At moderate temperatures in flowing gas, pentacene undergoes a disproportionation reaction to produce 6,13-dihydropentacene (DHP) and a series of polycondensed aromatic hydrocarbons, including the previously unknown peripentacene (PP). The process requires activation by heating to 320 degrees C and is possibly catalyzed by impurities such as DHP, 6,13-pentacenequinone (PQ), Al, or Fe found in the starting materials. These impurities also result in a decrease in the intrinsic field-effect mobility (FEM) of pentacene crystals. Subsequent purifications remove such impurities, thus inhibiting the formation of the disproportionation products and increasing the FEM of pentacene (2.2 cm(2)/Vs). These results clarify the importance of purification of semiconductive materials for measurements of intrinsic mobility and optimal device performance.

Recently, it has been demonstrated that bacteria can be characterized using whole cells and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). However, identification of specific bacterial proteins usually requires analysis of cellular fractions or purified extracts. Here, the first application of Fourier transform mass spectrometry (FTMS) to analysis of bacterial proteins directly from whole cells is reported. It is shown that accurate mass MALDI-FTMS can be used to characterize specific ribosomal proteins directly from Escherichia coli cells. High-accuracy mass measurements and high-resolution isotope profile data confirm posttranslational modifications proposed previously on the basis of low-resolution mass measurements. Seven ribosomal proteins from E. coli whole cells were observed with errors of less than 27 ppm. This was accomplished directly from whole cells without fractionation, concentration, or overt overexpression of characteristic cellular proteins. MALDI-FTMS also provided information regarding E. coli lipids in the low-mass region. Although ions with m/z values below 1000 have been observed by FTMS of whole cells, this represents the first report of detection of ions in the 5000 to 10,000 m/z range by MALDI-FTMS using whole cells.

Ions attributed to lipids and phospholipids are directly observed by desorption from whole bacteria using intact cell (IC) matrix-assisted laser desorption-ionization (MALDI) Fourier transform mass spectrometry (FTMS). Saccharomyces cerevisiae are grown in rich media broth, concentrated, and applied directly to the MALDI surface without lysis or chemical treatment. FTMS of MALDI ions gives excellent signal to noise ratios with typical resolving powers of 90,000 and mass precision better than 0.002 Da. Use of accurate mass measurements and a simple set of rules allow assignment of major peaks into one of twelve expected lipid classes. Subsequently, fractional mass versus whole number mass plots are employed to enhance visual interpretation of the high-resolution data and to facilitate detection of related ions such as those representing homologous series or different degrees of unsaturation. This approach, coupled with rules based on bacterial biochemistry, is used to classify ions with m/z up to about 1000. Major spectral peaks in the range m/z 200-1000 are assigned as lipids and phospholipids. In this study, it is assumed that biologically-derived ions with m/z values lower than 1000 are lipids. This is not unreasonable in view of the facts that molecular weights of lipids are almost always less than 1000 Da, that the copy numbers for lipids in a cell are higher than those for any single protein or other component, and that lipids are generally collections of distinct homologous partners, unlike proteins or other cell components. This paper presents a new rapid lipid-profiling method based on IC MALDI-FTMS.

Previous work has shown that red wines, grape juices, and other grape products cause endothelium-dependent relaxation (EDR) of blood vessels in vitro by increasing nitric oxide production. In this paper we describe the isolation and characterization of some of the compounds responsible for EDR activity. Concord grape seeds were extracted with methanol and the compounds were separated by Toyopearl TSK HW-40S chromatography. Resulting fractions (primarily phenolic acids, catechins, and proanthocyanidins) were further separated semipreparatively by reversed-phase HPLC, and peaks were collected and bioassayed for EDR activity using the rat aorta preparation. EDR-active compounds were subsequently characterized by HPLC retention times and electrospray-ion-trap mass spectrometry. The compounds exhibiting the most EDR activity were proanthocyanidin trimers, tetramers, pentamers, and polymers and their gallates, as well as a dimer gallate (EC50 values in the range of 0.6-2.5 microg catechin equivalents/mL). These compounds should be useful for in vitro and in vivo studies, particularly as they relate to improvement of cardiovascular function.

We have shown in previous work that extracts of grape seeds (GSE) and skins, grape juice, and many red wines exhibit endothelium-dependent relaxing (EDR) activity in vitro. This EDR activity involves endothelial nitric oxide (NO) release and subsequent increase in cyclic GMP levels in the vascular smooth muscle cells. The NO/cyclic GMP pathway is known to be involved in many cardiovascular-protective roles. The current study focuses on the isolation and identification of EDR-active compounds (procyanidins) from GSE. Crushed Concord grape seeds were extracted with methanol and the extract was separated into seven fractions (A-G) on a Toyopearl TSK-HW-40 column. EDR-active fractions (D-G) were further separated into 25 individual compound peaks by HPLC, 16 of which were EDR active (threshold for relaxation ranged between less than 0.5 microg/mL and greater than 4 microg/mL). Procyanidin identification was accomplished by electrospray-ion trap mass spectrometry (ES-ITMS), MS/MS, and by tannase treatment and acid thiolysis, followed by HPLC and ES-ITMS of the products. Activity of isolated procyanidins tended to increase with degree of polymerization, epicatechin content, and with galloylation. These EDR-active compounds (many of which also possess antioxidant activity), individually or in the form of wines, juices, or nutritional supplements, may be useful in preventing or treating cardiovascular diseases.