The Ticklish Gene
131
This was the first time that a complete circuit diagram of a growth
process could be made. To us, this seemed an achievement of some note,
but, although we got published, no one seemed to pay any attention.
The scientific community wasn't ready for biological semiconduction,
and the notion of diodes in living tissue seemed ridiculously farfetched
to most of the people I told about it. For that reason, I never even
bothered to try publishing one of our follow-up experiments. It was just
too weird.
In the mid-1960s, solid-state devices were only beginning to hit the
market, and one of the PN junction's most interesting properties hadn't
yet been exploited. When you run a current through it in forward bias,
some of its energy gets turned into light and emitted from the surface.
In other words, electricity makes it glow. Nowadays various kinds of
these PN junctions, called light-emitting diodes (LEDs), are everywhere
as digital readouts in watches and calculators, but then they were labora-
tory curios.
We found that bone was an LED. Like many such materials, it re-
quired an outside source of light before an electric current would make it
release its own light, and the light it emitted was at an infrared fre-
quency invisible to us, but the effect was consistent and undeniable.
Even though we'd already proved our hypothesis, Charlie and I did a
few more experiments on bone semiconduction, partly for additional
confirmation and partly for the fun of it. It was known that some semi-
conductors fluoresced—that is, they absorbed ultraviolet light and emit-
ted part of it at a lower frequency, as visible light. We checked, and
whole bone fluoresced a bluish ivory, while collagen yielded an intense
blue and apatite a dull brick-red. Here we found a puzzling discrepancy,
however, which eventually led to a discovery that could benefit many
people. When we combined the fluoresced light from collagen with that
from apatite, we should have gotten the fluoresced light from whole
bone. We didn't. That indicated there was some other material in the
bone matrix, something we'd been washing out in the chemical separa-
tion.
Charlie and I were stumped on that line of research for a couple of
years, until our attention was caught by a new development in solid-
state technology called doping. Tiny amounts of certain minerals mixed
into the semiconductor material could change its characteristics enor-
mously. The making of semiconductors to order by selective doping
would become a science in itself; to us it suggested trace elements in
bone. We already knew that certain trace metals - such as copper, lead,
silver, and beryllium - bonded readily to bone. Beryllium miners had a