Changes in lipid composition of tritosomes during lysis

Membrane phospholipids and free fatty acids were analyzed after lysis of lysosomes which had engulfed Triton WR 1339 (tritosomes). Significant elevations of lysophosphatidyl choline and lysophosphatidyl ethanolamine were seen. Phosphatidyl choline, phosphatidyl ethanolamine and sphingomyelin decreased significantly. Triglyceride also fell. The released free fatty acids paralleled closely the liberation of β-glucuronidase from the tritosomes. Thus, lipases hydrolyzed endogenous phospholipids and neutral lipids of tritosomes during incubation at 37°C at pH 5.0 to produce significant elevations of lysophospholipids and free fatty acids. The known surface-active properties of these latter compounds raise the possibility of their participation in the process of lysis of the tritosomes.     

Titanocene complexes with nonlinear pseudohalide ligands: Synthesis, spectroscopic characterization and crystal structure

Binuclear titanocene complexes [Cp₂Ti(tcm)]₂O (4), [Cp₂Ti(dca)]₂O (5) and [Cp₂Ti(dcnm)]₂O (6) (tcm⁻ = tricyanomethanide, dca⁻ = dicyanamide and dcnm⁻ = dicyanonitrosomethanide) were synthesized in moderate yields by the reaction of Cp₂TiCl₂ (1) with respective alkali metal pseudohalide salts in the aqueous solution. When the reaction was carried out in dry organic solvents, mononuclear compounds Cp₂Ti(tcm)₂ (2) and Cp₂Ti(dca)₂ (3) were isolated. Preparation of dipseudohalide complex Cp₂Ti(dcnm)₂ by this manner was unsuccessful due to decomposition of dcnm ligand resulting in formation of oxygen-bridged compound 6. All prepared compounds were characterized by elemental analysis, NMR, Raman, infrared and UV-Vis spectroscopy. Molecular structures of 2, 4 and 6 (two polymorphs) have been determined by single-crystal X-ray diffraction analysis.     

Synthesis, characterization and cytotoxic effect of ring-substituted and ansa-bridged vanadocene complexes

The cytotoxic effect of vanadocene dichloride (Cp₂VCl₂, 1) and its ring-substituted, (η⁵-C₅H₄Me)₂VCl₂ (2), (η⁵-C₅Me₅)₂VCl₂ (3), (η⁵-C₅H₄R)₂VCl₂ (4: R = MeOCH₂CH₂-, 5: R = 2-MeOC₆H₄CH₂-, 6: R = 4-MeOC₆H₄CH₂-) and ansa-bridged analogs Me₂C(η⁵-C₅H₄)₂VCl₂ (7) and Me₄C₂(η⁵-C₅H₄)₂VCl₂ (8) was investigated. Synthesis of two new methoxy-functionalized compounds (4 and 5) is described. They were characterized by spectroscopic methods and X-ray diffraction analysis. The cytotoxicity studies were performed with leukemic cells MOLT-4.     

Insertion sequence IS5 contains a sharply curved DNA structure at its terminus

Summary It was demonstrated that insertion sequence IS5 contains a sequence-directed bent (sharply curved) DNA structure at its terminus, close to one of its 16 bp terminal repeats. The minimal number of copies of IS5 related sequences and the locations of the latter on the Escherichia coli K12 W3110 chromosome were determined. Evidence is presented of the occurrence of IS5 mediated translocation and duplication of a large DNA segment on the E. coli chromosome.     

The sequence-directed bent DNA detected in the replication origin of Chlamydomonas reinhardtii chloroplast DNA is important for the replication function

Summary We demonstrated that the 1055 by restriction fragment containing OriA, a chloroplast DNA replication origin of Chlamydomonas reinhardtii, has electrophoretic anomalies characteristic of bent DNA. A tandem dimer of the region was constructed. Quantitative measurement of the relative gel mobility of a set of permuted fragments was used to extrapolate the approximate position of the bent DNA segment. By analyzing the gel mobility of short, sequenced fragments of the bent DNA region, the putative bending locus was identified. Two A₄ tracts and two A5 tracts were located in the bending locus. Oligonucleotide-directed mutagenesis was then used to disrupt the A tract or the spacing between A tracts and the effect of site-specific mutation on electrophoretic mobility was analyzed. To assess the functional role of the bent DNA region, subclones containing the bending locus, mutated bending locus, and regions flanking the bending locus were constructed. Each subclone was used as template in an in vitro DNA replication system which preferentially initiated DNA replication at OriA. A 224 by subclone with the bending locus positioned in the middle displayed the highest replication function and was sufficient to initiate DNA replication in vitro. Site-specific mutations or alterations of the A tracts resulted in decreased DNA bending and decreased DNA replication activity.     

Coordinated nitroxyl anion is produced and released as nitrous oxide by the decomposition of iridium-coordinated nitrosothiols

The aqueous decomposition of the iridium coordinated nitrosothiols (RSNOs) trans-K[IrCl₄(CH₃CN)NOSPh] (1), and K₂[IrCl₅(NOECyS)] (2, ECyS = cysteine ethyl ester), was studied by MS analysis of the gaseous products, ESI-MS, NMR, and UV-Vis spectroscopy. Bent NO (NO⁻, nitroxyl anion), sulfenic acids and nitrite were observed as coordinated products in solution, while nitrous oxide (N₂O) and nitrogen were detected in the gas phase. The formation of coordinated NO⁻ and N₂O, a nitroxyl dimerization product, allows us to propose the formation of free nitroxyl (HNO) as an intermediate. Complex 1 decomposes 300 times slower than free PhSNO does. In both cases (1 and 2) kinetic results show a first order decomposition behavior and a very negative ΔS^≠, which strongly indicates an associative rate-determining step. A proposed decomposition mechanism, supported by the experimental data and DFT calculations, involves, as the first step, nucleophilic attack of H₂O on to the sulfur atom of the coordinated RSNO, producing an NO⁻ complex and free sulfenic acid, followed by two competing reactions: a ligand exchange reaction of this NO⁻ with the sulfenic acid or, to a minor extent, coordination of N₂O to produce an NO⁻/N₂O complex which finally renders free N₂ and coordinated NO₂⁻. Some of the produced NO⁻ is likely to be released from the metal center producing nitroxyl by protonation and finally N₂O by dimerization and loss of H₂O. In conclusion, the decomposition of these coordinated RSNOs occurs through a different mechanism than for the decomposition of free RSNOs. It involves the formation of sulfenic acids and coordinated NO⁻, which is released from the complexes and protonated at the reaction pH producing nitroxyl (HNO), and ultimately N₂O.     

A biomechanical model of artery buckling

The stability of arteries under blood pressure load is essential to the maintenance of normal arterial function and the loss of stability can lead to tortuosity and kinking that are associated with significant clinical complications. However, mechanical analysis of arterial bent buckling is lacking. To address this issue, this paper presents a biomechanical model of arterial buckling. Using an elastic cylindrical arterial model, the mechanical equations for arterial buckling were developed and the critical buckling pressure was found to be a function of the wall stiffness (Young's modulus), arterial radius, length, wall thickness, and the axial strain. Both the model equations and experimental results demonstrated that the critical pressure is related to the axial strain. Arteries may buckle and become tortuous due to reduced (subphysiological) axial strain, hypertensive pressure, and a weakened wall. These results are in accordance with, and provide a possible explanation to the clinical observations that hypertension and aging are the risk factors for arterial tortuosity and kinking. The current model is also applicable to veins and ureters.     

Synthesis and structural investigation of vanadocene(IV) complexes of non-linear pseudohalides

Two series of vanadocene complexes of the type (Cp′ = η⁵-C₅H₅, η⁵-C₅H₄Me; X = dicyanamide, tricyanomethanide, dicyanonitrosomethanide) were prepared by the reaction of appropriate vanadocene dichloride complex with alkali salt of non-linear pseudohalide. The bonding mode of pseudohalide ligands was determined by spectroscopic measurements and X-ray diffraction analyses.     

Longevity and quality of cut 'Master' carnation and 'Red Sandra' rose flowers as affected by red light

Cut flowering stems (45 cm long) of carnation (cv. Master) and rose (cv. Red Sandra) were placed in test tubes containing distilled water with or without commercial preservative (20 ml l^–1), under fluorescent tubes of 50 ± 10 mol m^–2 s^–1 Photosynthetic photon flux (PPF). A mixed radiation from fluorescent tubes with red light provided by light emitting diodes (LEDs) and monochromic red light of low 50 or high 90 ± 10 mol m^–2 s^–1 was also tested in the absence of preservative solution. Both red light with high PPF and the mixed radiation under low PPF extended the vase life of cut carnations, and flower freshness could be maintained for 10.9 days compared with a water/fluorescent light control. In cut rose, the treatment containing the preservative solution under fluorescent tubes alone and in red alone, regardless of light intensity, prolonged vase life for 4.6 and 4.2 days longer than the control, respectively. Treatment with red LEDs plus high PPF resulted in complete petal opening in carnation flowers.