Quantitative mapping of triacylglycerol chain length and saturation using broadband CARS microscopy

Abstract

Lipid droplets (LDs) are highly dynamic organelles that store neutral lipids, primarily triacylglycerols (TAGs), and are found in many cell types. While their primary function is to store excess energy, LDs are also modified in different disease states and during developmental processes. In many cases, not only the presence, but also the composition, of LDs can be equally important. In humans, LD composition has been linked to diseases such as type 2 diabetes; in plants and yeast, LD composition is relevant for engineering these organisms into biological factories in, e.g., algal bioenergy or food oil production.Therefore, lipid analysis of biological LDs with high speed and accuracy in situ is a very active area of research. Here we present an approach for in situ, quantitative TAG analysis using label-free, coherent Raman microscopy to decipher LD TAG composition in different biochemically complex samples. Our method allows direct visualization of inter-LD compositional heterogeneity of physiological quantities -TAG chain length and number of C=C bondswith sub-micrometer spatial resolution within 5-100 milliseconds. Combined with virtually no sample preparation, this approach should enable rapid and accurate TAG LD analysis for a variety of applications.

Lipid-driven condensation and interfacial ordering of FUS

“…To that end, we used molecular microscopy via nonlinear Raman scattering to quantify the composition of protein-lipid clusters. We have previously used quantitative BCARS microscopy for measurements of protein structure and composition in pure FUS LC BCs, peptide-polymer phase-separated systems ( 28 ), and lipid droplets ( 23 , 29 ). BCARS can also shed light on the subtle differences between DOPS and DOPG SUVs from, e.g., lipid packing ( 29 ), that potentially cause the differences in turbidity or FRAP seen for FUS LC–lipid clustering.…”

The role of ApoE-mediated microglial lipid metabolism in brain aging and disease

“…Many studies of microglial immunometabolism rely on primary microglial cultures from animal models. Employing new chemical imaging techniques, such as Coherent Anti-Stokes Raman Scattering (CARS) microscopy, to analyze temporal or spatial alterations in LDs will be important to bridge the gap in our understanding of microglial lipid metabolism [115,116] . Moreover, the evolving mass spectrometry techniques can allow us to apply the spatiotemporal characterizations of lipid signaling via mass spectrometry imaging [117,118] or use lipidomics approaches to profile highly diverse lipid species in microglia.…”