Vinh Phung is the research fellow of the month for May 2010. He is a trained molecular biologist from the University of Oslo. He now works in the research group for muscle processing on mitochondrial influence in post-mortem muscle.
Master's degree in molecular biology
Vinh Thanh Phung
Photo: Vinh Thanh Phung
I am 26 years old and was born in Vietnam but grew up in Norway. I have a master's degree from the University of Oslo (UiO) in molecular biology, biochemistry, and physiology. During my master thesis I made deletion mutants of the prion protein with a green fluorescent tag at the N-terminus to examine protein stability and intracellular localization. The prion protein is involved in neurodegenerative diseases in both animals and humans, such as scrapie in sheep, mad cow disease in cattle and Creutzfeldt-Jakob in humans. The thesis was a collaboration between Prof. Kristian Prydz at UiO and Prof. Michael Tranulis at the Norwegian School of Veterinary Science (NVH).
After graduation I began an internship in the group of Prof. Hiroyuki Katayama at the University of Tokyo. The project was to isolate and concentrate Cryptosporidium parasites and enteroviruses from water reservoirs using hydroxyapatite, which is commonly used in column chromatography.
From life sciences to food science Back in Norway I was offered by Prof. Bjørg Egelandsdal and Prof. Erik Slinde a position as research fellow at the University of Life Sciences (UMB). The work involves study of protein stability in organelles isolated from muscle cells. The task suited my education background and experience, and in addition included a new and exciting field; Food Science. A doctoral degree at UMB was therefore a natural development from a master’s degree at NVH and UiO. The PhD degree is sponsored by collaboration between Tine BA, Nortura BA and UMB. My supervisors are inspiring and highly skilled researchers in food science (Prof. Bjørg Egelandsdal, UMB) and biochemistry (Prof. Erik Slinde, University of Bergen). Another incentive is the positive and international community at UMB which stimulates development and curiosity.
Oxygraph-2k for respiration measurements
Photo: Vinh Thanh Phung
The role of mitochondria in meat My doctoral project is to investigate the role of mitochondria in meat quality, color and taste. Mitochondria have a central role in many cellular processes as they cover ~ 90 % of the body's energy demands. Mitochondria facilitate oxidative phosphorylation and produces ATP in muscles. However, at high muscle activity anoxia arises and pyruvate becomes converted to lactic acid faster than it is metabolized. The same case happens in post-mortem tissue when muscle becomes converted to meat and ischemia prevents oxygen and substrate delivery. The result is that pH and oxygen consumption drops, and this leads to rancidity and discoloration of the meat as the reductive ability of mitochondria is reduced.
Meat is usually stored in a frozen state at -20oC. Under such circumstances ice crystals are formed and damages cells and mitochondria. Cell and organelle lysis leads to further inactivation of proteins and pH fall. Results up to now show that pH have a greater impact on mitochondrial reductive power than freezing, and that this property is reversible at low pH. The latter is in fact something that no one has shown before, and it also explains why some "classic" meat technologies also stabilize meat color. A regulation of pH in meat can therefore stimulate mitochondria’s ability to respire and reduce myoglobin. So far, I have isolated and concentrated mitochondria from liver and muscle and analyzed them using state-of-the-art respiration techniques. Did you know, that by taking a small biopsy from racing horses one can predict the winning sequence at the racetrack? A clever respiration protocol is all it takes…
Mitochondrial proteins that change over time In future work I will further look into the biological variations in muscle through mitochondria and proteomics. It is believed that the early post-mortem changes in mitochondria are the basis for biological variation in meat quality. Mapping of mitochondrial status and how the red-ox state is affected as a result of storage and aging will be particularly interesting. Here I will identify proteins that regulate the taste of meat by oxidation of polyunsaturated fatty acids and enzymes.
Future plans The fellowship period has so far been challenging and instructive, and I hope it will continue to be so. I aim to deliver the dissertation in the autumn 2011 and I am well motivated to continue as a researcher.
