Education

1983-1987 North Carolina State University B.S (Biochemistry)
1987-1994 North Carolina State University Ph.D. (Plant Physiology/Biochemistry)

Research Interest

• PROJECT 1 - Characterization of the chlorophyll content in algae after exposure to cadmium sulfide (CdS) nanocrystals.

  The purpose of this research is to observe what happens to the total chlorophyll content in algae after exposure to low concentrations of cadmium sulfide nanocrystals to understand the effect that heavy metals have on chlorophyll biosynthesis.  Our results show that adding CdS to algal cultures resulted in a decrease and shift in the separation of photosynthetic pigments.  In cells treated with CdS there was a decrease in a pigment with an R_f of 0.73. Our findings suggest that this compound is phycoerythrin.  It has been shown by Brekovskikh and Bekasova (2005) that phycoerythins can be used as a protein matrix in vitro. In the red alga, Galdieria sulphuraria, it may be possible to synthesize these complexes in vivo.  Proteins can be extracted from the culture cells and unlike other plant suspension culture cells the addition of CdS at 100 mM did not result in loss of the culture.

  PROJECT 2 - Biochemical Characterization of a Cyanide Sensitive, Hydrogen Peroxide Insensitive SOD from Galdieria sulphuraria.

  Antioxidants quench active oxygen species (AOS) without being converted to destructive radicals. Organisms have evolved a number of mechanisms to detoxify and prevent oxidative damage by AOS, and antioxidant pathways are highly conserved. The enzyme, superoxide dismutase (SOD) (EC 1.15.1.1), helps to limit AOS-induced damage when oxidative stress causes dramatic changes in growth conditions.

  SOD has been characterized from a number of organisms.  SOD scavenges free oxygen radicals generated by various physiological processes to prevent oxidation of other biological molecules. SOD catalyzes the dismutation of superoxide ion (O₂^-) to hydrogen peroxide (H₂O₂) and molecular oxygen (O₂), normal by-products of cellular metabolism.

  In plants rapid changes in AOS are known to accompany invasion by pathogens, which generate the classical oxidative burst, and extreme temperature fluctuations.  Several studies have shown that through heat shock or chilling, temperature-mediated oxidative stress induces cytotoxicity.  Changing temperatures were correlated with increased concentrations of superoxide anions, hydrogen peroxide, nitric oxide, and lipid peroxidation products.  Other cellular events that lead to AOS generation, include environmental changes in ion fluxes, pH, and salinity.

  Galdieria sulphuraria, the organism used in this study, is a unicellular thermo-acidophilic red alga found in geothermal areas.  It occupies sulfuric hot springs with temperatures up to 55^oC, and pHs ranging from 0.05 to 4.  Galdieria can also grow in complete darkness on a wide variety of organic substrates, including sorbitol, glycerol and mannitol.  These polyols have to be converted to sugars or sugar phosphates in order to be metabolized. Galdieria employs hydrogenases to convert these substrates to useful metabolites. The high adaptability of this organism to extreme environments  that cause oxidative stress makes it useful for studies of the regulation of AOS and the antioxidant scavenging system.

  In Galdieria sulphuraria, enzymes and products of the inositol signaling pathway change after oxidative stress. Because increasing evidence suggests that inositol signal transduction controls the onset of the oxidative burst from AOS, we hypothesized that Galdieria would have a very active antioxidant-scavenging mechanism.  Our long-term objective is to understand the antioxidant mechanism in this alga. Because high concentrations of AOS generated in oxidative bursts have direct cytotoxic effects, we are investigating what role SOD and other antioxidant scavenging enzymes play in helping cells prevent oxidative damage.  We characterized both detergent-solubilized and membrane-associated SOD activities in Galdieria sulphuraria.  The ability to adapt to such severe changes, which enhance the production of free radical formation, must be tightly coordinated and regulated.

  Growing Galdieria in continuous light influences SOD activity and this activity varies with days in culture.  We have also shown that the Galdieria SOD activity differs from other SODs in regard to inhibition by KCN and H₂O₂.  We are purifying and further characterizing the enzyme.

  PROJECT 3 - Combining the CTAB and DNAzol protocol for the extraction of DNA from woody plant tissue.

  We have developed a new protocol for extraction of plant genomic DNA based on a combination of two existing protocols, the cetyltrimethyl-ammonium bromide (CTAB) and the DNAzol protocol.  Each of these protocols has its limitations. The combined protocol yielded approximately 90μg DNA per 0.1g of fresh plant tissue and the DNA obtained was of suitable quality for PCR analysis. This extraction protocol will facilitate studies of a wider range of plant genomes.

   

Publications

Okpodu, C.M. 2003.  The Emancipation Oak - An Interdisciplinary Laboratory.  National Association of African American Studies Meeting, Houston, TX (Monograph).

Okpodu, C.M.  2001.  Project OAK.  Phytochemistry of North America Society News, Vol. 21-24.

Okpodu, Camellia M.  2001.  "If Booker T. can do it, so can she" in How Jane Won by Dr. Sylvia Rimm, Random House Publishers.

Okpodu, Camellia M.  Investigating Plant Physiology A Laboratory Manual.  2000.  Morton Publishing Company, Englewood, Colorado.

Okpodu, C.M. 1999.  Characterization of a nuclear Phosphatidylinositol (4) kinase.  Plant Physiol. Biochem 37(6): 473-480.

Honors and Awards

2001 Marshall Rauch Endowed Chair of Biology, Elizabeth City State University, North Carolina

Memberships