  Biological molecules are characterized by an intrinsic asymmetry known as
homochirality. The result is optical activity of biological materials and
circular polarization in the light scattered by microorganisms, cells of living
organisms, as well as molecules (e.g. amino acids) of biological origin. Lab
measurements (Sparks et al. 2009a, b) have found that light scattered by
certain biological systems, in particular photosynthetic organisms, is not only
circular polarized but contains a characteristic spectral trend, showing a fast
change and reversal of sign for circular polarization within absorption bands.
Similar behavior can be expected for other biological and prebiological
organics, especially amino acids. We begin our study by reproducing the
laboratory measurements for photosynthetic organisms through modeling the
biological material as aggregated structures and using the Multiple Sphere
T-matrix (MSTM) code for light scattering calculations. We further study how
the spectral effect described above depends on the porosity of the aggregates
and the size and number of the constituent particles (monomers). We show that
larger aggregates are characterized by larger values of circular polarization
and discuss how light-scattering characteristics of individual monomers and
electromagnetic interaction between them affect this result. We find that
circular polarization typically peaks at medium (40-140{\deg}) scattering
angles, and discuss recommendations for efficient remote observation of
circular polarization from (pre)biological systems.
