Dissociation of Alginic Acid.

Quantifying Pb and Cd Complexation by Alginates and the Role of Metal Binding on Macromolecular Aggregation

“…An apparent pK a value of 3.44 was obtained, in good agreement with the literature for alginic acid containing brown algae (pK a ) 3.49) 32 and values corresponding to the carboxylic groups of the mannuronic (3.38) 33 and guluronic acids (3.65). 33 The concentration of carboxylic acid groups determined here, 4.4 × 10 -6 mol kg -1 , corresponded well to values obtained previously by 13 C NMR (4.5 × 10 -6 equiv kg -1 ) 34 and potentiometric titration (4.39 × 10 -6 mol kg -1 ). 8 This concentration of carboxylic groups also corresponds well to theoretical estimates that can be calculated from the alginate structural unit (4.4 × 10 -6 mol kg -1 ), if the water content (19.8%) is taken into account.…”

Copper isotope fractionation during its interaction with soil and aquatic microorganisms and metal oxy(hydr)oxides: Possible structural control

“…Carboxylate groups of the cell surface polysaccharides are expected to be deprotonated above pH 3.5 as measured pK a values of alginic acid and microbially produced exopolysaccharides are close to 3.4 (Lamelas et al, 2005(Lamelas et al, , 2006, in agreement with values corresponding to the carboxylic groups of the mannuronic (3.38) and guluronic (3.65) acids (Haug, 1961). Carboxylate moieties of the cell surface have been demonstrated to be the primary sites of divalent metals binding to the biological surfaces in circumneutral pH range (Beveridge and Murray, 1980;Fein et al, 1997;Sarret et al, 1998;Tiemann et al, 2002;Pokrovsky et al, 2005a;Guiné et al, 2006).…”

Evaluation of the Intrinsic Acid-Dissociation Constant of Alginic Acid by Considering the Electrostatic Effect

“…8 In polyacrylic acid, the unity of the acidic group is acetic acid, and this pK a (4.7) is larger than that for L-guluronic acid (3.7) in AA. 5 Therefore, the smaller values of n in the AA suggest that AA is a strong acid, rather than a polyacrylic acid.…”

“…4 Haug determined the pK a values for AA from two types of seaweeds at an ionic strength of 0.1 M NaCl (pK a =3.74 and 3.42). 5 However, the pK a,int have not been reported because of a lack of information about the AA polymer. In the present work, while taking electrostatic effect of AA into account, the pK a values were determined based on the potentiometry at a variety of ionic strengths.…”