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Left: raw data; Right: smoothed image.

Sample description: Transversal cut of a native cocoon fiber produced by the domesticated Bombyx mori silkworm. This image clearly shows the structure of the fiber and the distribution of different components: two fibroin threads (green) surrounded by a sericin matrix (blue) embedded in an acrylic matrix (red). It also illustrates the non-circular shape of such natural fibers. This is the first Raman image of a silk fiber.

Experimental conditions:

Image obtained on a LabRAM HR system Grating: 600 lines/mm Objective: 100x (numerical aperture of 0.9) Laser wavelength: 514.5 nm of an Argon laser (water cooled) Optical density filter: 0.6, approx. 0.5 mW/cm2 at the sample. Pin hole diameter: 200 µm Slit: 100 µm Image size: 17x17 µm2; 1 µm step Acquisition time: 1x80 sec. Thickness of the microtomed cut : 1.5 µm

Work carrying out: Our group is particularly interested in studying protein conformation and orientation in silkworm and spider silk using Raman microspectroscopy. The high numerical aperture objectives, the high quality of the optics in the high resolution configuration allows one to obtain spectra with very good signal to noise ratio and to optimize the acquisition time for point by point imaging.