Long-Term Modeling of Plutonium Solubility at a Desert Disposal Site,Including CO2 Diffusion,Cellulose Decay,and Chelation

The solubility of plutonium was estimated for waste buried at the Greater Confinement Disposal site in Nevada. The EQ3/6 thermochemical database was modified to include recent data on Pu complex formation, and the solubilities of two critical phases (probertite (CaNaB₅O₉·5H₂O), added as a backfill material; and Ca sac-charate) were determined by experiment. Reaction path runs were used to model effects of cellulose degradation, including complexation of actinides by organic acids and carbonate, decay of the complexing agents, and the buildup and diffusive loss of CO₂ through the permeable alluvium. For most waste interaction scenarios, long-term (≈10³ years) concentrations of Pu in pore waters are ≤10^?7 molal and are dominated by carbonate complexes, although organic complexes could dominate in the first ≈10³ years. In unusual circumstances, carbonation of buried lithium could produce very high Pu solubilities; however, even in such a system, a slight lowering of the effective redox potential dramatically lowers Pu solubility. A sensitivity analysis suggests that the “base case” calculations are conservative, tending to overestimate long-term solubility, with the system redox and the identity of the organic acids the major sources of uncertainty.     

Assessment of the biodegradability of a monosulfonated azo dye and aromatic amines

Biodecolourisation of an azo dye by anaerobic cultures using a liposomal textile levelling agent as primary substrate was assessed. Liposomes seem to facilitate the uptake of the dye (Acid Orange 7) by anaerobic biomass, leading to a fast decolourisation (colour removal of 96% was achieved in the first sample port of the reactor profiles). On the other hand, the presence of dye (60–300 mg l⁻¹) caused a decrease in the chemical oxygen demand (COD) degradation rate (4.1–2.5 g COD removed l⁻¹ d⁻¹ for 60 and 300 mg l⁻¹ of dye, respectively), suggesting inhibitory effects.Aerobic degradation of aromatic amines was investigated in aerobic respirometric assays with different types of inocula. Sulfanilic acid and aniline were mineralised by inocula with a significant microbiological diversity, even with domestic effluent. These results were confirmed by a significant reduction of COD, total organic carbon (TOC) and a high oxygen consumption (biochemical oxygen demand/theoretical oxygen demand), 92±4%. Kinetic analysis showed that a sigmoid function describes quite well the experimental data, even better than the exponential model. Orthanilic and metanilic acids and 1-amino-2-naphtol were persistent under the tested conditions.     

Lipid polarity and sorting in epithelial cells

Apical and basolateral membrane domains of epithelial cell plasma membranes possess unique lipid compositions. The tight junction, the structure separating the two domains, forms a diffusion barrier for membrane components and thereby prevents intermixing of the two sets of lipids. The barrier apparently resides in the outer, exoplasmic leaflet of the plasma membrane bilayer. First data are now available on the generation of these differences in Madin-Darby canine kidney (MDCK) cells, grown on filter supports. Experiments in which fluorescent precursors of apical lipids were introduced into the cell have demonstrated that upon biosynthesis apical lipids are sorted from basolateral lipids in an intracellular compartment. In this paper we present a model for the sorting process, the central point of which is that the two sets of lipids laterally segregate into microdomains that bud to form vesicles delivering the lipids to the apical and the basolateral plasma membrane domains, respectively.     

Enantioselective inclusion complexation of 2,3,4,6-tetra-O-acetyl-D-glycopyranose as a chiral host with (+)-(r)-phenylethylamine: x-ray characterization of the complex

X-ray analysis of the crystalline product obtained by reaction of 2,3,4,6-Tetra-O-acetyl-D-glycopyranose with phenylethylamine revealed the formation of a real one-to-one inclusion complex. This complexaion is highly stereoselective, because only the (+)-R-enantiomeric form of the amine is included. Analogies to the mode of complexation of cellulose triaceate with chiral molecules in ?inclusion chromatography”? are discussed.     

Hormone-dependent processing of the avian progesterone receptor

Avian progesterone receptor exists as two forms, A and B, with molecular weights of 79,000 and 110,000 daltons, respectively. The origin and significance of these two forms is an area of active investigation and debate. Monoclonal antibodies produced against these two forms were used to examine receptor stability in cytosol and changes in the receptor forms induced by hormone binding. The lability of hormone binding at elevated temperatures is well documented. Analysis by Western blotting showed the receptor was stable in freshly prepared oviduct cytosol for 2 hr at 37°C, while hormone binding was lost within 30 min. However, loss of receptor through degradation was seen when cytosol was prepared from frozen tissue or when homogenization was excessive. Progesterone was injected into diethylstilbestrol-stimulated chicks to examine, in vivo, effects of hormone treatment on receptor forms in the cytosol and nuclear fractions. Progesterone treatment caused a time- and dose-dependent conversion of the A receptor to a form (A′) with a slower electrophoretic mobility. The cytosolic progesterone receptor was divided equally between the B and A forms, while the nuclear receptor was predominantly A′. The amount of nuclear receptor was consistently less than cytosolic receptor. Receptor phosphorylation was analyzed by incubating tissue minces with [³²P]orthophosphate with or without progesterone followed by immune isolation of receptor forms. Progesterone treatment caused a time-dependent increase in cytosol receptor phosphorylation which was evident after 5 min of treatment. This phosphorylation was observed with both the A and B receptor forms. The results indicate that receptor phosphorylation is a very early event during progesterone action.     

Profilin 1 mutants form aggregates that induce accumulation of prion-like TDP-43

Mutations in the profilin 1 (PFN1) gene have been identified as a cause of familial amyotrophic lateral sclerosis (ALS), and neuropathological studies indicate that TDP-43 is accumulated in brains of patients with PFN1 mutation. Here, we investigated the role of PFN1 mutations in the formation of prion-like abnormal TDP-43. Expression of PFN1 with pathogenic mutations resulted in the formation of cytoplasmic aggregates positive for p62 and ubiquitin, and these aggregates sequestered endogenous TDP-43. TDP-43 accumulation was facilitated in the presence of proteasome or lysosome inhibitor. Co-expression of mutant PFN1 and TDP-43 increased the levels of detergent-insoluble and phosphorylated TDP-43, and this increase required the C-terminal region of TDP-43. Moreover, detergent-insoluble fractions prepared from cells expressing ALS-linked mutant PFN1 induced seed-dependent accumulation of TDP-43. These findings indicate that expression of PFN1 mutants induces accumulation of TDP-43, and promotes conversion of normal TDP-43 into an abnormal form. These results provide new insight into the mechanisms of TDP-43 proteinopathies and other diseases associated with amyloid-like protein deposition.     

一株能分解纤维素放线菌的固态发酵研究

对一株从食草动物的粪便中分离出来的放线菌菌株(XW5),以秸杆粉和麸皮为底物,进行固态发酵,并提取纤维素酶粗酶。采用DNS法,进行酶活测定,研究发现该菌株的固态发酵酶活为4-7u/mg。并对酶活的影响因子、pH、温度以及金属离子等的影响进行了探讨,同时发现该酶为碱性纤维素酶。     

Modeling Historical Ecology, Thinking about Contemporary Systems

One way to make archaeological trajectories compelling to contemporary audiences is through detailed computer simulation with graphical interfaces that allow students or researchers to explore historical sequences and ask "what if" questions of them. We discuss progress on modeling coupled human systems and ecosystems over long periods in the Mesa Verde region of the U.S. Southwest, a project developed with both research and educational products in mind. The project has many foci, but here we concentrate on fuel-wood availability and its pre-Hispanic use in the pygmy forests of this region. Our preliminary results tend to indicate that wood for fuels became sufficiently limited in this sequence to become a factor of considerable importance in decisions about where to live, how to build, and even whether to remain in the region. The same logic of modeling can be used to study problems of contemporary forest use in other parts of the world.     

Catalytic activity, stability, unfolding, and degradation pathways of engineered and reconstituted myoglobins

The structural and functional consequences of engineering a positively charged Lys residue and replacing the natural heme with a heme-L-His derivative in the active site of sperm whale myoglobin (Mb) have been investigated. The main structural change caused by the distal T67K mutation appears to be mobilization of the propionate-7 group. Reconstitution of wild-type and T67K Mb with heme-L-His relaxes the protein fragment around the heme because it involves the loss of the interaction of one of the propionate groups which stabilize heme binding to the protein. This modification increases the accessibility of exogenous ligands or substrates to the active site. The catalytic activity of the reconstituted proteins in peroxidase-type reactions is thus significantly increased, particularly with T67K Mb. The T67K mutation slightly reduces the thermodynamic stability and the chemical stability of Mb during catalysis, but somewhat more marked effects are observed by cofactor reconstitution. Hydrogen peroxide, in fact, induces pseudo-peroxidase activity but also promotes oxidative damage of the protein. The mechanism of protein degradation involves two pathways, which depend on the evolution of radical species generated on protein residues by the Mb active species and on the reactivity of phenoxy radicals produced during turnover. Both protein oligomers and heme-protein cross-links have been detected upon inactivation.