Solvent effects phospholipid environment

While transient phenoxyl radicals for the above resonance Raman measurements were produced by radiolysis, other investigators used photolysis to produce phenoxyl radicals for Raman studies. Such studies were carried out with several tocopherols in various organic solvents and in miceUar solutions and phospholipid bilayers . From the solvent effect on the Raman frequencies and the spectra observed in sodium dodecyl sulfate micelles it was concluded that the chromanoxyl group of tocopherol was located in a highly polar environment. However, the spectra in neutral and positively charged micelles and in the membranes suggested that the chromanoxyl group is in an environment of intermediate polarity. 

Another method was found by Findley and White [288]. In this study the determination of PHA after extraction with a one-phase chloroformrmethanol solvent is shown to be as effective as the boiling chloroform method which is quantitative for PHA added to environmental samples. The one-phase chloroform.methanol extraction also quantitatively recovers the ester-linked fatty acids of the phospholipids (PLFA). The lipid extract is then partitioned on a disposable silicic acid column with quantitative elution of neutral lipids with chloroform, glycolipids and PHB with acetone, and phospholipids with methanol for analysis of each component. This extraction and simple column fractionation method for determination of PHA and PLFA simplifies previous methods for the assessment of the ratio of rates of formation of PHA and PLFA after a brief exposure to [14C] acetate which has been shown to be a sensitive measure of the nutritional status of bacteria in the environment. 

For MCOs that are not secreted to extracellular environment, a method is required to disrupt cell membranes in order to release the proteins. Cell dismption can be separated into either mechanically or nonmechanically driven processes [47]. Nonmechanical systems rely on a chemical, enzymatic, or osmotic shock to destabilize cell membranes. Organic solvents can also destabilize the hydrophilic and hydrophobic properties of the phospholipid bilayer. Osmotic shock induced by high-sucrose medium will cause rapid changes in the internal pressure of cells, causing them to rupture. In other instances, ethylenediaminetetraacetic acid (EDTA) is used to destabilize the outer membrane, but this can be detrimental for purification of MCOs as EDTA is a potent metal chelator and may effectively remove copper atoms from the MCOs [18,48]. 

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