The influence of dielectric permittivity of the nonaqueous phase on the photooxidation of water at the interface of two immiscible liquids in the presence of a hydrated oligomer of chlorophyll. The role of a proton acceptor

1991 ◽  
Vol 69 (1) ◽  
pp. 151-156 ◽  
Author(s):  
Mikhail D. Kandelaki ◽  
Alexander G. Volkov
Keyword(s):  
Dielectric Permittivity ◽  
Water System ◽  
Water Soluble ◽  
Proton Acceptor ◽  
Immiscible Liquids ◽  
Liquid Phases ◽  
Oil Water ◽  
Water Photooxidation ◽  
Photooxidation Reaction

We have investigated polarographically the dependence of the dioxygen yield on the concentration of 2,4-dinitrophenol in photooxidation of water in an octane/water system containing hydrated oligomer of chlorophyll, a water-soluble electron acceptor ferricyanide and a buffer. A linear correlation between the rate of dioxygen evolution and the photopotential at the interface between the two liquid phases is observed. Investigation of the dependences of photopotential and rate of dioxygen evolution on the dielectric permittivity of the nonaqueous phase has shown that with increasing dielectric permittivity, one can observe a decrease in both the reaction rate and the potential difference. The lifetime of chlorophyll in the course of water photooxidation reaction has been measured. Key words: chlorophyll, oxygen, water photooxidation, oil/water interface, artificial photosynthesis.

scholarly journals New insights into the mechanisms of ultrasonic emulsification in the oil-water system and the role of gas bubbles

2021 ◽  
pp. 105501
Author(s):  
W.H. Wu ◽  
D.G. Eskin ◽  
A. Priyadarshi ◽  
T. Subroto ◽  
I. Tzanakis ◽  
...  
Keyword(s):  
Water System ◽  
Gas Bubbles ◽  
Ultrasonic Emulsification ◽  
Oil Water

Room-Temperature-Cured Polydimethylsiloxane Elastomers from Aqueous Dispersion

1981 ◽  
Vol 54 (5) ◽  
pp. 976-987 ◽  
Author(s):  
J. C. Saam ◽  
D. Graiver ◽  
M. Baile
Keyword(s):  
Room Temperature ◽  
Colloidal Silica ◽  
Aqueous Dispersion ◽  
Water Soluble ◽  
Alkaline Media ◽  
Water Interface ◽  
Anionic Charge ◽  
Oil Water ◽  
Emulsion Particle

Abstract The observations are consistent with the formation of grafts of hydrophilic silicates to the silanol chain ends at the surface of the PDMS emulsion particles prior to removal of the water. The silicates may be introduced into the system directly or through the alkaline colloidal silica, which contains appreciable amounts of dissolved silicates. Monomeric, or possibly dimeric, silicate grafted to more than one chain end could migrate to the interior of the PDMS emulsion particle to form further crosslinks. Grafts to higher molecular weight silicates and silicate grafts bearing anionic charge would be solvated with water and tend to remain at the oil-water interface. This could provide steric as well as ionic stabilization to the PDMS particles, and the system would no longer respond to electrolytes as a simple, ionically stabilized, hydrophobic colloid but more as a hydrophilic colloid resembling silica. The role of the dioctyltin dilaurate is to interact in the water phase with the water-soluble silicates to render them, in effect, hydrophobic and to transport them to the oil-water interface. There the dialkyltin species can catalyze condensation between silanol on the silicate with silanol on the PDMS chain ends. Alkyltin acylates are known to hydrolyze in aqueous alkaline media, and the product can condense with silanol on the silicate to form silastannoxane intermediates. These are relatively stable to hydrolysis, provided bulky groups are present on tin as in dioctyltin dilaurate.

scholarly journals Spontaneous non-linear oscillations of interfacial tension at oil/water interface

2015 ◽  
Vol 13 (1) ◽  
Author(s):  
Nina M. Kovalchuk
Keyword(s):  
Interfacial Tension ◽  
Surfactant Solution ◽  
Immiscible Liquids ◽  
Abrupt Decrease ◽  
Liquid Phases ◽  
Pure Solvent ◽  
Non Linear ◽  
Surfactant Transfer ◽  
Linear Effects ◽  
Oil Water

AbstractThree particular systems are considered where transfer of a surfactant across the interface between two immiscible liquids, water and oil, is accompanied by spontaneous oscillations of relaxation type with an abrupt decrease of interfacial tension followed by its gradual increase. These oscillations cannot be explained in the frameworks of linear stability analysis, because they are related to essentially non-linear effects. The oscillations characteristics depend on the properties of a surfactant (interfacial activity, solubility, partition coefficient, density difference between the surfactant solution and pure solvent), other solutes present in one or both liquid phases, and, usually, also on the system geometry. If the transferred surfactant is an ionic one, then, the oscillations of interfacial tension are synchronised with the oscillations of electric potential across the interface. The available hypothesis about oscillations mechanism are discussed, in particular, the model proposed recently for oscillations due to Marangoni instability by surfactant transfer from a point source located in one of the liquid bulk phases.

scholarly journals Did Cyclic Metaphosphates Have a Role in the Origin of Life?

2021 ◽  
Author(s):  
Thomas Glonek
Keyword(s):  
Organic Molecules ◽  
Water Soluble ◽  
Holliday Junction ◽  
Additional Energy ◽  
Condensed Phosphate ◽  
Geological Processes ◽  
The Origin Of Life ◽  
Complex Forms ◽  
Self Replication

AbstractHow life began still eludes science life, the initial progenote in the context presented herein, being a chemical aggregate of primordial inorganic and organic molecules capable of self-replication and evolution into ever increasingly complex forms and functions.Presented is a hypothesis that a mineral scaffold generated by geological processes and containing polymerized phosphate units was present in primordial seas that provided the initiating factor responsible for the sequestration and organization of primordial life’s constituents. Unlike previous hypotheses proposing phosphates as the essential initiating factor, the key phosphate described here is not a polynucleotide or just any condensed phosphate but a large (in the range of at least 1 kilo-phosphate subunits), water soluble, cyclic metaphosphate, which is a closed loop chain of polymerized inorganic phosphate residues containing only phosphate middle groups. The chain forms an intrinsic 4-phosphate helix analogous to its structure in Na Kurrol’s salt, and as with DNA, very large metaphosphates may fold into hairpin structures. Using a Holliday-junction-like scrambling mechanism, also analogous to DNA, rings may be manipulated (increased, decreased, exchanged) easily with little to no need for additional energy, the reaction being essentially an isomerization.A literature review is presented describing findings that support the above hypothesis. Reviewed is condensed phosphate inorganic chemistry including its geological origins, biological occurrence, enzymes and their genetics through eukaryotes, polyphosphate functions, circular polynucleotides and the role of the Holliday junction, previous biogenesis hypotheses, and an Eoarchean Era timeline.

The biological activity of glucagon–phospholipid complexes

1983 ◽  
Vol 61 (7) ◽  
pp. 688-691 ◽  
Author(s):  
J. J. Liepnieks ◽  
P. Stoskopf ◽  
E. A. Carrey ◽  
C. Prosser ◽  
R. M. Epand
Keyword(s):  
Biological Activity ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Bovine Brain ◽  
Water Soluble ◽  
Dipalmitoyl Phosphatidylcholine ◽  
Dimyristoyl Phosphatidylcholine ◽  
Lipoprotein Complex ◽  
Stimulation Of

Glucagon can form water-soluble complexes with phospholipids. The incorporation of glucagon into these lipoprotein particles reduces the biological activity of the hormone. The effect is observed only at temperatures below the phase transition temperature of the phospholipid and results in a decreased stimulation of the adenylate cyclase of rat liver plasma membranes by the lipoprotein complex as compared with the hormone in free solution. Two- to five-fold higher concentrations of glucagon are required for half-maximal stimulation of adenylate cyclase when the hormone is complexed with dimyristoyl phosphatidylcholine, dipalmitoyl phosphatidylcholine, or bovine brain sphingomyelin. A possible role of lipoprotein-associated hormones in the development of insulin resistance is discussed.

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