High pressure trapping in Fourier transform mass spectrometry: A radiofrequency-only-mode event

A new event for the Fourier transform mass spectrometry (FTMS) sequence is developed and demonstrated. During this event, called a radiofrequency (RF)-only mode event, the typical passive cubic trap of a Fourier transform mass spectrometer is made to operate as an active quadrupole ion trap. The transition between active and passive modes is developed so that ion loss as a consequence of the transition can be held to 15% or less. The adduct of the ion-molecule reaction of the 1,3-butadiene radical cation and methyl vinyl ether was detected during the Rf-only-mode event at a helium pressure of ～1×10^?3 torr even though this adduct is not detectable under standard FTMS operating conditions.     

THE EFFECT OF LIPOSOMES'' MEMBRANE COMPOSITION ON THE BINDING OF THE PHOTOSENSITIZERS HPD AND PHOTOFRIN II

Abstract— Photofrin II (PF-II) is the commercial name of the active photosensitizer which is used in photodynamic therapy of cancer. The effect of the composition of lipid membranes on the binding of PF-II was studied and compared to hematoporphyrin derivative (Hpd), which is a complex mixture of porphyrins and from which PF-II is separated. We find that increasing the content of cholesterol in the bilayer decreases the partitioning of PF-II into the bilayer, similar to what we have found earlier with Hpd. However, inserting DMPC or DPPC into the membrane, which was shown to decrease the binding of Hpd, causes the opposite trend with PF-H. A membrane fluidizer such as benzyl alcohol also has different effects on the membrane binding of Hpd and PF-II. The rate of binding of PF-II to a lipid membrane is about 10 times lower than that of Hpd. These results as well as I^- quenching of the fluorescence of the two porphyrins indicate that PF-II is immersed less homogeneously and deeper in the bilayer than Hpd. The unique additive-dependent binding of PF-II to lipid membranes calls for care in using Hpd as a model photosensitizer.     

Synthesis of di-t-alkylamines

Di-$\text{t}$-alkylamines can be synthesized efficiently by a three-step process: (1) oxidation of a $\text{t}$-alkylamine to a $\text{t}$-alkylnitroso compound with peracetic acid in ethyl acetate (2) conversion of the $\text{t}$-alkylnitroso compound to a tri-$\text{t}$-alkylhydroxylamine by successive trapping of two $\text{t}$-butyl radicals and (3) sodium naphthalide reduction to the di-$\text{t}$-alkylamine.     

Monitoring of water content and water distribution in ischemic hearts

We determined water content and water distribution by fitting dielectric spectra of ischemic canine hearts between 5 MHz and 3 GHz with a newly developed model which describes heart cells and subcellular organelles as rotational ellipsoids filled with electrolyte enclosed by an isolating membrane. The fraction of dry material is modelled by spherical particles with a small dielectric permittivity. Free model parameters were water content, cell volume fraction, and the conductivity of the electrolytes. Resulting model parameters were compared to data from tissue desiccation and to conductivity changes produced by protons and lactate ions. We investigated hearts in two states: during ischemia after interruption of blood flow (pure ischemia, PI, n=5) and during ischemia after resuscitation with Tyrode's solution (IAR, n=14).The difference between water content determined by tissue desiccation and by dielectric spectroscopy was less than 0.5%. During 360 min of ischemia, water content in IAR decreased from 85+/-1.6% to 83+/-2.2% and in PI from 80+/-0.8% to 78+/-1.5%. Cellular volume fraction in IAR increased from 0.47+/-0.045 to 0.63+/-0.031 and in PI from 0.62+/-0.014 to 0.73+/-0.013, which is consistent with published morphometric data. After 180 min of ischemia, the increase of the cytosolic conductivity was 0.14+/-0.02 S/m as calculated from the dielectric spectrum and was similar to the conductivity increase which was roughly estimated on the basis of tissue lactate concentration.In conclusion, dielectric spectroscopy combined with our model analysis facilitates the monitoring of water content and distribution by means of nondestructive surface probes.     

Modeling the competitive dissociation of protonated 2,3-butanedione. The enthalpy of formation of methylhydroxycarbene

The enthalpy of formation of methylhydroxycarbene, CH(3)COH, has been determined from measurements of the threshold energy for collision-induced dissociation of protonated 2,3-butanedione in a flowing afterglow-triple quadrupole mass spectrometer and found to be 16 +/- 4 kcal/mol, 57 +/- 4 kcal/mol higher than that of acetaldehyde. From the measured enthalpy of formation, the difference between the first and second C-H BDEs in ethanol is found to be 17 kcal/mol, which implies a singlet-triplet splitting of 28 kcal/mol in the carbene. The activation energies for loss of ketene and carbon monoxide from protonated butanedione are found to be 60 +/- 4 and 50 +/- 4 kcal/mol, respectively. On the basis of experimental and computational results, the loss of carbon monoxide is proposed to proceed through a tight transition state. Although calculations also suggest a tight transition state for loss of ketene, the experimental data indicate that it occurs via a loose transition state, possibly forming by proton transfer along the direct dissociation pathway.     

Quantum mechanics versus realism

Quantum theory accepts the point-like indivisible (classical) character of a particle as a mere product of a measuring process, or what has become known as a collapse. Following the notion of empty waves, which accepts the particle as a real existent entity without regard to the measurement process, we propose an experiment that may shed some light on the reality of the particle and the consequences of that reality.