The Geometry The Nucleus

Helical pathway of the beams in (a)
Two waves of the
same amplitude
whose phase difference
is 90°
Figure 6
SCHEMAT C OF CIRCULARLY POLARIZED BEAMS
Circularly pc larized light is composed of two waves
of the same amplitude whose oscillations are not in
the same ph jse. In (a) the phase difference between
the two wax es is n/2 or 90°. One beam is polarized
along xy am' the other is polarized 90° phase-shifted
along the yz axis. Thus, when the phase difference is
n/2 and the amplitudes are equal, one wave superimposed
on the other will generate a helical pathway.
The helical oathway of circularly polarized light of
n/2 radians ihase difference is illustrated in (b) and
(0.
Two bear is—one left circularly polarized and the
other right :ircularly polarized are superimposed on
one anothe • in (d) and (e). The beam is left circularly
polarized if the rotational action goes around counterclockwis
: looking at the beam head-on, and right
circularly p ilarized if the rotational action is clockwise.
Two c ircularly polarized beams of equal amplitude
are sh( >wn in (d) where the E vector is rotating in
a right-hani 'ed (R) and left-handed (L) sense. The resultant
oft! ese two components is a plane-polarized
wave.
The clasi ic geometry for circular dichroism (CD)
studies is s Town in (e). The left and right circularly
polarized b :ams have different amplitudes after passing
through the biological sample. In other words, (e)
shows that i wo circularly polarized beams combine to
give an ellif tically polarized beam. The sample interacts
with the beams to alter their amplitude depending
upon fi >e geometric organization of the sample
being studied—both the way in which the molecular
sample org inizes its own space and the way it folds
upon itself.
a Raman spectrum appeared. Later when the spectra were
analyzed with respect to time, lines between 200 and 3,400
cm" 1 were found to gradually move to higher frequencies,
while those between 5 and 200 cm -1 moved to lower ones.
Interestingly, just before cell division, the spectrum became
essentially devoid of lines except for one or two lines
of high intensity and high frequency, around 2,100 cm -1 ,
which suggested that all available energy at this stage was
devoted to the division process. Webb comments on the
work:
A recent rr athematical analysis of the lines above 200
cm -1 has sh( wn that they all emanate from 2 to 4 fundamental
m >des; that is, all lines appear to be the
nonlinear "r armonics" of 2 to 4 fundamental in vivo
oscillations. The implication, therefore, is that, because
these lines move to higher frequencies as the
cell progres! es through its life cycle, each successive
metabolic st ;p it makes requires a higher energy input,
thus higher and higher energies must be directed to
and concent ated in given areas of the cell as it ages. . . .
21st CI NTURY May-June 1988 39