EPR, optical absorption and photoluminescence properties of MnO(2) doped 23B(2)O(3)-5ZnO-72Bi(2)O(3) glasses

Electron paramagnetic resonance (EPR), transmission electron microscopy (TEM), optical absorption and photoluminescence (PL) spectroscopic measurements are performed on Mn(2+) doped high bismuth containing zinc-bismuth-borate glasses. TEM images reveal homogeneously dispersed Bi(circle) nanoparticles (NPs) of spherical shape with size about 5 nm. EPR spectra exhibit predominant signals at g approximate to 2.0 and 4.3 with a sextet hyperfine structure. The resonance signal at g approximate to 2.0 is due to Mn(2+) ions in an environment close to octahedral symmetry, where as the resonance at g approximate to 4.3 is attributed to the rhombic surrounding of the Mn(2+) ions. The hyperfine splitting constant (A) indicates that Mn(2+) ions in these glasses are moderately covalent in nature. The zero-field splitting parameter D has been calculated from the allowed hyperfine lines. The optical absorption spectrum exhibits a single broad band centered at 518 nm (19,305 cm(-1)) is assigned to the (6)A(1g)(S) —> (4)T(1g)(G) transition of Mn(2+) ions. The visible and near infrared (NIR) luminescence bands at 548, 652 and 804 nm have been observed when excited at 400 and 530 nm, respectively. These luminescence centers are supposed to be caused by the lower valence state of bismuth, such as Bi(2+) and Bi(+) ions, generated during melting process. (C) 2010 Elsevier B.V. All rights reserved

EPR, FTIR, optical absorption and photoluminescence studies of Fe(2)O(3) and CeO(2) doped ZnO-Bi(2)O(3)-B(2)O(3) glasses

Glasses containing heavy metal oxide of the composition (wt.%) 23B(2)O(3)-5ZnO-72Bi(2)O(3)-xFe(2)O(3)/CeO(2) (0 <= x <= 0.0058 at.% in excess) were prepared by melt quenching technique. The glass formation was confirmed by XRD. FTIR spectra exhibit characteristic absorption bands for B(2)O(3) and Bi(2)O(3) for their various structural units. The EPR spectra exhibit two resonance signals at g approximate to 6.4 and g approximate to 4.2 for Fe(2)O(3) doped glasses. The resonance signals at g approximate to 4.2 and g approximate to 6.4 are attributed to Fe(3+) ions in rhombic and axial symmetry sites. respectively. The number of spins participating in resonance (N) and its paramagnetic susceptibility (chi) with composition has been evaluated. The effect of CeO(2) and Fe(2)O(3) on optical and structural properties of zinc bismuth borate glass was investigated. From EPR and optical studies it is observed that iron ions are present in trivalent state with distorted octahedral symmetry. The cerium is present in Ce(4+) state. Upon 400 nm excitation the emission at 548 and 652 nm are attributed to the Bi(2+) species. The emission at 804 nm upon 530 nm excitation suggests that Bi(+) ions are present in the sample. It is interesting to observe that the optical band gap energy (E(opt)) decreases with the increase of transition metal and rare-earth ion doping. (C) 2009 Elsevier B.V. All rights reserved

Role of Heat Shock Proteins in Improving Heat Stress Tolerance in Crop Plants

High temperature response (HTR) or heat stress response (HSR) is a highly conserved phenomenon, which involves complex networks among different crop species. Heat stress usually results in protein dysfunction by improper folding of its linear amino acid chains to non-native proteins. This leads to unfavourable interactions and subsequent protein aggregation. To tackle this, plants have developed molecular chaperone machinery to maintain high quality proteins in the cell. This is governed by increasing the level of pre-existing molecular chaperones and by expressing additional chaperones through signalling mechanism. Dissecting the molecular mechanism by which plants counter heat stress and identification of important molecules involved are of high priority. This could help in the development of plants with improved heat stress tolerance through advanced genomics and genetic engineering approaches. Owing to this reason molecular chaperones/Heat shock proteins (Hsps) are considered as potential candidates to address the issue of heat stress. In this chapter, recent progress on systematic analyses of heat shock proteins, their classification and role in plant response to heat stress along with an overview of genomic and transgenic approaches to overcome the issue, are summarized

Molecular characterization and expression analysis of pearl millet plasma membrane proteolipid 3 (Pmp3) genes in response to abiotic stress conditions

Plasma membrane proteolipid 3 (Pmp3) is a gene family involved in abiotic stress response and cellular protection. Here we report cloning of two genes PgPmp3-1 and PgPmp3-2 from Pennisetum glaucum, and characterization with respect to their functions and responsiveness to various abiotic stresses. Both PgPmp3-1 and PgPmp3-2 genes are 171 bp long and encode for 56 amino acid long peptides. PgPmp3 sequences share 70–99% sequence identity with their homologs. Protein secondary structure prediction revealed membrane-spanning regions containing a membrane potential modulator domain in both PgPmp3 proteins. In silico network analyses revealed Pmp3 co-expression and association with proteins conferring abiotic stress tolerance in plants. Expression profiles of PgPmp3-1 and PgPmp3-2 revealed their up-regulation in P. glaucum under cold and salt stresses, but showed reduced expression in response to heat stress. These findings provide insight into the role of P. glaucum Pmp3 in abiotic stress amelioration

Ion beam-induced luminescence and photoluminescence of 100 MeV Si8+ ion irradiated kyanite single crystals

lonoluminescence (IL) of kyanite single crystals during 100 MeV Si8+ ion irradiation has been studied in the fluence range 1.87-7.50 x 10(11) ions/cm(2). Photoluminescence (PL) of similar dimensional crystals was recorded with same ions and energy in the fluence range 1 x 10(11) -5 x 10(13) ions/cm(2) with an excitation of 442 non He-Cd laser beam. A sharp IL and broad PL peaks at similar to 689 and 706 run were recorded. This is attributed to luminescence centers activated by Fe2+ and Fe3+ ions. It is observed that up to a given fluence, the IL and PL peak intensities increase with increase of Si8+ ion fluence. The stability of the chemical species was Studied on with and without irradiated samples by means of FT-IR spectroscopy. The results confirm that the O-Si-H type bonds covering on the surface of the sample. This layer might be acting as a protective layer and there by reducing the number of non-radiative recombination centers. (c) 2008 Elsevier Ltd. All rights reserved

Accumulation of CCR4+ CTLA-4hi FOXP3+CD25hi Regulatory T Cells in Colon Adenocarcinomas Correlate to Reduced Activation of Conventional T Cells

BACKGROUND: Colorectal cancer usually gives rise to a specific anti-tumor immune response, but for unknown reasons the resulting immunity is not able to clear the tumor. Recruitment of activated effector lymphocytes to the tumor is important for efficient anti-tumor responses, while the presence of regulatory T cells (Treg) down-modulate tumor-specific immunity. We therefore aimed to determine homing mechanisms and activation stage of Treg and effector T cell infiltrating colon tumors compared to cells from the unaffected mucosa in patients suffering from colon adenocarcinoma. METHODOLOGY/PRINCIPAL FINDINGS: Lymphocytes were isolated from unaffected and tumor mucosa from patients with colon adenocarcinoma, and flow cytometry, immunohistochemistry, and quantitative PCR was used to investigate the homing mechanisms and activation stage of infiltrating Treg and conventional lymphocytes. We detected significantly higher frequencies of CD25(high)FOXP3⁺CD127(low) putative Treg in tumors than unaffected mucosa, which had a complete demethylation in the FOXP3 promotor. Tumor-associated Treg had a high expression of CTLA-4, and some appeared to be antigen experienced effector/memory cells based on their expression of αEβ7 (CD103). There were also significantly fewer activated T cells and more CTLA-4⁺ conventional T cells susceptible to immune regulation in the tumor-associated mucosa. In contrast, CD8⁺granzyme B⁺ putative cytotoxic cells were efficiently recruited to the tumors. The frequencies of cells expressing α4β7 and the Th1 associated chemokine receptor CXCR3 were significantly decreased among CD4⁺ T cells in the tumor, while frequencies of CD4⁺CCR4⁺ lymphocytes were significantly increased. CONCLUSIONS/SIGNIFICANCE: This study shows that CCR4⁺CTLA4(hi) Treg accumulate in colon tumors, while the frequencies of activated conventional Th1 type T cells are decreased. The altered lymphocyte composition in colon tumors will probably diminish the ability of the immune system to effectively attack tumor cells, and reducing the Treg activity is an important challenge for future immunotherapy protocols

Genomic-based-breeding tools for tropical maize improvement

Maize has traditionally been the main staple diet in the Southern Asia and Sub-Saharan Africa and widely grown by millions of resource poor small scale farmers. Approximately, 35.4 million hectares are sown to tropical maize, constituting around 59% of the developing worlds. Tropical maize encounters tremendous challenges besides poor agro-climatic situations with average yields recorded <3 tones/hectare that is far less than the average of developed countries. On the contrary to poor yields, the demand for maize as food, feed, and fuel is continuously increasing in these regions. Heterosis breeding introduced in early 90 s improved maize yields significantly, but genetic gains is still a mirage, particularly for crop growing under marginal environments. Application of molecular markers has accelerated the pace of maize breeding to some extent. The availability of array of sequencing and genotyping technologies offers unrivalled service to improve precision in maize-breeding programs through modern approaches such as genomic selection, genome-wide association studies, bulk segregant analysis-based sequencing approaches, etc. Superior alleles underlying complex traits can easily be identified and introgressed efficiently using these sequence-based approaches. Integration of genomic tools and techniques with advanced genetic resources such as nested association mapping and backcross nested association mapping could certainly address the genetic issues in maize improvement programs in developing countries. Huge diversity in tropical maize and its inherent capacity for doubled haploid technology offers advantage to apply the next generation genomic tools for accelerating production in marginal environments of tropical and subtropical world. Precision in phenotyping is the key for success of any molecular-breeding approach. This article reviews genomic technologies and their application to improve agronomic traits in tropical maize breeding has been reviewed in detail