Alteration hydrocarbon-induced

Schumacher, D. 1996. Hydrocarbon-induced alteration of soils and sediments. In Schumacher, D. Abrams, M.A. (eds.), Hydrocarbon migration and its near-surface expression AAPG Memoir, 66, 71-89. 

Remote sensing has the potential to detect hydrocarbon-induced alteration in rocks, soils and vegetation. Extensive studies have been performed on the reduction of ferric iron (red-bed bleaching), the conversion of feldspars and mixed-layer clays to kaolinite, the increase of carbonate content and the anomalous spectral reflectance of vegetation. 

The attraction of remote sensing is that it offers a rapid and cost-effective means of conducting reconnaissance for hydrocarbon-induced alteration. 

In addition, data obtained from infrared, thermal, and fluorescence spectroscopic studies of the outermost layer of skin, stratum corneum (SC), and its components imply enhancer-improved permeation of solutes through the SC is associated with alterations involving the hydrocarbon chains of the SC lipid components. Data obtained from electron microscopy and x-ray diffraction reveals that the disordering of the lamellar packing is also an important mechanism for increased permeation of drugs induced by penetration enhancers (for a recent review, see Ref. 206). 

Sunscreens and their degradation metabolites analyzed in this study are potential inducers of the oestrogen (ER) and aryl hydrocarbon receptors (AhR, also known as Dioxin Receptor). Ectopic activation of these pathways can cause severe damage to organisms and their ecosystem by altering reproduction, hormonal and/or circulatory systems [73-75] as well as they have been associated with carcinogenic and mutagenic effects [76-78]. 

Staples, J., et. al., Thymic alterations induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin are strictly dependent on aryl hydrocarbon receptor activation in hemopoietic cells, J. Immunol., 160, 3844, 1998. 

In many mammals induction of monooxygenation by polycyclic aromatic hydrocarbons is accompanied by the formation of a hemoprotein not seen to any appreciable extent in non-induced animals. This leads to an alteration in the microsomal hemoprotein populations, a change in the metabolic activity of the microsomes and, hence, possible alterations in the toxicity of other chemicals (27, 8). 

The alteration of hemoprotein(s) P-450 subpopulations in the rat may be observed spectrally, because after treatment of rats with polycyclic aromatic hydrocarbons, the Soret maximum of the carbonmonoxyferrocytochrome complex undergoes a hypsochromic shift from 450 to 448nm (50). This blue shift was not seen with rainbow trout hepatic microsomes (29,30). However, this does not preclude the induction of novel hemoproteins P-450 since (a) the induced hemoprotein(s) maty not differ spectrally from the constitutive enzymes and (b) the induced-hemoprotein may account for only a small proportion of total hemoprotein P-450, and hence its contribution to the position of the Soret maximum of carbon monoxide-treated reduced microsomes may be negligible. The latter suggestion is supported by the work of Bend et al. with the little skate. These workers have shown that hepatic microsomes from 1, 2,3,4-dibenzanthracene treated skates did not exhibit a hypsochromic shift when compared to control microsomes, however, partially purified hemoprotein exhibited an absorbance maxima at 448 nm (51). 

Environmental chemicals and pollutants are also capable of inducing P450 enzymes. As previously noted, exposure to benzo[a]pyrene and other polycyclic aromatic hydrocarbons, which are present in tobacco smoke, charcoal-broiled meat, and other organic pyrolysis products, is known to induce CYP1A enzymes and to alter the rates of drug metabolism. Other environmental chemicals known to induce specific P450s include the polychlorinated biphenyls (PCBs), which were once used widely in industry as insulating materials and plasticizers, and 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin, TCDD), a trace byproduct of the chemical synthesis of the defoliant 2,4,5-T (see Chapter 56). 

Studies with monolayers and bilayers as models show that modifications of chain conformation can alter the effective thickness of the hydrocarbon portion of a bilayer this, in turn, can have profound effects on its permeability. Suppose, for example, that a two-dimensional phase transition involved cooperatively inducing just one kink per molecule in otherwise fully extended chains. Such a kink shortens the extension of the chain by 0.127 nm, or thins a bilayer by 0.25 nm. We saw in Example 8.2 that this distance is about the length projected by two carbon-carbon bonds in the direction of the chain. Therefore, cooperative induction of such kinks has the same effect on the thickness of the hydrocarbon part of the bilayer as removing two carbon atoms from the tail groups. 

Microwave heating was also used to induce catalytic oligomerization of methane to afford C2-C4 hydrocarbons.571 Changing the catalysts and the applied power and the use of diluent gas (He) allowed significant alteration of product selectivities. Selectivity to benzene over nickel powder or activated carbon was 24 and 33%, respectively. 

Kappeli, O., Mueller, M. and Fiechter, A. (1978). Chemical and structural alterations of the cell surface of Candida tropicalis, induced by hydrocarbon substrate. Journal of Bacteriology, 133, 952. 

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