Nonlinear diamagnetism due to the fluctuation superconductivity

Nonlinear susceptibility due to the fluctuation superconductivity is calculated microscopically in the Ginzburg-Landau-Garkov approximation. The characteristic field of the nonlinearity is given by H_c2.     

A novel, intracellular antifreeze protein in an antarctic bacterium, Flavobacterium xanthum

One strain of Antarctic bacteria, Flavobacterium xanthum IAM12026, has a highly active antifreeze protein (AFP) in the intracellular space. The cell-free extract from strain IAM12026 after culturing at 4 degree C for 7 days in TSB medium, had activity of 0.04 degree C at a concentration of 0.7 mg/ml. The ice crystals formed do not have distinct facets without typically rounded shape and the changes of their morphology during the course of the thermal hysteresis (TH) measurement. The ice crystal 'burst' occurring at the end-point of the TH is dendritic with hexagonal symmetry. Also, this activity was not affected by the treatment of dialysis and the addition of EDTA. Furthermore, this cell-free extract had high levels of ice recrystallization-inhibiting (RI) activity like those of Fish AFPs. The AFP (FlAFP) was homogeneity purified using chromatography. A relative molecular mass of approximately 59,000 was calculated from gel filtration and SDS-PAGE data. The thermal stability of FlAFP was below 50 degree C, and TH value was absent above 60 degree C. The TH value of FlAFP was activated at 5.2 degree C by the addition of 0.5 M malate. This activation was decreased with increasing protein concentration. To our knowledge this is the first report on the high level of TH and RI activities of bacterial intracellular AFP.     

Multi-Component Ion Modifiers and Arcing Suppressants to Enhance Differential Mobility Spectrometry for Separation of Peptides and Drug Molecules

The optimization of ion/molecule chemistry in a differential mobility spectrometer (DMS) is shown to result in improved peak capacity, separation, and sensitivity. We have experimented with a modifier composed of multiple components, where each component accomplishes a specific task on mixtures of peptides and small drug molecules. Use of a higher proton affinity modifier (hexanol) provides increased peak capacity and separation. Analyte ion/modifier proton transfer is suppressed by adding a large excess of low proton affinity modifier (water or methanol), significantly increasing signal intensity and sensitivity for low proton affinity analytes. Finally, addition of an electrical arcing suppressant (chloroform) allows the device to operate reliably at higher separation fields, improving peak capacity and separation. We demonstrate a 20 % increase in the device peak capacity without any loss of sensitivity and estimate that further optimization of the modifier composition can increase this to 50 %. Use of 3-, 4-, or even 5-component modifiers offers the opportunity for the user to fine-tune the modifier performance to maximize the device performance, something not possible with a single component modifier.      

Packing atomic metal cations with C60: Mass spectrometric observation of M(C60)n with M = Sr and Mo and n = 0–4

The atomic cations of Sr and Mo have been observed to add sequentially up to four molecules of C₆₀ in helium at 0.35 Torr and room temperature in the flow tube of a modified inductively coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The available center-of-mass energy in collision-induced dissociation experiments of approximately 1.3 eV failed to remove C₆₀ from M⁺(C₆₀)₄. A structure is proposed for M⁺(C₆₀)₄ cations in which the bonding involves η⁶ interaction of the metal with the C₆₀ ligands and η²-to-η² interactions between the C₆₀ ligands.     

Chemical stability and reactivity of deprotonated oligonucleotides (DNA) in the gas phase: protonation and solvation with hydrogen bromide

Selected deprotonated oligodeoxynucleotides generated by electrospray ionization were exposed to a variety of neutral molecules in the gas phase at room temperature in flowing helium gas at 0.35 Torr. Single-stranded [AGTCTG-nH]n- and single- and double-stranded [GCATGC-nH]n- anions were found to be remarkably unreactive with strong oxidants (O3, O2, N2O) and potential intercalators (benzene, pyridine, toluene, and quinoxaline). Hydration also was observed to be inefficient. However, [AGTCTG-nH]n- anions with n=2, 3, 4, and 5 were seen to be sequentially protonated and/or hydrobrominated with HBr (but not damaged) and displayed an interesting "end effect" against protonation. Measurements are provided for the rate coefficients of reaction and the efficiencies of protonation. These experimental results point toward the exciting prospect of measuring the intrinsic chemistry of other bare DNA-like anions, including double-stranded oligonucleotide anions in the gas phase at room temperature.     

Heavy water reactions with alkaline-earth metal dications in the gas phase: Kinetics at room temperature

Room temperature rate coefficients and product distributions are reported for the reactions initiated in D₂O with dications of the alkaline-earth metals Mg, Ca, Sr and Ba. The measurements were performed with a selected-ion flow tube (SIFT) tandem mass spectrometer and electrospray ionization (ESI). Mg²⁺ reacts with water by a fast electron transfer leading to charge separation with a rate coefficient of 1.4 × 10⁻⁹ cm³ molecule⁻¹ s⁻¹. Ca²⁺ reacts with D₂O in a first step to form the adduct Ca²⁺(D₂O), with an effective bimolecular rate coefficient of 2.3 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, which then undergoes rapid charge separation by deuteron transfer to form CaOD⁺ and D₃O⁺ in a second step with k = 7.9 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The CaOD⁺ ion reacts further by clustering up to five more D₂O molecules. Sr²⁺ clusters up to eight D₂O molecules and Ba²⁺ up to seven D₂O molecules, with the first addition of D₂O being rate determining in each case and the last addition being distinctly slower, as might be expected from a transition in the occupation of the added water molecules from an inner to an outer hydration shell.