scholarly journals Optical Configuration Effect on the Structure and Reactivity of Diastereomers Revealed by Spin Effects and Molecular Dynamics Calculations

2021 ◽  
Vol 23 (1) ◽  
pp. 38
Author(s):  
Aleksandra A. Ageeva ◽  
Alexander B. Doktorov ◽  
Olga Yu. Selyutina ◽  
Ilya M. Magin ◽  
Margarita G. Ilyina ◽  
...  
Keyword(s):  
Molecular Dynamic ◽  
High Sensitivity ◽  
Spin Effects ◽  
Parkinson’S Diseases ◽  
Donor Acceptor ◽  
Specific Proteins ◽  
Optical Configuration ◽  
The Difference ◽  
Modeling Data ◽  
Experimental Values

The peculiarities of spin effects in photoinduced electron transfer (ET) in diastereomers of donor-acceptor dyads are considered in order to study the influence of chirality on reactivity. Thus, the spin selectivity—the difference between the enhancement coefficients of chemically induced dynamic nuclear polarization (CIDNP)—of the dyad’s diastereomers reflects the difference in the spin density distribution in its paramagnetic precursors that appears upon UV irradiation. In addition, the CIDNP coefficient itself has demonstrated a high sensitivity to the change of chiral centers: when one center is changed, the hyperpolarization of all polarized nuclei of the molecule is affected. The article analyzes the experimental values of spin selectivity based on CIDNP calculations and molecular dynamic modeling data in order to reveal the effect of optical configuration on the structure and reactivity of diastereomers. In this way, we succeeded in tracing the differences in dyads with L- and D-tryptophan as an electron donor. Since the replacement of L-amino acid with D-analog in specific proteins is believed to be the cause of Alzheimer’s and Parkinson’s diseases, spin effects and molecular dynamic simulation in model dyads can be a useful tool for investigating the nature of this phenomenon.

The metachor as a characteristic of the association of electrolytes in aqueous solutions

1984 ◽  
Vol 49 (5) ◽  
pp. 1061-1078 ◽  
Author(s):  
Jiří Čeleda ◽  
Stanislav Škramovský
Keyword(s):  
Aqueous Solutions ◽  
Apparent Volume ◽  
Solutions Of Electrolytes ◽  
Molal Volumes ◽  
The Difference ◽  
High Concentrations ◽  
Experimental Values ◽  
Suitable Characteristic ◽  
Association Of Ions ◽  
Very High

Based on the earlier paper introducing a concept of the apparent parachor of a solute in the solution, we have eliminated in the present work algebraically the effect which is introduced into this quantity by the additivity of the apparent molal volumes. The difference remaining from the apparent parachor after substracting the contribution corresponding to the apparent volume ( for which the present authors suggest the name metachor) was evaluated from the experimental values of the surface tension of aqueous solutions for a set of 1,1-, 1,2- and 2,1-valent electrolytes. This difference showed to be independent of concentration up to the very high values of the order of units mol dm-3 but it was directly proportional to the number of the free charges (with a proportionality factor 5 ± 1 cm3 mol-1 identical for all studied electrolytes). The metachor can be, for this reason, a suitable characteristic for detection of the association of ions and formation of complexes in the solutions of electrolytes, up to high concentrations where other methods are failing.

scholarly journals The Mechanical Properties and Damage Evolution of UHPC Reinforced with Glass Fibers and High-Performance Polypropylene Fibers

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2455
Author(s):  
Jiayuan He ◽  
Weizhen Chen ◽  
Boshan Zhang ◽  
Jiangjiang Yu ◽  
Hang Liu
Keyword(s):  
Mechanical Properties ◽  
Glass Fiber ◽  
Damage Evolution ◽  
High Performance ◽  
High Performance Concrete ◽  
Glass Fibers ◽  
Ultra High Performance Concrete ◽  
Concrete Damaged Plasticity ◽  
The Difference ◽  
Experimental Values

Due to the sharp and corrosion-prone features of steel fibers, there is a demand for ultra-high-performance concrete (UHPC) reinforced with nonmetallic fibers. In this paper, glass fiber (GF) and the high-performance polypropylene (HPP) fiber were selected to prepare UHPC, and the effects of different fibers on the compressive, tensile and bending properties of UHPC were investigated, experimentally and numerically. Then, the damage evolution of UHPC was further studied numerically, adopting the concrete damaged plasticity (CDP) model. The difference between the simulation values and experimental values was within 5.0%, verifying the reliability of the numerical model. The results indicate that 2.0% fiber content in UHPC provides better mechanical properties. In addition, the glass fiber was more significant in strengthening the effect. Compared with HPP-UHPC, the compressive, tensile and flexural strength of GF-UHPC increased by about 20%, 30% and 40%, respectively. However, the flexural toughness indexes I5, I10 and I20 of HPP-UHPC were about 1.2, 2.0 and 3.8 times those of GF-UHPC, respectively, showing that the toughening effect of the HPP fiber is better.

scholarly journals Use of high-sensitivity digital ELISA improves the diagnostic performance of circulating brain-specific proteins for detection of traumatic brain injury during triage

2020 ◽  
Vol 42 (4) ◽  
pp. 346-353 ◽  
Author(s):  
Grant C. O’Connell ◽  
Megan L. Alder ◽  
Christine G. Smothers ◽  
Carolyn H. Still ◽  
Allison R. Webel ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Diagnostic Performance ◽  
High Sensitivity ◽  
Specific Proteins ◽  
Brain Specific Proteins ◽  
Digital Elisa

Transverse Young's Moduli and Cell Shapes in Coniferous Early Wood

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Ugai Watanabe ◽  
Minoru Fujita ◽  
Misato Norimoto
Keyword(s):  
Young’S Modulus ◽  
Young's Modulus ◽  
Bending Moment ◽  
Cell Models ◽  
Young’S Moduli ◽  
Cell Shapes ◽  
The Difference ◽  
Square Cells ◽  
Experimental Values ◽  
The Relationship

Summary The relationship between transverse Young's moduli and cell shapes in coniferous early wood was investigated using cell models constructed by two dimensional power spectrum analysis. The calculated values of tangential Young's modulus qualitatively explained the relationship between experimental values and density as well as the difference in experimental values among species. The calculated values of radial Young's modulus for the species having hexagonal cells agreed well with the experimental values, whereas, for the species having square cells, the calculated values were much larger than the experimental values. This result was ascribed to the fact that the bending moment on the radial cell wall of square cell models was calculated to be small. It is suggested that the asymmetrical shape of real wood cells or the behavior of nodes during ell deformation is an important factor in the mechanism of linear elastic deformation of wood cells.

Thermoelectric Power of the Liquid Sn—Te Alloy

1982 ◽  
Vol 37 (10) ◽  
pp. 1127-1131 ◽  
Author(s):  
D. H. Kurlat ◽  
M. Rosen
Keyword(s):  
Thermoelectric Power ◽  
Hard Sphere ◽  
Stoichiometric Composition ◽  
Band Model ◽  
Liquid Alloys ◽  
Sphere Approximation ◽  
The Difference ◽  
Predicted Values ◽  
Experimental Values ◽  
Two Band Model

The Seebeck coefficient (S) of Sni1-x- Tex liquid alloys was measured as a function of concentration and temperature. For 0 ≦ x <0.45 the behaviour is metallic; S values are small and negative, rising linearly with temperature. The predicted values of Ziman's theory when using the hard sphere approximation disagree with the experimental ones. The change in sign occurs for 0.45. For x = 0.5 (stoichiometric composition) the thermoelectric power decreases linearly with temperature. This fact is explained assuming a two-band model. For x ≧ 0.6 the liquid alloy becomes more semiconducting and presents a maximum in the isotherms of S for x = 0.65. For the excess tellurium concentration range we have calculated the difference EF - EV and γ/kB, assuming a S(1/T) law. The experimental values are compared with those of Dancy and Glazov.

Experimental and computed dipole moments in donor–bridge–acceptor systems with p-phenylene and p-carboranediyl bridges

2009 ◽  
Vol 74 (1) ◽  
pp. 131-146 ◽  
Author(s):  
Ladislav Drož ◽  
Mark A. Fox ◽  
Drahomír Hnyk ◽  
Paul J. Low ◽  
J. A. Hugh MacBride ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Dipole Moments ◽  
Electronic Effects ◽  
Electronic Interactions ◽  
Donor And Acceptor ◽  
Homo And Lumo ◽  
Pull Systems ◽  
The Difference ◽  
Experimental Values ◽  
2D And 3D

Dipole moments were measured for a series of substituted benzenes, biphenyls, terphenyls, C-monoaryl- and C,C′-diaryl-p-carboranes. For the donor–bridge–acceptor systems, Me2N–X–NO2, where X is 1,4-phenylene, biphenyl-4,4′-diyl, terphenyl and 1,4-C6H4-p-CB10H10C-1,4-C6H4, the measured interaction dipole moments are 1.36, 0.74, 0.51 and 0.00 D, respectively. The magnitude of the dipole moment reflects the ability of the bridge to transmit electronic effects between donor and acceptor groups. Thus, whilst the 1,4-phenylene bridges allow moderate electronic interactions between the remote groups, the p-carboranediyl unit is less efficient as a conduit for electronic effects. Averaged dipole moments computed at the DFT (B3LYP/6-31G*) level of theory from two distinct molecular conformers are in good agreement with the experimental values. Examination of the calculated electronic structures provides insight into the nature of the interactions between the donor and acceptor moieties through these 2D and 3D aromatic bridges. The most significant cooperative effect of the bridge on the dipole moment occurs in systems where there is some overlap between the HOMO and LUMO orbitals. This orbital overlap criterion may help to define the difference between “push-pull” systems in which electronic effects are mediated by the bridging moiety, and simpler systems in which the bridge acts as an electronically innocent spacer unit and through-space charge transfer/separation is dominant.

Bruch’s membrane opening-minimum rim width: An alternative OCT biomarker study for multiple sclerosis

2021 ◽  
pp. 112067212199663
Author(s):  
Kemal Turgay Özbilen ◽  
Tuncay Gündüz ◽  
Selva Nur Çukurova Kartal ◽  
Ali Ceyhun Gedik ◽  
Mefküre Eraksoy ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
High Sensitivity ◽  
The Novel ◽  
Bruch's Membrane ◽  
Bruch’S Membrane ◽  
Spectral Domain Oct ◽  
Neuroretinal Rim ◽  
Bruch’S Membrane Opening ◽  
The Difference ◽  
Therapeutic Decision Making

Purpose: Bruch’s membrane opening-minimum rim width (BMO-MRW) and RNFL measured using anatomic positioning system (APS-RNFL) are novel OCT methods and remained unexplored in MS patients. To investigate the novel parameters of spectral-domain OCT as an alternative biomarker in patients with multiple sclerosis (MS). Methods: Retrospective cohort study; participants consisted of relapsing-remitting MS (RRMS) patients and healthy controls (HC). Eyes were classified according to the presence of MS and previous optic neuritis (ON). Measurements of standard peripapillary RNFL (S-RNFL), BMO-MRW, and APS-RNFL were performed. Result: A total of 244 eyes of 122 participants (MS-patients: 63, HC: 59) were included in the study. Fifty-one eyes had a history of previous ON. In almost all measured parameters, neuroretinal rim thicknesses were observed the thinnest in eyes with ON history between all subgroups. S-RNFL and APS-RNFL techniques showed the difference in neuroretinal rim thickness in all three subjects (ON+, ON−, and HC). However, BMO-MRW, on the other hand, could not distinguish between ON(−) patients and HC. The relationship between OCT parameters and EDSS were observed only in eyes with an ON history in all three techniques. A meaningful model with 78% accuracy was obtained by using only the OCT parameters as risk factors. In the ROC analysis, no parameters were found to have acceptable high sensitivity and specificity. BMO-MRW was statistically weaker in every aspect than other RNFL techniques. Conclusion: The novel APS-RNFL technique appears to be a bit more reliable alternative to S-RNFL technique to support therapeutic decision-making in MS. BMO-MRW has not been found as a successful alternative to S-RNFL.

Core-shell Cu@C@ZIF-8 composite: a high-performance electrode material for electrochemical sensing of nitrite with high selectivity and sensitivity

2021 ◽  
Author(s):  
Feng Gao ◽  
Xiaolong Tu ◽  
Yongfang Yu ◽  
Yansha Gao ◽  
Jin Zou ◽  
...  
Keyword(s):  
High Performance ◽  
High Selectivity ◽  
Limit Of Detection ◽  
Metal Organic Framework ◽  
High Sensitivity ◽  
Electrochemical Sensing ◽  
Core Shell ◽  
Zeolitic Imidazolate Framework ◽  
Sensing Platform ◽  
The Difference

Abstract Herein, an efficient electrochemical sensing platform is proposed for selective and sensitive detection of nitrite on the basis of Cu@C@Zeolitic imidazolate framework-8 (Cu@C@ZIF-8) heterostructure. Core-shell Cu@C@ZIF-8 composite was synthesized by pyrolysis of Cu-metal-organic framework@ZIF-8 (Cu-MOF@ZIF-8) in Ar atmosphere on account of the difference of thermal stability between Cu-MOF and ZIF-8. For the sensing system of Cu@C@ZIF-8, ZIF-8 with proper pore size allows nitrite diffuse through the shell, while big molecules cannot, which ensures high selectivity of the sensor. On the other hand, Cu@C as electrocatalyst promotes the oxidation of nitrite, thereby resulting high sensitivity of the sensor. Accordingly, the Cu@C@ZIF-8 based sensor presents excellent performance for nitrite detection, which achieves a wide linear response range of 0.1 µM to 300.0 µM, and a low limit of detection (LOD) of 0.033 µM. In addition, the Cu@C@ZIF-8 sensor possesses excellent stability and reproducibility, and was employed to quantify nitrite in sausage samples with recoveries of 95.45-104.80%.

scholarly journals Proteomic Analysis of Capacitated and Non-Capacitated Spermatozoa of Yanbian Yellow Cattle

2020 ◽  
Author(s):  
Xuan Chen ◽  
Zuochen Li ◽  
Yanqiu Lv ◽  
Yichao Xu ◽  
Mimi Cheng ◽  
...  
Keyword(s):  
Protein Transport ◽  
Expression Level ◽  
Molecular Processes ◽  
Proteomics Data ◽  
Pathway Enrichment ◽  
Protein Protein Interaction ◽  
Go Enrichment ◽  
Yellow Cattle ◽  
Specific Proteins ◽  
The Difference

Abstract Background: Sperm capacitation is a process which occurs prior to fertilization, and is essential for producing high-quality living embryos. The main purpose of this study was to explore the difference of proteomics between capacitated and non-capacitated sperm of Yanbian yellow cattle. Bioinformatic analyses of LC-MS/MS data included GO enrichment, KEGG pathway enrichment, and protein-protein interaction (PPI) analysis. Results: The results revealed 23 specific proteins in the capacitated group and 345 in the non-capacitated group. Compared with non-capacitated sperm, capacitated sperm exhibited 89 upregulated proteins and 509 downregulated proteins. Western blotting was used to confirm our proteomics data. The expression level of PSMD1 in the capacitated sperm group was significantly lower than that in the non-capacitated sperm group, and the expression level of HSPA5 was significantly higher than in the non-capacitated sperm group. Conclusions: Our results revealed that many proteins were differentially expressed between capacitated and non-capacitated sperm, particularly those involved in the proteasome signaling and protein transport signaling pathways. This work enhances our understanding of molecular processes involved in sperm viability in Yanbian yellow cattle, and provides a framework for future studies.

scholarly journals Effects of External Acidification on the Blood Acid-Base Status and Ion Concentrations of Lamprey

1988 ◽  
Vol 136 (1) ◽  
pp. 351-361
Author(s):  
LEONA MATTSOFF ◽  
MIKKO NIKINMAA
Keyword(s):  
High Sensitivity ◽  
Co2 Concentration ◽  
Acid Base ◽  
Ion Concentrations ◽  
Ph Response ◽  
Ph Values ◽  
Blood Ph ◽  
Acid Base Status ◽  
The Difference ◽  
K Concentration

We studied the effects of acute external acidification on the acid-base status and plasma and red cell ion concentrations of lampreys. Mortality was observed within 24 h at pH5 and especially at pH4. The main reason for the high sensitivity of lampreys to acid water appears to be the large drop in blood pH: 0.6 and 0.8 units after 24 h at pH5 and pH4, respectively. The drop of plasma pH is much larger than in teleost fishes exposed to similar pH values. The difference in the plasma pH response between lampreys and teleosts probably results from the low buffering capacity of lamprey blood, since red cells cannot participate in buffering extracellular acid loads. Acidification also caused a decrease in both Na+ and C− concentrations and an elevation in K+ concentration of plasma. The drop in plasma Na+ concentration occurred faster than the drop in plasma Cl− concentration which, in turn, coincided with the decrease in total CO2 concentration of the blood.

Sign in / Sign up

Export Citation Format

Share Document