Molecular organization of axo-glial junctions

Axo-glial interactions are required for the organization of highly specialized molecular domains in myelinated axons. The molecular composition of these domains includes cell adhesion molecules, ion channels and cytoskeletal proteins. Recent genetic and molecular studies provide new insights into how these macromolecular complexes are assembled and organized into functional domains, and how the loss of individual components affects domain organization and function. More importantly, the key molecular components identified at the vertebrate axo-glial septate junctions are also present at the Drosophila septate junctions. In addition, new roles for axo-glial paranodal septate junctions have emerged, which suggest that the paranodal region may act as an ionic barrier and a molecular fence in myelinated axons.     

Excited state intermolecular hydrogen bond’s effect on the luminescent behaviour of the 2D covalent organic framework (PPy-COF): A TDDFT insight

The theoretical investigation of electronically excited stated intermolecular hydrogen bonding dynamics of the 2D luminescent polypyrene covalent organic framework and methanol molecule (PPy-COF-MeOH) was performed using the density functional theory (DFT) and time-dependent (TD-DFT) method. The strengthening of Hydrogen bonds C-H---O-H and B-O---H-O upon photoexcitation was confirmed via comparison of geometric structures, electronic transition energies, ¹H-NMR, binding energies, UV-Vis and infrared spectra in S0 and S1 states. Frontier molecular orbitals (MOs) analysis, electronic configuration, Mulliken charge analysis; and the charge density variation in hydrogen bonding proximity demonstrated that the strengthened hydrogen bonds facilitate the nonradiative path which may consequently proceed the luminescence quenching. Hence, the molecular material property prediction package (MOMAP) programme verified the fluorescence quenching because PPy-COF-MeOH complex showed a lower fluorescent rate constant compared to isolated PPy-COF fragment. The S1-T1 energy gap analysis also revealed the possibility of the Intersystem crossing (ISC). Above results significantly highlighted the role of the hydrogen bonding dynamics on luminescence property of the PPy-COF.     

Preparation of novel authentication film by screen printing of anthocyanin biomolecular extract: Thermochromism and vapochromism

Novel thermochromic and vapochromic paper substrates were prepared via screen printing with anthocyanin extract in the presence of ferrous sulfate mordant, resulting in multi-stimuli responsive colorimetric paper sheets. Environmentally friendly anthocyanin extract was obtained from red-cabbage (Brassica oleracea var. capitata L.) to function as spectroscopic probe in coordination with ferrous sulfate mordant. Pink anthocyanin/resin nanocomposite films immobilized onto paper surface were developed by well-dispersion of anthocyanin extract as a colorimetric probe in a binding agent without agglomeration. As demonstrated by CIE colorimetric studies, the pink (λ_max = 418 nm) film deposited onto paper surface turns greenish-yellow (λ_max = 552 nm) upon heating from 25 to 75°C, demonstrating new thermochromic film for anti-counterfeiting applications. The thermochromic effects were investigated at different concentrations of the anthocyanin extract. Upon exposure to ammonia gas, the color of the anthocyanin-printed sheets changes rapidly from pink to greenish-yellow, and then immediately returns to pink after taking the gaseous ammonia stimulus away, demonstrating vapochromic effect. The current sensor strip showed a detection limit for ammonia gas in the range 50–300 ppm. Both thermochromism and vapochromism showed high reversibility without fatigue. In addition to studying the rheological properties of the prepared composites, the morphological and mechanical properties of the printed cellulose substrates were also studied.     

Role of green fluorescent proteins and their variants in development of FRET-based sensors

Since the last decade, a lot of advancement has been made to understand biological processes involving complex intracellular pathways. The major challenge faced was monitoring and trafficking of metabolites in real time. Although a range of quantitative and imaging techniques have been developed so far, the discovery of green fluorescent proteins (GFPs) has revolutionized the advancement in the field of metabolomics. GFPs and their variants have enabled researchers to ‘paint’ a wide range of biological molecules. Fluorescence resonance energy transfer (FRET)-based genetically encoded sensors is a promising technology to decipher the real-time monitoring of the cellular events inside living cells. GFPs and their variants, due to their intrinsic fluorescence properties, are extensively being used nowadays in cell-based assays. This review focuses on structure and function of GFP and its derivatives, mechanism emission and their use in the development of FRET-based sensors for metabolites.     

Drosophila contactin, a homolog of vertebrate contactin, is required for septate junction organization and paracellular barrier function

Septate junctions (SJs) in epithelial and neuronal cells play an important role in the formation and maintenance of charge and size selective barriers. They form the basis for the ensheathment of nerve fibers in Drosophila and for the attachment of myelin loops to axonal surface in vertebrates. The cell-adhesion molecules NRX IV/Caspr/Paranodin (NCP1), contactin and Neurofascin-155 (NF-155) are all present at the vertebrate axo-glial SJs. Mutational analyses have shown that vertebrate NCP1 and its Drosophila homolog, Neurexin IV (NRX IV) are required for the formation of SJs. In this study, we report the genetic, molecular and biochemical characterization of the Drosophila homolog of vertebrate contactin, CONT. Ultrastructural and dye-exclusion analyses of Cont mutant embryos show that CONT is required for organization of SJs and paracellular barrier function. We show that CONT, Neuroglian (NRG) (Drosophila homolog of NF-155) and NRX IV are interdependent for their SJ localization and these proteins form a tripartite complex. Hence, our data provide evidence that the organization of SJs is dependent on the interactions between these highly conserved cell-adhesion molecules.     

Replication,maturation and physical mapping of bacteriophage MB78 genome

Bacteriophage MB78 is a virulent phage ofSalmonella typhimurium. The viral DNA is 42 kb in size and seems to be circularly permuted. We show that viral DNA replication is through concatemeric DNA formation which is subsequently converted into full length DNA through headful packaging. A restriction map of MB78 DNA for six restriction endonucleases e.g.BgIII,PvuII, ECORI, ClaI, SalI and SmaI has been constructed. The yield of certain fragments in less than molar amount is explained in terms of permutation and the headful mechanism of packaging. The packaging site (pac site) has been suggested.     

Urease inhibitors from Indigofera gerardiana Wall

Three new phloroglucinol type compounds Indigoferin-A (1), Indigoferin-B (2) and Indigoferin-C (3), along with a known compound β-sitosterol were isolated from the Indegofera gerardiana Wall. The structures of Indigoferin-A (1), Indigoferin-B (2), and Indigoferin-C (3) were deduced on the basis of spectroscopic techniques (EI-MS, HREI-MS, (1)H NMR, (13)C NMR, HMQC, and HMBC). The urease inhibition studies on all the four compounds have also been carried out.