Following the Crystallization Process of Polyethylene Single Chain by Molecular Dynamics: The Role of Lateral Chain Defects

2012 ◽  
Vol 312 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Sara Sanmartín ◽  
Javier Ramos ◽  
Javier Martínez-Salazar
Keyword(s):  
Molecular Dynamics ◽  
Crystallization Process ◽  
Single Chain ◽  
Chain Defects

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

The Role of the Low-Density Lipoprotein Receptor-Related Protein (LRP) in the Plasma Clearance and Liver Uptake of Recombinant Single-chain Urokinase-type Plasminogen Activator in Rats

1997 ◽  
Vol 77 (04) ◽  
pp. 710-717 ◽  
Author(s):  
Marieke E van der Kaaden ◽  
Dingeman C Rijken ◽  
J Kar Kruijt ◽  
Theo J C van Berkel ◽  
Johan Kuiper
Keyword(s):  
Plasminogen Activator ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Single Chain ◽  
Liver Uptake ◽  
Type Plasminogen Activator ◽  
Parenchymal Liver ◽  
Urokinase Type Plasminogen Activator ◽  
Density Lipoprotein Receptor

SummaryUrokinase-type plasminogen activator (u-PA) is used as a thrombolytic agent in the treatment of acute myocardial infarction. In vitro, recombinant single-chain u-PA (rscu-PA) expressed in E.coli is recognized by the Low-Density Lipoprotein Receptor-related Protein (LRP) on rat parenchymal liver cells. In this study we investigated the role of LRP in the liver uptake and plasma clearance of rscu-PA in rats. A preinjection of the LRP inhibitor GST-RAP reduced the maximal liver uptake of 125I-rscu-PA at 5 min after injection from 50 to 30% of the injected dose and decreased the clearance of rscu-PA from 2.37 ml/min to 1.58 ml/min. Parenchymal, Kupffer and endothelial cells were responsible for 40, 50 and 10% of the liver uptake, respectively. The reduction in liver uptake of rscu-PA by the preinjection of GST-RAP was caused by a 91 % and 62% reduction in the uptake by parenchymal and Kupffer cells, respectively. In order to investigate the part of rscu-PA that accounted for the interaction with LRP, experiments were performed with a mutant of rscu-PA lacking residues 11-135 (= deltal25- rscu-PA). Deletion of residues 11-135 resulted in a 80% reduction in liver uptake and a 2.4 times slower clearance (0.97 ml/min). The parenchymal, Kupffer and endothelial cells were responsible for respectively 60, 33 and 7% of the liver uptake of 125I-deltal25-rscu-PA. Preinjection of GST-RAP completely reduced the liver uptake of delta 125-rscu-PA and reduced its clearance to 0.79 ml/min. Treatment of isolated Kupffer cells with PI-PLC reduced the binding of rscu-PA by 40%, suggesting the involvement of the urokinase-type Plasminogen Activator Receptor (u-PAR) in the recognition of rscu-PA. Our results demonstrate that in vivo LRP is responsible for more than 90% of the parenchymal liver cell mediated uptake of rscu-PA and for 60% of the Kupffer cell interaction. It is also suggested that u-PAR is involved in the Kupffer cell recognition of rscu-PA.

Adiabatic large polarons in anisotropic molecular crystals

2011 ◽  
Vol 35 (1) ◽  
pp. 15-27
Author(s):  
Zoran Ivić ◽  
Željko Pržulj
Keyword(s):  
Energy Transfer ◽  
Effective Mass ◽  
Molecular Crystals ◽  
Single Chain ◽  
Proper Understanding ◽  
One Dimensional ◽  
Interchain Coupling ◽  
Large Polaron ◽  
The One

Adiabatic large polarons in anisotropic molecular crystals We study the large polaron whose motion is confined to a single chain in a system composed of the collection of parallel molecular chains embedded in threedimensional lattice. It is found that the interchain coupling has a significant impact on the large polaron characteristics. In particular, its radius is quite larger while its effective mass is considerably lighter than that estimated within the one-dimensional models. We believe that our findings should be taken into account for the proper understanding of the possible role of large polarons in the charge and energy transfer in quasi-one-dimensional substances.

The localized electron: magnetic properties

2018 ◽  
Author(s):  
Jean-Pierre Launay ◽  
Michel Verdaguer
Keyword(s):  
Single Molecule ◽  
Model Systems ◽  
Ferromagnetic Coupling ◽  
Single Chain ◽  
Single Molecule Magnets ◽  
Magnetic Systems ◽  
Orbital Interactions ◽  
Prussian Blue Analogues ◽  
Mononuclear Complexes

After preliminaries about electron properties, and definitions in magnetism, one treats the magnetism of mononuclear complexes, in particular spin cross-over, showing the role of cooperativity and the sensitivity to external perturbations. Orbital interactions and exchange interaction are explained in binuclear model systems, using orbital overlap and orthogonality concepts to explain antiferromagnetic or ferromagnetic coupling. The phenomenologically useful Spin Hamiltonian is defined. The concepts are then applied to extended molecular magnetic systems, leading to molecular magnetic materials of various dimensionalities exhibiting bulk ferro- or ferrimagnetism. An illustration is provided by Prussian Blue analogues. Magnetic anisotropy is introduced. It is shown that in some cases, a slow relaxation of magnetization arises and gives rise to appealing single-ion magnets, single-molecule magnets or single-chain magnets, a route to store information at the molecular level.

The role of density reduction in lithiated amorphous silicon: Molecular dynamics and ab-initio studies

2021 ◽  
Author(s):  
Jay Krishan Dora ◽  
Charchit Saraswat ◽  
Ashish Gour ◽  
Sudipto Ghosh ◽  
Natraj Yedla ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Ab Initio ◽  
Amorphous Silicon ◽  
Density Reduction

scholarly journals Molecular Dynamics of Chloroplast Membranes Isolated from Wild-Type Barley and a Brassinosteroid-Deficient Mutant Acclimated to Low and High Temperatures

Biomolecules ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 27
Author(s):  
Iwona Sadura ◽  
Dariusz Latowski ◽  
Jana Oklestkova ◽  
Damian Gruszka ◽  
Marek Chyc ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Temperature Stress ◽  
High Temperatures ◽  
Biological Membrane ◽  
Hydrophobic Core ◽  
Wild Type ◽  
Chloroplast Membranes ◽  
Paramagnetic Resonance ◽  
Photosynthetic Membranes

Plants have developed various acclimation strategies in order to counteract the negative effects of abiotic stresses (including temperature stress), and biological membranes are important elements in these strategies. Brassinosteroids (BR) are plant steroid hormones that regulate plant growth and development and modulate their reaction against many environmental stresses including temperature stress, but their role in modifying the properties of the biological membrane is poorly known. In this paper, we characterise the molecular dynamics of chloroplast membranes that had been isolated from wild-type and a BR-deficient barley mutant that had been acclimated to low and high temperatures in order to enrich the knowledge about the role of BR as regulators of the dynamics of the photosynthetic membranes. The molecular dynamics of the membranes was investigated using electron paramagnetic resonance (EPR) spectroscopy in both a hydrophilic and hydrophobic area of the membranes. The content of BR was determined, and other important membrane components that affect their molecular dynamics such as chlorophylls, carotenoids and fatty acids in these membranes were also determined. The chloroplast membranes of the BR-mutant had a higher degree of rigidification than the membranes of the wild type. In the hydrophilic area, the most visible differences were observed in plants that had been grown at 20 °C, whereas in the hydrophobic core, they were visible at both 20 and 5 °C. There were no differences in the molecular dynamics of the studied membranes in the chloroplast membranes that had been isolated from plants that had been grown at 27 °C. The role of BR in regulating the molecular dynamics of the photosynthetic membranes will be discussed against the background of an analysis of the photosynthetic pigments and fatty acid composition in the chloroplasts.

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