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II. AMINO ACID POOL TURNOVER 
LIMITING FACTORS IN BIOSYNTHESIS OF MACROMOLECULES 
JOHN M. REINER 
Department of Microbiology, Emory University, Atlanta, Georgia (U.S.A.) 
It is a source of some satisfaction to me to be invited here, not in my capacity as an 
experimenter, but in my alternative role of mathematical theoretician. The satis- 
faction stems not from vanity satiated—for my preceptors in applied mathematics, 
CaRL ECKART AND NICOLAS RASHEVSKY, set a standard of skill and ingenuity that 
would deflate the most swollen head—but from the evidence that quantitative 
theoretical analysis is today an accepted partner in my chosen field, instead of the 
half-ignored, half-resented stranger that it was when I began. 
This happy situation demands a commensurate candor from the theorist; and so 
I must warn you not to expect to hear earth-shaking revelations today. Every problem 
has a history, during which the apt strategies shift as understanding develops. 
There are, and always will be, areas in which it is easier to do the experiments, 
however complex and demanding these may be, than to try to predict the answers 
theoretically. This holds, in particular and as of today, for the problem of the mecha- 
nisms of macromolecular biosynthesis: it would be presumptuous now (though in 
five years it may turn out to be reasonable) to try to derive the mechanisms of 
protein synthesis from physicomathematical first principles. For this problem, at 
this time, the callouses must be put on the feet rather than the seat; and we have a 
model, in the work of ARTHUR KORNBERG and his collaborators, of a beautifully 
simple solution to what seemed a few years ago to be the terrifying complex problem 
of the synthesis of DNA*, achieved by the classical biochemical stratagems of clean 
and assiduous labor. 
A more modest role must be assigned, for the present, to the mathematical theorist. 
What he can and should do is to formulate in quantitative terms the mechanisms 
we know, or think we know, or hope to substantiate the day after tomorrow, and 
to inquire concerning the more interesting consequences of these mechanisms. In 
short, here as elsewhere, the function of the applied mathematician is to take what 
we know (or what we are willing to assume) and examine it from every angle—to 
turn it over and sideways and inside out by means of the devices of mathematics, 
in order to ascertain its full content. 
When mechanisms interact in complex networks, a mathematical formulation 
becomes particularly helpful. As patterns become increasingly complex, their modus 
operandi ever more successfully eludes our unaided intuitions. But mathematics is 
par excellence the science of pattern; and it should help us to see how the intricate 
patterns will function. An obvious example is the field of kinetics, where we ask 
* Abbreviations to be used are: DNA for deoxyribonucleic acid; RNA for ribonucleic acid; 
ATP for adenosine triphosphate. 
References p. 632 
