# Coumarin-Based Photolabile Solid Support Facilitates Nonchromatographic Purification of RNA Oligonucleotides

## TL;DR

This paper introduces a new coumarin-based method for purifying RNA without using chromatography, using visible light instead of UV.

## Contribution

A visible-light-responsive coumarin anchor for RNA purification that avoids UV incompatibility with phosphorothioate backbones.

## Key findings

- The coumarin anchor was successfully used to purify a 20-nt poly-U RNA model.
- The method works for both structured and unstructured RNA with phosphodiester and phosphorothioate backbones.
- A 103-nt sgRNA was purified and shown to function correctly in CRISPR experiments.

## Abstract

We describe the synthesis and application of a coumarin-based
photocleavable
anchor for solid-phase synthesis and nonchromatographic purification
of RNA oligonucleotides. In contrast to standard nitroaryl anchors,
which are cleaved with ultraviolet (UV) light, the described construct
requires visible light (λ = 456 nm) for photocleavage. This
is especially important for RNAs that contain a phosphorothioate backbone,
which is not compatible with UV light. We optimized the synthesis
and purification process using a model 20-nt poly-U RNA and subsequently
applied it to structured and unstructured RNA oligonucleotides that
contain both phosphodiester and phosphorothioate backbones. Lastly,
we purified 103-nt sgRNA and checked its functional fidelity by CRISPR
experiments.