Nanomedicine, Volume I: Basic Capabilities
© 1999 Robert A. Freitas Jr. All Rights Reserved.
Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999
220.127.116.11 Construction Costs
The active binding site of a receptor consisting of (2.7 nm)3 ~ 19 nm3 of structural atoms and constructed with 0.001-nm feature sizes in theory requires information from 2 x 1010 voxels (volume pixels) for complete description. However, there are only Natom ~ 1000 atoms involved in the structure and their locations cannot be arbitrarily chosen. Atomic scale (~0.1 nm) resolution would require ~19,000 voxels; each voxel minimally requires an index number (~log2(19,000) ~ 14 bits), an atomic identifier (~log2(92) ~ 7 bits), and a charge identifier (~log2(3) ~ 2 bits), for a total of 23 bits/voxel which gives 4 x 105 bits/receptor at atomic scale resolution. Drexler10 estimates the number of configurational options per atom Nopt ~ 150; hence a description of the receptor could require as few as Natom log2(Nopt) ~ 7 x 103 bits.* Assuming energy dissipation of ~3 zJ/bit for rod logic register reading10 or ~kT ln(2) (Eqn. 7.1), then each time the receptor description is retrieved, stored or processed may require a minimum energy dissipation of ~104-106 zJ. Reversible computing may reduce this energy requirement by a factor of 10-100 or more (Section 10.2.4.1). Construction of a receptor containing ~1000 atoms using the nanomanipulator arm mentioned in Section 3.4.3 requires ~10-2 sec and consumes ~0.001 picojoule (~106 zJ) of mechanical energy.
* Higher level descriptions may allow considerable additional information compaction, as for instance where a 30-bit word indexes a single receptor structure stored in a library containing perhaps 109 distinct designs.
Last updated on 7 February 2003