Rotational diffusion of organic solutes: the role of dielectric friction in polar solvents and electrolyte solutions

1998 ◽  
Vol 77 (1-3) ◽  
pp. 37-60 ◽  
Author(s):  
N. Balabai ◽  
A. Sukharevsky ◽  
I. Read ◽  
B. Strazisar ◽  
M. Kurnikova ◽  
...  
Keyword(s):  
Rotational Diffusion ◽  
Electrolyte Solutions ◽  
Organic Solutes ◽  
Polar Solvents ◽  
Dielectric Friction

Studies on Water in Barnacle Muscle Fibres II. Role of ions and Organic Solutes in Swelling of Chemically-skinned Fibres

1981 ◽  
Vol 90 (1) ◽  
pp. 43-63
Author(s):  
M. E. CLARK ◽  
J. A. M. HINKE ◽  
M. E. TODD
Keyword(s):  
Water Content ◽  
Fibre Volume ◽  
Tween 20 ◽  
Muscle Fibres ◽  
Skinned Fibres ◽  
Organic Solutes ◽  
Net Charge ◽  
Trimethylamine Oxide ◽  
Organic Solute

Single muscle fibres from the giant barnacle, Balanus nubilis, were chemically skinned (2% Tween 20), then equilibrated for 40 h in salt solutions ranging in ionic strength from 0·025 to 0·6M at pH 7·0. The water content of the fibres and the net charge on the myofilaments increased with increasing salt concentration. Cation accumulation in the fibres was about equal to anion exclusion at all salt concentrations. When an organic solute (trimethylamine oxide, glycine, alanine, serine, proline, or glycerol) in the concentration range from 0·1 to 0·6 M was added to the salt solution, cation accumulation increased and water content decreased. Myofilament architecture was disrupted when the fibres were equilibrated in high salt (> 0·4 M) solutions and preserved when 0·5 M-triethylamine oxide was also added. The results are consistent with the view that organic solutes enhance the association between the fixed charge sites and their counterions. This hypothesis is examined quantitatively using the Oosawa relationship between the volume and the counterion association for cylindrical polyelectrolytes. The results illustrate that organic solutes can influence fibre volume in a way other than through osmo-regulation.

scholarly journals Efficient utilization of renewable feedstocks: the role of catalysis and process design

2017 ◽  
Vol 376 (2110) ◽  
pp. 20170064 ◽  
Author(s):  
Regina Palkovits ◽  
Irina Delidovich
Keyword(s):  
Elevated Temperature ◽  
Gas Phase ◽  
Process Design ◽  
Circular Economy ◽  
Paradigm Shift ◽  
Efficient Utilization ◽  
Polar Solvents ◽  
Platform Chemicals ◽  
Renewable Feedstocks

Renewable carbon feedstocks such as biomass and CO 2 present an important element of future circular economy. Especially biomass as highly functionalized feedstock provides manifold opportunities for the transformation into attractive platform chemicals. However, this change of the resources requires a paradigm shift in refinery design. Fossil feedstocks are processed in gas phase at elevated temperature. In contrast, biorefineries are based on processes in polar solvents at moderate conditions to selectively deoxygenate the polar, often thermally instable and high-boiling molecules. Here, challenges of catalytic deoxygenation, novel strategies for separation and opportunities provided at the interface to biotechnology are discussed in form of showcases. This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

scholarly journals The Effect of Weak Electrolyte Solutions on the Hatching Rate of the Eggs of Tricho-Strongylus Retortaeformis (Zeder) and its Interpretation in Terms of a Proposed Hatching Mechanism of Strongyloid Eggs

1958 ◽  
Vol 35 (3) ◽  
pp. 584-601
Author(s):  
P. A. G. WILSON
Keyword(s):  
Water Permeability ◽  
Electrolyte Solutions ◽  
Hatching Rate ◽  
Natural Conditions ◽  
Ionic Solutions ◽  
Rate Of Increase ◽  
Egg Membrane ◽  
Hatching Eggs ◽  
Colligative Properties

1. The influence of solutions of NaCl on the hatching of eggs of Trichostrongylus retortaeformis is studied. It is shown that the effects are not the consequence of colligative properties, but are related to ionic phenomena. 0.05 N-NaCl slows down the rate of hatch without impairing the ultimate ‘hatchability’ of the eggs. Processes of development up to hatching are not slowed down. 2. The effect demonstrated in the case of NaCl is shown to be shared by eight other electrolytes, the depression in the rate of hatch being proportional to the mobility of the ions in solution. On the assumption that the effect of the ions is due to a penetration of the egg membrane(s) the rate of entry is shown to be controlled by the speed of the slower ion in any one salt. 3. The influence of NaCl on the permeability of hatching eggs to water is studied. It is shown that the rate of increase in permeability is slowed down sufficiently in NaCl to control the rate of hatch. The inference that water permeability is a necessary prerequisite for hatching is made, a further hypothetical process being invoked to account for the rate of hatch in the absence of NaCl, since it is not then controlled by changes in water permeability. 4. The probability that the net effect of ionic solutions on the eggs is one concerned with the rate of breakdown of the inner wax-like layer of the egg is strengthened by experiments demonstrating that the depressing influence of NaCl is antagonized by ‘Teepol’, though the comparable influence of other, non-emulsifying, compounds cannot be explained. 5. The role of water permeability in the hatching mechanism is investigated. 6. A hatching mechanism of strongyloid eggs is proposed which involves two processes, the first dependent upon the osmotic relationships of the unhatched larva to its environment, the second being some sort of chemical weakening of the outer shell. 7. It is suggested that the effect of ions on hatching rate assists the ‘embryonated egg’ to survive under natural conditions when the hatched first-stage larva might otherwise be destroyed by desiccation.

scholarly journals Thermodynamics of primary antioxidant action of flavonols in polar solvents

2019 ◽  
Vol 12 (1) ◽  
pp. 108-118 ◽  
Author(s):  
Martin Michalík ◽  
Ján Rimarčík ◽  
Vladimír Lukeš ◽  
Erik Klein
Keyword(s):  
Reaction Pathway ◽  
Hydrogen Atom Transfer ◽  
Antioxidant Effect ◽  
Antioxidant Action ◽  
Polar Solvents ◽  
Polar Media ◽  
Primary Antioxidant ◽  
Intramolecular Hydrogen

Abstract Very recently, a report on the antioxidant activity of flavonoids has appeared, where authors concluded that Hydrogen Atom Transfer mechanism represents the thermodynamically preferred mechanism in polar media (https://doi.org/10.1016/j.foodres.2018.11.018). Unfortunately, serious errors in the theoretical part of the paper led to incorrect conclusions. For six flavonols (galangin, kaempferol, quercetin, morin, myricetin, and fisetin), reaction enthalpies related to three mechanisms of the primary antioxidant action were computed. Based on the obtained results, the role of intramolecular hydrogen bonds (IHB) in the thermodynamics of the antioxidant effect is presented. Calculations and the role of solvation enthalpies of proton and electron in the determination of thermodynamically preferred mechanism is also briefly explained and discussed. The obtained results are in accordance with published works considering the Sequential Proton-Loss Electron-Transfer thermodynamically preferred reaction pathway.

Major Compatible Solutes and Structural Adaptation of Proteins in Extremophiles

2022 ◽  
pp. 161-186
Author(s):  
Hardik Shah ◽  
Khushbu Panchal ◽  
Amisha Panchal
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Osmotic Stress ◽  
Amino Acid Composition ◽  
Scientific Community ◽  
Compatible Solutes ◽  
Organic Solutes ◽  
Structural Adaptation ◽  
Extreme Habitats

Extremophiles are the most ancient microbes on the Earth and also a center of attraction for the scientific community for research because of their ability to adapt to extreme habitats. Compatible solutes are among those factors which enable these microorganisms to thrive in such extreme habitats. Under osmotic stress, the majority of extremophiles accumulate specific organic solutes such as amino acids, sugars, polyols, and their derivatives. In addition, proteins in extremophiles are found to be evolved by changing their amino acid composition to alter the hydrophobicity of its core and surface charge to maintain activity. This chapter encompasses a comprehensive study about the role of various compatible solutes in the endurance of microorganisms under extremophilic conditions, synthesis of compatible solutes, nature of extremophilic proteins, and their applications. Furthermore, an attempt has been made to cover various strategies adopted by the scientific community while pursuing research on compatible solutes.

Organic solutes in fluid absorption by renal proximal convoluted tubules

1976 ◽  
Vol 231 (2) ◽  
pp. 627-637 ◽  
Author(s):  
M Burg ◽  
C Patlak ◽  
N Green ◽  
D Villey
Keyword(s):  
Epithelial Cell ◽  
Organic Solutes ◽  
Fluid Absorption ◽  
Transepithelial Voltage ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

Proximal convoluted tubules were dissected from rabbit kidneys and perfused with artificial solutions in vitro. The effect of various organic solutes on rate of fluid absorption and transepithelial voltage was tested by removing solutes from or adding them to perfusate and/or bath. Omission of albumin from the bath caused rate of fluid absorption to descrease 33% without any change in voltage. Omission of glucose, lactate, alanine, and citrate from the bath had no effect. In contrast, when they were removed from perfusate, rate of fluid absorption fell by 45-75% (depending on whether they were replaced by NaCl or mannitol and NaCl), and voltage (normally negative in lymen) decreased to near zero. Adding glucose or alanine individually to perfusate caused a small increase in rate of fluid absorption and a relatively large increase in voltage. alpha-Methyl-D-glucoside and cycloleucine (which are transported but not metabolized) had effects similar to glucose and alanine, except that voltage changes were not as great. Phlorizin (10(-5) M in perfusate) had the same effect as removing glucose from perfusate. When glucose and alanine were added to perfusate, epithelial cell swelled significantly. Lactate and citrate also caused rate of fluid absorption to increase when they were added to perfusate, but they did not affect transepithelial voltage nor did they cause cells to swell significantly. Possible mechanisms of these effects and the role of organic solutes in fluid absorption by proximal convoluted tubules are discussed.

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