Singlet oxygen production by pyrano and furano 1,4-naphthoquinones in non-aqueous medium

The influence of ring size on the photobehaviour of condensed 1,4-naphthoquinone systems, such as pyrano- and furano-derivatives (1 and 2, respectively) has been investigated. The absorption spectra for both families of naphthoquinones reveal clear differences; in the case of 2 they extend to longer wavelengths. A solvatochromic red shift in polar solvents is consistent with the π,π* character of the S(0)→ S(1) electronic transition in all cases. Theoretical (B3LYP) analysis of the HOMO and LUMO Kohn-Sham molecular orbitals of the S(0) state indicates that they are π and π* in nature, consistent with the experimental observation. A systematic study on the efficiency of singlet oxygen generation by these 1,4-naphthoquinones is presented, and values larger than 0.7 were found in every case. In accordance with these results, laser flash photolysis of deoxygenated acetonitrile solutions led to the formation of detectable triplet transient species with absorptions at 390 and 450 nm (1) and at 370 nm (2), with φ(ISC) close to 1. Additionally, the calculated energies for the T(1) states relative to the S(0) states at UB3LYP/6-311++G** are ca. 47 kcal mol(-1) for 1 and 43 kcal mol(-1) for 2. A comparison of the geometrical parameters for the S(0) and T(1) states reveals a marked difference with respect to the arrangement of the exocyclic phenyl ring whilst a comparison of electronic parameters revealed the change from a quinone structure to a di-dehydroquinone diradical structure.     

Producing transglutaminases by molecular farming in plants: Minireview article

Summary. Transglutaminases have a range of catalytic activities, most of which concern the post-translational modification of proteins. The most important of these activities, both in terms of biology and biotechnology, is the cross-linking of proteins into large supramolecular networks. The widespread use of transglutaminases in research, medicine and industry has increased the demand for an inexpensive, efficient and safe source of recombinant enzymes. We describe initial results concerning the production of a mammalian transglutaminase in transgenic rice plants as a first step towards the large-scale molecular farming of this enzyme.     

Dedifferentiation-mediated changes in transposition behavior make the Activator transposon an ideal tool for functional genomics in rice

There is an inverse relationship between the level of cytosine methylation in genomic DNA and the activity of plant transposable elements. Increased transpositional activity is seen during early plant development when genomic methylation patterns are first erased and then reset. Prolonging the period of hypomethylation might therefore result in an increased transposition frequency, which would be useful for rapid genome saturation in transposon-tagged plant lines. We tested this hypothesis using transgenic rice plants containing Activator (Ac) from maize. R₁ seeds from an Ac-tagged transgenic rice line were either directly germinated and grown to maturity, or induced to dedifferentiate in vitro, resulting in cell lines that were subsequently regenerated into multiple mature plants. Both populations were then analyzed for the presence, active reinsertion and amplification of Ac. Plants from each population showed excision-reinsertion events to both linked and unlinked sites. However, the frequency of transposition in plants regenerated from cell lines was more than nine-fold greater than that observed in plants germinated directly from seeds. Other aspects of transposon behavior were also markedly affected. For example, we observed a significantly larger proportion of transposition events to unlinked sites in cell line-derived plants. The tendency for Ac to insert into transcribed DNA was not affected by dedifferentiation. The differences in Ac activity coincided with a pronounced reduction in the level of genomic cytosine methylation in dedifferentiated cell cultures. We used the differential transposon behavior induced by dedifferentiation in the cell-line derived population for direct applications in functional genomics and validated the approach by recovering Ac insertions in a number of genes. Our results demonstrate that obtaining multiple Ac insertions is useful for functional annotation of the rice genome.These authors contributed equally to the work     

ACETYLCHOLINESTERASE IN FROG SYMPATHETIC AND DORSAL ROOT GANGLIA : A Study by Electron Microscope Cytochemistry and Microgasometric Analysis with the Magnetic Diver

The localization and chemical determination of acetylcholin esterase in the frog sympathetic and dorsal root ganglia were studied by a combination of the methods of electron microscopy, histochemistry, and microgasometric analysis with the magnetic diver. The Koelle-Friedenwald copper thiocholine histochemical method was modified by eliminating the sulfide conversion and by treatment of the tissue with potassium permanganate. In fixed tissue, enzymatic activity was demonstrated on the inner surface of the endoplasmic reticulum, nuclear envelope, subsurface cisternae, and agranular reticulum of the perikaryon and axon. In briefly fixed tissue, end product appeared also at the axon-sheath and the sheath-sheath interface. Activity at the synaptic junction was most readily obtained in unfixed tissue. Isolated neurons recovered from the diver following chemical analysis were studied with the electron microscope. Cells having a high enzyme activity showed a badly ruptured or absent neural plasmalemma and sheath. In this case the measured activity was apparently due to the enzyme present in the endoplasmic reticulum. Neurons having low activity exhibited an intact plasmalemma and sheath. This may reflect the effectiveness of the neural plasmalemma and sheath as a penetration barrier. The effects of fixation on enzyme activity are discussed. Electron microscopic examination of cells following microgasometric analysis is shown to be essential for the interpretation of the biochemical data.     

New insights in mechanisms for development of ovarian hyperstimulation syndrome

The ovarian hyperstimulation syndrome (OHSS) is typically an iatrogenic complication of induction ovulation occurring during the luteal phase or early pregnancy. However, the spontaneous form of OHSS is extremely rare and always reported during pregnancy. Several cases have been observed during multiple pregnancies and other cases were associated with hypothyroidism. Moreover, a few mutations of the follicle-stimulation hormone receptor (FSHr) were recently described in spontaneous OHSS and normal levels of human chorionic gonadotrophin (HCG). In these cases, a molecular basis for the pathogenesis of the spontaneous OHSS was identified. These mutations displayed promiscuous sensitivity and activation by both HCG and thyroid stimulating hormone (TSH). The disease always occurs in the presence of either exogenous or endogenous HCG which is thought to play a crucial role in the development of OHSS. The hallmark of OHSS is an increase in capillary permeability resulting in a fluid shift from the intravascular compartment into the third space. It is assumed that HCG induces the release of certain ovarian vasoactive substances or mediators that have potent and direct systemic effects on the vascular system. It was demonstrated that the endothelium, along with the ovary is a primary target for HCG. Of all the different vasoactive components, vascular endothelial growth factor (VEGF) is the principal mediator and the most responsible for increased capillary permeability. It is produced and secreted in the ovary or in the endothelium, and acts through the VEGF receptor-2 or high affinity receptors (KDR and flt 1), respectively. In addition to VEGF HCG may trigger activation of the renin-angiotensin system and kinin-kallikrein system together with releasing of interleukins (6,18), endothelial-cell adhesion molecules, von Willebrand factor, angiogenin and endothelin-1, that also increase vascular permeability.