In Vitro Photodynamic Inactivation of Cryptococcus neoformans Melanized Cells with Chloroaluminum Phthalocyanine Nanoemulsion

The selection of fungi resistant to currently used fungicides and the emergence of new pathogenic species make the development of alternative fungus-control techniques highly desirable. Photodynamic antimicrobial chemotherapy (PACT) is a promising method which combines a nontoxic photosensitizer (PS) with visible light to cause selective killing of microbial cells. The development of PACT to treat mycoses or kill fungi in the environment depends on identifying effective PS for the different pathogenic species and delivery systems able to expand and optimize their use. In the present study, the in vitro susceptibility of Cryptococcus neoformans melanized cells to the photodynamic effects of the PS agent ClAlPc in nanoemulsion (ClAlPc/NE) was examined. Cells were killed in a PS concentration- and light dose-dependent manner. Treatment with ClAlPc/NE, using PS concentrations (e.g. 4.5 mu m) and light doses (e.g. 10 J cm-2) compatible with PACT, resulted in a reduction of up to 6 logs in survival. Washing the cells to remove unbound PS before light exposure did not inhibit fungal photodynamic inactivation. Internalization of ClAlPc by C.neoformans was confirmed by confocal fluorescence microscopy, and the degree of uptake was dependent on PS concentration.

Infrared (810 nm) Low-Level Laser Therapy in Experimental Model of Strain-Induced Skeletal Muscle Injury in Rats: Effects on Functional Outcomes

Muscle strains are among the most prevalent causes for athletes absence from sport activities. Low-level laser therapy (LLLT) has recently emerged as a potential contender to nonsteroidal anti-inflammatory drugs in muscle strain treatment. In this work we investigated effects of LLLT and diclofenac on functional outcomes in the acute stage after muscle strain injury in rats. Muscle strain was induced by overloading the tibialis anterior muscle of rats during anesthesia. The injured groups received either no treatment, or a single treatment with diclofenac 30 min prior to injury, or LLLT (810 nm, 100 mW) with doses of 1, 3, 6 or 9 J, at 1 h after injury. Functional outcome measures included a walking index and assessment of electrically induced muscle performance. All treatments (except 9 J LLLT) significantly improved the walking index 12 h postinjury compared with the untreated group. The 3 J group also showed a significantly better walking index than the drug group. All treatments significantly improved muscle performance at 6 and 12 h. LLLT dose of 3 J was as effective as the pharmacological agent in improving functional outcomes in the early phase after a muscle strain injury in rats.

Observation of vinylidene emission in mixed phosphine/diimine complexes of Ru(II) at room temperature in solution

The mixed ruthenium(II) complexes trans-[RuCl(2)(PPh(3))(2)(bipy)] (1), trans-[RuCl(2)(PPh(3))(2)(Me(2)bipy)](2), cis-[RuCl(2)(dcype)(bipy)](3), cis-[RuCl(2)(dcype)(Me(2)bipy)](4) (PPh(3) = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2'-bipyridine, Me(2)bipy = 4,4'-dimethyl-2,2'-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(=C=CHPh)(PPh(3))(2)(bipy)]PF(6) (5), [RuCl(=C=CHPh)(PPh(3))(2)(Me(2)bipy)]PF(6) (6), [RuCl(=C=CHPh)(dcype)(bipy)]PF(6) (7), [RuCl(=C=CHPh)(dcype)(bipy)]PF(6) (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the pi-pi* excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH(2)Cl(2), CH(3)CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(-0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry. (C) 2011 Elsevier B.V. All rights reserved.

In vitro evaluation of combined hyperthermia and photodynamic effects using magnetoliposomes loaded with cucurbit[7]uril zinc phthalocyanine complex on melanoma

The aims of this study were two fold; to develop magnetoliposomes (MLs) loaded with zinc phthalocyanine (ZnPc) complexed with cucurbituril (CB) (CB:ZnPc-MLs) and to evaluate their in vitro photodynamic (PD) and/or hyperthermia (HT) effects while using melanoma cells (B16-F10) as model. The liposomal formulations were characterized by both average diameter and zeta potential. The vesicle average size ranged from 150 to 200 nm and the polydispersity index (PdI) from 0.093 to 0.230. The zeta potential was significantly positive with values between 48 and 57 mV. The cell viability (CV) after PD and HT treatments was assessed by colorimetric MTI method. Melanoma cells were initially treated with the liposome formulation without light and magnetic field application, revealing cell viability not different from the control cells (p > 0.05). Photodynamic and hyperthermia assays were also applied separately, demonstrating that PD is more effective than HT in reducing the CV of the neoplastic cells. Combined application of both PD and HT treatments was even more effective in reducing the CV of B16-F10 cells. At the highest light dose (2 J/cm(2)) and under magnetic field activation the CV was about half than PD applied alone. Therefore, the use of the photosensitizer-loaded magnetoliposome for combined photodynamic therapy (PDT) and magnetohyperthermia (MHT) application can be considered as a potential tool to treat malignant melanoma. (C) 2012 Elsevier B.V. All rights reserved.

Photo-induced electron transfer in supramolecular materials of titania nanostructures and cytochrome c

In the present paper, we report on the molecular interaction and photochemistry of TiO2 nanoparticles (NPs) and cytochrome c systems for understanding the effects of supramolecular organization and electron transfer by using two TiO2 structures: P25 TiO2 NPs and titanate nanotubes. The adsorption and reduction of cytochrome c heme iron promoted by photo-excited TiO2, arranged as P25 TiO2 NPs and as nanotubes, were characterized using electronic absorption spectroscopy, thermogravimetric analysis, and atomic force microscopy. In an aqueous buffered suspension (pH 8.0), the mass of cytochrome c adsorbed on the P25 TiO2 NP surface was 2.3 fold lower (0.75 mu g m(-2)) than that adsorbed on the titanate nanotubes (1.75 mu g m(-2)). Probably due to the high coverage of titanate nanotubes by adsorbed cytochrome c, the low amount of soluble remaining protein was not as efficiently photo-reduced by this nanostructure as it was by the P25 TiO2 NPs. Cytochrome c, which desorbed from both titanium materials, did not exhibit changes in its redox properties. In the presence of the TiO2 NPs, the photo-induced electron transfer from water to soluble cytochrome c heme iron was corroborated by the following findings: (i) identification by EPR of the hydroxyl radical production during the irradiation of an aqueous suspension of TiO2 NPs, (ii) impairment of a cytochrome c reduction by photo-excited TiO2 in the presence of dioxane, which affects the dielectric constant of the water, and (iii) change in the rate of TiO2-promoted cytochrome c reduction when water was replaced with D2O. The TiO2-promoted photo-reduction of cytochrome c was reverted by peroxides. Cytochrome c incorporated in the titanate nanotubes was also reversibly reduced under irradiation, as confirmed by EPR and UV-visible spectroscopy.

Photoprotection and the Photophysics of Acylated Anthocyanins

The proposed role of anthocyanins in protecting plants against excess solar radiation is consistent with the occurrence of ultrafast (525 ps) excited-state proton transfer as the major de-excitation pathway of these molecules. However, because natural anthocyanins absorb mainly in the visible region of the spectra, with only a narrow absorption band in the UV-B region, this highly efficient deactivation mechanism would essentially only protect the plant from visible light. On the other hand, ground-state charge-transfer complexes of anthocyanins with naturally occurring electron-donor co-pigments, such as hydroxylated flavones, flavonoids, and hydroxycinnamic or benzoic acids, do exhibit high UV-B absorptivities that complement that of the anthocyanins. In this work, we report a comparative study of the photophysics of the naturally occurring anthocyanin cyanin, intermolecular cyanincoumaric acid complexes, and an acylated anthocyanin, that is, cyanin with a pendant coumaric ester co-pigment. Both inter- and intramolecular anthocyaninco-pigment complexes are shown to have ultrafast energy dissipation pathways comparable to those of model flavylium cationco-pigment complexes. However, from the standpoint of photoprotection, the results indicate that the covalent attachment of co-pigment molecules to the anthocyanin represents a much more efficient strategy by providing the plant with significant UV-B absorption capacity and at the same time coupling this absorption to efficient energy dissipation pathways (ultrafast internal conversion of the complexed form and fast energy transfer from the excited co-pigment to the anthocyanin followed by adiabatic proton transfer) that avoid net photochemical damage.

Photophysical properties and interactions of xanthene dyes in aqueous micelles

Photosensitizers (PS) photodynamic activities are regulated by their location in the biological target, which modulates their photophysical and photochemical features. In this work the PS partition for the Xanthene Dyes Fluorescein (FSC), Eosin Y(EOS), Erythrosin B (ERY) and Rose Bengal B (RBB) in biomimetic models (SDS, CTAB and Pluronic P-123 micelles) and the effects on their photophysical characteristics are evaluated. The hydrophobic and electrostatic forces that govern the PS-micelle interaction are analyzed. At physiological pH (7.25), the ability of the dianionic protolytic form of the dyes to be positioned into the micelle palisade and its micelle interaction depends not only on the hydrophobicity of the dye but also on the micellar surface charge. The Binding Constants obey exactly the same order of the Partition Coefficients for the dyes in P-123 and CTAB micelles. The Stern-Volmer treatment pointed out that dyes are located inside the micelle, especially ERY and RBB. The magnitude of the dye-micelle interaction increased from SDS, P-123 and finally CTAB micelles due to the charges between dye and micelle, and among the xanthenes, their hydrophobic characteristics. Within the micelle pseudo phase, ERY and RBB are still very efficient photosensitizers exhibiting high quantum yield of singlet oxygen, which turns them very attractive especially with P-123 polymeric system as drug delivery systems in photodynamic therapy. (C) 2012 Elsevier B.V. All rights reserved.

Photo- and electroluminescence in a series of PPV type terpolymers containing fluorene, thiophene and phenylene units

The emissive properties of terpolymers with fluorene, thiophene and phenylene groups, forming alternating PPV type structures, are discussed in terms of their composition, photo- and electroluminescence properties. The fluorene groups were inserted in each phenylene-vinylene and thiophene-vinylene units, and their concentration did not vary, representing 50% of the molar composition. The ratio of thiophene-vinylene/phenylene-vinylene varied in the range 25,50 and 75%. Photo- and electroluminescence properties were strongly dependent on the thiophene-vinylene content and were compared with the fluorene-vinylene-thiophene and fluorene-vinylene-phenylene parent copolymers. (C) 2012 Elsevier B.V. All rights reserved.

Photoisomerization for a model protonated Schiff base in solution: Sloped/peaked conical intersection perspective

The topographical character of conical intersections (CIs)-either sloped or peaked-has played a fundamental and important role in the discussion of the efficiency of CIs as photochemical "funnels." Here this perspective is employed in connection with a recent study of a model protonated Schiff base (PSB) cis to trans photoisomerization in solution [Malhado et al., J. Phys. Chem. A 115, 3720 (2011)]. In that study, the calculated reduced photochemical quantum yield for the successful production of trans product versus cis reactant in acetonitrile solvent compared to water was interpreted in terms of a dynamical solvent effect related to the dominance, for the acetonitrile case, of S-1 to S-0 nonadiabatic transitions prior to the reaching the seam of CIs. The solvent influence on the quantum yield is here re-examined in the sloped/peaked CI topographical perspective via conversion of the model's two PSB internal coordinates and a nonequilibrium solvent coordinate into an effective branching space description, which is then used to re-analyze the generalized Langevin equation/surface hopping results. The present study supports the original interpretation and enriches it in terms of topographical detail. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754505]

Adjunct effect of the antimicrobial photodynamic therapy to an association of non-surgical and surgical periodontal treatment in modulation of gene expression

Background: This study has evaluated the effect of antimicrobial photodynamic therapy (aPDT) used in conjunction with non-surgical and surgical periodontal treatment (PT) in modulating gene expression during periodontal wound healing. Methods: Fifteen patients with chronic periodontitis, presenting bilaterally lower molars with class III furcation lesions and scheduled for extraction, were selected. In initial therapy, scaling and root planing (SRP) was performed in the Control Group (CG), while SRP + aPDT were performed in the Test Group (TG). 45 days later, flap surgery plus SRP, and flap surgery plus SRP + aPDT were performed in the CG and TG, respectively. At 21 days post-surgery, the newly formed granulation tissue was collected, and Real-time PCR evaluated the expression of the genes: tumor necrosis factor-?, interleukin-1?, interleukin-4, interleukin-10, matrix metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinase-2 (TIMP-2), osteoprotegerin (OPG), receptor activator of nuclear factor- ?B ligand (RANKL), type I collagen, alkaline phosphatase, osteopontin, osteocalcin, and bone sialoprotein. Results: There were statistically significant differences between the groups in relation to mRNA levels for MMP-2 (TG = 3.26 ± 0.89; CG = 4.23 ± 0.97; p = 0.01), TIMP-2/MMP-2 ratio (TG = 0.91 ± 0.34; CG = 0.73 ± 0.32; p = 0.04), OPG (TG = 0.84 ± 0.45; CG = 0.30 ± 0.26; p = 0.001), and OPG/RANKL ratio (TG = 0.60 ± 0.86; CG = 0.23 ± 0.16; p = 0.04), favoring the TG. Conclusion: The present data suggest that the aPDT associated to nonsurgical and surgical periodontal therapy may modulate the extracellular matrix and bone remodeling by up regulating the TIMP- 2/MMP-2 and OPG/RANKL mRNA ratio, but the clinical relevance needs to be evaluated in further studies.

Computational chemistry studies of UV induced processes in human skin

This thesis presents and uses the techniques of computational chemistry to explore two different processes induced in human skin by ultraviolet light. The first is the transformation of urocanic acid into a immunosuppressing agent, and the other is the enzymatic action of the 8-oxoguanine glycosylase enzyme. The photochemistry of urocanic acid is investigated by time-dependent density functional theory. Vertical absorption spectra of the molecule in different forms and environments is assigned and candidate states for the photochemistry at different wavelengths are identified. Molecular dynamics simulations of urocanic acid in gas phase and aqueous solution reveals considerable flexibility under experimental conditions, particularly for for the cis isomer where competition between intra- and inter-molecular interactions increases flexibility. A model to explain the observed gas phase photochemistry of urocanic acid is developed and it is shown that a reinterpretation in terms of a mixture between isomers significantly enhances the agreement between theory and experiment , and resolves several peculiarities in the spectrum. A model for the photochemistry in the aqueous phase of urocanic acid is then developed, in which two excited states governs the efficiency of photoisomerization. The point of entrance into a conical intersection seam is shown to explain the wavelength dependence of photoisomerization quantum yield. Finally some mechanistic aspects of the DNA repair enzyme 8-oxoguanine glycosylase is investigated with density functional theory. It is found that the critical amino acid of the active site can provide catalytic power in several different manners, and that a recent proposal involving a SN1 type of mechanism seems the most efficient one.

Liquid crystal polymers: macromolecular design for enhanced performances

During this work, done mainly in the laboratories of the department of Industrial Chemistry and Materials of the University of Bologna but also in the laboratories of the Carnegie Mellon University in collaboration with prof. K. Matyjaszewski and at the university of Zaragoza in collaboration with prof. J. Barberá, was focused mainly on the synthesis and characterization of new functional polymeric materials. In the past years our group gained a deep knowledge about the photomodulation of azobenzene containing polymers. The aim of this thesis is to push forward the performances of these materials by the synthesis of well defined materials, in which, by a precise control over the macromolecular structures, better or even new functionality can be delivered to the synthesized material. For this purpose, besides the rich photochemistry of azoaromatic polymers that brings to the application, the control offered from the recent techniques of controlled radical polymerization, ATRP over all, gives an enormous range of opportunity for the developing of a new generation of functional materials whose properties are determinate not only by the chemical nature of the functional center (e.g. azoaromatic chromophore) but are tuned and even amplified by a synergy with the whole macromolecular structure. Old materials in new structures. In this contest the work of this thesis was focused mainly on the synthesis and characterization of well defined azoaromatic polymers in order to establish, for the first time, precise structure-properties correlation. In fact a series of well defined different azopolymers, chiral and achiral, with different molecular weight and highly monodisperse were synthesized and their properties were studied, in terms of photoexpansion and photomodulation of chirality. We were then able to study the influence of the macromolecular structure in terms of molecular weight and ramification on the studied properties. The huge amount of possibility offered by the tailoring of the macromolecular structure were exploited for the synthesis of new cholesteric photochromic polymers that can be used as a smart label for the certification of the thermal history of any thermosensitive product. Finally the ATRP synthesis allowed us to synthesize a total new class of material, named molecular brushes: a flat surface covered with an ultra thin layer of polymeric chain covalently bond onto the surface from one end. This new class of materials is of extreme interest as they offer the possibility to tune and manage the interaction of the surface with the environment. In this contest we synthesized both azoaromatic surfaces, growing directly the polymer from the surface, and mixed brushes: surfaces covered with incompatible macromolecules. Both type of surfaces acts as “smart” surfaces: the first it is able to move the orientation of a LC cell by simply photomodulation and, thanks to the robustness of the covalent bond, can be used as a command surface overcoming all the limitation due to the dewetting of the active layer. The second type of surface, functionalized by a grafting-to method, can self assemble the topmost layer responding to changed environmental conditions, exposing different functionality according to different environment.

Photochemie von ungesättigten Sternverbindungen

Photochemie von ungesättigten Sternverbindungen.Wirt-Gast-Systeme bei stilbenoiden Dendrimeren. Diese Arbeit beschäftigt sich mit der Synthese und denphotochemischen Eigenschaften stilbenoider und chalkonoiderSternverbindungen.Die Synthese der stilbenoiden Dendrimere gelingt über einekonvergente in einzelnen Generationen gekoppelteSynthesestrategie durch Wittig-Horner-Olefinierung inKombination mit einer Schutzgruppentechnik.Experimente mit den stibenoiden Dendrimeren 1. Generationhaben gezeigt, dass geänderte Belichtungsbedingungen(monochromatisches Licht in Gegenwart einesTriplett-Sensibilisators) die photochemische[2+2]Cycloaddition bzw. CC-Verknüpfung unterdrücken. Dabeiverläuft selektiv eine cis/trans-Isomerisierung, die füroptische Schaltung genutzt werden könnte.Mit Triplett-Sensibilisatoren wie Diacetyl oder Acetonkonnten auch Wirt-Gast-Systeme mit stilbenoiden Dendrimerengebildet werden. Das zeigt die Möglichkeit der Einlagerungvon Gastmolekülen in freie Kavitäten der Dendrimere.Die Synthese der chalkonoiden Sternverbindungen gelingt übereine dreifache Aldolkondensation des 1,3,5-Triacetylbenzolsmit unsubstituierten oder 3,4,5-trialkoxysubstituiertenBenzaldehyden. Mit einer geeigneten Verzweigungseinheitwurden auch Armbauteile zur Generationenerweiterungsynthetisiert.Die photochemischen Eigenschaften der chalkonoidenSternverbindungen in Lösung und im Festzustand wurdenstudiert und die entstandenen Produkte charakterisiert. BeiBelichtung im Festzustand läuft bei topochemischer Kontrolleeine Photodimerisierung unter Bildung eines Cyclobutanringsdurch Cycloaddition olefinischer Doppelbindungen ab, wobeiein Kopf-Schwanz-anti-Dimer erhalten wird. BeiPhotodimerisierung in Lösung entsteht einKopf-Kopf-anti-Dimer als Hauptprodukt. Das kann zur Syntheseder sonst schwer zugänglichen [4.4.4](1,3,5)Cyclophanegenutzt werden.

Design, synthesis and photochemical studies of stilbenoid dendrimers

Stilbenoid dendrimers with stilbene in the periphery and stilbene in periphery as well as core were synthesized by convergent approach except 2nd generation dendrimer with stilbene in the periphery as well as in core (D-5). All dendrimers were characterized by standard techniques such as 1H NMR, 13C NMR, MS and IR spectroscopy. The MALDI-TOF technique proved to be very helpful in the identification of the 2nd generation dendrimer (D-5) with a mass of 3231 a.m.u. The dendrimers were designed in such a way that an intramolecular photochemical CC bond formation was favored. As two stilbene units of the same molecule were close enough so they preferred an intramolecular cyclic process except for zero generation dendrimers. Apart from the cycloaddition, some E/Z isomerization and oligomer formation was also observed on irradiation. These processes were observed by 1H NMR and MALDI-TOF MS. The photochemical behavior was also studied by UV absorption spectroscopy. Irradiating by monochromatic light led to an initial E/Z isomerization and by prolonged irradiation, an irreversible cyclic structure was formed. The choice of the wavelength of incident light is very important as irradiation at 320 nm leads to a reversible E/Z isomerization and a non-reversible cyclobutane formation, but irradiation at 340 nm favors the one-way process E Z. The [2+2] cycloaddition of molecule Tm2De was also studied by irradiating thin films on a quartz surface. An AFM image was taken before irradiation, after 3 sec irradiation and after long irradiation (1 hour). AFM studies show that a short irradiation leads to a cyclic structure as formation of hills of about 20-30 nm on the surface. A prolonged irradiation leads to a CC cross linking which can be monitored on AFM images as disappearance of hills. The roughness goes back to an almost smooth surface. These results prove a very complex material transport, which accompanies the reaction in the surface region.

Synthese und Photochemie von Dendrimeren mit stilbenoiden Chromophoren

Dendrimere spielen als strukturtreue Nanopartikel eine herausragende Rolle. Ziel dieser Arbeit war, Dendrimere mit einer hohen Dichte an photoaktiven Chromophoren herzu-stellen und zu untersuchen. Dazu wurden die terminalen Aminogruppen von Poly(propylenimin)dendrimeren 1. und 2. Generation, Astramol DAB-Am-4R und DAB-Am-8R, mit Stilbenen und Styrylstilbenen als Chromophor verknüpft. Mittels Wittig-Horner- und Heck-Reaktion wurden (E)-Stilbene aufgebaut, die auf der einen Seite drei Propoxygruppen zur Verbesserung der Löslichkeit und auf der anderen Seite eine passende Funktionalität zur Verknüpfung mit dem dendritischen Core tragen. Als Verknüpfungsmethoden wurden die Verknüpfung als Amid (PSDA), Schiffsche Base (PSDS) und Harnstoff (PSDH) getestet. Die Schiffschen Basen wurden außerdem zur Erhöhung der Hydrolysestabilität zum sekundären Amin reduziert (PSDR und PQDR). Durch die Verknüpfung mit dem Core werden die stilbenoiden Chromophore sehr stark photoaktiviert. Das beruht auf einem Singulett-Energietransfer (Förster-Mechanismus) von Chromophor zu Chromophor. Dieser Prozeß konkurriert zu den Deaktivierungsprozessen, verlängert die mittlere S1-Lebensdauer und erhöht somit die Chancen der Photochemie. Der Styrylstilben-Chromophor hat darüber hinaus einen erheblichen Teil seiner UV-Absorbtion bereits im Tageslicht und photopolymerisiert daher bereits im Tageslicht. Vor allem bei den Dendrimeren 2. Generation stellte sich die Frage nach der vollständigen, d.h. achtfachen Umsetzung; das Core sollte als Knäuel vorliegen, die Arme zum Teil nach innen gefaltet und somit dem Reaktand nur bedingt zugänglich. Auch dort konnten unter optimierten Reaktionsbedingungen alle Aminogruppen umgesetzt werden. Die vollständige Umsetzung der Dendrimere wurde mittels NMR und massenspektroskopischen Methoden untersucht. Bei den Absorptionsspektren der Dendrimere 1. Generation ändert sich die Lage der Maxima je nach Art der Verknüpfung der Chromophore mit dem Core. Die Verlängerung des Chromophors um eine Styryleinheit bedingt eine beträchtliche Rotverschiebung. Die Lage der Emissionsmaxima differiert stärker als die Lage der Absorptionsmaxima. Den geringsten Stokes-Shift weist der Harnstoff auf, dann folgt das sekundäre Amin, dann die Schiffsche Base. Dies weist auf unterschiedlich relaxierte S1-Geometrien hin. Die Verbindungen PSDS1, PSDR1 und PSDH1 aus 3,4,5-Tripropoxystilbeneinheit und Astramol-Core 1. Generation DAB-Am-4 wurden in einer Konzentration von 10-5 mol/L belichtet. Der vollständige Photoabbau durch Belichtung in Chloroform mit einer Xenon-Lampe erfolgte ohne jeglichen Filter innerhalb von zehn Minuten (PSDH1), 20 Minuten (PSDR1) und einer Stunde (PSDS1). Allen drei Verbindungen gemeinsam ist das Entstehen eines intermediären neuen Maximums geringer Intensität, das um etwa 100 nm bathochrom verschoben ist. Das Harnstoffsystem weist außerdem ein weiteres intermediäres Maximum bei 614 nm auf. Diese Maxima können (laut früherer Untersuchungen) durch Oxidation entstandenen chinoiden Strukturen zugeordnet werden, deren Lebensdauer (im Sekundenbereich) zu kurz für eine NMR-Charakterisierung ist. PSDR1 wurde außerdem bei höheren Konzentrationen (10-4 und 10-3 mol/L) mit einer Quecksilberlampe mit Pyrex-Filter (lambda > 300 nm) belichtet. Dabei wird, wie erwartet, eine Verbreiterung der NMR-Signale beobachtet. Es bildet sich zunächst cis-Stilben. Außerdem läßt sich bei 4.3 ppm ein Signal beobachten, das von inter- oder intramolekular gebildeten Methinprotonen herrührt. Auch wenn laut MOPAC- und Kraftfeldrechnung die Doppelbindungen ungünstig für eine [pi2s + pi2s]-Cyclodimerisierung zueinander stehen, kann im photochemisch angeregten Zustand eine Geometrie vorherrschen, die die intramolekulare Kopf-Kopf-Cyclobutanbildung ermöglicht. Die massenspektrometrischen Untersuchungen der Belichtungsprodukte (FD, ESI, MALDI-TOF) zeigen als höchste Masse lediglich das Monomer. Allerdings kann dadurch nicht auf eine rein intramolekulare Reaktion geschlossen werden. Die fortschreitende statistische CC-Verknüpfung kann schnell zu vernetzten Nanopartikeln führen, die im Massenspektrometer nicht fliegen. Die NMR-Spektren der mit zunehmender Vernetzung immer schlechter löslich werdenden Teilchen belegen die Oligomerisierung.