In order to improve our understanding of membrane protein solubilization by sodium dodecylsulphate, sarcoplasmic reticulum vesicles have been treated with this surfactant at different detergent: protein mole ratios. Effects on Ca2(+)-ATPase activity, membrane protein solubilization, and protein conformation have been independently monitored, and correlations among the various parameters have been observed. The thermal denaturation of sarcoplasmic reticulum proteins in the presence of sodium dodecylsulphate has also been characterized spectroscopically.