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  • 1
    In: Biointerphases, American Vacuum Society, Vol. 1, No. 1 ( 2006-03-01), p. 22-34
    Abstract: The formation of highly ordered self-assembled monolayers (SAMs) on gold from an unusually long and linear compound HS(CH2)15CONH(CH2CH2O)6CH2CONH(CH2)15CH3 is investigated by contact angle goniometry, ex situ null ellipsometry, cyclic voltammetry and infrared reflection-absorption spectroscopy. The molecules are found to assemble in an upright position as a complete monolayer within 60 min. The overall structure of the SAM reaches equilibrium within 24 h as evidenced by infrared spectroscopy, although a slight improvement in water contact angles is observed over a period of a few weeks. The resulting SAM is 60 Å thick and it displays an advancing water contact angle of 112° and excellent electrochemical blocking characteristics with typical current densities about 20 times lower as compared to those observed for HS(CH2)15CH3 SAMs. The dominating crystalline phases of the supporting HS(CH2)15 and terminal (CH2)15CH3 alkyl portions, as well as the sealed oligo(ethylene glycol) (OEG) “core,” appear as unusually sharp features in the infrared spectra at room temperature. For example, the splitting seen for the CH3 stretching and CH2 scissoring peaks is normally only observed for conformationally trapped alkylthiolate SAMs at low temperatures and for highly crystalline polymethylenes. Temperature-programmed infrared spectroscopy in ultrahigh vacuum reveals a significantly improved thermal stability of the SAM under investigation, as compared to two analogous OEG derivatives without the extended alkyl chain. Our study points out the advantages of adopting a “modular approach” in designing novel SAM-forming compounds with precisely positioned in plane stabilizing groups. We demonstrate also the potential of using the above set of compounds in the fabrication of “hydrogel-like” arrays with controlled wetting properties for application in the ever-growing fields of protein and cell analysis, as well as for bioanalytical applications.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2006
    detail.hit.zdb_id: 2234510-3
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  • 2
    Online Resource
    Online Resource
    American Vacuum Society ; 2008
    In:  Biointerphases Vol. 3, No. 2 ( 2008-06-01), p. 29-37
    In: Biointerphases, American Vacuum Society, Vol. 3, No. 2 ( 2008-06-01), p. 29-37
    Abstract: We demonstrate a convenient chip platform for the addressable immobilization of protein-loaded vesicles on a microarray for parallelized, high-throughput analysis of lipid-protein systems. Self-sorting of the vesicles on the microarray was achieved through DNA bar coding of the vesicles and their hybridization to complementary strands, which are preimmobilized in defined array positions on the chip. Imaging surface plasmon resonance in ellipsometric mode was used to monitor vesicle immobilization, protein tethering, protein-protein interactions, and chip regeneration. The immobilization strategy proved highly specific and stable and presents a mild method for the anchoring of vesicles to predefined areas of a surface, while unspecific adsorption to both noncomplementary regions and background areas is nonexistent or, alternatively, undetectable. Furthermore, histidine-tagged receptors have been stably and functionally immobilized via bis-nitrilotriacetic acid chelators already present in the vesicle membranes. It was discovered though that online loading of proteins to immobilized vesicles leads to cross contamination of previously loaded vesicles and that it was necessary to load the vesicles offline in order to obtain pure protein populations on the vesicles. We have used this cross-binding effect to our benefit by coimmobilizing two receptor subunits in different ratios on the vesicle surface and successfully demonstrated ternary complex formation with their ligand. This approach is suitable for mechanistic studies of complex multicomponent analyses involving membrane-bound systems.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2008
    detail.hit.zdb_id: 2234510-3
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  • 3
    In: The American Journal of Clinical Nutrition, Elsevier BV, Vol. 112, No. 5 ( 2020-11), p. 1252-1266
    Type of Medium: Online Resource
    ISSN: 0002-9165
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 1496439-9
    SSG: 12
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  • 4
    In: Bioinformatics, Oxford University Press (OUP), Vol. 38, No. 4 ( 2022-01-27), p. 1022-1029
    Abstract: Gene expression-based multiclass prediction, such as tumor subtyping, is a non-trivial bioinformatic problem. Most classifier methods operate by comparing expression levels relative to other samples. Methods that base predictions on the expression pattern within a sample have been proposed as an alternative. As these methods are invariant to the cohort composition and can be applied to a sample in isolation, they can collectively be termed single sample predictors (SSP). Such predictors could potentially be used for preprocessing-free classification of new samples and be built to function across different expression platforms where proper batch and dataset normalization is challenging. Here, we evaluate the behavior of several multiclass SSPs based on binary gene-pair rules (k-Top Scoring Pairs, Absolute Intrinsic Molecular Subtyping and a new Random Forest approach) and compare them to centroids built with centered or raw expression values, with the criteria that an optimal predictor should have high accuracy, overcome differences in tumor purity, be robust across expression platforms and provide an informative prediction output score. Results We found that gene-pair-based SSPs showed excellent performance on many expression-based classification tasks. The three methods differed in prediction score output, handling of tied scores and behavior in low purity samples. The k-Top Scoring Pairs and Random Forest approach both achieved high classification accuracy while providing an informative prediction score. Although gene-pair-based SSPs have been touted as being cross-platform compatible (through training on mixed platform data), out-of-the-box compatibility with a new dataset remains a potential issue that warrants cohort-to-cohort verification. Availability and implementation Our R package ‘multiclassPairs’ (https://cran.r-project.org/package=multiclassPairs) (https://doi.org/10.1093/bioinformatics/btab088) is freely available and enables easy training, prediction, and visualization using the gene-pair rule-based Random Forest SSP method and provides additional multiclass functionalities to the switchBox k-Top-Scoring Pairs package. Supplementary information Supplementary data are available at Bioinformatics online.
    Type of Medium: Online Resource
    ISSN: 1367-4803 , 1367-4811
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 1468345-3
    SSG: 12
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  • 5
    In: Biointerphases, American Vacuum Society, Vol. 2, No. 1 ( 2007-03-01), p. 6-15
    Abstract: The authors present in this paper how the extended Mie theory can be used to translate not only end-point data but also temporal variations of extinction peak-position changes, δλpeak(t), into absolute mass uptake, Γ(t), upon biomacromolecule binding to localized surface plasmon resonance (SPR) active nanoparticles (NPs). The theoretical analysis is applied on a novel sensor template composed of a three-layer surface architecture based on (i) a self-assembled monolayer of HS(CH2)15COOH, (ii) a 1:1 mixture of biotinylated and pure poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), and (iii) NeutrAvidin. Assisted by independent estimations of the thickness of the three-layer architecture using quartz crystal microbalance with dissipation (QCM-D) monitoring, excellent agreement with parallel mass-uptake estimations using planar SPR is obtained. Furthermore, unspecific binding of serum to PLL-g-PEG was shown to be below the detection limit, making the surface architecture ideally suited for label-free detection of immunoreactions. To ensure that the immunocomplex formation occurred within the limited sensing depth (∼10 nm) of the NPs, a compact model system composed of a biotinylated human recombinant single-chain antibody fragment (∅∼2 nm) directed against cholera toxin was selected. By tracking changes in the centroid (center of mass) of the extinction peak, rather than the actual peak position, signal-to-noise levels and long-term stability upon cholera toxin detection are demonstrated to be competitive with results obtained using conventional SPR and state-of-the-art QCM-D data.
    Type of Medium: Online Resource
    ISSN: 1934-8630 , 1559-4106
    Language: English
    Publisher: American Vacuum Society
    Publication Date: 2007
    detail.hit.zdb_id: 2234510-3
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