Jolanta Prywer

Unique surface and internal structure of struvite crystals formed by Proteus mirabilis

Crystallization of struvite from artificial urine in the presence of Proteus mirabilis microorganisms depends strongly on pH value. At small value of pH, struvite yields crystals of coffin-like habit with very specific structure. The analysis using scanning electron microscopy shows that the crystals possess well-defined faces, but higher magnifications show very specific structuration as if the crystals were built from small three-dimensional subunits. The possible role of microorganisms in the formation of such a structuration is analyzed. At higher pH value, the crystals exhibit dendritic growth with main trunk and branches. Although the formation mechanism of the specific structuration as well as dendritic structures is unknown, the nature of forces for such an alignment is analyzed. The revealed porous internal structure of struvite is also analyzed. The investigations provide evidence for the importance of biological regulation in crystallization process.

Effect of crystal geometry on disappearance of slow-growing faces

The subject of this paper is research and mathematical analysis of the phenomenon of the disappearance of slow-growing faces. Results of this mathematical analysis show that some faces, for which a given geometrical condition is fulfilled, may disappear if they are growing more slowly than one of the neighbouring faces. For other faces there is no such possibility. It is shown that the crystal habit is determined not only by the growth conditions which influence the relative growth rates, but also, in great degree, by the geometry of the crystal.

Effect of Curcumin Against Proteus mirabilis During Crystallization of Struvite from Artificial Urine

We investigated the activity of curcumin against Proteus mirabilis and the struvite crystallization in relation to urinary stones formation. In order to evaluate an activity of curcumin we performed an in vitro experiment of struvite growth from artificial urine. The crystallization process was induced by Proteus mirabilis to mimic the real urinary tract infection, which usually leads to urinary stone formation. The results demonstrate that curcumin exhibits the effect against Proteus mirabilis inhibiting the activity of urease—an enzyme produced by these microorganisms. Addition of curcumin increases the induction time and decreases the efficiency of growth of struvite compared with the absence of curcumin. Interestingly, the addition of curcumin does not affect the crystal morphology and habit. In conclusion, curcumin has demonstrated its significant potential to be further investigated for its use in the case of struvite crystallization induced for the growth by Proteus mirabilis in relation to urinary stone formation.

Three-dimensional model of any shape face disappearance in crystal habit

The formulae to evaluate the length of any edge of a face of any shape and to evaluate critical growth velocity, above which the edge disappears have been derived for a three-dimensional case. These formulae make possible the analysis of the disappearance of any shape face. All theoretical predictions have been verified by computer modeling performed for triclinic potassium bichromate (KBC) crystals.

Three-dimensional model of faces disappearance in crystal habit

The formula to evaluate critical growth velocity, above which a face transforms to an edge or a corner, has been derived for a three-dimensional case. Using computed critical growth velocities for triclinic potassium bichromate (KBC) crystals, it was possible to draw crystal forms showing how a face transforms to an edge or a corner.

Theoretical analysis of changes in habit of growing crystals in response to variable growth rates of individual faces

Abstract The subject of this paper is research and analysis of the kinetic conditions corresponding to changes in habits of growing crystals. In particular, the formula to evaluate the rate of changes in length of any edge in any three-dimensional crystal is presented. This formula is the basis for the analysis of changes in habits depending on growth rates of individual faces which may be described by any time-dependent or time-independent function. The theoretical predictions are verified by computer modeling performed for crystal grown in nature – wulfenite. On the example of this crystal it is shown that the presented formulae may be used as a tool to describe the evolution of crystal morphologies and to predict the habits of growing crystals at given growth rates of individual faces.

On the crystal geometry influence on the growth of fast-growing surfaces

The external morphology of a given crystal is determined by the growth conditions, growth time and geometry of the crystal. Up to now, it has been believed that the growth conditions which influence the relative growth rates of surfaces play the key role in the formation of the final crystal morphology. In this paper, it is shown that the geometry of a given crystal, expressed by the trigonometric function of appropriate interfacial angles, may influence to a great degree the crystallisation process and the morphology of crystals. For example, it is shown that at particular geometry of a crystal, a given surface may exist in the habit and develop its size although it grows much faster than the neighbouring surfaces.

Density Functional Theory Determination of Structural and Electronic Properties of Struvite

Crystallographic structure, total energy, electronic structure, and the most important elastic properties of struvite, NH(4)MgPO(4).6H(2)O, the main component of infectious urinary stones, are presented. The calculations were performed using ab initio full-electron calculations within the density functional theory-generalized gradient approximation (DFT-GGA) framework. The obtained crystallographic symmetry and the calculated lattice parameters and also the elastic constants are in good agreement with the experimental data. The elastic properties are essential for establishing an optimal response of urinary stones during shock-wave lithotripsy. The calculated electronic charge distribution confirms the layered structure of the struvite crystals. The polar character of the crystal, well-known from crystal growth experiments, was also confirmed by the magnitude of spontaneous polarization which was obtained from direct determination of the electrical dipole density. The calculated value of spontaneous polarization is equal to -8.8 microC cm(-2). This feature may play a key role in struvite crystallization, electrically binding the charged active impurities and other active species, and consequently determining urinary stone formation. We also present the results of our own experiment of the mineralization of struvite induced to growth by Proteus bacteria which are mainly isolated from infectious urinary stones.

Bacterially Induced Formation of Infectious Urinary Stones: Recent Developments and Future Challenges

Infectious urinary stones make a serious medical problem concerning up to 20% of population. Additionally, recurrence after treatment reaches 50%. The formation of infectious urinary stones is connected with urinary tract infection with various bacteria. These are mainly the bacteria from Proteus species which have been isolated in 70% of bacteriainduced urinary stone cases. These microorganisms produce urease - a bacterial enzyme which plays a principal role in the crystallization process and is one of the main virulence parameters of these bacteria. The most common solid components of infectious urinary stones are the crystals of struvite and amorphous carbonate apatite. The formation of this kind of stones involves two main processes. The first one is the nucleation process of solid phases and the second is the aggregation of the precipitated phases, both crystalline and amorphous. In recent years, both these processes have been deeply investigated. In particular, different active compounds have been reported as potentially novel therapeutic agents to prevent or inhibit the formation of infectious urinary stones. In addition, there is rich scientific evidence regarding the chemical mechanisms of inhibitory effect of these active compounds. In recent years, specific interior and exterior structure of struvite and its porous nature have also been reported. In this article, we summarize and discuss recent development in this field of research. The paper concludes with future goals and challenges.

GaN Single Crystal Habits and Their Relation to GaN Growth Under High Pressure of Nitrogen

In the growth of GaN from nitrogen dissolved in Ga under high N 2 pressure, two main habits are observed: plate-like and needle-like. The plate-like crystals can be divided into those having (0001), (000 ) and {10 0} faces and those with the additional {10 1} and {10 2} faces. The needle-like crystals belong to three classes: with or without (0001) faces and a third with unusual, star-like needles. The plate-like and needle-like habits and transformation between these habits are discussed in greater detail. It is shown that it is possible to evaluate the relative growth rates corresponding to such transitions.