Virus Transport Through Percolating Beds

The movement of viruses in soil has important implications for land treatment of waste water. An adsorption mass transfer model is developed to describe the movement of single virus particles through packed beds of soils and soil components. The model predicted that ox0174 bacteriophage will breakthrough one meter of silt loam soil in 60 days for percolation rates of about 40 in/wk. Experimental determinations of equilibrium adsorption parameters for particular virus/adsorbent combinations are required to make similar predictions for enteric virus breakthrough from soil columns. Experimental measurements for attenuated poliovirus I (a typical enteric virus) show that: (1.) single virus particles are likely to be present in treated wastewaters that are land spread, (2.) poliovirus association with sand is about 50-fold stronger than ox-174 phage association with silt loam soil, and (3.) poliovirus interaction with 1-2 um montmorillonite clay particles is affected by clay aggregation at high virus titers. The needs for future research are indicated. These include measurements of enteric value inactivation in soil-water and incorporation of inactivation kinetic expressions in future versions of the adsorption mass-transfer model

Temperature dependence of the formal reduction potential of putidaredoxin

AbstractPutidaredoxin (Pdx), a [2Fe–2S] redox protein of size Mr 11 600, transfers two electrons in two separate steps from the flavin containing putidaredoxin reductase to the heme protein, cytochrome CYP101 in the P450cam catalytic cycle. It has recently come to light, through NMR measurements, that there can be appreciable differences in the Pdx conformational dynamics between its reduced and oxidized states. The redox reaction entropy, ΔSrc0′=(SPdxr0′−SPdxo0′), as determined from measurements of the variation in formal potential with temperature, E0′(T), provides a measure of the strength of this influence on Pdx function. We designed a spectroelectrochemical cell using optically transparent tin oxide electrodes, without fixed or diffusible mediators, to measure E0′(T) over the temperature range 0–40°C. The results indicate that the redox reaction entropy for Pdx is biphasic, decreasing from −213±27 J mol−1 K−1 over 0–27°C, to −582±150 J mol−1 K−1 over 27–40°C. These redox reaction entropy changes are significantly more negative than the changes reported for most cytochromes, although our measurement over the temperature interval 0–27°C is in the range reported for other iron–sulfur proteins. This suggests that Pdx (and other ferredoxins) is a less rigid system than monohemes, and that redox-linked changes in conformation, and/or conformational dynamics, impart to these proteins the ability to interact with a number of redox partners