Chapter 4, Problem 13P

Answers to all problems are at the end of this book. Detailed solutions are available in the Student Solutions Manual, Study Guide, and Problems Book.

13. Determining Tyrosine Content of an Unknown Protein A previously unknown protein has been isolated in your laboratory. Others in your lab have determined that the protein sequence contains 172 amine acids. They have also determined that this protein has ne tryptophan and no phenylalanine. You have been asked to determine the possible tyrosine content of this protein. You know from your Study of this chapter that there is a relatively easy way to do this. You prepare a pure 50 mM solution of the protein, and you place it in a sample cell with a 1-em path length, and yen measure the absorbance of this sample at 280 nm in a U V-visible spectrophotometer. The absorbance of the solution is 0.372. Are there tyrosines in this protein? How many? (Hint: You will need to use Beer's law, which is described in any good general chemistry or physical chemistry textbook. You will also find it useful le know that the units of molar absorptivity are M^-1cm^-1.)