scholarly journals The formation of pyridine haemochromogen

1965 ◽  
Vol 97 (1) ◽  
pp. 187-193 ◽  
Author(s):  
WA Gallagher ◽  
WB Elliott
Keyword(s):  
Ionic Strength ◽  
Aqueous Medium ◽  
Spectral Properties ◽  
Graphical Analysis ◽  
Alkaline Media ◽  
Compound I ◽  
Low Concentrations ◽  
Compound Ii ◽  
Low Ionic Strength ◽  
Hydrophobic Bonding

1. Titration of haem with pyridine in alkaline media of low ionic strength yields a true pyridine haemochromogen, compound III, at very low concentrations of pyridine. 2. Graphical analysis of this titration gives the first spectrophotometric evidence for a dimeric haem. 3. Compound III is unstable and tends to aggregate to a second compound, compound II, whose formation is enhanced under those conditions favourable to hydrophobic bonding. 4. At higher concentrations of pyridine, compound II is dispersed to yield the classical pyridine haemochromogen, compound I, whose spectral properties are essentially those of pyridine haemochromogen in a non-aqueous medium.

scholarly journals Affinity chromatography of immobilized actin and myosin

1975 ◽  
Vol 149 (2) ◽  
pp. 365-379 ◽  
Author(s):  
R C Bottomley ◽  
I P Trayer
Keyword(s):  
Ionic Strength ◽  
Salt Concentration ◽  
Free Solution ◽  
Heavy Meromyosin ◽  
Chemical Modifications ◽  
Low Concentrations ◽  
Myosin Subfragment ◽  
Myosin Subfragment 1 ◽  
One Step ◽  
Low Ionic Strength

Actin and myosin were immobilized by coupling them to agarose matrices. Both immobilized G-actin and immobilized myosin retain most of the properties of the proteins in free solution and are reliable over long periods of time. Sepharose-F-actin, under the conditions used in this study, has proved unstable and variable in its properties. Sepharose-G-actin columns were used to bind heavy meromyosin and myosin subfragment 1 specifically and reversibly. The interaction involved is sensitive to variation in ionic strength, such that myosin itself is not retained by the columns at the high salt concentration required for its complete solubilization. Myosin, rendered soluble at low ionic strength by polyalanylation, will interact successfully with the immobilized actin. The latter can distinguish between active and inactive fractions of the proteolytic and polyalanyl myosin derivatives, and was used in the preparation of these molecules. The complexes formed between the myosin derivatives and Sepharose-G-actin can be dissociated by low concentrations of ATP, ADP and pyrophosphate in both the presence and the absence of Mg2+. The G-actin columns were used to evaluate the results of chemical modifications of myosin subfragments on their interactions with actin. F-Actin in free solution is bound specifically and reversibly to columns of insolubilized myosin. Thus, with elution by either ATP or pyrophosphate, actin has been purified in one step from extracts of acetone-dried muscle powder.

Viscosimetric studies of chitosan nitrate and chitosan chlorhydrate in acid free NaCl aqueous solution

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Cristóbal Lárez Velásquez ◽  
Joel Sánchez Albornoz ◽  
Enrique Millán Barrios
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Aqueous Solutions ◽  
Aqueous Medium ◽  
Intrinsic Viscosity ◽  
Free Acid ◽  
Film Formation ◽  
Stiffness Parameter ◽  
Low Ionic Strength

AbstractTwo salts of the biopolymer chitosan were prepared in aqueous medium by employing an excess of HCl or HNO3 in order to ensure neutralization of all NH2-chitosan groups. Chitosan salts were extensively dialyzed in dionised water and dried at 40 ºC until film formation. The films were characterized by thermogravimetry, FTIR and conductimetric tritration. QH+Cl− and QH+NO3− salts were viscosimetrically evaluated in free acid aqueous solutions in the presence of NaCl to control ionic strength of the medium. Unexpected high intrinsic viscosity values were obtained at low ionic strength when QH+NO3− salt were evaluated. Smidsrod´s approach was employed to estimate the stiffness parameter of both salts and B = 0.084 and 0.120 for QH+Cl− and QH+NO3−, respectively, were obtained.

scholarly journals Mechanism of nitrite oxidation by eosinophil peroxidase: implications for oxidant production and nitration by eosinophils

2006 ◽  
Vol 394 (3) ◽  
pp. 707-713 ◽  
Author(s):  
Christine J. van Dalen ◽  
Christine C. Winterbourn ◽  
Anthony J. Kettle
Keyword(s):  
Nitrogen Dioxide ◽  
Active Site ◽  
Tissue Injury ◽  
Spectral Studies ◽  
Compound I ◽  
Eosinophil Peroxidase ◽  
Hypohalous Acids ◽  
Low Concentrations ◽  
Oxidant Production ◽  
Compound Ii

Eosinophil peroxidase is a haem enzyme of eosinophils that is implicated in oxidative tissue injury in asthma. It uses hydrogen peroxide to oxidize thiocyanate and bromide to their respective hypohalous acids. Nitrite is also a substrate for eosinophil peroxidase. We have investigated the mechanisms by which the enzyme oxidizes nitrite. Nitrite was very effective at inhibiting hypothiocyanous acid (‘cyanosulphenic acid’) and hypobromous acid production. Spectral studies showed that nitrite reduced the enzyme to its compound II form, which is a redox intermediate containing FeIV in the haem active site. Compound II does not oxidize thiocyanate or bromide. These results demonstrate that nitrite is readily oxidized by compound I, which contains FeV at the active site. However, it reacts more slowly with compound II. The observed rate constant for reduction of compound II by nitrite was determined to be 5.6×103 M−1·s−1. Eosinophils were at least 4-fold more effective at promoting nitration of a heptapeptide than neutrophils. This result is explained by our finding that nitrite reacts 10-fold faster with compound II of eosinophil peroxidase than with the analogous redox intermediate of myeloperoxidase. Nitration by eosinophils was increased 3-fold by superoxide dismutase, which indicates that superoxide interferes with nitration. We propose that at sites of eosinophilic inflammation, low concentrations of nitrite will retard oxidant production by eosinophil peroxidase, whereas at higher concentrations nitrogen dioxide will be a major oxidant formed by these cells. The efficiency of protein nitration will be decreased by the diffusion-controlled reaction of superoxide with nitrogen dioxide.

scholarly journals The Passive Permeability of the Red Blood Cell to Cations

1966 ◽  
Vol 50 (1) ◽  
pp. 171-188 ◽  
Author(s):  
Paul L. LaCelle ◽  
Aser Rothstein
Keyword(s):  
Ionic Strength ◽  
Inflection Point ◽  
Ph Effect ◽  
Human Red Blood Cells ◽  
Low Concentrations ◽  
Goldman Equation ◽  
Low Ionic Strength ◽  
Straight Lines ◽  
The Relationship ◽  
Determining Factor

The efflux of salt from human red blood cells suspended in isotonic sucrose plus low concentrations of salt, was measured under steady-state conditions. The relationship between the efflux and the log of the salt concentration can be fitted by two straight lines with a sharp inflection point, the steeper slope occurring at concentrations below 0.2 mM NaCl. The determining factor in the rate of efflux is the ionic strength rather than the specific monovalent cations or anions and the effects are completely reversible. With an increase in temperature, the effects of reduced ionic strength are more pronounced and the inflection point is shifted toward higher salt concentrations. An increase in pH leads to an increased efflux at a given ionic strength, but the size of the pH effect is small at low ionic strength. At a given pH, the data can be fitted by a simplified form of the Goldman equation suggesting that with reduction in ionic strength, the permeability remains constant until the inflection point is reached. At that ionic strength, a sharp reversible transition to a new permeability state occurs. The permeability increases with an increase in the external but not the internal pH.

Modulation Of Adenylate Cyclase Activity In Platelets By β2-Glycoprotein I

1981 ◽  
Author(s):  
Inger Schousboe
Keyword(s):  
Ionic Strength ◽  
Adenylate Cyclase ◽  
Human Serum ◽  
Human Platelets ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Glycoprotein I ◽  
Low Concentrations ◽  
Low Ionic Strength

β2GlycoProtein I, purified from human serum, has been shown to bind to negatively charged phospholipids. Such phospholipids axe essential reactants in several surface mediated reactions. In blood coagulation, platelets, to which β2-glycoprotein I recently has been shown to bind, furnish a major portion of these phospholipids. Concomitant with this binding, a change in platelet adenylate cyclase activity has been observed. The purpose of this study is to further investigate the effect of β2-glycoprotein I on the adenylate cyclase activity in platelets.Human platelets isolated immediately after bleeding were washed in buffered isotonic solutions at low ionic strength. At 0 °C intact or sonicated platelets were incubated with various concentrations of β2-glycoprotein I and prostaglandin E1xs. Intact platelets were then sonicated, platelet membranes isolated and frozen at -180 °C, and adenylate cyclase activity of the membranes determined.The results showed that adenylate cyclase activity in platelets increases about 4 times when intact platelets are preincubated with β2-glycoprotein I at saturation. This increase is also seen when low concentrations of PGE1 (≤ lµM) are present in the preincubation mixture. There was no increase in adenylate cyclase activity when sonicated platelets were incubated with β2-glycoprotein I.On the basis of these results it is suggested that in vivo β2-glycoprotein I may have one or both of the following functions, l) It may prevent circulating platelets from aggregation by protecting the negatively charged phospholipids and/or by increasing the adenylate cyclase activity and 2) it may catalyze the deaggregation of aggregated platelets.

Isolation of Antithrombin Globulin from Human Blood Plasma

1960 ◽  
Vol 4 (01) ◽  
pp. 017-030
Author(s):  
George Y. Shinowara ◽  
Dimite J. Buckley
Keyword(s):  
Ionic Strength ◽  
Test Procedure ◽  
Human Blood Plasma ◽  
First Order ◽  
Antithrombin Activity ◽  
Low Concentrations ◽  
Fractionation Procedure ◽  
The Mean ◽  
Low Ionic Strength ◽  
Kinetics Of

SummaryFraction III + IV obtained by a low temperature — low ionic strength fractionation procedure was found to contain 97 percent of the antithrombin activity of whole plasma. The mean antithrombin activity in this fraction from 88 normal plasma specimens was 172.6 ± S. D. 19.8 units per ml. Further purification experiments resulted in fraction III representing 96 per cent of the antithrombin activity in fraction III + IV. There was no evidence for fibrinogen, prothrombin and antihemophilic globulin contamination in fraction III. Over 90 per cent of the plasma gamma globulins was present in this fraction.The kinetics of the thrombin-antithrombin reaction were investigated. Under the specific conditions employed, the reaction was found to follow a first order course. The heat of activation was determined to be 11,300 calories. A standard antithrombin unit is defined. A quantitative test procedure which is accurate at both high and low concentrations of the circulating anticoagulant is described and its application on fractions, heat defibrinated plasma and serum is discussed.

The Modification of Actomyosin ATPase Activity by Tropomyosin-Troponin and its Dependence on Ionic Strength, ATP-Concentration, and Actin-Myosin Ratio

1974 ◽  
Vol 29 (9-10) ◽  
pp. 496-505 ◽  
Author(s):  
Peter Daneker
Keyword(s):  
Ionic Strength ◽  
Atpase Activity ◽  
Actin Filaments ◽  
Regulatory Proteins ◽  
High Affinity ◽  
Low Concentrations ◽  
Dependence On Ionic Strength ◽  
High Concentrations ◽  
Low Ionic Strength ◽  
Better Than

Abstract At millimolar concentrations of ATP the ATPase activity of regulated actomyosin (which consisted of myosin and of actin containing the regulatory proteins tropomyosin and troponin) was lower than that of unregulated actomyosin (containing actin devoid of the regulatory proteins) when the ionic strength was high (> 0 .0 3 ᴍ KCl). At low ionic strength (0.03 ᴍ KCl) the ATPase activity of regulated actomyosin was similar to or even higher than that of unregulated acto­ myosin. Besides increasing ionic strength an increasing actin-myosin ratio tended to depress the ATPase activity of regulated actomyosin below that of unregulated one. At lower ATP concen­ trations (0.1 mᴍ or lower) the ATPase activity of regulated actomyosin was higher than that of unregulated actomyosin at any ionic strength and at any actin-myosin ratio. EGTA inhibited the ATPase of regulated actomyosin under any conditions at high ATP concentrations. At lower ATP concentrations EGTA inhibited either at higher ionic strength or at a higher actin-myosin ratio. The inhibition of the ATPase activity of acto-HMM by increasing ionic strength was not in­ fluenced by the regulatory proteins. - For the interpretation of these results it has been assumed that in actomyosin regulated actin can adopt three states: A low-affinity state which activates the ATPase of myosin only slightly (occurring at high ATP concentrations and in the absence of Ca2+), a high affinity state which activates the ATPase of myosin better than does unregulated actin (occurring at low concentrations of ATP and in the presence of Ca2+), and an intermediate state. This latter state (occurring at high concentrations of ATP and in the presence of Ca2+ or at low concentrations of ATP and in the absence of Ca2+) activates the ATPase of myosin less than does unregulated actin when the actin-myosin ratio is high (wide spacing of myosin on the actin filaments) but activates more (or at least not less) when the actin-myosin ratio is low (dense spacing of myosin on the actin filaments)

Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM

1988 ◽  
Vol 46 ◽  
pp. 176-177
Author(s):  
J.S. Wall ◽  
V. Maridiyan ◽  
S. Tumminia ◽  
J. Hairifeld ◽  
M. Boublik
Keyword(s):  
Ionic Strength ◽  
Three Dimensional ◽  
Conformational Transitions ◽  
Dark Field ◽  
Dimensional Structure ◽  
Ribosomal Rnas ◽  
Field Mode ◽  
Freeze Dried ◽  
High Resolution Images ◽  
Low Ionic Strength

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).

An Evaluation of a Plasma Fractionation System

1960 ◽  
Vol 4 (01) ◽  
pp. 031-044
Author(s):  
George Y. Shinowara ◽  
E. Mary Ruth
Keyword(s):  
Biological Activity ◽  
Ionic Strength ◽  
Plasma Proteins ◽  
High Concentration ◽  
Significant Evidence ◽  
Native Proteins ◽  
Mobility Data ◽  
Fractionation Procedure ◽  
The Individual ◽  
Low Ionic Strength

SummaryFour primary fractions comprising at least 97 per cent of the plasma proteins have been critically appraised for evidence of denaturation arising from a low temperature—low ionic strength fractionation system. The results in addition to those referable to the recovery of mass and biological activity include the following: The high solubilities of these fractions at pH 7.3 and low ionic strengths; the compatibility of the electrophoretic and ultracentrifugal data of the individual fractions with those of the original plasma; and the recovery of hemoglobin, not hematin, in fraction III obtained from specimens contaminated with this pigment. However, the most significant evidence for minimum alterations of native proteins was that the S20, w and the electrophoretic mobility data on the physically recombined fractions were identical to those found on whole plasma.The fractionation procedure examined here quantitatively isolates fibrinogen, prothrombin and antithrombin in primary fractions. Results have been obtained demonstrating its significance in other biological systems. These include the following: The finding of 5 S20, w classes in the 4 primary fractions; the occurrence of more than 90 per cent of the plasma gamma globulins in fraction III; the 98 per cent pure albumin in fraction IV; and, finally, the high concentration of beta lipoproteins in fraction II.

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