Three conformers

We consider a finite space, which contains the NA sample and is in contact with a bath of water or water vapor. That allows one to maintain the r.h. in the experimental space at a constant level and change it when necessary. Such a scheme corresponds to the real experiments with wet NA samples. A NA molecule is simulated by a sequence of units of the same type. Thus, in the present study, we consider the case of a homogeneous NA or the case where averaging over the unit type is possible. Every unit can be found in the one of three conformational states unordered. A- or B- conformations. The units can reversibly change their conformational state. A unit corresponds to a nucleotide of a real NA. We assume that the NA strands do not diverge during conformational transitions in the wet NA samples [18]. The conformational transitions are considered as cooperative processes that are caused by the unfavorable appearance of an interface between the distinct conformations. 

The model suggested can be easily extended to the case of inhomogeneous NAs by means of introducing the dependence of the model parameters on the number of the NA unit in the chain and solving (4) and (7) for every NA unit. This seems important as natural NAs such as DNA and RNA are inhomogeneous. The extension of the model on the case of more than three conformations also can be done easily. 

A molecule has three nondegenerate conformers (Fig. 5-8). One is 450 x 10 J above the ground state, and the second high-energy conformer is 900 x 10 J above the ground state. What are the percentages of each of the three conformers relative to the total number of molecules in a sample of the normal conformational mixture at 300 K ... 

Section 3 7 Three conformations of cyclohexane have approximately tetrahedral angles at carbon the chair the boat and the skew boat The chair is by far the most stable it is free of torsional strain but the boat and skew boat are not When a cyclohexane ring is present m a compound it almost always adopts a chair conformation... 

Of the three conformations of propane shown which one is the most stable" Which one is the least stable" Why" ... 

Difluorobutane contains two chiral atoms, and can exist as any one of three stereoisomers. Predicting the properties of these molecules is complicated due to the fact that each exists as a mixture of three conformers because of rapid internal rotation about the central carbon-carbon bond. 

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