Exchangeable and Nonexchangeable Protons

With larger biopolymers, the solvent of choice is an aqueous medium since, in most cases, water is required to maintain the native conformation in solution. In addition, the exchangeable protons are of importance because they are involved in such things as hydrogen bonding and salt bridges, which are critical in stabilizing the native structure. The total spectrum 

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The exchangeable and nonexchangeable netropsin protons have been monitored in detail for the 1 antibiotic per dG-dG-dA-dA-dT-dT-dC-dC octanucleotide duplex complex in our laboratory (9 7). 

Nucleic Acid Base Resonances The chemical shifts of the nonexchangeable protons in poly(dA-dT), the Nuc/D = 24 complex and the Nuc/D = 8 complex in 1 M NaCl solution are plotted as a function of temperature in Figure 19. The nucleic acid nonexchangeable proton chemical shifts in the duplex state are either unperturbed (adenosine H-8, H-2, and thymidine CH3-5) or shift slightly upfield (thymidine H-6) on complex formation (Figure 19). By contrast, the thymidine H-3 exchangeable proton located in the center of the duplex resonates 0.35 ppm to higher field in the Nuc/D = 8 proflavine complex compared to its position in the... 

We have attempted to investigate the daunomycin complex with poly(dA-dT) in order to set constraints on possible overlap geometries in the intercalation complex (26) using methods described in the previous section on the proflavine complex (25). There are nonexchangeable proton markers on ring D and exchangeable proton markers on ring B of the planar portion of the... 

Fig. 6.6 Schematics of hydrogen bonds between purine and pyrimidine bases with indicated trans-hydrogen bond scalar interactions and related coupling constants, which can be measured using NMR. In addition to correlations between exchangeable protons and nitrogens, also a relayed transfer to nonexchangeable aromatic protons, shown by a dashed arrow, can be employed. The...

The -ENDOR spectra obtained on T. roseopersicina H2ase reveal resonances attributable to two of the three types of protons observed for the D. gigas enzyme, the nonexchangeable cysteine /3-CH2 protons (A = 12 MHz) and the more strongly coupled exchangeable proton (A = 21.5 MHz). The weakly coupled exchangeable proton (4 MHz) is not... 

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