Frederick Sanger, a British scientist who deciphered the structure of proteins and other chemical building blocks of life, achievements that helped lead to the mapping of the human genome and that were honored by two Nobel Prizes in chemistry, died Nov. 19 at a hospital in Cambridge, England. He was 95.

His death was announced by the Medical Research Council’s Laboratory of Molecular Biology, in Cambridge, an institution he helped found. No cause was cited.

Dr. Sanger was one of four people in history to receive two Nobel Prizes, the others being the Polish-born French scientist Marie Curie, the American chemist Linus Pauling and the American physicist John Bardeen.

Dr. Sanger received his first Nobel Prize in 1958, at age 40, for “his work on the structure of proteins, especially that of insulin.” He was credited with decoding the amino acids that make up insulin, which is secreted by the pancreas. That advance — the product of 10 years of research — helped lead to the unmasking of other, more complex proteins that help control the most basic functions of life.

“Many hormones, all enzymes so far known, viruses, toxins which cause disease and antibodies which give immunity to disease, are all proteins,” the Royal Swedish Academy of Sciences said at the time.

Frederick Sanger, who twice received the Nobel Prize in chemistry, died Nov. 19 at 95. (AP)

“In all tissues of the body, in muscle, nerve and skin, proteins form an essential functional constituent. Sanger’s methods and results have opened a road to the determination of their detailed structure, and thus one of chemistry’s greatest problems has found its solution in principle.”

Twenty-two years later, in 1980, he collected his second Nobel Prize, one that he shared with the American scientists Paul Berg and Walter Gilbert. Along with Gilbert, Dr. Sanger was honored for his “contributions concerning the determination of base sequences in nucleic acids” — which contain the basic hereditary material for living organisms.

Dr. Sanger’s discoveries were regarded as milestones in the field of genetics. He achieved them quietly, through methodical trial in the classic scientific tradition. He was so modest and retiring, a colleague once told an interviewer, that he could have been mistaken for a lab caretaker.

Dr. Sanger started small by studying insulin, a relatively simple protein. Later, he confronted the vastly more complex nucleic acids and showed that, they, too, could be understood.

“Although at the time it seemed to be a major change from proteins to nucleic acids,” he wrote in his Nobel biographical sketch, “the concern with the basic problem of ‘sequencing’ remained the same.”

Perhaps the best known “sequencing” enterprise is the Human Genome Project, the massive international endeavor to determine the human genetic blueprint. Completed in 2003, it has been described as one of the boldest scientific ventures ever embarked upon. Scientists conducted a large portion of the work at the Wellcome Trust Sanger Institute in Cambridgeshire, which was named for Dr. Sanger.

By understanding the human genetic makeup, scientists are equipped to make dramatic advances in the treatment of diseases and genetic disorders.

“When I started on proteins, I hadn’t thought about anything like that,” Dr. Sanger told the Ottawa Citizen in 2000, remarking on the scale of the genome project. “I used to dream about being able to sequence a protein. What they do now is nothing like I used to do. I was messing about with chemicals and test tubes, and nowadays it’s sitting in front of your PC.”

Frederick Sanger was born on Aug. 13, 1918, in Rendcomb, Gloucestershire. His mother was the daughter of a cotton manufacturer, and family wealth allowed him to support himself through his studies. He had planned to become a physician but decided that science and, ultimately, biochemistry appealed to him more.

“It seemed to me,” he wrote in his Nobel biographical sketch, “that here was a way to really understand living matter and to develop a more scientific basis to many medical problems.”

He received a bachelor’s degree in 1939 and a doctorate in 1943, both from the University of Cambridge. Dr. Sanger came from a Quaker family and was a conscientious objector during World War II. He continued his studies at Cambridge, where he spent most of his career.

In 1940, he married Margaret Joan Howe. They had three children, Robin, Peter and Sally, all of whom survive.

His honors, besides the Nobel Prizes, included a 1979 Albert Lasker Basic Medical Research Award. Dr. Sanger turned down a knighthood, according to the Laboratory of Molecular Biology, because he did not wish to be called “Sir.”