Transferability of potentials

FIGURE 3.1 Transfer of potentially toxic substance between environmental compartments Q and C2. 

Triantafyllou et al. (2005), in studies on transfer of potential contaminants from paper and board to food, measured partition coefficients between packaging and air for a range of substances. This was, therefore, an attempt to measure the potential for gas-phase transfer. A mixture of acetophenone (b.p. 203 °C), naphthalene (b.p. 218 °C), benzophenone (b.p. 306 °C), dibutyl phthalate (b.p. 340 °C) and methyl stearate (b.p. 443 °C) was placed in a vial together with samples of test liner made from virgin fibres or triplex board made from 100% recycled fibre. There was no contact between the substances and the paper or board. Vials were sealed and heated at 70 °C or 100 °C and then the paper removed and analysed for uptake of substances. Conclusions from the studies were that ... 

With system of this size, accurate ab initio calculations of interaction energies are practically ruled out. At the same time, extracting useful information from experimental measurements becomes more and more complicated as the number of atom, or groups of atom, types increases. As a consequence, it is convenient, or even necessary, to assume transferability of potential parameters, considered peculiar of a given atom or group of atoms. In other words, the effects of the different molecular environments on these parameters is neglected and atomic transferability is accepted. 

Figure 2. Transfer of potential to cause change from one commodity (charge) to...

Some further comments regarding the accuracy of Figure 8.4 appear to be in order at this point. This figure is a fairly good example of the accuracy and transferability of potential functions that can be obtained with molecular mechanics. Note that in the parameterization of the MM4 force field for alcohols, ethers, and related compounds. 

Masks are used to prevent hospital healthcare workers from acquiring infections from splashes of blood and body fluid, and to reduce the transfer of potentially infectious body fluids in the sterile area. They are also used by coughing patients to try and prevent the spread of infections (AkaUn, Usta, Kocak, Ozen, 2010 Chughtai et al.,... 

The concept of transferability of potential functions is closely linked with that of additivity, as already noted in the preceding chapter. Transferability means that the energy functions which give a satisfactory description of the physico-chemical properties of one molecule may be used with confidence to describe the properties of any other molecule of similar structure. Thanks to the transferability of potential functions it is possible to determine them by studying simple, small-size molecules, and then use them in complex, large molecules such as proteins and nucleic acids. However, in doing so we should always remember that transferability, like additivity, is an empirical and approximate rule, valid only if the concept of similar structure is used properly. 

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