Nuclear magnetic resonance spectroscopy

Eutrophication is an increase in primary plant nutrients (Nitrogen [N] and Phosphorus [P]) in oceans, estuaries and lakes. The consequences of eutrophication are harmful algal blooms (HABs), resulting in algal toxin production and the depletion of oxygen as the extensive biomass decays. P is often the limiting nutrient and is viewed as a significant environmental problem. Most of the excess P that enters aquatic ecosystems originates from anthropogenic sources such as fertilizers, sewage, animal wastes, compost, crop residues, and wastewater. Over time, one of the main reservoirs of P becomes organic P (Po). We investigated the chemical nature and dynamics of P in cyanobacteria, horse manure, stormwater treatment areas, and rice fields. To better understand the chemical nature of P, the identification of specific P compounds was required, which was achieved through 31P nuclear magnetic resonance (NMR) spectroscopy. We investigated how paramagnetic metals and quadrupolar nuclei cause severe line broadening, peak shifts, and decreased the signal to noise ratio. Results revealed that certain Po forms are readily bioavailable to Microcystis aeruginosa. Additionally, the potential heterotrophic use of the organic portion (e.g., glucose, glycerol) of these P compounds are indicated for the growth and persistence of Microcystis aeruginosa. We showed that the cultivation of rice (Oryza sativa L.) had been found to effectively reduce P from agrarian soil and water through plant uptake and, therefore, minimizing downstream eutrophication. Soil, water, sugarcane, and rice plants at two different stages were analyzed for twelve different elements. Finally, we examined how a “relic” agrarian ditch in Stormwater Treatment Area 1 East (STA-1E) can be used for the retention and sequestration of P and other nutrients. The STAs were established to capture P from agricultural and other sources before reaching the Everglades. Retained P is primarily stored in the wetland soils and sediments, generated through a collection of interrelated physical, chemical, and biological processes.

The alpha-conotoxin EI is an 18-residue peptide (RDOCCYHPTCNMSNPQIC; 4-10, 5-18) isolated from the venom of Conus ermineus. This peptide targets the nicotinic acetylcholine receptor (nAChR) found in mammalian skeletal muscle and the electric organ of Torpedo. 2D-NMR methods and dynamical simulated annealing protocols have been used to determine the 3D structure of EI. 133 NOE-derived distances were used to produce 13 structures with minimum energy that complied with the NOE restraints. The structure of EI is characterized by a helical loop between T9 and M12 that is stabilized by the C4-C10 disulfide bond and turns involving C4-C5 and N14-P15. The overall fold of EI is similar to that of other alpha4/7 conotoxins (PnIA/B, MII, EpI). However, unlike these other alpha4/7 conotoxins, EI targets the muscular type nAChR. The differences in selectivity can be attributed to the surface charge distribution among these alpha4/7 conotoxins.