Fig. 2.

Increased level of labeling in K10 without (red) and with (blue) ¹³C-formate in a ¹³C-2-glycerol background. The experiments were performed on mixtures of the four rNMPs isolated from the K10 bacterial culture. a Direct carbon detection 1D spectrum showing all the carbon positions for nucleotides labeled with glycerol and no formate (bottom, red) or glycerol with formate (top, blue). A long recycle delay of 5 s were used to allow for sufficient magnetization recovery and proton decoupling was limited to the acquisition period only. The level of enrichment at the adenine (Ade) and guanine (Gua) C8 positions increases by spiking with ¹³C-labeled formate. The C5′ region has an impurity that resonates in a distinct region in the 2D spectrum. b 2D non-constant time HSQC spectrum of a mixture all four labeled rNMPs showing the protonated base region. For ease of comparison the spectrum obtained without labeled formate (red contours) are displaced vertically relative to the formate labeled spectrum (blue contours). c 2D non-constant time HSQC spectrum of a mixture of all four labeled nucleotides showing the ribose region. The cytosine (Cyt) and Uracil (Ura) C5 resonances at 96.67 ppm and 102.69 ppm respectively are folded into the spectrum. The boxed resonances highlight the increased labeling level seen for C1′, C3′ and C5′ with spiking the growth medium with ¹³C-labeled formate