Abstract
Tissue amino groups undergo dithiocarbamylation on treatment (12 hr, 22-25 degrees C) with a carbon disulfide:triethylamine:tetrahydrofuran (1:1:0.5, v/v) mixture. After washing with tetrahydrofuran:triethylamine (4:1, v/v) followed by tetrahydrofuran:pyridine (4:1,v/v) and ice-cold distilled water tissues were immersed into ice-cold 10% (w/v) lead acetate to yield yellowish lead dithiocarbamates. At 22-25 degrees C the derivatives obtained from primary amines decompose to lead sulfide. After washing with 5% lead acetate in 10% acetic acid followed by three changes of distilled water tissues are dehydrated and embedded in paraffin or Maraglas as usual. In proteins the reaction is given by the epsilon-amino group of lysine and alpha-terminal amino groups, while nucleic acids do not react. Results are shown in tetrahydrofuran-delipidized ethanol or formalin-fixed 1) plant root tips where brown-colored and electron-dense lead sulfide deposits are localized in condensed chromatin and chromosomes attributable to lysine-rich histones and 2) rat skeletal muscle where an interfibrillar component is visualized in a repeating pattern, possibly related to terminal regions of the sarcoplasmic reticulum.