CHM 371 1D 2D NMR

CHM 371 1D 2D NMR - David Grauer October 11,2007 CHM 371 1D...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
David Grauer October 11,2007 CHM 371 1D and 2D NMR Analysis of a Mixture of Amino Acids and the Polypeptide Gramicidin Preparation – Through the use of 1D and 2D NMR (COSY, NOESY and TOCSY) spectra, we sought to determine the presence of three separate, unknown amino acids in a series of four samples. This report will concern itself with the elucidation of the three amino acids contained within Sample C. In the second part of the experiment, 2D NMR (COSY and NOESY) spectra were used to determine the sequence of the ten amino acid dimer, Gramicidin. Part I – Amino Acid Identification Data Collection and Discussion – Note: The lettering below corresponds to labeled amino acid hydrogens following the data. Also, in the case of Leu, Protons B should not COSY correlate with the methyl region, the correlation listed is a result of the shift overlap with the methine proton C. Histidine Hydrogen Shift (ppm) Integration Multiplicity A 3.95 1 t B 3.27 2 d of t C 7.31 1 t (faint) D 8.6 1 t (faint) COSY, TOCSY, NOESY A B C D A C, T, N T (faint), N T (faint) B C, T, N T C C (faint), T D Leucine Hydrogen Shift (ppm) Integration Multiplicity A 4.17 1 d of d B 1.54 2 multiplet C 1.54 1 multiplet D 0.85 3 d E 0.805 3 d COSY, TOCSY, NOESY A B C D E
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
A C, T, N T, N T, N T, N B C, T, N C, T, N C, T, N C C, T, N C, T, N D T, N E Proline Hydrogen Shift (ppm) Integration Multiplicity A 4.25 1 quad of d B 2.00 1 obscured by amine C 2.21 1 multiplet D 1.90 1 obscured by amine E 1.82 1 multiplet F 3.55 1 multiplet G 3.41 1 multiplet COSY, NOESY, TOCSY A B C D E F A B C, T, N C C, T, N C, T, N D T, N C(messy),T C, T, N E T, N C, T C, T, N C(messy), T F T, N T, N T, N C, T, N C, T, N G T, N T, N T, N C, T, N C, T, N C, T, N To start, we looked at the aromatic region of the 1D NMR. There we saw two peaks, one at 7.31 ppm and one at 8.6 ppm. Looking at the shift list for amino acids, these peaks corresponded to peaks for His (8.12 ppm and 7.14 ppm expected). We then looked at the integration values for that peak and found that the two peaks corresponded to a hydrogen in the alpha region at 3.95 ppm. We then looked to the COSY and found
Background image of page 2
that 3.95 ppm had a correlation with a peak at 3.2 ppm. This peak at 3.2 ppm corresponds to the beta methylene hydrogens. To confirm this, the integration value for the doublet of triplet is twice that of the alpha hydrogen. His is the only amino acid with only one methylene carbon and such high shift values for its aromatic protons. The next thing we looked at was the methyl region shifts at .85 ppm and .805 ppm which had the same integration ratio. This indicated that the amino acid could be one of three – Val, Leu or Ile. Ile was ruled out because the alpha hydrogen’s splitting pattern was a doublet of doublets, not a simple doublet like we would expect in the case of Ile. We therefore had to choose between Val and Leu.
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 8

CHM 371 1D 2D NMR - David Grauer October 11,2007 CHM 371 1D...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online