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We have verified if these results can be extended to not vegetable biological systems. For this pourpose, we have studied the Delayed Luminescence emitted by type I collagen in solution (Sigma C4243) and Achilles’ bovin tendon. Type I collagen is been chosen because it has a well defined elementary structure organized until macroscopic levels.  The collagen has a primary structure obtained by the sequence (Gly-XY) n where Gly is the amino acid glycine, X and Y are most often the imino acid proline and hydroxyproline. The amino acids are linked together by a bond said polypeptide which involves the release of a water molecule. The peptide groups are linked to each other to form a polypeptide chain twisted (helical) around itself to form a rigid cylinder. The secondary structure of collagen is dextrorotatory consists of three  left-handed helices wrapped around the same axis. These secondary structures are further aggregated to one another to form structures fibrils and these collagen fibers. Collagen in its native state exists only in hydrated: water molecules mediate some networks of hydrogen bonds intra-chain and inter-chain contributing to stability and self assembling of the structure. Infact type I collagen is constituted by macromolecoles wich form a one-dimensional system, with unit cell formed by a tripeptide, long-range order, capability of self-organization. These characteristics can favore the existence of collective excitations. From a point of view of the electronic structure, the secondary structure of the collagen (the model for the interaction protein-water) can be seen as a system type semiconductor nearly one-dimensional with the valence band full, the empty conduction band separated by a gap of finite amplitude in which you can find metastable energy levels associated with the existence of collective electronic states: excitonic states in general and in particular solitons. 

We conducted emission measurements of DL varying the level of hydration of the collagen, highlighting that, while the fluorescence emission is not affected by the level of hydration of native samples, this does not happen for the DL. The data showed that the DL suddenly changes when the level of dehydration is such that you are removing the water more closely linked to polypeptide chains. The measurements were related to impedance measurements.  The dielectric permittivity has been measured  in the frequency range 500Hz-10MHz as a function of the water content. Moreover the values of dielectric permittivity for low frequency are very high, like in some ferroelectric materials, and can not be explained using classical models. Changes in the dielectric permittivity as a function of the water content are similar to changes of the total number of photons emitted in DL experiments.

We have verified if these results can be extended to not vegetable biological systems. For this pourpose, we have studied the Delayed Luminescence emitted by type I collagen in solution (Sigma C4243) and Achilles’ bovin tendon. Type I collagen is been chosen because it has a well defined elementary structure organized until macroscopic levels. The collagen has a primary structure obtained by the sequence (Gly-XY) n where Gly is the amino acid glycine, X and Y are most often the imino acid proline and hydroxyproline. The amino acids are linked together by a bond said polypeptide which involves the release of a water molecule. The peptide groups are linked to each other to form a polypeptide chain twisted (helical) around itself to form a rigid cylinder. The secondary structure of collagen is dextrorotatory consists of three left-handed helices wrapped around the same axis. These secondary structures are further aggregated to one another to form structures fibrils and these collagen fibers. Collagen in its native state exists only in hydrated: water molecules mediate some networks of hydrogen bonds intra-chain and inter-chain contributing to stability and self assembling of the structure. Infact type I collagen is constituted by macromolecoles wich form a one-dimensional system, with unit cell formed by a tripeptide, long-range order, capability of self-organization. These characteristics can favore the existence of collective excitations. From a point of view of the electronic structure, the secondary structure of the collagen (the model for the interaction protein-water) can be seen as a system type semiconductor nearly one-dimensional with the valence band full, the empty conduction band separated by a gap of finite amplitude in which you can find metastable energy levels associated with the existence of collective electronic states: excitonic states in general and in particular solitons. 

We conducted emission measurements of DL varying the level of hydration of the collagen, highlighting that, while the fluorescence emission is not affected by the level of hydration of native samples, this does not happen for the DL. The data showed that the DL suddenly changes when the level of dehydration is such that you are removing the water more closely linked to polypeptide chains. The measurements were related to impedance measurements.  The dielectric permittivity has been measured  in the frequency range 500Hz-10MHz as a function of the water content. Moreover the values of dielectric permittivity for low frequency are very high, like in some ferroelectric materials, and can not be explained using classical models. Changes in the dielectric permittivity as a function of the water content are similar to changes of the total number of photons emitted in DL experiments.

The experimental results agree to a theoretical model which assimilates the structure of collagen, with its chains of water bound by hydrogen bonds, to a one-dimensional crystal with different vibration modes dependent on the degree of hydration:
- In the case of dehydrated collagen it is assumed the existence of an optical phonon mode;
- In the case of collagen low hydration it is supposed the existence of two optical phonon modes;
- In the case of high hydration of it supposed the existence of optical modes and acoustic.

Other interesting results were obtained from measurements on solutions of collagen in water (with corrected PH) left to polymerize at constant temperature. The solution evolves from the sol state to the gel one. As the collagen polymerization progresses, an increase of the DL emission is measured. These results show that the individual monomer protein exhibits no emission in the DL, but the structure in which they self-assemble may instead emit a signal not negligible.

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