Abstract Dissolved organic matters are important photosensitizer for the photochemical reactions in natural water. In this study, the photochemical reactions sensitized by seawater were collected from Kaoshiung harbor and coastal areas. The steady-state concentrations of singlet oxygen [1O2]ss were determined by using furfuryl alcohol as a trapping agent. PNAP-PYR actinometer were used to measure the integrated intensity incident on the sample during sunlight irradiation. The objectives of this study are : ¡]1¡^ Measure the mean [1O2]ss of seawater in the Kaoshiung sea area. ¡]2¡^ Test the correlation between TOC and [1O2]ss ¡]3¡^ Test the correlation between UV-VIS A370 and [1O2]ss ¡]4¡^ Test the correlation between fluorescence and [1O2]ss According to the experimental results, we have found that sunlight of different seasons have quite an influence to [1O2]ss. Dissolved organic matters play an important role in photochemical reactions in natural waters although the results show non-significant correlation between dissolved organic matters and [1O2]ss. Then we use SPSS to calculate the correlation of [1O2]ss and TOC¡BUV-VIS A370¡Bfluorescence. Only UV-VIS A370 and [1O2]ss is apparently correlated ¡]P¡Õ0.05¡^. We suggest that [1O2]ss can be estimated via the following equation [1O2]ss¡Ñ1015 ¡× 11.81A370¡Ï6.49. On November 2000, the mean [1O2]ss of seawater observed in Da-Lin-Pu outfall area and Tso-Ying outfall area are 6.91 ¡Ñ 10-16 M and 2.13 ¡Ñ 10-16 M respectively.

Intramolecular singlet-singlet (SSET) and triplet-triplet (TTET) energy transfer have been studied in two cyclic octapeptides, 1A and 2A, and their open chain analogs, 1B and 2B. The peptides are constructed by a solid phase synthetic technique from enantiomerically pure amino acids with alternating chirality. Cyclic peptides with this arrangement of amino acids preferentially adopt flat, disk-like conformations where the peptide side chains lie on the outside of the ensemble. In 1A, benzophenone and naphthalene chromophores are incorporated as 4-benzoyl-L-phenylalanine and 2-naphtyl-L-alanine at positions 1 and 5 in the peptide sequence while in 2A, these chromophores occupy positions 1 and 3. Molecular modeling studies indicate that the interchromophore separation is larger in 1A than in 2A. This difference in separation is apparent from the observation of TTET energy transfer in 2A, which is consistent with the short range nature of TTET. Low temperature phosphorescence results indicate that intramolecular TTET is efficient in 2A and 2B and occurs with a rate of kTTET > 9.4x103 s-1. Intramolecular SSET occurs efficiently within these cyclic and open chain peptides. 1A undergoes intramolecular SSET from the naphthalene chromophore to the benzophenone chromophore with kSSET > 3.7x107 s-1, while in 2A with kSSET >3.0x107 s-1. Results obtained by modeling, UV-Visible spectroscopy, fluorescence and phosphorescence spectroscopies and transient absorption experiments are described.

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1 / Tingting Feng

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Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department: Department of Biophysics and Physical Chemistry Candidate: Lenka Hrubá Supervisor: Assoc. Prof. Veronika Nováková, Ph.D. Title of Thesis: Optimization of methods for determination of singlet oxygen production and fluorescence emission of azaphthalocyanine derivatives Photodynamic therapy (PDT) with a singlet oxygen as an essential agent is believed to be an alternative way of cancer treatment or treatment of some cutaneous diseases. The principle of PDT is based on excitation of a photosensitizer by light absorption, followed by transfer of energy to tissue oxygen (3 O2) forming cytotoxic singlet oxygen (1 O2). The efficiency by which photosensitizer transforms absorbed energy to singlet oxygen is characterized by singlet oxygen quantum yields (ΦΔ). The aim of this thesis was to develop and optimize absolute method for determination of ΦΔ. In comparison to a relative method, no reference is needed in this case, which enables accurate results with lower error. Verification of the new method was performed in N,N- dimethylformamide with a zinc phthalocyanine as a model photosensitizer because of its well-known ΦΔ and with 1,3-diphenylisobenzofuran as a chemical quencher of 1 O2. Different sources of light for excitation...

Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department Department of Biophysics and Physical Chemistry Candidate Jiří Demuth Supervisor Assoc. Prof. Veronika Nováková, PhD. Title of Thesis Synthesis and photophysical study of hydrophilic tetrapyridoporphyrazines bearing charged substituents on the periphery Phthalocyanines are planar organic molecules, which have a metal cation coordinated in their centre. This work deals with their aza-analogues - tetra-3,4-pyridoporphyrazines (TPyPz). TPyPz can absorb light in red part spectrum and then produce singlet oxygen. Due to this ability, they may be used in photodynamic therapy (PDT) of cancer. PDT's mechanism is based on three components: photosensitizer, light and singlet oxygen. Photosensitizer transfers energy of absorbed light to oxygen making, thus, cytotoxic singlet oxygen. The goal of this thesis was to synthesize water soluble TPyPzs absorbing in red part of absorption spectrum. TPyPzs bearing different charged substituents will be compared within the series. The synthesis consisted of preparation of 2-chloro-5,6-dimethylpyridine-3,4-dicarbonitrile (1), which was the starting precursor for other reactions. Nucleophilic substitution of 1 was used for the introducing of various hydrophilic substituents. Prepared precursors...

In photodynamic therapy (PDT), the combination of light, photosensitizer and molecular oxygen generates reactive oxygen species, including singlet oxygen (1O2), which is regarded as the primary cytotoxin and effector with most clinical photosensitizers. PDT has gained some acceptance for the treatment of cancer and other conditions. However, its clinical utility and effectiveness has been limited by variability in treatment response and failure to integrate adequate treatment planning and dosimetry. Direct PDT dosimetry through the detection of ultra-weak near-infrared 1O2 luminescence emission at 1270 nm (SOL) collapses the complexity of PDT into a single parameter, the 1O2 concentration. Prior to the present studies, it was shown that SOL was well correlated with PDT response in vitro and in vivo under controlled experimental conditions. However, SOL detection is technically challenging because of the very low radiative probability of 1O2 (~ 10-8 in biological environments), dynamic background signals and limited sensitivity of suitable photodetectors in this wavelength region. A technologically simpler and less costly PDT dosimetry approach is to use photosensitizer photobleaching to estimate the 1O2 dose. The first objective in this thesis was to characterize the dynamics of SOL measurements, in particular the influence of oxygen depletion, in order to improve the quantification of SOL and its use as an accurate PDT dose metric. Subsequently, direct comparison of SOL and photobleaching-based dosimetry during in vitro PDT treatment with meso-tetra(hydroxyphenyl)chlorin (mTHPC) showed that SOL dosimetry is robust but that photobleaching-based dosimetry can fail under hypoxic conditions. However, the latter can be salvaged through the identification of a previously unreported 613 nm emission from mTHPC that indicates hypoxia. These studies were carried forward into an in vivo dorsal skin-fold window chamber tumor model, which showed promising initial correlation between 1O2 dose and tumor response. This work also identified SOL detection limitations and opportunities for further development. Additionally, SOL measurements were used as a ‘gold standard’ to evaluate novel activatable PDT beacons and a novel “PDT biodosimeter” based on STAT3 cross-linking. Future work includes further tumor dose-response studies, characterization of novel photosensitizing agents, improvement on signal detection and processing, and studies in normal human skin.

In photodynamic therapy (PDT), the combination of light, photosensitizer and molecular oxygen generates reactive oxygen species, including singlet oxygen (1O2), which is regarded as the primary cytotoxin and effector with most clinical photosensitizers. PDT has gained some acceptance for the treatment of cancer and other conditions. However, its clinical utility and effectiveness has been limited by variability in treatment response and failure to integrate adequate treatment planning and dosimetry. Direct PDT dosimetry through the detection of ultra-weak near-infrared 1O2 luminescence emission at 1270 nm (SOL) collapses the complexity of PDT into a single parameter, the 1O2 concentration. Prior to the present studies, it was shown that SOL was well correlated with PDT response in vitro and in vivo under controlled experimental conditions. However, SOL detection is technically challenging because of the very low radiative probability of 1O2 (~ 10-8 in biological environments), dynamic background signals and limited sensitivity of suitable photodetectors in this wavelength region. A technologically simpler and less costly PDT dosimetry approach is to use photosensitizer photobleaching to estimate the 1O2 dose. The first objective in this thesis was to characterize the dynamics of SOL measurements, in particular the influence of oxygen depletion, in order to improve the quantification of SOL and its use as an accurate PDT dose metric. Subsequently, direct comparison of SOL and photobleaching-based dosimetry during in vitro PDT treatment with meso-tetra(hydroxyphenyl)chlorin (mTHPC) showed that SOL dosimetry is robust but that photobleaching-based dosimetry can fail under hypoxic conditions. However, the latter can be salvaged through the identification of a previously unreported 613 nm emission from mTHPC that indicates hypoxia. These studies were carried forward into an in vivo dorsal skin-fold window chamber tumor model, which showed promising initial correlation between 1O2 dose and tumor response. This work also identified SOL detection limitations and opportunities for further development. Additionally, SOL measurements were used as a ‘gold standard’ to evaluate novel activatable PDT beacons and a novel “PDT biodosimeter” based on STAT3 cross-linking. Future work includes further tumor dose-response studies, characterization of novel photosensitizing agents, improvement on signal detection and processing, and studies in normal human skin.

<p> An energy gap or "pseudogap", where there is spin pairing without phase coherence, has been observed in a number of unconventional superconductors that has been detected even above the superconducting transition. It has been proposed that this "pseudogap" region is intimately related to the appearance of high Tc superconductivity. Comparable spin gaps have been observed in a number of low dimensional quantum spin systems with a spin-singlet ground state. Therefore quantum magnets which show collective singlet ground states have been receiving much interest recently. </p> <p> As an example of these; CuGe03 is one of the few quasi-one dimensional magnetic insulators which displays a Spin-Peierls transition. This novel transition results from the coupling of the lattice with S=l/2 spin degrees of freedom to break transitional symmetry below some characteristic phase transition temperature, and a collective singlet magnetic ground state with a characteristic energy gap is observed. </p> <p> In my thesis I have studied the critical phenomena associated with the SpinPeierls transition which occurs in the inorganic compound Cul-xCdxGe03by means of Xray Scattering. I also conducted inelastic neutron scattering experiments and studied the temperature dependence of the singlet-triplet excitation of this system. I applied different theoretical methods to determine the best model describing the behavior observed for this material and compared the results with those obtained on the pure compound. </p> <p> There are few quasi two dimensional experimental examples of interacting dimers such as SrCu2(B03)2 which has been proposed as a realization of the Shastry-Sutherland model. This system has been modeled as Heisenberg spins in a square lattice with two exchange coupling constants of magnitudes J and J' along the diagonal and the edges of the lattice. Its ground state is known to be a collective singlet state. It is known theoretically that its ground state changes from a gapped singlet to a gapless antiferromagnetic state as a function of J/J'. Recently, subleading terms in the Hamiltonian have been considered, such as Dzyaloshinski-Moriya interactions, which are needed to understand the precise physical properties of this material. </p> <p> I performed high resolution, inelastic neutron scattering measurements on this material aim at clarifying the nature of the singlet-triplet excitation spectrum. The results revealed the dispersion relations along with the Q-dependence of the excitations. Finally, neutron powder diffraction measurements were also performed in order to investigate any possible structural phase transition in this material. </p> / Thesis / Master of Science (MSc)