Publications (30) View all
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Article: Dopamine-assisted rapid fabrication of nanoscale protein arrays by colloidal lithography.
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ABSTRACT: The development of cost-effective methodologies for the precise nanometer-scale positioning of biomolecules permits the low-cost production of various biofunctional devices for a range of biomedical and nanotechnological applications. By combining colloidal lithography and the mussel-inspired multifunctional polydopamine coating, we present a novel parallel benchtop method that allows rapid nanoscale patterning of proteins without the need for electrically powered equipment in the fabrication process. The PDA-immobilized binary nanopattern consisting of BSA surrounded by PLL-g-PEG is fabricated over a large area, and the integrity of the pattern is confirmed using AFM and FM.Langmuir 05/2012; 28(23):8594-9. · 4.19 Impact Factor -
Article: Probing electron-induced bond cleavage at the single-molecule level using DNA origami templates.
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ABSTRACT: Low-energy electrons (LEEs) play an important role in nanolithography, atmospheric chemistry, and DNA radiation damage. Previously, the cleavage of specific chemical bonds triggered by LEEs has been demonstrated in a variety of small organic molecules such as halogenated benzenes and DNA nucleobases. Here we present a strategy that allows for the first time to visualize the electron-induced dissociation of single chemical bonds within complex, but well-defined self-assembled DNA nanostructures. We employ atomic force microscopy to image and quantify LEE-induced bond dissociations within specifically designed oligonucleotide targets that are attached to DNA origami templates. In this way, we use a highly selective approach to compare the efficiency of the electron-induced dissociation of a single disulfide bond with the more complex cleavage of the DNA backbone within a TT dinucleotide sequence. This novel technique enables the fast and parallel determination of DNA strand break yields with unprecedented control over the DNA's primary and secondary structure. Thus the detailed investigation of DNA radiation damage in its most natural environment, e.g., DNA nucleosomes constituting the chromatin, now becomes feasible.ACS Nano 04/2012; 6(5):4392-9. · 10.77 Impact Factor -
Article: Metastable fragmentation of a thymidine-nucleotide and its components
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ABSTRACT: In aqueous biological environment DNA is typically deprotonated. The metastable deprotonated DNA nucleobases are important reaction intermediates in low-energy electron induced damage to DNA. By comparing the metastable decay of small deprotonated DNA building blocks (thymine, thymidine, dribose, d-ribose 5-monophosphate) with the metastable decay of thymidine 5�-monophosphate and the hexameric oligonucleotide dT6 we show that the most intense fragmentation pathways of the individual components are inherited to their next larger compositions of one step further in complexity, i.e., from thymine and ribose to thymidine, from thymidine and 2-deoxyribose 5-monophosphate to thymidine 5�-monophosphate, and from thymidine 5�-monophosphate to thymine oligonucleotides. However, fragmentation channels that are dominant in the smaller, principle building blocks such as d-ribose and thymidine do not necessarily prevail beyond their composition, i.e., in thymidine 5�-monophosphate and thymine oligonucleotides. The comparison of the metastable decay mass spectra of molecules of increasing complexity reveals detailed fragmentation mechanisms and shows that the individual fragmentation pathways are determined by the initial deprotonation sites.International Journal of Mass Spectrometry 01/2012; 313:15-20. · 2.55 Impact Factor -
Article: Fast and metastable fragmentation of deprotonated d-fructose – A combined experimental and computational study
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ABSTRACT: Metastable and prompt fragmentation of the deprotonated monosaccharide d-fructose was studied. By using the isotope labelled molecules 1-13C-d-fructose, 2-13C-d-fructose and 6-13C-d-fructose the origin of the observed fragments could unambiguously be identified. It was found that prompt fragmentation (<200 ns) is characterized by pronounced site selectivity, i.e. the neutral fragments contain C6 and the negative charge remains on the fragment containing the anomeric centre (C2). The selectivity is preserved in metastable dissociation (≈8 �s) only for the generation of the fragment ion C4H4O3− (m/z 100). For all other metastable decay channels fragments with charge retention on the C6 containing fragment contribute appreciably. Density functional theory (DFT) and classical dynamics simulations are applied to predict the formation of fragment ions. Most of the experimentally detected fragment ions were also observed in the simulations thereby revealing detailed information about the fragmentation pathways. We found that the deprotonation site strongly influences the pathway of the dissociation reactions.International Journal of Mass Spectrometry 06/2011; 305:50– 57. · 2.55 Impact Factor -
Article: Tuning the hydrophobicity of mica surfaces by hyperthermal Ar ion irradiation.
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ABSTRACT: The hydrophobicity of surfaces has a strong influence on their interactions with biomolecules such as proteins. Therefore, for in vitro studies of bio-surface interactions model surfaces with tailored hydrophobicity are of utmost importance. Here, we present a method for tuning the hydrophobicity of atomically flat mica surfaces by hyperthermal Ar ion irradiation. Due to the sub-100 eV energies, only negligible roughening of the surface is observed at low ion fluences and also the chemical composition of the mica crystal remains almost undisturbed. However, the ion irradiation induces the preferential removal of the outermost layer of K(+) ions from the surface, leading to the exposure of the underlying aluminosilicate sheets which feature a large number of centers for C adsorption. The irradiated surface thus exhibits an enhanced chemical reactivity toward hydrocarbons, resulting in the adsorption of a thin hydrocarbon film from the environment. Aging these surfaces under ambient conditions leads to a continuous increase of their contact angle until a fully hydrophobic surface with a contact angle >80° is obtained after a period of about 3 months. This method thus enables the fabrication of ultrasmooth biological model surfaces with precisely tailored hydrophobicity.The Journal of chemical physics 03/2011; 134(10):104705. · 3.09 Impact Factor
