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PubMed1979

Effects of ionization and counterion binding on the surface areas of phosphatidic acids in monolayers.

At 24-26 degrees C, force-area isotherms show that unionized dipalmitoyl phosphatidic acid forms a solid-condensed film while unionized egg and dioleoyl phosphatidic acids form liquid-expanded films. Surface area is a characteristic feature of a specific phosphatidic acid and the purity of a phosphatidic acid preparation can be established by the surface area of the unionized phosphatidic acid (acid subphase) at 17 dynes/cm (castor oil piston). Ionized dipalmitoyl phosphatidic acid desorbs from a monolayer at a measurable rate while ionized egg and dioleoyl phosphatidic acids desorb too slowly for rate studies. The apparent surface pK(2) for dipalmitoyl phosphatidic acid, calculated from desorption rates, is 9.4. Surface areas of the phosphatidic acids expand with ionization. Solid dipalmitoyl phosphatidic acid films expand only in the pK(2) region, showing one inflection point which indicates that the K(1)/K(2) ratio is less than 100 and that, as a consequence of this ratio, the apparent surface pK(1) is greater than 7.4. Liquid egg and dioleoyl phosphatidic acid films have two inflection points, expanding in both the pK(1) and pK(2) regions. The apparent surface pK(1) and pK(2) values, calculated from inflection points in surface area data, are 3.5 and 8.0, respectively. Film expansion with phosphatidate anions is less than anticipated, showing the presence of weak transient hydrogen bonds. Expanded phosphatidate anion films are condensed by alkaline earth cations. The Ca(2+) and Ba(2+) salts of completely ionized phosphatidic acids collapse from monolayers, showing that the phosphatidate anion may function as an ionophore for the transport of alkaline earth ions.-Patil, G. S., N. J. Dorman, and D. G. Cornwell. Effects of ionization and counterion binding on the surface areas of phosphatidic acids in monolayers.

Barium↗

PubMed1983

The circadian rhythms of blood ionized calcium in humans.

It is well known that several hormones and minerals develop daily variation in human blood. Recently the presence of circadian rhythms of blood ionized calcium and serum phosphate concentrations in man reported (Science 213: 672-674, 1981). To clarify the difference in race and age, we examined the serum concentration of minerals such as ionized calcium, inorganic phosphate, total calcium and magnesium, and venous blood pH during 24 hours in three 31 to 40 years old Japanese males in good health. Result [1]. There was a correlation between concentration of ionized calcium and blood pH (r = -0.467 p less than 0.001), and between concentration of ionized calcium and total calcium (r = 0.366 p less than 0.005). [2]. Apparent rhythms of ionized calciums and inorganic phosphate concentrations has been noticed.

Adult↗

PubMed1983

Clinical studies on ionized calcium using the radiometer ICA1 analyzer.

It is generally believed that measurement of ionized calcium in blood should more clearly reflect changes in calcium metabolism than measurements of total calcium concentration. We have investigated ionized calcium levels using the Radiometer ICA1 Analyzer in number of clinical situations where total calcium, hydrogen ion or protein concentrations are abnormal. While there are a number of clearcut situations in which ionized calcium measurements are superior to total calcium, it is apparent that chemical activity of calcium ions in blood may sometimes not reflect their physiological activity. In addition, the problem of clinical interpretation of ionized calcium levels found in patients with extreme disorders of acid-base balance or of plasma protein concentration remains to be resolved. The role of ionized calcium measurement in routine clinical chemistry will be discussed.

Acid-Base Equilibrium↗

PubMed1975

[Ionization of the acid-base groups of polyene antibiotics in aqueous solutions].

The acid-base characteristics of polyenic antibiotics, such as nystatin, mycoheptin and levorin in aqueous solutions were studied. A special procedure provided the use of potentiometric titration for investigation of ionization of the groups of vater-insoluble substances. The ionization constants of the carboxylic and amine groups of the antibiotics at several temperatures were determined. It was found that ionization of the acid group did not practically depend on the temperature. At the same time the heat effect of the amine group ionization was significant and amounted to about 10 kcal/mole. Thermodynamic analysis of the ionization process of the polyenic antibiotics in aqueous solutions was performed. Integral components defining the process energetics were calculated.

Acid-Base Equilibrium↗

PubMed1994

Induction of nuclear factor kappa B after low-dose ionizing radiation involves a reactive oxygen intermediate signaling pathway.

Reactive oxygen intermediates (ROIs) have been found to be the messengers in the activation of the kappa B transcription regulator in mitogen- or cytokine-stimulated cells, operating in conjunction with or independently of various other mechanisms; these include Ca(++)-dependent and PKC-dependent cytoplasmic signaling pathways. We have recently reported that low-dose ionizing radiation induces NF-kappa B in human lymphoblastoid 244B cells. Since ionizing radiation generates free radicals in cells, we have investigated whether the ROIs generated by ionizing radiation induce NF-kappa B activity, and also whether they do so by a similar mechanism as in cells treated with PMA or H2O2. The results not only confirm a previous observation from our laboratory that low-dose ionizing radiation (0.1-2.0 Gy) activates kappa B transcription factor transiently with a maximal induction at 0.5 Gy exposure, but also demonstrate mechanistically that the activation of NF-kappa B by low-dose ionizing radiation can be inhibited considerably by the antioxidant N-acetyl-L-cysteine, indicating that at least the major part of the activation process is mediated by ROIs. These findings support the idea that ROIs can regulate the kappa B elements which in turn can serve as response elements for oxidant stress.

Acetylcysteine↗

PubMed1998

Intracellular and extracellular blood magnesium fractions in hemodialysis patients; is the ionized fraction a measure of magnesium excess?

To establish the best measure for determining magnesium overload, we measured ionized and total magnesium in serum and mononuclear blood cells and total magnesium in erythrocytes in blood of 23 hemodialysis patients, known for their disturbed magnesium homeostasis. When comparing the mean magnesium values obtained in the patient population with those of a control population, all of these magnesium markers, including the biologically active fractions, were significantly (P < 0.05) increased. Because serum total magnesium was not increased in all dialysis patients studied, the population was divided into two groups, according to total serum magnesium > 1.0 mmol/L or less than that. Results in these two populations showed that ionized serum magnesium and ionized magnesium in mononuclear blood cells might give a better indication about the magnesium status of the tested patients than the currently used total serum magnesium data. However, neither of the two markers, especially ionized serum magnesium, was able to discriminate fully between normal magnesium homeostasis and magnesium excess. We therefore conclude that the two ionized magnesium markers offer minimal advantage for this discrimination, and that the total magnesium concentration in serum remains the measurement of choice.

Adult↗

PubMed1998

Controlling Legionella in hospital water systems: experience with the superheat-and-flush method and copper-silver ionization.

OBJECTIVE: To evaluate the effect of copper-silver ionization on Legionella colonization and nosocomial legionnaires' disease and to compare the efficacy of metal ions versus the superheat-and-flush method of disinfection. DESIGN: Prospective determination over a 36-month period of copper and silver ion concentrations in the recirculating hot-water system, Legionella colonization of the hospital water distribution system, and cases of nosocomial legionnaires' disease. Retrospective comparison of results with the previous 13 years, during which the superheat-and-flush method was used. SETTING: The Pittsburgh Veterans' Affairs Health Care System (University Drive Division) acute-care hospital. INTERVENTION: Three copper-silver ionization systems were installed on the hot-water distribution system in November 1994. RESULTS: The average number of cases of legionnaires' disease per year and the percentage of distal sites positive for Legionella pneumophila for the superheat-and-flush method versus the copper-silver ionization method was six cases with 15% positivity versus two cases with 4% positivity, respectively. The reduction in Legionella colonization after copper-silver ionization was significant (P<.05) compared to the superheat and flush. Mean copper and silver ion concentrations (mg/L) were 0.29 and 0.054 from hot-water tanks, and 0.17 and 0.04 from distal outlets, respectively. CONCLUSIONS: We conclude that a properly maintained and monitored copper-silver ionization system was more effective than the superheat-and-flush method for reducing the recovery of Legionella from the hospital water distribution system.

Copper↗

PubMed1998

The effect on blood pressure of an acute fall in ionized calcium during hemodialysis. A randomized study in two patients.

AIM: Elevating serum ionized calcium levels is known to stabilize blood pressure during and after a hemodialysis session. The data on lowering calcium levels is limited. SUBJECTS AND METHODS: This study examined the responses to an acute drop in ionized calcium during a four hour hemodialysis session in two subjects who differed in the presence (patient 1) or absence (patient 2) of anti-hypertensive medication and average weight loss of 4 kg (patient 1) or 2 kgs (patient 2) with each dialysis. Parathyroid hormone (PTH) levels were normal (patient 1) or very high (patient 2). A calcium free dialysate was used and the calcium infusion rate distal to the dialyzer was varied to produce either no change in ionized calcium for 10 dialyses, or a fall of at least 0.2 mmol/l for 10 dialyses. The sequence was randomized and was blinded to the observers and patients. RESULTS: The fall in ionized calcium was similar in each individual, 0.37 +/- 0.11 and 0.34 +/- 0.05 mmol/l. PTH rose from 8.6 +/- 1.6 to 24.2 +/- 6.6 pmol/l for patient 1 and 144.6 +/- 59.9 to 234.8 +/- 32.3 pmol/l for patient 2: patient 1 showed a fall in blood pressure after dialysis associated with the fall in calcium. This was most pronounced in the upright position whereas there was no change for Patient 2. For Patient 1 standing mean blood pressure post-dialysis was 104 +/- 6 mmHg when the calcium was stable and 94 +/- 10 mmHg with hypocalcemia p <0.01. Mean blood pressure during dialysis was also lower with hypocalcemia 100 +/- 7 versus 92 +/- 9 p <0.05. There were no significant changes in blood pressure for patient 2. Neither of the patients had any symptoms attributable to hypotension or hypocalcemia. CONCLUSION: It was concluded that modest falls in ionized calcium were associated with a drop in standing blood pressure only when combined with other factors predisposing to vascular instability. Even so these decreases were small enough to be asymptomatic.

Adult↗

PubMed2004

Mass spectrometry of N-linked oligosaccharides using atmospheric pressure infrared laser ionization from solution.

An atmospheric pressure (AP) infrared (IR) laser ionization technique, implemented on a quadrupole ion trap mass spectrometer, was used to analyze underivatized, N-linked oligosaccharides in solution. Experiments were conducted on an atmospheric pressure infrared ionization from solution (AP-IRIS) ion source which differed from previous AP IR matrix-assisted laser desorption/ionization (MALDI) interfaces in that the ion source operated in the absence of an extraction electric field with a higher power 2.94 microm IR laser. The general term 'IRIS' is used as the mechanism of ionization differs from that of MALDI, and is yet to be fully elucidated. The AP-IRIS ion source demonstrated femtomole-level sensitivity for branched oligosaccharides. AP-IRIS showed approximately 16 times improved sensitivity for oligomannose-6 and the core-fucosylated glycan M3N2F over optimal results obtainable on a AP UV-MALDI with a 2,4,6-trihydroxyacetophenone matrix. Comparison between IR and UV cases also showed less fragmentation in the IR spectrum for a glycan with a conserved trimannosyl core, core-substituted with fucose. A mixture of complex, high-mannose and sialylated glycans resulted in positive ion mass spectra with molecular ion peaks for each sugar. Tandem mass spectrometry of the sodiated molecular ions in a mixture of glycans revealed primarily glycosidic (B, Y) cleavages. The reported results show the practical utility of AP-IRIS while the ionization mechanism is still under investigation.

Air Pressure↗

PubMed2002

Investigation of cytolysin variants by peptide mapping: enhanced protein characterization using complementary ionization and mass spectrometric techniques.

Matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) have been used in conjunction with time-of-flight (TOF) and quadrupole ion trap (IT) mass spectrometry, respectively, to analyze various cytolysin proteins isolated from the sea anemone Stichodactyla helianthus and digested by the protease trypsin. By employing different ionization methods, the subsequent changes in ionization selectivity for the peptides in the digested protein samples resulted in ion abundance variation reflected in the mass spectra. Upon investigation of this variation generated by the two ionization processes, it has been shown in this study that enhanced protein coverage (e.g., >95% for cytolysin III) can be achieved. Additionally, capillary and microbore reversed-phase high-performance liquid chromatography (RP-HPLC) coupled with ESI mass spectrometry (MS) as well as flow injection analysis by nanoflow ESI-MS afforded the necessary limit of detection (LOD) for detailed structural information of the cytolysin proteins by tandem mass spectrometry (MS/MS) methods. It can be concluded that cytolysins II and III correspond to sticholysins I and II, that "cytolysin I" is a mixture of modified forms of cytolysins II and III, and that "cytolysin IV" is an incompletely processed precursor of cytolysin III.

Amino Acid Sequence↗

PubMed2006

Generation and detection of multiply-charged peptides and proteins by matrix-assisted laser desorption electrospray ionization (MALDESI) Fourier transform ion cyclotron resonance mass spectrometry.

We report the coupling of a hybrid ionization source, matrix-assisted laser desorption electrospray ionization (MALDESI), to a Fourier transform-ion cyclotron resonance mass spectrometer (FT-ICR MS). The details of the source design and initial data are presented. Analysis of peptides and proteins ranging from 1 to 8.6 kDa resulted in high resolving power single-acquisition FT-ICR mass spectra with average charge-states highly correlated to those obtained by nanoESI, thus, providing strong evidence that the ESI process dictates the observed charge-state distribution. Importantly, unlike the recently introduced electrospray assisted laser desorption ionization (ELDI) source reported by Shiea and coworkers [1, 2], the data we have obtained to date rely on the use of an organic acid matrix. The results presented herein provide insight into the charging mechanism of this emerging ionization approach, while also expanding the utility of FT-ICR MS for top-down protein and complex mixture analysis.

Algorithms↗

PubMed2002

Laser desorption-atmospheric pressure chemical ionization mass spectrometry for the analysis of peptides from aqueous solutions.

A recently reported ionization method, comprising an infrared (IR) laser pulse to desorb (LD) analyte species, followed by atmospheric pressure chemical ionization (APCI) with a corona discharge (LD-APCI) to effect ionization of the desorbed neutral analyte molecules, is described for the direct analysis of aqueous peptide solutions. The source employs a heated capillary atmospheric pressure (AP) inlet coupled to a quadrupole ion trap mass spectrometer and allows sampling under normal ambient air conditions. By use of the corona discharge, signals of the atmospheric pressure infrared matrix-assisted laser desorption/ionization (AP-IR-MALDI)-generated analyte protonated molecule were enhanced by factors as large as 1400. In addition, the acid modifier trifluoroacetic acid (TFA) was found to improve the AP-IR-MALDI-generated signal by a factor of approximately 10, whereas the LD-APCI generated signal yielded a 100-fold increase. In this study, the use of the corona discharge is described to enhance the analyte signal generated via AP-IR-MALDI and, as a tool, to probe the gas-phase neutral molecule population generated by the MALDI process. Finally, through the decoupling of desorption from ionization, implications regarding the application of LD-APCI for the direct analysis of numerous new analyte containing matrixes (e.g., polyacrylamide gel electrophoresis (PAGE), tissue, etc.) are discussed.

Peptides↗

PubMed2006

Derivatization in mass spectrometry--8. Soft ionization mass spectrometry of small molecules.

This is the first of two reviews devoted to derivatization approaches for "soft" ionization mass spectrometry (FAB, MALDI, ESI, APCI) and deals, in particular, with small molecules. The principles of the main "soft" ionization mass spectrometric methods as well as the reasons for derivatizing small molecules are briefly described. Derivatization methods for modification of amines, carboxylic acids, amino acids, alcohols, carbonyl compounds, monosaccharides, thiols, unsaturated and aromatic compounds etc. to improve their ionizability and to enhance structure information content are discussed. The use of "fixed"-charge bearing derivatization reagents is especially emphasized. Chemical aspects of derivatization and "soft" ionization mass spectrometric properties of derivatives are considered.

Amines↗

PubMed2001

Ionization mechanism of oligonucleotides in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

The ionization of nucleosides in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was systematically investigated using adenine (A), thymine (T), guanine (G) and cytosine (C) with several common matrices. Experimental results of the protonation and deprotonation of the bases of A, T, G and C in the matrices 2,5-dihydroxybenzoic acid (2,5-DHB), alpha-cyano-4-hydroxycinnamic acid (alpha-CHCA) and 3-hydroxypicolinic acid (3-HPA) provide an insight into the ionization mechanism of oligonucleotides in MALDI. It was found that the low ion signal from DNA in poly-G in MALDI as reported in earlier work could be attributed to the fact that the base of G is difficult to ionize. Our results suggest that the ionization of DNA in MALDI is dominated by the protonation and deprotonation of bases and it is basically independent of the backbone of DNA. Both the protonation and deprotonation are strongly structure dependent. The protonation is dominated by pre-protonation before laser ablation, while the deprotonation is controlled by the thermal reaction.

Coumaric Acids↗

PubMed2005

Mortality of workers exposed to ionizing radiation at the French National Electricity Company.

BACKGROUND: Exposure to ionizing radiation increases the risk of cancer in humans. Nuclear workers receive low doses over a relatively long period of time. METHODS: A mortality study of a cohort of workers exposed to ionizing radiation at Electricité de France (EDF) was conducted. The cohort consisted of 22,395 individuals monitored for radiation exposure between 1961 and 1994, and followed-up for an average of 11.7 years. RESULTS: Our study demonstrates a clear healthy worker effect (HWE) since mortality is less than half what is expected from National mortality statistics. The HWE is greater among workers who have spent most of their career in the nuclear sector. The analysis by cancer site shows no excess compared with the general population. No significant trend was observed according to level of exposure to ionizing radiation. CONCLUSIONS: The mortality of workers exposed to ionizing radiation at the French National Electricity company is very low compared to the French national mortality.

Adolescent↗

PubMed2005

A silica-based monolithic column in capillary HPLC and CEC coupled with ESI-MS or electrospray-atmospheric-pressure laser ionization-MS.

We describe the successful coupling of CEC and capillary HPLC with the recently developed atmospheric-pressure laser ionization (APLI) method. APLI is suitable for selectively and sensitively ionizing nonpolar aromatic compounds at ambient pressure for subsequent mass-selective detection. The polycyclic aromatic hydrocarbons used as analytes are first separated either by CEC on a silica-based monolithic column or by capillary HPLC. The eluent, along with a sheath flow, is volatilized by microelectrospray and then selectively ionized by excimer laser (KrF*) radiation via two-photon excitation. A QTOF-MS is used as mass-selective detector. This interface combination makes soft ionization of thermally labile nonpolar aromatic analytes possible.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Alterations in gene expression profiles and the DNA-damage response in ionizing radiation-exposed TK6 cells.

Identifying genes that are differentially expressed in response to DNA damage may help elucidate markers for genetic damage and provide insight into the cellular responses to specific genotoxic agents. We utilized cDNA microarrays to develop gene expression profiles for ionizing radiation-exposed human lymphoblastoid TK6 cells. In order to relate changes in the expression profiles to biological responses, the effects of ionizing radiation on cell viability, cloning efficiency, and micronucleus formation were measured. TK6 cells were exposed to 0.5, 1, 5, 10, and 20 Gy ionizing radiation and cultured for 4 or 24 hr. A significant (P < 0.0001) decrease in cloning efficiency was observed at all doses at 4 and 24 hr after exposure. Flow cytometry revealed significant decreases in cell viability at 24 hr in cells exposed to 5 (P < 0.001), 10 (P < 0.0001), and 20 Gy (P < 0.0001). An increase in micronucleus frequency occurred at both 4 and 24 hr at 0.5 and 1 Gy; however, insufficient binucleated cells were present for analysis at the higher doses. Gene expression profiles were developed from mRNA isolated from cells exposed to 5, 10, and 20 Gy using a 350 gene human cDNA array platform. Overall, more genes were differentially expressed at 24-hr than at the 4-hr time point. The genes upregulated (> 1.5-fold) or downregulated (< 0.67-fold) at 4 hr were those primarily involved in the cessation of the cell cycle, cellular detoxification pathways, DNA repair, and apoptosis. At 24 hr, glutathione-associated genes were induced in addition to genes involved in apoptosis. Genes involved in cell cycle progression and mitosis were downregulated at 24 hr. Real-time quantitative PCR was used to confirm the microarray results and to evaluate expression levels of selected genes at the low doses (0.5 and 1.0 Gy). The expression profiles reflect the cellular and molecular responses to ionizing radiation related to the recognition of DNA damage, a halt in progression through the cell cycle, activation of DNA-repair pathways, and the promotion of apoptosis.

Analysis of Variance↗

PubMed2006

Green's function study of the one-electron and shake-up ionization spectra of unsaturated hydrocarbon cage compounds.

The valence one-electron and shake-up ionization spectra of stella-2,6-diene, stella-2,6-dione, bicyclo-[2.2.2]-octane-2,5-dione, and bicyclo-[2.2.1]-heptane-2,5-dione have been exhaustively studied, up to the double ionization threshold and beyond, by means of one-particle Green's function theory. This study is based on calculations employing the outer-valence Green's function and the third-order algebraic diagrammatic construction schemes, along with a variety of basis sets. A comparison is made with available ultraviolet (He I) photoelectron and (e, 2e) electron-impact ionization spectra, with main focus on the identification of spectral fingerprints for cyclic strains and through-bond pi-conjugation. As a byproduct, our results demonstrate that it is impossible to reliably assign complex (e, 2e) ionization spectra by resorting only to Hartree-Fock or Kohn-Sham orbital energies and to the related electron momentum distributions.

Alkenes↗