ChemSemBlog

On January 25^th our chem seminar speaker traveled ALL the way from South Bend, IN to give us a very informative lecture on how unnatural amino acids & multivalent antibody aggregation is crucial to science research. Our presenter was Başar Bilgiçer, assistant professor in both the Chemical and Bimolecular Engineering Department and the Chemistry and Biochemistry Department at the University of Notre Dame. He completed his B.S. in Chemistry at Bogazici University, Turkey; he then went on to receive his Ph.D. in chemistry at Tufts University. Bilgiçer conducted his Postdoctoral Fellow at Harvard University.  Dr. Bilgiçer seemed very comfortable and relaxed during his presentation; he was very easy to follow and did a great job at explaining his research so that we could understand it.

The essence of Bilgiçer’s talk was multivalent antibodies and how important the number of bonds to its antigen is in eliciting an immune response to expel the foreign pathogen. In biology class we learn that anything that triggers an immune response is an antigen. When an antigen enters the body, antibodies attach to it forming an antibody-antigen complex that signals the immune system to come and destroy the invading substance. However the efficiency of this system is dependent upon several things, one of which is the valence of the responding antibody.

Antibodies can either be Monovalent or divalent. Bilgiçer easily explained the difference between the two by comparing the arms of the antibody to human body arms. If you are pulling something with your arms it is a lot easier to hold on to it with two arms than with one, this is the same concept with antibodies holding on to antigens. An antibody can hang on to an antigen better when both “arms” of the antibody are attached; this creates bonds that are stronger and tighter; therefore it is harder for the antigen to escape and an immune response can quickly be initiated.

Although this may seem thermodynamically unfavorable, surprising Bilgiçer discovered that it wasn’t; in fact, the entropy decrease for monvalent and divalent antibodies was equitant. This is because whether the antibody bonds with one “arm” or two they would occur that the same time. The multivalent nature of antibodies is advantages in that currently most drugs containing antibodies are monovalent, thus we can create more effective drugs by applying multivalent properties to these antibodies.

Overall I really enjoyed this presentation the only question I have left are: 1. I thought Immune response amplification corresponds with signaling molecules, and so although divalent molecules can hold on better, does the decrease in available antibody binding sites decrease the signal amplification?  2. Most of the antibody aggregates formed very complex arrangements; however, can all of the aggregates bind to the antibody? will a single molecule be just as efficient?  3. If these antibodies are able to elicit a better immune response will lower medicine dosages be required?

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