Melo A.A.,Max Delbrück Center for Molecular Medicine |
Melo A.A.,Free University of Berlin |
Hegde B.G.,Rani Channamma University |
Shah C.,Max Delbrück Center for Molecular Medicine |
And 8 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2017
Eps15 (epidermal growth factor receptor pathway substrate 15)-homology domain containing proteins (EHDs) comprise a family of dynamin-related mechano-chemical ATPases involved in cellular membrane trafficking. Previous studies have revealed the structure of the EHD2 dimer, but the molecular mechanisms of membrane recruitment and assembly have remained obscure. Here, we determined the crystal structure of an amino-terminally truncated EHD4 dimer. Comparedwith the EHD2 structure, the helical domains are 50° rotated relative to the GTPase domain. Using electron paramagnetic spin resonance (EPR), we show that this rotation aligns the two membrane-binding regions in the helical domain toward the lipid bilayer, allowing membrane interaction. A loop rearrangement in GTPase domain creates a new interface for oligomer formation. Our results suggest that the EHD4 structure represents the active EHD conformation, whereas the EHD2 structure is autoinhibited, and reveal a complex series of domain rearrangements accompanying activation. A comparison with other peripheral membrane proteins elucidates common and specific features of this activation mechanism.
Hegde B.G.,Rani Channamma University
Resonance | Year: 2015
Recently, electron paramagnetic resonance (EPR) spectroscopy has emerged as a powerful tool to study the structure and dynamics of biological macromolecules such as proteins, protein aggregates, RNA and DNA. It is used in combination with molecular modelling to study complex systems such as soluble proteins, membrane proteins and protein aggregates like amyloid fibrils and oligomers. This article describes how the EPR technique can be used to elucidate the structural reorganization taking place in a membrane-bound protein by taking a few examples from the literature including some of the earlier works of the author. © 2015, Indian Academy of Sciences.
Ambroso M.R.,University of Southern California |
Hegde B.G.,University of Southern California |
Hegde B.G.,Rani Channamma University |
Langen R.,University of Southern California
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014
Membrane remodeling is controlled by proteins that can promote the formation of highly curved spherical or cylindrical membranes. How a protein induces these different types of membrane curvature and how cells regulate this process is still unclear. Endophilin A1 is a protein involved in generating endocytotic necks and vesicles during synaptic endocytosis and can transform large vesicles into lipid tubes or small and highly curved vesicles in vitro. By using EM and electron paramagnetic resonance of endophilin A1, we find that tubes are formed by a close interaction with endophilin A1's BIN/amphiphysin/Rvs (BAR) domain and deep insertion of its amphipathic helices. In contrast, vesicles are predominantly stabilized by the shallow insertion of the amphipathic helical wedges with the BAR domain removed from the membrane. By showing that the mechanism of membrane curvature induction is different for vesiculation and tubulation, these data also explain why previous studies arrived at different conclusions with respect to the importance of scaffolding and wedging in the membrane curvature generation of BAR proteins. The Parkinson disease-associated kinase LRRK2 phosphorylates S75 of endophilin A1, a position located in the acyl chain region on tubes and the aqueous environment on vesicles. We find that the phosphomimetic mutation S75D favors vesicle formation by inhibiting this conformational switch, acting to regulate endophilin A1-mediated curvature. As endophilin A1 is part of a protein superfamily, we expect these mechanisms and their regulation by posttranslational modifications to be a general means for controlling different types of membrane curvature in a wide range of processes in vivo.
Nayaka G.P.,Kuvempu University |
Manjanna J.,Rani Channamma University |
Pai K.V.,Kuvempu University |
Vadavi R.,Bk College |
And 2 more authors.
Hydrometallurgy | Year: 2015
A well characterized cathode material (LiCoO2) recovered from spent lithium-ion battery is dissolved in aqueous mixture of citric acid (chelating agent) and ascorbic acid (reductant) at 80 °C. The dissolution proceeds with a reductive-complexing mechanism, and complete dissolution occurs in about 6 h when stoichiometric amount of C/A is used. The dissolution rate constants (k) are 3.1 × 10- 3 min- 1 for Li and 0.8 × 10- 3 min- 1 for Co ions as determined by 'cubic rate law' plots. The formation of Co(III)- to Co(II)-citrate during the dissolution is confirmed from the UV-Vis spectra. The dissolved solution was subjected for selective precipitation of cobalt as Co-oxalate and lithium as LiF using oxalic acid and NH4F, respectively. The present study has a merit when compared to literature reports as we make use of mild organic acids as alternatives to mineral acids. © 2014 Elsevier B.V.
Yallappa S.,Kuvempu University |
Manjanna J.,Rani Channamma University |
Dhananjaya B.L.,Jain University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy | Year: 2015
A green chemistry approach for the synthesis of Au, Ag and Au-Ag alloy nanoparticles (NPs) using the corresponding metal precursors and Jasminum sambac leaves extract as both reducing and capping media, under microwave irradiation, is reported. During the formation, as expected, the reaction mixture shows marginal decrease in pH and an increase in solution potential. The formation of NPs is evident from their surface plasmon resonance (SPR) peak observed at ∼555 nm for Au, ∼435 nm for Ag and ∼510 nm for Au-Ag alloy. The XRD pattern shows fcc structure while the FTIR spectra indicate the presence of plant residues adsorbed on these NPs. Such a bio-capping of NPs is characterized by their weight loss, ∼35% due to thermal degradation of biomass, as observed in TG analysis. The colloidal dispersion of NPs is stable for about 6 weeks. The near spherical shape of NPs (20-50 nm) is observed by FE-SEM/TEM images and EDAX gives the expected elemental composition. Furthermore, these NPs showed enhanced antimicrobial activity (∼1-4-fold increase in zone of inhibition) in combination with antimicrobials against test strains. Thus, the phytosynthesized NPs could be used as effective growth inhibitors for various microorganisms. © 2014 Elsevier B.V. All rights reserved.
Vinoda B.M.,Kuvempu University |
Manjanna J.,Kuvempu University |
Manjanna J.,Rani Channamma University
Applied Clay Science | Year: 2014
Bentonite is used as part of engineered barrier in the geological disposal of high-level nuclear waste (HLW) from nuclear plants. Fe(II)-montmorillonite, Fe(II)-Mt, is a potential altered clay in such a system due to clay mineral interaction with the carbon steel (overpack material) under reducing water chemistry conditions. To understand the long-term integrity of the HLW, the basic studies on Fe(II)-Mt are needed. In this study, we have focused on the synthesis of homoionic Fe(II)-Mt by using weak ferrous complexe for cation-exchange with Na-Mt. We prepared Fe(II)-salicylate by dissolving Fe0 in salicylic acid at 80°C under N2 atmosphere. Dissolution rate constants are in the range of 0.8-1.6×10-3min-1. A colorless Fe(II)-L, was reasonably stable in the inert atmosphere, but was rapidly oxidized in air to a red colored Fe(III)-L (λmax 475nm). The solution redox potential and UV-Vis absorption spectra of these complexes are recorded here. Na-Mt was subjected for ion-exchange reaction with Fe(II)-L to form Fe(II)-Mt. The formation of Fe(II)-Mt was confirmed from the interlayer Fe2+ ions released by interacting with 0.5M H2SO4. The cumulative amount of Fe2+ ions are equivalent to CEC of 1.10meq/g and Fe2+/Fetotal≈ 1. The X-ray diffraction patterns (d001) and infrared spectra also support the formation of Fe(II)-Mt. The cation exchange achieved here was possible through dissociation of Fe(II)-L owing to its intermediate stability constant (log K=6.55), unlike the Fe(III)-L (log K=16.35). We believe the present method is one of the best approaches for obtaining homoionic Fe(II)-Mt. © 2014 Elsevier B.V.
Hosamani S.M.,Rani Channamma University |
Basavanagoud B.,Karnatak University
Match | Year: 2015
The first Zagreb index M1(G) of a graph G is defined as the sum of squares of the degrees of the vertices. This paper presents some new upper bounds for the first Zagreb index.
Lakshmikantha R.,KLE University |
Ayachit N.H.,Rani Channamma University |
Anavekar R.V.,Bangalore University
Journal of Physics and Chemistry of Solids | Year: 2014
Glasses in the compositions (Li2O)25-(BaO) 25-(P2O5)50-x-(V2O 5)x (with x=0.5,1.0,1.5,2.0,2.5, and 3.0 mol%) have been prepared by the conventional melt quenching technique. X-ray powder diffractrogram show broad peaks which conforms glassy nature of the sample. Differential scanning calorimetry (DSC) thermograms show characteristic glass transition temperature (Tg) and it increases with increasing substitution of V2O5 for P2O5. The measured physical parameters like density, refractive index, ionic concentration and electronic polarizability are found to vary linearly with increasing x. Infrared spectra exhibits few bands, which are attributed to (P=O)AS, (P=O)S, (V=O), (P-O-P)AS,P-O-V, (P-O-P)AS ferroelectric domain and O-P-O vibrations. The optical absorption spectra of VO2+ ions in these glasses show three bands and are assigned to the 2B2→ 2E,2B2→ 2B1 and 2B2→ 2A 1 transitions. Electron paramagnetic resonance spectra of all the glass samples exhibit resonance signals characteristic of VO2+ ions. The values of Spin-Hamiltonian parameters indicate that the VO2+ ions are present in octahedral sites with tetragonal compression and belong to C4V symmetry. © 2013 Elsevier Ltd.
Algur S.P.,Rani Channamma University |
Biradar J.G.,Rani Channamma University
Proceedings - IEEE International Conference on Information Processing, ICIP 2015 | Year: 2015
Opinions and attitudes of others highly influence the human behavior and are central to almost all decision making activities which is known as the word-of-mouth effect in shaping decision making. Large amounts of online reviews, the valuable voice of the customer, benefit consumers and product designers. Posting reviews online has become an increasingly popular way for people to express opinions and sentiments towards the products bought or services received. Identifying and analyzing helpful reviews efficiently and accurately to satisfy both current and potential customer's needs have become a critical challenge for market-driven product design. Hence, an efficient and effective Linguistic technique Sentiwordnet and a tool NLTK (Natural Language Tool Kit), Word Count and a method known as Counting method is proposed to find spamicity of the reviews based on the rating consistency and review content. The experimental results shows that the proposed technique has comparatively effective spamicity detection than other technique based on helpfulness votes (rating) and content of the reviews. © 2015 IEEE.
Awati V.B.,Rani Channamma University
Journal of Naval Architecture and Marine Engineering | Year: 2016
The paper presents the semi-numerical solution for the magnetohydrodynamic (MHD) viscous flow due to a shrinking sheet caused by boundary layer of an incompressible viscous flow. The governing three partial differential equations of momentum equations are reduced into ordinary differential equation (ODE) by using a classical similarity transformation along with appropriate boundary conditions. Both nonlinearity and infinite interval demand novel mathematical tools for their analysis. We use fast converging Dirichlet series and Method of stretching of variables for the solution of these nonlinear differential equations. These methods have the advantages over pure numerical methods for obtaining the derived quantities accurately for various values of the parameters involved at a stretch and also they are valid in much larger parameter domain as compared with HAM, HPM, ADM and the classical numerical schemes. © 2016 ANAME Publication. All rights reserved.