Complex coordinated extracellular metabolism: Acid phosphatases activate diluted human leukocyte proteins to generate energy flow as NADPH from purine nucleotide ribose.

Complex metabolism is thought to occur exclusively in the crowded intracellular environment. Here we report that diluted enzymes from lysed human leukocytes produce extracellular energy. Our findings involve two pathways: the purine nucleotide catabolic pathway and the pentose phosphate pathway, which function together to generate energy as NADPH. Glucose6P fuel for NADPH production is generated from structural ribose of purine ribonucleoside monophosphates, ADP, and ADP-ribose. NADPH drives glutathione reductase to reduce an oxidized glutathione disulfide-glutathione redox couple. Acid phosphatases initiate ribose5P salvage from purine ribonucleoside monophosphates, and transaldolase controls the direction of carbon chain flow through the nonoxidative branch of the pentose phosphate pathway. These metabolic control points are regulated by pH. Biologically, this energy conserving metabolism could function in perturbed extracellular spaces.

A distonic radical-ion for detection of traces of adventitious molecular oxygen (O2) in collision gases used in tandem mass spectrometers.

We describe a diagnostic ion that enables rapid semiquantitative evaluation of the degree of oxygen contamination in the collision gases used in tandem mass spectrometers. Upon collision-induced dissociation (CID), the m/z 359 positive ion generated from the analgesic etoricoxib undergoes a facile loss of a methyl sulfone radical [(•)SO(2)(CH(3)); 79-Da] to produce a distonic radical cation of m/z 280. The product-ion spectrum of this m/z 280 ion, recorded under low-energy activation on tandem-in-space QqQ or QqTof mass spectrometers using nitrogen from a generator as the collision gas, or tandem-in-time ion-trap (LCQ, LTQ) mass spectrometers using purified helium as the buffer gas, showed two unexpected peaks at m/z 312 and 295. This enigmatic m/z 312 ion, which bears a mass-to-charge ratio higher than that of the precursor ion, represented an addition of molecular oxygen (O(2)) to the precursor ion. The exceptional affinity of the m/z 280 radical cation towards oxygen was deployed to develop a method to determine the oxygen content in collision gases.

Gas-phase fragmentations of anions derived from N-phenyl benzenesulfonamides.

In addition to the well-known SO2 loss, there are several additional fragmentation pathways that gas-phase anions derived from N-phenyl benzenesulfonamides and its derivatives undergo upon collisional activation. For example, N-phenyl benzenesulfonamide fragments to form an anilide anion (m/z 92) by a mechanism in which a hydrogen atom from the ortho position of the benzenesulfonamide moiety is specifically transferred to the charge center. Moreover, after the initial SO2 elimination, the product ion formed undergoes primarily, an inter-annular H2 loss to form a carbazolide anion (m/z 166) because the competing intra-annular H2 loss is significantly less energetically favorable. Results from tandem mass spectrometric experiments conducted with deuterium-labeled compounds confirmed that the inter-ring mechanism is the preferred pathway. Furthermore, N-phenyl benzenesulfonamide and its derivatives also undergo a phenyl radical loss to form a radical ion with a mass-to-charge ratio of 155, which is in violation of the so-called "even-electron rule."

Infection and nitric oxide.

The author describes how his experience as an infectious disease fellow at Stanford University with Jack Remington from 1969 to 1971 influenced the direction of his subsequent laboratory investigation. The author reviews a series of studies that were intended to provide a mechanistic understanding of an in vitro cytotoxicity assay developed while he was a fellow with Jack Remington. These investigations resulted in the 1987 discovery of the synthesis of nitric oxide from L-arginine by cytokine-activated macrophages. This work provided the components (the precursor, products, and an inhibitor) of the enzymatic synthesis of nitric oxide by all three later-identified nitric oxide synthase isoforms. The significance of cytokine-induced nitric oxide synthesis during innate resistance and cell-mediated immune reactions is discussed briefly.