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The presence of enteric viruses on fresh berries poses a health risk to consumers. After berries are picked, a washing step can reduce microbial counts on fruit surfaces to increase their safety. This study compared the effectiveness of tap water, commercial solutions of fruit and vegetable sanitizer composed of peroxyacetic acid and hydrogen peroxide (PAA) and neutral electrolyzed oxidizing water (NEW) for washing fresh blueberries that had been inoculated with either murine norovirus (MNV-1), bacteriophage MS2, bovine rotavirus (boRV) or hepatitis A virus (HAV). Initially, inactivation levels were measured after blueberries were washed for 1, 3, 5, 10 and 20 min. Subsequently, the effect of combining up to three sequential 1-min washes was evaluated. Washes with water lasting up to 20 min reduced MNV-1, MS2 and HAV populations by 1–2 log10 (PFU) and boRV by less than 4 log10. Increasing washing time did not have a significant effect, except where NEW washes were increased by up to 3 min for MS2 and by 10 min for boRV, with viral titers decreasing by > 4 log10 and >5 log10, respectively. Viral counts were further reduced through additional washes as follows: reduction of MS2 with water, of MNV-1 with NEW and HAV with PAA. PAA achieved significant and rapid inactivation of boRV (>6 log10 PFU after 1 min), MNV-1 (>4 log10 after 10 min) and MS2 (>3 log10 after 3 min). HAV was moderately affected ( 4 log10 after 1 min), MS2 (>4 log10 after 3 min) and HAV (>4 log10 after 1 min). For boRV, washing time needed to be increased to 10 min or three sequential washes were needed to reach >5 log10 reduction. These results highlight the efficiency of PAA at reducing infectivity of MNV-1, MS2 bacteriophage and boRV, and NEW to inactivate the four viruses.

The viability of murine norovirus (MNV-1), bovine rotavirus (boRV), and hepatitis A virus (HAV) was evaluated at 21 °C, 4 °C, and −20 °C on stainless steel surfaces, in bottled water, and on blueberries for up to 21 days. After 14 days of incubation at 21 °C on stainless steel, a viability loss >4 log for MNV-1, >8 log for boRV, and >1 log for HAV was observed. Losses were observed for MNV-1 (>1 log) and HAV (>2 log) incubated in water at 21 °C for 21 days. No significant loss was detected for MNV-1 and HAV at 4 °C and −20 °C and for boRV at 21 °C, 4 °C, and −20 °C. On blueberries incubated at 4 °C and −20 °C, they all maintained their infectivity. After 7 days at 21 °C, a loss >2 log, a loss of 3 log, and no loss were observed for boRV, MNV-1, and HAV, respectively. After RNase pretreatment, the detection of extracted RNA from infectious and noninfectious samples suggested the protection of RNA inside the capsid. Even though they all are enteric viruses, their persistence varied with temperature and the nature of the commodity. It is therefore important to use more than one viral surrogate, during inactivation treatments or implementation of control measures.

Lipases (triacylglycerol acylhydrolase, EC 3.1.1.3) are part of the family of hydrolases that act on carboxylic ester bonds. The physiologic role of lipases is to hydrolyze triglycerides into diglycerides, monoglycerides, fatty acids, and glycerol. These enzymes are widely found throughout the animal and plant kingdoms, as well as in molds and bacteria. Of all known enzymes, lipases have attracted the most scientific attention. In addition to their natural function of hydrolyzing carboxylic ester bonds, lipases can catalyze esterification, interesterification, and transesterification reactions in nonaqueous media. This versatility makes lipases the enzymes of choice for potential applications in the food, detergent, pharmaceutical, leather, textile, cosmetic, and paper industries. The most significant industrial applications of lipases have been mainly found in the food, detergent, and pharmaceutical sectors. Limitations of the industrial use of these enzymes have mainly been owing to their high production costs, which may be overcome by molecular technologies, enabling the production of these enzymes at high levels and in a virtually purified form.

The halonium metathesis reaction of ketones and aldehydes, C=O + XF + → C=F + + X=O is difficult to harness for three reasons: (1) the interchange of F + for O is so exothermic that the C=F + product ion often decomposes further; (2) the adduct of XF + to the carbonyl oxygen frequently undergoes side reactions to the virtual exclusion of metathesis; and (3) the metathesis ion is liable to rearrange to a mixture of isomers. Several approaches have been explored to make this reaction a useful source of gaseous fluoroalkyl cations. DFT calculations reinforce the intuition that cyclopentenone should give a good yield of metathesis ions in its ion–molecule reaction with CF3 + , an expectation that is borne out by experiment. Other approaches have met with less dramatic success. Variation of XF + gives a number of interesting results, but little improvement over CF3 + . Deuterium substitution at the carbon adjacent to the carbonyl (-position) does not restrain further decomposition, but deuteration of the next carbon (-position) does appear to do so. The isotopic labeling experiments indicate that the prevalent mode of decomposition requires hydrogen shift followed by a 1,3-elimination of HF. Observed side reactions of adduct ions include alkene expulsion to yield CF3-containing products (such as m/z 125 from the reaction of cycloalkanones with CF3 + ) and direct elimination of HF (as conjectured for the reaction of CFO + with diethyl ketone, with concurrent loss of CO2). Structures of ion–molecule reaction products can be reliably inferred only when the expected mechanism yields the minimum energy structure for that molecular formula. (Int J Mass Spectrom 222 (2003) 451–463) © 2002 Published by Elsevier Science B.V.

In the cell of an FT-ICR spectrometer, (CH3)(X)C(OCR)( + OHR ′ ) and (CH3)(X)Si(OCR) + OHR ′ (R and R′=H, CH3 or C2H5; X=H or CH3) covalent ions were generated by reaction of the (CH3)(X)+SiOCR′ cations with water or alcohols. In the so-formed covalent ions, experiment shows that 1,3-H+ transfers from oxygen to oxygen are often easy in silicon containing ions while they are not observed in the corresponding ions containing only carbon. Calculations indicate that the energy required for a 1,3-H+ transfer from oxygen to oxygen is almost identical whether the transition state contains a silicon atom or not. The greater strength of the SiO bond in cations, compared to that of the CO bond or, in other words, the great electrophilic character of cations possessing a Si+, is the main factor explaining the difference in the behavior of the studied silicon containing ions and ions containing exclusively carbon.

Products of the F+-for-O metathesis between a variety of fluorinated cations and α,β-unsaturated ketones have been examined using FT-ICR and sector mass spectrometry. The reactant ions CF3+, C3F7+, and CFO+ all undergo ion–molecule reactions with carbonyl compounds to replace oxygen with F+. In principle, the simple transposition of atoms corresponds to the transformation  C  O → C  F + and ought to produce monofluorinated allylic cations, which DFT calculations predict to be highly stable. The metathesis, however, is so exothermic that cationic rearrangements take place, as attested by several experimental data, including: (1) unimolecular loss of HF from the ion created by methacrolein; (2) the Bronsted acidity of the ion created by methacrolein in its subsequent ion–molecule reactions; and (3) unimolecular loss of ethylene from the ion created by senecialdehyde. DFT calculations suggest that cyclization of unsaturated cations takes place, even though that mechanism removes the positive charge from conjugation with double bonds. Evidence for cyclization is to be found in CF3+-adduct ions as well as the metathesis ions (for instance, the reaction of sorbital with CF3+, which forms CH2OCF3+, as well as the metathesis ion). Electrocyclic ring closure of fluoroallylic ions creates cyclopropyl cations, which represent transition states rather than stable structures on the DFT potential energy surface. Calculated energy barriers to forming monofluorinated cyclopropyl cations range from ΔH=160 to 266 kJ mol−1. The exothermicities of metatheses with CF3+ are calculated to be >50 kJ mol−1 higher than the respective barrier heights.

Waters Silica Sep-Pak cartridges were evaluated for their performance in trapping short chain fatty acid ethyl esters. Liquid solutions of ethyl butyrate, ethyl valerate and ethyl caproate were injected onto cartridges. All the esters bound to the matrix and were eluted with four bed volumes of ethanol for ethyl butyrate and two bed volumes of ethanol for ethyl valerate and ethyl caproate. Samples of esters stripped with an air stream for 1 min and trapped on cartridges were found to vary by less than 8% for ethyl propionate, ethyl butyrate, ethyl valerate and ethyl caproate. Production of ethyl butyrate by Pseudomonas fragi CRDA 037 resting cells during biotransformation was efficiently evaluated using these cartridges. Variations between samples were found to be less than 10%. © 2000 Society of Chemical Industry

After selection from eight yeast commercial or type strains based on their aromatic potential to valorize bread by-products, Geotrichum candidum ATCC 62217 formed fruity aroma compounds (pineapple-like) on fermented waste bread (35% white bread crumb and 65% water). Fatty acids esters were identified, including ethyl esters of acetic acid, propionic acid, butyric acid and isobutyric acid. Their production corresponded to the stationary growth phase of the strain and, after 48 h, it was improved by agitation and, to a lesser extent, at 30°C compared to 25 or 20°C. Aromatic properties of the strain were linked to its ability to metabolize organic acids.

In the gas phase, (CH(3))(3)SiOSi(+)(CH(3))(2) and (CH(3))CH(2)SiOSi(+)(CH(3))(2) ions 1 and 2 were formed in the external source of a Fourier transform ion cyclofrom resonance (FT-ICR) spectrometer by electron impact ionization of (CH(3))(3)SiOSi(CH(3))(3). In the FT-ICR cell, the electrophilic center of these ions reacts with acetone to give product ions whose structures are probed by comparison with those of the products formed by reaction with water. The mechanisms of formation of these products, studied by labeling, involve facile 1,3-methyl transfer from silicon to silicon and cyclic intermediates. Copyright 1999 John Wiley & Sons, Ltd.

Molecules containing a benzene ring and an oxygen atom typically have two types of protonation sites: on the ring (where facile intramolecular hydrogen transposition from carbon to carbon probably takes place) or on an oxygen lone pair. Four aryl ethers are compared: the isomers phthalan (1, a cyclic benzylic ether) and coumaran (2, a cyclic phenyl ether), as well as isochroman (3) and isopropyl phenyl ether (iPrOPh). The proton affinities of 1–3 have been measured using FT-ICR techniques as 830, 855 and 838 kJ/mol, respectively. Comparison with model compounds and Hartree-Fock-based SCF calculations indicate that protonated phthalan (1H) and protonated isochroman (3H) have O-protonated structures. By contrast, the conjugate acids of coumaran and iPrOPh prefer ring-protonated structures. Acidification/neutralization experiments in the ICR, as well as MIKE spectra, demonstrate that chemical ionization of iPrOPh produces noninterconverting O- and ring-protonated forms. Metastable ion decompositions of protonated phthalan and protonated isochroman give evidence of separate decomposition pathways for both types of tautomers. Protonated coumaran exhibits complete randomization of hydrogen between oxygen and the ring, which is attributed to high barriers for expulsion of neutral fragments.

In the gas phase, the (CH 3 )) 3 SSiOSi(CH 3 )) 2 + and (CH 3 )) 2 SSi + OOSi(CH 3 ))CH 2 ions were formed in the external source of a FT-ICR mass spectrometer by fragmentation of (CH 3 )) 3 SSiOSi(CH 3 )) 3 + . In the c. In the cell, the electrophilic center of these ions reacts with water to give product-ions which undergo, spontaneously or upon collision, sequential losses of methane and water. The reactions of D 2 OO and H 2 8 OO indicate that a permutation of the oxygen atom of the reactant and that of water takes place prior to the dissociation of the productions. This means that both oxygens play a symmetric role in an intermediate step of the reaction pathway.

The proton affinities of 2(5H)-furanone, 1 (836 kJ/mol), 5,6-dihydro-2H-pyran-2-one, 2 (862 kJ/mol), cyclopentenone, 3 (857 kJ/mol), and cyclohexenone, 4 (863 kJ/mol), have been measured by Fourier transform ion cyclotron resonance techniques. A comparison is made with (reexamined) data concerning saturated cyclic and unsaturated aliphatic analogs. Three general observations are made. First, the basicity is found to increase with the size of the ring. Second, unsaturated lactones are more basic than their corresponding aliphatic unsaturated esters. Third, unsaturated and saturated lactones have almost identical gas-phase basicities, while unsaturated and saturated lactones have almost identical gas-phase basicities, while unsaturated cyclic ketones are more basic than their saturated analogs. All these experimental findings have been rationalized by means of ab initio calculations up to the G2(MP2,SVP) level. The basicity trends along the series are the result of two main factors: the different hybridization pattern of the carbonyl carbon as the size of the ring changes and, in the case of lactones, the nonbonding interaction between the proton attached to the carbonyl group and the ether-like oxygen which contributes to the enhanced stability of the protonated form. For unsaturated ketones the C=C double bond participates fully in the change in charge distribution induced by the protonation, while for unsaturated lactones the existence of an oxygen atom within the ring impedes this shift of the electron density.

Cyclic amide amidohydrolases are important biocatalysts for the in vitro synthesis of chiral amino acids. This paper is the first description of the occurrence of three cyclic amide amidohydrolase activities in hulls, by-products of pea crop. Partial purification of these cyclic amide amidohydrolases extracted from hulls of Pisum sativum revealed the presence of dihydropyrimidinase, d -hydantoinase and l -hydantoinase activities. Our study shows that diversity of cyclic amide amidohydrolases also exists in plants such as legume seeds, since cyclic amide amidohydrolases from pea hulls were shown to hydrolyse dihydrouracil, hydantoin, l -MMEH and dl -MMEH.

The proton affinity at the heteroatom PAX of four α-radicals (CH2OH, CH3CHOH, CH2OCH3 and CH2NH2) was measured by studying the deprotonation of the corresponding α-distonic ions in the cell of a FTICR spectrometer. This method can only be used for α-distonic ions which are more stable than their molecular ion counterpart. It was found that the PAX of the CH2OH, CH3CHOH, CH2OCH3 and CH2NH2 α-radicals lies respectively 15.7, 14.5, 10.1 and 17.2 kcal mol−1 under that of CH3OH, CH3CH2OH, CH3OCH3 and CH3NH2. These results are in good agreement with the PA obtained by high level ab initio calculations.

For the proton transfer reaction [MH]+ + B → M + [BH]+ (I) a correlation is observed between the experimental reaction rate kexp and the standard free energy variation ΔG°. This correlation may be described by a relationship of the type k exp /k coll = 1 [1 + exp (ΔG° + G a °)/RT] where kcoll is the collision rate constant and ΔGa° an apparent energy barrier for reaction (I). It is found that ΔGa° is of the same order as RT and thus the preceding relationship allows the determination of unknown gas-phase basicities. Implications for the use of the “bracketing” and the “kinetic” methods are discussed.

The reaction of the ˙CH2CH2OHCH3+ distonic ion with CH2O was studied by Fourier transform ion cyclotron resonance spectrometry. The process is induced by an initial regiospecific attack of the carbon CH2O at the radical site of the distonic ion, leading to an intermediate adduct ion which loses water. The mechanism was demonstrated by labelling, by studying the structure of the product ion and by examining independently the behaviour of the putative intermediate radical cation.

Enterobacter agglomerans isolated from a soil sample collected in the vicinity of a sugar house was grown on low-grade maple sap. When cultivated in shake flask, Ent. agglomerans produced exopolysaccharide and α-ketoglutarate. No polysaccharide and no α-ketoglutarate were produced during growth at dissolved oxygen concentrations lower than 1% saturation in a 3.51 bioreactor, but succinate, lactate and formate were accumulated. In order to increase polysaccharide production, various agitation systems were adapted to 7 1 bioreactors with working volumes of 4 1. Highest polysaccharide yield (Y p/s = 0.70) and biomass yield ( Y x/s = 0.17) were obtained with bioreactors agitated with four- and six-bladed Rushton turbines. Accumulation of mixed organic acids during polysaccharide production indicated that both aerobic and anaerobic conditions prevailed inside the bioreactors. Maple sap concentration higher than 60 g l -1 (as sucrose equivalent) decreased both growth and exopolysaccharide production.

The ions corresponding to metastable formyl loss from ionized ethylene glycol and 2-methoxyethanol are the conjugate acids of methanol and dimethyl ether, respectively. The structures of the fragments of deuterated analogues reveal that a hydroxylic hydrogen transfers to carbon to create the new methyl group, while a hydrogen originally attached to carbon migrates to oxygen in the course of this double hydrogen transfer. This is the only metastable decomposition of ethylene glycol radical cation, while 2-methoxyethanol radical cation also loses water to form oxetane radical cation

The tert -butyl cation ( t Bu + ) is widely used as a chemical ionization reagent ion, for which it is often assumed that simple proton transfer to neutral substrates is the dominant reaction. Mass-analyzed ion kinetic energy (MIKE) spectrometry and the collisionally activated decomposition (CAD) of ions corresponding to the adducts R′O(H)R + formed from mixtures of ROH and R′OH (R = t Bu, R′ = t Bu or 1-methylcyclopentyl, and their deuterated analogues) show a much more complicated pattern of reactivity, which is mirrored in the bimolecular reactions of t Bu + with R′OH in the Fourier transform ion cyclotron resonance (FT-ICR) technique. Production of R′ + in the CAD and FT-ICR experiments is accompanied by isotopic exchange between the alkyl groups, which implicates ion-neutral complexes as accessible intermediates in addition to the covalent adduct ions. A unified pathway for MIKE spectrometry, CAD, and FT-ICR regimes is presented, involving terbody complexes of the form [cation water alkene] as well as two-body complexes of the form [cation alcohol].

A 180-ml grinding vessel was adapted to a commercially available mixer mill used for small-scale cell disruption by grinding with glass beads and was compared to the currenly used 12.5 ml mortar. The disruption of the following microorganismswas monitored by estimating the protein content of the cell extract and the release of intracellular enzymes: β-galactosidase from Bifidobacterium infantis strain ATCC 27920, hydantoinase from Pseudomonas putida strain DSM 84 and maltase from commercial baker's yeast Saccharomyces cerevisiae strain Bud. Maximun enzyme release occurred within 2.5–10 min and maximum protein release by 10–30 min depending on the organism used. The 180-ml jar is proposed as an alternative to other expensive equipments used for continuous large-scale disruption.

The ions corresponding to metastable formyl loss from ionized ethylene glycol and 2-methoxyethanol are the conjugate acids of methanol and dimethyl ether, respectively. The structures of the fragments of deuterated analogues reveal that a hydroxylic hydrogen transfers to carbon to create the new methyl group, while a hydrogen originally attached to carbon migrates to oxygen in the course of this double hydrogen transfer. This is the only metastable decomposition of ethylene glycol radical cation, while 2-methoxyethanol radical cation also loses water to form oxetane radical cation

Propene radical cations undergo proton transfer reactions with water and methanol at low pressure (Fourier transform ion cyclotron resonance), whereas cyclopropane radical cations react with methanol by addition—fragmentation and with water by collision-induced isomerization to form propene. The isomerization of cyclopropane into propene is slower than the hydrogen exchange between propene and water, making the reaction between C 3 H + 6 and H 2 O a sensitive probe for the structure of the hydrocarbon ion. The structural distinction between the two C 3 H + 6 isomers can also be based on the reactions with methanol.

International audience; The gas-phase basicities of a representative set of hydroxy- and methoxycarbonyl compounds (hydroxyacetone, 1, 3-hydroxybutanone, 2, 3-hydroxy-3-methylbutanone, 3, 1-hydroxy-2-butanone, 4, 4-hydroxy-2-butanone, 5, 5-hydroxy-2-pentanone, 6, methoxyacetone, 7, 3-methoxy-2-butanone, 8, 4-methoxy-2-butanone, 9, and 5-methoxy-2-pentanone, 10) were experimentally determined by the equilibrium method using Fourier transform ion cyclotron resonance and high-pressure mass spectrometry techniques. The latter method allows the measurement of proton transfer equilibrium constants at various temperatures and thus the estimate of both the proton affinities and the protonation entropies of the relevant species. Quantum chemical calculations at the G3 and the B3LYP/6-311+G(3df,2p)//6-31G(d) levels of theory were undertaken in order to find the most stable structures of the neutrals 1-10 and their protonated forms. Conformational and vibrational analyses have been done with the aim of obtaining a theoretical estimate of the protonation entropies.

International audience; The methyl cation and CF(3)(+) attack saturated, acyclic ketones to make vibrationally excited adduct ions. Despite their high internal energies and short lifetimes, these adducts undergo deep-seated rearrangements that parallel slower processes in solution. Observed pathways include alkene and alkane expulsions, in addition to (in the case of CF(3)(+)) the precedented loss of CF(2)O + HF. For the vast majority of ketones, the principal charged products are the CF(3)(+) adducts of lighter carbonyl compounds, ions that are not easily prepared by other avenues. Evidence for ion structures comes from collisionally activated unimolecular decomposition and bimolecular ion-molecule reactions. Typical examples are di-n-propyl and diisopropyl ketones (both of which produce CH(3)CH=OCF(3)(+) as the principal ion-molecule reaction product) and pentamethylacetone (which produces (CH(3))(2)C=OCF(3)(+) as virtually the sole ion-molecule reaction product). Isotopic labeling experiments account for mechanisms, and DFT calculations provide a qualitative explanation for the relative abundances of products from unimolecular decompositions of the chemically activated CF(3)(+) adduct ions that are initially formed.

In the second field-free region of a double focusing mass spectrometer, the spontaneous fragmentation of the ( CH 3 ) 3 C  O  + C ( CD 3 ) 2 ion is not preceded by direct methyl cation migrations. In contrast, a complete exchange of the methyl groups occurs prior to dissociation of the ( CH 3 ) 3 Si  O  + Si ( CD 3 ) 2 ion. This is in agreement with the calculated energy diagram which shows that two factors explain this behavior. (i) The simple cleavage of ( CH 3 ) 3 C  O  + C ( CD 3 ) 2 giving (CH3)3C+ only requires 25.8 kcal mol−1 while the corresponding fragmentation in ( CH 3 ) 3 Si  O  + Si ( CD 3 ) 2 necessitates 74.2 kcal mol−1. (ii) The transition state for the 1,3-CH3+ transfer from carbon to carbon lies in energy 59.1 kcal mol−1 above the covalent structure ( CH 3 ) 3 C  O  + C ( CD 3 ) 2 and only 12.4 kcal mol−1 for the 1,3-CH3+ transfer from silicon to silicon. Calculations and experiments show that the situation is intermediate for the 1,3-CH3+ from silicon to carbon.

The bimolecular reaction of . CH 2 OH 2 + with a variety of neutral molecules in the gas phase were studied by Fourier transform ion cyclotron resonance experiments. The distonic ion is found to be considerably more acidic than protonated methanol; bracketing experiments provide a value of 695 ± 8 kJ mol −1 for the proton affinity of the conjugate base, the hydroxymethyl radical. Efficient hydrogen atom abstraction is only observed from neutral species less basic than . CH 2 OH. Transfer of CH 2 +. to CS 2 , CH 3 I and C 6 H 2 F 4 is observed

International audience; Frequently found in hydrocarbon oxidation and in the photochemistry of carbonyl compounds, the β-carbonyl radicals are of interest. The experimental proton affinities of the two title radicals have been determined from proton transfer reactions (as shown) monitored in an FT-ICR mass spectrometer. This led to an estimation of their heats of formation (1: 13±3; 2: -34±3 kJ mol(-1)). Ab initio molecular orbital calculations, up to the G2 level, confirmed these results.

International audience; Charge transfer reactions of the type M*++B?B*++M have been studied in order to test the applicability of the "thermokinetic" method to the determination of ionization energies (IEs). Three examples are presented with M=benzene, cyclopentanone, and vinyl alcohol. The correlation observed between the bimolecular rate constants and IE(B) allows the determination of IE(M) with a mean deviation of ~0.02 eV with respect to spectroscopic values. One other advantage of the method is to provide ionization energies of unstable neutrals. The role of various corrective terms, and of possible geometry changes during charge transfer reactions are discussed. © 2001 Elsevier Science B.V.

CH2=Si(CH3)OSi(CH3)2+ ions 1 were formed in the external source of a Fourier-transform ion cyclotron resonance (FT-ICR)mass spectrometer by fragmentation of (CH)3SiOSi(CH3)3. In the cell, their reactions with acetaldehyde were studied by using labeled reactants and compared with those with acetone, studied in previous work, which gives a general view of the reactions of ion 1 with carbonyl compounds. In contrast with the behavior of the corresponding carbon-containing ions, the results confirm facile 1,3-methyl group transfers from silicon to silicon. Otherwise, the silicon-containing adducts often eliminate C nH2 n. This process, not observed in (C,O,H)-containing ions, is studied by using selectively deuterated reactants.

Gas-phase basicities of ethyl halides have been accurately determined from experimental proton-transfer reaction rates. Proton affinities (PA) were deduced after consideration of the entropy change associated with the protonation process and from G2 ab initio calculations. The present PA(C2H5X) assessment (653, 679, 685, and 709 kJ mol(-1) for X=F, Cl, Br and I, respectively) indicates that the currently tabulated values should be revised downward by 10 to 30 kJ mol(-1).

A series of proton transfer reactions monitored in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer allows the determination of the gas-phase basicity ( GB) and the proton affinity ( PA) of formaldehyde. The values determined by the thermokinetic method, GB(CH2O) = 681.5 ± 0.7 kJ mol−1 and PA(CH2O) = 711.5 ± 2.1 kJ mol−1 are in excellent agreement with data originating from proton transfer equilibrium constant determinations or from G2 calculations.

International audience; A combination of experiments based on proton transfer reactions monitored in a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer and molecular orbital calculations up to the G2 and the CBS-Q levels demonstrates that the structure of the ions produced by electron ionization of cyclopropylamine, 1, and relaxed at thermal energy, possess the ionized 1-propene amine structure [CH3CHCHNH2]*+, 3*+. The experimental deprotonation enthalpy of ions 3*+ is equal to 915.3 ± 3.2 kJ mol−1. CBS-Q calculations are in good agreement with experiment. A value of 919-923 kJ mol−1 is calculated for the deprotonation enthalpy of ions 3*+; 298 K heat of formation values of 852 kJ mol−1 and 783 kJ mol−1 are predicted from G2 atomization energies for ions 2*+ and 3*+, respectively. The heat of formation of [CH2CHCHNH2]+ ions has been evaluated to 757.6 ± 5.7 kJ mol−1 from experiment and 755.8 kJ mol−1 from G2 atomization energy.

Of 373 anaerobic microbial isolates screened for the enzymatic conversion of dihydrouracil to N-carbamyl-beta-alanine, several strains of Clostridium spp., C. glycolicum, C. subterminale and Peptococcus anaerobius were positive. These Clostridium and Peptococcus strains produced also N-carbamyl-d-amino acids from the respective 5prime-monosubstituted hydantoins. The d-hydantoinase activity from whole cell suspensions of P. anaerobius strain CRDA 303 was characterized with regard to pH and temperature stability and activity by using dihydrouracil (DHU) and isopropylhydantoin (IPH) as substrates. The d-hydantoinase from P. anaerobius was optimal at 60°C and at pH 6.5–9.5 for the substrate DHU. It was stable up to 55°C and at pH 5.0–9.5 and could be stored at 4°C under an aerobic atmosphere for at least 14 days.

Radical cations of aliphatic phenyl ethers [from electron ionization (EI)] and their conjugate acid ions [from chemical ionization (CI)] exhibit similar decomposition mechanisms. The M•+ and MH+ ions of the title compound (1-phenoxy-3-chloropropane, 1) both expel chloropropene, with hydrogen transfer coming from all chain positions. This result has ample precedent and is taken as proof of the intermediacy of ion–neutral complexes in both EI and CI. Isomerization of 1•+ to PhOCH(CH3)CH2Cl•+ prior to metastable chloropropene expulsion can be ruled out on the basis of isotope effect measurements, despite the prediction of this rearrangement by ab initio calculations. The results also preclude collapse of ion–neutral complexes back to their isomeric molecular ions, even though there appears to be no energy barrier to reforming a covalent bond between the ion and its neutral partner. Competing pathways for dissociation of 1•+ via distonic ions are assessed by means of deuterated analogues. In addition, M•+ and...

Interaction with polar neutral molecules can cause α-distonic radical cations and conventional molecular ions to interconvert in the gas phase, in spite of substantial energy barriers for the unassisted isomerization; the interconversion is particularly facile when the proton affinity of the neutral molecule is close to that of the deprotonated radical cation.

From a study of the elimination of carbonylated radicals from 2,3-diphenyl-1,4-benzodioxin and certain specifically deuterated derivatives, it has been possible to calculate the relative abundances of the different isomeric molecular ions formed. A comparison with phenylbenzocyclobutenyl derivatives of 1,4-benzodioxin indicates that the isomerization schemes are similar.

Differents isomeres de I'ion moleculaire de derives benzocyclobuteniques du benzodioxinne 1,4 specifiquement marques au deuterium ont ete mis en evidence. L'abondance de l'Blimination des radicaux benzoyles et formyles differement marques ont permis de determiner l'importance relative des isomeres de l'ion moleculaire. The existence of different isomers of phenyl benzocyclobutene derivatives of specifically deuterium labelled 1,4-benzodioxin molecular ions have been demonstrated. The number of differently labelled benzoyl and formyl radicals being lost facilitated the determination of the relative importance of the various molecular ion isomers.