A threefold approach including quantum chemical, molecular docking and molecular dynamic studies to explore the natural compounds from Centaurea jacea as the potential inhibitors for COVID-19 / Uma abordagem tríplice incluindo química quântica, docking molecular e estudos dinâmicos moleculares para explorar os compostos naturais de Centaurea jacea como inibidores potenciais para Covid-19

Abstract In the current report, we studied the possible inhibitors of COVID-19 from bioactive constituents of Centaurea jacea using a threefold approach consisting of quantum chemical, molecular docking and molecular dynamic techniques. Centaurea jacea is a perennial herb often used in folk medicines of dermatological complaints and fever. Moreover, anticancer, antioxidant, antibacterial and antiviral properties of its bioactive compounds are also reported. The Mpro (Main proteases) was docked with different compounds of Centaurea jacea through molecular docking. All the studied compounds including apigenin, axillarin, Centaureidin, Cirsiliol, Eupatorin and Isokaempferide, show suitable binding affinities to the binding site of SARS-CoV-2 main protease with their binding energies -6.7 kcal/mol, -7.4 kcal/mol, -7.0 kcal/mol, -5.8 kcal/mol, -6.2 kcal/mol and -6.8 kcal/mol, respectively. Among all studied compounds, axillarin was found to have maximum inhibitor efficiency followed by Centaureidin, Isokaempferide, Apigenin, Eupatorin and Cirsiliol. Our results suggested that axillarin binds with the most crucial catalytic residues CYS145 and HIS41 of the Mpro, moreover axillarin shows 5 hydrogen bond interactions and 5 hydrophobic interactions with various residues of Mpro. Furthermore, the molecular dynamic calculations over 60 ns (6×106 femtosecond) time scale also shown significant insights into the binding effects of axillarin with Mpro of SARS-CoV-2 by imitating protein like aqueous environment. From molecular dynamic calculations, the RMSD and RMSF computations indicate the stability and dynamics of the best docked complex in aqueous environment. The ADME properties and toxicity prediction analysis of axillarin also recommended it as safe drug candidate. Further, in vivo and in vitro investigations are essential to ensure the anti SARS-CoV-2 activity of all bioactive compounds particularly axillarin to encourage preventive use of Centaurea jacea against COVID-19 infections.

Resumo No presente relatório, estudamos os possíveis inibidores de Covid-19 de constituintes bioativos de Centaurea jacea usando uma abordagem tripla que consiste em técnicas de química quântica, docking molecular e dinâmica molecular. Centaurea jacea é uma erva perene frequentemente usada em remédios populares de doenças dermatológicas e febre. Além disso, as propriedades anticâncer, antioxidante, antibacteriana e antiviral de seus compostos bioativos também são relatadas. A Mpro (proteases principais) foi acoplada a diferentes compostos de Centaurea jacea por meio de docking molecular. Todos os compostos estudados, incluindo apigenina, axilarina, Centaureidina, Cirsiliol, Eupatorina e Isokaempferide, mostram afinidades de ligação adequadas ao sítio de ligação da protease principal SARS-CoV-2 com suas energias de ligação -6,7 kcal / mol, -7,4 kcal / mol, - 7,0 kcal / mol, -5,8 kcal / mol, -6,2 kcal / mol e -6,8 kcal / mol, respectivamente. Dentre todos os compostos estudados, a axilarina apresentou eficiência máxima de inibidor, seguida pela Centaureidina, Isokaempferida, Apigenina, Eupatorina e Cirsiliol. Nossos resultados sugeriram que a axilarina se liga aos resíduos catalíticos mais cruciais CYS145 e HIS41 do Mpro, além disso a axilarina mostra 5 interações de ligações de hidrogênio e 5 interações hidrofóbicas com vários resíduos de Mpro. Além disso, os cálculos de dinâmica molecular em uma escala de tempo de 60 ns (6 × 106 femtossegundos) também mostraram percepções significativas sobre os efeitos de ligação da axilarina com Mpro de SARS-CoV-2 por imitação de proteínas como o ambiente aquoso. A partir de cálculos de dinâmica molecular, os cálculos RMSD e RMSF indicam a estabilidade e dinâmica do melhor complexo ancorado em ambiente aquoso. As propriedades ADME e a análise de previsão de toxicidade da axilarina também a recomendaram como um candidato a medicamento seguro. Além disso, as investigações in vivo e in vitro são essenciais para garantir a atividade anti-SARS-CoV-2 de todos os compostos bioativos, particularmente a axilarina, para encorajar o uso preventivo de Centaurea jacea contra infecções por Covid-19.

A threefold approach including quantum chemical, molecular docking and molecular dynamic studies to explore the natural compounds from Centaurea jacea as the potential inhibitors for COVID-19 / Uma abordagem tríplice incluindo química quântica, docking molecular e estudos dinâmicos moleculares para explorar os compostos naturais de Centaurea jacea como inibidores potenciais para Covid-19

In the current report, we studied the possible inhibitors of COVID-19 from bioactive constituents of Centaurea jacea using a threefold approach consisting of quantum chemical, molecular docking and molecular dynamic techniques. Centaurea jacea is a perennial herb often used in folk medicines of dermatological complaints and fever. Moreover, anticancer, antioxidant, antibacterial and antiviral properties of its bioactive compounds are also reported. The Mpro (Main proteases) was docked with different compounds of Centaurea jacea through molecular docking. All the studied compounds including apigenin, axillarin, Centaureidin, Cirsiliol, Eupatorin and Isokaempferide, show suitable binding affinities to the binding site of SARS-CoV-2 main protease with their binding energies -6.7 kcal/mol, -7.4 kcal/mol, -7.0 kcal/mol, -5.8 kcal/mol, -6.2 kcal/mol and -6.8 kcal/mol, respectively. Among all studied compounds, axillarin was found to have maximum inhibitor efficiency followed by Centaureidin, Isokaempferide, Apigenin, Eupatorin and Cirsiliol. Our results suggested that axillarin binds with the most crucial catalytic residues CYS145 and HIS41 of the Mpro, moreover axillarin shows 5 hydrogen bond interactions and 5 hydrophobic interactions with various residues of Mpro. Furthermore, the molecular dynamic calculations over 60 ns (6×106 femtosecond) time scale also shown significant insights into the binding effects of axillarin with Mpro of SARS-CoV-2 by imitating protein like aqueous environment. From molecular dynamic calculations, the RMSD and RMSF computations indicate the stability and dynamics of the best docked complex in aqueous environment. The ADME properties and toxicity prediction analysis of axillarin also recommended it as safe drug candidate. Further, in vivo and in [...].

No presente relatório, estudamos os possíveis inibidores de Covid-19 de constituintes bioativos de Centaurea jacea usando uma abordagem tripla que consiste em técnicas de química quântica, docking molecular e dinâmica molecular. Centaurea jacea é uma erva perene frequentemente usada em remédios populares de doenças dermatológicas e febre. Além disso, as propriedades anticâncer, antioxidante, antibacteriana e antiviral de seus compostos bioativos também são relatadas. A Mpro (proteases principais) foi acoplada a diferentes compostos de Centaurea jacea por meio de docking molecular. Todos os compostos estudados, incluindo apigenina, axilarina, Centaureidina, Cirsiliol, Eupatorina e Isokaempferide, mostram afinidades de ligação adequadas ao sítio de ligação da protease principal SARS-CoV-2 com suas energias de ligação -6,7 kcal / mol, -7,4 kcal / mol, - 7,0 kcal / mol, -5,8 kcal / mol, -6,2 kcal / mol e -6,8 kcal / mol, respectivamente. Dentre todos os compostos estudados, a axilarina apresentou eficiência máxima de inibidor, seguida pela Centaureidina, Isokaempferida, Apigenina, Eupatorina e Cirsiliol. Nossos resultados sugeriram que a axilarina se liga aos resíduos catalíticos mais cruciais CYS145 e HIS41 do Mpro, além disso a axilarina mostra 5 interações de ligações de hidrogênio e 5 interações hidrofóbicas com vários resíduos de Mpro. Além disso, os cálculos de dinâmica molecular em uma escala de tempo de 60 ns (6 × 106 femtossegundos) também mostraram percepções significativas sobre os efeitos de ligação da axilarina com Mpro de SARS-CoV-2 por imitação de proteínas como o ambiente aquoso. A partir de cálculos de dinâmica molecular, os cálculos RMSD e RMSF indicam a estabilidade e dinâmica do melhor complexo ancorado em ambiente [...].

A threefold approach including quantum chemical, molecular docking and molecular dynamic studies to explore the natural compounds from Centaurea jacea as the potential inhibitors for COVID-19

Abstract In the current report, we studied the possible inhibitors of COVID-19 from bioactive constituents of Centaurea jacea using a threefold approach consisting of quantum chemical, molecular docking and molecular dynamic techniques. Centaurea jacea is a perennial herb often used in folk medicines of dermatological complaints and fever. Moreover, anticancer, antioxidant, antibacterial and antiviral properties of its bioactive compounds are also reported. The Mpro (Main proteases) was docked with different compounds of Centaurea jacea through molecular docking. All the studied compounds including apigenin, axillarin, Centaureidin, Cirsiliol, Eupatorin and Isokaempferide, show suitable binding affinities to the binding site of SARS-CoV-2 main protease with their binding energies -6.7 kcal/mol, -7.4 kcal/mol, -7.0 kcal/mol, -5.8 kcal/mol, -6.2 kcal/mol and -6.8 kcal/mol, respectively. Among all studied compounds, axillarin was found to have maximum inhibitor efficiency followed by Centaureidin, Isokaempferide, Apigenin, Eupatorin and Cirsiliol. Our results suggested that axillarin binds with the most crucial catalytic residues CYS145 and HIS41 of the Mpro, moreover axillarin shows 5 hydrogen bond interactions and 5 hydrophobic interactions with various residues of Mpro. Furthermore, the molecular dynamic calculations over 60 ns (6×106 femtosecond) time scale also shown significant insights into the binding effects of axillarin with Mpro of SARS-CoV-2 by imitating protein like aqueous environment. From molecular dynamic calculations, the RMSD and RMSF computations indicate the stability and dynamics of the best docked complex in aqueous environment. The ADME properties and toxicity prediction analysis of axillarin also recommended it as safe drug candidate. Further, in vivo and in vitro investigations are essential to ensure the anti SARS-CoV-2 activity of all bioactive compounds particularly axillarin to encourage preventive use of Centaurea jacea against COVID-19 infections.

Resumo No presente relatório, estudamos os possíveis inibidores de Covid-19 de constituintes bioativos de Centaurea jacea usando uma abordagem tripla que consiste em técnicas de química quântica, docking molecular e dinâmica molecular. Centaurea jacea é uma erva perene frequentemente usada em remédios populares de doenças dermatológicas e febre. Além disso, as propriedades anticâncer, antioxidante, antibacteriana e antiviral de seus compostos bioativos também são relatadas. A Mpro (proteases principais) foi acoplada a diferentes compostos de Centaurea jacea por meio de docking molecular. Todos os compostos estudados, incluindo apigenina, axilarina, Centaureidina, Cirsiliol, Eupatorina e Isokaempferide, mostram afinidades de ligação adequadas ao sítio de ligação da protease principal SARS-CoV-2 com suas energias de ligação -6,7 kcal / mol, -7,4 kcal / mol, - 7,0 kcal / mol, -5,8 kcal / mol, -6,2 kcal / mol e -6,8 kcal / mol, respectivamente. Dentre todos os compostos estudados, a axilarina apresentou eficiência máxima de inibidor, seguida pela Centaureidina, Isokaempferida, Apigenina, Eupatorina e Cirsiliol. Nossos resultados sugeriram que a axilarina se liga aos resíduos catalíticos mais cruciais CYS145 e HIS41 do Mpro, além disso a axilarina mostra 5 interações de ligações de hidrogênio e 5 interações hidrofóbicas com vários resíduos de Mpro. Além disso, os cálculos de dinâmica molecular em uma escala de tempo de 60 ns (6 × 106 femtossegundos) também mostraram percepções significativas sobre os efeitos de ligação da axilarina com Mpro de SARS-CoV-2 por imitação de proteínas como o ambiente aquoso. A partir de cálculos de dinâmica molecular, os cálculos RMSD e RMSF indicam a estabilidade e dinâmica do melhor complexo ancorado em ambiente aquoso. As propriedades ADME e a análise de previsão de toxicidade da axilarina também a recomendaram como um candidato a medicamento seguro. Além disso, as investigações in vivo e in vitro são essenciais para garantir a atividade anti-SARS-CoV-2 de todos os compostos bioativos, particularmente a axilarina, para encorajar o uso preventivo de Centaurea jacea contra infecções por Covid-19.

Termoquímica computacional: en la búsqueda de la precisión química

Introducción: La termoquímica computacional es un campo de gran interés por sus diversas aplicaciones en diferentes campos de la química. En la actualidad, con el avance en el desarrollo de los supercomputadores se pueden emplear diversas metodologías que emplean cálculos de estructura electrónica para estimar valores termodinámicos con errores ~ 1,0 kcal/mol en comparación con los datos experimentales. Metodología: En este artículo se describen brevemente los principales métodos compuestos empleados en la termoquímica computacional como la serie de Petersson, los métodos Weizmann, el modelo HEAT y con especial énfasis en las teorías Gaussian-n. Aplicaciones: Diversas aplicaciones de la termoquímica computacional se presentan en este trabajo tales como el estudio de la reactividad y las estabilidades de nuevos derivados de compuestos químicos con potencialidades como fármacos, estudios de contaminantes en la química de la atmosfera donde se estiman valores importantes de entalpias de formación sobre compuestos derivados del gas de efecto invernadero SF6, estudios de compuestos derivados del petróleo de potencial importancia como nuevos combustibles y el desarrollo de explosivos con estimaciones energéticas de las entalpias de disociación de enlace y de combustión de nuevos compuestos orgánicos. Conclusiones: La termoquímica computacional es una herramienta actual para resolver problemas de la química donde la experimentación es difícil y con un alto costo económico. Se espera en un futuro que esta área desarrolle nuevos métodos y códigos computacionales que permitan estudiar sistemas moleculares de gran tamaño importantes en otras áreas de las ciencias como la física, la biología, ciencias de los materiales, entre otros.

Introdução: A termoquímica computacional é uma área de grande interesse devido às suas diversas aplicações em diferentes campos da química. Hoje em dia, com o avanço no desenvolvimento de supercomputadores, várias metodologias podem ser utilizadas que utilizam cálculos de estrutura eletrônica para estimar valores termodinâmicos com erros de ~ 1,0 kcal/mol em comparação com os dados experimentais. Metodologia: Este artigo descreve resumidamente os principais métodos compostos usados em termoquímica computacional, como a série Petersson, os métodos de Weizmann, o modelo HEAT e com especial ênfase nas teorias Gaussianas-n. Aplicações: Várias aplicações da termoquímica computacional são apresentadas neste trabalho tais como o estudo da reatividade e estabilidades de novos derivados de compostos químicos com potencial como drogas, estudos de poluentes em química atmosférica onde valores importantes de entalpias são estimados de treinamento em compostos derivados do gás de efeito estufa SF6, estudos de compostos derivados do petróleo com potencial importância como novos combustíveis e o desenvolvimento de explosivos com estimativas energéticas das entalpias de dissociação de ligações e combustão de novos compostos orgânicos. Conclusões: A termoquímica computacional é uma ferramenta atual para resolver problemas de química onde a experimentação é difícil e com alto custo econômico. Espera-se que no futuro esta área desenvolva novos métodos e códigos computacionais que permitam estudar grandes sistemas moleculares importantes em outras áreas da ciência como física, biologia, ciência dos materiais, entre outras.

SUMMARY Introductión: Computational thermochemistry is an area of great interest for its various applications in many different fields of chemistry. With the increase of the computational power readily available, it is currently possible to use various calculation based on the electronic structure methods for estimate thermodynamic properties with an error on the order of ~1.0 kcal/mol, which is comparable to experimental values. Methodology: In this work we briefly describe the main composite methods such as Petersson series, the Weizmann methods the HEAT model and with special focus on the Gaussian-n theories. Applications: Various applications of computational thermochemistry are presented in this work such as the study of reactivity and stabilities of new derivatives of chemical compounds with potential use as drugs, studies of pollutants in atmospheric chemistry where important values of enthalpies are estimated of training on compounds derived from the greenhouse gas SF6, studies of compounds derived from petroleum of potential importance as new fuels and the development of explosives with energy estimates of the enthalpies of bond dissociation and combustion of new organic compounds. Conclusions: Computational thermochemistry is a current tool to solve chemistry problems where experimentation is difficult and with a high economic cost. It is expected in the future that this area will develop new methods and computational codes that allow studying large molecular systems important in other areas of science such as physics, biology, materials science, among others.

Establishment and mechanisms of chemical interaction between phosphate monomer and zirconia model / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To analyze chemical mechanism of bonding improvement of zirconia via 10-methacryloyloxydecyl dihydrogen phosphate (MDP) conditioning.</p><p><b>METHODS</b>Various models were created for tetragonal zirconia crystals, molecular MDP, and MDP complex, and tetragonal zirconia crystal. Thermodynamic methods were used to analyze configuration between MDP and tetragonal zirconia crystal through calculation of their Gibbs free energy values and equilibrium constants.</p><p><b>RESULTS</b>Two potential configurations (double- and single-coordinate) may occur between MDP and ZrO2 crystal clusters. Thermodynamic calculations showed that -147.761 and -158.073 kJ·mol⁻¹ Gibbs free energy were required to form single- and double-coordinate configurations; their negative signs indicate that reactions for both configurations can occur. Equilibrium constant for single-coordinate configuration was 7.72×10²⁵, which was less than that of double-coordinate configuration (4.95×10²⁷), suggesting that the latter was more stable.</p><p><b>CONCLUSIONS</b>MDP can spontaneously establish a double-coordinate configuration with zirconia.
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Application of computational simulation and spectral analysis in preparation of Tanshinone IIA imprinted polymer / 中草药

To prepare Tanshinone IIA (TSIIA) molecularly imprinted polymers (MIPs) with affinity and high selectivity to TSIIA and study its mechanism. Taking TSIIA as the template molecular, synthesizing the MIPs at the surface of silica nanoparticles by grafting copolymerization in the toluene solution. A molecular modeling approach was used to elucidate template-monomer interaction. The interaction between template molecule and functional monomer was studied by UV spectrometry. The theoretical molar ratio of template-monomer was 1∶3 and methyl acrylic acid (MAA) was a better functional monomer than acrylamide (AAM) for MIPs synthesis. The MIPs can be used for the extraction and separation of TSIIA.

The mechanism and the kinetics of thermal decomposition of brivudine / 中国药学杂志

OBJECTIVE: To understand the thermal stability, mechanism and kinetics of thermal decomposition of brivudine (BVDU). METHODS: The thermal decomposition process of BVDU was studied by means of thermogravimetry (TG), differential scanning calorimetry (DSC), and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA-FTIR). The infrared spectra of BVDU, its gaseous products and remainders of thermal decomposition at various temperatures were determined. The molecular bond orders were calculated by GAMESS program of quantum chemistry, and the mechanism of the thermal decomposition of BVDU is discussed. The parameters of thermal decomposition kinetics, such as activation energy Es and pre-exponential factor A, were obtained by using Ozawa method. The prospective lifetime of BVDU was estimated by using Dakin equation. RESULTS: The thermal decomposition of BVDU is a three-stage process. Disconnection of the C-N bond between thymine ring and tetrahydrofuran ring occurrs in the initial step of the decomposition. In nitrogen atmosphere, the average Ea and A of the first stage are 171.1 kJ·mol-1 and 2.630×10 min-1 respectively. In air atmosphere, the corresponding Ea and A are 152.9 kJ·mol-1 and 1.660×10 min-1 respectively. CONCLUSION: The thermal property of BVDU is quite stable in the routine temperature.

Basic property of baicalin-phospholipid complex / 中草药

Objective To investigate the basic property of baicalin complex with phospholipid. Methods To study the baicalin complex with phospholipid by means of IR, 1H-NMR, quantum chemistry, dissolubility, and the property of permeation membrane. Results The result of IR indicated that spectrogram of baicalin complex with phospholipid had the same tendency in property with baicalin and mixture. While the peak shape and wave number of -C=O, -N-H appeared abnormal. The 1H-NMR indicated that the phospholipid complex did not produce new chemical bonds between the two molecules. But the peak shape and chemical shift produced a certain change. The quantum chemistry result revealed that the two molecules did not form new compounds. On the basis of space matching, the two formed a relatively stable spatial relation by a weaker atomic orbitaols overlap method. The solubility of baicalin was significantly improved, the permeation membrane ratio of baicalin was boost. Conclusion The formation of baicalin-phospholipid complex does not produce new chemical bonds. The two form a relatively stable complex by some weak interaction force. The physicochemical properties and biological characteristics of the complex are greatly improved.

Molecular Recognition Properties of p-Phenylenediamine-Imprinted Polymers / 分析化学

Two p-phenylenediamine (p-PD)-imprinted polymers, P (MAA) and P (AA), were synthesized using methacrylic acid (MAA) and acrylamide(AA) as functional monomer, respectively, in order to prepare molecular recognition material with high selectivity for p-PD and explore the feasibility of methods such as molecular spectrometry and computational approach of quantum chemistry for the selection of functional mono mer with high imprinting efficiency.The molecular recognition properties of the imprinted polymers were evaluated by high performance liquid chromatography.The results indicated that P(AA) exhibited no imprint ing effect for p-PD, while P(MAA) can bind p-PD selectively(k' =3.57), which showed remarkable imprint ing effect (IF=2.95), and p-PD and its analogues o-phenylenediamine and p-aminobenzoic acid can almost realize baseline separation on P (MAA) column in the mobile phase of methanol.Furthermore, we made a comparative study on the interaction of p-PD with MAA and AA by spectroscopic techniques such as UV and fluorometry as well as HF/6-31G~* computational approach.The results demonstrated that the complex of p-PD-MAA was more stable than that of p-PD-AA, which can give a good explanation for the molecular recog nition properties of P (MAA) and P (AA).The study indicated that both molecular spectrometry (UV and fluorometry)and computational approach of quantum chemistry can be employed as efficient means for the selection of efficient functional monomer.The results showed that fluorometry is sensitive and convenient for the choice of functional monomer if the template molecule is fluorescent.

Isomerización dll 1-ciclohexiloctano en zeolitas h-zsm-22 y h-y / 1-cyclohexyloctane isomerizationinto h-zsm-22 and h-yzeolites / Isoerizacáo de 11-ciclohexiloctano na zeólitas h-zsm-22 yh-y

En este trabajo se presentan los resultados de la evaluación energética de los intermediarios de la isomerización del 1-ciclohexiloctano en dos etapas. La primera etapa corresponde a la isomerización del 1-ciclohexiloctano en fase gaseosa vía carbocationes clásicos, usando el nivel de teoría DFT/B3LYP y conjunto de funciones base 6-31G. En la segunda etapa se desarrolló la coordenada de reacción de la isomerización del 1-ciclohexiloctano en presencia de zeolitas acidas H-ZSM-22 y H-Y empleando el método ONIOM, usando los niveles de teoría B3LYP/ 6-31G:UFF. Los resultados muestran diferencias significativas entre las reacciones en fase gaseosa y condensada. Estas diferencias ponen de manifiesto la influencia del confinamiento cuántico que sufren las moléculas al interior de los sistemas microporosos del tipo zeolitas.

We studied the isomerization mechanism of 1-cycle-hexyloctane either in gas phase or inside zeolites using quantum models. In the gas phase the reaction was simulated following the classical scheme via carbocations. On the other hand, the isomerization reaction was modeled with 1-cycle-hexyloctane inside HZSM-22 and H-Y acid zeolites (condensed phase). We used the ONIOM(B3LYP/6-31G: UFF) hybrid method to study such behavior in both zeolites. Our results show that the reaction follows different pathways when the simulations are performed either in gas phase or within the zeolites pores. Such differences show the importance of quantum confinement inside microporous materials.

Neste trabalho foram desenvolvidos os mecanismos das reacção de isomerização de 1-ciclo-hexil-octano através de duas etapas. Na primeira etapa, a reação foi realizada como carbocátions clasicos, utilizando-se o método DFT/B3LYP e as funções básicas 6-31G. Na segunda, a reação de isomerização de 1-ciclo-he-xil-octano foi estudou em zeolites ácido H-ZSM-22 e H-Y utilizando-se o método híbrido ONIOM o nível B3LYP e funções básicas 6-31G.

Estudio teóricoppara evaluar la conductividad dl polifurano y el efecto de loss sustituyentes sobre la cadena polimérica / Theoretcal studyy to evaluate polyfuranelectrical conductivity and thee substituent effects on the polymeri cchain / Estud teorico paara avaliar a conductvidade do polifurano o e efeitoo dos substituintes sobre a cadeia polmmerica

Una serie de oligómeros de furano y furano sustituido fueron estudiados desde el punto de vista teórico con el objeto de conocer las propiedades electroconductoras de estos compuestos, y su respectiva extrapolación a polímeros, aprovechando la capacidad de la química computacional para proponer y diseñar nuevos materiales y sus posibles propiedades. Se relacionaron las propiedades electrónicas de estos oligómeros tales como la afinidad electrónica (AE), el potencial de ionización (PI), el band-gap (HOMOLUMO), y la relación de éstos con la conductividad; además, se demostró cómo cambia la longitud de los enlaces de los oligómeros al estar cargados; la longitud de los oligómeros de estudio fuer de dos, cuatro, seis y ocho anillos. En este estudio se realizaron cálculos a niveles AM1 y DFT/B3LYP/6-31G (d).

DFT/B3LYP/6-31G (d) calculations were carried out on a series of molecules of furan and substituted furan to observe the type of variables that affect the conductivity of these molecules. In order to propose and design new molecules and its possible properties. The Ionization potential (IP), band-gap (HOMO-LUMO), electronic affinity (EA), was related with its conductivity. It was also shown how change the length of the olygomers bond when the number of the rings is changed from two to four, six and eight.

Uma serie de oligômeros de furano y furano substituido foram estudados teoricamente com a intenção de conhecer as propriedades electro-conductoras desses compostos e sua respectiva extrapolação a polímeros, aproveitando a capacidade da química computacional para propor e desenhar novos materiais e suas possíveis propriedades. Relacionaram-se as propriedades eletrônicas destes oligômeros, tais como a afinidade eletrônica (AE), o potencial de ionização (PI), o band-gap (HOMO-LUMO) e a relação destes com a condutividade, também se demostrou a mudança do comprimento das ligações dos oligômeros ao estar carregados, o comprimento dos oligômeros em estudo foram de dois, quatro, seis e oito anéis. Em este estudo realizaram-se cálculos a níveis AM1 e DFT/B3LYP/6-31G (d).

Mutations in E154 of Diphtheria Toxin (DT) and Their Biologic Activity / 生物化学与生物物理进展

According to the results of quantum chemistry calculation and the present research status in the relationship between the structures and the functions of DT, the E154 in DT catalyzing domain was mutated to aspartic acid and arginine in order to study the effects of the alteration on the biological activities. By means of gene site-direct mutation, two mutated genes were prepared and the high performance expression was obtained in E.coli system. The results of toxcity studies indicated that the acute toxicity in guinea pig and cytotoxicities of mutant E154D increased slightly in compared with those of recombination wild toxin, and contrarily, those of E154R decreased obviously.

A Quantum Chemical Study on The Catalytic Mechanism of Serine Proteases(Ⅰ) / 昆明医科大学学报

Using the semi-empirical MNDO/H method several systems simulating the reaction of tetrahetral intermediate formation in the active site of serine proteases have been studied. The role played by elements of the《catalytic triad》in increasing the reactivity of serine hydroxyl has been discussed.The formation of a strong hydrogen bond between His and Asp was shown to be important in lowering the activation energy in the reaction of Ser with substrate.The change in position of the proten located between Ser and His and between His and Asp was analysed.The influence of substrate distortion on the energy of intermediate formation has been considered.

Recognition schemes for protein-nucleic acid interactions.

The molecular forces involved in protein-nucleic acid interaction are electrostatic, stacking and hydrogen-bonding. These interactions have a certain amount of specificity due to the directional nature of such interactions and the spatial contributions of the steric effects of different substituent groups. Quantum chemical calculations on these interactions have been reported which clearly bring out such features. While the binding energies for electrostatic interactions are an order of magnitude higher, the differences in interaction energies for structures stabilised by hydrogen-bonding and stacking are relatively small. Thus, the molecular interactions alone cannot explain the highly specific nature of binding observed in certain segments of proteins and nucleic acids. It is therefore logical to assume that the sequence dependent three dimensional structures of these molecules help to place the functional groups in the correct geometry for a favourable interaction between the two molecules. We have carried out 2D-FT nuclear magnetic resonance studies on the oligonucleotide d- GGATCCGGATCC. This oligonucleotide sequence has two binding sites for the restriction enzyme Bam H1. Our studies indicate that the conformation of this DNA fragment is predominantly B-type except near the binding sites where the ribose ring prefers a 3E conformation. This interesting finding raises the general question about the presence of specificity in the inherent backbone structures of proteins and nucleic acids as opposed to specific intermolecular interactions which may induce conformational changes to facilitate such binding.