Chemistry Reference
In-Depth Information
-tubulin dimer and DDMC/PTX complex have Mg
2+
and GTP on the (+)
growth edge and the tubulin polymerization (rescue) proceeds as follows:
This
α
,
β
Mg
2
þ
þ
n
TaTb
þ
GTP
þ
DDMC
=
PTX
!
Complex
Mg
2
þ
þ
!ð
TaTb
Þ
n
þ
GDP
þ
DDMC
=
PTX
(6.51)
where TaTb is the
-tubulin dimer.
The catalytic power of enzymes to efficiently form transition states has been
proposed to involve an equilibrium between the Michaelis complex and a stabilized
transition state.
Gibbs free energy in the transition state is considered:
α
,
β
ð
6
:
52
Þ
ࠠ
ࠠ
ࠠ
Ǎ
G
=ΔH
- TΔS
ΔG
キ
is the free energy of activation,
ΔS
キ
is the entropy of activation, and
where
ΔH
キ
is also the enthalpy of activation.
Figure
6.48
shows the potential energy curve and activation energy
E
a
.where,
Ea
ѳ
ΔH
ࠠ
.
With paclitaxel, many signals from gene expression in melanoma cells yield a
huge
ΔH
キ
as in Fig.
6.46
.
As
R / e
ΔH
キ
/RT
with apoptosis for melanoma cells (
R
), melanoma cells can
overcome paclitaxel at low concentrations.
On the other hand, Fig.
6.48
shows a small activation energy
E
0
a
with the DDMC/
PTX complex, and the supramolecular enzyme facility yields a small
ΔG
キ
owing to large
ΔS
キ
and large
ΔG
キ
owing to
ΔS
キ
and low
ΔH
キ
, which is why apoptosis for melanoma cells (
R
) should
low
progress.
6.5.9 Supramolecular Template
The
α
-tubulin side is a negative edge, and the
β
-tubulin side is a positive edge. Most
of the microtubule is polymerized
-tubulin dimer bound to GTP.
Many microtubules place a negative edge in the microtubule organizing center
(MTOC) (centrosome in animal cells) to extend the (+) growth edge to each place
of the cell. Of course, the microtubules are formed outside of centrosome and are
searched and transported to it to be associated [
68
]. In one embodiment, the tubulin-
binding agent is a microtubule-stabilizing agent.
Cell division will usually be initiated when polymerization stops forming the
complete long hollow tubes to support myosin and actin proteins of the cell surface
by gathering the13 fibers. Nevertheless, although the
α
,
β
-tubulin dimer is stabilized
extremely by DDMC/PTX, polymerization does not stop and many poor short
hollow tubes are formed, leading to apoptosis of the cell.
α
,
β
