scholarly journals Programming in situ accelerated DNA walkers in diffusion-limited microenvironments

2019 ◽  
Vol 10 (10) ◽  
pp. 3103-3109 ◽  
Author(s):  
Feng Chen ◽  
Jing Xue ◽  
Min Bai ◽  
Jing Qin ◽  
Yongxi Zhao
Keyword(s):  
Enzyme Catalysis ◽  
Cytoplasmic Enzyme ◽  
Diffusion Limited ◽  
Dna Walkers

In situ accelerated DNA walkers in diffusion-limited microenvironments are reported and utilized to monitor cytoplasmic enzyme catalysis and pathways.

In situ tailoring bimetallic-organic frameworks derived yolk-shell NiS2/CuS hollow microspheres: an extraordinary kinetically pseudocapacitive nanoreactor for effective sodium-ion storage anode

2021 ◽  
Author(s):  
wen xi zhao ◽  
Xiaodeng Wang ◽  
Xiaoqing Ma ◽  
Luchao Yue ◽  
Qian Liu ◽  
...  
Keyword(s):  
Sodium Ion ◽  
Ion Adsorption ◽  
Redox Kinetics ◽  
Diffusion Limited ◽  
Ion Storage ◽  
Sluggish Diffusion ◽  
Fast Ion ◽  
Adsorption Desorption ◽  
Sodium Ion Storage

Pseudocapacitive electrochemical Na+-storage has been highlighted as one of the exploitable strategies in overcoming sluggish diffusion-limited redox kinetics due to effectively structural preserving and fast ion adsorption/desorption at the surface...

scholarly journals Experimental and Theoretical Bases of Specific Affinity, a Cytoarchitecture-Based Formulation of Nutrient Collection Proposed To Supercede the Michaelis-Menten Paradigm of Microbial Kinetics

2004 ◽  
Vol 70 (9) ◽  
pp. 5511-5521 ◽  
Author(s):  
D. K. Button ◽  
Betsy Robertson ◽  
Elizabeth Gustafson ◽  
Xiaoming Zhao
Keyword(s):  
Kinetic Curve ◽  
Enzyme Concentration ◽  
Whole Cells ◽  
Cytoplasmic Enzyme ◽  
Multiple Substrates ◽  
Microbial Kinetics ◽  
Solute Uptake ◽  
Sufficient Energy ◽  
Specific Affinity

ABSTRACT A theory for solute uptake by whole cells was derived with a focus on the ability of oligobacteria to sequester nutrients. It provided a general relationship that was used to obtain the kinetic constants for in situ marine populations in the presence of naturally occurring substrates. In situ affinities of 0.9 to 400 liters g of cells−1 h−1 found were up to 103 times smaller than those from a “Marinobacter arcticus ” isolate, but springtime values were greatly increased by warming. Affinities of the isolate for usual polar substrates but not for hydrocarbons were diminished by ionophores. A kinetic curve or Monod plot was constructed from the best available data for cytoarchitectural components of the isolate by using the theory together with concepts and calculations from first principles. The order of effect of these components on specific affinity was membrane potential > cytoplasmic enzyme concentration > cytoplasmic enzyme affinity > permease concentration > area of the permease site > translation coefficient > porin concentration. Component balance was influential as well; a small increase in cytoplasmic enzyme concentration gave a large increase in the effect of permease concentration. The effect of permease concentration on specific affinity was large, while the effect on Km was small. These results are in contrast to the Michaelis-Menten theory as applied by Monod that has uptake kinetics dependent on the quality of the permease molecules, with Km as an independent measure of affinity. Calculations demonstrated that most oligobacteria in the environment must use multiple substrates simultaneously to attain sufficient energy and material for growth, a requirement consistent with communities largely comprising few species.

An In Situ STM Investigation of Stranski - Krastanov Growth of Ag on Au (111) Electrodes

1993 ◽  
Vol 317 ◽  
Author(s):  
S. G. Corcoran ◽  
G. S. Chakarova ◽  
K. Sieradzki
Keyword(s):  
Heterogeneous Nucleation ◽  
Three Dimensional ◽  
Growth Front ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Diffusion Limited Aggregation ◽  
Experimental Conditions ◽  
Diffusion Limited ◽  
Ag Crystallites

ABSTRACTWe present in situ scanning tunneling Microscopy (STM) results which show the morphological aspects of Ag electrodeposition on Au (111). The experimental conditions enabled us to follow, in real time, with monolayer resolution, the morphological details of Stranski-Krastanov (SK) growth under a fixed electrochemical potential (constant supersaturation). Two epitaxial layers of Ag were sequentially formed prior to the heterogeneous nucleation of three-dimensional Ag crystallites. STM images are presented showing that the second silver monolayer has a coarsened (surface) diffusion-limited-aggregation growth front. IMMediately after the completion of the second silver monolayer which took approximately five Minutes, we observed the formation of 3D clusters preferentially at step edges. Our analysis of the SK growth process indicates that it is not well described by heterogeneous-nucleation thermodynamics owing to the almost identical lattice parameters of Ag and Au. Instead, we argue that the wetting-nonwetting transition we observed was kinetically stabilized by the relatively high activation energy involved with the motion of Ag adatoms over a descending Ag step.

scholarly journals Synthesis of Chitosan-Functionalized Fibrous Membrane for Immobilization of Horseradish Peroxidase: Interfacial Property and Application for Catalytic Oxidation of P-Nitrophenol

2018 ◽  
Vol 13 (2) ◽  
pp. 155892501801300
Author(s):  
Cuie Wang ◽  
Xinhua Liu
Keyword(s):  
Catalytic Oxidation ◽  
Enzyme Catalysis ◽  
Fibrous Membrane ◽  
Interfacial Property ◽  
Mass Loading ◽  
Hydrophobic Polymer ◽  
Immobilization Of Enzymes ◽  
Wide Ph Range ◽  
Ph Range

A hydrophilic fibrous membrane consisting of a network of a non-crystalline hydrophobic polymer and an in situ crosslinked hydrophilic chitosan polymer is studied. This chitosan-functionalized membrane can be employed as a support for immobilization of horseradish peroxidases (HRPs). The immobilized HRPs (mass loading ~110 mg /g) show high stabilities over a wide pH range of 4~10 and temperature range of 25~60°C. In addition, the immobilized HRPs can function as a recyclable biocatalyst for catalytic oxidation of p-nitrophenol (PNP). After 10 cycles, the PNP removal efficiency is 70 percent. The results demonstrate that the chitosan-functionalized fibrous membrane is a promising support for immobilization of enzymes and has applications related to enzyme catalysis.

Layer thickness determinations with X-ray diffraction

1989 ◽  
Vol 22 (2) ◽  
pp. 150-154 ◽  
Author(s):  
D. E. Anderson ◽  
W. J. Thomson
Keyword(s):  
Absorption Coefficient ◽  
Layer Thickness ◽  
Single Equation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Practical Difficulty ◽  
Diffusion Limited ◽  
Crystalline Substrate ◽  
New Equation

A new equation involving an absorption coefficient is presented for calculating the thickness of a layer of a crystalline specimen deposited on a crystalline substrate. This new equation is particularly applicable to in situ X-ray diffraction studies of diffusion-limited kinetics; it is demonstrated that the practical difficulty of optimally partitioning count time between the peak of the substrate and peak of the layered specimen is overcome by making use of all available data in this single equation. This can result in more precise thickness determinations for intermediate specimen thicknesses than would be possible with either of the existing methods.

Electroactive Polymerized Vesicles as Stable Biomaterials for Charge Storage Systems and Electron Coupling Applications

2001 ◽  
Vol 711 ◽  
Author(s):  
Ivan Stanish ◽  
Alok Singh
Keyword(s):  
Electron Transport ◽  
Transport Model ◽  
Storage Systems ◽  
Phospholipid Vesicle ◽  
Initial Current ◽  
Surface Stability ◽  
Diffusion Limited ◽  
Vesicle Membranes ◽  
Membrane Bound

ABSTRACTDiacetylenic phospholipids with disulfide functionality were synthesized and incorporated at dopant levels with unmodified diacetylenic phosphatidylcholine lipids in polymerized vesicles. These polymerized vesicles were immobilized on Au films and structurally characterized in situ using AFM and ESEM and demonstrated surface stability of at least three days. Polymerized diacetylenic phospholipid vesicles displayed retention of entrapped ferricyanide with a half-life of 2.4 weeks at pH 7 and 25 oC. Membrane-bound benzoquinone mediated electron transport across polymerized vesicle membranes providing an initial current of 25 mA and a final charge capacity based on entrapped ferricyanide of 3.5 Ahr/kg. Electron transport across polymerized diacetylenic phospholipid vesicle membranes was described by a pseudosteady-state transport model and was found to be diffusion limited.

scholarly journals Architectural RNA is required for heterochromatin organization

2019 ◽  
Author(s):  
Jitendra Thakur ◽  
He Fang ◽  
Trizia Llagas ◽  
Christine M. Disteche ◽  
Steven Henikoff
Keyword(s):  
Protein Synthesis ◽  
Chromatin Structure ◽  
Enzyme Catalysis ◽  
Pericentric Heterochromatin ◽  
Chromatin Organization ◽  
Non Coding Rna ◽  
Binding Factor ◽  
Chromatin Profiling ◽  
Long Non Coding Rna

AbstractIn addition to its known roles in protein synthesis and enzyme catalysis, RNA has been proposed to stabilize higher-order chromatin structure. To distinguish presumed architectural roles of RNA from other functions, we applied a ribonuclease digestion strategy to our CUT&RUN in situ chromatin profiling method (CUT&RUN.RNase). We find that depletion of RNA compromises association of the murine nucleolar protein Nucleophosmin with pericentric heterochromatin and alters the chromatin environment of CCCTC-binding factor (CTCF) bound regions. Strikingly, we find that RNA maintains the integrity of both constitutive (H3K9me3 marked) and facultative (H3K27me3 marked) heterochromatic regions as compact domains, but only moderately stabilizes euchromatin. To establish the specificity of heterochromatin stabilization by RNA, we performed CUT&RUN on cells deleted for the Firre long non-coding RNA and observed disruption of H3K27me3 domains on several chromosomes. We conclude that RNA maintains local and global chromatin organization by acting as a structural scaffold for heterochromatic domains.

Formation of TiO2 Thin Films by Oxidation of TiN

1992 ◽  
Vol 282 ◽  
Author(s):  
J. K. Truman ◽  
P. H. Ballentine ◽  
E. Terzioglu ◽  
A. M. Kadin
Keyword(s):  
Thin Films ◽  
Relative Dielectric Constant ◽  
X Ray Diffraction ◽  
Electrical Measurements ◽  
Tio2 Thin Films ◽  
Si Substrates ◽  
Diffusion Limited ◽  
Device Processing ◽  
Tin Thin Films

ABSTRACTTiN thin films were deposited by reactive sputtering onto Si substrates. TiO2 films were formed by subsequent oxidation of the TiN films, using either conventional furnace heating or rapid thermalprocessing (RTP). The materials properties of the resulting films were characterized by x-ray diffraction and Rutherford backscattering, and indicate conversion of the TiN to fully-oxidized rutile TiO2 by a diffusion-limited process. Electrical measurements of the insulating properties of the TiO2 films indicated a relative dielectric constant greater than 100, although the leakage current was greater than optimum. A fully in-situ process for the fabrication of microcapacitors is proposed, which involves the sputter deposition of TiN, the formation of TiO2 by RTP, and the deposition of a top TiN counterelectrode. This can be carried out under conditions that are compatible with Si microelectronic device processing.

Intracoronary administration of FGF-2: a computational model of myocardial deposition and retention

2005 ◽  
Vol 288 (1) ◽  
pp. H263-H279 ◽  
Author(s):  
Renee J. Filion ◽  
Aleksander S. Popel
Keyword(s):  
Extracellular Matrix ◽  
Basement Membrane ◽  
Computational Model ◽  
Cellular Level ◽  
Surface Receptors ◽  
Diffusion Limited ◽  
In Situ Conditions ◽  
Free Interstitial ◽  
Plasma Pharmacokinetics

This study uses a computational model to characterize the myocardial deposition and retention of basic fibroblast growth factor (FGF-2) at the cellular level after intracoronary (IC) administration of exogenous FGF-2. The model is applied to the in situ conditions present within the myocardium of a dog for which the plasma pharmacokinetics resulting from IC injection of FGF-2 were recorded. Our estimates show that the processes involved in FGF-2 signaling are not diffusion limited; rather, the response time is determined by the reaction time of FGF-2 binding to cell surface receptors. Additionally, the processes of receptor secretion and internalization are found to play crucial roles in the FGF-2 dynamics; future experiments are required to quantify these processes. The model predictions obtained in this study suggest that IC administration of FGF-2 via either a single bolus or repetitive injections causes a transient increase (time scale of hours) in myocardial FGF-2 concentration if the endogenous level of free interstitial FGF-2 is low enough to allow permeation of FGF-2 molecules from the microvascular to the interstitial spaces. The model shows that the majority (64%) of the extracellular FGF-2 ligands are located within the interstitium, and similar fractions are found in the basement membrane and extracellular matrix. Among the FGF-2 molecules found within the interstitium, 2% are free and 98% are bound to interstitial heparan sulfate proteoglycans. These results support the theory of extracellular control of the bioavailability of FGF-2 via dynamic storage of FGF-2 within the basement membrane and extracellular matrix.

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