Fritz, Monika
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Item-typ:Veröffentlichung, Investigation of Biopolymer - Mineral Interactions in the Natural Composite Material Nacre(2008-12-19); ; ; Nacre consists of platelets of aragonite, arranged in a regular manner. An organic matrix is intercalated between the mineral, necessary for the growth. Aspects of growth as well as properties of the organic matrix from nacre of Haliotis laevigata were investigated. The influence of the interlamellar matrix on CaCO3 formation was investigated. Crystallization under constant conditions and investigation with electron microscopy and X-ray diffraction revealed that interlamellar matrix nucleates flat aragonite crystals. The surface energy of the interlamellar matrix was determined with contact angle measurements. It is mainly of non-polar origin. The influence of soluble matrix proteins on precipitation rates was determined. Soluble proteins from nacre had a high influence on precipitation rates compared to other proteins. The soluble matrix was subject to an amino acid analysis. The result was dependent on the method protein purification. In general, pro, gly, leu and ala were dominant.Dissertation299 254 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Charakterisierung biomineralisierender Proteine aus dem Proteom der Meeresschnecke Haliotis laevigata(2013-01-28); ; ; The formation of the biogenic composite material nacre is a process of self-assembling and occurs at standard ambient conditions. The highly ordered structure of nacre is composed of approximately 98 wtR0calcium carbonate crystals and less than 2 wtR0organic materials (proteins and polysaccharides). Proteins obviously play a key role in structure formation and regulation of nacre, they guide and control its growth. In this thesis, the biomineralizing proteins from nacre of the marine gastropod Haliotis laevigata were characterized with different techniques. The focus was set on the nacre protein perlucin because this protein was shown to be the major component of the total protein fraction. Furthermore it became evident that most of the biomineralizing proteins are tightly bound to the chitin matrix. A precipitation assay was used to investigate the influence of soluble matrix proteins on CaCO3 precipitation rates. The nacre proteins showed an enormous specific and concentration depending function on CaCO3 precipitation. Using mass spectrometry an overview of the proteome of the shell of Haliotis laevigata could be achieved (without de novo-results).Dissertation258 138 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Protein-Mineral Interaction of Purified Nacre Proteins with Calcium Carbonate Crystals(2006-07-26); ; ; Nacre, a fascinating biogenic material consisting of calcium carbonate and organic molecules, presents remarkable mechanical and chemical properties that far exceed those of the pure components. Nacre is created by a self-organizing process guided by organic macromolecules. In particular proteins specifically control and regulate the nucleation and growth of the mineral phase, influencing the crystal morphology and polymorph selection.In this work new strategies to extract and purify proteins from the nacre of Haliotis laevigata in their native and functional state were developed and mechanisms of interaction between native nacre proteins with calcium carbonate in solution and calcium carbonate minerals were investigated. In particular the function of the intracrystalline proteins, a novel group of proteins characterized for the first time in nacre, and perlucin and perlinhibin, two already sequenced nacre proteins, were elucidated. It has been shown that each nacre protein presents a very specific and unique function in terms of calcium carbonate mineralization.Dissertation359 138 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Molecular Modelling and Functional Studies of the Biomineralising Protein Perlucin(2014-06-24); ; ; ; Nacre is a biogenic composite material. One protein from the organic fraction of the nacreous layers of Haliotis laevigata is perlucin. It is supposed to be involved in nacre formation. This thesis presents a molecular model of the C-type lectin-like domain (CTLD) of perlucin. The model was calculated by means of comparative modelling and tested with molecular dynamic simulations. One computational study with the newly available perlucin structures is presented in this thesis. A rigid docking analysis of several structures of the CTLD of perlucin led to the proposal of several residues that could be involved in homodimer formation. The experimental part of this thesis consists of size-exclusion chromatography (SEC) experiments performed with nacre proteins. A suitable buffer solution composition - near neutral pH value of 7.3 and 1 M NaCl - is given that can serve as a basis for future SEC experiments with perlucin. Current SEC results could point to a dimerization of perlucin.Dissertation265 223 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Direkte Beobachtung des Wachstums von Calciumcarbonatkristallen auf den Oberflächen von frisch gewachsenen "flat pearls" und auf frisch gespaltenen Perlmuttoberflächen(2023-07-04); ; ; Diese Dissertation beschäftigt sich mit dem biogenen Polymer-Mineral Verbundmaterial Perlmutt. Hier werden die mittels Rasterkraftmikroskopie (AFM) und Rasterelektronenmikroskopie (REM) durchgeführten Untersuchungen zur Struktur und zu künstlich induzierten Wachstumsprozessen dargestellt, ausführlich analysiert und diskutiert. Das hier untersuchte Perlmutt stammt von Meeresschnecken der Art Haliotis tuberculata und besteht aus polygonalen Aragonitplättchen, die in eine weiche organische Matrix eingebettet sind. Diese organische Matrix wird dabei aus Chitinfilamenten, die netzwerkartig über- und untereinander verlaufen, und an den Filamenten anhaftenden Proteinmolekülen gebildet. In dieser Arbeit werden für die Strukturuntersuchungen und Wachstumsexperimente zwei verschiedene Probenoberflächen, frisch gewachsene „flat pearls“ und frisch gespaltene Perlmuttoberflächen genutzt. Zur Herstellung der „flat pearls“ finden lebende Meeresschnecken Verwendung. Die frisch gespaltenen Perlmuttoberflächen werden direkt aus den Schneckenschalen erzeugt. Auf beiden Probenoberflächen wird mittels AFM die künstlich induzierte Nukleation und das Wachstum von nadelförmigen Calciumcarbonatkristallen direkt beobachtet. Dazu werden jeweils Bildsequenzen desselben Probenbereichs über einen längeren Zeitraum (mehrere Stunden) mit dem AFM aufgenommen. Während des Abbildens wird das Kristallwachstum durch Einspülen von übersättigten Calciumcarbonatlösungen initiiert. Zusätzlich werden Struktur und Verteilung der während der AFM-Wachstumsexperimente auf den Probenoberflächen gewachsenen Calciumcarbonatkristalle mit dem REM untersucht. Zudem wird die Oberflächenstruktur der Proben mit dem AFM detailliert charakterisiert.Dissertation248 146 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Untersuchungen der Bildungsprozesse und der Struktur des Perlmutts von Abalonen(2011-05-04); ; ; Nacre is the inner iridescent layer in the shells of snails and mussels. It is composed of mineral platelets, which consist of aragonite, a CaCO3-polymorph, and of a small amount of organic matter, the so called organic matrix. The organic matrix can be subdivided into the soluble and the insoluble matrix, whereby this definition is preparation dependent. The nacre and the organic components used in this thesis originated from the marine gastropods Haliotis laevigata and Haliotis tuberculata. This thesis contains mainly three parts presenting results. The first part concentrates on the investigation of the growth of calciumcarbonate crystals on the insoluble matrix and the influence of the soluble matrix on this growth process. In the experiment a crystallization device was used, which contained the insoluble matrix and was flowed through by NaHCO3- and CaCl2-solutions and by different concentrations of the soluble matrix as an additive. Investigations via scanning electron microscopy (SEM) revealed that besides vaterite and calcite crystals, also flat crystals develop on the insoluble matrix. With the addition of a relatively high concentration of 1ug/ml soluble matrix CaCO3-crystal growth was totally inhibited, whereas the addition of 0.02ug/ml soluble matrix slightly increases growth of flat crystals compared to experiments without any additive. By analyzing diffraction pattern recorded in a transmission electron microscope (TEM) the flat crystals could be identified as aragonite. Furthermore some of the flat crystals formed a layered structure induced by growth between the horizontal layers of the insoluble matrix. Thus, the morphology as well as the crystal polymorph remind on natural grown nacre. In the second part of the thesis a central feature in the aragonite platelets was investigated by TEM to obtain information on the growth processes in natural nacre. Contrary to publications, in which is stated that the central features contain organic residua, in this thesis no such organic material could be detected. Instead of that aragonite with the same orientation as the surrounding platelet was observed within the central feature (apart from one sample of eight, which contained amorphous CaCO3). This, together with SEM investigations, suggests that the reason for the central feature is a depression and a bulge, respectively, in the middle of the aragonite platelets. The position of the feature coincides with the nucleation site that is located on the insoluble matrix and contains different molecules and proteins that may affect the nucleation of aragonite. The third part deals with the investigation of the location of calcium ions in the mantle epithelium of Haliotis tuberculata. This analysis should give insight into the transportation processes of calcium ions through the epithelial cells into the extrapallial space from where they are build into the shell. The detection of calium ions was performed in a TEM using electron energy loss spectroscopy (EELS). For preparation the tissue was first chemically fixed and afterwards embedded. The disadvantage of this preparation procedure was the formation of artifacts in terms of additional calcium in the cells. This contamination hindered a correct detection of the endogenous calcium.Dissertation461 654