Atomic orientation following predissociation of the C 3Πg Rydberg state of molecular oxygen.

(2 + 1) resonance enhanced multiphoton ionization in combination with time-of-flight mass spectroscopy (TOF-MS) has been used to detect both the O((3)P) and O((1)D) fragments produced as a result of predissociation of the C (3)Πg (v = 0) and (v = 1) Rydberg states of O2, accessed via two-photon absorption from the ground X (3)Σg(-) state. In particular, TOF profiles have been recorded at various fixed two-photon absorption wavelengths within the two bands, with circular polarized probe laser light used to probe the angular momentum orientation of these photofragments. All photofragments are found to display coherent orientation resulting from interference between two possible two-photon absorption pathways. The measured orientation is affected by rotational depolarization due to the long lifetime of the excited C state; once this effect is accounted for the orientation is found to be nearly constant over all dissociation wavelengths. The origin of the coherent orientation is attributed to two-photon absorption to different spin-orbit components of the C state.

Predissociation dynamics of the C 3Πg Rydberg state of molecular oxygen.

(2+1) resonance enhanced multiphoton ionization time-of-flight mass spectroscopy (TOF-MS) has been used to detect both the O((3)P) and O((1)D) fragments produced as a result of predissociation of the C (3)Πg (v = 0) and (v = 1) Rydberg states of O2. In particular, TOF profiles have been recorded at various fixed wavelengths within the two bands in order to investigate the differences in predissociation dynamics of intermediate levels with different values of |Ω| (=0, 1, 2 in this case). TOF profiles have been recorded in multiple geometries to determine both the translational anisotropy and angular momentum alignment of both photofragments as well as the O((3)P) spin-orbit branching ratios produced following a two-photon dissociation. The translational anisotropy is found to be dependent on the dissociation wavelength with the variations found to be consistent with rotational depolarization due to the long lifetime of the excited C state. All photofragments have been found to be aligned, with the relationship between the measured O((3)P) and O((1)D) alignment being found to be consistent with a diabatic model of the dissociation.

Electronic polarization effects in the photodissociation of Cl2.

Velocity mapped ion imaging and resonantly enhanced multiphoton ionization time-of-flight methods have been used to investigate the photodissociation dynamics of the diatomic molecule Cl(2) following excitation to the first UV absorption band. The experimental results presented here are compared with high level time dependent wavepacket calculations performed on a set of ab initio potential energy curves [D. B. Kokh, A. B. Alekseyev, and R. J. Buenker, J. Chem. Phys. 120, 11549 (2004)]. The theoretical calculations provide the first determination of all dynamical information regarding the dissociation of a system of this complexity, including angular momentum polarization. Both low rank K = 1, 2 and high rank K = 3 electronic polarization are predicted to be important for dissociation into both asymptotic product channels and, in general, good agreement is found between the recent theory and the measurements made here, which include the first experimental determination of high rank K = 3 orientation.

Plakoglobin regulates the expression of the anti-apoptotic protein BCL-2.

Plakoglobin is a cytoplasmic protein and a homologue of beta-catenin and Armadillo of Drosophila with similar adhesive and signaling functions. These proteins interact with cadherins to mediate cell-cell adhesion and associate with transcription factors to induce changes in the expression of genes involved in cell fate determination and proliferation. Unlike the relatively well characterized role of beta-catenin in cell proliferation via activation of c-MYC and cyclin D1 gene expression, the signaling function of plakoglobin in regulation of cell growth is undefined. Here, we show that high levels of plakoglobin expression in plakoglobin-deficient human SCC9 cells leads to uncontrolled growth and foci formation. Concurrent with the change in growth characteristics we observe a pronounced inhibition of apoptosis. This correlates with an induction of expression of BCL-2, a prototypic member of apoptosis-regulating proteins. The BCL-2 expression coincides with decreased proteolytic processing and activation of caspase-3, an executor of programmed cell death. Our data suggest that the growth regulatory function of plakoglobin is independent of its role in mediating cell-cell adhesion. These observations clearly implicate plakoglobin in pathways regulating cell growth and provide initial evidence of its role as a pivotal molecular link between pathways regulating cell adherence and cell death.

Some features of secretory systems in plants.

Recent work on secretion in plants is reviewed, with emphasis on the anatomy and physiology of root cap cells in higher plants, the stalked glands of Drosera capensis, and the secretory mechanism of Dionaea muscipula. Cells of the root cap of higher plants switch from a geo-perceptive role to one of mucilage secretion at maturation. Features of this process, the role of the Golgi and the pathway for mucilage distribution are reviewed. In contrast, the stalked glands of the leaves of Drosera capensis are much longer lived and have a complex anatomy. The mechanisms for mucilage secretion, protein absorption and the role of the cell membranes in the internal secretion of the protein are described, using data from X-ray microscopv. The secretion of fluid and protein by Dionaea is stimulated by various nitrogen-containing compounds. Uric acid, often excreted by captured insects, is particularly effective in this respect.

An excitable membrane in the stalked glands of Drosera capensis L.

Shortly after feeding the surface of the gland of Drosera capensis L. with whole milk or other protein sources the plasmalemma adjacent to the tracheid becomes highly modified. No vesicle is seen to approach the membrane from within the cytoplasm, but the surface of the membrane grows and evaginates outwards forming a small protruding papilla or bleb about 50-100 nm across. Finally the bleb is pinched off at the base and disappears into the tracheid.This form of stimulated "exocytosis" does not appear to have been observed in any other plant tissue, but may be a feature of those specialised organs that take up rapidly large quantities of externally applied nutrient.