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Lysozyme Crystals (lysozyme + crystal)
Kinds of Lysozyme Crystals Selected AbstractsTemplate-Directed Synthesis of Nanoplasmonic Arrays by Intracrystalline Metalization of Cross-Linked Lysozyme Crystals,ANGEWANDTE CHEMIE, Issue 3 2010Mina Guli Redoxreaktionen dienten dazu, periodisch angeordnete Ag- und Au-Nanostrukturen in den Lösungsmittelkanälen vernetzter Lysozymkristalle abzuscheiden (siehe Bild für einen Ag-dotierten Lysozymkristall). Da Lysozym in zahlreichen polymorphen Formen kristallisiert werden kann, besteht die Möglichkeit, über die Wahl des Proteingitters zu maßgeschneiderten metallischen Nanostrukturen zu gelangen. [source] FBR: a robust method to determine the basis matrix of the Bravais lattice from oscillation imagesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 3-2 2000Klaus Döhring The FBR (Fourier basis reconstruction) method described in this paper has been designed to determine the basis matrix of the Bravais lattice with respect to the laboratory frame of reference and without prior knowledge of cell constants, particularly for protein crystals of comparatively low quality. It is based on Fourier analysis of a three-dimensional intensity distribution in reciprocal space, which is directly obtained from observed intensity distributions, provided that they are recorded by the rotation method using a fixed X-ray wavelength, resulting in a direct-space determination of the basis vectors. After a description of the motivation and theory behind the method, it is tested by application to numerically generated images of a virtual sample crystal and to experimental data of a lysozyme crystal with well known cell constants. Finally, FBR is applied to a set of images of bacteriorhodopsin crystals suffering from strong anisotropic spot broadening; this case provided the original motivation for the present work. [source] Overview and new developments in softer X-ray (2Å < , < 5Å) protein crystallographyJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2004John R. Helliwell New methodologies with synchrotron radiation and X-ray free electron lasers (XFELs) in structural biology are being developed. Recent trends in harnessing softer X-rays in protein crystallography for phase determination are described. These include reference to a data-collection test at 2.6 Å wavelength with a lysozyme crystal on SRS station 7.2 (Helliwell, 1983) and also use of softer X-rays (2,Å wavelength) to optimise f," at the xenon L1 absorption edge in the Single Isomorphous Replacement Optimised Anomalous Scattering ('SIROAS') structure determination of apocrustacyanin A1 with four, partially occupied, xenon atoms (Cianci et al., 2001; Chayen et al., 2000). The hand of the protein was determined using the f," enhanced sulphur anomalous signal from six disulphides in the protein dimer of 40,kDa. In a follow-up study the single wavelength xenon L1 -edge f," optimised data set alone was used for phase determination and phase improvement by solvent flattening etc. (CCP4 DM) (Olczak et al., 2003). Auto-tracing of the protein was feasible but required additional diffraction data at higher resolution. This latter could be avoided in future by using improved tilted detector settings during use of softer X-rays, i.e. towards back-scattering recording (Helliwell, 2002). The Olczak et al. study has already led to optimisation of the new SRS beamline MPW,MAD,10 (see www.nwsgc.ac.uk) firstly involving the thinning of the beryllium windows as much as possible and planning for a MAR Research tilted detector `desk top beamline' geometry. Thus the use of softer, i.e. 2 to 3,Å wavelength range, X-rays will allow optimisation of xenon and iodine L -edge f," and enhancing of sulphur f," signals for higher throughput protein crystallography. Softer X-rays utilisation in protein crystallography includes work done on SRS bending-magnet station 7.2 in the early 1980s by the author as station scientist (Helliwell, 1984). In the future development of XFELs these softer X-ray wavelengths could also be harnessed and relax the demands to some extent on the complexity and cost of an XFEL. Thus, by use of say 4,Å XFEL radiation and use of a back-scattering geometry area detector the single molecule molecular transform could be sampled to a spatial resolution of 2,Å, sufficient, in principle, for protein model refinement (Miao et al., 1999). Meanwhile, Miao et al. (2003) report the first experimental recording of the diffraction pattern from intact Escherichia coli bacteria using coherent X-rays, with a wavelength of 2,Å, at a resolution of 30,nm and a real-space image constructed. The new single-particle X-ray diffraction-imaging era has commenced. [source] Identification of dislocations in large tetragonal hen egg-white lysozyme crystals by synchrotron white-beam topographyJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2003M. Tachibana Large tetragonal hen egg-white (HEW) lysozyme crystals have been grown by a salt concentration-gradient method. The grown crystals, of thicknesses greater than 1.5,mm, were observed by means of X-ray topography using white-beam synchrotron radiation. Line contrasts clearly appeared on the Laue topographs. Extinction of the line images was observed in specific reflections. These results mean that the observed lines correspond to dislocation images. From the extinction criterion it is shown that the predominant dislocations are of screw character with ,110, Burgers vectors. In addition, dislocation loops with [001] Burgers vectors have been found in a tetragonal HEW lysozyme crystal including some cracks. These results are discussed in the light of dislocation elastic energy and slip systems in the crystals. [source] Diffraction and imaging study of imperfections of crystallized lysozyme with coherent X-raysACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2004Z. W. Hu Phase-contrast X-ray diffraction imaging and high-angular-resolution diffraction combined with phase-contrast radiographic imaging were employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in the symmetric Laue case. The full-width at half-maximum (FWHM) of a 4,4,0 rocking curve measured from the original crystal was ,16.7,arcsec and imperfections including line defects, inclusions and other microdefects were observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the ,1,1,0, growth front and have been found to originate mostly in a central growth area and occasionally in outer growth regions. Inclusions of impurities or formations of foreign particles in the central growth region are resolved in the images with high sensitivity to defects. Slow dehydration led to the broadening of a fairly symmetric 4,4,0 rocking curve by a factor of ,2.6, which was primarily attributed to the dehydration-induced microscopic effects that are clearly shown in X-ray diffraction images. The details of the observed defects and the significant change in the revealed microstructures with drying provide insight into the nature of imperfections, nucleation and growth, and the properties of protein crystals. [source] Phase transition of triclinic hen egg-white lysozyme crystal associated with sodium bindingACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2004Kazuaki Harata A triclinic crystal of hen egg-white lysozyme obtained from a D2O solution at 313,K was transformed into a new triclinic crystal by slow release of solvent under a temperature-regulated nitrogen-gas stream. The progress of the transition was monitored by X-ray diffraction. The transition started with the appearance of strong diffuse streaks. The diffraction spots gradually fused and faded with the emergence of diffraction from the new lattice; the scattering power of the crystal fell to a resolution of 1.5,Å from the initial 0.9,Å resolution. At the end of the transition, the diffuse streaks disappeared and the scattering power recovered to 1.1,Å resolution. The transformed crystal contained two independent molecules and the solvent content had decreased to 18% from the 32% solvent content of the native crystal. The structure was determined at 1.1,Å resolution and compared with the native structure refined at the same resolution. The backbone structures of the two molecules in the transformed crystal were superimposed on the native structure with root-mean-square deviations of 0.71 and 0.96,Å. A prominent structural difference was observed in the loop region of residues Ser60,Leu75. In the native crystal, a water molecule located at the centre of this helical loop forms hydrogen bonds to main-chain peptide groups. In the transformed crystal, this water molecule is replaced by a sodium ion with octahedral coordination that involves water molecules and a nitrate ion. The peptide group connecting Arg73 and Asn74 is rotated by 180° so that the CO group of Arg73 can coordinate to the sodium ion. The change in the X-ray diffraction pattern during the phase transition suggests that the transition proceeds at the microcrystal level. A mechanism is proposed for the crystal transformation. [source] Macromolecular crystallography at high pressure with pneumatic diamond anvil cells handled by a six-axis robotic armJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010Eric Girard A new pneumatic diamond anvil cell has been constructed, generating continuous pressure and temperature variations in the range 0,2.5,GPa and 293,393,K. The cell is designed mainly for high-pressure macromolecular crystallography and should facilitate pressure and temperature annealing of the sample. The analysis is reported of several diffraction data sets of tetragonal hen egg-white lysozyme crystals loaded either in the new cell or in a currently used membrane-based cell. These experiments were performed on beamline FIP-BM30A at the ESRF, Grenoble, a macromolecular crystallography beamline on a bending magnet. Cells were handled and automatically centred by a six-axis robotic arm that was used as a goniometer for data collection by the oscillation method. [source] Dose dependence of radiation damage for protein crystals studied at various X-ray energiesJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2007Nobutaka Shimizu Radiation damage to protein crystals is the most serious problem in obtaining accurate structures from protein crystallography. In order to examine the photon energy dependence of radiation damage, 12 to 15 data sets from each of nine tetragonal lysozyme crystals were collected at nine different X-ray energies (6.5, 7.1, 8.3, 9.9, 12.4, 16.5, 20.0, 24.8 and 33.0,keV) using beamline BL41XU at SPring-8. All results were compared on the basis of absorbed dose, expressed in Gray (Gy). Crystallographic statistics, such as the values of lattice constants, Rmerge and I/,(I), for each data set degraded at all nine energies as the exposure time for each crystal increased. In all data sets, radiation damage was observed after the absorbed dose exceeded 106,Gy. However, from the point of view of crystallographic statistics normalized to the absorbed dose, no clear dependence on photon energy was observed in these results. Structural refinement showed that the average B -factor for the last data set was larger than that for the first data set at all energies tested. However, no energy dependence of radiation damage on B -factor was found. Furthermore, disruption of disulfide bonds due to radiation damage was observed in electron density maps even at the highest photon energy (33,keV) used in this study. Therefore, these results suggest that radiation damage in the energy range investigated could be evaluated based on absorbed dose without energy dependence, and that it is important to minimize the absorbed dose in a crystal sample for obtaining an accurate protein structure. [source] µGISAXS and protein nanotemplate crystallization: methods and instrumentationJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2005Eugenia Pechkova Microbeam grazing-incidence small-angle X-ray scattering (µGISAXS) has been used and the technique has been improved in order to investigate protein nucleation and crystal growth, assisted by a protein nanotemplate. The aim is to understand the protein nanotemplate method in detail, as this method has been proved capable of accelerating and increasing crystal size and quality as well as inducing crystallization of proteins that are not crystallizable by classical methods. The nanotemplate experimental setup was used for drops containing growing lysozyme crystals at three different stages of growth. [source] Identification of dislocations in large tetragonal hen egg-white lysozyme crystals by synchrotron white-beam topographyJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2003M. Tachibana Large tetragonal hen egg-white (HEW) lysozyme crystals have been grown by a salt concentration-gradient method. The grown crystals, of thicknesses greater than 1.5,mm, were observed by means of X-ray topography using white-beam synchrotron radiation. Line contrasts clearly appeared on the Laue topographs. Extinction of the line images was observed in specific reflections. These results mean that the observed lines correspond to dislocation images. From the extinction criterion it is shown that the predominant dislocations are of screw character with ,110, Burgers vectors. In addition, dislocation loops with [001] Burgers vectors have been found in a tetragonal HEW lysozyme crystal including some cracks. These results are discussed in the light of dislocation elastic energy and slip systems in the crystals. [source] Feasibility of one-shot-per-crystal structure determination using Laue diffractionACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2010Sterling Cornaby Crystal size is an important factor in determining the number of diffraction patterns which may be obtained from a protein crystal before severe radiation damage sets in. As crystal dimensions decrease this number is reduced, eventually falling to one, at which point a complete data set must be assembled using data from multiple crystals. When only a single exposure is to be collected from each crystal, the polychromatic Laue technique may be preferable to monochromatic methods owing to its simultaneous recording of a large number of fully recorded reflections per image. To assess the feasibility of solving structures using single Laue images from multiple crystals, data were collected using a `pink' beam at the CHESS D1 station from groups of lysozyme crystals with dimensions of the order of 20,30,µm mounted on MicroMesh grids. Single-shot Laue data were used for structure determination by molecular replacement and correct solutions were obtained even when as few as five crystals were used. [source] The effect of protein,precipitant interfaces and applied shear on the nucleation and growth of lysozyme crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 11 2009Nuno M. Reis This paper is concerned with the effect of protein,precipitant interfaces and externally applied shear on the nucleation and growth kinetics of hen egg-white lysozyme crystals. The early stages of microbatch crystallization of lysozyme were explored using both optical and confocal fluorescence microscopy imaging. Initially, an antisolvent (precipitant) was added to a protein drop and the optical development of the protein,precipitant interface was followed with time. In the presence of the water-soluble polymer poly(ethylene glycol) (PEG) a sharp interface was observed to form immediately within the drop, giving an initial clear separation between the lighter protein solution and the heavier precipitant. This interface subsequently became unstable and quickly developed within a few seconds into several unstable `fingers' that represented regions of high concentration-gradient interfaces. Confocal microscopy demonstrated that the subsequent nucleation of protein crystals occurred preferentially in the region of these interfaces. Additional experiments using an optical shearing system demonstrated that oscillatory shear significantly decreased nucleation rates whilst extending the growth period of the lysozyme crystals. The experimental observations relating to both nucleation and growth have relevance in developing efficient and reliable protocols for general crystallization procedures and the controlled crystallization of single large high-quality protein crystals for use in X-ray crystallography. [source] The interdependence of wavelength, redundancy and dose in sulfur SAD experimentsACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2008Michele Cianci In the last decade, the popularity of sulfur SAD anomalous dispersion experiments has spread rapidly among synchrotron users as a quick and streamlined way of solving the phase problem in macromolecular crystallography. On beamline 10 at SRS (Daresbury Laboratory, UK), a versatile design has allowed test data sets to be collected at six wavelengths between 0.979 and 2.290,Å in order to evaluate the importance and the interdependence of experimental variables such as the Bijvoet ratio, wavelength, resolution limit, data redundancy and absorbed X-ray dose in the sample per data set. All the samples used in the experiments were high-quality hen egg-white lysozyme crystals. X-radiation damage was found to affect disulfide bridges after the crystals had been given a total dose of 0.20 × 107,Gy. However, with such a total dose, it was still possible in all cases to find a strategy to collect data sets to determine the sulfur substructure and produce good-quality phases by choosing an optimum combination of wavelength, exposure time and redundancy. A ,|,ano|/,(,ano), greater than 1.5 for all resolution shells was a necessary requirement for successful sulfur SAD substructure location. Provided this is achieved, it seems possible to find an optimum compromise between wavelength, redundancy and dose to provide phasing information. The choice of the wavelength should then follow the sample composition and the diffracting properties of the crystal. For strongly diffracting crystals, wavelengths equal or shorter than 1.540,Å can be selected to capture the available data (provided the Bijvoet ratio is reasonable), while a longer wavelength, to gain as high a Bijvoet ratio as possible, must be used for more weakly diffracting crystals. These results suggest that an approach to a sulfur SAD experiment based on a complete description of the crystal system and the instrument for data collection is useful. [source] Regular arrangement of periodates bound to lysozymeACTA CRYSTALLOGRAPHICA SECTION D, Issue 9 2005Jan Ondrá The structure of tetragonal hen egg-white lysozyme soaked in a periodate solution has been determined to a resolution of 1.8,Å. Four high-occupancy periodate positions have been identified on the basis of the anomalous signal of the I atoms. The four periodates exhibit a regular rectangular arrangement on the surface of the lysozyme molecule. No similar regular arrangement was found either in lysozyme crystals soaked in other heavy-atom anions or in other structures from the Protein Data Bank. Depending on their position on the surface of the protein, the periodate ions deviate to a varying extent from ideal octahedral geometry. [source] Structure determination of a novel protein by sulfur SAD using chromium radiation in combination with a new crystal-mounting methodACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2005Yu Kitago A novel and easy crystal-mounting technique was developed for the sulfur SAD method using Cr,K, radiation (2.29,Å). Using this technique, the cryo-buffer and cryoloop around the protein crystal can be removed before data collection in order to eliminate their X-ray absorption. The superiority and reproducibility of the data sets with this mounting technique were demonstrated using tetragonal hen egg-white lysozyme crystals. The structure of a novel protein, PH1109, from Pyrococcus horikoshii OT3 was solved using this technique. At the wavelength of Cr,K, radiation, the anomalous signal ,|,F|,/,|F|, of PH1109 is expected to be 1.72% as this protein of 144 residues includes four methionines and two cysteines. Sulfur SAD phasing was performed using SHELXD and SHELXE. In the case of the data set obtained using this novel crystal-mounting technique, 54.9% of all residues were built with side chains automatically by RESOLVE. On the other hand, only 16.0% were built with side chains for the data set collected using the standard cryoloop. These results indicated that this crystal-mounting technique was superior to the standard loop-mounting method for the measurement of small anomalous differences at longer wavelength and yielded better results in sulfur-substructure solution and initial phasing. The present study demonstrates that the sulfur SAD method with a chromium source becomes enhanced and more practical for macromolecular structure determination using the new crystal-mounting technique. [source] Crystal quality and differential crystal-growth behaviour of three proteins crystallized in gel at high hydrostatic pressureACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2005A. Kadri Pressure is a non-invasive physical parameter that can be used to control and influence protein crystallization. It is also found that protein crystals of superior quality can be produced in gel. Here, a novel crystallization strategy combining hydrostatic pressure and agarose gel is described. Comparative experiments were conducted on hen and turkey egg-white lysozymes and the plant protein thaumatin. Crystals could be produced under up to 75,100,MPa (lysozymes) and 250,MPa (thaumatin). Several pressure-dependent parameters were determined, which included solubility and supersaturation of the proteins, number, size and morphology of the crystals, and the crystallization volume. Exploration of three-dimensional phase diagrams in which pH and pressure varied identified growth conditions where crystals had largest size and best morphology. As a general trend, nucleation and crystal-growth kinetics are altered and nucleation is always enhanced under pressure. Further, solubility of the lysozymes increases with pressure while that of thaumatin decreases. Likewise, changes in crystallization volumes at high and atmospheric pressure are opposite, being positive for the lysozymes and negative for thaumatin. Crystal quality was estimated by analysis of Bragg reflection profiles and X-ray topographs. While the quality of lysozyme crystals deteriorates as pressure increases, that of thaumatin crystals improves, with more homogeneous crystal morphology suggesting that pressure selectively dissociates ill-formed nuclei. Analysis of the thaumatin structure reveals a less hydrated solvent shell around the protein when pressure increases, with ,20% less ordered water molecules in crystals grown at 150,MPa when compared with those grown at atmospheric pressure (0.1,MPa). Noticeably, the altered water distribution is seen in depressurized crystals, indicating that pressure triggers a stable structural alteration on the protein surface while its polypeptide backbone remains essentially unaltered. [source] Structural consequences of hen egg-white lysozyme orthorhombic crystal growth in a high magnetic field: validation of X-ray diffraction intensity, conformational energy searching and quantitative analysis of B factors and mosaicityACTA CRYSTALLOGRAPHICA SECTION D, Issue 3 2005Shinya Saijo A novel method has been developed to improve protein-crystal perfection during crystallization in a high magnetic field and structural studies have been undertaken. The three-dimensional structure of orthorhombic hen egg-white (HEW) lysozyme crystals grown in a homogeneous and static magnetic field of 10,T has been determined and refined to a resolution of 1.13,Å and an R factor of 17.0%. The 10,T crystals belonged to space group P212121, with unit-cell parameters a = 56.54,(3), b = 73.86,(6), c = 30.50,(2),Å and one molecule per asymmetric unit. A comparison of the structures of the 0,T and 10,T crystals has been carried out. The magnitude of the structural changes, with a root-mean-square deviation value of 0.75,Å for the positions of all protein atoms, is similar to that observed when an identical protein structure is resolved in two different crystalline lattices. The structures remain similar, with the exception of a few residues e.g. Arg68, Arg73, Arg128 and Gln121. The shifts of the arginine residues result in very significant structural fluctuations, which can have large effects on a protein's crystallization properties. The high magnetic field contributed to an improvement in diffraction intensity by (i) the displacement of the charged side chains of Arg68 and Arg73 in the flexible loop and of Arg128 at the C-terminus and (ii) the removal of the alternate conformations of the charged side chains of Arg21, Lys97 or Arg114. The improvement in crystal perfection might arise from the magnetic effect on molecular orientation without structural change and differences in molecular interactions. X-ray diffraction and molecular-modelling studies of lysozyme crystals grown in a 10,T field have indicated that the field contributes to the stability of the dihedral angle. The average difference in conformational energy has a value of ,578,kJ,mol,1 per charged residue in favour of the crystal grown in the magnetic field. For most protein atoms, the average B factor in the 10,T crystal shows an improvement of 1.8,Å2 over that for the 0,T control; subsequently, the difference in diffraction intensity between the 10,T and 0,T crystals corresponds to an increase of 22.6% at the resolution limit. The mosaicity of the 10,T crystal was better than that of the 0,T crystal. More highly isotropic values of 0.0065, 0.0049 and 0.0048° were recorded along the a, b and c axes, respectively. Anisotropic mosaicity analysis indicated that crystal growth is most perfect in the direction that corresponds to the favoured growth direction of the crystal, and that the crystal grown in the magnetic field had domains that were three times the volume of those of the control crystal. Overall, the magnetic field has improved the quality of these crystals and the diffracted intensity has increased significantly with the magnetic field, leading to a higher resolution. [source] Accurate rocking-curve measurements on protein crystals grown in a homogeneous magnetic field of 2.4,TACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2004Daniel Lübbert Differences in mosaicity between lysozyme crystals grown inside and outside a homogeneous magnetic field of 2.4,T and with and without agarose gel were investigated by X-ray diffraction rocking-curve measurements. High angular resolution was achieved using an Si(113) four-reflection Bartels monochromator. The results show that (i) all crystals were highly perfect, (ii) the mosaicities were clearly anisotropic and (iii) the mosaicities varied more strongly within each group of crystals (grown under identical conditions) than the average values across groups. In particular, the effect of the magnetic field on crystal mosaicity was found to be very small. Finally, the spatial distribution of mosaic blocks inside a protein crystal was visualized with a novel diffraction technique using a high spatial resolution two-dimensional CCD detector. [source] Morphology and the strength of intermolecular contacts in protein crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 8 2003Yoshiki Matsuura The strengths of intermolecular contacts (macrobonds) and the areas occupied by each contact on the molecular surface were estimated in four polymorphic modifications of lysozyme crystals based on the bond strengths between individual atomic pairs belonging to the molecules in contact. It has been shown that the periodic bond chains of these macrobonds account for the morphology of protein crystals. The Coulombic contribution to the macrobond strength has also been estimated. Making use of the contact strengths and taking into account bond hydration, crystal,water interfacial energies were also estimated for different crystal faces. The areas of all contacts are mapped on the molecular surface, making use of a polar-coordinate representation of the contact. Comparing the locations of the intermolecular contacts in the different polymorphic crystal modifications, it is shown that these contacts can form a wide variety of patches on the molecular surface. The patches are located practically everywhere on the surface except for the inside of a concave active site. It is also shown that the contacts, which frequently involve water molecules, are formed by specific intermolecular hydrogen bonds on a background of non-specific attractive electrostatic interactions. Typical values of the macrobond strength are compared with the strength of association in other protein-complex systems. [source] Apocrustacyanin C1 crystals grown in space and on earth using vapour-diffusion geometry: protein structure refinements and electron-density map comparisonsACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2003Jarjis Habash Models of apocrustacyanin C1 were refined against X-ray data recorded on Bending Magnet 14 at the ESRF to resolutions of 1.85 and 2,Å from a space-grown and an earth-grown crystal, respectively, both using vapour-diffusion crystal-growth geometry. The space crystals were grown in the APCF on the NASA Space Shuttle. The microgravity crystal growth showed a cyclic nature attributed to Marangoni convection, thus reducing the benefits of the microgravity environment, as reported previously [Chayen et al. (1996), Q. Rev. Biophys.29, 227,278]. A subsequent mosaicity evaluation, also reported previously, showed only a partial improvement in the space-grown crystals over the earth-grown crystals [Snell et al. (1997), Acta Cryst. D53, 231,239], contrary to the case for lysozyme crystals grown in space with liquid,liquid diffusion, i.e. without any major motion during growth [Snell et al. (1995), Acta Cryst. D52, 1099,1102]. In this paper, apocrustacyanin C1 electron-density maps from the two refined models are now compared. It is concluded that the electron-density maps of the protein and the bound waters are found to be better overall for the structures of apocrustacyanin C1 studied from the space-grown crystal compared with those from the earth-grown crystal, even though both crystals were grown using vapour-diffusion crystal-growth geometry. The improved residues are on the surface of the protein, with two involved in or nearby crystal lattice-forming interactions, thus linking an improved crystal-growth mechanism to the molecular level. The structural comparison procedures developed should themselves be valuable for evaluating crystal-growth procedures in the future. [source] Soaking: the effect of osmotic shock on tetragonal lysozyme crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2002F. J. López-Jaramillo Protein crystals crack when they are soaked in a solution with ionic strength sufficiently different from the environment in which they grew. It is demonstrated for the case of tetragonal lysozyme that the forces involved and the mechanisms that lead to the formation of cracks are different for hypertonic and hypotonic soaking. Tetragonal lysozyme crystals are very sensitive to hypotonic shocks and, after a certain waiting time, cracks always appear with a characteristic pattern perpendicular to the crystallographic c axis. Conversely, a hypertonic shock is better withstood: cracks do not display any deterministic pattern, are only visible at higher differences in ionic strength and after a certain time a phenomenon of crystal reconstruction occurs and the cracks vanish. At the lattice level, the unit-cell volume expands in hypotonic shock and shrinks under hypertonic conditions. However, the compression of the unit cell is anisotropic: the c axis is compressed to a minimum, beyond which it expands despite the unit-cell volume continuing to shrink. This behaviour is a direct consequence of the positive charge that the crystals bear and the existence of channels along the crystallographic c axis. Both features are responsible for the Gibbs,Donnan effect which limits the free exchange of ions and affects the movement of water inside the channels and bound to the protein. [source] Structural effects of monovalent anions on polymorphic lysozyme crystalsACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2001M. C. Vaney Understanding direct salt effects on protein crystal polymorphism is addressed by comparing different crystal forms (triclinic, monoclinic, tetragonal and orthorhombic) for hen, turkey, bob white quail and human lysozymes. Four new structures of hen egg-white lysozyme are reported: crystals grown in the presence of NapTS diffracted to 1.85,Å, of NaI to 1.6,Å, of NaNO3 to 1.45,Å and of KSCN to 1.63,Å. These new structures are compared with previously published structures in order to draw a mapping of the surface of different lysozymes interacting with monovalent anions, such as nitrate, chloride, iodide, bromide and thiocyanate. An analysis of the structural sites of these anions in the various lysozyme structures is presented. This study shows common anion sites whatever the crystal form and the chemical nature of anions, while others seem specific to a given geometry and a particular charge environment induced by the crystal packing. [source] Precipitants and additives for membrane crystallization of lysozymeBIOTECHNOLOGY JOURNAL, Issue 11 2006Xinmiao Zhang Abstract Membrane crystallization is a newly developed crystallization technique that has proven to be superior in producing good crystal forms under operating conditions that are not appropriate to perform the crystallization process by other traditional techniques. In this work, static membrane crystallization was carried out on lysozyme, with hollow-fiber microporous hydrophobic membranes. Numerous precipitant and additive types and concentrations were employed in the crystallization processes in order to select the most appropriate precipitant and additive types and to find their corresponding concentration levels that can yield the best crystal forms. The crystallization processes were analyzed in two ways: firstly, by evaluation of the transmembrane fluxes obtained by using different precipitants and additives; secondly, by utilization of the images and results obtained from the micrography and IR spectra in comparisons and evaluations of the crystals formed under all kinds of conditions. Moreover, the size distributions of the crystals yielded under several typical crystallization conditions were analyzed, and turbidity and induction time periods obtained during typical crystallization experiments were also measured. Amongst the numerous precipitants and additives tested, the most appropriate precipitant type and additive were chosen and their concentrations were optimized. Good lysozyme crystals were obtained using a certain precipitant and additive. The obtained results from this work further support the advantages of utilizing the membrane crystallization technique for macromolecule crystallizations. [source] | ||||||||||