DESCRIPTION (provided by applicant) Structural studies will be conducted on oligodeoxynucleotides site-specifically modified with specific adducts of the vinyl chloride metabolites chlorooxirane and chloroacetaldehyde, and the alpha, beta-unsaturated aldehydes acrolein, crotonaldehyde, and hydroxynonenal. The adduction sites will be the N1, N2, and N3 positions of guanine, the N1 and N6 positions of adenine, and the N3 and N4 positions of cytosine. The goal is to correlate differences in chemistry between different classes of cyclic adducts, and intra- and inter-strand crosslinks, with structural and conformational properties in DNA. In turn, the structural information derived in this project will be correlated with biological data from the second Project. Vinyl chloride metabolites add a C2 unit, whereas acrolein, crotonaldehyde, and hydroxynonerial add a C3 unit to the DNA base. One class of cyclic adducts to be examined are termed "distal" adducts. In these, a hydroxy group in the hydroxy ethano or hydroxy propano exocyclic adduct is positioned adjacent to an amino nitrogen. These are postulated to be highly disruptive to DNA structure because they interfere with Watson-Crick base pairing. Studies will be geared towards understanding how the DNA duplex accommodates these distortions. Another class of cyclic adducts to be examined are termed "proximal" adducts, in which a hydroxy group of the cyclic hydroxy ethano or hydroxy propano adduct is positioned adjacent to an imino nitrogen. For these it is anticipated that the ring-opened form in which the monodentate adduct is attached at the amino nitrogen will be stabilized in duplex DNA. Effort will focus on understanding how duplex DNA modulates the position of this equilibrium, and how the aldehyde that is the product of ring-opening is accommodated by the DNA duplex. This is important because the aldehyde, once formed, has the potential to crosslink the DNA. The structures of site-specific DNA crosslinks identified in the second Project will be examined, as will the role of DNA sequence in controlling crosslinking. The role of linker length (C2 versus C3) on the ability to crosslink and the resulting distortions introduced into duplex DNA by the crosslinks will also be examined.