Effect of the Cysteine-Rich Mdm2 Peptide in the Crystal Growth of Hydroxyapatite in Aqueous Solution

Abstract

The crystal growth of hydroxyapatite (HAP), the most stable calcium phosphate phase at 37 °C, pH 7.40, and ionic strength of 0.15 M NaCl, in the presence of the cysteine-rich Mdm2 peptide (containing 48 aminoacids in ring finger configuration) has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized HAP crystals in supersaturated solutions only with respect to this calcium phosphate salt. The kinetic results indicated a surface diffusion spiral growth mechanism. The presence of the Mdm2 peptide inhibited the crystal growth of HAP by 59-92% through adsorption onto the active growth sites of the HAP crystal surface. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k aff ) (258 ( 21) × 10 4 dm 3 mol -1 .

Calcium Orthophosphates: Crystallization and Dissolution

“…The presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in ring finger configuration) inhibited HAP crystal growth by 59–92% through adsorption at active growth sites. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k aff = (258 ± 21) × 10 4 dm 3 mol −1 276. At 37 °C, I = 0.15 M, pH 7.40, the rates of crystal growth measured in the presence of acetaminophen 1.654 × 10 −4 mol dm −3 to 6.616 × 10 −4 mol dm −3 were reduced by 43% to 79%, respectively.…”

“…The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k aff ) (258 ( 21) × 10 4 dm 3 mol -1 . 276 At 37 °C, I ) 0.15 M, pH 7.40, the rates of crystal growth measured in the presence of acetaminophen 1.654 × 10 -4 mol dm -3 to 6.616 × 10 -4 mol dm -3 were reduced by 43% to 79%, respectively. Kinetic analysis again suggested a Langmuir-type adsorption on the HAP surfaces with an affinity of 2.4 × 10 -4 dm 3 mol -1 .…”

Crystal Growth with Macromolecular Additives

“…There are many well-documented examples of growth inhibition by macromolecular additives including decreased precipitate yield of ApOH with the proline-rich salivary protein, statherin, and related peptides, ,,,,− OPN and related peptides, ,, − and urinary proteins. ,,, Octacalcium phosphate precipitation was inhibited with polyAsp and phosphophoryn . Brushite was inhibited with alginate and its oligomers; its morphology can also be modified by the protein amelogenin .…”

Plate-like hydroxyapatite nanoparticles synthesized by the hydrothermal method

“…However, the concentration of additive is much smaller than the reactants concentration. In addition, according to Gibbs free energy theory and the Burton, Cabrera Frank theory law (BCF theory) for the crystal growth relationship between the rates and the relative supersaturation ó is given by (for relatively high s HAP value [27])…”

“…where k aff (equal to k a /k d , k a (1Àa ads y)c i ¼ a ads yk d ) is the affinity constant that measures the affinity of the adsorbent for the surface, and c i is the concentration of the additive [27]. Eq.…”