Biomedical Engineering Reference
In-Depth Information
important issue [Deckers et al., 2004; Radwan et al., 1994; Lesnierowski et al., 2004]. AHBs
realize modifying functions through weak non-specific interaction with enzymes and wide
variety of biopolymers of a bacterial cell [El'-Registan et al., 2006; El'-Registan et al., 2005].
One of the homologous - 5-methylresorcinol exhibited the most stimulating effect on
enzymatic activity of some hydrolases [Martirosova, 2007]. 5-Methylresorcinol has been
noted to stimulate the lysozyme activity within the range of concentrations 10
-7
- 10
-3
M up to
200% when peptidoglycane from the
Micrococcus luteus
is used as a substrate, and up to
470% when a nonspecific substrates (colloid chitin,
Saccharomyces cerevisiae
cells) are used
[Petrovskii et al., 2009]. Non-specific influence of these auto-regulators on enzymatic
proteins is associated with the chemical structure of AHB and the type of their interplay with
protein molecules [Martirosova et al., 2004; Nikolaev et al., 2008]. Also correlation between
the alteration of the catalytic activity of lysozyme under the influence of MR and its
destabilizing effect on the native conformation of the enzyme was established [Plashchina et
al., 2009]. This effect was exhibited in the drop of excess Gibbs's denaturation free energy
(∆
d
G), as well as in the rise of difference of the heat capacity between a native and denatured
state (Δ
d
С
р
) with the increase of the modifier concentration. This testifies to destabilization of
the native conformation of the protein and a predominant interaction of MR with its denatured
form. The activity and thermostability of the lysozyme has been shown to depend on the MR
concentration and the incubation time of their combined solutions [Martirosova et al., 2010a].
Increase in the time of enzyme modification up to 120 hours results in a significant drop of an
activating effect of MR. The obtained data provide evidence that under a long-term exposure
of lysozyme in a combined solution with MR, hydrophobic hydration of the protein grows
and the cooperative unit of a conformational transition alters. Effect of MR on the alteration
of kinetic parameters (K
m
and V
max
) of lysozyme in the hydrolysis reaction of colloid chitin
indicated on activation of an uncompetitive type [Martirosova et al., 2010b] and also is
confirmed for other model enzymes (tripsin, β-amylase) whose modification by MR led to an
uncompetitive activation [Nikolaev et al., 2008; Martirosova, 2007]. The effect of 5-
methylresorcinol on structure, equilibrium fluctuations and nonspecific activity of lysozyme
have been studied in the broad range of concentrations [Krupyanskii et al., 2011]. It is shown
that 5-methylresorcinol interact with the surface of lysozyme molecule directly, not via
hydrogen bonds. This leads to an increase in the amplitude of equilibrium fluctuations which
allows him to be effective activator. Influence of the MR concentration on thermodynamic
parameters of its interaction with hen egg white lysozyme in 0.05М PBS at рН 7.4 and 37
о
С
has been investigated by ITC [Martirosova, 2011]. It is shown that interaction between
lysozyme and MR has an exothermic character and is characterized by low value of binding
constant (26.6 M
-1
for 37
o
C). To record a thermal effect of the MR dilution, we performed a
single titrant injection into the buffer solution. The resulting isotherm demonstrates that an
exothermal mode of MR interaction with the buffer is replaced by an endothermal one as the
ligand concentration grows. The transition region corresponds to the MR concentration of 20
mM (2.5 mg/mL), which is likely to be due to the process of self- association of 5-
methylresorcinol molecules. We propose that MR in own aqueous solutions and mixed
solutions with lysozyme behaves similar to nonionic surfactants due to the diphylic character
and ability to self-organization. The data on surface activity of MR in literature are not found.
The aim of this paper is to investigate the dynamic of adsorption of MR from aqueous
solutions at the air/water interface depend on concentration, storage time at 25
O
C and the
presence of hen egg white lysozyme.
Search WWH ::
Custom Search