[Effects of soil water stress and atmospheric CO2 concentration on photosynthetic and post-photosynthetic fractionation]

Analysis of plant photosynthesis and post-photosynthetic fractionation can improve our understanding of plant physiology and water management. By measuring δ¹³C in the atmosphere, and δ¹³C of soluble compounds in leaves and branch phloem of Platycladus orientalis, we examined discrimination pattern, including atmosphere-leaf discrimination during photosynthesis (ΔC_a-leaf) and leaf-twig discrimination during post-photosynthesis (ΔC_leaf-phlo), in response to changes of soil water content (SWC) and atmospheric CO₂ concentration (C_a). The results showed that ΔC_a-leaf reached a maximum of 13.06‰ at 95%-100% field water-holding capacity (FC) and C_a 400 μmol·mol^-1, and a minimum of 8.63‰ at 35%-45% FC and C_a 800 μmol·mol^-1. Both stomatal conductance and mesophyll cell conductance showed a significant linear positive correlation with ΔC_a-leaf, with a correlation coefficient of 0.43 and 0.44, respectively. ΔC_leaf-phlo was not affected by SWC and C_a. Our results provide mechanism of carbon isotopes fractionation and a theoretical basis for plant survival strategies in response to future climate change.

Pillared-Layer Microporous Metal−Organic Frameworks Constructed by Robust Hydrogen Bonds. Synthesis, Characterization, and Magnetic and Adsorption Properties of 2,2‘-Biimidazole and Carboxylate Complexes

Two new isostructural complexes [M(H2biim)3][M(btc)(Hbiim)].2H2O (M = Co, (1); M = Ni, (2)) (btc = 1,3,5-benzenetricarboxylate; H2biim = 2,2'-biimidazole) have been synthesized and characterized by single-crystal X-ray diffraction. They present a unique structure consisting of two distinct units: the monomeric cations [M(H2biim)3]2+ and the two-dimensional (2D) anionic polymer [M(Hbiim)(btc)]2-. In the anionic moiety, the Hbiim- monoanion is simultaneously coordinated to one metal atom in a bidentate mode and further to another metal atom in a monodentate mode. The imidazolate groups bridge the two adjacent metal ions into a helical chain which is further arranged in left- and right-handed manners. These chains are bridged by btc ligands into a 2D brick wall structure. The most interesting aspect is that the [M(H2biim)3]2+ cations act as pillars and link the anionic layers via robust heteromeric hydrogen-bonded synthons (9) and (7) formed by the uncoordinated oxygen atoms of carboxylate groups and the H2biim ligands, resulting in a microporous metal-organic framework with one-dimensional (1D) channels (ca. 11.85 angstroms x 11.85 angstroms for 1 and 11.43 angstroms x 11.43 angstroms for 2). Magnetic properties of these two complexes have also been studied in the temperature range of 2-300 K, and their magnetic susceptibilities obey the Curie-Weiss law in the temperature range of 20-300 K (for 1) and 2-300 K (for 2), respectively, showing anti-ferromagnetic coupling through imidazolate bridging. Taking into consideration the Heisenberg infinite chain model as well as the possibility of chain-to-chain and chain-to-cation interactions, the anti-ferromagnetic exchange of 2 is analyzed via a correction for the molecular field, giving the values of g(cat) = 2.296, g(Ni) = 2.564, J = -13.30 cm(-1), and zJ' = -0.017 cm(-1). The microporous frameworks are stable at ca. 350 degrees C. They do not collapse after removal of the guest water molecules in the channels, and they adsorb methanol molecules selectively.

Formation of One-Dimensional Metal−Water Chain Containing Cyclic Water Hexamers

Cyclic water hexamers containing 1-D metal--water chains have been observed in the complexes of [M(H(2)biim)(2)(OH(2))(2)](ina)(2) x 4H(2)O [M = Zn (1) and Co (2), H(2)biim = 2,2'-biimidazole, ina = isoniconate]. The water clusters are trapped by the cooperative association of coordination interactions as well as hydrogen bonds.

[Immunocytochemical localization of fertilin beta on human sperm]

Fertilin is a kind of sperm plasma membrane protein that mimics snake venom protein. It belongs to the ADAMs family of surface proteins that contain a disintegrin and a metalloprotease domain. Fertilin functions in the sperm-egg binding process by connecting the sperm to the egg plasma membrane via a binding site in the disintegrin domain of fertilin beta (HF93). Its localization on the sperm is in the change. In this study, the monoclonal antibody against human fertilin beta was prepared and used to analyze the localization of fertilin beta on capacitated and acrosome-reacted sperm by immunofluorescence and immunoelectron microscopy techniques. The results were as follows: (1) fertilin beta became restricted to the anterior head during the course of capacitation. (2) During the course of acrosome reaction, the expression and localization of fertilin beta changed immensely on the anterior head and restricted to the lateral of posterior head at last. The restrictions of fertilin beta to the anterior head of capacitated sperm of human beings indicated that fertilin beta may be involved in the binding the sperm to the epithelial cells of the oviduct; the restrictions of fertilin beta to the posterior head domain of acrosome-reacted sperm implied its function in sperm-egg binding and fusion.