| 1. |
- Petoral, Rodrigo M., et al.
(författare)
-
Adsorption of n-butyl-substituted tetrathiafulvalene dodecanethiol on gold
- 2005
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 287:2, s. 388-393
-
Tidskriftsartikel (refereegranskat)abstract
- Tetrathiafulvalene (TTF) derivative substituted with two butyl- and two dodecylthiol chains is adsorbed on polycrystalline gold. The TTF-derived thiol adsorbates were characterized by ellipsometry, contact angle goniometry, infrared and X-ray photoelectron spectroscopy and cyclic voltammetry. The molecule is strongly anchored on the gold surface through the sulfur terminating the alkylthiol chains. On the average, the TTF moiety is oriented extended away from the gold surface. The topmost layer of the film containing the dibutyl chains is disordered with gauche defects. The molecule was organized with majority of the alkylthiol chains bound to the gold surface. There are indications of pinholes in the monolayer due to steric hindrance of the bulky TTF rings. The molecular systems consisting of an electroactive pi-system such as TTF, are promising for thin-film field effect transistor application.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
- Petoral, Rodrigo Jr, 1975-, et al.
(författare)
-
Arg–Cys and Arg–cysteamine adsorbed on gold and the G-protein–adsorbate interaction
- 2002
-
Ingår i: Colloids and Surfaces B. - 0927-7765 .- 1873-4367. ; 25:4, s. 335-346
-
Tidskriftsartikel (refereegranskat)abstract
- The dipeptide, Arg–Cys, and the related molecule, Arg–cysteamine, are adsorbed to gold surfaces and the monolayers are characterized. Chemical binding and electronic structure of the monolayers are obtained by X-ray photoelectron spectroscopy (XPS). Strong molecular binding of the adsorbates to gold surface through the sulfur atom is attained. Orientation of the adsorbates on gold is studied using infrared reflection absorption spectroscopy (IRAS). Arg–Cys is interpreted to be adsorbed on gold in a compact configuration. The Arg–cysteamine molecule is adsorbed on gold with the main molecular axis perpendicular to the surface. Interaction of G-protein with the adsorbates was studied using the surface plasmon resonance (SPR) technique. It is believed that arginine has a major role in G-protein recognition since the G-protein-coupled receptor (GPCR) α2A has an arginine-rich region in the G-protein-binding part of the third intracellular loop.
|
|
| 11. |
- Petoral, Rodrigo Jr, 1975-
(författare)
-
Bioactive adsorbates on gold surfaces : structural properties and bio-interaction studies
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the properties of biomolecular, model adsorbates on gold such as amino acid derivatives, peptides and related organic molecules. Subsequent bin-interaction studies were also conducted. The physico-chemical and structural properties of the adsorbates were characterized using X-ray Photoelectron Spectroscopy (XPS), Infrared-Reflection Absmption Spectroscopy (IRAS) and Near-Edge X-ray Absmption Fine Structures spectroscopy (NEXAFS). Complementary techniques such as Null ellipsometry and Cyclic Voltammetry (CV) were also used. The interaction of the bioactive monolayers with biologically relevant molecules, such as proteins and metal ions, were investigated using Surface Plasmon Resonance (SPR) spectroscopy and Electrochendcallmpedance Spectroscopy (EIS).The first part of the thesis is directed towards the interaction of bovine-brain G-protein with adsorbates involving arginine residues and receptor-derived peptides mimicking the 2nd and 3rd intracellular (ic) loop of the α2A Adrenergic G-protein coupledreceptor (GPCR). The general aim is to find a peptide sequence that will selectively, with high affinity, interact with the G-protein. The specific aims were to examine the importance of the presence of positively charged arginine residues, to investigate the influence of molecular orientation of the adsorbates, and to verify which intracellular loop has the highest affinity to the G-protein. The investigation involved characterizing the chemical composition and the molecular orientation of Arginine-based dipeptide adsorbates (Arg-Cys and Arg-Cysteandne) and receptor-detived peptides (GPR1R also labeled GPRi3c, GPR1K, GPR1A, GPRi2c, GPRi3n) innnobilized on gold surfaces, followed by G~protein interaction studies. On all the adsorbates subjected to interact with G-proteins, the presence of arginine residues was proven to be of special importance in the affinity of G-proteins. A molecularly"oriented Arg-Cysteamine, with main molecular axis perpendicular to the gold surface, showing more available arginines, attracts more G-proteins as compared to Arg-Cys that has a compact configuration when adsorbed on gold. The peptide adsorbates derived from the third ic loop (GPRi3c and GPRi3n) have higher affinity than peptides derived from the second ic loop (GPRi2c). This shows that this arginine-rich area of the third ic loop has a major influence on the affinity and selectivity of G-proteins.
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Petoral, Rodrigo Jr, 1975-, et al.
(författare)
-
NEXAFS study of amino acid analogues assembled on gold
- 2005
-
Ingår i: Physica scripta. T. - 0281-1847. ; T115, s. 851-854
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, near-edge x-ray absorption fine structure spectroscopy (NEXAFS) experiment is done to obtain the chemical and structural information about the occurrence and the average orientation of unoccupied molecular orbitals within the organic films. Amino acid, such as Tyrosine and 3,4-dihydroxyphenylalanine (DOPA), is linked to a thiol through a peptide bond and is adsorbed and self-assembled to polycrystalline gold surfaces. Results from the C k-edge and O k-edge spectra serves as fingerprints to each amino acid analogues. The average orientation of the molecules relative to the gold surface is determined from the polarization effects observed as intensity changes of the peaks in the spectra when the x-ray incidence angle is varied. It is assumed that the average tilt angle of the main molecular axis of amino acid linked to short amidethiol is based on the deduced orientation of the peptide bond. © Physica Scripta 2005.
|
|
| 15. |
- Petoral, Rodrigo Jr, 1975-, et al.
(författare)
-
Structural investigation of 3,4-dihydroxyphenylalanine-terminated propanethiol assembled on gold
- 2003
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 107:48, s. 13396-13402
-
Tidskriftsartikel (refereegranskat)abstract
- 3,4-Dihydroxyphenylalanine-terminated propanethiol (DOPA-PT), an amino acid DOPA linked to 3-mercaptopropionic acid through an amide bond, is adsorbed and self-assembled to polycrystalline gold surfaces. The structure of the adsorbates was characterized by means of X-ray photoelectron spectroscopy (XPS), infrared reflection−absorption spectroscopy (IRAS), and near-edge X-ray absorption fine structure spectroscopy (NEXAFS). Strong molecular binding of a DOPA derivative on gold surfaces through the sulfur atom was attained. Angle-dependent XPS results showed that the aromatic ring is oriented away from the gold surface. Both IRAS and NEXAFS results showed parallel orientation of the C=O bond of the amide moiety relative to the gold surface. Hydrogen bonding between amide moieties is achieved, and it seemed to provide additional orientation stabilization. Deduced orientation of the amide moiety on the short alkyl chain (or the peptide plane) is assumed to give the average orientation of the main molecular axis. The main molecular axis is estimated to have an average tilt angle of approximately 37° relative to the gold surface normal based on NEXAFS results. The aromatic ring exhibits a preferred orientation with an average tilt angle of about 64°. The experimental results showed that DOPA-thiol with amide linkage is able to self-assemble and form a layered structured film consisting of a layer of alkane chains with a gauche conformation beneath an oriented layer of DOPA.
|
|
| 16. |
|
|
| 17. |
|
|
| 18. |
|
|
| 19. |
|
|
| 20. |
- Uvdal, Kajsa, 1961-, et al.
(författare)
-
Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold
- 2006
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 110:46, s. 23410-23416
-
Tidskriftsartikel (refereegranskat)abstract
- Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection−absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
- Yakimova, Rositsa, 1942-, et al.
(författare)
-
Novel material concepts of transducers for chemical and biosensors
- 2007
-
Ingår i: Biosensors & bioelectronics. - : Elsevier BV. - 0956-5663 .- 1873-4235. ; 22:12, s. 2780-2785
-
Tidskriftsartikel (refereegranskat)abstract
- The objectives of this work are to contribute to the knowledge about physical and chemical properties of WBG semiconductors, such as ZnO and GaN towards development of advanced bio- and chemical sensors. For the semiconductors, growth techniques typically yielding single crystal material are applied. Thin epitaxial quality films of ZnO and GaN are fabricated on SiC or sapphire substrates. An emphasis is given to ZnO due to the interesting combination of the semiconductor and oxide properties. Surface bio-functionalization of ZnO is performed by APTES, MPA or MP-TMS molecules. We have compared some of the results to (hydroxylated) GaN surfaces functionalized by MP-TMS. The covalent attachment of the self-assembled biomolecular layers has been proven by XPS analysis. For complementary electrical characterization impedance spectroscopy measurements were performed. The results are intended to serve the realization of bioelectronic transducer devices based on SiC or GaN transistors with a ZnO gate layer. To take advantage of the catalytic properties of ZnO, initial prototypes of chemical sensors for gas sensing are processed on ZnO deposited either on SiC or on sapphire and they are further tested for the response to reducing or oxidizing gas ambient. The sensor devices show sensitivity to oxygen in the surface resistivity mode while a Pt Schottky contact ZnO/SiC device responds to reducing gases. These results are compared to published results on Pt/GaN Schottky diodes. © 2007 Elsevier B.V. All rights reserved.
|
|
| 25. |
- Yakimova, Rositsa, 1942-, et al.
(författare)
-
Surface functionalization and biomedical applications based on SiC
- 2007
-
Ingår i: Journal of Physics D. - 0022-3727 .- 1361-6463. ; 40:20, s. 6435-6442
-
Tidskriftsartikel (refereegranskat)abstract
- The search for materials and systems, capable of operating long term under physiological conditions, has been a strategy for many research groups during the past years. Silicon carbide (SiC) is a material, which can meet the demands due to its high biocompatibility, high inertness to biological tissues and to aggressive environment, and the possibility to make all types of electronic devices. This paper reviews progress in biomedical and biosensor related research on SiC. For example, less biofouling and platelet aggregation when exposed to blood is taken advantage of in a variety of medical implantable materials while the robust semiconducting properties can be explored in surface functionalized bioelectronic devices. © 2007 IOP Publishing Ltd.
|
|
