STOCKHOLM, Sweden - American, Japanese and Swiss scientists won the Nobel Prize in chemistry Wednesday for developing methods of identifying and analyzing large biological molecules, such as proteins.

American John B. Fenn, 85, of Virginia Commonwealth University, and Koichi Tanaka, 43, of Shimadzu Corp. in Kyoto, Japan, will share half of the $1 million prize. The other half of the prize goes to Kurt Wuethrich, 64, a scientist with the Swiss Federal Institute of Technology in Zurich and the Scripps Research Institute in San Diego, Calif.

Their work has revolutionized the development of new medicines and has shown early promise in early diagnosis of ovarian, breast and prostate cancer, the Royal Swedish Academy of Sciences said.

The laureates' research in methods to analyze large molecules has "meant a revolutionary breakthrough, making chemical biology into the 'big science of our time,'" the academy said in its citation.

"Chemists can now rapidly and reliably identify what proteins a sample contains. They can also produce three-dimensional images of protein molecules in solution. Hence, scientists can both 'see' the proteins and understand how they function in the cells," the academy said.

The Nobel science awards were to culminate later Wednesday with the announcement of the economics prize, the only award not established in the will of Swedish industrialist Alfred Nobel, the inventor of dynamite.

The winner of the Nobel Prize in literature was to be named on Thursday in Stockholm and the Nobel Peace Prize was to be announced Friday in Oslo, Norway.

The prizes for medicine and physics were announced earlier this week.

For the second year in a row, the academy decided to award the chemistry and physics honors separately, changing a yearslong practice of announcing them the same day after determining that pairing the awards made it too easy for one to be overlooked.

The medicine, physics, chemistry, literature and peace prizes were first awarded in 1901. The Nobel Memorial Prize in Economic Sciences was established separately in 1968 by the Swedish central bank, but it is grouped with the other awards.

Nobel Foundation statutes stipulate that no more than three winners can share a prize and the scientific committees often choose the maximum number, finding it hard to single out researchers. Often the awards are given for discoveries made after decades of research.

Nobel gave little guidance other than to say the chemistry prize should go to those who "shall have conferred the greatest benefit on mankind" and "shall have made the most important chemical discovery or improvement."

The prizes are presented to the winners on Dec. 10, the anniversary of Nobel's death in 1896.