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Crystal Nucleation (crystal + nucleation)
Selected AbstractsOn slow protein crystal nucleation: cluster-cluster aggregation on diffusional encountersCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2009C. N. NanevArticle first published online: 7 NOV 200 Abstract With a view to experimental results on protein crystal nucleation the effects of cluster coalescence are probed semi-quantitatively. The steric association restriction, which stems from the patchy surface of the protein molecules, explains both experimentally measured low crystal nucleation rate and coalescence limitations for crystalline clusters of protein molecules. The conclusion is that due to its action, and the impact of rotational diffusion, the coalescence of critical (and/or supercritical) clusters should be rejected as a conceivable alternative for explaining the slow nucleation of protein crystals. Besides, the analysis of cluster-cluster aggregation on diffusional encounters may be of more general interest; it may be helpful by considering the coalescence of structured bio-nano-particles. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Application of mean-separation-works method to protein crystal nucleationCRYSTAL RESEARCH AND TECHNOLOGY, Issue 3 2008Christo N. Nanev Abstract Using mean-separation-works method of Stranski and Kaischew calculations of nucleus form and energy barrier for its formation are performed for globular protein crystals. This is done on the basis of a simple model suggested for crystal nucleation of such proteins. The prerequisite for the model is the fact that strict selection of definite sticky patches on protein molecule surface is obligatory for forming crystal lattices. The calculation results are in agreement with experimental data. (© 2008 WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Protein crystal nucleation: Recent notionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1 2007Christo N. Nanev Abstract The nucleation of protein crystals is reconsidered taking into account the specificity of the protein molecules. In contrast to the homogeneous surface properties of small molecules, the protein molecule surface is highly inhomogeneous. Over their surfaces proteins exhibit high anisotropic distribution of patches, which are able to form crystalline bonds, the crystallization patch representing only a small fraction of the total surface of the protein molecule. Therefore, an appropriate spatial orientation of the colliding protein molecules is required in order to create a crystalline cluster. This scenario decreases considerably the success ratio of the attempt frequency for crystal nucleation. On the other hand a heterogeneous nucleation of (protein) crystals may be accelerated due to the arrival on some support of under-critical clusters that are formed in bulk solution; when arriving there they may acquire the property of critical nuclei. Thus, a plausible explanation of important peculiarities of protein crystal nucleation, as inferred from the experimental data, is suggested. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Quantification of gypsum crystal nucleation, growth, and breakage rates in a wet flue gas desulfurization pilot plantAICHE JOURNAL, Issue 10 2009Brian B. Hansen Abstract The aim of this work is to study the influence of nucleation, growth and breakage on the particle size distribution (PSD) of gypsum crystals produced by the wet flue gas desulfurization (FGD) process. The steady state PSD, obtained in a falling film wet FGD pilot plant during desulfurization of a 1000 ppm(v) SO2 gas stream, displayed a strong nonlinear behaviour (in a ln(n(l)) vs. l plot) at the lower end of the particle size range, compared to the well-known linear mixed suspension mixed product removal model. A transient population balance breakage model, fitted to experimental data, was able to model an increase in the fraction of small particles, but not to the extent observed experimentally. A three-parameter, size-dependent growth model, previously used for sodium sulphate decahydrate and potash alum, was able to describe the experimental data, indicating either size-dependent integration kinetics or growth rate dispersion. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Crystallization of Silicate Magmas Deciphered Using Crystal Size DistributionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007Bruce D. Marsh The remoteness and inhospitable nature of natural silicate magma make it exceedingly difficult to study in its natural setting deep beneath volcanoes. Although laboratory experiments involving molten rock are routinely performed, it is the style and nature of crystallization under natural conditions that is important to understand. This is where the crystal size distributions (CSD) method becomes fundamentally valuable. Just as chemical thermodynamics offers a quantitative macroscopic means of investigating chemical processes that occur at the atomic level, crystal size distribution theory quantitatively relates the overall observed spectrum of crystal sizes to both the kinetics of crystallization and the physical processes affecting the population of crystals themselves. Petrography, which is the qualitative study of rock textures, is the oldest, most comprehensively developed, and perhaps most beautiful aspect of studying magmatic rocks. It is the ultimate link to the kinetics of crystallization and the integrated space,time history of evolution of every magma. CSD analysis offers a quantitative inroad to unlocking and quantifying the observed textures of magmatic rocks. Perhaps the most stunning feature of crystal-rich magmatic rocks is that the constituent crystal populations show smooth and often quasi-linear log-normal distributions of negative slope when plotted as population density against crystal size. These patterns are decipherable using CSD theory, and this method has proven uniquely valuable in deciphering the kinetics of crystallization of magma. The CSD method has been largely developed in chemical engineering by Randolph and Larson,1,2 among many others, for use in understanding industrial crystallization processes, and its introduction to natural magmatic systems began in 1988. The CSD approach is particularly valuable in its ease of application to complex systems. It is an aid to classical kinetic theory by being, in its purest form, free of any atomistic assumptions regarding crystal nucleation and growth. Yet the CSD method provides kinetic information valuable to understanding the connection between crystal nucleation and growth and the overall cooling and dynamics of magma. It offers a means of investigating crystallization in dynamic systems, involving both physical and chemical processes, independent of an exact kinetic theory. The CSD method applied to rocks shows a systematic and detailed history of crystal nucleation and growth that forms the foundation of a comprehensive and general model of magma solidification. [source] Conventional and nanometric nucleating agents in poly(,-caprolactone) foaming: Crystals vs. bubbles nucleationPOLYMER ENGINEERING & SCIENCE, Issue 2 2008Carlo Marrazzo The aim of this article was to investigate the nucleating ability of different nucleating agents for the foaming of poly(,-caprolactone), a biodegradable, semicrystalline polymer. In particular, the efficiency of the nucleating agent in inducing the formation of the gaseous phase has been compared to the efficiency in inducing the formation of the crystalline phase. In effect, in foaming of semicrystalline polymers, bubble nucleation and crystal nucleation are concurrent and somehow interacting phenomena. Here, these two aspects have been evidenced and clarified. Foams were prepared by using a batch process with the pressure quench method, with nitrogen and carbon dioxide as the blowing agents. Conventional and novel nucleating agents were used: talc has been compared to several novel nanometric particles of different geometries and dimensions, such as titanium dioxide and alumina powders, exfoliated and intercalated clays, and carbon nanotubes. Foam densities and morphologies, in terms of number of cells per initial unit volume, were measured and found to depend both on crystalline phase nucleation and gaseous phase nucleation. In fact, the different nucleating agents, depending on shape, dimension, and surface functionalization, selectively nucleated the crystallites and/or the bubbles, affecting, respectively, bubble growth (and, hence, final foam density) and bubble nucleation (and, hence, cell number density,morphology). POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] Promoting crystallization of antibody,antigen complexes via microseed matrix screeningACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2010Galina Obmolova The application of microseed matrix screening to the crystallization of antibody,antigen complexes is described for a set of antibodies that include mouse anti-IL-13 antibody C836, its humanized version H2L6 and an affinity-matured variant of H2L6, M1295. The Fab fragments of these antibodies were crystallized in complex with the antigen human IL-13. The initial crystallization screening for each of the three complexes included 192 conditions. Only one hit was observed for H2L6 and none were observed for the other two complexes. Matrix self-microseeding using these microcrystals yielded multiple hits under various conditions that were further optimized to grow diffraction-quality H2L6 crystals. The same H2L6 seeds were also successfully used to promote crystallization of the other two complexes. The M1295 crystals appeared to be isomorphous to those of H2L6, whereas the C836 crystals were in a different crystal form. These results are consistent with the concept that the conditions that are best for crystal growth may be different from those that favor nucleation. Microseed matrix screening using either a self-seeding or cross-seeding approach proved to be a fast, robust and reliable method not only for the refinement of crystallization conditions but also to promote crystal nucleation and increase the hit rate. [source] In situ measurement of erythromycin crystal size distribution by focused beam reflective measurement technologyASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009Kui Chen Abstract Many factors such as temperature, solvent and water-dosing rate have impact on erythromycin solventing-out process. This article studies the water dosing effect on erythromycin solventing-out process measured by focused beam reflective measurement technology. Our experiments showed that the overall number of nucleated particles went through an explosive increasing after the metastable zone. Followed by a slight decreasing, it reached a relative constancy for a long time. This suggests that earlier crystal nucleation can be induced with higher water dosing rate, nevertheless, it is the same amount of water dosed when the overall crystal number reached its peak during the explosive emergence of crystals. After the overall particle number climaxed, further extension of crystal growth time would not bring any significant increase in crystal size. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Crystallization and preliminary X-ray diffraction study of mammalian mitochondrial seryl-tRNA synthetaseACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2004Sarin Chimnaronk The mitochondrial seryl-tRNA synthetase (mt SerRS) from Bos taurus was overexpressed in Escherichia coli and crystallized using the sitting-drop vapour-diffusion method. Crystals grew in a very narrow range of conditions using PEG 8000 as precipitant at room temperature. An appropriate concentration of lithium sulfate was critical for crystal nucleation. Crystals diffracted well beyond a resolution of 1.6,Å and were found to belong to the orthorhombic space group C2221, with unit-cell parameters a = 79.89, b = 230.42, c = 135.60,Å. There is one dimer (Mr, 113,kDa) in the asymmetric unit, with a solvent content of 55%. Efforts to solve the phase problem by molecular replacement are under way. [source] Experimental observations and numerical modelling of diffusion-driven crystallisation processesACTA CRYSTALLOGRAPHICA SECTION D, Issue 10-1 2002Luigi Carotenuto This paper reports experimental results and modelling on the crystallisation processes induced by counter diffusion method of a precipitant agent in a lysozyme protein solution. Comparison between experimental observations and numerical simulations in the presence of convection and sedimentation and without them (suppressed using gel) provides a validation of the model. Different values of the initial protein concentration are used, in order to investigate the effects of supersaturation conditions on the process, and in particular on nucleation. The model and the experimental approach may represent a useful methodology for the determination of the parameters and conditions that may lead to protein crystallisation. A Mach-Zehnder interferometer is used to monitor the transport dynamics insitu in the fluid phase by observing the compositional field. The effect of the solute transport gives rise to a "nucleation front" that propagates inside the protein solution. The crystal formation, caused by progressing of the front, results in a modulation in time and in space (similar to Liesegang patterns), due to the non-linear interplay among transport, crystal nucleation and growth. Both experimental observation and numerical modelling show spatial and size distributions of crystals that demonstrate comparable evidences of the phenomena. [source] The Corynebacterium glutamicum aconitase repressor: scratching around for crystalsACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 9 2010Javier García-Nafría Imperfections on the surfaces of crystallization containers are known to influence crystal formation and are thought to do so by helping to overcome the nucleation barrier. The intentional creation of imperfections has been widely applied to induce crystallization of small molecules, but has not been reported for protein crystallization. Here, the crystallization and preliminary X-ray analysis of the TetR-type aconitase repressor are reported. This regulator was the first transcription factor to be identified in the regulation of the tricarboxylic acid cycle in Corynebacterium glutamicum, an organism that is of special industrial interest and is an emerging model organism for Corynebacterineae. Successful crystallization involved introducing manual scratches on the surface of standard commercial plates, which led to a substantial improvement in crystal nucleation and quality. [source] | |||||||||||||||||||||||||