Steric Hindrance as a Mechanistic Probe for Olefin Reactivity: Variability of the Hydrogenic Canopy over the Isomeric Adamantylideneadamantane/Sesquihomoadamantene Pair (A Combined Experimental and Theoretical Study)

Access to each CC face of adamantylideneadamantane (AA) and sesquihomoadamantene (SA) is hindered by the hydrogenic canopy consisting of four β-hydrogens; otherwise, these olefins have quite normal environments. X-ray crystallography and density functional (DFT) calculations show a 0.5 Å larger annular opening in the protective cover of AA than that in SA. This contributes to the remarkable differences in reactivity toward various reagents, not only by limiting access to the olefin site in SA but also by inhibiting reactions which force these hydrogens closer together. Thus, AA is subject to typical olefin-addition reactions with bromine, sulfuryl chloride, m-chloroperbenzoic acid, dioxygen, and so forth, albeit sometimes at attenuated rates. On the other hand, SA is singularly unreactive under identical reaction conditions, except for the notable exceptions that include Brønsted (protonic) acids, a nitrosonium cation, and dichlorine. The exceptions are characterized as three sterically limited (electrophilic) reagents whose unique reactivity patterns are shown to be strongly influenced by steric access to the CC center. As such, the different degrees of steric encumbrance in the isomeric donors AA and SA shed considerable light on the diverse nature of olefinic reactions. In particular, they evoke mechanistic features in electrophilic addition versus electron transfer, which are otherwise not readily discernible with other less hindered olefinic donors. Transient structures of the olefinic-reaction intermediates such as the protonated carbocations AA−H+ and SA−H+ as well as the cation radicals AA•+ and SA•+ are probed by the combination of X-ray crystallographic analyses and density functional theoretical computations

Developmental regulation and complex organization of the promoter of the non-coding hsrω gene of Drosophila melanogaster

The nucleus-limited large non-coding hsrω-n RNA product of the93D or the hsrω gene of Drosophila melanogaster binds to a variety of RNA-binding proteins involved in nuclear RNA processing. We examined the developmental and heat shock induced expression of this gene by in situ hybridization of nonradioactively labelled riboprobe to cellular transcripts in intact embryos, larval and adult somatic tissues of wild type and an enhancer-trap line carrying the hsrω05241 allele due to insertion of aP-LacZ-rosy + transposon at - 130 bp position of the hsrω promoter. We also examined LacZ expression in the enhancer-trap line and in two transgenic lines carrying different lengths of the hsrω promoter upstream of the LacZ reporter. The hsrΩ gene is expressed widely at all developmental stages; in later embryonic stages, its expression in the developing central nervous system was prominent. In spite of insertion of a big transposon in the promoter, expression of the hsrω05241 allele in the enhancer-trap line, as revealed byin situ hybridization to hsrω transcripts in cells, was similar to that of the wild type allele in all the embryonic, larval and adult somatic tissues examined. Expression of the LacZ gene in this enhancer-trap line was similar to that of the hsrω RNA in all diploid cell types in embryos and larvae but in the polytene cells, the LacZ gene did not express at all, neither during normal development nor after heat shock. Comparison of the expression patterns of hsrω gene and those of the LacZ reporter gene under its various promoter regions in the enhancer-trap and transgenic lines revealed a complex pattern of regulation, which seems to be essential for its dynamically varying expression in diverse cell types

Male sterility associated with overexpression of the noncoding hsrω gene in cyst cells of testis of Drosophila melanogaster

Of the several noncoding transcripts produced by the hsrΩ gene of Drosophila melanogaster, the nucleus-limited > 10-kb hsrΩ-n transcript colocalizes with heterogeneous nuclear RNA binding proteins (hnRNPs) to form fine nucleoplasmic omega speckles. Our earlier studies suggested that the noncoding hsrΩ-n transcripts dynamically regulate the distribution of hnRNPs in active (chromatin bound) and inactive (in omega speckles) compartments. Here we show that a P transposon insertion in this gene's promoter (at -130 bp) in the hsrΩ05241 enhancer-trap line had no effect on viability or phenotype of males or females, but the insertion-homozygous males were sterile. Testes of hsrΩ05241 homozygous flies contained nonmotile sperms while their seminal vesicles were empty. RNA:RNA in situ hybridization showed that the somatic cyst cells in testes of the mutant male flies contained significantly higher amounts of hsrΩ-n transcripts, and unlike the characteristic fine omega speckles in other cell types they displayed large clusters of omega speckles as typically seen after heat shock. Two of the hnRNPs, viz. HRB87F and Hrp57A, which are expressed in cyst cells, also formed large clusters in these cells in parallel with the hsrΩ-n transcripts. A complete excision of the P transposon insertion restored male fertility as well as the fine-speckled pattern of omega speckles in the cyst cells. The in situ distribution patterns of these two hnRNPs and several other RNA-binding proteins (Hrp40, Hrb57A, S5, Sxl, SRp55 and Rb97D) were not affected by hsrΩ mutation in any of the meiotic stages in adult testes. The present studies, however, revealed an unexpected presence (in wild-type as well as mutant) of the functional form of Sxl in primary spermatocytes and an unusual distribution of HRB87F along the retracting spindle during anaphasetelophase of the first meiotic division. It appears that the P transposon insertion in the promoter region causes a misregulated overexpression of hsrΩ in cyst cells, which in turn results in excessive sequestration of hnRNPs and formation of large clusters of omega speckles in these cell nuclei. The consequent limiting availability of hnRNPs is likely totrans-dominantly affect processing of other pre-mRNAs in cyst cells. We suggest that a compromise in the activity of cyst cells due to the aberrant hnRNP distribution is responsible for the failure of individualization of sperms in hsrΩ05241 mutant testes. These results further support a significant role of the noncoding hsrΩ-n transcripts in basic cellular activities, namely regulation of the availability of hnRNPs in active (chromatin bound) and inactive (in omega speckles) compartments

Activity of radon (222Rn) in the lower atmospheric surface layer of a typical rural site in south India

Analysis of one year measurements of in situ radon (222Rn) and its progenies along with surface air temperature, relative humidity and pressure near to the Earth’s surface has been carried out for the first time at the National Atmospheric Research Laboratory (NARL, 13.5∘N and 79.2∘E) located in a rural site in Gadanki, south India. The dataset was analysed to understand the behaviour of radon in relation to the surface air temperature and relative humidity at a rural site. It was observed that over a period of the 24 hours in a day, the activity of radon and its progenies reaches a peak in the morning hours followed by a remarkable decrease in the afternoon hours. Relatively, a higher concentration of radon was observed at NARL during fair weather days, and this can be attributed to the presence of rocky hills and dense vegetation surrounding the site. The high negative correlation between surface air temperature and activity of radon (R = – 0.70, on an annual scale) suggests that dynamical removal of radon due to increased vertical mixing is one of the most important controlling processes of the radon accumulation in the atmospheric surface layer. The annual averaged activity of radon was found to be 12.01±0.66 Bq m−3 and 4.25±0.18 Bq m−3 for its progenies, in the study period

Variation of Radon Progeny Concentration over a Continental Location

Background: The variation of the radon progeny concentration in outdoor environment and meteorological parameters at fine resolution were studied for one year at a continental location, National Atmospheric Research Laboratory, Gadanki, India.Materials and Methods: The concentrations were measured using Alpha Progeny Meter by collecting air samples at a height of 1 m above the Earth’s surface at a known flow rate. Results: Radon progeny concentration shows temporal variations on diurnal and monthly scales, and is due to mixing in the atmosphere. Peak in the early morning hours and low values during afternoon compared to nighttime are due to differential heat contrast between earth’s surface and its atmosphere. However, the activity during February shows maximum compared to June/July months.The diurnal variation of radon progeny shows positive correlation with the relative humidity and negative correlation with ambient temperature.The monthly mean activity of radon progeny for the year 2012 was found to be 4.76 ± 0.73 mWL. Conclusion: The mean concentration of radon progeny in the study region is relatively high compared to the other locations in India and may be due to the rocky terrains and trapping of air-masses near the observation site due to its topography

Characterizations of GEM detector prototype

At NISER-IoP detector laboratory an initiative is taken to build and test Gas Electron Multiplier (GEM) detectors for ALICE experiment. The optimisation of the gas flow rate and the long-term stability test of the GEM detector are performed. The method and test results are presented.Comment: 3 Pages, 4 figure

Global transcriptome profile of Cryptococcus neoformans during exposure to hydrogen peroxide induced oxidative stress

The ability of the opportunistic fungal pathogen Cryptococcus neoformans to resist oxidative stress is one of its most important virulence related traits. To cope with the deleterious effect of cellular damage caused by the oxidative burst inside the macrophages, C. neoformans has developed multilayered redundant molecular responses to neutralize the stress, to repair the damage and to eventually grow inside the hostile environment of the phagosome. We used microarray analysis of cells treated with hydrogen peroxide (H(2)O(2)) at multiple time points in a nutrient defined medium to identify a transcriptional signature associated with oxidative stress. We discovered that the composition of the medium in which fungal cells were grown and treated had a profound effect on their capacity to degrade exogenous H(2)O(2). We determined the kinetics of H(2)O(2) breakdown by growing yeast cells under different conditions and accordingly selected an appropriate media composition and range of time points for isolating RNA for hybridization. Microarray analysis revealed a robust transient transcriptional response and the intensity of the global response was consistent with the kinetics of H(2)O(2) breakdown by treated cells. Gene ontology analysis of differentially expressed genes related to oxidation-reduction, metabolic process and protein catabolic processes identified potential roles of mitochondrial function and protein ubiquitination in oxidative stress resistance. Interestingly, the metabolic pathway adaptation of C. neoformans to H(2)O(2) treatment was remarkably distinct from the response of other fungal organisms to oxidative stress. We also identified the induction of an antifungal drug resistance response upon the treatment of C. neoformans with H(2)O(2). These results highlight the complexity of the oxidative stress response and offer possible new avenues for improving our understanding of mechanisms of oxidative stress resistance in C. neoformans

Fresnel scatter revisited-comparison of 50 MHz radar and radiosondes in the Arctic, the Tropics and Antarctica

High-resolution radiosondes and calibrated radars operating close to 50 MHz, are used to examine the relationship between the strength of radar scatter and refractive index gradient. Three radars are used, in Kiruna in Arctic Sweden, at Gadanki in southern India and at the Swedish/Finnish base Wasa/Aboa in Queen Maud Land, Antarctica. Calibration is accomplished using the daily variation of galactic noise measured at each site. Proportionality between radar scatter strength and the square of the mean gradient of potential refractive index, M2, is found in the upper troposphere and lower stratosphere at all three sites, confirming previously reported results from many VHF radars. If the radar scatter is interpreted as Fresnel scatter, the constant of proportionality between radar scatter and M2 is found to be the same, within the calibration uncertainties, for all three radars. The radiosondes show evidence of distinct layering with sharp gradients, extending over 10s of kilometers horizontally, but the scatter is found to be two orders of magnitude weaker than would be expected from true Fresnel scatter from such layers. Using radar reflectivities resolved to a few 100 ms, we show that this is due to strong temporal variability in the scattering conditions, possibly due to undulations of the scattering layers. The constancy of the radar scatter – M2 relationship between the different sites suggests an unexpected uniformity in these perturbations between very different regions of the globe

Sea erosion along the Andhra Pradesh coast

Andhra Pradesh with a coastline of around 974 km has frequently been affected by cyclones and inundated by storm surges. Sea erosion is noticed at Visakhapatnam, Bhimunipatnam and in the East and West Godavari districts. Vishakhapatnam coast is facing erosion since long specially at Ramakrishna Beach. In 2013 and 2014, the cyclones ‘Phailin’ and ‘Hudhud’ further hastened erosion of the Ramakrishna Beach, severely damaging the adjacent protection wall and road. Uppada village which is 22 kilometres away from Kakinada also faces severe erosion. The Kakinada-Uppada road is gradually disappearing due to shoreline erosion