Department of Pharmaceutics, College of Pharmacy, University of Minnesota, 308 Harvard St. SE, Minneapolis, Minnesota 55455, United States.
Characterization Facility, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Mol Pharm. 2021 Dec 6;18(12):4459-4474. doi: 10.1021/acs.molpharmaceut.1c00666. Epub 2021 Oct 28.
The aims of this work were to evaluate the effect of freezing and thawing stresses on lactate dehydrogenase (LDH) stability under three conditions. (i) In a solution buffered with sodium phosphate (NaP; 10 and 100 mM). The selective crystallization of disodium hydrogen phosphate during freezing caused a pronounced pH shift. (ii) In a solution buffered with histidine, where there was no pH shift due to buffer salt crystallization. (iii) At different concentrations of LDH so as to determine the self-stabilizing ability of LDH. The change in LDH tetrameric conformation was measured by small-angle neutron scattering (SANS). The pH of the phosphate buffer solutions was monitored as a function of temperature to quantify the pH shift. The conditions of buffer component crystallization from solution were identified using low-temperature X-ray diffractometry. Dynamic light scattering (DLS) enabled us to determine the effect of freeze-thawing on the protein aggregation behavior. LDH, at a high concentration (1000 μg/mL; buffer concentration 10 mM), has a pronounced self-stabilizing effect and did not aggregate after five freeze-thaw cycles. At lower LDH concentrations (10 and 100 μg/mL), only with the selection of an appropriate buffer, irreversible aggregation could be avoided. While SANS provided qualitative information with respect to protein conformation, the insights from DLS were quantitative with respect to the particle size of the aggregates. SANS is the only technique which can characterize the protein both in the frozen and thawed states.
本工作旨在评估在三种条件下,冻结和融化应力对乳酸脱氢酶(LDH)稳定性的影响。(i)在磷酸盐(NaP;10 和 100mM)缓冲溶液中。在冻结过程中二水合磷酸氢二钠的选择性结晶导致 pH 值发生明显偏移。(ii)在组氨酸缓冲溶液中,由于缓冲盐结晶,pH 值没有发生偏移。(iii)在不同浓度的 LDH 下,以确定 LDH 的自稳定能力。通过小角中子散射(SANS)测量 LDH 四聚体构象的变化。监测磷酸盐缓冲溶液的 pH 值随温度的变化,以量化 pH 值偏移。使用低温 X 射线衍射法确定了缓冲成分从溶液中结晶的条件。动态光散射(DLS)使我们能够确定冻融对蛋白质聚集行为的影响。在高浓度(1000μg/mL;缓冲浓度 10mM)下,LDH 具有明显的自稳定作用,经过五次冻融循环后不会聚集。在较低的 LDH 浓度(10 和 100μg/mL)下,只有选择合适的缓冲液,才能避免不可逆的聚集。虽然 SANS 提供了有关蛋白质构象的定性信息,但 DLS 提供了有关聚集颗粒大小的定量信息。SANS 是唯一可用于对冷冻和融化状态下的蛋白质进行表征的技术。