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

A Story of “ How Do We K now What W e K now ?” Part 1 – X-ray Diffraction. Matthew Sender Mentor: Dr. Grant Krow Teacher: Maria Fitzgerald. Structure & Function. Molecules can take many shapes and forms Especially important for chains of molecules DNA, Proteins. Structure A.

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

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## A Story of“How Do We KnowWhatWe Know?”Part 1 – X-ray Diffraction

Matthew Sender

Mentor: Dr. Grant Krow

Teacher: Maria Fitzgerald

### 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 ?

### Structure & Function

Would we predict this structure

to have function A, B, or ?

What can we predict for an unknown structure?

### 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

### Hook a bunch together

Guess what shape they take?

### 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!

### 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?”

Detector

X-ray Source

Sample A

Complex Math

X-ray Source

Sample B

Complex Math

### 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

### 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!