Selective Phosphonylation of 5′-Adenosine Monophosphate (5′-AMP) via Pyrophosphite [PPi(III)]

We describe here experiments which demonstrate the selective phospho-transfer from a plausibly prebiotic condensed phosphorus (P) salt, pyrophosphite [H2P2O52−; PPi(III)], to the phosphate group of 5′-adenosine mono phosphate (5′-AMP). We show further that this P-transfer process is accelerated both by divalent metal ions (M2+) and by organic co-factors such as acetate (AcO−). In this specific case of P-transfer from PPi(III) to 5′-AMP, we show a synergistic enhancement of transfer in the combined presence of M2+ & AcO−. Isotopic labelling studies demonstrate that hydrolysis of the phosphonylated 5′-AMP, [P(III)P(V)-5′-AMP], proceeds via nuceophilic attack of water at the Pi(III) terminus

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

A Raman Spectroscopic Study of a Fulgurite

A Raman microspectroscopic study of several fulgurites has been undertaken. A fulgurite is an amorphous mineraloid, a superheated glassy solid that is formed when a lightning bolt hits a sandy or rocky ground and thermal energy is transferred. The Raman spectra revealed several forms of crystalline and fused silica and also the presence of polyaromatic hydrocarbons found in an interfacial zone of a glass bubble. This, together with the presence of anatase, a low-temperature polymorph of TiO2, suggested that some regions of the fulgurite specimen were not subjected to temperatures of 1800°C, which are attained when lightning hits the surface of sand or a rock

Rapid Raman Mapping of a Fulgurite

A fulgurite is a naturally occurring glass formed when lightning hits sand, rock, or soil. The formation of fulgurites is accompanied by mineralogical and sometimes compositional changes, and may record information about the environment in which they were formed. A previous investigation using Raman point spectroscopy discovered the presence of anatase, a low-temperature polymorph of TiO2, and polyaromatic hydrocarbons within a fulgurite. These findings indicate that there were regions within the sample that were not subjected to temperatures of 2,000 K or more that the matrix is reported to attain when struck by lightning. This paper seeks to expand the previous research by utilizing the capabilities of a new Raman spectroscopic technological development that enables rapid mapping. The entire surface area of a cross-sectioned fulgurite (∼40 mm × 23 mm) sample was mapped allowing several regions of polyaromatic hydrocarbons and anatase to be located. Furthermore, shocked quartz was found within the boundary regions of the fulgurite, and is proposed to have resulted from contact with vaporized material during the lightning strike. Shocked quartz is typically indicative of extraterrestrial impact, yet its discovery here suggests that its formation is not exclusive to the impact process

On the Prebiotic Potential of Reduced Oxidation State Phosphorus: the H-phosphinate–pyruvate System

H-Phosphinic acid and pyruvic acid, both plausible prebiotic chemicals, react selectively in water to build structural complexity including amide bond formation under remarkably mild conditions and oxidative coupling of P1 compounds to condensed pyrophosphorus compounds

Archean Phosphorus Liberation Induced by IRON Redox Geochemistry

The element phosphorus (P) is central to ecosystem growth and is proposed to be a limiting nutrient for life. The Archean ocean may have been strongly phosphorus-limited due to the selective binding of phosphate to iron oxyhydroxide. Here we report a new route to solubilizing phosphorus in the ancient oceans: reduction of phosphate to phosphite by iron(II) at low (°C) diagenetic temperatures. Reduction of phosphate to phosphite was likely widespread in the Archean, as the reaction occurs rapidly and is demonstrated from thermochemical modeling, experimental analogs, and detection of phosphite in early Archean rocks. We further demonstrate that the higher solubility of phosphite compared to phosphate results in the liberation of phosphorus from ferruginous sediments. This phosphite is relatively stable after its formation, allowing its accumulation in the early oceans. As such, phosphorus, not as phosphate but as phosphite, could have been a major nutrient in early pre-oxygenated oceans