24 research outputs found
Facile fabrication of robust superhydrophobic surfaces: comparative investigation
Superhydrophobic (SH) surfaces have various unique and important properties, including extreme water-repellency, self-cleaning, anti-icing and cell repellency. The range of applications and the interest in these surfaces have increased enormously during the last years. To obtain superhydrophobicity a surface requires both micro- and nano-scale roughness and a low surface energy coating. During the last 15 years many methods have been published to produce SH surfaces. Most of the methods described in the literature require multiple steps and harsh conditions. In addition, the comparability of the distinct studies is challenging, due to the fact that the produced surfaces were not characterized with sufficiently standardized parameters and methods. A comparative study with a wide space of parameters, characterizing both the method and the surface properties, could be helpful to find the right functionalization method for a certain application. The goal of this study was to compare the most facile methods for the fabrication of superhydrophobic surfaces. We selected eight coating methods and characterized produced surfaces in respect of water contact angles (WCAs) (static, advancing, receding), sliding angle, mechanical stability, stability in water/buffer/solvent, transparency and micro/nano surface topography
Valine-Induced Packing Deficiencies of Transmembrane Domains Promote Helix Flexibility and Membrane Fusion
Improved extraction repeatability and spectral reproducibility for liquid extraction surface analysis–mass spectrometry using superhydrophobic–superhydrophilic patterning
A major problem limiting reproducible use of liquid extraction surface analysis (LESA) array sampling of dried surface-deposited liquid samples is the unwanted spread of extraction solvent beyond the dried sample limits, resulting in unreliable data. Here, we explore the use of the Droplet Microarray (DMA), which consists of an array of superhydrophilic spots bordered by a superhydrophobic material giving the potential to confine both the sample spot and the LESA extraction solvent in a defined area. We investigated the DMA method in comparison with a standard glass substrate using LESA analysis of a mixture of biologically relevant compounds with a wide mass range and different physicochemical properties. The optimized DMA method was subsequently applied to urine samples from a human intervention study. Relative standard deviations for the signal intensities were all reduced at least 3-fold when performing LESA-MS on the DMA surface compared with a standard glass surface. Principal component analysis revealed more tight clusters indicating improved spectral reproducibility for a human urine sample extracted from the DMA compared to glass. Lastly, in urine samples from an intervention study, more significant ions (145) were identified when using LESA-MS spectra of control and test urine extracted from the DMA. We demonstrate that DMA provides a surface-assisted LESA-MS method delivering significant improvement of the surface extraction repeatability leading to the acquisition of more robust and higher quality data. The DMA shows potential to be used for LESA-MS for controlled and reproducible surface extraction and for acquisition of high quality, qualitative data in a high-throughput manner
Start-up success of freelancers New microeconometric evidence from the German Socio-Economic Panel
If certain start-up characteristics will indicate a business success, knowing such characteristics
could generate more successful start-ups and more efficient start-up counseling. Our study
will contribut e to this by quantifying individual success determinants of freelance start-ups.
The data base for the microeconometric analyses of the survival of the first three years is a
revised German Socio-Economic Panel (SOEP) for 1992 until 2002, which allows to
incorporate institutional, personal and family/household socio-economic variables. We
describe and discuss the datawork to achieve compatible information over time within a
revised GSOEP and present microeconometric rare events logit, logit and probit results.
The start-up success measured as the probability to survive the first three years is first of all
influenced by an active labour force participation with its acquired skills and working
experiences just before the start-up period (rank 1), followed by a non-university degree as
the highest general human capital indicator (rank 2), a general (non-linear) experience
indicated by age (rank 3) and the business related background (rank 4) as the type of liberal
profession in the group of the liberal medical professions and the liberal technical and
scientific professions
Valine-Induced Packing Deficiencies of Transmembrane Domains Promote Helix Flexibility and Membrane Fusion
The Backbone Dynamics of the Amyloid Precursor Protein Transmembrane Helix Provides a Rationale for the Sequential Cleavage Mechanism of γ‑Secretase
The etiology of Alzheimer’s disease depends on
the relative
abundance of different amyloid-β (Aβ) peptide species.
These peptides are produced by sequential proteolytic cleavage within
the transmembrane helix of the 99 residue C-terminal fragment of the
amyloid precursor protein (C99) by the intramembrane protease γ-secretase.
Intramembrane proteolysis is thought to require local unfolding of
the substrate helix, which has been proposed to be cleaved as a homodimer.
Here, we investigated the backbone dynamics of the substrate helix.
Amide exchange experiments of monomeric recombinant C99 and of synthetic
transmembrane domain peptides reveal that the N-terminal Gly-rich
homodimerization domain exchanges much faster than the C-terminal
cleavage region. MD simulations corroborate the differential backbone
dynamics, indicate a bending motion at a diglycine motif connecting
dimerization and cleavage regions, and detect significantly different
H-bond stabilities at the initial cleavage sites. Our results are
consistent with the following hypotheses about cleavage of the substrate:
First, the GlyGly hinge may precisely position the substrate within
γ-secretase such that its catalytic center must start proteolysis
at the known initial cleavage sites. Second, the ratio of cleavage
products formed by subsequent sequential proteolysis could be influenced
by differential extents of solvation and by the stabilities of H-bonds
at alternate initial sites. Third, the flexibility of the Gly-rich
domain may facilitate substrate movement within the enzyme during
sequential proteolysis. Fourth, dimerization may affect substrate
processing by decreasing the dynamics of the dimerization region and
by increasing that of the C-terminal part of the cleavage region
High voltage asymmetric hybrid supercapacitors using lithium- and sodium-containing ionic liquids
Hydrogen-treated, sub-micrometer carbon beads for fast capacitive deionization with high performance stability
Modification of the genome of Rhodobacter sphaeroides and construction of synthetic operons
The α-proteobacterium Rhodobacter sphaeroides is an exemplary model organism for the creation and study of novel protein expression systems, especially membrane protein complexes that harvest light energy to yield electrical energy. Advantages of this organism include a sequenced genome, tools for genetic engineering, a well-characterized metabolism, and a large membrane surface area when grown under hypoxic or anoxic conditions. This chapter provides a framework for the utilization of R. sphaeroides as a model organism for membrane protein expression, highlighting key advantages and shortcomings. Procedures covered in this chapter include the creation of chromosomal gene deletions, disruptions, and replacements, as well as the construction of a synthetic operon using a model promoter to induce expression of modified photosynthetic reaction center proteins for structural and functional analysis.20 page(s