scholarly journals The role of Mg2+ in the light activation process of the H+ -ATPase in intact chloroplasts

FEBS Letters ◽  
1982 ◽  
Vol 145 (2) ◽  
pp. 223-229 ◽  
Author(s):  
Yosepha Shahak
Keyword(s):  
Activation Process ◽  
Light Activation ◽  
Intact Chloroplasts

AN "ACTIVATION" PROCESS FOR ENTREPRENEURIAL ENGINEERING EDUCATION: THE MODEL AND APPLICATION

2011 ◽  
Vol 19 (02) ◽  
pp. 147-168 ◽  
Author(s):  
GIANLUCA ELIA ◽  
A. MARGHERITA ◽  
G. SECUNDO ◽  
K. MOUSTAGHFIR
Keyword(s):  
Engineering Education ◽  
Research Training ◽  
Economic Value ◽  
Activation Process ◽  
Technology Entrepreneurship ◽  
Hands On ◽  
Research Training Program ◽  
Develop Technology ◽  
Market Solutions

The pervasiveness of scientific developments has raised the role of entrepreneurship as a driver of socio-economic value. Higher education institutions are thus asked to create entrepreneurial mindset and competencies with the purpose to make students people able to proactively identify opportunities and transform them in market solutions. In particular, engineering education programs can be of relevance to develop technology entrepreneurship competencies through hands-on and experiential approaches. In such vein, this paper proposes a model of entrepreneurship education as an "activation" process which uses four critical levers with the purpose to infuse the essence of entrepreneurship in tomorrow's engineering professionals. The application of the model is exemplified through the analysis of a research training program grounded in the aerospace domain. The key features of the initiative are discussed in the perspective of exploring new models of entrepreneurial engineering education.

Photoreceptor rod outer segment 48-kDa protein has ATPase activity

1990 ◽  
Vol 5 (6) ◽  
pp. 585-589 ◽  
Author(s):  
Ari Sitaramayya ◽  
Shereen Hakki
Keyword(s):  
Atpase Activity ◽  
Cyclic Gmp ◽  
Slow Rate ◽  
Binding Protein ◽  
Rod Outer Segments ◽  
Light Activation ◽  
Visual Transduction ◽  
Gtp Binding Protein ◽  
Gtp Binding

AbstractThe role of 48-kDa protein in Visual transduction remains unresolved. Two hypotheses for its role in quenching the light activation of cyclic GMP cascade suggest that the protein binds to either phosphodiesterase or phosphorylated rhodopsin. Since the protein is also reported to bind ATP, we anticipated that the protein may have ATP hydrolyzing activity, and in analogy with the GTP-binding protein of the rod outer segments, such activity may be greatly enhanced by the elements of transduction cyclic GMP cascade, permitting the protein to function cyclically as GTP-binding protein does. We found that purified 48-kDa protein hydrolyzes ATP but at a slow rate of 0.04–0.05 per min. The Km for ATP is about 45–65 μM. The activity is inhibited noncompetitively by ADP with a Ki of about 50 μM. The ATPase activity of 48-kDa protein is not affected by rhodopsin, bleached rhodopsin, phosphorylated rhodopsin, unactivated cyclic GMP phosphodiesterase, or phosphodiesterase (PDE) activated by GMP PNP-bound G-protein. These data show that although 48-kDa protein has ATPase activity, lack of regulation of this activity by the elements of visual transduction makes it unlikely for this activity to have a role in quenching the light activation of cyclic GMP cascade.

The Influence of the Proton Gradient on the Activation of Ferredoxin-NADP+-oxidoreductase by Light

1988 ◽  
Vol 43 (3-4) ◽  
pp. 207-212 ◽  
Author(s):  
Roland Pschorn ◽  
Wolfgang Rühle ◽  
Aloysius Wild
Keyword(s):  
Active Form ◽  
Cytochrome F ◽  
Proton Gradient ◽  
Activation Process ◽  
Dark Light ◽  
Induction Kinetics ◽  
Fluorescence Quench ◽  
Steady State Rate ◽  
State Rate

Ferredoxin-NADP+-oxidoreductase (FNR, EC 1.18.1.2) has been shown to be activated by light within a few seconds during dark-light transitions and inactivated in the dark. In previous papers this could be pointed out by the correlation of cytochrome f induction kinetics to the rate of NADP-photoreduction and the variable fluorescence. The present study deals with the role of the proton gradient during the activation process. The transition from an inactive to an active form is followed continuously in an in situ system. The steady-state rate of NADP-photoreduction is affected only by ionophores which inhibit a formation of the proton gradient, but not by inhibitors of the electric field. It correlates to the 9-aminoacridine fluorescence quench and the light scattering signals at 535 nm. The perception of the pH-gradient through the enzyme is still a matter of discussion.

scholarly journals Rapid Loss of Factor XII- and XI-Activity in Ellagic Acid Activated Normal Plasma: Role of Plasma Inhibitors and Implications for Automated Aptt-Recording

1977 ◽  
Author(s):  
J. H. Joist ◽  
J. F. Cowan ◽  
M. Khan
Keyword(s):  
Ellagic Acid ◽  
Clinical Laboratory ◽  
Coagulation Factors ◽  
Activation Process ◽  
Factor Xii ◽  
Naturally Occurring ◽  
Normal Plasma ◽  
Factor Xiia ◽  
Loss Of Contact

Rapid prolongation of the activated partial thromboplastin time (aPTT) of normal plasma upon incubation with ellagic acid containing aPTT reagents was observed. The aPTT prolongation was not due to time dependent changes in pH in the incubation mixtures or loss of activity of the labile coagulation factors VIII and V, but occurred as a result of rapid progressive inactivation of ellagic acid activated factors XII and XI. Prolongation of the aPTT and loss of contact factor activities was not observed in plasma incubated with particulate activator reagents. This finding seemed to indicate that adsorption of factors XII and XI to larger particles during the activation process may protect these factors from inactivation by naturally occurring plasma inhibitors. Evidence is presented which supports previous observations that Ci-inhibitor, α1-antitrypsin and antithrombin III (in the presence of heparin contribute to factor XIIa- and XIa-inactivation in ellagic acid activated plasma and that plasma albumin may compete with factor XII for ellagic acid binding. The findings indicate that ellagic acid containing aPTT reagents have unfavorable properties which seriously limit their usefulness in the clinical laboratory, particularly in respect to recording of the aPTT with certain fully automated clot timers.

Role of Primary Sensory Cortex in Generalized Electrocortical Activation

1957 ◽  
Vol 189 (1) ◽  
pp. 137-140
Author(s):  
Aaron J. Beller ◽  
Gidon F. Gestring ◽  
Dominick P. Purpura
Keyword(s):  
Sensory Stimulation ◽  
Sensory Cortex ◽  
Activation Process ◽  
Afferent Activity ◽  
Primary Sensory Cortex ◽  
Cortical Regions ◽  
Somatic Sensory Cortex ◽  
Bilateral Destruction

Experiments were performed on intact unanesthetized-succinylcholine paralyzed cats in order to compare the effects of ablations of primary cortical regions on the ability to evoke generalized activation to specific sensory stimulation with those obtained by Bremer on encéphale isolé preparations. Bilateral destruction of the auditory or somatic sensory cortex in intact preparations does not block generalized activation to auditory or sciatic stimulation. It is concluded that in the presence of spinal afferent activity as exists in the intact preparation corticifugal influences arising in either the auditory or somatic sensory cortex are not necessary for the activation process that follows auditory or sciatic stimulation.

The role of the chloroplast in inorganic carbon acquisition by Chlamydomonas reinhardtii

1991 ◽  
Vol 69 (5) ◽  
pp. 1017-1024 ◽  
Author(s):  
James V. Moroney ◽  
Catherine B. Mason
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Inorganic Carbon ◽  
Published Data ◽  
Carbon Uptake ◽  
Intact Chloroplasts ◽  
Inorganic Carbon Transport ◽  
Inorganic Carbon Uptake ◽  
Carbon Transport ◽  
Inorganic Carbon Acquisition

The role of the chloroplast in algal inorganic carbon acquisition is reviewed. Unicellular green algae possess the ability to grow photoautotrophically at very low CO2 concentrations. The presence of a CO2-concentrating system that elevates the CO2 level within the cell can account for the algae's ability to reduce photorespiration and grow under these conditions. The mechanism of this inorganic carbon transport is unclear at present, although both the plasmalemma and the chloroplast have been implicated in this process. Three aspects of the role of the chloroplast in Chlamydomonas reinhardtii inorganic carbon uptake are discussed in this review. First, the present models of inorganic carbon uptake are summarized. Second, the purity and integrity of intact chloroplast preparations are discussed. Third, an evaluation of the published data on inorganic carbon uptake by isolated intact chloroplasts is presented. Key words: Chlamydomonas reinhardtii, carbonic anhydrase, chloroplast, active CO2 uptake.

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