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Graven en bronsdepots uit de periode van het late neolithicum tot en met het begin van de midden-bronstijd (2850-1500 voor Christus) kennen we goed. De vraag die in dit artikel centraal staat, is of de contractarcheologie dit beeld heeft bevestigd, of dat grootschalige opgravingen in ‘Malta-context’ andere soorten bewijs hebben opgeleverd. Zijn we in staat geweest huizen uit deze perioden te ontdekken, of nederzettingen? Zijn deze vergelijkbaar voor alle regio’s of zijn er regionale verschillen? Hebben we indicaties voor sociale gelaagdheid, voor migraties? Uit een recent verschenen synthese blijkt dat vooral nederzettingsgegevens onze perceptie van de periode hebben veranderd. Het traditionele beeld gebaseerd op grafgegevens moet volledig worden aangepast.

Background: Collecting data on the localization of users is a key issue for the MASK (Mobile Airways Sentinel network: the Allergy Diary) App. Data anonymization is a method of sanitization for privacy. The European Commission’s Article 29 Working Party stated that geolocation information is personal data. To assess geolocation using the MASK method and to compare two anonymization methods in the MASK database to find an optimal privacy method. Methods: Geolocation was studied for all people who used the Allergy Diary App from December 2015 to November 2017 and who reported medical outcomes. Two different anonymization methods have been evaluated: Noise addition (randomization) and k-anonymity (generalization). Results: Ninety-three thousand one hundred and sixteen days of VAS were collected from 8535 users and 54,500 (58. 5%) were geolocalized, corresponding to 5428 users. Noise addition was found to be less accurate than k-anonymity using MASK data to protect the users’ life privacy. Discussion: k-anonymity is an acceptable method for the anonymization of MASK data and results can be used for other databases.

International audience; Airborne pollution is a rising concern in urban areas. Epidemiological studies in humans and animal experiments using rodent models indicate that gestational exposure to air- borne pollution, in particular diesel engine exhaust (DE), reduces birth weight. These effects depend on exposure duration, ges- tational window, and nanoparticle (NP) concentration. Our aim was to evaluate the effects of exposure to diluted DE on F0 on feto-placental development in a rabbit model in the F1 and F2 generations. Pregnant females were exposed to diluted (1 mg/m3), filtered DE (NP diameter ≈ 69 nm) or clean air (controls) for 2 h/day, 5 days/week by nose-only exposure (total exposure: 20 days in a 31-day gestation). DE exposure induced early signs of growth retarda- tion at mid gestation with decreased head length (p = 0.04) and umbilical pulse (p = 0.018). Near term, fetal head length (p = 0.029) and plasma insulin and IGF1 concentrations (p = 0.05 and p = 0.019) were reduced. Placental function was also affected, with reduced placental efficiency (fetal/placental weight) (p = 0.049), decreased placental blood flow (p = 0.009) and fetal vessel volume (p = 0.002). Non-aggregated and “fingerprint” NP were observed at various locations, in maternal blood space, in trophoblastic cells and in the fetal blood, demonstrating transplacental transfer. Adult female offspring were bred with control males. Although fetoplacental biometry was not affected near term, second generation fetal metabolism was modified by grand-dam exposure with decreased plasma cholesterol (p = 0.008) and increased triglyceride concentrations (p = 0.015). Repeated daily gestational exposure to DE at levels close to urban pollution can affect feto-placental development in the first and second generation.

A series of saccharide-thiourea functionalized cavitands was prepared in good yields (72-86 %) by reaction of a tetrakis(aminomethyl) cavitand with the thiocyanate derivatives of acetylated glucose, galactose, and cellobiose. The anion complexation behavior of the acetylated and deacetylated glycocluster thioureamethyl cavitands was studied with electrospray ionization mass spectrometry (ESI-MS) in acetonitrile and in a 1:1 acetonitrile/water mixture, respectively. All compounds show a preference for Cl(-). A linear relationship was found between the square root of the intensity and the concentration of the formed host-guest complex. Based on this relationship, novel methods have been developed to determine K(a) values, by means of direct titration and competition experiments.

A dual-coded dynamic material was created by the bimodal self-assembly protocol sketched in the scheme. The combination of two orthogonal and reversible interactions, namely solvophobic aggregation (SA) and metal coordination (MC), allows precise control at each step of the self-assembly cycle, leading to the formation of rodlike supramolecular architectures.

This article describes the noncovalent synthesis of water-soluble coordination assemblies based on SCS PdII pincer moieties. Two neutral solubilizing moieties, one based on a linear carbohydrate chain and the other on tetraethylene glycol residues, have been functionalized with pyridine and phosphane ligands. The coordination of the resulting molecules to various hydrophobic, cationic mono- and multimeric SCS PdII pincer systems has been investigated by 1H and 31P NMR spectroscopy, and by MALDI-TOF mass spectrometry. In general, the assemblies with tetraethylene glycol chains display a higher solubility in water than the ones containing linear sugar moieties. A hexapincer core decorated with six linear carbohydrates forms a hydrogel. Finally, a noncovalent water-soluble metallodendrimer having 18 peripheral tetraethylene glycol groups was constructed in a convergent manner.

The structural characterization of the ions generated by the electron ionization-induced loss of ammonia from the molecular ions of α,ω-diamines, using ion/molecule reactions in combination with collision-induced dissociation (CID) studies, is described. The results of the experiments of ion/molecule reactions using dimethyl disulfide exclude the distonic radical cation structure for those long-lived ions proposed earlier by other authors for ions generated within a few microseconds following ionization. The unimolecular and CID characteristics of the ions [M---NH3]√+ of 1,4-diaminobutane and 1,5-diaminopentane and of their fragment ion m/z=56, are discussed in terms of the structures CH3CH2CH=CHNH2√+ and CH3CH2CH2CH=CHNH2√+ for the ions [M---NH3]√+, respectively. The structure of the closed shell ions resulting from loss of ammonia from the protonated α,ω-diamines was also probed through the CID spectra of model ions prepared by chemical ionization with methane in the chemical ionization source of the mass spectrometer.

The molecular structure of a series of hyperbranched polyesteramides was studied using size exclusion chromatography (SEC), mass spectrometry (MS) and small-angle neutron scattering (SANS). Products with increasing molecular mass were obtained through the polycondensation of in situ produced AB2-like monomeric units. Electrospray ionization MS indicates that narrow SEC fractions consist of different isomers, the number of which increases with molecular mass. Molecular mass moments and polydispersity numbers increase with polycondensation degree. The SANS measurements and SEC−DV data yield values for the polymers fractal dimension, which can be rationalized in the framework of percolation theory that originally was designed for randomly branched polymers. Randomly branched polymer behavior in this particular case possibly results from a side reaction involving reactivity among B-end groups.

The noncovalent synthesis of "layer-block" metallodendrimers containing hydrophobic shells of covalent dendritic wedges at the periphery is described. Starting from first- and second-generation Fréchet wedges having phosphines at their focal point, convergent dendritic growth yields third- and fourth-generation metallodendrimers in which the coordination of nitriles, pyridines, and phosphines to SCS Pd(II) pincers is used as the assembly motif. In this convergent growth, the number of terminal hydrophobic phosphine wedges increases with generation. The solubility of the dendritic structures in apolar organic solvents such as chloroform and dichloromethane increases accordingly, in contrast to previously reported metallodendrimers. All dendritic structures were characterized by (1)H and (31)P NMR spectroscopy, elemental analysis, and MALDI-TOF mass spectrometry.

There is a general fascination with regard to the origin of life on Earth. There is an intriguing possibility that prebiotic precursors of life occurred in the interstellar space and were then transported to the early Earth by comets, asteroids and meteorites. It is probable that some part of the prebiotic molecules may have been generated by gas-phase ion/molecule reactions. Here we show experimentally that gaseous ion/molecule reactions of the amino acids, Glu and Met, may promote the synthesis of protonated dipeptides such as (Glu-Glu)H(+) and (Glu-Met)H(+) and their chemical growth to larger protonated peptides.

Hyperbranched polyesteramides (DA2), prepared from hexahydrophthalic anhydride (D) and diisopropanolamine (A) have been characterized, by use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), field desorption (FD)-MS, and electrospray ionization (ESI)-MS. MALDI of polyesteramides produces protonated molecules. The spectra show a complex chemical composition distribution and end-group distribution which are mainly composed of two series of homologous oligomers DnA(n)+1 - mH2O and DnA(n) - mH2O, where m = 1-2. Signals from protonated molecules DnAn+1 and DnAn are almost absent in the MALDI spectrum, whereas these ions are responsible for the base peak of DnA(n)+1 - mH2O and DnA(n) - mH2O (m = 1-2) clusters in the ESI spectrum. The absence of -OH end-groups signals in the MALDI spectrum is due to a metastable decay of protonated DnA(n)+1 and DnAn ions in the ion source of the MALDI mass spectrometer prior to ion extraction. In-source decay results in the formation of protonated lower DnA(n)+1 - mH2O and DnA(n) - mH2O oligomers and their corresponding neutrals, leading to wrong conclusions concerning the relative end-group distribution as a function of the degree of polymerization and the chemical composition.

The reactivity of the nitrosonium ion, NO+, with the amino acid Glu and the dipeptide γ‒Glu–Met in the gas phase has been investigated using the combination of chemical ionisation mass spectrometry and MS/MS. It is shown that NO+reacts efficiently with both Glu and Glu–Met leading to the formation of the nitroso‒group containing ions atm/z159 and 288.The formation ofm/z159, (GluNO‒18)+, is rationalized by a mechanism involving an electrophilic attack of NO+upon the carbonyl oxygen atom of one of the carboxylic groups of Glu and the N‒terminal carboxylic group of Glu–Met leading to the neutral losses of H2O and Met, respectively. The unimolecular decompositions of the metastable and collisionally activatedm/z159 ions lead primarily to the elimination of the neutral species HNO (major) and the (Glu‒18) residue (minor). The formation of them/z288 ions can be described by a mechanistic scheme which involves the ion‒molecule interaction ofm/z159 with Glu and Glu–Met and subsequent losses of H2O and Met, respectively. Unimolecular and collisionally activated dissociations ofm/z288 suggest the formation of the proton‒bridged ion‒neutral complex [(GluNO‒18)···H+···(Glu‒18)].

It is shown using (high-resolution) mass spectrometry that treatment of 4,5-dihydrobenz[ l ]acephenanthrylene ( 2 , C 20 H 14 ) and S 8 in the melt gives the insoluble 532 a.m.u. (C 40 H 20 S) and 750 a.m.u. (C 60 H 30 ) bisbenz[ l ]acephenanthrothiophenes ( 4a–c ) and, trinaphtho[2,1- b ,2,1- m ,2,1- x ]- ( 3a ) and trinaphtho[2,1- b ,2,1- m ,1,2- a ′]decacyclene ( 3b ), respectively (estimated ratio 4a–c / 3a–b 20:1). Whereas 3a fits the `C 60 Schlegel diagram' and might be converted into C 60 (720 a.m.u.) after full cyclodehydrogenation, 3b can only give a curved C 60 H 12 /C 60 H 10 (732:730 a.m.u.). MALDI time-of-flight mass spectrometry shows that cyclodehydrogenations of 3a–b down to 732:730 a.m.u. occur; no evidence for C 60 formation was found. This is attributed to the preferred formation of 3b , the lack of cyclodehydrogenation selectivity and the occurrence of C 2 extrusions.

C70O dissolved in toluene transforms to as yet undetermined compounds when exposed to light at room temperature. After 140 days, only 21% of the original C70O remained. C70 was not formed. C139, or C140O were not found. One possible explanation is that the compounds formed were very insoluble in toluene and that their solids either remained in colloidal solution or attached themselves to the glass walls of the container bottles.

The molecular ion of 3-phenyl-1-bromopropane is known to eliminate ethylene containing the methylene groups of positions 1 and 2 following an exchange between the hydrogen atoms from position 1 and the ortho positions of the phenyl ring. During this reaction migration of the bromine atom to some position in the molecular ion must take place. The eventual position to which the bromine atom has migrated has been probed by studying the metastable behaviour and collision-induced dissociation reactions of the (M–C 2 H 4 ) •+ ion. From comparison with appropriate reference ions it is found that the (M–C 2 H 4 ) •+ ion has the structure of ionized benzyl bromide. The mechanistic implication of this finding is briefly discussed.

The high affinity of Ag+ ions for aromatic pi donors and cyano groups is exploited in a novel MALDI-TOF mass spectrometric method for the identification of hydrogen-bonded assemblies. The interaction with the Ag+ ions - which, for example, can be complexed by two phenyl groups in a sandwich-type manner (see drawing on the right) - provides positively charged assemblies in a nondestructive way.

Die hohe Affinitat von Ag+-Ionen fur aromatische π-Donoren und Cyangruppen wird bei einer neuen MALDI-TOF-MS-Methode zur Identifizierung von H-Brucken-Aggregaten genutzt (MALDI-TOF-MS=Matrix-unterstutzte Laser-Desorptions-Ionisierungs-Flugzeit-Massenspektrometrie): Durch das Ag+-Ion, das z. B. sandwichartig von zwei Phenylgruppen komplexiert werden kann (siehe rechts), lassen sich die Aggregate - ohne Zersetzung - mit einer positiven Ladung versehen.

Triphenyltin compounds are widely introduced into the Dutch aquatic environment. To be able to detect them in environmental samples, the ionization methods of electron ionization, chemical ionization, fast atom bombardment, field desorption, thermospray and electrospray have been applied to triphenyltin acetate, chloride, fluoride and hydroxide to find out which of these methods is best suited to obtain molecular weight information on the intact molecules. For this purpose, field desorption is shown to be the most appropriate method giving, without fragmentation, molecular ion peaks, with the exception of triphenyltin hydroxide. The latter compound gives rise to the base peak at mz 716, due to the formation of bis(triphenyltin)oxide. Field desorption tandem mass spectrometry, applied to the molecular ions, has shown that the main decomposition pathway corresponds to the loss of a phenyl radical. Subsequently, sediment and surface water samples from the Dutch inland water, without and with the use of clean-up procedures, have been analyzed by the application of field desorption in combination with tandem mass spectrometry. Within the limits of detection, no signals for the presence of triphenyltin compounds in these environmental samples has been found. Upon spiking these samples with triphenyltin acetate, chloride, fluoride and hydroxide, it has appeared that the covalently bonded non-aromatic substituent of the molecules is exchanged for hydroxyl.

Some synthetically obtained linear and cyclic phosphopeptides of low molecular weight have been studied by fast-atom bombardment and tandem mass spectrometry to verify the position of the phosphate group in these compounds. Based upon the occurrence/non-occurrence of loss of phosphoric acid from low abundance fragment ions induced by low- and high-energy collisions with target gases, it is shown that the position of the phosphate group in the phosphopeptides studied can be determined unequivocally.

It is shown that metastably decomposing molecular ions of the title compounds eliminate sulfur dioxide via two reaction pathways provided that an α-hydrogen atom adjacent to the heterocyclic ring nitrogen atom is present. One of the channels leads to the initial formation of an o-azaxylylene ionic species and is associated with the narrow component of the accompanying composite metastable peak. The other channel involvel a multistep pathway which eventually leads to the formation of an aldimine ionic species and which is associated with the broad component of the accompanying composite metastable peak. Collision-induced dissociation and deuterium-labelling experiments have provided evidence that the initially generated o-azaxylylene ionic species, both as long-lived and as decomposing ions, have rearranged to the aldimine ionic species via a 1,5-shift of the α-hydrogen atom adjacent to the heterocyclic ring nitrogen atom.

The electron impact-induced fragmentation patterns of 2,1-benzisothiazoline 2,2-dioxide nitro derivatives were studied. The rationalizations proposed for the fragmentations are supported by accurate mass measurements, daughter ion (mass analysed ion kinetic energy and B/E linked-scan), parent ion, and constant neutral loss spectra in metastable and collision-induced dissociation modes and deuterium labelling.

MALDI TOF-MS of tribenzo[l∶l′∶l″]benzo[1,2-e∶3,4-e′∶5,6-e″]triacephenanthrylene (1a, C60H30) gives C60.+ by multiple intramolecular cyclodehydrogenation reactions.

Gas-phase reactions of MnO2− and MnO3− ions with a series of monofluoro- and pentafluoro-aromatic compounds, i.e. C6H4FX with X = o-, m- and p-CHO and o-, m- and p-OH and C6F5Y with Y = OH, OCH3, CHO, CN, NO2, COCH3 and F, were studied at low pressures by Fourier transform ion cyclotron resonance mass spectrometry. The principal reaction channels identified involve electron transfer from the MnO2− and MnO3− ions to the fluorinated aromatic substrates and proton abstraction and nucleophilic displacement of fluorine by these oxometallate ions. The results obtained indicate that in the gas phase MnO2− is less basic than MnO3− and that neutral MnO2 has a lower electron affinity than MnO3, both values lying between 0.52 and 0.94 eV.

The mechanism of [H, C, N) loss from metastable molecular ions of benzyl cyanides containing an F, Cl, CF3, CH3, HO or CH3O substituent was investigated by deuterium and 13C labelling. The elimination of [H, C, N] from the metastable molecular ions of benzyl cyanides substituted with F, CI or CF3 is preceded by randomization of the hydrogen atoms and tc some extent by a skeletal rearrangement of the CH2CN function, which leads to incorporation of the benzylic carbon atom in 20–30% of the expelled [H, C, N] molecules. By contrast, the metastable molecular ions of benzyl cyanides with a CH3, HO or CH3O substituent eliminate [H, C, N] molecules containing the intact cyano function and predominantly a hydrogen atom from fhe substituent. This preference for a hydrogen atom from the substituent irrespective of its position with respect to the CH2CN function is proposed to be the result of a rearrangement of the meta and para isomers to the ortho isomer possibly involving norcaradiene/cycloheptatriene radical cations. In addition to (H, C, N] loss, the metastable ions of o-, m- and p-methoxybenzyl cyanide eliminate a [H2, C2, N]˙ radical consisting of the cyano function and the carbon atom and mainly two of the hydrogen atoms from the methoxy substituent. The occurrence of this reaction from the metastable ions of m- and p-methoxybenzyl cyanide supports the indicated isomerization to the ortho configuration prior to dissociation. This skeletal rearrangement is manifested also in the loss of [H, C, N, O] from the metastable ions of m-andp-hydroxybenzyl cyanide.

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Positive and negative ion fast atom bombardment (FAB) combined with tandem mass spectrometry (MS/MS) has been used to sequence four fully protected nucleopeptides. Protonated and deprotonated molecules and some structurally significant fragments, predominantly sodium cationized/decationized adducts, are observed. The tandem mass spectra of the protonated/deprotonated molecules help to identify (bidirectionally) the main building blocks and the sequence ions of the peptide part of the nucleopeptide components. It is found that the cleavage of the peptide-phosphate backbone mainly occurs due to 1,5-H shift from the side chain of the neighbouring amino acid to the oxygen of the phosphate. It is also observed that the number of amino acids present in the peptide part has a potential influence on the location of the cationization (Na+) which in turn influences the fragmentation pattern in the mass spectrometer.

The regioselectivity of methyl cation transfer from (CH3)2F+, (CH3)2Cl+ and (CH3)3O+ to 1-phenyl-2-aminopropane was studied by Fourier transform ion cyclotron resonance in combination with collision-induced dissociation and neutralization-reionization mass spectrometry of the stable [M + CH3]+ ions formed in a chemical ionization source. The (CH3)2F+ ion transfers a methyl cation to the NH2 group and the phenyl ring with almost equal probability. Predominant CH3+ transfer to the NH2 group is observed for the (CH3)2Cl+ ion whereas the (CH3)3O+ ion reacts almost exclusively at the amino group. The preference for methylation at NH2 is discussed in terms of a lower methyl cation affinity of the phenyl ring than of the amino group and the existence of an energy barrier for methylation of the phenyl moiety.

The unimolecular gas-phase chemistry of CNCN +· and NCCN · has been investigated by electron-impact mass spectrometry, mass-analysed ion kinetic energy mass spectrometry and a theoretical density-functional method. The CN + formation appears to compete with the C +· 2 formation in the microsecond time scale, in spite of an energy gap of 3.5 eV (CNCN) and 3.0 eV (NCCN) between the two processes. This observation is explained by assuming that the fragmentation to CN + proceeds via an isolated excited electronic state of the molecular ion. The C +· 2 fragment ion must be formed from both isomeric C 2 N 2 +· parent ions by a rearrangement reaction. While NCCN +· is more stable than CNCN +· by 0.6 eV, the kinetic energies released in both rearrangements and theoretical calculations indicate that the corresponding intermediates are not only much closer in energy, but even reversed in energetic order with respect to their precursor ions.

Fourier transform ion cyclotron resonance and tandem mass spectrometry in combination with deuterium and 13 C-labelling have been applied to study the product C 3 H 4 N + ion from the gas phase reaction of the C 2 H 2 N + ion from CH 3 CN with its neutral precursor. This has provided evidence for associative cyclization of the cyanomethyl CH 2 CN + cation generated by electron bombardment of acetonitrile. The unimolecular dissociation of the metastably decomposing C 3 H 4 N + ion leads predominantly to HCNH + + C 2 H 2 . This reaction proceeds through a multistep pathway involving cyclic intermediates and is discussed in terms of structures and energies of the C 3 H 4 N + system. Collision-induced dissociation of the C 3 H 4 N + ions shows competitive fragmentations being higher energy demanding than that generating HCNH + + C 2 H 2 .

Inaugurele rede Universiteit van Leiden

MALDI TOF-MS of tribenzo[l:1':1"]benzo[1,2-e:3,4-e':5,6-e"]triacephenanthrylene (1a, C60H30) gives C60.+ by multiple intramolecular cyclodehydrogenation reactions.

A continuous flow micro total analysis system (micro-TAS) consisting of an on-chip microfluidic device connected to a matrix assisted laser desorption ionization [MALDI] time-of-flight [TOF] mass spectrometer (MS) as an analytical screening system is presented. Reaction microchannels and inlet/outlet reservoirs were fabricated by powderblasting on glass wafers that were then bonded to silicon substrates. The novel lab-on-a-chip was realized by integrating the microdevice with a MALDI-TOFMS standard sample plate used as carrier to get the microfluidic device in the MALDI instrument. A novel pressure-driven pumping mechanism using the vacuum of the instrument as a driving force induces flow in the reaction microchannel in a self-activating way. Organic syntheses as well as biochemical reactions are carried out entirely inside the MALDI-MS ionization vacuum chamber and analyzed on-line by MALDI-TOFMS in real time. The effectiveness of the micro-TAS system has been successfully demonstrated with several examples of (bio)chemical reactions.

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Trimethylsilylation of target substances in a mixture of N-methyl-N-trimethylsilyltrifluoroacetamide (MSTFA), ammonium iodide and ethanethiol is frequently applied for the application of gas chromatography–mass spectrometry (GC–MS) in steroid analysis. However, artifacts were formed when using this mixture to silylate the steroids androsterone and etiocholanolone obtained from a urine matrix. The artifacts were identified as ethyl thio-containing products of the respective trimethylsilyl derivatives. The conversion of the studied products increased slowly as a function of time, was dependent on the presence of the urine matrix and was significantly accelerated by adding diethyl disulfide to the reagent before incubation. Also ethyl thio-incorporation into testosterone and epitestosterone was established. A mechanism for ethyl thio-incorporation is proposed. The conversion achieved after 120-h sample storage at room temperature was insufficient to significantly influence the analysis of androsterone and etiocholanolone under the studied conditions. However, the results provide fundamental insight into the mechanism of silylation and the occurring side-reactions. Moreover, when investigating the formation of new metabolites, the ethyl thio-incorporation can lead to misinterpretation.

A combined chemical ionisation and tandem mass spectrometry (MS/MS) approach has been used for investigation of the gas-phase ion chemistry of systems containing the amino acids Glu and Met, and the dipeptides γ-Glu-Met and Met-Glu. The metastable fragmentation of the protonated dimer, (Glu)2H+, reveals an intracluster reaction leading to the elimination of the Glu residue. The main features of the ion-molecule reactions observed in the systems containing Glu and Glu + Met can be described in terms of sequential adduct formation. The results obtained for the thermal dehydration of Glu were used to rationalise the formation of the proton-bound structures (Glu − H2O)···H+··· (Glu − H2O) and (Glu − H2O)3·H+. The adduct ions, [(Glu − H2O) + H + Glu]+ and [(Glu − H2O) + H + Met]+, and further association products were also observed. The results lead to a reconsideration of the structural aspects proposed earlier for these species in the sense that they suggest that the systems correspond to a mixture of isomeric covalent and proton-bound structures. The thermal effects on the decomposition of the neutral (γ-Glu-Met) and its protonated form, (γ-Glu-Met)H+, at m/z 279 were investigated, and dramatic changes in the MI spectra of the m/z 279 ion with temperature were found. A mechanistic explanation for the observed evolution of higher mass ion peaks in the mass spectra is developed. Copyright © 2001 John Wiley & Sons, Ltd.

This paper describes the spontaneous and reversible assembly of approximately 20 kDa synthetic hydrogen-bonded assemblies via the formation of 144 cooperative hydrogen bonds. These nanostructures ( approximately 3.0 x 5.5 nm), consisting of 27 different components, have been carefully characterized using a combination of (1)H NMR spectroscopy, MALDI-TOF MS using Ag(+)-labeling, gel permeation chromatography, and CD spectroscopy.

The possibility of creating a robust mass spectral library with use of high-performance liquid chromatography-atmospheric pressure-electrospray ionization (HPLC-AP-ESI) for the identification of drugs misused in cases of clinical toxicology has been examined. Factors reported as influencing the fragmentation induced by "source transport region collision induced dissociation" (CID) have been tested in this study (i.e. solvent, pH, different acids or buffer salts and their concentration, different organic modifiers and the modifier concentration). The tests performed on a few "model drugs" were analysed with use of two different single quadrupole instruments. The large number of mass spectra obtained appears to be affected by the mobile phase conditions to only a minor extent. This also holds for the mass spectra obtained at two different instruments (laboratories). Subsequently breakdown curves have been measured for about 20 randomly chosen drugs by variation of the kinetic energy of their ions in the CID zone through changing the fragmenter voltage. These breakdown curves were used to optimize the fragmenter voltage for each drug. The optimized fragmenter voltages were then applied by use of a variably ramped fragmenter voltage to acquire mass spectra for the library. The chromatographic separations were run on a Zorbax Stable bond column using a 10-mM ammonium formate-acetonitrile gradient method. Spiked blank serum and patient samples with a total of 40 different drugs were extracted with use of a standard basic liquid-liquid extraction (LLE) method. A search of significant peaks in the chromatogram by application of the developed mass spectral library is shown to result in a more than 95% positive identification. reserved.

The application of the “Lab-on-a-Chip” concept to synthetic chemistry [1, 2] is still at its infancy. In this work a borofloat microchip (Fig. 1) was designed and fabricated by means of the powderblasting technique and used as chemical microreactor in which different solution-phase syntheses have been performed successfully. The stream flowing from the outlet of the chip has been transferred directly onto a gold-coated sample plate. The chemical reaction products were analysed using matrix assisted laser desorption ionization [MALDI] - time-of-flight [TOF] mass spectrometry [3]. MALDI-TOF mass spectrometry in combination with post source decay [PSD] experiments shows to be an excellent method in obtaining molecular weights and structural information. The Schiff base reaction, in which primary amines react with aldehydes to give imines, was chosen as a primary study, because the Schiff base reaction is straightforward and products are obtained in high yields. Lab-scale experiments are carried out under acidic conditions (pH = 3–4), however, pH control is not necessary under the “Labon-a-Chip” conditions. Open image in new window Figure 1 Schematic representation of the chip used in this work and of the MALDI sample plate on which the stream flowing from the chip is analysed.

There is a general fascination with regard to the origin of life on Earth. There is an intriguing possibility that prebiotic precursors of life occurred in the interstellar space and were then transported to the early Earth by comets, asteroids and meteorites. It is probable that some part of the prebiotic molecules may have been generated by gas-phase ion/molecule reactions. Here we show experimentally that gaseous ion/molecule reactions of the amino acids, Glu and Met, may promote the synthesis of protonated dipeptides such as (Glu-Glu)H(+) and (Glu-Met)H(+) and their chemical growth to larger protonated peptides.

Herein we describe our results on the characterization of a wide variety of different hydrogen-bonded assemblies by means of a novel matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) technique with Ag+ labeling. The labeling technique with Ag+ ions is extremely mild and provides a nondestructive way to generate charged assemblies that can be detected by mass spectrometry. Up to now more than 25 different single (1(3).2(3)), double (3(3).2(6)), and tetrarosettes (4(3).2(12)) have been successfully characterized by the use of this method. The success of the method entirely depends on the presence of a suitable binding site for the Ag+ ion. A variety of functionalities has been identified that provide strong binding sites for Ag+, either acting in a cooperative way (pi-arene and pi-alkene donor functionalities) or individually (cyano and crown ether functionalities). The method works well for assemblies with molecular weights between 2,000 and 8,000 Da, and most likely far beyond this limit.

Results of gas-phase reactions of MnO and MnO ions with a series of aliphatic C1C4 alcohols show that C2C4 primary alcohols are oxidized by MnO in reaction channels which involve proton abstraction and hydride-ion transfer, along with the appearance of [H.Mn.O.OH]− ions. Secondary alcohols are oxidized in slower processes while menthanol and t-butanol are unreactive. MnO/alcohol reactions are more complex and involve the formation of [H.MnO3]−, [H.Mn.O2.OH]−, [RO.Mn.O.OH]−, [(RO)2 Mn.O]− and the terminal solvated ion [(RO)3.Mn.OH]−.

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Fullerene contents of chlorinated C60 and C70 were determined with HPLC. n-Values of C60Cln and C70Cln were determined from mass increase during synthesis, MALDI-TOF mass spectrometry, PIXE, Nuclear Microprobe (12C[d,p]13C), and Electron Microprobe analysis. n-Values obtained immediately after synthesis were in the range 31-45. Best values obtained later were in the range 10-20. It is suggested that (i) the samples lost CS2 or CS2/CCl4, or Cl of “crystallization” after synthesis, (ii) after synthesis the samples lost Cl bound to C60 (iii) Cl was lost during the analysis, or (iv) some of all three.

It is shown by mass-analyzed ion kinetic energy spectrometry that the metastably decomposing molecular ions of octopamine (p-HOC6H4CH(OH)CH2NH2) and synephrine (p-HOC6H4CH(OH)CH2NHCH3) yield only protonated methylamine and dimethylamine, respectively, as product ions. From deuterium labeling and variation of the internal energy of the molecular ions, experimental support has been obtained that these product ions are generated via the occurrence of a distonic ion-neutral complex. In the case of octopamine, this complex would consist of a nitrogen-protonated aminomethyl radical and p-hydroxylbenzaldehyde in which the former species abstracts the aldehydic or phenolic hydrogen atom from the latter to give protonated dimethylamine.

MALDI TOF-MS of tribenzo[l∶l′∶l″]benzo[1,2-e∶3,4-e′∶5,6-e″]triacephenanthrylene (1a, C60H30) gives C60.+ by multiple intramolecular cyclodehydrogenation reactions.

Methanoculleus thermophilicum was shown to contain two pterin derivatives. The structures of these pterin derivatives were established from amino acid analysis, 1H-NMR and fast-atom bombardment mass spectrometry data. One of the pterins was identified as tatiopterin-O, an aspartyl derivative of methanopterin with a proton at position 7 of the pterin moiety. The other pterin, which we named thermopterin, differed in the structure of the aniline group, containing two additional hydroxyl residues. The IUPAC name of thermopterin is N-[-1'-(2"-amino-4"-hydroxy-6"-pteridinyl)ethyl]-4- [2',3',4',5'-tetrahydroxypent-1'-yl(5'----1") O-alpha-ribofuranosyl-5"-phosphoric acid]-2,5-dihydroxyaniline, in which the phosphate group is esterified with alpha-hydroxyglutarylaspartic acid.