Light Reactions

Top PDF Light Reactions:

Triterpenes from Cabralea canjerana as in Vitro Inhibitors to Light Reactions of Photosynthesis

Triterpenes from Cabralea canjerana as in Vitro Inhibitors to Light Reactions of Photosynthesis

Aims: Cabraleadiol (1), Ocotilone (2) and Odoratone (3) are three triterpenes isolated from Ca- bralea canjerana (Vell.) Mart. (Meliaceae). They were chemically characterized, and their effect was tested on the light reaction of photosynthesis. Study Design: Natural products were used as models to find new models for inhibitors of photosynthesis. Place and Duration of Study: Depart- mento de Química, Universidade Federal de São Carlos and Departmento de Bioquímica, Facultad de Química, Universidad Nacional Autonoma de México, between May 2013 and January 2014. Methodology: The natural products had their effect on the light reaction of photosynthesis studied by pollarography and Chlorophyll a (Chl a) fluorescence transients. Results: The compounds inhi- bited ATP synthesis and electron transport rate (basal, phosphorylating and uncoupled). There- fore, they act as Hill reactions inhibitors. Their inhibition site were located in the range of electron flow from OEC complex and between P 680 to Q A of PS II, and inhibited the photosystem II (PS II) by
Show more

14 Read more

Photosynthetic light reactions at the gold interface

Photosynthetic light reactions at the gold interface

The design characteristics of photosynthesis are paradigm in solar cell research primarily because of the high, near unity quantum efficiency of the light driven steps in this process. 1 The primary photo-conversion reactions involve light absorption, energy transfer and charge transfer. The process relies on the interplay between various types of light-harvesting protein complexes, structurally well- defined polymers with embedded light-absorbing chromophores held in exact geometries. Besides mimicking individual aspects of photosynthesis there is a growing interest for the direct application of the protein complexes in biosolar cells and biosensors. 2-12 However, the interconnection of proteins and protein complexes with electrodes, in terms of electronic contact, structure, alignment and orientation, remains a challenge. Several immobilization techniques have been examined in the past, which mostly involved bio-films formed by self-assembly on the surface of electrodes by incubation in a solution of photosynthetic complexes. 13-19 Even though photosynthetic proteins readily adsorb on the electrode, these techniques often produce monolayers with a non-uniform protein orientation. In order to control the orientation of the complexes on the electrodes, much research has been aimed at the development of genetically engineered complexes that bind specifically to an electrode that has been pre-modified with a suitable monolayer of linker molecules. 5,20-26 A drawback of this method is the decrease in electron transfer (ET) efficiency due to the increased tunneling distance introduced by the thickness of the monolayer of linker molecules. A variety of photosynthetic proteins have been explored within the context of bio-hybrid devices, with emphasis on photosystem I (PSI), photosystem II (PSII), and reaction center (RC) complexes from different photosynthetic organisms. 4-6,9,10,12,13,18-20,24,27-36 As far as we know the quantum efficiency of any photosynthesis based biohybrid device reported has always been extremely low, with one moderate exception of 12% reported by Das et al. albeit upon illumination by monochromatic laser light of 10W/cm 2 , the equivalent of more than 100 suns. 5
Show more

120 Read more

AP Biology Chapter 10 Photosynthesis

AP Biology Chapter 10 Photosynthesis

 How linear electron flow in the light reactions results in.. the formation of ATP, NADPH, and O 2.[r]

61 Read more

lecture 9

lecture 9

Light Chloroplast Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma Electro ns. LIGHT REACTIONS CALVIN CYCLE[r]

33 Read more

LABORATORY EXPLORATION The Light-dependent Reactions of Photosynthesis

LABORATORY EXPLORATION The Light-dependent Reactions of Photosynthesis

Plants are autotrophs, self-feeding organisms that capture light energy (photons) and store it as chemical energy (carbohydrates). During the light reactions of photosynthesis, the light energy of photons is converted briefly to electrical energy (the flow of electrons through chlorophylls in the photosystems), and then into chemical energy (in the bonds of ATP and NADPH). During the Calvin Cycle (sometimes known as the light-independent reactions, since it can proceed either in dark or light), the chemical energy briefly stored as ATP and NADPH is transferred for long-term storage into the bonds of sugar.
Show more

12 Read more

EFFECT OF MOISTURE STRESS ON PHOTOSYNTHESIS DURING THE ONTOGENY OF SUNFLOWER (HELIANTHUS ANNUUS L.)

EFFECT OF MOISTURE STRESS ON PHOTOSYNTHESIS DURING THE ONTOGENY OF SUNFLOWER (HELIANTHUS ANNUUS L.)

Net photosynthesis (Pn), leaf stomatal conductance, chlorophyll content and rate of partial light reactions were measured in the upper fully expanded leaves at varying degre[r]

7 Read more

Ch. 10 Photosynthesis F15

Ch. 10 Photosynthesis F15

 How linear electron flow in the light reactions results in the formation of ATP, NADPH, and O 2..  How chemiosmosis generates ATP in the light reactions.[r]

65 Read more

Status and perspectives of fragmentation beams at LNS with CHIMERA detector

Status and perspectives of fragmentation beams at LNS with CHIMERA detector

During next measurements, we will improve the angular and energy reso- lution in the detection of the heavy projectile like fragments, by using the highly segmented, first four prototypes, of the FARCOS detection system [7]. A FARCOS module is a three stage telescope composed by two DSSSD, 32 strips for each side, 300 and 1500 μ m thick, with a total surface of 64x64 mm 2 . These DSSSD are followed by four CsI(Tl) detectors with a surface of 32x32 mm 2 each one, 6 cm thick, with photo-diode readout, for the de- tection of light particles. The two stages of silicon detectors guarantee a much better energy resolution than CHIMERA telescopes. Also the angular resolution will be much better, due to the 2x2 mm 2 size of the detection pixels. Also the CsI(Tl), due to the smaller size, and the better doping uni- formity, have an energy resolution improved respect to CHIMERA CsI(Tl). Moreover, due to the DSSSD pixellation, we can correct for position de- pendence of CsI(Tl) light response, so further improving energy resolution. This will allow to study, with very good accuracy, excited levels of 10 Be or
Show more

7 Read more

Synthesis and photophysical studies of porphyrin arrays

Synthesis and photophysical studies of porphyrin arrays

Electronic energy transfer (EET) or Förster resonance energy transfer (FRET) mechanism was implied in the explanation of energy donor-acceptor system associated in photosynthetic system. The excited donor usually generates exciton and interacts coulombically to an acceptor either through bond or space. The general requirements for excitation energy transfer between a donor and an acceptor are: (i) the energy of donor excited state should be higher than that of acceptor excited state and (ii) the rate of energy transfer should be more rapid than the decay rate of the donor excited state (Ayyappanpillai et al., 2008). In this study, the donor-acceptor systems were introduced based on extended conjugation of porphyrins via diphenylacetylene linkers to generate promising energy transfer efficiency within the porphyrinic oligomers. Covalently sp meso-meso linked porphyrin conjugated systems were reported as the essential π-overlapping connections for more effective electron and energy transmission (Ambroise et al., 2000; Yu and Lindsey, 2001). The light harvesting fluorenone pendants also acted as the energy donating groups transferred the energy towards porphyrins and methoxy or methylbenzoate porphyrin acceptors through the diphenylacetylene bonds.
Show more

76 Read more

The Synthesis of Arylsulfonylphthalimides and Their Reactions with Several Amines in Acetonitrile

The Synthesis of Arylsulfonylphthalimides and Their Reactions with Several Amines in Acetonitrile

In this study, several N-(p-substituted-arylsulfonyl)phthalimides (1a-e) were synthesized. The synthesized compounds were then examined with respect to their substitution reactions with t-butylamine, diethylamine, cyclohexylamine, and trans-1,2-diaminocyclohexane in acetonitrile. In order to determine the mechanism, substituent effect, activation entropy, and nucleophile effect were used as criteria.

5 Read more

Sugar Versus the Intuitive Choice of Foods by Livestock.

Sugar Versus the Intuitive Choice of Foods by Livestock.

In light of the observed reactions of the grazing animals to sugar it seems certain that the animals did not eschew the lush, manure-influenced forage plants beca[r]

7 Read more

Download
			
			
				Download PDF

Download Download PDF

The essential feature of the late EP components in the visual analyzer in response to flashes of light is the similarity of their genesis and that of the background slow oscillations in the electroencephalogram (EEG). Such a similarity was suggested long ago (Bishop & Clare, 1952). Experiments using intracellular recording revealed the compliance of background oscillation of single-neuron membrane potential depolarization and hyperpolarization with the alternation of activation and inhibition of neurons firing and with slow EEG waves both in the visual and sensorimotor cortex in animals and humans (Andersen & Anderssson, 1968; Creutzfeldt & Ito, 1968; Creutzfeldt, Watanabe, & Lux, 1966; Jasper & Stefanis, 1965, Morell, 1967; Steriade, 1999, 2001) Statistical analysis also showed that the firing of a considerable part of the neurons in the visual and sensorimotor cortex depended on slow EEG oscillation (Shulgina, 1987). In turn, this dependence was observed in the neurons of the visual field in which alternations of activation and inhibitory pauses in reactions to light flashes coincided with late EP components, which confirmed the concept of the identical genesis of the EEG and the late EP components. Both processes are caused by the alternating of the relative prevalence of depolarization and hyperpolarization of a considerable part of the neurons in the recorded area of the brain cortex. Thus, the results of the study on the genesis of the phase activity of neocortex neurons and of corresponding summary background and evoked SPO allow us to use the dynamics of these indexes of brain activity to study the interaction of inhibitory and activating processes in learning of conscious nonimmobilized animals, using extracellular recording of biopotentials.
Show more

14 Read more

Developing Techniques for High Fidelity Studies of Reactions with Light Weakly Bound Nuclei

Developing Techniques for High Fidelity Studies of Reactions with Light Weakly Bound Nuclei

Following the energy selection magnet, the beam is transported to the target area. The experiment was carried out in the CUBE scattering chamber shown in figure (2.3). This is a multi-purpose vacuum chamber, which is also home to large-area multi- wire proportional counter (MWPC) gas detectors, utilised for fission measurements [102–105]. A selection of up to 7 targets and 1 aperture can be mounted on a multi-target ladder which is computer controlled. A tuning aperture with a central 2 mm hole is placed in the path of the beam, mounted on the hub that holds two double-sided silicon strip detectors (DSSDs), downstream from the target. It serves, when used in combination with a beam current measurement from the beam dump (downstream of CUBE), to allow operators to (a) minimise the beam spot size and (b) maximise its intensity at the centre of the target. Charged breakup fragments were detected using the ‘Breakup Array for Light Nuclei’ (BALiN), a large area position sensitive detector array that consists of four DSSDs, as shown in figure (2.4) (a) and (b).
Show more

223 Read more

Light charged particle production in heavy ion induced fusion fission reactions

Light charged particle production in heavy ion induced fusion fission reactions

data using asp/a eq = 1.0, aeq=A/10.0 MeV-1 and id = 7 0 x l 0 “21 s, or x(j=xss=20xl0~21 s or xss=30xl0-21 s. Gavron et al. [GAV87] have measured Vpre for 158Er formed with a range of beams from 160 to 50Ti. Grange et al. [GRA86] have analysed the reaction 160 + 142Nd -> 158Er at 207 MeV, where 2.7±0.4 neutrons prior to scission were measured [GAV87] compared to 1.6 neutrons calculated with a standard statistical model. This result suggests a value of ß <, 5 x l0 21 s-1, which implies a value of the transient time x <, 20xl0-21 s and a saddle-to-scission time xss < 5xl0~21 s. The 24Mg and 32S induced reactions exclude the region of low ß and indicate a value of ß ~ 6 x l0 21 s-1 [GAV87], a value 2-3 times that required for critical damping. Hinde et al. [HIN89] claimed that the multiplicities of [GAV87] are too low, and made a new measurement for the reaction of 178 MeV 160 + 142Nd which resulted in a vpre of 3.95±0.30, considerably higher than the 207 MeV result of Gavron et al. This new result leads to much longer transient and saddle-to-scission times and a higher value of the reduced frictional constant than concluded from the measurements of [GAV87].
Show more

156 Read more

Expected impact from weak reactions with light nuclei in corecollapse supernova simulations

Expected impact from weak reactions with light nuclei in corecollapse supernova simulations

The simulations are launched from a 11.2 M progenitor [36]. It was evolved consistently though core collapse, bounce and post bounce phases using the EOS HS(DD2), taking fully into account light nuclear clusters. We compare results from two simulations, i.e. with and without including weak rates with light clusters based on the selection given in the right panel of Table 1. In general, the post bounce phase of core-collapse supernovae is determined from mass accretion from the still

7 Read more

New Schiff Base Fluorescent Chemosensors for Metals: Synthesis Characterization and Applications

New Schiff Base Fluorescent Chemosensors for Metals: Synthesis Characterization and Applications

In the case of electron transfer (ET) between organic donors and recipients, the Marcus theory is very close to satisfying these requirements. Within the classic (simplified) framework, the activation energy (AGe*t) of the electron transfer depends on the driving force (-AGet) and the reorganization energy. Excited state of the Transferred Proton Excited state intramolecular proton transfer (E.S.I.P.T) reactions occur when the acidity and basicity of groups on the same molecule are sufficiently enhanced by excitation to allow proton transfer between these sites. Most studies have been conducted on proton transfers between hetero atomes, although E.S.I.P.Ts to carbon atoms (alkenyl or alkynyl) have been reported, resulting in new and predictable products.
Show more

13 Read more

π0 production in dC- and dCu-interactions at a momentum of 4.5 GeV/c per nucleon

π0 production in dC- and dCu-interactions at a momentum of 4.5 GeV/c per nucleon

the each event. The combinatorial invariant mass spectra of the γγ combinations, selected according to the criteria (1) ÷ (3) for the dC and dCu reactions, are shown in figure 1 (light color histograms). The dark color histograms in figure 1 represent the invariant mass distributions for γγ combinations selected accidentally from di ff erent events. These combinatorial distributions, so-called "events mix- ing" were used to determine the background. The dashed line on the dC histogram indicates the invariant mass spectrum of γγ pairs from a Monte Carlo simulation (for details, see [6]).
Show more

6 Read more

395G Exam 3 11 Dec 2002

395G Exam 3 11 Dec 2002

Light absorption by PSI and PSII causes excitation of an electron to its singlet state. Electron is ejected and it enters electron transport chain . Protons are pumped during electron transport through the cytochrome bf complex to produce a proton gradient across the thylakoid membrane, This protonmotive force provides energy for ATP synthesis via ATP synthase. The electrons eventually flow to reduce NADP + to NADPH .

7 Read more

Chemical Reactions Students use the scientific method to explore a set of chemical reactions and discover how organisms use chemistry to survive.

Chemical Reactions Students use the scientific method to explore a set of chemical reactions and discover how organisms use chemistry to survive.

In many biological processes, molecules must be taken apart to form new molecules. When the bonds holding atoms in the molecule are broken, energy is often released in the form of heat. When more heat is released than it takes to break up the molecules, the processes is called exothermic. When chemical reactions take in heat instead, they are called

7 Read more

Electron transfer reactions : KOtBu (but not NaOtBu) photoreduces benzophenone under activation by visible light

Electron transfer reactions : KOtBu (but not NaOtBu) photoreduces benzophenone under activation by visible light

All reagents were purchased from commercial sources and used without further purification, except where stated. Anhydrous diethyl ether, tetrahydrofuran, dichloromethane and hexane were dried using a Pure-Solv 400 solvent purification system (Innovative Technology Inc., U.S.A.). Tetrahydrofuran was further distilled over sodium “wire” using benzophenone as indicator using a still. The distilled THF was used for all the ketyl radical development. Anhydrous benzene was purchased from Sigma Aldrich and dried over 3Å molecular sieves, previously activated by microwave heating. Thin layer chromatography analyses were carried out on silica gel pre-coated aluminum foil sheets and were visualized using UV light (254 nm). Flash column chromatography was carried out using slurry packed silica gel (SiO 2 ),
Show more

122 Read more

Show all 10000 documents...