Hands-on Research Complex Systems School SJTU, Shanghai, China (June 17-29, 2012) Biophysics. Eva-Maria Schötz

Transcription

1 Hands-on Research Complex Systems School SJTU, Shanghai, China (June 17-29, 2012) Biophysics Eva-Maria Schötz Lewis-Sigler Institute for Integrative Genomics Princeton University

2 What is biophysics? The branch of biology that applies the methods of physics to the study of biological structures and processes. A branch of science concerned with the application of physical principles and methods to biological problems. Biophysics is a bridge between biology and physics. (Biophysical society)

3 Study & understanding of physical aspects of the living world

4 What Biophysics do biophysicists spans many study? scales All of Biology is Fair Game (Biophysical society website)

5 Examples Areas of areas of biophysics of biophysics Biomechanics (Goldman) Cell biophysics (Rericha) Bioelectricity Photobiophysics keratocyte migration Theoretical & computational biophysics Radiation biophysics Protein biophysics images from various sources on the web

6 Biophysics spans many scales Quantum biophysics Molecular biophysics Cell level Tissue level Organism Population dynamics Ecosystems images from various sources on the web

7 Research overview Physical properties of biological tissues Mechanism of asexual reproduction Nervous system regeneration ASA Collective phenomena Population & Evolution Behavior & Learning movie from zfin.org

8 Role of mechanics for development Wetting? movie: F. Ulrich Do experiments in culture EMS et al., HFSPJ (2008)

9 Embryonic tissues behave like fluids on long times EMS et al., HFSPJ (2008)

10 Embryonic tissues behave like fluids on long times EMS et al., HFSPJ (2008)

11 Surface tension governs cell arrangement surface tension Laplace: liquid-air interface cell-medium interface EMS et al., HFSPJ (2008) Manning, Foty, Steinberg & EMS, PNAS 107 (2010)

12 Mechanical oscillations in hydra Bode, 2011 amazing regenerative capabilities reproduce asexually by budding (supposedly) immortal image: web

13 Hydras have fascinated people over centuries 13

14 Regeneration from hydra stew in collaboration with A. Ott

15 Mechanical oscillations are necessary for regeneration

16 Soriano et al, 2009

17 Oscillations are regulated by osmotic pressure Higher concentration of sucrose creates higher osmotic pressure which slows down hydra oscillation

18 Gamba et al., PRL 2012 True symmetry breaking event

19 Oscillations in planarian locomotion Planarians: masters of regeneration cut Morgan (1910) 1 week later 30% stem cells Rescue Wagner et al., Science 2011

20 When stressed (cut), planarians start to inchworm Mickolajczyk, et al. (in preparation)

21 Asexual reproduction in planarians Mechanics: how do they do it? Statistics: Reproduction strategy, time scales Evolution: How create diversity? perry-planaria-p2/ Aging: Immortal because asexual? image sequence: B. Lincoln

22 Experiment : > 3 years; > 10,000 divisions 5 families (individuals)

23 Tracking thousands of individual planarians Thomas & EMS, J Exp Biol 214 (2011)

24 Thomas & EMS, J Exp Biol 214 (2011) FREE!

25 Asexual reproduction dynamics What determines the time it takes for a worm to divide? 25

26 It matters who your parent was Dunkel, Talbot &EMS (Phys. Biol. 8, 2011)

27 It matters how big you were at birth Worms born bigger divide faster faster Area at division and area at birth are uncorrelated Thomas, Quinodoz & EMS (J. Stat. Phys, in print)

28 Area at division determines the number of offspring k=1 k=2 k=3 Worms grow bigger before dividing and making more offspring, i.e. no real tradeoff between size and number Thomas, Quinodoz & EMS (J. Stat. Phys, in print) see also: Quinodoz, Thomas, Dunkel & EMS (J. Stat. Phys.,2011)

29 Biophysics has many faces There are many interesting problems waiting that can be addressed with little cost image: web

30 Working interdisciplinary Is difficult! (Language, Culture, Meetings, etc.) Requires a revision of our educational system. More programs promoting Integrated Science : Combination of physics, chemistry, biology, mathematics, computer science

31 Two related but distinct goals 1. Educate biologists who find it natural to do quantitative experiments, sophisticated analyses of their data, and meaningful comparisons with theory. The book of Nature is written in the language of mathematics. (Galileo Galilei, 1623) 2. Educate physicists who find it natural to bring the physicist s style of thought to study a broader class of systems, including biological systems. (this can t be accomplished by learning less physics!) based on slide by W. Bialek

32 Basic ideas Start interdisciplinary as early as possible (ideally high school) Teach physics using examples from biology wherever possible. Hands on research experience! Labs! Independent research project design & execution Bialek, W., & Botstein, D. (2004). Introductory Science and Mathematics Education for 21st-Century Biologists. Science, 303(5659), Schötz & Calhoun, Raising the bar in freshman science education (in review)

33 Example for inexpensive interdisciplinary lab module Tissue mechanics and aging

34 Tissue mechanics and aging Chicken skin 95-year old woman holding 5-year old boy all pictures are from web sources

35 Tissue mechanics and aging image source: image source:

36 slide courtesy W. Bialek The pioneers (now, mostly, PhD students) and this is after the final exam Fall 2009: 58 students in the freshman class ~1/3 of Juniors majoring in Physics came through our course ~1/2 of students so far major in Molecular Biology, instantly the go to people for quantitative analysis, changing what gets done in the labs

37 Some concluding remarks There are a lot of interesting problems awaiting in biophysics, many of which can be addressed at little cost. Just open your eyes see and play. The excitement we feel about science (and about teaching science) needs to be passed on. Don t be too shy to admit: This is so cool!

38 Thanks to Collaborators: J. Dunkel (Cambridge) M. L. Manning (Syracuse) R. Foty (UMDNJ) R. Austin (Princeton) Int. Material Solutions (Princeton) P. Newmark (Illinois, HHMI) B. Pearson (Toronto) A. Ott (Saarland) assistants: Kristine & Sofi