Molecules, the Ultimate Nanomotor: Linking Chemical Reaction Intermediates to their Molecular Diffusivity

ACS Nano ◽  
2021 ◽  
Vol 15 (9) ◽  
pp. 14947-14953
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Reaction Intermediates ◽  
Molecular Diffusivity

scholarly journals Linking Chemical Reaction Intermediates of the Click Reaction to Their Molecular Diffusivity

2021 ◽  
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Click Reaction ◽  
Activation Barrier ◽  
Copper Catalyst ◽  
Enzymatic Reactions ◽  
Reaction Intermediates ◽  
Elementary Reactions ◽  
Molecular Diffusivity ◽  
Catalyst Complex ◽  
Pfg Nmr

Bipolar reactions have been provoked by reports of boosted diffusion during chemical and enzymatic reactions. To some, it is intuitively reasonable that relaxation to truly Brownian motion after passing an activation barrier can be slow, but to others the notion is so intuitively unphysical that they suspect the supporting experiments to be artifact. Here we study a chemical reaction according to whose mechanism some intermediate species should speed up while others slow down in predictable ways, if the boosted diffusion interpretation holds. Experimental artifacts would do not know organic chemistry mechanism, however. Accordingly, we scrutinize the absolute diffusion coefficient (D) during intermediate stages of the CuAAC reaction (coppercatalyzed azide-alkyne cycloaddition click reaction), using proton pulsed field-gradient nuclear magnetic resonance (PFG-NMR) to discriminate between the diffusion of various reaction intermediates. For the azide reactant, its D increases during reaction, peaks at the same time as peak reaction rate, then returns to its initial value. For the alkyne reagent, its D decreases consistent with presence of the intermediate large complexes formed from copper catalyst and its ligand, except for the 2Cu-alk complex whose more rapid D may signify that this species is the real reactive complex. For the product of this reaction, its D increases slowly as it detaches from the triazolide catalyst complex. These examples of enhanced diffusion for some molecular species and depressed diffusion for others causes us to conclude that diffusion coefficients during these elementary reactions are influenced by two components: hydrodynamic radius increase from complex formation, which slows diffusion, and energy release rate during the chemical reaction, which speeds it up. We discuss possible mechanisms and highlight that too little is yet understood about slow solvent reorganization during chemical reactions.<br>

scholarly journals Linking Chemical Reaction Intermediates of the Click Reaction to Their Molecular Diffusivity

2021 ◽  
Author(s):  
Tian Huang ◽  
Bo Li ◽  
Huan Wang ◽  
Steve Granick
Keyword(s):  
Chemical Reaction ◽  
Click Reaction ◽  
Activation Barrier ◽  
Copper Catalyst ◽  
Enzymatic Reactions ◽  
Reaction Intermediates ◽  
Elementary Reactions ◽  
Molecular Diffusivity ◽  
Catalyst Complex ◽  
Pfg Nmr

Bipolar reactions have been provoked by reports of boosted diffusion during chemical and enzymatic reactions. To some, it is intuitively reasonable that relaxation to truly Brownian motion after passing an activation barrier can be slow, but to others the notion is so intuitively unphysical that they suspect the supporting experiments to be artifact. Here we study a chemical reaction according to whose mechanism some intermediate species should speed up while others slow down in predictable ways, if the boosted diffusion interpretation holds. Experimental artifacts would do not know organic chemistry mechanism, however. Accordingly, we scrutinize the absolute diffusion coefficient (D) during intermediate stages of the CuAAC reaction (coppercatalyzed azide-alkyne cycloaddition click reaction), using proton pulsed field-gradient nuclear magnetic resonance (PFG-NMR) to discriminate between the diffusion of various reaction intermediates. For the azide reactant, its D increases during reaction, peaks at the same time as peak reaction rate, then returns to its initial value. For the alkyne reagent, its D decreases consistent with presence of the intermediate large complexes formed from copper catalyst and its ligand, except for the 2Cu-alk complex whose more rapid D may signify that this species is the real reactive complex. For the product of this reaction, its D increases slowly as it detaches from the triazolide catalyst complex. These examples of enhanced diffusion for some molecular species and depressed diffusion for others causes us to conclude that diffusion coefficients during these elementary reactions are influenced by two components: hydrodynamic radius increase from complex formation, which slows diffusion, and energy release rate during the chemical reaction, which speeds it up. We discuss possible mechanisms and highlight that too little is yet understood about slow solvent reorganization during chemical reactions.<br>

Separation of Chemical Reaction Intermediates by Metal-Organic Frameworks

Small ◽  
2011 ◽  
Vol 7 (16) ◽  
pp. 2356-2364 ◽  
Author(s):  
Andrea Centrone ◽  
Erik E. Santiso ◽  
T. Alan Hatton
Keyword(s):  
Chemical Reaction ◽  
Metal Organic Frameworks ◽  
Reaction Intermediates ◽  
Metal Organic

scholarly journals Effect of Thermal Radiation, Chemical Reaction and Viscous Dissipation on MHD Flow

2018 ◽  
Vol 23 (3) ◽  
pp. 787-801
Author(s):  
B. Zigta
Keyword(s):  
Kinetic Energy ◽  
Differential Equations ◽  
Thermal Radiation ◽  
Viscous Dissipation ◽  
Chemical Reaction ◽  
Energy Equation ◽  
Eckert Number ◽  
Radiation Chemical ◽  
Thermal Buoyancy ◽  
Molecular Diffusivity

Abstract This study examines the effect of thermal radiation, chemical reaction and viscous dissipation on a magnetohydro- dynamic flow in between a pair of infinite vertical Couette channel walls. The momentum equation accounts the effects of both the thermal and the concentration buoyancy forces of the flow. The energy equation addresses the effects of the thermal radiation and viscous dissipation of the flow. Also, the concentration equation includes the effects of molecular diffusivity and chemical reaction parameters. The gray colored fluid considered in this study is a non-scattering medium and has the property of absorbing and emitting radiation. The Roseland approximation is used to describe the radiative heat flux in the energy equation. The velocity of flow transforms kinetic energy into heat energy. The increment of the velocity due to internal energy results in heating up of the fluid and consequently it causes increment of the thermal buoyancy force. The Eckert number being the ratio of the kinetic energy of the flow to the temperature difference of the channel walls is directly proportional to the thermal energy dissipation. It can be observed that increasing the Eckert number results in increasing velocity. A uniform magnetic field is applied perpendicular to the channel walls. The temperature of the moving wall is high enough due to the presence of thermal radiation. The solution of the governing equations is obtained using regular perturbation techniques. These techniques help to convert partial differential equations to a set of ordinary differential equations in dimensionless form and thus they are solved analytically. The following results are obtained: from the simulation study it is observed that the flow pattern of the fluid is affected due to the influence of the thermal radiation, the chemical reaction and viscous dissipation. The increment in the Hartmann number results in the increment of the Lorentz force but a decrement in velocity of the flow. An increment in the radiative parameter results in a decrement in temperature. An increment in the Prandtl number results in a decrement in thermal diffusivity. An increment in both the chemical reaction parameter and molecular diffusivity results in a decrement in concentration.

scholarly journals Effect of heat source and chemical reaction on MHD flow past a vertical plate with variable temperature

2016 ◽  
Vol 13 (1) ◽  
pp. 101-110 ◽  
Author(s):  
P. K. Rout ◽  
S. N. Sahoo ◽  
G. C. Dash
Keyword(s):  
Heat Source ◽  
Chemical Reaction ◽  
Vertical Plate ◽  
Variable Temperature ◽  
Mhd Flow ◽  
Governing Equations ◽  
Molecular Diffusivity ◽  
Flow Parameters ◽  
Flow Past ◽  
Chemical Reaction Parameter

An analysis has been carried out to study the effect of heat source and chemical reaction on MHD flow past a vertical plate subject to a constant motion with variable temperature and concentration. The governing equations are solved by the Laplace transformation technique. The effects of various flow parameters on the flow dynamics are discussed. Findings of the present study reveal that the velocity of the fluid reduces due to the dominating effect of kinematic viscosity over molecular diffusivity in case of heavier species. Presence of heat source reduces the velocity of the flow. Presence of chemical reaction parameter decreases the concentration distribution.

Solvent dependent structural perturbations of chemical reaction intermediates visualized by time-resolved x-ray diffraction

2009 ◽  
Vol 130 (15) ◽  
pp. 154502 ◽  
Author(s):  
Jonathan Vincent ◽  
Magnus Andersson ◽  
Mattias Eklund ◽  
Annemarie B. Wöhri ◽  
Michael Odelius ◽  
...  
Keyword(s):  
Chemical Reaction ◽  
Reaction Intermediates ◽  
X Ray Diffraction ◽  
Time Resolved ◽  
X Ray ◽  
Structural Perturbations

Analyzing reactions of single mechanoenzyme molecules by light microscopy

1992 ◽  
Vol 50 (1) ◽  
pp. 426-427
Author(s):  
Jeff Gelles
Keyword(s):  
Image Processing ◽  
Reaction Mechanisms ◽  
Transient State ◽  
Nanometer Scale ◽  
Reaction Intermediates ◽  
Enzyme Molecule ◽  
Directed Movement ◽  
Enzyme Molecules ◽  
Individual Enzyme ◽  
Single Reaction

Mechanoenzymes are enzymes which use a chemical reaction to power directed movement along biological polymer. Such enzymes include the cytoskeletal motors (e.g., myosins, dyneins, and kinesins) as well as nucleic acid polymerases and helicases. A single catalytic turnover of a mechanoenzyme moves the enzyme molecule along the polymer a distance on the order of 10−9 m We have developed light microscope and digital image processing methods to detect and measure nanometer-scale motions driven by single mechanoenzyme molecules. These techniques enable one to monitor the occurrence of single reaction steps and to measure the lifetimes of reaction intermediates in individual enzyme molecules. This information can be used to elucidate reaction mechanisms and determine microscopic rate constants. Such an approach circumvents difficulties encountered in the use of traditional transient-state kinetics techniques to examine mechanoenzyme reaction mechanisms.

Directional observation on lipid of male nectary of Lindera megaphylla hemsl. by the rapid embedding method with polyethylene glycol (PEG)

1990 ◽  
Vol 48 (3) ◽  
pp. 718-719
Author(s):  
Dai Dalin ◽  
Guo Jianmin
Keyword(s):  
Electron Microscope ◽  
Polyethylene Glycol ◽  
Chemical Reaction ◽  
Traditional Method ◽  
Osmium Tetroxide ◽  
Unsaturated Lipid ◽  
Embedding Method ◽  
Long Period ◽  
New Methods

Lipid cytochemistry has not yet advanced far at the EM level. A major problem has been the loss of lipid during dehydration and embedding. Although the adoption of glutaraldehyde and osmium tetroxide accelerate the chemical reaction of lipid and osmium tetroxide can react on the double bouds of unsaturated lipid to from the osmium black, osmium tetroxide can be reduced in saturated lipid and subsequently some of unsaturated lipid are lost during dehydration. In order to reduce the loss of lipid by traditional method, some researchers adopted a few new methods, such as the change of embedding procedure and the adoption of new embedding media, to solve the problem. In a sense, these new methods are effective. They, however, usually require a long period of preparation. In this paper, we do research on the fiora nectary strucure of lauraceae by the rapid-embedding method wwith PEG under electron microscope and attempt to find a better method to solve the problem mentioned above.

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