Dr. Xuefeng Wang is a postdoctal researcher who is working with us on heme crystal growth. Here's her explaining a little about her work:
Hemoglobin is the main amino acid source for blood-feeding organisms. Catabolism of hemoglobin results in a build-up of toxic free heme. Crystallization of free heme into a dark brown pigment named hemozoin is the major heme detoxification pathway in some organisms, such as, maralia parasites, avain protozoan, the rediae of the trematode and some blood-feeding insects. Moreover, it has been widely accepted that heme crystallization is the target of anti-malaria and anti-schistosomiasis drugs. Crystal nucleation, growth and morphology of β-hematin, a synthetic Fe(III) protoporphyrin product with the same chemical composition and structure as hemozoin and mechanism of heme-drug interaction have been studied using a series of techniques, yet there is still a lack of fundamental knowledge about heme crystal nucleation and growth and the role of additives (e.g. anti-maralia drugs, histine-rich proteins and lipids) on a molecular scale. We are concentrating on examining β-hematin formation by AFM, which will help us understand the mechanism of hemozoin formation in vivo and may help in the design of effective anti-malaria drugs.
Stack Group Members
Stack Group Members
Dr. Wang is checking some crystal growth experiments using our anaerobic chamber.
Ms. Mengni Zhang is working with me on her Ph.D. on the mechanisms of bacterial reduction of iron (oxy)(hydr)oxides:
Dissimilatory iron reducing bacteria (DIRB) utilize ferric iron to provide energy for metabolic activities. Understanding the interaction of DIRB and iron oxyhydroxide surfaces is essential for studying the kinetics of bacterial respiration. This interaction has important implications for environmental processes such as the biogeochemical cycling of Fe, Mn, and U, which potentially cause metal pollution. Furthermore, the interaction may influence the efficiency of bioremediation strategies, since DIRB are known to be able to oxidize organic contaminants. However, the interaction is not very well understood because the mechanism of DIRB respiration is still unclear. Much work has supported a direct contact mechanism, which means DIRB directly use enzymes mounted on the cell wall to reduce ferric iron. Other research suggests that DIRB use an electron shuttle mechanism, where a dissolved species in the solution such as 9,10-anthraquinone-2,6-disulfonate (AQDS) transfer electrons between DIRB and iron oxyhydroxide surfaces. Still other mechanisms such as nanowires mechanism and chelating ligand mechanism have also been suggested. Surface microscopy, in combination with wet-chemistry analytical and microbiological techiques, may help us identify different mechanisms that DIRB use to respire.
Mengni is preparing a solution of AQDS, an exogeneous bacterial electron shuttle.
Ms. Cynthia Jackson is an undergraduate in the School of Earth and Atmospheric Sciences who is working with us on aerosols:
The climate forcing effect of aerosols are one of the larger uncertainties in our understanding of global climate (see e.g., the IPCC TAR). When in the atmosphere, these small mineral particles nucleate ice crystals causing clouds to form. As you can imagine, the extent to which they do that depends on parameters like particle size and shape, yet surprisingly, precise quantification of these parameters remains elusive. We're working with an atmospheric phsycist to help better constrain climate models with physical data taken in our laboratory.
Cyndi has just finished a hard day's work analyzing aerosols from Niger.
Ms. Meg Grantham is a research scientist who specializes in atomic force microscopy. She's currently working with us on aerosols and crystal growth and biomineralization of calcite:
Organisms commonly use calcium carbonates as a biomineral, i.e. to create their shells and other skeletal material. The ability of biological organisms to control and modify inorganic crystal growth far exceeds our capacity to engineer such crystals. We're trying to understand the chemical reactions that make such sophistication possible. The principal method we're using here is the atomic force microscope, and we're using it to measure the rates of movement of monomolecular steps on the calcite surface as a function of things like salt concentration, temperature, and cation to anion ratios. We're coupling these reactions to atomistic simulations of the steps on calcite surfaces to see if we can understand the what reactions are controlling the growth and dissolution of calcite.
