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- Höök, Fredrik, 1966, et al.
(författare)
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Characterization of PNA and DNA Immobilization and Subsequent Hybridization with DNA Using Acoustic-Shear-Wave Attenuation Measurements
- 2001
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 17:26, s. 8305-8312
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Tidskriftsartikel (refereegranskat)abstract
- We report here how the quartz crystal microbalance with dissipation monitoring (QCM-D) technique, simultaneously measuring changes in the induced energy dissipation, D (cf. viscoelastic properties), and the frequency, f (cf. coupled mass), can be used to characterize the bound state of single-stranded peptide nucleic acid (PNA) and deoxyribose nucleic acid (DNA) in relation to their ability to function as selective probe(s) for fully complementary and single-mismatch DNA. The possibility to use the QCM-D technique for detection of binding kinetics and structural differences in the formed duplexes is also presented. We found that thiol-PNA and thiol-DNA attached via a sulfur group directly on a bare-gold surface are less efficient as probes for DNA than are biotin-PNA and biotin-DNA, coupled on top of a two-dimensional (2-D) arrangement of streptavidin, formed on a biotinylated phospholipid bilayer on a SiO2 surface. The fully complementary and singly mismatched DNA oligomers hybridize with the immobilized PNA and DNA. A single mismatch is discriminated via a significant difference in the binding and dissociation kinetics, demonstrating a high selectivity and thus successful immobilization of functional single strands. The observed ratios between hybridization-induced energy dissipation (DeltaD) and the frequency shift (Deltaf) made it possible to discriminate thiol-PNA directly attached to a gold surface from biotin-PNA coupled to the streptavidin 2-D arrangement, where the former were shown to be inefficient for detecting subsequent hybridization. Structural differences of the immobilized layers composed of biotin-PNA-DNA and biotin-DNA-DNA were clearly reflected by the DeltaD and Deltaf response.
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- Kamp, Carl Justin, 1982, et al.
(författare)
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Nanofabricated catalyst particles for the investigation of catalytic carbon oxidation by oxygen spillover
- 2017
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 1520-5827 .- 0743-7463. ; 33:20, s. 4903-4912
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Tidskriftsartikel (refereegranskat)abstract
- The catalytic oxidation of carbon by molecular oxygen was studied using C/Pt, Pt/C, Pt/Al2O3/C, Pt/CeO2/C, Al2O3/C and CeO2/C model samples prepared by hole-mask colloidal lithography. By this technique the degree of contact between platinum and carbon was controlled with high precision. The oxidation of carbon was monitored using atomic force microscopy and scanning electron microscopy. The results show that Pt in direct contact with carbon catalyzes the oxidation of carbon by spillover of dissociated oxygen from Pt to carbon. By physically separating Pt and carbon with a 10 nm thin spacer layer of Al2O3, the oxygen spillover was entirely blocked. However, through a corresponding spacer layer of CeO2, carbon oxidation was still observed, either by oxygen spillover from Pt to carbon or directly dissociated on the ceria, although at a slower rate compared to the case with no spacer layer between Pt and carbon.
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- Strömquist, Johan, 1967, et al.
(författare)
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Ballistic motion and abstraction in dimer dissociation at surfaces: Cl-2 on K
- 1996
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Ingår i: Surface Science. - 0039-6028. ; 352:435-441, s. 7-
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Tidskriftsartikel (refereegranskat)abstract
- Non-traditional dissociation dynamics at surfaces, with charge transfer and diabatic motion, is studied for the model system of Cl-2 molecules impinging on the metal K. Three-dimensional molecular dynamics on simple but physically reasonable potential-energy surfaces is used to investigate the final fates of the dissociation fragments (Cl, Cl-) of the molecular ion, Cl-2(-), that is formed by electron transfer (harpooning) to Cl-2 from the K surface. The model study demonstrates that both abstraction (emission of neutrals) and ballistic motion can result from dissociative chemisorption. Our qualitative reasoning has strong implications on other chemisorption systems, like O-2 on alkali and other metals and halogens on Si, e.g., a proposed explanation for ballistically moving O atoms on Al.
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- Wittung Stafshede, Pernilla, 1968, et al.
(författare)
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Detection of point mutations in DNA by PNA-based quartz-crystal biosensor
- 2000
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 1873-4359 .- 0927-7757. ; 174:1-2, s. 269-273
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Tidskriftsartikel (refereegranskat)abstract
- Currently there is an extensive search for biosensors for detecting genetic defects by hybridisation to immobilised oligonucleotides. A concept able to detect a single mismatch in a 15mer single-strand target of the p53 tumor suppresser gene is presented (a mutation found in many types of cancer cells). In this method, the unique hybridisation properties of the DNA mimic peptide nucleic acid (PNA) are combined with electronically detected mass and shear dissipation at the surface of a quartz crystal. Cysteine-labeled PNA efficiently immobilises on crystal-gold surface at 20 degrees C. At 60 degrees C, addition of complementary DNA results in a signal response corresponding to hybridisation between DNA and the PNA-covered surface, whereas addition of DNA differing in only one of the 15 bases gives no response at all.
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- Andersson, Ann-Sofie, et al.
(författare)
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Cell adhesion on supported lipid bilayers
- 2003
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Ingår i: Journal of biomedical materials research. Part A. - : Wiley. - 1549-3296 .- 1552-4965. ; 64:4, s. 622-9
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Tidskriftsartikel (refereegranskat)abstract
- The cell and protein repellent properties of supported phospholipid bilayer (SPB) membranes were investigated. The SPBs were prepared by vesicle adsorption on SiO(2) surfaces. The vesicles of phosphatidylcholine fuse and rupture, and form a supported bilayer covering the surface. We carried out cell culture experiments on several surfaces, including SPBs, using two types of epithelial cells to address the cell adhesional properties. The Quartz Crystal Microbalance Dissipation (QCM-D) technique was used to monitor the SPB formation and subsequent protein adsorption. Neither cell type adhered or proliferated on SiO(2) surfaces coated with SPBs, whereas both cell types adhered and proliferated on the three control surfaces of SiO(2), tissue culture glass, and TiO(2). The QCM-D measurements showed that about two orders of magnitude less mass adsorbed on a SPB surface compared to a TiO(2) surface, from serum-containing media (10% fetal bovine serum). The reduced adsorption on the SPB is a likely explanation for the nondetectable epithelial cell adhesion on the SPB surface. Biomembranes are therefore attractive candidate systems to achieve alternating cell-resistant and cell-interacting regions on surfaces, by including specific cell-binding proteins in the latter regions.
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