论文部分内容阅读
在ｐＨ６．３０、３７℃条件下，采用离心超过滤技术测定了１１种稀土离子（Ⅲ）与牛血清白蛋白（Ｂ８Ａ）的专一性结合常数Ｋ＿ｓ和非专一性结合常数Ｋ＿（ｎｓ）观察到Ｋ＿ｓ随稀土系列原子序数（Ｚ＿（ＲＥ））的变化有明显的＂四分组效应＂和＂钆断现象＂，而Ｋ＿（ｎｓ）～Ｚ＿（ＲＥ）类似于一元羧酸－稀土配合物稳定常数的变化规律。求出Ｔｂ（Ⅲ）－ＢＳＡ结合反应的热力学函数分别为ΔＨ＿ｓ＝４４．５±０．８ｋＪ／ｍｏｌ，ΔＳ＿ｓ＝２４３．２±２．４Ｊｍｏｌ·Ｋ，ΔＨ＿（ｎｓ）＝１９．９±１．１ＫＪ／ｍｏｌ，ΔＳ＿（ｎｓ）＝１４１．４±３．２Ｊ／ｍｏｌ·Ｋ。根据不同ｐＨ下测得的Ｔｂ（Ⅲ）与ＢｓＡ结合的Ｋ＿ｓ和Ｋ＿（ｎｓ）拟合出ＢＳＡ分子中参与稀土配位的基团的质子解离常数ｐＫ＝４．６０，进而确定出这些基团主要为天冬氨酸和谷氨酸残基侧链中的β、γ－ＣＯＯ￣－。
The specific binding constants K_s and nonspecific binding constants K_ (ns) of 11 rare earth ions (Ⅲ) and bovine serum albumin (B8A) were determined by centrifugal ultrafiltration at pH6.30 and 37 ℃. It is observed that K_s has obvious “quadruple group effect” and “gadolinium breakage phenomenon” with the change of rare earth series atomic number (Z RE), while K ns ~ Z RE is similar to that of monocarboxylic acid-rare earth complex The law of stability constant. The thermodynamic functions of Tb (Ⅲ) -BSA binding reaction were obtained as ΔH_s = 44.5 ± 0.8kJ / mol, ΔS_s = 243.2 ± 2.4Jmol · K, and ΔH ns = 19.9 ± 1. 1KJ / mol, ΔS_ (ns) = 141.4 ± 3.2 J / mol · K. The proton dissociation constants pK = 4.60 of the groups participating in rare earth coordination in BSA were fitted according to the K_s and K_ (ns) of Tb (Ⅲ) combined with BsA at different pHs, The groups are mainly β, γ-COO ~ - in the side chains of aspartic acid and glutamic acid residues.