11 September 2006 Growth of single yeast cells in an optical trap monitored by Rayleigh and Raman scattering
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One of the most promising ways to study the biochemistry of single floating cells is to combine the techniques of optical tweezers and Raman spectroscopy (OTRS). This can reveal the information that is lost when ensemble averages are made over cell populations, like in biochemical assays. However, the interpretation of the acquired data is often ambiguous. Indeed, the trapped living cell continues to move and rotate in the optical trap not only because of the Brownian motion, but also because of its inherent biological motility and the variation of its shape and size. This affects both Rayleigh and Raman light scattering. We propose the use of Rayleigh scattering to monitor the growth of a single optically trapped yeast cell, while OTRS measurements are being performed. For this purpose, we added a quadrant photodiode to our OTRS setup. The cell orientation in the optical trap is shown to vary as the cell growth proceeds, especially when it becomes asymmetrical (budding) or it changes its size or shape considerably (living and growing cell). Control experiments, performed using heat-treated cells and polystyrene beads, confirm that this behavior is a consequence of the cell growth. These measurements have to be taken into account in the interpretation of Raman spectra so as not to incorrectly attribute variations in the spectra to change in the biochemical constituents of the cell if they are in fact due to a change of the orientation of the cell in the trap.
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Gajendra P. Singh, Gajendra P. Singh, Giovanni Volpe, Giovanni Volpe, Raul A. Hijano, Raul A. Hijano, Dmitri V. Petrov, Dmitri V. Petrov, } "Growth of single yeast cells in an optical trap monitored by Rayleigh and Raman scattering", Proc. SPIE 6326, Optical Trapping and Optical Micromanipulation III, 632629 (11 September 2006); doi: 10.1117/12.679371; https://doi.org/10.1117/12.679371

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