Increment topological

FIGURE 10.2 A small area of a raw electron density map of a protein, directly from the Fourier calculation as it comes off the computer. The location of each number on the plane corresponds to a specific x, y, z fractional coordinate in the unit cell. In general, one of the three coordinates will be constant for the entire plane, and rows and columns will correspond to the other two coordinates. The value of the number at each position is p(x, y, z), the electron density at that point. Contours are incrementally drawn around areas having p(x, y, z) greater than certain values. This yields a topological map of the electron density on each plane of the unit cell. 

Basicity or acidity are estimated by using topology-based increment systems. No software package is available so far that is able to predict basicity precisely for arbitrary structures. Basicity is a very important drug property, and therefore also a very rough estimation of pJ A values is useful in describing a library. 

Conversely, any valid topology must be able to reach a state described by the following key equation AIon = AIoff = AI. If it can t get this to happen, it is not a topology. Therefore, this simple current increment/decrement equation forms the litmus test for validating any new switching topology. 

This is clearly true for any topology. We can therefore work out the (negative) incremental input resistance for the other topologies in a similar manner. 

Fig. 7 Node-strut topology for series of CMPs networks produced by Sonagashira-Hagihara cross-coupling chemistry [19]. The benzene nodes are shown in red. The total number of ethyne plus benzene links per strut increases in increments of one from two (CMP-0) to six (CMP-5) in this series of samples. It should be stressed that these are simple representations of the repeat unit structures for the networks. The actual three-dimensional materials have more complex structures and include both terminal alkyne and halogen end groups (see also molecular simulations, Fig. 9)...

In the case of polypeptides, one could in principle improve the fit errors by making use of amino acid-type-dependent sets of Karpins coefficients. Schmidt [82] introduced a clever scheme in which fundamental Karpins parameters for a given J-coupUng were combined with a dihedral angle-independent term (incremental coefficient) that accounts for the different amino acid topologies. 

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