The agglomeration state of nanosecond laser-generated aerosol particles entering the ICP

Fundamental understanding of aerosol formation and particle transport are important aspects of understanding and improving laser-ablation ICP–MS. To obtain more information about particles entering the ICP, laser aerosols generated under different ablation conditions were collected on membrane filters. The particles and agglomerates were then visualised using scanning electron microscope (SEM) imaging. To determine variations between different sample matrices, opaque (USGS BCR-2G) and transparent (NIST SRM 610) glass, CaF₂, and brass (MBH B26) samples were ablated using two different laser wavelengths, 193 and 266 nm. This study showed that the condensed nano-particles (∼10 nm in diameter) formed by laser ablation reach the ICP as micron-sized agglomerates; this is apparent from filters which contain only a few well-separated particles and particle agglomerates. Ablation experiments on different metals and non-metals show that the structure of the agglomerates is matrix-dependent. Laser aerosols generated from silicates and metals form linear agglomerates whereas particle-agglomerates of ablated CaF₂ have cotton-like structures. Amongst other conditions, this study shows that the absorption characteristics of the sample and the laser wavelength determine the production of micron-sized spherical particles formed by liquid droplet ejection.     

Dynamics of Arabidopsis thaliana soluble proteome in response to different nutrient culture conditions

In an effort to determine the best extraction procedure compatible with the high-reproducible 2-DE, different methods of soluble protein extraction from Arabidopsis cell culture suspensions grown in Gamborg B5 medium were tested. A reference 2-DE map was established for this soluble extract revealing 1184 spots. The most abundant protein spots were excised, trypsin-digested, and mass spectra obtained via MALDI-TOF and/or LC coupled to ESI-MS. Three hundred and thirty one proteins were identified and their functions were defined based on sequence comparisons and classified in different protein families. In order to analyze the impact of culture medium on the Arabidopsis proteome, we performed the 2-DE map from Arabidopsis cell suspensions cultured in another growth medium Murashige and Skoog (M-S) and 327 major spots were identified. Using PDQuest imaging analysis, significant increases in the amount of several housekeeping enzymes, stress/defense proteins, and heat shock proteins were found in M-S medium. Modified expression of certain proteins and detection of new isoforms involved in nitrate assimilation, nitrogen, and sulfur metabolism were also observed in the M-S medium. This study provides the first 2-DE maps of the soluble proteome of Arabidopsis cell suspensions. The comparative analysis of the Arabidopsis proteome in respect to different nutrient supplies shows that the culture medium may significantly influence the expression pattern of major soluble proteins in Arabidopsis cells. This work also constitutes an important step for further proteomic analysis concerning cell responses to abiotic or biotic stresses.     

Mössbauer investigations of intermolecular interactions of Fe(CO)5 in frozen organic solutions

The Mössbauer spectra of Fe(CO)₅ dissolved in 39 organic solvents were investigated. An influence on the quadrupole split was found only for those solvents containing carbonylic CO, but not for solvents containing another polar group. The change of the quadrupole split means always a reduction and is independent of temperature. The concentration dependence of the additional split indicates that it is caused only by nearest neighbours.—These results give a hint for a specific weak interaction between the carbonylic CO group of Fe(CO)₅ and the solvents. This cannot be a general dipole-dipole interaction because of the missing influence of other polar solvents, so that a weak chemical bond is suggested.     

Charged multiplicities in K−p interactions at 100 GeV/c

The charged multiplicity distribution is presented for K^?p interactions produced in the hydrogen bubble chamber, BEBC, using an r.f. separated, tagged K^? beam of 110 GeV/c momentum. A comparison with K⁺p, πp and pp data at lower energies shows that the main features of the multiplicity distributions depend on energy and charge of the incident particles, but not on their strangeness. At high energies, only the energy is important.     

Nucleophilic substitution approach towards 1,3-dimethylbarbituric acid derivatives—new synthetic routes and crystal structures

We describe simple, convenient and high-yielding nucleophilic substitution reactions to synthesize new derivatives of 1,3-dimethylbarbituric acid (1a). Based on its active C5 position, condensing 1a with sulfuryl chloride gives the corresponding 5,5-dichloro-1,3-dimethylbarbituric acid (13). The latter was reacted with silver nitrite and potassium cyanide to afford 5-chloro-5-nitro-1,3-dimethylbarbituric acid (14) and 5-cyano-1,3-dimethylbarbiturate (17), respectively. Furthermore, by employing the nucleophilic character of 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (8) the obtained compounds 13 and 14 have been converted to 2-chloro-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium-1,3-dimethyl-5-nitro-1,3-dimethylbarbiturate (18) and 1,3-dimethylbarbituric acid trimer (21), respectively. X-ray structures for compounds 13, 14, 17, 18 and 21 were determined.     

A novel ultra-sensitive method for the quantification of glycosaminoglycan disaccharides using an automated DNA sequencer

Analysis of glycosaminoglycans (GAGs) is of increasing importance concerning alterations in extracellular matrix composition and selectivity of glomerular basement membrane. In this report we describe the analysis of chondroitin sulfate disaccharides as an example of GAG delta disaccharide analysis using standard DNA sequencing equipment (DNA sequencer-assisted GAG disaccharide separation, DSA-GAGS). The presented methodology allows nanomolar quantification of 8-aminopyrene-1,3,6-trisulfonic acid (APTS)-derived GAG disaccharides. In comparison to RP-HPLC the established method is much more sensitive, showing detection limits of 38 fmol/microL. Variation coefficients were approximately 10%, enabling exact quantifications after run times of 17 min at 30 degrees C and an electrophoresis voltage of 15 kV; using a capillary DNA sequencer, available in many molecular laboratories, presented advantages like automated sample injection, opportunity of high-throughput analyses, separation of even sulfated disaccharide epimers, and the possibility of using APTS-derived fucose as an internal standard. Furthermore, highly reproducible retention times rendered easy identification of specific signals (SD 0.02). With regard to these results, the described method is a useful tool for the quantification of GAG disaccharides in low amounts, indicating advantages of obverse RP-HPLC and slab gel polyacrylamide electrophoresis in sensitivity, error-proneness, automation, and handling.