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133 results on '"Pornsuwan, Soraya"'

30. Inhibition of Tau Filament Formation by Conformational Modulation

Author

Markus Zweckstetter, Michal J. Gajda, Christian Griesinger, Pornsuwan Soraya, Eckhard Mandelkow, Elias Akoury, Marcus Pickhardt, and Jacek Biernat

Subjects
Magnetic Resonance Spectroscopy, Indoles, Tau protein, Molecular Conformation, tau Proteins, Biochemistry, Catalysis, Molecular conformation, law.invention, Protein filament, Colloid and Surface Chemistry, law, Spectroscopy, Fourier Transform Infrared, mental disorders, Humans, Mode of action, Electron paramagnetic resonance, Polyacrylamide gel electrophoresis, biology, Chemistry, chemistry [tau Proteins], General Chemistry, Nuclear magnetic resonance spectroscopy, Small molecule, tetrasulfophthalocyanine, Crystallography, antagonists & inhibitors [tau Proteins], ddc:540, Biophysics, biology.protein, Electrophoresis, Polyacrylamide Gel, chemistry [Indoles]
Abstract

Antiaggregation drugs play an important role in therapeutic approaches for Alzheimer’s disease. Although a large number of small molecules that inhibit the aggregation of the tau protein have been identified, little is known about their mode of action. Here, we reveal the mechanism and the nature of tau species that are generated by interaction of tau with the organic compound pthalocyanine tetrasulfonate (PcTS). We demonstrate that PcTS interferes with tau filament formation by targeting the protein into soluble oligomers. A combination of NMR spectroscopy, electron paramagnetic resonance, and small-angle X-ray scattering reveals that the soluble tau oligomers contain a dynamic, noncooperatively stabilized core with a diameter of 30–40 nm that is distinct from the core of tau filaments. Our results suggest that specific modulation of the conformation of tau is a viable strategy for reduction of pathogenic tau deposits.

Published
2013

33. Nitroxide spin-relaxation over the entire motional range

Author

Bonora, Marco, Pornsuwan, Soraya, and Saxena, Sunil

Subjects
Nitro compounds -- Analysis, Nitro compounds -- Chemical properties, Peptides -- Analysis, Peptides -- Chemical properties, Chemicals, plastics and rubber industries
Abstract

Homogenous line widths, characterized by the phase memory time Tm, of a nitroxide spin-labeled peptide, were measured over the entire optional range (~10 (super -10)-10(super -4) s at the spectrometer resonance frequency of 9.7 GHZ using spin-echo correlated spectroscopy (SECSY) ESR.

Published
2004

35. Effects of appended hydroxyl groups and ligand chain length on copper coordination and oxidation activity.

Author

Pornsuwan, Soraya, Jehdaramarn, Attawit, Sangtrirutnugul, Preeyanuch, Chumsaeng, Phongnarin, and Phomphrai, Khamphee

Subjects
*HYDROXYL group, *LIGANDS (Chemistry), *BENZYL alcohol
Abstract

Treatment of a series of (imino)pyridine ligands bearing appended hydroxyl groups 2-((pyridin-2-ylmethylene)amino)phenol (Hpyph), 2-((pyridin-2-ylmethylene)amino)ethanol (Hpyet), and 3-((pyridin-2-ylmethylene)amino)propanol (Hpypr) with one equiv. of CuCl2·2H2O afforded the corresponding Cu(ii) complexes in low to moderate yields. The crystal structure of (μ-Cl)2[CuCl(κ2-N,N-Hpyet)]2 reveals a symmetric dinuclear structure with the bidentate N,N-coordination mode of (imino)pyridine with no Cu–OH interaction. On the other hand, the dinuclear Cu(ii) complex of the related propyl ligand Hpypr possesses a significantly different crystal structure involving nucleophilic addition of the hydroxyl group to the aldehyde group of 2-pyridinecarboxaldehyde. The Cu complex/Cu0/TEMPO/Na2CO3 (TEMPO = 2,2,6,6-tetramethylpiperidinyl-1-oxyl) catalyst system generally exhibited good activity for aerobic oxidation of benzyl alcohol to benzaldehyde in H2O at room temperature. The dinuclear Cu(ii) complex (μ-Cl)2[CuCl(κ2-N,N-Hpyet)]2 was demonstrated as an effective catalyst toward aerobic oxidation of various benzyl alcohol derivatives, cinnamyl alcohol, and 2-thiophenemethanol. [ABSTRACT FROM AUTHOR]

Published
2018
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38. Measurements of dynamics, structure, and flexibility of macromolecules by pulsed Electron Spin Resonance

Author

Pornsuwan, Soraya and Pornsuwan, Soraya

Abstract

This thesis discusses the measurement of molecular dynamics and distances in spin-labeled macromolecules by pulsed electron spin resonance (ESR). We present a scheme to reduce the dead-time in a commercial ESR spectrometer. This achievement facilitates the acquisition of the ESR signal even when it is largely reduced due to short relaxation times. As a result, we obtain the two-dimensional (2D) ESR signal for a nitroxide labeled peptide over a temperature range of 192 K to 310 K. In that temperature range, molecular reorientations over the range of 10-10 to 10-4 s are sampled. The phase memory time (Tm) is measured at each experimental temperature. The phase memory times, Tm, as a function of rotational correlation are calculated using spectral simulations based on the stochastic Liouville equation. By comparing the plots of Tm versus temperature obtained from experiment and theoretical models, the details of molecular dynamics are elucidated. This accomplishment expands the application of 2D ESR to the measurement of dynamics in large proteins.The second part of this research employs a pulsed ESR technique, double electron-electron resonance (DEER), to measure large-scale distances in bis-peptide materials composed of 4-8 monomers. Constraints on overall structure and flexibility of the oligomers are rapidly determined by the end-to-end distance distribution measured from the DEER data. The distance distributions from DEER data are compared with those obtained from molecular dynamics (MD) simulations. Discrepancies between the DEER and MD results are evident, especially for longer oligomers. In order to rapidly predict the shapes of the oligomers, we introduce a joint stiff-segment model to represent the oligomer backbone. A scheme is established to exploit information on the end-to-end distance distribution functions obtained by ESR to optimize the force fields used in the joint-stiff segment model. The results provide information on the distribution of orientatio

Published
2008

47. Integrated LED-photodiode chemical sensor

Author

Yeh, Jeng-Ya, primary, Rusli, Suwandi, additional, Pornsuwan, Soraya, additional, Ivanisevic, Albena, additional, Nickel, Anne-Marie, additional, Ellis, Arthur B., additional, Kuech, Thomas F., additional, and Mawst, Luke J., additional

Published
2001
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49. The Role of L-DOPA on Melanization and Mycelial Production in Malassezia Furfur.

Author

Youngchim, Sirida, Nosanchuk, Joshua D., Pornsuwan, Soraya, Kajiwara, Susumu, and Vanittanakom, Nongnuch

Subjects
MELANOGENESIS, DOPA, MALASSEZIA, POLYMERS, PATHOGENIC microorganisms, MONOCLONAL antibodies
Abstract

Melanins are synthesized by organisms of all biological kingdoms and comprise a heterogeneous class of natural pigments. Certain of these polymers have been implicated in the pathogenesis of several important human fungal pathogens. This study investigated whether the fungal skin pathogen Malassezia furfur produces melanin or melanin-like compounds. A melanin-binding monoclonal antibody (MAb) labelled in vitro cultivated yeast cells of M. furfur. In addition, melanization of Malassezia yeasts and hyphae was detected by anti-melanin MAb in scrapings from patients with pityriasis versicolor. Treatment of Malassezia yeasts with proteolytic enzymes, denaturant and concentrated hot acid yielded dark particles and electron spin resonance spectroscopy revealed that these particles contained a stable free radical compound, consistent with their identification as melanins. Malassezia yeasts required phenolic compounds, such as L-DOPA, in order to synthesize melanin. L-DOPA also triggered hyphal formation in vitro when combined with kojic acid, a tyrosinase inhibitor, in a dose-dependent manner. In this respect, L-DOPA is thought to be an essential substance that is linked to both melanization and yeast-mycelial transformation in M. furfur. In summary, M. furfur can produce melanin or melanin-like compounds in vitro and in vivo, and the DOPA melanin pathway is involved in cell wall melanization. [ABSTRACT FROM AUTHOR]

Published
2013
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50. Distance Distributions of End-Labeled Curved Bispeptide Oligomers by Electron Spin Resonance

Author

H. Bird, Gregory, Pornsuwan, Soraya, Saxena, Sunil, E. Schafmeister, Christian, and E. Schafmeister, Christian

Abstract

We demonstrate the synthesis of a series of spin-labeled curved oligomers to determine their end-to-end lengths and distance distributions using electron spin resonance. We synthesize shape-persistent macromolecules from conformationally restricted, asymmetric monomers that are coupled through pairs of amide bonds to create water-soluble, spiro-ladder oligomers with well-defined three-dimensional structures. We synthesized seven different macromolecules, each containing eight monomers but differing in the sequence to create macromolecules with different curved shapes. The ends of the oligomers were labeled with nitroxide spin probes, and double electron−electron resonance (DEER) electron spin resonance (ESR) experiments were carried out to obtain quantitative information about the shapes and flexibility of the oligomers. The most probable end-to-end distance of the oligomers ranges from 23 to 36 Å, a range of length that we previously accessed by assembling rod-like homo-oligomers that contain 4−8 bisamino acid monomers. The relative distances measured for the oligomers confirm that, by varying the sequence of an oligomer, we are able to control its shape. The shapes of the ESR-derived population distributions allow us to compare the degree of shape persistence and flexibility of spiro-ladder oligomers to other well-studied nanoscale molecular structures such as p-phenylethynylenes.

Published
2008
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