heavier and heavier elements in the core. When that progression of elements reaches iron, which is incapable of releasing energy through nuclear reactions, a supernova ex- plosion blasts away the outer layers of the star and, in most cases, leaves behind an ultra-dense object known as a neutron star. In Fryer’s model, the more massive star in a binary star system evolves through its life, ultimately collapsing to form a neutron star. As the second star evolves into a red giant in the final stages of its life, it expands and envelops the neutron star, causing the neutron star to spiral into its helium core. Meanwhile, the outer layers of the red giant are flung outward by the neutron star’s passage, creating a shell of material surrounding the colliding pair. When the collision takes place, the helium drives the neutron star over its maximum stable mass, causing it to collapse into a black hole. The energy released by that collapse powers an explosion and a jet of matter slams into the surrounding shell. This sequence of events—black hole for- mation, explosion with a jet, and interaction with the ejected shell—led to the compli- cated spectrum of radiation observed in the Christmas Burst. As the jet progressed through the helium core, it deposited energy into the core, causing the core to emit the strong x-ray afterglow that followed the initial GRB. And when the weakened jet sub- sequently passed through the surrounding shell, the shell produced ultraviolet, visible, and infrared light, also exactly as observed. “What’s great is that we’re starting to be able to identify the rare types of GRB that used to be considered too weird to explain,” says Fryer. “And often it’s the weird ones that have the most to teach you.” v —Craig Tyler 24 Deciphering DNA and Disease More than a decade ago, the field of medicine waited with bated breath while the international Human Genome Project was completed. This project’s goal was to reveal and provide understanding of the genetic makeup of humans, no small task. The se- quence of the 3 billion chemical base pairs that make up human DNA was determined, potentially opening the door to finding the genetic roots of disease and developing treatments. A tremendous amount of data was compiled, but the question remained, how to decipher it? As Los Alamos molecular biologist Csaba Kiss describes, “We have the book, now we have to translate it.” Scientists still do not know the function of more than half of the discovered genes. Los Alamos researchers are attacking that problem by trying to link the genes to the corresponding proteins they specify in order to determine their role in cellular activity—a lofty goal with the potential for many applications, including drug design. Kiss is a member of a Los Alamos research team led by renowned molecular biologist Andrew Bradbury. A former physi- cian, Bradbury thinks that one key to future medical advances is the use of antibodies, proteins naturally produced by the immune system that help the body fight infectious diseases. Antibodies are also necessary for basic research purposes on a bench-top scale in order to identify key protein interac- tions without using animals as surrogates. In fact the ability to selectively target proteins with engineered antibodies is a major goal in biotechnology. Success offers a route to attack human diseases such as cancer, a means to stay ahead of evolving infectious bacteria such as multi-drug-re- sistant tuberculosis, and a countermeasure for potential bioagents used in weapons of mass destruction. Antibodies are Y-shaped proteins that each respond to a specific antigen, or 1663 los alamos science and technology magazine june 2012 antibody generator. Usually a protein, an antigen is any substance—either formed within the body such as a cancer cell, or in the external environment such as pollen or a virus—that causes the immune system to produce antibodies against it. Each antibody has a special section (at the tip of each branch of the Y) that binds to an antigen, as a lock to a key. Antibodies act as body- guards by blocking entrance to human cells, disabling the antigen’s cellular function, or triggering other parts of the immune system to attack the antigen. Bradbury aims to generate antibodies that react to human proteins, using the proteins as antigens. What is the benefit of finding an antibody that attacks a protein from your own body? Consider how it could fight breast cancer, using antibodies made from human cells to destroy these cancer cells that kill nearly 40,000 American women every year. In fact, the anti-breast cancer drug Herceptin is an antibody that recog- nizes a specific human protein found fre- quently on some breast cancer cells. More broadly, antibodies against human proteins can be used as treatments to fight many types of cancers and autoimmune disorders, such as multiple sclerosis, Crohn’s disease, and rheumatoid arthritis. Bradbury starts with the approximately 30,000 genes identified in the human ge- nome encoding for the proteins that will serve as the antigens. His goal is to identify an antibody that matches and binds tightly to each specific antigen. Los Alamos col- league Geoff Waldo uses a fluorescence technique to help Bradbury select the best proteins, or parts of proteins, to use as anti- gens. The technique allows for rapid detec- tion of the antibody-antigen interaction. Selection involves testing one antigen at a time against many different antibodies. To begin the antibody selection process, Bradbury and his team insert the genes for billions of different antibodies into a bacte- riophage, a virus that infects bacteria. The phage infects an E. coli cell. Each bacte-