Improved proton affinity measurements for proline and modified prolines using triple quadrupole and ion trap mass spectrometers

Proton affinity (PA) of compounds such as proline, cis-3-methylproline, cis-3-ethylproline, cis-3-isopropylproline and cis-3-isopentanylproline was determined by kinetic method with amines as the reference bases. The effective temperatures determined using ion trap and triple quadrupole mass spectrometers were found to be significantly different. In the case of the triple quadrupole instruments, the effective temperature depends significantly on the collision energy. The influence of the apparent basicity (GBapp) on the effective temperature may be used to estimate the difference in protonation entropy (DeltaDeltaS degrees) between the sample and reference compounds. In case of the ion trap mass spectrometer, the variation of the effective temperature as a function of the excitation amplitude is small, so it is difficult to account for the contribution of the entropy effects to the proton affinity value. A better estimation of the PA and DeltaDeltaS degrees values for the investigated molecules is obtained by combining the GBapp and Teff data pairs that are obtained from both the mass spectrometers.

Activated Surfaces for Laser Desorption Mass Spectrometry: Application for Peptide and Protein Analysis

Thanks to the development of matrix assisted laser desorption/ionisation (MALDI), laser desorption based mass spectrometry became an essential method for the analysis of biomolecules. This review will discuss the various surface modifications used in combination with laser desorption mass spectrometry and their application for the analysis of peptides and proteins. In the first hand, some modified surfaces are designed to enhance the laser desorption/ionisation process; this includes the use of carbon, porous silicon surfaces and also immobilised matrix. In an other hand chemical and biochemical modified surfaces developed to isolate species with more or less specific interactions can be used for on-slide sample clean-up before MALDI-MS analysis. In addition, different experimental devices as mass spectrometers and microfluidic devices used for such a purpose will be presented.

Structural characterization of fatty acids cationized with copper by electrospray ionization mass spectrometry under low-energy collision-induced dissociation

Fatty acids have for many years been characterized by mass spectrometry using electron ionization after chemical derivatization. When fatty acids are ionized using desorption/ionization methods such as electrospray ionization or fast atom bombardment, structural information is usually obtained through high-energy collision-induced dissociation (CID) using sector instruments. It has been shown that copper displays very interesting properties in the gas phase during CID. In this study, the reactivity of saturated and unsaturated fatty acid-copper [M-H+Cu(II)]+ complex and the role of the copper ion in promoting fragmentations were investigated under low-energy collisional activation conditions. The decomposition of these species in an ion trap instrument led to diagnostic ion series that reflect C--C bond cleavage, which involves Cu(II) reduction followed by the release of an alkyl radical. It was demonstrated that in this way the localization of one or two homoconjugated double bonds is possible using low-energy CID. Moreover, the distinction of cis and trans isomers is possible through characteristic product ions related to a specific loss of CO2. When these experiments are repeated using a triple-quadrupole instrument with argon as collision gas, a different behavior is observed as in this case, in addition to the product ion distributions observed in the ion trap, other distributions are observed that reflect the influence of the different kinetic shifts and the occurrence of consecutive decompositions. Different examples are presented with various saturated and unsaturated fatty acid chains. Mechanisms are proposed in order to rationalize the experimental observations.

Investigation of the reactivity of arylamines, organo-hydrazines and tolylisocyanate towards [PW12–xMxO40]n– Keggin anions

Reaction of K7[A,alpha-PW9Mo2O39] with Na2MoO4.2H2O in a mixture of water/dioxane/hydrochloric acid and further precipitation with (Bu4N)Br provided (Bu4N)3[A,alpha-PW9Mo3O40](3). Analogous reaction with K7-xNax[alpha-PW11O39] is an alternative to the synthesis of (Bu4N)3[alpha-PW11O39{MoVIO}]2. Multinuclear NMR and ESI mass spectrometry have been used to interpret the reaction of (Bu4N)x[alpha-PW11O39{ReO}](x=3 1; x=4 1I), (Bu4N)x[alpha-PW11O39{MoO}](x=3 2; x=4 2I) and (Bu4N)3[A,alpha-PW9Mo3O40]3 by organohydrazines, arylamines, tolylisocyanate and tetraphenylphosphine imide.

Anionic copper complex fragmentations from enkephalins under low-energy collision-induced dissociation in an ion trap mass spectrometer

Peptide metallation with Cu2+ was explored in the negative ESI mode using an ion trap mass spectrometer. Under these conditions, the [(M-3H) + CuII]- species formed were investigated under low-energy collision-induced dissociation conditions. MS2 experiments indicate a very different behavior of CuII metallated complexes compared with [M-H]- species. CuII induces an easy loss of CO2 and specific side-chain cleavages (by radical losses) at the C-terminal residue, as observed previously by prompt 'in source' dissociation experiments. The loss of CO2 yields an unstable carbylide that leads to further dissociations involving the migration of a proton or a hydrogen radical (through the reduction of CuII). Multistage MS3 experiments were carried out to rationalize this behavior. Fragmentation pathways are proposed in order to explain the product ions observed. The side-chain radical loss at the C-terminus was demonstrated to be a consecutive process. Finally, evidence is provided that the specific side-chain cleavages can be used for the differentiation of Leu/Ile and Gln/Lys residues when they are located at the C-terminus. The existence of a zwitterionic form in the case of the anionic YGGFK-CuII complex is proposed.

Siderophore Peptide, a New Type of Post-translationally Modified Antibacterial Peptide with Potent Activity

Microcin E492 (MccE492, 7886 Da), the 84-amino acid antimicrobial peptide from Klebsiella pneumoniae, was purified in a post-translationally modified form, MccE492m (8717 Da), from culture supernatants of either the recombinant Escherichia coli VCS257 strain harboring the pJAM229 plasmid or the K. pneumoniae RYC492 strain. Chymotrypsin digestion of MccE492m led to the MccE492m-(74-84) C-terminal fragment that carries the modification and that was analyzed by mass spectrometry and nuclear magnetic resonance at natural abundance. The 831-Da post-translational modification consists of a trimer of N-(2,3-dihydroxybenzoyl)-l-serine linked via a C-glycosidic linkage to a beta-d-glucose moiety, itself linked to the MccE492m Ser-84-carboxyl through an O-glycosidic bond. This modification, which mimics a catechol-type siderophore, was shown to bind ferric ions by analysis of the collision-induced dissociation pattern obtained for MccE492m-(74-84) by electrospray ion trap mass spectrometry experiments in the presence of FeCl(3). By using a series of wild-type and mutant isogenic strains, the three catechol-type siderophore receptors Fiu, Cir, and FepA were shown to be responsible for the recognition of MccE492m at the outer membrane of sensitive bacteria. Because MccE492m shows a broader spectrum of antibacterial activity and is more potent than MccE492, we propose that by increasing the microcin/receptor affinity, the modification leads to a better recognition and subsequently to a higher antimicrobial activity of the microcin. Therefore, MccE492m is the first member of a new class of antimicrobial peptides carrying a siderophore-like post-translational modification and showing potent activity, which we term siderophore-peptides.

Functionalization of Polyoxometalates: From Lindqvist to Keggin Derivatives. 1. Synthesis, Solution Studies, and Spectroscopic and ESI Mass Spectrometry Characterization of the Rhenium Phenylimido Tungstophosphate [PW11O39{ReNC6H5}]4-

Reaction of [Bu(4)N](4)[H(3)PW(11)O(39)] with [Re(NPh)Cl(3)(PPh(3))(2)], in acetonitrile and in the presence of NEt(3), provided the first Keggin-type organoimido derivative [Bu(4)N](4)[PW(11)O(39)(ReNPh)] (Ph = C(6)H(5)) (1). The functionalization was clearly demonstrated by various techniques including (1)H and (14)N NMR, electrochemistry, and ESI mass spectrometry. Conditions for the formation of 1 are also discussed.

Structure of Thermolysin Cleaved Microcin J25: Extreme Stability of a Two-Chain Antimicrobial Peptide Devoid of Covalent Links†,‡

The structure of a two-chain peptide formed by the treatment of the potent antimicrobial peptide microcin J25 (MccJ25) with thermolysin has been characterized by NMR spectroscopy and mass spectrometry. The native peptide is 21 amino acids in size and has the remarkable structural feature of a ring formed by linkage of the side chain of Glu8 to the N-terminus that is threaded by the C-terminal tail of the peptide. Thermolysin cleaves the peptide at the Phe10-Val11 amide bond, but the threading of the C-terminus through the N-terminal ring is so tight that the resultant two chains remain associated both in the solution and in the gas phases. The three-dimensional structure of the thermolysin-cleaved peptide derived using NMR spectroscopy and simulated annealing calculations has a well-defined core that comprises the N-terminal ring and the threading C-terminal tail. In contrast to the well-defined core, the newly formed termini at residues Phe10 and Val11 are disordered in solution. The C-terminal tail is associated to the ring both by hydrogen bonds stabilizing a short beta-sheet and by hydrophobic interactions. Moreover, unthreading of the tail through the ring is prevented by the bulky side chains of Phe19 and Tyr20, which flank the octapeptide ring. This noncovalent two-peptide complex that has a remarkable stability in solution and in highly denaturing conditions and that survives in the gas phase is the first example of such a two-chain peptide lacking disulfide or interchain covalent bonds.

Characterization of the ceramide moieties of sphingoglycolipids from mouse brain by ESI-MS/MS

Sphingoglycolipids (SGLs) are cell membrane constituents. As the ceramide structure influences the biological properties of the SGL, we characterized by electrospray ionization tandem mass spectrometry the molecular species of ceramides present in SGL of mouse brain. We report here for the first time the presence in mammalian brain of sphingadienine (d18:2). Sphingenine (d18:1) is present in all SGL species, in contrast to eicosasphingenine (d20:1), which is a constituent of only gangliosides. Sphingadienine is present in galactosylceramide and sulfatides. Free ceramides contain the three types of bases. Thus, there could be two separate pools of free ceramides (d18:1, d18:2 and d20:1, d18:1) as precursors of complex SGL.

Dissection of proteolytic 18O labeling: endoprotease-catalyzed 16O-to-18O exchange of truncated peptide substrates

Proteolytic labeling in H2(18)O has been recently revived as a versatile method for proteomics research. To understand the molecular basis of the labeling process, we have dissected the process into two separate events: cleavage of the peptide amide bonds and exchange of the terminal carboxyl oxygens. It was demonstrated that both carboxyl oxygens can be catalytically labeled, independent of the cleavage step. Reaction kinetics of the tryptic 16O-to-18O exchange of YGGFMR, YGGFMK, and the tryptic digest of apomyoglobin were studied by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry. A larger KM for the Lys-peptide (4400 +/- 700 microM), when compared to that of the Arg-peptide (KM 1300 +/- 300 microM), was mainly responsible for the slower reaction with YGGFMK (kcat/KM 0.64 +/- 0.14 microM(-1)min(-1)) compared to YGGFMR (kcat/KM 2.6 +/- 0.9 microM(-1)min(-1)). Multiplexed kinetic studies showed that endoprotease-catalyzed oxygen exchange is a general phenomenon, allowing homogeneous 18O2-coding of a variety of peptides. It was demonstrated for the first time that chymotrypsin 18O2-codes peptides during proteolysis. On the basis of the analyses reported here, we propose that proteolytic 18O labeling can be advantageously decoupled from protein digestion, and endoproteases can be used in a separate step to 18O2-code peptides for comparative studies after proteolysis has taken place.

Use of bioactive glass slides for matrix-assisted laser desorption/ionization analysis: application to microorganisms

Glass slides are widely used in high-throughput analysis and are available commercially with surfaces activated, etched, and channeled. Thin glass microscope slides are shown here to be suitable sample supports for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. As a demonstration, lectins immobilized on glass slides with activated surfaces are used to concentrate and purify agglutinated Bacillis spores. It is expected that such slides will provide a rapid, inexpensive way to evaluate and implement new strategies involving MALDI MS readout.

Proton affinity of proline and modified prolines using the kinetic method: role of the conformation investigated by ab initio calculations

The proton affinities of proline, cis-3-methylproline and cis-3-ethylproline have been measured by the kinetic method using an ion trap instrument; the values obtained are 936, 940.5, and 943 kJ mol(-1), respectively. The experimental values are consistent with those obtained by high-level ab initio calculations (B3LYP/6-31+G*//B3LYP/6-31G* and B3P86/6-31+G*//B3LYP/6-31G*). Several conformations of neutral and protonated proline were considered, in particular the endo and exo ring structure and the position of the carboxyl group. These results show the importance of the position of the hydrogen atom of the carboxyl group in determining the most stable protonated proline structure.

Qualitative characterization of biomolecular zinc complexes by collisionally induced dissociation

Nanospray and collisionally induced dissociation (CID) on a quadrupole/time-of-flight mass spectrometer were used to examine the complexes formed between the zinc ion binding protein metallothionein and a series of peptides related to glutathione. The objective of the study was to determine if CID could be used to distinguish complexes that are stabilized by co-chelation of a zinc ion from non-covalent complexes that were formed in some other way. Differences in the collision energy required for dissociation and, more importantly, differences in the distribution of zinc ions between the pairs of dissociation products suggest that mass spectrometry can provide qualitative information about the bimolecular chelation of metal ions. The potential application to zinc chelates is particularly important, since biological chelates do not provide signals directly detectable by NMR, Mössbauer or other spectroscopies. The observations reported here also allowed a molecular mechanism to be proposed to explain the differences observed by others in the physiological interactions of reduced and oxidized glutathione with metallothionein.

Physical activity in European seniors: attitudes, beliefs and levels

BACKGROUND

It is important to study the factors which modulate ageing, among which physical activity (PA) seems to have a very important role on the health status and quality of life of the elderly. To be effective, any intervention specifically targeted to promote PA should be based on the knowledge of the population, namely on their needs, attitudes and behaviour.

OBJECTIVE

To identify in the elderly European population, the attitudes to PA and health, in order to define adequate strategies of promotion.

DESIGN

Cross-sectional survey using a face-to-face interview-assisted questionnaire. This project belongs to the multicentric Pan-EU Survey on Consumer Attitudes to PA, Body Weight and Health under the leadership of the Institute of European Food Studies - Dublin with the cooperation of members from all European Union countries. 1914 European citizens, aged > or = 65, were interviewed. The data's descriptive analysis, was followed by univariate analysis to characterise the study's sample.

RESULTS

PA was not viewed by the elderly as a major health determinant as it was ranked only 5th (18%), preceded by food (42%), smoking habits (40%) and alcohol (24%). 41% of elderly were not engaged in any type of PA, but 50% dedicated more than 3,5 hours/week on various activities. At EU level the most common activities included walking, gardening, cycling and swimming. 64% of the elderly thought that they do not need to do more PA, and 37% were in the pre-contemplation stage as they were currently not very physically active and they didn't intend to become physically active in the next 6 months. A large variation in attitudes, and behaviours in relation to PA, was found amongst European countries.

CONCLUSION

Programmes to promote PA need to be tailored to the different countries in order to increase/maintain PA in the elderly.

Healthy eating in European elderly: concepts, barriers and benefits

BACKGROUND

The promotion of healthy eating is more likely to be effective if based on the understanding of how the elderly perceive their own diets and healthy eating.

OBJECTIVES

The objectives of this study were to identify in the elderly European population, the attitudes to food, nutrition and health, in order to define adequate strategies of health promotion.

DESIGN

Cross-sectional survey using a face-to-face interview-assisted questionnaire. This project belongs to the multicentric Pan-EU Survey on Consumer Attitudes to Food, Nutrition and Health under the leadership of the Institute of European Food Studies - Dublin with the cooperation of members from all EU countries. 1843 European citizens, aged > or = 65, were interviewed. The data's descriptive analysis, was followed by univariate analysis to characterise the study's sample according to the defined objectives.

RESULTS

The most important factors influencing elderly's food choice were quality and freshness (54%), trying to eat healthy and price (8%). Healthy eating was defined as "less fat" (37%) "more fresh vegetables and fruit" (34%), and "natural foods" (11%). To stay healthy (36%), to prevent disease (26%) and to promote quality of life (10%) were the major benefits associated to healthy eating. However several barriers to the adoption of healthy eating were identified, namely self-control (27%), the resistance to change (23%) and price (15%). 86% of the elderly people believe they don't need to change their eating habits as they already eat healthily.

CONCLUSION

Results of this study will help to improve eating habits in the elderly, as health professionals will be able to choose the most appropriate strategies for the different groups and settings, and provide a base for future interventions in European countries for this growing age group.

Rapid microorganism identification with on-slide proteolytic digestion followed by matrix-assisted laser desorption/ionization tandem mass spectrometry and database searching

A simple method for microorganism identification is proposed in this paper. In this method, no isolation or fractionation of microorganisms and no special search algorithm or database are needed. Experimentally, a sample of the unfractionated intact microorganism is subjected to brief on-slide proteolytic digestion and the digestion product ions detected in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) are selected for tandem mass spectrometry (MS/MS). Database searching using the MS/MS spectrum identifies the microorganism protein, and thereby, according to the source of the protein, the microorganism. The method was demonstrated to be feasible with enterobacteriophage MS2 as the model microorganism. The novel method is simple, rapid, and requires a small quantity of sample.

[Influence of helminthic infections and nutritional status on immune response in Venezuelan children]

We investigated the influence of nutritional status, as determined from anthropometric measurement, and of helminthic infections on the immune response of children of low socioeconomic status in two rural communities in Venezuela: El Cardón in the state of Nueva Esparta and San Daniel in the state of Miranda. A total of 125 boys and girls between 2 and 15 years old participated in the study. Their socioeconomic stratum was determined by a modified Graffar method. A physical examination was performed, as was also an anthropometric evaluation that took into account three indicators--weight-for-height, weight-for-age, and height-for-age--according to parameters established by the World Health Organization. Other examinations included feces, secretory IgA in saliva, total serum IgE, and anti-Ascaris-specific immunoglobulins. The children in both of the communities were in strata IV and V of the of Graffar scale, with a significantly greater number of stratum V inhabitants in San Daniel (P < 0.001). The results suggest that exposure level and individual susceptibility to the parasites are determining factors in parasitic infection and immune system behavior. The intensity of the parasitic burden plays an important role in stimulating polyclonal IgE, which diminishes the effectiveness of the specific response to those infections. On the other hand, nutritional deficiencies could change the immune mechanisms of the mucous membranes, negatively influence the synthesis of secretory IgA, and stimulate the production of polyclonal IgE. Poor sanitary and socioeconomic conditions promote more exposure to gastrointestinal parasites and a deficient nutritional status, which modulates the immune response and affects serum IgE and secretory IgA production mechanisms.

Physical activity levels and body weight in a nationally representative sample in the European Union

OBJECTIVES

The main objectives of this pan-European study were: (1) to identify different types of physical activity and the time devoted to them, (2) to assess physical activity/inactivity at work and in leisure time, and (3) to determine self-reported body weight and height.

DESIGN AND SUBJECTS

In each member state of the EU, approximately 1000 adults, aged 15 years or more, were selected to participate in an interview-assisted face-to-face questionnaire on physical activity and body weight. In each country, sample selection was quota-controlled to ensure national representativeness. Overall, 15,239 subjects in the EU completed the study.

RESULTS

On average in the EU, nearly three-quarters of the population participate in some kind of activity. In general, the highest proportions of participants were found in the Nordic countries and the lowest in the southern ones. At the European level, the five most common activities include walking, gardening, cycling, keep fit and swimming. Higher participation rates were found among men, younger subjects and those with a higher level of education. The majority of Europeans fall within the normal body mass index (BMI) range but more than one-third are overweight (31%) or obese (10%) and 11% have a BMI below 20.

CONCLUSIONS

Several risk groups related to physical activity emerge from this survey: women, those with a lower level of education, older subjects, the overweight/obese and the underweight. Programmes to promote physical activity need to be tailored to the different groups identified in each country/region in order to increase adherence of non-participants and for the maintenance of those already engaged in activities.

Influence of dietary protein content on Trypanosoma cruzi infection in germfree and conventional mice

Germfree (GF) and conventional (CV) mice were fed on diets containing 4.4, 13.2 or 26.4% of protein (weight/weight). CV mice fed on low protein diet did not gain weight during four weeks, whereas the protein deficient diet did not affect the growth of GF mice. After four weeks on these diets, the mice were inoculated with 5 x 10(3) trypomastigotes of Trypanosoma cruzi. The protein deficiency affected less the GF than the CV mice, according to the following parameters: weight gain, hemoglobin, plasma protein and albumin levels and water and protein contents of the carcass. Infection with T. cruzi produced a significant decrease in hemoglobin levels, red blood cell count, and water and protein contents in the carcass. This decrease was more pronounced in the GF mice. Histopathologically, there was no difference between the treatments in animals with the same microbiological status (GF or CV). However, the disease was more severe in the GF than in the CV mice.

Renal dopaminergic system in nephrotic syndrome and after remission

BACKGROUND

Although intrarenal dopamine is known to behave as an endogenous natriuretic hormone the role of the renal dopaminergic system in the sodium handling of nephrotic oedema remains unknown.

STUDY DESIGN

We monitored the daily urinary excretion of free dopamine, L-DOPA-its precursor, and its metabolites, DOPAC and HVA, during sodium retention accompanying the nephrotic state and natriuresis leading to oedema mobilization in eight patients (mean age 8.0+/-2.4 years) with drug-induced remission of minimal-change nephrotic syndrome (MCNS).

RESULTS

During natriuresis the urinary levels of dopamine did not increase in parallel with sodium excretion in any of the eight patients studied. Moreover, after remission of the nephrotic syndrome the urinary levels of dopamine were significantly lower than during the nephrotic state (1565.3+/-361.7 vs 2416.1+/-558.4, P= 0.02). In contrast, the urinary excretion of L-DOPA increased markedly during natriuresis resulting from remission of proteinuria (from 87.0+/-40.5 up to 296.9+/-86.3 nmol/24 h; P< 0.01).

CONCLUSION

We conclude that the natriuretic response resulting from drug-induced remission of proteinuria in MCNS is accompanied by a decrease in the renal uptake/decarboxylation of L-DOPA to dopamine.

[Hepatic fascioliasis]

Hepatic fascioliasis is a pathology with an increasing incidence, morbidity and mortality all over the world and most particularly in our country, where endemic spots have been found, particularly in rural areas. Based on a clinical case which is supported by a revision of appropriate literature, the authors have made relevant considerations on bio-ecology, diagnosis, prognostic and treatment of this disease.

Biomarks in secondary osteoporosis

The existence of a metabolic disease in rheumatoid arthritis in distant zones of the active synovitis areas, remains controversial. Indeed, the variations found, by different authors, in PTH, in alkaline phosphatase and in serum and/or in the calcium urinary values, as well as in phosphate and hydroxyproline, have not clarified this problem, despite the demonstration by histomorphometry and by densitometrical methods, of a greater loss of the bone mass in rheumatoid arthritis. At the same time, metabolic changes in sexual hormones, primary or secondary, can modulate the immune response and interfere in the clinic expression of rheumatoid arthritis and also in the bone turnover. Therefore, the purpose of this study was to compare some parameters of the bone metabolism and of the hormonal condition, in women with rheumatoid arthritis, with and without corticotherapy and in an age-related control group. In Group RA (patients), we found relatively higher levels of phosphates, alkaline phosphatase and osteocalcin, just as in the nephrogenic c'AMP and the hydroxyproline/creatinine quotient. The blood levels of calcitonin, PTH, T3, T4, cortisol and estradiol did not show significant differences between the 2 groups, although they were lower in Group RA. On the contrary, the plasma levels of testosterone, of 4-androstenedione and DHEA.S were significantly reduced in patients with rheumatoid arthritis. These results are compatible with the existence of bone metabolic hyperactivity in rheumatoid arthritis, which can be related, directly or indirectly to the reduced androgens plasma levels, since these seem to play a protective role in auto-immune diseases and also on the bone metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)