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Rotavirus infections in nursing or post-weaning piglets are known to cause diarrhea, which can lead to commercial losses. Probiotic supplementation is used as a prophylactic or therapeutic approach to dealing with microbial infections in humans and animals. To evaluate the effect of probiotic bacteria on porcine rotavirus infections, non-transformed porcine intestinal epithelial IPEC-J2 cells were used as an in vitro model, and three different procedures were tested. When cells were exposed to seven probiotics at concentrations of 105, 106, or 107 CFU/mL for 16 h and removed before rotavirus challenge, infection reduction rates determined by flow cytometry were as follows: 15% (106) and 18% (105) for Bifidobacterium longum R0175, 15% (107) and 16% (106) for B. animalis lactis A026, and 15% (105) for Lactobacillus plantarum 299V. When cells were exposed to three selected probiotic strains for 1 h at higher concentrations, that is, 108 and 5 × 108 CFU/mL, before infection with rotavirus, no significant reduction was observed. When the probiotic bacteria were incubated with the virus before cell infection, a significant 14% decrease in the infection rate was observed for B. longum R0175. The results obtained using a cell-probiotics-virus platform combined with flow cytometry analysis suggest that probiotic bacteria can have a protective effect on IPEC-J2 cells before infection and can also prevent rotavirus infection of the cells.

BACKGROUND: Characterizing the multiorgan manifestations and outcomes of patients hospitalized with COVID-19 will inform resource requirements to address the long-term burden of this disease. We conducted a descriptive analysis using prospectively collected data to describe the clinical characteristics and spectrum of organ dysfunction, and in-hospital and longer-term clinical outcomes of patients hospitalized with COVID-19 during the first wave of the pandemic at a Canadian centre. METHODS: We conducted a prospective case series involving adult patients (aged ≥ 18 yr) with COVID-19 admitted to 1 of 2 hospitals in London, Ontario, from Mar. 17 to June 18, 2020, during the first wave of the pandemic. We recorded patients' baseline characteristics, physiologic parameters, measures of organ function and therapies administered during hospitalization among patients in the intensive care unit (ICU) and in non-ICU settings, and compared the characteristics of hospital survivors and nonsurvivors. Finally, we recorded follow-up thoracic computed tomography (CT) and echocardiographic findings after hospital discharge. RESULTS: We enrolled 100 consecutive patients (47 women) hospitalized with COVID-19, including 32 patients who received ICU care and 68 who received treatment in non-ICU settings. Respiratory sequelae were common: 23.0% received high-flow oxygen by nasal cannula, 9.0% received noninvasive ventilation, 24.0% received invasive mechanical ventilation and 2.0% received venovenous extracorporeal membrane oxygenation. Overall, 9.0% of patients had cerebrovascular events (3.0% ischemic stroke, 6.0% intracranial hemorrhage), and 6.0% had pulmonary embolism. After discharge, 11 of 19 patients had persistent abnormalities on CT thorax, and 6 of 15 had persistent cardiac dysfunction on echocardiography. INTERPRETATION: This study provides further evidence that COVID-19 is a multisystem disease involving neurologic, cardiac and thrombotic dysfunction, without evidence of hepatic dysfunction. Patients have persistent organ dysfunction after hospital discharge, underscoring the need for research on long-term outcomes of COVID-19 survivors.

To evaluate the impact of the COVID-19 pandemic on Canadian intensive care unit (ICU) workers.Between June and August 2020, we distributed a cross-sectional online survey of ICU workers evaluating the impact of the pandemic, coping strategies, symptoms of post-traumatic stress disorder (PTSD; Impact of Events Scale-Revised), and psychological distress, anxiety, and depression (Kessler Psychological Distress Scale). We performed regression analyses to determine the predictors of psychological symptoms.We analyzed responses from 455 ICU workers (80% women; 67% from Ontario; 279 nurses, 69 physicians, and 107 other healthcare professionals). Respondents felt that their job put them at great risk of exposure (60%), were concerned about transmitting COVID-19 to family members (76%), felt more stressed at work (67%), and considered leaving their job (37%). Overall, 25% had probable PTSD and 18% had minimal or greater psychological distress. Nurses were more likely to report PTSD symptoms (33%) and psychological distress (23%) than physicians (5% for both) and other health disciplines professionals (19% and 14%). Variables associated with PTSD and psychological distress included female sex (beta-coefficient [B], 1.59; 95% confidence interval [CI], 1.20 to 2.10 and B, 3.79; 95% CI, 1.79 to 5.78, respectively; P0.001 for differences in scores across groups) and perceived increased risk due to PPE shortage or inadequate PPE training (B, 1.87; 95% CI, 1.51 to 2.31 and B, 4.88; 95% CI, 3.34 to 6.43, respectively). Coping strategies included talking to friends/family/colleagues (80%), learning about COVID-19 (78%), and physical exercise (68%). Over half endorsed the following workplace strategies as valuable: hospital-provided scrubs, clear communication and protocols by hospitals, knowing their voice is heard, subsidized parking, and gestures of appreciation from leadership.This survey study shows that ICU workers have been impacted by the COVID-19 pandemic with high levels of stress and psychological burden. Respondents endorsed communication, protocols, and appreciation from leadership as helpful mitigating strategies.RéSUMé: OBJECTIF: Évaluer l’impact de la pandémie de COVID-19 sur les travailleurs canadiens des unités de soins intensifs (USI). MéTHODE: Entre juin et août 2020, nous avons fait parvenir un sondage transversal en ligne aux travailleurs des soins intensifs pour évaluer l’impact de la pandémie, les stratégies d’adaptation et les symptômes de stress post-traumatique (SPT; Échelle révisée de l’impact de l’événement - IES-R), ainsi que la détresse psychologique, l’anxiété et la dépression (Échelle de détresse psychologique de Kessler). Nous avons réalisé des analyses de régression pour déterminer les prédicteurs de symptômes psychologiques. RéSULTATS: Nous avons analysé les réponses de 455 travailleurs des soins intensifs (80 % de femmes; 67 % de l’Ontario; 279 infirmières/infirmiers, 69 médecins et 107 autres professionnels de la santé). Les répondants ont estimé que leur emploi les plaçait face à un risque élevé d’exposition (60 %), craignaient de transmettre la COVID-19 aux membres de leur famille (76 %), se sentaient plus stressés au travail (67 %) et avaient envisagé de quitter leur emploi (37 %). Dans l’ensemble, 25 % souffraient probablement d’un SPT et 18 % présentaient une détresse psychologique minimale ou supérieure. Les infirmières et infirmiers étaient plus susceptibles de rapporter des symptômes de SPT (33 %) et de détresse psychologique (23 %) que les médecins (5 % pour les deux) et les professionnels de la santé des autres disciplines (19 % et 14 %). Les variables associées à un SPT et à la détresse psychologique comprenaient le sexe féminin (coefficient bêta [B], 1,59; intervalle de confiance [IC] à 95 %, 1,20 à 2,10 et B, 3,79; IC 95 %, 1,79 à 5,78, respectivement; P0,001 pour les différences de scores entre les groupes) et la perception d’un risque accru en raison des pénuries d’EPI ou d’une formation inadéquate en EPI (B, 1,87; IC 95 %, 1,51 à 2,31 et B, 4,88; IC 95 %, 3,34 à 6,43, respectivement). Les stratégies d’adaptation comprenaient le fait de parler aux amis, à la famille ou aux collègues (80 %), l’acquisition de connaissances concernant la COVID-19 (78 %) et l’exercice physique (68 %). Plus de la moitié ont estimé que les stratégies de travail suivantes étaient utiles : des uniformes fournis par les hôpitaux, une communication et des protocoles clairs de la part des hôpitaux, le fait de savoir que leur voix est entendue, un stationnement subventionné et des gestes d’appréciation de la part des dirigeants. CONCLUSION: Cette étude montre que les travailleurs des soins intensifs ont été touchés par la pandémie de COVID-19 avec des niveaux élevés de stress et de fardeau psychologique. Les répondants ont déclaré que la communication, les protocoles et les gestes d’appréciation de la direction constituaient des stratégies d’atténuation utiles.

Aims: To demonstrate that produce rinsates used for RT-qPCR detection of foodborne viruses may cause significant PCR inhibition and propose a means to reduce its impact on sensitivity. Methods and Results: Here, it is shown that rinsing and concentration from spinach and precut lettuce have the potential to generate RNA extracts that are inhibitory to RT-qPCRs assembled from commercial kits for the detection of norovirus GII (NoV GII), hepatitis A virus (HAV), hepatitis E virus (HEV), rotavirus (RV) and feline calicivirus (FCV) as sample process control. It is further shown that the addition of bovine serum albumin (BSA) to those reactions restored a positive signal in all cases. The effect of BSA was dependent upon the primer/probe combination. Moreover, two of the detection systems (FCV and HAV) strongly benefited from the addition of BSA even in the absence of PCR inhibitors. Conclusions: BSA was shown to restore positive signals in five different RT-qPCR systems that were otherwise completely inhibited by produce rinsate extracts. It is therefore suggested to consider the addition of BSA to RT-qPCRs for the detection of foodborne viruses when inhibition is observed. Significance and Impact of the Study: This study clearly demonstrates the potency of PCR inhibitors generated during routine virus concentration from produce and that it can be alleviated by the addition of BSA to the RT-qPCRs. Although used elsewhere, the addition of BSA to PCRs is not a common practice in this growing field of research.

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.

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.

Aims The aim of this study was to compare the performance of four RT-qPCR assays for the detection of human and bovine group A rotaviruses and to characterize the positive samples by sequence analysis of VP4 and VP7 genes. Methods and Results RNA extracted from eight human rotavirus strains, and a panel of 33 human and 25 bovine faecal samples was subjected to different RT-qPCR detection systems. Among these assays, only RT-qPCR primers and probe systems B and C were able to detect all human rotavirus strains from cell culture solutions and faecal samples. However, the results showed that the system C was generally more sensitive by one or two logs than the other RT-qPCR assays tested. With the bovine faecal samples, the most efficient RT-qPCR systems were B and A with the detection in 100 and 92% of samples tested, respectively. Human group A rotavirus G1P[8] and bovine G6P[11] were the most frequently used strains identified in this study. A G3P[9] strain, closely related to a feline rotavirus isolated in the USA, was also discovered in a human rotavirus infection. Conclusion The RT-qPCR system B was the only TaqMan assay evaluated in this study able to detect rotavirus RNA in all positive human and bovine faecal samples. Significance and Impact of the Study Utilization of only one RT-qPCR for the detection of human and bovine group A rotaviruses and the possibility of human infection by a feline rotavirus strain.

Background Haemozoin crystals, produced by Plasmodium during its intra-erythrocytic asexual reproduction cycle, can generate UV light via the laser-induced, non-linear optical process of third harmonic generation (THG). In the current study the feasibility of using haemozoin, constitutively stored in the parasite’s food vacuole, to kill the parasite by irradiation with a near IR laser was evaluated. Methods Cultured Plasmodium parasites at different stages of development were irradiated with a pulsed NIR laser and the viability of parasites at each stage was evaluated from their corresponding growth curves using the continuous culture method. Additional testing for germicidal effects of haemozoin and NIR laser was performed by adding synthetic haemozoin crystals to Escherichia coli in suspension. Cell suspensions were then irradiated with the laser and small aliquots taken and spread on agar plates containing selective agents to determine cell viability (CFU). Results Parasites in the late-trophozoites form as well as trophozoites in early-stage of DNA synthesis were found to be the most sensitive to the treatment with ~4-log reduction in viability after six passes through the laser beam; followed by parasites in ring phase (~2-log reduction). A ~1-log reduction in E. coli viability was obtained following a 60 min irradiation regimen of the bacteria in the presence of 1 μM synthetic haemozoin and a ~2-log reduction in the presence of 10 μM haemozoin. Minimal (≤15%) cell kill was observed in the presence of 10 μM haemin. Conclusions Laser-induced third-harmonic generation by haemozoin can be used to inactivate Plasmodium. This result may have clinical implications for treating severe malaria symptoms by irradiating the patient’s blood through the skin or through dialysis tubing with a NIR laser.

Little is known about the role of herpes simplex virus (HSV) type 1 (HSV1) in the epidemiology of genital herpes in Canada. Data on herpes viral cultures for two consecutive years obtained from L'Hôpital Dr GL Dumont, which performs all the viral culture testing in New Brunswick, were reviewed. It was hypothesized that HSV1 was the main cause of genital herpes in New Brunswick.Samples of genital origin sent to the laboratory for HSV culture testing between July 2006 and June 2008 were analyzed. Samples from an unspecified or a nongenital source were excluded from analysis. Multiple positive samples collected from the same patient were pooled into a single sample.HSV was isolated from 764 different patients. HSV1 was isolated in 62.6% of patients (male, 55%; female, 63.8%). HSV1 was isolated in 73.2% of patients 10 to 39 years of age and in 32% of patients ≥40 years of age. The difference in rates of HSV1 infection between the 10 to 39 years of age group and the ≥40 years of age group was statistically significant (P0.001 [χ(2)]). In a similar Canadian study performed in Nova Scotia, HSV1 was recovered in 53.7% of positive cultures (male, 36.7%; female, 58.1%). The rates of HSV1 infection reported by this study and the present study were significantly different (P0.001 [χ(2)] for male, P=0.012 for female).In New Brunswick, HSV1 is the dominant type of HSV isolated in samples collected from a genital site. Significant rate differences were demonstrated between the groups 10 to 39 years of age and ≥40 years of age.Little is known about the role of herpes simplex virus (HSV) type 1 (HSV1) in the epidemiology of genital herpes in Canada. Data on herpes viral cultures for two consecutive years obtained from L’Hôpital Dr GL Dumont, which performs all the viral culture testing in New Brunswick, were reviewed. It was hypothesized that HSV1 was the main cause of genital herpes in New Brunswick.Samples of genital origin sent to the laboratory for HSV culture testing between July 2006 and June 2008 were analyzed. Samples from an unspecified or a nongenital source were excluded from analysis. Multiple positive samples collected from the same patient were pooled into a single sample.HSV was isolated from 764 different patients. HSV1 was isolated in 62.6% of patients (male, 55%; female, 63.8%). HSV1 was isolated in 73.2% of patients 10 to 39 years of age and in 32% of patients ≥40 years of age. The difference in rates of HSV1 infection between the 10 to 39 years of age group and the ≥40 years of age group was statistically significant (P0.001 [χIn New Brunswick, HSV1 is the dominant type of HSV isolated in samples collected from a genital site. Significant rate differences were demonstrated between the groups 10 to 39 years of age and ≥40 years of age.On ne sait pas grand-chose du rôle du virus de l’herpès simplex de type 1 (VHS1) dans l’épidémiologie de l’herpès génital au Canada. Les chercheurs ont analysé les données des cultures d’herpès viral obtenues pendant deux années consécutives à L’Hôpital Dr-Georges-L.-Dumont, où toutes les cultures virales sont effectuées au Nouveau-Brunswick. Ils ont postulé que le VHS1 était la principale cause d’herpès génital dans la province.Les chercheurs ont analysé les prélèvements génitaux envoyés en laboratoire entre juillet 2006 et juin 2008, en vue de cultures du virus d’herpès simplex (VHS). Ils ont exclu de l’analyse les prélèvements tirés d’une source non précisée ou d’origine non génitale. Ils ont regroupé dans un seul échantillon les multiples échantillons positifs prélevés chez le même patient.Le VHS a été isolé chez 764 patients, et le VHS1, chez 62,6 % des patients (55 % chez les hommes, et 63,8 % chez les femmes), soit 73,2 % des patients de dix à 39 ans et 32 % des patients de 40 ans et plus. La différence de taux d’infection par le VHS1 entre le groupe des dix à 39 ans et celui des 40 ans et plus était statistiquement significative (χAu Nouveau-Brunswick, le VHS1 est le principal type de VHS isolé dans des échantillons d’origine génitale. On a établi des différences de taux significatives entre le groupe des dix à 39 ans et celui des 40 ans et plus.

Pseudomonas putida DSM 84 produces N-carbamyl-D-amino acids from the corresponding D-5-monosubstituted hydantoins. The gene encoding this D-hydantoinase enzyme was cloned and expressed in Escherichia coli. The nucleotide sequence of the 1.8-kb insert of subclone pGES19 was determined. One open reading frame of 1,104 bp was found and was predicted to encode a polypeptide with a molecular size of 40.5 kDa. Local regions of identity between the predicted amino acid sequence and that of other known amidohydrolases (two other D-hydantoinases, allantionase and dihydroorotase) were found. The D-hydantoinase gene was used as a probe to screen DNA isolated from diverse organisms. Within Pseudomonas strains of rRNA group I, the probe was specific. The probe did not detect D-hydantoinase genes in pseudomonads not in rRNA group I, other bacteria, or plants known to express D-hydantoinase activity.

d -Hydantoinase (E.C.3.5.2.2) from Pseudomonas fluorescens (strains 1.2 and 1.9), Pseudomonas putida (strains 2.2, 2.5 and DSM 84), Serratia liquefaciens (strain 1.15) and Corynebacterium pseudodiphtheriticum (strain 14.10) were compared according to their stability to different purification procedures. With exception to C. pseudodiphtheriticum where between 75 and 85% of the enzyme was recovered after purification, yields less than 30% were observed for all other strains. These low recovery levels were not due to the removal of essential ions or to the absence of substrate during chromatography. Purification yields could not be improved by the addition of detergents and of a cryoprotectant to prevent aggregation and/or to increase hydantoinase stability. Hydantoinases from all the strains examined except C. pseudodiphtheriticum , were stable up to 37°C and at pH 5. The C. pseudodiphtheriticum enzyme was stable at temperatures up to 57°C and at pH values above 8. All hydantoinases exhibited maximum activity at temperatures between 45 and 55°C and at pH 8.0 or above. Native and SDS-PAGE gave M r estimates ranging from 160 000 to 235 000 and 60 000 ± 4000 for the native enzymes and their subunits, respectively.

The purpose of the study, carried out in a beef processing plant, was to evaluate the effectiveness of a new prototype for steam pasteurization treatment in controlling microbiological hazards. Samples were taken by swabbing randomly selected sites before and after pasteurization and again after chilling to obtain total aerobic counts (TAC), total coliform counts (TCC), and generic Escherichia coli counts (ECC) on Petrifilm plates and to determine the prevalence of Salmonella spp., Listeria monocytogenes, and E. coli O157:H7 using standard enrichment techniques. Escherichia coli and L. monocytogenes strains were tested for various factors associated with their virulence by using colony hybridization and polymerase chain reaction (PCR), respectively. Antimicrobial susceptibility was determined for each isolate that was potentially pathogenic to humans by using the disk-diffusion method. Mean values for TAC, TCC, and ECC were 2.18, 0.16, and 0.06 log10 CFU/cm2, respectively, before pasteurization; 1.17, 0.03, and 0.01 log10 CFU/cm2 after pasteurization; and 0.89, 0.02, and 0.01 log10 CFU/cm2 after chilling. Prevalence of L. monocytogenes, Salmonella spp., and E. coli O157:H7 on carcasses was 0.8%, 0.0%, and 0.0%, respectively, before pasteurization; 2.6%, 0.0%, and 0.0% after pasteurization; and 3.1%, 0.1%, and 0.0% after chilling. The prevalence of E. coli containingor = 1 virulence gene was 14.7%. More specifically, 11.88% of the isolates obtained before pasteurization, 22.2% obtained after pasteurization, and 31.2% obtained after chilling had virulence genes. All L. monocytogenes isolates tested positive for the presence of 3 major virulence factors (hlyA, inlB, and plcB). Antibiograms showed that certain isolates were susceptible to all antibiotics, some showed an intermediate sensitivity, and others were multiresistant. Overall, these results suggest that steam pasteurization is an effective means of improving safety quality of beef carcasses. However, pasteurization may indirectly contribute to the growth of some pathogenic microorganisms, such as L. monocytogenes.

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.

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.

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.

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.