Question

TLC Analysis Of Egg Lipids Lab

1. The TLC plates were pre-baked at >120C. Why is this step necessary?

2. Below is the structure of your lipid staining dye, Naphthol Blue-Black. Explain which noncovalent interactions would be most important in allowing the dye to adhere to lipids (consider the chemical property of lipids as well as the dye).

3. You ran a solution of a fatty acid and a wax on a TLC plate using the exact conditions used in our lab exercise. Which lipid would you expect to migrate further up the TLC plate (which will have the larger Rf value)? Briefly explain your reasoning.

fatty acid:

wax:

4. In this lab you will be running two membrane lipid standards: DOPE (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine). These two membrane lipids differ only in their head group substituents. Review chapter 10.2 in your textbook and draw the head group substituents for DOPE and DOPC below (label your drawings).

Please help! I am unsure how to answer these questions and can't find any useful information on them.

Answer 1

Answer:-

1. The TLC plates were pre-baked at >120 degree Celsius in order to reactivate the precoated plates of silica gel for some minutes into a hot air oven which also results in the removal of moisture which is absorbed to the plates.
2. Polar polar interactions would be most important .For analysing of egg lipids we have to perform thin layer chromatography and we will use Naphthol Blue Black as lipid staining dye. Generally the separation of the lipids in TLC is determined on the basis of their absorption on the thin layer. Those lipid substances which is interacting weakly with the matrix moves faster thorough the solvent and doesn't dissolve in solvent and vice versa. After the separation of TLC plates takes place , the dye will be added to them which results in the color to them and lipid can be easily classified on the basis of their composition.
3. Wax have the larger Rf value than fatty acids. Rf value is defined as the movement of substance along a chromatography paper. More polar substance less will be the Rf value and vice versa. Triglycerides are non polar and they don't stick to the chromatography strip and have larger value than any phospholipids as they stick to the chromatography strip. Fatty lipids lies between them and have lower Rf value than waxes.
4. DOPE and DOPC are two lipid structures having very small but pivotal difference in the structure of their head groups. Figure is drawn below :-

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