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It is this lab’s theory that the large muscle protein titin binds actin and wraps around it to cause a stiffer “spring”. This spring, when pulled, caused recoil energy that we call elastic energy. There are two types of elastic filaments, passive (like collagen, cell structures) and active elastic filaments (we believe titin). We believe that Titin becomes receptive to binding after Calcium interaction at Titin’s N2A region. Once activated, titin is capable of binding to to actin filament and making that spring stiffer.

Theories are great and all, but here in the Nishikawa lab, our bread and butter is facts. Therefore, a slew of new studies are underway to prove our new theory. Some studies work on the molecular level (RNA work I am conducting…more in a few weeks), some are at the cellular level (Transmission Electron Microscopy studies by Kari, Kit, Shane (awesome undergrad) and myself), while others work at the whole muscle level (Rene, Jenna and Deidra).

Today we will look at the muscle level studies going on. Rene D. Fuqua, Jenna Monroy and Deidra Jensen are putting the calcium-binding-titin theory to the test. This is how their experiment plays out:From previous studies, we know that when muscle is stretched, a tension is create that is measurable. Compared to a non-active muscle, an active muscle that is stretched causes a higher tension…this is called force enhancement. Our lab believed that this force enhancement, or that added tension, comes from the activation of titin. SOOOO if we block titin from becoming active, or can show that something that is NOT part of the myosin- actin cross bridge is causing the force enhancement we can strengthen our lab’s titin theory.

The experiment design is like this: Rene compares active and inactive stretched muscles under different conditions to see if residual force enhancement is altered. One condition is blocking Calcium (which activates cross-bridges and titin in theory), blocking only cross bridge formation (not effecting titin in theory) and no blocking, which will have the normal process of the muscle. If she observes that cross-bridge inhibition still leads to a larger force enhancement then calcium-inhibition. We can assume that some other aspect of the muscle, besides the myosin/actin cross bridge, is causing the force enhancement. And in this lab, we believe that to be Titin, since it will not be effected by this inhibition, but will be affected by calcium inhibition, which is what this study hopes to show.

More information can be attained from Rene at rene.fuqua@nau.edu