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Transformation of crops, including maize (Zea mays L.), with the cry1Ab gene from Bacillus thuringiensis to combat lepidopteran pests results in pleiotropic effects regarding lignin biosynthesis. Lignin patterns in stems and leaves of two genetically modified Bt-maize varieties (Novelis T and Valmont T) were studied along with their non-Bt near-isolines (Nobilis and Prelude, respectively). Molecular-level based thermochemolysis using tetramethylammonium hydroxide (TMAH) in combination with gas chromatography-mass spectrometry (GC-MS) was used to quantitate the total lignin contents and to identify monomeric lignin subunits including p-hydroxyphenyl (P), guaiacyl (G), and syringyl (S) moieties. The results were supplemented and confirmed by cupric oxide oxidation. The stems of the transgenic lines had higher concentrations of total lignin than the respective isogenic lines: Valmont T/Prelude by 18% and Novelis T/Nobilis by 28%. In contrast, differences in the total lignin concentration of leaves between the transgenic and the respective near-isogenic lines were marginal. There were significant modifications in the ratio of p-hydroxyphenyl/guaiacyl/syringyl molecular marker units of stem lignin between transgenic and isogenic lines. The guaiacyl units (in particular the G18 marker) accounted chiefly for the higher total lignin contents in the transgenic lines. The leaf lignin patterns did not show significant differences in molecular markers between isogenic and transgenic lines. TMAH-induced thermochemolysis--conducted in both the on-line and off-line modes--provided detailed information on the molecular composition of lignin, thus proving superior to the established "wet chemistry" methods of lignin determination.

Sorption phenomena of very hydrophobic compounds (VHOCs, log K(OW) > 5) on dissolved humic organic matter (DOM) are overwhelmingly based on partitioning processes. In this respect, DOM is very similar to "rubbery" soil/sediment OM. To exclude system adsorption effects, the DOM sorption coefficients (K(DOM)) of VHOCs were determined using a dynamic approach based on the VHOCs' aqueous solubility enhancement in the presence of DOM. Partition coefficients are strongly correlated to the analytes' Kow across the alkane, PAH, and PCB groups under study. These three "families" are regarded to be good models of hydrophobic partitioning. On the basis of a uniform one-parameter concept characterizing sorption on amorphous polymers, Hildebrand solubility parameters of amorphous polymeric sorbents, including DOM, and of sorbates can be calculated on the basis of partition coefficients. Likewise, partition coefficients can be estimated using Hildebrand solubility parameters. Literature-based partition coefficients on DOM fit very well in this universal one-parameter concept. On using our own sorption data of PAHs, PCBs, and alkanes on DOM, an almost identical solubility parameter for the DOM polymer under study is obtained. The concept is also very useful in understanding both waterborne and airborne bioconcentration processes, which are considered to be partitioning phenomena.

Fatty acid profiles were used to characterize nutritional pathways in Chlamydomonas sp. isolated from an acidic mining lake (pH 2.7). Surprisingly, profiles of Chlamydomonas sp. grown in the lab under photoautotrophic, mixotrophic, and heterotrophic conditions at in situ deep strata lake water temperatures (8 degrees C) were very similar, polyunsaturated fatty acids including alpha-linolenic acid (18:3omega3) and 16:4omega3 along with palmitic acid (16:0) being most abundant. Therefore, heterotrophic growth of Chlamydomonas sp. at low temperatures can result in high concentrations of polyunsaturated fatty acids, as previously only described for some psychrophilic bacteria. By contrast, the cultivation of isolated Chlamydomonas sp. at 20 degrees C, reflecting surface water temperatures, provided fatty acid patterns characteristic of the nutrition strategy applied: the concentration of polyunsaturated fatty acids decreased when the growth pathway changed from photoautotrophic via mixotrophic to heterotrophic. Total fatty acid concentration also diminished in this order. Principal component analysis confirmed the significance of FA profiling to mirror nutritional pathways. Lake-water analysis revealed low concentrations of dissolved organic carbon, mainly consisting of polymeric fulvic acids that are unable to support heterotrophic growth of Chlamydomonas sp. Polymeric fulvic acids present in the deeper strata of the lake turned out to be formed in situ on the basis of organic monomers including reduced sulfur-containing ones, as revealed by thermochemolysis and pyrolysis. Growth of Chlamydomonas sp. in the deep chlorophyll maximum is therefore assumed to mainly result from photosynthesis, despite very low photon densities. Phytol-including metabolites proved to be significant biomarkers to indicate the nutritional pathway of Chlamydomonas sp. alpha, omega-Dicarboxylic acids-light-induced degradation products of unsaturated fatty acids-appeared to be good indicators of photooxidative alterations to the algal species under study.

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Solid phase microextraction (SPME) was used to investigate the sorption behavior of ionogenic and non-ionogenic alkylated organotin compounds onto humic organic matter (HOM). The basic idea of these investigations is to measure selectively the freely dissolved proportion of the target analytes rather than the proportion bound to the polymer. This allows partition coefficients of non-ionic organic chemicals to be determined without any disturbance of the sorption equilibrium in both particulate and dissolved HOM matrices. For SPME, the ionogenic organotin compounds have to be alkylated. This can easily be achieved after centrifugation of particulate HOM, whereas for SPME in the presence of dissolved HOM an in-fiber derivatization is proposed. The sorption coefficients of a given ionogenic or non-ionogenic organotin compound are similar for particulate and dissolved HOM from the same source, indicating that the same type of interaction accounts for the sorption process. The higher the degree of alkylation in the target analyte, the more pronounced the nonspecific interactions and the faster the sorption equilibrium are established. Kinetic studies performed by SPME indicate that the sorption equilibrium on dissolved HOM, is reached within a few minutes; on particulate HOM the process takes longer due to diffusion pathways.

Solid-phase microextraction (SPME) using nonpolar fiber coatings is a very useful method for determining concentrations (more precisely, activities) of environmentally relevant very hydrophobic organic compounds (VHOC:  alkanes, PCBs, and PAHs). The issue of adsorption (surface effect) versus absorption (partitioning) is of huge importance for the application of SPME to determine VHOC in environmental samples. Competition effects, which are associated with adsorption processes, would result in concentration-dependent and mixture-dependent responses. The confusion in the literature about the processes responsible for analyte extraction by the poly(dimethylsiloxane) (PDMS) fiber coatings turned out to be mainly attributed to experimental errors when applying conventional static SPME approaches. Determining fiber coating distribution coefficients (K f) using dynamic systems is more accurate in comparison with static systems because analyte losses in the system (due to the fiber uptake, sorption on the walls, etc.) can be compensated for, thus ensuring constant concentration of the dissolved analyte(s) during the experiment. Fiber distribution coefficients of VHOC on PDMS coatings are strongly correlated with the analyte hydrophobicity, expressed by the octanol−water partitioning coefficient (K ow). This indicates that partitioning between the sample and the coating is the prevailing process. Therefore, equilibrium SPME extractions in multicomponent systems allow the determi nation of concentrations of any of the VHOC, provided that the extraction is carried out in a depletion-free system and that appropriate partition coefficients of the analytes, which can be estimated on the basis of their K ow data, are available.