Kinetics and equilibria of Ga(III)---thiocyanate complex formation. Mechanism of ligand substitution reactions of Ga(III) in aqueous solution

The kinetics and equilibria of complex formation by Ga(III) with NCS⁻ in aqueous solution have been measured over a range of acidities and temperatures, the contributing paths to the reaction resolved, and their rate constants and activation parameters determined. The hydrolysis equilibria required to carry out this resolution of kinetic behaviour have also been measured.

Unlike the other reported complexation reactions of Ga(III) in aqueous solution, the separate reaction pathways can be assigned with no ambiguity. At 25 °C and ionic strength 0.5 M, the observed forward rate constant for the complex formation is described by {k₁ + k₂K_1h/[H⁺] + k₃K_1hK_2h/[H⁺]²} M⁻¹ s⁻¹. For these conditions, the first and second successive hydrolysis constants of Ga(H₂O)₆³⁺ are given by pK_1h = 3.69 ± 0.01 and pK_2h = 3.74 ± 0.04. The rate constants corresponding to the reactions of the species Ga(H₂O)₆³⁺, Ga(H₂O)₅(OH)²⁺ and Ga(H₂O)₄(OH)₂⁺ with NCS⁻ are k₁ = 57 ± 4 M^{−1 −1}, k₂ = (1.08 ± 0.01) × 10⁵ M⁻¹ s⁻¹ and k₃ = 3 × 10⁶ M⁻¹ s⁻¹ respectively. The complexation equilibrium quotient [GaNCS²⁺]/([Ga³⁺][NCS⁻]) has been independently determined by spectrophotometric titration to be 20.8 ± 0.3 M⁻¹ at 25 °C and ionic strength 0.5 M.

These kinetic results lead to an interpretation of the data, and a reinterpretation of other data for aquo-Ga(III) complex formation kinetics from the literature which support the assignment of a dissociative interchange mechanism for these reactions rather than the associative activation mode sometimes proposed.     

Cellular Senescence Is Induced by the Environmental Neurotoxin Paraquat and Contributes to Neuropathology Linked to Parkinson’s Disease

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Pre-Cushing's syndrome: a case report.

A 67-year-old man affected by prostate cancer was incidentally found to have a nodular enlargement of the left adrenal gland without apparent changes in hormonal status. The adrenal mass was found to be scintigraphically active, the radiolabelled compound being concentrated in its context with a consensual suppression of the contralateral uptake. The patient underwent a resection of the adrenal tumor. Histologically and biochemically, the adrenal mass was found to be a non-functioning adenoma. The radioisotopic uptake along with the non-hormonal activity prompted us to call this tumor "Pre-Cushing's syndrome" of the adrenal cortex.     

Kinetics of G1 transit following brief starvation for serum factors

Growing fibroblasts such as 3T3 cells are well-known to enter a quiescent state (G0) after many hours of serum deprivation. They emerge from G0 upon readdition of serum and initiate DNA synthesis about 12 h later. In this paper, we analyzed the effects of brief periods of serum deprivation on the ability of cells in G1 to initiate DNA synthesis. Exponentially growing 3T3 fibroblasts were briefly deprived of serum and their progress into S phase was monitored by autoradiography of labeled nuclei. When 10% serum was added back to cultures deprived of serum for a few hours, the progress of G1 cells into S phase was delayed for intervals far in excess of the length of the serum deprivation. Longer serum starvations resulted in longer excess delays. Several transformed 3T3 derivatives were markedly less sensitive to this serum-induced G1 regression following deprivation. When 1 microgram/ml insulin (rather than 10% serum) was added back to the starved cultures, the G1 cells entered S phase immediately. Delay in S phase entry following serum readdition was completely prevented if insulin (and, to a lesser extent, EGF) was present during the starvation, was diminished if a lower serum concentration was used for readdition, and was partially abolished if 10% serum plus insulin was restored to the cultures. The above results, then, suggest that serum deprivation sensitizes the cells to an unidentified serum component which sets the cells back in G1, unless insulin is present to maintain the flow of cells into S.     

Volatile Constituents of the Aerial Parts of Pulicaria sicula (L.) Moris Growing Wild in Sicily: Chemotaxonomic Volatile Markers of the Genus Pulicaria Gaertn.

The chemical composition of the essential oil isolated from the aerial parts of Pulicaria sicula (L.) Moris was characterized by GC‐FID and GC/MS analyses. The oil was particularly rich in oxygenated terpenoids. Among the oxygenated monoterpenes (content of 44.5%), the most abundant were borneol (23.7%), bornyl acetate (6.5%), and isothymol isobutyrate (6.2%). Caryophyllene oxide (10.2%), caryophylladienol I (4.3%), and caryophylla‐3,8(13)‐dien‐5β‐ol (4.4%) were identified as the main constituents among the oxygenated sesquiterpenes. Furthermore, a complete literature review on the composition of the essential oils of all the Pulicaria taxa studied so far was performed and a principal component analysis (PCA) was carried out.     

Biotreatability of polycyclic aromatic hydrocarbons in brackish sediments: Preliminary studies of an integrated monitoring

An integrated monitoring, of chemical, microbiological and ecotoxicological parameters, was performed for a biotreatability study of polycyclic aromatic hydrocarbons (PAHs)—contaminated brackish sediments. Three slurry reactors were prepared, consisting of (a) a slurry with sediment and seawater called TQ slurry, to evaluate the intrinsic bioremediation potential, (b) a slurry with the addition of a selected microbial consotrium called BIO slurry, to evaluate the bioaugmentation effect, (c) a slurry with the addition of Soya lecithin called LEC slurry, to evaluate the effect of the addition of a natural surfactant. Biodegradation results showed that both BIO and LEC slurries enhanced PAHs removal, increasing the biodegradation rate for 5- and 6-ring PAHs. Furthermore, ecotoxicological response (Microtox® assay on whole sediment, aqueous extract and organic extract) demonstrated a detoxification of the PAHs initial mixture only for BIO slurry. The findings that aerobic PAHs degradation can be stimulated via inoculation with adapted sediment bacteria suggest that a bioaugmentation process may be a useful strategy for ex-situ treatment.     

A Versatile Viral System for Expression and Depletion of Proteins in Mammalian Cells

The ability to express or deplete proteins in living cells is crucial for the study of biological processes. Viral vectors are often useful to deliver DNA constructs to cells that are difficult to transfect by other methods. Lentiviruses have the additional advantage of being able to integrate into the genomes of non-dividing mammalian cells. However, existing viral expression systems generally require different vector backbones for expression of cDNA, small hairpin RNA (shRNA) or microRNA (miRNA) and provide limited drug selection markers. Furthermore, viral backbones are often recombinogenic in bacteria, complicating the generation and maintenance of desired clones. Here, we describe a collection of 59 vectors that comprise an integrated system for constitutive or inducible expression of cDNAs, shRNAs or miRNAs, and use a wide variety of drug selection markers. These vectors are based on the Gateway technology (Invitrogen) whereby the cDNA, shRNA or miRNA of interest is cloned into an Entry vector and then recombined into a Destination vector that carries the chosen viral backbone and drug selection marker. This recombination reaction generates the desired product with >95% efficiency and greatly reduces the frequency of unwanted recombination in bacteria. We generated Destination vectors for the production of both retroviruses and lentiviruses. Further, we characterized each vector for its viral titer production as well as its efficiency in expressing or depleting proteins of interest. We also generated multiple types of vectors for the production of fusion proteins and confirmed expression of each. We demonstrated the utility of these vectors in a variety of functional studies. First, we show that the FKBP12 Destabilization Domain system can be used to either express or deplete the protein of interest in mitotically-arrested cells. Also, we generate primary fibroblasts that can be induced to senesce in the presence or absence of DNA damage. Finally, we determined that both isoforms of the AT-Rich Interacting Domain 4B (ARID4B) protein could induce G1 arrest when overexpressed. As new technologies emerge, the vectors in this collection can be easily modified and adapted without the need for extensive recloning.