Study of charged particle activation analysis (II): Determination of boron concentration in human blood samples

Boron Neutron Capture Therapy (BNCT) is a radiotherapy for the treatment of intractable cancer. In BNCT precise determination of ¹⁰B concentration in whole blood sample before neutron irradiation of the patient, as well as accurate neutron dosimetry, is crucial for control of the neutron irradiation time. For this purpose ICP-AES and neutron induced prompt γ-ray analysis are generally used. In Ibaraki Neutron Medical Research Center (iNMRC), an intense proton beam will be accelerated up to 8 MeV, which can also be used for Charged Particle Activation Analysis (CPAA). Thus, in this study, we apply the CPAA utilizing the proton beam to non-destructive and accurate determination of ¹⁰B concentration in whole blood sample. A CPAA experiment is performed by utilizing an 8 MeV proton beam from the tandem accelerator of Nuclear Science Research Institute in Japan Atomic Energy Agency. The 478 keV γ-ray of ⁷Be produced by the ¹⁰B(p, α)⁷Be reaction is used to quantify the ¹⁰B in human blood. The 478 keV γ-ray intensity is normalized by the intensities of the 847 keV and 1238 keV γ-rays of ⁵⁶Co originating from Fe in blood. The normalization methods were found to be linear in the range of 3.27 μg ¹⁰B/g to 322 μg ¹⁰B/g with correlation coefficients of better than 0.9999.

Nuclear chemistry. Synthesis and detection of a seaborgium carbonyl complex

Experimental investigations of transactinoide elements provide benchmark results for chemical theory and probe the predictive power of trends in the periodic table. So far, in gas-phase chemical reactions, simple inorganic compounds with the transactinoide in its highest oxidation state have been synthesized. Single-atom production rates, short half-lives, and harsh experimental conditions limited the number of experimentally accessible compounds. We applied a gas-phase carbonylation technique previously tested on short-lived molybdenum (Mo) and tungsten (W) isotopes to the preparation of a carbonyl complex of seaborgium, the 106th element. The volatile seaborgium complex showed the same volatility and reactivity with a silicon dioxide surface as those of the hexacarbonyl complexes of the lighter homologs Mo and W. Comparison of the product's adsorption enthalpy with theoretical predictions and data for the lighter congeners supported a Sg(CO)6 formulation.

Sulfate complexation of element 104, Rf, in H2SO4/HNO3 mixed solution

The cation-exchange behavior of 261Rf (T 1/2= 78 s) produced in the 248Cm(18O, 5n) reaction was studied on a “one-atom-at-a-time” scale in 0.15–0.69 M H2SO4/HNO3 mixed solutions ([H+]=1.0 M) using an automated ion-exchange separation apparatus coupled with the detection system for alpha-spectroscopy (AIDA). It was found that adsorption probabilities ( decrease with an increase of [HSO4 −], showing a successive formation of Rf sulfate complexes. Rf exhibits a weaker complex formation tendency compared to the lighter homologues Zr and Hf. This is in good agreement with theoretical predictions including relativistic effects.

Development of radioactive ion beam production systems for Tokai Radioactive Ion Acceleration Complex-High temperature ion source for short-lived isotopes

We have developed a new ion source system in the isotope separator on-line at Japan Atomic Energy Agency, for separation of short-lived isotopes produced by proton-induced fission of (238)U. The ion source system is a forced electron beam induced arc discharge version E type ion source with a target container. We successfully operated this system at 2000 degrees C as a result of reductions in volume of the ion source and the target container, introduction of heating method by electron bombardment, and improvement to the heat shield. This new ion source system was tested using (238)U of 640 mg/cm(2) with a proton primary beam of 30 MeV, 350 nA. Release times were measured for Kr, In, and Xe. The values of release times are 2.6 s for Kr, 1.8 s for In, and 4.6 s for Xe. In this work, the ion source system enabled us to mass-separate short-lived isotopes such as (93)Kr(T(1/2)=1.286 s), (129)In(T(1/2)=0.61 s), and (141)Xe(T(1/2)=1.73 s) with intensity of 10(3) ions/s.

KEKCB electron cyclotron resonance charge breeder at TRIAC

The KEKCB is an electron cyclotron resonance (ECR) ion source for converting singly charged ions to multicharged ones at Tokai Radioactive Ion Accelerator Complex. By using the KEKCB, singly charged gaseous and nongaseous ions were converted to multicharged ones of A/q approximately 7 with efficiencies of 7% and 2%, respectively. The conversion efficiency was found to be independent of the lifetime of the radioactive nuclei having lifetimes of the order of one second. Three collimators located at the entrance and the exit of the KEKCB defined the beam axis and facilitated beam injection. Grinding and washing the surfaces of aluminum electrode and plasma chamber dramatically reduced impurities originating from the ECR plasma of the KEKCB.

Location, location, location: membrane targeting directed by PX domains

Phosphoinositide (PI)-binding domains play critical roles in the intracellular localization of a variety of cell-signaling proteins. The 120-amino acid Phox homology (PX) domain targets proteins to organelle membranes through interactions between two conserved basic motifs within the PX domain and specific PIs. The combination of protein-lipid and protein-protein interactions ensures the proper localization and regulation of PX domain-containing proteins. Upon proper localization, PX domain-containing proteins can then bind to additional proteins and execute their functions in a diverse set of biological pathways, including intracellular protein transport, cell growth and survival, cytoskeletal organization, and neutrophil defense.

Phox domain interaction with PtdIns(3)P targets the Vam7 t-SNARE to vacuole membranes

Specific recognition of phosphoinositides is crucial for protein sorting and membrane trafficking. Protein transport to the yeast vacuole depends on the Vam7 t-SNARE and its phox homology (PX) domain. Here, we show that the PX domain of Vam7 targets to vacuoles in vivo in a manner dependent on phosphatidylinositol 3-phosphate generation. A novel phosphatidylinositol-3-phosphate-binding motif and an exposed loop that interacts with the lipid bilayer are identified by nuclear magnetic resonance spectroscopy. Conservation of key structural and binding site residues across the diverse PX family indicates a shared fold and phosphoinositide recognition function.

New component of the vacuolar class C-Vps complex couples nucleotide exchange on the Ypt7 GTPase to SNARE-dependent docking and fusion

The class C subset of vacuolar protein sorting (Vps) proteins (Vps11, Vps18, Vps16 and Vps33) assembles into a vacuole/prevacuole-associated complex. Here we demonstrate that the class C-Vps complex contains two additional proteins, Vps39 and Vps41. The COOH-terminal 148 amino acids of Vps39 direct its association with the class C-Vps complex by binding to Vps11. A previous study has shown that a large protein complex containing Vps39 and Vps41 functions as a downstream effector of the active, GTP-bound form of Ypt7, a rab GTPase required for the fusion of vesicular intermediates with the vacuole (Price, A., D. Seals, W. Wickner, and C. Ungermann. 2000. J. Cell Biol. 148:1231-1238). Here we present data that indicate that this complex also functions to stimulate nucleotide exchange on Ypt7. We show that Vps39 directly binds the GDP-bound and nucleotide-free forms of Ypt7 and that purified Vps39 stimulates nucleotide exchange on Ypt7. We propose that the class C-Vps complex both promotes Vps39-dependent nucleotide exchange on Ypt7 and, based on the work of Price et al., acts as a Ypt7 effector that tethers transport vesicles to the vacuole. Thus, the class C-Vps complex directs multiple reactions during the docking and fusion of vesicles with the vacuole, each of which contributes to the overall specificity and efficiency of this transport process.

Class C Vps protein complex regulates vacuolar SNARE pairing and is required for vesicle docking/fusion

In yeast, the Class C Vps protein complex (C-Vps complex), composed of Vps11, Vps16, Vps18, and Vps33, functions in Golgi-to-vacuole protein transport. In this study, we characterized and purified this complex and identified its interaction with the syntaxin homolog Vam3. Vam3 pairs with the SNAP-25 homolog Vam7 and VAMP homolog Vti1 to form SNARE complexes during vesicle docking/fusion with the vacuole. The C-Vps complex does not bind to Vam3-Vti1-Vam7 paired SNARE complexes but instead binds to unpaired Vam3. Antibodies to a component of this complex inhibited in vitro vacuole-to-vacuole fusion. Furthermore, temperature-conditional mutations in the Class C VPS genes destabilized Vam3-Vti1-Vam7 pairing. Therefore, we propose that the C-Vps complex associates with unpaired (activated) Vam3 to mediate the assembly of trans-SNARE complexes during both vesicle docking/fusion and vacuole-to-vacuole fusion.

Vam7p, a SNAP-25-like molecule, and Vam3p, a syntaxin homolog, function together in yeast vacuolar protein trafficking

A genetic screen to isolate gene products required for vacuolar morphogenesis in the yeast Saccharomyces cerevisiae identified VAM7, a gene which encodes a protein containing a predicted coiled-coil domain homologous to the coiled-coil domain of the neuronal t-SNARE, SNAP-25 (Y. Wada and Y. Anraku, J. Biol. Chem. 267:18671-18675, 1992; T. Weimbs, S. H. Low, S. J. Chapin, K. E. Mostov, P. Bucher, and K. Hofmann, Proc. Natl. Acad. Sci. USA 94:3046-3051, 1997). Analysis of a temperature-sensitive-for-function (tsf) allele of VAM7 (vam7(tsf)) demonstrated that the VAM7 gene product directly functions in vacuolar protein transport. vam7(tsf) mutant cells incubated at the nonpermissive temperature displayed rapid defects in the delivery of multiple proteins that traffic to the vacuole via distinct biosynthetic pathways. Examination of vam7(tsf) cells at the nonpermissive temperature by electron microscopy revealed the accumulation of aberrant membranous compartments that may represent unfused transport intermediates. A fraction of Vam7p was localized to vacuolar membranes. Furthermore, VAM7 displayed genetic interactions with the vacuolar syntaxin homolog, VAM3. Consistent with the genetic results, Vam7p physically associated in a complex containing Vam3p, and this interaction was enhanced by inactivation of the yeast NSF (N-ethyl maleimide-sensitive factor) homolog, Sec18p. In addition to the coiled-coil domain, Vam7p also contains a putative NADPH oxidase p40(phox) (PX) domain. Changes in two conserved amino acids within this domain resulted in synthetic phenotypes when combined with the vam3(tsf) mutation, suggesting that the PX domain is required for Vam7p function. This study provides evidence for the functional and physical interaction between Vam7p and Vam3p at the vacuolar membrane, where they function as part of a t-SNARE complex required for the docking and/or fusion of multiple transport intermediates destined for the vacuole.

Endosomal transport function in yeast requires a novel AAA-type ATPase, Vps4p

In a late-Golgi compartment of the yeast Saccharomyces cerevisiae, vacuolar proteins such as carboxypeptidase Y (CPY) are actively sorted away from the secretory pathway and transported to the vacuole via a pre-vacuolar, endosome-like intermediate. The vacuolar protein sorting (vps) mutant vps4 accumulates vacuolar, endocytic and late-Golgi markers in an aberrant multilamellar pre-vacuolar compartment. The VPS4 gene has been cloned and found to encode a 48 kDa protein which belongs to the protein family of AAA-type ATPases. The Vps4 protein was purified and shown to exhibit an N-ethylmaleimide-sensitive ATPase activity. A single amino acid change within the AAA motif of Vps4p yielded a protein that lacked ATPase activity and did not complement the protein sorting or morphological defects of the vps4 delta1 mutant. Indeed, when expressed at normal levels in wild-type cells, the mutant vps4 gene acted as a dominant-negative allele. The phenotypic characterization of a temperature-sensitive vps4 allele showed that the immediate consequence of loss of Vps4p function is a defect in vacuolar protein delivery. In this mutant, precursor CPY was not secreted but instead accumulated in an intracellular compartment, presumably the pre-vacuolar endosome. Electron microscopy revealed that upon temperature shift, exaggerated stacks of curved cisternal membranes (aberrant endosome) also accumulated in the vps4ts mutant. Based on these and other observations, we propose that Vps4p function is required for efficient transport out of the pre-vacuolar endosome.