An anonymous donor has given $30 million to the Salk Institute for Biological Studies, the institute announced Tuesday. It is the largest single gift in the institute's 43-year history, and one of the largest ever to a local biomedical research institution.

Local biomedical leaders said the gift highlights San Diego's role as a center of biomedical research and biotechnology, and will increase the institute's ability to explore the frontiers of science.

The $30 million gift will be added to the institute's $115 million endowment, Richard A. Murphy, president and chief executive of the Salk Institute, said in a statement.

Murphy said the gift will help ensure the institute's "future financial health and independence, its operating flexibility and its ability to respond to the demands imposed by rapidly progressing science."

Founded by the late Jonas Salk, creator of the first effective polio vaccine, the institute has 56 faculty members, including several Nobel Prize winners, and a scientific staff of more than 850.

UC San Diego, The Scripps Research Institute, the Burnham Institute and the Salk Institute -- all in La Jolla -- are mainly responsible for attracting and training the scientists responsible for creating hundreds of biotechnology companies in San Diego County.

Gifts such as the one given to independent research organizations like the Salk Institute are especially significant, said Cary Thomas, chief operating officer for the Sidney Kimmel Cancer Center, also in La Jolla. That's because the money can support the most advanced -- and risky -- research.

"For a place like the Salk or the Sidney Kimmel Cancer Center, this is in essence our most valuable money," Thomas said.

While the National Institutes of Health and other government agencies are prodigious funders of research, they tend to fund research in well-explored areas, Thomas said.

"That makes it almost impossible for us to explore new science or unproven ideas," Thomas said.

Research institutes must be well-run to attract such large donations, Thomas said, singling out for praise Delbert Glanz, executive vice president of the Salk Institute, as an "unsung hero." Glanz is responsible for managing the Salk's finances.

Charity Navigator, a nonprofit group that rates charities for their effective use of donations, gives the Salk a rating of 63 on a 70-point scale. For example, the institute spends 3 cents to raise $1. This means 97 cents of every dollar donated goes to support the institute, considerably more than the case with most charities.

The Kimmel center has also benefited from large gifts, beginning in 1995 when it received $5 million from Sidney Kimmel, founder and chairman of Jones Apparel Group. Kimmel has given a total of $22 million to the center.

Giving thanks to the donor won't be easy. The identity is being kept confidential by the institute under terms of the gift, Murphy said.

Motives of donors vary, said Al Deisseroth, president and chief executive of the Kimmel center.

"Often donors are driven by the need to expand the significance of their own life by committing their resources to a noble goal and noble mission, such as the alleviation of suffering and preservation of human life that can come through such a gift," Deisseroth said.

Many people in San Diego County are rich enough to make such a gift. Some recent examples:

• Last month, the estate of Joan Kroc left $200 million to National Public Radio.

• In March, Qualcomm Inc. founder Irwin Jacobs and his wife, Joan, gave $110 million to UCSD's engineering school, renamed the Jacobs School of Engineering in their honor.

• In 2000, John and Rebecca Moores gave $20 million to UCSD to build a cancer center, named in their honor.

Whatever the source, such large donations are a "huge morale boost for an institution," said Abi Barrow, managing director of Von Liebig Center for Entrepreneurism and Technology Advancement at UCSD's Jacobs School of Engineering.

"Furthermore, it gives you additional funding to try experimental things or help in recruiting faculty," Barrow said.

Contact staff writer Bradley J. Fikes at bfikes@nctimes.com or (760) 739-6641.