Cell Language Theory, The: Connecting Mind And Matter

166 The Cell Language Theory: Connecting Mind and Matter

b2861 The Cell Language Theory: Connecting Mind and Matter “6x9”

Each of the steps shown in Figure 3.47(b) can be expanded using the

pre-fit (or generalized Franck–Condon) hypothesis discussed in

Section 3.2.9. For example, step (b, 1) may implicate the following pro-

cesses: M•A 1 + ATP  M′ + A 1 + ATP  M′•ATP + A 1 , where M′ rep-

resents a high-energy (or thermally excited) conformation whose shape is

complementary to that of ATP. To account for some of the unexpected

observations reported by Ishijima et al. [232], for example, the negative

time values in the histogram of the temporal relation between actin

displacement and the release of nucleotides from myosin (see [232,

Figure 7]), it may be necessary to invoke a role of the pre-fit mechanisms

in the operation of the actomyosin motor. More specifically, M′ may have

a long enough lifetime (without violating the Second Law of

Thermodynamics) to begin to exert force on the actin filament before

receiving free energy input from ATP hydrolysis, thus accounting for the

negative time values in Figure 7 of Ishijima et al. [232].

The conformon mechanism of muscle contraction proposed in

Figure 3.47 is supported by the data obtained from the single-molecule

measurements of myosin moving along the actin filament in the presence

of ATP (Figure 3.48). Such a single-molecule experiment was made pos-

sible because of the development of the optical (or laser) tweezers and the

total internal reflection fluorescence (TIRF) microscopy [233]. A “laser

tweezer” or “optical tweezer” is a laser beam focused down to a diffrac-

tion-limited spot of about 1 μm in diameter. The laser beam provides an

electric field with a gradient in every direction such that there is one point

of maximum field strength. Due to the polarizing effect of the focused

field, any dielectric object feels a force proportional to the magnitude of

the gradient that pulls the object into the region of maximum field

strength. The laser beam therefore can be used to apply a force to any

dielectric particle to manipulate its position [233]. Employing optical

tweezers, biophysicists during the last decade were able to measure simul-

taneously both the translational motion of the myosin head (which has the

ATPase activity) along actin filament and the hydrolysis of ATP that

powers the myosin movement [232, 233]. A typical example of such

experiments is shown in Figure 3.48.

According to the conformon model, two processes are crucial in mus-

cle contraction: (i) the transduction of the chemical free energy of ATP to

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