© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

3.1 Human Body Chemical Composition

The human body consists of ~7 x 10²⁷ atoms arranged in a highly aperiodic physical structure. Although 41 chemical elements are commonly found in the body's construction (Table 3.1), CHON comprises 99% of its atoms. Fully 87% of human body atoms are either hydrogen or oxygen.

Somatic atoms are generally present in combined form as molecules or ions, not individual atoms. The molecules of greatest nanomedical interest are incorporated into cells or circulate freely in blood plasma or the interstitial fluid. Table 3.2 summarizes the gross molecular contents of the typical human cell, which is 99.5% water and salts, by molecule count, and contains ~5000 different types of molecules. Appendix B lists 261 of the most common molecular and cellular constituents of human blood, and their normal concentrations in whole blood and plasma. This listing is far from complete. The human body is comprised of ~10⁵ different molecular species, mostly proteins -- a large but nonetheless finite molecular parts list. By 1998, at least ~10⁴ of these proteins had been sequenced, ~10³ had been spatially mapped, and ~7,000 structures (including proteins, peptides, viruses, protein/nucleic acid complexes, nucleic acids, and carbohydrates) had been registered in the Protein Data Bank which at that time was maintained at Brookhaven National Laboratory.¹¹⁴⁴ Given the current accelerating pace of improving technology,¹¹⁴⁵ it is likely that the sequences and 3-D or tertiary structures of all human proteins will have been determined by the second decade of the 21st century.

Transporting and sorting such a broad range of essential molecular species will be an important basic capability of many nanomedical systems. The three principal methods for distinguishing and conveying molecules that are most useful in nanomedicine are diffusion transport (Section 3.2), membrane filtration (Section 3.3), and receptor-based transport (Section 3.4). The Chapter ends with a brief discussion of binding site engineering (Section 3.5).

Last updated on 7 February 2003