My experience here has been INCREDIBLE! I can’t believe how fast it’s gone by and that tomorrow we will all be leaving. 🙁 I have loved every moment here and to be honest, I don’t really want to leave. The connections and memories I’ve made here this summer will stick with me forever. It was so great getting to know all of the fellow REUs and working with so many awesome mentors and professors. If you ever get an opportunity to participate in an REU, do not hesitate to accept! It will be the greatest decision you ever make! It’s been fun Port A, hopefully I see you again soon. <3
Elucidating small leucine-like peptides in marine dissolved organic matter using liquid chromatography mass spectrometry
Presenter: Andrea Reynolds – Minnesota State University Moorhead – Biochemistry & Biotechnology
Mentors: Kaijun Lu & Dr. Zhanfei Liu
Dissolved organic matter (DOM) is important in the biogeochemical processes of the ocean. Annually, there is between 15 and 25 Pg of DOM that is added to, and removed from, seawater by various processes. Labile DOM such as peptides and proteins are key factors that support the growth of bacteria. Identification and characterization of DOM is essential because it can provide insight into the functions and metabolisms of microbes that direct the ocean carbon cycle. Preliminary data in Liu Lab (Kaijun Lu) showed that two peptide-like compounds, dileucine and trileucine, were present in Ship Channel seawater using high resolution liquid chromatography mass spectrometry (LC/MS). The objectives of this study were to determine if the compounds found previously in the seawater were in fact dileucine and trileucine by comparing it to known standards using LC/MS, tandem MS (MS/MS) and Ion Mobility (IM). An incubation experiment was also performed to investigate the degradation of trileucine. The presence of dileucine in the ship channel seawater was confirmed and its concentration ranged from 15 nM to 20 nM between different seasons, while an exact signal of trileucine could not be detected. However, the molecular weight of the trileucine-like compound in Ship Channel shared a very similar retention time and fragmentation pattern with the trileucince standard, suggesting that this natural DOM compound may share a similar structure with trileucine. It may be a cyclic trileucine peptide yet could not be confirmed in the duration of the program but will be studied further in the future. Trileucine was found to fully degrade within 96 hours at a rate of 0.0165 μM h-1. Bacteria abundance followed a natural trend of increasing and then decreasing after 24 hours. Overall, this study showed that peptides are an important component of marine DOM and play an important role in carbon and nitrogen cycling in marine environments.