1. (4 points) Write the structure of the dipeptide ArgGlu as it would be expected at pH 7.
2. (2 points) How many distinct tripeptides could be made from the components Ala2Val ? Give their names using the three-letter abbreviations.
3. (2 points) Write resonance forms that illustrate why rotation around the C-N bond of an amide is relatively restricted.
4. (2 points) Explain what is meant by a beta-sheet structure that is antiparallel. Explain what forces hold this structure together.
