scholarly journals Stabilizing Effect of Various Polyols on the Native and the Denatured States of Glucoamylase

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Mohammed Suleiman Zaroog ◽  
Habsah Abdul Kadir ◽  
Saad Tayyab
Keyword(s):  
Aspergillus Niger ◽  
Sulfonic Acid ◽  
Thermal Denaturation ◽  
Structural Changes ◽  
Enzyme Stability ◽  
Tertiary Structures ◽  
Fluorescence Characteristics ◽  
Stabilizing Effect ◽  
Denatured States ◽  
Denaturation Curve

Different spectral probes were employed to study the stabilizing effect of various polyols, such as, ethylene glycol (EG), glycerol (GLY), glucose (GLC) and trehalose (TRE) on the native (N), the acid-denatured (AD) and the thermal-denatured (TD) states ofAspergillus nigerglucoamylase (GA). Polyols induced both secondary and tertiary structural changes in the AD state of enzyme as reflected from altered circular dichroism (CD), tryptophan (Trp), and 1-anilinonaphthalene-8-sulfonic acid (ANS) fluorescence characteristics. Thermodynamic analysis of the thermal denaturation curve of native GA suggested significant increase in enzyme stability in the presence of GLC, TRE, and GLY (in decreasing order) while EG destabilized it. Furthermore, CD and fluorescence characteristics of the TD state at 71°C in the presence of polyols showed greater effectiveness of both GLC and TRE in inducing native-like secondary and tertiary structures compared to GLY and EG.

Thermo-Optical Properties of Perfluorinated Sulfonic Acid Membranes: An Investigation of Hydration Based on Absorption Spectra

2017 ◽  
Vol 71 (11) ◽  
pp. 2504-2511 ◽  
Author(s):  
Daniele T. Dias ◽  
Guy Lopes ◽  
Tales Ferreira ◽  
Ivanir L. Oliveira ◽  
Caroline D. Rosa
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Water Retention ◽  
Structural Changes ◽  
Optical Characterization ◽  
Scanning Calorimetry ◽  
Experimental Procedure ◽  
Nafion Membranes ◽  
Perfluorinated Sulfonic Acid

The Nafion membranes are widely used in electrochemical applications such as fuel cells, chlor-alkali cells, and actuators–sensors. In this work, the thermal-optical characterization of Nafion in acid form was performed by photoacoustic spectroscopy, thermogravimetry, and differential scanning calorimetry. In the experimental procedure three distinct hydration levels were considered: (1) pristine membrane (λ ≅ H2O/–SO3H ≅ 5.6); (2) swelling process (λ ≅ 17.4); and (3) drying at controlled room temperature after swelling process (λ ≅ 6.5). The discovered behaviors showed significant irreversible structural changes induced by water retention in the membrane. These structural changes depend on the water population present in the clusters and also affect the directional thermal diffusivity of the membrane irreversibly.

scholarly journals Characterization of Aspergillus Niger 65i6 lipase from solid-state fermentation using Jatropha seed cake medium

2017 ◽  
Vol 20 (2) ◽  
pp. 108 ◽  
Author(s):  
Chusnul Hidayat ◽  
Sari Darmasiwi ◽  
Maulina Nurikasari ◽  
Muhammad Nur Cahyanto
Keyword(s):  
Solid State ◽  
Aspergillus Niger ◽  
Solid State Fermentation ◽  
Jatropha Curcas ◽  
Enzyme Stability ◽  
Water Concentration ◽  
Lipase Production ◽  
Seed Cake ◽  
Effects Of Ph ◽  
Jatropha Seed

Jatropha curcas seed cake contains a high amount of protein, and consequently has very high potentialas a medium for lipase production. The objective of this research was to characterize lipase from Aspergillusniger 6516, which was produced by solid-state fermentation on Jatropha curcas seed cake as the medium. The effects of pH and temperature on enzyme activity were evaluated, along with substrate specifcity and enzyme stability. Fermentation was performed at a water concentration of 63% and temperature of 30 °C for 7 days. The results showed that the optimum pH and temperature for Aspergillus niger 6516 lipase activities were 8.0 and 40 °C, respectively. The lipase had the substrate specifcity to hydrolyze long-chain fatty acids and was stable in polar organic solvents. The lipase had a molecular weight, Km and vmax about 19 kDa, 0.27 µmol/ml, and 52.63 µmol/ml/min, respectively. The results also suggested that the produced lipase from Aspergillus niger 6516 was an alkaline lipase. Based on these results, we conclude that Jatropha seed cake is a suitable medium for lipase production.

scholarly journals Computationally designed GPCR quaternary structures bias signaling pathway activation

2021 ◽  
Author(s):  
Justine S Paradis ◽  
Xiang Feng ◽  
Brigitte Murat ◽  
Robert E Jefferson ◽  
Martyna E Szpakowska ◽  
...  
Keyword(s):  
G Protein ◽  
Intracellular Signaling ◽  
Structural Changes ◽  
Tertiary Structures ◽  
Cellular Processes ◽  
Pathway Activation ◽  
Biased Signaling ◽  
Vasopressin Receptors ◽  
State Models ◽  
Quaternary Structures

Communication across membranes controls critical cellular processes and is achieved by receptors translating extracellular signals into selective cytoplasmic responses. While receptor tertiary structures can now be readily characterized, receptor associations into quaternary structures are very challenging to study and their implications in signal transduction remain poorly understood. Here, we report a computational approach for predicting membrane receptor self-associations, and designing receptor oligomers with various quaternary structures and signaling properties. Using this approach, we designed chemokine receptor CXCR4 dimers with reprogrammed stabilities, conformations, and abilities to activate distinct intracellular signaling proteins. In agreement with our predictions, the designed CXCR4s dimerized through distinct conformations and displayed different quaternary structural changes upon activation. Consistent with the active state models, all engineered CXCR4 oligomers activated the G protein Gi, but only a few specific dimer structures also recruited β-arrestins. Overall, we demonstrate that quaternary structures represent an important unforeseen mechanism of receptor biased signaling and reveal the existence of a conformational switch at the dimer interface of several G protein-coupled receptors including CXCR4, mu-Opioid and type-2 Vasopressin receptors that selectively control the activation of G proteins vs β-arrestin-mediated pathways. The approach should prove useful for predicting and designing receptor associations to uncover and reprogram selective cellular signaling functions.

scholarly journals Role of non-compatible osmolytes in the stabilization of proteins during heat stress

1998 ◽  
Vol 329 (1) ◽  
pp. 137-143 ◽  
Author(s):  
Vikas RISHI ◽  
Farah ANJUM ◽  
Faizan AHMAD ◽  
Wolfgang PFEIL
Keyword(s):  
Thermal Denaturation ◽  
Rnase A ◽  
Transition Curve ◽  
Evolutionary Perspective ◽  
Inhibitory Effects ◽  
Absorption Coefficients ◽  
Ph Values ◽  
Stabilizing Effect ◽  
Compatible Osmolytes

This study is a systematic attempt to understand the roles of non-compatible osmolytes, i.e. solutes that have inhibitory effects on enzymes, in the stabilization of proteins against denaturing stress. Thermal denaturation of RNase A, holo-α-lactalbumin, apo-α-lactalbumin, lysozyme and metmyoglobin in the absence and presence of various concentrations of free basic amino acids was studied by observing changes in the absorption coefficients of these proteins. It has been observed that arginine and histidine destabilize all proteins in terms of the midpoint of the transition curve and Gibbs energy change on denaturation. Study of the heat-induced denaturation of the proteins in the presence of various concentrations of arginine at different pH values demonstrated that arginine binds to the denatured molecules. In contrast with the effect of arginine and histidine on protein stability, it was observed that the effect of lysine on proteins stability is unpredictable, i.e. it may have a stabilizing effect, no effect or a destabilizing effect on proteins during denaturing stress. The results of this study are considered from an evolutionary perspective.

Strategy and Tactics in the Raman Spectroscopy of Biomolecules

1977 ◽  
Vol 31 (3) ◽  
pp. 187-194 ◽  
Author(s):  
Richard C. Lord
Keyword(s):  
Molecular Structure ◽  
Aqueous Solution ◽  
Raman Spectroscopy ◽  
Thermal Denaturation ◽  
Structural Changes ◽  
Molecular Geometry ◽  
X Ray Diffraction ◽  
New Developments ◽  
X Ray ◽  
New Correlation

The strategic bases for the application of Raman spectroscopy to the problems of molecular biology and the tactics used in exploiting them are examined and discussed with the help of specific examples. The correlation of vibrational frequencies and intensities with molecular geometry is illustrated by several group frequencies of importance in the analysis of the Raman spectra of proteins, including those of the disulfide and amide groups. A new correlation between the amide-III frequency and peptide geometry is proposed and utilized to follow the reversible thermal denaturation of the enzyme ribonuclease. How other physical techniques may be combined with Raman methods is shown by the comparison of the Raman spectrum of a crystalline transfer ribonucleic acid, whose molecular structure is known from x-ray diffraction, with the spectra of the same substance in aqueous solution under different conditions of ionic strength, pH, and temperature. From the quantitative variation of the spectra the structural changes produced by temperature are evaluated. Possible improvements and new developments in the strategy and tactics of Raman spectroscopy are considered briefly.

Effect of deglycosylation of N-linked sugar chains on glucose oxidase from Aspergillus niger

1989 ◽  
Vol 67 (8) ◽  
pp. 460-464 ◽  
Author(s):  
Kaoru Takegawa ◽  
Kentaro Fujiwara ◽  
Shojiro Iwahara ◽  
Kenji Yamamoto ◽  
Tatsurokuro Tochikura
Keyword(s):  
Aspergillus Niger ◽  
Glucose Oxidase ◽  
Ammonium Sulfate ◽  
Trichloroacetic Acid ◽  
Enzyme Stability ◽  
High Solubility ◽  
Catalytic Activities ◽  
Carbohydrate Depletion ◽  
Sugar Chains

Endo-β-N-acetylglucosaminidase from Flavobacterium sp. released about 30% of the N-linked sugar chains from the glucose oxidase of Aspergillus niger. To elucidate the role of the carbohydrate moiety, the enzymatic properties of native and carbohydrate-depleted glucose oxidases were compared. It was found that their catalytic activities and thermal and pH stabilities were identical. However, the carbohydrate-depleted glucose oxidase was more rapidly precipitated by the addition of trichloroacetic acid and ammonium sulfate than the native enzyme. These results show that the N-linked sugar chains of the glucose oxidase contributed to the high solubility of the enzyme in water.Key words: glucose oxidase, Aspergillus niger, carbohydrate depletion, endo-β-N-acetylglucosaminidase, enzyme stability.

scholarly journals Response surface methodology for optimal immobilization of Aspergillus niger ATCC 1015 lipase by adsorption method

2016 ◽  
Vol 4 (1) ◽  
pp. 56 ◽  
Author(s):  
Michael Osho ◽  
Tope Popoola ◽  
Tolulope Adeleye ◽  
Christianah Adetunji
Keyword(s):  
Response Surface Methodology ◽  
Aspergillus Niger ◽  
Response Surface ◽  
Enzyme Stability ◽  
Immobilized Lipase ◽  
Crosslinking Agent ◽  
Lipase Production ◽  
Full Potential ◽  
Enzyme Loading ◽  
Adsorption Method

<p>Optimization of Vegetable Sponge (<em>Luffa aegyptiaca</em>) (VS) - immobilization conditions of <em>Aspergillus niger</em> ATCC 1015 lipase on Solid State Fermentation (SSF) was carried out using Response Surface Methodology (RSM). Four independent variables (temperature, pH, enzyme loading and enzyme stability) were optimized using Central Composite Design of RSM for lipase production in a solid rice bran-physic nut cake medium. The optimal immobilization conditions obtained were 45 °C, pH 7.0, 2.5% (w/v) enzyme loading and 32.5% (v/v) enzyme stability (using glutaraldehyde as crosslinking agent) resulted into lipase activity of 98.6 Ug<sup>-1</sup>. The result demonstrates the potential application of vegetable sponge under SSF system in immobilizing lipase, thus contributed to efficiency of the use of this biomatrix as an immobilizing agent. The statistical tools employed predicted the optimal conditions for the production of the immobilized lipase thus revealing the full potential of the support.</p>

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