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- Margittai, M., et al.
(författare)
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Single-molecule fluorescence resonance energy transfer reveals a dynamic equilibrium between closed and open conformations of syntaxin 1
- 2003
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 100:26, s. 15516-15521
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Tidskriftsartikel (refereegranskat)abstract
- Protein conformational transitions form the molecular basis of many cellular processes, such as signal transduction and membrane traffic. However, in many cases, little is known about their structural dynamics. Here we have used dynamic single-molecule fluorescence to study at high time resolution, conformational transitions of syntaxin 1, a soluble N-ethylmaleimide-sensitive factor attachment protein receptors protein essential for exocytotic membrane fusion. Sets of syntaxin double mutants were randomly labeled with a mix of donor and acceptor dye and their fluorescence resonance energy transfer was measured. For each set, all fluorescence information was recorded simultaneously with high time resolution, providing detailed information on distances and dynamics that were used to create structural models. We found that free syntaxin switches between an inactive closed and an active open configuration with a relaxation time of 0.8 ms, explaining why regulatory proteins are needed to arrest the protein in one conformational state.
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- Srinivas, V., et al.
(författare)
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Electronic transport properties of high-resistivity icosahedral AlPdRe below 1 K
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:9
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependence of the conductivity, sigma(T), and the magnetoresistance up to B = 6 T have been studied in the temperature range 0.01 Kless than or equal toTless than or equal to1 K for two differently prepared i-AlPdRe samples on the insulating side of the metal-insulator transition. sigma(T) for both samples was observed to saturate in zero magnetic field below about 20 mK. With increasing magnetic field the temperature dependence of the conductivity increased, and at 6 T, or(T,B = 6 T) was found to decrease linearly with decreasing temperature down to the lowest measurement temperature of 10 mK. The estimated value of the conductivity at T=0 K, sigma(0 K), was found to decrease strongly with increasing resistance ratio R [ = rho(4 K)/rho(295 K)] over a wide range of R values and for differently prepared samples, suggesting that a finite sigma(0,R) is a characteristic property of the icosahedral phase of high-resistivity i-AlPdRe. The magnetoresistance is positive below 1 K. The relation Deltarho(B)/rhosimilar toB(2) is followed at larger fields by a B-2/3 dependence. With decreasing temperature these characteristic field regions are successively depressed towards smaller magnetic fields and eventually become unobservable. A scaling of the magnetoresistance is found for data in the region Tless than or equal to1 K, Bless than or equal to6 T of the form [Deltarho(B)/rho]/T-alpha=f(B/T) for each sample, with alpha about 0.3 for both samples.
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