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University of Texas at Austin

Dept, of Chemistry & Biochemistry

105 E. 24th St. Stop, A5300

Austin, TX 78712-0165

After studying the three-dimensional structure of a protein or DNA, one cannot help but marvel at the large size, complexity and asymmetry of biological molecules; all of which enable a remarkable array of functions such as precise recognition (i.e. antibodies), exquisite catalysis (i.e. enzymes) and information storage (i.e. DNA) to name a few.  These remarkable properties are only possible because non-covalent interactions control folding and assembly of biological molecules sufficient to overcome conformational chaos.

Historically, the field of organic chemistry has focused on controlling molecular structure by creating new covalent bonds.  Organic chemistry is evolving in many new and exciting directions, and among them are attempts to control molecular structure through the harnessing of non-covalent forces. Once harnessed, non-covalent interactions will hold the key to developing engineered molecular systems capable of important new functions that are far beyond the capacities of even the most sophisticated synthetic molecules of today.  Research in the Iverson group is centered on the construction and manipulation of large molecular systems in water, ranging from abiotic molecules to proteins. 


On the chemistry side of the laboratory, our work is built around the interconnected themes of folding, assembly, and recognition in water.  In particular, our laboratory has pioneered the use of electron rich and electron deficient aromatic units that stack in a characteristic alternating fashion in water, which has led to the development of various folding and assembling systems of increasingly large size and complexity.  Noteworthy recent achievements include the first abiotic molecules exhibiting amyloid behavior, in other words, physical properties reminiscent of the α,β peptide observed to make fibrils in the brains of Alzheimer’s patients.  Our results have shed considerable light on the fundamental molecular requirements for conversion of an amphiphilic folded molecule into a highly ordered aggregate that is characteristic of not only Alzheimer’s disease, but also the growing list of prion diseases such as bovine spongiform encephalitis (BSE or mad cow disease).  The goal is to understand this process at the fundamental level sufficient to overcome the neurochemical chaos caused by the growing list of protein misfolding diseases.

Another focus of the lab is the further development of threading polyintercalators.  Our threading polyintercalators are the first molecules shown to recognize specifically up to 14 base pair sequences of DNA using electron deficient aromatic intercalating units connected “head-to-tail” by flexible linking chains that slide back and forth through the DNA helix, analogous to how a snake might climb a ladder.  Current efforts involve studying the relatively long lifetimes (half-lives of weeks) of this class of molecule when bound to DNA as well as the mechanism by which the binding site is recognized among long stretches of unrecognized DNA.  The goal is to control DNA binding duration and specificity sufficient to influence gene expression in predictable fashion.

We have also begun to explore the alternating stacking
interactions of electron rich
and electron deficient aromatic units to develop brand new materials with interesting properties such liquid crystalline behavior, thermochromic properties (colors change with temperature) and hopefully photovoltaic activity (a new class of solar cells). 

Students or post-doctoral fellows working on these projects will acquire a comprehensive knowledge of computer guided molecular design, organic synthesis, and especially the manipulation of non-covalent interactions in water or the solid state.  Depending on the project, they will also become experts in nucleic acid chemistry, materials science or photovoltaic technology.  Recent graduates from the laboratory have been successful in academic positions as well as industry because the focus on the lab is on innovation and the control of molecular systems in aqueous solution, both of which are of growing interest to academic researchers and companies alike.



The molecular biology side of the laboratory embraces the notion that proteins are the most exquisite approach to the modular construction of large and functional molecules in water.  The laboratory is focused on the engineering of proteins with the aim of developing proteins of therapeutic interest.  In close collaboration with Dr. George Georgiou, a prominent engineer, we have developed a number of technologies for the enhancement of antibody ligand affinity and alteration of the substrate specificity of enzymes.  Although we cannot yet overcome the chaos caused by the uncertainty in folding and therefore function of engineered proteins by design, we can use laboratory directed evolution to control function.  Our patented APEx technology involves display of mutagenized antibody libraries on bacteria coupled to fluorescence activated cell
sorting (FACS) to isolated antibodies with dramatically enhanced affinity and specificity for a ligand of interest.  Among several examples, the lab is best known for the production of an engineered antibody that can prevent and cure anthrax.  This antibody, now known as AnthimTM, is currently being commercialized by Elusys, Inc. of Pinebrook New Jersey (http://www.elusys.com/anthim-anthrax.html).

A second major project in the lab
involves the engineering of proteases for eventual use as catalytic therapeutic proteins.  Proteases are enzymes that cleave other proteins with exceptional specificity and efficiency.  A protease engineered to cleave only a therapeutic target in a patient would have the unique ability to catalytically destroy that target.  As opposed to antibodies that can only bind a therapeutic target and therefore must be present in stoichiometric amounts to be effective, a single engineered protease would have the ability to cleave large numbers of therapeutic target proteins by virtue of catalytic turnover.  Such an ability would dramatically decrease the amount of material required for treatment, thereby reducing side effects associated with the relatively large amount of protein required for antibody therapies.  The key is specificity, as the introduction of a protease that is not sufficiently specific to cleave only the desired therapeutic would lead to chaos in a patient. Ours is the first lab to succeed in controlling the specificity of a prototypical protease called OmpT to cleave a large number of
new substrates.  Importantly, the overall specificities and catalytic activities of the engineered OmpT variants were shown to be equivalent to the wild-type OmpT reacting with its preferred substrate.

Students or post-doctoral fellows working in the laboratory become experts in protein engineering, a field that is at the forefront of the biotechnology industry.  They are experts in computer visualization and prediction of protein structure, high yield cloning procedures in a variety of host organisms, high throughput protein analysis and screening technologies, and high level protein production and purification.  Recent graduates from the molecular biology side of the laboratory have been very successful in academic positions as well as industry.  There remain relatively few academic laboratories in the protein engineering field, despite its growing importance of engineered proteins in the clinic.  The unique opportunity to work in a lab run by both a basic scientist (Iverson) and an engineer (Georgiou) has turned out to be a fertile environment for launching successful and creative careers.



The Chemistry of Large Molecules in Water

M18 Antibody-PA


OmpT: E. coli surface protease that strongly prefers Arg-arg cleavage sites