Sedimentation coefficients organisms

Ribosomes are ancient ribonucleoprotein complexes that are the sites of protein synthesis in living cells. Their core structures and fundamental functional mechanisms have been conserved throughout the three domains of life bacteria, archaea and eukaryotes. All ribosomes are organized into two subunits that are defined by their apparent sedimentation coefficient, measured in Svedberg units (S). There is a general... 

For example, when we are interested in the accumulation of SOCs in earthworms, we may adopt a similar approach as we used for sediment-dwelling organisms. Since earthworms have a significant lipid content (ca. 5%, Table 10.1) and we are interested in relatively hydrophobic substances, we use lipid- and organic carbon-normalized biota-soil accumulation partition coefficients CK, jpoC) and bioaccumulation factors (BSAFnipoc). These correspond exactly to the biota-sediment accumulation partition coefficients and factors defined by Eqs. 10-21 and 10-24 (for an application see Problem P 10.2),... 

The diffusion path is often altered by the presence of solid boundaries. For example, in the subsurface organic chemicals must diffuse around soil and sediment grains. Within soil and sediment grains, organic chemicals must diffuse inside narrow and possibly undulating pores. To account for these effects the effective diffusion coefficient is modified by a restrictivity factor, Kr [-], and a tortuosity factor, r [-], as follows ... 

Koc carbon-referenced sediment partition coefficient organic chemicals partition coefficient... 

Figure 9-11. Sedimentation coefficients of various biological molecules, subcellular organelles, and organisms. (Courtesy of Beckman Instruments, Palo Alto, Calif.)...

Soil Organic Matter. A variety of soils and sediments sorb organic compounds in patterns that can be approximated by linear isotherm models, at least over relatively narrow (e.g., 1 decade) concentration ranges. Such isotherms are generally, although often imprecisely, expressed in terms of a partitioning coefficient, fy such that... 

A typical eukaryotic ribosome has a sedimentation coefficient of about 80 and consists of two subunits 408 and 608. These sizes may vary by as much as 10% from one organism to another in contrast with the homogeneity of bacteria ribosomes. The components of the subunits of eukaryotic ribosomes are as follows ... 

Example 3.4 Compare the rate of migration of lindane (C HgClg) and endrin (Cl HgCl O) with respect to groundwater seepage velocity in the sediments with organic matter content of 0.3%, porosity 0.3% and bulk density 1.9 g em We find the values of the partition coefficients of insecticides between the water and the carbon of organic matter of sediments K j which are 5.250 ml g for lindane and 89,100 ml-g" for endrin. 

Kojn soil/sediment partition coefficient (organic matter basis)... 

Protein biosynthesis takes place on ribosomes, which are small organelles present in all organisms. In prokaryotes (bacteria and blue-green algae) the ribosomes are somewhat smaller (sedimentation coefficient 70S) than those in the cytoplasm of eukaryotic cells (SOS), whereas ribosomes from chloroplasts and mitochondria have approximately the same size as prokaryotic ribosomes. All ribosomes consist of two subunits of unequal size those from SOS ribosomes sediment at 40S and 60S and those from 70S at 30S and SOS, respectively. Protein biosynthesis can occur only when the two subunits are associated and combined with messenger RNA. 

S. W. Karickhoff and D. S. Brown, determination of Octanol Water Distribution Coefficients, Water Solubilities, and Sediment/Water Partitions Coefficientsfor Hydrophobic Organic Pollutants, EPA-600/4-79-032, report, EPA, Washington, D.C., 1979. 

Table I summarizes some typical distribution coefficients. Sediments become enriched in plutonium with respect to water, usually with a factor of vlO5. Also living organisms enrich plutonium from natural waters, but usually less than sediments a factor of 103 - 101 is common. This indicates that the Kd-value for sediment (and soil) is probably governed by surface sorption phenomena. From the simplest organisms (plankton and plants) to man there is clear evidence of metabolic discrimination against transfer of plutonium. In general, the higher the species is on the trophic level, the smaller is the Kd-value. One may deduce from the Table that the concentration of plutonium accumulated in man in equilibrium with the environment, will not exceed the concentration of plutonium in the ground water, independent of the mode of ingestion.

The toxicological or cumulative effect of illicit drugs on the ecosystems has not been studied yet. Moreover, their fate and transport in the environment is to a big extent still unknown. Due to their physical-chemical properties (octanol-water partition coefficient, solubility, etc.) some of them, such as cannabinoids, are likely to bioaccumulate in organisms or concentrate in sediments whereas the rest, much more polar compounds, will tend to stay in aqueous environmental matrices. However, continuous exposure of aquatic organisms to low aquatic concentrations of these substances, some of them still biologically active (e.g., cocaine (CO), morphine (MOR) and MDMA) may cause undesirable effects on the biota. 

The BUSES model provides an estimate of the organic carbon/water partition coefficient (Koc) based on the octanol/water partition coefficient (Kow)- From these data, it is evident that the methyltins are less likely to partition onto organic carbon (in sediments, soils, biota) than are the butyl- and octyltin compormds due to then-lower partition coefficients and higher water solubilities. The 7/oc value can then be used to derive sohds/water partition coefficients in suspended matter, in sediment, and in soil using values of 10%, 5%, and 2% for organie carbon, representing typical organic carbon contents of suspended matter, sediment, and soil, respeetively. 

Adsorption Coefficient (K c)—The ratio of the amount of a chemical adsorbed per unit weight of organic carbon in the soil or sediment to the concentration of the chemical in solution at equilibrium. 

LymanWJ. 1990. Adsorption coefficient for soils and sediment. In Handbook of chemical property estimation methods. Environmental behavior of organic compounds. Lyman WJ, Reehl WE, Rosenblatt DH, eds. Washington, DC American Chemical Society. ... 

---