Function Of Alcohol Chain Length Research Articles

Freezing of Dilute Aqueous-Alcohol Nanodroplets: The Effect of Molecular Structure.

We investigate vapor-liquid nucleation and subsequent freezing of aqueous-alcohol nanodroplets containing 1-pentanol, 1-hexanol, and their 3-isomers. The aerosols are produced in a supersonic nozzle, where condensation and freezing are characterized by static pressure and Fourier transform Infrared (FTIR) spectroscopy measurements. At fixed water concentrations, the presence of alcohol enables particle formation at higher temperatures since both the equilibrium vapor pressure above the critical clusters and the cluster interfacial free energy are decreased relative to the pure water case. The disappearance of a small free OH peak, observed for pure water droplets, when alcohols are added and shifts in the CH peaks as a function of alcohol chain length reveal varying surface partitioning preferences of the alcohols. Changes in the FTIR spectra during freezing, as well as changes in the ice component derived from self-modeling curve resolution analysis, show that 1-hexanol and 1-pentanol perturb freezing less than their branched isomers do. This behavior may reflect the molecular footprints of the alcohols, the available surface area of the droplets, and not only alcohol solubility. The presence of alcohols also lowers the freezing temperature relative to that of pure water, but when there is clear evidence for the formation of ice, the ice nucleation rates change by less than a factor of ∼2-3 for all cases studied.

The Effect of Solutes on the Temperature of Miscibility Transitions in Multicomponent Membranes

We address questions posed by experiments that show small-chain alcohols reduce the miscibility transition temperature when added to giant plasma membrane vesicles (GPMVs), but increase that temperature when added to giant unilamellar vesicles. In giant unilamellar vesicles the change in temperature displays a definite minimum, between decanol and tetradecanol, as a function of alcohol chain length; in GPMVs there is no such minimum. To emphasize the competition between internal entropies of the components and the interactions between them, we model the system as consisting of three different linear polymers. Two of them are the constituents of a liquid, one that can undergo a miscibility transition. To this liquid is added the third polymer component, which represents the short-chain alcohol. We show that, within Flory-Huggins theory, the addition of alcohol causes an increase or decrease of the miscibility transition temperature depending upon the competition of two effects. The first is the dilution of the interactions between the two components of the liquid caused by the introduction of the alcohol. This tends to lower the transition temperature. The second effect is the preferential partitioning of the alcohol into one phase of the liquid or the other. This tends to raise the transition temperature irrespective of which phase the alcohol prefers. This second effect is the smallest, and the decrease in transition temperature the largest, when the alcohol partitions equally between the two phases. Such equal partitioning occurs when the effect of the entropic excluded volume interactions (which cause the alcohol to prefer one phase) just balances the effect of the direct interactions, which cause it to prefer the other. These results allow us to make several predictions, and to propose an explanation for the different behavior of the transition temperature in GPMVs and giant unilamellar vesicles that results from the addition of alcohols.

Formulation of Microemulsions Based on Sugar Surfactant as an Alternative Fuel

Microemulsion systems that serve as water in diesel fuel were formulated using minimum amount of sucrose laurate at 25°C. Comparative experiments were also conducted using n-heptane. It was found that in order to formulate diesel and microemulsions a cosurfactant should be added. Alcohols such as 1-butanol,1-pentanol, 1-hexanol, and 1-heptanol served as cosurfactants. The area of the one-phase microemulsion region varies depending on the cosurfactant structure and composition. A continuous microemulsion region was observed with 1-butanol and 1-pentanol. Water solubilization capacity and thermodynamics as a function of alcohol chain length was determined.

Partially Oxidised Cellulose Nanofibril Gels for Rheology Modification

Partially C6-oxidised cellulose nanofibrils form a transparent, slightly viscous suspension in water. These materials, sourced from soft-wood waste, have shown excellent potential for use as a rheology modifier in aqueous formulations, when mixed with salt and minimal amounts of anionic surfactants [1] or with short chain alcohols. The interaction with anionic surfactants is particularly surprising as the cellulose fibrils themselves carry a net negative charge. The gels formed are transparent, mild on the skin and have excellent suspending properties while also being strongly shear thinning making application eg via spraying possible. The partially oxidised cellulose nanofibrils can also be used to stabilize oil-in-water Pickering emulsions. Both the gels and emulsions are of interest for use in personal care products such as creams, sanitizers and shower gels. We have probed the micelle-fibril interactions in water and in the presence of ethanol using contrast matching SANS on the gels and also on the cellulose-stabilized Pickering emulsion droplets. SAXS has also been used to probe the effect of short chain alcohols on the nanofibril structures in the gels as a function of alcohol chain length, while neutron reflectivity was used to probe surfactant-fibril binding for anionic and nonionic surfactants in thin nanofibril layers. The nanostructures formed in suspensions of partially oxidised cellulose nanofibrils with a range of salts, alcohols and surfactants will be correlated with their rheological behaviour. These factors will be discussed and brought together to give insights into how and why these systems form gels.

Alcohols Reduce Lateral Membrane Pressures: Predictions from Molecular Theory

We explore the effects of alcohols on fluid lipid bilayers using a molecular theory with a coarse-grained model. We show that the trends predicted from the theory in the changes in area per lipid, alcohol concentration in the bilayer, and area compressibility modulus, as a function of alcohol chain length and of the alcohol concentration in the solvent far from the bilayer, follow those found experimentally. We then use the theory to study the effect of added alcohol on the lateral pressure profile across the membrane, and find that added alcohol reduces the surface tensions at both the headgroup/solvent and headgroup/tailgroup interfaces, as well as the lateral pressures in the headgroup and tailgroup regions. These changes in lateral pressures could affect the conformations of membrane proteins, providing a nonspecific mechanism for the biological effects of alcohols on cells.

Specificity of a Lipase in Ester Synthesis: Effect of Alcohol

AbstractEster synthesis by the Mucor miehei lipase has been studied for various alcohol substrates: n‐propanol, n‐butanol, isoamyl alcohol, n‐hexanol, n‐octanol, 2‐ethylhex‐anol, n‐decanol, and lauryl alcohol. The effects of temperature, the nature of the acid, and immobilization of the lipase on its substrate specficity have been elucidated by carrying out esterifications at 29 and 50 °C with lauric and oleic acids and by using both the soluble and immobilized (resin‐adsorbed) forms of the lipase as catalysts. Higher synthesis rates were obtained with oleic acid than with lauric acid. A bimodal distribution pattern was observed for the reaction rate as a function of alcohol chain length. Two superimposed “bells” were obtained with maxima at C4 (butanol) and C10 (decanol) at 29 °C. Whereas immobilization of the lipase did not influence this substrate specificity, an increase in temperature to 50 °C caused a shift in the first peak from C4 to C6 (hexanol), while the second peak position was not affected. The minimum, in all cases, was found to be at C8 (octanol).

Synthetic carotenoids as internal standards for plasma micronutrient analyses by high-performance liquid chromatography

A method is described for the synthesis of new carotenoids by transesterification of ethyl-β-apo-8'-carotenoate. The rate of transesterification was temperature-dependent with highest yields using primary alcohols. Reaction conditions were found avoiding Z isomerization. The structures of the new products were confirmed by ultraviolet, mass, 1H and 13C nuclear magnetic resonance spectroscopy. The synthetic carotenoids were used as internal standards for reversed-phase high-performance liquid chromatographic (HPLC) analyses of lipid phase plasma micronutrients. Retention times for the transesterified products increased as a function of alcohol chain length allowing a choice of synthetic carotenoids for use as internal standards for carotenoid quantitation without interference with the detection of analytes during HPLC analysis.

Phospholipids and Oligomycin Sensitivity of Mitochondrial Adenosine Triphosphatase: a Spin Label Study

There are observations suggesting that phospholipids are involved in the oligomycin sensitivity of mitochondria1 ATPase (adenosine triphosphatase) (Palatini & Bruni, 1970). Lenaz et al. (1971) have shown that alcohols make the mitochondria1 ATPase oligomycin insensitive, with an efficacy which is a function of alcohol chain length. This effect points out that hydrophobic bonds are involved in the inhibitor sensitivity of ATPase; a similar relation was found between alcohol chain length and phospholipid extractability, although higher alcohol concentrations were required for phospholipid extraction than for the effect on ATPase. I t was suggested that oligomycin sensitivity in mitochondria is related to the intactness of hydrophobic lipid-protein interactions. Electron spin resonance (e.s.r.) with spin-labelled lipids has become a very useful technique in probing the physical state of phospholipids in biological membranes (Hubbell & McConnell, 1968). In this communication we report the effect of butan-1-01 on the mobility of a 5-(4',4'-dimethyl-N-oxyloxazolidine) derivative of stearic acid in