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R. Barbieri et al.
iiLMeSn(SPyh(DNA monomer) in the gel phase corresponds to the gel Me2Sn(SPym)
(DNA monomer) as well as to Alk2Sn(DNA monomerh and MeSnCln(DNA
monomerh_n (Table 12.3).
iv. Lyophilized MeSn(SPyMDNA monomer) shows a phase transition around T = 210 K;
in the range 210-290 K, the In A I T function shows a slope of the order of magnitude similar to that for the gel phase, as well as for Me2Sn(SPym)(DNA monomer)
and lyophilized Alk2Sn(DNA monomerh (Table 12.3).
It is concluded that the complex cation species Me2Sn(SPymt and MeSn(SPy)i bind
DNA analogously to MeSn(IV) and Alk2Sn(IV), Tables 12.2 and 12.3; the type of interaction does not depend upon the water content of the system for Me2Sn(SPym)
(DNA monomer) and MeSnCln(DNA monomerh_n (Table 12.3), Et2Sn(DNA monomerh
(Table 12.3), Et 3 Sn(DNA monomer) (Table 12.3), and MeSn(SPyh(DNA monomer) in
the temperature range 77-3-207.5 K (Table 12.5). The variations detected in the gelled
phases with respect to freeze-dried specimens could be ascribed to outer sphere DNA
bonding (Nordmeier 1995) through Sn coordinated H20 molecules, analogous to findings for Mg(H20)~+ (Black et al. 1994).
The interaction of nucleic acids with proteins, and constituent molecules, is widely
studied (Harrison and Sauer 1994; Phillips and Moras 1995; Sauer and Harrison 1996;
Rhodes and Burley 1997; Richmond and Steitz 1998). The affinity between the proteinnucleic acid systems is demonstrated in peptide nucleic acid, PNA (Nielsen 1997;
Nielsen and Haaima 1997), and its interaction with DNA (Nielsen 1997; Kosaganov et al.
1998). Metal ions and complexes interact with nucleic acids and proteins, and their
constituents, in ternary systems (Sabat 1996; Long et al. 1996; Harada et al. 1996).
Polypeptides bind also to toroidal DNA condensates (Reich et al. 1990). In this context, the interaction of organotins with nucleic acid in the presence of amino acids
has been investigated by 119Sn Mossbauer spectroscopy, and the results obtained are
reported in Table 12.6 (Barbieri 1995).
The following considerations can be made:
i. The aqueous systems NO.1 and 2 consist of species Me2Sn[S(CH2hCOO] and
Me2Sn[SCH2CH(NH2)COO], with trigonal bipyramidal tin environments (equatorial C 2 SnS; axial 2 H 2 0, H 2 0 and N, H 2 0 and OH-, as function of pH; Silvestri et al.
1988; Barbieri and Musmeci 1988; Barbieri et al. 1990). Then, the complexes above
do not interact with DNA in systems 1, Table 12.6. In fact, the Mossbauer parameters
of NO.1 strictly correspond to those of the complexes NO.2, so that the latter, formally characterized by partial positive charge on tin (Silvestri et al. 1988; Barbieri
and Musmeci 1988), do not induce DNA condensation nor bonding to DNA
phospho diester groups in solution phases (which would be expected to occur in 1/1
ratio by assuming the occurrence of R 2 Sn + 1 ).
ii. The system NO.3, Table 12.6, produces the condensed phase species Et2Sn(DNA
monomerh, with trans-Et2 octahedral tin environment (No.7 in Table 12.2, structure
in Fig. lub; in the supernatant, NO.4 in Table 12.6, both Et2Sn(DNA monomerh and
Et2Sn[SCH 2 CH(NH2)COO] (No.5 in Table 12.6) could be assumed to occur, according to the magnitude of the M parameters. The complex Et2Sn[SCH2CH(NH2)COO],
NO.5, corresponds to the Me2Sn(IV) complexes, NO.1, the same hyperfine parameters being detected (Table 12.6).
R. Barbieri et al.
iiLMeSn(SPyh(DNA monomer) in the gel phase corresponds to the gel Me2Sn(SPym)
(DNA monomer) as well as to Alk2Sn(DNA monomerh and MeSnCln(DNA
monomerh_n (Table 12.3).
iv. Lyophilized MeSn(SPyMDNA monomer) shows a phase transition around T = 210 K;
in the range 210-290 K, the In A I T function shows a slope of the order of magnitude similar to that for the gel phase, as well as for Me2Sn(SPym)(DNA monomer)
and lyophilized Alk2Sn(DNA monomerh (Table 12.3).
It is concluded that the complex cation species Me2Sn(SPymt and MeSn(SPy)i bind
DNA analogously to MeSn(IV) and Alk2Sn(IV), Tables 12.2 and 12.3; the type of interaction does not depend upon the water content of the system for Me2Sn(SPym)
(DNA monomer) and MeSnCln(DNA monomerh_n (Table 12.3), Et2Sn(DNA monomerh
(Table 12.3), Et 3 Sn(DNA monomer) (Table 12.3), and MeSn(SPyh(DNA monomer) in
the temperature range 77-3-207.5 K (Table 12.5). The variations detected in the gelled
phases with respect to freeze-dried specimens could be ascribed to outer sphere DNA
bonding (Nordmeier 1995) through Sn coordinated H20 molecules, analogous to findings for Mg(H20)~+ (Black et al. 1994).
The interaction of nucleic acids with proteins, and constituent molecules, is widely
studied (Harrison and Sauer 1994; Phillips and Moras 1995; Sauer and Harrison 1996;
Rhodes and Burley 1997; Richmond and Steitz 1998). The affinity between the proteinnucleic acid systems is demonstrated in peptide nucleic acid, PNA (Nielsen 1997;
Nielsen and Haaima 1997), and its interaction with DNA (Nielsen 1997; Kosaganov et al.
1998). Metal ions and complexes interact with nucleic acids and proteins, and their
constituents, in ternary systems (Sabat 1996; Long et al. 1996; Harada et al. 1996).
Polypeptides bind also to toroidal DNA condensates (Reich et al. 1990). In this context, the interaction of organotins with nucleic acid in the presence of amino acids
has been investigated by 119Sn Mossbauer spectroscopy, and the results obtained are
reported in Table 12.6 (Barbieri 1995).
The following considerations can be made:
i. The aqueous systems NO.1 and 2 consist of species Me2Sn[S(CH2hCOO] and
Me2Sn[SCH2CH(NH2)COO], with trigonal bipyramidal tin environments (equatorial C 2 SnS; axial 2 H 2 0, H 2 0 and N, H 2 0 and OH-, as function of pH; Silvestri et al.
1988; Barbieri and Musmeci 1988; Barbieri et al. 1990). Then, the complexes above
do not interact with DNA in systems 1, Table 12.6. In fact, the Mossbauer parameters
of NO.1 strictly correspond to those of the complexes NO.2, so that the latter, formally characterized by partial positive charge on tin (Silvestri et al. 1988; Barbieri
and Musmeci 1988), do not induce DNA condensation nor bonding to DNA
phospho diester groups in solution phases (which would be expected to occur in 1/1
ratio by assuming the occurrence of R 2 Sn + 1 ).
ii. The system NO.3, Table 12.6, produces the condensed phase species Et2Sn(DNA
monomerh, with trans-Et2 octahedral tin environment (No.7 in Table 12.2, structure
in Fig. lub; in the supernatant, NO.4 in Table 12.6, both Et2Sn(DNA monomerh and
Et2Sn[SCH 2 CH(NH2)COO] (No.5 in Table 12.6) could be assumed to occur, according to the magnitude of the M parameters. The complex Et2Sn[SCH2CH(NH2)COO],
NO.5, corresponds to the Me2Sn(IV) complexes, NO.1, the same hyperfine parameters being detected (Table 12.6).