Adsorption of the trimethylamine adduct of aluminium hydride on silicon oxide

X-Ray photoelectron spectroscopy (XPS) and static secondary ion mass spectroscopy (SSIMS) studies of surface adsorbed HAINMe on a SiO substrate support molecular adsorption, most likely as a five coordinate species, HAINMe(O=), and an aluminium rich species (Al: N 2: 1) sensitive to the amount of exposure to the vapour; ab initio molecular orbital calculations on HAINH and HO gave formation of HAINH(OH) as energetically favoured by 4.53 kcal mol, and fragmentation of HAINH(OH) to HAIOH and NH requiring 13.16 kcal mol (1 cal = 4.184 J)

Surface modification and functionalization of polytetrafluoroethylene films via graft copolymerization

Polymers for Advanced Technologies811683-69

Seismic stratigraphy and evolution of the Raggatt Basin, southern Kerguelen Plateau

Six major seismic stratigraphic sequences in the Raggatt Basin on the southern Kerguelen Plateau overlie a basement complex of Cretaceous or greater age. The complex includes dipping reflectors which were apparently folded and eroded before the Raggatt Basin developed. The seismic stratigraphic sequences include a basal unit F, which fills depressions in basement; a thick unit, E, which has a mounded upper surface (volcanic or carbonate mounds); a depression-filling unit, D; a thick unit C which is partly Middle to Late Eocene; and two post-Eocene units, A and B, which are relatively thin and more limited in areal extent than the underlying sequences. A mid or Late Cretaceous erosional episode was followed by subsidence and basin development, interrupted by major erosion in the mid Tertiary. Late Cenozoic sedimentation was affected by vigorous ocean currents

Chromium functionalized diglyme plasma polymer coating enhances enzyme-linked immunosorbent assay performance

Ensuring the optimum orientation, conformation, and density of substrate-bound antibodies is critical for the success of sandwich enzyme-linked immunosorbent assays (ELISAs). In this work, the authors utilize a diethylene glycol dimethyl ether plasma polymer (DGpp) coating, functionalized with chromium within a 96 well plate for the enhanced immobilization of a capture antibody. For an equivalent amount of bound antibody, a tenfold improvement in the ELISA signal intensity is obtained on the DGpp after incubation with chromium, indicative of improved orientation on this surface. Time-of-flight secondary-ion-mass-spectrometry (ToF-SIMS) and principal component analysis were used to probe the molecular species at the surface and showed ion fragments related to lysine, methionine, histidine, and arginine coupled to chromium indicating candidate antibody binding sites. A combined x-ray photoelectron spectroscopy and ToF-SIMS analysis provided a surface molecular characterization that demonstrates antibody binding via the chromium complex. The DGpp+Cr surface treatment holds great promise for improving the efficacy of ELISAs.<br/

Orientation and conformation of anti-CD34 antibody immobilised on untreated and plasma treated polycarbonate

The conformation and orientation of proteins immobilised on synthetic materials determine their ability to bind their antigens and thereby the sensitivity of the microarrays and biosensors employing them. Plasma immersion ion implantation (PIII) of polymers significantly increases both their wettability and protein binding capacity. This paper addresses the hypothesis that a PIII treated polymer surface modifies the native protein conformation less significantly than a more hydrophobic untreated surface and that the differences in surface properties also affect the protein orientation. To prove this, the orientation and conformation of rat anti-mouse CD34 antibody immobilized on untreated and PIII treated polycarbonate (PC) were investigated using ToF-SIMS and FTIR-ATR spectroscopy. Analysis of the primary structure of anti-CD34 antibody and principal component analysis of ToF-SIMS data were applied to detect the difference in the orientation of the antibody attached to untreated and PIII treated PC. The difference in the antibody conformation was analysed using deconvolution of the Amide I peak (in FTIR-ATR spectra) and curve-fitting. It was found that compared to the PIII treated sample, the antibody immobilized on the untreated PC sample has a secondary structure with a lower fraction of β-sheets and a higher fraction of α-helices and disordered fragments. Also, it was found that anti-CD34 antibody has a higher tendency to occur in the inactive ‘tail-up’ orientation when immobilized on an untreated PC surface than on a PIII treated surface. These findings confirm the above hypothesis

MAJOR EVOLUTIONARY PHASES OF A FORE-ARC BASIN OF THE ALEUTIAN TERRACE - RELATION TO NORTH PACIFIC TECTONIC EVENTS AND THE FORMATION OF THE ALEUTIAN SUBDUCTION COMPLEX

Combined geologic and seismic reflection data from the Atka Basin region of the Aleutian forearc show that the upper 2-3 km of slightly deformed sediment filling the\ud basin are probably of late Miocene to Holocene age. The depositional axis of the basin shifted arcward over time because of the progressive and differential rise of the\ud basin's outer ridge. Units filling the basin unconformably overlie and, along the edges of the basin, onlap beds of Oligocene age and older(?). The basal units of the basin fill are characterized by little variation in thickness, somewhat irregular internal reflectors, fault offsets, and possible wedge outs against units of Eocene(?) age. A fault\ud with at least 500 m of vertical displacement cuts the outer high of the forearc basin and displaces beds of the basin-filling series relative to those trenchward of the trenchslope break. The Atka Basin appears to have\ud formed in response to a combination of (1) initiation of trench-floor-filling turbidite deposition, in part derived from glacial marine sedimentation from mainland Alaska;\ud (2) an increased rate and normal component in Pacific plate subduction beneath the central Aleutian arc beginning in early Pliocene time; and (3) formation of a broad\ud and thick accretionary wedge that progressively uplifted the outer high of the Aleutian terrace

Gold nanoparticle labelled DNA hairpin grafting on transparent and conductive oxide (TCO) films: Characterization of grafting and hybridization

Biosensors and biochips can be hybrid nanobiosystems involving different kinds of components, i.e. solid surface, bio-molecules and nanoparticles. These components are confined in a very small area (nanometre range). It is expected that interactions are produced between both components due to their close proximity. So to optimize the performance of these biosensors, it is very important to get a deeper insight of their surface characteristics. In this context, nanoparticles linked to DNA strands (in a ratio of 1:1) immobilized on a solid surface give the opportunity to combine complementary techniques to characterize the hybrid system. A typical example will be illustrated in this study. We have grafted DNA hairpins at their 3'-end via a silanisation process using aminopropyltriethoxysilane (APTES) on different transparent and conductive (TCO) oxide film surfaces. DNA hairpins comprise a stem in which both strands are complementary and a loop. These molecules exhibit a particularly high sensitivity for the detection of mismatches compared to the corresponding linear strands. They have been monolabelled at their 5'-end by a 1.4 nm gold nanoparticle. Because of the hairpin conformation, the label is close to the surface. Upon hybridization with a complementary target, the formation of a linear duplex structure with relative rigidity forces the label away from the surface. Due to their conductive properties, TCO films are attractive materials for biochips. They can advantageously replace the classical gold electrodes as working electrodes for direct electrochemical detection of DNA hybridization. As for silica, their surface chemistry allows the covalent and strong binding of DNA. Here, we used different TCO films: ITO films, doped SnO2 films as well as insulating SiO2 films. Thanks to the presence of gold nanoparticles bounded to DNA probes, the effects of grafting and hybridization of DNA could be studied on both conductive oxide surfaces. Particularly, we studied the modifications of surface morphology and chemistry as well as fluorescence results. By coupling AFM with SEM-FEG analyses, dispersed and well-resolved groups of gold nanoparticles linked to DNA were emphasized on the SnO2 films. Their surface density is 2.1 ± 0.3 x 1011 groups.cm2. TEM images obtained after silver enhancement of gold nanoparticles on ITO films revealed round spheres corresponding to silver coated gold nanoparticles. Their density was in agreement with the data obtained by AFM on SnO2 films. The evolution of the chemical state of the modified oxide surfaces was monitored using XPS and ToF-SIMS. As expected, the XPS N 1s peak intensity increased after grafting and hybridization of DNA. The Au 4d peak was detected only on samples modified with Au labelled hairpin probes. Its intensity decreased with probe concentration. From the ratio Au/Si (Si belonging to APTES), the surface DNA density was estimated to be 9.6x1011 cm2 and 3.7x1011 cm2 for SnO2 and ITO films respectively. The P 2p peak was observed only after hybridization with a weak intensity. Its presence was essentially correlated to phosphate residues originating from the hybridization solution. Positive and negative fragments of sugar, bases and phosphates from DNA probes were identified by TOF-SIMS. Positive and negative ions from Au nanoparticles were detected only in the case of Au labelled hairpin probes before and after hybridization. After hybridization of Au labelled hairpin probes with complementary Cy3 targets, quenching of the Cy3 fluorescence by gold nanoparticles was evidenced using fluorescence microscopy. This phenomenon was obtained for both oxides and is in agreement with the Nanometal Surface Energy Transfer (NSET) theory