A FRUITFUL FUSION 
OF TWO TECHNIQUES 
The study of biochemistry goes back 
to Antoine Lavoisier, the 1 8th-century 
French scientist who explained the 
role of oxygen in the respiration of 
both plants and animals, established 
the composition of water and other 
compounds, and introduced quantita- 
tive methods in the study of chemical 
reactions, thereby laying the founda- 
tion for modern chemistry. 
In the 19th century, biochemists 
isolated and identified many cellular 
chemicals — for example, hemoglobin, 
the red pigment of blood, and chloro- 
phyll, the green pigment in plants. 
They discovered that compounds 
taken from animal tissue consisted of 
the same chemical elements as nonliv- 
ing materials. They isolated the 
nucleic acids, which are now known 
to govern heredity and protein synthe- 
sis. They began to study proteins, 
especially enzymes, which catalyze 
chemical reactions in cells. 
When dealing with cells, biochem- 
ists behave quite unlike microscopists, 
who have enormous respect for the 
details of the cell's structure. Biochem- 
ists simply grind up large quantities of 
cells to release their contents into a 
solution (this is called "homogenizing") 
and then analyze the mixture (called 
the homogenate). Often, the homoge- 
nate is fractionated, or separated, into 
individual components. Usually this 
is done with a centrifuge, a machine 
that separates particles according to 
their size and density by whirling them 
around at varying speeds. The 
heaviest and largest particles are 
thrown to the bottom of the test tube 
most rapidly, followed by somewhat 
lighter and smaller components, until 
at the highest speed there remain only 
the smallest and lightest particles at 
the top. 
In 1925, a Swede, Theodor 
Svedberg, developed an instrument 
that would prove at least as revolu- 
tionary as the electron microscope: 
the ultracentrifuge, a machine that 
could spin its samples at such high 
speeds and with such force (it could 
attain hundreds of thousands of times 
the force of gravity) that many of the 
smaller and lighter components of the 
cell and even proteins and nucleic 
acids could be collected separately 
and studied for the first time. 
The significance of this new instru- 
ment did not become apparent until 
years later. For a long time, bio- 
chemists seemed interested only in the 
chemical reactions of the cell as a 
whole — for example, how the cell 
obtains energy or synthesizes pro- 
teins. The scientists gave little thought 
to what the various fragments they 
dealt with represented in the cell — 
what they looked like, how they were 
organized, or how they related to 
one another. Very often, biochemists 
gave these fragments names of their 
own, unaware that microscopists had 
already examined and named them. 
"There were two classes of people, 
and they didn't communicate with 
each other at all!" recalls DeWitt 
Stetten, Jr., Deputy Director for 
Science, Emeritus, at the National 
Institutes of Health (NIH). Finally, in 
the 1 950's, the two groups began to 
15 
