Fig. 1: Whole-cell confocal Raman micro-spectroscopy of O-H stretch region.
From: Probing the structure of water in individual living cells
a Optical schematics of a home-built confocal micro-Raman system. We purposely underfilled the back aperture of a 20× objective (beam diameter is 9–10 mm) to spread the illumination volume (~ 2 µm × 2 µm × 10 µm) inside a single cell. Details in Supplementary Information. L: lens; LPD1, LPD2: long-pass dichroic beamsplitter; SP: short-pass filter; LP: long-pass filter. L1/L2 (f = 40/300 mm), L3/L4 (f = 150/50 mm), L5/L6 (f = 100/100 mm) (b) Comparison of Raman spectra of representative live HeLa cells and bulk liquid water, obtained at room temperature (24 °C) and 0.1 MPa (1 atm pressure) with 35 mW power on sample during 400 sec acquisitions. c Zoom-in view of Raman spectra with normalized 3400 cm−1 peak. A small but non-negligible discrepancy in spectra shape can be identified between live cells and bulk water. Shaded area depicts the standard deviation of 80 repeated measurements of 5-sec spectral acquisition.
