THE EFFECT OF TEMPERATURE AND IONIC-STRENGTH ON THE APPARENT CA-AFFINITY OF EGTA AND THE ANALOGOUS CA-CHELATORS BAPTA AND DIBROMO-BAPTA
THE EFFECT OF TEMPERATURE AND IONIC-STRENGTH ON THE APPARENT CA-AFFINITY OF EGTA AND THE ANALOGOUS CA-CHELATORS BAPTA AND DIBROMO-BAPTA
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DOI：
10.1016/0304-4165(87)90102-4
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发表时间：
1987-08-13
期刊：
影响因子：
--
通讯作者：
BERS, DM
中科院分区：
文献类型：
--
作者：
HARRISON, SM;BERS, DM
乙二醇双（β-聚乙二醇）的表观钙缔合常数（K“Ca）氨基乙基醚）-N，N，N“，N”-四乙酸（EGTA）、1，2-双（邻氨基苯氧基）乙烷-N，N，N“，N”-四乙酸（BAPTA）和1，2-双[2-双（邻氨基-5-溴苯氧基）乙烷]-N，N，N“，N”-四乙酸（二溴-BAPTA）使用Bers（Am. 242（1982）C404-408）。从Scatchard图的x-截距确定的三种配体的纯度分别为96.3%，79.0%和97.3%，对于EGTA，BAPTA和二溴-BAPTA。通过将几个样品干燥至恒重，发现BAPTA的杂质是水。温度从1 ℃升高到36 ℃导致K ″ ca的增加，这对于三种配体具有相似的幅度。在所有情况下，离子强度从0.104 M增加到0.304 M导致K“Ca减少，尽管EGTA受到的影响远小于BAPTA或二溴-BAPTA。将实验结果与由钙和质子的配体的单个缔合常数计算的K“Ca值进行比较，所述配体的单个缔合常数针对实验条件分别使用Debye-Huckel限制定律和Van”t霍夫等容线来校正离子强度和温度。EGTa的K“Ca实验值与文献值和计算值符合得很好。BAPTA和二溴-BAPTA的温度和离子强度依赖性的K“Ca的实验值和计算值之间也发现了良好的一致性。
The apparent calcium association constants (K''Ca) of ethylene glycol bis(.beta.-aminoethyl ether)-N, N, N'', N''-tetraacetic acid (EGTA), 1,2-bis(o-aminophenoxy)ethane-N, N, N'', N''--tetraacetic acid (BAPTA) and 1, 2-bis[2-bis(o-amino-5-bromophenoxy)ethane-N, N, N'', N''-tetraacetic acid (dibromo-BAPTA) were measured using the method described by Bers (Am. J. Physiol. 242 (1982) C404-408). The purity of the three ligands determined from the x-intercept of Scatchard plots were 96.3%, 79.0% and 97.3% for EGTA, BAPTA and dibromo-BAPTA, respectively. The impurity of BAPTA was found to be water by drying several samples to constant weight. Increasing temperature from 1 to 36.degree.C led to an increase in K''ca which was of similar magnitude for the three ligands. Increasing ionic strength from 0.104 to 0.304 M led to a reduction of K''Ca in all cases, though EGTA was affected much less than BAPTA or dibromo-BAPTA. Experimental results were compared with values of K''Ca calculated from the individual association constants of the ligands for calcium and protons which were modified for the experimental conditions using the Debye-Huckel limiting law and the Van''t Hoff Isochore to correct for ionic strength and temperature respectively. The experimental values of K''Ca of EGTa agree well with those in the literature and with the calculated values. Good agreement was also found between the experimental and calculated values of K''Ca for the temperature and ionic strength dependence of BAPTA and dibromo-BAPTA.