TSP does interact with proteins. It is thus advisable not to use TSP in serum samples. If calibrating the spectra with an internal standard is a concern you can calibrate with glucose (5.23ppm).

Thank you for your answer Mainak. I have heard of people calibrating with the solvent signal only, such as the D2O signal. Is this acceptable for publication in the metabolomic area?

D2O doesn't give any NMR signal. However, it exchanges with H2O and you will see signal at the H2O region. I won't suggest using this signal for calibration because the peak is very broad and it may affect your metabolomics results. For plasma samples, if you use the crude sample for NMR, it's best to calibrate with glucose. For tissue samples you will have to do metabolite extraction which will take care of the proteins. That way you can use TSP as internal standard.

You can follow this article: http://www.nature.com/nprot/journal/v2/n11/abs/nprot.2007.376.html

Thank you for your answers Mainak. I have another small (and which may seem stupid) question: I have been told by a Bruker technician that for metabolomic analysis I should never reuse an NMR tube. However, 5 tubes here in Brazil are about 200 US dollars, too expensive, so I´ll go bankrupt if this is true...

You can reuse the tubes. Wash with water followed by rinsing with an organic solvent like acetone, ethanol.

Thanks again! I´m stilll analyzing protocols, but will do a test run tomorrow, with rat samples. There are thousands of protocols available, I´ll take a look at what u sent me. Thanks!

No problem. Once you are done let me know if you need further help.

Pure isolated bioactive compounds from plants are not proteins or amino acids they are mostly heterocyclic compounds. You need a special procedure for amino acid detection or analysis. Thanks.

Dear Rachel,

we gave up cleaning NMR tubes a long time ago...have a look at (for example!) the Bruker on-line shop store.bruker-biospin.com where they charge 174 USD for 100 tubes...you may consider this! We NEVER had problems with their quality!

Kind regards

Alfred

Hello Alfred, thank you for your answer! I just checked the site you mentioned, however they don't ship to Brazil, unfortunately... I'll see what Bruker Brazil has to offer, I'll check 2morrow. We just bought 5 new tubes from Tedia and they cost about 200 dollars (since 1 Brazilian real is now equivalent to 3.50 dollars... We're all doomed since everything regarding science is already super expensive over here due to taxes - example: An HPLC column (Superdex 75) which costs one thousand and seven hundred dollars in the US costs 7 thousand reais here in Brazil...)... :(

I've run dozens of NMR small molecule screens against proteins and nucleic acids.  As others have mentioned, TSP and DSS bind both proteins and nucleic acids, however there is a nice work around.  I've used the internal reference DSA, similar to TSP/DSS, and described in the attached pdf.  From all my screening work with enzymes, structure proteins, and nucleic acids I can attest I do not detect any significant binding (as designed). This "new-ish" internal standard works well for relaxation based experiments, STD/Waterlogsy, trNOE and DOSY.  Bonus, as stated at the end of the paper, they will supply sample if you have your PI write the authors directly.  

Article DSA: A new internal standard for NMR studies in aqueous solution

Hi Rachel,

You can use in your NMR tube a seal capillarity filled with TSP dissolved in D2O, it will resolve the problem if TSP interact with protein or any other metabolite.

The may interfere if they are mixed with the protein. It is better to use a coaxial insert in such cases and calibrate the ratio of coaxial insert to annular space volume to perform quantification.

https://pubs.acs.org/doi/full/10.1021/ac010809+