De Stefano Concetta, Gianguzza Antonio, Piazzese Daniela, Porcino Nunziatina, Sammartano Silvio
Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Università di Messina, Salita Sperone 31, I-98166, Messina (Vill. S. Agata), Italy.
Biophys Chem. 2006 Aug 1;122(3):221-31. doi: 10.1016/j.bpc.2006.03.015. Epub 2006 May 9.
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,N'-bis(3-aminopropyl)-1,4-diaminobutane (or spermine); pentamine: tetraethylene-pentamine; hexamine: pentaethylenehexamine] was studied at T=25 degrees C by potentiometry and calorimetry. Measurements were performed without supporting electrolyte, in order to avoid interference, and results were reported at I=0 mol L(-)(1). For all the systems, the formation of (am)L(2)H(i) species was found (am=amine; L=polyelectrolyte; i=1...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)H(i)+2L=(am)L(2)H(i) we found log K(i)=6.0, 6.5 and 10.8 for i=1, 2 and 3, respectively, in the system alginate-spermidine. Low and positive formation DeltaH(degrees) 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 DeltaG(degrees) and TDeltaS(degrees) are reported. Mean values per salt bridge of formation thermodynamic parameters (DeltaX(degrees) (n)) are DeltaG(degrees) (n)=-5.8+/-0.4, DeltaH degrees (n)=0.7+/-0.5 and TDeltaS(degrees) (n)=6.5+/-0.5 kJmol(-)(1) for all the systems studied in this work.
在25℃下，通过电位滴定法和量热法研究了天然（海藻酸和富里酸）和合成（2.0 kDa聚丙烯酸）聚电解质与一些质子化多胺[二胺：乙二胺、1,4 - 二氨基丁烷（或腐胺）、1,5 - 二氨基戊烷（或尸胺）；三胺：N -（3 - 氨丙基）-1,4 - 二氨基丁烷（或亚精胺）、二乙烯三胺；四胺：N,N'-双（3 - 氨丙基）-1,4 - 二氨基丁烷（或精胺）；五胺：四乙烯五胺；六胺：五乙烯六胺]之间的相互作用。为避免干扰，测量在无支持电解质的情况下进行，结果报告为I = 0 mol L⁻¹时的数据。对于所有体系，均发现形成了(am)L₂Hᵢ物种（am = 胺；L = 聚电解质；i = 1...4，取决于所考虑的胺）。聚阴离子 - 聚铵阳离子络合物的稳定性始终显著，对于高电荷聚阳离子，我们观察到其稳定性与强金属络合物相当。例如，考虑形成反应(am)Hᵢ + 2L = (am)L₂Hᵢ，在海藻酸盐 - 亚精胺体系中，i = 1、2和3时，我们分别发现log Kᵢ = 6.0、6.5和10.8。低且为正的形成焓变（ΔH°）值表明稳定性的主要贡献本质上是熵的贡献。聚电解质对胺的螯合能力通过S型玻尔兹曼型方程进行建模。报告了稳定性、电荷与ΔG°和TDeltaS°之间的一些经验关系。本工作中研究的所有体系，每个盐桥形成热力学参数（ΔX°(n)）的平均值为：ΔG°(n) = -5.8 ± 0.4、ΔH°(n) = 0.7 ± 0.5和TDeltaS°(n) = 6.5 ± 0.5 kJmol⁻¹。
