lecture14 - A. S. Edison University of Florida 2006 Todays...

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Unformatted text preview: A. S. Edison University of Florida 2006 Todays Lecture 14) Wed, Nov 1: Assignments: II a.Important 2D heteronuclear experiments b.3D NMR c.Assignment strategies in proteins d.Intro to protein structure determination A. S. Edison University of Florida 2006 TOCSY/COSY NOESY/ROESY 1 H-based Peptide Resonance Assignments N C C N C C H O H O H CH 3 H CH CH 3 CH 3 N H A. S. Edison University of Florida 2006 1 H-based Resonance Assignments F2 G3 E5 G10 M6 M8 F14 V11 D4 L12 R13 "NH" 2 8.7 8.4 8.1 7.8 ppm 4.8 4.5 4.2 3.9 GFGDEMSMPGVLRFamide S7 A. S. Edison University of Florida 2006 Some Heteronuclear 2D Experiments Name Type of correlation Notes HMQC H eteronuclear M ultiple Q uantum C orrelation 1 H atoms directly bonded to X (usually 13 C or 15 N) mediated by J-coupling. Starts with and detects 1 H and very sensitive. One of the simplest heteronuclear NMR experiment HSQC H eteronuclear S ingle Q uantum C orrelation 1 H atoms directly bonded to X (usually 13 C or 15 N) mediated by J-coupling. Similar information to HMQC Sensitive and better relaxation properties for proteins. Very important and common experiment for proteins. HMBC H eternuclear M ultiple B ond C orrelation 1 H atoms 2-3 bonds away from X (usually 13 C) mediated by J-coupling. Very important experiment for natural products. One of the best (sometimes only) ways to identify quaternary carbons. INADE QUATE I ncredible N atural A bundance D ouble Qua ntum T ransfer E xperiment 13 C- 13 C directly bonded correlations mediated by J-coupling. Useful for natural products. Not very sensitive, because it starts with and detects 13 C and not proton. A. S. Edison University of Florida 2006 Why Heteronuclear NMR? A. S. Edison University of Florida Beyond relatively small peptides, most NMR of proteins or nucleic acids requires isotopically labeled samples. Proteins are usually produced by over-expressing them in bacteria with 15 N-labeled, 13 C-labeled, 15 N+ 13 C-labeled, or 15 N+ 13 C+ 2 H- labeled nutrients. Specific labeling strategies have been developed, but uniform isotopic enrichment is most common. There are several reasons to isotopically label a sample: Overlapping 1 H resonances can be resolved using the frequencies of the attached heteronucleus. The heteronuclei create efficient pathways to correlate atoms along the backbone and side-chains of proteins and nucleic acids....
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This note was uploaded on 06/07/2011 for the course BCH 6745 taught by Professor Staff during the Spring '08 term at University of Florida.

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lecture14 - A. S. Edison University of Florida 2006 Todays...

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