Synthesis of a Potentially Bioactive, Hydroxyapatite-Nucleating Molecule

Abstract

A human phosphophoryn (PP) cDNA was previously cloned from immature root apex total RNA in our laboratory. This cDNA comprises 2,364 bp, encoding 788 amino acids. More than 80% of the sequences are arranged as (DSS)(n) (n = 1-16), DS, and NSS motifs. We hypothesize that the capability of PP to bind Ca(2+) and nucleate hydroxyapatite may depend on these repeated sequences. Two polypeptides were synthesized based on the human PP cDNA sequence to test the hypothesis. One polypeptide has the amino acid sequence DDPNSSDESNGNDD (synthetic polypeptide 1, SP1), which is from the N-terminal end of PP; the other polypeptide, DSKSDSSKSESDSS (synthetic polypeptide 2, SP2), is the PP repeated sequence motif. Phosphorylation of the polypeptides was accomplished by reacting them with adenosine triphosphate and casein kinases I and II. The ability of these molecules to cause mineralization was tested in a steady-state agarose gel system. The results show that phosphorylated SP2 (P-SP2) precipitated approximately 60% of the total Ca + PO(4) precipitated by PP. P-SP1 precipitated about 23% of that precipitated by PP and was similar to the amount precipitated in the control gel, that is, without added peptides. Transmission electron microscopy and X-ray diffraction analysis showed that the precipitate formed in the P-SP2-containing gel was hydroxyapatite. The capability of P-SP2 to nucleate Ca + PO(4) and precipitate hydroxyapatite is a result of the repeated sequence motif, which contains a high percentage of phosphorylated serine. This molecule could be used in the repair and regeneration of dental tissue.

Synergistic Inhibition of Enamel Demineralization by Peptide 8DSS and Fluoride

“…The second process is mineral loss, which occurs as the intraprismatic mineral dissolves; the rate of mineral loss depends on the degree of undersaturation with respect to the intraprismatic mineral and is limited by slow diffusion between crystals [Shellis, 1996]. In our study, 8DSS may exert its effects after permeating the inner enamel by passing through the larger pores, consistent with previous studies showing that it can promote the remineralization of demineralized enamel [Chang et al, 2006]. The peptide is predicted to have an overall negative charge at pH 7, since serine and aspartic acid are negatively charged under those conditions.…”

Assembly of collagen-binding peptide with collagen as a bioactive scaffold for osteogenesis in vitro and in vivo

“…Mineral deposition by the CBM is primarily due to the existence of acidic aspartic and glutamic acid. Other reports have indicated that a sequence of Asp-Ser-Ser or Asp-Ser/ Lys-Ser/Glu-Ser provides a place for calcium phosphate binding and mineral deposition [34]. The presence of serine in CBM could partially contribute to mineralization by capturing phosphate in the mineralization process.…”

Polymeric Nanomaterials in Biomineralization

“…The aim of this templating is to develop a synthetic approach to mimic a specific part of a biomineralization process, starting from the molecular level. In this respect, self-assembled peptide amphiphiles for hydroxyapatite crystallization to mimic bone, copolypeptides to mimic properties of silicatein in SiO 2 mineralization are important examples 66,67 where block copolypeptides of poly(L-cystine30-L-lysine200) were used. Recently, Deming and coworkers have reported synthesis of hexagonal silica platelets using poly(lysine) polypeptide templates.…”