CO2 exchange and evapotranspiration across dryland ecosystems of southwestern North America

Global‐scale studies suggest that dryland ecosystems dominate an increasing trend in the magnitude and interannual variability of the land CO₂ sink. However, such analyses are poorly constrained by measured CO₂ exchange in drylands. Here we address this observation gap with eddy covariance data from 25 sites in the water‐limited Southwest region of North America with observed ranges in annual precipitation of 100–1000 mm, annual temperatures of 2–25°C, and records of 3–10 years (150 site‐years in total). Annual fluxes were integrated using site‐specific ecohydrologic years to group precipitation with resulting ecosystem exchanges. We found a wide range of carbon sink/source function, with mean annual net ecosystem production (NEP) varying from ‐350 to +330 gCm^?2 across sites with diverse vegetation types, contrasting with the more constant sink typically measured in mesic ecosystems. In this region, only forest‐dominated sites were consistent carbon sinks. Interannual variability of NEP, gross ecosystem production (GEP), and ecosystem respiration (R_eco) was larger than for mesic regions, and half the sites switched between functioning as C sinks/C sources in wet/dry years. The sites demonstrated coherent responses of GEP and NEP to anomalies in annual evapotranspiration (ET), used here as a proxy for annually available water after hydrologic losses. Notably, GEP and R_eco were negatively related to temperature, both interannually within site and spatially across sites, in contrast to positive temperature effects commonly reported for mesic ecosystems. Models based on MODIS satellite observations matched the cross‐site spatial pattern in mean annual GEP but consistently underestimated mean annual ET by ~50%. Importantly, the MODIS‐based models captured only 20–30% of interannual variation magnitude. These results suggest the contribution of this dryland region to variability of regional to global CO₂ exchange may be up to 3–5 times larger than current estimates.     

Neuronal ceroid lipofuscinoses caused by defects in soluble lysosomal enzymes (CLN1 and CLN2)

Infantile and classical late infantile neuronal ceroid lipofuscinoses (NCL) are two recent additions to the expanding spectrum of lysosomal storage disorders caused by deficiencies in lysosomal hydrolases. They are latecomers to the lysosomal storage disorders, probably because of the heterogeneous nature of the storage material, which precluded meaningful biochemical analysis. Infantile NCL is caused by deficiency in palmitoyl-protein thioesterase, an enzyme that hydrolyzes fatty acids from cysteine residues in lipid-modified proteins. Classical late-infantile NCL is caused by a deficiency in tripeptidyl amino peptidase-I, a lysosomal peptidase that removes three amino acids from the free amino terminus of peptides or small proteins. Late-onset forms of these disorders have been described. The clinical, biochemical, and molecular genetic aspects of these two latest lysosomal storage disorders are discussed in this review. In addition, approaches to treatment and future directions for research are examined.     

Synthesis, SAR, and antibacterial activity of novel oxazolidinone analogues possessing urea functionality

The syntheses of a number of novel oxazolidinone analogues possessing an urea functionality are reported. While the urea derivatives possessing aliphatic and aromatic groups were prepared by the more conventional isocyanate method, the derivatives possessing heterocyclic rings were synthesized by a relatively uncommon but otherwise efficient carbamate chemistry. Though the SAR resulted in novel compounds possessing in vitro activity equivalent to Linezolid, the compounds possess a range of substituents that are amenable for altering physicochemical properties of the resultant drug. The antibacterial activity was found to be not sensitive to the functional groups attached to the urea site regardless of the size and electronic characteristics. Based on in vivo results, one molecule has been identified as a candidate and additional work such as salt selection, scale-up, etc., are currently underway to take the molecule further through development.     

Performance of 4,5-diphenyl-1H-imidazole derived highly selective ‘Turn-Off’ fluorescent chemosensor for iron(III) ions detection and biological applications

Two fluorescent chemosensors, denoted as chemosensor 1 and chemosensor 2 , were synthesized and subjected to comprehensive characterization using various techniques. The characterization techniques employed were Fourier-transform infrared (FTIR), proton (¹H)- and carbon-13 (¹³C)-nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization (ESI) mass spectrometry, and single crystal X-ray diffraction analysis. Chemosensor 1 is composed of a 1H-imidazole core with specific substituents, including a 4-(2-(4,5-c-2-yl)naphthalene-3-yloxy)butoxy)naphthalene-1-yl moiety. However, chemosensor 2 features a 1H-imidazole core with distinct substituents, such as 4-methyl-2-(4,5-diphenyl-1H-imidazole-2-yl)phenoxy)butoxy)-5-methylphenyl. Chemosensor 1 crystallizes in the monoclinic space group C2/c. Both chemosensors 1 and 2 exhibit a discernible fluorescence quenching response selectively toward iron(III) ion (Fe³⁺) at 435 and 390 nm, respectively, in dimethylformamide (DMF) solutions, distinguishing them from other tested cations. This fluorescence quenching is attributed to the established mechanism of chelation quenched fluorescence (CHQF). The binding constants for the formation of the 1 + Fe³⁺ and 2 + Fe³⁺ complexes were determined using the modified Benesi–Hildebrand equation, yielding values of approximately 2.2 × 10³ and 1.3 × 10⁴ M⁻¹, respectively. The calculated average fluorescence lifetimes for 1 and 1 + Fe³⁺ were 2.51 and 1.17 ns, respectively, while for 2 and 2 + Fe³⁺, the lifetimes were 1.13 and 0.63 ns, respectively. Additionally, the applicability of chemosensors 1 and 2 in detecting Fe³⁺ in live cells was demonstrated, with negligible observed cell toxicity.     

ZnCl2 catalyzed new coumarinyl-chalcones as cytotoxic agents

A new series of coumarin-yl-chalcone derivatives (3a-m) had been designed and synthesized through different reactions such as aromatic addition, cyclization and Claisen-Schmidt reactions in good yields (54–78%). 5-acetyl-4-(2-hydroxyphenyl) -6-methyl-3, 4-dihydropyrimidin-2(1H) -one (1) has been synthesized by multi-component one pot reaction of salicylaldehyde, methyl acetoacetate and urea, which was further reacted with malonic acid employing ZnCl₂ catalyst to yield 5-acetyl-4-(4-hydroxy-2-oxo-2H-chromen-8-yl) -6-methyl-3, 4-dihydropyrimidin-2(1H) -one (2). The title compounds (3a-m) were synthesised by reacting 5-acetyl-4-(4-hydroxy-2-oxo-2H-chromen-8-yl) -6-methyl-3, 4-dihydropyrimidin-2(1H)-one (2) with different aromatic aldehydes in the presence of potassium hydroxide. In silico studies, a preliminary screening method for predicting the anti-cancer activity was performed for the synthesized compounds (3a-m) against Src, Alb tyrosine kinase and homology model protein (PDB ID: 4csv). The derivatives 3h and 3m showed moderate binding energies. The in vitro cytotoxic activity was evaluated for the compounds 3h and 3m by using human cancer cell-line morphology and MTT assay against three human cell-lines A549 (Lung), Jurkat (Leukemia) and MCF-7 (Breast). The results indicate that the derivatives 3h and 3m display significant anti-cancer activity, however it was found to be less cytotoxic when compared to the standard used i.e. Imatinib.     

The crystal structure of palmitoyl protein thioesterase-2 (PPT2) reveals the basis for divergent substrate specificities of the two lysosomal thioesterases,PPT1 and PPT2

Mutations in palmitoyl protein thioesterase-1 (PPT1) have been found to cause the infantile form of neuronal ceroid lipofuscinosis, which is a lysosomal storage disorder characterized by impaired degradation of fatty acid-modified proteins with accumulation of amorphous granular deposits in cortical neurons, leading to mental retardation and death. Palmitoyl protein thioesterase-2 (PPT2) is a second lysosomal hydrolase that shares a 26% identity with PPT1. A previous study had suggested that palmitoyl-CoA was the preferred substrate of PPT2. Furthermore, PPT2 did not hydrolyze palmitate from the several S-palmitoylated protein substrates. Interestingly, PPT2 deficiency in a recent transgenic mouse model is associated with a form of neuronal ceroid lipofuscinosis, suggesting that PPT1 and -2 perform non-redundant roles in lysosomal thioester catabolism. In the current paper, we present the crystal structure of PPT2 at a resolution of 2.7 A. Comparisons of the structures of PPT1 and -2 show very similar architectural features; however, conformational differences in helix alpha4 lead to a solvent-exposed lipid-binding groove in PPT1. The limited space between two parallel loops (beta3-alphaA and beta8-alphaF) located immediately above the lipid-binding groove in PPT2 restricts the binding of fatty acids with bulky head groups, and this binding groove is significantly larger in PPT1. This structural difference accounts for the ability of PPT2 to hydrolyze an unbranched structure such as palmitoyl-CoA but not palmitoylcysteine or palmitoylated proteins. Furthermore, differences in fatty acid chain length specificity of PPT1 and -2, also reported here, are explained by the structure and may provide a biochemical basis for their non-redundant roles.     

Evaluation of Antimicrobial Activity of Aryl/Alkyl Cyanamides and Substituted Tetrazole Compounds

Russian Journal of Bioorganic Chemistry - Cyanamides, tetrazole and their derivatives have pharmaceutically attracted much attention because of their wide range of biological activities such as...     

Significance of Microsclerotia in the Epidemiology of Black Pepper Anthracnose and an Approach for Disease Management in Nurseries

Anthracnose incited by Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. is a wide spread and economically important disease of black pepper. In the present study, role of microsclerotia (MS) in the trans‐seasonal perpetuation of C. gloeosporioides was investigated. Microscopical examination of the runner shoots exhibiting necrotic lesions revealed the presence of dark, melanized structures which resembled MS. The excised necrotic regions when subjected to high humidity produced acervulus with setae. Under in vitro conditions, C. gloeosporioides produced MS predominantly on the aerial surface as inseparable congregations, enmeshed in the mycelial mats in potato dextrose broth and as individual units 7–8 days after incubation on glass slides. Sequential events in the formation of MS included germination of conidia, formation of conidial anastomosis tubes, aggregation of hyphae, and the formation of melanized microsclerotial bodies. Three types of microsclerotial germination were observed under in vitro conditions viz., sporogenic, myceliogenic and both. PCR confirmation with CgInt species‐specific primer and ITS4 resulted in 450‐bp amplification. Since, runner shoots are predominantly used as propagating material in black pepper, an approach was devised to manage anthracnose under nursery conditions by treating the 2‐ to 3‐node cuttings (nursery planting material) with carbendazim (12%)—mancozeb (63%) @ 0.1% for 30 min. The results of the study suggests a new facet in the disease cycle of black pepper anthracnose, indicating that the pathogen survives as microsclerotia in planta and could act as a potential source of inoculum.