6 The Dynamics of Water Molecules Confined in the Interior of DMPC. . .
91
Fig. 6.1 The structure of 1,2-dimyristoyl-sn-glycero-3phosphocholine (DMPC) molecule (VMD
software [35] picture)
Figure 6.4 shows for several temperatures the calculated mean square displacement
→
r (t)
2
of the center of mass of confined water molecule, where
→
r (t) =
→
r (t) −
→
r (0) and
→
r is the position of a single molecule mass center.
Figure 6.4 indicates that the displacement
→
r (t)
2
is quite sensitive to the
change of temperature; it substantially increases with increasing temperature of the
sample. Taking into account that the mean square displacement is connected with
the translational diffusion coefficient D, via Einstein relation
→
r (t)
2 ≈ 6Dt,
one can see that nonzero slope of
→
r (t)
2
is an indicator of a mobility of
molecules (translational diffusion) [37–39]. The values of D, related to the shorttime translational dynamics of confined water, were estimated from the linear part
of the slope of
→
r (t)
2
and are shown in Table 6.1.
91
Fig. 6.1 The structure of 1,2-dimyristoyl-sn-glycero-3phosphocholine (DMPC) molecule (VMD
software [35] picture)
Figure 6.4 shows for several temperatures the calculated mean square displacement
→
r (t)
2
of the center of mass of confined water molecule, where
→
r (t) =
→
r (t) −
→
r (0) and
→
r is the position of a single molecule mass center.
Figure 6.4 indicates that the displacement
→
r (t)
2
is quite sensitive to the
change of temperature; it substantially increases with increasing temperature of the
sample. Taking into account that the mean square displacement is connected with
the translational diffusion coefficient D, via Einstein relation
→
r (t)
2 ≈ 6Dt,
one can see that nonzero slope of
→
r (t)
2
is an indicator of a mobility of
molecules (translational diffusion) [37–39]. The values of D, related to the shorttime translational dynamics of confined water, were estimated from the linear part
of the slope of
→
r (t)
2
and are shown in Table 6.1.