A method for bioconjugation of carbohydrates using Diels-Alder cycloaddition

Diels-Alder-type cycloaddition of an electronically matched pair of saccharide-linked conjugated dienes and a dienophile-equipped protein gives neoglycoproteins at ambient temperature in pure water with a reaction half-life of approximately 2 h. Uncoupled saccharides can be recovered by diafiltration with complete conservation of the diene moiety, thus allowing their repeated use. The procedure described is the first for creating a carbon-carbon covalent bond in the bioconjugation step between a saccharide and a protein.     

Porphyrin-containing molecular capsules: metal mediated dimerization of a bis-porphyrin cavity

[reaction] A self-complementary V-shaped bis-porphyrin cavity has been synthesized that is capable of dimerization to form a capsule structure. Self-assembly of the dimer occurs via metal ion coordination and produces an internal volume for guest encapsulation.     

Dysregulation of Na+/K+ ATPase by amyloid in APP+PS1 transgenic mice

Background  

The pathology of Alzheimer's disease (AD) is comprised of extracellular amyloid plaques, intracellular tau tangles, dystrophic neurites and neurodegeneration. The mechanisms by which these various pathological features arise are under intense investigation. Here, expanding upon pilot gene expression studies, we have further analyzed the relationship between Na+/K+ ATPase and amyloid using APP+PS1 transgenic mice, a model that develops amyloid plaques and memory deficits in the absence of tangle formation and neuronal or synaptic loss.     

Identification of proteases employed by dendritic cells in the processing of protein purified derivative (PPD)

Dendritic cells (DC) are known to present exogenous protein Ag effectively to T cells. In this study we sought to identify the proteases that DC employ during antigen processing. The murine epidermal-derived DC line Xs52, when pulsed with PPD, optimally activated the PPD-reactive Th1 clone LNC.2F1 as well as the Th2 clone LNC.4k1, and this activation was completely blocked by chloroquine pretreatment. These results validate the capacity of XS52 DC to digest PPD into immunogenic peptides inducing antigen specific T cell immune responses. XS52 DC, as well as splenic DC and DCs derived from bone marrow degraded standard substrates for cathepsins B, C, D/E, H, J, and L, tryptase, and chymases, indicating that DC express a variety of protease activities. Treatment of XS52 DC with pepstatin A, an inhibitor of aspartic acid proteases, completely abrogated their capacity to present native PPD, but not trypsin-digested PPD fragments to Th1 and Th2 cell clones. Pepstatin A also inhibited cathepsin D/E activity selectively among the XS52 DC-associated protease activities. On the other hand, inhibitors of serine proteases (dichloroisocoumarin, DCI) or of cystein proteases (E-64) did not impair XS52 DC presentation of PPD, nor did they inhibit cathepsin D/E activity. Finally, all tested DC populations (XS52 DC, splenic DC, and bone marrow-derived DC) constitutively expressed cathepsin D mRNA. These results suggest that DC primarily employ cathepsin D (and perhaps E) to digest PPD into antigenic peptides.     

Structure and photoluminescence of a benzil nanocolumn in a C-methylcalix[4]resorcinarene-based framework

A new framework based on C-methylcalix[4]resorcinarene and the flexible nonconjugated spacer 1,4-bis(imidazol-1yl-methyl)benzene encloses a large one-dimensional channel, containing benzil nanocolumns. Unlike in a previously reported series of benzil-containing supramolecular solids with conjugated linker molecules, benzil luminescence is observed, but the lifetime of 580 ns at 77 K is considerably shorter than the 145 micros reported for neat benzil at room temperature.     

Protein microarray scanning in label-free format by Kelvin nanoprobe

Surface-immobilized protein species deposited in the microarray format have been detected by time-of-flight secondary ion mass spectrometry and by scanning Kelvin nanoprobe. The former method was used to examine the nature of protein deposition on amine-coated glass slides and gold substrates in preparation for Kelvin measurements. Both gallium and SF(5)(+) ion sources were employed to produce positive and negative ion spectra of amino acids and polypeptides. Scanning Kelvin technology has been used to detect antibody-antigen interactions in a label-free protocol through measurement of the surface potential of the biochemical pair on indium tin oxide, amine-treated slides and gold substrates. The results show that good inter-spot reproducibility can be achieved and that deposited areas can be examined for homogeneity at 100 nm resolution. This work represents the first report on surface potential detection in protein microarray technology.     

Anomalous absorption of bulk shear sagittal acoustic waves in a layered structure with viscous fluid

It is demonstrated theoretically that the absorptivity of bulk shear sagittal waves by an ultra-thin layer of viscous fluid between two different elastic media has a strong maximum (in some cases as good as 100%) at an optimal layer thickness. This thickness is usually much smaller than the penetration depths and lengths of transverse and longitudinal waves in the fluid. The angular dependencies of the absorptivity are demonstrated to have significant and unusual structure near critical angles of incidence. The effect of non-Newtonian properties and non-uniformities of the fluid layer on the absorptivity is also investigated. In particular, it is shown that the absorption in a thin layer of viscous fluid is much more sensitive to non-zero relaxation time(s) in the fluid layer than the absorption at an isolated solid-fluid interface.     

Ultrasonic absorption in polymer gel dosimeters

Ultrasonic absorption in polymer gel dosimeters was investigated. An ultrasonic interferometer was used to study the frequency (f) dependence of the absorption coefficient (alpha) in a polyacrylamide gel dosimeter (PAG) in the frequency range 5-20 MHz. The frequency dependence of ultrasonic absorption deviated from that of an ideal viscous fluid. The presence of relaxation mechanisms was evidenced by the frequency dependence of alpha/f(2) and the dispersion in ultrasonic velocity. It was concluded that absorption in polymer gel dosimeters is due to a number of relaxation processes which may include polymer-solvent interactions as well as relaxation due to motion of polymer side groups.The dependence of ultrasonic absorption on absorbed dose and formulation was also investigated in polymer gel dosimeters as a function of pH and chemical composition. Changes in dosimeter pH and chemical composition resulted in a variation in ultrasonic dose response curves. The observed dependence on pH was considered to be due to pH induced modifications in the radiation yield while changes in chemical composition resulted in differences in polymerisation kinetics.