Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 5 de 5
Filter
Add more filters










Database
Language
Publication year range
1.
Environ Sci Process Impacts ; 26(7): 1116-1129, 2024 Jul 17.
Article in English | MEDLINE | ID: mdl-38623703

ABSTRACT

Plastic pollution in aquatic ecosystems has become a significant problem especially microplastics which can encapsulate into the skeletons of organisms that produce calcium carbonates, such as foraminifera, molluscs and corals. The encapsulation of microplastics into precipitated aragonite, which in nature builds the coral skeleton, has not yet been studied. It is also not known how the dissolved organic matter, to which microplastics are constantly exposed in aquatic ecosystems, affects the encapsulation of microplastics into aragonite and how such microplastics affect the mechanical properties of aragonite. We performed aragonite precipitation experiments in artificial seawater in the presence of polystyrene (PS) and polyethylene (PE) microspheres, untreated and treated with humic acid (HA). The results showed that the efficiency of encapsulating PE and PE-HA microspheres in aragonite was higher than that for PS and PS-HA microspheres. The mechanical properties of resulting aragonite changed after the encapsulation of microplastic particles. A decrease in the hardness and indentation modulus of the aragonite samples was observed, and the most substantial effect occurred in the case of PE-HA microspheres encapsulation. These findings raise concerns about possible changes in the mechanical properties of the exoskeleton and endoskeleton of calcifying marine organisms such as corals and molluscs due to the incorporation of pristine microplastics and microplastics exposed to dissolved organic matter.


Subject(s)
Calcium Carbonate , Environmental Monitoring , Microplastics , Water Pollutants, Chemical , Microplastics/analysis , Calcium Carbonate/chemistry , Water Pollutants, Chemical/analysis , Animals , Humic Substances/analysis , Polyethylene/chemistry , Anthozoa/chemistry
2.
Chemistry ; 25(45): 10616-10624, 2019 Aug 09.
Article in English | MEDLINE | ID: mdl-30840343

ABSTRACT

The biomineralization of corals occurs under conditions of high and low supersaturation with respect to aragonite, which corresponds to day- or night-time periods of their growth, respectively. Here, in vitro precipitation of aragonite in artificial seawater was investigated at a high supersaturation, allowing spontaneous nucleation and growth, as well as at low supersaturation conditions, which allowed only the crystal growth on the deliberately introduced aragonite seeds. In either chemical systems, soluble organic matrix (SOM) extracted from Balanophyllia europaea (light sensitive) or Leptopsammia pruvoti (light insensitive) was added. The analyses of the kinetic and thermodynamic data of aragonite precipitation and microscopic observations showed that, at high supersaturation, the SOMs increased the induction time, did not affect the growth rate and were incorporated within aggregates of nanoparticles. At low supersaturation, the SOMs affected the aggregation of overgrowing crystalline units and did not substantially change the growth rate. On the basis of the obtained results we can infer that at high supersaturation conditions the formation of nanoparticles, which is typically observed in the skeleton's early mineralization zone may occur, whereas at low supersaturation the overgrowth on prismatic seeds observed in the skeleton fiber zone is a predominant process. In conclusion, this research brings insight on coral skeletogenesis bridging physicochemical (supersaturation) and biological (role of SOM) models of coral biomineralization and provides a source of inspiration for the precipitation of composite materials under different conditions of supersaturation.


Subject(s)
Anthozoa/chemistry , Calcium Carbonate/chemistry , Animals , Anthozoa/metabolism , Crystallization , Kinetics , Microscopy, Electron, Scanning , Nanoparticles/chemistry
3.
Chem Commun (Camb) ; 50(97): 15370-3, 2014 Dec 18.
Article in English | MEDLINE | ID: mdl-25350140

ABSTRACT

Recently, the results of experimental and theoretical investigations have revealed that, in vaterite, two or even more crystalline structures coexist. In this communication we report evidence of diverse vaterite structures in biogenic samples of different origin. In addition, it is shown that the synthetic vaterite precipitated in the presence of poly-l-aspartate has structures similar to those of biogenic samples.


Subject(s)
Calcium Carbonate/chemistry , Animals , Calcium Carbonate/chemical synthesis , Calcium Chloride/chemistry , Calorimetry, Differential Scanning , Carbonates/chemistry , Chemical Precipitation , Crystallization , Cyprinidae , Microscopy, Electron, Scanning , Molecular Structure , Peptides/chemistry , Sodium Bicarbonate/chemistry , Spectroscopy, Fourier Transform Infrared , Unionidae , Urochordata , X-Ray Diffraction
4.
Chemistry ; 18(45): 14367-74, 2012 Nov 05.
Article in English | MEDLINE | ID: mdl-22996327

ABSTRACT

Mineralized tissues grow through biologically controlled processes in which specific macromolecules are involved. Some of these molecules, which are present in very low concentrations and are difficult to localize and characterize, become entrapped inside the mineralized tissue. Herein, a protein fragment, GP, which was obtained by the alkaline digestion of the green sheet of the abalone shell, is used as a probe to study the changes in molecular structure that occur during the precipitation of calcium carbonate. This important goal was achieved by exploiting a fluorescent tag in GP. The experimental results that were obtained by using spectroscopic-, chromatographic-, and microscopic techniques indicate that GP controls the precipitation kinetics and morphology of calcium carbonate crystals, and that it only undergoes structural reorganization when entrapped inside calcium carbonate crystals. To the best of our knowledge, this report represents one of the first studies on the conformational changes of a protein fragment that is involved in biomineralization processes on moving from the solution phase into the mineral phase.


Subject(s)
Calcium Carbonate/chemistry , Proteins/chemistry , Animals , Crystallization , Fluorescent Dyes/chemistry , Gastropoda , Proteins/metabolism , Spectrometry, Fluorescence
5.
J Colloid Interface Sci ; 343(2): 553-63, 2010 Mar 15.
Article in English | MEDLINE | ID: mdl-20060980

ABSTRACT

Spontaneous precipitation of calcium carbonate was investigated in two precipitation systems: (1) with initial supersaturation lower than that corresponding to the solubility of amorphous calcium carbonate (ACC), at which vaterite precipitated, and (2) with initial supersaturation higher than that of ACC solubility, at which a mixture of calcite and vaterite was formed. After the addition of an acidic polypeptide, poly-L-glutamic acid (pGlu) or poly-L-aspartic acid (pAsp), into (1) a significant inhibition of nucleation, expressed as an increase in induction time, and growth of vaterite, perceived as a dead zone, was observed. Extent of inhibition decreased in the order: Inh(pAps)>Inh(pGlu)>>Inh(pLys). The addition of a polypeptide into (2) caused the inhibition of precipitation and changed the morphology and polymorphic composition of the precipitate; only vaterite appeared at approximately c(pAsp)=3 ppm, c(pGlu)=6 ppm, or c(pLys)=7 ppm. This finding is explained as a consequence of kinetic constraints through the inhibition of calcite nucleation and stronger binding of acidic polypeptide by the calcite surfaces than by the vaterite surfaces. Laboratory precipitation studies using conditions that resemble those in living organism should be run at an initial supersaturation corresponding to the solubility of ACC as a limiting condition.


Subject(s)
Amino Acids/chemistry , Calcium Carbonate/chemistry , Polymers/chemistry , Chemical Precipitation , Spectroscopy, Fourier Transform Infrared , Static Electricity
SELECTION OF CITATIONS
SEARCH DETAIL
...