM units and inline PDA detection at 260 nm. The column was an ACQUITY Premier Oligonucleotide BEH C18 300 Å (2.1 × 150 mm, 1.7 µm) maintained at 60 °C. A binary ion-pairing mobile phase containing 100 mM octylammonium acetate in acetonitrile/HFIP gradients was employed at 0.3 mL/min over 40 minutes.

Main Results and Discussion

Optimized conditions provided n/n-1 resolution for oligoribonucleotides up to approximately 150 nt. A synthetic 100 nt oligo(A) standard and its shorter impurities were used to construct a linear calibration of retention time versus chain length. Application to RNase T1 digests of EPO and Fluc Beta mRNA revealed dominant poly(A) species at 124 nt and 128 nt, respectively. Results were corroborated by complementary LC-MS and size-exclusion UV analyses.

Benefits and Practical Applications

• High-resolution profiling of poly(A) length distributions for quality control.
• UV-based detection enables straightforward implementation in regulated labs.
• Calibration with synthetic standards allows accurate length assignment.

Future Trends and Opportunities

Advancements may include integration with mass spectrometry for detailed sequence analysis, automated sample preparation workflows, novel stationary phase chemistries for improved resolution beyond 150 nt, and expanded use of complementary nucleases to interrogate adjacent regions.

Conclusion

We report a robust IP RP LC-UV platform capable of resolving and quantifying mRNA poly(A) tail heterogeneity up to ~150 nt. This method supports critical quality attributes in mRNA therapeutic development, offering reliable, calibrated, and reproducible length measurements using standard chromatographic equipment.

Reference

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