Environmental Molecular Sciences Laboratory

About: Environmental Molecular Sciences Laboratory is a facility organization based out in Richland, Washington, United States. It is known for research contribution in the topics: Mass spectrometry & Ion. The organization has 1471 authors who have published 3010 publications receiving 169961 citations.

Multireference Configuration Interaction Calculations on Cr2: Passing the One Billion Limit in MRCI/MRACPF Calculations

Abstract: The region around the minimum of the potential-energy curve of Cr{sub 2} has been calculated at the multireference configuration interaction (CI) level including almost 1.3 billion configurations in the CI calculation. The computational techniques as implemented on massively parallel computers which enabled this calculation are described. The calculated results are R{sub e} = 1.72 {angstrom}, D{sub e} = 1.09 eV, and {omega}{sub e} = 338.7 cm{sup {minus}1} as compared to experimental values of R{sub e} = 1.679 {angstrom}, D{sub e} = 1.50 {+-} 0.05 eV, and {omega}{sub e} = 452.34 ({Delta}G{sub 1/2}) cm{sup {minus}1}. The error of 0.4 eV in the dissociation energy can be attributed to relativistic effects following other authors (0.2 eV) and the need for higher angular momentum basis functions in the one-particle set (0.2 eV).

Simple Sodium Dodecyl Sulfate-Assisted Sample Preparation Method for LC-MS-Based Proteomics Applications

Abstract: Sodium dodecyl sulfate (SDS) is one of the most popular laboratory reagents used for biological sample extraction; however, the presence of this reagent in samples challenges LC-MS-based proteomics analyses because it can interfere with reversed-phase LC separations and electrospray ionization. This study reports a simple SDS-assisted proteomics sample preparation method facilitated by a novel peptide-level SDS removal step. In an initial demonstration, SDS was effectively (>99.9%) removed from peptide samples through ion substitution-mediated DS– precipitation using potassium chloride (KCl), and excellent peptide recovery (>95%) was observed for <20 μg of peptides. Further experiments demonstrated the compatibility of this protocol with LC-MS/MS analyses. The resulting proteome coverage obtained for both mammalian tissues and bacterial samples was comparable to or better than that obtained for the same sample types prepared using standard proteomics preparation methods and analyzed using LC-MS/MS. These ...

Volatility and lifetime against OH heterogeneous reaction of ambient isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA)

Abstract: . Isoprene-epoxydiols-derived secondary organic aerosol (IEPOX-SOA) can contribute substantially to organic aerosol (OA) concentrations in forested areas under low NO conditions, hence significantly influencing the regional and global OA budgets, accounting, for example, for 16–36 % of the submicron OA in the southeastern United States (SE US) summer. Particle evaporation measurements from a thermodenuder show that the volatility of ambient IEPOX-SOA is lower than that of bulk OA and also much lower than that of known monomer IEPOX-SOA tracer species, indicating that IEPOX-SOA likely exists mostly as oligomers in the aerosol phase. The OH aging process of ambient IEPOX-SOA was investigated with an oxidation flow reactor (OFR). New IEPOX-SOA formation in the reactor was negligible, as the OFR does not accelerate processes such as aerosol uptake and reactions that do not scale with OH. Simulation results indicate that adding ∼ 100 µg m−3 of pure H2SO4 to the ambient air allows IEPOX-SOA to be efficiently formed in the reactor. The heterogeneous reaction rate coefficient of ambient IEPOX-SOA with OH radical (kOH) was estimated as 4.0 ± 2.0 × 10−13 cm3 molec−1 s−1, which is equivalent to more than a 2-week lifetime. A similar kOH was found for measurements of OH oxidation of ambient Amazon forest air in an OFR. At higher OH exposures in the reactor (> 1 × 1012 molec cm−3 s), the mass loss of IEPOX-SOA due to heterogeneous reaction was mainly due to revolatilization of fragmented reaction products. We report, for the first time, OH reactive uptake coefficients (γOH = 0.59 ± 0.33 in SE US and γOH = 0.68 ± 0.38 in Amazon) for SOA under ambient conditions. A relative humidity dependence of kOH and γOH was observed, consistent with surface-area-limited OH uptake. No decrease of kOH was observed as OH concentrations increased. These observations of physicochemical properties of IEPOX-SOA can help to constrain OA impact on air quality and climate.

High-throughput global peptide proteomic analysis by combining stable isotope amino acid labeling and data-dependent multiplexed-MS/MS.

Abstract: In this work, we describe the application of a stable isotope amino acid (lysine) labeling in conjunction with data-dependent multiplexed tandem mass spectrometry (MS/MS) to facilitate the characterization and identification of peptides from proteomic (global protein) digests. Lysine auxotrophic yeast was grown in the presence of 13C-labeled or unlabeled lysine and combined after harvesting in equal proportions. Endoproteinase LysC digestion of the cytosolic fraction produced a global proteomic sample, consisting of heavy/light labeled peptide pairs. Then data-dependent multiplexed-MS/MS was applied to simultaneously select and dissociate only labeled peptide ion pairs. The approach allows differentiation between N-terminal (e.g., b-type ions) and C-terminal fragment ions (e.g., y-type ions) in resulting tandem mass spectra, as well as the capability of differentiation between near-isobaric glutamine and lysine residues. We also describe the utility of peptide composition and fragment information to suppo...

Electronic structure of small titanium clusters: Emergence and evolution of the 3d band.

Abstract: The electronic structure of titanium clusters $({\mathrm{Ti}}_{n},n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3--65)$ is probed by size-selected anion photoelectron spectroscopy. It is observed that the 3d band emerges at the eight-atom cluster beyond which the d band broadens and evolves toward that of the bulk. The electronic structure of the titanium clusters is found to become bulklike at relatively small cluster sizes. This is discussed in terms of the delocalization of the titanium 3d orbitals and the implications for the cluster structures.