Dr. Sames added: "I would not do anything like this lightly. To retract a paper is very difficult for any scientist."

Dr. Sezen, now a doctoral student in another field at the University of Heidelberg in Germany, has vigorously disputed the retractions. She said she had not been told that the papers were being withdrawn, and she questioned whether other members of Dr. Sames's group had even tried to repeat the experiments.

The retraction of one paper, published in the journal Organic Letters in 2003, appears today. The three others were published in The Journal of the American Chemical Society in 2002 and 2003, and the retractions will appear later this month.

Columbia has opened an inquiry into why the experiments were not reproducible.

The research in question lies in an esoteric field known as carbon-hydrogen bond activation. But the ability to manipulate precisely the bonds between hydrogen and carbon atoms in molecules could lead to important practical applications. For example, scientists might one day be able to change simple hydrocarbon molecules like methane into more complex ones like those in plastic and pharmaceuticals.

In e-mail messages yesterday, Dr. Sezen said that other members of Dr. Sames's group had not followed detailed procedures for the experiments and that the catalysts needed to shepherd the chemical reactions had not been made.