1

Synthesis, characterization and biological activity of Zn coordination

compounds with the quinolone gatifloxacin

Chrisoula Kakoulidou,a Stavros Kalogiannis,

b Panagiotis Angaridis,

a George Psomas,

a,*

a Department of General and Inorganic Chemistry, Faculty of Chemistry, Aristotle University of

Thessaloniki, GR-54124 Thessaloniki, Greece.

b Department of Nutrition and Dietetics, Faculty of Agriculture, Food Technology and Nutrition,

Alexander Technological Educational Institution, Sindos, Thessaloniki, Greece.

Supplementary Information

S1. Interaction with CT DNA

The binding constant, Kb, can be obtained by monitoring the changes in the absorbance at

the corresponding λmax with increasing concentrations of CT DNA and it is given by the ratio of

slope to the y intercept in plots [DNA]/(εA-εf) versus [DNA], according to the Wolfe-Shimer

equation [1]:

)ε(εK

1

)ε(ε

[DNA]

)ε(ε

[DNA]

fbbfbfA

(eq. S1)

where [DNA] is the concentration of DNA in base pairs, εA = Aobsd/[compound], εf = the extinction

coefficient for the free compound and εb = the extinction coefficient for the compound in the fully

bound form.

S2. Competitive studies with EB

The Stern-Volmer constant (KSV, in M-1

) is used to evaluate the quenching efficiency for

each compound according to the Stern–Volmer equation [2]:

]Q[K+1=]Q[τk+1=I

IoSV0q (eq. S2)

where Io and I are the emission intensities of the EB-DNA solution in the absence and the presence

of the quencher, respectively, [Q] is the concentration of the quencher (i.e. complexes 1-4), τo = the

average lifetime of the emitting system without the quencher and kq = the quenching constant. KSV

may be obtained from the Stern-Volmer plots by the slope of the diagram Io/I versus [Q]. Taking τo

= 23 ns as the fluorescence lifetime of the EB-DNA system [3], the quenching constants (kq, in M-

1s

-1) of the compounds can be determined according to eq. S3.

* Corresponding author’s e-mail: gepsomas@chem.auth.gr (G. Psomas)

2

KSV = kqτo (eq. S3)

S3. Interaction with serum albumins

The extent of the inner-filter effect can be roughly estimated with the following equation:

2

cd)(

2

cd)(

meascorr

emexc

1010II (eq. S4)

where Icorr = corrected intensity, Imeas = the measured intensity, c = the concentration of the

quencher, d = the cuvette (1 cm), ε(λexc) and ε(λem) = the ε of the quencher at the excitation and the

emission wavelength, respectively, as calculated from the UV-vis spectra of the complexes [4].

The Stern-Volmer and Scatchard graphs are used in order to study the interaction of a

quencher with serum albumins. According to Stern-Volmer quenching equation (eq. S2) [2], where

Io = the initial tryptophan fluorescence intensity of SA, I = the tryptophan fluorescence intensity of

SA after the addition of the quencher, kq = the quenching constant, KSV = the Stern-Volmer

constant, τo = the average lifetime of SA without the quencher, [Q] = the concentration of the

quencher. KSV (M-1

) can be obtained by the slope of the diagram Io/I versus [Q], and subsequently

the quenching constant (kq, M-1

s-1

) is calculated from equation S3 (eq. S3) with τo = 10-8

s, as

fluorescence lifetime of tryptophan in SA.

From the Scatchard equation [4]:

Io

ΔIKnK

[Q]

IoI

(eq. S5)

where n is the number of binding sites per albumin and K is the SA-binding constant. K (in M-1

) is

calculated from the slope in plots [Q]

IoI

versus Io

ΔI and n is given by the ratio of y intercept to the

slope [5].

References

[1] A. Wolfe, G. Shimer, T. Meehan, Biochemistry 26 (1987) 6392-6396.

[2] J.R. Lakowicz, Principles of Fluorescence Spectroscopy, 3rd

ed. Plenum Press, New York,

2006.

[3] D.P. Heller, C.L. Greenstock, Biophys. Chem. 50 (1994) 305-312.

[4] L. Stella, A. L. Capodilupo, M. Bietti, Chem. Commun. (2008) 4744-4746.

[5] Y. Wang, H. Zhang, G. Zhang, W. Tao, S. Tang, J. Lumin. 126 (2007) 211-218.

3

Table S1. The HSA constants and parameters for gatifloxacin and its complexes 1-4.

Compound Ksv (M-1

) kq (M-1

s-1

) K (M-1

) n

Gatifloxacin 7.85(±0.26)×104

7.85(±0.26)×1012

7.54(±0.42)×104

1.00

[Ζn(gati)2(CH3OH)2], 1 2.64(±0.16)×104 2.64(±0.16)×10

12 5.76(±0.17)×10

4 0.31

[Ζn(gati)2(bipy)], 2 8.17(±0.41)×104 8.17(±0.41)×10

12 4.43(±0.09)×10

4 1.31

[Ζn(gati)2(phen)], 3 5.28(±0.25)×104 5.28(±0.25)×10

12 7.87(±0.63)×10

3 4.04

[Zn(gati)2(bipyam)], 4 8.10(±0.40)×104 8.10(±0.40)×10

12 9.13(±0.15)×10

4 0.91

Table S2. The BSA constants and parameters for gatifloxacin and its complexes 1-4.

Compound Ksv (M-1

) kq (M-1

s-1

) K(M-1

) n

Gatifloxacin 2.04(±0.07)×105 2.04(±0.07)×10

13 1.17(±0.05)×10

5

[Ζn(gati)2(CH3OH)2], 1 3.67(±0.20)×104 3.67(±0.20)×10

12 2.35(±0.20)×10

4 1.09

[Ζn(gati)2(bipy)], 2 1.65(±0.10)×105

1.65(±0.10)×1013

4.75(±0.29)×104 1.74

[Ζn(gati)2(phen)], 3 9.13(±0.47)×104 9.13(±0.47)×10

12 3.53(±0.21)×10

4 1.66

[Zn(gati)2(bipyam)], 4 7.94(±0.37)×104 7.94(±0.37)×10

12 2.06(±0.07)×10

4 2.33

4

Figure S1. ESI-MS(+) spectra of complex 1 in methanol solution. Molecular ion (m/z): found,

876.0; calcd., 878.25.

5

Figure S2. ESI-MS(+) spectra of complex 2 in methanol solution. Molecular ion (m/z): found,

968.0; calcd., 970.3.

6

Figure S3. ESI-MS(+) spectra of complex 3 in methanol solution. Molecular ion (m/z): found,

993.0; calcd., 994.37.

7

Figure S4. ESI-MS(+) spectra of complex 4 in methanol solution. Molecular ion (m/z): found,

984.0; calcd., 985.37.

8

(a)

(b)

Figure S5. Geometry optimized molecular structures of the lowest-energy isomers of

[Zn(gati)2(phen)], 3: (a) in gas-phase; isomer 3h, (b) in methanol; isomer 3f. (The atoms of the

coordination sphere of Zn are labeled. The colors of the rest atom are as follows: Zn in dark green,

C in grey, O in red, N in blue, F in light blue).

9

(a)

(b)

Figure S6. Geometry optimized molecular structures of the lowest-energy isomers of

[Zn(gati)2(bipyam)], 4: (a) in gas-phase; isomer 4h, (b) in methanol; isomer 4g. (The atoms of the

coordination sphere of Zn are labeled. The colors of the rest atom are as follows: Zn in dark green,

C in grey, O in red, N in blue, F in light blue).

10

0 2 4 6 8 10 12

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

[DNA] ( M)

{[D

NA

]/(

A-

F)}

x1

08,

(M2cm

)(A)

2 4 6 8 10 12 14-6

-5

-4

-3

-2

-1

{[D

NA

]/(

A-

F)}

x1

09,

(M2cm

)

[DNA] ( M)

(B)

4 6 8 10 12 14 16 18 20 22 243

4

5

6

7

8

9

10

11

{[D

NA

]/(

A-

F)}

x10

9,

(M2cm

)

[DNA] ( M)

(C)

14 16 18 20 22 24 26 28 30 32 34

2

3

4

5

6

7

8

9

[DNA] ( M)

{[D

NA

]/(

A-

F)}

x1

09, (M

2cm

)

(D)

Figure S7. Plot of )ε(ε

[DNA]

fA

vs [DNA] for complex (A) 1, (B) 2, (C) 3, (D) 4.

11

0 1 2 3 4 5

1.0

1.2

1.4

1.6

1.8

2.0

[1] ( M)

Io/I

(A)

0 1 2 3 4 5 6

1.0

1.5

2.0

2.5

3.0

3.5

4.0

[2] ( M)

Io/I

(B)

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

1.0

1.1

1.2

1.3

1.4

1.5

[3] ( M)

Io/I

(C)

0 1 2 3 4 5

1

2

3

[4] ( M)

Io/I

(D)

Figure S8. Stern-Volmer quenching plot of EB-DNA fluorescence for complex (A) 1, (B) 2, (C) 3,

(D) 4.

12

0 2 4 6 8 10 12 14 16

1.0

1.1

1.2

1.3

1.4

1.5

Io/I

[1] ( M)

(A)

0 2 4 6 8 10 12 14 16

1.0

1.5

2.0

2.5

3.0

3.5

Io/I

[2] ( M)

(B)

0 2 4 6 8 10 12 14 16 18

1.0

1.5

2.0

2.5

[3] ( M)

I/Io

(C)

0 2 4 6 8 10 12 14 16

1.0

1.2

1.4

1.6

1.8

2.0

2.2

I/Io

[4] ( M)

(D)

Figure S9. Stern-Volmer quenching plot of BSA for complex (A) 1, (B) 2, (C) 3, (D) 4.

13

0 2 4 6 8 10 12 14 16

1.0

1.1

1.2

1.3

1.4

I/Io

[1] ( M)

(A)

0 5 10 15 20

1.0

1.5

2.0

2.5

I/Io

[2] ( M)

(B)

0 5 10 15

1.0

1.2

1.4

1.6

1.8

2.0

I/Io

[3] ( M)

(C)

0 5 10 15 20

1.0

1.5

2.0

2.5

I/Io

(D)

Figure S10. Stern-Volmer quenching plot of HSA for complex (A) 1, (B) 2, (C) 3, (D) 4.

14

0.0 0.1 0.2 0.3 0.4 0.5

14000

16000

18000

20000

22000

24000

26000

28000

( I/Io)

(I/

Io)/

[1]

(A)

0.3 0.4 0.5 0.6 0.7 0.840000

50000

60000

70000

( I/Io)

(I/

Io)/

[2]

(B)

0.3 0.4 0.5 0.6 0.7

35000

40000

45000

( I/Io)

(I/

Io)/

[3]

(C)

0.1 0.2 0.3 0.4 0.5 0.6 0.7

35000

40000

45000

( I/Io)

(I/

Io)/

[4]

(D)

Figure S11. Scatchard plot of BSA for complex (A) 1, (B) 2, (C) 3, (D) 4.

15

0.02 0.04 0.06 0.08 0.10

13000

14000

15000

16000

17000

( I/Io)

(I/

Io)/

[1]

(A)

0.40 0.45 0.50 0.55 0.60

32000

34000

36000

38000

40000

( I/Io)

(I/

Io)/

[2]

(B)

0.2 0.3 0.4 0.528000

29000

30000

( I/Io)

(I/

Io)/

[3]

(C)

0.48 0.50 0.52 0.54 0.56

32000

34000

36000

38000

40000

( I/Io)

(I/

Io)/

[4]

(D)

Figure S12. Scatchard plot of HSA for complex (A) 1, (B) 2, (C) 3, (D) 4.