35 Amino acids are joined in a protein by the formation of a peptide bond + H 3 N C C N C C O - + H 2 O H R 1 H R 2 O O H + H 3 N C C O - + + H 3 N C C O-H R 1 H R 2 O O Peptide (amide) bond Dipeptide â contains two amino acid residues planar. 36 20 amino acids can form 20 2 or 400 dipeptides.
Hydroxylapatite, also called hydroxyapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca 5 (PO 4) 3 (OH), but is usually written Ca 10 (PO 4) 6 (OH) 2 to denote that the crystal unit cell comprises two entities.Hydroxylapatite is the hydroxyl endmember of the complex apatite group.The OH â ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system.ydroxylapatite is the hydroxyl endmember of the complex apatite group. The OH â ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system.
The tooth mineral hydroxyapatite de-composes and calcium fluoride adheres tothe apatite and can serve as a source of flu-oride for subsequent conversion of hydroxy-apatite to fluorapatite.6Recently there has been interest in theapplication of physical chemistry principles to hydroxyapatite, the primary mineral of teeth.ith the aid of a computer, it ispossible to calculate initial rates of reactionthat can be used to evaluate a priori thefluoride uptake potential of various fluoridesolutions. The variables that can be exam-ined are the fluoride concentration, phos-phate concentration, pH, buffer type (pKa), and buffer concentration.