Effect of Pd Precursor Salts on the Chemical State, Particle Size, and Performance of Activated Carbon-Supported Pd Catalysts for the Selective Hydrogenation of Palm Biodiesel.

To improve the oxidative stability of biodiesel fuel (BDF), the polyunsaturated fatty acid methyl esters (poly-FAME) presented in commercial palm oil-derived biodiesel fuel (palm-BDF) were selectively hydrogenated to monounsaturated fatty acid methyl esters (mono-FAME) under a mild condition (80 °C, 0.5 MPa) using activated carbon (AC)-supported Pd catalysts with a Pd loading of 1 wt.%. The partially hydrotreated palm-BDF (denoted as H-FAME) which has low poly-FAME components is a new type of BDF with enhanced quality for use in high blends. In this study, we reported that the chemical states and particle sizes of Pd in the prepared Pd/AC catalysts were significantly influenced by the Pd precursors, Pd(NO3)2 and Pd(NH3)4Cl2, and thus varied their hydrogenation activity and product selectivity. The 1%Pd/AC (nit) catalyst, prepared using Pd(NO3)2, presented high performance for selective hydrogenation of poly-FAME into mono-FAME with high oxidation stability, owning to its large Pd particles (8.4 nm). Conversely, the 1%Pd/AC (amc) catalyst, prepared using Pd(NH3)4Cl2, contained small Pd particles (2.7 nm) with a little Cl residues, which could be completely removed by washing with an aqueous solution of 0.1 M NH4OH. The small Pd particles gave increased selectivity toward unwanted-FAME components, particularly the saturated fatty acid methyl esters during the hydrogenation of poly-FAME. This selectivity is unprofitable for improving the biodiesel quality.

Molecular dynamics study on the interaction of a mithramycin dimer with a decanucleotide duplex.

The complex of a minor groove binding drug mithramycin (MTR) and the self-complementary d(TAGCTAGCTA) 10-mer duplex was investigated by molecular dynamics (MD) simulations using the AMBER 7.0 suite of programs. There is one disaccharide and trisaccharide segment projecting from opposite ends of an aglycone chromophore of MTR. A MTR dimer complex (MTR)2Mg2+ is formed in the presence of a coordinated ion Mg2+. A NMR solution structure of two (MTR)2Mg2+ complexes bound with one DNA duplex, namely, the 2:1 duplex complex, was taken as the starting structure for the MD simulation. The partial charge on each atom was calculated using the multiple-RESP fitting procedure, and all of the missing parameters in the Parm99 force field used were adapted comparably from the literature. The length of the MD simulation was 5 ns, and the binding free energy for the formation of a 1:1 or 2:1 duplex complex was determined from the last 4 ns of the simulation. The binding free energies were decomposed to components of the contributions from different energy types, and the changes in the helical parameters of the bound DNA duplex plus the glycosidic linkages between sugar residues of the bound MTR dimer were determined. It was found that binding of the first (MTR)2Mg2+ complex with the DNA duplex to form a 1:1 duplex complex does not cause stiffening of the duplex especially in the unoccupied site of the duplex. However, the overall flexibility of the DNA duplex is reduced substantially once the second (MTR)2Mg2+ complex is bound with the unoccupied site to form the 2:1 duplex complex. The van der Waals interactions were found to be dominant in the central part of the DNA duplex where sugar residues from each bound (MTR)2Mg2+ complex were inwardly pointing and the corresponding minor groove was widened.

An in vitro short time-high dose drug exposure assay for predicting 5FU-resistance of colorectal cancer.

The goal of this study was to develop a simple and rapid in vitro drug resistance assay to ascertain the effectiveness of 5-fluorouracil (5-FU) for the individual therapy of colorectal cancer. Colorectal cancer cells were isolated from tumor specimens and, after 4h exposure to high doses of 5-FU cell viability was measured with an ATP assay. The average IC50 concentration for 5-FU was calculated as 4000 microg/ml from 35 patients' tumors. The tumor cells were defined as extreme drug resistance with a survival rate 1 standard deviation (SD) over IC50, low drug resistance (LDR) with a survival rate 1 SD below IC50, and intermediate drug resistance (IDR) with survival rate between these two. The drug resistant assay for 102 patients' cancer cells showed that the proportion of patients with LDR to 5-fluorouracil was 19%. The in vitro drug resistance of the cancer cells was not correlated with cancer stages or by patient sex or age. However, most mucinous and poor differentiated cancer cells showed extreme or IDR. The in vitro ATP assay values for 25 Duke's D patients receiving postoperative 5-FU chemotherapy were comparable with clinical postchemotherapy responses. The sensitivity and specificity of the assay were 100 and 95%, respectively. This short time-high dose drug exposure assay may serve as an aid to improve 5-FU treatment for individual chemotherapy.