Top-Down LESA Mass Spectrometry Protein Analysis of Gram-Positive and Gram-Negative Bacteria

We have previously shown that liquid extraction surface analysis (LESA) mass spectrometry (MS) is a technique suitable for the top-down analysis of proteins directly from intact colonies of the Gram-negative bacterium Escherichia coli K-12. Here we extend the application of LESA MS to Gram-negative Pseudomonas aeruginosa PS1054 and Gram-positive Staphylococcus aureus MSSA476, as well as two strains of E. coli (K-12 and BL21 mCherry) and an unknown species of Staphylococcus. Moreover, we demonstrate the discrimination between three species of Gram-positive Streptococcus (Streptococcus pneumoniae D39, and the viridans group Streptococcus oralis ATCC 35037 and Streptococcus gordonii ATCC35105), a recognized challenge for matrix-assisted laser desorption ionization time-of-flight MS. A range of the proteins detected were selected for top-down LESA MS/MS. Thirty-nine proteins were identified by top-down LESA MS/MS, including 16 proteins that have not previously been observed by any other technique. The potential of LESA MS for classification and characterization of novel species is illustrated by the de novo sequencing of a new protein from the unknown species of Staphylococcus.

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Solid‐State Dynamics of Uranyl Polyoxometalates

Understanding fundamental uranyl polyoxometalate (POM) chemistry in solution and the solid state is the first step to defining its future role in the development of new actinide materials and separation processes that are vital to every step of the nuclear fuel cycle. Many solid‐state geometries of uranyl POMs have been described, but we are only beginning to understand their chemical behavior, which thus far includes the role of templates in their self‐assembly, and the dynamics of encapsulated species in solution. This study provides unprecedented detail into the exchange dynamics of the encapsulated species in the solid state through Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectroscopy. Although it was previously recognized that capsule‐like molybdate and uranyl POMs exchange encapsulated species when dissolved in water, analogous exchange in the solid state has not been documented, or even considered. Here, we observe the extremely high rate of transport of Li⁺ and aqua species across the uranyl shell in the solid state, a process that is affected by both temperature and pore blocking by larger species. These results highlight the untapped potential of emergent f‐block element materials and vesicle‐like POMs.     

Degenerate Two‐Photon Absorption and Effective Optical‐Power‐Limiting Properties of Multipolar Chromophores Derived from 2,3,8‐Trisubstituted Indenoquinoxaline

Two analogous multipolar chromophores ( 1 and 2 ) that contained 2,3,8‐trisubstituted indenoquinoxaline moieties have been synthesized and characterized for their two‐photon absorption properties, both in the femtosecond and nanosecond time regimes. We demonstrated that their multi‐branched framework structures, which incorporated appropriately functionalized indenoquinoxaline units, afforded large molecular nonlinear absorptivities within the studied spectroscopic range. Effective optical‐power‐limiting and stabilization behaviors in the nanosecond regime of dye molecule ( 2 ) were also investigated and the results indicated that such a structural motif could be a useful approach to the molecular design of highly active two‐photon systems for quick‐response and related broadband optical‐suppressing applications, in particular for confronting laser pulses of a long duration.     

A high-spin square-planar Fe(ii) complex stabilized by a trianionic pincer-type ligand and conclusive evidence for retention of geometry and spin state in solution

Square-planar high-spin Fe(ii) molecular compounds are rare and the only three non-macrocyclic or sterically-driven examples reported share a common FeO₄ core. Using an easily modifiable pincer-type ligand, the successful synthesis of the first compound of this type that breaks the FeO₄ motif was achieved. In addition, we present the first evidence that geometry and spin state persist in solution. Extensive characterization includes the first high-field EPR and variable field/temperature Mössbauer spectra for this class of compounds. Analysis of the spectroscopic data indicates this complex exhibits a large and positive zero-field splitting tensor. Furthermore, the unusually small ΔE _Q value determined for this compound is rationalized on the basis of DFT calculations.     

Solution and Gas‐Phase Acidities of all‐trans (all‐E) Retinoic Acid: An Experimental and Computational Study

Retinoic acid is of fundamental biological importance. Its acidity was determined in the gas phase and in acetonitrile solution by means of mass spectrometry and UV/Vis spectrophotometry, respectively. The intrinsic acidity is slightly higher than that of benzoic acid. In solution, the situation is opposite. The experimental systems were described theoretically applying quantum chemical methods (wave function theory and density functional theory). This allowed the determination of the molecular structure of the acid and its conjugate base, both in vacuo and in solution, and for computational estimates of its acidity in both phases.     

Dynamic viscosity of various samples of polypropene and polyvinylchloride

Summary Complex dynamic viscosity experiments carried out on a balance rheometer CONTRAVES (Dr. Képès' system) for the polypropene samples and on a RHEOMETRICS viscometer apparatus for the polyvinylchloride formulations have allowed to determine the rheological behaviour of these materials. In the case of polypropene, the Maxwell-Wiechert model seems to be in good agreement with the rheological behaviour of this material. For the polyvinylchloride, a dynamic power-law has been proposed. This law correlates the complex dynamic viscosity modulus | ^*| with the pulsation of the frequency. It shows a certain analogy with that determined in the static mode.With 7 figures and 8 tables     

Yttrium ionization scheme development for Ti:Sa laser based RILIS

Resonant ionization laser ion sources (RILIS) are popular ion sources if intense, radioactive ion beams (RIBs) with minimal isobaric contamination are required. The intensity of the ion beam depends strongly on the applied resonant laser ionization scheme. Based on the all solid state laser system TRIUMF’s RILIS (TRILIS) is using, the off-line development towards an efficient ionization scheme for yttrium is presented. Several continuous wavelength scans have been performed to compare different nonresonant ionization schemes and to identify suitable Rydberg or autoionizing states for resonant ionization schemes.     

Review of Laser-Induced Plasma,Its Mechanism,and Application to Quantitative Analysis of Hydrogen and Deuterium

Abstract

A comprehensive review of important progress achieved over the last 30 years regarding knowledge of laser-induced plasmas generated by CO₂ and Nd:YAG lasers in a variety of ambient gases is presented in this article, as well as research results on the extension of laser-induced breakdown spectroscopy (LIBS) for quantitative analysis of light elements, especially hydrogen and deuterium. First, the formation of shock wave–induced expanding secondary plasma in low-pressure ambient gases is discussed along with the dynamic characteristics of the secondary plasma expansion process. The unique advantages of low-pressure gas plasma are explained in relation to the successful detection of the sharp H and D emission lines. The experimental results using helium ambient gas are presented with emphasis on the role of He gas plasma in introducing an additional delayed excitation mechanism involving the helium metastable excited state, which resulted in the complete resolution of H and D emission lines, separated by only 0.18 nm. The development of a laser precleaning treatment and special double-pulse techniques further produced a linear calibration line with zero intercept applicable to quantitative H and D analyses of zircaloy sample, with either low- or high-pressure ambient He gas. More recent use of a transversely excited atmospheric (TEA) CO₂ laser in place of an Nd:YAG laser has demonstrated the much desired larger excited helium plasma and thereby resulted in significant emission enhancement and improved detection sensitivity.     

RECIPROCATING IMPINGEMENT JET HEAT TRANSFER WITH SURFACE RIBS

This article presents the experimental heat transfer results of an impinging jet onto a flat surface with discrete ribs in a reciprocating confinement. The test flows were systemically varied from static to reciprocating conditions with oscillating frequencies of 0.83, 1.25, and 1.67 Hz. Parametric ranges of tests in terms of Reynolds, pulsating, and buoyancy numbers were 10,000-25,000, 0-0.15, and 0-4.12 x 10^-7, respectively. It was found that the nonreciprocating heat transfer close to and away from the stagnation point was respectively reduced and improved from the smooth-walled values, which led to the more spatially uniform heat transfer distribution. An empirical correlation was developed to permit the evaluation of nonreciprocating local Nusselt numbers. Under reciprocating environment with relatively weak pulsating force effects, a tendency of heat transfer deterioration from static reference developed, which trend could lead to about 20% of heat transfer reduction. Further increase of pulsating force ratio caused the subsequent heat transfer recovery, and the local reciprocating Nusselt number could be enhanced to a level about 240% of the equivalent static value at a pulsating number of 0.014. Considerable influence of reciprocating buoyancy interaction on heat transfer was detected to impede local heat transfer. As the present flow system in a reciprocating confinement could result in higher and more spatially uniform heat transfer rates in general, it could be an applicable cooling method for pistons.