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From Black Widows to Bulletproof Vests

Dec 10, 2009

Black Widow Spider Dissection
Dr. Craig Vierra and student Coby La Mattina microdissect a black
widow spider in the Biology Lab.

While most of us try to avoid black widow spiders haunting the lonely recesses of our homes and yards, Biology Professor and Co-Chair Craig Vierra seeks an intimate understanding of these arachnids.

For the past 10 years, Dr. Vierra has been studying the molecular mechanics of black widow spider silk. Because of its high tensile strength—it is five times stronger than steel—extraordinary elasticity, and toughness, spider silk has attracted the attention of material scientists.

Scientists are currently seeking methods to produce synthetic spider silk using expression systems in yeast, bacteria and goats. With support from a Pacific Fund grant, Pacific's Department of Biological Sciences plans to lead in this effort.

Synthetic spider silk has the potential to be used in a wide range of medical, military and commercial applications, including bulletproof vests, medical sutures, artificial ligaments and tendons, fishing lines, ropes and chords, seat belts and airbags. And because silk fibers are predominantly made of protein, synthetic silk is non-toxic when degraded and has many environmental advantages over "toxic organic" materials.

"Our laboratory has cloned a number of different silk genes that produce proteins assembled into silk threads," said Dr. Vierra. "We are considered spider gene hunters because we 'fish' for new genes that encode silk proteins. Currently, we are trying to understand how these silk proteins are assembled into the fibers."

To date, only a handful of labs across the world have been able to produce synthetic silk fibers. As a leader in the spider silk community, the Biology lab wants to transition from silk "gene hunting" to the production of synthetic silk materials.

Equipment
The protein concentrator is used to evaporate large amounts of fluid, one of the critical steps required to concentrate dilute spider silk protein mixtures obtained from genetically modified yeast or bacteria. Without concentrating the samples, the silk solutions are too dilute to spin fibers.

The Pacific Fund grant will be used to purchase a protein concentrator, which will enable Pacific to refine the process for spinning artificial silk fibers. With this new equipment, large amounts of silk proteins can be produced and purified on the Stockton campus, and faculty and student researchers will then analyze the structure and properties of the various synthetic fibers created. For example, tensile strength and extensibility can be evaluated with engineering tools.

Real-world learning opportunities will be an integral component of the spider silk research project. Several undergraduate students currently work with Dr. Vierra, and this new phase of research will rely heavily on student participation for operation of the protein concentrator.

There is a strong collaborative aspect of the research that will pull students and faculty together from different schools and disciplines within the University (see sidebar).

The black widow spider silk research led by Dr. Vierra is gaining momentum and is starting to attract national and international recognition for the University through peer-reviewed scientific journals. His research was highlighted in the National Science Foundation's NSF Currents newsletter (June 2009).

"It is imperative that we remain innovative, exploring new, emerging areas of science that investigate the potential for synthetic silk and its uses as future biomaterials," said Dr. Vierra. "If successful, this technology could revolutionize the field of engineering, nanotechnology and medicine."

Protein Concentrator Invites Interdisciplinary Collaboration

The spider silk work with the new protein concentrator integrates chemistry, biology, engineering and physics, and it will create teamwork across schools and departments at Pacific. Drs. Hector Estrada and Simong Tang of the School of Engineering and Computer Science will assist in testing the material properties of the spun fibers, such as elasticity and strength. Bioengineering students will interface with Biology majors to help spin fibers, with a common goal of understanding the relationship between silk protein sequences and their mechanical properties. Chemistry faculty members, including Drs. Andreas Franz, Jerry Tsai and Liang Xue, will also play a role in helping elucidate the structural features of the silk proteins.

In addition, the concentrator will be used for other research projects:

• Drs. Joan and Geoff Lin-Cereghino (Biology) will benefit by concentrating proteins used to fight the human virus HIV.

• Drs. Lisa Wrischnik and Kirk Land (Biology) will use the instrument to help develop immunological tools to study the human parasite that causes vaginal cancer.

• Dr. Eric Thomas (Biology) will be able to concentrate samples to search for sex attractants involved in frog mating.

• Dr. William Chan (Pharmacy and Health Sciences) has a need for concentrating proteins that play a role in the breakdown of liver toxins, which is an important aspect of his pharmaceutical research program.