HENRY M. SOBELL

PREFACE

As a younger scientist, I could never have imagined that crystallographic studies of intercalation complexes would ever lead to understanding the mechanism of intercalation. And - even more unlikely - that this subject would be connected with concepts coming from theoretical physics and applied nonlinear mathematics.

However, incredibly, this is exactly what has happened, and more.

Topics such as the physical nature of DNA premelting and melting, structural phase transitions involving A-, B- and Z-DNA, single- and double-stranded branch migration, site specific DNA melting and gene activation, nuclease hypersensitive sites in both naked DNA and DNA in active and inactive chromatin, the structure of DNA within the transcriptional complex and perhaps, in extremely active genes, between transcriptional complexes, the mechanism of action of actinomycin and other related antibiotics - all find logical explanation. And - of most importance - my theory explains a wide range of additional data and makes a number of testable experimental predictions.

So - let us examine the theory, and the data that supports it.