Ni2 nitrilotriacetate ni2 nta affinity column

PC (purity 95%, from soybean), 1, 2-dihexanoyl-sn-glycero-3-phosphocholine (6:0/6:0-PC) (purity > 99%), 1, 2-dioctanoyl-sn-glycero-3-phosphocholine (8:0/8:0-PC) (purity > 99%), 1, 2-dilauroyl-sn-glycero-3-phosphocholine (12:0/12:0-PC) (purity > 99%), 1, 2-dimyristoyl-sn-glycero-3-phosphocholine (14:0/14:0-PC) (purity > 99%), 1, 2-di-palmitoyl-sn-glycero-3-phosphocholine (16:0/16:0-PC) (purity > 99%) and 1, 2-distearoyl-sn-glycerol-3-phosphocholine (18:0/18:0-PC) (purity > 99%) were purchased from Avanti Polar Lipids, Inc. (Alabaster, AL, USA). PS standard (purity > 97%) was purchased from Sigma-Aldrich (St. Louis, MO, USA). Choline oxidase was prepared by the previously reported method [40 (link)]. Horseradish peroxidase was purchased from Sangon Biotech Co., Ltd. (Shanghai, China). Hypersil GOLD Silica column (Dim. 4.6 × 250 mm, particle size 5.0 µm) was obtained from Thermo Fisher Scientific (Waltham, MA, USA). Escherichia coli SHuffle T7 Express competent cell were purchased from New England BioLabs (Beijing, China). The plasmid pET28a vector was purchased from Invitrogen (Carlsbad, CA, USA). Ni²⁺-nitrilotriacetate (Ni²⁺-NTA) affinity column, desalting column, Q-Sepharose column and Hiload 16/60 Superdex 200 pg gel filtration column were obtained from GE Healthcare Life Sciences (Pittsburgh, PA, USA). All other chemicals used in the present study were analytical grade.

Escherichia coli DH5α and isopropyl β-D-1-thiogalactopyranoside (IPTG) were purchased from Takara Co., Ltd. (Dalian, China). SHuffle T7 Express competent E. coli cell was purchased from New England BioLabs (Beijing, China). pET-21a expression vector was purchased from Stratagene (La Jolla, CA, USA). Ni²⁺-nitrilotriacetate (Ni²⁺-NTA) affinity column, Sephadex G-25 Fine desalting column and Superdex-200 gel filtration column were obtained from GE Healthcare Life Sciences (Pittsburgh, PA, USA). Bradford Protein Assay Kit was obtained from Shanghai Sangon Biological Engineering Technology (Shanghai, China). The eleven Crystallization Kits (crystal screen 1 and 2 (HR2-130), Wizard Class 1 and 2 and 3 and 4, SaltRx (HR2-107, HR2-109, HR2-136), Index (HR2-134) and Stock Options pH (HR2-241)) were all purchased from Hampton research company (Aliso Viejo, California, USA)). All other chemicals used in the present study were analytical grade.