Water-insoluble substance through

Contribution of Micelles to the Transport of a Water-Insoluble Substance through a Membrane... 

Some fundamentals of micelle formation and of the solubilization of water-insoluble substances by micelles are reviewed. The accelerating effect of micellization upon the rate of dissolution and of transport of solubilizate through bulk liquid is then considered. Membranes present an obstacle to transport. A larger fraction of the total driving force can be brought to bear upon this obstacle as other resistances are reduced by solubilization. Hence, transport across a membrane will, in general, be accelerated whether micelles are effective within the membrane or not. It is now possible to determine also this contribution of micelles to the transport within the membrane. In a specific case it was found to be negligible. 

Selenium Determine as directed in Method II under Selenium Limit Test, Appendix IIIB, using a 1.2-g sample. Water-Insoluble Substances Dissolve 50 g of sample in 300 mL of hot water contained in a 600-mL beaker allow the insoluble matter to settle and filter by decanting through a tared, sintered-glass filter cmcible, washing the insoluble matter into the crucible with additional hot water. Dry at 100° to 110° for 1 h, cool in a desiccator, and weigh. 

Certain steroid bile acids such as cholic acid (Section 4-7) also have surfactant or detergent-like properties and are found in the bile duct. These substances are released into the upper intestinal tract, where they emulsify water-insoluble fats through the formation of micelles. Hydrolytic enzymes can then digest the dispersed fat molecules. 

Most hydrophilic, or water-soluble, substances are repelled by this hydrophobic interior and cannot simply diffuse through the membrane. Instead, these substances must cross the membrane using specialized transport mechanisms. Examples of lipid-insoluble substances that require such mechanisms include nutrient molecules, such as glucose and amino acids, and all species of ions (Na+, Ca++, H+, Cl, and HC03). Therefore, the plasma membrane plays a very important role in determining the composition of the intracellular fluid by selectively permitting substances to move in and out of the cell. 

During the past decades, liposomes have been used for drug delivery on account of their unique solubilization characteristics for water-insoluble organic substances. A liposome encapsulates a region of aqueous solution inside a hydrophobic membrane dissolved hydrophilic solutes cannot readily pass through the lipids. Hydrophobic chemicals can be dissolved into the membrane, and this way, the liposome can carry... 

Acid-Insoluble Substances Dissolve 2 g of sample in 30 mL of 1 3 hydrochloric acid, and heat to boiling. Filter the mixture through a suitable tared, porous-bottom porcelain crucible, wash the residue with hot water until the last washing is free from chloride, ignite at 800° 25° for 45 min, cool, and weigh. 

Acid-Insoluble Substances Slake 5 g of sample, then mix it with 100 mL of water and sufficient hydrochloric acid, added dropwise, to effect solution. Boil the solution, cool, add hydrochloric acid, if necessary, to make the solution distinctly acid, and filter through a tared glass filter crucible. Wash the residue with water until free of chlorides, dry at 105° for 1 h, cool, and weigh. 

Fluoride Determine as directed in Method III under the Fluoride Limit Test, Appendix IIIB, using a 1.0-g sample. Insoluble Substances Dissolve 10 g of sample in 100 mL of hot water, filter through a tared filtering crucible, wash the insoluble residue with hot water, and dry at 105° to constant weight. 

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