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Biomimetic synthesis of struvite with biogenic morphology and implication for pathological biomineralization.

Li H, Yao QZ, Wang YY, Li YL, Zhou GT - Sci Rep (2015)

Bottom Line: Recent studies have found that certain urinary proteins can efficiently inhibit stone formation.These discoveries are significant for developing effective therapies for stone disease, but the inhibition mechanism of crystallization remains elusive.Concentration-dependent experiments show that PASP can inhibit struvite growth and the inhibitory capacity increases with increasing PASP concentration, whereas aspartic acid monomers do not show a significant effect.

View Article: PubMed Central - PubMed

Affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, P. R. China.

ABSTRACT
Recent studies have found that certain urinary proteins can efficiently inhibit stone formation. These discoveries are significant for developing effective therapies for stone disease, but the inhibition mechanism of crystallization remains elusive. In the present study, polyaspartic acid (PASP) was employed as a model peptide to investigate the effect of urinary proteins on the crystallization and morphological evolution of struvite. The results demonstrate that selective adsorption/binding of PASP onto the {010} and {101} faces of struvite crystals results in arrowhead-shaped morphology, which further evolves into X-shaped and unusual tabular structures with time. Noticeably, these morphologies are reminiscent of biogenic struvite morphology. Concentration-dependent experiments show that PASP can inhibit struvite growth and the inhibitory capacity increases with increasing PASP concentration, whereas aspartic acid monomers do not show a significant effect. Considering that PASP is a structural and functional analogue of the subdomains of aspartic acid-rich proteins, our results reveal that aspartic acid-rich proteins play a key role in regulating biogenic struvite morphology, and aspartic acid residues contribute to the inhibitory capacity of urinary proteins. The potential implications of PASP for developing therapeutic agents for urinary stone disease is also discussed.

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FTIR spectra of the products grown for 8 h with 0.2 mM (a) and 0 mM (b) PASP.
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f2: FTIR spectra of the products grown for 8 h with 0.2 mM (a) and 0 mM (b) PASP.

Mentions: In order to understand the effect of PASP on the morphological evolution of struvite, a series of time-resolved mineralization experiments from 20 min to 20 h was carried out at PASP concentrations of 0 and 0.2 mM, respectively. The composition and phase purity of the products were first examined by the XRD technique, and the results confirm that all of the mineralized products are orthorhombic struvite with space group Pmn21. The representative XRD patterns for the products obtained with and without PASP are shown in Figure 1a–c. Compared with the standard diffraction pattern of struvite (in Figure 1, JCPDS file No.15–0762), all of the diffraction peaks could be well indexed as struvite, and no other impurity phases could be found. At the same time, it is not difficult to find from Figure 1a–c that the products obtained in the presence of PASP had dramatically strong (020) and (040) diffractions, indicating that the mineralized products were preferentially oriented along the [010] direction. Moreover, FT-IR analysis has also been proved to be a valuable method to distinguish the different phases and compositions42. Therefore, FT-IR analyses were performed on the mineralized products. The typical FT-IR spectra of the mineralized products with and without PASP are depicted in Figure 2. The absorption bands located at 1007, 572 and 462 cm−1 can be assigned to the PO43− antisymmetric stretch (ν3), the P-O bend (ν4) and the PO43− ν2 modes, respectively. The absorption bands at 1469, 1435 and 1400 cm−1 can be attributed to ν4 (NH4+) antisymmetric bending. Water-water H bonding at 761 cm−1 and ammonium-water H bonding at 892 cm−1 can also be recognized from this FTIR spectrum. These are in good agreement with the results for pure struvite reported by Banks et al.42, further confirming that the mineralized products are struvite. Therefore, the XRD and FT-IR results reveal that pure phase of struvite can always be obtained in the presence and absence of PASP, and dissolved PASP in the mineralization solution does not influence the phase composition of the mineralized products. Moreover, the characteristic vibrational bands [band of ν (C = O) in amide group at approximately 1645 cm−1, band of ν (C = O) in carboxylic group near 1731 cm−1, band of ν (C-H) in methylene group at approximately 2969 and 2904 cm−1] belonging to PASP molecules43 do not appear in Figure 2a, suggesting that no detectable content of PASP is occluded in the mineralized product after extensive washing.


Biomimetic synthesis of struvite with biogenic morphology and implication for pathological biomineralization.

Li H, Yao QZ, Wang YY, Li YL, Zhou GT - Sci Rep (2015)

FTIR spectra of the products grown for 8 h with 0.2 mM (a) and 0 mM (b) PASP.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4296295&req=5

f2: FTIR spectra of the products grown for 8 h with 0.2 mM (a) and 0 mM (b) PASP.
Mentions: In order to understand the effect of PASP on the morphological evolution of struvite, a series of time-resolved mineralization experiments from 20 min to 20 h was carried out at PASP concentrations of 0 and 0.2 mM, respectively. The composition and phase purity of the products were first examined by the XRD technique, and the results confirm that all of the mineralized products are orthorhombic struvite with space group Pmn21. The representative XRD patterns for the products obtained with and without PASP are shown in Figure 1a–c. Compared with the standard diffraction pattern of struvite (in Figure 1, JCPDS file No.15–0762), all of the diffraction peaks could be well indexed as struvite, and no other impurity phases could be found. At the same time, it is not difficult to find from Figure 1a–c that the products obtained in the presence of PASP had dramatically strong (020) and (040) diffractions, indicating that the mineralized products were preferentially oriented along the [010] direction. Moreover, FT-IR analysis has also been proved to be a valuable method to distinguish the different phases and compositions42. Therefore, FT-IR analyses were performed on the mineralized products. The typical FT-IR spectra of the mineralized products with and without PASP are depicted in Figure 2. The absorption bands located at 1007, 572 and 462 cm−1 can be assigned to the PO43− antisymmetric stretch (ν3), the P-O bend (ν4) and the PO43− ν2 modes, respectively. The absorption bands at 1469, 1435 and 1400 cm−1 can be attributed to ν4 (NH4+) antisymmetric bending. Water-water H bonding at 761 cm−1 and ammonium-water H bonding at 892 cm−1 can also be recognized from this FTIR spectrum. These are in good agreement with the results for pure struvite reported by Banks et al.42, further confirming that the mineralized products are struvite. Therefore, the XRD and FT-IR results reveal that pure phase of struvite can always be obtained in the presence and absence of PASP, and dissolved PASP in the mineralization solution does not influence the phase composition of the mineralized products. Moreover, the characteristic vibrational bands [band of ν (C = O) in amide group at approximately 1645 cm−1, band of ν (C = O) in carboxylic group near 1731 cm−1, band of ν (C-H) in methylene group at approximately 2969 and 2904 cm−1] belonging to PASP molecules43 do not appear in Figure 2a, suggesting that no detectable content of PASP is occluded in the mineralized product after extensive washing.

Bottom Line: Recent studies have found that certain urinary proteins can efficiently inhibit stone formation.These discoveries are significant for developing effective therapies for stone disease, but the inhibition mechanism of crystallization remains elusive.Concentration-dependent experiments show that PASP can inhibit struvite growth and the inhibitory capacity increases with increasing PASP concentration, whereas aspartic acid monomers do not show a significant effect.

View Article: PubMed Central - PubMed

Affiliation: CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, P. R. China.

ABSTRACT
Recent studies have found that certain urinary proteins can efficiently inhibit stone formation. These discoveries are significant for developing effective therapies for stone disease, but the inhibition mechanism of crystallization remains elusive. In the present study, polyaspartic acid (PASP) was employed as a model peptide to investigate the effect of urinary proteins on the crystallization and morphological evolution of struvite. The results demonstrate that selective adsorption/binding of PASP onto the {010} and {101} faces of struvite crystals results in arrowhead-shaped morphology, which further evolves into X-shaped and unusual tabular structures with time. Noticeably, these morphologies are reminiscent of biogenic struvite morphology. Concentration-dependent experiments show that PASP can inhibit struvite growth and the inhibitory capacity increases with increasing PASP concentration, whereas aspartic acid monomers do not show a significant effect. Considering that PASP is a structural and functional analogue of the subdomains of aspartic acid-rich proteins, our results reveal that aspartic acid-rich proteins play a key role in regulating biogenic struvite morphology, and aspartic acid residues contribute to the inhibitory capacity of urinary proteins. The potential implications of PASP for developing therapeutic agents for urinary stone disease is also discussed.

Show MeSH