Determination by electrospray mass spectrometry of the outersphere association constants of DNA/platinum complexes using 20-mer oligonucleotides and ([Pt(NH(3))(4)](2+), 2Cl(-)) or ([Pt(py)(4)](2+), 2Cl(-)).

The cytotoxic effects of cisplatin, cis-diamminedichloroplatinum(II), are generally ascribed to the formation of DNA adducts. Several in vitro as well as in vivo studies showed that cisplatin binds preferentially to guanines belonging to (G)(n) sequences (n > or = 2). After mono- or diaquation of cisplatin, giving the cationic complexes cis-[PtCl(NH(3))(2)(H(2)O)](+) and cis-[Pt(NH(3))(2)(H(2)O)(2)](2+), DNA platination occurs in two steps: the cationic complex gives an outersphere association with DNA and the actual coordination then occurs by substitution of one aqua ligand by guanine-N7. For a better understanding of the (G)(n) selectivity of cisplatin giving the biologically active adducts, also necessary for the conception of new platinum drugs, the respective contribution of the outersphere association and actual guanine platination must be investigated. To check the role of outersphere association in the overall platination process, we used electrospray mass spectrometry (ESMS) to detect and quantify outersphere association between 20-mer oligonucleotides and platinum complexes. The 20-mer oligonucleotides were single- or double-stranded, with the same number of guanines either isolated or adjacent to each other. To deal only with outersphere association and check the influence of platinum ligands, the [Pt(NH(3))(4)](2+) and [Pt(py)(4)](2+) complexes were used. We characterized by ESMS all the different outersphere association species formed during titration of each oligonucleotide with the various platinum complexes and evaluated their affinity constants. The ESMS results demonstrate that the outersphere association depends on electrostatic interactions and on the ability of the platinum ligands to participate to hydrogen bonding, particularly within the duplex form.

Platination of a GG site on single-stranded and double-stranded forms of a 14-base oligonucleotide with diaqua cisplatin followed by NMR and HPLC -- influence of the platinum ligands and base sequence on 5'-G versus 3'-G platination selectivity.

Detailed studies of the kinetics of platination of the single-stranded 14-base DNA oligonucleotide d(ATACATGGTACATA) and the corresponding duplex by cis-[Pt(NH3)2(H2O)2]2+ show that HPLC and NMR are complementary methods which provide similar results. The 5'-G and 3'-G monofunctional intermediates were trapped, separated and characterized by NMR (via 15NH3 labeling) and enzymatic digestion followed by mass spectrometry. The kinetic data are compared with those for the corresponding reactions of cis-[PtCl2(NH3)2] (cisplatin) and its monohydrolysed analogue. For both single and double strands of the oligonucleotide, the aqua complex shows little selectivity for the 5'-G or the 3'-G in the initial platination step, whereas the chloro-complex preferentially platinates the 3'-G. The base on the 3' side of the GG sequence appears to play an important role in controlling this selectivity; replacement of T by C increases the selectivity of duplex platination by the diaqua complex by a factor of about 6, and the selectivity of chelation of the 3'-G monofunctional adduct by a factor of about 3. In general the reactivity of the 5'-G in a GG sequence appears to be enhanced in a duplex compared with a single-strand. For both the aqua-monoadduct and chloro-monoadduct, cis-[Pt(NH3)2(N7G)(H2O or Cl)], the 5'-G monoadduct is much longer lived (t1/2 approximately 4 h at 288 K for aqua, 80 h at 298 K for chloro) than the 3'-G monoadduct (t1/2 < or = 45 min at 288 K for aqua, 6 h at 298 K for chloro). Inspection of molecular mechanics models of the end states of various monofunctional adducts provided insight into H-bonding and destacking interactions in these adducts and the sequence selectivity observed in their formation. Such adducts may play an important role in the mechanism of action of platinum anticancer drugs.

The science of unitary human beings and interpretive human science.

Natural science and human science are identified as the bases of most nursing theories and research programs. Natural science has been disclaimed by Martha Rogers as the philosophy of science that undergirds her work. The question remains, is the science of unitary human beings an interpretive human science? The author explores the works of Rogers through a dialectic with two human scientists' works. Wilhelm Dilthey's works represent the founding or traditional view, and Jurgen Habermas' works represent a contemporary, reconstructionist view. The ways Rogerian thought contributes to human studies but is distinct from traditional and reconstructionist human sciences are illuminated.

Philosophical issues in the Rogerian science of unitary human beings.

In the Rogerian science of unitary human beings, the requirements for meaning and evidence are problematic. Four-dimensionality, a major building block, is postulated to be nonspatiotemporal, nonlinear, and not predictable through knowledge of the parts. A problem arises primarily because the Rogerian system also presents "verification of concepts" as the means of testing "fit" with the real world. Evidence usually understood in the criterion of verifiability in the logical empiricist tradition is specifiable through physicalistic terms under particular three-dimensional conditions. What are the consequences if integral (phenomenologic) evidence is taken as the criterion of meaning in the Rogerian conceptual system?