scholarly journals The interaction and photostability of some xanthenes and selected azo sensitizing dyes withTiO2nanoparticles

2005 ◽  
Vol 7 (2) ◽  
pp. 95-101 ◽  
Author(s):  
D. EL Mekkawi ◽  
M. S. A. Abdel-Mottaleb
Keyword(s):  
Reduction Potential ◽  
Organic Dyes ◽  
Action Spectrum ◽  
Surface Complexes ◽  
Alizarin Yellow ◽  
Semiconductor Thin Films ◽  
Rhodamine 101 ◽  
Apparent Association Constants ◽  
Apparent Association ◽  
Absorption Measurements

We have tested simple Graetzel-type solar cells using semiconductor thin films consisting ofTiO2nanoparticles and some electron injecting dyes. The possibility of using xanthenes (rhodamine 101, fluorescein and 5(6)-carboxyfluorescein) and selected azo dyes (alizarin yellowR, alizarin yellow 2G and carboxyaesenazo) as sensitizers has been explored. Fluorescence and electronic absorption measurements revealed complex formation between the chosen dyes and the surface of the colloidalTiO2. The apparent association constants (Kapp) of the surface complexes have been estimated and are correlated with the dyeinduced negative shifts of the reduction potential of colloidalTiO2nanoparticles. Moreover, due to its utmost importance, photostability of the organic dyes in absence and presence of colloidalTiO2nanoparticles and the influence of the used electrolyte have been examined. The results point to a remarkable enhancement of photostability in the presence of the electrolyte (I3−/I−), which is attributed to fast regeneration of the neutral dye via the redox couple of the electrolyte. Furthermore, photocurrent action spectrum of the fabricated and tested DSC shows the origin of photoelectric output to be optical absorption of the dye used.

Potassium, sodium, water, and Donnan potential changes in the myofibrils of intact muscle fibres after exposure to ouabain and K-free Ringer

1988 ◽  
Vol 66 (8) ◽  
pp. 1057-1065
Author(s):  
C. N. Fong ◽  
J. A. M. Hinke
Keyword(s):  
Water Content ◽  
Compartment Model ◽  
Muscle Fibres ◽  
Donnan Potential ◽  
Two Compartment Model ◽  
Free Treatment ◽  
Intact Muscle ◽  
Frog Sartorius ◽  
Apparent Association Constants ◽  
Apparent Association

Frog sartorius muscles were superfused for 40 min with solutions of K-free Ringer, normal Ringer containing ouabain, or K-free Ringer containing ouabain. Changes in myoplasmic K and Na were measured with ion-selective microelectrodes; changes in total fibre K and Na were measured by means of atomic absorption spectroscopy; and changes in total fibre water content were obtained from wet and dry weights. Application of a two-compartment model permitted one to calculate (i) the K, Na, and water changes in the myofibrils and in the surrounding myoplasm (extramyofibrillar space); (ii) the changes in the transmyofibrillar Donnan potential (ED); and (iii) the changes in the ratio of the apparent association constants (kNa/kK) of the myofilament charge sites to Na and K. In the resting fibres, the K, Na, and water content of the myofibrils were calculated to be 82, 87, and 80% of total fibre content, respectively; ED was calculated as −4.5 mV; kNa/kK was calculated as 1.4. After a 40-min ouabain treatment, 12 mmol (per kg fibre water) of intrafibre K exchanged with 7.5 mmol of extrafibre Na, 6.4 mmol of myofibrillar K exchanged with an equal amount of extramyofibrillar Na, ED increased to −8.3 mV, and kNa/kK remained relatively constant. After a 40-min K-free treatment, the fibres gained 5.5 mmol of Na without any change in fibre K or water, the myofibrils shifted 9.3% of their water into the extramyofibrillar space instead of exchanging K for Na, ED increased to −10.7 mV, and kNa/kK decreased to 0.47. When ouabain and zero K were combined, an equimolar transmembrane K for Na exchange occurred, the myofibrils appeared to shift water and to exchange K for Na, ED increased to −14.3 mV, and kNa/kK decreased to 0.63. Analyses of other experiments involving Na-free superfusions suggest that the zero K-induced intrafibre water shift is dependent on an uncompensated net accumulation of Na in the extramyofibrillar myoplasm. These results indicate that the myofibrils in the intact fibre may adjust their water and electrolyte content quite differently during different perturbations, and that the myofibrillar changes need not mimic the whole fibre water and electrolyte changes.

scholarly journals Association of neutral red with micelles and its effect on the pKa

1993 ◽  
Vol 71 (11) ◽  
pp. 1785-1791 ◽  
Author(s):  
Robin K. Dutta ◽  
Subray N. Bhat
Keyword(s):  
Equilibrium Constants ◽  
Sodium Dodecyl ◽  
Surfactant Solution ◽  
Neutral Red ◽  
Association Constants ◽  
Alkyltrimethylammonium Bromides ◽  
Surfactant Solutions ◽  
Constant Ph ◽  
Apparent Association Constants ◽  
Apparent Association

The interactions of neutral red with cationic surfactants, viz., N-hexadecylpyridinium chloride and alkyltrimethylammonium bromides; a nonionic surfactant, viz., Triton X100; and an anionic surfactant, viz., sodium dodecyl sulfate, were investigated spectroscopically. The equilibrium constants for the association of the indicator with the micelles were determined from the apparent association constants at constant pH at 298 K. The effects of the indicator-micelle association on the apparent pKa of the indicator in aqueous surfactant solutions are discussed. It was shown that the apparent pKa of the indicator in cationic surfactant solution can be predicted from knowledge of the indicator-micelle association constant.

Cadmium transport in blood serum

2010 ◽  
Vol 26 (4) ◽  
pp. 195-201 ◽  
Author(s):  
Amir Shokooh Saljooghi ◽  
SJ Fatemi
Keyword(s):  
Human Serum ◽  
Association Constants ◽  
Appreciable Amount ◽  
Binding Assays ◽  
Molar Ratios ◽  
Cadmium Transport ◽  
Decreasing Ph ◽  
Ethanesulfonic Acid ◽  
Apparent Association Constants ◽  
Apparent Association

The binding of Cd2+ to human serum transferrin in 0.1 M N-(2-hydroxyethyl) piperazine-N ′-2-ethanesulfonic acid and 5 mM sodium bicarbonate at pH 7.4 has been studied by difference ultraviolet spectrophotometry. The apparent association constants were found to be 2.61 × 105 M —1 and 8.51 × 104M— 1, respectively. These association constants are pH-dependent, reducing with both increasing and decreasing pH. The apparent pKa values were found to be 4.93 and 5.42. Competitive assays of binding of Cd2+ to transferrin in the presence of citrate and human serum albumin at molar ratios corresponding to those found in normal plasma showed that a considerable amount of Cd2+ was not bound to transferrin. The competitive binding assays indicate that ∼50% of Cd2+ is bound to transferrin, ∼37% to albumin and reminder to citrate. These results therefore suggest that, although transferrin at pH 7.4 is the major Cd 2+-binding component of plasma, an appreciable amount of Cd2+ may be bound to albumin.

scholarly journals Carbohydrate-structure-dependent recognition of desialylated serum glycoproteins in the liver and leucocytes. Two complementary systems

1985 ◽  
Vol 227 (2) ◽  
pp. 345-354 ◽  
Author(s):  
K Bezouska ◽  
O Táborský ◽  
J Kubrycht ◽  
M Pospísil ◽  
J Kocourek
Keyword(s):  
Plasma Membranes ◽  
Recognition System ◽  
Carbohydrate Structure ◽  
Pathological Conditions ◽  
Different Types ◽  
Recognition Systems ◽  
Specificity Pattern ◽  
Apparent Association Constants ◽  
Reversed Order ◽  
Apparent Association

Oligosaccharides with four different types of branching were prepared from purified human transferrin, alpha 2-macroglobulin, caeruloplasmin and alpha 1-acid glycoprotein and labelled with NaBH3 3H. Binding of these oligosaccharides to rat liver plasma membrane, rat leucocytes, pig liver plasma membranes and pig leucocyte plasma membranes was investigated. A striking dependence of binding on oligosaccharide branching was observed. The values of apparent association constants Ka at 4 degrees C vary from 10(6) M-1 (biantennary structure) to 10(9) M-1 (tetra-antennary structure) in the liver, whereas in the leucocytes the Ka values were found to be of reversed order, from 1.8 × 10(9) M-1 for biantennary to 2.2 × 10(6) M-1 for tetra-antennary structures. The binding is completely inhibited by 150 mM-D-galactose, but 150 mM-D-mannose has almost no effect on binding. Leucocyte plasma membranes bind preferentially 125I-asialoglycoproteins with biantennary oligosaccharides, thus completing the specificity pattern of the hepatic recognition system for desialylated glycoproteins. Possible physiological roles of these two complementary recognition systems under normal and pathological conditions are discussed.

Molecularly Imprinted Polymers (MIPs) Against Uracils: Functional Monomer Design, Monomer-Template Interactions In Solution And MIP Performance In Chromatography

2002 ◽  
Vol 723 ◽  
Author(s):  
Andrew J. Hall ◽  
Panagiotis Manesiotis ◽  
Jakob T. Mossing ◽  
Börje Sellergren
Keyword(s):  
Molecularly Imprinted Polymers ◽  
Chloroform Solution ◽  
The Novel ◽  
Molecularly Imprinted ◽  
Functional Monomers ◽  
H Nmr ◽  
Recognition Elements ◽  
Substituted Uracils ◽  
Apparent Association Constants ◽  
Apparent Association

AbstractThe interaction of N1-substituted uracils (cyclohexyl (1) and benzyl (2)) with three polymerisable recognition elements, the novel monomers 9-(3/4-vinylbenzyl)adenine (3) and 2,6-diamino-9-(3/4-vinylbenzyl)purine (4) and the previously synthesised monomer 2,6-bis(acrylamido)pyridine (5), has been studied via1H NMR in deuterio-chloroform solution. MIPs against (2) have been prepared using each of the monomers and tested in the chromatographic mode. The effect of the number and type of hydrogen bonds formed between the templates and the functional monomers is reflected in the values of the apparent association constants obtained from the solution study and by the performance of the subsequently prepared MIPs in the chromatographic mode.

scholarly journals Aluminium transport in blood serum. Binding of aluminium by human transferrin in the presence of human albumin and citrate

1991 ◽  
Vol 280 (2) ◽  
pp. 527-532 ◽  
Author(s):  
S J Fatemi ◽  
F H A Kadir ◽  
G R Moore
Keyword(s):  
Human Serum ◽  
Human Albumin ◽  
Association Constants ◽  
Appreciable Amount ◽  
Competitive Binding Assay ◽  
Molar Ratios ◽  
Decreasing Ph ◽  
Apparent Association Constants ◽  
Apparent Association ◽  
Binding Component

The binding of Al3+ by human serum transferrin has been investigated by u.v.-visible difference spectroscopy. In the presence of 25 mM-HCO3- at pH 7.4, the apparent association constants were found to be 1.69 x 10(12) M-1 and 5.36 x 10(11) M-1. These association constants are pH-dependent, reducing with both increasing and decreasing pH. The apparent pKa values were found to be 6.7 and 8.2. Competitive assays of binding of Al3+ to transferrin in the presence of citrate and human serum albumin at molar ratios corresponding to those found in normal plasma showed that a considerable amount of Al3+ was not bound to transferrin. Taking a concentration of 5 microM as a typical value observed for the plasma of patients on haemodialysis [Harris & Sheldon (1990) Inorg. Chem. 29, 119-124] the competitive binding assay indicate that approximately 60% of it is bound to transferrin, approximately 34% to albumin and the remainder to citrate. These results therefore suggest that, although transferrin at pH 7.4 is the major Al(3+)-binding component of plasma, an appreciable amount of Al3+ present in patients on haemodialysis may be bound to albumin.

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