N1-Methoxymethyl Pseudouridine: Properties & mRNA Research Guide

N1-Methoxymethyl pseudouridine is a chemically modified nucleoside analog of pseudouridine bearing a methoxymethyl protecting or modifying group at the N1 position, of interest in mRNA research for its potential to modulate innate immune recognition and translational efficiency.

Chemical Class

Modified nucleoside (pseudouridine analog)

Modification Site

N1 position of pseudouridine

Modifying Group

Methoxymethyl (MOM) group at N1

Primary Research Application

mRNA modification and nucleoside chemistry research

Aladdin SKU

N1426081

Reference Catalog Cross-reference

MCE-TJY: HY-152342

Background and Chemical Identity

Pseudouridine (Ψ) is the most abundant naturally occurring RNA modification, differing from uridine by a C-glycosidic bond between the C5 position of the uracil base and ribose, rather than the canonical N1-glycosidic bond. This rearrangement frees the N1 nitrogen, creating a unique hydrogen-bond donor site that influences RNA secondary structure and protein interactions.

N1-Methoxymethyl pseudouridine is a synthetic derivative in which a methoxymethyl (MOM) group is installed on the N1 nitrogen of pseudouridine. The MOM group is a well-established protecting group in organic synthesis and can also serve as a stable chemical modification that alters the electronic environment and steric profile of the nucleobase. This structural change distinguishes N1-methoxymethyl pseudouridine from both natural pseudouridine and the widely studied N1-methyl pseudouridine (m1Ψ), making it a subject of interest for structure–activity relationship (SAR) studies in nucleoside and mRNA research.

Researchers investigating modified nucleosides for therapeutic mRNA applications assess such analogs for their capacity to evade pattern-recognition receptors such as Toll-like receptors (TLR7 and TLR8), which recognize exogenous single-stranded RNA and trigger innate immune responses.

Rationale for N1-Position Modification of Pseudouridine

The decision to modify the N1 position of pseudouridine is grounded in mechanistic RNA biology. In natural pseudouridine, the free N1-H is implicated in enhanced base-stacking and hydrogen-bonding interactions that stabilize mRNA structure. However, in the context of in-vitro-transcribed (IVT) mRNA, the presentation of unmodified or partially modified nucleosides can activate innate immune sensors.

Introducing a bulky or polar substituent such as a methoxymethyl group at N1 may accomplish several goals: (1) sterically shield the nucleobase from recognition by immune-sensing proteins; (2) modulate the pKa and tautomeric equilibrium of the uracil ring; and (3) potentially affect Watson–Crick face geometry during ribosomal decoding, influencing translational fidelity and yield.

Compared to N1-methyl pseudouridine, the methoxymethyl group is larger and introduces an ether oxygen that may participate in additional polar interactions. This makes N1-methoxymethyl pseudouridine a distinct chemical probe for dissecting the contribution of N1 substitution size and polarity to biological activity. Such SAR data are valuable for rational design of next-generation modified nucleotides for mRNA therapeutics.

Research Applications and Handling Guidelines

mRNA Transcription Studies: N1-methoxymethyl pseudouridine may be incorporated into IVT reactions as a UTP analog to produce modified mRNA transcripts. Researchers should validate incorporation efficiency using HPLC or mass spectrometry, as T7 or other RNA polymerases may show variable tolerance for bulky N1-substituted pseudouridine analogs. Optimization of the UTP:analog ratio is typically required.

Immunogenicity Assessment: Modified transcripts can be evaluated in cell-based assays (e.g., HEK-Blue TLR reporter cells, human PBMCs) to measure cytokine induction and innate immune activation relative to unmodified and m1Ψ-modified controls.

Translational Efficiency: Capped and polyadenylated mRNA incorporating N1-methoxymethyl pseudouridine should be assessed for protein expression in relevant cell lines using luciferase or GFP reporters before application to target proteins.

Storage and Handling: As with other modified nucleosides, N1-methoxymethyl pseudouridine should be stored according to manufacturer specifications, typically at −20 °C, protected from light and moisture, dissolved in appropriate anhydrous solvents (e.g., DMSO or nuclease-free water) at recommended concentrations. Avoid repeated freeze-thaw cycles to maintain compound integrity.

Safety: Consult the Safety Data Sheet (SDS) prior to handling. Standard laboratory PPE (gloves, eye protection, lab coat) is recommended. Dispose of waste in compliance with institutional and local regulations.

Comparison with Related Pseudouridine Modifications

Understanding N1-methoxymethyl pseudouridine requires contextualizing it within the landscape of pseudouridine-based modifications used in RNA research:

• Unmodified Pseudouridine (Ψ): Improves mRNA stability and reduces some innate immune activation compared to uridine, but free N1-H remains available for interactions.
• N1-Methyl Pseudouridine (m1Ψ): Currently the most clinically validated modified nucleoside for mRNA therapeutics (used in approved COVID-19 mRNA vaccines). Blocks N1-H with a methyl group, substantially reducing TLR activation and improving translation.
• N1-Methoxymethyl Pseudouridine: Introduces a larger MOM substituent at N1. Biological properties relative to m1Ψ are under investigation; this compound serves primarily as a research tool for SAR studies and exploratory mRNA platform development.
• Other Analogs (e.g., 5-methoxyuridine, N1-ethyl pseudouridine): Represent additional points in chemical space for tuning immune evasion and translational performance.

Researchers selecting among these analogs should consider polymerase compatibility, the degree of immune evasion required, and the availability of biochemical and translational efficacy data for the specific application.

Frequently asked questions

What distinguishes N1-methoxymethyl pseudouridine from N1-methyl pseudouridine (m1Ψ)?

Both compounds bear a substituent at the N1 position of pseudouridine that blocks the free N1-H. However, N1-methoxymethyl pseudouridine carries a methoxymethyl (–CH2OCH3) group, which is larger and contains an ether oxygen compared to the simple methyl group of m1Ψ. This difference in steric bulk and polarity may influence polymerase incorporation efficiency, ribosomal decoding, and immune recognition, making N1-methoxymethyl pseudouridine a useful research probe for structure–activity relationship studies.

Can N1-methoxymethyl pseudouridine be used directly in IVT reactions?

N1-methoxymethyl pseudouridine may be evaluated as a UTP analog in IVT reactions, but researchers should expect that RNA polymerase tolerance for bulky N1-substituted analogs may differ from that for canonical UTP or m1Ψ-TP. Systematic optimization of nucleotide ratios, reaction conditions, and purification steps is advised, and incorporation should be confirmed by LC-MS or similar analytical methods before downstream biological experiments.

How should N1-methoxymethyl pseudouridine be stored to ensure stability?

N1-methoxymethyl pseudouridine should be stored at −20 °C, protected from light and moisture, in accordance with the manufacturer's SDS and certificate of analysis. Stock solutions should be prepared in an appropriate solvent such as DMSO or nuclease-free water and aliquoted to avoid repeated freeze-thaw cycles, which can degrade sensitive nucleoside compounds over time.

What analytical methods are recommended for purity verification of this compound?

Purity of N1-methoxymethyl pseudouridine is typically assessed by reverse-phase HPLC with UV detection at 254 nm or 260 nm, complemented by LC-MS to confirm molecular identity. Nuclear magnetic resonance (NMR) spectroscopy (1H and 13C) provides definitive structural confirmation. Researchers should request a certificate of analysis (CoA) from the supplier for lot-specific purity data.

References

1. Karikó K, Buckstein M, Ni H, Weissman D. Suppression of RNA recognition by Toll-like receptors: the impact of nucleoside modification and the evolutionary origin of RNA. Immunity. 2005;23(2):165-175. doi:10.1016/j.immuni.2005.06.008
2. Karikó K, Muramatsu H, Welsh FA, et al. Incorporation of pseudouridine into mRNA yields superior nonimmunogenic vector with increased translational capacity and biological stability. Mol Ther. 2008;16(11):1833-1840. doi:10.1038/mt.2008.200
3. Andries O, Mc Cafferty S, De Smedt SC, et al. N1-methylpseudouridine-incorporated mRNA outperforms pseudouridine-incorporated mRNA by providing enhanced protein expression and reduced immunogenicity in mammalian cell lines and mice. J Control Release. 2015;217:337-344. doi:10.1016/j.jconrel.2015.08.051
4. N1-Methoxymethyl pseudouridine. Aladdin Scientific product page, SKU N1426081. Cross-reference: MCE-TJY HY-152342.

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