Analytical Chemistry, in its 12th issue and 80th volume in 2008, featured a fundamental review of electrochemical sensors written by past and present Schoenfisch Lab members B.J. Privett, Jae Ho Shin, and Mark H. Schoenfisch. The review detailed the 200 most significant advancements in the fields of potentiometric, voltammetric, and electrochemical biosensors from publications throughout the preceding two years. Sections of the invited review highlighted advancements in topics of notable interest to the Schoenfisch group, such as the voltammetric detection of nitric oxide as well as the employment of nitric oxide-releasing sensor coatings used to enhance the utility and lifetime of implanted in vivo sensors.
Associate professor Mark Schoenfisch in the analytical division, along with two of his senior graduate students, Susan Deupree and Evan Hetrick, recently returned from the Eighth World Biomaterials Congress, held this year in Amsterdam. The Congress featured posters and presentations from over 2800 papers, including three from the Schoenfisch group. Research presented by our lab showcased the efficacy of novel nitric oxide-releasing nanoparticles as anti-biofilm agents, the ability of these materials to aid in mediating the biocompatibility of implantable sensors, as well as an atomic force microscopy study of the mechanism of nitric oxide’s antimicrobial action.
Capping proteins are among the most important regulatory proteins involved in controlling complicated stochastic dynamics of filopodia, which are dynamic finger-like protrusions used by eukaryotic motile cells to probe their environment and help guide cell motility. They attach to the barbed end of a filament and prevent polymerization, leading to effective filament retraction due to retrograde flow. When researchers in the Papoian Group simulated filopodial growth in the presence of capping proteins, qualitatively different dynamics emerged, compared with actin-only system.
Pavel Zhuravlev and Garegin Papoian discovered that molecular noise due to capping protein binding and unbinding leads to macroscopic filopodial length fluctuations, compared with minuscule fluctuations in the actin-only system. Their findings have been published in Proceedings of The National Academy of Sciences, USA, and also appears as the cover story of the current issue of The Journal of Physical Chemistry B.
The work of the Papoian Group, shows that molecular noise of signaling proteins may induce micrometer-scale growth–retraction cycles in filopodia. When capped, some filaments eventually retract all the way down to the filopodial base and disappear. This process endows filopodium with a finite lifetime. Additionally, the filopodia transiently grow several times longer than in actin-only system, since less actin transport is required because of bundle thinning. The researchers have also developed an accurate mean-field model that provides qualitative explanations of our numerical simulation results. These results are broadly consistent with experiments, in terms of predicting filopodial growth retraction cycles and the average filopodial lifetimes.
As published in Physical Review E, using a technique first established in the Papoian Lab, researchers with the Pedersen Group tested a hypothesis that the closed form of the C2 domain of coagulation factor V is more stable than the open form in an aqueous environment using a two-dimensional free-energy calculation with a simple dielectric solvent model. Their result shows that while the free-energy difference between two forms is small, favoring the closed form, a two-dimensional free-energy surface (FES) reveals that a transition state (1.53 kcal/mol) exists between the two conformations.
By mapping the one-dimensional order parameter ΔQ onto the two-dimensional FES, the investigators search the conformational change path with the highest Boltzmann weighting factor between the closed and open form of the factor V C2 domain. The predicted transition path from the closed to open form is not that of simple side chain movements, but instead concerted movements of several loops. The team also presents a one-dimensional free-energy profile using a collective order parameter, which in a coarse manner locates the energy barriers found on the two-dimensional FES.
Michael Crimmins, the Mary Ann Smith Professor and Chair of Chemistry, will become Senior Associate Dean for the Natural Sciences at the College of Arts and Sciences, effective July 1.
Crimmins has served as Chair of our department since 2007. He also serves as Professor of Medicinal Chemistry-Natural Products in the School of Pharmacy. He previously served as Vice Chair of Graduate Studies and Vice Chair of Facilities for the Chemistry Department. Michael is also an award-winning teacher and scholar. His research has focused on synthetic organic chemistry: development of new synthetic methods, novel synthetic strategies and total synthesis of biologically active and structurally interesting natural products.
Michael previously chaired the North Carolina Section of the American Chemical Society, and he received the Society’s Arthur C. Cope Scholar Award in 2001 and the Charles Holmes Herty Medal in 2004. He received a Tanner Faculty Award for Excellence in Undergraduate Teaching in 1999.
All of his fellow faculty members, staff, and students at the department of chemistry will miss Mike's daily presence, his wit, patience, and leadership skills. We all wish him the very best in his new duties.
Senior Associate Dean for Natural Sciences, and former Department Chair, Michael Crimmins, announced that as of July 1st, Matthew Redinbo, Professor of Chemistry, Biochemistry and Biophysics, is the new Chair of the Chemistry Department. Redinbo has served as the department's Vice Chair for the previous two years.
In a message to faculty and staff, Michael Crimmins expressed both his gratitude to professor Redinbo for his willingness to step forward to take on this important responsibility, as well as his confidence in Redinbo's skills and experience to serve the department well as its new Chair.
In collaboration with scientists at the Academy of Sciences of the Czech Republic, the Berkowitz Group presents molecular dynamics simulations of a multicomponent, asymmetric bilayer in mixed aqueous solutions of sodium and potassium chloride. Because of the geometry of the system, there are two aqueous solution regions in these simulations: one mimics the intracellular region, and one mimics the extracellular region. Ion-specific effects are evident at the membrane/aqueous solution interface. Namely, at equal concentrations of sodium and potassium, sodium ions are more strongly adsorbed to carbonyl groups of the lipid headgroups.
A significant concentration excess of potassium is needed for this ion to overwhelm the sodium abundance at the membrane. Ion-membrane interactions also lead to concentration-dependent and cation-specific behavior of the electrostatic potential in the intracellular region because of the negative charge on the inner leaflet. In addition, water permeation across the membrane was observed on a timescale of similar to 100 ns. This study represents a step toward the modeling of realistic biological membranes at physiological conditions in intracellular and extracellular environments.
Ruth Hyde, the administrative manager for the Chemistry Department, has won the 2009 Award in Management, given by the College of Arts and Sciences for "outstanding accomplishments in leadership and management." Ruth coordinates all of the administrative needs of our complex department, which has 50 faculty, approximately 50 staff members, 75 postdoctoral associates, 250 graduate students and some 7,000 students registered for chemistry courses each year.
Commenting on Ruth's contributions to the department, Chair Michael Crimmins said, "Ruth handles a constantly heavy workload with courtesy and professionalism. She recognizes that the human resources are the most important in our unit, and Ruth is extremely well respected by staff, faculty and students who all consider her an invaluable resource for everything imaginable: human resource issues, student services, budgets, event planning, hiring, etc." Crimmins concluded in saying, "Ruth is a truly remarkable department administrator. I cannot imagine doing my job without her." Congratulations, Ruth for a well-deserved recognition!