Problem 16
Effect of Polarity on Solubility Rank a triacylglycerol, a diacylglycerol, and a monoacylglycerol in order of decreasing solubility in water. Assume that each acylglycerol contains only palmitic acid.
Problem 19
Using the LIPID MAPS Database to Find Solubility Information Lipidomics has identified thousands of cellular lipids. LIPID MAPS is an online database containing over 40,000 unique lipid structures, as well as information on the chemical and physical properties of each lipid (www.lipidmaps.org). One important parameter when working with lipids is \(\log P\), where \(P\) is the octanol:water partition coefficient, an indicator of lipophilicity. a. Look up cholesterol, sphingosine, linoleic acid, and stearic acid in LIPID MAPS and use the reported \(\log P\) values to place them in order of increasing solubility in octanol. b. Pharmacologists often study \(\log P\) values when developing new drugs. Why would knowing a drug's \(\log\) \(P\) value be informative?
Problem 20
Characteristics of Lipid Transport Proteins Often when lipids are transported between different tissues, they are carried by proteins. In this exercise, you will explore the interactions between a lipid and a protein using the PDB (www.rcsb,org). Use the PDB identifier 2YG2 and study the structure of the complex between HDL-associated apolipoprotein \(\mathrm{M}\) and sphingosine-1-phosphate. Navigate to 3D View: Structure to answer the following questions. a. What protein motif is adopted by apolipoprotein M? b. Which amino acid residues do you find lining the sphingosine binding pocket? What do they have in common? c. The phosphoryl group of sphingosine-1-phosphate is exposed on the surface of the protein. Why do you suppose it is important that the transport protein binds the hydrocarbon tail of sphingosine-1-phosphate but not necessarily the polar head group?
