Genomic survey of high-throughput RNA-Seq data implicates involvement of long intergenic non-coding RNAs (lincRNAs) in cytoplasmic male-sterility and fertility restoration in pigeon pea

BACKGROUND

Long-intergenic non-coding RNAs (lincRNAs) originate from intergenic regions and have no coding potential. LincRNAs have emerged as key players in the regulation of various biological processes in plant development. Cytoplasmic male-sterility (CMS) in association with restorer-of-fertility (Rf) systems makes it a highly reliable tool for exploring heterosis for producing commercial hybrid seeds. To date, there have been no reports of lincRNAs during pollen development in CMS and fertility restorer lines in pigeon pea.

OBJECTIVE

Identification of lincRNAs in the floral buds of cytoplasmic male-sterile (AKCMS11) and fertility restorer (AKPR303) pigeon pea lines.

METHODS

We employed a computational approach to identify lincRNAs in the floral buds of cytoplasmic male-sterile (AKCMS11) and fertility restorer (AKPR303) pigeon pea lines using RNA-Seq data.

RESULTS

We predicted a total of 2145 potential lincRNAs of which 966 were observed to be differentially expressed between the sterile and fertile pollen. We identified, 927 cis-regulated and 383 trans-regulated target genes of the lincRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the target genes revealed that these genes were specifically enriched in pathways like pollen and pollen tube development, oxidative phosphorylation, etc. We detected 23 lincRNAs that were co-expressed with 17 pollen-related genes with known functions. Fifty-nine lincRNAs were predicted to be endogenous target mimics (eTMs) for 25 miRNAs, and found to be associated with pollen development. The, lincRNA regulatory networks revealed that different lincRNA-miRNA-mRNA networks might be associated with CMS and fertility restoration.

CONCLUSION

Thus, this study provides valuable information by highlighting the functions of lincRNAs as regulators during pollen development in pigeon pea and utilization in hybrid seed production.

Comparative transcriptome analyses revealed different heat stress responses in pigeonpea (Cajanus cajan) and its crop wild relatives

Comparative transcriptome analyses accompanied by biochemical assays revealed high variability in heat stress response in Cajanus species. Among the studied species, C. scarabaeoides was the most thermotolerant followed by C. cajanifolius, C. cajan, and C. acutifolius. Pigeonpea is one of the climate-resilient grain legumes. Though the optimum temperature for cultivated pigeonpea is ~ 25-35 °C, its wild relatives grow in temperatures ranging between 18 and 45 °C. To gain insight into molecular mechanisms responsible for the heat stress tolerance in pigeonpea, we conducted time-series transcriptome analysis of one pigeonpea cultivar (Cajanus cajan) and two wild relatives, Cajanus acutifolius, and Cajanus scarabaeoides subjected to heat stress at 42 ± 2 ºC for 30 min and 3 h. A total of 9521, 12,447, and 5282 identified transcripts were differentially expressed in C. cajan, C. acutifolius, and C. scarabaeoides, respectively. In this study, we observed that a significant number of genes undergo alternative splicing in a species-specific pattern during heat stress. Gene expression profiling analysis, histochemical assay, chlorophyll content, and electrolyte leakage assay showed that C. scarabaeoides has adaptive features for heat stress tolerance. The gene set enrichment analyses of differentially expressed genes in these Cajanus species during heat stress revealed that oxidoreductase activity, transcription factor activity, oxygen-evolving complex, photosystem-II, thylakoid, phenylpropanoid biosynthetic process, secondary metabolic process, and flavonoid biosynthetic process were highly affected. The histochemical assay showed more lipid peroxidation in C. acutifolius compared to other Cajanus species inferring the presence of higher quantities of polyunsaturated fatty acids in the plasma membrane which might have led to severe damage of membrane-bound organelles like chloroplast, and high electrolyte leakage during heat stress. This study paves the way for the identification of candidate genes, which can be useful for the development of thermo-tolerant pigeonpea cultivars.

Exploring the edible gum (galactomannan) biosynthesis and its regulation during pod developmental stages in clusterbean using comparative transcriptomic approach

Galactomannan is a polymer of high economic importance and is extracted from the seed endosperm of clusterbean (C. tetragonoloba). In the present study, we worked to reveal the stage-specific galactomannan biosynthesis and its regulation in clusterbean. Combined electron microscopy and biochemical analysis revealed high protein and gum content in RGC-936, while high oil bodies and low gum content in M-83. A comparative transcriptome study was performed between RGC-936 (high gum) and M-83 (low gum) varieties at three developmental stages viz. 25, 39, and 50 days after flowering (DAF). Total 209,525, 375,595 and 255,401 unigenes were found at 25, 39 and 50 DAF respectively. Differentially expressed genes (DEGs) analysis indicated a total of 5147 shared unigenes between the two genotypes. Overall expression levels of transcripts at 39DAF were higher than 50DAF and 25DAF. Besides, 691 (RGC-936) and 188 (M-83) candidate unigenes that encode for enzymes involved in the biosynthesis of galactomannan were identified and analyzed, and 15 key enzyme genes were experimentally validated by quantitative Real-Time PCR. Transcription factor (TF) WRKY was observed to be co-expressed with key genes of galactomannan biosynthesis at 39DAF. We conclude that WRKY might be a potential biotechnological target (subject to functional validation) for developing high gum content varieties.

HiPHET: A Hybrid Approach to Translate Code Mixed Language (Hinglish) to Pure Languages (Hindi and English)

Bilingual code mixed (hybrid) languages has become very popular in India as a result of the spread of Western technology in the form of the television, the Internet and social media. Due to this increase in usage of code-mixed languages in day-to-day communication, the need for maintaining the integrity of Indian languages has arisen. As a result of this need the tool named Hinglish to Pure Hindi and English Translator was developed. The tool translated in three ways, namely, Hinglish to Pure Hindi and Pure English, Pure Hindi to Pure English and vice versa. The tool has achieved accuracy of 91% in giving Hindi sentences as output and of 84% in giving English sentences as output, where the input sentences were in Hinglish. The tool has also been compared with another similar tool in the paper.

Comparative RNA editing profile of mitochondrial transcripts in cytoplasmic male sterile and fertile pigeonpea reveal significant changes at the protein level

RNA editing is a process which leads to post-transcriptional alteration of the nucleotide sequence of the corresponding mRNA molecule which may or may not lead to changes at the protein level. Apart from its role in providing variability at the transcript and protein levels, sometimes, such changes may lead to abnormal expression of the mitochondrial gene leading to a cytoplasmic male sterile phenotype. Here we report the editing status of 20 major mitochondrial transcripts in both male sterile (AKCMS11) and male fertile (AKPR303) pigeonpea genotypes. The validation of the predicted editing sites was done by mapping RNA-seq reads onto the amplified mitochondrial genes, and 165 and 159 editing sites were observed in bud tissues of the male sterile and fertile plant respectively. Among the resulting amino acid alterations, the most frequent one was the conversion of hydrophilic amino acids to hydrophobic. The alterations thus detected in our study indicates differential editing, but no major change in terms of the abnormal protein structure was detected. However, the above investigation provides an insight into the behaviour of pigeonpea mitochondrial genome in native and alloplasmic state and could hold clues in identification of editing factors and their role in adaptive evolution in pigeonpea.

Genome-wide identification and characterization of InDels and SNPs in Glycine max and Glycine soja for contrasting seed permeability traits

BACKGROUND

Water permeability governed by seed coat is a major facet of seed crops, especially soybean, whose seeds lack physiological dormancy and experience rapid deterioration in seed viability under prolonged storage. Moreover, the physiological and chemical characteristics of soybean seeds are known to vary with seed coat color. Thus, to underpin the genes controlling water permeability in soybean seeds, we carried out an in-depth characterization of the associated genomic variation.

RESULTS

In the present study, we have analyzed genomic variation between cultivated soybean and its wild progenitor with implications on seed permeability, a trait related to seed storability. Whole genome resequencing of G.max and G. soja, identified SNPs and InDels which were further characterized on the basis of their genomic location and impact on gene expression. Chromosomal density distribution of the variation was assessed across the genome and genes carrying SNPs and InDels were characterized into different metabolic pathways. Seed hardiness is a complex trait that is affected by the allelic constitution of a genetic locus as well as by a tricky web of plant hormone interactions. Seven genes that hold a probable role in the determination of seed permeability were selected and their expression differences at different stages of water imbibition were analyzed. Variant interaction network derived 205 downstream interacting partners of 7 genes confirmed their role in seed related traits. Interestingly, genes encoding for Type I- Inositol polyphosphate 5 phosphatase1 and E3 Ubiquitin ligase could differentiate parental genotypes, revealed protein conformational deformations and were found to segregate among RILs in coherence with their permeability scores. The 2 identified genes, thus showed a preliminary association with the desirable permeability characteristics.

CONCLUSION

In the light of above outcomes, 2 genes were identified that revealed preliminary, but a relevant association with soybean seed permeability trait and hence could serve as a primary material for understanding the molecular pathways controlling seed permeability traits in soybean.

Serial perioperative cell-free DNA levels in donors and recipients undergoing living donor liver transplantation

BACKGROUND

Effect of anaesthesia and surgery on cell-free DNA (cfDNA) is not known. Given that surgical stress augments inflammation and injury, we hypothesized that levels of cfDNA will fluctuate during perioperative period. Therefore, in this study serial perioperative cfDNA concentration was measured in donors and recipients undergoing living donor liver transplantation (LDLT).

METHODS

Baseline, post-induction, intraoperative and post-operative plasma cfDNA levels were evaluated in 21 donors and recipients each, by Sytox green method. In addition, qPCR was performed in a subset of samples.

RESULTS

Baseline cfDNA levels were higher in recipients (37.62 ng/ml) than in donors (25.49 ng/ml). A decrease in cfDNA was observed following anaesthesia induction in both recipients (11.90 ng/ml) and donors (10.75 ng/ml). When the kinetics of the cfDNA was monitored further, an increase was noted intraoperatively in donors (46.18 ng/ml) and recipients (anhepatic phase: 56.25 ng/ml, reperfusion phase: 54.36 ng/ml). cfDNA levels remained high post-operatively. One recipient who developed post-operative sepsis had the highest cfDNA level (94.72 ng/ml).

CONCLUSION

Plasma cfDNA levels are high in recipients indicative of liver injury. Lower cfDNA levels following induction may be attributed to the subduing effect of anaesthetic agents on cell death. High cfDNA levels seen in intra- and post-operative phases reflect cellular trauma and inflammation. This similar pattern of fluctuation of cfDNA level in donors and recipients is suggestive of its possible utility as a surgical stress marker. In addition, comparable cfDNA levels in anhepatic and reperfusion phase reflect less ischemia reperfusion injury during LDLT.

Immune balance in Hepatitis B Infection: Present and Future Therapies

Chronic hepatitis B virus (HBV) infection affects millions of people worldwide and about half a million people die every year. India represents the second largest pool of chronic HBV infections with an estimated 40 million chronically infected patients. Persistence or clearance of HBV infection mainly depends upon host immune responses. Chronically infected individuals remain in immune tolerant phase unless HBV flares and leads to the development of chronic active hepatitis or acute-on-chronic liver failure. Strategies based on inhibition of viral replication (nucleoside analogues) or immune modulation (interferons) as monotherapy, or in combination in sequential therapies, are currently being used globally for reducing HBV viral load and mediating HBsAg clearance. However, the immune status and current therapies for promoting sustained virological responses in HBV-infected patients remain suboptimal. Elimination of cccDNA is major challenge for future therapies, and new molecules such as NTCP, Toll-like receptor (TLR)7 agonist (GS9620) and cyclophilin have emerged as potential targets for preventing HBV entry and replication. Other than these, HBV cccDNA elimination is the major target for future therapies.

De novo Assembly and Characterization of Cajanus scarabaeoides (L.) Thouars Transcriptome by Paired-End Sequencing

Pigeonpea [Cajanus cajan (L.) Millsp.] is a heat and drought resilient legume crop grown mostly in Asia and Africa. Pigeonpea is affected by various biotic (diseases and insect pests) and abiotic stresses (salinity and water logging) which limit the yield potential of this crop. However, resistance to all these constraints is not readily available in the cultivated genotypes and some of the wild relatives have been found to withstand these resistances. Thus, the utilization of crop wild relatives (CWR) in pigeonpea breeding has been effective in conferring resistance, quality and breeding efficiency traits to this crop. Bud and leaf tissue of Cajanus scarabaeoides, a wild relative of pigeon pea were used for transcriptome profiling. Approximately 30 million clean reads filtered from raw reads by removal of adaptors, ambiguous reads and low-quality reads (3.02 gigabase pairs) were generated by Illumina paired-end RNA-seq technology. All of these clean reads were pooled and assembled de novo into 1,17,007 transcripts using the Trinity. Finally, a total of 98,664 unigenes were derived with mean length of 396 bp and N50 values of 1393. The assembly produced significant mapping results (73.68%) in BLASTN searches of the Glycine max CDS sequence database (Ensembl). Further, uniprot database of Viridiplantae was used for unigene annotation; 81,799 of 98,664 (82.90%) unigenes were finally annotated with gene descriptions or conserved protein domains. Further, a total of 23,475 SSRs were identified in 27,321 unigenes. This data will provide useful information for mining of functionally important genes and SSR markers for pigeonpea improvement.

Synthesis and biological evaluation of imidazo[1,5-a]pyridine-benzimidazole hybrids as inhibitors of both tubulin polymerization and PI3K/Akt pathway

A series of imidazo[1,5-a]pyridine-benzimidazole hybrids (5a–aa) were prepared and evaluated for their cytotoxic activity against a panel of sixty human tumor cell lines. Among them compounds 5d and 5l showed significant cytotoxic activity with GI50 values ranging from 1.06 to 14.9 μM and 0.43 to 7.73 μM, respectively. Flow cytometric analysis revealed that these compounds arrest the cell cycle at G2/M phase and induced cell death by apoptosis. The tubulin polymerization assay (IC50 of 5d is 3.25 μM and 5l is 1.71 μM) and immunofluorescence analysis showed that these compounds effectively inhibited the microtubule assembly in human breast cancer cells (MCF-7). Further, the apoptotic effects of compounds were confirmed by Hoechst staining, mitochondrial membrane potential, cytochrome c release, ROS generation, caspase 9 activation and DNA fragmentation analysis. After treatment with these compounds for 48 h, p-PTEN and p-AKT levels were markedly decreased. Moreover, these compounds did not significantly inhibit the normal human embryonic kidney cells, HEK-293. The molecular docking simulations predicted the binding interactions of 5d and 5l with colchicine binding site of the tubulin, which is in compliance with the antiproliferative activity data.

Role of flux on morphology and luminescence properties of Sm(3+) doped Y2SiO5 nanopowders for WLEDs

The study involves preparation of samarium doped Y2SiO5 (YSO) nano powders by solution combustion method using urea as a fuel for the first time. Effect of different fluxes on the crystallization behavior, morphology and photoluminescence (PL) properties of YSO:Sm(3+) (1-9 mol%) were investigated. The final product was characterized by Powder X-ray diffraction (PXRD), Scanning Electron Microscopy (SEM) and UV-Vis spectroscopy. The average crystallite size estimated by Debye-Scherer's and Williamson-Hall plots were found to be in the range of 10-50 nm. Samples calcined at 1100°C show pure monoclinic X1 phase; whereas, samples calcined at 1200 and 1300°C show pure X2 phase of YSO. Photoluminescence (PL) studies of Sm(3+) (1-9 mol%) doped YSO for near ultra violet (NUV) excitation (407 nm) was studied in order to investigate the possibility of its use in white light emitting diode (WLED) applications. The emission spectra consists of intra 4f transitions of Sm(3+), such as (4)G5/2→(6)H5/2 (∼560 nm), (4)G5/2→(6)H7/2 (600-613 nm), (4)G5/2→(6)H9/2 (∼650 nm), (4)G5/2→(6)H11/2 (715 nm) and (4)G5/2→(6)H13/2 (763 nm) respectively. The emission intensity of the phosphor was found to be enhancing after addition of fluxes. Further, the emission at 600-613 nm show strong orange-red emission and can be applied to the orange-red emission of phosphor for near ultra violet excitation.

Effect of different fuels on structural, photo and thermo luminescence properties of solution combustion prepared Y(2)SiO(5) nanopowders

Y(2)SiO(5) nanopowders are prepared by solution combustion method using DFH, sugar and urea as fuels. The final product was well characterized by powder X-ray diffraction, Scanning Electron Microscopy and UV-Vis spectroscopy. The average crystallite size was estimated using Debye-Scherer's formula and Williamson-Hall plots and are found to be in the range 34-40nm for DFH, 45-50nm for urea and 35-42nm for sugar respectively. X1-X2 type YSO phase was obtained for all the samples calcined from 1200 to 1400°C. The optical energy band gaps (Eg) of the samples were estimated from Tauc relation and varies from 5.58 to 5.60eV. SEM micrographs of sugar and urea used Y(2)SiO(5) show agglomerated particles with porous morphology. However, for the sample prepared using DFH fuel observed to be almost spherical in shape. Thermoluminescence (TL) properties of γ-irradiated (1-5kGy) and UV irradiated (1-30min) Y(2)SiO(5) nanopowder at a heating rate of 2.5°Cs(-1) was studied. The samples prepared by using urea and sugar fuels show a broad TL glow peak at 189°C. However, DFH used Y(2)SiO(5) show a well resolved peak at 196°C with shouldered peak at 189°C. Among the fuels, DFH used Y(2)SiO(5) show simple glow peak structure which perhaps useful in radiation dosimetry. This may be due to fuel and particle size effect. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics are estimated by Chens glow peak shape method.

Synthesis and anticancer activity of oxindole derived imidazo[1,5-a]pyrazines

A series of oxindole derivatives of imidazo[1,5-a]pyrazines were prepared and confirmed by 1H NMR, mass and HRMS data. These compounds were evaluated for their anticancer activity against a panel of 52 human tumor cell lines derived from nine different cancer types: leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast. Among them compound 7l showed significant anticancer activity with GI50 values ranging from 1.54 to 13.0 μM. Cell cycle arrest was observed in G0/G1 phase upon treatment of A549 cells with 6.5 μM (IC50) concentration of compound 7l and induced apoptosis. This was confirmed by Annexin V-FITC as well as DNA fragmentation analysis and interestingly this compound (7l) did not affect the normal cells.

Synthesis and anti-cancer activity of chalcone linked imidazolones

A series of novel chalcone linked imidazolones were prepared and evaluated for their anti-cancer activity against a panel of 53 human tumour cell lines derived from nine different cancer types: leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast. Some of these hybrids (6, 7 and 8) showed good anti-cancer activity with GI(50) values ranging from 1.26 to 13.9 microM. When breast carcinoma cells (MCF-7) were treated with 10 microM concentration of compounds TMAC, CA-4, 6 and 8 cell cycle arrest was observed in G2/M phase. Surprisingly, the increased concentration of the same compound to 30 microM caused accumulation of cells in G0/G1 phase of the cell cycle.

The burden of fatal and non-fatal injury in rural India

BACKGROUND

Little is known about the burden or causes of injury in rural villages in India.

OBJECTIVE

To examine injury-related mortality and morbidity in villages in the state of Andhra Pradesh, India.

METHODS

A verbal-autopsy-based mortality surveillance study was used to collect mortality data on all ages from residents in 45 villages in 2003-2004. In early 2005, a morbidity survey in adults was carried out using stratified random sampling in 20 villages. Participants were asked about injuries sustained in the preceding 12 months. Both fatal and non-fatal injuries were coded using classification methods derived from ICD-10.

RESULTS

Response rates for the mortality surveillance and morbidity survey were 98% and 81%, respectively. Injury was the second leading cause of death for all ages, responsible for 13% (95% CI 11% to 15%) of all deaths. The leading causes of fatal injury were self-harm (36%), falls (20%), and road traffic crashes (13%). Non-fatal injury was reported by 6.7% of survey participants, with the leading causes of injury being falls (38%), road traffic crashes (25%), and mechanical forces (16.1%). Falls were more common in women, with most (72.3%) attributable to slipping and tripping. Road traffic injuries were sustained mainly by men and were primarily the result of motorcycle crashes (48.8%).

DISCUSSION

Injury is an important contributor to disease burden in rural India. The leading causes of injury-falls, road traffic crashes, and suicides-are all preventable. It is important that effective interventions are developed and implemented to minimize the impact of injury in this region.

Physicochemical and Photophysical Studies on Porphyrin-Based Donor−Acceptor Systems: Effect of Redox Potentials on Ultrafast Electron-Transfer Dynamics

We report new polychromophoric complexes, where different porphyrin (P) derivatives are covalently coupled to a redox active Mo center, MoL*(NO)Cl(X) (L* is the face-capping tridentate ligand tris(3,5-dimethylpyrazolyl) hydroborate and X is a phenoxide/pyridyl/amido derivative of porphyrin). The luminescence quantum yields of the bichromophoric systems (1, 2, and 5) were found to be an order of magnitude less than those of their respective porphyrin precursors. Transient absorption measurements revealed the formation of the porphyrin radical cation species (P(.)(+)) and photoinduced electron transfer from the porphyrin moiety to the respective Mo center in 1, 2, and 5. Electrochemical studies showed that the reduction potentials of the acceptor Mo centers in a newly synthesized pyridyl derivative (2; E(1/2)[Mo(I/0)] = approximately -1.4 V vs Ag/AgCl) and previously reported phenoxy- (1; E(1/2)[Mo(II/I)] = approximately -0.3 V vs Ag/AgCl) and amido- (3; E(1/2)[Mo(II/I)] = approximately -0.82 V vs Ag/AgCl) derivatives were varied over a wide range. Thus, studies with these complexes permitted us to correlate the probable effect of this potential gradient on the electron-transfer dynamics. Time-resolved absorption studies, following excitation at the Soret band of the porphyrin fragment in complexes 1, 2, and 5, established that forward electron transfer took place biexponentially from both S2 and S1 states of the porphyrin center to the Mo moiety with time constants 150-250 fs and 8-20 ps, respectively. In the case of MoL*(NO)ClX (where X is pyridine derivative 2), the high reduction potential for the MoI/0 couple allowed electron transfer solely from the S2 state of the porphyrin center. Time constants for the charge recombination process for all complexes were found to be 150-300 ps. Further, electrochemical and EPR studies with the trichromophoric complexes (3 and 4) revealed that the orthogonal orientation of the peripheral phenoxy/pyridyl rings negated the possibility of any electronic interaction between two paramagnetic Mo centers in the ground state and thereby the spin exchange, which otherwise was observed for related Mo complexes when two Mo centers are separated by a polyene system with comparable or larger separation distances.

Ultrafast Dynamics and Excited State Deactivation of [Ru(bpy)2Sq]+ and Its Derivatives

Femtosecond transient absorption spectroscopy has been employed to understand the excited state dynamics of [Ru(bpy)(2)Sq](+) (I; bpy is 2,2'-bipyridyl, and Sq is the deprotonated species of the semiquinone form of 1,2-dihydroxy benzene) and its derivatives, a widely studied near-infrared (NIR) active electrochromic dye. Apart from the well-defined dpi(Ru) --> pi(bpy)-based metal-to-ligand charge transfer (MLCT) transition bands at approximately 480 nm, this class of molecules generally shows another dpi(Ru) --> pi(Sq)(SOMO)-based intense MLCT band at around 900 nm, which is known to be redox active and bleaches reversibly upon a change in the oxidation state of the coordinated dioxolene moiety. To have better insight into the photoinduced electron transfer dynamics associated with this MLCT transition, detailed investigations have been carried out on exciting this MLCT band at 800 nm. Immediately after photoexcitation, bleach at 900 nm has been observed, whose recovery is found to follow a triexponential function with major contribution from the ultrafast component. This ultrafast component of approximately 220 fs has been ascribed to the S(1) to S(0) internal conversion process. In addition to the bleach, we have detected two transient species absorbing at 730 and 1000 nm with a formation time approximately 220 fs for both species. The excited state lifetimes for these two transient species have been measured to be 1.5 and 11 ps and have been attributed to excited singlet ((1)MLCT) and triplet ((3)MLCT) states, respectively. Transient measurements carried out on the different but analogous derivatives (II and III) have also shown similar recovery dynamics except that the rate for the internal conversion process has increased with the decrease in the S(1) to S(0) energy gap. The observed results are consistent with the energy gap law for nonradiative decay from S(1) to S(0).

Interfacial Electron Transfer between the Photoexcited Porphyrin Molecule and TiO2 Nanoparticles: Effect of Catecholate Binding

Interfacial electron transfer (ET) dynamics of 5,10,15-trisphenyl-20-(3,4-dihydroxybenzene) porphyrin (TPP-cat) adsorbed on TiO2 nanoparticles has been studied by femtosecond transient absorption spectroscopy in the visible and near-IR region exciting at 400 and 800 nm. TPP-cat molecule forms a charge transfer (CT) complex with TiO2 nanoparticles through the catechol moiety with the formation of a five-membered ring. Optical absorption measurements have shown that the Q-band of TPP-cat interacts strongly with TiO2 due to chelation; however, the Soret band is affected very little. Optical absorption measurements indicate that the catechol moiety also interacts with TiO2 nanoparticles showing the characteristic band of pure catechol-TiO2 charge transfer (CT) in the visible region. Electron injection has been confirmed by monitoring the cation radical, instant bleach, and injected electron in the conduction band of TiO2 nanoparticles. Electron injection time has been measured to be < 100 fs and recombination kinetics has been best fitted with a multiexponential function, where the majority of the injected electrons come back to the parent cation radical with a time constant of approximately 800 fs for both excitation wavelengths. However, the reaction channel for the electron injection process has been found to be different for both wavelengths. Excitation at 800 nm, found to populate the CT state of the Q-band, and from the photoexcited CT state electron injection into the conduction band, takes place through diffusion. On the other hand, with excitation at 400 nm, a complicated reaction channel takes place. Excitation with 400 nm light excites both the CT band of Cat-TiO2 and also the Soret band of TPP-cat. We have discussed the reaction path in the TPP-cat/TiO2 system after exciting with both 400 and 800 nm laser light. We have also compared ET dynamics by exciting at both wavelengths.

Electron Injection into the Surface States of ZrO2 Nanoparticles from Photoexcited Quinizarin and Its Derivatives: Effect of Surface Modification

The effect of surface modification on interfacial electron transfer (IET) dynamics into the surface states of ZrO(2) nanoparticles sensitized by quinizarin (Qz) and its derivatives has been carried out using time-resolved emission spectroscopy. The surface of ZrO(2) nanoparticles has been modified by sodium dodecyl benzyl sulfonate . We have observed that Qz's can form a strong charge-transfer (CT) complex with both unmodified and surface-modified (SM) ZrO(2) nanoparticles. We have confirmed electron injection into the surface states of ZrO(2) nanoparticles from the photoexcited Qz molecule in our earlier work (J. Phys. Chem. B 2004, 108, 4775; Langmuir 2004, 20, 7342). In the present investigation, we have observed electron injection from photoexcited Qz derivatives into the surface states of both unmodified and SM ZrO(2) nanoparticles and also detected CT emission. Monitoring CT emission, we have determined back electron transfer (BET) dynamics of the dye-nanoparticle systems. We have found that the BET rate for the QZs/ZrO(2) systems decreases as the relative driving force increases following Marcus inverted region kinetic behavior for an IET process. BET dynamics was found to be faster on SM ZrO(2) nanoparticles as compared to that of the unmodified (bare) one. Our time-resolved emission data indicates that upon surface modification the majority of the deeper trap states of ZrO(2) nanoparticles can be removed with the formation of some new shallower trap states in the band gap region.

Ultrafast Intermolecular Hydrogen Bond Dynamics in the Excited State of Fluorenone

Steady-state fluorescence and time-resolved absorption measurements in pico- and femtosecond time domain have been used to investigate the dynamics of hydrogen bond in the excited singlet (S(1)) state of fluorenone in alcoholic solvents. A comparison of the features of the steady-state fluorescence spectra of fluorenone in various kinds of media demonstrates that two spectroscopically distinct forms of fluorenone in the S(1) state, namely the non-hydrogen-bonded (or free) molecule as well as the hydrogen-bonded complex, are responsible for the dual-fluorescence behavior of fluorenone in solutions of normal alcoholic solvents at room temperature (298 K). However, in 2,2,2-trifluoroethanol (TFE), a strong hydrogen bond donating solvent, emission from only the hydrogen-bonded complex is observed. Significant differences have also been observed in the temporal evolution of the absorption spectroscopic properties of the S(1) state of fluorenone in protic and aprotic solvents following photoexcitation using 400 nm laser pulses. An ultrafast component representing the solvent-induced vibrational energy relaxation (VER) process has been associated with the dynamics of the S(1) state of fluorenone in all kinds of solvents. However, in protic solvents, in addition to the VER process, further evolution of the spectroscopic and dynamical properties of the S(1) state have been observed because of repositioning of the hydrogen bonds around the carbonyl group. In normal alcohols, two different kinds of hydrogen-bonded complex of the fluorenone-alcohol system with different orientations of the hydrogen bond with respect to the carbonyl group and the molecular plane of fluorenone have been predicted. On the other hand, in TFE, formation of only one kind of hydrogen-bonded complex has been observed. These observations have been supported by theoretical calculations of the geometries of the hydrogen-bonded complexes in the ground and the excited states of fluorenone. Linear correlation between the lifetimes of the equilibration process occurring because of repositioning of the hydrogen bonds and Debye or longitudinal relaxation times of the normal alcoholic solvents establish the fact that, in weakly hydrogen bond donating solvents, the hydrogen bond dynamics can be described as merely a solvation process. Whereas, in TFE, hydrogen bond dynamics is better described by a process of conversion between two distinct excited states, namely, the non-hydrogen-bonded form and the hydrogen-bonded complex.

Calcific retinal embolism as an indicator of severe unrecognised cardiovascular disease

OBJECTIVE

To describe the association between calcific retinal embolism (CRE) and cardiac valve stenosis.

DESIGN AND SETTING

Retrospective chart review of patients with clinical criteria for CRE.

PATIENTS

24 patients with CRE who underwent two dimensional echocardiography between 1976 and 1998.

RESULTS

Nine patients (38%) had calcific valve stenosis, which was haemodynamically severe in five patients (four aortic and one mitral), four of whom had no cardiac symptoms. Six patients underwent surgical intervention (aortic valve replacement in three patients, mitral and aortic valve replacement in one patient, removal of calcific cardiac pseudotumour in one patient, and carotid endarterectomy in one patient).

CONCLUSIONS

CRE may be the presenting feature of otherwise asymptomatic, clinically important underlying cardiovascular disease and, in particular, haemodynamically severe calcific valve stenosis.

Strongly Coupled Ruthenium−Polypyridyl Complexes for Efficient Electron Injection in Dye-Sensitized Semiconductor Nanoparticles

Dynamics of interfacial electron transfer (ET) in the ruthenium-polypyridyl complex [{bis(2,2'-bpy)-(4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol)} ruthenium(II) hexafluorophosphate] (Ru-cat)-sensitized TiO(2) nanoparticles has been investigated using femtosecond transient absorption spectroscopy detecting in the visible and near-infrared region. It has been observed that Ru-cat is coupled strongly with the TiO(2) nanoparticles through its pendant catechol moiety. Electron injection has been confirmed by direct detection of electrons in the conduction band, cation radical of the adsorbed dye, and a bleach of the dye in real time as monitored by transient absorption spectroscopy. A single-exponential and pulse width limited (<100 fs) electron injection has been observed, and the origin of it might have been from the nonthermalized excited states of the Ru-cat molecule. The result gave a strong indication that the electron injection competes with the thermalization of the photoexcited states due to large coupling elements for the forward ET reaction. Back-ET dynamics has been determined by monitoring the decay kinetics of the cation radical and injected electron and also from recovery kinetics of the bleach of the adsorbed dye. It has been fit with a multiexponential function, where approximately 30% of the injected electrons are recombined with a time constant of <2 ps, again indicating large coupling elements for the charge recombination reaction. However, our results have shown relatively long-lived charge separation in the Ru-cat/TiO(2) system as compared to other organic dye-sensitized TiO(2) nanoparticles with similar interactions.

Synthesis, Characterization, Physicochemical, and Photophysical Studies of Redox Switchable NIR Dye Derived from a Ruthenium−Dioxolene−Porphyrin System

Newly synthesized semi-quinone derivatives of the ruthenium polypyridyl, covalently linked to a porphyrin core, show very high epsilon values (59,000-83,500 M(-1)cm(-1)) for the absorption band in the near infrared (NIR) region of the spectrum. Further, complexes 1-4 show an interesting reversible electrochromic behavior as a function of the redox state of the coordinated dioxolene functionality, and a switching phenomenon between bleaching and the restoration of the NIR peak could be achieved electrochemically. Thus, complexes 1-4 could be ideal candidate materials for NIR-active electrochromic devices. Ultrafast studies on 1 and its mononuclear components, 5-(3,4-dihydroxyphenyl)-10,15,20-triphenyl-21H,23H-porphyrin (H2L1) and Ru(bpy)2(bsq)+, reveal that there is no electron or energy transfer from the porphyrin to the Ru(bpy)2sq+ (bpy is 2,2'-bipyridine and sq is the deprotonated species of a substituted semi-quinone fragment) fragment or vice versa in 1. The observed decrease in the luminescence quantum yield for 1 compared to that of H2L1 can be ascribed to the increased nonradiative pathway due to higher vibronic coupling because of the direct linkage of the metal center to the porphyrin moiety.

Ultrafast Intermolecular Electron Transfer Dynamics: Perylene in Electron-Accepting Micellar Medium

The dynamics of ultrafast photoinduced intermolecular electron transfer (ET) from the excited singlet (S1) state of perylene (Pe) to an electron-accepting cationic surfactant molecule, N-cetylpyridinium chloride (CPC), in aqueous micellar solutions has been investigated using the femtosecond transient absorption spectroscopic technique with temporal resolution of 120 fs. The Pe molecule is localized at or near the micellar surface, where it coexists with the pyridinium moieties (headgroups of the micelle) of the surfactant molecule. Following photoexcitation of Pe, an electron is transferred to the neat and geometrically restricted headgroup of the micelle. Dynamics of the forward ET process as well as the geminate recombination or back ET (BET) process have been followed by monitoring the temporal evolution of the S1 state of Pe and the cation radical of Pe (Pe*+), respectively. The multiexponential forward ET process indicates that the ET dynamics is highly correlated with the spatial distributions of the micellar headgroups around a donor Pe molecule and thus dependent on the donor-acceptor distance. The distance-dependent ET and BET rates have been calculated following the method of Weidemaier and Fayer (J. Chem. Phys. 1995, 102, 3820) to get the best fit parameters for the multiexponetial temporal profiles for the S1 state of Pe as well as Pe*+. Because the acceptor is a constituent of the neat micellar medium, their confinement on the surface of the microheterogeneous medium provides a very large concentration such that, even though the forward transfer rate is 0.06 ps(-1) at the distance of closest approach, the ET process is complete within a 200-ps time domain. If the concepts of distribution of ET distances are utilized, the possible role of material diffusion on the kinetics of forward ET is ruled out. This is an experimental study to show, for the first time, the ultrafast distance-dependent light-induced ET dynamics following both the excited state of the donor and the cation radical formed in an ET process using the transient absorption spectroscopic technique in a self-reactive restrictive environment.

Effect of surface modification on back electron transfer dynamics of dibromo fluorescein sensitized TiO2 nanoparticles

Electron injection and back electron transfer (BET) dynamics have been carried out for dibromo fluorescein (DBF) sensitized TiO2 nanoparticles capped (modified) with sodium dodecyl benzene sulfonate using transient absorption techniques in picosecond and microsecond time domain. BET dynamics have been compared with bare (unmodified) nanoparticles for the same DBF/TiO2 system. It has been observed that BET reaction is slow on the modified surface compared to a bare surface in earlier time domain (picosecond). This observation has been explained by the fact that on surface modification the energy levels of the semiconductor nanoparticles are pushed up in energy. As a result, the free energy of reaction (-deltaG zero) for BET reaction of a dye/SM-TiO2 system increases as compared to the dye/bare TiO2 system. High exoergic BET reaction in dye-sensitized TiO2 nanoparticles surfaces fall in the Marcus inverted regime, so with increasing free energy of reaction, BET rate decreases on the modified surface. However, a reversible trend in BET dynamics has been observed for the above systems in the longer time domain (microsecond). In microsecond time domain BET reaction is faster on the modified surface as compared to on the bare surface. Modification of this surface reduces the density of deep trap states. Recombination dynamics between deep-trapped electron and parent cation is slow due to low coupling strength of BET reaction. As the density of deep-trapped electrons is high in bare particles, BET reaction is slow in longer time domain.