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Structure and thermal reactivity of Zn(II) salts of isocinchomeronic acid (2,5-pyridinedicarboxylic acid)

SILEO, Elsa E.; PIRO, Oscar E.; RIGOTTI, Graciela; BLESA, Miguel A.; ARAUJO, Alexandre S. de; CASTELLANO, Eduardo Ernesto
Fonte: SPRINGER/PLENUM PUBLISHERS Publicador: SPRINGER/PLENUM PUBLISHERS
Tipo: Artigo de Revista Científica
ENG
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55.67%
The synthesis, an improved refined crystal and molecular structure re-determination, and the thermal decomposition behavior of two Zn(II) derivatives of isocinchomeronic acid (2,5-pyridinedicarboxylic acid or H(2)2,5-pydc) are presented. [Zn(2,5-pydc)(H(2)O)(3)Zn(2,5-pydc)(H(2)O)(2)](2) (1) crystallizes in the triclinic P-1 space group with a = 7.106(2), b = 11.450(2), c = 11.869(1) angstrom, alpha = 107.29(1), beta = 104.08(1), gamma = 90.32(2)degrees, and Z = 2. [Zn(2,5-pydc)(H(2)O)(2)] center dot H(2)O (2) is orthorhombic (P2(1)2(1)2(1) space group), with a = 7.342(1), b = 9.430(1), c = 13.834(2) angstrom, and Z = 4. The structures were refined to agreement R(1)-factors of 0.0315 (1) and 0.0336 (2). Complex (1) is arranged as molecular Zn(4)(2,5-pydc)(4)(H(2)O)(10) tetramers, the cages of which define channels that remain unblocked by anions. Compound (2) is polymeric with Zn(2,5-pydc)(H(2)O)(2) and Zn(2,5-pydc)(H(2)O)(3) units linked through bridging ligands. Both compounds were synthesized under mild conditions in aqueous media, without need to resort to hydrothermal media. Changing the pH from 4.51 to 5.75 suffices to direct the chemical processes toward the orthorhombic compound rather than to the triclinic one.

Estrutura cristalina e molecular de derivados de ditiocarbamatos. ; Crystaline and molecular structure of dithiocarbamates derivades.

Landgraff, Ana Carolina Mafud
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/08/2006 PT
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A parte intodutória deste trabalho descreve os conceitos básicos da teoria de determminação de estruturas cristalinas, além de alguns aspéctos de ditiocarbamatos. Na parte experimental estão descritas as estruturas cristalinas e moleculares de quatro compostos: Morfolinoditiocarbamato de potássio monoidratado: Sistema cristalino monoclínico; grupo espacial P21/c; Z=4; a=6,723(5); b=17,260(4); c=8,190(8) Å; Beta =108,99(1)0; V=898,7(3) Å3; D=1,621 Mg/m3. O índice de discordância é R(F)=0,0472 (R (F)*= 0,1064 para todas as reflexões), com S=1,012 para 1615 reflexões observadas com I > ou = 2 gama(I) e 107 parâmetros refinados. Morfolinoditiocarbamato de Morfolina: Sistema cristalino monoclínico; grupo espacial P21/c; Z=4; a=7,938(5); b=18,323(1); c=8,826(5) Å; Beta =110,21(5)0; V=1206,16(25) Å3; D=1,381 Mg/m3. O índice de discordância é R(F)= 0,0505 (R (F)*= 0,1273para todas as reflexões), com S=0,997 para 2021 reflexões observadas com I > ou = 2 gama(I) e 191 parâmetros refinados. Morfolinoditiocarbamato de Amônio: Sistema cristalino monoclínico; grupo espacial P21/a; Z=4; a=8,881(9); b=9,002(9); c=11,889(5) Å; beta =104,318(5) 0; V=921,85(12) Å3; D=1,30 Mg/m3. O índice de discordância é R(F)= 0...

Estrutura molecular e espectros de EPR do composto monocristalino CuBr2(fdmp)2.; Molecular structure and EPR spectra of the monocrystalline compound CuBr2(fdmp)2.

Munte, Claudia Elisabeth
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 19/07/1995 PT
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55.66%
Estão sendo apresentados, neste trabalho, estudos estruturais e magnéticos do composto de [CuBr2(fdmp)2] utilizando as técnicas de difração de Raio-X e espectroscopia de EPR. a complexo cristaliza no grupo espacial P21/n com a=8.1653(47)Å, b=10.432(3)Å, c=13.385(4)Å, β=100.12(4)° e Z=2. Os íons de Cu(II), que estão em coordenação quadrado-planar trans ligando-se a dois Nitrogênios e dois Bromos, se encontram em centros de inversão. Somente urna linha de EPR e observada, proveniente do colapso das ressonâncias relativas aos dois íons de Cu(II) magneticamente não equivalentes, causado pela interação de troca. Devido a diferença significativa entre os pesos atômicos do Nitrogênio e Bromo, não e esperada urna simetria axial para o tensor g como é comum ocorrer em vários complexos de Cu(II); de fato, a decomposição de g cristalino para os dois g moleculares revela três autovalores distintos. Alem disso, a direção de maior g não coincide exatamente com a normal ao quadrado-planar, como é comum nesses complexos: se encontra rodada de ∼ 5° em direção ao Bromo, caracterizando um estado fundamental do tipo dx2-y2 com mistura de dyz. Outro fato incomum verificado foi a dependência do fator g com a freqüência e a presença de contribuições não-seculares...

Caracterização da estrutura molecular e propriedades viscográficas de amidos de mandioca (Manihot esculenta Crantz) para aplicações industriais

Silva, Fábio Iachel da
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: x, 85 f. : il. color, grafs., tabs.
POR
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55.67%
Pós-graduação em Agronomia (Energia na Agricultura) - FCA; A fécula de mandioca (Manihot esculenta Crantz) contém aproximadamente 98 % de amido, em peso seco. Este amido é constituído por dois tipos de polissacarídeos: a amilose ( de 16 a 20 % ), com cadeias lineares de monômeros de glicose e peso molecular 1,5.105 a 1,0.106 Da; e amilopectina ( de 80 a 84 % ), com cadeias ramificadas e peso molecular 5,0.106 a 1,0.108 Da. A estrutura molecular desses polissacarídeos influi diretamente nas propriedades funcionais dos amidos, as quais são interessantes para diversos usos industriais. O principal objetivo desta pesquisa é avaliar e adaptar a técnica de separação de moléculas conhecida por cromatografia de permeação em gel, seguida da caracterização das frações coletadas na permeação e verificar as propriedades viscográficas do amido. Nesta principal técnica utilizada, conhecida também por cromatografia por exclusão de tamanho, as moléculas se separam de acordo com seus tamanhos e pesos moleculares. Sendo assim, moléculas maiores que os poros do gel, saem primeiro da coluna, enquanto moléculas de tamanhos intermediários aos dos poros do gel, saem no final da permeação. As amostras usadas neste trabalho foram féculas extraídas de sete etnovariedades de mandioca...

Phase-morphology and molecular structure correlations in model fullerene-polymer nanocomposites

Bernardo, Gabriel; Bucknall, David G.; Shofner, Meisha; Sumpter, Bobby; Karim, Alamgir; Nabankur, Deb; Raghavan, Dharmaraj; Sides, Scott; Huq, Abul
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2011 ENG
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Organic or polymer based photovoltaic devices promise solar technologies that are inexpensive enough to be widely exploited and therefore provide a significant fraction of the future energy needs. There are many promising polymer-fullerene mixtures that are promising materials candidates for achieving high performance device, but their exploitation requires an improved understanding of their structure-property relationships. Of particular relevance is the molecular structural as well as mesoscale phase behaviour. In order to guide the use of electron acceptor fullerenes in these systems we are using multi-scale molecular modelling coupled with neutron and X-ray scattering to determine the structure behavior of model polymer-fullerene mixtures. Neutron scattering is particularly useful for these types of studies since the fullerene generally have a high scattering contrast with respect to most polymers. This natural contrast, enhanced by careful selective deuteration allows us to carefully probe the atomic and molecular interactions in these complex systems. We are studying model polymer systems to establish fullerene-polymer phase behaviour. To establish how fullerene addition changes polymer phase behaviour, using advanced scattering techniques we are studying phase morphology and molecular structure. Control of morphology development is being examined with particular relevance to solid state processing.

Molecular structure-affinity relationship of dietary flavonoids for bovine serum albumin

Shi,Jian; Cao,Hui
Fonte: Sociedade Brasileira de Farmacognosia Publicador: Sociedade Brasileira de Farmacognosia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 EN
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The relationship between the molecular structure of dietary flavonoids and their affinities for bovine serum albumin (BSA) were fully investigated by fluorescence titration analysis. The binding process with BSA was significantly affected by the molecular structure of flavonoids under study. The methylation of hydroxyl group in flavonoids enhanced their binding affinities for BSA by 1 to 794 times. Hydroxylation on rings A, B and C also strongly influenced the affinity for BSA. The glycosylation weakened the affinities for BSA by 1-2 orders of magnitude depending on the conjugation site and the class of sugar moiety. The hydrogenation of the C2=C3 double bond slightly increased the binding affinity. The galloylated catechins and pyrogallol-type catechins exhibited higher binding affinities for BSA than non-galloylated and catechol-type catechins, respectively. The affinities for BSA increased with increasing partition coefficients and decreased with increasing hydrogen bond donor and acceptor numbers of flavonoids, which suggested that the binding interaction was mainly caused by hydrophobic forces.

Novel Organophosphorus Cage Compound Produced by an Unexpected Oxidative Coupling of 1,2,4-Triphosphole: Crystal and Molecular Structures of Two Isomers of Formula P6C4Bu t4 CHSiMe3

Araujo,Maria Helena; Rajão,Daniel A.; Doriguetto,Antonio C.; Ellena,Javier; Castellano,Eduardo E.; Hitchcock,Peter B.; Caliman,Vinicius
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2002 EN
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Reaction of Li(P3C2Bu t2 ) with BrCH(SiMe3)2 results in a novel organophosphorus compound with the formula, P6C4Bu t4 CHSiMe3 (1). Compound 1 was fully characterised spectroscopically and its unique molecular structure determined by single crystal X-ray diffraction. Another isomer (2) with a saturated structure was also fully characterised.

Oxidative Addition Reactions of I2 with [HIr4(CO)10-n(PPh3 )n(μ-PPh2)] (n = 1 and 2) and Crystal and Molecular Structure of [HIr4(μ-I)2(CO)7 (PPh3)(μ-PPh2)]

Braga,Dario; Grepioni,Fabrizia; Vargas,Maria D.; Ziglio,Claudio M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2002 EN
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65.64%
The reactions of the cluster compounds [HIr4(CO)10-n(PPh3 )n(μ-PPh2)] [n = 0, (1); 1, (2) and 2, (3)] with I2 have been investigated. Compound 1 does not react, however, the presence of PPh3 in place of CO ligand(s) activates the cluster. Both compounds 2 and 3 react with I2 under mild conditions to give [HIr4(μ-I)2(CO)7(PPh3)(μ-PPh 2)] (4), as the result of oxidative addition of I2 and dissociation of two CO ligands, or one CO and one PPh3 ligands, respectively. The molecular structure of 4, determined by an X-ray diffraction study, exhibits a butterfly arrangement of iridium atoms with the wings spanned by a μ-PPh2 ligand, the hinge bridged by a μ-H ligand, two hinge to wing tip edges bridged by iodine atoms and all metal atoms bearing two CO ligands, with the exception of one of the hinge atoms that contains a CO and a PPh3 ligands. This cluster exhibits the shortest average Ir–Ir bond length [2.698(2) Å] observed so far for a derivative of 1 and this is in accord with the relatively high average oxidation state of its metal atoms (+1) for a carbonyl cluster compound.

Tautomerism in quinoxalines derived from the 1,4-naphthoquinone nucleus: acid mediated synthesis, X-ray molecular structure of 5-chlorobenzo[f]quinoxalin-6-ol and density functional theory calculations

Gomez,Javier A. G.; Lage,Mateus R.; Carneiro,José Walkimar de M.; Resende,Jackson A. L. C.; Vargas,Maria D.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 EN
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The reaction of tert-butyl 2-(3-chloro-1,4-dioxo-1,4-dihydronaphthalen-2-ylamino) ethylcarbamate with CF3COOH/CH2Cl2 yields 5-chloro-3,4-dihydrobenzo[f]quinoxalin6(2H)-one which undergoes acid-promoted dehydrogenation in the presence of water to give novel 5-chlorobenzo[f]quinoxalin-6-ol. The molecular structure of 5-chlorobenzo[f]quinoxalin6-ol in the solid state, determined by an X-ray diffraction (XRD) study, and the solution data confirm that it exists as the enol-imine tautomer, both in the solid state and in solution, differently from 5-chloro-3,4-dihydrobenzo[f]quinoxalin-6(2H)-one, which exhibits the keto-amine arrangement. Density functional theory (DFT) calculations confirmed the preference of 5-chlorobenzo[f]quinoxalin-6-ol and of the derivatives containing H and CH3 groups in place of the Cl atom for the enol-imine tautomer. It is suggested that the enol-imine structure is preferred for 5-chlorobenzo[f]quinoxalin-6-ol as a consequence of the higher aromatic character of this structure in comparison with the keto-amine form. DFT calculations carried out on the two tautomers of the benzo[a]phenazin-5(7H)-ones analogous to the benzo[f]quinoxalin-6(4H)-ones showed that the relative stabilities are dominated by solvation effects in the first case and the degree of aromaticity...

Synthesis, Molecular Structure of Diethyl Phenylenebis(Methylene)Dicarbamates and FTIR Spectroscopy Molecular Recognition Study with Benzenediols

Saucedo-Balderas,Marlene M.; Delgado-Alfaro,Rogelio A.; Martínez‑Martínez,Francisco J.; Ortegón-Reyna,David; Bernabé-Pineda,Margarita; Zúñiga-Lemus,Oscar; González-González,Juan S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2015 EN
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55.64%
The synthesis, density functional theory (DFT) molecular structure and Fourier transform infrared spectroscopy (FTIR) molecular recognition study of diethyl phenylenebis(methylene) dicarbamates with 1,2- and 1,3-benzenediols is described. The formation of the complexes was confirmed by the shift of the O-H stretching bands in the IR spectra of the complexes compared with the IR spectra of the noncomplexed benzenediols.

In Situ D-periodic Molecular Structure of Type II Collagen*

Antipova, Olga; Orgel, Joseph P. R. O.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
55.67%
Collagens are essential components of extracellular matrices in multicellular animals. Fibrillar type II collagen is the most prominent component of articular cartilage and other cartilage-like tissues such as notochord. Its in situ macromolecular and packing structures have not been fully characterized, but an understanding of these attributes may help reveal mechanisms of tissue assembly and degradation (as in osteo- and rheumatoid arthritis). In some tissues such as lamprey notochord, the collagen fibrillar organization is naturally crystalline and may be studied by x-ray diffraction. We used diffraction data from native and derivative notochord tissue samples to solve the axial, D-periodic structure of type II collagen via multiple isomorphous replacement. The electron density maps and heavy atom data revealed the conformation of the nonhelical telopeptides and the overall D-periodic structure of collagen type II in native tissues, data that were further supported by structure prediction and transmission electron microscopy. These results help to explain the observed differences in collagen type I and type II fibrillar architecture and indicate the collagen type II cross-link organization, which is crucial for fibrillogenesis. Transmission electron microscopy data show the close relationship between lamprey and mammalian collagen fibrils...

Filament Structure, Organization, and Dynamics in MreB Sheets*

Popp, David; Narita, Akihiro; Maeda, Kayo; Fujisawa, Tetsuro; Ghoshdastider, Umesh; Iwasa, Mitsusada; Maéda, Yuichiro; Robinson, Robert C.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
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55.64%
In vivo fluorescence microscopy studies of bacterial cells have shown that the bacterial shape-determining protein and actin homolog, MreB, forms cable-like structures that spiral around the periphery of the cell. The molecular structure of these cables has yet to be established. Here we show by electron microscopy that Thermatoga maritime MreB forms complex, several μm long multilayered sheets consisting of diagonally interwoven filaments in the presence of either ATP or GTP. This architecture, in agreement with recent rheological measurements on MreB cables, may have superior mechanical properties and could be an important feature for maintaining bacterial cell shape. MreB polymers within the sheets appear to be single-stranded helical filaments rather than the linear protofilaments found in the MreB crystal structure. Sheet assembly occurs over a wide range of pH, ionic strength, and temperature. Polymerization kinetics are consistent with a cooperative assembly mechanism requiring only two steps: monomer activation followed by elongation. Steady-state TIRF microscopy studies of MreB suggest filament treadmilling while high pressure small angle x-ray scattering measurements indicate that the stability of MreB polymers is similar to that of F-actin filaments. In the presence of ADP or GDP...

A Molecular–Structure Hypothesis

Boeyens, Jan C. A.
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 01/11/2010 EN
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55.69%
The self-similar symmetry that occurs between atomic nuclei, biological growth structures, the solar system, globular clusters and spiral galaxies suggests that a similar pattern should characterize atomic and molecular structures. This possibility is explored in terms of the current molecular structure-hypothesis and its extension into four-dimensional space-time. It is concluded that a quantum molecule only has structure in four dimensions and that classical (Newtonian) structure, which occurs in three dimensions, cannot be simulated by quantum-chemical computation.

Structure-Function Analysis of the C-terminal Domain of CNM67, a Core Component of the Saccharomyces cerevisiae Spindle Pole Body*

Klenchin, Vadim A.; Frye, Jeremiah J.; Jones, Michele H.; Winey, Mark; Rayment, Ivan
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
55.66%
The spindle pole body of the budding yeast Saccharomyces cerevisiae has served as a model system for understanding microtubule organizing centers, yet very little is known about the molecular structure of its components. We report here the structure of the C-terminal domain of the core component Cnm67 at 2.3 Å resolution. The structure determination was aided by a novel approach to crystallization of proteins containing coiled-coils that utilizes globular domains to stabilize the coiled-coils. This enhances their solubility in Escherichia coli and improves their crystallization. The Cnm67 C-terminal domain (residues Asn-429—Lys-581) exhibits a previously unseen dimeric, interdigitated, all α-helical fold. In vivo studies demonstrate that this domain alone is able to localize to the spindle pole body. In addition, the structure reveals a large functionally indispensable positively charged surface patch that is implicated in spindle pole body localization. Finally, the C-terminal eight residues are disordered but are critical for protein folding and structural stability.

A Quantitative Structure-Property Relationship (QSPR) Study of Aliphatic Alcohols by the Method of Dividing the Molecular Structure into Substructure

Liu, Fengping; Cao, Chenzhong; Cheng, Bin
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 07/04/2011 EN
Relevância na Pesquisa
55.74%
A quantitative structure–property relationship (QSPR) analysis of aliphatic alcohols is presented. Four physicochemical properties were studied: boiling point (BP), n-octanol–water partition coefficient (lg POW), water solubility (lg W) and the chromatographic retention indices (RI) on different polar stationary phases. In order to investigate the quantitative structure–property relationship of aliphatic alcohols, the molecular structure ROH is divided into two parts, R and OH to generate structural parameter. It was proposed that the property is affected by three main factors for aliphatic alcohols, alkyl group R, substituted group OH, and interaction between R and OH. On the basis of the polarizability effect index (PEI), previously developed by Cao, the novel molecular polarizability effect index (MPEI) combined with odd-even index (OEI), the sum eigenvalues of bond-connecting matrix (SX1CH) previously developed in our team, were used to predict the property of aliphatic alcohols. The sets of molecular descriptors were derived directly from the structure of the compounds based on graph theory. QSPR models were generated using only calculated descriptors and multiple linear regression techniques. These QSPR models showed high values of multiple correlation coefficient (R > 0.99) and Fisher-ratio statistics. The leave-one-out cross-validation demonstrated the final models to be statistically significant and reliable.

Charge Transport Across Insulating Self-Assembled Monolayers: Non-equilibrium Approaches and Modeling To Relate Current and Molecular Structure

Mirjani, Fatemeh; Thijssen, Joseph M.; Whitesides, George McClelland; Ratner, Mark A.
Fonte: American Chemical Society (ACS) Publicador: American Chemical Society (ACS)
Tipo: Artigo de Revista Científica
EN_US
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55.71%
This paper examines charge transport by tunneling across a series of electrically insulating molecules with the structure HS(CH2)4CONH(CH2)2R) in the form of self-assembled monolayers (SAMs), supported on silver. The molecules examined were studied experimentally by Yoon et al. (Angew. Chem. Int. Ed. 2012, 51, 4658–4661), using junctions of the structure AgS(CH2)4CONH(CH2)2R//Ga2O3/EGaIn. The tail group R had approximately the same length for all molecules, but a range of different structures. Changing the R entity over the range of different structures (aliphatic to aromatic) does not influence the conductance significantly. To rationalize this surprising result, we investigate transport through these SAMs theoretically, using both full quantum methods and a generic, independent-electron tight-binding toy model. We find that the highest occupied molecular orbital, which is largely responsible for the transport in these molecules, is always strongly localized on the thiol group. The relative insensitivity of the current density to the structure of the R group is due to a combination of the couplings between the carbon chains and the transmission inside the tail. Changing from saturated to conjugated tail groups increases the latter but decreases the former. This work indicates that significant control over SAMs largely composed of nominally insulating groups may be possible when tail groups are used that are significantly larger than those used in the experiments of Yoon et al.; Chemistry and Chemical Biology

BE.442 Molecular Structure of Biological Materials, Fall 2002; Molecular Structure of Biological Materials

Zhang, Shuguang, Dr.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
EN-US
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55.72%
Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular design of new biological materials for nanotechnology, biocomputing and regenerative medicine. Graduate students are expected to complete additional coursework.

BE.442 Molecular Structure of Biological Materials, Fall 2005; Molecular Structure of Biological Materials

Zhang, Shuguang, Dr.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
EN-US
Relevância na Pesquisa
55.73%
Basic molecular structural principles of biological materials. Molecular structures of various materials of biological origin, including collagen, silk, bone, protein adhesives, GFP, self-assembling peptides. Molecular design of new biological materials for nanotechnology, biocomputing and regenerative medicine. Graduate students are expected to complete additional coursework. Description from course home page: This course, intended for both graduate and upper level undergraduate students, will focus on understanding of the basic molecular structural principles of biological materials. It will address the molecular structures of various materials of biological origin, such as several types of collagen, silk, spider silk, wool, hair, bones, shells, protein adhesives, GFP, and self-assembling peptides. It will also address molecular design of new biological materials applying the molecular structural principles. The long-term goal of this course is to teach molecular design of new biological materials for a broad range of applications. A brief history of biological materials and its future perspective as well as its impact to the society will also be discussed. Several experts will be invited to give guest lectures.

Non-Newtonian behavior and molecular structure of Cooee bitumen under shear flow: a non-equilibrium molecular dynamics study

Lemarchand, Claire A.; Bailey, Nicholas P.; Todd, Billy D.; Daivis, Peter J.; Hansen, Jesper S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.64%
The rheology and molecular structure of a model bitumen (Cooee bitumen) under shear are investigated in the non-Newtonian regime using non-equilibrium molecular dynamics simulations. The shear viscosity, normal stress differences and pressure of the bitumen mixture are computed at different shear rates and different temperatures. The model bitumen is shown to be a shear-thinning fluid at all temperatures. In addition, the Cooee model is able to reproduce experimental results showing the formation of nanoaggregates composed of stacks of flat aromatic molecules in bitumen. These nanoaggregates are immersed in a solvent of saturated hydrocarbon molecules. At a fixed temperature, the shear-shinning behavior is related to the inter- and intramolecular alignment of the solvent molecules, but also to the decrease of the average size of the nanoaggregates at high shear rates. The variation of the viscosity with temperature at different shear rates is also related to the size and relative composition of the nanoaggregates. The slight anisotropy of the whole sample due to the nanoaggregates is considered and quantified. Finally, the position of bitumen mixtures in the broad literature of complex systems such as colloidal suspensions, polymer solutions and associating polymer networks is discussed.; Comment: 44 pages...

Strength and deformation of rigid polymers: structure and topology in amorphous polymers

Stachurski, Zbigniew
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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Glassy polymer is formed because the irregular chain architecture prevents crystallisation. Computer simulations allow Voronoi tessellation of atomic groups (for example monomers) to be carried out and measured along the molecular chain, which reveals significant density fluctuations. A Voronoi polyhedron is constructed for each particle according to a unique mathematical procedure [J Reiner Angew Math 134 (1908) 198]. When measured in terms of Voronoi polyhedra, amorphous structures show wide variations in packing density on the atomic/monomer scale, with a characteristic skewed distribution. The Voronoi method can be applied to all polymers; however, in this paper only uncrosslinked amorphous polymers are considered. Constriction points around a chain segment are defined as a locally specific configuration and arrangement of adjacent chains such that the local density within a sphere of radius approximately equal to two monomer diameters comes close to or below the hypothetical crystalline density. The topological theory of molecular structure developed by Bader defines the concepts of atoms and bonds in terms of the topological properties of the observable charge distribution [Rep Prog Phys 44 (1981) 893]. In polymers the high density regions become an even stronger topological feature...