The absorption spectra of azobenzene and 10 para-substituted derivatives have been determined for the trans, and where sufficiently stable, the cis isomers also. With the aid of an assumption of untested validity estimates are made of the influence of the substituents upon the energies of the individual electronic levels of the trans isomers. The changes in the energy levels are interpreted in terms of the mesomeric and inductive effects of the substituent. The behaviour of the cis forms is complicated by interaction of the benzene rings.

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Prepared with nonimmunospecific proteins were covalent conjugates of triaziquone [2,3,4-tris(1-aziridinyl)-p-benzoquinone] (hereafter referred to by the tradename, Trenimon). The bound Trenimon that absorbs maximally at 350 nm (epsilon = 8,200) was assayed by titration of the acid uptake during alkylation of thiosulfate ion and by the color produced during alkylation of 4-(p-nitrobenzyl)pyridine. Conjugates of Trenimon with nonimmune IgG were toxic to cells in culture, although no firm binding of conjugate to cell surface could be measured by fluorescein labeling. Inhibition of cellular pinocytotic activity with cytochalasin B had no effect on the cytotoxic response. Polyoma virus-transformed baby hamster kidney (BHK) cells that were threefold more resistant to the action of a conjugate than was the parent cell line were as sensitive as normal BHK cells when grown in the presence of dibutyryl cyclic AMP or when acted on in suspension by the conjugate. These conditions did not affect the response of the parent BHK line. Cysteine acted to protect both cell lines. The results suggest that Trenimon bound to nonimmmune protein reacted primarily with a component of the cell surface. The reaction did not appear to depend on a firm attachment of the conjugate to the cell.

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