scholarly journals The interaction between β-lactoglobulin and sodium N-dodecyl sulphate

1976 ◽  
Vol 153 (3) ◽  
pp. 713-718 ◽  
Author(s):  
M N Jones ◽  
A Wilkinson
Keyword(s):  
Ionic Strength ◽  
Equilibrium Dialysis ◽  
Protein Molecule ◽  
Enthalpies Of Formation ◽  
Enthalpy Of Interaction ◽  
Surfactant Anion ◽  
Ionic Nature ◽  
Ph Range ◽  
Low Ionic Strength ◽  
Β Lactoglobulin

1. The binding of sodium n-dodecyl sulphate to β-lactoglobulin was studied in the pH range 3.5-7.0 by equilibrium dialysis, ultracentrifugation and microcalorimetry. 2. At low binding concentrations (less than 30 bound surfactants anions per protein molecule) the complexes formed aggregates in solution. 3. At higher binding concentrations aggregation does not occur at low ionic strength (0.01 mol/litre), but continues at high ionic strength (0.1 mol/litre). 4. At 25 degrees C the enthalpy of interaction of sodium n-dodecyl sulphate with β-lactoglobulin can be interpreted as the sum of the enthalpies of formation of a complex with 2 bound surfactant anions, with an enthalpy change of -9.5 kJ-mol-1 of bound surfactant, and complexes containing at least 22 bound surfactant anions, with limiting enthalpies per bound surfactant anion of -12.4 kJ-mol-1 at pH 3.5 and -3.25 kJ-mol-1 at pH 5.5. 5. The binding of surfactant and the enthalpy of interaction at pH 3.5 ARE NOT SIGNIFICANTLY AFFECTED BY THE ADDITION Of 8 M-urea. 6. The data indicate that at low binding concentrations the interaction is of an ionic nature, and is accompanied by a conformational change in the protein.

The binding of Zinc by S-Carboxymethyl Kerateine 2 from wool

1957 ◽  
Vol 10 (3) ◽  
pp. 344 ◽  
Author(s):  
JM Gillespie ◽  
PH Springell
Keyword(s):  
Ionic Strength ◽  
Chelating Agents ◽  
Zinc Concentration ◽  
Equilibrium Dialysis ◽  
Acetate Solution ◽  
Free Zinc ◽  
Zinc Acetate Solution ◽  
The Difference ◽  
Protein Components ◽  
Ph Range

The binding of zinc from zinc acetate solution by the S-carboxymethyl derivative of kerateine 2 (SCMK2), a soluble protein extracted from reduced wool, has been studied by the method of equilibrium dialysis over the pH range 5.5 to 8.0 using radioactive 65Zn to determine the zinc concentration. The binding increases as the pH increases from 5.5 to 7.5. The extent of binding is also a function of free zinc concentration, but it is not affected by changes in ionic strength between 0.15 and 1.0. The difference in solubility between the zinc complexes of the two protein components of SCMK2 is probably not due to the differences in the amount of zinc bound. The binding of zinc is reversible over the concentration range studied at both pH 6.0 and 7.5, and its removal is accelerated by treatment with chelating agents. Over the pH range 6.0 to 7.5 more zinc is bound by this protein than can be accounted for by histidine binding alone, assuming a 1 : 1 zinc-histidine ratio.

The precipitation of proteins by carboxymethyl cellulose

1975 ◽  
Vol 42 (2) ◽  
pp. 267-275 ◽  
Author(s):  
J. G. Zadow ◽  
R. D. Hill
Keyword(s):  
Ionic Strength ◽  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Carboxymethyl Cellulose ◽  
Degree Of Substitution ◽  
Maximum Precipitation ◽  
Ph Range ◽  
High Degree ◽  
Β Lactoglobulin

SummaryCarboxymethyl cellulose (CMC) formed insoluble complexes with β-lactoglobulin, bovine serum albumin and Na caseinate. Maximum precipitation of the β-lactoglobulin-CMC complex occurred at pH 3·2, whereas maximum precipitation of the bovine serum albumin-CMC complex and the Na caseinate-CMC complex occurred at pH 2·8. The ratio of CMC to protein for maximum precipitation depended on the protein, being greatest for Na caseinate and least for bovine serum albumin. The percentage of protein precipitated by CMC decreased with increasing ionic strength of the solution, the rate of decrease being least for bovine serum albumin. At a given ionic strength, more protein was precipitated by CMC of high degree of substitution than by CMC of low degree of substitution. The change in pH (ΔpH) occurring on mixing CMC and unbuffered protein solutions, each initially at the same pH, was measured. ΔpH was negative for β-lactoglobulin-CMC mixtures over the pH range 7–2 (minimum at pH 5·5). For bovine serum albumin-CMC and Na caseinate-CMC mixtures, ΔpH was positive between pH 7 and 3·2 (maximum at pH 4·5), zero at pH 3·2 and negative between pH 3·2 and 2·0 (minimum at pH 2·8).

Electrostatically Driven Protein Aggregation:  β-Lactoglobulin at Low Ionic Strength

Langmuir ◽  
2006 ◽  
Vol 22 (22) ◽  
pp. 9150-9159 ◽  
Author(s):  
Pinaki R. Majhi ◽  
Reddy R. Ganta ◽  
Ram P. Vanam ◽  
Emek Seyrek ◽  
Katie Giger ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Protein Aggregation ◽  
Low Ionic Strength ◽  
Β Lactoglobulin

Mesoscopic structure and viscoelastic properties of β-lactoglobulin gels at low pH and low ionic strength

2002 ◽  
Vol 16 (3) ◽  
pp. 207-213 ◽  
Author(s):  
Leonard M.C. Sagis ◽  
Cecile Veerman ◽  
Renate Ganzevles ◽  
Mariëlle Ramaekers ◽  
Suzanne G. Bolder ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Viscoelastic Properties ◽  
Low Ph ◽  
Mesoscopic Structure ◽  
Low Ionic Strength ◽  
Β Lactoglobulin

Buffers of Low Ionic Strength for Spectrophotometric pK Determinations

1963 ◽  
Vol 16 (4) ◽  
pp. 572 ◽  
Author(s):  
DD Perrin
Keyword(s):  
Ionic Strength ◽  
Constant Ionic Strength ◽  
Ultraviolet Region ◽  
Thermodynamic Quantities ◽  
Small Constant ◽  
Ph Range ◽  
Experimental Values ◽  
Low Ionic Strength

Buffers of low and constant ionic strength (I = 0.01), covering the pH range 2.2 to 11.6 at 20�C, are described. Their near-transparency in the ultraviolet region makes these buffers suitable for spectrophotometric pK determinations, and only small, constant corrections are needed to convert the experimental values to thermodynamic quantities.

Binding of zinc to bovine and human milk proteins

1989 ◽  
Vol 56 (2) ◽  
pp. 235-248 ◽  
Author(s):  
Harjinder Singh ◽  
Albert Flynn ◽  
Patrick F. Fox
Keyword(s):  
Ionic Strength ◽  
Binding Sites ◽  
Binding Capacity ◽  
Equilibrium Dialysis ◽  
Whey Proteins ◽  
Milk Proteins ◽  
Association Constants ◽  
Zn Concentration ◽  
Β Lactoglobulin ◽  
Scatchard Plots

SummaryZn binding by whole bovine and human casein and by purified bovine caseins and whey proteins was investigated by equilibrium dialysis. Bovine αs1 casein had the greatest Zn-binding capacity (˜ 11 atoms Zn/mol). Protein aggregation was observed as Zn concentration was increased and- the protein precipitated at a free Zn concentration of 1·7 mM. Zn binding increased with increasing pH in the range 5·4–7·0 and decreased with increasing ionic strength. Competition between Zn and Ca was observed for binding to αs1-casein indicating common binding sites for these two metals. Bovine β-casein bound up to 8 atoms Zn/ mol and precipitated at a free Zn concentration of ˜ 2·5 mM, while K-casein bound 1–2 atoms Zn/mol. Whole bovine and human casein bound 5–8 atoms Zn/mol and precipitated at a free Zn concentration of ˜ 2·0 mM. Scatchard plots for Zn binding to caseins showed upward convexity, possibly due to Zn-induced association of caseins. Apparent average association constants (K¯app) for all caseins were similar (log K¯app 3·0–3·2). Enzymic dephosphorylation of αs1- or whole bovine casein markedly reduced, but did not eliminate, Zn binding. Thus, phosphoserine residues appeared to be the primary Zn-binding sites in caseins. With the exception of bovine serum albumin. which bound over 8 atoms Zn/mol, the bovine whey proteins, β-lactoglobulin, α-lactalbumin and lactotransferrin, had little capacity for Zn binding.

Structure of bovine β-lactoglobulin (variant A) at very low ionic strength

2006 ◽  
Vol 154 (3) ◽  
pp. 246-254 ◽  
Author(s):  
Julian J. Adams ◽  
Bryan F. Anderson ◽  
Gillian E. Norris ◽  
Lawrence K. Creamer ◽  
Geoffrey B. Jameson
Keyword(s):  
Ionic Strength ◽  
Low Ionic Strength ◽  
Β Lactoglobulin

Interaction of Proteoglycans and Chondroitin Sulfates with Calcium or Phosphate Ions

1971 ◽  
Vol 49 (4) ◽  
pp. 417-425 ◽  
Author(s):  
E. A. MacGregor ◽  
J. M. Bowness
Keyword(s):  
Ionic Strength ◽  
Chondroitin Sulfate ◽  
Calcium Binding ◽  
Equilibrium Dialysis ◽  
Equilibrium System ◽  
Chondroitin Sulfates ◽  
Phosphate Ions ◽  
Wide Range ◽  
The Difference ◽  
Low Ionic Strength

Equilibrium dialysis was used to study the distribution of calcium or phosphate ions at equilibrium in dialysis cells containing proteoglycan or chondroitin sulfate in one compartment. A higher concentration of calcium or lower concentration of phosphate was found in the cell compartment containing the polymer than in the compartment separated from it by a semipermeable membrane. The difference in calcium concentration across the boundary represents bound calcium. The formation constant (K) for the complex of bound calcium with chondroitin sulfate was investigated and found to be affected by two main factors: ionic strength and calcium/glucuronate ratio. K decreased rapidly with increasing ionic strength up to 0.15. At low ionic strength and high Ca2+/glucuronate ratios, evidence has been obtained that more calcium is bound by the polymers than can be accounted for by the simple equilibrium system, involving the combination of one calcium per disaccharide unit period, whose operation is consistent with the K values found at low Ca/glucuronate ratios over a wide range of ionic strengths. Infrared spectra obtained at high and low Ca2+/glucuronate ratios also indicate the existence of two calcium forms of proteoglycans. Viscosity and ultracentrifugal data show that differences exist between proteoglycans in calcium and sodium solutions. The data for disaggregated proteoglycan preparations indicate that their calcium-binding properties are very similar to those of chondroitin 4-sulfate and are determined by the same factors. One aggregated puppy rib proteoglycan, however, showed significantly greater K values than chondroitin 4-sulfate; these decreased after disaggregation.

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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