Metalloporphyrin Interaction with DNA
Research
in the group involves the synthesis of neutral "tentacle" water-soluble
porphyrins to be tested as possible intercalators of DNA.
Metalloporphyrins of this nature have been shown to be tumor specific and
thus have potential as possible tumor therapy agents. It has been recently
demonstrated that the synthesis of these neutral porphyrins containing poly-alcohol
functionalities to achieve water-solubility can be carried out (Figure 1). The
rational for the proposed investigation is that the cationic natures of the
porphyrins that have been studied thus far (+2 to +4) most probably influence
DNA binding due to charge considerations alone.
Furthermore, by utilizing neutral water-soluble porphyrins, changing the
metal (M = Ni2+, Zn2+, Cu2+, Mn3+,
Fe3+, Co3+) within the porphyrin core can provide insight
into question of the metal center/oxidation state role in DNA binding.
The specific interaction of these new metalloporphyrins and a
“hair-pin” oligonucleotide are studied using polyacrylamide gel
electrophoresis, PAGE, to determine whether inside/outside binding or cleavage
of the oligonucleotide occurs. This project will provide preliminary evidence into the
ability of these novel water-soluble porphyrins to interact with DNA bases.
Figure 1
Rb family protein complexes in the terminal differentiation of 3T3L1 cells
My research interests center on the mechanisms involved in the permanent exit of cells from the cell cycle as they terminally differentiate. Cells that previously proliferated in response to external signals now respond to those same signals in a different way. What changes in the cell to alter its response?
The major project in my lab looks at this question using the terminal differentiation of pre-adipocytes as a model. Pre-adipocytes proliferate rapidly and can be cultured like fibroblasts. When they are contact inhibited they can be treated with 2 signals, insulin and IBMX and will respond by differentiating. Over the course of the next 4 days they express fat cell proteins, produce lipid droplets and turn into adipocytes. During this time many of the cells divide once or twice but once this period is past they are post-mitotic- they never divide again.
Preadipocytes express the 3 members of the retinoblastoma family- the retinoblastoma protein (RB), p107 and p130. RB was first characterized as the protein which is inactivated in the tumor hereditary retinoblastoma. It acts to halt the onset of S phase by binding to and inactivating the E2F family transcription factors. Late in G1, RB is phosphorylated by the cyclin-dependent kinases, causing it to release the E2Fs, which then stimulate transcription of genes necessary for S phase. The expression of RB is unchanged throughout preadipocyte differentiation. Before the cells are stimulated to differentiate, the expression of p130 is high and p107 is low. Over the first 24 hours after stimulation, the levels of p130 decline while those of p107 increase dramatically. As the cells differentiate, the levels revert back to high p130 and low p107.
It appears that the increase in p107 is critical for preadipocytes to exit the cell cycle and terminally differentiate. My lab is working on experiments designed to identify the proteins to which p107 binds, based on the assumption that p107 acts through relatively stable interactions with other proteins, similar to RB. Our experiments utilize cell culture, protein techniques (chromatography, electrophoresis, Western blotting, etc.) and molecular biology techniques (transfection, mRNA isolation, PCR, etc.)
The Life and Works of Frederick Sanger, Nobel Laureate in Chemistry 1958, Nobel Laureate in Chemistry 1980
Dr.
Frederick Sanger was awarded the Nobel Prize in Chemistry in 1958 for his work
in determining the structure of insulin, the first protein molecule sequenced.
He became only the third two-time recipient of the Nobel Prize when he shared
the 1980 Nobel Prize in Chemistry for developing techniques for sequencing DNA
molecules. Dr. Sanger worked first in the Biochemistry Department at Cambridge
University in England. Then he worked at the Medical Research Council Laboratory
of Molecular Biology in Cambridge. I have interviewed Dr. Sanger and many of his
colleagues and family members. I continue research to prepare articles for the Bulletin
for the History of Chemistry and to write a biography of Frederick Sanger.
Molecular
Modeling and Simulations
of Sleep-inducing Molecules
The
objective of this project is to improve the quality of the sleep-wake cycle in
astronauts. Our approach involves the study of the structure-activity
relationships of novel compounds that modulate sleep patterns using
computational techniques such as molecular modeling and quantitative
structure-activity relationships to identify templates to design improved
medications the astronauts may take during a mission. The goals are:
Goal 1 To
compile and build a database of chemicals affecting sleeping patterns. The
database will include quantitative descriptors for physiological,
pharmacological, and toxicological effects, including potency, mechanism of
action, and drug interactions. The physicochemical properties will be obtained
using theoretical methods or retrieved from the literature.
Goal
2
To perform quantitative structure activity relationships studies using
the classic Hansch's extra-thermodynamic approach, 3-D comparative molecular
field analysis, and neural networks to identify best pharmacological agents to
use them as templates to design new improved medications the astronauts may take
during a mission.
Summaries and presentations of work accomplished to date can be found on my personal webpage. This work continues in collaboration with Drs. Lilia and Cesar Compadre in the Department of Pharmaceutical Sciences at the University of Arkansas for Medical Sciences. This research has been funded by a Virgil and June Waggoner Grant, by a J.D. Patterson Grant, and by NASA through the Arkansas Space Grant Consortium.
Last update: September 2002
School of Natural Sciences | Biology | Chemistry | Math and Computer Sci. | Physics