Mon, Sep 29, 1997
4:00 pm
8th Floor Conference Room of Building 38A
National Library of Medicine
Bethesda, MD.
We plan to go out to dinner at a resturant in Bethesda afterwards. Please contact Steve Garavelli by September 26th if you would like to join us to dinner. Remember: no food fights ... ;-)
In previous publications a formalism to assess quantitatively the structural complexity of selected molecules and biosystems was proposed (Yagil, 1985;1993). The basic tenet was that structural complexity is determined by the size of the minimal set of numerical and symbolical specifications necessary to define a structure in terms of its lower level components. In quantitative terms the structural complexity C of a system can be expressed by:
C = Sigma [c(k)/k] - c'where c(k) is the number of coordinates sharing a regularity of order k (a feature repeated k times) and c' is the number of coordinates necessary to place the system in the external framework (normally six). The idea is that any regular feature, such as a repeat or a symmetry, reduces the complexity by the number of times that the repeat appears in that system. A self consistent set of rules was formulated and is shown to be valid for a series of simple molecular structures. It is shown that only the ordered coordinates, i.e. those which assume the same value for every member of a particular ensemble of structures, contribute to the complexity of the system.
The formalism can be applied to various biostructures. First, two viral structures are compared: That of the small RNA tobacco mosaic virus (TMV), chosen to represent strictly self- organizing, and that of the larger dsDNA bacteriophage T4, for which genome directed instructions are required for correct virion assembly. A large difference in complexity values is found: C = 4 for the TMV virion versus C = 117 for the tail part of the T4 virion. This large difference reflects the different pattern coding requirements of the two organisms. The correlation between structural complexity and coding requirements is further demonstrated by the analysis of the wing patterns of certain butterflies. The structural complexity of these patterns is shown to be equal to the number of genes found, by classical genetic analysis (Bakerfield et al. ,1996), to participate in the specification of those patterns. It is consequently proposed to utilize complexity analysis for the evaluation of genomic contributions to structural specifications.
Bakerfield,P.M. et al., (1996) Development, plasticity and evolution of butterfly eyespot patterns . Nature, 384: 236-242
Yagil, G. (1985). On the structural complexity of simple biosystems. J. Theor. Biol., 112: 1-23.
Yagil, G. (1993). On the structural complexity of templated systems. in: "1992 lectures in complex systems" , L. Nadel and D. Stein, Eds., The Santa Fe Institute and Addison-Wesley, N.Y. 519-530.
Yagil. G., (1995). Complexity analysis of a self-organizing versus a template directed system. Lectures in artificial intelligence, 929: 179-187.
Seminar arrangements:
John Spouge
(spouge@ncbi.nlm.nih.gov)
Announcements:
Tom Schneider
(toms@alum.mit.edu)
Dinner arrangements:
Steve Garavelli
(garavelli@NBRF.Georgetown.Edu)
This announcement is at https://alum.mit.edu/www/toms/bitcs/yagil1997.html
Schneider Lab.
origin: 1997 September 15
updated: 1999 November 24