Ibanez Arizza Chiara S, Marji Elaine, Luk Yan-Yeung
Chemistry Department, Syracuse University Syracuse NY 13244-4100 USA
RSC Adv. 2018 Aug 21;8(52):29598-29606. doi: 10.1039/c8ra05226c. eCollection 2018 Aug 20.
Disodium cromoglycate (5'DSCG) belongs to a class of nonamphiphilic molecules that form nematic chromonic liquid crystals in aqueous solutions. As the concentration increases, it is believed that the molecules first form isodesmic assemblies in water, which further align to form liquid crystal phases. However, the reports on isodesmic assemblies of 5'DSCG have been scarce. Herein, we show that the presence of peptides can promote the isodesmic assembly of 5'DSCG over a broad range of concentrations before reaching the liquid crystal phase. The presence of peptides can lower the 5'DSCG concentration in the aqueous solution to ∼1.5 wt% (from 11-12 wt%, forming a nematic liquid crystal phase) for isodesmic assembly formation. This result indicates a demixing between 5'DSCG and peptides in aqueous solution. We further explored this demixing mechanism to precipitate a wide range of proteins, namely, lectin A, esterase, lipase, bovine serum albumin, trypsin, and a pilin protein from bacterium . We found that 5'DSCG caused the aggregation of all these proteins except trypsin. These results, along with past findings, suggest that 5'DSCG isodesmic assemblies have the potential to assist in protein purification and crystallization.
色甘酸钠（5'DSCG）属于一类非两亲性分子，其在水溶液中形成向列型色团液晶。随着浓度增加，据信分子首先在水中形成等键组装体，这些组装体进一步排列形成液晶相。然而，关于5'DSCG等键组装体的报道很少。在此，我们表明肽的存在可以在达到液晶相之前的广泛浓度范围内促进5'DSCG的等键组装。肽的存在可以将水溶液中5'DSCG的浓度降低至约1.5 wt%（从11 - 12 wt%，形成向列型液晶相）以形成等键组装体。这一结果表明5'DSCG和肽在水溶液中发生了相分离。我们进一步探索了这种相分离机制以沉淀多种蛋白质，即凝集素A、酯酶、脂肪酶、牛血清白蛋白、胰蛋白酶以及一种来自细菌的菌毛蛋白。我们发现5'DSCG导致了除胰蛋白酶外所有这些蛋白质的聚集。这些结果与以往的发现一起表明，5'DSCG等键组装体有潜力辅助蛋白质纯化和结晶。
