High light inhibits chlorophyll biosynthesis at the level of 5-aminolevulinate synthesis during de-etiolation in cucumber (Cucumis sativus) cotyledons

Using the vascular plant Cucumis sativus (cucumber) as a model, we studied the effects of high (intense and excess) light upon chlorophyll biosynthesis during de-etiolation. When illuminated with high light (1500-1600 microE/m2/s), etiolated cucumber cotyledons failed to synthesize chlorophyll entirely. However, upon transfer to low light conditions (40-45 microE/m2/s), chlorophyll biosynthesis and subsequent accumulation resumed following an initial 2-12 h delay. Duration of high light treatment negatively correlated with chlorophyll biosynthetic activity. Specifically, we found that high light severely inhibited 5-aminolevulinic acid (ALA) synthesis. This effect partly could be because of the decrease in protein level of glutamyl-tRNA reductase (GluTR) observed. Protein level of glutamate-1-semialdehyde (GSA-AT) remained unchanged. It was also found that high light did not suppress HEMA 1 expression. Therefore, we speculated that this significant inhibition of ALA synthesis might have occurred mainly because of concomitant inactivation of GluTR and/or inhibition of complex formation between GluTR and GSA-AT. Our further observation that both methyl viologen and rose bengal similarly inhibit ALA synthesis under low light conditions suggested that reactive oxygen species (ROS) could be responsible for the inhibition of ALA synthesis in cotyledons exposed to high light conditions.     

Synthesis of 2-(Triazolyl,Oxadiazolyl, and Pyrazolyl) Substituted 1,5-Benzothiazepin-S,S-Dioxide Derivatives of Potential Medicinal Interest

Abstract

The synthetic potential of 2,3,4,5-tetrahydrobenzo[b] [1,5]thiazepine-1,1,4-trione-2-carbohydrazide (5) which resulted from ethyl-4-oxo-2,3,4,5-tetrahydrobenzo[b] [1,5]thiazepine-2-carboxylate (3), on its oxidation with H₂O₂/AcOH followed by treatment with NH₂NH₂.H₂O, was exploited to provide an access to 2-triazolo, 2-oxadiazolo, and 2-pyrazolo substituted derivatives of 1,5-benzothiazepin-4-oxo-1,1-dioxides (6–10), respectively.     

Ligand-exchange dependent properties of hybrid nanocomposites based on luminescent colloidal CdSe nanocrystals in P3HT matrix

In this work, a suitable ligand-exchange process has been proposed which elucidates the possibility to modulate charge/energy transfer rate between polymer and semiconductor quantum dots. The photoluminescence studies of CdSe emission as well as transient absorption measurements confirm mainly electron transfer for P3HT:CdSe (TOPO) and electron/energy transfer for P3HT:CdSe (OA) nanocomposites, respectively. The dominance of charge transfer for P3HT:CdSe (TOPO) as compared to P3HT:CdSe (OA) nanocomposites can be attributed to complete and partial removal of the surface ligands (TOPO, OA) upon ligand exchange with pyridine as elucidated from FTIR results. The various characterization techniques viz. Fourier transform infrared (FTIR), Raman, photoluminescence (PL), optical and transient absorption (UV-Vis and TA) spectroscopies used in this work provide an insight into the charge separation, charge accumulation and/or trapping of charge carriers for the better understanding of hybrid organic-inorganic photovoltaics. Composites of CdSe (OA) quantum dots in particular with P3HT polymer owing to its higher crystallinity and ordered morphology provide a new and promising direction toward developing effective light energy harvesting strategies in organic photovoltaics.     

Determination of lignin by size exclusion chromatography using multi angle laser light scattering

A method was developed using high-performance size exclusion liquid chromatography (HPSEC) with multi-angle laser light scattering (MALLS), quasi-elastic light scattering (QELS), interferometric refractometry (RI) and UV detection to characterize and monitor lignin. The combination proved very effective at tracking changes in molecular conformation of lignin molecules over time; i.e. changes in molecular weight distribution, radius of gyration, and hydrodynamic radius. Until this study, UV detection (280 nm) had been the primary lignin determination method for chromatography. Three different HPLC columns were used to study the effects of pH, flow conditions, and mobile phase compositions (dimethyl sulphoxide, water, 0.1M NaOH, and lithium bromide) on the chromatography of lignin. Since light scattering accuracy is highly dependent on solute concentration, both the UV and RI detectors were calibrated for use as concentration detectors. Shodex Asahipak GS-320 HQ column with 0.1M NaOH (pH 12.0) run at 0.5 ml/min was found to give the highest separation and most consistent recovery. The study also revealed that the lignin aggregated at pH below 8.5. This aggregation was detected only by MALLS and was not observed on UV or RI detectors. It is very important to take this loss in apparent concentration due to aggregation into consideration before collecting reliable depolymerization data.     

An insight into the surface engineering of colloidal PbSe quantum dots for polymer hybrid photovoltaic applications

Journal of Sol-Gel Science and Technology - In this article, the beneficial effect of surface passivation rendered by the amalgamation of co-ordinating tri-n-octylphophine (TOP), oleylamine (OLA),...     

Paal–Knorr Pyrrole Synthesis Using Recyclable Amberlite IR 120 Acidic Resin: A Green Approach

Amberlite IR 120 acidic resin, a polymer matrix, has been demonstrated as a catalyst for Paal-Knorr condensation of 2,5-hexadione with primary amines under solvent-free conditions. This is an efficient, mild, and green methodology for N-substituted pyrrole derivatives.