Ammonium acetate

β-galactosidase from E. coli was purchased from
Sigma Aldrich. The lyophilized solid was reconstituted in a 150 mM ammonium
acetate (Sigma Aldrich) buffer to create a stock solution at a concentration of
10 μM (calculated using the mass of the tetramer). The sample underwent
adduct removal, via centrifugation, a minimum of four times with the same buffer
adjusted to pH 7 using a 10 kDa molecular weight cutoff Amicon Ultra 0.5 mL
filter (Millipore Sigma). The recovered sample (17 μL) was diluted with
the same buffer to achieve the same original concentration from the stock
solution. GroEL (Sigma Aldrich) lyophilized powder preparation was described
before in detail^{36 (link)}. E.
coli 70S ribosome solution was purchased from New England Biolabs.
The original sample, with an initial concentration of 13 μM, was
constituted in a buffer containing 10 mM magnesium acetate, which is necessary
for the 70S ribosome to be intact in the condensed phase. The sample preparation
for the working solutions was described in detail previously^{41 (link)} and modified accordingly. Briefly, the
stock solution was buffer exchanged 8 times with 150 mM ammonium acetate and 10
mM magnesium acetate (Sigma Aldrich) at pH 7.4 with the same filter mentioned
above. The sample was then diluted with 150 mM ammonium acetate buffer at pH 7.4
to obtain a final concentration of 0.5 mM Mg²⁺ for the working
solution.

Truncated hepatitis B virus (HBV) capsid protein (Cp149) (kindly provided by Prof. Adam Zlotnick of Indiana University) was assembled in 300 mM sodium chloride for 24 h, dialyzed into 100 mM ammonium acetate (Sigma-Aldrich, 99.999% trace metal basis), and stored for at least a week before use (to give assembly errors time to self-correct^{39 (link)}). The initial concentration of the capsid protein was 1 mg/mL. Assembly yields predominantly the icosahedral T = 4 capsid (around 32 nm in diameter) composed of 120 capsid protein dimers along with a smaller amount (around 5% in this case) of the icosahedral T = 3 capsid with 90 protein dimers. The pseudo critical concentration for HBV assembly in 300 mM NaCl is 3.7 μM and so the final capsid concentration is around 0.22 μM.^{54 (link)} Samples of the stock solution were purified by size exclusion chromatography (SEC) with a 6 kDa cutoff (Bio Rad Micro Bio-Spin P-6 Column). Aliquots of the purified solution were then diluted with 100 mM ammonium acetate to the required concentration which ranged from 0.05 to 100 μg/mL.
Pyruvate kinase (PK), purchased from Sigma-Aldrich, was prepared at 10 mg/mL in ammonium acetate. Aliquots of the stock solution were purified by SEC with a 6 kDa cutoff (Bio Rad Micro Bio-Spin P-6 Column). The purified solution was then diluted to 2 mg/mL with 100 mM ammonium acetate.