NMR _problem+answers

NMR _problem+answers - What are the differences and how is...

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MCB124 PRACTICE NMR PROBLEM This question is for the tetrapeptide A-G-S-T. Sketch the 2-D proton-proton COSY spectrum of the free peptide (the N-terminus and C-terminus are not observable)- Hint: start with the individual amino acids. Sketch the 2-D proton-proton NOSEY spectrum of the peptide in an extended (beta) configuration (the N- terminus and C-terminus are not observable). It is possible to use N-15 labelled samples and a specific editing technique to observe ONLY the N-H amide protons and no others. While the N-15 is present it is not observed. Sketch the COSY spectrum (Hint it is quite simple!!!) Sketch the NOSEY for a beta configuration? Sketch the NOSEY for an alpha configuration?
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Unformatted text preview: What are the differences and how is this useful in protein structure determination? ANSWERS TO PRACTICE NMR PROBLEM The key here is to start with the individual amino acids spectra and build up cross peaks from there based on J-coupled pairs for COSY and presumed distances within 5 Å for NOSEY spectra. In the N-15 edited spectrum only the N-H protons show and there are NO COSY cross peaks and NOESY cross peaks only between 2-3, 3-4, and 2-4 in alpha helix and only 2 -3 and 3-4 in beta. These differences indicate the secondary structure. (See spectra diagrams on next page-Note that C-gamma of Thr is not shown but it would be slightly upfield of the C-beta of Ala)...
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This note was uploaded on 04/06/2011 for the course MCB 124 taught by Professor Baldwin during the Summer '09 term at UC Davis.

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NMR _problem+answers - What are the differences and how is...

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