Precipitation Kinetics of Hydroxyapatite Revealed by the Continuous-Angle Laser Light-Scattering Technique

Abstract

The precipitation kinetics of hydroxyapatite from calcium phosphate aggregates was investigated by the continuous-angle laser light-scattering technique in the systems CaCl 2 -H 3 PO 4 -H 2 O and KCl-CaCl 2 -H 3 PO 4 -H 2 O at 25 °C. The apparent molecular weights of aggregates increased with time, and precipitation of hydroxyapatite occurred in both systems. However, the radius of gyration of the aggregate was almost constant in the former system, while it increased with the increase of the molecular weight in the latter system. Fractal dimension analysis revealed that loosely distributed particles in the aggregate transformed to a three-dimensional closely packed structure during the precipitation of hydroxyapatite in the former system, while the aggregate and the crystalline particles within it increased in size with the increased density and act as growth centers of hydroxyapatite in the latter system.

Direct transformation from amorphous to crystalline calcium phosphate facilitated by motif-programmed artificial proteins

“…Earlier studies that used conditions similar to the ones we used (1.0 mM CaCl 2 and 2.5 mM KH 2 PO 4 , pH 8.0 at 25°C) revealed that ACP particles with radii ranging from 200 to 500 nm formed first in the solution (13,17). Our conditions also produced initial particles having an R g of Ϸ340 nm and a d f of Ϸ1.8, irrespective of the presence of the #64.…”

“…Time-resolved static light scattering (TR-SLS) measurements enabled us to observe changes in the apparent molecular mass (M w ), gyration radius (R g ), and fractal dimension (d f ) of calcium phosphate particles at an early stage during HAP formation (16,17). Earlier studies that used conditions similar to the ones we used (1.0 mM CaCl 2 and 2.5 mM KH 2 PO 4 , pH 8.0 at 25°C) revealed that ACP particles with radii ranging from 200 to 500 nm formed first in the solution (13,17).…”

“…These changes in M w and d f are thus indicative of the transformation of ACP particles to crystalline particles. The R g remained nearly constant during phase T in the presence of #64 means that the amorphous-to-crystalline transformation proceeded via the ''direct transformation'' mode (17). To confirm that the reorganization of ACP proceeded without an increase in size, we prepared freeze-dried samples of calcium phosphate deposits from phase L, phase T, and phase P and observed their sizes and ordered states.…”

“…The purpose of our experiment was to gain insight into the molecular mechanism by which the peptide motifs of DMP1 facilitate HAP formation through our synthetic approach (15). Because immobilization of a specimen poses impediments to time-resolved analyses, such as lightscattering photometry (16,17), we first synthesized motifprogrammed artificial proteins from the two DMP1 motifs, because their isolated clones were found to accelerate HAP formation without immobilization, and then investigated the effects of the proteins on HAP mineralization using timeresolved static light-scattering analyses, TEM observations, and Raman spectroscopy.…”

Crystallization of Cellobiohydrolase in the Presence of Cellulose-Degraded Cellobiose: Analysis of Intermolecular Interactions and Association Dynamics

“…The association of cellobiohydrolase molecules after the protein solution (containing cellobiose) was mixed with the crystallization buffer at a volume ratio of 1:1 was observed using a multi-angle SLS detector [28][29][30][31][32]. The concentration of cellobiohydrolase in the mixed solution was 7 mg/mL and that of lithium sulfate was 1.25 M. The scattering intensities at q from 20˚ to 150˚ with a step of 1˚ were simultaneously measured over time at intervals of 3 s for each R(cb/ce) condition.…”