A Story of “ How Do We K now What W e K now ?” Part 1 – X-ray Diffraction

1. A Story of“How Do We KnowWhatWe Know?”Part 1 – X-ray Diffraction Matthew Sender Mentor: Dr. Grant Krow Teacher: Maria Fitzgerald

2. Structure & Function • Molecules can take many shapes and forms • Especially important for chains of molecules • DNA, Proteins Structure A Structure B Structure ? Function A Function B Function ?

3. Structure & Function Would we predict this structure to have function A, B, or ? What can we predict for an unknown structure?

4. My Molecules!b-methanoprolines My Beta Amino Acid Beta Amino Acid Alpha Amino Acid Nitrogen = Amino CO2H = Acid 1 carbon in between = alpha Nitrogen = Amino CO2H = Acid 2 carbons in between = beta

5. Hook a bunch together Guess what shape they take?

6. Hook a bunch together Or is it this structure? Or is the real structure another one altogether? Maybe even a structure without a repeating pattern!

7. Hypothesis_ In the absence of hydrogen bonding b-methanoprolineoligomers will adopt an ordered structure How do we prove or disprove our hypothesis? In other words, “How do we know what we know?”

8. X-ray Diffraction Detector X-ray Source Sample A Complex Math X-ray Source Sample B Complex Math

9. X-ray structure of our compound

10. Result • We were able to see the structure of our molecule • It does have an ordered structure in crystalline form • Comparable to other known structures with known functions

11. Problems • X-ray diffraction represents a molecule in the solid phase • Molecules in the liquid phase can have quite different structures • For a solution to the solution we must turn to a technique known as NMR • Nuclear magnetic resonance here we come!