The titration curve of wool keratin

Speakman, J. B.; Stott, E.

doi:10.1039/tf9343000539

Cited by 65 publications

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“…T he pH values at which half of the maximum amount of acid or base is combined (a convenient measure of the position of the curve and, in simple substances, directly related to the acid strengths of the groups titrated), are shifted considerably toward the two extremes of the pH scale. Thus, the S-shaped portions of the curves found .on the acid side of pH 7 are centered, in the case of almost all dissolved proteins, about a pH very close to 4.0, but in earlier published work on wool this point appears to be 2.3 [43, 44,45]. If these curves are regarded as resulting from the titration of many groups which possess identical dissociation constants this difference in the position of the midpoints would represent a fifty-fold increase in the acid strength of the insoluble protein, although its dissociating groups are presumed to be the same as those present in proteins which may be titrated in the dissolved state.…”

Section: Introductionmentioning

confidence: 81%

“…Among those who have recognized the existence of these differences between the titration curves of dissolved and undissolved proteins, Speakman and his collaborators [43,44,45] and Lloyd and Bidder [34], have preferred to attribute them to fundamental differences between the structures of insoluble and soluble oroteins rather than to factors introduced by the existence of two-phase equilibria. Thus Speakman appears to believe that salt linkages, between acidic and basic groups, prevent the functioning of these groups in their customary ranges of acidity because certain minimal acid or base concentrations must be exceeded before such salt linkages are broken.…”

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confidence: 99%

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Combination of wool protein with acid and base: hydrochloric acid and potassium hydroxide

Steinhardt¹,

Harris²

1940

J. RES. NATL. BUR. STAN.

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As an initial part of a general program for the study of the acidic and basic characteristics of textile fibers, a study has been made of the dependence on pH of the amounts of hydrochloric acid and of potassium hydroxide taken up by wool from aqueous solutions. The effect on this dependence of the maintenance of a constant ionic strength by additions of a neutral salt, potassium chloride, has also been determined. Most of the measurements were made at 0° C to minimize the effects of decomposition brought about by exposure to extreme concentrations of acid or base.The maximum acid-binding capacity, independent of ionic strength, is 0.82 millimole per gram; the maximum base-binding capacity is greater than 0.78 millimole. With salt absent, no appreciable binding of acid or base occurs in the pH interval, 5 to 10, but the amount bound increases very sharply as these limits are exceeded. When salt is present, the amount of acid or base bound changes with pH more gradually, and there is no wide region in which combination fails to occur; the point of zero combination is sharply defined and is near pH 6.4. The positions of the titration curves with respect to the pH axis are different at every ionic strength. The differences are larger than can be attributed to the effect of salts on the dissociation of acids; thus, in dilute solutions an n-fold change in the total concentration of chloride ions produces a change almost as great as would be produced by a similar n-fold change in the concentration of hydrogen ions. This approach to stoichiometric dependence of the acid bound on the concentration of anions as well as of hydrogen ions accounts for the greater steepness of the titration curve when the source of both ions is the acid alone.The dependence of acid bound on anion concentration or base bound on concentration of cations is explained by treating the electrostatic restrictions arising from the existence of two phases as a case of partial dissociation of protein salts. A possible alternative analysis by means of the Donnan equilibrium is also presented, and factors to be considered in making a final choice between the two treatments are described in detail. Either analysis predicts that the positions of the curves wi, th res~t to the pH axis should, at high salt concentrations, approach a limit which should correspond to the titration curve of the same protein in the dissolved state. This prediction is supported by the fact that the data for wool agree very closely at high salt concentrations with those for a similar but soluble protein, egg albumin.On the basis of this comparison, a detailed analysis is undertaken of the composition of the titration curve in terms of the constituent di-acidic and di-basic amino acids of wool. This analysis leads to the conclusion that the binding of acid and base by wool occurs at the free carboxyl, imidazole, amino, and guanidino groups, but that no combination of base with the tyrosine hydroxyl group takes place in the pH range of this investigation.I The state of comb...

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Section: Introductionmentioning

confidence: 81%

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confidence: 99%

Combination of wool protein with acid and base: hydrochloric acid and potassium hydroxide

Steinhardt¹,

Harris²

1940

J. RES. NATL. BUR. STAN.

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“…The assumption was made that the isoelectric state of a substance is dependent only on the state of its dissociable acid and basic groups (its combination with hydrogen or hydroxyl ions)-that the isoionic and isoelectric points are necessarily Identical. This probably accounts for the discrepancy pointed out by Speakman and Stott [4] between the figures pH 5 and pH 3.4 for the "isoelectric" point of wool. The former was determined by titration and may therefore be considered as the isoionic point.…”

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confidence: 79%

“…Dyeing with soluble dyes [21], felting, and removal of ash constituents from the fiber are processes that probably fall within this category. In addition, the swelling and tensile properties of wet fibers are a function of the state of their acidic and basic groups [4,22].…”

Section: Significance Of the Isoelectric And Isoionic Pointsmentioning

confidence: 99%

“…Values for the isoelectric point of wool obtained by a number of investigators are reviewed by Speakman and Stott [4] and for that reason need not be given here. The important fact which should be emphasized is that, with the exception of Harris' earlier value [5], practically all of the values were based either directly or indirectly on determinations of the amount of hydrogen or hydroxyl ion bound by the fiber.…”

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confidence: 99%

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Electrophoretic studies of wool

Sookne

Harris

1939

J. RES. NATL. BUR. STAN.

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A new investigation of the electrophoretic properties of wool shows that phthalate ion, used in buffers in earlier work, exhibits a specific ion effect, and shifts the isoelectric point to lower pH values. In acetate buffers, the isoelectric point of wool scales and cortical cells was found to be at pH 4.5. Samples of ground or powdered wool show an isoelectric point at pH 4.2. Much of the confusion which exists concerning the location of the isoelectric point has arisen from the assumption that the isoionic and isoelectric points are identical. The significance of both of these points in wool processing is discussed.

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Notiz über die Säureaufnahme der Wolle

Henning¹

1934

Angewandte Chemie

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Angedtandte Chemie 47. Jahrg. 1934. Nr. 461 nicht nur gegen dieses Praparat, sondern auch eine gewisse Festigkeit gegen Tryparsamid unld die ihm nahestehenden Phenylarsinsaurederivate erzielt wird, bewirkte zwar das Arsenpyridinpraparat BR 1 eine Festigung der Trypanosomen gegen Tryparsamid, die Vwbehandlung rnit Tryparsamid aber nur eine geringe Resistenzerhohung gegen BR 1; vom Praparat BR 23 wurde der tryparsamidfeste Stamm sagar gerade so stark beeinfldt wie der Ausgangsstamm. Die beiden ArsenpyrSdinpraparate BR1 un'd BR23 mussen tdaher allem Anschein nach ebenso wie das Arsenophenylglycin uber Affinitaten zurn Trypanosomenprotoplasma verfugen, welche dem Tryparsamid und anderen Derivaten der Phenylarsinsaure fehlen. Da aber der gegen BR 1 gefestigte Stamm durch Arsenophenylglycin noch cdeutlich beeinflufit wurde, miissen die Angriffspunkte der Arsenpyridinverbindungen auch von denen des Arsenophenylglycins zum Teil verschieden sein.Zusammenfassenld lafit sich 'demnach auf Grund iinserer Versuche sagen, dai3 die AEfinitaten der Arsenpyrimdinverbinldungen BR 1 und BR 23 zum Trypanosomenprotoplasma rnit denen des Tryparsamides und der diesem gleichzustellenden Derivate der Phenylarsinsaure sowie denen des Arsenophenylglycins nur zum Teil iibereinstimmen. Im Sinne der Ehrliehschen Chemoceptorentheorie verfugen die beiden genannten Arsenpyridinverbhdungen ebenso wie das Arsenophenylglycin iiber ,,sekundare Haptophore", die aber von denen des Arsenophenylglycins verschieden sind; da das Praparat BR 20 diese Besonderheit nicht aufweist, ware es denkbar, dai3 es sich hierbei um die 2-Pyridon-Gruppierung handelt. Vem praktischen Standpunkt aus ist diese F a tstellung insofern wichtig, als dadurch offenbar eine weitere Moglichkeit gegeben ist, auch bei Vorliegen von Erregern, welche eine Festigkeit gegen Tryparsamid, Atoxyl, Neosalvarsan und dergleichen aufweisen, noch eine Heilwirkung zu erzielen. L i t e r a t u r v e r z e i c h n is.

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The titration curve of wool keratin

Cited by 65 publications

References 0 publications

Combination of wool protein with acid and base: hydrochloric acid and potassium hydroxide

Combination of wool protein with acid and base: hydrochloric acid and potassium hydroxide

Electrophoretic studies of wool

Notiz über die Säureaufnahme der Wolle

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