Complex carbohydrate-lectin interaction at the interface: a model for cellular adhesion. I. Effect of vesicle size on the kinetics of aggregation between a fatty acid conjugate of lectin and a liposomal asialoganglioside

Two types of phospholipid vesicles capable of mutual recognition have been tailor-made to serve as a model system for the study of carbohydrate-mediated cellular adhesion. One of the vesicles contained a fatty acid conjugate of a galactose specific lectin (lectin vesicle) and the other an asialoganglioside with a reactive terminal galactose residue (galactose vesicle). The kinetics of aggregation of these two types of vesicles was followed by monitoring time-dependent change in turbidity. A 10-100-fold enhancement in the forward rate constant (kf ranging from 7.1 x 10(5) to 4.5 x 10(7) M-1.s-1 at 27 degrees C) was observed when compared with that for the lectin-galactose system in solution (kf being 4.5 x 10(5) M-1.s-1), reported in the literature. A study of the influence of vesicle size on the rate of aggregation showed that enhancement depended on the curvature of the galactose vesicle rather than the density of asialoganglioside suggesting a possible diffusion in the plane of the membrane. The ratio, kf/kd is found to be approx. 10(10) M-1 indicating that the formation of multiple bonds plays a role for stable adhesion.     

Reactivity of glycoconjugate in membrane system II: Can a neutral glycolipid function as lectin receptor in the presence of gangliosides in plasma membrane?

To examine how surface Potential controls the reactivity of glycoconjugates at cell surface, the interaction of galactose-sPecific lectinse.g. peanut agglutinin,Ricinus cummunis agglutinin with liPosomes bearing asialo GM₁ were studied in the Presence of varying amount of ganglioside mixture, GM_n. The Presence of 5% GM_n causes comPlete slowing down of PreciPitin reaction and thereby make carbohydrate moiety of asialo GM₁ comPletely inaccessiblei.e. ‘cryPtic’. In contrast the Presence of 1–2% GM_n enhances the aPParent rate and amPlitude of the PreciPitin reaction as surface Potential becomes more negative. The relevance of the findings has been discussed in relation to the exPression and involvement of the cell-surface sialic acid residues during develoPment and differentiation.     

Majvinine: A new indole alkaloid of Vinca major

A new alkaloid, majvinine, was isolated from aerial parts of Vinca major. Its structure was determined by chemical and spectroscopic investigations     

Length–weight relationships of three freshwater fish species from Rupnaryan and Kangsabati River,West Bengal,India

The length–weight relationships (LWRs) of three freshwater fish species from the Kangsabati and Rupnaryan river in West Bengal, India are presented, namely as Amblypharyngodon microlepis (Bleeker, 1853), Parambassis lala (Hamilton, 1822) and Macrognathus aculeatus (Bloch, 1786). Gill‐nets (mesh sizes with 0.5 cm–4 cm), cast‐nets (up to 1 × 1 cm mesh size with up to 4.0 m² area) and scoop‐nets (0.3 × 0.3 cm and 0.5 × 0.5 cm mesh size) were used from January, 2017 to April, 2018. Sampling was done every 15 days during this period. The value of parameter “b” ranged from 2.751 to 2.895 with highly significant correlations (r² > 0.95).     

Multiphoton ANS fluorescence microscopy as an in vivo sensor for protein misfolding stress

The inability of cells to maintain protein folding homeostasis is implicated in the development of neurodegenerative diseases, malignant transformation, and aging. We find that multiphoton fluorescence imaging of 1-anilinonaphthalene-8-sulfonate (ANS) can be used to assess cellular responses to protein misfolding stresses. ANS is relatively nontoxic and enters live cells and cells or tissues fixed in formalin. In an animal model of Alzheimer’s disease, ANS fluorescence imaging of brain tissue sections reveals the binding of ANS to fibrillar deposits of amyloid peptide (Aβ) in amyloid plaques and in cerebrovascular amyloid. ANS imaging also highlights non-amyloid deposits of glial fibrillary acidic protein in brain tumors. Cultured cells under normal growth conditions possess a number of ANS-binding structures. High levels of ANS fluorescence are associated with the endoplasmic reticulum (ER), Golgi, and lysosomes—regions of protein folding and degradation. Nuclei are virtually devoid of ANS binding sites. Additional ANS binding is triggered by hyperthermia, thermal lesioning, proteasome inhibition, and induction of ER stress. We also use multiphoton imaging of ANS binding to follow the in vivo recovery of cells from protein-damaging insults over time. We find that ANS fluorescence tracks with the binding of the molecular chaperone Hsp70 in compartments where Hsp70 is present. ANS highlights the sensitivity of specific cellular targets, including the nucleus and particularly the nucleolus, to thermal stress and proteasome inhibition. Multiphoton imaging of ANS binding should be a useful probe for monitoring protein misfolding stress in cells.     

Spatial pattern of freshwater habitats and their prioritization using additive partitions of beta diversity of inhabitant piscine assemblages in the Terai–Dooars ecoregion of Eastern Himalayas

Limnology - Underlying spatial and habitat attributes of a river network are crucial to comprehend the bio-spatial arrangements within it, the study of which suffers from a paucity of information....     

Comparative studies on kinetics of inhibition of protein synthesis in intact cells by ricin and conjugate of ricin B-chain with momordin

Cofilin is an actin-binding protein of low molecular weight which is widely distributed in eukaryotes and is deeply involved in the dynamics of actin assembly in the cytoplasm. The actin-binding ability of cofilin is inhibited by inositol phosphates (PIP2), and the PIP2- and actin-binding site(s) has been localized in residues W104 - M115 of the cofilin primary sequence (Yonezawa et al. 1991). In the present study, in order to further clarify the functional domains in cofilin molecule, we constructed expression vectors containing cDNAs of different size with deletion at the 3-region of the open reading frame. The truncated cofilin molecules produced in E. coli were purified and examined for their actin-binding and PIP2-binding ability. We found that the truncated cofilin molecule without C-terminal residues #100-#166 including the previously-described actin-binding site could be cross-linked with actin by EDC, a zero-length cross-linker. In addition, these truncated peptides as well as synthetic peptides corresponding to the N-terminal sequence of cofilin suppressed the inhibitory action of PIP2 on actin-cofilin interaction. These results strongly suggest that additional actin- and PIP2-binding sites exist in the N-terminal region of cofilin.