756 research outputs found

    Evidence of Conformational Changes in Adsorbed Lysozyme Molecule on Silver Colloids

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    In this article, we discuss metal-protein interactions in the Ag-lysozyme complex by spectroscopic measurements. The analysis of the variation in relative intensities of SERS bands reveal the orientation and the change in conformation of the protein molecules on the Ag surface with time. The interaction kinetics of metal-protein complexes has been analyzed over a period of three hours via both Raman and absorption measurements. Our analysis indicates that the Ag nanoparticles most likely interact with Trp-123 which is in close proximity to Phe-34 of the lysozyme molecule.Comment: 15 pages, 6 figure

    Carboxylated acyclonucleosides: synthesis and RNase A inhibition

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    Strategically designed carboxylated acyclonucleosides have been probed as a new class of RNase A inhibitors. Several experimental and theoretical studies have been performed to compile relevant qualitative and quantitative information regarding the nature and extent of inhibition. The inhibition constant (Ki) values were determined using a UV-based kinetics experiment. The changes in the secondary structure of the enzyme upon binding with the inhibitors were obtained from circular dichroism studies. The binding constants for enzyme-inhibitor interactions were determined with the help of fluorescence spectroscopy. Docking studies were performed to reveal the possible binding sites of the inhibitors within the enzyme. The cytosine analogues were found to possess better inhibitory properties in comparison to the corresponding uracil derivatives. An increment in the number of carboxylic acid groups (-COOH) in the inhibitor backbone was found to result in better inhibition

    A docking interaction study of the effect of critical mutations in ribonuclease a on protein-ligand binding

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    Enzymes with ribonucleolytic activity play a pivotal role in gene expression and cellular homeostasis by altering the levels of cellular RNA. Ribonuclease A has been the most well studied of such enzymes whose histidine residues (His12 and His119) play a crucial role in the catalytic mechanism of the protein. The ligands chosen for this study, 2′CMP and 3′CMP, act as competitive substrate analog inhibitors of this enzyme. Using molecular graphics software freely available for academic use, AutoDock and PyMol, we demonstrate that substitution of either histidine residue by alanine causes marked changes in the distances between these critical residues of the enzyme. The ligands in the docked conformation (particularly on mutation of His119 to Ala) compensate for the altered free energy and hydrogen bonding abilities in these new protein‐ligand complexes

    A spectroscopic study of the interaction of the antioxidant naringin with bovine serum albumin

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    The interaction of naringin with bovine serum albumin has been performed using fluorescence, circular dichroism and fourier transform infrared spectroscopy in 20 mM phosphate buffer of pH 7.0 as well as molecular docking studies. The changes in enthalpy (ΔH°) and entropy (ΔS°) of the interaction were found to be +18.73 kJ/mol and +143.64 J mol-1 K-1 respectively, indicating that the interaction of naringin with bovine serum albumin occurred mainly through hydrophobic interactions. Negative values of free energy change (ΔG°) at different temperatures point toward the spontaneity of the interaction. Circular dichroism studies reveal that the helical content of bovine serum albumin decreased after interaction with naringin. According to the Förster non-radiative energy transfer theory the distance between Trp 213 residue and naringin was found to be 3.25 nm. Displacement studies suggest that naringin binds to site 1 (subdomain IIA) of bovine serum albumin (BSA) which was also substantiated by molecular docking studies

    A comparative study of interaction of tetracycline with several proteins using time resolved anisotropy, phosphorescence, docking and FRET

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    A comparative study of the interaction of an antibiotic Tetracycline hydrochloride (TC) with two albumins, Human serum albumin (HSA) and Bovine serum albumin (BSA) along with Escherichia Coli Alkaline Phosphatase (AP) has been presented exploiting the enhanced emission and anisotropy of the bound drug. The association constant at 298 K is found to be two orders of magnitude lower in BSA/HSA compared to that in AP with number of binding site being one in each case. Fluorescence resonance energy transfer (FRET) and molecular docking studies have been employed for the systems containing HSA and BSA to find out the particular tryptophan (Trp) residue and the other residues in the proteins involved in the binding process. Rotational correlation time (θc) of the bound TC obtained from time resolved anisotropy of TC in all the protein-TC complexes has been compared to understand the binding mechanism. Low temperature (77 K) phosphorescence (LTP) spectra of Trp residues in the free proteins (HSA/BSA) and in the complexes of HSA/BSA have been used to specify the role of Trp residues in FRET and in the binding process. The results have been compared with those obtained for the complex of AP with TC. The photophysical behaviour (viz., emission maximum, quantum yield, lifetime and θc) of TC in various protic and aprotic polar solvents has been determined to address the nature of the microenvironment of TC in the protein-drug complexes

    Prediction-based protein engineering of domain I of Cry2A entomocidal toxin of Bacillus thuringiensis for the enhancement of toxicity against lepidopteran insects

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    Issues relating to sustenance of the usefulness of genetically modified first generation Bt crop plants in the farmer’s field are of great concern for crop scientists. Additional biotechnological strategies need to be in place to safeguard the possibility for yield loss of Bt crop by other lepidopteran insects that are insensitive to the Cry1A toxin, and also against the possibility for emergence of resistant insects. In this respect, Cry2A toxin has figured as a prospective candidate to be the second toxin to offer the required protection along with Cry1A. In the present study, the entomocidal potency of Cry2A toxin was enhanced through knowledge-based protein engineering of the toxin molecule. Deletion of 42 amino acid residues from the N-terminal end of the peptide followed by the replacement of Lys residues by nonpolar amino acids in the putative transmembrane region including the introduction of Pro resulted in a 4.1–6.6-fold increase in the toxicity of the peptide against three major lepidopteran insect pests of crop plants

    Sinteza izoamilnog acetata pomoću lipaze u sustavu bez otapala s vinilnim acetatom kao donorom acila

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    Synthesis of isoamyl acetate, a flavour ester extensively used in food industry, has been carried out in a solvent-free system. In the present study, an attempt has been made to enhance the isoamyl acetate synthesis yield by transesterification of isoamyl alcohol with vinyl acetate using immobilized Rhizopus oryzae NRRL 3562 lipase. In the present synthesis, substrates had no inhibitory effect on immobilized lipase. The effects of various reaction parameters on isoamyl acetate synthesis were studied and maximum conversion was achieved at 16 % (by mass per volume) of immobilized lipase, 40 °C and 200 rpm. Under these conditions, 8-hour reaction time was sufficient to reach a high ester conversion of 95 % with 0.5 mol/L of isoamyl alcohol. The structure of the transesterified product was confirmed by infrared and nuclear magnetic resonance spectroscopic studies. Immobilized lipase had Km and vmax values of 306.53 mmol/L and 99 µmol/(h·g) respectively, for isoamyl acetate synthesis in a solvent-free system.Provedena je sinteza izoamilnog acetata, estera koji se često koristi kao pojačivač okusa u prehrambenoj industriji, u sustavu bez otapala. Pokušao se poboljšati prinos izoamilnog acetata transesterifikacijom s vinilnim acetatom pomoću imobilizirane lipaze izolirane iz soja Rhizopus oryzae NRRL 3562. Pri tome supstrat nije inhibirao imobiliziranu lipazu. Istražen je utjecaj različitih parametara reakcije na sintezu te ustanovljeno da je maksimalna pretvorba postignuta sa 16 % (m/V) imobilizirane lipaze pri 40 °C i 200 rpm. Pri tim je uvjetima nakon 8 sati postignuta 95 %-tna konverzija s 0,5 mol/L izoamilnog acetata. Struktura produkta utvrđena je infracrvenom spektroskopijom i nuklearnom magnetskom rezonancijom. Imobilizirana lipaza imala je Km vrijednost od 306,53 mmol/L i υmax od 99 µmol/(h∙g)

    Biosorption of Acid dye by Jackfruit Leaf Powder: Isotherm, kinetics and Response surface methodology studies

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    A green adsorbent derived from Jackfruit leaf powder (JLP) was used to eliminate Acid Yellow 99 (AY 99) dye from an aqueous medium in this study. We checked the effect of pH, biomass dosage, and temperature (process parameters) on the adsorption potential of AY 99 was explored using the CCD model integrating the RSM approach. At a pH of 2.5, biosorbent dosage of 4 gL-1, and a 30°C temperature, maximum removal was preferred. ANOVA was incorporated to observe the importance of experimental variables and their interactions. The solution pH (A) and biomass dose (C) had the greatest effects on the decolorization of AY 99, according to the findings. ANOVA was used to identify the most important factors, which included two independent variables (A and C) and two quadratic model terms (A2 and C2). The kinetic data were effectively interpreted using a pseudo 2nd order with film diffusion model combination, indicating the chemisorptions phenomenon. Following the model of Langmuir isotherm, the utmost capacity for adsorption was determined to be 418.15 mg g-1 in terms of initial dye concentration. The findings of the maximum adsorption capacity showed that JLP could be employed as a useful adsorbent to eliminate AY 99 from its aqueous medium