ABSTRACT
As zinc has been included in several oral health products as an anticalculus and antiplaque agent, the interaction of zinc with a synthetic phosphate was investigated. The synthetic calcium phosphate used in this study was beta-tricalcium phosphate, or whitlockite, which is a major constituent of mature calculus. The aim of this work was to study the mechanism of uptake of zinc to this mineral. Zinc was readily taken up by the calcium phosphate to a maximum level of 13.9 mumol/m2. The interaction was reversible and followed a Langmuir adsorption isotherm. There was no concomitant release of calcium with zinc uptake. Inclusion of calcium in the exposure solution did however marginally depress the acquisition of zinc (12% max), but fluoride had no significant effect on uptake.
Subject(s)
Biocompatible Materials/chemistry , Calcium Phosphates/chemistry , Zinc/chemistry , Adsorption , Apatites/chemistry , Calcium/chemistry , Chemical Phenomena , Chemistry, Physical , Dental Calculus/prevention & control , Dental Plaque/prevention & control , Fluorides/chemistry , Humans , Radiopharmaceuticals , Spectrophotometry, Atomic , Temperature , Zinc RadioisotopesABSTRACT
Human whole saliva was collected at 4 degrees C into a protein inhibitor cocktail to prevent proteolytic degradation. Saliva was clarified by centrifugation and fractionated by immobilized metal affinity chromatography (IMAC) after charging the column with zinc ions. Proteins with an affinity for zinc were eluted from the IMAC column, characterized by sodium dodecylsulphate-polyacrylamide gel electrophoresis, and probed with 65ZnCl2 after electrotransfer on to polyvinylidenefluoride membranes. A zinc-binding protein of approx. 11 kDa was characterized by N-terminal sequencing followed by a FASTA search of Genbank. The first 40 residues were sequenced, of which the first 34 residues were used to conduct a FASTA search and yielded and homology > 97% coding for sequences of mRNA of two proteins, a cystic fibrosis antigen with an M(r) of 10,938 and a calcium-binding inflammatory protein MRP8 with an M(r) of 10,835 expressed in chronic inflammation. The identity of the last 15 residues of the sequence and the likelihood that the protein is secreted via saliva indicates that the 11-kDa protein is the cystic fibrosis antigen, a protein not previously reported in saliva.
