[unionized]

I have a lab exercise wherein I am supposed to determine the compounds (a mixture of one or two amino acids) from a variety of NMR spectra:
http://imgur.com/a/UrdRm

I am having trouble with the specifics of it all. I have determined that it is a mixture of two of the following AAs:
Ala, Asp, Gly, Arg, Glu

And the DEPTs appear to indicate that there are 3 CH₂ groups, one CH, and one CH₃ (my TA claims the 90 DEPT should have one peak only). However, the corresponding number of CH, CH₂, and CH₃ groups for these five amino acids cannot add up in this way.

Alanine has the only methyl group, which would indicate that the other species would have to contain 1 CH and 3 CH₃, which is not possible.

However my TA also claims the HSQC and HNMR are sufficient for species determination, but the shifts are really like the literature values (and most of the spin-spin splitting yields peaks that the species do not predict).

I think it's alanine and glutamic acid, but again the data a bit off.

Here is the HSQC literature value overlay:
http://i.imgur.com/7L8eb.png

I am really stumped. If you could point me in the direction, that would be fantastically helpful!

[Dan]

There is only one CH. If it is a mixture of two amino acids, one of the amino acids must contain no CH at all. That narrows it down.

[unionized]

Thanks for taking the time to respond!

Given that fact, it would imply that Glycine and Alanine were present since the DEPT 135 two upward peaks and three downward ones.

However, the chemical shift doesn't look right. For instance, Gly's characteristic alpha carbon shift is about 40-45 ppm, it seems. Yet my 135 peaks occur at 53 and 13 ppm. I do have a downward peak at 40, but that would indicate a CH₂.

Perhaps less nebulously, my HNMR peak at 3.5 (the expected location for Glycine) is a doublet, whereas I would expect a quartet given the SSS with the amine Hs or even perhaps a singlet. Not a doublet by any expectation.

Also, G+A lacks crucial HNMR peaks at 2.5 ppm, which makes me think something is awry. :/