RM1 semi empirical and DFT: B3LYP/3-21G theoretical insights on the confocal Raman experimental observations in qualitative water content of the skin dermis of healthy young, healthy elderly and diabetic elderly women's.

In the confocal Raman spectra of skin dermis, the band area of proline and hydroxyproline in the fingerprint spectral region of 800-1000 cm(-1), where their vibrational modes are assigned, varied according to the age of the woman volunteers. The other aging effect observed in the Raman spectra is in the Amide I band in the spectral region between 1580 and 1720 cm(-1), where a softening in the Raman shift and intensity variation is detected depending of the vibrational groups. It is well known that the water quantity in healthy human skin dermis increases with age. However, in the elderly with diabetic disease, the increased sugar content directly affect the proline and hydroxyproline peaks as well as the water content in the dermis. The first approach in this work was theoretically modeling these systems using the RM1 semi empirical method, which represent proline and hydroxyproline interacting with one to four water molecule and with glucose. This task predicted how many hydrogen bonds were formed with the two amino acids and glucose. The subsequent model was built using DFT/B3LYP:3-21G procedures considering the amino acids chain formed by hydroxyproline and proline alone, which interact with one and four water molecules. We analyzed the dipole moment and polarizability variation to determine the hydrogen bonds in these systems. We chose the DFT/B3LYP:3-21G method to assign the vibrational modes of the skin dermis as a way to correlate the experimental trends. To explain the profile of lower intensity in the hydroxyproline and proline spectral region in diabetic elderly women, we proposed a chemical reaction of water interchange between the bonding amino acids and glucose, and we considered also the natural decreasing of collagen due to the glycation process. Theoretical results agree well with the observed experimental results.