Michael L. Johnson

Education

  • PhD, University of Connecticut

Primary Appointment

  • Professor, Pharmacology

Contact

Research Interest(s)

Mathematical modeling of biological processes

Research Description

My research interests center on understanding the biochemical, physical chemical, and thermodynamic pathways by which one portion of a biological organism transfers information to other portions of the same organism. This interest has spawned research at the level of whole organisms, at the cellular level and at the molecular level.

At the molecular and cellular levels my research interest pertains to understanding the relationships between thermodynamics, dynamics and structural changes within biological macromolecule and how these can transfer information to other portions of the macromolecular structure and modify the physiological functioning. Of particular interest are the molecular mechanisms of cooperativity. I am currently involved in experimental and theoretical studies on several systems, including the the molecular mechanisms by which human hemoglobin binds oxygen and other ligands.

The human hemoglobin system provides a unique opportunity for detailed analysis into the question of correlating structural and thermodynamic information at the molecular level. I am formulating a series of thermodynamic models which include the effects of subunit dissociation and ligand binding. Results of analyses on experimental data provide important new insights into the general problem of correlating thermodynamic and structural information, the underlying mechanisms of cooperativity, and the phenomena of ligand-linked polymerization processes.

On the whole organism level I am studying the information transfer capabilities and properties of human serum hormones. We have developed a number of mathematical and statistical procedures which allow us to analyzes the temporal nature of the secretion of single hormone and the simultaneous secretion of multiple hormones. We anticipate that an understanding of the temporal nature of the secretion of these hormones will lead to a better understanding of the function of these hormones and the interaction between hormones in humans.

Recently, in collaboration with Joseph Lakowicz of the Center for Fluorescence Spectroscopy at the University of Maryland I have been developing the mathematical methods needed for fluorescence lifetime imaging (FLIM). This method is conceptually analogous to MRI but uses fluorescence lifetime as the imaged parameter. This method should allow investigators to use most fluorescent dyes to image spatial information in real time within a single cell.

Also, in collaboration with Michelle Lampl of the Anthropology Department of Emory University I have been developing methods to mathematically model the patterns of saltatory growth in children.

Selected Publications

  • Beck E, Mandalia S, Sangha R, Sharott P, Youle M, Baily G, Brettle R, Gompels M, Johnson M, McCarron B, Ong E, Pozniak A, Schwenk A, Taylor S, Walsh J, Wilkins E, Williams I, Gazzard B. The cost-effectiveness of early access to HIV services and starting cART in the UK 1996-2008. PloS one. 2011;6(12): e27830. PMID: 22194795 | PMCID: PMC3237423
  • Duplessis C, Sklar M, Maves R, Spichler A, Hale B, Johnson M, Bavaro M, Vinetz J. Hemoptysis associated with leptospirosis acquired in Hawaii, USA. Emerging infectious diseases. 2011;17(12): 2375-7. PMID: 22172093 | PMCID: PMC3311216
  • Duplessis C, You D, Johnson M, Speziale A. Efficacious outcome employing fecal bacteriotherapy in severe Crohn's colitis complicated by refractory Clostridium difficile infection. Infection. 2011;40(4): 469-72. PMID: 22161290
  • Kotiw M, Johnson M, Pandey M, Fry S, Hazell S, Netter H, Good M, Olive C. Immunological response to parenteral vaccination with recombinant hepatitis B virus surface antigen virus-like particles expressing Helicobacter pylori KatA epitopes in a murine H. pylori challenge model. Clinical and vaccine immunology : CVI. 2011;19(2): 268-76. PMID: 22205658 | PMCID: PMC3272931
  • Verne S, Johnson M, Bouchon D, Grandjean F. Effects of parasitic sex-ratio distorters on host genetic structure in the Armadillidium vulgare-Wolbachia association. Journal of evolutionary biology. 2011;25(2): 264-76. PMID: 22188300
  • Williams A, Johnson M. Persistent pain: not a medically unexplained symptom. The British journal of general practice : the journal of the Royal College of General Practitioners. 2011;61(591): 638-9. PMID: 22152842 | PMCID: PMC3177126
  • Woll K, Schuchardt E, Willis C, Ortengren C, Hendricks N, Johnson M, Gaidamauskas E, Baruah B, Sostarecz A, Worley D, Osborne D, Crans D. Gel formulation containing mixed surfactant and lipids associating with carboplatin. Chemistry & biodiversity. 2011;8(12): 2195-210. PMID: 22162158
  • Zhou E, Krishnan R, Stamer W, Perkumas K, Rajendran K, Nabhan J, Lu Q, Fredberg J, Johnson M. Mechanical responsiveness of the endothelial cell of Schlemm's canal: scope, variability and its potential role in controlling aqueous humour outflow. Journal of the Royal Society, Interface / the Royal Society. 2011;9(71): 1144-55. PMID: 22171066 | PMCID: PMC3350739