Measurement of Quantum Yield, Quantum Requirement, and Energetic Efficiency of the O2-Evolving System of Photosynthesis by a Simple Dye Reaction

1996 ◽  
Vol 73 (11) ◽  
pp. 1034 ◽  
Author(s):  
A. Ros Barcelò ◽  
J. M. Zapata
Keyword(s):  
Quantum Yield ◽  
Energetic Efficiency ◽  
Quantum Requirement ◽  
Evolving System

scholarly journals TIME COURSE AND QUANTUM EFFICIENCY OF PHOTOSYNTHESIS IN CHLORELLA

1953 ◽  
Vol 36 (4) ◽  
pp. 563-579 ◽  
Author(s):  
Frederick S. Brackett ◽  
Rodney A. Olson ◽  
Robert G. Crickard
Keyword(s):  
Steady State ◽  
Quantum Yield ◽  
Dark Adaptation ◽  
Time Course ◽  
Random Distribution ◽  
Initial Rate ◽  
Chlorophyll Concentration ◽  
Intermittent Light ◽  
Quantum Requirement ◽  
Different Cultures

1. Though the quantum yield remains constant for different samples of the same culture despite great changes in respiration due to dark adaptation, the quantum requirement for different cultures varies from 6.1 to 13.5 quanta per molecule of oxygen evolved (q/m). 2. This variation from one culture to another appears to depend upon chlorophyll concentration, though other paralleling factors cannot be ruled out. 3. Both chlorophyll concentration and quantum requirement show a random distribution. A statistical median for 50 cultures and 99 determinations gives q/m = 8.5 with a systematic uncertainty of perhaps 10 per cent. Since the variations are real, the median is regarded as less important than the lower limit approached (about q/m = 6). 4. Dark adaptation under aerobic conditions produces an initial photosynthetic rate of nearly zero. The immediate rise to steady state is somewhat logarithmic in character and may require over 3 minutes. 5. In intermittent light (of periods from 1 to 6 minutes) the induction observed in subsequent light periods starts from a finite initial rate and occupies a shorter time, often as little as 30 seconds. 6. The theoretical importance of aerobic induction is discussed. A chlorophyll cycle of two photochemical steps is found to satisfy most of the observed characteristics and to be compatible with an efficiency independent of intensity.

scholarly journals Constraint-based modelling revealed changes in metabolic flux modes associated with the Kok effect

2020 ◽  
Author(s):  
Wei Qiang Ong ◽  
C. Y. Maurice Cheung
Keyword(s):  
Quantum Yield ◽  
Light Intensity ◽  
Energy Demand ◽  
Metabolic Flux ◽  
Net Photosynthesis ◽  
Quantum Yields ◽  
Energetic Efficiency ◽  
Low Light ◽  
Subtle Change ◽  
Low Light Intensity

AbstractConstraint-based modelling was applied to provide a mechanistic understanding of the possible metabolic origins of the ‘Kok effect’ – the change in quantum yield of net photosynthesis at low light intensity. The well-known change in quantum yield near the light-compensation point (LCP) was predicted as an emergent behaviour from a purely stoichiometric model. From our modelling results, we discovered another subtle change in quantum yield at a light intensity lower than the LCP. Our model predicted a series of changes in metabolic flux modes in central carbon metabolism associated with the changes in quantum yields. We demonstrated that the Kok effect can be explained by changes in metabolic flux modes between catabolism and photorespiration. Changes in RuBisCO carboxylation to oxygenation ratio resulted in a change in quantum yield at light intensities above the LCP, but not below the LCP, indicating the role of photorespiration in producing the Kok effect. Cellular energy demand was predicted to have no impact on the quantum yield. Our model showed that the Kok method vastly overestimates day respiration – the CO2 released by non-photorespiratory processes in illuminated leaves. The theoretical maximum quantum yield at low light intensity was higher than typical measured values, suggesting that leaf metabolism at low light may not be regulated to optimise for energetic efficiency. Our model predictions gave insights into the set of energetically optimal changes in flux modes in low light as light intensity increases from darkness.One sentence summaryThe Kok effect can be explained by the changes in flux modes between catabolism and photorespiration.

Designing work-centered performance support solutions for operators of a complex and evolving system

2003 ◽  
Author(s):  
Kelly Neville ◽  
Jerry M. Owens ◽  
Susan M. Eitelman ◽  
Charles A. Barba ◽  
Jack Ennis ◽  
...  
Keyword(s):  
Performance Support ◽  
Evolving System

Size-dependent emission of a dipole coupled to a metal nanoparticle

MRS Advances ◽  
2020 ◽  
Vol 5 (62) ◽  
pp. 3315-3325
Author(s):  
Viktoriia Savchuk ◽  
Arthur R. Knize ◽  
Pavlo Pinchuk ◽  
Anatoliy O. Pinchuk
Keyword(s):  
Numerical Analysis ◽  
Quantum Yield ◽  
Electric Dipole ◽  
Incident Radiation ◽  
Metal Nanoparticle ◽  
Plasmonic Nanoparticle ◽  
Size Dependent ◽  
Emission Enhancement ◽  
Electric Dipoles

AbstractWe present a systematic numerical analysis of the quantum yield of an electric dipole coupled to a plasmonic nanoparticle. We observe that the yield is highly dependent on the distance between the electric dipole and the nanoparticle, the size and permittivity of the nanoparticle, and the wavelength of the incident radiation. Our results indicate that enhancement of the quantum yield is only possible for electric dipoles coupled to a nanoparticle with a radius of 20 nm or larger. As the size of the nanoparticle is increased, emission enhancement occurs at wavelengths dependent on the coupling distance.

Complexity and the Art of Public Policy

2016 ◽  
Author(s):  
David Colander ◽  
Roland Kupers
Keyword(s):  
Social Systems ◽  
Policy Framework ◽  
Government Control ◽  
Institutional Structures ◽  
Policy Models ◽  
Benefit Corporations ◽  
Evolving System ◽  
Societal Problems ◽  
Modern Analytical ◽  
Policy Solutions

Complexity science—made possible by modern analytical and computational advances—is changing the way we think about social systems and social theory. Unfortunately, economists’ policy models have not kept up and are stuck in either a market fundamentalist or government control narrative. While these standard narratives are useful in some cases, they are damaging in others, directing thinking away from creative, innovative policy solutions. This book outlines a new, more flexible policy narrative, which envisions society as a complex evolving system that is uncontrollable but can be influenced. The book describes how economists and society became locked into the current policy framework, and lay out fresh alternatives for framing policy questions. Offering original solutions to stubborn problems, the complexity narrative builds on broader philosophical traditions, such as those in the work of John Stuart Mill, to suggest initiatives that the authors call “activist laissez-faire” policies. The book develops innovative bottom-up solutions that, through new institutional structures such as for-benefit corporations, channel individuals’ social instincts into solving societal problems, making profits a tool for change rather than a goal. It argues that a central role for government in this complexity framework is to foster an ecostructure within which diverse forms of social entrepreneurship can emerge and blossom.

Highly Fluorescent Au25-xAgx Nanoclusters Protected with Poly(ethylene glycol) - and Zwitterion-Modified Thiolate Ligands

2018 ◽  
Author(s):  
Dinesh Mishra ◽  
Sisi Wang ◽  
Zhicheng Jin ◽  
Eric Lochner ◽  
Hedi Mattoussi
Keyword(s):  
Quantum Yield ◽  
Near Infrared ◽  
Small Diameter ◽  
Binding Energies ◽  
Thiolate Ligands ◽  
Nir Emission ◽  
Thiolate Complexes ◽  
Long Lifetime ◽  
Poly Ethylene

<p>We describe the growth and characterization of highly fluorescing, near-infrared-emitting nanoclusters made of bimetallic Au<sub>25-x</sub>Ag<sub>x</sub> cores, prepared using various monothiol-appended hydrophobic and hydrophilic ligands. The reaction uses well-defined triphenylphosphine-protected Au<sub>11</sub> clusters (as precursors), which are reacted with Ag(I)-thiolate complexes. The prepared nanoclusters are small (diameter < 2nm, as characterized by TEM) with emission peak at 760 nm and long lifetime (~12 µs). The quantum yield measured for these materials was 0.3 - 0.4 depending on the ligand. XPS measurements show the presence of both metal atoms in the core, with measured binding energies that agree with reported values for nanocluster materials. The NIR emission combined with high quantum yield, small size and ease of surface functionalization afforded by the coating, make these materials suitable to implement investigations that address fundamental questions and potentially useful for biological sensing and imaging applications.<br></p>

The Influence of Buildings Envelope on its Energetic Efficiency

2017 ◽  
Author(s):  
Paulo Roberto Wander ◽  
Daniel Medeiros ◽  
Bruna Ferrari
Keyword(s):  
Energetic Efficiency

The Law of Property and the Evolving System of Property Rights in China

2010 ◽  
Author(s):  
Albert H. Y. Chen
Keyword(s):  
Property Rights ◽  
Evolving System ◽  
The Law

Synthesis and Characterization of ROSA Dye - A Rhodamine B-type Fluorophore, Suitable for Bioconjugation and Fluorescence Studies in Live Cells

2019 ◽  
Vol 26 (10) ◽  
pp. 758-767
Author(s):  
Vicente Rubio ◽  
Vijaya Iragavarapu ◽  
Maciej J. Stawikowski
Keyword(s):  
Quantum Yield ◽  
Cancer Cells ◽  
Fluorescent Probe ◽  
Extinction Coefficient ◽  
Rhodamine B ◽  
Solid Phase ◽  
Total Yield ◽  
Molar Extinction Coefficient ◽  
Αvβ3 Integrin ◽  
Αvβ3 Integrins

Background: Herein we report the multigram-scale synthesis, characterization and application of a rhodamine B-based fluorophore (ROSA) suitable for fluorescent studies in biological applications. This fluorophore is devoid of rhodamine spirolactone formation and furthermore characterized by a high molar extinction coefficient (ϵ=87250 ± 1630 M-1cm-1) and quantum yield (φ) of 0.589 ± 0.070 in water. Reported here is also the application of ROSA towards synthesis of a ROSA-PEG-GRGDS-NH2 fluorescent probe suitable for live cell imaging of αvβ3 integrins for in vitro assays. Objective: The main objective of this study is to efficiently prepare rhodamine B derivative, devoid of spirolactone formation that would be suitable for bioconjugation and subsequent bioimaging. Methods: Rhodamine B was transformed into rhodamine B succinimide ester (RhoB-OSu) using N-hydroxysuccinimide. RhoB-OSu was further coupled to sarcosine to obtain rhodamine Bsarcosine dye (ROSA) in good yield. The ROSA dye was then coupled to a αvβ3 integrin binding sequence using standard solid-phase conditions. Resulting ROSA-PEG-GRGDS-NH2 probe was used to image integrins on cancer cells. Results: The rhodamine B-sarcosine dye (ROSA) was obtained in multigram scale in good total yield of 47%. Unlike rhodamine B, the ROSA dye does not undergo pH-dependent spirolactone/spirolactam formation as compared with rhodamine B-glycine. It is also characterized by excellent quantum yield (φ) of 0.589 ± 0.070 in water and high molar extinction coefficient of 87250 ± 1630 M-1cm-1. ROSA coupling to the RGD-like peptide was proved to be efficient and straightforward. Imaging using standard filters on multimode plate reader and confocal microscope was performed. The αvβ3 integrins present on the surface of live WM-266-4 (melanoma) and MCF- 7 (breast cancer) cells were successfully imaged. Conclusion: We successfully derivatized rhodamine B to create an inexpensive, stable and convenient to use fluorescent probe. The obtained derivative has excellent photochemical properties and it is suitable for bioconjugation and many imaging applications.

Sign in / Sign up

Export Citation Format

Share Document