Regioselective Homolytic C2-H Borylation of Unprotected Adenosine and Adenine Derivatives via Minisci Reaction.

A Minisci-type borylation of unprotected adenosine, adenine nucleotide, and adenosine analogues was successfully achieved through photocatalysis or thermal activation. Despite the challenges posed by the presence of two potential reactive sites (C2 and C8) in the purine motif, the unique nucleophilic amine-ligated boryl radicals effortlessly achieved excellent C2 site selectivity and simultaneously avoided the formation of multifunctionalized products. This protocol proved effective for the late-stage borylation of some important biomolecules as well as a few antiviral and antitumor drug molecules, such as AMP, cAMP, Vidarabine, Cordycepin, Tenofovir, Adefovir, GS-441524, etc. Theoretical calculations shed light on the site selectivity, revealing that the free energy barriers for the C2-Minisci addition are further lowered through the chelation of additive Mg2+ to N3 and furyl oxygen. This phenomenon has been confirmed by an IGMH analysis. Preliminary antitumor evaluation, derivation of the C2-borylated adenosine to other analogues with high-value functionalities, along with the CuAAC click reactions, suggest the potential application of this methodology in drug molecular optimization studies and chemical biology.

Advances in ionic liquids as fluorescent sensors.

Ionic liquids (ILs) are a class of liquid salts with characteristics such as a low melting point, an ionic nature, non-volatility, and tunable properties. Because of their adaptability, they have a significant influence in the field of fluorescence. This paper reviews the primary literature on the use of ILs in fluorescence sensing technologies. The kind of target material is utilized to classify the fluorescence sensors made with the use of ILs. They include using ILs as probes for metals, nitro explosives, small organic compounds, anions, and gases. The efficacy of an IL-based fluorescence sensor depends on the precise design to guarantee specificity, sensitivity, and a consistent reaction to the desired analyte. The precise method can differ depending on the chemical properties of the IL, the choice of fluorophore, and the interactions with the analyte. Overall, the viability of the aforementioned materials for chemical analysis is evaluated, and prospective possibilities for further development are identified.

Protective effect of jasmonic acid and potassium against cadmium stress in peas (Pisum sativum L.).

A combination of mineral nutrients and plant growth regulators should be assessed to improve crop performance under various abiotic stresses. There is a need to include plant growth regulators in fertilization regime of various crops along with essential mineral nutrients, especially when they are irrigated with polluted water with higher levels of heavy metals. The performance of pea was evaluated under cadmium (Cd) stress coupled with potassium (K) and jasmonic acid (JA) supplementation. The Cd stress (50 µM) was applied to soil (sandy loam) grown pea plants as basal dose after a month of sowing. The control and stressed plants were then supplemented with K (5 M), JA (0.5 mM) and their collective application along with control as distilled water. Cd stress showed a marked reduction in growth pattern, however, the collective supplementation sufficiently improved the growth pattern of stressed peas plants as evidenced by improvement in shoot length (cm), root length (cm), number of leaves per plant, leaf area (cm2), plant fresh and dry weight (gm). Potassium application under Cd stress significantly enhanced internodal distance (cm) while the number of seeds per pod and relative water contents remained nonsignificant. The applied treatment (JA + K) under Cd stress prominently improved enzymatic activities, which were measured as nitrate reductase activity (NRA), nitrite reductase activity (NiRA), superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Cd stress impacted the biochemical profile by enhancing antioxidant capacity (AC), antioxidant activity (AA), total phenols (TP), while reducing total soluble protein (TSP), chlorophyll 'a', chlorophyll 'b' and carotenoids. The combined application of JA and K under Cd stress enhanced AC, AA, TP, Chl a and b, TSP and carotenoids. The results indicate that foliar application of JA and K efficiently negated the harmful effects of Cd stress on peas.

Exogenous application of silicon improves the performance of wheat under terminal heat stress by triggering physio-biochemical mechanisms.

Due to climate change, temperature in late February and early March raised up which cause heat stress at reproductive stage (terminal growth phase of wheat crop) which has become the major causative factor towards low wheat production in arid and semiarid regions. Therefore; strategies need to be adopted for improving terminal heat stress tolerance in wheat. In this study, we assessed whether foliar application of silicon (Si) (2 and 4 mM) at terminal growth phase i.e. heading stage of wheat imposed to heat stress (37 ± 2 °C) under polythene tunnel could improve the performance of wheat. Results of the study revealed that heat stress significantly reduced the photosynthetic pigments (chlorophyll a, b and a + b and carotenoids) leading to a lower grain yield. However, a 4 mM Si application (foliar applied) at heading stage prominently increased the chlorophyll a, b and a + b and carotenoids of flag leaf by improving the activities of enzymatic antioxidants (catalase, peroxidase and superoxide dismutase) and osmoprotectants (soluble sugar protein and proline) under terminal heat stress. Improvements in the performance of wheat (chlorophyll contents, carotenoids, soluble sugar and proteins and proline and yield) with foliar application of Si were also observed under control conditions. Correlation analysis revealed strong association (r > 0.90) of chlorophyll contents and carotenoids with grain and biological yield. Negative correlation (-0.81 < r > -0.63) of physio-biochemical components (antioxidants, proline, soluble sugars and proteins) with yield revealed that under heat stress these components produced in more quantities to alleviate the effects of heat, and Si application also improved these physio biochemical components. In crux, foliar application of Si alleviates the losses in the performance of wheat caused by terminal heat stress by improving the antioxidant mechanism and production of osmoprotectants.

Morpho-physiological and biochemical attributes of Chili (Capsicum annum L.) genotypes grown under varying salinity levels.

Climate change is causing soil salinization, resulting in huge crop losses throughout the world. Multiple physiological and biochemical pathways determine the ability of plants to tolerate salt stress. Chili (Capsicum annum L.) is a salt-susceptible crop; therefore, its growth and yield is negatively impacted by salinity. Irreversible damage at cell level and photo inhibition due to high production of reactive oxygen species (ROS) and less CO2 availability caused by water stress is directly linked with salinity. A pot experiment was conducted to determine the impact of five NaCl salinity levels, i.e., 0,1.5, 3.0, 5.0 and 7.0 dS m-1 on growth, biochemical attributes and yield of two chili genotypes ('Plahi' and 'A-120'). Salinity stress significantly reduced fresh and dry weight, relative water contents, water use efficiency, leaf osmotic potential, glycine betaine (GB) contents, photosynthetic rate (A), transpiration rate (E), stomatal conductance (Ci), and chlorophyll contents of tested genotypes. Salinity stress significantly enhanced malondialdehyde (MDA) contents and activities of the enzymatic antioxidants such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). In addition, increasing salinity levels significantly reduced the tissue phosphorus and potassium concentrations, while enhanced the tissue sodium and chloride concentrations. Genotype 'Plahi' had better growth and biochemical attributes compared to 'A-120'. Therefore, 'Plahi' is recommended for saline areas to improve chili production.

Combined application of zinc and silicon alleviates terminal drought stress in wheat by triggering morpho-physiological and antioxidants defense mechanisms.

Wheat is an important global staple food crop; however, its productivity is severely hampered by changing climate. Erratic rain patterns cause terminal drought stress, which affect reproductive development and crop yield. This study investigates the potential and zinc (Zn) and silicon (Si) to ameliorate terminal drought stress in wheat and associated mechanisms. Two different drought stress levels, i.e., control [80% water holding capacity (WHC) was maintained] and terminal drought stress (40% WHC maintained from BBCH growth stage 49 to 83) combined with five foliar-applied Zn-Si combinations (i.e., control, water spray, 4 mM Zn, 40 mM Si, 4 mM Zn + 40 mM Si applied 7 days after the initiation of drought stress). Results revealed that application of Zn and Si improved chlorophyll and relative water contents under well-watered conditions and terminal drought stress. Foliar application of Si and Zn had significant effect on antioxidant defense mechanism, proline and soluble protein, which showed that application of Si and Zn ameliorated the effects of terminal drought stress mainly by regulating antioxidant defense mechanism, and production of proline and soluble proteins. Combined application of Zn and Si resulted in the highest improvement in growth and antioxidant defense. The application of Zn and Si improved yield and related traits, both under well-watered conditions and terminal drought stress. The highest yield and related traits were recorded for combined application of Zn and Si. For grain and biological yield differences among sole and combined Zn-Si application were statistically non-significant (p>0.05). In conclusion, combined application of Zn-Si ameliorated the adverse effects of terminal drought stress by improving yield through regulating antioxidant mechanism and production of proline and soluble proteins. Results provide valuable insights for further cross talk between Zn-Si regulatory pathways to enhance grain biofortification.

Impedance Model of Cylindrical Nanowires for Metamaterial Applications.

In metamaterials, metallic nanowires are used for creating artificial materials to functionalize them for various nanophotonics applications. Strong polarization-dependent response coupled with complex dielectric function at optical frequencies gives additional degrees of freedom to achieve scattering, absorption, and other benefits that go much beyond what is possible with conventional materials. In this paper, we propose an extended cylindrical wave impedance approach at optical frequencies to model the internal and external impedance of the metallic nanowire. Equivalent analytical expression for the scattering, extinction, and absorption cross-sectional area efficiencies are derived in terms of impedances. The motivation is to develop an all-mode solution ( TM n and TE n modes), by bringing the complex problem of plasmonic nanowire to linear system theory, where established methods can be applied to enable new applications. The equivalence of the impedance solution is compared with electromagnetic field solution and numerical full-wave field simulations. The proposed solution is accurate and may contribute to the rapid and efficient future designs for the metallic nanowire-based nanophotonic metamaterials.

Salicylic acid confers salt tolerance in potato plants by improving water relations, gaseous exchange, antioxidant activities and osmoregulation.

BACKGROUND: Potato is an important vegetable; however, salt stress drastically affects its growth and yield. A pot experiment was therefore conducted to assess salicylic acid efficacy in improving performance of potato cultivars, grown under salt stress (50 mmol L-1 ). Salicylic acid at 0.5 mmol L-1 was sprayed on to potato plants after 1 week of salinity application. RESULTS: Salt stress effects were ameliorated by salicylic acid effectively in both the studied cultivars. N-Y LARA proved more responsive to salicylic acid application than 720-110 NARC, which confirmed genetic variation between cultivars. Salicylic acid scavenged reactive oxygen species by improving antioxidant enzyme activities (superoxide dismutase, catalase, peroxidases) and regulating osmotic adjustment (proline, phenolic contents), which led to enhanced water relation and gaseous exchange attributes, and thereby increased potassium availability and reduced sodium content in potato leaves. Moreover, potato tuber yield showed a positive correlation with potassium content, photosynthesis and antioxidant enzyme activities. CONCLUSION: Salt tolerance efficacy of salicylic acid is authenticated in improving potato crop performance under salt stress. Salicylic acid effect was more pronounced in N-Y LARA, reflecting greater tolerance than 720-110 NARC, which was confirmed as a susceptible cultivar. Hence salicylic acid at 0.5 mmol L-1 and cultivation of N-Y LARA may be recommended in saline soil. © 2016 Society of Chemical Industry.