Actinomycin D (ACD), Figure 1, is the most important member of a family of naturally occurring actinomycine whose primary biological function is the inhibition of DNA dependent RNA synthesis (5). If mechanisms propoaed for the biological activity of ACD ( 6) are to have a plausible structural basis, it is eusential fo have detailed knowledge of the conformational properties of ACD. Such information can be obtainea from an analysis of the proton magnetic reeonance spectrom of ACD, and we report the reaulta of ouch a study in this camrwnication.
The proton rewnance spectm of a 0.011 M eolotion of ACD in C6D6, recorded at 60 Hcps and 80°C, is illustrated in Figure 1. Spectra were also recorded in a variety of aqueous and nonaqueoas solvents over a *de temperature range. However, the beat resolution of signals in the high-field region of the spectrum was obtained in C6D6. As is apparent from Figure 1, the spectrum is quite complicated, and a detailed assignment required the use of deuterim exchange, solvent perturbation, and spin decoupling techniques.
Deuterium exchange measurements, carried out in dioxane-d8 containing small amounts of D20,