Relaxation process of photoexcited berberine via aggregation and dissociation state-dependent intramolecular electron transfer.

The fluorescence quantum yield of berberine in aqueous solution is significantly smaller than those of organic solution. The time profile of fluorescence intensity of berberine was analyzed by a bi-exponential function, showing that two kinds of states of berberine exist in the solutions. The observed fluorescence lifetime of shorter lifetime species of berberine in water (0.

Evaluation of the photosensitizer activity of hydrophobic phosphorus(V)porphyrins using the absorption spectral change of 1-benzyl-1,4-dihydronicotinamide.

Under visible light irradiation, water-insoluble P(V)porphyrins oxidized 1-benzyl-1,4-dihydronicotinamide (BNADH), a model compound for nicotinamide adenine dinucleotide, and diminished the typical absorption of BNADH at around 340 nm. A singlet oxygen quencher, sodium azide, partially inhibited photosensitized BNADH oxidation. This BNADH oxidation photosensitized by P(V)porphyrins in the presence of sodium azide can be explained by electron transfer oxidation from BNADH to the photoexcited P(V)porphyrins.

Protein Photodamaging Activity and Photocytotoxic Effect of an Axial-Connecting Phosphorus(V)porphyrin Trimer.

An axial-connecting trimer of the porphyrin phosphorus(V) complex was synthesized to evaluate the relaxation process of the photoexcited state and the photosensitizer activity. The photoexcitation energy was localized on the central unit of the phosphorus(V)porphyrin trimer. The photoexcited state of the central unit was relaxed through a process similar to that of the monomer phosphorus(V)porphyrin.

Photosensitized Protein Damage by DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin Through Electron Transfer: Activity Control Through Self-aggregation and Dissociation.

DiethyleneglycoxyP(V)tetrakis(p-n-butoxyphenyl)porphyrin (EGP(V)TBPP) forms a self-aggregation in an aqueous solution, and the photoexcited state of this molecule was effectively deactivated. Association with human serum albumin (HSA), a water-soluble protein, causes dissociation of the self-aggregation, resulting in recovery of the photosensitizer activity of EGP(V)TBPP. Under visible light irradiation, EGP(V)TBPP photosensitized HSA oxidation.

Phenothiazine Dyes Induce NADH Photooxidation through Electron Transfer: Kinetics and the Effect of Copper Ions.

Phenothiazine dyes, methylene blue, new methylene blue, azure A, and azure B, photosensitized the oxidation of nicotinamide adenine dinucleotide (NADH), an important coenzyme in the living cells, through electron transfer. The reduced forms of these phenothiazine dyes, which were produced through electron extraction from NADH, underwent reoxidation to the original cationic forms, leading to the construction of a photoredox cycle. This reoxidation process was the rate-determining step in the photoredox cycle.

Fluorescence lifetime probes for detection of RNA degradation.

To investigate RNA degradation in live cells, detection methods that do not require RNA extraction from cells are necessary. In this study, we examined the utility of fluorescence lifetime measurements using a probe attached to the end of an RNA molecule for detecting RNA degradation. We optimized a short fluorescein-labeled RNA sequence whose fluorescence lifetime varied significantly before and after degradation.

Photooxidation Activity Control of Dimethylaminophenyl-tris-(-methyl-4-pridinio)porphyrin by pH.

To control the activity of photodynamic agents by pH, an electron donor-connecting cationic porphyrin, -(,-dimethyl-4-aminophenyl)-tris(-methyl--pyridinio)porphyrin (DMATMPyP), was designed and synthesized. The photoexcited state (singlet excited state) of DMATMPyP was deactivated through intramolecular electron transfer under a neutral condition. The p of the protonated DMATMPyP was 4.

Controlled Photodynamic Action of Axial Fluorinated DiethoxyP(V)tetrakis(-methoxyphenyl)porphyrin through Self-Aggregation.

DiethoxyP(V)tetrakis(-methoxyphenyl)porphyrin (EtP(V)TMPP) and its fluorinated derivative (FEtP(V)TMPP) were synthesized to examine their photodynamic action. These P(V)porphyrins were aggregated in an aqueous solution, resulting in the suppression of their photodynamic activity. In the presence of human serum albumin (HSA), a water-soluble protein, the aggregation states were resolved and formed a binding complex between P(V)porphyrin and HSA.

Sequence selective photoinduced electron transfer of a pyrene-porphyrin dyad to DNA.

The binding modes of a pyrene-porphyrin dyad, (1-pyrenyl)-tris(N-methyl-p-pyridino)porphyrin (PyTMpyP), to various DNAs (calf thymus DNA (Ct-DNA), poly[d(G-C)2], and poly[d(A-T)2]) have been investigated using circular dichroism and linear dichroism measurements. Based on the polarization spectroscopic results, it can be shown that the pyrenyl and porphryin planes are skewed to a large extent for PyTMPyP in an aqueous environment and in the binding site of poly[d(G-C)2]. In this complex, a photoinduced electron transfer (PET) process between the pyrenyl and porphyrin moieties occurs.

Kinetics of Spontaneous Bimetallization between Silver and Noble Metal Nanoparticles.

A physical mixture of polymer-protected Ag nanoparticles and Rh, Pd, or Pt nanoparticles spontaneously forms Ag-core bimetallic nanoparticles. The formed nanoparticles were smaller than the parent Ag nanoparticles. In the initial process of this reaction, the surface plasmon absorption of Ag nanoparticles diminished and then almost ceased within one hour.

Photosensitized Protein-Damaging Activity, Cytotoxicity, and Antitumor Effects of P(V)porphyrins Using Long-Wavelength Visible Light through Electron Transfer.

Photodynamic therapy (PDT) is a less-invasive treatment for cancer through the administration of less-toxic porphyrins and visible-light irradiation. Photosensitized damage of biomacromolecules through singlet oxygen (O) generation induces cancer cell death. However, a large quantity of porphyrin photosensitizer is required, and the treatment effect is restricted under a hypoxic cellular condition.

Mechanism of oxidative DNA damage induced by metabolites of carcinogenic naphthalene.

Naphthalene is a carcinogenic polycyclic aromatic hydrocarbon, to which humans are exposed as an air pollutant. Naphthalene is metabolized in humans to reactive intermediates such as 1,2-hydroxynaphthalene (1,2-NQH), 1,4-NQH, 1,2-naphthoquinone (1,2-NQ), and 1,4-NQ. We examined oxidative DNA damage by these naphthalene metabolites using P-labeled DNA fragments from human cancer-relevant genes.

Relationship between the photoinduced electron transfer and binding modes of a pyrene-porphyrin dyad to DNA.

The binding modes of a pyrene-porphyrin dyad, (1-pyrenyl)-tris(N-methyl-p-pyridino)porphyrin (PyTMpyP), to DNA and its photophysical properties have been investigated using various spectroscopic techniques. The circular dichroism (CD) spectrum of PyTMpyP bound to DNA (PyTMpyP-DNA) showed one negative and two positive bands in the Soret region. The CD signal in the pyrene absorption region was positive.

Photosensitized enzyme deactivation and protein oxidation by axial-substituted phosphorus(V) tetraphenylporphyrins.

The activity for photodynamic therapy of water-soluble cationic porphyrins, tetraphenylporphyrin P(V) complexes, was investigated. Bis(cyclohexylmethoxy)P(V)tetraphenylporphyrin (DCHMP(V)TPP), dichloroP(V)tetraphenylporphyrin (ClP(V)TPP), and dimethoxyP(V)tetraphenylporphyrin (DMP(V)TPP) could cause the photosensitized deactivation of tyrosinase. The tryptophan residue of human serum albumin (HSA) and several kinds of amino acids could be damaged by these P(V)porphyrins under visible light irradiation.

Photosensitized oxidation of nicotinamide adenine dinucleotide by diethoxyphosphorus(V)tetraphenylporphyrin and its fluorinated derivative: Possibility of chain reaction.

Water-soluble porphyrins, diethoxyphosphorus(V)tetraphenylporphyrin (EtP(V)TPP) and its fluorinated analogue (FEtP(V)TPP), decreased the typical absorption around 340nm of nicotinamide adenine dinucleotide (NADH) under visible light irradiation, indicating oxidative decomposition. A singlet oxygen quencher, sodium azide, and a triplet quencher, potassium iodide, slightly inhibited photosensitized NADH oxidation. However, these inhibitory effects were very small.

The molecular mechanism of photochemical internalization of cell penetrating peptide-cargo-photosensitizer conjugates.

In many drug delivery strategies, an inefficient transfer of macromolecules such as proteins and nucleic acids to the cytosol often occurs because of their endosomal entrapment. One of the methods to overcome this problem is photochemical internalization, which is achieved using a photosensitizer and light to facilitate the endosomal escape of the macromolecule. In this study, we examined the molecular mechanism of photochemical internalization of cell penetrating peptide-cargo (macromolecule)-photosensitizer conjugates.

Relaxation Process of Photoexcited meso-Naphthylporphyrins while Interacting with DNA and Singlet Oxygen Generation.

Electron donor-connecting cationic porphyrins meso-(1-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (1-NapTMPyP) and meso-(2-naphthyl)-tris(N-methyl-p-pyridinio)porphyrin (2-NapTMPyP) were designed and synthesized. DFT calculations speculate that the photoexcited states of 1- and 2-NapTMPyPs can be deactivated via intramolecular electron transfer from the naphthyl moiety to the porphyrin moiety. However, the quenching effect through the intramolecular electron transfer is insufficient, possibly due to the orthogonal position of the electron donor and the porphyrin ring and the relatively small driving force: Gibbs energies are 0.

Determination of Singlet Oxygen and Electron Transfer Mediated Mechanisms of Photosensitized Protein Damage by Phosphorus(V)porphyrins.

The mechanism of photosensitized protein damage byphosphorus(V) tetraphenylporphyrin derivatives (P(V)TPPs) wasquantitatively clarified. P(V)TPPs bound to human serum albumin(HSA), a water-soluble protein, and damaged its tryptophan residueduring photoirradiation. P(V)TPPs photosensitized singlet oxygen ((1)O(2))generation, and the contribution of (1)O(2) to HSA damage was confirmedby the inhibitory effect of sodium azide, a (1)O(2) quencher.

Effect of DNA microenvironment on photosensitized reaction of watersoluble cationic porphyrins.

Endogenous and exogenous photosensitizers induce DNA damage, leading to carcinogenesis. Further, DNA is an important target biomacromolecule of photodynamic therapy (PDT) for cancer. Since the solar-induced DNA damage and PDT reaction occur in a complex biological environment, the interaction between biomolecule and photosensitizer is important.

Nile blue can photosensitize DNA damage through electron transfer.

The mechanism of DNA damage photosensitized by Nile blue (NB) was studied using (32)P-5'-end-labeled DNA fragments. NB bound to the DNA strand was possibly intercalated through an electrostatic interaction. Photoirradiated NB caused DNA cleavage at guanine residues when the DNA fragments were treated with piperidine.

Singlet oxygen generating activity of an electron donor connecting porphyrin photosensitizer can be controlled by DNA.

To control the activity of singlet oxygen ((1)O2) generation by photosensitizer through interaction with DNA, the electron- donor-connecting water-soluble porphyrin, meso-(9-anthryl)tris(N-methyl-p-pyridinio)porphyrin (AnTMPyP), was designed and synthesized. Molecular orbital calculation speculated that the photoexcited state of AnTMPyP can be deactivated via intramolecular electron transfer from the anthracene moiety to the porphyrin moiety, forming a charge-transfer (CT) state. The electrostatic interaction between the cationic porphyrin and anionic DNA predicts a rise in the CT state energy, leading to the inhibition of the electron transfer quenching.

Photosensitized protein damage by dimethoxyphosphorus(V) tetraphenylporphyrin.

For the purpose of the basic study of photodynamic therapy, the activity of the water-soluble P(V)porphyrin, dimethoxyP(V)tetraphenylporphyrin chloride (DMP(V)TPP), on photosensitized protein damage was examined. The quantum yield of singlet oxygen generation by DMP(V)TPP (0.64) was comparable with that of typical porphyrin photosensitizers.

Controlled generation of singlet oxygen by a water-soluble meso-pyrenylporphyrin photosensitizer through interaction with DNA.

An electron donor-connecting water-soluble porphyrin, meso-(1-pyrenyl)-tris(N-methyl-p-pyridinio)porphyrin, did not demonstrate singlet oxygen generating activity under photo-irradiation. The interaction with DNA successfully recovered the photosensitized singlet oxygen generation by this porphyrin.

Dynamics of singlet oxygen generation by DNA-binding photosensitizers.

The dynamics of photosensitized singlet oxygen generation in a DNA microenvironment were examined using the DNA-binding photosensitizers berberine and palmatine. These photosensitizers generate singlet oxygen only under interaction with DNA because the singlet excited state deactivates rapidly in a nonbinding environment. A kinetic study demonstrated the reaction process whereby singlet oxygen is generated through energy transfer from the triplet excited state of DNA-binding berberine (or palmatine) to molecular oxygen.

Control of singlet oxygen generation photosensitized by meso-anthrylporphyrin through interaction with DNA.

To control the activity of photosensitized singlet oxygen ((1)O(2)) generation, the electron donor-connecting porphyrin, 5-(9'-anthryl)-10,15,20-tris(p-pyridyl)porphyrin (AnTPyP), was designed and synthesized. AnTPyP became water-soluble by the protonation of the pyridyl moieties in the presence of 5 mM trifluoroacetic acid (pH 2.3).