Sequence, Salt, Charge, and the Stability of DNA at High Pressure

1996 ◽  
Author(s):  
Robert B. Macgregor Jr ◽  
John Q. Wu
Keyword(s):  
Molar Volume ◽  
Volume Change ◽  
Salt Concentration ◽  
Electrostatic Interactions ◽  
Proposed Model ◽  
Dna Strands ◽  
Positive Volume ◽  
Ion Radius ◽  
The Stability ◽  
Kinetics Of

The effect of pressure on the helix-coil transition temperature (Tm) is reported for the double-stranded polymers poly(dA)poly(dT), poly[d(A-T)], poly[d(l-C], and poly[d(G-C] and triple-stranded poly(dA)2poly(dT). The Tm increases as a function of pressure, implying a positive volume change for the transition and leading to the conclusion that the molar volume of the coil form is larger than the molar volume of the helix. From the change in Tm as a function of pressure, molar volume changes of the transition (ΔVt) are calculated using the Clapeyron equation and calorimetrically determined enthalpies. For the doublestranded polymers, ΔVt, increases in the order poly[d(l-C] < polyt[d(A-T)] < poly(dA)-poly(dT) < polylcl(G-C)]. The value of ΔVt, for the triple-stranded to single-stranded transition of poly(dA) 2poly(dT) is larger than that of poly[d(G-C)I. The magnitude of ΔVt increases with salt concentration in all cases studied; however, the change of ΔVt with salt concentration depends on the sequence of the DNA and the number of strands involved in the transition. In the model proposed to explain the results, the overall molar volume change of the transition is a function of a negative volume change arising from changes in the electrostatic interactions of the DNA strands, and a positive volume change due to unstacking the bases. The model predicted the direction of the change in the ΔVt for several experiments. The magnitude of AVJ increases with counter ion radius, thus for polyld(A-T)], ΔVt, increases in the series Na+ , K+, Cs+, The ΔVt also increases if the charge on the phosphodiester groups is removed. The kinetics of the formation of double-stranded (dA)19(dT)19 in 50 mM NaCI are slowed approximately 14-fold at 200 MPa relative to atmospheric pressure. The implied volume of activation of +37 ml mol−l in the direction of this change is also in agreement with the proposed model. The stability of double- and triple-stranded DNA helices in water around neutral pH depends on the base composition and sequence, as well as on the ionic strength of the solution. Each of these dependencies also defines how DNA interacts with water.

scholarly journals Liquid-State Volumetric Properties of a Set of Alcohols with Up to Five Carbon Atoms

Liquids ◽  
2022 ◽  
Vol 2 (1) ◽  
pp. 1-13
Author(s):  
Beatriz Lorenzo ◽  
José Aythami Yánez ◽  
Juan Ortega ◽  
Adriel Sosa ◽  
Luis Fernández
Keyword(s):  
Experimental Data ◽  
Molar Volume ◽  
Liquid State ◽  
Volumetric Properties ◽  
Tait Equation ◽  
General State ◽  
Density Data ◽  
Proposed Model ◽  
The Stability

This work provides density data (~1300 values) of 14 alcohols with up to five carbon atoms at p ∈ [0.1–40] MPa and T ∈ [278–358] K. The information obtained is modeled with a convenient reformulation of the Tait equation from which the volumetric coefficients, α and β, are derived both analytically and numerically. The general EoS containing α and β is also used for checking the consistency of the hypothesis on the invariability of the cited thermophysic parameters. The results obtained can be considered reliable because of the low estimated errors between the experimental data and those of the literature, which are below 0.4% for volume, while for the volumetric coefficients there is always a reference diverging 10%, or less, from the proposed model estimations. By including the averages of α and β into the general state of equation the errors increase, being <15%, compared to those based on the Tait equation. Hence, the assumption on the stability of the volumetric coefficients in this working interval is sufficient to make rough estimations of the molar volume of the selected alcohols.

Kinetics of Various 99mTc-Sn-Pyrophosphate Compounds in the Rat

1977 ◽  
Vol 16 (04) ◽  
pp. 157-162 ◽  
Author(s):  
C. Schümichen ◽  
B. Mackenbrock ◽  
G. Hoffmann
Keyword(s):  
Normal Saline ◽  
Half Life ◽  
Compound A ◽  
Short Half Life ◽  
Low Concentrations ◽  
The Stability ◽  
Kinetics Of ◽  
In Vitro Stability

SummaryThe bone-seeking 99mTc-Sn-pyrophosphate compound (compound A) was diluted both in vitro and in vivo and proved to be unstable both in vitro and in vivo. However, stability was much better in vivo than in vitro and thus the in vitro stability of compound A after dilution in various mediums could be followed up by a consecutive evaluation of the in vivo distribution in the rat. After dilution in neutral normal saline compound A is metastable and after a short half-life it is transformed into the other 99mTc-Sn-pyrophosphate compound A is metastable and after a short half-life in bone but in the kidneys. After dilution in normal saline of low pH and in buffering solutions the stability of compound A is increased. In human plasma compound A is relatively stable but not in plasma water. When compound B is formed in a buffering solution, uptake in the kidneys and excretion in urine is lowered and blood concentration increased.It is assumed that the association of protons to compound A will increase its stability at low concentrations while that to compound B will lead to a strong protein bond in plasma. It is concluded that compound A will not be stable in vivo because of a lack of stability in the extravascular space, and that the protein bond in plasma will be a measure of its in vivo stability.

Persistent Photoconductivity And Thermal Recovery Kinetics Of Low Energy Ar + Bombarded GaAs

1991 ◽  
Vol 223 ◽  
Author(s):  
A. Vaseashta ◽  
L. C. Burton
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Thermal Recovery ◽  
Low Energy ◽  
Persistent Photoconductivity ◽  
Transport Parameters ◽  
Excellent Correlation ◽  
Proposed Model ◽  
Transient Spectroscopy ◽  
Kinetics Of

ABSTRACTKinetics of persistent photoconductivity, photoquenching, and thermal and optical recovery observed in low energy Ar+ bombarded on (100) GaAs surfaces have been investigated. Rate and transport equations for these processes were derived and simulated employing transport parameters, trap locations and densities determined by deep level transient spectroscopy. Excellent correlation was obtained between the results of preliminary simulation and the experimentally observed values. The exponential decay of persistent photoconductivity response curve was determined to be due to metastable electron traps with longer lifetime and is consistent with an earlier proposed model.

In situ Time-Resolved Small-Angle X-ray Scattering Reveals the Formation Kinetics of Polyelectrolyte Complex Micelles

2019 ◽  
Author(s):  
Hao Wu ◽  
Jeffrey Ting ◽  
Siqi Meng ◽  
Matthew Tirrell
Keyword(s):  
Small Angle ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Polyelectrolyte Complex ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Kinetics Of ◽  
Ray Scattering

We have directly observed the <i>in situ</i> self-assembly kinetics of polyelectrolyte complex (PEC) micelles by synchrotron time-resolved small-angle X-ray scattering, equipped with a stopped-flow device that provides millisecond temporal resolution. This work has elucidated one general kinetic pathway for the process of PEC micelle formation, which provides useful physical insights for increasing our fundamental understanding of complexation and self-assembly dynamics driven by electrostatic interactions that occur on ultrafast timescales.

Modeling of sorption kinetics of U(VI) micro-quantities nanostructured materials with anatase mesoporous structures

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Veniamin Zheleznov ◽  
Aleksey Golikov ◽  
Tatiana Sokolnitskaya ◽  
Sergey Ivannikov
Keyword(s):  
Nanostructured Materials ◽  
Sorption Kinetics ◽  
Uranyl Ion ◽  
Competitive Sorption ◽  
Hydroxyl Groups ◽  
Complex Ions ◽  
The Stability ◽  
Kinetics Of ◽  
Mesoporous Structures ◽  
Ionic Forms

Abstract The sorption kinetics of uranyl ions micro-quantities from fluoride solutions by nanostructured materials with anatase mesoporous structures has been studied. Using the model of competitive sorption of ions and positively charged complexes of uranyl ion on deprotonated hydroxyl groups of an anatase, kinetic curves of changes in the ratio of ionic forms of uranium in solution were calculated. Modeling was carried out under the assumption of a two-stage mechanism of uranium complex ions sorption. The modeling considered the influence of the uranyl ion carbonate complexes formation. The shift in equilibrium among ionic forms of uranyl correlates with the stability of the complexes in solution.

scholarly journals Contribution of engineered electrostatic interactions to the stability of cytosolic malate dehydrogenase

2001 ◽  
Vol 14 (11) ◽  
pp. 911-917 ◽  
Author(s):  
Francesca Trejo ◽  
Josep Ll. Gelpí ◽  
Albert Ferrer ◽  
Albert Boronat ◽  
Montserrat Busquets ◽  
...  
Keyword(s):  
Malate Dehydrogenase ◽  
Electrostatic Interactions ◽  
The Stability ◽  
Cytosolic Malate Dehydrogenase

scholarly journals Experimental Study on the Softening Characteristics of Sandstone and Mudstone in Relation to Moisture Content

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Gui-chen Li ◽  
Chong-chong Qi ◽  
Yuan-tian Sun ◽  
Xiao-lin Tang ◽  
Bao-quan Hou
Keyword(s):  
Moisture Content ◽  
Vertical Displacement ◽  
Surface Porosity ◽  
Shear Tests ◽  
Moisture Contents ◽  
Dynamic Finite Element ◽  
Rock Types ◽  
Underground Roadway ◽  
The Stability ◽  
Kinetics Of

The kinetics of fluid-solid coupling during immersion is an important topic of investigation in rock engineering. Two rock types, sandstone and mudstone, are selected in this work to study the correlation between the softening characteristics of the rocks and moisture content. This is achieved through detailed studies using scanning electron microscopy, shear tests, and evaluation of rock index properties during exposure to different moisture contents. An underground roadway excavation is simulated by dynamic finite element modeling to analyze the effect of moisture content on the stability of the roadway. The results show that moisture content has a significant effect on shear properties reduction of both sandstone and mudstone, which must thus be considered in mining or excavation processes. Specifically, it is found that the number, area, and diameter of micropores, as well as surface porosity, increase with increasing moisture content. Additionally, stress concentration is negatively correlated with moisture content, while the influenced area and vertical displacement are positively correlated with moisture content. These findings may provide useful input for the design of underground roadways.

Light-Induced Metastable Defects in a-Si:H: Towards an Understanding

1985 ◽  
Vol 49 ◽  
Author(s):  
Martin Stutzmann ◽  
Warren B. Jackson ◽  
Chuang Chuang Tsai
Keyword(s):  
Amorphous Silicon ◽  
Mechanical Stress ◽  
Hydrogenated Amorphous Silicon ◽  
Material Parameters ◽  
Kinetic Behaviour ◽  
Proposed Model ◽  
Special Cases ◽  
The Stability ◽  
Hydrogenated Amorphous

AbstractThe dependence of the creation and the annealing of metastable dangling bonds in hydrogenated amorphous silicon on various material parameters will be discussed in the context of a recently proposed model. After a brief review of the kinetic behaviour governing defect creation and annealing in undoped a- Si:H, a number of special cases will be analyzed: the influence of alloying with O, N, C, and Ge, changes introduced by doping and compensation, and the role of mechanical stress. Finally, possibilities to increase the stability of a-Si:H based devices will be examined.

Adhesion of Fine Particles at Solid/Solution Interfaces

MRS Bulletin ◽  
1990 ◽  
Vol 15 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Nikola Kallay
Keyword(s):  
Fine Particles ◽  
Plane Surface ◽  
Solid Surfaces ◽  
Liquid Media ◽  
Latex Dispersions ◽  
Colloid Particles ◽  
The Subject ◽  
Kinetic Investigations ◽  
The Stability ◽  
Kinetics Of

The adhesion of particles at solid surfaces in liquid media has attracted the attention of scientists because of its various applications as well as the theoretical significance of the processes involved. Early studies were characterized either by poorly defined systems or limited by the properties of a few morphologically well-defined model colloids, such as latex dispersions. Consequently, results were either of semiquantitative nature or were related to some specific cases, which eluded general conclusions. New methods for preparing uniform particles of different compositions, shapes, and sizes make it possible to approach the problem in a more comprehensive manner. For example, to demonstrate difficulties caused by polydispersity, it is sufficient to mention that the electrostatic interaction energy between a plane surface and a particle is approximately proportional to the particle radius, yet the rate of deposition depends exponentially on the height of the energy barrier.In principle, static and dynamic approaches may be employed in the study of particle adhesion. The static method yields the force required to detach an adhered particle, while kinetic investigations of attachment and detachment give the rates of the respective processes. Both methods offer information on the stability of the system in terms of the bond strength of adhered solids. For small colloid particles, which are the subject of thermal random Brownian motion, the dynamic approach is more appropriate. This article emphasizes the kinetics of deposition and detachment of small colloid particles in liquid media.

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