PubMed · 5367995
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H K Leetz. 1969. [Dose computation for telecobalt therapy using a computer].. https://pubmed.ncbi.nlm.nih.gov/5367995/
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Although magnesium fulfills several essential biochemical roles, direct studies on this ion are complicated by its unfavorable spectroscopic characteristics. This contribution explores the possibility of monitoring magnesium-nucleic acid binding via a combination of [Co(NH3)6]3+ as surrogate for [Mg(H2O)6]2+, and of high-resolution solid-state 59Co NMR as a spectroscopic probe. Such strategy quenches fast cationic exchanges between bound and free states, while exploiting the superior NMR properties of the 59Co spin. Experiments on relatively small amounts of tRNA can then discern resonances corresponding to different metal binding environments. These characterizations were assisted by studies on model compounds and by multinuclear 31P-59Co recoupling experiments.
The first investigation and analysis of (59)Co 2D NMR homonuclear chemical shift correlation spectra are reported for the tetrahedral mixed-metal cluster HFeCo(3)(CO)(11)PPh(2)H. For this cluster in solution, the (59)Co 2D COSY and DQF COSY NMR spectra prove the existence of a scalar coupling between (59)Co nuclei. In order to obtain a value of this coupling, the 2D COSY and DQF COSY NMR spectra for a three-spin 7/2 AX(2) system have been simulated by numerical density matrix calculations. The comparison between experimental and theoretical 2D NMR spectra gives a spin-coupling constant |(1)J((59)Co - (59)Co)| = (115 +/- 20) Hz for this cluster. Experimental measurements of T(1) and of the line widths for cobalt 59 as well as theoretical (59)Co 1D NMR spectra are reported and support our findings.
Experiments were made to determine the dependence of CO3(3-) signal intensity on radiation dose in the low dose region from 3.1 x 10(-4) C/kg to 865.6 x 10(-4) C/kg. After all human tooth enamel samples were crushed into 350-500 micrometers particles, they were irradiated with 60Co gamma rays. Irradiated samples were measured with the ESR instrument, and the CO3(3-) signal appearance and the true signal have been determined. It is confirmed that the relation between the true intensity of the CO3(3-) signal and the exposure have linearity from 25.0 x 10(-4) C/kg to 865.6 x 10(-4) C/kg. It is difficult to confirm this in the case of less than 25.0 x 10(-4) C/kg due to the effect of organic signal and noise.