Page 29 - The Biochemistry of Inorganic Polyphosphates

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Physico-chemical properties of condensed inorganic polyphosphates 13
phosphates to precipitate proteins from acidic solutions has been known from a very early
date (Perlmann, 1938; Ebel, 1951; Van Wazer, 1958; Wiame, 1958). It has been shown that
this property of polyphosphates is due to a simple total charge, which is dependent on the
pH. Katchman and Van Wazer (1954) showed that the higher the molecular weight of a
water-soluble protein, then the less polyphosphate is required.
A similar polycation–polyanion interaction is found in the metachromatic reaction, in
which high-molecular-weight polyphosphates cause a shift in the absorption maximum
of cationic dyes, such as toluidine blue, towards shorter wavelengths (Ebel, 1951; Berg-
eron and Singer, 1958). This reaction essentially involves polymerization of the dye on
the macromolecular anion (Wiame and Lefebvre, 1946; Wiame, 1947a,b). In the case of
toluidine blue, addition of polyphosphate to the solution results in a change in colour from
blue to violet–red, and a shift in the position of the absorption maximum from 630 nm
(which is characteristic of solutions of the monomeric form of toluidine blue) to 530 nm
(typical of the complex of polyphosphate and the polymerized dye) (Arloing and Richard,
1921; Damle and Krishnan, 1954; Tewari and Krishnan, 1959; Correll and Tolbert, 1964).
However, only comparatively high-molecular-weight polyphosphates are capable of under-
going the metachromatic reaction, either in solution or on paper (Ebel and Muller, 1958;
Tewari and Krishnan, 1959; Correll and Tolbert, 1964) Tripoly- and cyclotriphosphates, for
example, do not react with toluidine blue (Kornberg, 1956).
Linear polyphosphates possess properties very similar to those of cross-linked, solid ion-
exchange agents (Thilo, 1955). The behavior of polyphosphates as dissolved ion-exchange
agents is yet further evidence of their ability to form complexes with counter-ions. Polyphos-
phates are known to be very good complexing agents for many metal ions (Van Wazer,
1958). This property is widely exploited in the fractionation of polyphosphates, and for
other analytical purposes.
The information given above concerning the chemical and physico-chemical properties
of the inorganic polyphosphates will assist in the better understanding and prediction of
the behaviour of these compounds during their extraction from cells and their subsequent
fractionation. Knowledge of these properties will facilitate the development and use of
efficient and reliable biochemical procedures for the isolation, purification, identification
and determination of polyphosphates.