Cytochemical studies on RNP complexes produced by puff 2-48BC in Drosophila hydei: uranyl acetate and phosphotungstic acid staining

Differential staining of the core and RNP particles of RNP complexes in puff 2--48 BC in salivary gland chromosomes of Drosophila hydei was achieved with aqueous uranyl acetate (UA) at low pH, with UA in acetone, with phosphotungstic acid (PTA) in organic solvents, and with aqueous PTA at pH 5 And 6. A comparison of the results of UA and PTA staining under various conditions indicate that the proteins in the core region and in the RNP particles connected to it differ with respect to their amino-acid composition (arginine and lysine residues).--The staining mechanism of PTA and UA is discussed.