Reagentless detection and classification of individual bioaerosol particles in seconds

The rapid chemical analysis of individual cells is an analytical capability that will profoundly impact many fields including bioaerosol detection for biodefense and cellular diagnostics for clinical medicine. This article describes a mass spectrometry-based analytical technique for the real-time and reagentless characterization of individual airborne cells without sample preparation. We characterize the mass spectral signature of individual Bacillus spores and demonstrate the ability to distinguish two Bacillus spore species, B. thuringiensis and B.atrophaeus, from one another very accurately and from the other biological and nonbiological background materials tested with no false positives at a sensitivity of 92%. This example demonstrates that the chemical differences between these two Bacillus spore species are consistently and easily detected within single cells in seconds.     

On the use of spectroscopic techniques for interaction studies, part I: complexation between europium and small organic ligands

In the framework of environmental studies, it is important to understand the interaction of humic substances with cations (heavy metals, radionuclides) and to determine their complexation constants in order to evaluate their potential impact on their fate. For this purpose, two techniques have been used: electrospray ionization mass spectrometry, a newly used technique in speciation studies, and time-resolved laser-induced fluorescence spectrometry, a well-known technique for such studies. As a first step, for simplification purposes and to compare both techniques, simple molecules having functional groups present in humic substances have been selected, such as acetic, glycolic, and 4-hydroxyphenylacetic acids. Both techniques have been used to obtain stoichiometries and complexation constants between these simple molecules and europium (III).     

Multiplexed liquid arrays for simultaneous detection of simulants of biological warfare agents

Liquid array-based multiplexed immunoassays designed for rapid, sensitive, specific, and simultaneous detection of multiple simulants of biological warfare agents have been developed. In both blind and standard laboratory trials, we demonstrate the simultaneous detection of four simulant agents from a single sample. The challenge agents comprise broad classes of pathogens (virus, protein toxins, bacterial spores, vegetative cells). Assay performance of each analyte was optimized, and dose-response curves and the limits of detection (LODs) for individual analytes are presented. Assay performance, including dynamic range, sensitivity, and LODs for liquid arrays and enzyme-linked immunosorbant assay were compared and are shown to be similar. Maximum assay sensitivity is obtained in approximately 1 h, and good sensitivity is achieved in as little as 30 min. Although the sample matrixes are very complex, even for highly multiplexed assays the samples do not exhibit evidence of nonspecific binding, demonstrating that the assays also have high specificity.     

High pressure homogenisation of milk (b) effects on indigenous enzymatic activity

The objective of this study was to determine the effect of high pressure homogenisation (HPH) on alkaline phosphatase activity and plasmin and plasminogen-derived activities in raw whole bovine milk. Milk (approximately 4% fat) was treated by two-stage conventional homogenisation (18 MPa) or single or two-stage HPH at 50, 100, 150 or 200 MPa. Inactivation of plasmin and plasminogen-derived activities was evident in conventionally homogenised samples, and increased as HPH pressure increased. Two-stage HPH reduced both activities to a greater extent than single-stage HPH. Milk inlet temperature had a significant effect on residual plasmin and plasminogen activities of HPH-treated milk samples, especially those treated at 50 MPa. Inactivation of plasmin and plasminogen on HPH-treatment (150 MPa) of milk samples of varying fat contents (0-10%) was also investigated; there was a curvilinear relationship between residual plasmin and plasminogen-derived activities and fat content in the ranges 0-2% and 0-4%, respectively, with little additional inactivation at higher fat contents. Thus, indigenous proteolytic activity of milk is clearly affected by HPH. However, all homogenised milk samples retained active alkaline phosphatase, indicating that thermal conditions during HPH did not equate to that of conventional high temperature short time pasteurisation, and that the wide range of forces experienced by milk during HPH treatment does not inactivate the latter enzyme.     

Relaxation Motion and Possible Memory of Domain Structures in Barium Titanate Ceramics Studied by Mechanical and Dielectric Losses

The relaxation motion and memory effect of domain structures have been investigated using mechanical and dielectric loss measurements in BaTiO₃ ceramics with grains sizes varied from 1 m to 50 m. The measurements of mechanical loss, elastic modulus, dielectric loss and permittivity show that each phase transition induces a loss peak and an anomaly in the dielectric constants and elastic modulus, furthermore, a number of relaxation loss peaks due to ferroelectric domains in the samples with large grain have been observed. All the relaxation peaks can be analysed by Arrhenius relationship for a wide range of frequency from 10^–2 to 10⁶ Hz. The activation energies of relaxation peaks have been determined as 0.92 eV, 0.68 eV, 0.47 eV, and 0.29 eV for the peaks located in the tetragonal, orthorhombic, and rhombohedral phase, with Arrhenius perfactor in the order of 10^–13 s. Moreover, one relaxation process is insensitive to ferroelectric phase transitions, and it can exist in all the ferroelectric phases. This implies a possible memory effect of ferroelectric domain structures. Such a motion of domain wall is limited in fine-grained materials. Effect of vacuum annealing on the relaxation peak in the tetragonal phase is also studied to clarify the mechanisms of the peak. These relaxation peaks could be explained by the interaction between different domain walls and the diffusion of oxygen vacancy in the domains.     

CD28 co-stimulation is intact and contributes to prolonged ex vivo survival of hyporesponsive synovial fluid T cells in rheumatoid arthritis

In rheumatoid arthritis (RA), T cells in the inflamed joint are considered to play a crucial role in the pathogenesis. However, despite the fact that synovial T cells have an activated memory phenotype, they are functionally suppressed upon combined CD3 and CD28 stimulation. Here, we analyzed the contribution of both CD3 and CD28 to the hyporesponsiveness of synovial T cells in RA. In contrast to the low CD3 responsiveness of synovial fluid (SF) T cells compared to peripheral blood (PB) T cells, the CD28 co-stimulatory response was observed to be unaffected. Hyporesponsiveness of SF T cells has previously been associated with decreased levels of intracellular glutathione (GSH), an antioxidant and regulator of the intracellular redox state. Treatment of SF T cells with N-acetylcysteine, an antioxidant and replenisher of GSH, selectively improved CD3-induced responses, while leaving CD28 responsiveness unaffected. These data show that the CD3 pathway is highly sensitive to intracellular GSH alterations, whereas CD28 responsiveness is relatively refractory. Furthermore, in support for a functional role of CD28 co-stimulation, it was demonstrated that CD28 ligation acted in synergy with the IL-2 receptor gamma chain signaling cytokine IL-15 in the enhancement of the ex vivo survival of SF T cells. These data indicate that CD28 co-stimulatory capacity of SF T cells, in contrast to CD3 stimulation, remains intact despite an altered intracellular redox state. Thereby, CD28 stimulation may contribute to the persistence of T cells at the site of inflammation, which might be of relevance in the pathogenesis of RA.     

The thermodynamic properties of liquids,including solutions: Part 2. Polymer solutions considered as ditonic systems

The author's new theory of the thermodynamic properties of solutions is outlined. Theoretical equations are presented for applying it to polymer solutions. These equations are tested by applying them to poly(propylene oxide) + carbon tetrachloride and rubber + benzene solutions. The results are gratifying.