[From science's archives, a centennial: Rutherford and the discovery of alpha and beta rays].
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Alpha Particles↗
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Structure determination of histidine decarboxylase from Lactobacillus 30a at 3.0 A resolution.
The crystal structure of histidine decarboxylase from Lactobacillus 30a has been determined by X-ray diffraction methods to a resolution of 3.0 A. This protein is a pyruvoyl-dependent enzyme that is formed by an unusual self-activation process. The structure was determined from an electron density map calculated using multiple isomorphous replacement phases from two heavy-atom derivatives and included contributions from anomalous scattering measurements. The final mean figure of merit was 0.79, based on 28,805 independent reflections. The molecule has an (alpha beta)6 subunit composition and crystallizes in the space group 14122 with a = b = 221.7 A and c = 107.1 A. There is one (alpha beta)3 half molecule per asymmetric unit. The (alpha beta)6 particle is dumbbell-shaped, with each (alpha beta)3 unit being approximately spherical, with a diameter of about 65 A. There is a large central cavity approximately 30 A deep around the molecular 3-fold axis of the (alpha beta)3 unit. The 3-fold related active site pockets are located around the bottom of this cavity and are separated from each other by a distance of approximately 23 A. The inner portion of each (alpha beta) unit, which lies near the interface between the two (alpha beta)3 particles, consists mainly of random coil with several small helical and sheet regions. The outer region of each (alpha beta) unit has an unusual structure consisting of two overlapping, predominantly antiparallel beta-pleated sheets, lined on each side by an alpha-helix. The walls of the central cavity are formed by the 3-fold repeat of two strands from this beta-sandwich structure and one of the helices.
Carboxy-Lyases↗
Electric Properties of Adsorbed Polystyrenesulfonate.
The influence of molecular weight on the counterion polarization of sodium polystyrenesulfonate (NaPSS) is investigated by electric light scattering. The polyelectrolyte is adsorbed in excess on beta-ferric hydrous oxide particles (beta-FeOOH), which are shown to assume the charge characteristics of the polymer. Two dispersion regions of the electro-optical effect (below and above 10 kHz) are found to exist due to the polarization of counterions. The high-frequency (HF) effect is attributed to polarization of free counterions along the polymer-coated particle axis and does not depend on the molecular weight of the adsorbed polymer. The amplitude and critical frequency of relaxation of the low-frequency (LF) effect, which is attributed to polarization of bound counterions along the polymer axis, depend on the polyelectrolyte molecular weight. The polarization of bound counterions seems to be responsible for the permanent-like dipole moment behavior of NaPSS at low frequencies of the applied electric field. Copyright 1999 Academic Press.
Journal Article↗
Electric Properties of Adsorbed Polystyrenesulfonate.
Counterion polarization of sodium and magnesium polystyrenesulfonate (NaPSS and MgPSS), adsorbed in an excess onto ellipsoidal beta-ferric hydrous oxide particles (beta-FeOOH), is studied in both the absence and the presence of added simple electrolytes, NaCl and MgCl(2). The amplitude of the low-frequency (10(2)-10(4) Hz) and the high-frequency (10(4)-10(6) Hz) electro-optical effects of NaPSS is found to decrease with increasing NaCl concentration, while the critical frequency of relaxation of both effects remains unchanged. Addition of MgCl(2) to the suspension containing MgPSS also reduces the amplitude of the low-frequency electro-optical effect, but the amplitude of the high-frequency effect increases. The increased number of mobile (not bound) divalent ions, which produce larger charge fluctuation, could explain the high-frequency effect increase in the presence of a small excess of MgCl(2). Substitution of Na(+) counterions of PSS by Mg(2+) is found to increase the critical frequency of relaxation and to reduce the amplitude of the low-frequency effect, probably due to the strong repulsion between bound divalent counterions. The polyion length remains nearly unchanged during this substitution, as evidenced by the constant relaxation time of the polyelectrolyte-coated particles. The increase of counterion valence is not found to affect the amplitude of the high-frequency electro-optical effect in the absence of added salt. Copyright 1999 Academic Press.
Journal Article↗
Scaling properties in the average number of attempts until saturation in random sequential adsorption processes.
In the present paper we investigate the exact average number of attempts until saturation when a square lattice is ceaselessly bombarded with beta-bell (beta> or =1) particles, i.e., linear particles that require beta consecutive lattice sites to be adsorbed. When that average number is normalized with the corresponding single-particle average, a scale invariant behavior is revealed with a scaling exponent alpha=0.017 +/- 0.001, independent of beta (beta>1). The scale behavior is suggested by the branching characteristics governing the sequential random adsorption of beta-bell (beta>1) particles, which is indeed a consequence of configurational correlations.
Journal Article↗
Beta VLDL uptake by pigeon monocyte-derived macrophages: correlation of binding dynamics with three-dimensional ultrastructure.
Endocytosis of pigeon beta migrating very-low-density lipoprotein (beta VLDL) by monocyte-derived macrophages (monocyte/macrophages), cultured from Random Bred White Carneau (RBWC) pigeons, occurs by both coated and non-coated regions of the plasma membrane (Henson et al.: Exp. Mol. Pathol. 51:243-263, 1989). Secondary to binding, the beta VLDL is translocated to lysosomes for degradation. Ultimately these events lead to foam cell formation in vitro. Utilizing video-enhanced contrast light microscopy in conjunction with whole mount intermediate-voltage transmission electron microscopy (IVEM) and high-resolution scanning EM, the dynamics of beta VLDL binding have been correlated with ultrastructure. Beta VLDL conjugated to gold colloids was visualized at the surface of living cells by using Allen video-enhanced contrast-differential interference contrast microscopy (AVEC-DIC). Subsequent to AVEC-DIC, direct observation of the identical cells by IVEM and SEM was facilitated through the use of gold finder grids, and these EM observations confirmed identification of the video-observed beta VLDL particles. Upon addition of beta VLDL, pigeon monocyte/macrophages underwent gross morphological changes. These changes were recorded by video as movements at the cytoplasmic periphery, and the movements involved extension of microvilli, expression of retraction fibers, and elaboration of membrane ruffles. When secondarily observed by stereo (3-D) IVEM and SEM, the identification of microvilli, retraction fibers, and membrane ruffles was confirmed and the lipoprotein-gold conjugates were associated with these ligand-induced membrane structures. Beta VLDL-gold conjugates were also associated with pit-like regions at the base of microvilli, while at the base of ruffles, beta VLDL-gold conjugates were located in membrane invaginations and cytoplasmic vesicles.
Animals↗
Ac-225 and her daughters: the many faces of Shiva.
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Actinium↗
Transuranic isotopes and 90Sr in attic dust in the vicinity of two nuclear establishments in northern Germany.
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Air Pollutants, Radioactive↗
Osteosarcoma risk after simultaneous incorporation of the long-lived radionuclide 227Ac and the short-lived radionuclide 227Th.
The effect of injection of 1.85 kBq/kg of the long-lived radionuclide 227Ac on the induction of osteosarcomas in female NMRI mice by different dose levels (18.5, 74, and 185 kBq/kg) of the short-lived radionuclide 227Th was investigated. The highest absolute osteosarcoma incidence was observed with the highest doses of 227Th. Addition of 227Ac resulted in an additional osteosarcoma incidence only at the lowest dose of 227Th and did not affect the osteosarcoma incidence resulting from higher doses of 227Th. The longest times to tumor appearance were observed with 227Ac alone. The latent period in two different age groups (4 weeks and 10-12 weeks) appeared to be similar following injection with combined doses of 227Th and 227Ac but different after injection of each radionuclide alone.
Actinium↗
Targeted alpha particle immunotherapy for myeloid leukemia.
Unlike beta particle-emitting isotopes, alpha emitters can selectively kill individual cancer cells with a single atomic decay. HuM195, a humanized anti-CD33 monoclonal antibody, specifically targets myeloid leukemia cells and has activity against minimal disease. When labeled with the beta-emitters (131)I and (90)Y, HuM195 can eliminate large leukemic burdens in patients, but it produces prolonged myelosuppression requiring hematopoietic stem cell transplantation at high doses. To enhance the potency of native HuM195 yet avoid the nonspecific cytotoxicity of beta-emitting constructs, the alpha-emitting isotope (213)Bi was conjugated to HuM195. Eighteen patients with relapsed and refractory acute myelogenous leukemia or chronic myelomonocytic leukemia were treated with 10.36 to 37.0 MBq/kg (213)Bi-HuM195. No significant extramedullary toxicity was seen. All 17 evaluable patients developed myelosuppression, with a median time to recovery of 22 days. Nearly all the (213)Bi-HuM195 rapidly localized to and was retained in areas of leukemic involvement, including the bone marrow, liver, and spleen. Absorbed dose ratios between these sites and the whole body were 1000-fold greater than those seen with beta-emitting constructs in this antigen system and patient population. Fourteen (93%) of 15 evaluable patients had reductions in circulating blasts, and 14 (78%) of 18 patients had reductions in the percentage of bone marrow blasts. This study demonstrates the safety, feasibility, and antileukemic effects of (213)Bi-HuM195, and it is the first proof-of-concept for systemic targeted alpha particle immunotherapy in humans.
Alpha Particles↗
Beta-1,3-glucanase of sea urchin eggs: release from particles at fertilization.
beta-1,3-Glucanase is a latent enzyme found in large and small particles in unfertilized eggs. At fertilization, the enzyme in the large particles is released into the surrounding perivitelline space. The enzyme may be involved in transformations of extracellular glycoproteins.
Animals↗
Protein-coated beta-ferric hydrous oxide particles. An electrokinetic and electrooptic study.
Using microelectrophoresis and electric light scattering techniques, we investigated the adsorption characteristics, surface coverage and surface electric parameters of superstructures from two isoforms of plastocyanin, PCa and PCb, in an oxidized state adsorbed on beta-ferric hydrous oxide particles. The surface electric charge and electric dipole moments of the composite particles and the thickness of the protein adsorption layer are determined in a wide pH range, at different ionic strengths and concentration ratios of PC to beta-FeOOH. The adsorption of the two proteins was found to shift the particles' isoelectric point and to alter the total electric charge and the electric dipole moments of the oxide particles to different extent. A "reversal" in the direction of the permanent dipole moment is observed at lower pH for PCb- than for PCa-coated oxide particles. Strict correlation is found between the changes in the electrokinetic charge of the composite particles and the variation in their "permanent" dipole moments. Data suggest that the adsorption of the proteins is driven by electrostatic and/or hydrophobic interactions with the oxide surfaces dependent on pH. The adsorption behaviour is consistent with the involvement of the "eastern" and "northern" patches of the plastocyanin molecules in their adsorption on the oxide surfaces that are differently charged depending on pH.
Adsorption↗
Lectin-recognizable colloidal dispersions stabilized by n-dodecyl beta-D-maltoside: particle-particle and particle-surface interactions.
Recently, we reported that it is possible to utilize sugars as stabilizing agents for colloidal particles. This study shows that when n-dodecyl beta-D-maltoside (DDM) is utilized as a dispersing and stabilizing agent in the synthesis and stabilization of poly[methyl methacrylate-co-(n-butyl acrylate)] (p-MMA/nBA) colloidal particles, stable colloidal dispersions can be formed. Since understanding of sugar-protein interactions have numerous practical and scientific implications, these studies examine DDM-stabilized p-MMA/nBA colloidal particles and their specific binding properties with concanavalin A (Con A). By use of spectroscopic analysis, unique binding characteristics that are a function of DDM concentration, time, and the concentration of Con A are detected. When DDM-stabilized p-MMA/nBA particles are allowed to coalesce, DDM is released from the particle surfaces and, under suitable conditions, selectively stratifies in the areas of the excess of interfacial energy near the film-air (F-A) interface, thus providing sites for attracting Con A via alpha-glucose-OH hydrogen bonding. Consequently, adsorption of Con A at the F-A interfaces occur and the degree of adsorption is controlled by the amount of DDM at the F-A interface.
Adsorption↗
Preparation and characterization of porous beta-tricalcium phosphate/collagen composites with an integrated structure.
Porous beta-tricalcium phosphate (TCP)/collagen composites with different beta-TCP/collagen weight ratio were prepared. The influences of the preparation conditions on the microstructure of porous composite and the joint status of beta-TCP particles with collagen fibrils were characterized by X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The results showed: (1) an acid treatment could effectively disassemble collagen fibrils; (2) in the resulting porous composites, beta-TCP particles homogenously existed on the skeleton of the collagen fibril network and bonded tightly to both the fibrils and themselves. The tight bonding formation could be due to the reaction between Ca ions in the particles and carboxyl groups in collagen polypeptide chains and due to the reprecipitation of partially dissolved beta-TCP during synthesis. The tight bonding between beta-TCP particles and collagen fibrils in the composites demonstrated an integrated structure, which was reproducible when beta-TCP/collagen ratio ranged from 2 to 4. Such integrated structure would make significant contributions in reliably tailoring properties of the porous composites by varying beta-TCP content. In addition, the porous composites had large porosity (approximately 95%) and appropriate pore size (approximately 100 microm), showed no negative impact in cytotoxicity assay and complete bone tissue regeneration after 12 weeks in animal test.
Animals↗
Formation Mechanism of Monodispersed alpha-Fe2O3 Particles in Dilute FeCl3 Solutions
Some ambiguity is still involved in the interpretation of the growth mechanism of monodispersed hematite (alpha-Fe2O3) particles in dilute FeCl3 solutions. Namely, there are two entirely different proposals on this issue, viz. aggregation of preformed primary particles of alpha-Fe2O3 itself and reprecipitation of the ionic species through dissolution of the preformed beta-FeOOH particles. In order to resolve this problem, the formation process was followed in detail through TEM, Electron Diffraction, XRD, FT-IR, and ICP spectrometry along with quantitative analyses on seed effects. As a result, it has been concluded that the nuclei of the hematite particles are initially generated with the formation of beta-FeOOH particles and that they are grown by deposition of the solute originally present in the solution phase and indirectly furnished from the beta-FeOOH by dissolution. As the concentration of the solute is lowered by the growth of the hematite particles, they continue to grow with the solute provided mainly from the beta-FeOOH in a steady-state of the dissolution of beta-FeOOH and growth of alpha-Fe2O3. The basic formation mechanism is common to the ellipsoidal particles grown in the presence of phosphate ions and spherical particles in their absence.
Journal Article↗
Presence and formation of 'free apolipoprotein A-I-like' particles in human plasma.
The influence of dilution on apolipoprotein (apo) A-I-containing subpopulations was studied in human plasma. Agarose electrophoresis and two-dimensional agarose nondenaturing gradient polyacrylamide gel electrophoresis were used. Both in one- and two-dimensional electrophoresis, an increase of charge was observed that resulted in an increase of subpopulations with pre-alpha mobility. Dilution of plasma also resulted in a decrease in the size of apo A-I-containing pre-beta 1 subpopulations. The existence of smaller pre-beta 1 particles was confirmed by subjecting undiluted and 8x diluted plasma to 3% to 16% nondenaturing gradient gel electrophoresis for 4 hours. In addition to the generally observed pre-beta 1 subpopulations, smaller particles similar in size to the free apo A-I were detected even in the undiluted plasma. During dilution, the proportion of larger pre-beta 1 particles decreased while the smaller ones increased, and in 8x diluted plasma, almost all the pre-beta 1 was present in smaller sizes. Using 3% to 35% nondenaturing polyacrylamide gels run for 24 hours, no pre-beta 1 particles could be detected in 8x diluted plasma because the small pre-beta 1 electrophoresed out. These studies show that pre-beta 1 particles can be converted to smaller ones during dilution. It also was demonstrated that "free apo A-I-like" pre-beta 1 particles are present in undiluted plasma. The presence of these particles may have important physiological and pathophysiological functions.
Apolipoprotein A-I↗
Systematic control of size, shape, structure, and magnetic properties of uniform magnetite and maghemite particles.
As an application of the gel-sol method especially developed for the synthesis of general monodisperse particles in large quantities, uniform hematite (alpha-Fe2O3), magnetite (Fe3O4), and maghemite (gamma-Fe2O3) particles, precisely controlled in size, aspect ratio, and internal structure, have been prepared. For the synthesis of uniform ellipsoidal single-crystal particles of alpha-Fe2O3, a highly condensed suspension of fine beta-FeOOH particles doped with a prescribed amount of PO4(3-) ion in their interiors was aged at 140 degrees C for 24 h with seed particles of alpha-Fe2O3 in an acidic medium containing optimum concentrations of HCl and NaNO3. Systematic control of the aspect ratio and mean size was achieved by regulating the concentration of PO4(3-) ion incorporated into the beta-FeOOH particles and the number of seeds added. The resulting hematite particles were converted into magnetite by reduction in a H2 stream at 330 degrees C for 6 h; the magnetite was then oxidized to maghemite in an air stream at 240 degrees C for 2 h. Magnetite and maghemite thus prepared retained the original shape of the hematite. On the other hand, polycrystalline hematite particles of different sizes and aspect ratios were also prepared by aging a condensed Fe(OH)3 gel in the presence of different concentrations of SO4(2-) ion and seeds. The polycrystalline hematite particles were similarly converted into magnetite and then maghemite. The magnetic properties of these magnetite and maghemite particles were analyzed as a function of their mean particle volume, aspect ratio, and internal structure.
Journal Article↗
Solid-phase microextraction of phenol compounds using a fused-silica fiber coated with beta-cyclodextrin-bonded silica particles.
A novel solid-phase microextraction (SPME) fiber was prepared by coating an HPLC beta-cyclodextrin bonded silica stationary phase (CDS) on the surface of a fused-silica fiber. The fiber was evaluated for the determination of five phenol compounds (phenol, 2,4-dimethylphenol, 4-nitrophenol, 3-chlorophenol, 4-methylphenol). Compared with commercially available polymer coatings, the CDS coating showed high sensitivity and fast velocity of mass transfer for phenol compounds because of its porous structure and a unique molecular structure of beta-cyclodextrin. In addition, the CDS coating was proved to be very stable at a relatively high temperature (up to 300 degrees C). The method was suitable for the determination of phenol compounds in aqueous samples. The determination of 4-nitrophenol in soil by microwave-assisted extraction (MAE) coupled to solid-phase microextraction was also investigated.
Journal Article↗