Photoisomerization action spectroscopy: flicking the protonated merocyanine-spiropyran switch in the gas phase

Laser spectroscopy and ion mobility spectrometry are combined to provide structural and photochemical information on photoisomerizing molecules in the gas phase. The strategy exploits the fact that an ion packet propelled through buffer gas by an electric field separates spatially and temporally into its constituent isomers because of small differences in their collision cross sections. Isomers selected by an electrostatic ion gate are exposed to wavelength tunable radiation, promoting formation of photoisomers that are separated in a second ion mobility stage. The approach is demonstrated for protonated merocyanine and spiropyran isomers formed through electrospray ionization. Four isomers are observed whose relative abundances depend on pretreatment of the electrosprayed solution with either ultraviolet or visible light, and on collisional excitation before the ions are launched into the drift tube. The observations are interpreted in the light of accurate double-hybrid density functional theory calculations for the protonated spiropyran and merocyanine isomers that are used to predict structures, relative energies, isomerization barriers, collision cross sections and electronic absorption spectra. The two most abundant isomers, are merocyanine forms, in which the proton resides on the quinone oxygen atom, with either a trans or cis central bond in the linking polymethine chain. These two mero forms can be interconverted through photoexcitation, with different wavelength dependences for the forward and reverse photoisomerization processes. Protonated spiropyran is formed from protonated merocyanine isomers through collisional activation, but in only minor amounts through their photo-excitation over the 300-700 nm range

Arachidonic acid supplementation transiently augments the acute inflammatory response to resistance exercise in trained men

Strenuous exercise can result in skeletal muscle damage, leading to the systemic mobilization, activation and intramuscular accumulation of blood leukocytes. Eicosanoid metabolites of arachidonic acid (ARA) are potent inflammatory mediators, but whether changes in dietary ARA intake influence exercise-induced inflammation is not known. This study investigated the effect of 4 weeks of dietary supplementation with 1.5 g/day ARA (n=9, 24 {plus minus} 1.5 years) or corn-soy oil placebo (n=10, 26 {plus minus} 1.3 years) on systemic and intramuscular inflammatory responses to an acute bout of resistance exercise (8 sets each of leg press and extension at 80% 1RM) in previously trained men. Whole EDTA blood, serum, peripheral blood mononuclear cells (PMBCs), and skeletal muscle biopsies were collected prior to exercise, immediately post-exercise and at 2, 4 and 48 h of recovery. ARA supplementation resulted in higher exercise-stimulated serum creatine kinase activity (incremental area under the curve (iAUC) p=0.046) and blood leukocyte counts (iAUC for total white cells p<0.001, neutrophils p=0.007, monocytes p=0.015). The exercise-induced fold change in PBMC mRNA expression of interleukin-1 beta (IL1B), CD11b (ITGAM) and neutrophil elastase (ELANE), as well as muscle mRNA expression of the chemokines interleukin-8 (CXCL8) and monocyte chemoattractant protein 1 (CCL2) was also greater in the ARA group than placebo. Despite this, ARA supplementation did not influence the histological presence of leukocytes within muscle, perceived muscle soreness or the extent and duration of muscle force loss. These data show that ARA supplementation transiently increased the inflammatory response to acute resistance exercise, but did not impair recovery