Tetrahymena ribozyme, counterion

Heilman-Miller, S. L., Thirumalai, D., and Woodson, S. A. (2001). Role of counterion condensation in folding of the Tetrahymena ribozyme. I. Equilibrium stabilization by cations. J. Mol. Biol. 306, 1157—1166. 

To explain the folding characteristics of Tetrahymena ribozyme, a simple generalization of counterion condensation model was proposed [108, 109], In this two state model, equilibrium is considered between condensed and free counterions [108]. The chemical potential for each phase is approximately calculated as follows. If the volume fraction occupied by the counterions is denoted by < ), then the chemical potential of the free counterions is [108]... 

S. L. Heilman-Miller, D. Thirumalai, andS. A. Woodson,/. Molec. Biol., 306,1157 (2001). Role of Counterion Condensation in Folding of the Tetrahymena Ribozyme. I. Equilibrium Stabilization by Cations. 

To measure the folding equilibrium of the Tetrahymena L-21Sca ribozyme in various counterions, 32P-labeled ribozyme is prepared by T7 in vitro transcription with a-[32P]-ATP, according to established protocols (Zaug et al, 1988). Free label is removed with a size-exclusion spin column (e.g., TE-10, BD Sciences), and the RNA used without further purification (Emerick and Woodson, 1993). If desired, the RNA can be end-labeled with 32P and purified by denaturing PAGE. As for all biochemical experiments on RNA, care must be taken to use water, reagents, and plastic consumables that are free of RNase. 

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