I enjoyed the general content and applaud the overall message of Charles Day’s column “Thinking like a biologist” (Physics Today, April 2018, page 8). In examining biophysical systems, physicists are often biased toward parameters they can readily alter, such as temperature and pressure, and may overlook parameters that they have less familiarity with or control over, such as chemical composition.
An error slipped into the discussion on fats, however: Liquid fats, like many vegetable oils, tend to have more double bonds than solid fats, like tallow. Indeed, small chemical changes can have big physical effects. For example, the replacement of one single carbon bond with a double carbon bond can drop the melting transition temperature of a hydrocarbon-based compound by more than 50 °C. Likewise, even the type of double bond—cis or trans—has dramatic physical and biophysical effects.
Furthermore, at the risk of not minding my own beeswax, I’ll be bold enough to hazard a possible explanation for the different behaviors of the beeswaxes obtained from different sources. The information that the usual source was sold out and yet the other source was not only available but cheaper is perhaps suggestive. Beeswax is generally much more costly than paraffin; it turns out that adulteration of beeswax with paraffin is common and generally seems to result in a lower melting temperature.1
