Reducing Variability in Pollution Data: The Use of Lipid Classes for Normalization of Pollution Data in Marine Biota

Abstract

Organochlorine residues (PCBs and pesticides) are usually normalized on lipid content, gravimetrically quantified after extraction in organic solvents. In this study, the lipid content of different biotic groups (e.g. phytoplankton, shrimp, bivalves, fish), obtained through different types of extraction (total extraction versus specific extraction of apolar lipids) and quantification techniques (total gravimetric determinations versus specific determinations of lipid classes (latroscan)) were compared. The different lipid quantification methods were interrelated. An overestimation of lipid content due to non-lipid co-extracts was shown to interfere with gravimetric lipid quantifications. The relative contribution of these co-extracts depended on the type of sample studied. Differences in pollution levels (individual PCB congeners) between different biotic groups (phytoplankton, shrimp, cockles, fish) and between different fish tissues are discussed in relation to lipid content, determined by the different methods. An important reduction in the variability of pollution levels was noted when data were normalized on total neutral lipid content (latroscan). Highly significant linear regression parameters were obtained between the pollutant and the total neutral lipid content of marine biotic samples from the same water mass. Water mass specific bio-lipid contamination levels, characteristic for the whole biotic community (excluding seabirds and sea mammals), were determined for the different PCB congeners, normalized on total neutral lipid content. These bio-lipid contamination levels were related to the K_ow of the congeners. This functional relationship could be described by a second order polynomial regression.     

Multiwalled carbon nanotubes drive the activity of metal@oxide core-shell catalysts in modular nanocomposites

Rational nanostructure manipulation has been used to prepare nanocomposites in which multiwalled carbon nanotubes (MWCNTs) were embedded inside mesoporous layers of oxides (TiO(2), ZrO(2), or CeO(2)), which in turn contained dispersed metal nanoparticles (Pd or Pt). We show that the MWCNTs induce the crystallization of the oxide layer at room temperature and that the mesoporous oxide shell allows the particles to be accessible for catalytic reactions. In contrast to samples prepared in the absence of MWCNTs, both the activity and the stability of core-shell catalysts is largely enhanced, resulting in nanocomposites with remarkable performance for the water-gas-shift reaction, photocatalytic reforming of methanol, and Suzuki coupling. The modular approach shown here demonstrates that high-performance catalytic materials can be obtained through the precise organization of nanoscale building blocks.     

Identifying residual structure in intrinsically disordered systems: a 2D IR spectroscopic study of the GVGXPGVG peptide

The peptide amide-I vibration of a proline turn encodes information on the turn structure. In this study, FTIR, two-dimensional IR spectroscopy and molecular dynamics simulations were employed to characterize the varying turn conformations that exist in the GVGX(L)PGVG family of disordered peptides. This analysis revealed that changing the size of the side chain at the X amino acid site from Gly to Ala to Val substantially alters the conformation of the peptide. To quantify this effect, proline peak shifts and intensity changes were compared to a structure-based spectroscopic model. These simulated spectra were used to assign the population of type-II β turns, bulged turns, and irregular β turns for each peptide. Of particular interest was the Val variant commonly found in the protein elastin, which contained a 25% population of irregular β turns containing two peptide hydrogen bonds to the proline C═O.     

A block variational procedure for the iterative diagonalization of non-Hermitian random-phase approximation matrices

We present a technique for the iterative diagonalization of random-phase approximation (RPA) matrices, which are encountered in the framework of time-dependent density-functional theory (TDDFT) and the Bethe-Salpeter equation. The non-Hermitian character of these matrices does not permit a straightforward application of standard iterative techniques used, i.e., for the diagonalization of ground state Hamiltonians. We first introduce a new block variational principle for RPA matrices. We then develop an algorithm for the simultaneous calculation of multiple eigenvalues and eigenvectors, with convergence and stability properties similar to techniques used to iteratively diagonalize Hermitian matrices. The algorithm is validated for simple systems (Na(2) and Na(4)) and then used to compute multiple low-lying TDDFT excitation energies of the benzene molecule.     

The effect of solvent on the morphology of ZnO nanostructure assembly by dielectrophoresis and its device applications

Different zinc oxide nanostructured morphologies were grown on photolithographically patterned silicon/silicon dioxide substrates by dielectrophoresis technique using different solvents, such as water and ethanol, obtaining rod-like and net-like nanostructures, respectively. The formation of continuous nanostructures was confirmed by scanning electron microscopic, atomic force microscopic images, and electrical characterizations. The rod-like zinc oxide nanostructures were observed in the 10 μm gap between the fingers in the pattern, whereas net-like nanostructures were formed independently of microgap. A qualitative study about the mechanism for the assembly of zinc oxide continuous nanostructures was presented. Devices were electrically characterized, at room temperature, in controlled environment to measure the conductance behavior in ultraviolet and humidity environment. Devices based on zinc oxide nanostructures grown in ethanol medium show better responses under both ultraviolet and humidity, because of the net-like structure with high surface-to-volume ratio.     

Synthesis and biological evaluation of glyco-GA compounds as anticancer agents

A series of novel glyco-gambogic acid（GA） compounds were synthesized and evaluated for their in vitro anti-proliferative activity against human hepatocellular carcinoma（HCC） cells.All compounds showed much better aqueous solubility（0.92- 1.89 mg/mL） than GA（0.013 mg/mL）,and displayed potent inhibition on HCC cells(IC₅₀:0.21-12.23μmol/L) and little affects on non-tumor liver cells(IC₅₀:42.56-86.43μmol/L),suggesting that glyco-GA compounds selectively inhibit HCC proliferation,and may be promising candidates for further intensive study.     

Determination of plutonium isotopes in seawater samples by Semiconductor Alpha Spectrometry,ICP-MS and AMS techniques

Analysis of plutonium isotopes by Semiconductor Alpha Spectrometry (SAS), ICP-sector field mass spectrometry (ICP-MS) and Accelerator Mass Spectrometry (AMS) was carried out in seawater samples collected from the Northeast Atlantic Ocean (nuclear waste dumping sites) and Northwest Pacific Ocean. No particularly elevated levels of the atom ratios of ²⁴⁰Pu/²³⁹Pu compared to global fallout ratio (0.18) were found in the Northeast Atlantic Ocean seawater samples. The higher levels of atom ratios of ²⁴⁰Pu/²³⁹Pu were found in the Northwest Pacific Ocean. This is mainly due to contribution from the local fallout from nuclear weapon tests carried out at the Pacific Proving Grounds at the Marshall Islands.     

Effect of phase transfer chemistry, segmented fluid flow, and sonication on the synthesis of cinnamic esters

Wittig reaction under Phase Transfer conditions was performed in a flow reaction system. Different bases, aldehydes, phosphonium salts, and flow reaction parameters were investigated, in absence of a phase transfert catalyst. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath.