Resonant Raman of OH/OD vibrations and photoluminescence studies in LiTaO3 thin film

Resonant Raman spectra (RRS) of O-H and O-D vibration and libration modes, their combinations and higher harmonics have been observed in LiTaO3 polycrystalline thin films. RRS peaks are superimposed on photoluminescence (PL) spectrum. Monochromatic light from a xenon lamp is used as excitation source. PL spectrum shows two broad peaks, first near the band gap in UV (4.4-4.8eV) and another in the sub band gap region (< 4.0 eV). Band gap PL along with RRS peaks are reported for the first time. Photoluminescence excitation spectrum (PLE) shows a peak at 4.8 eV. Peak positions and full width at half maximum (FWHM) of RRS peaks depend upon the excitation energy. Dispersions of the fundamental and the third harmonic of the stretching mode of O-H with excitation energy are about 800 cm-1/eV and 2000 cm-1/eV respectively. This dispersion is much higher than reported in any other material.Comment: 20 page

Genome mining of mycosporine-like amino acid (MAA) synthesizing and non-synthesizing cyanobacteria: A bioinformatics study

AbstractMycosporine-like amino acids (MAAs) are a family of more than 20 compounds having absorption maxima between 310 and 362 nm. These compounds are well known for their UV-absorbing/screening role in various organisms and seem to have evolutionary significance. In the present investigation we tested four cyanobacteria, e.g., Anabaena variabilis PCC 7937, Anabaena sp. PCC 7120, Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 6301, for their ability to synthesize MAA and conducted genomic and phylogenetic analysis to identify the possible set of genes that might be involved in the biosynthesis of these compounds. Out of the four investigated species, only A. variabilis PCC 7937 was able to synthesize MAA. Genome mining identified a combination of genes, YP_324358 (predicted DHQ synthase) and YP_324357 (O-methyltransferase), which were present only in A. variabilis PCC 7937 and missing in the other studied cyanobacteria. Phylogenetic analysis revealed that these two genes are transferred from a cyanobacterial donor to dinoflagellates and finally to metazoa by a lateral gene transfer event. All other cyanobacteria, which have these two genes, also had another copy of the DHQ synthase gene. The predicted protein structure for YP_324358 also suggested that this product is different from the chemically characterized DHQ synthase of Aspergillus nidulans contrary to the YP_324879, which was predicted to be similar to the DHQ synthase. The present study provides a first insight into the genes of cyanobacteria involved in MAA biosynthesis and thus widens the field of research for molecular, bioinformatics and phylogenetic analysis of these evolutionary and industrially important compounds. Based on the results we propose that YP_324358 and YP_324357 gene products are involved in the biosynthesis of the common core (deoxygadusol) of all MAAs

DNA damage

Even under the best of circumstances, DNA is constantly subjected to chemical modifications. Several types of DNA damage such as SSB (single strand break), DSB (double strand break), CPDs (cyclobutane pyrimidine dimers), 6-4PPs (6-4 photoproducts) and their Dewar valence isomers have been identified that result from alkylating agents, hydrolytic deamination, free radicals and reactive oxygen species formed by various photochemical processes including UV radiation. There are a number of strategies such as PCR (polymerase chain reaction), comet, halo, TUNEL (Terminal deoxyribonucleotidyltransferase-mediated deoxyuridine triphosphate nick end labeling) assay, HPLC-Electrospray tandem mass spectrometry, FISH (Fluorescence in situ hybridization), FCM (Flow cytometry), annexin V labeling, immunological assays including immunofluorescent and chemiluminescence thymine dimer detection, immunohistochemical assay, Enzyme-linked immunosorbent assay (ELISA), Radio immunoassay (RIA), Gas chromatography-mass spectrometry and electrochemical methods, that are commonly used to detect DNA damage in various organisms. The main aim of this review is to present a brief account of the above mentioned DNA damage detection strategies for the convenience of interested readers