Ben Loos1, Andre du Toit2, Jan-Hendrik S Hofmeyr3. 1. Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa. bloos@sun.ac.za. 2. Department of Physiological Sciences, Stellenbosch University, Stellenbosch, South Africa. 3. Department of Biochemistry, Stellenbosch University, Stellenbosch, South Africa.