Determination of labeled adenine by means of adsorption on cellulose nitrate filters: a sensitive method for estimation of nucleosidase activity.

Cellulose nitrate filters strongly adsorb adenine up to 4.4 nmoles/cm² of the filter with a constant 90% efficiency. Based on this phenomenon a sensitive and fast method of estimation of labeled adenine in amounts over three orders of magnitude was developed. This method has been successfully applied to estimate the activity of minute amounts of a nucleosidase system, catalyzing the decomposition of ATP to adenine. Other purines and pyrimidines are also adsorbed by cellulose nitrate filters in the following order: Adenine > cytosine ? thymine > uracil > guanine. The affinity of corresponding nucleosides as well as nucleotides toward cellulose nitrate filters is greatly reduced. The kinetics of adsorption and desorption of ¹⁴C]adenine was studied with regard to temperature and time of adsorption, additives, source of the filters and their pore size. The mechanism of adsorption is discussed.