Exploring color tunable emission characteristics of Eu3+-doped La2(MoO4)3 phosphors in the glass-ceramic form.

The glass-ceramic form of phosphor materials can overcome the many serious issues of phosphor/silicone composite in commercial phosphor-converted LEDs and are considered as new-generation color converters. In this report, we have shown a novel approach of developing inorganic red phosphor [Eu3+:La2(MoO4)3] in the glass-ceramic form based on lanthanum molybdate system. The ceramic form of the compound was found to have a glass transition temperature of 1002 °C, as confirmed by TGA and DSC studies. Further, XRD, FTIR and Raman studies also confirmed that the compounds prepared at 1050 °C are in glass-ceramic form, while those prepared at 750 °C are in ceramic form. Photoluminescence studies showed that both the ceramic and glass-ceramic forms of the phosphor are red color-emitting materials. However, the glass-ceramic forms have better color purity and more radiation transition probabilities. Further, the decay kinetics of both ceramic and glass-ceramic forms confirmed that only those Eu3+ ions which exist in the grain boundaries of the ceramics go inside the glass network structure upon heating the compound at or above the glass transition temperature. On the other hand, Eu3+ ions which exist at the La-site in the bulk of the particles are retained in the ceramic form in the glass-ceramic mixture.

Solid state speciation of uranium and its local structure in Sr2CeO4 using photoluminescence spectroscopy.

An effort was taken to carry our speciation study of uranium ion in technologically important cerate host Sr2CeO4 using time resolved photoluminescence spectroscopy. Such studies are not relevant only to nuclear industry but can give rich insight into fundamentals of 5f electron chemistry in solid state systems. In this work both undoped and varied amount of uranium doped Sr2CeO4 compound is synthesized using complex polymerization method and is characterized systematically using X-ray diffraction (XRD), Raman spectroscopy, impedance spectroscopy and scanning electron microscopy (SEM). Both XRD and Raman spectroscopy confirmed the formation of pure Sr2CeO4 which has tendency to decompose peritectically to SrCeO3 and SrO at higher temperature. Uranium doping is confirmed by XRD. Uranium exhibits a rich chemistry owing to its variable oxidation state from +3 to +6. Each of them exhibits distinct luminescence properties either due to f-f transitions or ligand to metal charge transfer (LMCT). We have taken Sr2CeO4 as a model host lattice to understand the photophysical characteristics of uranium ion in it. Emission spectroscopy revealed the stabilization of uranium as U (VI) in the form of UO66- (octahedral uranate) in Sr2CeO4. Emission kinetics study reflects that uranate ions are not homogeneously distributed in Sr2CeO4 and it has two different environments due to its stabilization at both Sr2+ as well as Ce4+ site. The lifetime population analysis interestingly pinpointed that majority of uranate ion resided at Ce4+ site. The critical energy-transfer distance between the uranate ion was determined based on which the concentration quenching mechanism was attributed to electric multipolar interaction. These studies are very important in designing Sr2CeO4 based optoelectronic material as well exploring it for actinides studies.

Energy transfer dynamics and luminescence properties of Eu(3+) in CaMoO4 and SrMoO4.

Undoped and europium doped CaMoO4 and SrMoO4 scheelites are synthesized using a complex polymerization method. The phase purity of the sample is confirmed using powder X-ray diffraction (PXRD). X-ray photoelectron spectroscopy (XPS) was carried out to confirm the oxidation states of various constituents and dopant elements and also the presence of oxygen vacancies. Interestingly both CaMoO4 and SrMoO4 on irradiation with UV light give blue and green emission respectively. On europium doping, it was found that molybdate to Eu(3+) ion energy transfer is more efficient in SrMoO4:Eu compared to CaMoO4:Eu. It is also justified using a luminescence lifetime study which shows biexponential decay in the case of CaMoO4:Eu corresponding to both the host and europium ion; whereas a single lifetime is observed in the case of SrMoO4:Eu. Anomalies in host-dopant energy transfer are suitably explained using density functional theory (DFT) calculations and XPS. The actual site symmetry for the europium ion in CaMoO4 and SrMoO4 was also evaluated based on a Stark splitting pattern which turns out to be D2 and C2v respectively although it is S4 for Ca/Ba(2+) in AMoO4. This is also reflected in higher Ω2 values for SrMoO4:Eu than CaMoO4:Eu.

Cloning, sequencing, and in silico characterization of Omp 28 of Salmonella Typhi (strain MTCC 733) to develop r-DNA vaccine for typhoid fever.

BACKGROUND: Typhoid is one of the most important diseases of human beings caused by Salmonella Typhi. There are many vaccine reported against Salmonella Typhi, but search for new candidate vaccine antigens is still going on because presently available vaccines have several limitations such as short-term immunity, high cost, and allergic reaction. Several approaches such as subunit vaccines, Vi polysaccharide, mutant vaccines, and r-DNA vaccines have been tested. r- DNA vaccines have shown some promising potential (targeted Omp). Omp 28 had shown very promising results and suggests that it should be used in further studies of animal protection against the disease. OBJECTIVE: Cloning, Sequencing and In silico analysis of Omp 28 gene to develop r-DNA vaccine of S. Typhi. MATERIALS AND METHODS: Omp 28 is made up of three identical subunits of 9.6 kDa showing PCR amplicon of 330 bp which has been cloned in the pJET vector. Recombinant clones has been sequenced, and data submitted to NCBI. Secondary structure was deduced by the Chou Fasman and Garnier method. The sequence of Omp 28 was studied for antigenic indexing, epitope mapping, and MHC mapping using various bioinformatics tool. RESULTS AND CONCLUSION: The sequence of Omp 28 has been assigned accession no GQ 907044.1 by NCBI. Secondary structure has shown it has more alpha region. Hydrophobic plot and surface probability plot shows most amino acids are surface exposed which is a requirement to develop a r-DNA vaccine. Antigenic sites are located within surface exposed regions and eight antigenic determinants are present in Omp 28. On Prosite analysis of Protein shown two motifs i.e. anaphylatoxin domain signature motif at position 219-252 and other one was iron sulphur binding region signature motif at position 36-44. On epitope analysis total six major B cell epitopes were observed which can provoke humoral immunity. On T cell epitope mapping several major epitopes has been found in case of MHC class I and MHC class II. It indicates that Omp 28 can provoke cell mediated as well as humoral immunity and can be proven a promising candidates of Salmonella Typhi.

Cloning, sequencing and in silico analysis of omp C of salmonella typhimurium.

Salmonella Typhimurium is an important pathogen having a broad host range. In human population it causes mostly gastroenteritis but there are reports in which it was found to be responsible to cause several lethal diseases like endocarditis and meningitis. Poultry products are the major sources of this organism in India as these are consumed at various stages of cooking. The available vaccines have their own limitations such as short-term immunity. Outer membrane proteins have shown some promising potential, so in the present study Omp C of Salmonella Typhimurium was cloned and sequenced to explore the possibility of development of r-DNA vaccine against Salmonella Typhimurium for poultry. The sequence of Omp C was studied for antigenic indexing, epitope mapping, and MHC mapping using various bioinformatic tools. The ORF analysis revealed a complete coding region of approximately 1000 bp. Five major and 13 minor B-cell epitopes were identified having an antigenic index of 1.7. The sequences also showed major histocompatibility complex (MHC) class I and class II binding region indicating a potential of eliciting cell-mediated immune response. The findings indicate that Omp C may be proven as promising candidate for development of r-DNA vaccine against Salmonella Typhimurium.

REP-PCR analysis of Pasteurella multocida isolates from wild and domestic animals in India.

Repetitive extragenic palindromic sequence-based PCR (REP-PCR) was used to characterize 67 field isolates of Pasteurella multocida originating from different animal species and geographical regions of India. REP-PCR was found to be rapid and reproducible (three repeats were done). These isolates yielded different 23 profiles which were clustered into eight groups. The discrimination index was moderate (D value 0.83). Somatic and antigenic typing of the isolates did not reveal any correlation with REP-PCR profiles. There was no host-specific, type-specific, region-specific or pathenogenicity-specific pattern. The REP profiles of isolates obtained from wild animals were similar to those obtained from domestic animals. Two common bands were present in all the isolates irrespective of somatic or antigenic types. The results were not comparable with earlier findings, which had shown high discrimination index and correlation with disease presentation.

Detection of Pasteurella multocida in experimentally infected embryonated chicken eggs by PCR assay.

Applicability of polymerase chain reaction (PCR) assay to detect Pasteurella multocida in experimentally infected embryonated chicken egg was assessed in the present study. PCR assay rapidly and specifically detected the genome of P. multocida in amniotic fluid, allantoic fluid and homogenates of infected embryo and its membranes. The sensitivity of detection was as low as 20 bacterial cells/ml of allantoic or amniotic fluids. Detection of P. multocida in dead embryos by PCR was possible up to 6 and 30 days or more following storage of dead embryos at 37 degrees C, and at 4 degrees C as well as at -20 degrees C, respectively. The study revealed that PCR assays could be employed directly for detection and confirmation of P. multocida infection in experimentally infected chicken embryos.

Characterization of avian strains of Pasteurella multocida by restriction endonuclease and amplified fragment length polymorphism.

Avian strains of Pasteurella multocida were typed by employing restriction endonuclease analysis (REA) and single enzyme-amplified fragment length polymorphism (AFLP) to evaluate their applicability for epidemiological studies of fowl cholera outbreaks. A total of 72 strains isolated from different avian species (chicken, duck, turkey, quail and goose) belonging to various geographical regions of India were characterized. REA using two different enzymes HhaI and HpaII produced 9 and 18 clusters respectively, whereas Single enzyme-AFLP recognized 32 patterns out of 72 strains typed. The study indicated that REA using HpaII is a simple and resource efficient method, however, further typing with more stringent and rapid method like Single enzyme-AFLP, could drastically enhance investigation in epidemiological studies of fowl cholera outbreaks.

Identification of avian strains of Pasteurella multocida in India by conventional and PCR assays.

The prevalence of capsular and somatic serotypes were studied among 123 Pasteurella multocida strains isolated from chickens (n=94), ducks (22), quails (4), turkeys (2) and geese (1) from different geographical regions of India. All strains exhibited similar cultural and morphological characteristics. Ninety-two of the isolates belonged to serotype A:1, the most prevalent serotype, with serotypes A:3, A:1,3, D:3 and F:3 having two isolates each. Only one isolate was positive for serotypes A:4 and D:1. Twenty isolates were untyped. A multiplex capsular PCR assay generated amplicons of sizes approximately 460, approximately 1044, approximately 657 and approximately 854 bp in 106 isolates identified as capsular serotype-A, 15 in serotype D and two in serotype F. Capsular types B and E were not detected in any of the avian isolates studied. The present findings suggest that a multiplex capsular PCR assay may be suitable for the rapid initial identification serotypes P. multocida during epidemiological studies of fowl cholera.

Ribotyping of Indian isolates of Pasteurella multocida based on 16S and 23S rRNA genes.

The applicability of ribotyping based on 16S and 23S rRNA was evaluated for molecular epidemiological studies. Forty-eight isolates of Pasteurella multocida isolated from different hosts and geographical locations and one reference isolate were ribotyped. Only four ribotypes were found. All the isolates including reference isolate from wild carnivores had the same ribotype, though they had different serotypes. The isolate from a tiger had one band in addition to the bands present in the major ribotype. The isolates from lions represented two ribotypes; of these ribotypes, one (r2) had an additional band of 3.6 kbp, which was absent in all other ribotypes. The second ribotype (r4) from a lion had one band missing (6 kbp) that was present in the other ribotypes. These isolates were further typed using ERIC-PCR and REP-PCR. With ERIC-PCR and REP-PCR, higher D values of 0.83 and 0.89 were obtained. The current study revealed that ribotyping is not a very efficient typing tool for use in molecular epidemiology for differentiation of isolates.

Detection of multiple strains of Pasteurella multocida in fowl cholera outbreaks by polymerase chain reaction-based typing.

Applicability of molecular methods for the detection and differentiation of Pasteurella multocida strains involved in two separate fowl cholera outbreaks in a single poultry farm was investigated. A total of 12 and 18 strains of P. multocida obtained from two separate outbreaks were subjected to phenotypic and genotypic characterization. Phenotypically, all strains were similar; however, DNA-based techniques by employing polymerase chain reaction (PCR) assays were found to be highly specific and sensitive for rapid detection and differentiation of strains. All 30 strains gave amplicons of approximately 460 bp and approximately 1,044 bp specific for P. multocida and capsular serogroup A in the Multiplex Capsular PCR typing system. Molecular typing techniques such as repetitive extragenic palindromic PCR, enterobacterial repetitive intergenic consensus PCR and single primer PCR differentiated all 30 strains into different profiles. However, similar patterns of genome fragments were observed among all strains following restriction endonuclease analysis using the enzyme HpaII. The current investigation revealed involvement of the same and multiple strains of P. multocida in two outbreaks. The results also indicated that molecular methods of detection and typing are rapid in comparison with conventional methods for epidemiological investigations of fowl cholera outbreaks.

Molecular variability among strains of Pasteurella multocida isolated from an outbreak of haemorrhagic septicaemia in India.

The applicability of conventional and molecular methods for rapid detection and differentiation of Pasteurella multocida serogroup B isolates involved in an outbreak of haemorrhagic septicaemia affecting Indian buffaloes, was studied. Five isolates were obtained and were subjected to phenotypic and genotypic characterization. None of the five isolates could be differentiated on the basis of cultural, biochemical, pathogenicity and antimicrobial sensitivity patterns. Polymerase chain reaction (PCR)-based techniques were found to be specific and sensitive for rapid detection and differentiation of isolates. Repetitive extragenic palindromic (REP-) PCR, enterobacterial repetitive intergenic consensus (ERIC-) PCR and single-primer PCR differentiated all the five isolates into different profiles. All the isolates involved in the outbreak were found to have a genetic profile different from standard P. multocida strain (P52). However, three isolates had similar profiles, whereas each of the remaining two had a different profile. The study indicates the involvement of multiple strains of P. multocida in a single outbreak of haemorrhagic septicaemia in buffaloes. The results also indicate that molecular methods of detection and typing are superior to conventional methods for rapid epidemiological investigations of haemorrhagic septicaemia.

Strain differentiation of Indian isolates of Salmonella by ERIC-PCR.

Enterobacterial repetitive intergenic consensus (ERIC) sequences are the repetitive elements present in the family enterobacteriacae. In the present study, ERIC-PCR (target ERIC sequence) was used for the molecular typing of 24 isolates of Salmonella serovars, namely abortusequi, choleraesuis, bareilly and dublin. In ERIC-PCR, seven molecular types were observed with ERIC-Cl primer, and nine molecular types with ERIC-C2 primer. When the results of both the ERIC-PCR were combined for molecular typing, 21 molecular types were observed, which indicated a high degree of discrimination. Both the ERIC primers are designed from the ERIC consensus sequence, yet they gave different profiles, indicating that they supplement each other. ERIC sequences were found to be useful targets for molecular typing. The different profiles observed appear to be due to differences in ERIC sequences and differences in inter-ERIC distance. The study indicates that ERIC-PCR is a very efficient tool for molecular typing of Salmonella species.