RESUMO
Modern agricultural cultivation relies heavily on genetically modified plants that survive after exposure to herbicides that kill weeds. Despite this biotechnology, there is a growing need for new sustainable, environmentally friendly, and biodegradable herbicides. We developed a novel [CuL2]Br2 complex (L = bis{4H-1,3,5-triazino[2,1-b]benzothiazole-2-amine,4-(2-imidazole) that is active on PSII by inhibiting photosynthetic oxygen evolution on the micromolar level. [CuL2]Br2 reduces the FV of PSII fluorescence. Artificial electron donors do not rescind the effect of [CuL2]Br2. The inhibitory mechanism of [CuL2]Br2 remains unclear. To explore this mechanism, we investigated the effect of [CuL2]Br2 in the presence/absence of the well-studied inhibitor DCMU on PSII-containing membranes by OJIP Chl fluorescence transient measurements. [CuL2]Br2 has two effects on Chl fluorescence transients: (1) a substantial decrease of the Chl fluorescence intensity throughout the entire kinetics, and (2) an auxiliary "diuron-like" effect. The initial decrease dominates and is observed both with and without DCMU. In contrast, the "diuron-like" effect is small and is observed only without DCMU. We propose that [CuL2]Br2 has two binding sites for PSII with different affinities. At the high-affinity site, [CuL2]Br2 produces effects similar to PSII reaction center inhibition, while at the low-affinity site, [CuL2]Br2 produces effects identical to those of DCMU. These results are compared with other PSII-specific classes of herbicides.
Assuntos
Diurona , Herbicidas , Diurona/metabolismo , Diurona/farmacologia , Clorofila/metabolismo , Cobre/farmacologia , Spinacia oleracea , Complexo de Proteína do Fotossistema II/metabolismo , Fotoquímica , Fluorescência , Herbicidas/farmacologiaRESUMO
Carborane-intercalated layered double hydroxide nanohybrids (CB-LDH) and a magnesium ferrite (MF) supported-CB-LDH core-shell nanocomposite (CB-LDH@MF) are reported. The preparation of nanohybrids were carried out by exchanging the interlayer nitrate groups of Mg-Al-NO3-LDH with monothiol-o-carborane (SCB), 1-methyl-2-carboxyl-o-carborane (MeCB), 1-phenyl-2-carboxyl-o-carborane (PhCB) and 1,12-dicarboxyl-p-carborane (COOHCB) molecules. A magnetic core-shell nanocomposite was further prepared by supporting the COOHCB-LDH nanohybrid on MF nanoparticles. The obtained materials were characterized by means of several physical and chemical methods. Chemical compositions were determined by elemental analysis, ICP measurements and SEM-EDX data. Structural characterization was performed with powder-XRD, FTIR and magnetization measurements. Morphological analyses were conducted with electron microscopy imaging (SEM and TEM). Thermal stabilities were investigated by TGA/DTA. Carborane release from LDH layers was tested by tracing the amount of boron species transferred to the solution phase with ICP-MS measurements. The results verified that the prepared nanohybrids have the potential to be used in Boron Neutron Capture Therapy (BNCT) and magnetically targeted-BNCT applications.