Novel Surface Phenomena
Abstract
A novel form of electrochemical and surface phenomena occurs in transmembrane biological rotary motors, such as F1F0 -ATP Synthase. They involve electric potentials, ion gradients, membrane-water surfaces, and proton transfers. The latter occurs via an intricate acid-base reaction across offset ion? conducting channels in the membrane, one channel leading to one side of the membrane and the other channel leading to the other side1 ¥ This proton transfer event in turn causes the rotor of the motor and its accompanying asymmetric spindle to rotate (C/ Junge1 and references cited therein), resulting in an opening of a subunit of the motor and permitting an adenosine diphosphate (ADP) and inorganic phosphate (Pi) to enter it. A further rotation closes the subunit and accelerates the synthesis of the energy-rich adenosine triphosphate (ATP) from the ADP and the Pi, followed by the release of the ATP. The focus in the present renewal proposal is on these molecular motors, on how they function at the molecular level, by interpreting recent data from single molecule experiments that supplement the previous ensemble (bulk) type experiments. In the hydrolysis direction the closing of a subunit accompanying the rotation of the asymmetric spindle catalyzes an ATP binding and subsequent hydrolysis and ADP+ Pi release1 ¥ Added insight is being provided by the different kinds ofmechano-chemical experiments on the F1 part of this motor at the single molecule level e.g., z-s. As part of our current ARO sponsored research we have formulated a theory to treat these single molecule experiment6s- 8¥ It is planned to extend the theory so as to include a quite different type of single molecule experiment, the "free rotation" experiment,5 which is also a more natural (less constrained) condition for the F1-ATP Synthase. It involves an added theoretical challenge since several time scales in the process are now involved and are comparable, instead of previous types of single molecule experiments in which one contributing process is slow and the others are fast. Thus, several coordinates are now participating in a dynamically significant way in these experiments. The analysis now involves the solution ofa partial differential equation that we formulated in the current research for the treating the probability densities of the various events. It is also intended to combine the solution of the equation with a theory9 for the role of the membrane bound (the F0) part of the ATP synthase in transporting ions across membrane and so develop a detailed theory of this widely occurring chemo-mechanical motor. It is proposed to extend the theory so as to treat linear motors, for which there is now also a large body of single molecule experiments. These latter motors are as varied as myosin, which converts chemical energy into mechanical energy, and ribozyme, which synthesizes proteins. In this work we again combine chemical reaction rate theory with the coupled mechanical motion, as in ow recent PNAS articles for F1-ATP Synthase.6- 8 As described in the body of the present proposal there are strong similarities as well as some differences between the two types of motors, and each sheds light on the other...
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 14, 2019
- Source ID
- W911NF1810070
Entities
People
- Rudolph A. Marcus
Organizations
- Army Contracting Command
- California Institute of Technology
- United States Army