Glucose exchange parameters in a subset of physiological conditions.

The chemical exchange of labile protons of the hydroxyl groups can be exploited in a variety of magnetic resonance experiments to gain information about the groups and their physicochemical environment. The exchangeable -OH protons provide important contributions to the T2 of water signals thus contributing to the T2-weighted contrast of MRI images. This exchange can be exploited more specifically and sensitively in chemical exchange saturation transfer (CEST) or longitudinal rotating frame relaxation (T1,ρ) experiments. Since glucose is omnipresent in living organisms, it may be seen as a rather universal probe. Even though the potential was first recognized many years ago, practical use has remained scarce due to numerous challenges. The major limitation is the rather low glucose concentration in most tissues. The other obstacles are related to multiple dependencies of the exchange parameters, such as temperature, pH, and concentration of various ions that are not known in sufficient detail for glucose. Thus, we embarked on evaluating the exchange parameters of a model that included every relevant chemical site for all -OH protons in both dominant enantiomers of glucose. We have (1) obtained conventional one-dimensional proton NMR spectra of glucose solutions in suitable temperature ranges, (2) we have iterated through several exchange models with various degrees of freedom determined by the number of distinguishable -OH proton sites and compared their performance, (3) we extrapolated the parameters of the best model of physiological temperature and (4) we demonstrated the use of the parameters in virtual experiments. As the main results, (1) we have obtained the temperature dependence of exchange parameters with reliable confidence intervals in three different pH values, with two of them reaching physiological temperature, and (2) we show how the parameters can be used in virtual experiments, helping to develop new applications for glucose as an NMR/MRI probe.

Molecular weight determinations of proteins by californium plasma desorption mass spectrometry.

The plasma desorption mass spectrometry method is used to determine the molecular weights of larger molecules than before, to determine the molecular weights of proteins and peptides in mixtures, and to monitor protein modification reactions. Proteins up to molecular weight 25,000 can now be studied with a mass spectrometric technique. Protein-peptide mixtures that could not be resolved with conventional techniques were successfully analyzed by this technique. The precision of the method is good enough to permit one to follow the different steps in the conversion of porcine insulin to human insulin.

Forces applied at the footrest during ergometer kayaking among female athletes at different competing levels - a pilot study.

BACKGROUND: Power output and force development during exercise are thought to be important indices of performance in elite athletes. The aim of this preliminary study was to determine the forces applied at the footrest during ergometric kayaking in individual kayakers at different competitive levels. METHODS: Three elite female kayakers participated voluntarily in the study. Oxygen consumption (VO2) and mean power were measured during paddling at three different work levels (15 W below onset of blood lactate accumulation (OBLA), at OBLA, 15 W above OBLA and all-out paddling) on a modified kayak ergometer. External force sensors were attached to the wires on right and left side connecting the paddle to the flywheel of the kayak ergometer. Individual footrests were built to enable measurements of pushing and pulling forces and to distinguish between the left and right foot. RESULT: The relative differences between the three athletes were similar for power, VO2peak and forces at the paddle. There were, however, differences in the forces applied at the footrest, where the most accomplished paddler generated forces 3 to 26 times as high as the least accomplished paddler. CONCLUSION: The relative differences between the three athletes were similar for power, VO2 and forces at the paddle. There were, however, dramatic differences in the forces applied at the footrest.

Efficient and robust quantum Monte Carlo estimate of the total and spin electron densities at nuclei.

The computational performance of two different variational quantum Monte Carlo estimators for both the electron and spin densities on top of nuclei are tested on a set of atomic systems containing also third-row species. Complications due to an unbounded variance present for both estimators are circumvented using appropriate sampling strategies. Our extension of a recently proposed estimator [Phys. Rev. A 69, 022701 (2004)] to deal with heavy fermionic systems appears to provide improved computational efficiency, at least an order of magnitude, with respect to alternative literature approaches for our test set. Given the importance of an adequate sampling of the core region in computing the electron density at a nucleus, a further reduction in the overall simulation cost is obtained by employing accelerated sampling algorithms.

A constant-momentum/energy-selector time-of-flight mass spectrometer.

A matrix assisted laser desorption/ionization time-of-flight mass spectrometer has been built with an ion source that can be operated in either constant-energy or constant-momentum acceleration modes. A decreasing electric field distribution in the ion-accelerating region makes it possible to direct ions onto a space-focal plane in either modes of operation. Ions produced in the constant-momentum mode have velocities and, thus, flight times that are linearly dependent on mass and kinetic energies that are inversely dependent on mass. The linear mass dispersion doubles mass resolving power of ions accelerated with space-focusing conditions in constant-momentum mode. The mass-dependent kinetic energy is exploited to disperse ions according to mass in a simple kinetic energy filter constructed from two closely spaced, oblique ion reflectors. Focusing velocity of ions of the same mass can substantially improve ion selection for subsequent post source decay or tandem time-of-flight analyses.

Molecular differentiation of ischemic and valvular heart disease by liquid chromatography/fourier transform ion cyclotron resonance mass spectrometry.

Proteomic patterns of myocardial tissue in different etiologies of heart failure were investigated using a direct analytical approach with High Performance Liquid Chromatography (HPLC)/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS). Right atrial appendages from 20 patients, 10 with hemodynamically significant isolated aortic valve disease and 10 with symptomatic coronary artery disease were collected during elective cardiac surgery. After preparation of tissue samples and tryptic digestion of proteins, the peptide mixture was HPLC-separated and on-line analyzed by electrospray FT-ICR MS. Data obtained from HPLC / FT-ICR MS runs were compared for classification. To extract the classification features, the selection of best individual features was applied and the "nearest mean classifier" was used for the classification of test samples and the sample projection onto classification patterns. The pattern distribution characteristics of aortic and coronary diseases were clearly different. No interference between samples of both disease categories was registered, even if the distribution of unsupervised classified test samples were closer. Samples representing aortic valve disease showed a closer accumulation pattern of spots compared to the samples representing coronary disease, which indicated a more specific protein classification. Through selective identification of specific peptides and protein patterns with FTMS, valvular and coronary heart disease is for the first time clearly distinguished at molecular level. The described methodology could also be feasible in search for specific biomarkers in plasma or serum for diagnostic purposes.

Establishment and phenotypic characterization of human U937 cells with inducible P210 BCR/ABL expression reveals upregulation of CEACAM1 (CD66a).

Chronic myeloid leukemia (CML) is characterized by the expression of the P210 BCR/ABL fusion protein. The molecular mechanisms behind this oncogene-mediated hematological disease are, however, not fully understood. Here, we describe the establishment and phenotypic characterization of U937 cells in which P210 BCR/ABL can be conditionally expressed using tetracycline. The induction of BCR/ABL in the obtained clones resulted in a rapid phosphorylation of the STAT1, STAT3 and STAT5 molecules, consistent with the findings in other model systems. Phenotypic characterization of the clones revealed that BCR/ABL induces a slight decrease in the proliferation and viability, without a marked effect on cell cycle distribution, the rate of apoptosis or on cellular differentiation, as judged by several cell surface markers and capacity to reduce nitro blue tetrazolium. Interestingly, BCR/ABL was found to upregulate the expression of carcinoembryonic-related antigen (CEA)CAM1 (CD66a), which is a plasma membrane-linked glycoprotein belonging to the CEAs and involved in signal transduction and cellular adhesion. The expression of CEACAM1 was reversible upon imatinib treatment in BCR/ABL-expressing U937 cells as well as in BCR/ABL-positive K562 cells. The established cell lines may prove useful in further modeling and dissection of BCR/ABL-induced leukemogenesis.

Automatic analysis of hydrogen/deuterium exchange mass spectra of peptides and proteins using calculations of isotopic distributions.

High mass-resolving power has been shown to be useful for studying the conformational dynamics of proteins by hydrogen/deuterium (H/D) exchange. A computer algorithm was developed that automatically identifies peptides and their extent of deuterium incorporation from H/D exchange mass spectra of enzymatic digests or fragment ions produced by collisionally induced dissociation (CID) or electron capture dissociation (ECD). The computer algorithm compares measured and calculated isotopic distributions and uses a fast calculation of isotopic distributions using the fast Fourier transform (FFT). The algorithm facilitates rapid and automated analysis of H/D exchange mass spectra suitable for high-throughput approaches to the study of peptide and protein structures. The algorithm also makes the identification independent on comparisons with undeuterated control samples. The applicability of the algorithm was demonstrated on simulated isotopic distributions as well as on experimental data, such as Fourier transform ion cyclotron resonance (FTICR) mass spectra of myoglobin peptic digests, and CID and ECD spectra of substance P.

Mechanistic studies of multipole storage assisted dissociation.

The degree and onset of fragmentation in multipole storage assisted dissociation (MSAD) have been investigated as functions of several hexapole parameters. Strict studies of hexapole charge density (number of ions injected) and hexapole storage time were made possible by placing a pulsed shutter in front of the entrance to the mass spectrometer. The results obtained show that the charge density is the most critical parameter, but also dependencies on storage time, radio-frequency (rf) -amplitude, and pressure are seen. From these data, and from simulations of the ion trajectories inside the hexapole, a mechanism for MSAD, similar to the ones for sustained off-resonance irradiation (SORI), and for low energy collisionally induced dissociation in the collision multipole of a triple quadrupole mass spectrometer, is proposed. It is believed that, at higher charge densities, ions are pushed to larger hexapole radii where the electric potential created by the rf field is higher, forcing the ions to oscillate radially to higher amplitudes and thereby reach higher (but still relatively low) kinetic energies. Multiple collisions with residual gas molecules at these elevated energies then heat up the molecules to their dissociation threshold. Further support for this mechanism is obtained from a comparison of MSAD and SORI spectra which are almost identical in appearance.

Inter- and intra-molecular migration of peptide amide hydrogens during electrospray ionization.

The isotopic exchange of amide hydrogens in proteins in solution strongly depends on the surrounding protein structure, thereby allowing structural studies of proteins by mass spectrometry. However, during electrospray ionization (ESI), gas phase processes may scramble or deplete the isotopic information. These processes have been investigated by on-line monitoring of the exchange of labile deuterium atoms in homopeptides with hydrogens from a solvent suitable for ESI. The relative contribution of intra- and inter-molecular exchange in the gas phase could be studied from their distinct influence on the well-characterized exchange processes in the spraying solution. The deuterium content of individual labile hydrogens was assessed from the isotopic patterns of two consecutive collision-induced dissociation fragments, as observed with a 9.4 T Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Results demonstrate that gas phase exchange in the high-pressure region between the capillary and the skimmer cause substantial depletion of the isotopic information of penta-phenylalanine and penta-aspartic acid. For penta-alanine and hexa-tyrosine, the amide hydrogens located close to the N-terminus are depleted from deuterium during mass analysis. Amide hydrogens located close to the C-terminus still retain the information of the isotopic state in solution, but they are redistributed by intra-molecular exchange of the amide hydrogens with the C-terminal hydroxyl group.

A test for cleaning and disinfection processes in a washer-disinfector.

Disinfection processes such as heat, aldehydes or alcohols kill vegetative microorganisms but do not necessarily remove other organic contamination. Organic residues impair the result of low-temperature sterilisation processes. Heat-stable organic residues may give rise to clinical symptoms in the patient. Standards are available in Britain and in Sweden for the examination of cleaning processes in washer-disinfectors. The test substances are artificial soil or blood. These standards are based on visual inspection of instruments or equipment. They cannot be used for examination of tubular instruments, nor can they be quantified. For validation of cleaning procedures a simple quantifiable method, which can be performed in an infection control laboratory is needed. We have used suspensions in horse blood of Enterococcus faecalis bacteria and Bacillus subtilis spores to test disinfection and cleaning in a washer-disinfector. Instruments used for laparoscopic surgery were contaminated with a blood bacteria suspension containing 10(7) organisms/ml and then dried and processed in a washer-disinfector using a regular process. Remaining microbial contamination was cultured quantitatively. Nineteen objects were investigated in 10 experiments each. Cleaning, measured as log reduction >5-6 of B. subtilis, was achieved on surfaces that were adequately in contact with the water flow in the machine. Disinfection (and cleaning) measured as log reduction >5-6 of E. faecalis was successful at all points examined. The test method is simple and quantifiable, and can be used to evaluate and to improve cleaning and disinfection processes.

Micro-capillary liquid chromatography Fourier transform ion cyclotron resonance mass spectrometry--a powerful tool for peptide and protein identification.

In order to be able to study complex biological samples, a micro-capillary liquid chromatography system was coupled to a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer. The setup was tested on a tryptic digest of bovine serum albumin, which resulted in high sequence coverage (> 92%) of the protein.

Interaction between explosive and analyte layers in explosive matrix-assisted plasma desorption mass spectrometry.

An HMX/insulin two-layer system was chosen as a model for further investigation of the matrix properties of explosive materials for protein analytes in plasma desorption mass spectrometry. The dependencies of the molecular ion yield and average charge state as a function of the analyte thickness were studied. An increase in the charge state of multiply protonated molecular species was confirmed as the major matrix effect, with the average charge state z at the smallest thickness studied being higher than in matrix-assisted laser desorption/ionization and closer to the value obtained in electrospray ionization under standard acidic conditions. Observed charge state distributions are significantly narrower than the corresponding Poisson distributions, which suggests that the protonation of insulin is limited in plasma desorption by the number of basic sites in the molecule, similar to electrospray ionization. Both the curve displaying total molecular ion yield and the one showing the total charge (proton) yield as a function of the insulin thickness have maxima at a thickness different from an insulin monolayer. These observations diminish the significance of a matrix/analyte interface mechanism for the explosive matrix assistance. Instead, a mechanism related to the chemical energy release during conversion of the explosive after the ion impact is proposed. As additional mechanisms, enhanced protonation of the analyte through collisions with products of the explosive decay is considered, as well as electron scavenging by other products, which leads to a higher survival probability of positively charged protein molecular ions. Copyright 1999 John Wiley & Sons, Ltd.

Lineshape-based polarimetry of dynamically-polarized (15)N2O in solid-state mixtures.

Dynamic nuclear polarization (DNP) of (15)N2O, known for its long-lived singlet-state order at low magnetic field, is demonstrated in organic solvent/trityl mixtures at ∼1.5 K and 5 T. Both (15)N polarization and intermolecular dipolar broadening are strongly affected by the sample's thermal history, indicating spontaneous formation of N2O clusters. In situ (15)N NMR reveals four distinct powder-pattern spectra, attributed to the chemical-shift anisotropy (CSA) tensors of the two (15)N nuclei, further split by the intramolecular dipolar coupling between their magnetic moments. (15)N polarization is estimated by fitting the free-induction decay (FID) signals to the analytical model of four single-quantum transitions. This analysis implies (10.2±2.2)% polarization after 37 h of DNP, and provides a direct, instantaneous probe of the absolute (15)N polarization, without a need for time-consuming referencing to a thermal-equilibrium NMR signal.

Mobile health in emerging countries: a survey of research initiatives in Brazil.

OBJECTIVE: To conduct a comprehensive survey of mobile health (mHealth) research initiatives in Brazil, discussing current challenges, gaps, opportunities and tendencies. METHODS: Systematic review of publicly available electronic documents related to mHealth, including scientific publications, technical reports and descriptions of commercial products. Specifically, 42 projects are analyzed and classified according to their goals. This analysis considers aspects such as security features provided (if any), the health condition that are focus of attention, the main providers involved in the projects development and deployment, types of devices used, target users, where the projects are tested and/or deployed, among others. RESULTS: The study shows a large number (86%) of mHealth solutions focused on the following categories: health surveys, surveillance, patient records and monitoring. Meanwhile, treatment compliance, awareness raising and decision support systems are less explored. The main providers of solutions are the universities (56%) and health units (32%), with considerable cooperation between such entities. Most applications have physicians (55%) and Community Health Agents (CHAs) (33%) as targeted users, the latter being important elements in nation-wide governmental health programs. Projects focused on health managers, however, are a minority (5%). The majority of projects do not focus on specific diseases but rather general health (57%), although solutions for hearth conditions are reasonably numerous (21%). Finally, the lack of security mechanisms in the majority of the surveyed solutions (52%) may hinder their deployment in the field due to the lack of compliance with general regulations for medical data handling. CONCLUSION: There are currently many mHealth initiatives in Brazil, but some areas have not been much explored, such as solutions for treatment compliance and awareness raising, as well as decision support systems. Another research trend worth exploring refers to creating interoperable security mechanisms, especially for widely explored mHealth categories such as health surveys, patient records and monitoring. Challenges for the expansion of mHealth solutions, both in number and coverage, include the further involvement of health managers in the deployment of such solutions and in coordinating efforts among health and research institutions interested in the mHealth trend, possibly exploring the widespread presence of CHAs around the country as users of such technology.