“…In a situation where B >> K B (as here, with B = 100 µ m and K B < 1 µ m ), simplification of predicts a residual glycine concentration which is proportional to K A and inversely proportional to K B (because, for B >> K B , in the numerator and in the square root in the denominator the terms in (B/ K B ) 2 are much larger than all the other terms, just as the term B/ K B is much larger than the other terms before the square root in the denominator, so the numerator is proportional to (B/ K B ) 2 and the denominator is proportional to B/ K B ; taking the ratio of the numerator and denominator gives an expression proportional to B/ K B ). Measured values of K A for glycine range between 18 and 800 n m (Johnson & Ascher, 1992; Benveniste et al ., 1990; Benveniste & Mayer, 1991; Priestley & Kemp, 1993; Priestley et al ., 1995; Kew et al ., 1998, 2000; Mugnaini et al ., 2001). Even taking the lowest value would only alter our lowest predicted value of residual glycine concentration from 4.6 µ m to 1.1 µ m , which is still 19–45‐fold higher than the glycine concentration expected to be maintained by transporters or present as a contaminant in the superfusion solution (see ).…”