scholarly journals Calculation of the magnetic resonance isotropy tensors of the nucleus of POPC phospholipid bilayers in a cell membrane

2018 ◽  
Vol 8 (1) ◽  
pp. 165-173
Author(s):  
A. Elsagh ◽  
K. Zare ◽  
M. Monajjemi
Keyword(s):  
Active Sites ◽  
Anisotropy Parameter ◽  
Mutual Effect ◽  
Cellular Membrane ◽  
Target Cells ◽  
Membrane Phospholipids ◽  
Active Centers ◽  
Nmr Parameters ◽  
Effective Delivery ◽  
Phospholipid Structure

Importance of membrane phospholipids and their various applications in various sciences and industries including chemistry and biochemistry, chemical sensors and treatment of diseases and effective delivery of drugs and materials through cellular membrane is clear. Investigation of the NMR parameters including isotropy of the isotropic value (σiso), anisotropy chemical shift (σaniso), reduced anisotropy (δ), asymmetric parameter (η) of the anisotropy parameter (Δσ) and skew parameter (Ҡ) enables the recognition of target active centers. Phospholipid structure was optimized using calculation of molecular mechanics and quantum mechanics. Then, using ab initio calculations, factors of NMR chemical isotropy tensor were calculated for membrane phospholipids. According to results, it was found out that carbon no. 2 bonded to nitrogen and after that, no. 32 carbon atom bonded to the oxygen have most contribution to the dynamics movements of phospholipid in membrane. It can be concluded that high electronegativity of the nitrogen and oxygen plays an important role in sensitivity of the phospholipid carbons. Increased number of electronegative agents in the phospholipid results in better control of the dynamic role of the membrane. Evaluation of the NMR parameters of phospholipid structure led to recognition of the active centers and owing to the mutual effect of these centers, transfer and exchange in these active sites and if agents similar to the human’s genetic structure are taken into account for transfer and exchange, they can be very useful and rapid transmitters for delivery of drugs to the target cells.

scholarly journals Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 735
Author(s):  
Yuhao Zheng ◽  
Chenghua Xu ◽  
Xia Zhang ◽  
Qiong Wu ◽  
Jie Liu
Keyword(s):  
Synergistic Effect ◽  
Active Sites ◽  
Intermediate Formation ◽  
Active Phase ◽  
Dissociative Adsorption ◽  
Co2 Hydrogenation ◽  
Chain Growth ◽  
Co2 Conversion ◽  
Light Hydrocarbons ◽  
Active Centers

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

scholarly journals Sites and Determinants of Early Cleavages in the Proteolytic Processing Pathway of Reovirus Surface Protein σ3

2002 ◽  
Vol 76 (10) ◽  
pp. 5184-5197 ◽  
Author(s):  
Judit Jané-Valbuena ◽  
Laura A. Breun ◽  
Leslie A. Schiff ◽  
Max L. Nibert
Keyword(s):  
Structural Changes ◽  
Proper Time ◽  
Strain Differences ◽  
Surface Protein ◽  
Cellular Membrane ◽  
Proteolytic Processing ◽  
Target Cells ◽  
Inactive Form ◽  
Reovirus Type ◽  
Type 3

ABSTRACT Entry of mammalian reovirus virions into target cells requires proteolytic processing of surface protein σ3. In the virion, σ3 mostly covers the membrane-penetration protein μ1, appearing to keep it in an inactive form and to prevent it from interacting with the cellular membrane until the proper time in infection. The molecular mechanism by which σ3 maintains μ1 in this inactive state and the structural changes that accompany σ3 processing and μ1 activation, however, are not well understood. In this study we characterized the early steps in σ3 processing and determined their effects on μ1 function and particle infectivity. We identified two regions of high protease sensitivity, “hypersensitive” regions located at residues 208 to 214 and 238 to 244, within which all proteases tested selectively cleaved σ3 as an early step in processing. Further processing of σ3 was required for infection, consistent with the fact that the fragments resulting from these early cleavages remained bound to the particles. Reovirus type 1 Lang (T1L), type 3 Dearing (T3D), and T1L × T3D reassortant virions differed in the sites of early σ3 cleavage, with T1L σ3 being cleaved mainly at residues 238 to 244 and T3D σ3 being cleaved mainly at residues 208 to 214. These virions also differed in the rates at which the early cleavages occurred, with cleavage of T1L σ3 occurring faster than cleavage of T3D σ3. Analyses using chimeric and site-directed mutants of recombinant σ3 identified carboxy-proximal residues 344, 347, and 353 as the primary determinants of these strain differences. The spatial relationships between these more carboxy-proximal residues and the hypersensitive regions were discerned from the σ3 crystal structure. The results indicate that proteolytic processing of σ3 during reovirus disassembly is a multistep pathway with a number of molecular determinants.

Active sites-enriched carbon matrix enables efficient triiodide reduction in dye-sensitized solar cells: An understanding of the active centers

Nano Energy ◽  
2018 ◽  
Vol 54 ◽  
pp. 138-147 ◽  
Author(s):  
Xiangtong Meng ◽  
Chang Yu ◽  
Xuepeng Zhang ◽  
Longlong Huang ◽  
Matthew Rager ◽  
...  
Keyword(s):  
Solar Cells ◽  
Active Sites ◽  
Dye Sensitized Solar Cells ◽  
Carbon Matrix ◽  
Active Centers ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

scholarly journals Structure analysis of an Fe-interlayer expanded zeolite.

2014 ◽  
Vol 70 (a1) ◽  
pp. C186-C186
Author(s):  
Hermann Gies ◽  
Mathias Feyen
Keyword(s):  
Structure Analysis ◽  
Active Sites ◽  
Hydrothermal Reaction ◽  
Uv Spectroscopy ◽  
Structure Refinement ◽  
Rietveld Analysis ◽  
Active Centers ◽  
Layer Silicates ◽  
New Material ◽  
Silicate Layers

Interlayer expansion using silylating agents to connect layer silicates to 3D framework structures has proofed to be a versatile synthesis route to new micro-porous frameworks (1). We show here that also Me-cations can be used as linker agents. An acidic Fe-chloride solution was used in a hydrothermal reaction to convert the hydrous layer silicate RUB-36 into an interlayer expanded zeolite, containing Fe at the linker site. Structure analysis of the new material Fe-COE-3, Si19.14Fe0.86O42, showed that the porous framework is stable after calcination and contains Fe on T-sites at the linker position which connects the two silicate layers. From chemical analysis it is confirmed that every other linker site is occupied by iron. The material crystallizes in space group Pm with a = 12.200(9) Å, b = 13.981(8) Å, c = 7.369(2) Å, ß = 106.9(1)0. Fig. 1 shows the results of the final Rietveld analysis (chi2= 8.8) and a projection of the framework structure along [001]. Because of the limited crystallinity of the material also the quality of the structure refinement is constricted. However, including complementary information from adsorption experiments, IR-, and UV-spectroscopy the structure model is confirmed without any doubt. Besides, the Rietveld analysis of the XRD data is the analytical tool to gain more detailed geometric information of the metallosilicate framework. The synthesis procedure is flexible and can be extended to other Me-cations as linker sites. We have prepared isostructural interlayer expanded metallosilicates of similar crystallinity with Ti, Sn, Zn, Eu, and Al as active centers. This method of inserting Me-cations as linkers in hydrous layer silicates shows for the first time that the active sites in the generated microporous silicate framework can be obtained in a controlled manner on well defined T-sites.

scholarly journals New Supports for Carbon-Metal Catalytic Systems Based on Shungite and Carbonizates of Plant Raw Materials

2015 ◽  
Vol 17 (3) ◽  
pp. 223 ◽  
Author(s):  
R.R. Tokpayev ◽  
A.A. Atchabarova ◽  
S.A. Abdullayeva ◽  
S.V. Nechipurenko ◽  
S.A. Yefremov ◽  
...  
Keyword(s):  
Active Sites ◽  
Raw Materials ◽  
Base Catalysis ◽  
Metal Catalyst ◽  
Active Centers ◽  
Catalytic Systems ◽  
Homogeneous Surface ◽  
Plant Raw Materials ◽  
Bet Method ◽  
Catalyst Systems

<p>In this paper, new carbon containing materials based on products of shungite ore enrichment and carbonizates of plant raw materials were studied. The phase transformations occurring during the carbonization process were studied. Scanning electron microscopy (SEM) was used to visualize the surface topography. It was established that supports based on plant raw materials have more developed and homogeneous surface. Specific surface area and porosity was studied by BET (Method of Brunauer-Emmet Taylor). It was found that supports based on plant raw materials have developed microporous surface (383–480 m<sup>2</sup>/g), with predominant micropores on the surface with dimensions of 1.8–2.5 nm. The mechanical strength of the obtained supports is higher than their industrial analogs and it equals 53–91%. Conversion of methylbutynol on active centers of supports was studied. Supports based on plant raw materials have basic active sites whereby they can be used in base catalysis. Supports based on carbon-mineral raw materials possess acid and basic active sites and they can be used to prepare bidirectional type action of catalysts. Conducted research have shown the possibility of using these materials as supports for creating carbon-metal catalyst systems.</p>

scholarly journals Potential of miRNA-Based Nanotherapeutics for Uveal Melanoma

Cancers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 5192
Author(s):  
Chun Yang ◽  
Rui Wang ◽  
Pierre Hardy
Keyword(s):  
Signaling Pathways ◽  
Uveal Melanoma ◽  
Intracellular Signaling ◽  
Complex Disease ◽  
Therapeutic Potential ◽  
Cancer Therapeutics ◽  
Delivery Systems ◽  
Epigenetic Mechanism ◽  
Target Cells ◽  
Effective Delivery

Uveal melanoma (UM) is the most common adult intraocular cancer, and metastatic UM remains deadly and incurable. UM is a complex disease associated with the deregulation of numerous genes and redundant intracellular signaling pathways. As understanding of epigenetic dysregulation in the oncogenesis of UM has increased, the abnormal expression of microRNAs (miRNAs) has been found to be an epigenetic mechanism underlying UM tumorigenesis. A growing number of miRNAs are being found to be associated with aberrant signaling pathways in UM, and some have been investigated and functionally characterized in preclinical settings. This review summarizes the miRNAs with promising therapeutic potential for UM treatment, paying special attention to the therapeutic miRNAs (miRNA mimics or inhibitors) used to restore dysregulated miRNAs to their normal levels. However, several physical and physiological limitations associated with therapeutic miRNAs have prevented their translation to cancer therapeutics. With the advent of nanotechnology delivery systems, the development of effective targeted therapies for patients with UM has received great attention. Therefore, this review provides an overview of the use of nanotechnology drug delivery systems, particularly nanocarriers that can be loaded with therapeutic miRNAs for effective delivery into target cells. The development of miRNA-based therapeutics with nanotechnology-based delivery systems may overcome the barriers of therapeutic miRNAs, thereby enabling their translation to therapeutics, enabling more effective targeting of UM cells and consequently improving therapeutic outcomes.

scholarly journals Nanocomposites SnO2/SiO2:SiO2 Impact on the Active Centers and Conductivity Mechanism

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3618 ◽  
Author(s):  
Dayana Gulevich ◽  
Marina Rumyantseva ◽  
Artem Marikutsa ◽  
Tatyana Shatalova ◽  
Elizaveta Konstantinova ◽  
...  
Keyword(s):  
Active Sites ◽  
Nitrogen Adsorption ◽  
Hydroxyl Groups ◽  
Pure Sno2 ◽  
Active Centers ◽  
Paramagnetic Resonance ◽  
Surface Hydroxyl ◽  
Chemisorbed Oxygen ◽  
Temperature Dependences ◽  
Sio2 Nanocomposites

This paper is focused on the effect of the stabilizing component SiO2 on the type and concentration of active sites in SnO2/SiO2 nanocomposites compared with nanocrystalline SnO2. Previously, we found that SnO2/SiO2 nanocomposites show better sensor characteristics in CO detection (lower detection limit, higher sensor response, and shorter response time) compared to pure SnO2 in humid air conditions. Nanocomposites SnO2/SiO2 synthesized using the hydrothermal method were characterized by low temperature nitrogen adsorption, XRD, energy dispersive X-ray spectroscopy (EDX), thermo-programmed reduction with hydrogen (TPR-H2), IR-, and electron-paramagnetic resonance (EPR)-spectroscopy methods. The electrophysical properties of SnO2 and SnO2/SiO2 nanocomposites were studied depending on the oxygen partial pressure in the temperature range of 200–400 °C. The introduction of SiO2 results in an increase in the concentration of paramagnetic centers Sn3+ and the amount of surface hydroxyl groups and chemisorbed oxygen and leads to a decrease in the negative charge on chemisorbed oxygen species. The temperature dependences of the conductivity of SnO2 and SnO2/SiO2 nanocomposites are linearized in Mott coordinates, which may indicate the contribution of the hopping mechanism with a variable hopping distance over local states.

scholarly journals Intensification of Catalytic Processes through the Pellet Structuring: Steady-State Properties of a Bifunctional Catalyst Pellet Applied to Generic Chemical Reactions and the Direct Synthesis of DME

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1020 ◽  
Author(s):  
Katarzyna Bizon ◽  
Krzysztof Skrzypek-Markiewicz ◽  
Dominik Pędzich ◽  
Natalia Reczek
Keyword(s):  
Chemical Reactions ◽  
Active Sites ◽  
Direct Synthesis ◽  
Fixed Bed ◽  
Product Yield ◽  
Bifunctional Catalyst ◽  
Active Centers ◽  
Entire Volume ◽  
Catalyst Pellet ◽  
Real Process

Structuring of different types of catalytic active centers at a single-pellet level appears to be a promising and powerful tool for integration and intensification of multistep solid-catalyzed chemical reactions. However, the enhancement in the product yield and selectivity strongly depends on the proper choice of the distribution of different catalysts within the pellet. To demonstrate potential benefits from properly designed catalyst pellet, numerical studies were conducted with the aid of the mathematical model of a single spherical bifunctional catalyst pellet. The analysis was performed both for a system of two generic chemical reactions and for a real process, i.e., direct synthesis of dimethyl ether (DME) from synthesis gas via methanol. Evaluation of the pellet performance was done for three arrangements of the catalytic active sites within the pellet, i.e., a uniform distribution of two types of catalytic active centers in the entire volume of the pellet, and two core–shell structures. It was demonstrated that, especially for the larger pellets typical for fixed-bed applications, the product yield might be significantly improved by selecting proper catalyst arrangements within the pellet.

DIRECT STIMULATIONOF CA2+-ACTIVATED HUMAN PLATELET PHOSPHOLIPASE A2 BY DIACYLGLYCEROL

1987 ◽  
Author(s):  
D Deykin ◽  
R M Karmer
Keyword(s):  
Enzymatic Activity ◽  
Phospholipase A2 ◽  
Conformational Changes ◽  
Cellular Membrane ◽  
Human Platelets ◽  
Stable Form ◽  
Membrane Phospholipids ◽  
Kinase C ◽  
Snake Venom Phospholipase ◽  
Phospholipase A2 Activity

These studies examined the effect of diacylglycerol on Ca2+-dependent phospholipase A2 from human platelets. Phospholipase A2 was solubilized and partially purified to a stable form in the presence of octylglucoside and its enzymatic activity determined using sonicated arachidonoyl phosphatidylcholine (PC) as substrate. (Kramer RM, et al: BBA 878:394, 1986) Phospholipase A2 activity was increased when dioleoylglycerc_ was incorporated into the substrate arachidonoyl-PC. In the presence of 1 uM (29 mol %) sn-1,2-dioleoylglycerol the enzymatic activity was stimulated 4.1-fold. Exogenously added sn-l-oleoyl-2-acetoylglycerol also enhanced phospholipase A2 activity, producing a maximal stimulation of 1.6-fold at a concentration of 25 uM. Comparative studies conducted with pancreatic, bee-venom and snake venom phospholipase A2 showed that the activity of these extracellular phospholipases towards the arachidonoyl-PC substrate was also increased by diacylglycerol, but the stimulation was less than observed for platelet phospholipase A2. We conclude that in stimulated platelets Ca2+-activated phospholipase A2 may be regulated by newly generated diacylglycerols, not only via protein kinase C-mediated events, but also directly through conformational changes imposed by the diglycerides on cellular membrane phospholipids.

scholarly journals Aging and chronic illnesses: Membrane Lipid Replacement for restoring mitochondrial function and reducing fatigue, pain, and other symptoms in aged individuals

2020 ◽  
Vol 3 (10) ◽  
pp. 194
Author(s):  
Garth Nicolson ◽  
Paul Breeding ◽  
Robert Settineri ◽  
Gonzalo Ferreira De Mattos
Keyword(s):  
Clinical Trials ◽  
Mitochondrial Function ◽  
Case Reports ◽  
Gastrointestinal Symptoms ◽  
Cellular Membrane ◽  
Membrane Lipid ◽  
Membrane Phospholipids ◽  
Membrane Function ◽  
Age Related ◽  
Clinical Diagnoses

Membrane Lipid Replacement (MLR) is the use of functional dietary supplements containing cell membrane glycerolphospholipids and antioxidants to safely replace and remove damaged essential membrane phospholipids that accumulate during aging and in various chronic and acute illnesses. Most, if not all, clinical conditions and aging are characterized by cellular membrane phospholipid free radical oxidative damage, resulting in loss of membrane and cellular functions. In particular, loss of mitochondrial function, the key organelle responsible for over 90% of cellular energy production, can result in excess fatigue and other symptoms, and this is a common problem in almost all, if not all, age-related chronic diseases. Clinical trials have shown the benefits of MLR supplements in replenishing damaged membrane phospholipids and restoring mitochondrial function, resulting in reductions in fatigue and other symptoms in aged subjects and patients with a variety of clinical diagnoses. Here we have specifically reviewed the beneficial results of MLR on subjects older than 60 years. MLR provides general membrane and nutritional support during aging and illnesses to improve membrane function and overall health without risk of adverse effects. The case reports here and elsewhere and published clinical trials demonstrate that this is a safe and effective alternative or addition to pharmaceutical approaches for alleviating fatigue, pain, gastrointestinal and other symptoms associated with normal aging and age-related chronic illnesses.Keywords: Aging, Fatigue, Pain, Gastrointestinal symptoms, Phospholipids, Clinical trials, Case reports, Cellular membranes

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