Mixed-ligand lanthanide complexes supported by ditopic bis(imino-methyl)-phenol/calix[4]arene macrocycles: synthesis, structures, and luminescence properties of [Ln2(L2)(MeOH)2] (Ln = La, Eu, Tb, Yb)

The lanthanide binding ability of a macrocyclic ligand H₆L² comprising two bis(iminomethyl)phenol and two calix[4]arene units has been studied. H₆L² is a ditopic ligand which provides dinuclear neutral complexes of composition [Ln₂(L²)(MeOH)₂] (Ln = La (1), Eu (2), Tb (3), and Yb (4)) in very good yield. X-ray crystal structure analyses for 2 and 3 show that (L²)^6- accommodates two seven coordinated lanthanide ions in a distorted monocapped trigonal prismatic/octahedral coordination environment. UV-vis spectroscopic titrations performed with La³⁺, Eu³⁺, Tb³⁺ and Yb³⁺ ions in mixed MeOH/CH₂Cl₂ solution (I = 0.01 M NBu₄PF₆) reveal that a 2 : 1 (metal : ligand) stoichiometry is present in solution, with log K₁₁ and K₂₁ values ranging from 5.25 to 6.64. The ratio α = K₁₁/K₂₁ of the stepwise formation constants for the mononuclear (L² + M = ML², log K₁₁) and the dinuclear complexes (ML² + M = M₂L², log K₂₁) was found to be invariably smaller than unity indicating that the binding of the first Ln³⁺ ion augments the binding of the second Ln³⁺ ion. The present complexes are less luminescent than other seven-coordinated Eu and Tb complexes, which can be traced to vibrational relaxation of excited Eu^III and Tb^III states by the coligated MeOH and H₂O molecules and/or low-lying ligand-to-metal charge-transfer (LMCT) states.

Dinuclear Tb and Dy complexes supported by hybrid Schiff-base/calixarene ligands: synthesis, structures and magnetic properties

The synthesis of the new lanthanide complexes [HNEt3][Dy2(HL1)(L1)] (5), and [Ln2(L2)2] (Ln = TbIII (7), DyIII (8)) supported by the hybrid Schiff-base/calix[4]arene ligands H4L1 (25-[2-((2-methylphenol)imino)ethoxy]-26,27,28-trihydroxy-calix[4]arene) and H3L2 (25-[2-((2-methylpyridine)imino)ethoxy]-26,27,28-trihydroxy-calix[4]arene) are reported. Spectroscopic data (for 5) and X-ray crystallographic analysis (for 7·4MeCN, 8·4MeCN) reveal the presence of dimeric structures, featuring doubly-bridged NO4Ln(μ-O)2LnO4N (5) or N2O3Ln(μ-O)2LnO3N2 cores (7, 8) with seven-coordinated Ln3+ ions. The magnetic properties of polycrystalline samples of 5, 7 and 8 were studied by variable temperature dc and ac magnetic susceptibility measurements. The χ''(T) vs. T plots show no maxima in zero field, but the maxima can be detected under a 3 kOe dc field. The relaxation times τ obey the Arrhenius law above 5 K. Anisotropy barriers of ∼18 cm-1 (26 K) for 5 and ∼23 cm-1 (33 K) for 8 were determined.

Dinuclear lanthanide complexes supported by a hybrid salicylaldiminato/calix[4]arene-ligand: synthesis, structure, and magnetic and luminescence properties of (HNEt3)[Ln2(HL)(L)] (Ln = SmIII, EuIII, GdIII, TbIII)

Salicylaldimine/calix[4]arenes support dinuclear, triply bridged, luminescent, lanthanide complexes.

Photoluminescence properties of tetrahedral zinc(ii) complexes supported by calix[4]arene-based salicylaldiminato ligands

The synthesis and photophysical properties of four new hybrid salicylaldiminato-calix[4]arene ligands and their corresponding zinc(ii) complexes are described. The Schiff bases were obtained from condensation reactions between cone-25,27-di(aminoethoxy)-26,28-dihydroxy-calix[4]arene and salicylaldehyde (H2L1) or o-vanillin (H2L2) and 1,3-alt-25,27-di(aminoethoxy)-26,28-di(n-propyloxy)-calix[4]arene and 3,5-di-tert-butyl-salicylaldehyde (H2L3) or o-vanillin (H2L4). Complexation reactions were investigated by ESI-MS, IR, NMR, UV-vis absorption and steady-state and time resolved fluorescence spectroscopy, and X-ray crystallography. All ligands support 1 : 1 complexes (ZnL1-ZnL4), with equilibrium constants derived from absorption spectrophotometry in the range log K11 = 5.5-8.2 (MeCN or MeOH/CH2Cl2, I = 0.01 M). The zinc complexes show blue fluorescence, both in solution as well as in the solid state, with λem, Φf, and τ ranging from 472-504 nm, 0.11-0.60, and 2-9 ns, respectively. The nature of the substituents on the salicylaldiminato fragments was found to be the main parameter that influences the photophysical properties of the zinc complexes. Insights into the electronic nature of the UV-vis transitions were obtained with time dependent density functional theory (TD-DFT) calculations.

The human health effects of Florida red tide (FRT) blooms: an expanded analysis

Human respiratory and digestive illnesses can be caused by exposures to brevetoxins from blooms of the marine alga Karenia brevis, also known as Florida red tide (FRT). K. brevis requires macro-nutrients to grow; although the sources of these nutrients have not been resolved completely, they are thought to originate both naturally and anthropogenically. The latter sources comprise atmospheric depositions, industrial effluents, land runoffs, or submerged groundwater discharges. To date, there has been only limited research on the extent of human health risks and economic impacts due to FRT. We hypothesized that FRT blooms were associated with increases in the numbers of emergency room visits and hospital inpatient admissions for both respiratory and digestive illnesses. We sought to estimate these relationships and to calculate the costs of associated adverse health impacts. We developed environmental exposure-response models to test the effects of FRT blooms on human health, using data from diverse sources. We estimated the FRT bloom-associated illness costs, using extant data and parameters from the literature. When controlling for resident population, a proxy for tourism, and seasonal and annual effects, we found that increases in respiratory and digestive illnesses can be explained by FRT blooms. Specifically, FRT blooms were associated with human health and economic effects in older cohorts (≥55 years of age) in six southwest Florida counties. Annual costs of illness ranged from $60,000 to $700,000 annually, but these costs could exceed $1.0 million per year for severe, long-lasting FRT blooms, such as the one that occurred during 2005. Assuming that the average annual illness costs of FRT blooms persist into the future, using a discount rate of 3%, the capitalized costs of future illnesses would range between $2 and 24 million.

Solventogenic enzymes of Clostridium acetobutylicum: catalytic properties, genetic organization, and transcriptional regulation

The enzymes acetoacetate decarboxylase and coenzyme A transferase catalyse acetone production from acetoacetyl-CoA in Clostridium acetobutylicum. The adc gene encoding the former enzyme is organized in a monocistronic operon, while the ctf genes form a common transcription unit with the gene (adhE) encoding a probable polyfunctional aldehyde/alcohol dehydrogenase. This genetic arrangement could reflect physiological requirements at the onset of solventogenesis. In addition to AdhE, two butanol dehydrogenase isozymes and a thiolase are involved in butanol synthesis. RNA analyses showed a sequential order of induction for the different butanol dehydrogenase genes, indicating an in vivo function of BdhI in low level butanol formation. The physiological roles of AdhE and BdhII most likely involve high level butanol formation, with AdhE being responsible for the onset of solventogenesis and BdhII ensuring continued butanol production. Addition of methyl viologen results in artificially induced butanol synthesis which seems to be mediated by a still unknown set of enzymes. Although the signal that triggers the shift to solventogenesis has not yet been elucidated, recent investigations suggest a possible function of DNA supercoiling as a transcriptional sensor of the respective environmental stimuli.

Solventogenic enzymes of Clostridium acetobutylicum: catalytic properties, genetic organization, and transcriptional regulation

The enzymes acetoacetate decarboxylase and coenzyme A transferase catalyse acetone production from acetoacetyl-CoA in Clostridium acetobutylicum. The adc gene encoding the former enzyme is organized in a monocistronic operon, while the ctf genes form a common transcription unit with the gene (adhE) encoding a probable polyfunctional aldehyde/alcohol dehydrogenase. This genetic arrangement could reflect physiological requirements at the onset of solventogenesis. In addition to AdhE, two butanol dehydrogenase isozymes and a thiolase are involved in butanol synthesis. RNA analyses showed a sequential order of induction for the different butanol dehydrogenase genes, indicating an in vivo function of BdhI in low level butanol formation. The physiological roles of AdhE and BdhII most likely involve high level butanol formation, with AdhE being responsible for the onset of solventogenesis and BdhII ensuring continued butanol production. Addition of methyl viologen results in artificially induced butanol synthesis which seems to be mediated by a still unknown set of enzymes. Although the signal that triggers the shift to solventogenesis has not yet been elucidated, recent investigations suggest a possible function of DNA supercoiling as a transcriptional sensor of the respective environmental stimuli.

Tryptase and histamine release due to a sting challenge in bee venom allergic patients treated successfully or unsuccessfully with hyposensitization

BACKGROUND

Hyposensitization with been venom leads to full protection in most, but not all patients with IgE-mediated systemic reactions to bee stings.

OBJECTIVE

To determine the relationship of clinical reactivity to the release of mediators and to changes of antibody concentrations in the peripheral circulation at a bee sting challenge test.

METHODS

Blood was sampled before (1 min) and at 15, 60 and 180 min after a sting challenge from 19 patients on hyposensitization. Of these six still reacted and 13 were protected. Histamine, mast cell tryptase, bee venom-specific IgE and IgG in the serum, and histamine release from peripheral blood leucocytes (PBL) upon exposure to bee venom were determined.

RESULTS

Tryptase above the detection level was found only at 15 (60) min in 4/6 (1/6) patients who reacted. After the sting challenge there was a significant increase of the histamine levels in patients who reacted at 15 min (P < 0.05) and in patients who did react at 60 and 180 min (P < 0.01). The total histamine content of PBL was significantly decreased after 15 and 60 min in patients who reacted (P < 0.01) and in those that did not (P < 0.05). Bee venom-induced histamine release was significantly reduced in patients reacting and those that did not at 15 min (P < 0.05), and was significantly decreased in reactors also at 60 and 180 min (P < 0.05/0.01). Specific IgG antibodies showed a minor decrease (P < 0.05) after the sting challenge in both groups, whereas specific IgE did not change significantly.

CONCLUSION

These results indicate that bee venom anaphylaxis is associated with the release of mediators from both mast cells as well as basophils. Successful hyposensitization does not induce a state of immunological non-reactivity, but rather alters the magnitude and the pattern of mediator release.

Increased thrombin generation during fibrinogen and platelet recovery as an explanation for hypercoagulability in children with L-asparaginase therapy for ALL or NHL: a preliminary report

Three out of 21 patients treated at the Children's Hospital of Eastern Switzerland for ALL or NHL with the respective BFM-90 protocols experienced thrombotic complications during Erwinia L-asparaginase therapy. We therefore investigated the development of the haemostatic imbalance in six children during the induction phase of both protocols. In the average, elevated thrombin generation was found simultaneously to an increase in fibrinogen, cross-linked fibrin degradation products and platelet counts between protocol days 28 to 35. This period thus seems to harbour an increased potential of hypercoagulability which could explain the accumulation of thrombotic complications described by Sutor et al. Moreover, day to day investigations just before and one day after L-asparaginase administration did not show any relevant change in the above named parameters, thus rather indicating a cumulative than a single dose effect of Erwinia L-asparaginase therapy on the coagulation system. These findings lead to the question if the prophylactic use of anticoagulants might reduce the hypercoagulability seen during L-asparaginase therapy, which is currently under investigation in our institutions.

[Dyskeratosis congenita in monozygous twins]

Dyskeratosis congenita (DC) is a very rare form of genodermatosis with variable manifestations, which mainly affects male patients. The main clinical symptoms are poikilodermia, nail dystrophy and leucoplakia; there are many other cutaneous and systemic symptoms. To avoid complications and improve the prognosis early diagnosis and regular close surveillance of the patients are important. We report on 13-year-old monozygotic twin brothers who, in addition to the typical symptoms, had increased vulnerability of the skin, scarring of the hands and atrophy of the oral mucosa as well as splenomegaly, pancytopenia with severe aplasia of bone marrow and aseptic necrosis of the hip. The two brothers had nearly synchronous clinical manifestation and progression. This paper reviews the clinical symptoms, pathogenesis, differential diagnosis and genetic aspects of DC.