Hexagonal Plate Crystals Research Articles

Hexagonal crystalline Magnus' green salt analogues prepared from hydroxy-functionalised Pt and Pd complexes.

New Magnus' green salt (MGS) analogues, [M(dabdOH)2][MCl4]·2H2O (dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol; M = Pd (1) and M = Pt(2)), in which [M(dabdOH)2]2+ and [MCl4]2- are stacked alternately to form linear chains, were obtained as hexagonal plate crystals. The hexagonal shape and large crystal size are unprecedented features as MGS analogues. An unusual trigonal grade separation of chain complexes has been revealed by the structural analysis. 1 and 2 exhibited remarkable yellow and pink colours, respectively, which are derived from weak M⋯M interactions. The dabdOH ligand, which has an additional hydrogen donor group (hydroxy group), produces a multiple-hydrogen-bond network. The combination of intrachain and interchain hydrogen bonds gives a two-dimensional (2D) hydrogen-bond sheet, and each 2D sheet is indirectly connected by hydrogen bonds via lattice water molecules. The OH-functionalised ligand greatly increases the hydrophilicity of the MGS analogues and yields the largest single crystals of all MGS analogues reported so far. The trigonal grade-separated chain structure is likely due to the geometric matching between the periodicity of chains and the short axis width of the chain. This strategy opens up new insight for preparing large crystals of MGS analogues and for constructing trigonal grade-separated nanowires in molecular crystals.

A Polarimetric Analysis of Ice Microphysical Processes in Snow, Using Quasi-Vertical Profiles

AbstractThis study implements a new quasi-vertical profile (QVP) methodology to investigate the microphysical evolution and significance of intriguing winter polarimetric signatures and their statistical correlations. QVPs of transitional stratiform and pure snow precipitation are analyzed using WSR-88D S-band data, alongside their corresponding environmental thermodynamic High-Resolution Rapid Refresh model analyses. QVPs of KDP and ZDR are implemented to demonstrate their value in interpreting elevated ice processes. Several fascinating and repetitive signatures are observed in the QVPs for differential reflectivity ZDR and specific differential phase KDP, in the dendritic growth layer (DGL), and at the tops of clouds. The most striking feature is maximum ZDR (up to 6 dB) in the DGL occurring near the −10-dBZ ZH contour within low KDP and during shallower and warmer cloud tops. Conversely, maximum KDP (up to 0.3° km−1) in the DGL occurs within low ZDR and during taller and colder cloud tops. Essentially, ZDR and KDP in the DGL are anticorrelated and strongly depend on cloud-top temperature. Analyses also show correlations indicating larger ZDR within lower ZH in the DGL and larger KDP within greater ZH in the DGL. The high-ZDR regions are likely dominated by growth of a mixture of highly oblate dendrites and/or hexagonal plates, or prolate needles. Regions of high KDP are expected to be overwhelmed with snow aggregates and crystals with irregular or nearly spherical shapes, seeded at cloud tops. Furthermore, QVP indications of hexagonal plate crystals within the DGL are verified using in situ microphysical measurements, demonstrating the reliability of QVPs in evaluating ice microphysics in upper regions of winter clouds.

Ice Crystal Habits and Growth Processes in Stratiform Clouds with Embedded Convection Examined through Aircraft Observation in Northern China

Abstract Ice crystal habits and growth processes in two cases of stratiform clouds with embedded convection are investigated using data observed simultaneously from three aircraft on 18 April 2009 and 1 May 2009 as part of the Beijing Cloud Experiment (BCE). The results show that the majority of ice crystal habits found in the two cases at temperatures between 0° and −16°C included platelike, needle column, capped column, dendrite, and irregular. A mixture of several ice crystal habits was identified in all of the clouds studied. However, the ice crystals recorded in the embedded convection regions contained more dendrites and possessed heavier riming degrees, and the ice crystals identified in the stratiform clouds contained more hexagonal plate crystals. Both riming and aggregation processes played central roles in the broadening of particle size distributions (PSDs), and these processes were more active in embedded convection regions than in stratiform regions. However, riming was more prevalent in the 18 April case than aggregation, though aggregates were evident. In contrast, the 1 May case had a more dominant aggregation processes, but also riming. With the decrease in height, PSDs broadened in both embedded convection regions and stratiform regions, but the broadening rates between 4.8 km (T ≈ −11.6°C) and 4.2 km (T ≈ −8°C) were larger than those between 4.2 km (T ≈ −8°C) and 3.6 km (T ≈ −5°C). In addition, the broadening rates of PSDs in the embedded convection regions were larger than those in the stratiform clouds, as the aggregation and riming processes of ice particles in embedded convection regions were active. High supercooled water content is critical to enhancing riming and aggregation processes in embedded convection regions.

Electron crystallography of MWW zeolites – filling the missing cone

Abstract Given that many zeolites crystallize in habits that lead to preferred orientation, and that there is a ±60° tilt limitation in many electron microscope goniometer stages, collection of a three 3-D electron diffraction data set from these materials is severely restricted. To overcome this, preparative measures must be taken to produce other sample orientations. Using a number of MWW framework zeolites (MCM-22, MCM-22P, MCM-49, ITQ-1) as examples, thin-sectioned views onto the edge stacking of lamellar layers can be prepared by a number of methods. While ultamicrotomy is a traditional approach to this problem, sections are often very thick and sparsely distributed. Other extreme mechanical processing techniques, such as extrusion and jet milling produce numerous thin crystals with the desired orientation. Dealumination, initiated by steaming, calcination or low pH, also yields a similar result. Additional intensity data from the ‘missing cone’ in addition to those obtained by tilting hexagonal plate crystals provides a more complete data set and hence a more easily interpreted structure analysis. Crystallographic phase determination by maximum entropy and likelihood, followed by Fourier refinement, yields a structural model very close to that of the known MWW framework.

Synthesis, characterization and thermal-property measurements of ionic semi-clathrate hydrates formed with tetrabutylphosphonium chloride and tetrabutylammonium acrylate

This paper reports an experimental study on the formation of the two new semi-clathrate hydrates with tetrabutylphosphonium chloride (TBPC) and tetrabutylammonium acrylate (TBAAc). The hydrate formation was demonstrated by the measurements of temperature-composition phase diagrams and dissociation heat of the hydrates, visual observations of the hydrate crystals, and single-crystal X-ray diffraction analyses. The highest equilibrium temperature for the TBPC system was 10.3 °C at wTBPC = 0.36, where wTBPC denotes the mass fraction of TBPC, (or the mole fraction of TBPC, xTBPC = 0.034). The TBAAc system was 18.2 °C at wTBAAc = 0.36, where wTBAAc is the mass fraction of TBAAc, (or the mole fraction of TBAAc, xTBAAc = 0.031). The greatest dissociation heat for TBPC system was 194 kJ kg−1 at wTBPC = 0.37 and the TBAAc system was 195 kJ kg−1 at wTBAAc = 0.33. For visual observations of the hydrate crystals, the major morphology in both systems was a columnar shape, but hexagonal plate crystals were observed at wTBPC = 0.10 in the TBPC system. It was also confirmed that the hydrate crystals grown at higher subcooling are finer than those at lower subcooling. The crystallographic structure of TBPC hydrate formed at wTBPC = 0.36 was identified to be tetragonal with 12.5 × 23.7 × 23.7 A lattice parameters by the single-crystal X-ray diffraction analysis. Similarly, the crystallographic structure of TBAAc hydrate formed at wTBAAc = 0.36 was tetragonal with 12.2 × 33.1 × 33.1 A lattice parameters. The above findings indicate that TBPC and TBAAc hydrates are promising for applications in hydrate based technologies, such as cool energy storage, gas storage and gas separation.

Formation of Hydroxyapatite Nanocrystals on the Surface of Ca–Al‐Layered Double Hydroxide

Highly crystalline Ca–Al layered double hydroxides (LDH) covered with needle‐like hydroxyapatite (HA) nanocrystals was prepared from Ca–Al–Cl LDH by an alkaline treatment at 40°C using a Na3PO4 solution at pH 9.0. The HA nanocrystals had lengths of 100–200 nm, widths of 30 nm, and were grown on the surface of hexagonal LDH plate crystals. A 80‐nm‐thick nanolayer was observed between the HA and LDH, and was found to contain calcium and phosphate, but no aluminum or chloride. This layer was initially formed by the anion exchange reaction of phosphate ions in solution with chloride ions in the LDH crystals. The LDH structure was retained during this reaction. The elution of calcium ions from the LDH basal layers initiated the precipitation of the HA crystals on the surface. The stability of LDH in hydrochloric acid (pH 3) was dramatically improved by the presence of the nanolayers. The LDH–HA nanocomposites are acid‐resistant and have potential in areas such as the sustainable removal of harmful anions and cations and as drug delivery carriers.

Study of the crystal shape and its influence on the anti‐tumor activity of tumor necrosis factor‐related apoptosis‐inducing ligand (Apo2L/TRAIL)

AbstractThis paper describes a method about the crystal shape control improving the anti‐tumor activity of tumor necrosis factor‐related apoptosis‐inducing ligand (Apo2L/TRAIL) in a batch cooling suspension crystallization by selecting pH values as a controllable variable. Three shaped TRAIL crystals could be obtained under different pH conditions, among which the hexagonal plate crystals had the highest specific activities against tumor cell line. The relationship among pH values, trimer contents and the specific activities of crystals and the purified TRAIL solutions were investigated. The results showed that different trimer contents resulted from pH altering in crystals and protein solutions is a main reason for their different specific activities. The studies may supply a new method to improve the bioactivity of TRAIL agent during its production and storage. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Comparison of hematite/Fe(II) systems with cement/Fe(II) systems in reductively dechlorinating trichloroethylene

Reactive reductants of cement/Fe(II) systems in dechlorinating chlorinated hydrocarbons are unknown. This study initially evaluated reactivities of potential reactive agents of cement/Fe(II) systems such as hematite (α-Fe 2O 3), goethite (α-FeOOH), lepidocrocite (γ-FeOOH), akaganeite (β-FeOOH), ettringite (Ca 6Al 2(SO 4) 3(OH) 12), Friedel’s salt (Ca 4Al 2Cl 2(OH) 12), and hydrocalumite (Ca 2Al(OH) 6(OH) · 3H 2O) in reductively dechlorinating trichloroethylene (TCE) in the presence of Fe(II). It was found that a hematite/Fe(II) system shows TCE degradation characteristics similar to those of cement/Fe(II) systems in terms of degradation kinetics, Fe(II) dose dependence, and final products distribution. It was therefore suspected that Fe(III)-containing phases of cement hydrates in cement/Fe(II) systems behaved similarly to the hematite. CaO, which was initially introduced as a pH buffer, was observed to participate in or catalyze the formation of reactive reductants in the hematite/Fe(II) system, because its addition enhanced the reactivities of hematite/Fe(II) systems. From the SEM (scanning electron microscope) and XRD (X-ray diffraction) analyses that were carried out on the solids from hematite/Fe(II) suspensions, it was discovered that a sulfate green rust with a hexagonal-plate structure was probably a reactive reductant for TCE. However, SEM analyses conducted on a cement/Fe(II) system showed that hexagonal-plate crystals, which were presumed to be sulfate green rusts, were much less abundant in the cement/Fe(II) than in the hematite/Fe(II) systems. It was not possible to identify any crystalline minerals in the cement/Fe(II) system by using XRD analysis, probably because of the complexity of the cement hydrates. These observations suggest that major reactive reductants of cement/Fe(II) systems may differ from those of hematite/Fe(II) systems.

Formation of large (≃100 μm) ice crystals near the tropical tropopause

Abstract. Recent high-altitude aircraft measurements with in situ imaging instruments indicated the presence of relatively large (≃100 μm length), thin (aspect ratios of ≃6:1 or larger) hexagonal plate ice crystals near the tropical tropopause in very low concentrations (<0.01 L−1). These crystals were not produced by deep convection or aggregation. We use simple growth-sedimentation calculations as well as detailed cloud simulations to evaluate the conditions required to grow the large crystals. Uncertainties in crystal aspect ratio leave a range of possibilities, which could be constrained by knowledge of the water vapor concentration in the air where the crystal growth occurred. Unfortunately, water vapor measurements made in the cloud formation region near the tropopause with different instruments ranged from <2 ppmv to ≃3.5 ppmv. The higher water vapor concentrations correspond to very large ice supersaturations (relative humidities with respect to ice of about 200%). If the aspect ratios of the hexagonal plate crystals are as small as the image analysis suggests (6:1, see companion paper (Lawson et al., 2008)) then growth of the large crystals before they sediment out of the supersaturated layer would only be possible if the water vapor concentration were on the high end of the range indicated by the different measurements (>3 ppmv). On the other hand, if the crystal aspect ratios are quite a bit larger (≃10:1), then H2O concentrations toward the low end of the measurement range (≃2–2.5 ppmv) would suffice to grow the large crystals. Gravity-wave driven temperature and vertical wind perturbations only slightly modify the H2O concentrations needed to grow the crystals. We find that it would not be possible to grow the large crystals with water concentrations less than 2 ppmv, even with assumptions of a very high aspect ratio of 15 and steady upward motion of 2 cm s−1 to loft the crystals in the tropopause region. These calculations would seem to imply that the measurements indicating water vapor concentrations less than 2 ppmv are implausible, but we cannot rule out the possibility that higher humidity prevailed upstream of the aircraft measurements and the air was dehydrated by the cloud formation. Simulations of the cloud formation with a detailed model indicate that homogeneous freezing should generate ice concentrations larger than the observed concencentrations (20 L−1), and even concentrations as low as 20 L−1 should have depleted the vapor in excess of saturation and prevented growth of large crystals. It seems likely that the large crystals resulted from ice nucleation on effective heterogeneous nuclei at low ice supersaturations. Improvements in our understanding of detailed cloud microphysical processes require resolution of the water vapor measurement discrepancies in these very cold, dry regions of the atmosphere.

Crystallization of lipopolysaccharide from a Salmonella typhimurium semi-rough (SR) mutant.

Salmonella typhimurium SR-form lipopolysaccharide (LPS), consisting of a single repeating unit of the O-antigenic polysaccharide, linked to the R-core consisting of oligosaccharide that is, in turn, linked to lipid A, formed crystals whose shapes were hexagonal plates, discoids, and solid columns when precipitated by the addition of 2 volumes of 95% ethanol containing 375 mM MgCl2 and kept in 70% ethanol containing 250 mm MgCl2 at 4 C for 10 days. Among these crystals, the basic form is considered to be the hexagonal plates. Analyses of hexagonal plate crystals showed that they consist of hexagonal lattices with a lattice constant (a axis) of 4.62 A and longitudinal axis (c axis) of approximately 100 A. In X-ray diffraction patterns in the low-angle region, crystals of S. typhimurium SR-form LPS exhibited much less distinct reflections when compared with crystals of synthetic Escherichia coli-type lipid A. In contrast to the previous finding that S. minnesota S-form LPS possessing the O-antigenic polysaccharide does not crystallize under the same experimental conditions as used in the present study, the presence of a single repeating unit of the O-antigenic polysaccharide does not inhibit crystallization.

Ventilation Coefficients for Falling Ice Crystals in the Atmosphere at Low–Intermediate Reynolds Numbers

The ventilation coefficients for columnar, hexagonal plate, and broad branch ice crystals falling in air are computed by first solving numerically the convective diffusion equation for water vapor density to obtain its profile around these ice crystals and then determining the total vapor flux on the surface of the crystal. The ratio of this flux to the flux on a stationary crystal gives the ventilation coefficient. The local flow velocity profiles around the falling crystals necessary for specifying the convective term in the convective diffusion equation were obtained previously by numerically solving the unsteady Navier–Stokes equations subject to appropriate crystal-shaped boundary conditions. Ventilation coefficients obtained in this way are illustrated as a function of the Schmidt and Reynolds numbers and are also fitted by empirical expressions. Applications of these ventilation coefficients are discussed.

AFM Study on Morphology Evolution of Zinc Electrodeposits.

Nano-size growth of zinc electrodeposit is studied by using atomic force microscopy (AFM). The (0001)η and {1010}η of hexagonal plate crystals are aligned parallel to the steel substrate with Sn++ as additive. An AFM cantilever is placed on these planes in order to focus the nano-size growth image on these planes. The (0001)η consists of both 30 nm of granular crystals and alignments of these granular crystals, i.e. steps. These steps grow laterally as a result of the embedment of zinc ion clusters to the kinks of steps. The {1010}η and initial deposit also consist of these granular crystals. The initial zinc deposits are made up of the edges of hexagonal platelet crystals oriented ten to twenty degree from the substrate. The (0001)η of hexagonal platelet crystals becomes parallel to the substrate as the deposit grows with Sn++ as additive. The {1010}η, on the other hand, becomes parallel to the substrate without Sn++ as additive. These changes in the texture are caused by the locations of nucleation sites of the steps on the (0001)η.

Modeling Cirrus Clouds. Part II: Treatment of Radiative Properties

A new radiation scheme, suitable for two-stream radiation transfer models, was developed for cirrus clouds. Analytical expressions were derived for the extinction and absorption coefficients and the asymmetry parameter. These are functions of the ice particle size distribution parameters, ice particle shapes, and wavelength. The ice particle shapes considered were hexagonal plates and columns, bullet rosettes, and planar polycrystals. These appear to be the principal crystal types found in cirrus clouds. The formulation of radiative properties accounts for the size distribution projected area and the distance radiation travels through ice particles. For absorption, refraction and internal reflection of radiation were parameterized. By assuming an idealized cirrus cloud, the dependence of the single scatter albedo, reflectance, and emissivity on wavelength, ice particle shape, and size distribution was demonstrated. Reflectance and emissivity exhibited a strong dependence on ice particle shape, with planar polycrystals and bullet rosettes often being twice or more reflective than hexagonal columns and plates. The radiation scheme was tested with microphysical and radiation measurements from two cirrus cloud field studies. It was shown for both case studies that, by matching observed and predicted albedo-emissivity curves, the radiation scheme could predict the observed mean ice particle size and ice water path (IWP), provided the dominant ice particle shape was known or inferred. Retrieved IWP values differed from measurement-derived values by ≤15% for the first case study and 18% on average for the second case study. Hence, it may be feasible to retrieve realistic IWP estimates from satellite data for a given ice particle shape. Other radiation schemes have not been able to explain the second case study, which was characterized by relatively high albedos. These high albedos appeared to result from unusually small hexagonal plate crystals having asymmetry parameter values similar to those of cloud droplets. An improved treatment of the asymmetry parameter was not the primary reason for the good agreement between theory and observations. Rather, key factors appeared to be improved treatments of ice particle photon path, projected area and mass, and the omission of certain physical processes included in Mie theory that may not be appropriate for ice particles. The radiative properties were predicted from analytical expressions, making this scheme useful for predicting radiative properties in large-scale models without excessive increases in computation time.

Crystallization of synthetic Escherichia coli-type lipid A.

Synthetic Escherichia coli-type lipid A formed hexagonal plate crystals when it was precipitated by the addition of 2 volumes of 95% ethanol containing 375 mM MgCl2 and incubated in 70% ethanol containing 250 mM MgCl2 at 4 C for 10 days. Analyses of crystals by electron diffraction and synchrotron X-ray diffraction showed that crystals consist of hexagonal lattices with the lattice constant (a side of the lozenge as a unit cell on the basal plane) of 4.62 angstrom and the longitudinal axis (perpendicular to the basal plane) of 49.3 +/- 1.3 angstrom. Results suggest that the previous finding that various kinds of R-form lipopolysaccharides crystallized but free lipid A isolated by acid hydrolysis from Re lipopolysaccharide did not crystallize under the same experimental conditions (Kato et al, J. Bacteriol., 172:1516-1528, 1990) is due to structural changes of lipid A occurring during the procedure of isolation of free lipid A.

Crystallization and analyses of crystals of various chemotypes of R-form lipopolysaccharides from Salmonella spp.

Various chemotypes (Re, Rd2, Rd1P-, Rd1, RcP-, Rc, Rb3, Rb2, Rb1, and Ra) of R-form lipopolysaccharides (LPSs) of Salmonella spp. were crystallized by treatment with 70% ethanol containing 250 mM MgCl2, and crystals of the LPSs were observed electron microscopically and analyzed by electron diffraction and synchrotron X-ray diffraction. All the LPSs tested formed three-dimensional crystals showing very similar shapes; hexagonal plate, solid column, discoid, square or rectangular plate, lozenge plate and truncated hexangular or rectangular pyramid forms. Electron diffraction patterns from the hexagonal plate crystals of all these LPSs obtained by electron irradiation from the direction perpendicular to the basal plane showed that they consist of hexagonal lattices with the lattice constant of 4.62 A. The crystals of all the LPSs thus formed gave ring-like X-ray diffraction patterns because of their small sizes. The long-axis values were calculated from the X-ray diffraction patterns from crystals of all the LPSs in the low-angle region and they corresponded roughly to the length of the proposed primary chemical structures of the R cores of the LPSs. The volume occupied by a single molecule of all the LPSs were calculated from the molecular weights based on the proposed structures and the crystallographic data obtained by electron diffraction, X-ray diffraction, and density determination.

ChemInform Abstract: The Layered, Metallic Scandium Iodide Sc0.93I2: Synthesis, Structure, and Properties.

AbstractThe title compound can be prepared in quantitative yield by reaction of liquid or gaseous ScI3 with excess metal in the temp. range 550‐870 °C. Large black hexagonal plate crystals are formed via an autogeneous vapor phase transport process (probably via gaseous ScI2).

Electron Microscopic Observation of Crystals of Escherichia coli K‐12 Lipopolysaccharide

Previously we showed that Salmonella minnesota Re and Ra lipopolysaccharides (LPSs) and Escherichia coli K-12 LPS formed three-dimensional crystals, either hexagonal plates or solid columns, when they were precipitated by the addition of 2 volumes of 95% ethanol containing 375 mM MgCl2 and incubated in 70% ethanol containing 250 mM MgCl2, and stored at 4 C for 10 days. Later, Escherichia coli K-12 LPS thus treated was found to form discoid crystals as well as hexagonal plate crystals and solid column crystals. Analysis by electron diffraction of the discoid crystals from the direction perpendicular to the basal plane showed that they consisted of hexagonal lattices with the a axis of 4.62 A. This result was quite the same as that of the hexagonal plate crystals. Electron micrographs of the edges of the discoid crystals revealed stacked sheets of the hexagonal plate crystals. From these results it was concluded that formation of the discoid crystals results from irregular overlapping of the hexagonal plate crystals.

Infrared transmission through cirrus clouds: a radiative model for target detection

An IR transmission model for thin and subvisual cirrus clouds composed of hexagonal ice crystals with a specific use for target detection has been developed. The present model includes parameterizations of the ice crystal size distribution and the position of cirrus clouds in terms of ambient temperature. To facilitate the scattering and absorption calculations for hexagonal column and plate crystals in connection with transmission calculations, we have developed parameterized equations for their single scattering properties by using the results computed from a geometric ray-tracing program. The successive order-of-scattering approach has been used to account for multiple scattering of ice crystals associated with a target-detector system. The direct radiance, path radiance, and radiances produced by multiple scattering and background radiation involving cirrus clouds have been computed for 3.7- and 10-,microm wavelengths. We show that the background radiance at the 3.7-,microm wavelength is relatively small so that a high contrast may be obtained using this wavelength for the detection of airborne and ground-based objects in the presence of thin cirrus clouds. Finally, using the present model, including a simple prediction scheme for the ice crystal size distribution and cloud position, the transmission of infrared radiation through cirrus clouds can be efficiently evaluated if the target-detector geometry is defined.

Purification, Crystallization, and Properties ofβ-Galactosidase fromBacillus macerans

β-Galactosidase (EC 3.2.1.23) from Bacillus macerans was produced in a medium containing lactose. The enzyme was purified through the following steps: precipitation with ammonium sulfate, gel filtration on Sephadex G-100, chromatography on DEAE-Sephadex A-50, a second chtomatography on DEAE-Sephadex A-50, and a second gel filtration on Sephadex G-100. Hexagonal plate crystals were formed when acetone was dropped into the purified enzyme solution containing calcium ion. The purified enzyme was homogeneous on polyacrylamide disc electrophoresis, and the molecular weight was estimated to be about 320,000 by gel filtration on Sephadex G-200 and about 78,000 by sodium dodecyl sulfate gel electrophoresis. The purified enzyme migrated as a single protein band in both assays of molecular weight. Therefore, the enzyme consisted of four probably identical subunits. The isoelectric point of the enzyme was about pH 4.4. The enzyme had its optimal pH at 6.5 and was stable between pH 6 and 9. The enzyme was relatively stable below 37°C but completely lost its activity after heating 60°C for 10 min. The Michaelis constants were 2.0 mm for p-nitrophenyl-β-galactoside and 30 mm for lactose. The enzymic activity was completely inhibited by Ag+, Hg2+, Cu2+, and p-chloromercuribenzoate, and it was considerably inhibited by monoiodoacetic acid, trisaminomethane, and galactose.

Purification, crystallization, and properties of .BETA.-galactosidase from Bacillus macerans.

β-Galactosidase (EC 3.2.1.23) from Bacillus macerans was produced in a medium containing lactose. The enzyme was purified through the following steps: precipitation with ammonium sulfate, gel filtration on Sephadex G-100, chromatography on DEAE-Sephadex A-50, a second chromatography on DEAE-Sephadex A-50, and a second gel filtration on Sephadex G-100. Hexagonal plate crystals were formed when acetone was dropped into the purified enzyme solution containing calcium ion. The purified enzyme was homogeneous on polyacrylamide disc electrophoresis, and the molecular weight was estimated to be about 320, 000 by gel filtration on Sephadex G-200 and about 78, 000 by sodium dodecyl sulfate gel electrophoresis. The purified enzyme migrated as a single protein band in both assays of molecular weight. Therefore, the enzyme consisted of four probably identical subunits. The isoelectric point of the enzyme was about pH 4.4. The enzyme had its optimal pH at 6.5 and was stable between pH 6 and 9. The enzyme was relatively stable below 37°C but completely lost its activity after heating 60°C for 10min. The Michaelis constants were 2.0mM for p-nitrophenyl-βgalactoside and 30mM for lactose. The enzymic activity was completely inhibited by Ag+, Hg2+, Cu2+, and p-chloromercuribenzoate, and it was considerably inhibited by monoiodoacetic acid, trisaminomethane, and galactose.