Peptide labeling using 188Re, 188Re-MAG3 and 153Sm-H1ETA: A comparison on their in vitro lipophilicity

Lanreotide peptide was labeled with ¹⁵³Sm-H₁ETA and ¹⁸⁸Re-MAG₃ in order to evaluate whether or not their conjugation to the peptide produce significant differences of the in vitro lipophilicity with respect to the ¹⁸⁸Re-lanreotide prepared by the direct labeling method (highly lipophilic). The differences of lipophilicity between the complexes, were evaluated using a reverse phase HPLC system. The measured lipophilicity of ¹⁵³Sm-H₁ETA-lanreotide, ¹⁸⁸Re-MAG₃-lanreotide and ¹⁸⁸Re-lanreotide was taken to be the capacity factor [k" = (t _R-t ₀)/t ₀ where t _R is the retention time and t ₀ is the dead time] for each of the complexes under identical chromatography conditions. Results showed that the in vitro lipophilicity decreased in the order ¹⁸⁸Re-lanreotide (direct labeling), ¹⁸⁸Re-MAG₃-lanreotide and ¹⁵³Sm-H₁ETA-lanreotide. Since the last one has a capacity factor (k") similar to that of ¹⁸⁸Re-MAG₃, some renal elimination for ¹⁵³Sm-H₁ETA-lanreotide could be expected, which probably would reduce the unnecessary radiation dose to normal tissues.     

Magydardiendiol,diterpenoid with a new skeleton from magydaris panacifolia (umbelliferae).

Three new diterpenoids with a substituted α-cyclogeraniol skeleton have been isolated from the umbelliferae $\text{Magydaris panacifolia}$ (Vahl) Lange, for which the names of magydar-2,13-dien-11,17-diol, $\text{1}$, magydar-2,10 (20), 13-trien-17-ol, $\text{2}$, and magydar-2,10(20), 13-trien-17-yl acetate, $\text{3}$, are proposed. The structures of these substances have been deduced from spectroscopic and chemical data.     

Structural Study of Silica Xerogel Composites Containing Pd Aggregates

Composites containing Pd aggregates dispersed in amorphous silica are of interest from both a fundamental and applied point of view because of their attractive catalytic properties. The silica powders added with palladium, prepared by the sol-gel method, were studied using X-ray diffraction, and IR- and UV-Vis-spectrophotometry. Silica xerogel samples were prepared using a ethanol/H₂O/TEOS molar ratio of 4:11.6:1 and loaded with sodium tetrachloropalladate. The silica xerogel microstructure of the powders was studied as a function of annealing temperature. Attention was paid to the evolution of the glass matrix as well as the palladium aggregates in the SiO₂ matrix. We found in our samples partial crystallization of the glass matrix in form of quartz and cristobalite phases with palladium oxide and metallic palladium phase at 1000^∘C. The Rietveld refinement method was used in order to determine the percentage of the phase contents.     

Experimental designs and response surface modeling applied for the optimization of metal-cyanide complexes analysis by capillary electrophoresis

The development of capillary zone electrophoresis (CZE) methods for the determination of metal cyanide complexes in real samples showed some problems, such as the low detection signal of Au (CN)2- and the low resolution between Ni(II) and Fe(II) cyanides in gold processing solutions, and the lack of separation of Pt(CN)4(2-) and Pd(CN)4(2-) in the leachates from automobile catalytic converters. To optimize some analytical parameters, the present study thus focused on the application of experimental designs and multiregression models. The following factors were examined by a two-level factorial design: applied voltage, injection time, detection wavelength, buffer ion, ionic strength and buffer modifiers. For optimization of the CZE method, subsequent response-surface experiments with the important factors were made with the two kinds of leaching solutions. Optimal analytical conditions were obtained in each case, giving good detection signals and resolution for the components of the studied leachates.     

Application of strategically designed sample composition to the rapid analytical screening of milk samples for polychlorinated biphenyls

Strategically designed sample composition (SSC) is a new technique that decreases the number of analytical determinations needed in routine screening to as few as the number of original sample specimens while providing information that is specific to them. Although this new technique has been applied to environmental studies, this paper describes its first application to food safety studies. Contamination of milk samples with polychlorinated biphenyls (PCBs) was chosen as a case study to show the usefulness and potential of the SSC technique with a fast analytical procedure that involves saponification of the samples and solid-phase microextraction of the PCBs. A total of 20 sample specimens can be analyzed in 11 determinations with excellent predictions of the positive samples and the concentration levels of the contaminants. The robustness of the strategy was investigated and demonstrated.     

Proton nuclear magnetic resonance characterisation of glycosaminoglycans using chemometric techniques

Various types of glycosaminoglycans (GAGs) including heparins, chondroitin sulfates, dermatan sulfate and hyaluronic acid were studied from their proton nuclear magnetic resonance (1H NMR) spectra using chemometric techniques. Despite the complexity of the 1H NMR signals, data analysis using principal component analysis enabled the different GAG classes to be distinguished and permitted their classification according to their chemical structure. The analysis of the composition of the major disaccharide unit and other relevant chemical structures in the heparin samples was performed using partial least squares regression.     

Molybdenum(VI) and molybdenum(V) mononuclear and dinuclear complexes with 1,3-diphenyl-1,3-propanedione

Summary The synthesis and the dinuclear or mononuclear nature of several molybdenum(VI) and molybdenum(V) oxocomplexes derived from 1,3-diphenyl-1,3-propanedione (HLL) are described. These complexes were identified by i.r. and electronic spectra, magnetic susceptibility and analytical data, and are assigned the following formulae: [MoO₂(LL)₂], [Mo₂O₅(LL)₂], [Mo₂O₄(LL)₂], [MoOCl(LL)₂], [MoCl₂(LL)] and [MoO(OH)(LL)₂)]. The low magnetic moments of the dinuclear complexes are due, in part, to intramolecular interactions. The i.r. data show that the dionate is bound by two oxygen atoms forming a chelate six-membered ring.     

Structure and aggregation number of a lyotropic liquid crystal: a fluorescence quenching and molecular dynamics study

The structure and aggregation number of a discotic lyotropic liquid crystal, prepared from tetradecyltrimethylammonium chloride (TDTMACl)/decanol (DeOH)/NaCl/H2O, have been examined using fluorescence quenching of pyrene by hexadecylpyridinium chloride and molecular dynamics (MD). The fluorescence method gives an aggregation number of 258 +/- 25 units (DeOH + TDTMACl). From the MD simulation, a lower limit for the aggregate dimension of 130 units of DeOH + TDTMACl is predicted. A stable oblate aggregate of 240 units was studied in detail. A strong polarization between the ammonium headgroups and chloride ions is observed from the calculated trajectory. DeOH headgroups are located, on average, 0.3 nm more to the interior of the aggregate than the TDTMACl headgroup and contribute to widening the interface by forming H-bonds with water. The radial distribution function of the ammonium headgroup shows that there are 16 water molecules in the first solvation sphere. The diagonal elements of the order parameter tensor of the tail atoms of both surfactants indicate that the interior of the micelle preserves about the same degree of order as at the interface, up to the last three atoms of the aliphatic chain, where the order starts to decrease.     

Intramolecular hydrogen bonds and hydrogen-bonded systems in di-Schiff bases of 4-methyl-isophthalaldehyde with 4-substituted anilines

Three di-Schiff bases of 2-hydroxy-5-methyl-isophthalaldehyde with 4-R-anilines (R=H, CH₃, OCH₃) and their 1:1 complexes with HClO₄ were studied by FT-IR, ¹H, and ¹³C NMR spectroscopy in acetonitrile and [²H₃]acetonitrile solutions, respectively. In di-Schiff bases intramolecular OH…N hydrogen bonds have been detected; however, they show no proton polarizability. Hydrogen-bonded systems with fast proton fluctuation and large proton polarizability have been found in the 1:1 complexes of di-Schiff bases with HClO₄.