Immobilized chemoattractant peptides mediate adhesion and distinct calcium-dependent cell signaling in human neutrophils

Chemotaxis is the stimulated directional migration of cells in response to chemotactic factors, manifested for instance during leukocyte interaction with chemoattractants in inflammation. The N-formyl-Met-Leu-Phe (fMLF) bacterial peptide family is particularly potent in attracting and activating neutrophilic granulocytes. To accomplish defined circumstances for recruitment and activation of cells, we fabricated semitransparent gold-coated glass coverslips functionalized with chemoattractant fMLF receptor peptide agonist analogues. Peptides based on a common leading four-amino-acid sequence Gly-Gly-Gly-Cys were thus coupled to two potent fMLF receptor agonists, N-formyl-Tyr-Nle-Phe-Leu-Nle-Gly-Gly-Gly-Cys and N-formyl-Met-Leu-Phe-Gly-Gly-Gly-Cys, and a formylated control peptide, N-formyl-Gly-Gly-Gly-Cys. They were anchored via the SH group of Cys either directly to the gold surface or a mixed self-assembled monolayer composed of maleimide- and hydroxyl-terminated oligo(ethylene glycol) alkyldisulfides. The overall peptide immobilization procedure was characterized with ellipsometry, contact angle measurement, and infrared spectroscopy. When exposed to granulocytes, the agonist surface rapidly recruited neutrophils and the cells responded with extensive spreading and intracellular calcium transients within minutes. The reference peptide generated no such activation, and the cells maintained a more spherical morphology, suggesting that we have been able to immobilize chemoattractant receptor agonist peptides with retained bioactivity. This is a crucial step in designing surfaces with specific effects on cellular behavior.     

Measurement uncertainty as a tool for evaluating the ‘grey zone’ to reduce the false negatives in immunochemical screening of blood donors for infectious diseases

The risk of misclassifying infected individuals as healthy constitutes a crucial challenge when screening blood donors by means of immunoassays. This risk is especially challenging when the numerical results are close to the clinical decision level, i.e. in the ‘grey zone’. The concept of using measurement uncertainty for evaluating the ‘grey zone’ has previously not been systematically applied in this context. This article explains methods, models and empirical (top-down) approaches for the calculation of measurement uncertainty using results from a blood bank according to the internationally accepted GUM principles, focusing on uncertainty sources in the analytical phase. Of the different approaches available, the intralaboratory empirical approaches are emphasised since modelling (bottom-up) approaches are impracticable due to the lack of reliable model equations for immunoassays. Different methods are applied to estimate the measurement uncertainty for the Abbott Prism^® HCV immunoassay. The expanded uncertainty obtained at the clinical decision level from the intralaboratory empirical approach was 36 %. The estimated uncertainty was used to set acceptance and rejection zones following the procedure set in the Eurachem guideline, emphasising the need to minimise the occurrence of false negatives.     

Understanding the meaning of accuracy,trueness and precision

Clear definitions of basic terms, used to describe the quality of measurements, is essential for communication among scientists as well as when reporting measurement results to clients. Even if appropriate definitions are given in international standards and guidelines, the understanding of some basic terms sometimes proves difficult. The reasons for this are various, e.g., the same words being defined rather differently in encyclopaedias and in international standards as well as concepts, well established in some languages, that may be relatively new in other national communities and at large in the international one. Here we present a matrix intended to clarify the relationships between the type of error affecting an analytical measurement, the respective qualitative concepts (performance characteristics) and their quantitative expression.

Structural, photophysical, and nonlinear absorption properties of trans-di-arylalkynyl platinum(II) complexes with phenyl and thiophenyl groups

Optical power limiting and luminescence properties of two Pt(II) complexes with thiophenyl and phenyl groups in the ligands, trans-Pt(P(n-Bu)3)2(C[triple bond]C-Ar)2, where Ar = -C4H2S-C[triple bond]C-p-C6H4-n-C5H11 (1) and -p-C6H4-C[triple bond]C-C4H3S (2), have been investigated. The fluorescence lifetimes were found to be on the sub-nanosecond time scale, and the quantum yields were low, in accord with fast intersystem crossing from the excited singlet to triplet manifold. The phosphorescence lifetimes of 1 and 2 were shorter than that of a Pt(II) complex having two phenyl groups in the ligands. In order to elucidate the C-Pt bonding nature in the ground state, the 13C NMR chemical shift of the carbon directly bonded to Pt, the coupling constants 1JPtC, 2JPtC, and 1JPtP, and IR nuC[triple bond]C wavenumbers were obtained for 1, 2, and three other trans-diarylalkynyl Pt(II) complexes. X-ray diffraction data of 1 and 2 and density functional theory calculated geometries of models of 1, 2, and trans-Pt(P(n-Bu)3)2(C[triple bond]C-p-C6H4-C[triple bond]C-C6H5)2 (3) show that 1 preferably exists in a different conformation from that of 2 and 3. The variations in photophysical, NMR, and IR data can be rationalized by differences in geometry and pi-backbonding from Pt to the alkynyl ligand.     

Particle swarm optimization and its application to the design of diffraction grating filters

Particle swarm optimization (PSO) is an evolutionary, easy-to-implement technique to design optical diffraction gratings. Design of reflection and transmission guided-mode resonance (GMR) grating filters using PSO is reported. The spectra of the designed filters are in good agreement with the design targets in a reasonable computation time. Also, filters are designed with a genetic algorithm (GA) and the results obtained by the GA and PSO are compared.     

Electromagnetic viewpoints on a 200 kW MgB2 induction heater

In this paper an electromagnetic system for a 200 kW MgB₂ induction heater was designed to verify the feasibility of MgB₂ superconductor in a DC induction heating system. The final master plan connects the electromagnetic design to the cryogenic and mechanical designs including the required measurement system. The electromagnetic design consists of conductor development, dimensioning the superconducting magnets and the quench protection system analysis. The coil system must guarantee appropriate heating distribution in the aluminium billet. The conductor has to fulfill the requirements of the current carrying capability required by the coil design. Furthermore, the conductor layout and constituent materials affect greatly to the coil stability in fault conditions. The coil behaviour during a fault was studied by quench simulations. The protection system design was based on the results of the quench analysis.     

2-(Trimethylsilyl)ethyl glycosides. Synthesis of the asialo-GM1-tetrasaccharide, spacer glycoside, and BSA and Sepharose glycoconjugates.

The tri and tetra-saccharide glycosides beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OTMSEt and beta-D-Gal-(1-3)-beta-D-GalNAc-(1-4)-beta-D-Gal-(1-4)-beta-D-Glc-1-OT MSEt (asialo-GM1) have been synthesized by sequential glycosylations of a suitably protected 2-(trimethylsilyl)ethyl (TMSEt) lactoside with 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl chloride and 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl bromide. The tetrasaccharide glycoside was transformed into the corresponding hemiacetal sugar as well as the 1-chloro sugar. The latter was used for glycosylation of 2-bromoethanol. The resulting glycoside was used to alkylate methyl 3-mercaptopropionate and the resulting spacer glycoside was used for the preparation of the title glycoconjugates.