A little help please
 

A little help please

I am studying intro to NMR and am a little stuck on these questions, my background is biochem and NMR is very tricky for me

6. A pharmaceutical company wishes to screen a protein target involved in a cancer pathway for small molecule drug inhibitors. Unfortunately, only a poor recombinant expression of the protein enriched in 15N isotopes is possible: 0.5 mg protein is available per L of culture. Following a 10 L culture, 5 mg of this protein is available. Obviously, you would like to make as many samples as possible using this batch of 5 mg. This will depend on the experimental setup: you can either measure the 1H spectrum at 700 MHz using a 5 mm room temperature probe or at 500 MHz using a 5 mm cryoprobe. a) Which instrument would you choose to get the highest signal to noise ratio on the protein sample per unit? In elaborating your answer, assume that all the compound is present inside the active volume of the coil (i.e. everything gets measured). B) What would be the time cost factor to achieve identical signal-to-noise on both instruments?

8. In the 13C spectrum of thioredoxin measured at 125 MHz (i.e. a 500 MHz instrument), a single 13C resonance is visible at 234 ppm with respect to the internal reference peak of DSS set at 0 ppm. a) Which is most shielded, the reference 13C nucleus or the one at 234 ppm (and explain your reasoning)? b) What is the difference in shielding constant (calculate) (s234ppm?sref) between both and c) what will the distance between both resonances be in Hz if you would measure this sample at 1000 MHz.

If someone could answer these questions i would be very grateful, Thanks



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