Solid Ammonium Sulfate Research Articles

The c-Myc Target Gene Rcl (C6orf108) Encodes a Novel Enzyme, Deoxynucleoside 5′-monophosphate N-Glycosidase

RCL is a c-Myc target with tumorigenic potential. Genome annotation predicted that RCL belonged to the N-deoxyribosyltransferase family. However, its putative relationship to this class of enzymes did not lead to its precise biochemical function. The purified native or N-terminal His-tagged recombinant rat RCL protein expressed in Escherichia coli exhibits the same enzyme activity, deoxynucleoside 5'-monophosphate N-glycosidase, never before described. dGMP appears to be the best substrate. RCL opens a new route in the nucleotide catabolic pathways by cleaving the N-glycosidic bond of deoxynucleoside 5'-monophosphates to yield two reaction products, deoxyribose 5-phosphate and purine or pyrimidine base. Biochemical studies show marked differences in the terms of the structure and catalytic mechanism between RCL and of its closest enzyme family neighbor, N-deoxyribosyltransferase. The reaction products of this novel enzyme activity have been implicated in purine or pyrimidine salvage, glycolysis, and angiogenesis, and hence are all highly relevant for tumorigenesis.

Assay of partially purified glutamate dehydrogenase isolated from asparagus beans for V<sub>MAX</sub> and K<sub>M</sub> as a measure of its role in ammonium ion assimilation

Glutamate dehydrogenase (E C 1.4.1.1) isolated from the seeds of asparagus beans was partially purified to a factor of 22 by dialysis after fractional precipitation with solid ammonium sulphate at 40 and 60% saturation. A specific activity of 11.78μmol min-1 mg-1 protein was calculated for the partially purified enzyme when the NAD+ - linked deaminating activity was assayed with glutamate as the substrate (ranging in concentration from 8.33 mM to 33.33 mM). From the Lineweaver – Burk plot, the Vmax and Km, representing the maximum velocity and Michaelis constant, respectively were deduced. Vmax was found to be 25 μmol min-1 while the Km was 33 mM. Keywords: Glutamate dehydrogenase, asparagus beans, enzyme, ammonium ion International Journal of Natural and Applied Sciences Vol. 2 (3) 2006: pp. 197-200

Molecular Cloning and Characterization of a Novel β-Agarase, AgaB, from Marine Pseudoalteromonas sp. CY24

Agarases are generally classified into glycoside hydrolase families 16, 50, and 86 and are found to degrade agarose to frequently generate neoagarobiose, neoagarotetraose, or neoagarohexaose as the main products. In this study we have cloned a novel endo-type beta-agarase gene, agaB, from marine Pseudoalteromonas sp. CY24. The novel agarase encoded by agaB gene has no significant sequence similarity with any known proteins including all glycoside hydrolases. It degrades agarose to generate neoagarooctaose and neoagarodecaose as the main end products. Based on the analyses of enzymatic kinetics and degradation patterns of different oligosaccharides, the agarase AgaB appears to have a large substrate binding cleft that accommodates 12 sugar units, with 8 sugar units toward the reducing end spanning subsites +1 to +8 and 4 sugar units toward the non-reducing end spanning subsites -4 to -1, and enzymatic cleavage taking place between subsites -1 and +1. In addition, 1H NMR analysis shows that this enzyme hydrolyzes the glycosidic bond with inversion of anomeric configuration, in contrast to other known agarases that are retaining. Altogether, AgaB is structurally and functionally different from other known agarases and appears to represent a new family of glycoside hydrolase.

Purification and Identification of Proteins That Bind to the Hereditary Persistence of Fetal Hemoglobin –198 Mutation in the γ-Globin Gene Promoter

Expression of the gamma-globin gene is silenced in adult humans. However, certain point mutations in the gamma-globin gene promoter are capable of maintaining expression of this gene during adult erythropoiesis, a condition called non-deletion hereditary persistence of fetal hemoglobin (HPFH). Among these, the British form of HPFH carrying a T-->C point mutation at position -198 of the Agamma-globin gene promoter results in 4-10% fetal hemoglobin in heterozygotes. In this study, we used nuclear extracts from murine erythroleukemia cells to purify a protein complex that binds the HPFH -198 gamma-globin gene promoter. Members of this protein complex were identified by mass spectrometry and include DNMT1, the transcriptional coactivator p52, the protein SNEV, and RAP74 (the largest subunit of the general transcription factor IIF). Sp1, which was previously considered responsible for HPFH -198 gamma-globin gene activation, was not identified. The potential role of these proteins in the reactivation and/or maintenance of gamma-globin gene expression in the adult transcriptional environment is discussed.

Ammonium sulfate on Titan: Possible origin and role in cryovolcanism

We model the chemical evolution of Titan, wherein primordial NH 3 reacts with sulfate-rich brines leached from the silicate core during its hydration. The resulting differentiated body consists of a serpentinite core overlain by a high-pressure ice VI mantle, a liquid layer of aqueous ammonium sulfate, and a heterogeneous shell of methane clathrate, low-pressure ice Ih and solid ammonium sulfate. Cooling of the subsurface ocean results in underplating of the outer shell with ice Ih; this gravitationally unstable system can produce compositional plumes as ice Ih ascends buoyantly. Ice plumes may aid in advection of melt pockets through the shell and, in combination with surface topography, provide the necessary hydraulic pressure gradients to drive such melts to the surface. Moreover, contact between the magma and wall rock (methane clathrate) will allow some methane to dissolve in the magma, as well as eroding fragments of wall rock that can be transported as xenoliths. Upon rising to the clathrate decomposition depth ( ∼ 2 MPa , or 1700 m), the entrained xenoliths will break down to ice + methane gas, powering highly explosive eruptions with lava fountains up to several kilometers high. Hence we predict that Titan is being resurfaced by cryoclastic ash consisting of ice and ammonium sulfate (or its tetrahydrate), providing an abundance of sedimentary grains, a potential source of bedload for fluvial transport and erosion, and of sand-sized material for aeolian transport and dune-building. The infrared reflectance spectrum of ammonium sulfate makes it a plausible candidate for the 5 μm-bright material on Titan's surface.

Biochemical and structural comparative study between bird and mammal pancreatic colipases

Three colipases were purified from pancreas of two birds (ostrich and turkey) and one mammal (dromedary). After acidic and/or heat treatment and precipitation by sulfate ammonium and then ethanol, cofactors were purified by Sephadex G-50 gel filtration followed by ion-exchange chromatography first on Mono S and then on Mono Q. One molecular form was obtained from each species with a molecular mass of approximately 10 kDa. Cofactors were not glycosylated. The N-terminal sequences of the three purified cofactors showed high sequence homology. A 90 amino acid sequence of the ostrich cofactor was established based on peptide sequences from four different digests of the denaturated protein using trypsin, chymotrypsin, thermolysin, or staphylococcal protease. This sequence exhibited a high degree of homology with chicken and mammal cofactors. Bile salt-inhibited pancreatic lipases from five species were activated to variable extents by colipases from bird and mammal origins. The bird pancreatic lipase-colipase system appears to be functionally similar to homologous lipolytic systems from higher mammals. Our comparative study showed that mammal colipase presents a lower activation level toward bird lipases than the bird counterpart. Three-dimensional modeling of ostrich colipase suggested a structural explanation of this fact.

Purification and characterization of lectin from humoral fluids ofCharybdis feriatus

To search new sources of lectin, an experiment on lectin distribution in humoral serum of crabCharybdis feriatus (in short, CFL) was conducted March, 2002. When adding solid ammonium sulfate into the fluids up to 50% saturation at 4°C, most CFL activity showed precipitates who were then continually extracted by ammonium sulfate of different concentrations. The supernatant, which was called primary CFL fluids, was given a 17.60-fold purification and 45.70% recovery of total activity. Finally, by using Sephadex G-100 column chromatography, the CFL in the primary CFL fluid was highly purified. Compared to the original humoral fluids, the last purified CFL got a 203.90-fold purification and 30.48% recovery of total activity, and demonstrated a single band on SDS-PAGE. In the same time, the purified CFL was detected for agglutination activity with 7 kinds of animal erythrocytes. Other characterization, such as sugar inhibition, and the effect of temperature on the agglutination activity of CFL were also studied. Our results indicate that agglutination activity of CFL was influenced by sugar and temperature.

Responses of Ammonium Sulfate Particles Coated with Glutaric Acid to Cyclic Changes in Relative Humidity: Hygroscopicity and Raman Characterization

Atmospheric particles, which may have an organic coating, exhibit cyclical phase changes of deliquescence and crystallization in response to changes in the ambient relative humidity(RH). Here, we measured the hygroscopicity and Raman spectra of solid ammonium sulfate ((NH4)2SO4) particles initially coated with water-soluble glutaric acid in two consecutive cycles of deliquescence and crystallization utilizing an electrodynamic balance. (NH4)2SO4 particles with glutaric acid coating (49 wt % glutaric acid) had different hygroscopicity and morphology in the two cycles. Once the particles deliquesced, the dissolution of the solid (NH4)2SO4 core and the glutaric acid coating formed mixed (NH4)2SO4-glutaric acid solution droplets, which was confirmed by Raman characterization. Coating studies with either deliquescence or crystallization measurements, or one complete cycle of these two measurements may not fully assess the effects of the organic coatings on aerosol hygroscopicity. We also present an analysis on the kinetic and chemical effects of organic coating on aerosol hygroscopicity. Glutaric acid coating does not impede the evaporation and condensation rates of water molecules compared to the rates of (NH4)2S04 particles in the two cycles. The coating likely affects the hygroscopicity of aerosol particles through dissolution and its chemical interactions with (NH4)2S04.

Solid Ammonium Sulfate Aerosols as Ice Nuclei: A Pathway for Cirrus Cloud Formation

Laboratory measurements support a cirrus cloud formation pathway involving heterogeneous ice nucleation by solid ammonium sulfate aerosols. Ice formation occurs at low ice-saturation ratios consistent with the formation of continental cirrus and an interhemispheric asymmetry observed for cloud onset. In a climate model, this mechanism provides a widespread source of ice nuclei and leads to fewer but larger ice crystals as compared with a homogeneous freezing scenario. This reduces both the cloud albedo and the longwave heating by cirrus. With the global ammonia budget dominated by agricultural practices, this pathway might further couple anthropogenic activity to the climate system.

On the Relationships of Substrate Orientation, Hydrogen Abstraction, and Product Stereochemistry in Single and Double Dioxygenations by Soybean Lipoxygenase-1 and Its Ala542Gly Mutant

Recent findings associate the control of stereochemistry in lipoxygenase (LOX) catalysis with a conserved active site alanine for S configuration hydroperoxide products, or a corresponding glycine for R stereoconfiguration. To further elucidate the mechanistic basis for this stereocontrol we compared the stereoselectivity of the initiating hydrogen abstraction in soybean LOX-1 and an Ala542Gly mutant that converts linoleic acid to both 13S and 9R configuration hydroperoxide products. Using 11R-(3)H- and 11S-(3)H-labeled linoleic acid substrates to examine the initial hydrogen abstraction, we found that all the primary hydroperoxide products were formed with an identical and highly stereoselective pro-S hydrogen abstraction from C-11 of the substrate (97-99% pro-S-selective). This strongly suggests that 9R and 13S oxygenations occur with the same binding orientation of substrate in the active site, and as the equivalent 9R and 13S products were formed from a bulky ester derivative (1-palmitoyl-2-linoleoylphosphatidylcholine), one can infer that the orientation is tail-first. Both the EPR spectrum and the reaction kinetics were altered by the R product-inducing Ala-Gly mutation, indicating a substantial influence of this Ala-Gly substitution extending to the environment of the active site iron. To examine also the reversed orientation of substrate binding, we studied oxygenation of the 15S-hydroperoxide of arachidonic acid by the Ala542Gly mutant soybean LOX-1. In addition to the usual 5S, 15S- and 8S, 15S-dihydroperoxides, a new product was formed and identified by high-performance liquid chromatography, UV, gas chromatography-mass spectrometry, and NMR as 9R, 15S-dihydroperoxyeicosa-5Z,7E,11Z,13E-tetraenoic acid, the R configuration "partner" of the normal 5S,15S product. This provides evidence that both tail-first and carboxylate end-first binding of substrate can be associated with S or R partnerships in product formation in the same active site.

Structural and conductivity study of a new protonic conductor Cs 0.86(NH 4) 1.14SO 4·Te(OH) 6

The crystal structure of Cs 0.86(NH 4) 1.14SO 4·Te(OH) 6 is determined by X-ray diffraction analysis. The space group is P 2 1 / c with a = 13.681 ( 3 ) Å , b = 6.608 ( 1 ) Å , c = 11.362 ( 2 ) Å , β = 106.65 ( 3 ) ° and Z = 4 at 293 K. The structure is refined to R = 2.9 % . The distribution of atoms can be described as isolated TeO 6 octahedra and SO 4 tetrahedra. The Cs + and NH 4 + cations, occupying the same positions, are located between these polyhedra. The main feature of this structure is the coexistence of two types of anions in the same crystal related by network hydrogen bonds. The mixed solid solution cesium ammonium sulphate tellurate exhibits two phase transitions at 470 and 500 K. These transitions, detected by differential scanning calorimetric, are analyzed by dielectric measurements using the impedance and modulus spectroscopy techniques.

Effects of the physical state of tropospheric ammonium-sulfate-nitrate particles on global aerosol direct radiative forcing

Abstract. The effect of aqueous versus crystalline sulfate-nitrate-ammonium tropospheric particles on global aerosol direct radiative forcing is assessed. A global three-dimensional chemical transport model predicts sulfate, nitrate, and ammonium aerosol mass. An aerosol thermodynamics model is called twice, once for the upper side (US) and once for lower side (LS) of the hysteresis loop of particle phase. On the LS, the sulfate mass budget is 40% solid ammonium sulfate, 12% letovicite, 11% ammonium bisulfate, and 37% aqueous. The LS nitrate mass budget is 26% solid ammonium nitrate, 7% aqueous, and 67% gas-phase nitric acid release due to increased volatility upon crystallization. The LS ammonium budget is 45% solid ammonium sulfate, 10% letovicite, 6% ammonium bisulfate, 4% ammonium nitrate, 7% ammonia release due to increased volatility, and 28% aqueous. LS aerosol water mass partitions as 22% effloresced to the gas-phase and 78% remaining as aerosol mass. The predicted US/LS global fields of aerosol mass are employed in a Mie scattering model to generate global US/LS aerosol optical properties, including scattering efficiency, single scattering albedo, and asymmetry parameter. Global annual average LS optical depth and mass scattering efficiency are, respectively, 0.023 and 10.7 m2 (g SO4-2)-1, which compare to US values of 0.030 and 13.9 m2 (g SO4-2)-1. Radiative transport is computed, first for a base case having no aerosol and then for the two global fields corresponding to the US and LS of the hysteresis loop. Regional, global, seasonal, and annual averages of top-of-the-atmosphere aerosol radiative forcing on the LS and US (FL and FU, respectively, in W m-2) are calculated. Including both anthropogenic and natural emissions, we obtain global annual averages of FL=-0.750, FU=-0.930, and DFU,L=24% for full sky calculations without clouds and FL=-0.485, FU=-0.605, and DFU,L=25% when clouds are included. Regionally, DFU,L=48% over the USA, 55% over Europe, and 34% over East Asia. Seasonally, DFU,L varies from 18% in DJF to 75% in SON over the USA. The global annual average contribution from anthropogenic aerosol is FL=-0.314 and FU=-0.404, which yield normalized direct radiative forcings (G) of GL=-205 W (g SO4-2)-1 and GU=-264 W (g SO4-2)-1.

EXTRACTION, FRACTIONATION AND ACTIVITY CHARACTERISTICS OF PROTEASES FROM SHRIMP PROCESSING DISCARDS

Proteases recovered from Northern pink shrimp (NPS) and Southern rough shrimp (SS) processing discards (heads, shells, tails) were characterized. Shrimp processing discards were extracted with water following homogenization and centrifugation in order to obtain the crude extract which was subsequently fractionated with solid ammonium sulfate. Two fractions sedimenting with 30-50% (designated as NPS-I and SS-I), and 50- 70% (designated as NPS-II and SS-II) ammonium sulfate were collected following centrifugation, respectively. Endoprotease activity of the crude extract was 0.02 U/mg for hemoglobin (Hb, pH 3.0), 0.16 U/mg for azocasein (Ac, pH 6.0) and 0.12 U/mg for benzoyl-Arg-β-naphthylamide (BANA, pH 7.0). The exoprotease activity was 0.11-0.17 U/mg for Arg-β-naphthylamide (ArgNA, pH7.0), 0.06-0.11 U/mg for Lys-β-naphthylamide (LysNA, pH 7.0) and 0.08-0.09 U/mg for Leu-β-naphthylamide (LeuNA, pH 7.0). Endoprotease activity increased 5-7.4 fold for NPS-I and SS-I, and 1.9-2. 7 fold for NPS-II and SS-II against crude extract. Meanwhile, exoprotease activity increased 3. 6-4. 8 fold for NPS-I and SS-I, and 5.6-7.2 fold for NPS-II and SS-II. Meat treated with NPS-I and SS-I was tenderized more extensively than that treated with NPS-II and SS-II. The results of this study suggest that proteases recovered from shrimp processing discards may potentially be used as processing aids in formulated foods.

Characterization of Escherichia coli MoeB and Its Involvement in the Activation of Molybdopterin Synthase for the Biosynthesis of the Molybdenum Cofactor

Amino acid sequence comparisons of Escherichia coli MoeB suggested that the MoeB-dependent formation of a C-terminal thiocarboxylate on the MoaD subunit of molybdopterin synthase might resemble the ubiquitin-activating step in the ubiquitin-targeted degradation of proteins in eukaryotes. To determine the exact role of MoeB in molybdopterin biosynthesis, the protein was purified after homologous overexpression. Using purified proteins, we have demonstrated the ATP-dependent formation of a complex of MoeB and MoaD adenylate that is stable to gel filtration. Mass spectrometry of the complex revealed a peak of a molecular mass of 9,073 Da, the expected mass of MoaD adenylate. However, unlike the ubiquitin activation reaction, the formation of a thioester intermediate between MoeB and MoaD could not be observed. There was also no evidence for a MoeB-bound sulfur during the sulfuration of MoaD. Amino acid substitutions were generated in every cysteine residue in MoeB. All of these exhibited activity comparable to the wild type, with the exception of mutations in cysteine residues located in putative Zn-binding motifs. For these cysteines, loss of activity correlated with loss of metal binding.

Comparability of three spectrometers for monitoring urban aerosol

The comparability was tested of three aerosol “spectrometers”, used in a program for monitoring the spectra of fine and ultrafine particles in three European cities. Droplets of sebacate, solid ammonium sulfate and agglomerates of elemental carbon were used in the tests, representing the major chemical and structural types of particles encountered in urban aerosol. Particles in the ultrafine range (10–100 nm) are sized by electrical mobility (SMPS, DMPS and EAS) and the “spectrometers” gave very similar size distributions for these aerosols. The integrated number concentrations were on average within 20% of the directly measured total number concentrations. Particles with a size between 0.1 and 2.5 μm, in which most of the volume/mass is concentrated, are being differently classified in the three “spectrometers”, respectively, with a low- and a high-flow LAS-X, and field charging in the EAS. The agreement between the three instruments in this size range was less good, which was partly caused by signal overload in the high-flow optical sizer, which was solved using a larger threshold. A complication occurred with the elemental carbon, which was composed of highly agglomerated entities. Particles, sized by the mobility instrumentation as being in the range of 100–400 nm, were not detected by the optical sizers. Volume (spectra) for ammonium sulfate deduced from the number spectra were compared with the mass (spectra) obtained with cascade impactors. The comparison was good for the LAS-Xs; the EAS overestimated volume/mass.

First Isolation of Human UDP-d-Xylose: Proteoglycan Core Protein β-d-Xylosyltransferase Secreted from Cultured JAR Choriocarcinoma Cells

Human UDP-d-xylose:proteoglycan core protein beta-d-xylosyltransferase (EC, XT) initiates the biosynthesis of glycosaminoglycan lateral chains in proteoglycans by transfer of xylose from UDP-xylose to specific serine residues of the core protein. In this study, we report the first isolation of the XT and present the first partial amino acid sequence of this enzyme. We purified XT 4,700-fold with 1% yield from serum-free JAR choriocarcinoma cell culture supernatant. The isolation procedure included a combination of ammonium sulfate precipitation, heparin affinity chromatography, ion exchange chromatography, and protamine affinity chromatography. Among other proteins an unknown protein was detected by matrix-assisted laser desorption ionization mass spectrometry-time of flight analysis in the purified sample. The molecular mass of this protein was determined as 120 kDa by SDS-polyacrylamide gel electrophoresis. The isolated protein was enzymatically cleaved by trypsin and endoproteinase Lys-C. Eleven peptide fragments were sequenced by Edman degradation. Searches with the amino acid sequences in protein and EST data bases showed no homology to known sequences. XT was enriched by immunoaffinity chromatography with an immobilized antibody against a synthetic peptide deduced from the sequenced peptide fragments and was specifically eluted with the antigen. In addition, XT was purified alternatively with an aprotinin affinity chromatography and was detected by Western blot analysis in the enzyme-containing fraction.

Structure and Mechanism of 3-Deoxy-d-manno-octulosonate 8-Phosphate Synthase

3-deoxy-D-manno-octulosonate 8-phosphate (KDO8P) synthase catalyzes the condensation of phosphoenolpyruvate (PEP) with arabinose 5-phosphate (A5P) to form KDO8P and inorganic phosphate. KDO8P is the phosphorylated precursor of 3-deoxy-D-manno-octulosonate, an essential sugar of the lipopolysaccharide of Gram-negative bacteria. The crystal structure of the Escherichia coli KDO8P synthase has been determined by multiple wavelength anomalous diffraction and the model has been refined to 2.4 A (R-factor, 19.9%; R-free, 23.9%). KDO8P synthase is a homotetramer in which each monomer has the fold of a (beta/alpha)(8) barrel. On the basis of the features of the active site, PEP and A5P are predicted to bind with their phosphate moieties 13 A apart such that KDO8P synthesis would proceed via a linear intermediate. A reaction similar to KDO8P synthesis, the condensation of phosphoenolpyruvate, and erythrose 4-phosphate to form 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAH7P), is catalyzed by DAH7P synthase. In the active site of DAH7P synthase the two substrates PEP and erythrose 4-phosphate appear to bind in a configuration similar to that proposed for PEP and A5P in the active site of KDO8P synthase. This observation suggests that KDO8P synthase and DAH7P synthase evolved from a common ancestor and that they adopt the same catalytic strategy.

2-Keto-3-deoxy-d-glycero-d-galacto-nononic Acid (KDN)- and N-Acetylneuraminic Acid-cleaving Sialidase (KDN-sialidase) and KDN-cleaving Hydrolase (KDNase) from the Hepatopancreas of Oyster, Crassostrea virginica

KDN (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid), a sialic acid analog, has been found to be widely distributed in nature. Despite the structural similarity between KDN and Neu5Ac, alpha-ketosides of KDN are refractory to conventional sialidases. We found that the hepatopancreas of the oyster, Crassostrea virginica, contains two KDN-cleaving sialidases but is devoid of conventional sialidase. The major sialidase, KDN-sialidase, effectively cleaves alpha-ketosidically linked KDN and also slowly cleaves the alpha-ketosides of Neu5Ac. The minor sialidase, KDNase, is specific for alpha-ketosides of KDN. We were able to separate these two KDN-cleaving enzymes using hydrophobic interaction and cation-exchange chromatographies. The rate of hydrolysis of 4-methylumbelliferyl-alpha-KDN (MU-KDN) by KDN-sialidase is 30 times faster than that of MU-Neu5Ac in the presence of 0.2 M NaCl, whereas in the absence of NaCl this ratio is only 8. KDNase hydrolyzes MU-KDN over 500 times faster than MU-Neu5Ac and is not affected by NaCl. KDN-sialidase purified to electrophoretically homogeneous form was found to have a molecular mass of 25 kDa and an isoelectric point of 8.4. One of the three tryptic peptides derived from KDN-sialidase contains the consensus motif, SXDXGXTW, that has been found in all conventional sialidases. Kinetic analysis of the inhibition of the hydrolysis of MU-KDN and MU-Neu5Ac by 2, 3-dehydro-2-deoxy-KDN (KDN2-en) and 2,3-dehydro-2-deoxy-(Neu5Ac2-en) suggests that KDN-sialidase contains two separate active sites for the hydrolysis of KDN and Neu5Ac. Both KDN-sialidase and KDNase effectively hydrolyze KDN-G(M3), KDNalpha2-->3Gal beta1-->4Glc, KDNalpha2-->6Galbeta1-->4Glc, KDNalpha2-->6-N-acetylgalactosaminitol, KDNalpha2-->6(KDNalpha2-->3)N-acetylgalactosaminitol, and KDNalpha2-->6(GlcNAcbeta1-->3)N-acetylgalactosaminitol. However, only KDN-sialidase also slowly hydrolyzes G(M3), Neu5Acalpha2-->3Galbeta1-->4Glc, and Neu5Acalpha2-->6Galbeta1-->4Glc. These two KDN-cleaving sialidases should be useful for studying the structure and function of KDN-containing glycoconjugates.

Production of endo-1,4-β- d-glucanase by Curvularia pallescens

Studies have been performed on the production and thermostability of endo-1, 4-β- d-glucanase enzyme produced by Curvularia pallescens. The strain of the microorganism was grown on a mineral medium suitable for cellulolytic fungi. Different cellulose concentrations, carbon sources, solid ammonium sulfate saturations, time and temperatures were used in order to determine the best conditions for cellulase production by this species. It was observed that it is capable of producing extracelular endoglucanase with a specific activity of 0.474 UI/mg. Protein was grown on the optimized liquid medium with microcrystalline cellulose as carbon source/enzyme inducer and the enzyme is stable at 45–60°C/20 min.

Gas/Particle Partitioning of Semivolatile Organic Compounds To Model Inorganic, Organic, and Ambient Smog Aerosols

Gas/particle (G/P) partitioning is an important process that affects the deposition, chemical reactions, long-range transport, and impact on human and ecosystem health of atmospheric semivolatile organic compounds (SOCs). Gas/particle partitioning coefficients (Kp) were measured in an outdoor chamber for a group of polynuclear aromatic hydrocarbons (PAHs) and n-alkanes sorbing to three types of model aerosol materials: solid ammonium sulfate, liquid dioctyl phthalate (DOP), and secondary organic aerosol (SOA) generated from the photooxidation of whole gasoline vapor. Kp values were also measured for ambient n-alkanes sorbing to urban particulate material (UPM) during summer smog episodes in the Los Angeles metropolitan area. Based on the Kp values obtained for the aerosols studied here, for environmental tobacco smoke (ETS), and for a quartz surface, we conclude that G/P partitioning of SOCs to UPM during summer smog episodes is dominated by absorption into the organic fraction in the aerosol. Comparison...