分泌颗粒膜的离子ogenic性质。分离的嗜铬颗粒的电动性质。

The ionogenic nature of the secretory-granule membrane. Electrokinetic properties of isolated chromaffin granules.

Matthews E K, Evans R J, Dean P M

Biochem J. 1972 Dec;130(3):825-32. doi: 10.1042/bj1300825.

Abstract

Chromaffin granules isolated from the bovine adrenal medulla possess an electrophoretic mobility of -1.12mum.s(-1).cm.V(-1), corresponding to a surface zeta potential of -14.4mV and surface charge density of 1.38x10(-6)C.cm(-2). 2. The mobility of chromaffin granules is pH-dependent, indicating an amphoteric surface with an isoelectric point at pH3.0 and acidic groups with a pK(a) of 3.11. 3. Addition of bi- and ter-valent cations decreased the mobility of chromaffin granules in a dose-dependent fashion with a relative potency of La(3+)>>Mn(2+)>Ca(2+) >Sr(2+)>Mg(2+)>Ba(2+). 4. Treatment with neuraminidase decreased the mobility of erythrocytes by 84%, whereas chromaffin-granule mobility was decreased by only 14%. This correlates well with the small complement of neuraminic acid present in the granule membrane. 5. The nature, origin and significance of the anionic surface charge of the chromaffin granule is discussed. It is concluded that the net negative charge at the surface of shear derives chiefly from a single type of chemical group, namely -CO(2) (-), contributed by the alpha-carboxyl group of constituent proteins, the phospholipid phosphatidylserine and, to a lesser extent, the sialic acid component of glycoproteins.

摘要

从牛肾上腺髓质分离出的嗜铬颗粒具有-1.12μm·s⁻¹·cm·V⁻¹的电泳迁移率，对应表面ζ电位为-14.4mV，表面电荷密度为1.38×10⁻⁶C·cm⁻²。2. 嗜铬颗粒的迁移率依赖于pH值，表明其表面具有两性性质，等电点在pH3.0，酸性基团的pK(a)为3.11。3. 二价和三价阳离子的加入以剂量依赖方式降低了嗜铬颗粒的迁移率，相对效力为La(3+)>>Mn(2+)>Ca(2+)>Sr(2+)>Mg(2+)>Ba(2+)。4. 用神经氨酸酶处理使红细胞迁移率降低84%，而嗜铬颗粒迁移率仅降低14%。这与颗粒膜中存在的少量神经氨酸含量密切相关。5. 讨论了嗜铬颗粒阴离子表面电荷的性质、来源和意义。得出结论，剪切表面的净负电荷主要来自单一类型的化学基团，即-CO₂⁻，由组成蛋白质的α-羧基、磷脂磷脂酰丝氨酸以及较少程度上糖蛋白的唾液酸成分贡献。