Eklund K K, Virtanen J A, Vuori K, Patrikainen J, Kinnunen P K
Department of Medical Chemistry, University of Helsinki, Finland.
Biochemistry. 1987 Dec 1;26(24):7542-5. doi: 10.1021/bi00398a002.
Cation-induced aggregation of small unilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphatidyl-sn-1'-glycerol (1'-DMPG), the corresponding 3' stereoisomer (3'-DMPG), and their 1:1 mixture was studied as a function of the concentration of different mono- and divalent cations. The order of efficiency, Na+ greater than Li+ greater than K+ greater than Cs+, of the monovalent cations to induce the aggregation of DMPG vesicles is the same for both stereoisomers and their mixture. However, significant differences in the Na+-induced aggregation of 1'-DMPG and 3'-DMPG were evident. The threshold concentration of aggregation by Na+ was 0.35 M for 3'-DMPG, 0.55 M for 1'-DMPG, and 0.50 M for the mixed liposomes. Such difference in the aggregation of DMPG stereoisomers was not observed for the other mono- and divalent cations. The higher affinity of 3'-DMPG for Na+ is suggested to be due to a slightly different favored conformation of the head group glycerol moiety. Aggregation of the stereoisomers by 1 M NaCl was identical, indicating that the differences in the affinity of 1'-DMPG and 3'-DMPG for sodium can be overcome by very high ionic strength. Inclusion of 20 mol % cholesterol in vesicles enhanced the aggregation of 1'-DMPG and decreased the aggregation of 3'-DMPG by Na+ and thus abolished the difference between the two stereoisomers.
研究了阳离子诱导的1,2-二肉豆蔻酰-sn-甘油-3-磷脂酰-sn-1'-甘油（1'-DMPG）、相应的3'立体异构体（3'-DMPG）及其1:1混合物的小单层囊泡聚集情况，该聚集情况是不同单价和二价阳离子浓度的函数。对于单价阳离子诱导DMPG囊泡聚集的效率顺序，即Na+＞Li+＞K+＞Cs+，对于两种立体异构体及其混合物而言是相同的。然而，1'-DMPG和3'-DMPG在Na+诱导的聚集中存在明显差异。3'-DMPG由Na+诱导聚集的阈值浓度为0.35M，1'-DMPG为0.55M，混合脂质体为0.50M。对于其他单价和二价阳离子，未观察到DMPG立体异构体在聚集中的这种差异。3'-DMPG对Na+的较高亲和力被认为是由于头部基团甘油部分的有利构象略有不同。1M NaCl诱导的立体异构体聚集是相同的，这表明1'-DMPG和3'-DMPG对钠亲和力的差异可以被非常高的离子强度克服。囊泡中加入20mol%的胆固醇会增强1'-DMPG的聚集，并降低Na+诱导的3'-DMPG的聚集，从而消除了两种立体异构体之间的差异。
