Impact of ligand environment on optical,luminescence and thermometric behavior of A3(PO4)2:Sm3+ (A = Ca,Sr) phosphors

The present study investigates the impact of the ligand environment on the luminescence and thermometric behavior of Sm³⁺ doped A₃(PO₄)₂ (A = Sr, Ca) phosphors prepared by combustion synthesis. The structural and luminescent properties of Sm³⁺ ions in the phosphate lattices were investigated using powder X-ray diffraction (PXRD) and photoluminescence (PL) techniques. PXRD results of the synthesized phosphors exhibit the expected phases that are in agreement with their respective standards. Fourier-transform infrared (FTIR) spectroscopy confirms the presence of PO₄ vibrational bands. Upon excitation with near ultraviolet light, the PL studies indicated that Sr₃(PO₄)₂:Sm³⁺ phosphors exhibit a yellow light emission, whereas Ca₃(PO₄)₂:Sm³⁺ phosphors exhibit an emission of orange light. The PL emission results are in accordance with the CIE coordinates, with the Sr₃(PO₄)₂:Sm³⁺ phosphors showing coordinates of (0.56, 0.44), and the Ca₃(PO₄)₂:Sm³⁺ phosphors displaying coordinates of (0.60, 0.40). Thermal analysis shows improved stability of Ca₃(PO₄)₂:Sm³⁺ based on lower weight reduction in thermogravimetric analysis. The effect of temperature on the luminescence properties of the phosphor has been examined upon a 405 nm excitation. By using the fluorescence intensity ratio (FIR) method, the temperature responses of the emission ratios from the Sm³⁺: the ⁴F_3/2 → ⁶H_5/2 transition to the ⁴G_5/2 → ⁶H_7/2 and ⁴F_3/2 → ⁶H_5/2 transition to the ⁴G_5/2 → ⁶H_9/2 emissions are characterized. The Ca₃(PO₄)₂:Sm³⁺ phosphors are more sensitive as compared with the Sr₃(PO₄)₂:Sm³⁺ phosphors. The earlier research findings strongly indicate that these phosphors hold great promise as ideal candidates for applications in non-invasive optical thermometry and solid-state lighting devices.     

Spatio-temporal dynamics of intra-host variability in SARS-CoV-2 genomes

During the course of the COVID-19 pandemic, large-scale genome sequencing of SARS-CoV-2 has been useful in tracking its spread and in identifying variants of concern (VOC). Viral and host factors could contribute to variability within a host that can be captured in next-generation sequencing reads as intra-host single nucleotide variations (iSNVs). Analysing 1347 samples collected till June 2020, we recorded 16 410 iSNV sites throughout the SARS-CoV-2 genome. We found ∼42% of the iSNV sites to be reported as SNVs by 30 September 2020 in consensus sequences submitted to GISAID, which increased to ∼80% by 30th June 2021. Following this, analysis of another set of 1774 samples sequenced in India between November 2020 and May 2021 revealed that majority of the Delta (B.1.617.2) and Kappa (B.1.617.1) lineage-defining variations appeared as iSNVs before getting fixed in the population. Besides, mutations in RdRp as well as RNA-editing by APOBEC and ADAR deaminases seem to contribute to the differential prevalence of iSNVs in hosts. We also observe hyper-variability at functionally critical residues in Spike protein that could alter the antigenicity and may contribute to immune escape. Thus, tracking and functional annotation of iSNVs in ongoing genome surveillance programs could be important for early identification of potential variants of concern and actionable interventions.     

Inhibition of mitochondrial respiration by analogs of 4-phenylpyridine and 1-methyl-4-phenylpyridinium cation (MPP+), the neurotoxic metabolite of MPTP

In order to clarify the structural requirements associated with the inhibition of mitochondrial respiration by MPP+, the neurotoxic metabolites of the Parkinsonian agent MPTP, ten sets of pyridine/N-methylpyridinium pairs and a few miscellaneous compounds were evaluated on rat liver intact mitochondria (Mw) and on submitochondrial particles (SMP). The pyridinium partners were much more potent inhibitors on Mw than on SMP, indicating that they are concentrated inside mitochondria by the energy-dependent process previously reported for MPP+, probably as a consequence of non-specific passive transport across the mitochondrial inner membrane in response to the transmembrane potential. In the SMP assay, the neutral pyridines were stronger inhibitors than were the pyridinium cations, and the inhibitory potency varied little with structural changes. The N-methylated forms of beta-carbolines may act as endogenous MPP+-like agents.     

Anthrax toxin lethal factor contains a zinc metalloprotease consensus sequence which is required for lethal toxin activity

Comparison of the anthrax toxin lethal factor (LF) amino acid sequence with sequences in the Swiss protein database revealed short regions of similarity with the consensus zinc-binding site, HEXXH, that is characteristic of metalloproteases. Several protease inhibitors, including bestatin and captopril, prevented intoxication of macrophages by lethal toxin. LF was fully inactivated by site-directed mutagenesis that substituted Ala for either of the residues (H-686 and H-690) implicated in zinc binding. Similarly, LF was inactivated by substitution of Cys for E-687, which is thought to be an essential part of the catalytic site. In contrast, replacement of E-720 and E-721 with Ala had no effect on LF activity. LF bound ⁶⁵Zn both in solution and on protein blots. The ⁶⁵Zn binding was reduced for several of the LF mutants. These data suggest that anthrax toxin LF is a zinc metallopeptidase, the catalytic function of which is responsible for the lethal activity observed in cultured cells and in animals.     

Microsecond motions of the lipids associated with trypsinized Na,K-ATPase membranes. Progressive saturation spin-label electron spin resonance studies.

The microsecond motions of spin-labeled lipids associated with the Na(+)/K(+)-transporting ATP hydrolase (Na,K-ATPase) in native and tryptically shaved membranes from Squalus acanthias have been studied by progressive saturation electron spin resonance (ESR). This includes both the segmental mobility of the lipid chains and the exchange dynamics of the lipids interacting directly with the protein. The lipids at the protein interface display a temperature-dependent chain mobility on the submicrosecond time scale. Exchange of these lipids with those in the bulk bilayer regions of the membrane takes place on the time scale of the nitroxide spin-lattice relaxation, i.e., in the microsecond regime. The off-rates for exchange directly reflect the specificity of ionized fatty acids relative to protonated fatty acids for interaction with the Na,K-ATPase. These essential features of the lipid dynamics at the intramembranous protein surface, namely, a temperature-dependent exchange on the microsecond time scale that reflects the lipid selectivity, are preserved on removing the extramembranous parts of the Na,K-ATPase by extensive trypsinization.     

Immunomodulation by liposome entrapped allergen

Liposomes are non-toxic, biodegradable and feebly immunogenic lipid vesicles made from natural and synthetic lipids. They are known to act as immunopotentiating agents and can be used to formulate sustained release preparation by encapsulation. In the present study, liposome entrapped allergen and free allergen were used to inject in Balb/C mice at different time intervals and their immune response in terms of specific IgG and specific IgE levels was quantitated by ELISA (Enzyme Linked Immuno sorbent Assay). The results indicated that specific IgE response was significantly higher in mice injected free allergen as compared to that of mice given liposome entrapped allergen. However, the specific IgG response was not statistically significant. Experiments carried out with liposome entrapped allergen and liposome coupled allergen showed no statistically significant difference in specific IgE and specific IgG titre between the two groups of mice. This type of immunomodulatory effect of liposomes in reducing IgE levels and without affecting IgG levels may be useful in Type I allergic disorders.     

Biodiesel production using heterogeneous catalysts

The production and use of biodiesel has seen a quantum jump in the recent past due to benefits associated with its ability to mitigate greenhouse gas (GHG). There are large number of commercial plants producing biodiesel by transesterification of vegetable oils and fats based on base catalyzed (caustic) homogeneous transesterification of oils. However, homogeneous process needs steps of glycerol separation, washings, very stringent and extremely low limits of Na, K, glycerides and moisture limits in biodiesel. Heterogeneous catalyzed production of biodiesel has emerged as a preferred route as it is environmentally benign needs no water washing and product separation is much easier. The present report is review of the progress made in development of heterogeneous catalysts suitable for biodiesel production. This review shall help in selection of suitable catalysts and the optimum conditions for biodiesel production.