Determination and validation of Henry's constant for ozone in phosphate buffers using different analytical methodologies

Different procedures for measuring the concentration of ozone in aqueous buffered solutions have been reviewed for the determination of Henry s constant at different temperatures and pH. Iodometry, indigo trisulfonate and iron (II) chemical methods were compared with the direct UV absorbance measurement of ozone at 258 nm. From these data a new value for the molar extinction coefficient of ozone is proposed as 3840 ± 109 M^(-)1 cm^(-1). After the verification of the ozone analysis methods, the solubility of ozone in phosphate buffer medium was studied with in-situ absorbance direct measurements in a device with high gas-liquid transference rate, minimizing the gas desorption process on sample manipulation. The decomposition of ozone was not detected at the experimental conditions tested and, consequently, the observed solubility of ozone is constant, with the pH ranging from 2 to 7.6. The solubility of ozone was measured between 5 and 35ºC, resulting in a dimensionless solubility ratio of HB0 = 1.797 exp[0.0277·t(ºC)].J.F. acknowledges the support of the doctoral fellowship from the Universitat Politecnica de Valencia (UPV-PAID-FPI-2010-04).Ferre Aracil, J.; Cardona, SC.; Navarro-Laboulais, J. (2015). Determination and validation of Henry's constant for ozone in phosphate buffers using different analytical methodologies. Ozone: Science and Engineering. 37(2):106-118. https://doi.org/10.1080/01919512.2014.927323S10611837

BMP signaling and microtubule organization regulate synaptic strength

The strength of synaptic transmission between a neuron and multiple postsynaptic partners can vary considerably. We have studied synaptic heterogeneity using the glutamatergic Drosophila neuromuscular junction (NMJ), which contains multiple synaptic connections of varying strengths between a motor axon and muscle fiber. In larval NMJs, there is a gradient of synaptic transmission from weak proximal to strong distal boutons. We imaged synaptic transmission with the postsynaptically targeted fluorescent calcium sensor SynapCam, to investigate the molecular pathways that determine synaptic strength and set up this gradient. We discovered that mutations in the Bone Morphogenetic Protein (BMP) signaling pathway disrupt production of strong distal boutons. We find that strong connections contain unbundled microtubules in the boutons, suggesting a role for microtubule organization in transmission strength. The spastin mutation, which disorganizes microtubules, disrupted the transmission gradient, supporting this interpretation. We propose that the BMP pathway, shown previously to function in the homeostatic regulation of synaptic growth, also boosts synaptic transmission in a spatially selective manner that depends on the microtubule system