The carbohydrate domain of calicheamicin gamma I1 determines its sequence specificity for DNA cleavage.

We have investigated the DNA cleaving properties of calicheamicinone, the synthetic core aglycone of calicheamicin gamma I1, a natural product with extremely potent antitumor activity. Our experiments have shown that the synthetic analog binds and cleaves DNA, albeit without any sequence selectivity and with less efficiency than the natural compound. We propose that a key element in the sequence recognition process is the thiobenzoate ring present in the natural compound.

Helical repeat and chirality effects on DNA gel electrophoretic mobility.

We determined a value of 10.34 +/- 0.04 base pairs (bp) per turn for the helical repeat of bent DNA sequences of the form A6N4-A6N5 by estimating the sequence repeat required to produce a planar curve, as judged from the maximum in the electrophoretic mobility anomaly of multimers containing different sequence repeats (10.

Determination of the extent of DNA bending by an adenine-thymine tract.

We determined the magnitude of the bend induced in DNA by an adenine-thymine tract by measuring the rate of cyclization of DNA oligonucleotides containing phased A tracts. A series of linear multimers with 2-bp single-stranded ends, in which the (A.T)6 tracts are separated by CG2-3C sequences and are positioned 10 and 11 bp apart alternately, were prepared from 21 bp long synthetic duplexed deoxyoligonucleotides.