Quantitative determination by derivative spectrophotometry of Triton X-100 in solubilized preparations of membrane proteins.

The amount of the nonionic detergent Triton X-100 in protein preparations cannot be determined spectrophotometrically from the normal spectrum because the spectral bands of the detergent and proteins overlap, but it was found that the detergent could be determined accurately by 4th-derivative spectrophotometry. The intensity of the derivative absorbance difference between the positive and negative peaks at about 277.5 and 281 nm, respectively, increased linearly with increase in the detergent concentration at more than its critical micelle concentration (about 0.03%). Proteins had little effect on these spectral bands of the detergent. This method is very simple and accurate for determination of the concentration of Triton X-100 in solubilized preparations of membrane proteins.