Metal Ions in Biological Systems: Vol. 11: Metal Complexes as Anticancer Agents.: General Editor: Helmut Sigel,multi-author work as listed below. Marcel Dekker,Inc., New York, 1980, xx + 427 pages,S.Fr.115 (≈£35), ISBN 0-8247-1004-5.

Treatment of methylene dioximes (I) with palladium(II) chloride gives [(R¹R²C=NO)₂CH₂]PdCl₂ (II), their ¹H NMR spectra exhibit resonances due to one of the methylene protons in remarkably lower fields (σ 8.99—8.28 ppm). X-ray analysis of IIb (R¹ = R² = n-Pr) shows that the ligand has boat-like conformation in which the distance between the Pd and the H atom of the OCH₂O-group is 2.46 Å, being much less than expected for the sum of the Van der Waals radii.     

Determination of virginiamycin in combination with chlortetracycline in feeds by anion-exchange chromatography

Standard additions experiments for chlortetracycline hydrochloride and virginiamycin at a ratio of 16:1 showed a positive bias for both the plate and turbidimetric methods. The bias was eliminated by anion-exchange chromatography in both the presence and absence of feed components. When chlortetracycline and virginiamycin pre-mixes were used for fortification of laboratory-prepared feeds at chlortetracycline to virginiamycin ratios of 8 or 16:1, the recovery of virginiamycin, without treatment, was 93-100% using the plate assay and 181-236% with the turbidimetric method. The corresponding values obtained using anion-exchange chromatography were 89-99 and 85-91%, respectively. The anion-exchange technique is necessary if the turbidimetric method is used for the assay.     

Analysis of 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nortropane in rat plasma. I. Method development and validation by capillary electrophoresis

Altropane, 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-(3-iodo-E-allyl)nor tropane, is an imaging agent that was developed recently for early detection of Parkinson's disease. Its promise as a useful radiopharmaceutical for single-photon emission computed tomography or positron emission tomography imaging of the brain has been well demonstrated, and it is currently undergoing clinical trials. This paper presents methods development and validation of capillary electrophoresis (CE) techniques to analyze Altropane in aqueous environments as well as in rat plasma, using an internal standard, nicotinamide. N-Allylaltropane, 2beta-carbomethoxy-3beta-(4-fluorophenyl)-N-allylnortropane, which is a known degradation product of the Altropane precursor (tributyltinaltropane), was used to verify the method's specificity. A solid-phase extraction method for extraction of Altropane from rat plasma is also described. The results presented in this paper demonstrate the applicability of CE methods to study the pharmacokinetic properties of Altropane in animal models. The results of the pharmacokinetic study will be published later, as Part II.     

Signal suppression in electrospray ionization Fourier transform mass spectrometry of multi-component samples

The high resolution, mass range and sensitivity of Fourier transform mass spectrometry (FTMS) suggest that it could be a valuable tool for the quantitative analysis of biomolecules. To determine the applicability of electrospray ionization combined with FTMS to the quantitation of biomolecules in multi-component samples, mixtures of varying compositions and concentrations of cytochrome c, angiotensin II, insulin and chicken egg white lysozyme were examined. The instrument used has an electrospray source with a hexapole trap to accumulate ions for injection into an ion cyclotron resonance mass analyzer. Linear responses for single component samples of angiotensin II and insulin were in the range 0.031-3 microM and those of both cytochrome c and lysozyme were between 0.031 and 1 microM. In examining various mixtures of the proteins with angiotensin II, it was found that the presence of the large molecules suppresses the signal of the smaller molecules. This is suggested to be a result of ion-ion interactions producing selective ion loss from either the hexapole trap or the ion cyclotron resonance mass analyzer trap. More massive, more highly charged ions can collisionally transfer large amounts of translational energy to smaller, less highly charged ions, ejecting the smaller ions from the trap. Mass discrimination effects resulting from the trapping voltage were also examined. It was found that relative signal intensities of ions of different masses depend on trapping voltage for externally produced ions. The effect is most significant for spectra including masses that differ by 30% or more. This suggests that for quantitation all samples and standards be run at a constant trapping potential.     

Association reactions of trimethylsilyl ions

Adduct ions, [M + (CH₃)₃Si]⁺, were produced by bimolecular association reactions of trimethylsilyl ions, (CH₃)₃Si⁺, with acetone, cydohexaoone, anisole, dimethyl ether, 2,5-dimethylfuran, 2-methylfuran and furan in ion cyclotron resonance experiments at 300 K and at pressures of ～10^?7 Torr (1 Torr = 133.3 Pa). The rate constants, k_a, for the association reactions varied from 100% to 2% of the collision rate constants, k_c. The rate constants were independent of pressure, except for furan. Measurements were also made of bond dissociation energies for these adduct ions, D[(CH₃)₃Si⁺–X], from equilibrium measurements. The association efficiency, k_a/k_c, increased with increasing bond dissociation energy and with increasing numbers of degrees of freedom, in qualitative agreement with theoretical predictions. Observations pertinent to the dependence of k_a on reactant temperature and relative kinetic energy are discussed. The possibility of determining ion-neutral complex binding energies from radiative association rate constants is considered.     

Gas-phase IR spectroscopy of anionic iron carbonyl clusters

The first gas-phase vibrational spectra are presented for several anionic iron carbonyl clusters, ranging in size from Fe(CO)4- to Fe5(CO)14- in the CO-stretching region (1600-2100 cm-1). The experimental spectra provide some immediate structural information about the clusters in the form of low-wavenumber (1750-1850 cm-1) bands marking the presence of bridging carbonyl ligands (mu2-COs). Supporting DFT calculations are presented for the smaller clusters (<3 Fe atoms) and give good agreement with the experimental data, allowing structural assignments for these cases. The Fe2(CO)7- spectrum suggests a structure lacking bridging carbonyl ligands, in agreement with the DFT results. For the case of Fe2(CO)8-, there are two possible structures based on the calculations, both with and without bridging carbonyls. The presence of a low-frequency band ( approximately 1770 cm-1) in the experimental spectrum conclusively demonstrates the existence of the bridged form. The ramifications of these data for metal-metal bonding in the clusters are also considered.     

Selective reagents in chemical ionization mass spectrometry: Tetramethylsilane with aliphatic alcohols

Mixtures of tetramethylsilane and helium have been found to form [M + 73]⁺ adducts, hydrated trimethylsilyl ions and alkyl ions with aliphatic alcohols. The adduct ions were found to be formed by displacement of water from the hydrated trimethylsilyl ion. Ratios of the abundances of the adduct ions to the hydrated trimethylsilyl ion can be used to differentiate among primary, secondary and tertiary alcohols. Sensitivities for a number of alcohols with the tetramethylsilane/helium chemical ionization reagent system are approximately equal.     

Selective reagents in chemical ionization mass spectrometry: Tetramethylsilane with ethers

Chemical ionization mass spectra of several ethers obtained with He/(CH₃)₄Si mixtures as the reagent gases contain abundant [M + 73]⁺ adduct ions which identify the relative molecular mass. For the di-n-alkyl ethers, these [M + 73]⁺ ions are formed by sample ion/sample molecule reactions of the fragment ions, [M + 73 ? C_nH_2n]⁺ and [M + 73 ? 2CnH_2n]⁺. Small amounts of [M + H]⁺ ions are also formed, predominantly by proton transfer reactions of the [M + 73 ? 2CnH_2n]⁺ or [(CH₃)₃SiOH₂]⁺ ions with the ethers. The di-s-alkyl ethers give no [M + 73] ⁺ ions, but do give [M + H]⁺ ions, which allow the determination of the relative molecular mass. These [M + H]⁺ ions result primarily from proton transfer reactions from the dominant fragment ion, [(CH₃)₃SiOH₂]⁺ with the ether. Methyl phenyl ether gives only [M + 73]⁺ adduct ions, by a bimolecular addition of the trimethylsilyl ion to the ether, not by the two-step process found for the di-n-alkyl ethers. Ethyl phenyl ether gives [M + 73]⁺ by both the two-step process and the bimolecular addition. Although the mass spectra of the alkyl etherr are temperature-dependent, the sensitivities of the di-alkyl ethers and ethyl phenyl ether are independent of temperature. However, the sensitivity for methyl phenyl ether decreases significantly with increasing temperature.     

Biomolecular Assemblies Combining Two Orthogonal Copper‐Mediated Ligations in a One‐Pot Reaction

The access to multifunctional biomolecular compounds involves multistep reactions usually with a complicated protection scheme and lengthy separation processes. The development of a strategy combining several orthogonal ligations is highly desirable. Herein, we introduce a new method that involves two orthogonal copper‐mediated ligations of azide with alkyne, and amine with thioacid. We established compatible conditions to carry out molecular assemblies of three different chemical components in a single one‐pot reaction. The effectiveness of the method was demonstrated in the synthesis of biomolecular compounds that are known to target tumor tissue. The simple reaction conditions suggest that this strategy of combining several orthogonal ligations could have wide potential for the chemical synthesis of complex macromolecules.     

STM characterization of size-selected V1, V2, VO,and VO2 clusters on a TiO2(110)-(1 × 1) surface at room temperature

We use ultra-high vacuum scanning tunneling microscopy (UHV–STM) to probe, at the atomic level, the structure of mass-selected isolated V₁, V₂, VO and VO₂ clusters deposited on rutile TiO₂(110) by ion soft landing. All four species interact differently with the TiO₂ surface and the ultimate binding site and configuration strikes a balance between the gas-phase structure and the ligation of this cluster by the TiO₂ surface. Our results show that vanadium atoms prefer to bind in the upper threefold hollow sites on the surface and have a slight tendency to pair along the [1–10] direction, while vanadium dimers bind to the surface oriented along the [001] direction exclusively. VO clusters bind with the vanadium atom in the upper threefold hollow site and with the oxygen atom bound to an adjacent fivefold coordinated Ti atom (5c-Ti). The VO₂ cluster also binds with the vanadium atom in the upper threefold hollow site and with both oxygen atoms bound to adjacent 5c-Ti atoms or with only one oxygen bound to the surface and the other directed out of the plane of the surface.