Papers by Keyword: Conformation

Abstract: The study of the intermolecular interactions is important to explain the phenomenon occurred on the human body. One of the most important processes that can be studied is the interaction of the peptide with metal ions. In this study, a computational approach was harnessed to predict the interaction and the changes in peptide’s conformation between Cys-Ala peptide which is one of the important amino acids in e-cadherin with some of alkaline earth metal ions. Cys-Ala peptide (Ac-CA-NH₂) was used as a molecular model in this calculation. All the molecular structure involved in the interaction was optimized by density functional theory DFT/M06-2X, and basis set 6-31G** to obtain minimum energy, the interaction energies, and the changes in its conformation. The results showed that the interaction energy of Ac-CA-NH₂ with alkaline earth metal ions from top to bottom based on the Periodic table is getting higher in a row. The interaction energies of Ac-CA-NH₂ with Be²⁺, Mg²⁺ and Ca²⁺ ions are -2.393kcal, -17.489 kcal, and -25.938 kcal respectively. These energies were obtained from the interaction of the peptide with ions in a water solvent. The changes in the peptide's bond length and dihedral angle indicate a conformational change in the Cys-Ala peptide, but it still maintains the trans conformation in its peptide bonds. The results and evaluations of this study may be used for further research considerations and may be applied to enzymes or other peptides that have the Cys-Ala residue.

Abstract: The author adopts Monte Carlo compute method to simulate the linear polymer chain lattice model in multiple chain systems of different volume fraction Φ while chain length n=50, and makes a research on the variational situation of the size (measured with the mean-square end-to-end distance <R²> and the mean-square radius of gyration <S²>), shape (measured with the mean asphericity factor ) with changing of the interaction energy between solvent molecule and polymer chain segment molecule ε_PS. Results indicate <R²>, <S²> and have the changing rules that they become small with the increase of the ε_PS.

Abstract: The author adopts Monte Carlo compute method to simulate the linear polymer chain lattice model in multiple chain systems of chain length n=20, 50, 100 while the volume fraction Φ=0.125, and makes a research on the variational situation of the size (measured with the mean-square end-to-end distance 2> and the mean-square radius of gyration 2>), shape (measured with the mean asphericity factor ) with changing of the interaction energy between solvent molecule and polymer chain segment molecule ε_PS. Results indicate 2>, 2> and have the changing rules that they become small with the increase of the ε_PS

Abstract: In this article, investigation on the effect of microwave treatment on the catalysis of papain had been carried out. According to the results, the thermal effect was found to be the main factor to cause inactivation of enzyme. The kinetic parameters and the fluorescence spectroscopy implied that the microwave processing had changed the conformation of the enzyme molecules and thus affected its activity. The results also showed that the microwave treatment had not changed the optimum pH value of the enzyme catalysis, and the inactivation rate of the enzyme was inversely proportional to the concentration of the enzyme. In addition, a certain concentration of the disodium EDTA media had been found to effectively protect the enzyme activity in microwave processing.

Abstract: Solid-state nuclear magnetic resonance (NMR) spectroscopy has emerged as a relatively facile technique for the characterization of multi-component polymer systems. In particular, it has emerged to be a useful technique for probing the molecular structure, conformation and dynamics of polymer chains at interfaces between phases in various types of multi-component polymer systems including nanomaterials. The usefulness of solid-state NMR stems from its ability to non-destructively probe not only the bulk of the polymer, but moreover its ability to selectively probe the interface or interphase. As such, the technique has been extensively exploited in the study of multi-component polymer systems. To achieve ¹³C spectral resolution in the solid-state magic angle spinning (MAS), dipolar decoupling and cross-polarization are applied which enables the study of individual carbon atoms directly with excellent resolution and sensitivity. Some examples of applications of this technique to the study of multiphase aliphatic polyesters are reviewed herein.

Abstract: In order to study the sterilization mechanism of pulsed electric fields（PEF） on microorganisms and the interaction between PEF conditions and cell membrane composed of phospholipids, the authors studied the phospholipid molecular conformation changes under various electric fields strength treatments using Raman spectra. It was demonstrated from the Raman spectra that there was little influence of PEF on the conformation of O-C-C-N⁺ backbone in the choline group of phospholipid. The intensity ratios of I₁₀₉₆/I₁₀₆₂ and I₁₀₉₆/I₁₁₂₆ represented the gauche/ trans ratioof C-C vibrations, but the first was increased directly, while the other one was increased firstly and then decreased with increasing electric fields strengths but the ratio was still higher than that of the control sample. I₂₈₈₅/I₂₈₅₀ represeted order/ disorder of chain-chain interactions which was decreased with increasing electric fields strengths. It was indicated that the intermolecular disordering in hydrocarbon chain of the lipid lattice was increased and the membrane fluidity was enhanced after PEF treatments.

Abstract: The activity of Horseradish Peroxidase (HRP) was enhanced with different strength of high voltage electric field. The results have shown that Ultraviolet-Visible spectra have been changed obviously. Experimental results indicate that the conformation of HRP can be changed by electric field. The study also showed that the activity index of HRP was increased by the certain strength of electric field. The activity index increase possibly was caused by the conformation variations of HRP. The result of this study has important meaning to explain the macroscopical electrostatic biological effects.

Abstract: N-(2-pyridylmethyl)-L-phenylalanine methyl ester was synthesized in our laboratory，and the title compound was synthesized by the reaction of N-(2-pyridylmethyl)-L-phenylalanine methyl ester and Zinc acetate dehydrate. Bis(L-α-N-(2-pyridylmethy)phenylalaninato-N, N', O)-Zinc(II) trihydrate was prepared and structurally characterized by X-ray diffraction. It crystallizes in orthorhombic, space group P2₁2₁2 with a= 15.0928 (8), b = 16.4209 (6), c = 5.9930 (3) Å, V = 1485.29 (12) ų, Z = 2, M_r = 630.00, D_x = 1.409 g/cm³, μ = 0.88 mm^-1, F(000) = 660, R_int = 0.0205, R = 0.028 and wR = 0.059 for 2943 observed reflections with I > 2σ(I). It is a mononuclear discrete structure. The zinc atom coordinates with two oxygen and four nitrogen atoms from two ligands in a distorted octahedral geometry, with the oxygen atom from the carboxylate, two of nitrogen atoms from NH parts and the other two nitrogen atoms from the pyridine ring. With three free water molecules, the present structure has a network of hydrogen bonds.

Abstract: In this paper, the relativity on the granularity with different mesh of konjac glucomannan (KGM) and molecular dimension was discussed. Laser particle size analyzer, laser light scattering and digital polarimeter were used to analyze the granularity distribution, molecular characteristics and polarity of KGM. The results showed that the granularity of KGM after gradient refining was gradually decreased and KGM was well dispersed in ethanol(D50=13.11μm).The Mw of KGM was gradually decreased with its granularity decrease and its molecular conformation was from globular to linear structure. The space asymmetry of KGM at 80-100 meshes was minimum and its polarity was maximum. The primary establishment on the relativity offered the references to KGM theoretical research and practical application.

Abstract: A series of poly(acrylic acid)(PAA)-graft-polypropylene membranes was prepared by UV-irradiation.The water flux of original PP membrane shows independence on pH and a linear increase with the rise of operating pressure. While the grafted membranes present great sensitivity to pH and a nonlinear relationship with operating pressure. As pH rises, grafted membranes are observed a rapid drop in flux since grafting PAA chains change from coiled to extended and then cause the decrease of pore size. It is evaluated by the change ratio of pore size that pH-sensitivity of grafted membranes increase with the rise of grafting degree till 17%. Furthermore, during Cross-flow microfiltration, the grafting chains on membrane surface tend to be bent at high operating pressure, so that membrane pores are partly blocked to cause a nonlinear rise of flux with operating pressure. In a conclusion, water permeability of grafted membranes greatly rely on the conformational change of grafting chains. These conformation alteration caused by pH or pressure may provide a new approach to control membrane filtration behaviors.