For simplicity and low cost, we used a bob and cup rotary viscometer and controlled temperature by immersing the cup in a 5-liter water bath kept at room temperature (19-21C). Temperature varia6ons were less than 0.2 C during the course of an experiment. Bob rota6on speed was 6 rpm, and viscosity data was updated every 10 seconds during experimental runs las6ng 1.5 hours. The results are shown in figure . Remarkably, in every run the viscosity of the 50-50 racemic mixture was lower either of the two enan6omers. were used without viscosity adjustments from the stock solu6ons. S is slightly more viscous than R. The raw data from the viscometer recordings is shown. Each panel shows one series of measurements in which the viscosi6es of R, S, and the freshly mixed racemic mixture of lac6c acid were measured. Measurements are made every ten seconds. Abscissa is in minutes. Aber an ini6al transient due in part to the viscometer performing a running average between successive measurements, the traces se]le to values varying by ≈2% during the period of measurement. Variability between and within experiments is likely due to imperfect temperature control in the simple setup used. In all experiments, the viscosity of the racemic mixture lies below the viscosity of either enan6omer. Assuming that racemic viscosity, absent any other effects, should be midway between R and S viscosi6es, the viscosity deficit is 3-5 mPa.s Molecular Dynamics. In order to rule out purely geometric factors poten6ally affec6ng viscosity, we performed molecular dynamics simula6ng a rotary viscometer. The bob is an alpha helix of 20 serines terminated with NH3+ and COO-groups. Serine was chosen to maximize hydrogen-bonded interac6ons between its side-chain hydroxyls and the solvent. The cup is a cubical box 7nm on the side, and the serine bob was placed in its center with its axis parallel to one face. To compare viscosi6es, we rotate the helix on its axis and monitor the resul6ng torque for both enan6omers of lac6c acid and for the racemic mixture. Viscous flow dissipates mechanical energy to heat, and in the linear regime, total energy dissipated is the integral of torque x angle. The results are shown in figure . An alpha helix of 20 serines is posi6oned at the center of a cube 7 nm on the side, its axis parallel to the bo]om face. The cube is filled with the appropriate enan6omer of lac6c acid or the racemic mix. For clarity, only half the lac6c acid molecules are shown. Right: The graph shows torque fluctua6ons in six separate MD runs of the serine helix in R-lactate solvent. Two regimes are visible. For the first 30 or so degrees (blue region), torque increases linearly with displacement, indica6ng elas6c behavior. Thereaber, a viscous regime is established and rota6on causes random changes in torque around a mean. integra6on of the torque curves yields work for each run.