Vibrational Raman spectra were acquired with a custom confocal Raman microscope. The system was built in back-scattering geometry using an Olympus IX70 inverted research microscope. The excitation source is a narrow linewidth, 785 nm diode laser (Innovative Photonic Solutions, Monmouth Junction, New Jersey) that delivers 45 mW maximum power onto the sample. The excitation laser beam is first expanded and collimated using a telescope (, ), reflected off of a dichroic mirror (Semrock, 785 nm RazorEdge) into the microscope to fill the back aperture of a water immersion IR objective (Olympus, Center Valley, Pennsylvania, UPlanSApo IR, ). The objective focuses the beam onto the sample with a focal spot measured to be . The scattered radiation is collected and collimated by the same objective lens and passes back through the dichroic. To further reject the inelastically scattered photons, the collimated beam is passed through a long-pass filter (Semrock, Rochester, New York, 785 nm Razor Edge Ultrastep) with a cutoff at 786.7 nm and a rejection OD of 6. The signal beam is then focused with a lens, , onto the center of a pinhole of diameter, , to achieve confocal confinement. The pinhole is imaged with a demagnifying telescope (, ) onto the entrance slit of a Czerny-Turner style imaging spectrograph (Acton SP2300 series, Princeton Instruments, Trenton, New Jersey). A grating spectrally disperses the signal onto the sensor plane of a back-illuminated, cooled CDD camera (Pixis 100, Princeton Instruments, Trenton, New Jersey). A flipper mirror is inserted before the long-pass filter in order to obtain a white light image of the sample on a CMOS camera for alignment. Multiple micro-Raman point measurements were acquired on intracellular LDs for each sample using a motorized scanning stage (ASI Inc. Eugene, Oregon, MS-2000) controlled by custom software written in C. Each point Raman spectra was obtained by averaging five acquisitions each with an integration time of 20 s.