Barnstead e pure

All chemicals were purchased from Sigma Aldrich (St. Louis, MO). Stock solutions of dopamine HCl (10 mM) were made in 0.1 N perchloric acid and diluted to the desired concentration the day of experiment in artificial cerebrospinal fluid (aCSF) described previously [19 (link)] and comprised of (in mM): 125 NaCl, 4 KCl, 1.3 CaCl₂, 1 MgCl₂, 0.66 NaH₂PO₄, 2 Na₂HPO₄, 1 glucose, pH 7.4. All solutions were made in 18 mOhm water (Barnstead E-Pure, Thermo Scientific, Waltham, MA).

β-lactoglobulin (Blg, lot# JE 001-0-415), with a reported composition of 97.9% protein (91.5% Blg), 0.2% fat, 1.8% ash, and 4.4% moisture, was donated by Davisco Food International (Le Sueur, MN, USA). Blg was further purified of non-native protein and ions using a previously published protocol [29 (link)]. Glutaraldehyde, Fast Green FCF, d-limonene, sodium azide, hexanol and hexadecane were obtained from Sigma Chemical Co. (St. Louis, MO, USA). Sodium dodecyl sulfate (SDS) and Tween 20 were obtained from Fisher Scientific (Asheville, NC, USA). All other chemicals used were of analytical grade unless stated otherwise. All solutions were prepared using ultrapure water (σ ≥ 18 mΩ-cm) obtained from a filtration system (Barnstead E-pure, Thermo Scientific, Waltham, MA, USA).