Analysis of interaction between dental structural protein and adhesive component substances by circular dichroism measurement

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In this project entitled "Analysis of interaction between dental structural protein and adhesive component substances by circular dichroism measurement," a circular dichroism (CD) technique was introduced to the dental research field to reveal the detailed interaction between collagen and dental-adhesive-related substances at a molecular level, and several important findings have been obtained as follows.1. CD measurements revealed a reversible two-state structural transition of a water-soluble collagen caused by pH change of the media. At pH 3, the collagen had a conformation similar to poly(Pro)II and a DSC measurement showed a distinct endothermic peak, both indicating that the collagen was not denatured at a weakly acid pH of 3. Though an existence of hydrophobic region was expected by the formation of aggregates of the collagen at a neutral pH, no such region was proven by a fluorescence spectroscopy experiments using pyrene as a hydrophobic probe.2. Alcoholic compounds did not af … More fect the secondary structure of the collagen, but they either lowered or raised the structural stability (denaturation temperature) of the collagen depending on their types and concentrations (and pH of the media), as observed by CD spectra and CD denaturation curves. While the great benefit of CD was shown, some limitations were also found : all materials should be soluble in appropriate solvents and the additives should be optically transparent so as not to interfere with the CD of the collagen, which are sometimes difficult in a dental adhesion research.3. In addition to the CD experiments, a "stabilization index" of the additives has been built up by systemic DSC measurements, which is a measure of how strongly an additive stabilizes or destabilizes the collagen helix. The more hydrophobic the additive is (i.e., the smaller the specific dielectric constant is), the more effectively it lowers the structural stability of collagen. This index must valuably serve to foresee the interaction between some newly developed dental materials and dentinal collagen. Less