Modeling supra-molecular helices: extension of the molecular surface recognition algorithm and application to the protein coat of the tobacco mosaic virus.

Geometric matching of molecular surfaces appears to be essential for the formation of binary molecular complexes and of supra-molecular aggregates. The structure of a binary complex is characterized by the best geometric match, whereas the structure of an aggregate is characterized by the best combined match, i.e.

Compact holographic beam expander.

A compact planar beam expander, composed of two holographic lenses that are recorded on a signal holographic plate, is presented. The smaller lens converts a narrow input beam into a diverging spherical wave at a high offaxis angle. This wave propagates toward the second lens, undergoing total internal reflections within the plate, and emerges from the larger lens as a magnified plane wave.

White-light holographic display based on planar optics.

A novel method for designing, recording, and reconstructing a planar-optics display holographic doublet, composed of two holograms on the same plate, is presented. The first hologram traps a light from a white-light source into the substrate by total internal reflection, whereas the second hologram couples out the trapped light from the plate to form the reconstructed three-dimensional image. The method is illustrated with a holographic doublet recorded at 488 nm and read out with a white-light source.

Molecular surface recognition: determination of geometric fit between proteins and their ligands by correlation techniques.

A geometric recognition algorithm was developed to identify molecular surface complementarity. It is based on a purely geometric approach and takes advantage of techniques applied in the field of pattern recognition. The algorithm involves an automated procedure including (i) a digital representation of the molecules (derived from atomic coordinates) by three-dimensional discrete functions that distinguishes between the surface and the interior; (ii) the calculation, using Fourier transformation, of a correlation function that assesses the degree of molecular surface overlap and penetration upon relative shifts of the molecules in three dimensions; and (iii) a scan of the relative orientations of the molecules in three dimensions.

All-optical bipolar neural network with polarization-modulating neurons.

A general all-optical implementation scheme for bipolar neural networks is presented. Bipolar operation is realized by exploiting two orthogonal light polarizations. A three-layer feed-forward bipolar network is demonstrated experimentally by using a liquid-crystal light valve for implementing an array of polarization modulating neurons.