# Unveiling the molecular dynamics of a nitrile-containing 5-lipoxygenase-activating protein antagonist in primary macrophages through Raman spectroscopy

## TL;DR

The study uses Raman spectroscopy to track a drug in macrophages, revealing it accumulates in lipid droplets rather than its target site.

## Contribution

A novel method using nitrile groups as Raman tags to visualize drug localization in cells without labels.

## Key findings

- BRP-685 accumulates in lipid droplets, not at its membrane-bound target site.
- Lipid droplets may act as reservoirs for lipophilic drugs like BRP-685.
- Raman imaging tracks drug distribution in live cells at low concentrations.

## Abstract

The nitrile (–C

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N) functional group is a versatile pharmacophore motif that also serves as an intrinsic, bioorthogonal Raman tag in the silent wavenumber region (1800–2700 cm−1). Here, we exploit this dual functionality to track the potent nitrile-containing 5-lipoxygenase-activating protein (FLAP) antagonist BRP-685 in primary human macrophages using label-free spontaneous and stimulated Raman scattering. This approach enables direct intracellular localization at biologically relevant, low micromolar concentrations without chemical modification or external labels. Quantitative Raman imaging reveals that BRP-685 preferentially accumulates in lipid droplets, distinct from its membrane-bound target site at the nuclear envelope/endoplasmic reticulum. Multiplexed analysis with an alkyne-tagged lipid analog uncovers a unique distribution pattern, suggesting that lipid droplets act as intracellular reservoirs for highly lipophilic drugs.

The nitrile group is a versatile pharmacophore that also functions as an intrinsic, bioorthogonal Raman tag in the silent wavenumber region. This dual role allows visualization of the storage sites and sites of action of the FLAP antagonist BRP-685 within differently polarized macrophages.