Cluster polar

FIGURE 10.35 The amino acid sequences of several amphipathic peptide antibiotics, a-Helices formed from these peptides cluster polar residues on one face of the helix, with nonpolar residues at other positions. 

Betz, A.G., Rada, C., Pannell, R., Milstein, C., Neuberger, M.S. (1993). Passenger transgenes reveal intrinsic specificity of the antibody hypermutation mechanism clustering, polarity, and specific hot spots. Proc. Natl. Acad. Sci. USA 90,2385-2388. 

The potential surfaces can be qualitatively expressed for these clusters through a model quite similar to that employed by Levy and coworkers (Tubergen et al. 1990 Tubergen and Levy 1991) for substituted indole clusters. Polar solvation in this case lowers the polar La state below the local excited Lb state, which is the first excited singlet state of the bare molecule. 

CCPPA coupled cluster polarization propagator approximation... 

Very recently we have formulated and tested a new coupled-cluster polarization propagator method (Geertsen and Oddershede, 1986a). We still use a perturbation expansion of the reference state but we replace the Rayleigh-Schrodinger correlation coefficients (i =1,2)... 

Inductive Cluster Polarization. Reiser 21) noted that the rate changes caused by dissolution inhibitors are disproportionate to the amount of inhibitor used. For example, the dissolution rate of novolac is decreased by several orders of magnitude with an inhibitor loading of only 10 % (wt/wt). The percolation model predicts that the inhibitor must block the active sites of the novolac to the point that p falls below Pc. Reiser concluded that for such small loadings of inhibitor to block so many active sites each inhibitor must block several phenolic sites in the percolation field. 

Figure 4. Inductive Cluster Polarization (Adapted from reference 22.)...

Still, the occurrence of polarization is at the same time an indication of some charge transfer. This is most clearly seen (see Ref [26]) when a configuration change is first achieved in the bare cluster so that becomes empty, corresponding to the cluster polarization, and next the charge-transfer (HOMO-LUMO) type of interaction between (p and is allowed to occur (cr donation). 

CCPPA Coupled Cluster Polarization Propagator Approximation... 

As the size of the Mo cluster was increased beyond n = 37 by sequential addition, as described in Section 6.3.1, the cluster polarization and strain in the C,go molecule... 

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