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Macromolecules of Polyamic Acids and Polyimides
Published in Michael I. Bessonov, Vladimir A. Zubkov, Polyamic Acids and Polyimides, 2020
Determination of the degree of hindrance to rotation requires the experimental determination of 〈h2〉/p and calculation of 〈hf2〉/p The latter value refers to the model chain comprising p linear units of length l which are joined at the bond angle (π — γ) and rotate freely. It can be calculated by using conformational statistics techniques with the macromolecule’s real chemical structure taken into account and X-ray data being used. Birshtein has discussed this problem for polymer chains having planar cyclic groups joined both directly and by means of bridge groups.21 Aromatic polyamic acids and polyimides are just such chains. The possible conformational set and flexibility of these chains depend on the structure and flexibility of the bridge groups. The conformations and flexibility affect, in their turn, the characteristics of chain packing in the block polymer which is also affected by strong intermolecular interactions between the planar rings.
Separating Signals from the Noise
Published in Perry D. Haaland, Experimental Design in Biotechnology, 2020
Among the primary concerns in the degradation of the antigen, antibody, enzymes, and antibody-enzyme conjugates included in enzyme-immunoassay materials are hydrolysis,dissociation,conformational changes, andclipping. Hydrolysis is a chemical process of decomposition which involves splitting a bond and adding the elements of water. Dissociation involves the loss of binding between the trapping antibody and the solid support or the loss of binding between the antibody and enzyme in the conjugate. Conformational changes in a protein involve a change in its shape or configuration which affects its function. Conformational changes may occur from denaturation or from binding to other molecules. As a consequence of a conformational change, an antibody may no longer recognize the target antigen or an enzyme may no longer react with the substrate to produce the measurable product. Clipping involves the loss of a segment from the protein which results in a loss of functionality.
Application of Bioresponsive Polymers in Drug Delivery
Published in Deepa H. Patel, Bioresponsive Polymers, 2020
Manisha Lalan, Deepti Jani, Pratiksha Trivedi, Deepa H. Patel
Smart polymers which are sensitive to the change in temperature and modify their microstructural features are the most commonly used and most safe polymers in drug administration systems. Thermo-responsive polymers exhibit these temperature-sensitive characteristics by striking a very sensitive balance between the hydrophobic and the hydrophilic groups. A minor change in the temperature can create new adjustments and alter structural conformations. The most common monomers are N-alkyl substituted poly(acrylamides), especially the poly(N-isopropyl acrylamide) (PNIPAAM) which undergoes a sharp phase transition at 32°C is the most widely explored polymer. The structural alterations are driven by entropic effects. The interest in PNIPAAM for drug delivery is by virtue of its safety profile and LCST close to body temperature. The transition temperature can be further adjusted by varying the alkyl part or upon copolymerization with other monomers [45].
Bio-conversion of whey lactose using enzymatic hydrolysis with β-galactosidase: an experimental and kinetic study
Published in Environmental Technology, 2022
K. Bella, Sridhar Pilli, P. Venkateswara Rao, R. D. Tyagi
Figure 2(A, B, C) illustrates the interactions between the independent variables and response variables. 3-D surface plots were generated by using the response surface method. Figure 2(A) shows change in lactose hydrolysis rates concerning temperature and pH. Initially, an increase in temperature caused an increase in lactose hydrolysis rates. Temperature changes the conformation of the enzyme. This protein has a sensitive temperature profile, due to which the activity decreases after 45°C and almost stops the activity at approximately 60°C. As substrate binding is so specific, the amino acids forming the active site for the same enzyme are highly conserved from one species to another. Upon protein conformation at optimum temperature, substrates cannot adhere to enzyme surfaces that have been altered [44]. Denaturation of the enzyme at 45°C may have occurred following the enzyme conformation. As a result, the lactose hydrolysis rate didn’t differ much beyond 45°C. Similarly, with an increase in pH, lactose hydrolysis rates are also increased. Beyond 6.5, the activity of enzyme gets reduced. Figure 2(A) shows maximum hydrolysis at pH 4.5 and temperature 40°C.
Kinetics, detergent compatibility and feather-degrading capability of alkaline protease from Bacillus subtilis AKAL7 and Exiguobacterium indicum AKAL11 produced with fermentation of organic municipal solid wastes
Published in Journal of Environmental Science and Health, Part A, 2020
Tanvir Hossain Emon, Al Hakim, Diptha Chakraborthy, Farhana Rumzum Bhuyan, Asif Iqbal, Mahmudul Hasan, Toasin Hossain Aunkor, Abul Kalam Azad
When temperature increases, it can cause conformational change or even denaturation of the enzyme which lowers the effectiveness of the enzyme. For this reason, the enzyme-catalyzed reaction may show more complex temperature dependence.[44] The alkaline protease activity from B. subtilis and E. indicum isolates is reduced above 55 and 50 °C, respectively, suggesting the thermal inactivation of the enzyme above these temperatures. Therefore, the activation energy (Ea) for the hydrolysis of azocasein was calculated at temperature 20–55 and 20–50 °C for alkaline protease from B. subtilis and E. indicum isolates, respectively by using Arrhenius plot. The Arrhenius plots (Figure 4) for the alkaline protease from both bacteria demonstrated a straight line variation with temperature increment, suggesting that the protease from both sources might have a solitary conformation up to the changing temperature.[45] The comparatively low Ea of the alkaline protease from B. subtilis isolate suggests that it needs less energy to form activated azocasein complex compared to the alkaline protease from E. indicum isolate.
Synthesis of 1,1′-(2,6-dihydroxy-2,6-dimethyl-3,7-dioxabicyclo [3.3.1]nonane-1,5-diyl)diethanone dihydrate: crystal structure and quantitative analysis of molecular interaction via molecular electrostatic potential and Hirshfeld surface analysis
Published in Phase Transitions, 2018
Debnath Saha, Soumen Ghosh, Shyamapada Shit
The molecular view of compound (1) with the atom numbering scheme is shown in Figure 1. The compound consists of a 3,7-dioxa-bicyclo[3.3.1]nonane system [C1 … C7, O1, O4] with di-substituted acetaldehyde groups at C2 and C5 and two hydroxyl and two methyl groups at C1, C4 positions. Structural analysis reveals that the title compound lies on a centre of inversion at the C7 atom with two dihydropyran moieties [A(C1, C2, C5, C6, C7, O1) and B(O4, C3, C2, C7, C5, C4)] adopting chair conformation with ring puckering parameters [55] Q = 0.592(2) Å, ϕ = 156.8(14)° and θ = 10.1(2)° for ring A and Q = 0.601(2) Å, θ = 171.2(2)°, ϕ = 42.3(2)° for ring B. Bond distances and bond angles for (1) are consistent with the analogous structures reported in the literature [33]. In the bicyclononane moiety, the C–C and C–O bond distances are lying in the ranges of 1.533(3)–1.562(3) Å and 1.429(3)–1.436(3) Å, respectively. The terminal C–C bond distances in the range 1.486(3)–1.518(3) Å agree well with the corresponding values reported in other [3.3.1] nonane derivatives [30,33]. A comparison of the molecular conformations as derived from quantum mechanical (solid-state DFT) calculation and X-ray structure analysis shows that the theoretically determined structure agreed well with the corresponding X-ray analysed structure, which probably indicates the stable conformation of the compound. The rms deviations of geometrically optimized bond lengths and bond angles from the corresponding crystallographically determined values are 0.03 Å and 2.8° as found in (1).