Determination of the cardiolipin content of individual mitochondria by capillary electrophoresis with laser-induced fluorescence detection

We report the application of capillary electrophoresis (CE) with postcolumn laser-induced fluorescence (LIF) detection to measure the cardiolipin content of individual mitochondria from cultured NS1 cells. Mitochondria were isolated by differential centrifugation and stained with the fluorescent dye 10-N-nonyl acridine orange which stoichiometrically binds to cardiolipin in a 1:1 or 2:1 ratio depending on the dye concentration. The green fluorescence resulting from the 1:1 complex was chosen for analysis because it is substantially more intense than the red fluorescence resulting from the 2:1 complex. Two dye concentrations that resulted in maximal and submaximal formation of the 1:1 10-N-nonyl acridine orange-cardiolipin complex were identified by spectrofluorometry. Individual mitochondria stained with both dye concentrations were separated and detected by CE with LIF detection. The data from mitochondria dosed with the lower dye concentration, where it is assumed that all the dye added to the mitochondrial sample was bound to cardiolipin, were used to derive a sensitivity factor relating fluorescence intensity of a mitochondrial event to its cardiolipin content. Using this factor, the cardiolipin contents of individual mitochondria stained with the higher dye concentration were determined, and ranged from 1.2 to 920 amol, with a median value of 4 amol. These results suggest a new strategy for estimating the organellar content of compounds that can be fluorescently tagged.     

Cold preservation of endothelial cells in sucrose-based solution (SbS) and University of Wisconsin (UW) solutions: comparison of normoxic or hypoxic storage

Cold preservation of endothelial cells was studied, comparing primary endothelial cells (human umbilical vein endothelial cells - HUVECs) and a continuously growing cell line (ECV304 cells). Viability at the end of 24h cold preservation was measured by dye exclusion, whilst metabolism was assessed by Alamar blue conversion. Two preservation solutions were studied (UW solution) and sucrose-based (SbS) in both cell types. The response was similar in both cell types to preservation under normoxic conditions (with percentage dye exclusion maintained at about 80 percent in both preservation solutions) whereas under hypoxic conditions ECV304 were more sensitive to preservation in UW solution (dye exclusion reduced to 43.5+/-1.4 percent versus 73.6+/-14 percent (P<0.01). Metabolism assessed by Alamar blue conversion after cold preservation and rewarming was similar in both ECV304 and HUVECs after storage under normoxic conditions in UW solution, but in both cell types, metabolism was higher in SbS (P<0.05 and p<0.01) than in UW solution. Under hypoxic conditions, both cell types showed similar recovery of metabolism after storage in either UW or SbS. If the cells (in this case ECV304 under aerobic conditions) were stored for 24h and then allowed to rewarm in either of the respective preservation solutions (UW or SbS for 1h) before the Alamar blue test, metabolism was higher (p less than 0.01) in those exposed to SbS. UW solution and SbS provide similar protection for endothelial cells under hypoxic conditions, but SbS has some advantages under normoxic storage or if the cells experience variable temperatures in the presence of residual preservation solution at the end of cold preservation period.     

On reflexivity of direct sums

Necessary and sufficient conditions are presented to insure that the direct sum of two reflexive representations of a finite dimensional algebra is reflexive, and it is shown that for each such algebra, there is an integer such that the direct sum of copies of each of its representations is reflexive. Given a ring our results are actually presented in the more general setting of -representations of a ring

     

Can a large neutron excess help solve the baryon loading problem in gamma-Ray burst fireballs?

We point out that the baryon loading problem in gamma-ray burst (GRB) models can be ameliorated if a significant fraction of the baryons which inertially confine the fireball is converted to neutrons. A high neutron fraction can result in a reduced transfer of energy from relativistic light particles in the fireball to baryons. The energy needed to produce the required relativistic flow in the GRB is consequently reduced, in some cases by orders of magnitude. A high neutron-to-proton ratio has been calculated in neutron star-merger fireball environments. Significant neutron excess also could occur near compact objects with high neutrino fluxes.     

Thermoelectric power of HfTe5 and ZrTe5

The thermoelectric power and the electrical resistance of the two low-dimensional conductors, HfTe₅ and ZrTe₅ have been measured over the temperature range of 7K to 380K. The thermoelectric power for both materials is large and positive at high temperatures and then drops precipitously and crosses zero at the temperature of the anomalous resistivity peak, T_p. At lower temperatures, the thermoelectric power reaches a large negative peak and then decreases to zero in a metallic fashion. The abrupt change in thermopower, which occurs at T_p for both materials, is indicative of a phase transition where the carrier type changes from hole-like to electron-like.     

A coercivity model with competing anisotropies

In standard coercivity theory, formulae derived for homogeneous material are applied to inhomogeneous situations. The model considered here contains inherent inhomogeneity in the form of competing volume and surface anisotropies. Its coercivity never exceeds half the Stoner-Wohlfarth value, decreases with particle size, and vanishes at a finite critical size.     

On fiber-preserving isotopies of surface homeomorphisms

We show that there are homeomorphisms of closed oriented genus surfaces which are fiber-preserving with respect to an irregular branched covering and isotopic to the identity, but which are not fiber-isotopic to the identity.

     

Investigation of the rh-catalyzed asymmetric reductive aldol reaction. Expanded scope based on reaction analysis

[reaction: see text] A series of experiments are described that suggest that the Rh-catalyzed reductive aldol reaction proceeds by addition of a Rh(I) hydride, generated in situ, to the reacting acrylate followed by a stereochemistry-controlling aldol addition reaction. On the basis of this hypothesis, reaction conditions are engineered that allow for increased substrate scope.