# A Dual Fluorescent-Raman Bioorthogonal Probe for Specific Biosynthetic Labeling of Gangliosides

## TL;DR

This paper introduces a new probe that can specifically label gangliosides in cells using both fluorescence and Raman spectroscopy, enabling detailed study of their biosynthesis and distribution.

## Contribution

The development of a dual fluorescent-Raman probe for selective ganglioside labeling and visualization in cells.

## Key findings

- The MM-JH-2 probe provides a unique Raman spectral signature for unambiguous ganglioside identification.
- The probe tracks ganglioside transport from synthesis to acidic compartments using fluorescence imaging.
- MM-JH-2 can distinguish cells with different ganglioside biosynthetic flux, including malignant vs. nonmalignant cells.

## Abstract

Gangliosides are sialic acid-containing glycosphingolipids integral to the cell membrane and are particularly abundant in the nervous system. Aberrant ganglioside metabolism contributes to pathological conditions including neurodegenerative diseases, lysosomal storage disorders, and cancer. Currently, tools to visualize and detect gangliosides are very limited and non-specific. Here, we describe a dual fluorescent and Raman-active ManNAlk derivative, phenanthrene-9-Pr4ManNAlk (MM-JH-2), capable of one-step selective labeling of gangliosides in cells. This modified ManNAlk derivative produces a biologically unique Raman spectral signature, which arise from the carbon-carbon triple bond augmented by conjugation to a fluorescent phenanthrene moiety. By using this dual probe, unambiguous identification is achieved within cells. Raman maps generated using the alkyne stretching frequency indicate a distribution of MM-JH-2 overlapping with intracellular membrane lipids. Using confocal fluorescence imaging, the cellular transport of labeled gangliosides was tracked from synthesis to recycling in the acidic compartments. Notably, MM-JH-2 can differentiate between cells that differ in ganglioside biosynthetic flux, such as malignant and nonmalignant cells, as well as distinguish between B cells and T cells. Thus, MM-JH-2 is a novel next-generation metabolic chemical reporter (MCR) that is Raman-active, fluorescent, and can be broadly applied to cellular studies investigating ganglioside biosynthetic flux.