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Thomas A. Link - One of the best experts on this subject based on the ideXlab platform.
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role of the rieske iron sulfur protein Midpoint potential in the protonmotive q cycle mechanism of the cytochrome bc1 complex
Journal of Bioenergetics and Biomembranes, 1999Co-Authors: Christopher H. Snyder, Thomas A. Link, Torsten Merbitzzahradnik, Bernard L TrumpowerAbstract:The Midpoint potential of the [2Fe–2S] cluster of the Rieske iron–sulfurprotein (Em7 = +280mV) is the primary determinant of the rate of electron transfer from ubiquinol to cytochromec catalyzed by the cytochrome bc1 complex. As the Midpoint potential of the Rieske clusteris lowered by altering the electronic environment surrounding the cluster, theubiquinol-cytochrome c reductase activity of the bc1 complex decreases; between 220 and 280 mV therate changes 2.5-fold. The Midpoint potential of the Rieske cluster also affects thepresteady-state kinetics of cytochrome b and c1 reduction. When the Midpoint potential of the Rieskecluster is more positive than that of the heme of cytochrome c1, reduction of cytochrome bis biphasic. The fast phase of b reduction is linked to the optically invisible reduction of theRieske center, while the rate of the second, slow phase matches that of c1 reduction. The ratesof b and c1 reduction become slower as the potential of the Rieske cluster decreases andchange from biphasic to monophasic as the Rieske potential approaches that of theubiquinone/ubiquinol couple. Reduction of b and c1 remain kinetically linked as the Midpoint potentialof the Rieske cluster is varied by 180 mV and under conditions where the presteady statereduction is biphasic or monophasic. The persistent linkage of the rates of b and c1 reduction isaccounted for by the bifurcated oxidation of ubiquinol that is unique to the Q-cycle mechanism.
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Alteration of the Midpoint Potential and Catalytic Activity of the Rieske Iron-Sulfur Protein by Changes of Amino Acids Forming Hydrogen Bonds to the Iron-Sulfur Cluster
Journal of Biological Chemistry, 1998Co-Authors: Elke Denke, Torsten Merbitz-zahradnik, Oliver M. Hatzfeld, Christopher H. Snyder, Thomas A. LinkAbstract:Abstract The crystal structure of the bovine Rieske iron-sulfur protein indicates a sulfur atom (S-1) of the iron-sulfur cluster and the sulfur atom (Sγ) of a cysteine residue that coordinates one of the iron atoms form hydrogen bonds with the hydroxyl groups of Ser-163 and Tyr-165, respectively. We have altered the equivalent Ser-183 and Tyr-185 in the Saccharomyces cerevisiae Rieske iron-sulfur protein by site-directed mutagenesis of the iron-sulfur protein gene to examine how these hydrogen bonds affect the Midpoint potential of the iron-sulfur cluster and how changes in the Midpoint potential affect the activity of the enzyme. Eliminating the hydrogen bond from the hydroxyl group of Ser-183 to S-1 of the cluster lowers the Midpoint potential of the cluster by 130 mV, and eliminating the hydrogen bond from the hydroxyl group of Tyr-185 to Sγ of Cys-159 lowers the Midpoint potential by 65 mV. Eliminating both hydrogen bonds has an approximately additive effect, lowering the Midpoint potential by 180 mV. Thus, these hydrogen bonds contribute significantly to the positive Midpoint potential of the cluster but are not essential for its assembly. The activity of thebc 1 complex decreases with the decrease in Midpoint potential, confirming that oxidation of ubiquinol by the iron-sulfur protein is the rate-limiting partial reaction in thebc 1 complex, and that the rate of this reaction is extensively influenced by the Midpoint potential of the iron-sulfur cluster.
Clive H. Bock - One of the best experts on this subject based on the ideXlab platform.
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quantitative ordinal scale estimates of plant disease severity comparing treatments using a proportional odds model
Phytopathology, 2020Co-Authors: Kuoszu Chiang, El M Jarroudi, Y. L. Chen, Clive H. BockAbstract:: Studies in plant pathology, agronomy, and plant breeding requiring disease severity assessment often use quantitative ordinal scales (i.e., a special type of ordinal scale that uses defined numeric ranges); a frequently used example of such a scale is the Horsfall-Barratt scale. Parametric proportional odds models (POMs) may be used to analyze the ratings obtained from quantitative ordinal scales directly, without converting ratings to percent area affected using range Midpoints of such scales (currently a standard procedure). Our aim was to evaluate the performance of the POM for comparing treatments using ordinal estimates of disease severity relative to two alternatives, the Midpoint conversions (MCs) and nearest percent estimates (NPEs). A simulation method was implemented and the parameters of the simulation estimated using actual disease severity data from the field. The criterion for comparison of the three approaches was the power of the hypothesis test (the probability to reject the null hypothesis when it is false). Most often, NPEs had superior performance. The performance of the POM was never inferior to using the MC at severity 40% is equivalent to other methods.
Bisri Tatang - One of the best experts on this subject based on the ideXlab platform.
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Korelasi antara Panjang Garis Sternoakromion dan Titik Penyuntikan Blokade Pleksus Brakialis pada Anestesi Vertical Infraclavicular Block Menggunakan Pencitraan Ultrasonografi pada Pria Dewasa
'Jurnal Anestesi Perioperatif (JAP)', 2016Co-Authors: Yadi, Dedi Fitri, Redjeki, Ike Sri, Bisri TatangAbstract:Anestesi regional untuk operasi di daerah lengan bawah dapat dilakukan blokade pleksus brakialis vertikal infraklavikula. Penelitian ini bertujuan menemukan korelasi antara panjang garis sternoakromion dan letak penyuntikan menggunakan pencitraan ultrasonografi untuk vertical infraclavicular block (VIB) pada pria dewasa. Penelitian potong lintang dengan mengukur titik tengah garis antara fosa jugularis dan akromion pada 48 pria dewasa. Pencitraan ultrasonografi dilakukan menggunakan probe linear untuk menentukan letak penyuntikan. Penelitian dilakukan di Rumah Sakit Dr. Hasan Sadikin Bandung periode Oktober 2011–Januari 2012. Hasil pengukuran didapatkan panjang garis sternoakromion kanan rata-rata 18,35±1,16 cm. dan kiri 18,39±1,22 cm. Titik tengah sternoakromion kanan rata-rata 9,18±0,59 cm dan kiri 9,19±0,61 cm. Jarak letak titik penyuntikan menggunakan ultrasonografi kanan 9,41±0,7 cm dan kiri 9,46±0,72. Terdapat korelasi positif (r kanan=0,874 dan r kiri=0,862) antara garis sternoakromion dan jarak letak titik penyuntikan menggunakan pencitraan ultrasonografi.Kata kunci: Blokade vertikal infraklavikular, letak penyuntikan blokade infraklavikular, pencitraan ultrasonografi Correlation between the Sternoacromion Line Length and Plexus Brachialis Vertical Infraclavicular Block Injection Site Using Ultrasonography Scan on Adult MalesAbstractSurgery on the lower part of the arm can be managed by brachial plexus vertical infraclavicular block. Needle placement for vertical infraclavicular block is not always at the Midpoint of the sternoacromion line. The aim of this study was to find the correlation between sternoacromion length and needle placement using ultrasond scan for vertical infraclavicular block on adults males. This was a cross sectional study measuring the midlle point of sternoacromion line on 48 adult male volunteers whom never had any injury or operation on shoulder areas. Linear probe ultrasound was used to determine the needle placement. This study was conducted in Dr. Hasan Sadikin General Hospital Bandung within the period of October 2011–January 2012. Pearson correlation test and linear regression were used to analyze the data. Result of this study showed an average right strernoacromion length of 18.35±1.16 cm, an average left sternoacromion leght of 18.39±1.22 cm, an average Midpoint right sternoacromion of 9.18±0.59 cm, and an average midmpoint left sternoacromion of 9.19±0.61. The average ultrasound right point was 9.41 cm and 9.46 cm for the left point. Hence, thereare significant correlations (r right=0.874, r left=0.862) between sternoacromion length and ultrasound injection point for vertical infraclavicular block.Key words: Injection site for infraclavicular block, ultrasound scan, vertical infraclavicular block DOI: 10.15851/jap.v4n1.73
Christopher H. Snyder - One of the best experts on this subject based on the ideXlab platform.
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role of the rieske iron sulfur protein Midpoint potential in the protonmotive q cycle mechanism of the cytochrome bc1 complex
Journal of Bioenergetics and Biomembranes, 1999Co-Authors: Christopher H. Snyder, Thomas A. Link, Torsten Merbitzzahradnik, Bernard L TrumpowerAbstract:The Midpoint potential of the [2Fe–2S] cluster of the Rieske iron–sulfurprotein (Em7 = +280mV) is the primary determinant of the rate of electron transfer from ubiquinol to cytochromec catalyzed by the cytochrome bc1 complex. As the Midpoint potential of the Rieske clusteris lowered by altering the electronic environment surrounding the cluster, theubiquinol-cytochrome c reductase activity of the bc1 complex decreases; between 220 and 280 mV therate changes 2.5-fold. The Midpoint potential of the Rieske cluster also affects thepresteady-state kinetics of cytochrome b and c1 reduction. When the Midpoint potential of the Rieskecluster is more positive than that of the heme of cytochrome c1, reduction of cytochrome bis biphasic. The fast phase of b reduction is linked to the optically invisible reduction of theRieske center, while the rate of the second, slow phase matches that of c1 reduction. The ratesof b and c1 reduction become slower as the potential of the Rieske cluster decreases andchange from biphasic to monophasic as the Rieske potential approaches that of theubiquinone/ubiquinol couple. Reduction of b and c1 remain kinetically linked as the Midpoint potentialof the Rieske cluster is varied by 180 mV and under conditions where the presteady statereduction is biphasic or monophasic. The persistent linkage of the rates of b and c1 reduction isaccounted for by the bifurcated oxidation of ubiquinol that is unique to the Q-cycle mechanism.
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Alteration of the Midpoint Potential and Catalytic Activity of the Rieske Iron-Sulfur Protein by Changes of Amino Acids Forming Hydrogen Bonds to the Iron-Sulfur Cluster
Journal of Biological Chemistry, 1998Co-Authors: Elke Denke, Torsten Merbitz-zahradnik, Oliver M. Hatzfeld, Christopher H. Snyder, Thomas A. LinkAbstract:Abstract The crystal structure of the bovine Rieske iron-sulfur protein indicates a sulfur atom (S-1) of the iron-sulfur cluster and the sulfur atom (Sγ) of a cysteine residue that coordinates one of the iron atoms form hydrogen bonds with the hydroxyl groups of Ser-163 and Tyr-165, respectively. We have altered the equivalent Ser-183 and Tyr-185 in the Saccharomyces cerevisiae Rieske iron-sulfur protein by site-directed mutagenesis of the iron-sulfur protein gene to examine how these hydrogen bonds affect the Midpoint potential of the iron-sulfur cluster and how changes in the Midpoint potential affect the activity of the enzyme. Eliminating the hydrogen bond from the hydroxyl group of Ser-183 to S-1 of the cluster lowers the Midpoint potential of the cluster by 130 mV, and eliminating the hydrogen bond from the hydroxyl group of Tyr-185 to Sγ of Cys-159 lowers the Midpoint potential by 65 mV. Eliminating both hydrogen bonds has an approximately additive effect, lowering the Midpoint potential by 180 mV. Thus, these hydrogen bonds contribute significantly to the positive Midpoint potential of the cluster but are not essential for its assembly. The activity of thebc 1 complex decreases with the decrease in Midpoint potential, confirming that oxidation of ubiquinol by the iron-sulfur protein is the rate-limiting partial reaction in thebc 1 complex, and that the rate of this reaction is extensively influenced by the Midpoint potential of the iron-sulfur cluster.
Kuoszu Chiang - One of the best experts on this subject based on the ideXlab platform.
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quantitative ordinal scale estimates of plant disease severity comparing treatments using a proportional odds model
Phytopathology, 2020Co-Authors: Kuoszu Chiang, El M Jarroudi, Y. L. Chen, Clive H. BockAbstract:: Studies in plant pathology, agronomy, and plant breeding requiring disease severity assessment often use quantitative ordinal scales (i.e., a special type of ordinal scale that uses defined numeric ranges); a frequently used example of such a scale is the Horsfall-Barratt scale. Parametric proportional odds models (POMs) may be used to analyze the ratings obtained from quantitative ordinal scales directly, without converting ratings to percent area affected using range Midpoints of such scales (currently a standard procedure). Our aim was to evaluate the performance of the POM for comparing treatments using ordinal estimates of disease severity relative to two alternatives, the Midpoint conversions (MCs) and nearest percent estimates (NPEs). A simulation method was implemented and the parameters of the simulation estimated using actual disease severity data from the field. The criterion for comparison of the three approaches was the power of the hypothesis test (the probability to reject the null hypothesis when it is false). Most often, NPEs had superior performance. The performance of the POM was never inferior to using the MC at severity 40% is equivalent to other methods.
