Analysis of the residual alignment of a paramagnetic multiheme cytochrome by NMR.

Residual dipolar couplings measured by NMR spectroscopy reveal that the rhombicity of the electronic structure of low-spin paramagnetic hemes determines their relative contribution to the preferential orientation of a protein with multiple hemes when placed in a strong magnetic field.

Simultaneous spontaneous bilateral pneumothoraces in an asthmatic / Neumotórax espontáneos bilaterales simultáneos en un asmático

The occurrence of simultaneous spontaneous bilateral pneumothoraces is a very rare event. We present a case of a 14-year old asthmatic female patient who presented to the emergency room for routine treatment. While receiving nebulizations, she suddenly developed supraclavicular fullness with crepitus. Further examination revealed a clinical diagnosis of bilateral pneumothoraces. Although this phenomenon is more commonly associated with patients on mechanical ventilation, this case illustrates that physicians must be cognizant of this unique presentation in order to initiate early and aggressive life- saving therapy. With rapid bilateral needle thoracocentesis followed by placement of bilateral thora-costomy tubes, the patient recovered well. In this report, we also attempt to briefly review the possible pathophysiology of this form of spontaneous pneumothorax.

La incidencia del neumotórax espontáneo bilateral simultáneo en un asmático es un acontecimiento raro. Presentamos un caso de una paciente asmática hembra de 14 años de edad, quien acudió a la sala de emergencia para tratamiento de rutina. Mientras recibía nebulizaciones, desarrolló súbitamente plenitud supraclavicular con crépito. El examen posterior reveló un diagnóstico clínico de pneumotórax bilateral. Aunque este fenómeno se halla más comúnmente asociado con pacientes en ventilación mecánica, este caso ilustra que los médicos tienen que tener conciencia de esta presentación única para iniciar una terapia agresiva y temprana que haga posible la salvación del paciente. Con una rápida toracocentesis bilateral mediante aguja, seguida de colocaciones de tubos de tora-costomía bilateral, la paciente se recuperó bien. En este reporte también intentamos realizar una breve revisión de la posible patofisiología de esta forma de neumotórax espontáneo.

Simultaneous spontaneous bilateral pneumothoraces in an asthmatic.

The occurrence of simultaneous spontaneous bilateral pneumothoraces is a very rare event. We present a case of a 14-year old asthmatic female patient who presented to the emergency room for routine treatment. While receiving nebulizations, she suddenly developed supraclavicular fullness with crepitus. Further examination revealed a clinical diagnosis of bilateral pneumothoraces. Although this phenomenon is more commonly associated with patients on mechanical ventilation, this case illustrates that physicians must be cognizant of this unique presentation in order to initiate early and aggressive lifesaving therapy. With rapid bilateral needle thoracocentesis followed by placement of bilateral thoracostomy tubes, the patient recovered well. In this report, we also attempt to briefly review the possible pathophysiology of this form of spontaneous pneumothorax.

The effect of diethylamine on Stille alkylations with tetraalkylstannanes.

The addition of diethylamine to Stille alkylation reactions using stannanes improves yields by reducing beta-hydride elimination and reduction reactions, it also serves as a substitute for other additives such as Cu(I)I.

Metabolism of 3-(13)C-malate in primary cultures of mouse astrocytes.

Malate, specifically labeled with carbon 13 on C(3), was synthesized by chemical means and used to study malate metabolism by primary cultures of mouse cortical astrocytes. 3-(13)C-Malate in combination with glucose as well as 3-(13)C-malate alone were used as substrates; the effect of 3-nitropropionic acid, an inhibitor of succinate dehydrogenase and fumarase was also examined. The consumption of malate was only 0.26 micromol/mg of protein, approx. 25-fold lower than the consumption of glucose. Besides lactate, glutamine and fumarate were the two major metabolites released to the medium. Very low and similar levels of isotopic enrichment were detected on C(2) and C(3) of lactate; glutamine was labeled on C(2) and C(3) to a similar extent as well and labeling on C(4) was only detected when glucose was not added. These labeling studies suggest that cytosolic malic enzyme is not active in primary astrocytes and support the occurrence of pyruvate recycling in astrocytes.

The first synthesis of (-)-asperpentyn and efficient syntheses of (+)-harveynone, (+)-epiepoformin and (-)-theobroxide.

A generally applicable strategy for the synthesis of a range of polyoxygenated cyclohexane natural products has been developed. The enantioselective syntheses of (-)-theobroxide, a polyoxygenated cyclohexane natural compound with potent growth inducing properties in potato microtubers has been achieved via a 1,2 O-silyl migration between trans-hydroxyl groups and a remote hydroxyl directed epoxidation of an enone derived from quinic acid. A thus derived alpha-iodoenone was subjected to Stille coupling with tetramethylstannane to afford the first title compound. A similar strategy enabled a route to the complete asymmetric synthesis of the acetylenic phytotoxin (+)-harveynone. By selective reduction of (-)-theobroxide, (+)-epiepoformin was also prepared in enantiopure form and similarly, stereoselective reduction of (+)-harveynone completed the first enantioselective synthesis of (-)-asperpentyn, another natural compound with antimicrobial activity.

Preparation of sucrose heptaesters unsubstituted at the C-1 hydroxy group of the fructose moiety via selective O-desilylation.

Selective O-desilylation of 6,1',6'-tri-O-tert-butyldiphenylsilyl-2,3,4,3',4'-penta-O-benzo ylsucrose with hydrofluoric acid in acetonitrile led to the 1'-O-tert-butyldiphenylsilyl derivative (96% yield), which was further perbenzoylated and deprotected at OH-1' with tetrabutylammonium fluoride (86%). An analogous sequence with the corresponding O-acetylated sucrose derivative and tetrabutylammonium fluoride as desilylating agent resulted in a lower yield of the C-1' hydroxy derivative.

Thermostabilization of proteins by diglycerol phosphate, a new compatible solute from the hyperthermophile Archaeoglobus fulgidus.

Diglycerol phosphate accumulates under salt stress in the archaeon Archaeoglobus fulgidus (L. O. Martins, R. Huber, H. Huber, K. O. Stetter, M. S. da Costa, and H. Santos, Appl. Environ. Microbiol. 63:896-902, 1997). This solute was purified after extraction from the cell biomass. In addition, the optically active and the optically inactive (racemic) forms of the compound were synthesized, and the ability of the solute to act as a protecting agent against heating was tested on several proteins derived from mesophilic or hyperthermophilic sources. Diglycerol phosphate exerted a considerable stabilizing effect against heat inactivation of rabbit muscle lactate dehydrogenase, baker's yeast alcohol dehydrogenase, and Thermococcus litoralis glutamate dehydrogenase. Highly homologous and structurally well-characterized rubredoxins from Desulfovibrio gigas, Desulfovibrio desulfuricans (ATCC 27774), and Clostridium pasteurianum were also examined for their thermal stabilities in the presence or absence of diglycerol phosphate, glycerol, and inorganic phosphate. These proteins showed different intrinsic thermostabilities, with half-lives in the range of 30 to 100 min. Diglycerol phosphate exerted a strong protecting effect, with approximately a fourfold increase in the half-lives for the loss of the visible spectra of D. gigas and C. pasteurianum rubredoxins. In contrast, the stability of D. desulfuricans rubredoxin was not affected. These different behaviors are discussed in the light of the known structural features of rubredoxins. The data show that diglycerol phosphate is a potentially useful protein stabilizer in biotechnological applications.