DETECTION OF CRYSTALLINE CHOLESTEROL MONOHYDRATE IN MODEL BIOMEMBRANES

模型生物膜中结晶一水胆固醇的检测

• 批准号: 6281263
• 负责人: GERALD W FEIGENSON
• 金额: $ 1.25万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-09-15 至 1999-08-14
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6281263
• 关键词: biological products; biomedical resource; proteins; radiography; structural biology

The mole fraction of cholesterol in biomembranes varies from nearly zero to about 0.5. The principles that determine how much cholesterol can be accomodated in a biomembrane are not yet understood. A phenomenon with a relatively simple thermodynamic description is the maximum solubility of cholesterol in a bilayer, beyond which cholesterol precipitates as crystals. We were able to detect trace amounts of cholesterol monohydrate crystals coexisting with phospholipid-cholesterol lamellae. This sensitive detection enabled us to establish the phase boundary for appearance of the crystalline phase. The x-ray source at CHESS provided the resolution needed to distinguish higher order lamellar repeats from the low angle cholesterol monohydrate lines. The value of cholesterol solubility in (16:0,18:19)-PC, (12:0,12:0)-PC, (22:113,22:113)-PC, and (16:0,18:19)-PS is mole fraction 0.66. In (16:0,18:19)-PE, the value is 0.50. The underlying molecular basis for this difference is not understood, but seems to involve headgroup area. However, a simple prediction is that the inner leaflet of cellular plasma membranes should contain less cholesterol than the outer leaflet, because of the nearly exclusive location of PE in the inner leaflet.

生物膜中胆固醇的摩尔分数为 几乎为零至约0.5。 决定多少的原则 胆固醇可以容纳在生物膜中尚未 明白了。 热力学相对简单的现象 描述是胆固醇在双层中的最大溶解度， 超过此胆固醇会以晶体形式沉淀。 我们能够 检测共存的痕量一水胆固醇晶体 具有磷脂-胆固醇片层。 这种灵敏的检测 使我们能够建立出现的相边界 结晶相。 CHESS 的 X 射线源提供了分辨率 需要区分高阶层状重复和低角度重复 一水胆固醇线。 胆固醇溶解度值 (16:0,18:1 9)-PC、(12:0,12:0)-PC、(22:1 13,22:1 13)-PC，以及 (16:0,18:1 9)-PS摩尔分数0.66。 在 (16:0,18:1 9)-PE 中， 值为 0.50。 这种差异的潜在分子基础是 不明白，但似乎涉及头组区域。 然而，一个 简单的预测是细胞血浆的内部小叶 膜的胆固醇含量应比外层的小叶少， 因为 PE 在内传单中几乎是唯一的位置。