scholarly journals Kinetic studies on mammalian cytochrome c modified with 2-hydroxy-5-hydroxy-5-nitrobenzyl bromide

1975 ◽  
Vol 149 (1) ◽  
pp. 179-185 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Flash Photolysis ◽  
Ph Dependence ◽  
Phase 1 ◽  
Kinetic Studies ◽  
Chromium Concentration ◽  
Stopped Flow ◽  
Phase 2 ◽  
Difference Spectra ◽  
Phase Phase

The reduction of 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c by the chromous ion was studied by stopped-flow techniques. At pH6.5 the reduction of 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c is complex, showing the presence of three distinct phases. Two chromium concentration-dependent phases are observed (1.1 × 105 M-1-S-1, phase 1; 1.25 × 104M-1-S-1, phase 2) and one slow first-order process (0.25S-1, phase 3). A comparison of the static and kinetic difference spectra, along with the data from the reduction of the reoxidized reduced protein, suggests that the slow chromium concentration-independent phase is due to a slow conformational event after fast reduction of the NO2 group. The rates of the chromium concentration-dependent phases show a marked variation with pH above 7.5. The activation energies for the three processes were also measured at 33.2, 38.6 and 69.7 kJ-mol-1 for phases 1, 2 and 3 respectively. The reaction of reduced 2-hydroxy-5-nitrobenzyl tryptophyl cytochrome c with CO was foollowed by means of both stopped-flow and flash photolysis. The combination with CO at pH 6.8 as measured in stopped-flow experiments showed two phases, one CO-dependent phase (phase 2, 2.4 × 102M-1-S-1) and one CO-independent phase (phase 1, 0.015S-1). Investigation of the pH-dependence of the phases showed both the rates and amounts of each phase to be pH-invariant. CO recombination, after photolytic removal, was found to be biphasic; a CO-dependent phase (phase 2, 2.4 × 102M-1-S-1) and a CO-independent phase (phase 1, 1.0s-1) were observed. A tentative model which can accommodate these observations is proposed.

scholarly journals Kinetic studies on (N-formyltryptophyl)cytochrome c

1975 ◽  
Vol 149 (3) ◽  
pp. 713-717 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Flash Photolysis ◽  
Reduction Process ◽  
Kinetic Studies ◽  
Tryptophan Residue ◽  
Kinetic Properties ◽  
Stopped Flow ◽  
Normal Environment ◽  
Two Phases ◽  
Flow Techniques

The formylation of the ring nitrogen atom of the tryptophan residue in cytochrome c was carried out and consequent changes in the kinetic properties of the protein were investigated. The reduction of formylated cytochrome c by Cr2+ was studied by stopped-flow techniques. At pH 6.5 the reduction process shows the presence of two phases. One phase (k = 4 × 104 M-1-s-1) is dependent on Cr2+ concentration and one phase (k = 5.0 s-1) is not. A study of the temperature dependence of the two phases yields values for their activation energies of 38.6kJ·mol-1 and 42.4kJ·mol-1 respectively. The reaction of the reduced formylated cytochrome c with CO was followed by means of both stopped-flow techniques and flash photolysis. The combination with CO at pH 6.8 measured in stopped-flow experiments shows two phases, both dependent on the concentration of CO (k1 = 1.8 × 102 M-1-s-1). If CO was dissociated from the protein by photolysis and then allowed to recombine with it, it was found to do so in a simple manner, at a rate which depended on the concentration of CO (k = 1.9 × 10M2 M-1-s-1). A tentative model which can accommodate these findings is proposed. The reaction of the oxidized form of formylated cytochrome c with NO was followed by means of stopped-flow techniques. The reaction was found to be biphasic with one phase dependent on the concentration of NO (k = 2.8 × 103 M-1-s-1) and one phase (k = 0.2s-1) independent of the concentration of NO. This behaviour is compared with that of the native molecule. A comparison of these kinetic observations with those on other tryptophan-specific modifications leads to the conclusion that the main alteration in kinetic properties is due, not to the nature of the modifying group, but rather to the disruption of the normal environment of the haem.

Hypoxic release of calcium from the sarcoplasmic reticulum of pulmonary artery smooth muscle

2001 ◽  
Vol 281 (2) ◽  
pp. L318-L325 ◽  
Author(s):  
Michelle Dipp ◽  
Piers C. G. Nye ◽  
A. Mark Evans
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Phase 1 ◽  
Transient Phase ◽  
Phase 2 ◽  
Hypoxic Response ◽  
Pulmonary Vessels ◽  
Intracellular Ca ◽  
Pulmonary Artery Smooth Muscle ◽  
Phase Phase

The hypoxic constriction of isolated pulmonary vessels is composed of an initial transient phase ( phase 1) followed by a slowly developing increase in tone ( phase 2). We investigated the roles of the endothelium and of intracellular Ca2+ stores in both preconstricted and unpreconstricted intrapulmonary rabbit arteries when challenged with hypoxia (Po 2 16–21 Torr). Removing the endothelium did not affect phase 1, but phase 2 appeared as a steady plateau. Removing extracellular Ca2+ had essentially the same effect as removing the endothelium. Depletion of sarcoplasmic reticulum Ca2+stores with caffeine and ryanodine abolished the hypoxic response. Omitting preconstriction reduced the amplitude of the hypoxic response but did not qualitatively affect any of the above responses. We conclude that hypoxia releases intracellular Ca2+ from ryanodine-sensitive stores by a mechanism intrinsic to pulmonary vascular smooth muscle without the need for Ca2+ influx across the plasmalemma or an endothelial factor. Our results also suggest that extracellular Ca2+ is required for the release of an endothelium-derived vasoconstrictor.

scholarly journals Transient kinetic studies of Neurospora crassa cytochrome c oxidase

1983 ◽  
Vol 215 (2) ◽  
pp. 425-427 ◽  
Author(s):  
M Brunori ◽  
M C Silvestrini ◽  
M T Wilson ◽  
H Weiss
Keyword(s):  
Cytochrome C ◽  
Neurospora Crassa ◽  
Cytochrome C Oxidase ◽  
Flash Photolysis ◽  
Kinetic Studies ◽  
Dissociation Rate ◽  
Steady State Kinetic ◽  
Kinetic Investigations ◽  
Dissociation Rate Constants

The reaction of Neurospora crassa cytochrome c oxidase with CO was studied by flash-photolysis and rapid-mixing experiments, leading to the determination of the association and dissociation rate constants (7 X 10(4) M-1 X s-1 and 0.02s-1 respectively). Pre-steady-state kinetic investigations of the catalytic properties of the enzyme showed that under proper conditions Neurospora cytochrome c oxidase can be ‘pulsed’, i.e. activated, like the mammalian enzyme. The ‘pulsed’ species is spectroscopically different from the ‘resting’ one, and the decay into the ‘resting’ state is fast (t1/2 approx. 3 min).

scholarly journals Creating an Interactive Aid to Mediate Obesity Diagnosis and Management

2019 ◽  
Vol 43 (2) ◽  
Author(s):  
Shariwa Oke ◽  
Kristin Mount ◽  
Kristina Varady ◽  
Samantha Bond
Keyword(s):  
Phase 1 ◽  
Comfort Level ◽  
Health And Wellness ◽  
Phase 2 ◽  
Future Health ◽  
Group Discussions ◽  
Iterative Design ◽  
Post Test ◽  
Phase Group ◽  
Phase Phase

The purpose of this research was to design an application using iterative design and usability testing to convey nutrition, exercise, and obesity information to a patient with obesity. The study consisted of three phases: the research phase (Pre-phase), prototype phase (Phase 1), and application phase (Phase 2).In the pre-phase, group discussions were held with four experts, where they discussed the desired functionality of the proposed application. Their suggestions were incorporated into a paper prototype that was developed for iterative design testing in Phase 1. Experts first answered questions about their patients and then were given tasks to complete using the prototype.In Phase 2, the application was developed in the Unity 2D gaming engine. User feedback from Phase 1 testing was considered for Phase 2 design and functionality choices. Test subjects were given either the mobile application or a handout with the identical written content. All subjects were given a pre-test, including questions about comfort level with their health care provider and knowledge of exercise and nutrition, before they were given either the application or the handout. A post-test was given after subjects had interacted with their materials for one week.Qualitative data from prototyping and iterative design testing is a valuable tool for improving future health and wellness applications.

Studies of knock and antiknock by kinetic spectroscopy

1956 ◽  
Vol 234 (1197) ◽  
pp. 178-191 ◽  
Keyword(s):  
Induction Period ◽  
Lead Oxide ◽  
Flash Photolysis ◽  
Phase 1 ◽  
Detonation Waves ◽  
Phase Reaction ◽  
Phase 2 ◽  
Strong Light ◽  
Amyl Nitrite ◽  
Lead Monoxide

The method of flash photolysis has been used to ignite mixtures of acetylene, oxygen and amyl nitrite, the latter serving as fuel and as sensitizer. The course of the explosive combustion was followed by flash spectroscopy and by photoelectric technique. Two phases have been conveniently distinguished in the explosion : (1) An induction period following the immediate disappearance of the spectrum of amyl nitrite during which no radical spectra were visible. (2) The fast build-up of diatomic radical spectra—predominantly OH, with a little NH and CN— at the point of ignition accompanied by strong light emission upon which were superimposed high-temperature emission peaks of only a few microseconds’ duration indicating detonation waves travelling through the reacting gases. On the addition of small amounts of lead tetraethyl the induction period was greatly lengthened, and during that time the waxing and waning of the lead oxide band system was observed. 0∙2 mm (Hg) of lead tetraethyl increased phase 2 up to 200%, and the strong emission caused by heavy detonation was often quenched completely. The entirely different behaviour of aromatics is also shortly discussed. It was established that the antiknock effect of lead tetraethyl is a completely homogeneous gas-phase reaction, and it was concluded that its effect is twofold in nature: first, by reacting with oxygenated intermediates produced in phase 1 of the combustion with the formation of lead oxide, it removes the sources of auto-ignition which lead to knock in phase 2; secondly, the lead monoxide so formed reduces the propagating and branching mechanisms leading to the final explosion by preferential reaction with the free radicals involved, and thus contributes to conditions which do not lead to detonation and knock. This reaction and also the conditions obtaining at the end of the explosion promote the final reduction of the lead monoxide to atomic lead.

scholarly journals The Positive Inotropic and Calcium-Mobilizing Effects of Growth Hormone-Releasing Peptides on Rat Heart

Endocrinology ◽  
2003 ◽  
Vol 144 (11) ◽  
pp. 5050-5057 ◽  
Author(s):  
Xiang-Bin Xu ◽  
Ji-Min Cao ◽  
Jing-Jiang Pang ◽  
Rong-Kun Xu ◽  
Chao Ni ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Phase 1 ◽  
Dependent Manner ◽  
Phase 2 ◽  
Perfused Heart ◽  
Voltage Gated ◽  
Kinase C ◽  
Phase Phase

Abstract GH-releasing peptides (GHRP) are synthetic peptides exerting GH-dependent or GH-independent effects via GH secretagogue receptor on many organs, including the heart. The underlying mechanisms of the cardiotropic properties of GHRP are poorly understood. This study investigates these effects of four GHRP in isolated perfused heart preparations and isolated neonatal and adult ventricular myocytes. The calcium response of cardiocytes to GHRP was visualized using confocal microscopy. All tested GHRP facilitated both ventricular contraction and relaxation in a dose-dependent manner, moderately decreasing coronary flow, but not modifying heart rate. GHRP induced a biphasic increase in intracellular free Ca2+ of the cardiocytes, consisting of a transient phase (phase 1), followed by a plateau phase (phase 2). Phase 1 was abolished by pretreatment with thapsigargin, a Ca2+-adenosine triphosphatase inhibitor of the sarcoplasmic reticulum. The phase 2 response was eliminated by removing extracellular free Ca2+, by verapamil, a voltage-gated Ca2+ channel blocker, or by 24-h pretreatment with phorbol 12-myristate 13-acetate, down-regulating protein kinase C. In isolated (denervated) heart, GHRP have a direct cardiotropic, without chronotropic, effect. GHRP elevate myocardial intracellular free Ca2+ through activating Ca2+ influx via voltage-gated Ca2+ channels and triggering Ca2+ release from thapsigargin-sensitive intracellular Ca2+ stores. Protein kinase C mediates the GHRP-induced Ca2+ influx, but not Ca2+ release. These finding support a number of roles for GHRP in the cardiovascular system.

scholarly journals Coordination and Symmetry Patterns During the Drop Vertical Jump in People With Chronic Ankle Instability and Lateral Ankle Sprain Copers

2016 ◽  
Vol 96 (8) ◽  
pp. 1152-1161 ◽  
Author(s):  
Cailbhe Doherty ◽  
Chris Bleakley ◽  
Jay Hertel ◽  
Brian Caulfield ◽  
John Ryan ◽  
...  
Keyword(s):  
Motor Control ◽  
Ankle Sprain ◽  
Ankle Instability ◽  
Phase 1 ◽  
Vertical Jump ◽  
Phase 2 ◽  
Lateral Ankle Sprain ◽  
Lateral Ankle ◽  
Control Patterns ◽  
Phase Phase

Abstract Background The drop vertical jump (DVJ) task has previously been used to identify movement patterns associated with a number of injury types. However, no current research exists evaluating people with chronic ankle instability (CAI) compared with people coping with lateral ankle sprain (LAS) (referred to as “LAS copers”) during this task. Objective The aim of this study was to identify the coping movement and motor control patterns of LAS copers in comparison with individuals with CAI during the DVJ task. Design This was a case-control study. Methods Seventy individuals were recruited at convenience within 2-weeks of sustaining a first-time acute LAS injury. One year following recruitment, these individuals were stratified into 2 groups: 28 with CAI and 42 LAS copers. They attended the testing laboratory to complete a DVJ task. Three-dimensional kinematic and sagittal-plane kinetic profiles were plotted for the lower extremity joints of both limbs for the drop jump phase (phase 1) and drop landing phase (phase 2) of the DVJ. The rate of impact modulation relative to body weight during both phases of the DVJ also was determined. Results Compared with LAS copers, participants with CAI displayed significant increases in hip flexion on their “involved” limb during phase 1 of the DVJ (23° vs 18°) and bilaterally during phase 2 (15° vs 10°). These movement patterns coincided with altered moment-of-force patterns at the hip on the “uninvolved” limb. Limitations It is unknown whether these movement and motor control patterns preceded or occurred as a result of the initial LAS injury. Conclusions Participants with CAI displayed hip-centered changes in movement and motor control patterns during a DVJ task compared with LAS copers. The findings of this study may give an indication of the coping mechanism underlying outcome following initial LAS injury.

An Evidence-based Approach to Developing the Collaborative, Client-Centred Nutrition Education (3CNE) Framework and Practice Points

2016 ◽  
Vol 77 (2) ◽  
pp. 78-83 ◽  
Author(s):  
Catherine Morley ◽  
Deborah MacLellan ◽  
Karol Traviss ◽  
Theresa Cividin
Keyword(s):  
Nutrition Education ◽  
Online Survey ◽  
Phase 1 ◽  
Phase 2 ◽  
Phase 3 ◽  
Progressive Development ◽  
Third Phase ◽  
Phase Study ◽  
Subsequent Phase ◽  
Phase Phase

Purpose: The purpose of this, the third phase of a 3-phase research project, was to develop guidelines for client-centred nutrition education (NE). Methods: A 3-phase study was conducted using a progressive development design, where each phase informed the subsequent phase. Phase 1 was a national online survey of dietitians’ perceptions of consumers’ NE needs and preferences; results informed the Phase 2 national online survey of consumers about their NE needs and preferences. Phase 3 involved national 2-part teleconference consultations with dietitians to discuss implications of the Phase 2 findings for NE practice. This paper is the report of Phase 3. Results: Discussion group participants were 22 dietitians from around Canada who had been in practice for an average of 14.5 years. Discussions resulted in the development of the Collaborative Client-Centred Nutrition Education (3CNE) conceptual framework and related Practice Points that explicate the complexity of NE practice. Conclusion: The 3CNE framework and Practice Points provide a means to inform precepting students and interns, and for use in planning for the professional development of practicing dietitians on providing client-centred NE.

scholarly journals Kinetic studies on [methionine sulphoxide] cytochrome c

1976 ◽  
Vol 159 (3) ◽  
pp. 621-626 ◽  
Author(s):  
T Brittain ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Reduction Process ◽  
Order Reduction ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Chemically Modified ◽  
Neutral Ph ◽  
Recombination Processes ◽  
Reduced Forms ◽  
Flow Experiments

A cytochrome c haem ligand, methionine-80, was photo-oxidized to methionine sulphoxide and the subsequent changes in redox properties and ligand binding were monitored kinetically. Isoelectric focusing of the product showed the presence of a single oxidized species, capable of binding CO when reduced. The binding of CO to the reduced protein was followed in stopped-flow experiments, which revealed the presence of two binding processes, at neutral pH, with rate constants of K+1 = 3.4 × 10(3)M-1-S-1 and k+2 = 5.80 × 10(2)M-1-S-1. When CO was photolytically dissociated from the reduced protein two recombination processes were observed with rates almost identical with those observed in the stopped-flow experiments (k+1 = 3.3 × 10(3)M-1-S-1 and k+2 = 6.0 × 10(2)M-1-S-1). These findings provide evidence of two reduced forms of the protein. The reduction of [methionine sulphoxide]cytochrome c by Cr2+ at neutral pH in stopped-flow experiments showed the presence of a single second-order reduction process (k = 7.2 × 10(3)M-1-S-1, activation energy = 44kJ/mol) and one first-order process. This protein was compared with some other chemically modified cytochromes.

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