Desorption ionization combined with tandem mass spectrometry: Advantages for investigating complex lipids,disaccharides and organometallic complexes

Combining desorption ionization with tandem mass spectrometry overcomes the disadvantage of limited fragmentation accompanying desorption and permits mixtures of closely related substances to be investigated directly. These features of the combination are illustrated by completing the structure-proof of a minor component of an ornithine-containing lipid mixture isolated from Thiobacillus thiooxidans. The minor component is a homolog of the major constituent and differs from the principal component owing to the presence of a double bond in lieu of a cyclopropyl ring in one of the constituent fatty acids. Another feature of the combined method is the potentially complementary nature of collision-activated dissociation spectra of protonated and cationized biomolecules. This is illustrated by the differences in the collision-activated dissociations of the [M + Na]⁺ of sucrose, desorbed by field desorption, and [M + H]⁺, desorbed by fast atom bombardment. A third illustration is the application of field desorption and tandem mass spectrometry to an organometallic compound. The combined approach allows the ligands to be identified and the relative ligand binding energies to be approximated.     

Cuprate-catalyzed Three-Component Couplings of Functionalized Organozinc Reagents

Organozinc reagents FG-(CH₂)_nZnX containing electrophilic centers (FG) upon conversion to their corresponding zincates (FG-(CH₂)_nZnMe₂Li) and in the presence of 5–8 mol % MeCu(CN)Li, undergo 1,4-additions to cyclic conjugated enones. The intermediate zinc enolates can be trapped with aldehydes to afford products of three-component couplings.     

Macrocyclization on the fullerene core: Direct regio- and diastereoselective multi-functionalization of [60]fullerene,and synthesis of fullerene-dendrimer derivatives

The macrocyclization between buckminsterfullerene, C₆₀, and bis-malonate derivatives in double Bingel reaction provides a versatile and simple method for the preparation of covalent bis-adducts of C₆₀ with high regio- and diastereoselectivity. A combination of spectral analysis, stereochemical considerations, and X-ray crystallography (Fig. 2) revealed that out of the possible in-in, in-out, and out-out stereoisomers, the reaction of bis-malonates linked by o-, m-, or p-xylylene tethers afforded only the out-out ones (Scheme 1). In contrast, the use of larger tethers derived from 1,10-phenanthroline also provided a first example, (±)- 19 (Scheme 2), of an in-out product. Starting from optically pure bis-malonate derivatives, the new bis-functionalization method permitted the diastereoselective preparation of optically active fullerene derivatives (Schemes 4 and 5) and, ultimately, the enantioselective preparation (enantiomeric excess ee > 97%) of optically active cis-3 bis-adducts whose chirality results exclusively from the addition pattern (Fig. 6). The macrocyclic fixation of a bis-malonate with an optically active, 9,9′-spirobi[9H-fluorene]-derived tether to C₆₀ under generation of 24 and ent- 24 with an achiral addition pattern (Scheme 4) was found to induce dramatic changes in the chiroptical properties of the tether chromophore such as strong enhancement and reversal of sign of the Cotton effects in the circular dichroism (CD) spectra (Figs. 4 and 5). By the same method, the functionafized bis-adducts 50 and 51 (Schemes 10 and 11) were prepared as initiator cores for the synthesis of the fullerene dendrimers 62 , 63 , and 66 (Schemes 12 and 13) by convergent growth. Finally, the new methodology was extended, to the regio- and diastereoselective construction of higher cyclopropanated adducts. Starting from mono-adduct 71 , a clipping reaction provided exclusively the all-cis-2 tris-adduct (±)- 72 (Scheme 14), whereas the similar reaction of bis-adduct 76 afforded the all-cis-2 tetrakis-adduct 77 (Scheme 15). Electrochemical investigations by steady-state voltammetry (Table 2) in CH₂Cl₂ (+0.1M Bu₄NPF₆) showed that all macroeyciic bis(methano)fullerenes underwent multiple reduction steps, and that regioisomerism was not much influencing the redox potentials, All cis-2 bis-adducts gave an instable dianion which decomposed during the electrochemical reduction. In CH₂Cl₂, the redox potential of the fullerene core in dendrimers 62, 63 , and 66 is not affected by differences in size and density of the surrounding poly(ether-amide) dendrons. The all-cis-2 tris- and tetrakis(meihano)fullercnes (±) -72 and 77 , respectively, are reduced at more negative potential than previously reported all-e tris- and tetrakis-adducts with methane bridges that are also located along an equatorial belt. This indicates a larger perturbation of the original fullerene π-chromophore and a larger raise in LUMO energy in the former derivatives.     

High pressure trapping in Fourier transform mass spectrometry: A radiofrequency-only-mode event

A new event for the Fourier transform mass spectrometry (FTMS) sequence is developed and demonstrated. During this event, called a radiofrequency (RF)-only mode event, the typical passive cubic trap of a Fourier transform mass spectrometer is made to operate as an active quadrupole ion trap. The transition between active and passive modes is developed so that ion loss as a consequence of the transition can be held to 15% or less. The adduct of the ion-molecule reaction of the 1,3-butadiene radical cation and methyl vinyl ether was detected during the Rf-only-mode event at a helium pressure of ～1×10^?3 torr even though this adduct is not detectable under standard FTMS operating conditions.     

A Mechanism for Poor High Mass Performance in Fourier Transform Mass Spectrometry

The discovery of a mass-dependent electrical mechanism for signal loss of high mass ions in Fourier transform mass spectrometry is reported. Theoretical calculations and experimental evidence show the existence of resonances involving the z-motion and radial motion of the ion. The resonances are intrinsic in the cubic trap. This results in energy transfer between modes, expansion of the ion cloud, and a corresponding loss of signal. Quadrupolar trapping potential wells are proposed as a solution.     

Synthesis,characterization and controlled toxicity of a novel hybrid material based on cisplatin and docetaxel

This paper is focused on the synthesis and characterization of a novel hybrid material based on cisplatin and docetaxel-loaded functionalized simultanously carbon nanotubes able to be used in cancer therapy as drug delivery system with controlled toxicity. This material was physico-chemically investigated by determining the structure, as evidenced by Fourier transform infrared (FTIR) spectroscopy, transmission electronmicroscopy (TEM) and its stability was studied with the aid of thermogravimetric analysis (TGA). The amount of platinum ions released into the solution of simulated body fluid (SBF) was highlighted by coupled plasma mass spectrometry (ICP-MS). Toxicology experiments were performed with MDA-MB 231 breast cancer epithelial cells. The performance of the new drug delivery hybrid material was compared with functionalised carbon nanotubes with therapeutic agents functionalized with a single therapeutic agent.