*4.5. Electron Microscopy*

For SEM analysis lyophilized collagen samples were placed on stubs by using a double face adhesive tape, covered with a thin layer of gold using a Bal-tec SCD 004 sputter coater and examined under either a Cambridge Stereoscan 240 scanning electron microscope or a Philips Quanta Inspect (FEI Company) scanning electron microscope with a tungsten filament (25 kV).

For TEM analysis a small amount of sample dispersed in distilled-deionized water was placed on a Formvar-coated grid and stained with 2% aqueous solution of PTA (phosphotungstic acid hydrate; pH adjusted to 3.3 by using a solution of 1 N NaOH), which revealed the banding pattern of the fibrils, but not the whole periodicity. Each grid was examined under a Philips CM10 transmission electron microscope equipped with an Olympus Veleta digital camera.

#### *4.6. Infrared Spectroscopy*

IR spectra of lyophilized collagen samples were measured on a Bruker Tensor 27 FT-IR spectrometer using the attenuated total reflection (ATR) method, at room temperature, in the range of 500–4000 cm<sup>−</sup>1.
