Photodamage in a Mitochondrial Membrane Model Modulated by the Topology of Cationic and Anionic Meso‐Tetrakis Porphyrin Free Bases

The photodynamic effects of the cationic TMPyP (meso‐tetrakis [N‐methyl‐4‐pyridyl]porphyrin) and the anionic TPPS4 (meso‐tetrakis[4‐sulfonatophenyl]porphyrin) against PC/CL phosphatidylcholine/cardiolipin (85/15%) membranes were probed to address the influence of phorphyrin binding on lipid damage. Electronic absorption spectroscopy and zeta potential measurements demonstrated that only TMPyP binds to PC/CL large unilamellar vesicles (LUVs). The photodamage after irradiation with visible light was analyzed by dosages of lipid peroxides (LOOH) and thiobarbituric reactive substance and by a contrast phase image of the giant unilamellar vesicles (GUVs). Damage to LUVs and GUVs promoted by TMPyP and TPPS4 were qualitatively and quantitatively different. The cationic porphyrin promoted damage more extensive and faster. The increase in LOOH was higher in the presence of D₂O, and was impaired by sodium azide and sorbic acid. The effect of D₂O was higher for TPPS4 as the photosensitizer. The use of DCFH demonstrated that liposomes prevent the photobleaching of TMPyP. The results are consistent with a more stable TMPyP that generates long‐lived singlet oxygen preferentially partitioned in the bilayer. Conversely, TPPS4 generates singlet oxygen in the bulk whose lifetime is increased in D₂O. Therefore, the affinity of the porphyrin to the membrane modulates the rate, type and degree of lipid damage.     

Immobilization of porphyrins in poly(hydroxymethylsiloxane)

Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O₂(¹Δ_g) with the lifetime of 10–30 μs.     

Interaction of water‐soluble tetrakis‐(1‐methyl‐4‐pyridiniyl)‐porphyrin and CdS naonoparticles

The interaction between positively charged porphyrin TMPyP(4) (tetrakis‐(1‐methyl‐4‐pyridiniyl) porphyrin) and negatively charged surface of colloidal CdS nanoparticles has been studied by absorption spectrum, fluorescence spectroscopy, and time‐correlated single‐photon‐counting methods. Addition of CdS colloid to a TMPyP(4) solution leads to TMPyP(4) adsorption onto the surface of CdS colloid with an apparent association constant of 4643 L/mol. This adsorption results in distinct changes in absorption spectrum of TMPyP (4) and the quenching of its′ fluorescence, but the biexponential fluorescence decay changes hardly. Nearly 90% of the fluorescence of 5 × 10^?6 mol/L TMPyP(4) can be quenched with 1.5 × 10^?4 mol/L CdS colloid. These spectral changes are attributed to the formation of a certain form complex TMPyP(4)‐CdS.     

Interactions between meso-tetrakis(4-(<Emphasis Type="Italic">N</Emphasis>-methylpyridiumyl))porphyrin TMPyP4 and DNA G-quadruplex of telomeric repeated sequence TTAGGG

The binding properties between meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) and the parallel DNA G-quadruplex (G4) of telomeric repeated sequence 5′-TTAGGG-3′ have been characterized by means of circular dichroism, steady-state absorption, steady-state fluorescence and picosecond time-resolved fluorescence spectroscopies. The binding constant and the saturated binding number were determined as 1.29×10⁶ (mol/L)⁻¹ and 3, respectively, according to steady-state absorption spectroscopy. Based on the findings by the use of time-resolved fluorescence spectroscopic technique, it is deduced that TMPyP4 binds to a DNA G-quadruplex with both the thread-intercalating and end-stacking modes and at the saturated binding state, one TMPyP4 molecule intercalates into the intervals of G-tetrads while the other two stack to the ends of the DNA G-quadruplex. Supported by the National Natural Science Foundation of China (Grant Nos. 20442004, 10576002 and 20703067)     

Interaction of water-soluble bridged porphyrin with DNA

A water-soluble porphyrin dimer (Por Dimer) containing eight positive charges, bridged by 4,4′-dicarboxy-2,2′-bipyridine, has been synthesized. With Meso-tetrakis(N-methyl-pyridium-4-yl)porphyrin (H₂TMPyP) as the reference compound, the water-soluble porphyrin dimer was investigated for its interaction with DNA by absorption, fluorescence, and circular dichroism (CD) spectroscopy. The apparent affinity binding constant (K _app = 1.2 × 10⁶) of Por Dimer binding to CT DNA was measured by a competition method with ethidium bromide (EB) (that of H₂TMPyP was 6.9 × 10⁶). The cleavage ability of Por Dimer to pBR322 plasmid DNA was studied by gel electrophoresis. The results suggest that the binding modes of Por Dimer were complex and involve both intercalation and outside binding. __________ Translated from Acta Chimica Sinica, 2007, 65(22): 2597–2603     

Electronic and vibrational circular dichroism spectroscopic study of non-covalent interactions of meso-5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin with (dG-dC)10 and (dA-dT)10

The non-covalent interactions of (dG-dC)₁₀ and (dA-dT)₁₀ with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) were studied using the combination of electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectroscopy, and UV–vis and IR absorption spectroscopy at different ratios of both components r = [oligonucleotide]/[TMPyP] = 2/1–10/1 where [oligonucleotide] and [TMPyP] are the amount concentrations of oligonucleotide per base-pair and TMPyP, respectively. It was shown that TMPyP with (dG-dC)₁₀ provided hemiintercalative binding mode for r = 4/1 that is manifested in vibrational spectra: The absorption band assigned to the C6O6 stretching vibration of guanine is shifted from 1683 to 1672 cm⁻¹, the corresponding VCD couplet from 1694(−)/1674(+) to 1684(−)/1663(+) cm⁻¹ and its intensity decreases. The absorption band assigned to the C2O2 stretching vibration of cytosine is shifted from 1652 to 1644 cm⁻¹ and its intensity increases. TMPyP with (dA-dT)₁₀ provided three binding modes: (i) external binding to the phosphate backbone, (ii) external minor groove binding for the ratios >6/1 and (iii) external major groove binging associated with the partial B- to Z-transition for the ratios <4/1. The major groove binding is manifested in VCD spectra by the intensity decrease of the bands 1655 and 1638 cm⁻¹ assigned to the thymine vibrations while the bands assigned to the adenine vibrations are unchanged. In the (dA-dT)₁₀–TMPyP complexes, the external binding to the phosphate backbone accompanied by self-stacking of porphyrins along the phosphate backbone chain is preferred at temperatures higher than 40 °C.     

Interactions of tetrakis(4-N-methylpyridyl)porphyrin with cyclodextrins and disodium phthalate in aqueous solution

In pH 7.3 buffers, the interactions of a cationic porphyrin, tetrakis(4-N-methylpyridyl)porphyrin (TMPyP), with cyclodextrins (CDs) and disodium phthalate (DSP) have been examined by means of absorption, fluorescence, and induced circular dichroism spectroscopy. α-CD, β-CD, and γ-CD form a 1:1 inclusion complex with a TMPyP monomer, which dimerizes in solution without CD. TMPyP also forms a 1:1 organic cation–organic anion complex with DSP. The 1:1 TMPyP–DSP complex forms a ternary CD–TMPyP–DSP inclusion complex with α-, β-, and γ-CD, in which a DSP molecule is not incorporated into the CD cavity. From the fluorescence intensity change, the␣equilibrium constants have been evaluated for the formation of the inclusion complexes and the organic cation–anion complexes.     

Stable Anticancer Gold(III)–Porphyrin Complexes: Effects of Porphyrin Structure

In the design of physiologically stable anticancer gold(III) complexes, we have employed strongly chelating porphyrinato ligands to stabilize a gold(III) ion [Chem. Commun. 2003 , 1718; Coord. Chem. Rev. 2009 , 253, 1682]. In this work, a family of gold(III) tetraarylporphyrins with porphyrinato ligands containing different peripheral substituents on the meso‐aryl rings were prepared, and these complexes were used to study the structure–bioactivity relationship. The cytotoxic IC₅₀ values of [Au(Por)]⁺ (Por=porphyrinato ligand), which range from 0.033 to >100 μM , correlate with their lipophilicity and cellular uptake. Some of them induce apoptosis and display preferential cytotoxicity toward cancer cells than to normal noncancerous cells. A new gold(III)–porphyrin with saccharide conjugation [Au(4‐glucosyl‐TPP)]Cl ( 2 a ; H₂(4‐glucosyl‐TPP)=meso‐tetrakis(4‐β‐D ‐glucosylphenyl)porphyrin) exhibits significant cytostatic activity to cancer cells (IC₅₀=1.2–9.0 μM ) without causing cell death and is much less toxic to lung fibroblast cells (IC₅₀>100 μM ). The gold(III)–porphyrin complexes induce S‐phase cell‐cycle arrest of cancer cells as indicated by flow cytometric analysis, suggesting that the anticancer activity may be, in part, due to termination of DNA replication. The gold(III)–porphyrin complexes can bind to DNA in vitro with binding constants in the range of 4.9×10⁵ to 4.1×10⁶ dm³ mol^?1 as determined by absorption titration. Complexes 2 a and [Au(TMPyP)]Cl₅ ( 4 a ; [H₂TMPyP]⁴⁺=meso‐tetrakis(N‐methylpyridinium‐4‐yl)porphyrin) interact with DNA in a manner similar to the DNA intercalator ethidium bromide as revealed by gel mobility shift assays and viscosity measurements. Both of them also inhibited the topoisomerase I induced relaxation of supercoiled DNA. Complex 4 a , a gold(III) derivative of the known G‐quadruplex‐interactive porphyrin [H₂TMPyP]⁴⁺, can similarly inhibit the amplification of a DNA substrate containing G‐quadruplex structures in a polymerase chain reaction stop assay. In contrast to these reported complexes, complex 2 a and the parental gold(III)–porphyrin 1 a do not display a significant inhibitory effect (<10 %) on telomerase. Based on the results of protein expression analysis and computational docking experiments, the anti‐apoptotic bcl‐2 protein is a potential target for those gold(III)–porphyrin complexes with apoptosis‐inducing properties. Complex 2 a also displays prominent anti‐angiogenic properties in vitro. Taken together, the enhanced stabilization of the gold(III) ion and the ease of structural modification render porphyrins an attractive ligand system in the development of physiologically stable gold(III) complexes with anticancer and anti‐angiogenic activities.     

Study on the Intercalation and Interlayer State of Porphyrins into α-Zirconium Phosphate

In this work, a new approach for TMPyP [5,10,15,20-tetrakis (1-methylpyridinium-4-yl) porphyrin] and TMAPP [5,10,15,20-tetrakis (N,N,N-trimethyl-anilinium-4-yl) porphyrin] intercalation into α-phase of zirconium hydrogen phosphate (α-ZrP) was described: porphyrins were inserted through exchanging pre-intercalated alkylamine. Pre-intercalated n-butylamine (BA) could form either a mobile monolayer or a stable bilayer in α-ZrP. The exchange speed between porphyrins and BA in mobile monolayer is obviously faster than that in stable bilayer. Therefore mobility of spacers is one important intercalation factor. In addition, we investigated the interlayer state of TMPyP by XRD, visible spectrum, fluorescence spectrum and molecular modeling. The results collectively revealed that the porphyrin was orderly arranged with their planes inclined to the host lamella and was presented as monomer instead of aggregation in the gallery of α-ZrP.     

Study on the Intercalation and Interlayer State of Porphyrins into <Emphasis Type="Italic">α</Emphasis>-Zirconium Phosphate

In this work, a new approach for TMPyP [5,10,15,20-tetrakis (1-methylpyridinium-4-yl) porphyrin] and TMAPP [5,10,15,20-tetrakis (N,N,N-trimethyl-anilinium-4-yl) porphyrin] intercalation into α-phase of zirconium hydrogen phosphate (α-ZrP) was described: porphyrins were inserted through exchanging pre-intercalated alkylamine. Pre-intercalated n-butylamine (BA) could form either a mobile monolayer or a stable bilayer in α-ZrP. The exchange speed between porphyrins and BA in mobile monolayer is obviously faster than that in stable bilayer. Therefore mobility of spacers is one important intercalation factor. In addition, we investigated the interlayer state of TMPyP by XRD, visible spectrum, fluorescence spectrum and molecular modeling. The results collectively revealed that the porphyrin was orderly arranged with their planes inclined to the host lamella and was presented as monomer instead of aggregation in the gallery of α-ZrP.This revised version was published online in July 2005 with a corrected issue number.     

Aggregation and solution behavior of 5-(1-(4-carboxybutyl) pyridinum-4-yl) 10,15,20-tris (1-methylpyridinium-4-yl) porphyrin: A resonance light scattering, fluorescence and absorption spectroscopic study

Aggregation behavior of water soluble porphyrins, 5-(1-(4-carboxybutyl) pyridinum-4-yl) 10,15,20-tris (1-methylpyridinium-4-yl) porphyrin (5-CBPyP) in the presence of various concentrations of calf thymus DNA (ct-DNA) and sodium chloride were studied in comparison with meso-tetrakis (4-N-methyl pyridinum) porphyrin (TMPyP), by optical absorption, fluorescence and resonance light scattering (RLS) spectroscopies. Both porphyrins obey Beer’s law in extended range of concentration. Optical absorption and RLS measurements demonstrated nonaggregation for both porphyrins under increasing concentration of ct-DNA and NaCl. However, in comparison, 5-CBPyP had less tendency for aggregation that may be taken as an advantage for its probable application in photodynamic therapy of cancer. The trend of changes in absorption spectra of both porphyrins in the presence of ct-DNA indicates the homogeneous intercalation binding mode. The values of (2.81 ± 0.28) × 10⁶ M^?1 and (0.95 ± 0.09) × 10⁶ M^?1 were obtained for apparent binding constant of TMPyP and 5-CBPyP from analysis of optical absorption data, respectively. This indicates the less affinity of 5-CBPyP to ct-DNA in comparison with TMPyP. The binding of both porphyrins to ct-DNA quenches fluorescence emission of Ethidium bromide (EB) that is bound to ct-DNA. The quenching process obeys linear Stern-Volmer relationship indicating the displacement of EB from its binding sites by these porphyrins. The results of this technique also represent the intercalation mode of binding for both porphyrins and higher binding affinity of TMPyP compared with 5-CBPyP.     

Conformational conversion of DNA G-quadruplex induced by a cationic porphyrin

The interactions between cationic meso-tetrakis(4-(N-methylpyridiumyl))porphyrin (TMPyP4) and the G-quadruplex (G4) of human telomeric single-strand oligonucleotide d(TTAGGG)₂ (S12) have been investigated by means of circular dichroism (CD), UV–visible absorption and fluorescence spectroscopies. It is found that TMPyP4 can preferentially induce the conformational conversion of the G4 structure from the parallel type to the parallel/antiparallel mixture in the presence of K⁺, and that it can directly induce the formation of antiparallel G4 structure from the single-strand oligonucleotide S12 in the absence of K⁺. Furthermore, the comparable experiments of TMPyP4 with two single-strand oligonucleotides S6 d(TTAGGG) and S24 d(TAGGG(TTAGGG)₃T) in the absence of K⁺ show that TMPyP4 can also induce the formation of antiparallel G4 from S24 but not from S6, indicating that the end-loops of the G4 structure are the key factors for the formation of G4 induced by TMPyP4.     

Cationic Porphyrin–Anionic Surfactant Mixtures for the Promotion of Self‐Organized 1:4 Ion Pairs in Water with Strong Aggregation Properties

We performed a systematic study on the spectroscopic and aggregation properties of stoichiometric mixtures (1:4) of the tetracationic meso‐tetrakis(4‐N‐methylpyridinium)porphyrin (H₂TMPyP) and three sodium alkylsulfate surfactants (tetradecyl, hexadecyl, and octadecylsulfate) in an aqueous solution. The objective was to build a supramolecular aggregate, which would favor the internalization of tetracationic porphyrins in cells without chemical modification of the structure of the porphyrin. We show that stoichiometric H₂TMPyP/alkylsulfate (1:4) mixtures lead to the formation of large hollow spherical aggregates (60–160 nm). The TEM images show that the membrane of these aggregates are composed of smaller aggregates, which are probably rod‐like micelles. These rod‐like micelles have a hydrophobic core composed of the alkyl chains of the alkylsulfate surfactant, whereas the charged surface corresponds to the tetracationic porphyrins.     

Role of structure-proteins in the porphyrin–DNA interaction

We studied the complexation of meso-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP) with HeLa nucleosomes and compared it to our earlier results on T7 phage nucleoprotein complex (NP) and isolated DNA. To identify binding modes and relative concentrations of the bound TMPyP forms, the porphyrin absorption spectra were analyzed at various base pair/porphyrin ratios. Spectral decomposition and circular dichroism measurements proved that the two main binding modes of TMPyP, i.e., external binding and intercalation occur also in the nucleosomes. The DNA superstructure maintained by the proteins decreases its accessibility for TMPyP similarly in both nucleoproteins. A difference is observed between the partitioning of the two binding modes: in the case of nucleosome the ratio of intercalation to groove-binding is changed from 60/40 to 40/60 as determined for T7 NP and for isolated DNA-s. Using UV and CD melting studies, we revealed that TMPyP destabilizes the DNA–protein interaction in the nucleosomes but not in the T7 phage. Lastly, photoinduced reaction of bound TMPyP caused alterations in DNA structures and DNA–protein interactions within both nucleoprotein complexes; the nucleosomes were found to be more sensitive to the photoreaction.     

Photodynamic efficiency of porphyrins encapsulated in polysilsesquioxanes

Mesoporous organosilica-porphyrin composites were obtained by entrapment of 5,10,15,20-tetraphenylporphyrin (TPP) and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (TMPyP) into three polysilsesquioxanes prepared by the sol-gel method from 1,2-bis(triethoxysilyl)ethane, 1,6-bis(triethoxysilyl)hexane, and 1,8-bis(triethoxysilyl)octane. The materials were characterised by their texture and optical properties (fluorescence and absorbance) and by light-induced antimicrobial activity against E. coli BL21(DE3) (pET16bDsRed) strain.     

Study on spectroscopic characterization of Pd porphyrin and its interaction with ctDNA

The fluorescence and solid substrate room temperature phosphorescence (SS-RTP) properties of Pd(II) meso-tetrakis (4-N-methyl-pyridiniumyl) porphyrin (Pd(II)TMPyP) were studied. The factors influencing the SS-RTP emission, such as filter type, inorganic salt sort, drying temperature, pre-drying time and drying time were investigated in detail. Strong SS-RTP signal can be induced on the slow speed filter paper in the presence of the external inorganic salt, Ca(NO₃)₂, with the maximum excitation and emission wavelengths at 421 nm and 675 nm, respectively. The interaction between calf thymus DNA (ctDNA) and Pd(II)TMPyP was investigated at pH 7.2 using SS-RTP, fluorescence and UV-vis spectroscopy. The SS-RTP intensity of Pd(II)TMPyP was enhanced efficiently with the increasing amount of ctDNA. This phenomenon demonstrates that the intercalated porphyrin is shielded by ctDNA to avoid collision quenching. This result was supported by SS-RTP lifetime measurement, SS-RTP anion quenching experiment and fluorescence polarization measurement. Furthermore, with the addition of ctDNA, the UV-vis spectra of Pd(II)TMPyP shows apparent hypochromicity (40%) at the Soret maximum of 417 nm and a red shift of Δλ = 15 nm, also indicating that Pd(II)TMPyP intercalates into ctDNA bases. The binding constant of Pd(II)TMPyP to ctDNA was calculated to be 4.41 × 10⁵ L/mol based on the derivative McGhee-von Hippel plots.     

Silica covered porphyrin microstructures obtained in sol–gel processes

In this article, we report on the formation of well-defined highly emissive silica-covered porphyrin microstructures in base-catalyzed sol–gel processes. The microstructures were obtained by self-assembly of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (mTHPP) at room temperature. Tetraethoxysilane (TEOS) was used as a silica precursor. The hybrid mTHPP- silica particles were characterized by means of reflectance UV–Vis and microscopy techniques including atomic force microscopy, scanning electron microscopy (SEM) and confocal fluorescence microscopy (CM). The SEM and TEM observations revealed that depending on the porphyrin concentration used in the synthesis, the shape of the hybrid mTHPP-silica particles has changed from ribbon-like (c _mTHPP = 2.09 mM) to rhombus-like structures (c _mTHPP = 4.35 mM). The ribbons were straight-edged, uniform in width (1.2–1.8 μm) and height (350–400 nm), and variable in length (40–100 μm). The rhombs were 1–3.7 μm in height, 7–25 μm in length, and 3.5–15 μm in width, and the ratio of length to width was uniform and equal to ca. 1.8–2. UV–Vis absorption spectra indicated that the J-aggregates and H-aggregates formed in the systems with lower and higher porphyrin content, respectively. Formation of different type of porphyrin aggregates in both systems resulted in different emission spectra, as it was shown with CM.     

AFM‐Correlated CSM‐Coupled Raman/Fluorescence Studies on Selective Interactions of Water Soluble Porphyrins with DNA

The Raman and fluorescence spectroscopic properties of water‐soluble oxo‐titanium(IV) mesotetrakis (1‐methyl pyridium‐4‐yl) porphyrin (O=Ti(TMPyP)⁴⁺) bound with calf thymus DNA and artificial DNAs such as double stranded poly[d(A‐T)₂] and poly[d(G‐C)₂] have been investigated on the single DNA molecule basis by AFM‐correlated confocal scanning microscope (CSM)‐coupled Raman and fluorescence spectroscopic techniques as well as the ensemble‐averaged spectroscopy. The ensemble‐averaged spectroscopic studies imply that the porphyrin interacts with DNA in different groove binding patterns depending on the base pairs. AFM‐images of the different DNAs bound with O=Ti(TMPyP)⁴⁺ were measured, and their morphologies are found to depend on kind of base pairs interacting with O=Ti(TMPyP)⁴⁺. Being correlated with the AFM images, the CSM‐coupled Raman and fluorescence spectral properties of the three different single O=Ti(TMPyP)⁴⁺‐DNA complexes were observed to be highly resolved and sensitive to base pair‐dependent axial ligation of Ti‐O bond as compared to the corresponding ensemble‐averaged spectral properties, which affect the groove binding and its strength of the O=Ti(TMPyP)⁴⁺ with DNA. The axial ligation was found to be accompanied by vibration structural change of the porphyrin ring, leading to keep the shape of double stranded poly[d(A‐T)₂] rigid while poly‐[d(G‐C)₂] and calf thymus DNA flexible after binding with the oxo‐titanyl porphyrin. The base pair dependence of the fluorescence decay times of the DNA‐bound porphyrins was also observed, implying that an excited‐state charge transfer takes place in the G‐C rich major groove in calf thymus DNA. These results suggest that binding of O=Ti(TMPyP)⁴⁺ is more preferential with the G‐C rich major groove than with the A‐T rich minor groove in calf thymus DNA so that the morphology of DNA is changed.     

N‐Annulated Perylene‐Substituted and Fused Porphyrin Dimers with Intense Near‐Infrared One‐Photon and Two‐Photon Absorption

Fusion of two N‐annulated perylene (NP) units with a fused porphyrin dimer along the S₀–S₁ electronic transition moment axis has resulted in new near‐infrared (NIR) dyes 1 a / 1 b with very intense absorption (ε>1.3×10⁵ M ^?1 cm^?1) beyond 1250 nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10^?6 and 6.0×10^?6 for 1 a and 1 b , respectively. The NP‐substituted porphyrin dimers 2 a / 2 b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited‐state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer‐like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two‐photon absorption cross‐sections in the NIR region due to extended π‐conjugation. Time‐dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra.     

“Turn-off-on” fluorescent sensor for (N-methyl-4-pyridyl) porphyrin -DNA and G-quadruplex interactions based on ZnCdSe quantum dots

As a new detection model, the reversible fluorescence “turn-off-on” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many biochemical materials, especially in the researches on the interactions between anticancer drugs. The previous studies, however, mainly focused on simple-structured oligonucleotides and Calf thymus DNA. G-quadruplex, an important target for anti-cancer drug with special secondary structure, has been stimulating increasing research interests. In this paper, we report a new detection method based on the fluorescence “turn-off-on” model with water-soluble ZnCdSe QDs as the fluorescent probe, to analyze the interactions between anticancer drug (N-methyl-4-pyridyl) porphyrin (TMPyP) and nucleic acid, especially the G-quadruplex. The fluorescence of QDs can be quenched by TMPyP via photo-induced electron transfer and fluorescence resonance energy transfer, while on the other hand, the combination between TMPyP and G-quadruplex releases QDs from their quenchers and thus recovers the fluorescence. Most importantly, the fluorescence “turn-off-on” model has been employed, for the first time, to analyze the impacts of special factors on the interaction between TMPyP and G-quadruplex. The excellent selectivity of the system has been verified in the studies of the interactions between TMPyP and different DNAs (double-stranded DNA, single-stranded G-quadruplex, and different types of G-quadruplexes) in Na⁺ or K⁺-containing buffer.