Single particle analysis

FIGURE 5.9 The count rate as a function of the cycle number obtained during the TIMS measurement of a single NBS-U200 particle. Each cycle represents an integration time of 1 s. (From Kraiem, M. et ah, Anal. Chim. Acta, 688,1, 2011a. With permission.) 

The development of a large geometry (LG-)SIMS with high transmission improved the performance of the technique by affording a high secondary ion yield (1.2%) at a resolution of 3000 (Ranebo et al. 2009). Other advantages were the reduction 

FIGURE 5.10 The SIMS mass spectrum from the hot particle found in a core sample at Thule, Greenland the crash site. Note isobaric interferences arising from hydride ions and overlapping isotopes in the 234-242 Da mass range. (From Ranebo, Y. et al., Microsc. Microanal, 13, 179, 2007. With permission.) 

Laser ablatiou-ICPMS has beeu applied to measurement of the isotopic composition and U) of single uranium oxide particles with dimensions 

2% (maximum of 0.24%). This inferred that a variety of batches with different isotopic compositions were processed at the plant and indicated that environmental sampling of the soil could help determine what activities took place there. 

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At present only low resolution (>30A) structures, all derived from single particle analysis of images from electron microscopy, are available for the entire DP3R. These structures differ in their details, but all show a roughly square structure with fourfold symmetry and lateral dimensions of about 20 nm (Fig. 2). 

Single particle analysis offers improved resolution of species in mixtures. 

Fig. 18.15 Advanced methods for single particle analysis in LC ARROW chips, (a) Nanopore added to reservoir for single particle entry into LC ARROW (b) Optical dual beam particle trap based on balancing the scattering force due to counter propagating beams...

Figure 9.55a shows the results of single-particle analysis (see Chapter ll.B.4a) of a typical particle in the upper troposphere (Murphy et al., 1998). In the negative ion spectra, a variety of fragments due to organics are observed, along with sulfates and some halogens. In other particles, soot and minerals were also common constituents. For comparison, Fig. 9.55b shows that a typical particle in the stratosphere is primarily sulfate (see Chapter 12.C.5). 

In short, care must be taken in sampling and analysis of airborne particles, as well as in the data interpretation, to minimize or at least recognize potential artifact problems. Such problems, along with a need to understand not only the bulk composition of a collection of airborne particles but also that of individual particles, have contributed to the development of realtime and single-particle analysis techniques discussed in the following section. 

McKeown, P. J., M. V. Johnston, and D. M. Murphy, On-Line Single-Particle Analysis by Laser Desorption Mass Spectrometry, Anal. Chem., 63, 2069-2073 (1991). 

More ambitious attempts at measuring the heterogeneity of the atmospheric aerosol have been undertaken as well. Single-particle analysis by mass spectrometry was demonstrated by Sinha and co-workers (31, 32). In this technique, an aerosol sample is introduced into a vacuum chamber in the form of a particle beam. The particles are injected into a Knudsen cell oven, where they undergo many collisions with the cell wall and are ultimately vaporized and ionized. The ions are then mass-analyzed with a quad-rupole or sector mass spectrometer. So that individual particles can be analyzed, the flux of particles into the Knudsen cell is limited so that coincidence errors are minimized. Ion pulses from individual particles allow the determination of the amount of the species being analyzed in the particular particle. The sensitivity of the technique is limited. For sodium, the detection... 

Fig. 18C. (B) Cross-sectional views of the three crowns of the EM 3D map shown in E. (C) Cross-sectional views of the densities between the crowns of the EM 3D map shown in E. (D) Stereo view of the X-ray model of Fig. 18C reconstructed to 50 A resolution. (E) Stereo view of the 3D reconstruction of the myosin filament structure obtained by single particle analysis using the classes shown in Fig. 19C (from Al-Khayat et ai, 2005a). The...

Al-Khayat, H. A., Morris, E. P., Powell, A. S., Kensler, R. W., and Squire,J. M. (2005a). 3D structure of vertebrate (fish) muscle myosin filaments by single particle analysis. 

Paul, D., Patwardhan, A., Squire, J. M., and Morris, E. P. (2004). Single particle analysis of filamentous and highly elongated macromolecular assemblies. /. Struct. Biol. 148, 236-250. 

X-ray powder diffraction data may be helpful but are often hard to interpret for complex mixtures use of computer data file search programs (6) and microcamera methods for single particle analysis (7) may be useful for identification. Comparative sample identification is generally less often possible than for metals since the latter are manufactured while the nonmetallic inorganic solids are often unprocessed materials with large property variations. However, where applicable, the following are some examples of determinations which might be made (a) particle size by microscopy (b) microstructure and sub-microstructure characterization... 

The puriflcation of the y-secretase complex (59) has allowed the first glimpse into its structure. Electron microscopy and single particle analysis reveals that the complex has a globular structure that at low resolution (10-15 A) appears rather amorphous (66). [Another structure, elucidated in a similar manner but of poorer resolution ( 45 A), also has been reported (67).] Nevertheless, two important features can be gleaned. The first is a rather large interior cavity of 20 A diameter that is presumably where the active site resides, a characteristic reminiscent of the proteasome. The second is the presence of two small openings that may be the site of entry for water. Other structural features have been revealed by cysteine mutagenesis with... 

In 2001, using cryo-electron microscopy and single particle analysis, Sato and colleagues provided the first three-dimensional view of the Nay channel isolated from the eel Electrophorus electricus. The channel was found to have a bell-shaped extracellular surface structure with square-shaped intracellular base and a spherical top (Figure 16.10). In addition to the pore-forming a-subunits, the Nay channels have four additional accessory subunits (Naypi,-Nayp4), each measuring... 

Single Particle Analysis and Surface Characterization of Airborne Particles... 

The cyanobacterial 33 kDa protein is characterized by a large amount of P-strand and contains a short helix in the region close to the C-terminus. According to Kamiya and Shen the structure of the 33 kDa protein has some similarities to the structure of the porin femily but is not compatible with the model predicted theoretically by Pazos et al or that analyzed by single particle analysis of cryoelectron microscopy images from higher plants. ... 

Determined Using Quantitative Single Particle Analysis... 

Kang S, Hwang H, Park Y, Kim H, Ro C-U (2008) Chemical compositions of subway particles in Seoul, Korea, determined by a quantitative single particle analysis. Environ Sci Technol 42 9051-9057... 

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