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**[SOLVED] BioChem Amino acid**

**1. Homework Statement**

A protein has a MW of 26,000 Daltons. The protein consist of 7 alpha helix segments that cross a cell membrane of 4.5 nm.

**2. Homework Equations**

What they want to know is the minimum number of AA's for a single segment to cross the membrane completely and the fraction of the protein involved in the membrane spanning helices.

**3. The Attempt at a Solution**

I really do not know where to being with this question and have been looking for a beginning for a while. I know the answers are 30 and 89%, but I don't know how to calculate them.

My thought process has led me to try (26000/(110x7)) the weight of the protein by the average AA weight and number of chains, but that brings me to 33.8. I also know that the 4.5 nm factors in there somewhere, but where? I have also tried (26000/(45x7x3.6) 45 is 4.5 nm in angstroms, 7 is the number of helices and 3.6 is the amount of AA's in one helix turn, but that makes it too low at ~23. As far as the fraction thing goes I figured I would figure out the first part and go from there.

Thanks for any help.