ⓘ Frances Arnold

Frances Arnold

ⓘ Frances Arnold

Frances Hamilton Arnold is an American chemical engineer and Nobel Laureate. She is the Linus Pauling Professor of Chemical Engineering, Bioengineering and Biochemistry at the California Institute of Technology. In 2018, she was awarded the Nobel Prize in Chemistry for pioneering the use of directed evolution to engineer enzymes.


1. Early life and education

Arnold is the daughter of Josephine Inman nee Routheau and nuclear physicist William Howard Arnold, and the granddaughter of Lieutenant General William Howard Arnold. She grew up in Pittsburgh suburb Edgewood, and Pittsburgh neighborhoods of Shadyside and Squirrel Hill, graduating from the citys Taylor Allderdice High School in 1974. As a high schooler, she hitchhiked to Washington, D.C. to protest the Vietnam War and lived on her own working as a cocktail waitress at a local jazz club and a cab driver.

Arnold graduated in 1979 with a B.S. degree in mechanical and aerospace engineering from Princeton University, where she focused on solar energy research. In addition to the courses required for her major, she took classes in economics, Russian, and Italian, and envisioned herself as becoming a diplomat or CEO, even considering getting an advanced degree in international affairs. She took a year off from Princeton after her second year to travel to Italy and work in a factory that made nuclear reactor parts, then returned to complete her studies. Back at Princeton, she began studying with Princetons Center for Energy and Environmental Studies – a group of scientists and engineers, at the time led by Robert Socolow, working to develop sustainable energy sources, a topic that would become a key focus of Arnolds later work.

After graduating from Princeton in 1979, Arnold worked as an engineer in South Korea and Brazil and at Colorados Solar Energy Research Institute. At the Solar Energy Research Institute now the National Renewable Energy Laboratory, she worked on designing solar energy facilities for remote locations and helped write United Nations UN position papers.

She then enrolled at the University of California, Berkeley, where she earned Ph.D. degree in chemical engineering in 1985 and became deeply interested in biochemistry in the process. Her thesis work, carried out in the lab of Harvey Warren Blanch, investigated affinity chromatography techniques.


2. Career

After earning her Ph.D., Arnold completed postdoctoral research in biophysical chemistry at Berkeley. In 1986, she joined the California Institute of Technology as a visiting associate. She was promoted to assistant professor in 1986, associate professor in 1992, and full professor in 1996. She was named the Dick and Barbara Dickinson Professor of Chemical Engineering, Bioengineering and Biochemistry in 2000 and, her current position, the Linus Pauling Professor of Chemical Engineering, Bioengineering and Biochemistry in 2017. In 2013, she was appointed director of Caltechs Donna and Benjamin M. Rosen Bioengineering Center.

Arnold served on the Science Board for the Santa Fe Institute from 1995–2000. She is a member of the Advisory Board of the Joint BioEnergy Institute and the Packard Fellowships in Science and Engineering, and she serves on the Presidents Advisory Council of the King Abdullah University of Science and Technology KAUST. She is currently serving as a judge for The Queen Elizabeth Prize for Engineering. She worked with the National Academy of Sciences Science & Entertainment Exchange to help Hollywood screenwriters accurately portray science topics.

She is co-inventor on over 40 US patents. She co-founded Gevo, Inc., a company to make fuels and chemicals from renewable resources in 2005. In 2013, she and two of her former students, Peter Meinhold and Pedro Coelho, cofounded a company called Provivi to research alternatives to pesticides for crop protection. She has been on the corporate board of the genomics company Illumina Inc. since 2016.

In 2019, she was named to the board of Alphabet Inc., making Arnold the third female director of the Google parent company.


2.1. Career Research

Arnold is credited with pioneering the use of directed evolution to create enzymes with improved and/or novel functions. The directed evolution strategy involves iterative rounds of mutagenesis and screening for proteins with improved functions and it has been used to create useful biological systems, including enzymes, metabolic pathways, genetic regulatory circuits, and organisms. In nature, evolution by natural selection can lead to proteins including enzymes well-suited to carry out biological tasks, but natural selection can only act on existing sequence variations mutations and typically occurs over long time periods. Arnold speeds up the process by introducing mutations in the underlying sequences of proteins; she then tests these mutations effects. If a mutation improves the proteins function she can keep iterating the process to optimize it further. This strategy has broad implications because it can be used to design proteins for a wide variety of applications. For example, she has used directed evolution to design enzymes that can be used to produce renewable fuels and pharmaceutical compounds with less harm to the environment.

One advantage of directed evolution is that the mutations do not have to be completely random; instead, they can be random enough to discover unexplored potential, but not so random as to be inefficient. The number of possible mutation combinations is astronomical, but instead of just randomly trying to test as many as possible, Arnold integrates her knowledge of biochemistry to narrow down the options, focusing on introducing mutations in areas of the protein that are likely to have the most positive effect on activity and avoiding areas in which mutations would likely be, at best, neutral and at worst, detrimental such as disrupting proper protein folding.

Arnold applied directed evolution to the optimization of enzymes although not the first person to do so, see e.g. Barry Hall. In her seminal work, published in 1993, she used the method to engineer a version of subtilisin E that was active in a highly unnatural environment, namely in the organic solvent DMF. She carried out the work using four sequential rounds of mutagenesis of the enzymes gene, expressed by bacteria, through error-prone PCR. After each round she screened the enzymes for their ability to hydrolyze the milk protein casein in the presence of DMF by growing the bacteria on agar plates containing casein and DMF. The bacteria secreted the enzyme and, if it were functional, it would hydrolyze the casein and produce a visible halo. She selected the bacteria that had the biggest halos and isolated their DNA for further rounds of mutagenesis. Using this method, she designed an enzyme that had 256 times more activity in DMF than the original.

Following her seminal work, Arnold has further developed her methods and applied them under different selection criteria in order to optimize enzymes for different functions. She showed that, whereas naturally evolved enzymes tend to function well at a narrow temperature range, enzymes could be produced using directed evolution that could function at both high and low temperatures. In addition to improving the existing functions of natural enzymes, Arnold has designed enzymes that perform functions for which no previous specific enzyme existed, such as when she evolved cytochrome P450 to carry out cyclopropanation and carbene and nitrene transfer reactions.

In addition to evolving individual molecules, Arnold has used directed evolution to co-evolve enzymes in biosynthetic pathways, such as those involved in the production of carotenoids and L-methionine in Escherichia coli which has the potential to be used as a whole-cell biocatalyst.

Arnold has applied these methods to biofuel production. For example, she evolved bacteria to produce the biofuel isobutanol; it can be produced in E. coli bacteria, but the production pathway requires the cofactor NADPH, whereas E. coli makes the cofactor NADH. To circumvent this problem, Arnold evolved the enzymes in the pathway to use NADH instead of NADPH, allowing for the production of isobutanol.

Arnold has also used directed evolution to design highly specific and efficient enzymes that can be used as environmentally-friendly alternatives to some industrial chemical synthesis procedures. She, and others using her methods, have engineered enzymes that can carry out synthesis reactions more quickly, with fewer by-products, and in some cases eliminating the need for hazardous heavy metals. The method has been adopted by some groups in pharmacology. For example, one of Arnolds former students, Jeffrey Moore, and colleagues used directed evolution to evolve an enzyme to produce the diabetes drug sitagliptin Januvia.

Arnold also uses structure-guided protein recombination to combine parts of different proteins to form protein chimeras with unique functions. She developed computational methods, such as SCHEMA, to predict how the parts can be combined without disrupting their parental structure, so that the chimeras will fold properly, and then applies directed evolution to further mutate the chimeras to optimize their functions.

At Caltech, Arnold runs a laboratory that continues to study directed evolution and its applications in environmentally-friendly chemical synthesis and green/alternative energy, including the development of highly active enzymes cellulolytic and biosynthetic enzymes and microorganisms to convert renewable biomass to fuels and chemicals. A paper published in Science in 2019, with Inha Cho and Zhi-Jun Jia, has been retracted on January 2, 2020, as the results were found to be not reproducible.


3. Personal life

Arnold lives in La Cañada Flintridge, California. She was married to James E. Bailey who died of cancer in 2001. They had a son named James Bailey. Arnold was herself diagnosed with breast cancer in 2005 and underwent treatment for 18 months.

Arnold married Caltech astrophysicist Andrew E. Lange in 1994, and they had two sons, William and Joseph. Lange committed suicide in 2010 and one of their sons, William Lange-Arnold, died in an accident in 2016.

Her hobbies include traveling, scuba diving, skiing, dirt-bike riding, and hiking.


4. Honors and awards

Arnolds work has been recognized by many awards, including the 2018 Nobel Prize in Chemistry, the 2011 National Academy of Engineering NAE Draper Prize the first woman to receive it, and a 2011 National Medal of Technology and Innovation. She was elected to the American Academy of Arts and Sciences in 2011 and inducted into the National Inventors Hall of Fame in 2014. She was the first woman to be elected to all three National Academies in the United States – the National Academy of Engineering 2000, the National Academy of Medicine, formerly called the Institute of Medicine 2004, and the National Academy of Sciences 2008.

Arnold is a Fellow of the American Association for the Advancement of Science, the American Academy of Arts and Sciences, the American Academy of Microbiology, the American Institute for Medical and Biological Engineering and an International Fellow of the UKs Royal Academy of Engineering in 2018.

In 2016 she became the first woman to win the Millennium Technology Prize, which she won for pioneering directed evolution. In 2017, Arnold was awarded the Raymond and Beverly Sackler Prize in Convergence Research by the National Academy of Sciences, which recognizes extraordinary contributions to convergence research.

In 2018 she was awarded the Nobel Prize in Chemistry for her work in directed evolution, making her the fifth woman to receive the award in its 117 years of existence, and the first American woman. She received a one-half share of the award, with the other half jointly awarded to George Smith and Gregory Winter "for the phage display of peptides and antibodies." She is the first female graduate of Princeton to be awarded a Nobel Prize and the first person who got their undergraduate degree from Princeton male or female to receive a Nobel Prize in one of the natural sciences categories. In November 2018, she was listed as one of BBCs 100 Women. On October 24, 2019, Pope Francis named her a member of the Pontifical Academy of Sciences.

  • Emanuel Merck Lecture of the Technische Universitat Darmstadt, Germany 2013
  • National Medal of Technology and Innovation 2011
  • Inducted into the National Inventors Hall of Fame 2014
  • Millennium Technology Prize 2016
  • Enzyme Engineering Award from Engineering Conferences International and Genencor 2007
  • Spiegelman Lecture, University of Illinois 2017
  • Elected fellow of American Institute for Medical and Biological Engineering 2001
  • Raymond and Beverly Sackler Prize in Convergence Research 2017
  • Francis P. Garvan–John M. Olin Medal, American Chemical Society 2005
  • FASEB Excellence in Science Award 2007
  • Honorary Degree of Doctor of Science from the ETH Zurich 2015
  • ENI Prize in Renewable and Nonconventional Energy 2013
  • Honorary Doctorate, Technical University of Denmark 2019
  • Honorary Doctorate, University of Chicago 2016
  • Golden Plate Award, American Academy of Achievement 2014
  • Elected an International Fellow of the Royal Academy of Engineering 2018
  • Elected fellow of the American Academy of Microbiology 2009
  • National Academy of Engineering 2000
  • Charles Stark Draper Prize 2011
  • Elected fellow of the American Association for the Advancement of Science 2010
  • Elected to the National Academy of Sciences 2008
  • Nobel Prize in Chemistry 2018
  • Society of Women Engineers 2017 Achievement Award
  • Honorary Degree of Doctor of Science from Stockholm University 2013
  • Honorary Degree of Doctor of Science from the Stockholm University 2013
  • Honorary Degree of Doctor of Science from Dartmouth College 2017
  • American Academy of Arts and Sciences 2011
  • Elmer Gaden Award, Biotechnology and Bioengineering 2015