Analytical chemist Grace Muna accompanied three students to the 5th annual 2017 Louis Stokes Midwest Center of Excellence (LSMCE) Conference this October where she served as one of the judges for the student poster competition. Physics major E-Lexus Thornton (shown presenting his poster, above left) and Biology major Keon Jones (with Muna, above right) showcased their summer work under the LSAMP program at IU South Bend. Award-winning biochemistry major Michele Costantino also attended the conference to present her summer work under an REU at IUPUI. Presenting at a conference is a great way to end a project, like icing on a cake, but can also be a great way to start new beginnings by making contact with students and faculty from other institutes. Special thanks are due to these three students for representing IU South Bend and showing the Midwest states what quality students our campus has. Abstracts of the students' posters are given below.
Michele Costantino (Poster #55)
The effect of ionic solutions on surface potential of lipid membranes
Cellular membranes provide a barrier between two environments and are composed of a variety of lipid molecules. The composition of the membrane determines its function and as such can be influenced by ions and molecules in the surrounding environment. Amongst the factors affected is the electric charge and the surface potential (zeta potential) of the membrane. The mechanism by which the zeta potential of membranes is affected by water soluble ions and molecules involves, not only the net electrical charge, but also a physical property called electrical polarizability. In the lab, we use a method by which electrical polarizability is determined from measurements of index of refraction and mass density as a function of solute concentration. This research will provide understanding in how polarizability of a molecule affects a cellular membrane by observing the zeta potential of a lipid vesicle at varying concentrations of one molecule in solution. The dioleoylphosphatidylserine (DOPS) lipid was utilized, which contains two monounsaturated hydrocarbon chains with eighteen carbons each and a negatively charged head group that consists of both an amine and carboxylic acid. The results showed that while the vesicles maintained approximately a -60 mV charge in water, addition of ions altered the zeta potential in the positive direction as the concentration increased. However, this trend does not immediately appear upon adding ions, instead the charge fluctuates at lower concentrations. The trend has been observed in both divalent chlorides and adenosine triphosphate solutions. Future research will focus on other divalent chlorides—including magnesium, manganese, and cobalt—as well as organic phosphates and phospholipids with different head groups such as dilauroylphosphatidylcholine (DLPC), a neutral lipid. This research will help us to further understand how molecules and ions in the surrounding environments affect cellular membranes in regards to zeta potential, size, and formation of multilamellar vesicles (MLVs). Funding: National Science Foundation Research Experience for Undergraduates (REU) Award #1659688
Keon Jones (Poster #82)
A sensitive electrochemical method to determine lead in water and soil
Lead is one of the most toxic heavy metal in the environment. Its presence is due to human activities notably, lead in gasoline, lead-based paint, lead-containing pesticides, lead in ammunition and sinkers, and incinerator ash or water from lead pipes. Lead poisoning can cause a number of adverse human health effects but it’s particularly detrimental to the neurological development of growing children. Therefore, frequent testing and precise monitoring of Pb in soil and water is important to assess and control lead contamination. We hereby report on developing a stripping voltammetric method using glassy carbon electrodes modified with bismuth nanoparticles (GC-BiNPs) to detect lead in drinking water and soil. Voltammetric stripping measurements have historically utilized mercury in the forms of hanging mercury drop and mercury film electrode to measure heavy metal ions. This is mainly because clean surfaces can be easily be regenerated with a new mercury drop. However, because of mercury toxicity and risks associated with its disposal its use as an electrode material for stripping measurements is severely restricted. We’re utilizing the unique properties of bismuth such as its ability to form alloys with different metals, to develop a sensitive method to detect lead. Preliminary results show that using GC-BiNPs we can detect low levels of lead down to 1 parts per billion in water. The research findings on the stripping voltammetric method development will be presented. Funding: LSAMP; SMART ; IUSB
E-Lexus Thornton (Poster #119)
Modification of the microchannel plate (MCP) detectors in the recoil mass separator St. George
The Recoil Mass Separator St George in Notre Dame’s Nuclear Science Laboratory (NSL) is being used for the study of low level (α,γ) reactions using inverse kinematics to better understand the helium burning processes in a star. ST GEORGE has two MCP detectors that amplify and multiply electrons into electrical pulses that can be seen on an oscilloscope. To make the MCP detectors display a better pulse, and to make the MCP detectors conveniently easy to remove from the mass separator, we decided to modify the makeup of both MCP detectors and add two delay boards and a basic circuit board to both MCP detectors. The Autodesk Inventor software was used for the drawing process and the circuit board was designed by hand. The process and/or results of the modifications and new additions will be described. Funding: NSF Grant PHY-0959816
