Recent Researches in Modern Medicine
Study of DNA interaction with 1-phenyl-2-methyl-aminopropanol
containing Palladium compound which reveal radiomodifying and
immunostimulatory activity
KASYANENKO N.A.1, MOROZOVA E.V.1, EFIMENKO I.A.2
1
Physical Faculty
1
St. Petersburg State University; 2 Institute of Inorganic Chemistry
1
St. Petersburg, Petrodvorec, Ulyanovskaya, 1; 2 Moskow, Leninskiy pr., 31.
RUSSIA
[email protected]
Abstract: - The interactions of Palladium acido complex (PhAPH2)2[PdCl4] (where PhAPH is 1-phenyl-2-methylaminopropanol) with DNA in 5 mM NaCl and 0.15 M NaCl solutions were studied by spectrophotometry, circular
dichroism, viscometry, flow birefringence, and atomic force microscopy. The significant changes in DNA conformation in
complexes with palladium due to intra- and intermolecular cross-linkings were observed by atomic force microscopy. This
correlates with data received from other methods giving the information about DNA conformation in a solution. The
comparison with Pd-compounds containing other ligands in cation was carried out. The absence of the influence of the
cation nature in Palladium complex on the final result of DNA binding with compounds was shown. Preliminary data
showed that (PhAPH2)2[PdCl4] exhibits the radioprotection properties.
Key-Words: - DNA, Palladium acido complexes, antitumor compound, atomic force microscopy, radioprotection.
stable supramolecular structure is formed due to the
hydrogen bonds between NH and Cl, and this is possible
only when the value of cation deprotonation constant
(рКа) is greater than 9.5 (see [7] for more details). For
instance, a solution of (AH)2[PdCl4], where A is
metilmorpholine with рКа = 10.5, which has greater
antineoplastic activity than cisplatin, does not get
hydrolysis during 2 years at concentration C(t) = 4·10–3 M
in 0.15 M NaCl, (C(t) is the therapeutic dose for in vivo
study of anti-tumour activity). This fact is confirmed by
the invariance of spectral characteristics of these solutions.
This proved to be essential for the development of the
medicinal form of this compound. In case of solution of
(AH2)2[PdCl4] (where A is 1-phenyl-2-methylaminopropanol) (hereafter compound 1) with рКа = 9.8
with concentration C(t) = 3·10–3 M in 0,15 M NaCl, the
hydrolysis starts within 2 hours after dissolution as
follows from spectral investigations. The decrease of ionic
strength or concentration of compounds in a solution
essentially accelerates the hydrolysis of both compounds
[7].
As far as DNA is the main target for the majority of
antitumor coordination drugs, studying the details of the
binding of such compounds to nucleic acids in a solution
(kinetics, mode of binding, etc.) can not only lead to a
better understanding of the mechanism of action, but may
also result in the directed development of new drugs.
In this study we present the results of studying of in
vitro DNA conformational changes induced by its
interaction with Pd-complex (1) which shows in vivo antimetastatic, immunomodulating and radioprotective
activity [8]
1 Introduction
Current platinum-based anticancer drugs are limited in
their use by their severe side effects, narrow spectrum of
anticancer activity, problems due to drug resistance and
toxicity. In order to obtain compounds with higher
cytotoxicity and lower nephrotoxicity, in the last years
there is a continuing search for the new potential
antitumor complexes [1]. Palladium(II) complexes are
very interesting candidates for alternative metal-based
drugs, since the coordination geometry and complex
forming processes of palladium(II) are very similar to
those of platinum(II). However Pd-complexes have much
higher lability in ligand exchange compared to Ptcomplexes [2]. This could be overcome by introduction of
the bulky heterocyclic ligands at the external coordination
sphere. In vivo research have shown that cationic-anionic
complexes like (AH)2[PdCl4] with heterocyclic ligand A
reveal strong antitumor properties similar to that of
cisplatin, or even greater. Moreover, such complex with
protonated amino-propanol in cation possesses radioprotective and immunomodulating activity [3–5].
Previously published results [6] indicate that Pd
compound with Morpholine ligands display similar and
more significant distortion of DNA conformation
compared to cis-DDP at the same concentration. Such Pd
compounds could be the attractive objects for the
development of new anticancer drugs instead of toxic cisDDP.
It is necessary to note, that stability of Palladium acidcompounds with protonated nitrogen-containing cations in
solutions is controlled by the acid-base properties of the
basis and tetrachloropalladous acid. In such complexes a
ISBN: 978-960-474-278-3
37
Recent Researches in Modern Medicine
The dependence of the birefringence value ∆n on the
velocity gradient g for DNA solution was determined on
an apparatus with a half-shade elliptical compensator. The
(∆n/g)0 determined for g → 0 was used for the calculation
2 Materials and methods
Spectral methods
Circular dichroism (CD) spectra were recorded on a Mark
4 Autodichrograph (Jobin Ivon, France). UV absorption
spectra of compounds under use were recorded on SF-56
Spectrophotometer (Russia).
of the reduced birefringence
independent on DNA concentration and coincides with the
[n]/[η] ratio (where [n] is the dynamooptical constant
(∆n / g )0
). The value [n]/[η] is proportional to
g →0
Cη0
c →0
( [n] = lim
Atomic force microscopy
Images were obtained with a NanoScope 4a (Veeco)
microscope operating in tapping mode. DNA fixation
from solution to the mica surface in the presence of Mg2+
ions (СMg2+ = 5·10–4М) was used.
the optical anisotropy of macromolecule (γ1 – γ2), where γ1
and γ2 are the main polarizabilities of macromolecule
(parallel and perpendicular to the main axis of molecular
ellipsoid which modeling polymer coil in a solution). In
this case [9]:
∆n
[n]
4π (ns 2 + 2)2
(3)
=
=
∆α
g (η − η0 ) [η ] 45kT
ns
where ns is the refraction index of the solvent; T is the
absolute temperature; k is Boltzmann's constant; ∆α is the
difference between the major polarizabilities of the Kuhn
2.3. Viscosimetry
The relative viscosity of solutions ηr = η/η0 (where η and
η0 — the viscosity of the solution and the solvent
correspondingly) was determined at different velocity
gradients g on a Zimm-Crothers type rotation low-gradient
viscosimeter. The values of ηr were extrapolated to the
zero velocity gradient. The intrinsic viscosity [η] was
determined by the extrapolating of concentration
statistical segment. Thus, from
(η r − 1)
dependence of reduced viscosity
to zero DNA
c
(1)
The [η] value is proportional to the specific volume of the
polymer coil in a solution. For macromolecules with a
large molecular mass, the Flory equation is valid:
Φ h2
[η ] =
M
3
2
Materials
Plasmid DNA pFL 44/EcoRI (4.4·103 base pairs) and calf
thymus DNA, Sigma (molecular mass M = 8·106 ) were
used. Molecular mass was determined from the intrinsic
viscosity of DNA in 0.15 M NaCl using the Doty-Eigner
equation [η] = 6.9·10–4M0,7 (for [η] expressed in dl/g). Calf
thymus DNA was dissolved in a water and then salted to
the required NaCl concentration. The DNA concentration
in a base solution was determined by Spirin’s method
[10]. DNA concentration is given in weight percent
throughout the text. Palladium compounds were dissolved
in 5mM NaCl at room temperature.
Compound (C10H16NO)2[PdCl4] (1) with protonated 1phenyl-2-methyl-aminopropanol
(PhAPH)
was
synthesized by the procedure [11]; compound
(C4H10NO)2[PdCl4] (2) with protonated morpholine was
synthesized by the procedure [5]. The interaction of Pdcompounds with DNA was investigated in low (5 mM)
and physiological (0,15 M) concentration of NaCl.
3
Φ LA 2 3
=
α
M
(2)
where <h2>1/2 is the mean square distance between the
ends of the polymer chain, which defines the linear size of
the molecular coil in a solution; M is the molecular mass;
Φ is the Flory parameter, which generally depends on the
swelling effects and polymer rigidity; α is the linear
swelling coefficient of the macromolecule; L is the
hydrodynamic length of macromolecule; A is the length of
the statistical segment that defines the bending chain
rigidity; For the long chains А = 2а , where a is the
persistent length of DNA.
Irradiation
The γ-rays 60Co source with dose rate 20 Gr/min and
photon energy 1.332 MeV (St.Petersburg Institute of
Nuclear Physics RAS) was used. The irradiation of
samples was carried out in aerobic conditions at room
temperature. Dosimetry was conducted by the ferrosulfate
method.
H
CH
OH
CH
N
CH 3
CH 3
PhAPH (1-phenyl-2-methyl-aminopropanol)
Flow birefringence
ISBN: 978-960-474-278-3
∆n
value we can
g (η − η0 )
determine the value ∆α = S ∆β . Here S is the number of
nucleotide pairs in a segment; ∆β is the difference between
the polarizabilities of the nucleotide pairs along the axis of
the DNA helix and perpendicularly to it.
concentration c :
 η −1 
[η ] = lim  r

c→o
 c 
(∆n / g )0
. This value is
(ηr − 1)η0
38
Recent Researches in Modern Medicine
Optical Density
0,8
0,6
1,20
430
1,15
425
1,10
420
1,05
415
λ, nm
It was shown that during the hydrolysis of the compound 1
in 0.15 M NaCl within рН interval from 3 up to 11 the
gradual replacement of Cl in [PdCl4]2– anion leads to the
formation of various derivatives of Palladium complex
ion. The most meaningful forms Pd(l-PhAP)Cl2– and Pd(lPhAP)20 exist within рН interval 4.5 – 6.5 [12]. The time
dependence of рН value for the solution of compound 1 in
0.15 M NaCl (C = 4·10–3 M) indicates that the hydrolysis
endures about 24 hours. So, it was observed the
decreasing of pH value from рН = 5.76 for initial solution
to pH = 4.43 after 3 hours, and pH = 4.35 after 24 hours.
The same experiment for compound 1 in 5 mM NaCl was
also carried out (Fig. 1). Figure 1 shows the timedependence of pH for the solution of 1 (C = 1.2·10–3) in 5
mМ NaCl and рН dependence of solutions of 1 on the
concentration after 4 day storage of the solutions. After a
week of storage it is visually seen that solution of 1 in 5
mM NaCl changes the colour and precipetates. Thus all
DNA complexes with compound 1 were preparing only
with fresh solutions of 1.
Dmax/Dmax t=1
transition band [12] and facilitates DNA interaction with
compound in the solution.
3 Results and discussion
410
1,00
0
0,4
30
0,2
0,0
350
400
450
60
90 120
405
time (h)
1
2
3
4
5
λ, nm
500
550
460
λ max
0,5
450
Optical Density
0,4
440
0,3
430
1
2
3
4
5
0,2
0,1
0
25
50
75
100
time (h)
4,5
0,0
6
400
pH
pH
4,0
3,5
3,0
0
5
10
Time (h)
15
20
0,0
0,3
0,6
0,9
1,2
Concentration of 1 (mM)
Figure 1. Left: Time-dependence of pH value for 1 (C = 1.2·10–
3
) in 5 mМ NaCl. Right: The dependence of рН value on the
concentration of solution of 1 in 5 mМ NaCl.
500
550
UV absorption spectra of DNA complexes with 1 in
0.15 M (a) and 5 mM NaCl (b) are presented in Figure 3.
These results show that DNA does not interact with 1 in
0.15 M NaCl. The calculated total spectrum of DNA and 1
coincides with the spectrum of the solution containing
same concentrations of both components. It can be
explained by the formation of a Pd-complex with
Figure 2 shows the absorption spectra of 1 in 5 mM
and 0.15 M NaCl depending on the time of storage of its
solution at room temperature. The spectral data presented
in Figure 2 reflect the variation of coordination sphere of
Palladium ion during the hydrolysis of 1. As it was shown
in the previous work [13] for the close system Pd(II)PhAPH-Cl-H2O (PhAPH is presented above) the shift of a
long-wave band in absorption spectra during hydrolysis is
connected with the substitution of chlorine atoms from the
Palladium coordination sphere on PhAPH-ligand with the
formation of Pd(l-PhAP)Cl2– and Pd(l-PhAP)20. We
propose that spectral changes for compound 1 in 0.15 M
NaCl (Fig. 2 right) indicate the same process. As it is seen
in Figure 2 (left) at the first moment after the dissolving of
1 in 5 mM NaCl the maximum of the long-wave band is
already at 425 nm. This testifies that some chlorine ions
from the coordination sphere of Palladium are already
replaced with the molecules of water. The hydrolysis of 1
in 5 mМ NaCl, at low concentration of chlorine ions, as a
rule, leads to the chlorine ion substitution in the Palladium
coordination sphere on water molecule. Such substitution
is accompanied by a significant decrease in the d-d
ISBN: 978-960-474-278-3
λ, nm
Figure 2. Above: Time-dependence of absorption spectra of 1
in 5mM NaCl; 1 – 5 min, 2 – 50 min, 3 – 2 h; 4 – 27 h, 5 – 95 h
C(1) = 30·10–4. Below: Time-dependence of absorption spectra
of 1in 0.15 M NaCl; 1 – 5 min; 2 – 50 min, 3 – 2 h, 4 – 27 h, 5 –
95 h; C(1) = 30·10–4. Inserts: Time dependence of the amplitude
and the position of appropriate bands in absorption spectra of 1
after dilution.
4
2
0
450
O
N
Pd
O ) complicating
chelating ligand PhAP (like N
its interaction with DNA. In contrast, at low ionic strength
one can see spectral changes indicating DNA interaction
with 1 (Fig. 3 b).
It is to be noted, that complex 2 with protonated
morpholine interacts with DNA even in 0.15 M NaCl.
Indeed, the morpholine molecule formed at the first stage
of complex 2 hydrolysis has only one nitrogen atom
capable for coordination with Palladium. Thus the vacant
positions in Palladium coordination sphere enable its
coordination to DNA.
At physiological NaCl concentration the hydrolysis of
compounds 1 and 2 with protonated amines in cation is
accompanied with the break of NH···Cl hydrogen bonds
and deprotonation of nitrogen-containing ligand with
further its coordination to Palladium with the formation of
amino compounds. Thus the high concentration of
39
Recent Researches in Modern Medicine
chlorine ions in 0.15 M NaCl prevents or slowing down
the hydrolysis depending on the nature of protonated
amine in compound. Thus the nature of cation is very
essential for the hydrolysis which finally leads to the
formation of amino compounds as per the following
scheme:
.15 MNaCl
[ AH ]m [ PdCl4 ] 0
→[ PdCl2 A2 ] + Am −2 + 2 HCl
Optical Density
The data presented in Figure 4 for DNA complexes
with 1 testifies, that the hydrolysis of Palladium
compound in a solutions with low concentration of a
compound (C = 0.23·10–4 M) and low concentration of
NaCl (5 mM NaCl) occurs very quickly. The coincidence
curves 4, 5 and 6 indicate that DNA interacts with the
same form of the complex ion, regardless of holding time
of solution of 1. After DNA-Pd complex formation the
coordination sphere remains stable in time.
Let us compare DNA interaction with Palladium
compounds 1, 2 and K2[PdCl4]. Figure 5 shows the
spectral changes resulting from the interaction of DNA
with these compounds in 5 mM NaCl. The absorption
spectra of resulting solutions show the identical results of
DNA interaction with 1, 2 and K2[PdCl4]. The
bathochromic shift of the calculated DNA absorption band
after the formation of complexes (maximum at 260 nm
moves up to 270 ± 2 nm) is observed for all systems under
discussion.
1
2
3
4
0,6
0,4
0,2
0,0
220
240
260
280
300
320
340
λ, nm
b)
1
2
3
4
0,6
à)
0,4
0,6
Optical Density
Optical Density
0,8
0,2
0,0
220
240
260
280
300
320
340
λ, nm
Optical Density
0,6
280
Optical Density
280
300
λ, nm
320
c)
1
2
3
0,2
260
280
300
λ, nm
320
Earlier it was shown that similar results were observed for
compounds binding in the major groove of DNA with
coordination to N7 Guanine [14]. Circular dichroism (CD)
spectra of DNA in complexes with 1, 2 and K2[PdCl4] in 5
mМ NaCl (Figure 6) also show the similarity in DNA
conformational changes. These results testify the absence
of the influence of the cation nature in Palladium complex
on the result of DNA binding with compounds under
consideration.
300
Figure 4. UV absorption spectra: 1 – DNA; 2 – 1 (20 min after
dilution); 3 – 1 (24 hours after dilution); 4 – a complex of DNA
ISBN: 978-960-474-278-3
260
Figure 5. Absorption spectra of DNA solutions in interaction
with 2 (a), 1 (b) and K2 [PdCl4] (c) in 5 mM NaCl after 24 hours
of solutions seasoning. 1 – DNA; 2 – DNA-Pd complex; 3 –
calculated spectra of DNA in complex with Pd-compounds.
Concentrations of Pd-compounds are 0.5·10–4М.
0,2
λ, nm
0,2
0,4
0,0
240
1
2
3
4
5
6
0,4
0,4
0,0
240
320
1
2
3
0,6
The hydrolysis of compounds at their low
concentrations and in low ionic strength (5 mM NaCl) is
accompanied by the breaking of hydrogen bonds NH···Cl
and the replacement of chlorine with a molecule of water
or hydroxyl group. In these cases the nature of cation in
Palladium compound does not influence on the hydrolysis
process.
260
0,2
260 280 300
Figure 3. UV absorption spectra of DNA in complex with 1 in
0.15 M NaCl (a) and 5 mM NaCl (b). 1 – DNA; 2 – 1; 3 –
Spectrum of DNA complex with 1; 4 – Calculated total
spectrum of DNA and 1. C(1) = 0.23·10–4 M.
240
0,4
b)
0,6
0,0
λ, nm
0,0
220
1
2
3
Optical Density
à)
0,8
with 1 after 20 min of the dilution of 1; 5 – spectrum of system
4 after 24 hours; 6 – DNA complex with 1 after 24 hours of
dilution of 1. C(1) = 0.23·10–4 M, 5 mM NaCl.
40
Recent Researches in Modern Medicine
dl/g) is four-times below than that for free DNA in 5 mМ
NaCl ([η] = (80±2) dl/g). According to Flori’s formula
(equation 2), it might be caused by reduction of DNA
persistent length or by decrease in volume effects
(magnitude α) because of less polyelectrolyte swelling of
macromolecule caused by screening of its negative
charges on phosphates by Palladium binding. According
to the results of Flow Birefringence experiments (Fig. 7 b)
we can propose that DNA persistent length changes during
the interaction with compounds. The experiment has
shown that the formation of DNA complexes with 1 and 2
is accompanied by decrease of DNA optical anisotropy. It
can be attributed to the fall of DNA persistent length or to
the reduction of average optical anisotropy of base pairs
due to the changing of its slope angle to helix axes owing
to binding. It may also be caused by the destabilization of
DNA double-strand structure due to the complex
formation. Nevertheless, the latter is not confirmed by
spectral experiments. Calculations and the comparison of
this result with the viscometric data have shown, that just
variation of DNA rigidity (persistent length) cannot
explain the experimentally observed reduction of optical
anisotropy during binding. We can assume that the
formation of a DNA-Pd complex provokes changing in the
nitrogen bases orientation or other deformation of a DNA
secondary structure. We can not also exclude the possible
bend of DNA chains at the points of binding with
Palladium as it is observed in case of Cisplatin. The
results of atomic force microscopy research confirm this
conclusion (Fig. 8, left).
∆ε (cm-1M-1)
2
1
0
1
2
3
4
-1
-2
-3
240
260
280
300
λ, nm
Figure 6. CD spectra of DNA (1), complexes of DNA with 1
(2), 2 (3) and K2[PdCl4] (4) in 5 mM NaCl. С(1, 2, K2[PdCl4]) =
2·10–5 М, С(DNA) = 1·10–3 %.
à)
ηsp/ηsp0
1,0
1
2
0,5
0,0
(γ1−γ2)/(γ1−γ2)0
0
50
100
150
Concentration µ M
b)
1,0
200
250
1
2
0,5
0,0
0
20
40
60
80
Concentration µ M
100
120
Figure 7. Relative change in specific viscosity (a) and optical
anisotropy (b) of DNA solutions with 1 (C(DNA) = 7.8·10–3 %)
(1) and 2 (C(DNA) = 7.7·10–3 %) (2). Measurements were taken
in 1 hour after preparation of DNA-Pd complexes; 5 mM NaCl.
Hydrodynamic experiments show the decrease of DNA
molecular coil in a solution, when linked with considered
Palladium compounds (Fig. 7). One can see the similarity
of relative changes in specific viscosity of the solutions
containing DNA complexes with 1 and 2 depending on
Pd-concentration. The dependence contains the region of
rapid viscosity decline and the area of its saturation. The
saturation of binding to a macromolecule is realized when
for each 10 DNA base pairs there are more than 8
Palladium atoms.
DNA intrinsic viscosity is proportional to the specific
volume of a molecular coil. The value of intrinsic
viscosity in the area of saturation of binding ([η] = (20±2)
ISBN: 978-960-474-278-3
Figure 8. Left: AFM images of linearized plasmid DNA (a),
DNA in complex with K2[PdCl4] (b) – С(K2[PdCl4]) = 6·10–7 М,
С(DNA) = 4·10–5 %; DNA in complex with 1 (c) –
С(1) = 7.5·10–7 M, С(DNA) = 4·10–5 %, (e) – С(1) = 0.5·10–4 М,
С(DNA) = 2·10–4 %; DNA in complex with 2 (d) – С(2) = 6·10–
7
М, С(DNA) = 4·10–5 %, (f) – С(2) = 0.25·10–4 М, С(DNA)
= 2·10–4 %. Image size is 1x1 µm. Right: AFM images of DNA
41
Recent Researches in Modern Medicine
(C = 2·10–4 %) (1), DNA exposed to a dose of 15 Krad radiation
(C(DNA) = 2·10–4 %) (2) DNA in complex with 1 and exposed
to a dose of 15 Krad (C(DNA) = 2·10–4 %, C(1) = 7·10–6 М) (3)
5 mM NaCl. Image size is 3x3 µm.
[2] D.S. Gill, in: M.P. Hacker, E.B. Douplr, I.H. Krakoff
(Eds.), Platinum Coordination Complexes in Cancer
Chemotherapy, Nijhoff, Boston, 1984, pp. 267–278.
[3] I. A. Efimenko, N. A. Ivanova, and B. V. Lokshin, RF
Patent No. Ru 2291872, C.2, Palladium complexes
with heterocyclic ligands. Published 20.01.2007; Byull.
Izobr., 2007, No 2.
[4] I. D. Treshchalin, Ros. Bioter. Zh., 1, No. 2, 2002, pp.
145-147.
[5] I.A. Efimenko and N.A. Ivanova, Palladium
coordination compound and method for its preparation.
Eurasian Patent No 010431 of 29.08.2008, Byull.
Izobr., No. 4 (2008).
[6] N.A.Kasyanenko, E.V. Levykina, O.S. Erofeeva, N.A.
Ivanova, I.A. Efimenko. Journal of Structural
Chemistry. Vol. 50, No. 5, 2009, pp. 996-1006.
[7] I.A.Zakharova. Moskow. Science, 1988, p. 171 (in
Russian).
[8] M.D. Pomeranceva, A.V. Chekhovich, L.K. Romaya,
I.A. Efimenko, S.R. Grap. Radiation Biology.
Radioecology, 1995, t. 35, No 5, p. 765 (in Russian).
[9] E. V. Frisman, L. V. Shchagina, V. I. Vorob’yov, and
G. V. Shapiro, Biokhimiya, 31, No. 5, 1966, pp. 10271032 (in Russian).
[10] A. S. Spirin, Biokhimiya, 23, No. 5, 1958, p. 655.
[11] I.A. Efimenko, A.P. kurbakova, N.A. Ivanova, Y.A.
Revazova et al. Patent No 2022968 of 15.11.94, Byull.
Izobr., No 21, 1994
[12] I.A. Efimenko, N.A. Ivanova, O.S. Erofeeva, M.E.
Akateva, N.A. Dobrinina. Coordination Chemistry, t.
35, No 4, 2009, p. 276.
[13] M.E.Akateva, O.S. Erofeeva, N.A. Dobrinina, N.A.
Ivanova, I.A. Efimenko. Coordination Chemistry, t.
30, No 8, 2004, p. 621.
[14] Kasyanenko, N.A.; Nikolenko, O.V.; Prokhorova,
S.A.; Smorygo, S.A.; Djaschenko, S.A.; Ivin, B.A.;
Frisman, E.V. Mol. Biol., 31, 1997, pp. 240-224.
[15] G.B. Onoa, G. Cervantes, V. Moreno, and M.J.
Prieto, Nucl. Acids Res., 26, No. 6, 1998, pp. 14731480.
Figure 8 shows AFM images of free DNA and DNA in
a complex with the considered compounds. For complexes
of DNA with 1 and 2 at concentration of compounds at the
rate of 10–4 M the homogeneous compact structures are
observed (fig. 8 e, f). Formation of compact
nanostructures of DNA in complex with Palladium
compounds was observed by other authors as well [15].
At lower concentration of a Palladium (using 1, 2 or
K2[PdCl4]) it is possible to see the formation of structures
of other type (Fig.8 b, c, d). DNA chains become shorter
and thicker. In some cases we can see structures like
«beads on a thread», that might be due to the formation of
intra-molecular DNA linkages, induced by the bonded
Palladium.
Preliminary data showed that 1 exhibits the
radioprotection properties. So the experiments with the
irradiation of DNA in the presence and absence of 1 were
carried out. They have shown smaller damage effects of
radiation on the solutions of DNA which have been
exposed to gamma rays (15 Krad) in the presence of 1,
comparing to the reference systems without 1 (Fig. 8,
right).
The received data about the influence of 1 on the
radioactive stability of DNA in a solution are interesting
for the understanding of the role of DNA stability during
the protection of organism against ionizing radiation.
Comparative study of antiradiation activity of compound 1
and similar compounds of Platinum (II) Platinum (IV) in
vivo (Table 1) unequivocally prove the absence of
antiradiation activity of the Platinum compounds in
contrast to compound 1.
Table 1. Comparative radiation-modified activity of acidcompounds of Pd and Pt☼
☼
Compound 15 mg/kg 30 minutes
before irradiation Dose – 9 Gr, τ – 83
sec. Male mice F1(CBA x C57Bl)
Control dose
(PhAPH2)2[PdCl4]
(PhAPH2)2[PtCl4]
(PhAPH2)2[PtCl6]
Survival
rate on the
20th day, %
50
100
50
40
Biological experiment carried out by a group of researchers
under the head of I. D. Treshalin at SU SRI for finding new
antibiotics named after G. F. Gause a part of RAMS (Russian
Academy of Medical Sciences)
References:
[1] M. Groessl, E. Reisner, C.G. Hartinger, R. Eichinger,
O.Semenova, A.R. Timerbaev, M.A. Jakupec, V.B.
Arion, B.K. Keppler, J. Med. Chem., 50 (2007) 2185
ISBN: 978-960-474-278-3
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