Biology Reference
In-Depth Information
4.15 Simple Enzymes Are to Enzyme Complexes
What Atoms Are to Quantum Dots
The quantization of energy levels is not only observed in atoms but also in
quatum
dots
,
single-molecule enzymes
(Ji 2008b) and
enzyme complexes
(Ji and So 2009d),
promoting me to suggest that
enzymes
and
enzyme complexes
are biological quantum
dots (or bio-quantum dots more briefly). This conjecture is elaborated in Table
4.8
.
What connects the quantum dot and enzymes (e.g., cholesterol oxidase) on the one
hand and the quantum dot and enzyme complexes (e.g., transcriptosomes,
degradosomes) on the other is the
quantization of energy levels
beyond the energy
answers.com/topic/potential-well
)
(seeRow6inTable
4.8
). The quantum confine-
ment effect is observed when the diameter of the particle involved is of the same
magnitude as the wavelength of electron's quantum mechanical wave function,
c
(Cahay 2001). When materials are this small (see Row 3 in Table
4.8
), the energy
levels become quantized and separated by the so-called
bandgap
, i.e., the separation in
energy levels between the
valence
and
conduction bands
in semiconductors
.
The
bandgap is given by
h
2
ma
2
D
E
¼
=
(4.39)
where
, m is the mass of the electron (or any
quon) and a is the width of the potential well confining the electron/quon move-
ment. Since the light emitted from quantum dot is determined by bandgap, which is
in turn inversely proportional to the width of the potential well, a, Eq.
4.39
predicts
that the color of a quantum dot (i.e., fluorescence) should shift from red to blue as
the size of the dot decreases. Thus, the experimental observation of the size-
dependent mission wavelengths of quantum dots (see the first figure in
http://en.
wikipedia.org/wiki/Quantum_dot
)
confirms the validity of the principle of quantum
confinement (Row 6 in Table
4.8
). The emergent properties of the “bio-quantum
dots” are suggested to be the conformation-dependent catalytic rate constants (see
differences between “physical” quantum dots and “bio-quantum dots” is the static
boundaries of the former and deformable and dynamic boundaries of the latter (see
Row 4, Table
4.8
). Consequently, the relation between the size of the physical
quantum dots and their emission wavelengths is fixed and constant while the
relation between the conformational states of “bio-quantum dots” and their cata-
lytic properties is predicted to be variable and dynamic. This latter prediction is
supported by the so-called “dynamic disorder” or “dynamic heterogeneity” of
enzymes predicted in (Zwanzig 1990) and experimentally observed by (Lu et al.
1998) (see Sect.
12.12
).
One of the major difficulties that prevent biologists to make rapid advances in
their research is the occurrence of multiplicity of names, nomenclatures, and terms
referring to common entities. For example, molecular biologists rarely distinguish
ћ
is the Planck constant divided by 2
p
