The macromolecular crowding influences the structural stability and functional properties of transferrin (Tf). The equilibrium as well as kinetic studies of Tf at different concentrations of crowding agents (dextran 40, dextran 70, and ficoll 70) and at a fixed concentration of dextran 40 under different concentrations of NaCl at pH 7.4 and 5.6 (±1) revealed that (i) the crowder environment increases the diferric-Tf (Fe₂Tf) stability against iron loss and overall denaturation of the protein, (ii) both in the absence and presence of crowder, the presence of salt promotes the loss of iron and overall denaturation of Fe₂Tf which is due to ionic screening of electrostatic interactions, (iii) the crowder environment retards iron release from monoferric N-lobe of Tf (Fe_NTf) by increasing enthalpic barrier, (iv) the retardation of iron release by crowding is enthalpically dominated than the entropic one, (v) both in the absence and presence of crowder, the presence of salt accelerates the iron release from Fe_NTf due to ionic screening of electrostatic interactions and anion binding to KISAB sites, and (vi) the crowders environment is unable to diminish (a) the salt-induced destabilization of Fe₂Tf against the loss of iron and overall denaturation and (b) the anion effect and ionic screening of diffusive counterions responsible to promote iron release from Fe_NTf.

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大分子拥挤对血清转铁蛋白稳定性和铁释放动力学的影响

大分子拥挤影响转铁蛋白（Tf）的结构稳定性和功能特性。在不同浓度的拥挤剂（右旋糖酐40，右旋糖酐70和聚蔗糖70）和固定浓度的右旋糖酐40在不同浓度的NaCl，pH 7.4和5.6（±1）下，Tf的平衡以及动力学研究表明： （i）拥挤环境增加了二铁-Tf（Fe ₂ Tf）的稳定性，可抵抗铁的损失和蛋白质的整体变性；（ii）在不存在和拥挤的情况下，盐的存在都会促进铁和铁的损失Fe ₂ Tf的变性是由于静电相互作用的离子筛选所致，（iii）拥挤环境阻碍了铁从Tf的单铁_N瓣释放（Fe _NTf）通过增加焓屏障，（iv）拥挤对铁释放的阻滞在熵上占主导地位，（v）在不存在和拥挤的情况下，盐的存在都会加速铁从_N Tf中的铁释放离子筛选静电相互作用和与KISAB位点结合的阴离子，并且（vi）拥挤环境无法减少（a）盐引起的Fe ₂ Tf失稳，防止铁的损失和整体变性，以及（b）阴离子效果和负责促进选自Fe铁释放扩散抗衡离子的离子屏蔽_ñ TF。