Organic Chemistry

Protein Solubility and Protein Denaturation

Purpose:

To determine the effects of a strong base, a strong acid, isopropyl alcohol, and a heavy metal salt on the structure of albumin.

Materials:

Albumin (egg whites), 3 M hydrochloric acid, 10% sodium hydroxide solution, isopropyl alcohol, 0.1 M silver nitrate solution, test tubes.

Safety:

Where goggles, apron, and gloves.  Work in a ventilated area and void inhaling the hydrochloric acid fumes.  Hydrochloric acid and sodium hydroxide solutions are corrosive liquids.  Silver nitrate solution is a corrosive liquid and toxic by ingestion; it will stain skin and clothes.

Procedure:

·      Obtain 4 test tubes and label them A through D

·      Using a pipette, add approximately 2 mL of albumin to each tube

·      Add 2 drops of 3 M hydrochloric acid to tube A. Gently swirl the tube to mix the contents. Record the appearance of the solution

·      Add 5 more drops of 3 M hydrochloric acid to tube A. Gently swirl the tube to mix the contents.  Record the appearance of the solution

·      Add 10 more drops of 3 M hydrochloric acid to tube A. Gently swirl the tube to mix the contents.  Record the appearance of the solution

·      Add 20 more drops of 3 M hydrochloric acid to tube A. Gently swirl the tube to mix the contents.  Record the appearance of the solution

·      Add 5 drops of 10% sodium hydroxide solution to test tube B. Gently swirl the tube to mix the contents. Record the appearance of the solution.

·      Add 10 more drops of 10% sodium hydroxide solution to test tube B. Gently swirl the tube to mix the contents. Record the appearance of the solution.

·      Add 10 more drops of 10% sodium hydroxide solution to test tube B. Gently swirl the tube to mix the contents. Record the appearance of the solution.

·      Add approximately 4 mL o isopropyl alcohol to test tube C. Gently swirl the tube to mix the contents. Record the appearance of the solution.

·      Add approximately 4 mL of 0.1 M silver nitrate solution to test tube D. Gently swirl the tube to mix the contents.  Record the appearance of the solution.

Data:

Effect of hydrochloric acid:

            Turned the albumin lighter in color, white chunks formed, turned white, denatured.

Effect of sodium hydroxide:

            Changed texture – lots of little bubbles trapped inside, smelled like sulfur, became more viscous, gelled. Later, after 24 hours, the substance became a very runny, but consistent liquid.

Effect of isopropyl alcohol:

            Didn’t mix right away, after some time it turned white, denatured.

Effect of silver nitrate:

            Turned white right where the silver nitrate was poured, happened quickly, white pieces formed, denatured.  Later, everything turned very brown.