کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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5372427 | 1388879 | 2006 | 11 صفحه PDF | دانلود رایگان |
The interaction of natural (alginic and fulvic acids) and synthetic (polyacrylic acid 2.0 kDa) polyelectrolytes with some protonated polyamines [diamines: ethylendiamine, 1,4-diaminobutane (or putrescine), 1,5-diaminopentane (or cadaverine); triamines: N-(3-aminopropyl)-1,4-diaminobutane (or spermidine), diethylenetriamine; tetramine: N,Nâ²-bis(3-aminopropyl)-1,4-diaminobutane (or spermine); pentamine: tetraethylene-pentamine; hexamine: pentaethylenehexamine] was studied at T = 25 °C by potentiometry and calorimetry. Measurements were performed without supporting electrolyte, in order to avoid interference, and results were reported at I = 0 mol Lâ 1. For all the systems, the formation of (am)L2Hi species was found (am = amine; L = polyelectrolyte; i = 1â¦4, depending on the amine considered). The stability of polyanion-polyammonium cation complexes is always significant, and for high-charged polycations, we observe a stability comparable to that of strong metal complexes. For example, by considering the formation reaction (am)Hi + 2L = (am)L2Hi we found log Ki = 6.0, 6.5 and 10.8 for i = 1, 2 and 3, respectively, in the system alginate-spermidine. Low and positive formation ÎH° values indicate that the main contribution to the stability is entropic in nature. The sequestering ability of polyelectrolytes toward amines was modelled by a sigmoid Boltzman type equation. Some empirical relationships between stability, charges and ÎG° and TÎS° are reported. Mean values per salt bridge of formation thermodynamic parameters (ÎX°n) are ÎG°n = â 5.8 ± 0.4, ÎH°n = 0.7 ± 0.5 and TÎS°n = 6.5 ± 0.5 kJmolâ 1 for all the systems studied in this work.
Journal: Biophysical Chemistry - Volume 122, Issue 3, 1 August 2006, Pages 221-231