| 1. |
- Huber, M., et al.
(författare)
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Phase memory relaxation times of spin labels in human carbonic anhydrase II : Pulsed EPR to determine spin label location
- 2001
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Ingår i: Biophysical Chemistry. - 0301-4622 .- 1873-4200. ; 94:3, s. 245-256
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Tidskriftsartikel (refereegranskat)abstract
- Phase memory relaxation times (TM or T2) of spin labels in human carbonic anhydrase II (HCA II) are reported. Spin labels (N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl)iodoacetamide, IPSL) were introduced at cysteines, by site-directed mutagenesis at seven different positions in the protein. By two pulse electron paramagnetic resonance (EPR), electron spin echo decays at 45 K are measured and fitted by stretched exponentials, resulting in relaxation parameters TM and x. TM values of seven positions are between 1.6 ╡s for the most buried residue (L79C) and 4.7 ╡s for a residue at the protein surface (W245C). In deuteriated buffer, longer TM are found for all but the most buried residues (L79C and W97C), and electron spin echo envelop modulation (ESEEM) of deuterium nuclei is observed. Different deuterium ESEEM patterns for W95C and W16C (surface residue) indicate differences in the local water concentration, or accessibility, of the spin label by deuterium. We propose TM as a parameter to determine the spin label location in proteins. Furthermore, these systems are interesting for studying the pertaining relaxation mechanism. ⌐ 2001 Elsevier Science B.V. All rights reserved.
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| 2. |
- Persson, Malin, et al.
(författare)
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Comparison of electron paramagnetic resonance methods to determine distances between spin labels on human carbonic anhydrase II
- 2001
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Ingår i: Biophysical Journal. - 0006-3495 .- 1542-0086. ; 80:6, s. 2886-2897
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Tidskriftsartikel (refereegranskat)abstract
- Four doubly spin-labeled variants of human carbonic anhydrase II and corresponding singly labeled variants were prepared by site-directed spin labeling. The distances between the spin labels were obtained from continuous-wave electron paramagnetic resonance spectra by analysis of the relative intensity of the half-field transition, Fourier deconvolution of line-shape broadening, and computer simulation of line-shape changes. Distances also were determined by four-pulse double electron-electron resonance. For each variant, at least two methods were applicable and reasonable agreement between methods was obtained. Distances ranged from 7 to 24 W. The doubly spin-labeled samples contained some singly labeled protein due to incomplete labeling. The sensitivity of each of the distance determination methods to the noninteracting component was compared.
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| 3. |
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| 4. |
- Dineva, Savka, et al.
(författare)
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Fluid-moderated seismicity in Great Lakes?
- 2002
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Ingår i: Seismological Research Letters. - 0895-0695 .- 1938-2057. ; 73:2, s. 254-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
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| 6. |
- Mereu, R.F., et al.
(författare)
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The Seismicity of the Western Lake Ontario Area : Results from the Southern Ontario Seismic Network (SOSN), 1992-2001
- 2002
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Ingår i: Seismological Research Letters. - : Seismological Society of America (SSA). - 0895-0695 .- 1938-2057. ; 73:4, s. 534-551
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Tidskriftsartikel (refereegranskat)abstract
- The Southern Ontario Seismic Network (SOSN) consists of eleven three-component short-period seismic stations, located mainly in the Toronto-Hamilton-Niagara area of Ontario, Canada. The network has been in operation by the University of Western Ontario (UWO) for Ontario Power Generation (OPG) since 1991 with the purpose of obtaining information on the seismicity and seismic hazards of a region of southern Ontario in which a number of nuclear power stations are located. Over the past decade, an average of more than ten local earthquakes per year in the western Lake Ontario area was detected by the SOSN. Most of the events were in the 2–3 magnitude (MN) range. The largest events during this time took place in the surrounding regions—Pymatuning, northwestern Pennsylvania (285 km southwest from Toronto, just south of Lake Erie, 25 September 1998, MN 5.4), northern Ontario/Quebec border (325 km north of Toronto, 1 January 2000, MN 5.2), Ashtabula, Ohio (262 km southwest of Toronto, 26 January 2001, MN 4.4), and Au Sable Forks, New York (436 km east of Toronto, 20 April 2002, MN 5.1). The largest earthquake (MN 3.8) in the western Lake Ontario region during the past ten years occurred on 26 November 1999 in Lake Ontario, 16 km southeast of the town of Pickering, which lies just east of Toronto. The estimated location uncertainty (±2 km) is significantly better than that which was possible before 1991. The focal depths, though poorly constrained for most events, are shown to lie in the 3–15 km range, well within the Grenvillian rocks of the Precambrian Shield. The new seismicity map shows that a definite pattern is emerging in the SOSN data set in Lake Ontario, one which is significantly different from the past historical earthquake patterns obtained when the instrumental coverage was poor. Most events occur in scattered clusters in the western part of Lake Ontario and the northwestern corner of New York State. The area of seismicity does not extend significantly to the north of western Lake Ontario and appears to end to the west rather abruptly along a 30 km small fault line running from south of Hamilton in a north-northeasterly direction to Burlington, Ontario. Although the area of seismicity coincides with a region of linear magnetic anomaly trends (suggesting a strong structural fabric in the basement rocks), the correlation of seismicity of the new SOSN data set with magnetic lineaments is still unclear. The cause of the seismicity is speculated to be related to water flows along various fissures below the lake. It is known from induced seismicity studies of reservoirs that the presence of fluids can cause earthquakes by changing the pore pressure and reducing the friction along any faults which may be present. From seismic reflection studies, dipping structures and shear zones have been imaged to extend southeastward under Lake Ontario. This may explain why most of the earthquakes are occurring under the lake or southeast of the lake.
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