Opto-aerodynamic focusing of aerosol particles

We describe a new method for focusing and concentrating a stream of moving micron-sized aerosol particles in air. The focusing and concentrating process is carried out by the combined drag force and optical force that is generated by a double-layer co-axial nozzle and a focused doughnut-shaped hollow laser beam, respectively. This method should supply a new tool for aerosol science and related research.

Copyright © 2018 American Association for Aerosol Research     

Polymer-assisted precipitation of ZnO nanoparticles with narrow particle size distribution

Zinc oxide nanoparticles were produced by aqueous precipitation in mild hydrothermal conditions (90 °C). Well crystallized regular roundish particles were obtained, with a very narrow size distribution. The influence of soft templates (organic species) to control size and size distribution in the final product was investigated. No effect was observed with polyvinylpyrrolidone (PVP M_w 8000 and 40,000), (d?)fructose and hydroxypropylmethylcellulose (HPMC). A significant decrease of the particle size towards 100 nm, while conserving a very narrow size distribution was observed for poly(acrylic acid) (PAA M_w 2000), Dispex A40 (commercial PAA from CIBA M_w ～10,000), and sodium dodecylsulfate (SDS). The influence of the pH was also investigated with PAA. By increasing the pH from slightly acidic to basic conditions, the morphology was spectacularly modified from roundish nanoparticles to micronic branched flower-like particles, with an elongated primary crystal morphology.     

A proteomic approach for quantitation of phosphorylation using stable isotope labeling in cell culture

Posttranslational modifications are major mechanisms of regulating protein activity and function in vertebrate cells. It is essential to obtain qualitative information about posttranslational modification patterns of proteins to understand signal transduction mechanisms in greater detail. However, it is equally important to measure the dynamics of posttranslational modifications such as phosphorylation to approach signaling networks from a systems biology perspective. Despite a number of advances, methods to quantitate posttranslational modifications remain difficult to implement due to a number of factors including lack of a generic method, elaborate chemical steps, and requirement for large amounts of sample. We have previously shown that stable isotope-containing amino acids in cell culture (SILAC) can be used to differentially label growing cell populations for quantitation of protein levels. In this report, we extend the use of SILAC as a novel proteomic approach for the relative quantitation of posttranslational modifications such as phosphorylation. We have used SILAC to quantitate the extent of known phosphorylation sites as well as to identify and quantitate novel phosphorylation sites.     

Surgical treatment of noniatrogenic trauma of the femoral arteries

Trauma to the femoral arteries corresponds to 30 percent of all arterial traumas. The authors reviewed 74 patients with noniatrogenic trauma of the femoral arteries treated from January 1991 to December 1993. Ages ranged from 11 to 50 years, with a mean of 24. Seventy-one patients were male and three female. Fifty-two patients (70.2 percent) were white, 20 (27 percent) were black and two (2.8 percent) were Asian. Trauma due to firearms had the highest incidence, with 61 cases (82.4 percent). Absence of pulse was the most frequent clinical symptom (62.5 percent). Severe ischemia, with risk of loss of limb, was found in 66.2 percent of the cases. The superficial femoral artery was impaired in 77 percent of the cases. A preoperative arteriography was performed on only five patients, victims of multiple penetrating trauma or an asymptomatic penetrating wound along a vessel passage. In six cases, arterial and venous ligature was the chosen procedure. In three cases, a primary arterial anantomosis was performed. Simple arterriorraphy was feasible in one patient. In 64 of the patients, a venous graft was undertaken using a segment of the inverted great saphenous vein withdrawn from the other lower limb. Fasciotomoy was used in 32 patients (43.2 percent), all of whom exhibited pasting of the lower limb muscles at admission. One patient died during the immediate postoperative period as the result of multiple organ failure caused by polytraumatism. Preservation of the limb was attained in 72 patients (97.3 percent) Severe, previously-incurred ischemia was responsible for the only two amputations, aggravated by an exceedingly long delay between the time of injury and surgery. One of these patients, in addition to severe ischemia, had extensive injuries to the soft tissues. We conclude that trauma of the femoral arteries, attended while the limb still maintains its vitality, has a positive clinical outcome with a high rate of limb preservation. Mortality usually results from injury to other organs.     

Purification, characterization, sequence determination, and mass spectrometric analysis of a trypsin inhibitor from seeds of the Brazilian tree Dipteryx alata (Leguminosae)

Dipteryx alata trypsin inhibitor (DATI) has been purified and completely sequenced. It showed homology to members of the Bowman-Birk family of inhibitors. The last step of DATI purification by RP-HPLC (narrow-borc C18 column) suggested the existence of some isoforms of the inhibitor due to the presence of a cluster of very close peaks in the chromatogram. By using electrospray ionization mass spectrometry (ESIMS) and laser desorption mass spectrometry (LDIMS), the identification of DATI isoforms was made possible. From the ESIMS data, the following molecular masses were found: 6803.22 +/- 0.92 for isoform a; 6890.94 +/- 0.73 for b; 6977.58 +/- 0.39 for c; 7065.07 +/- 0.67 for d; 7151.42 +/- 0.86 for e; and 7291.70 +/- 0.43 for f. Similar masses were found when using LDIMS. Isoform b was the most abundant and its molecular mass matched the molecular mass of 6893 calculated from the sequence of DATI. The mass differences between a and b, b and c, c and d, and d and e were equal to 87, which corresponds to Ser. Isoform a might not have the N-terminal Ser present in isoform b, while the other additional Ser residues might comprise a row localized in the C- or N-terminal. The appearance of all these isoforms could result from posttranslational N- and C-terminal processing.     

Changes in portlandite morphology with solvent composition: Atomistic simulations and experiment

Experimental work has been done to determine changes in the particle shape of portlandite grown in the presence of different ions. To quantify the experimentally observed changes in morphology a new analysis tool was developed, allowing the calculation of the relative surface energies of the crystal facets. The observed morphology in the presence of chlorides and nitrates was facetted particles of a similar shape, the addition of sulfates leads to hexagonal platelet morphology and the addition of silicates leads to the formation of large irregular aggregates. In addition to the experimental work, the surfaces of portlandite were studied with atomistic simulation techniques. The empirical force field used has first been validated. The equilibrium morphology of portlandite in vacuum and in water was then calculated. The results indicate that the presence of water stabilizes the [20.3] surface and changes the morphology. This is consistent with the experimental observation of [20.3] surfaces.     

Identification of protein ubiquitylation by electrospray ionization tandem mass spectrometric analysis of sulfonated tryptic peptides

We report here the application of electrospray ionization tandem mass spectrometry for the characterization of protein ubiquitylation, an important posttranslational modification of cellular proteins. Trypsin digestion of ubiquitin-conjugated proteins produces diglycine branched peptides containing the modification sites. Chemical derivatization by N-terminal sulfonation was carried out on several model peptides for the formation of a characteristic fragmentation pattern in their MS/MS analysis. The fragmentation of derivatized singly charged peptides results in a product ion distribution similar to that already observed by MALDI-TOF MS/MS. Signature fragments distinguished the diglycine branched peptides from other modified and unmodified peptides, while the sequencing product ions reveal the amino acid sequence and the location of the ubiquitylation site. Doubly charged peptide derivatives fragment in a somewhat different manner, but several fragments characteristic to diglycine branched peptides were observed under low collision energy conditions. These signature peaks can also be used to identify peptides containing ubiquitylation sites. In addition, a marker ion corresponding to a glycine-modified lysine residue produced by high-energy fragmentation provides useful information for identity verification. The method is demonstrated by the analysis of three ubiquitin-conjugated proteins using LC/MS/MS.