Deriving C4 photosynthetic parameters from combined gas exchange and chlorophyll fluorescence using an Excel tool: theory and practice

The higher photosynthetic potential of C₄ plants has led to extensive research over the past 50 years, including C₄‐dominated natural biomes, crops such as maize, or for evaluating the transfer of C₄ traits into C₃ lineages. Photosynthetic gas exchange can be measured in air or in a 2% Oxygen mixture using readily available commercial gas exchange and modulated PSII fluorescence systems. Interpretation of these data, however, requires an understanding (or the development) of various modelling approaches, which limit the use by non‐specialists. In this paper we present an accessible summary of the theory behind the analysis and derivation of C₄ photosynthetic parameters, and provide a freely available Excel Fitting Tool (EFT), making rigorous C₄ data analysis accessible to a broader audience. Outputs include those defining C₄ photochemical and biochemical efficiency, the rate of photorespiration, bundle sheath conductance to CO₂ diffusion and the in vivo biochemical constants for PEP carboxylase. The EFT compares several methodological variants proposed by different investigators, allowing users to choose the level of complexity required to interpret data. We provide a complete analysis of gas exchange data on maize (as a model C₄ organism and key global crop) to illustrate the approaches, their analysis and interpretation. © 2015 John Wiley & Sons Ltd     

Synthesis of highly fluorescent nitrogen and phosphorus doped carbon dots for the detection of Fe3+ ions in cancer cells

Highly fluorescent nitrogen and phosphorus‐doped carbon dots with a quantum yield 59% have been successfully synthesized from citric acid and di‐ammonium hydrogen phosphate by single step hydrothermal method. The synthesized carbon dots have high solubility as well as stability in aqueous medium. The as‐obtained carbon dots are well monodispersed with particle sizes 1.5–4 nm. Owing to a good tunable fluorescence property and biocompatibility, the carbon dots were applied for intercellular sensing of Fe³⁺ ions as well as cancer cell imaging. Copyright © 2015 John Wiley & Sons, Ltd.     

Is the fracto‐mechanoluminescence of ZnS:Mn phosphor dominated by charged dislocation mechanism or piezoelectrification mechanism?

Mathematical approaches made for both the charged dislocation model and piezoelectrically induced electron bombardment model of fracto‐mechanoluminescence (FML), the luminescence induced by fracture of solids, in ZnS:Mn phosphor indicate that the piezoelectrically induced electron bombardment model provides a dominating process for the FML of ZnS phosphors. The concentration of 3000 ppm Mn²⁺ is optimal for ML intensity of ZnS:Mn phosphor. The decay time of ML gives the relaxation time of the piston used to deform the sample and the time t_m of maximum of ML is controlled by both the relaxation time of the piston and decay time of charges on the newly created surfaces of crystals. As the product of the velocity of dislocations and pinning time of dislocations gives the mean free path of a moving dislocation. Both factors play an important role in the ML excitation of impurity doped II–VI semiconductors. The linear increase of total ML intensity I_T with the impact velocity indicates that the damage increases linearly with impact velocity of the load. Thus, the ML measurement can be used remotely to monitor the real‐time damage in the structures, and therefore, the ML of ZnS:Mn phosphor has also the potential for a structural health monitoring system. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,characterization and thermoluminescence studies of Mn‐doped ZnS nanoparticles

ZnS:Mn nanoparticles were prepared by a chemical precipitation method and characterized by X‐ray diffraction (XRD), field emission gun scanning electron microscope (FEGSEM), and high resolution transmission electron microscopy (HRTEM). Capping agent (mercaptoethanol) concentrations used were 0 M, 0.005 M, 0.01 M, 0.015 M, 0.025 M, 0.040 M, and 0.060 M, and resulted in nanoparticles sizes of 2.98 nm, 2.9 nm, 2.8 nm, 2.7 nm, 2.61 nm, 2.2 nm and 2.1 nm, respectively. The thermoluminescence (TL) glow curve was recorded by heating the sample exposed to UV‐radiation, at a fixed heating rate 1°C sec^–1. The TL intensity initially increased with temperature, attained a peak value I_m for a particular temperature, and then decreased with further increase in temperature. The peak TL intensity increased with decreasing nanoparticle size, whereas the temperature corresponding to the peak TL intensity decreased slightly with reducing nanocrystal size. As a consequence of increase in surface‐to‐volume ratio and increased carrier recombination rates, the TL intensity increased with decreasing nanoparticle size. It was found that, whereas activation energy slightly decreased with decreasing nanoparticle size, the frequency factor decreased significantly with reduction in nanoparticle size. Copyright © 2015 John Wiley & Sons, Ltd.     

Reactivation of mutant p53: Constraints on mechanism highlighted by principal component analysis of the DNA binding domain

Most p53 mutations associated with cancer are located in its DNA binding domain (DBD). Many structures (X‐ray and NMR) of this domain are available in the protein data bank (PDB) and a vast conformational heterogeneity characterizes the various free and complexed states. The major difference between the apo and the holo‐complexed states appears to lie in the L1 loop. In particular, the conformations of this loop appear to depend intimately on the sequence of DNA to which it binds. This conclusion builds upon recent observations that implicate the tetramerization and the C‐terminal domains (respectively TD and Cter) in DNA binding specificity. Detailed PCA analysis of the most recent collection of DBD structures from the PDB have been carried out. In contrast to recommendations that small molecules/drugs stabilize the flexible L1 loop to rescue mutant p53, our study highlights a need to retain the flexibility of the p53 DNA binding surface (DBS). It is the adaptability of this region that enables p53 to engage in the diverse interactions responsible for its functionality. Proteins 2016; 84:1443–1461. © 2016 Wiley Periodicals, Inc.