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The stability constants of the 1 : 1 complexes formed between Pb2+ and several simple phosphate monoesters (4-nitrophenyl phosphate, phenyl phosphate, d-ribose 5-monophosphate, n-butyl phosphate) or phosphonate ligands (methylphosphonate, ethylphosphonate) (R-PO2– 3) were determined by potentiometric pH titrations in aqueous solution (25 °C; I=0.1 M, NaNO3). The construction of a log KP P b b(R-PO3) versus p KH H(R-PO3) plot for the mentioned ligand systems results in a straight line on which the data pairs (the corresponding equilibrium constants were also measured) for uridine 5′-monophosphate (UMP2–) and thymidine 5′-monophosphate (dTMP2–) also fall; this result shows that in the Pb2+ complexes of UMP2– and dTMP2– the nucleobase residues do not interfere, in neither a positive nor a negative way, with the binding of Pb2+ and that the stability of all these complexes is determined by the basicity of the phosph(on)ate group. The mentioned straight-line correlation (as defined by the least-squares procedure) allowed us to demonstrate (via constants determined now) that the stability of the Pb2+) complexes]; clearly, more such comparisons are possible with the reference line given now. Based on the stability constants of the monoprotonated Pb(H;CMP)2–) is also solely determined by the basicity of its phosphate group. A similar evaluation, based on literature data, for the Pb(HPO4 species (which was also measured now), it is concluded that in Pb(H;CMP)3) data, though there is a slight hint that Pb(HPO4) may be somewhat more stable [which would be in agreement with previous observations of other M(HPO4) complexes]; clearly, more such comparisons are possible with the reference line given now. Based on the stability constants of the monoprotonated Pb(H;CMP)+ complex and the Pb(cytidine)2+ species (which was also measured now), it is concluded that in Pb(H;CMP)+ the proton is located at the phosphate group and Pb2+ mainly at the N3/(C2)O site of the cytosine residue. Regarding nucleic acids in solution, it is further concluded that the affinity of Pb2+ towards the negatively mono-charged phosphate unit, —O—P(O)2 –—O—, of a nucleic acid backbone is comparable to that of the cytosine moiety, the affinity towards other nucleobase residues being smaller. This information may prove helpful regarding the properties of lead ribozymes. [ABSTRACT FROM AUTHOR]

To determine the variation in the repeated evaluation of quantitative regional wall motion of the left ventricle (LV) from right anterior oblique (RAO) silhouettes, an intra- and inter-observer test was performed in 17 patients without wall motion abnormalities, using nine different methods of regional wall motion (RWM) analysis. The results were: 1. Around the cardiac apex and near the valve plane there are regions where the subjective contour delineation yields regional mean discrepancies up to 4-5 mm (2-3 mm, respectively, near the valves); while in the other regions the mean discrepancies are usually smaller than 1 mm. 2. Absolute regional contour discrepancies, calculated in mm, show only small differences in the various methods, applied for RWM analysis. 3. If these discrepancies instead are calculated as relative changes (in relative percent) of hemiaxial or segmental shortening or area diminution, the method applied is of great significance, since the length of the axes can vary considerably from method to method. 4. From all methods applied for RWM analysis, that of Mathes [10] (radial method) had the smallest average discrepancy. These results suggest, that the LV silhouette may be best defined in the anterior and inferior wall area, while in other regions subjective impressions of contour tracing may produce a considerable variation, which can be further enhanced by the method applied for RWM analysis. Methods that employ relatively large axes of as similar as possible length are therefore preferred. [ABSTRACT FROM AUTHOR]

A consecutive series of 56 patients with chest pain but no evidence of previous myocardial infarction was prospectively studied by radionuclide ventriculography to determine the value of global and regional radionuclide indices in detecting coronary artery disease. The results were correlated with the clinical judgment of chest pain, the results of the exercise electrocardiogram, and the right heart haemodynamic measurements during exercise. As a result of the criteria for entry, the study group was representative of the population seen in such a clinical setting. Only 25% of patients had coronary artery disease. The predictive power of radionuclide ventriculography was limited. The conventionally used criterion that normal subjects have an increase in left ventricular ejection fraction of at least 5% with exercise provided only 78% sensitivity and 57% specificity. Fourier analysis and visual interpretation of radionuclide studies wrongly diagnosed three out of 10 patients with extensive disease requiring surgery. These results suggest that radionuclide ventriculography is of limited value in the non-invasive diagnosis of coronary artery disease. [ABSTRACT FROM PUBLISHER]

The synthesis of cis-Pt(NH3)2(dCMP) is reported and by various physico-chemical methods it is demonstrated that it is a macrochelate in which Pt(II) is bound simultaneously to the N3 site of cytosine in dCMP2– and to a phosphate-oxygen atom. According to the NOESY spectra (cross-peaks between cytosine H6 and H2′ and H3′) the cytosine ring adopts an anti orientation. Highly unusual is the significant (1 ppm) downfield shift of the sugar proton H5″ in the 1H-NMR spectrum and the sensitivity of the cytosine H6 resonance on the protonation state of the phosphate group. Based on these three features a geometry for the macrochelate is proposed. The compound is a major product of the reaction of cis-[Pt(NH3)2(H2O)2]2+ with dCMP2– at neutral pH, but it even forms at pH 5. By applying pD-dependent NMR spectroscopy (1H, 31P) and potentiometric pH titration, it is demonstrated that the Pt-coordinated phosphate group can be protonated (p Ka/1=3.21±0.10 and 3.31±0.05, respectively), and 1H- and 31P-NMR spectra also indicate deprotonation (p Ka/2=13.35±0.25) of the exocyclic amino group of the cytosine moiety. The metal ion binding affinity of cis-Pt(NH3)2(dCMP) is very small, as shown for Cu2+ (log K<0.6). The cis-Pt(NH3)2(dCMP) complex reacts with nucleosides and nucleotides (L′) by losing its chelate structure and forming mixed ligand complexes, cis-Pt(NH3)2(dCMP)(L′); this means that the phosphate group is released from the coordination sphere of Pt(II), indicating that the Pt(II)-O(phosphate) bond is not very strong. [ABSTRACT FROM AUTHOR]

By means of UV difference spectra, the acidity constants KHLH of the N-1-proton in the nucleotides inonine, guanosine, uridine, and thymidine 5`-triphosphate were measured. The same deprotonation (KcuHLH) in the respective Cu2+ complexes was also determined. The measurement were carried out with and without (Table 1) addition of NaClO4 (0.1 M). It was found that the influence of the ionic strength is great, possibly due to the formation of Na+ complexes. The difference, ΔpKA = pKHLH-pK–H ≈ 2.0, for the nucleotide systems is of the same order as the respective value 2.2 of the Cu2+ guanosine system. This indicates a strong interaction between Cu2+ and the nucleic base in the Cu2+-nucleotide complexes. From experimental indices and the analogy to the Cu2+-ATP complex, it is concluded that macrochelates are formed. The acidity constants determined by means of UV difference spectra were confirmed by potentiometric titrations (Table 2). The Cu2+-nucleoside triphosphates are known to form stable complexes with 2,2`-bipyridyl. In such ternary complexes, the nucleic base can no longer coordinate to the Cu2+. The relatively small ΔpKBipy/A values (Table 2) are in agreement with this. The hydrolytic tendencies of Cu2+ bound to the different nucleotides were also estimated (Table 2). The pKCuL(H2O)xH values show that the hydrolytic tendency of the Cu2+ complexes decreases in the order CTP > ATP > TTP > UTP > ITP ≈ GTP. The influence of the coordination number of the different ligands and also other problems concerning nucleotide complexes were discussed. [ABSTRACT FROM AUTHOR]