Adsorption of Amines to Thylakoid Surfaces and Estimations of ΔpH

1985 ◽  
Vol 12 (1) ◽  
pp. 9 ◽  
Author(s):  
AB Hope ◽  
DB Matthews
Keyword(s):  
Steady State ◽  
Fluorescence Quenching ◽  
Binding Constant ◽  
Protonated Form ◽  
Proton Motive Force ◽  
Amine Concentration ◽  
Apparent Binding Constant ◽  
Mgcl2 Concentration ◽  
A Charge ◽  
Good Agreement

The adsorption of the fluorescent, weak amine ΔpH indicators 9-aminoacridine and N-(1-naphthyl)ethylenediamine to thylakoids of pea chloroplasts in the dark was measured as a function of amine concentration, at several pH's between 8 and 5, and with varied MgCl2 concentration. It was concluded that it was the protonated form of the amine that was adsorbed. Maximum amounts adsorbed, saturation occurring at about 1 mM amine concentration in the presence of 5 mM KCl and 10 mM MgCl2, were up to 1 mol (mol Chl)-1. This was calculated as exceeding the number of available surface negative charges (0.26 for a charge density of 0.025 C m-2). An apparent binding constant of 400-500 μM (concentration for half saturation) was noted for both amines under the above conditions. A model was developed that enabled the estimation of the relative amounts of amine bound to the inside and outside thylakoid surfaces in the steady state, in the light. By this means corrections to the apparent ΔpH calculated from fluorescence quenching of the amines could be established. These corrections amounted to about 1 pH unit for the diamine and more for 9-aminoacridine. The predictions of the model were in good agreement with experimental relations between estimated, light-induced ΔpH values and amine concentration. The implications of a lower ΔpH for earlier estimations of proton motive force in relation to photophosphorylation are briefly considered.

The Investigation of the Interaction between Daidzin and Bovine Serum Albumin by Fluorescence Spectroscopy

2014 ◽  
Vol 664 ◽  
pp. 402-409
Author(s):  
Qing Ming Wang ◽  
Jia Liu ◽  
Tian Xing Zhang ◽  
Feng Zhu ◽  
Xin Hui Tang
Keyword(s):  
Bovine Serum Albumin ◽  
Hydrogen Bonds ◽  
Fluorescence Quenching ◽  
Fluorescence Spectroscopy ◽  
Serum Albumin ◽  
Binding Constant ◽  
Bovine Serum ◽  
Hydrophobic Interactions ◽  
Binding Constants ◽  
Apparent Binding Constant

We investigated the mutual interaction of daidzin with bovine serum albumin (BSA) by fluorescence spectroscopy. The results revealed that daidzin cause the fluorescence quenching of BSA through a static quenching procedure. The Stern-Volmer quenching constant (Ksv) were calculated at different temperature. The binding site (n), apparent binding constant (Ka) and corresponding thermodynamic parameters △Go, △Ho, △Sowere calculated and the van der Waals interaction, hydrogen bonds and hydrophobic interactions play an important role in stabilizing the complex. Besides, we also studied the effect of Cu2+, Ni2+, Mn2+and Co2+on the binding constants between daidzin and BSA, it is shows that the binding of BSA and daidzin is strengthened in the presence metal ions.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

Analytical approach for transient photoconductivity in undoped a-Si:H

1995 ◽  
Vol 377 ◽  
Author(s):  
M. Goerlitzer ◽  
P. Pipoz ◽  
H. Beck ◽  
N. Wyrsch ◽  
A. V. Shah
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Analytical Approach ◽  
Room Temperature ◽  
Free Electrons ◽  
Recombination Time ◽  
Sample Quality ◽  
Transient Photoconductivity ◽  
Light Intensities ◽  
Good Agreement

ABSTRACTTransient photoconductive response of undoped a-Si:H has been studied; the changes were analysed between two slightly different steady-state illumination conditions, at room temperature. A theoretical model is developed to describe transient photoconductivity; it yields good agreement with the measured curves for a whole range of light intensities. Numerical evaluations allows one to extract the recombination time of electrons. Comparison with steady-state photoconductivity yields a band mobility of free electrons between 0.1 and 6 cm2V−1s−1, depending upon sample quality.

Steady-State stress distributions in circumferentially notched bars subjected to creep

1982 ◽  
Vol 17 (3) ◽  
pp. 123-132 ◽  
Author(s):  
K D Al-Faddagh ◽  
R T Fenner ◽  
G A Webster
Keyword(s):  
Steady State ◽  
Stress Distribution ◽  
Stress Index ◽  
Stress Distributions ◽  
Computer Solution ◽  
Time Intervals ◽  
Throat Region ◽  
Intermediate Time ◽  
State Stress ◽  
Good Agreement

The paper describes a procedure, based on a finite element method, for calculating directly the steady-state stress distribution in circumferentially notched bars subjected to creep without the need for obtaining solutions at intermediate time intervals. Good agreement is obtained with relevant approximate plasticity solutions and with numerical calculations which approach the steady-state over a period of time from the initial elastic stress distribution. Also, the procedure is equally applicable to primary, secondary, and tertiary creep, provided the variables of stress and time are separable in the creep law. Results obtained for a range of notch geometries and values of the stress index, n, are reported. It is found for each profile that a region of approximately constant effective stress, σ, independent of n, is obtained which can be used to characterise the overall behaviour of the notch throat region when a steady-state is reached sufficiently early in life. An approximate method for estimating the maximum equivalent steady-state stress across the notch throat is also presented which does not require a computer solution.

Coupling of Sloshing and Ship Motions

2003 ◽  
Vol 47 (03) ◽  
pp. 208-221 ◽  
Author(s):  
Olav F. Rognebakke ◽  
Odd M. Faltinsen
Keyword(s):  
Steady State ◽  
Transient Behavior ◽  
Frequency Domain Analysis ◽  
Ship Motions ◽  
Steady State Motion ◽  
Constant Coefficients ◽  
Incident Waves ◽  
Violent Sloshing ◽  
Different Levels ◽  
Good Agreement

The coupled effect between ship motions and sloshing is studied. Two-dimensional experiments of a hull section containing tanks filled with different levels of water excited in sway by regular waves have been conducted. Steady-state results are obtained for the sway amplitude. Even if violent sloshing occurs in the tanks, the steady-state motion is almost linear and sinusoidal with the frequency of the linear incident waves. This implies that higher-order harmonics of the sloshing force are filtered out by the system. Simulations of the modeled case are performed using a linear and a nonlinear sloshing model and mainly assuming linear external flow. For steady-state motion, a convolution formulation does not improve the results relative to using constant coefficients in the equation of motion. However, in order to properly model the transient behavior in an irregular sea, a convolution formulation must be included. The treatment of the retardation function for the external problem is discussed in detail. A good agreement between experiments and computations is reported. The calculated coupled motion is sensitive to the damping of the sloshing motion in a certain frequency range where the coupled sloshing and ship motions cause resonant ship motions. A quasilinear frequency domain analysis is used to explain this by introducing the sloshing loads as a frequency dependent spring.

Nitrite in Meat Products Determined by Fluorescence Quenching of p-Aminobenzoate Ion

1976 ◽  
Vol 59 (4) ◽  
pp. 783-786
Author(s):  
Elia D Coppola ◽  
Alphonse F Wickroski ◽  
J Gordon Hanna
Keyword(s):  
Fluorescence Quenching ◽  
Colorimetric Method ◽  
Meat Products ◽  
Aminobenzoic Acid ◽  
Average Difference ◽  
Fluorometric Method ◽  
Medium Ph ◽  
Standard Curve ◽  
Meat Samples ◽  
Good Agreement

Abstract A direct fluorometric method is presented for determining nitrites in meat products by means of quenching. The extracted sodium nitrite is consumed in a diazotization reaction with a measured excess of the fluorescent reagent p-aminobenzoic acid (PABA) in boiling water and at pH ≤1.4. The amount of decrease in fluorescence (quenching) of PABA, in alkaline medium (pH 11.0) with excitation at 265 nm and fluorescence at 339 nm, is directly related to the amount of nitrite present. The slope for the standard curve is 1 % decrease in relative fluorescence intensity per 2.76 ppm NaNO2. Results obtained for a series of 20 meat samples analyzed by this fluorometric method are in good agreement with results obtained by a colorimetric method with an average difference of ±6.1 ppm NaNO2.

scholarly journals Investigation of 1-Methylcytosine as a Ligand in Gold(III) Complexes: Synthesis and Protein Interactions

Inorganics ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 1 ◽  
Author(s):  
James Beaton ◽  
Nicholas Farrell
Keyword(s):  
Fluorescence Quenching ◽  
Zinc Finger ◽  
Protein Interactions ◽  
Nucleocapsid Protein ◽  
1H Nmr Spectroscopy ◽  
Ionization Mass ◽  
Target Interaction ◽  
Self Association ◽  
A Charge ◽  
First Time

The HIV nucleocapsid protein NCp7 was previously shown to play a number of roles in the viral life cycle and was previously identified as a potential target for small molecule intervention. In this work, the synthesis of the previously unreported complexes [Au(dien)(1MeCyt)]3+, [Au(N-Medien)(1MeCyt)]3+, and [Au(dien)(Cyt)]3+ is detailed, and the interactions of these complexes with the models for NCp7 are described. The affinity for these complexes with the target interaction site, the “essential” tryptophan of the C-terminal zinc finger motif of NCp7, was investigated through the use of a fluorescence quenching assay and by 1H-NMR spectroscopy. The association of [Au(dien)(1MeCyt)]3+ as determined through fluorescence quenching is intermediate between the previously reported DMAP and 9-EtGua analogs, while the associations of [Au(N-Medien)(1MeCyt)]3+ and [Au(dien)(Cyt)]3+ are lower than the previously reported complexes. Additionally, NMR investigation shows that the self-association of relevant compounds is negligible. The specifics of the interaction with the C-terminal zinc finger were investigated by circular dichroism spectroscopy and electrospray-ionization mass spectrometry. The interaction is complete nearly immediately upon mixing, and the formation of AuxFn+ (x = 1, 2, or 4; F = apopeptide) concomitant with the loss of all ligands is observed. Additionally, oxidized dimerized peptide was observed for the first time as a product, indicating a reaction via a charge transfer mechanism.

scholarly journals Liquid Brine in Ice Shelves

1975 ◽  
Vol 14 (70) ◽  
pp. 125-136 ◽  
Author(s):  
R. H. Thomas
Keyword(s):  
Steady State ◽  
Heat Transport ◽  
Thermal Equilibrium ◽  
Transport Model ◽  
Percolation Model ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Brine Layer ◽  
Good Agreement

Holes drilled into thin areas of the Brunt Ice Shelf encounter a layer of liquid brine less than 1 m thick approximately at sea-level. Assuming the brine to be moving horizontally, analysis of its effects on thermal equilibrium gives an estimate of steady-state annual brine flow that is in good agreement with the value deduced from a percolation model. The effect of firn density on percolation rates is such that the slope of an active brine layer increases rapidly as ice thickness increases. However, the heat transport model predicts that brine layers are unlikely to be active in both very thick and very thin ice shelves.

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