Fiber optics based surface plasmon resonance for label-free optical sensing

With the advancement in the laser technology and availability of low cost optical fibers, there is an increasing trend towards adoption of optical fibers as sensing element for development of optical sensors probes especially point-of-care sensing for environmental, biomedical and clinical application. Refractive index measurement through surface plasmon resonance has evolved to be, one of the most sensitive transducer for label-free sensing with high sensitivity. Surface plasmon resonance is a surface sensitive optoelectronic phenomenon, where light incident on a plasmonic metal surface at a given angle can excite a surface-bound electromagnetic wave, a surface plasmon. Associated with the surface plasmon is an evanescent field that probes local changes in the refractive index of the ambient medium that are used for monitoring analyte- supramolecular/ bio-molecular ligand interactions. Present review outlines a concise view on theoretical aspects of fiber optics based surface plasmon resonance phenomenon and comprehensive updated review on research and development for progression in the design of fiber optics based SPR sensors

Sm-Nd age and mantle source characteristics of the Dhanjori volcanic rocks, Eastern India

Trace, Rare Earth Element (REE), Rb-Sr and Sm-Nd isotope analyses have been carried out on selected basic-ultrabasic rocks of Dhanjori volcanic belt from the Eastern Indian Craton (EIC). The Sm-Nd isotopic data of these rocks yield an isochron age of 2072 ± 106 Ma (MSWD = 1.56). Chondrite normalized REE plots display shallow fractionated REE pattern with LREE enrichment. In primitive mantle normalized plots also these rocks show shallow fractionated pattern with depletion of Nb and Ba and enrichment of LILE like Rb, Th and U. Depletion of Nb, Ba and Zr and enrichment of Rb, Th and U are found in N-MORB normalized plots as well. Compatible elements like Tb, Y and Yb on the other hand, show a flat pattern. Isotope, trace and REE modelling indicate that these were produced by 3− 5% partial melting of a spinel lherzolite source. The Nd isotopic data suggest that an enriched (εNd = -2.4) mantle existed below the Dhanjori basin during ~2.1 Ga. The enrichment was possibly caused by continuous recycling of the earlier crust into the mantle whereby subducted slab derived fluid modified the surrounding mantle. The process also affected the more easily susceptible Rb-Sr systematics producing variable Sri (0.702-0.717). The enriched mantle material, part of a thermal plume, pierced through the deep fractures produced due to the cooling and readjustment of the Archaean continental crust and ultimately outpoured within the Dhanjori basin. The plume magmatism was manifested by the extrusion of komatiitic/basaltic flows and basic/ultrabasic intrusives. The residence time of the plume within the upper mantle was possibly very small as no depleted signature (even in Nd isotope) has been obtained. This means a deep plume was fed by a recycled oceanic crust via globally extensive subduction process, already initiated by the end-Archaean period

Late Archaean mantle metasomatism below eastern Indian craton: evidence from trace elements, REE geochemistry and Sr-Nd-O isotope systematics of ultramafic dykes

Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ~ 0:702 ± 0:004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; (ΣHREE)N ~ 2-3 times chondrite, (Gd/Yb)N ~ 1). The εNd(t) values vary from +1:23 to −3:27 whereas δ18O values vary from +3:16‰ to +5:29‰ (average +3:97‰±0:75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (± silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable εNd, low Sri(0:702) and low δ18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse

Rudra Interrupts Receptor Signaling Complexes to Negatively Regulate the IMD Pathway

Insects rely primarily on innate immune responses to fight pathogens. In Drosophila, antimicrobial peptides are key contributors to host defense. Antimicrobial peptide gene expression is regulated by the IMD and Toll pathways. Bacterial peptidoglycans trigger these pathways, through recognition by peptidoglycan recognition proteins (PGRPs). DAP-type peptidoglycan triggers the IMD pathway via PGRP-LC and PGRP-LE, while lysine-type peptidoglycan is an agonist for the Toll pathway through PGRP-SA and PGRP-SD. Recent work has shown that the intensity and duration of the immune responses initiating with these receptors is tightly regulated at multiple levels, by a series of negative regulators. Through two-hybrid screening with PGRP-LC, we identified Rudra, a new regulator of the IMD pathway, and demonstrate that it is a critical feedback inhibitor of peptidoglycan receptor signaling. Following stimulation of the IMD pathway, rudra expression was rapidly induced. In cells, RNAi targeting of rudra caused a marked up-regulation of antimicrobial peptide gene expression. rudra mutant flies also hyper-activated antimicrobial peptide genes and were more resistant to infection with the insect pathogen Erwinia carotovora carotovora. Molecularly, Rudra was found to bind and interfere with both PGRP-LC and PGRP-LE, disrupting their signaling complex. These results show that Rudra is a critical component in a negative feedback loop, whereby immune-induced gene expression rapidly produces a potent inhibitor that binds and inhibits pattern recognition receptors

Evolutionary origin of peptidoglycan recognition proteins in vertebrate innate immune system

<p>Abstract</p> <p>Background</p> <p>Innate immunity is the ancient defense system of multicellular organisms against microbial infection. The basis of this first line of defense resides in the recognition of unique motifs conserved in microorganisms, and absent in the host. Peptidoglycans, structural components of bacterial cell walls, are recognized by Peptidoglycan Recognition Proteins (PGRPs). PGRPs are present in both vertebrates and invertebrates. Although some evidence for similarities and differences in function and structure between them has been found, their evolutionary history and phylogenetic relationship have remained unclear. Such studies have been severely hampered by the great extent of sequence divergence among vertebrate and invertebrate PGRPs. Here we investigate the birth and death processes of PGRPs to elucidate their origin and diversity.</p> <p>Results</p> <p>We found that (i) four rounds of gene duplication and a single domain duplication have generated the major variety of present vertebrate PGRPs, while in invertebrates more than ten times the number of duplications are required to explain the repertoire of present PGRPs, and (ii) the death of genes in vertebrates appears to be almost null whereas in invertebrates it is frequent.</p> <p>Conclusion</p> <p>These results suggest that the emergence of new <it>PGRP </it>genes may have an impact on the availability of the repertoire and its function against pathogens. These striking differences in PGRP evolution of vertebrates and invertebrates should reflect the differences in the role of their innate immunity. Insights on the origin of <it>PGRP </it>genes will pave the way to understand the evolution of the interaction between host and pathogens and to lead to the development of new treatments for immune diseases that involve proteins related to the recognition of self and non-self.</p

Drosophila Immunity: Analysis of PGRP-SB1 Expression, Enzymatic Activity and Function

Peptidoglycan is an essential and specific component of the bacterial cell wall and therefore is an ideal recognition signature for the immune system. Peptidoglycan recognition proteins (PGRPs) are conserved from insects to mammals and able to bind PGN (non-catalytic PGRPs) and, in some cases, to efficiently degrade it (catalytic PGRPs). In Drosophila, several non-catalytic PGRPs function as selective peptidoglycan receptors upstream of the Toll and Imd pathways, the two major signalling cascades regulating the systemic production of antimicrobial peptides. Recognition PGRPs specifically activate the Toll pathway in response to Lys-type peptidoglycan found in most Gram-positive bacteria and the Imd pathway in response to DAP-type peptidoglycan encountered in Gram-positive bacilli-type bacteria and in Gram-negative bacteria. Catalytic PGRPs on the other hand can potentially reduce the level of immune activation by scavenging peptidoglycan. In accordance with this, PGRP-LB and PGRP-SC1A/B/2 have been shown to act as negative regulators of the Imd pathway. In this study, we report a biochemical and genetic analysis of PGRP-SB1, a catalytic PGRP. Our data show that PGRP-SB1 is abundantly secreted into the hemolymph following Imd pathway activation in the fat body, and exhibits an enzymatic activity towards DAP-type polymeric peptidoglycan. We have generated a PGRP-SB1/2 null mutant by homologous recombination, but its thorough phenotypic analysis did not reveal any immune function, suggesting a subtle role or redundancy of PGRP-SB1/2 with other molecules. Possible immune functions of PGRP-SB1 are discussed