232
R. Barbieri et al.
bipyramidal with equatorial C, C atoms; triorganotin derivatives would assume both
trigonal bipyramidal (equatorial C atoms) and tetrahedral configurations. The nature
of tin bonding atoms other than C has not been assigned. The field has been recently
reviewed, bond angles and structures being extensively reported together with 119Sn
Mossbauer parameters (Barbieri et al. 1998; Musmeci et al. 1992).
12.4
Hemoglobin
Bonding of Alk3Sn(IV) and Me2Sn(IV) with cat and rat hemoglobin tetramers has been
interpreted in terms of the primary coordination of tin by thiol functions of cysteine 13,
and eventually by heterocyclic nitrogen of histidine 113; regular, as well as distorted,
tetrahedral and trigonal bipyramidal structures of tin environments have been extracted
from point-charge model treatment of M parameters (Barbieri et al. 1998). It seems
worthwhile to note the recent publication of an extended review on the classification
and structure function analysis of metal binding sites in proteins (Holm et al. 1996).
12.5
Deoxyribonucleic Acid
The research field inherent to the interaction of metal ions with nucleic acids, as well
as the consequent condensation of DNA, is amply investigated (Berthon 1995; Bregadze
1996, Bloomfield 1996). Interactions involving organometal derivatives have been also
studied, such as organomercury-DNA (see e.g. Gruenwedel1985; Gruenwedel and
Cruikshank 1990), and the organotin-DNA systems treated below. The results of 119Sn
Mossbauer spectroscopy studies on structure and molecular dynamics of systems
AlknSn(IV)-deoxyribonucleic acid (DNA; n = 1-3), are here summarized and discussed;
for representative complexes and systems, values of hyper fine parameters are reported
in Table 12.2, and molecular dynamics data and functions in Table 12.3. The discussion
and structural assumptions in the following are based upon the research cited in
Table 12.2 and 12.3, according to the Mossbauer spectroscopy principles and data treatment procedures sketched in a recent review (Barbieri et al. 1998). Further work in the
field has been discussed previously (Piro et al. 1992; Barbieri et al. 1998).
The hyperfine parameters of the DNA condensates obtained by addition of MeSnCl 3
in ethanol solutions to aqueous buffered native DNA (calf thymus) appear to be constant at any ratio [Sn]-[DNA monomer] in the gel phases (Table 12.2, No. 1-4). Data
are invariant with temperature (in the ranges reported in Table 12.3, No.6), as well as
with the H 2 0 content in the condensed phases, the values for lyophilized samples exactly corresponding to those for the gels. A possible structure is shown in Fig. 12.1a;
no definite attributions from M data are possible, as often detected for RSn(IV) derivatives. The slopes of functions, total area under the resonant peaks vs. T, No.6 in
Table 12.3, are also invariant for gels and lyophilized condensates, and correspond to
the general occurrence of polymeric species. It is then concluded that a unique tin
coordination environment occurs in MeSnCI 3 (EtOH)n interacted with aqueous DNA,
independent from the water content in the condensed phases (gels and lyophilized
specimens) as well as from the temperature; the tin site in Fig. 12.1a, would account
for the experimental parameters and conditions, assuming the occurrence of bond-
R. Barbieri et al.
bipyramidal with equatorial C, C atoms; triorganotin derivatives would assume both
trigonal bipyramidal (equatorial C atoms) and tetrahedral configurations. The nature
of tin bonding atoms other than C has not been assigned. The field has been recently
reviewed, bond angles and structures being extensively reported together with 119Sn
Mossbauer parameters (Barbieri et al. 1998; Musmeci et al. 1992).
12.4
Hemoglobin
Bonding of Alk3Sn(IV) and Me2Sn(IV) with cat and rat hemoglobin tetramers has been
interpreted in terms of the primary coordination of tin by thiol functions of cysteine 13,
and eventually by heterocyclic nitrogen of histidine 113; regular, as well as distorted,
tetrahedral and trigonal bipyramidal structures of tin environments have been extracted
from point-charge model treatment of M parameters (Barbieri et al. 1998). It seems
worthwhile to note the recent publication of an extended review on the classification
and structure function analysis of metal binding sites in proteins (Holm et al. 1996).
12.5
Deoxyribonucleic Acid
The research field inherent to the interaction of metal ions with nucleic acids, as well
as the consequent condensation of DNA, is amply investigated (Berthon 1995; Bregadze
1996, Bloomfield 1996). Interactions involving organometal derivatives have been also
studied, such as organomercury-DNA (see e.g. Gruenwedel1985; Gruenwedel and
Cruikshank 1990), and the organotin-DNA systems treated below. The results of 119Sn
Mossbauer spectroscopy studies on structure and molecular dynamics of systems
AlknSn(IV)-deoxyribonucleic acid (DNA; n = 1-3), are here summarized and discussed;
for representative complexes and systems, values of hyper fine parameters are reported
in Table 12.2, and molecular dynamics data and functions in Table 12.3. The discussion
and structural assumptions in the following are based upon the research cited in
Table 12.2 and 12.3, according to the Mossbauer spectroscopy principles and data treatment procedures sketched in a recent review (Barbieri et al. 1998). Further work in the
field has been discussed previously (Piro et al. 1992; Barbieri et al. 1998).
The hyperfine parameters of the DNA condensates obtained by addition of MeSnCl 3
in ethanol solutions to aqueous buffered native DNA (calf thymus) appear to be constant at any ratio [Sn]-[DNA monomer] in the gel phases (Table 12.2, No. 1-4). Data
are invariant with temperature (in the ranges reported in Table 12.3, No.6), as well as
with the H 2 0 content in the condensed phases, the values for lyophilized samples exactly corresponding to those for the gels. A possible structure is shown in Fig. 12.1a;
no definite attributions from M data are possible, as often detected for RSn(IV) derivatives. The slopes of functions, total area under the resonant peaks vs. T, No.6 in
Table 12.3, are also invariant for gels and lyophilized condensates, and correspond to
the general occurrence of polymeric species. It is then concluded that a unique tin
coordination environment occurs in MeSnCI 3 (EtOH)n interacted with aqueous DNA,
independent from the water content in the condensed phases (gels and lyophilized
specimens) as well as from the temperature; the tin site in Fig. 12.1a, would account
for the experimental parameters and conditions, assuming the occurrence of bond-