4. Survey of Novel Multiphoton Active Materials 1257 4.1. Multiphoton Absorbing Systems 1257 4.2. Organic Molecules 1257 4.3. Organic Liquids and Liquid Crystals 1259 4.4. Conjugated Polymers 1259 4.4.1. Polydiacetylenes 1261 4.4.2. Polyphenylenevinylenes (PPVs) 1261 4.4.3. Polythiophenes 1263 4.4.4. Other Conjugated Polymers 1265 4.4.5. Dendrimers 1265 4.4.6. Hyperbranched Polymers 1267 4.5. Fullerenes 1267 4.6. Coordination and Organometallic Compounds 1271 4.6.1. Metal Dithiolenes 1271 4.6.2. Pyridine-Based Multidentate Ligands 1272 4.6.3. Other Transition-Metal Complexes 1273 4.6.4. Lanthanide Complexes 1275 4.6.5. Ferrocene Derivatives 1275 4.6.6. Alkynylruthenium Complexes 1279 4.6.7. Platinum Acetylides 1279 4.7. Porphyrins and Metallophophyrins 1279 4.8. Nanoparticles 1281 4.9. Biomolecules and Derivatives 1282 5. Nonlinear Optical Characterizations of Multiphoton Active Materials 1282

Multiphoton Absorbing Materials : Molecular Designs, Characterizations, and Applications

Half of all insect species are dependent on living plant tissues, consuming about 10% of plant annual production in natural habitats and an even greater percentage in agricultural systems, despite sophisticated control measures. Plants are generally remarkably well-protected against insect attack, with the result that most insects are highly specialized feeders. The mechanisms underlying plant resistance to invading herbivores on the one side, and insect food specialization on the other, are the main subjects of this book. For insects these include food-plant selection and the complex sensory processes involved, with their implications for learning and nutritional physiology, as well as the endocrinological spects of life cycle synchronization with host plant phenology. In the case of plants exposed to insect herbivores, they include the activation of defence systems in order to minimize damage, as well as the emission of chemical signals that may attract natural enemies of the invading herbivores and maybe exploited by neighbouring plants that mount defences as well.

Insect-plant biology

Human color vision is based on three light-sensitive pigments. The isolation and sequencing of genomic and complementary DNA clones that encode the apoproteins of these three pigments are described. The deduced amino acid sequences show 41 +/- 1 percent identity with rhodopsin. The red and green pigments show 96 percent mutual identity but only 43 percent identity with the blue pigment. Green pigment genes vary in number among color-normal individuals and, together with a single red pigment gene, are proposed to reside in a head-to-tail tandem array within the X chromosome.

https://science.sciencemag.org/content/sci/232/4747/193.full.pdf

Molecular genetics of human color vision: the genes encoding blue, green, and red pigments

https://www.cell.com/biophysj/pdf/S0006-3495(01)76183-8.pdf

Mechanisms of Tryptophan Fluorescence Shifts in Proteins

The retinal conformation and its environment in rhodopsin in light of a new 2.2 A crystal structure

An external point-charge model for bacteriorhodopsin to account for its purple color

An external point-charge model for wavelength regulation in visual pigments

Nonbleachable rhodopsins retaining the full natural chromophore

We studied the nature of the protein binding site of rhodopsin, using two-photon spectroscopy to assign the location of the low-lying "covalent" 1Ag*- -like pi pi * state in a model rhodopsin containing a locked-11-cis chromophore. The two-photon thermal lens maximum is observed at 22,800 cm-1, approximately equal to 2000 cm-1 above the one-photon absorption maximum, indicating that the protein environment has induced a level ordering reversal of the low-lying pi pi * states relative to that observed in retinyl Schiff bases in solution. The spectroscopic results clearly indicate that the chromophore is protonated and that the binding site is uncharged. Electrostatic energy contour maps of the binding site are calculated, showing possible locations for the external counterion(s). Two models of the binding site are proposed that accommodate the available spectroscopic data. One model involves a protonated Schiff base chromophore stabilized by a single negatively charged aspartic or glutamic acid residue. A more complicated model involving two residues (one charged, the other neutral) is also proposed. The latter model is interesting because it also accommodates the observed deuterium isotope effect in the form of a proton translocation between the two residues. The translocation is assumed to be a ground state process, initiated subsequent to the photoisomerization of the chromophore and energetically driven via destabilization of the counterion environment as a result of isomerization-induced charge separation.

https://www.pnas.org/content/pnas/82/12/4117.full.pdf

Two-photon spectroscopy of locked-11-cis-rhodopsin: evidence for a protonated Schiff base in a neutral protein binding site.

Im Zusammenhang mit Untersuchungen zur Interpretation der Absorptionseigenschaften von Retinen- Chromophoren bzw. Rhodopsin-Seh-Pigment-Systemen werden die Absorptionsdaten von ll-cis-Retinen (I), der Dihydroretinene (II)-(V), des Tetrahydroretinens (VI) sowie der entsprechenden durch Schiffbasenbildung entstehenden Rhodopsine ermittelt und vergleichend untersucht.

Valeria Balogh-Nair

Papers

An external point-charge model for bacteriorhodopsin to account for its purple color

An external point-charge model for wavelength regulation in visual pigments

Nonbleachable rhodopsins retaining the full natural chromophore

Two-photon spectroscopy of locked-11-cis-rhodopsin: evidence for a protonated Schiff base in a neutral protein binding site.

Hydroretinals and hydrorhodopsins