Search results for "surface"

Phenolic metabolites from 5,000-year-old coprolites of Myotragus balearicus, an extinct insular bovid

2020

Abstract To date, the identification of polyphenols in the archaeological and palaeontological record has been limited. Here, we demonstrate for the first time the presence of flavonoid and phenolic metabolites from non-mineralised coprolites belonging to a non-human mammal species. Myotragus balearicus is the last species of a bovid lineage that became extinct during the Holocene in the western Mediterranean basin. In this work, we characterize the phenolic metabolites of M. balearicus coprolites for the first time. The chemical analysis of coprolites revealed the presence of flavonoids, such as flavones and flavonols. Moreover, the detection of conjugates of hydroxyphenylvaleric, hydroxyp…

2021

Amino acids with small side chains and motifs of small residues in a distance of four are rather abundant in human single-span transmembrane helices. While interaction of such helices appears to be common, the role of the small residues in mediating and/or stabilizing transmembrane helix oligomers remains mostly elusive. Yet, the mere existence of (small)xxx(small) motifs in transmembrane helices is frequently used to model dimeric TM helix structures. The single transmembrane helix of the human carbonic anhydrases XII contains a large number of amino acids with small side chains, and critical involvement of these small amino acids in dimerization of the transmembrane domain has been sugges…

Biologically-induced transition of bio-silica sol to mesoscopic gelatinous flocs: a biomimetic approach to a controlled fabrication of bio-silica str…

2012

Siliceous sponges form their skeletal elements, the spicules, enzymatically via the sponge-specific enzyme silicatein. The enzymatic product of silicatein in vitro is a bio-silica polymer that is not processed/hardened by phase separation. In the present study we applied a two-phase system to investigate the transition of bio-silica, formed by silicatein, from the lucid state to the opaque/turbid state. We report for the first time that the polyether polyethylene glycol [PEG] causes a rapid transition of the lucid bio-silica to the opaque/turbid state. For the experiments the recombinant silicatein from the demosponge Suberites domuncula had been used. This process is rapid (1 h) and procee…

Reactive surface coatings based on polysilsesquioxanes: defined adjustment of surface wettability.

2009

We have investigated a generally applicable protocol for a substrate-independent reactive polymer coating that offers interesting possibilities for further molecular tailoring via simple wet chemical derivatization reactions. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylate) hybrid polymers have been synthesized by RAFT polymerization, and stable reactive surface coatings have been prepared by spin-coating on the following substrates: Si, glass, gold, PMMA, PDMS, and steel. These coatings have been used for a defined adjustment of surface wettability by surface-analogous reaction with various amines (e.g., glutamic acid to obtain hydrophilic surfaces (Theta(a) = 18 degrees) or per…

Solubilization by polysoaps

1994

The aqueous solubilization power of several series of micellar homopolymers and copolymers (''polysoaps'') is investigated. Using five insoluble or poorly water-soluble dyes, comparisons of the capacities are made with respect to the influence of structural variables such as the polymer backbone, the polymer geometry, the comonomer content, and the charge of the hydrophilic group. Some guidelines for polysoap structures suited for efficient solubilization are established. Noteworthy is that the solubilization capacities of the polysoaps are neither linked to the ability to reduce the surface tension of water, nor to the polarity of the solubilization sites deduced from spectroscopic probes.

Functionalization and patterning of reactive polymer brushes based on surface reversible addition and fragmentation chain transfer polymerization

2012

We present the synthesis of reactive polymer brushes prepared by surface reversible addition–fragmentation chain transfer polymerization of pentafluorophenyl acrylate. The reactive ester moieties can be used to functionalize the polymer brush film with virtually any functionality by simple post-polymerization modification with amines. Dithiobenzoic acid benzyl-(4-ethyltrimethoxylsilyl) ester was used as the surface chain transfer agent (S-CTA) and the anchoring group onto the silicon substrates. Reactive polymer brushes with adjustable molecular weight, high grafting density, and conformal coverage through the grafting-from approach were obtained. Subsequently, the reactive polymer brushes …

Substrate-Independent Stable and Adherent Reactive Surface Coatings and their Conversion with Amines

2007

To create stable, adherent and reactive surface coatings, a hybrid polymer composed of poly(methylsilsesquioxane) (PMSSQ) and poly(pentafluorophenyl acrylate) PFPA with a M n of 32000 g/mol was prepared by a RAFT polymerization procedure. These hybrid polymer has been used for coating experiments. The PFPA part enabled a variable functionalization of the coating afterwards. The stability on various substrates (e.g. glass, PMMA, steel) was tested in an ISO tape test. These reactive surface coatings were modified using different amines, such as amino-terminated PEG, dodecyl amine and N-isopropyl amine. The conversion was analyzed by FT-IR and contact angle measurements.

Versatile Responsive Surfaces via Hybrid Polymers Containing Acetal Side Groups

2009

Two hybrid polymers, poly(methylsilsesquioxane)-poly(2,2-diethoxyethyl acrylate) and poly-(methylsilsesquioxane)-poly(1,3-dioxolan-2-ylmethyl acrylate), were synthesized and used for preparation of stable surface coatings. Their acetal side groups could be functionalized via solution-dipping with different primary amines and hydroxylamines after acidic deprotection and thus allowed for flexible modification of the surface hydrophilicity. Functionalization with a thermo-responsive polymer resulted in a thermo-responsive surface with temperature-dependent contact angles. Further, the two types of acetals showed different stability toward acidic treatment and could be addressed independently.

Label-Free Detection of Protein-Ligand Interactions by the Quartz Crystal Microbalance

2005

In recent years the quartz crystal microbalance (QCM) has been accepted as a powerful technique to monitor adsorption processes at interfaces in different chemical and biological research areas. In the last decade, the investigation of adsorption of biomolecules on functionalized surfaces turned out to be one of the paramount applications of the QCM comprising the interaction of nucleic acids, specific molecular recognition of protein-receptor couples, and antigen-antibody reactions realized in immunosensors. The advantage of the QCM technique is that it allows for a label free detection of molecules. This is a result of the fact that the frequency response of the quartz resonator is propor…

Acid—base properties of azo dyes in the presence of surfactants

1991

Abstract The changes in the acid—base properties of an azo dye produced by the presence of surfactants, at surfactant concentrations below and above the CMC, are quantitatively described using a simple model and spectrophotometric and potentiometric measurements. The azo dye formed by aniline and N -(1-naphthyl)-ethylenediamine, and the surfactants sodium dodecyl sulphate, Triton X-100 and N -cetylpyridinium chloride (NCPC) are used. The protonation constants of the free and surfactant-bound dye species, the binding constant of the protonated and unprotonated forms of the dye, and the average aggregation number of the dye—NCPC aggregates are evaluated.