Base hemi-protonated

Schimanski, A., Ereisinger, E., Erxleben, A. and Lippert, B. (1998) Interactions between [AuX4] (X = Cl, CN) and cytosine and guanine model nucleobases salt formation with (hemi-) protonated bases, coordination, and oxidative degradation of guanine. Inorganica Chimica Acta, 283, 223. 

Fig. 16.3. The hemi-protonated base pair formed by cytosine has three hydrogen bonds...

The aldehyde products can be easily distinguished from the ketone products by the lone hydrogen. The hemi products can be distinguished from the acetals and ketals because the hemi products both have alcohols while the full acetals and ketals don t. Hemi formation is catalyzed by acid or base. In formation of acetal and kctal from the hemi forms the hydroxyl group must be protonated to make a good leaving group, thus this part of the reaction is catalyzed by acid only. 

Proton MRS combined with SCS-based analysis has been used to distinguish normal liver tissue, cirrhotic liver and HCC with a high degree of accuracy. Liver tissue specimens from 54 patients undergoing either partial (hemi) or total hepatectomy were analysed by (ID) H MRS at 8.5T. Histologically, these specimens were confirmed as normal (n = 31), cirrhotic (n = 59), and HCC (n = 32).76... 

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