Distance decay

The quantity and distribution of soil Pb have been studied in numerous places in North America (see Laidlaw Filippelli, 2008). All these North American cities exhibited the same distance decay characteristic of high soil Pb contamination in the inner city and decreasing contamination toward the outer parts of the city as initially identified... 

Cai et al. [7e] investigated electron and hole transfer in various polynucleotide duplexes and compared them with previous results found for salmon sperm DNA, to examine the effect of base sequence on excess electron and hole transfer along the DNA 71-way at low temperature. Electron and hole transfer in DNA was found to be clearly base sequence dependent. In glassy aqueous systems (7M LiBr glasses at 77 K), excess electron-transfer rates increase in the order polydIdC-polydIdC<salmon testes DNAexcess electron and hole transfer rates increase in the order polyC-polyG<salmon testes DNATransfer distances at 1 min and distance decay constants for electron and hole transfer from base radicals to MX in polynucleotides-MX and DNA-MX at 77 K are derived and compiled in Table 3. This table clearly shows that the electron-transfer rate from donor sites decreases in... 

Table 3 Transfer distances and distance decay constants for electron and hole transfer to...

DNA < polyA-polyU. The electron-transfer rate from donor sites decreases in the order U T > C(N3)D and the hole transfer rate from donor sites decreases in the order A + > G +. The distance decay constant, b, for electron... 

Kp determines the long-distance decay of all correlation functions of the system. The temperature dependence of the response functions becomes... 

R. Wagner, L. Richter, Y. Wu, J. Weissmuller, A. Kleewein, E. Hengge, Appl. Organometal. Chem., 1998, 12(4), 265-276. Silicon-modified carbohydrate surfactants. VII Impact of different silicon substructures on the wetting behavior of carbohydrate surfactants on low-energy surfaces - distance decay of donor-acceptor forces. ... 

Figure 4 Distance dependence of driving-force-optimized electron tunneling times in Ru-labeled P. aeruginosa azurin. The sohd line is the distance decay predicted by the tunneling-pathway model for ET along an ideal 8-strand ( 8 = 1.0 A ). The dashed line is the best fit to the data fi =. A ) ...

The Ru-protein data points are scattered around the Ru azurin fi = 1.1 A exponential distance decay. More than three-fourths of the Ru protein ET rates fall in a 1.0 to 1.3 A y3-value zone. The data in Figure 5 suggest that a canonical distance decay constant will not describe long-range electron tunneling in proteins. Rates at a single distance can differ by as much as a factor of 10 and D/A distances that differ by as much as 5 A can produce identical rates. The... 

Table 1. Transfer distance and distance decay constant for hole/electron transfer. ...

Figure 6. Tunneling timetable for ET in Ru-modified azurin. The solid line is the TP prediction for coupling along a p strand (P = 1.0 A ) the dashed line illustrates a 1.1 A distance decay.

Rates of Cu+ to Ru + electron transfer also have been measured in modified mutants of spinach plastocyanin, a blue copper protein from the photosynthetic ET chain [79], Ru-bipyridine complexes were introduced at surface sites, with Cu-Ru distances ranging from 13 to 24 A. ET rate constants, measured using laser flash-quench techniques, vary from 10" to 10 s. ET in Ru-modified plastocyanin is not activationless as it is in Ru-modified azurin, suggesting a slightly greater reorganization energy for the photosynthetic protein. The distance dependence of ET in Ru-modified plastocyanin is exponential with a distance decay factor identical with that reported for Ru-modified azurin (1.1 A ). 

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