Biological Units Reproduce

The hand of God is to be found in the very first molecule that was compelled to soak up energy and resources in order to replicate itself. 

Reproduction is the most basic of activities of living systems (and even nonliving systems, if we consider subcellular units such as viruses). The reproduction and evolution of RNA molecules in the test tube have been observed (Schuster et al., 1997). It is through reproduction that genetic material is perpetuated, and, in that sense, genes can be immortal as long as they are not mutated into different genes. 

---

Information implies order. Shannon s information theorem that relates information content to the probability of occurrence has been applied mainly to electronic communications systems. Information, however, is extremely important to biological units because information allows the unit to survive, grow, and reproduce. Thus, Shannon s theorem is relevant to biology and to maintaining the integrity of biological systems. See Section 4.7. 

Fig. 1. Ribbon diagrams of Dictyostelium discoideum G-actin (Matsuura et al., 2000) and the Ascaris suum aMSP dimer (Bullock et al., 1996) at the same magnification. Actin consists of four subdomains that surround a nucleotide-binding cleft. The G-actin molecule is asymmetric, so that when it polymerizes, the filament it forms has a characteristic polarity and its two ends differ structurally. By contrast, MSP does not contain a nucleotide binding site and the polymerizing unit is a dimer in which the two MSP molecules are related by twofold rotational symmetry. Polymerization produces filaments composed of two helical subfilaments in which the dimers twofold axes are oriented perpendicular to the helix axis. Consequently, the MSP helices have no polarity and the subfilament ends are identical structurally (Bullock et al., 1998). Reproduced from The Journal of Cell Biology, 2000, vol. 149, pp. 7-12 by copyright permission of the Rockefeller University Press.

Figure 8.5 PolyP accumulation, and polyphosphate kinase (PPK) and exopolyphosphatase (PPX) activities, under stringent conditions. E. coli MG1655 was grown on a MOPS medium containing 0.4 mM P . At A540 near 0.2, serine hydroxamate (SHX) was added (0.5 mg mO1) for induction of amino acid starvation and accumulation of (p)ppGpp. Symbols represent with ( ) and without (<0>) serine hydroxamate units of PPK and PPX in (b) are 1 nmol P muT1 (Kuroda et al., 1997). Reproduced with permission from Kuroda, A., Murphy, H., Cashel, M. and Kornberg, A., J. Biol. Chem., 272(34), 21240-21243 (1997). Copyright (1997) American Society for Biochemistry and Molecular Biology.

The general problem of lack of accurate reproducibility of the biological test data usually results in an unavoidable standard deviation of about 0.20 to 0.25 log 1/C units. Thus additivity really means that slight variations of this magnitude from strict additivity could not be detected. 

Figure 8 (a) Structure of the phycocyanin antenna complex from the cyanobacterimn Synechocystis 6701 and proposed structure of the complex from Thermosynechocystis vulgaris, (Ref. 32. Reproduced by permission of American Society for Biochemistry Molecular Biology), (b) Energy transfer route in the phycobilisomes. (c) Crystal structure of the allophycocyanin a-subunit. (d) Crystal structure of the allophycocyanin /3-subunit, (e) Hexameric arrangement of three a/8 units to make the disc-like aP)-i hexamer... 

The fact that dialysis is slow does not mean that it cannot be used efficiently or quickly. For example, the Autoanalyzer contains a dialyzer unit for biological materials. If you pass the sample through the dialyzer coils, only a few percent of the ions or molecules transfer before the sample passes through. However, this is a very reproducible few percent, and it is easy to quantitate these materials. 

---