Study on spectroscopic characterization of Cu porphyrin/Co porphyrin and their interactions with ctDNA

The luminescence behaviors of Cu(II) meso-tetrakis (4-N-methyl-pyridiniumyl) porphyrin (Cu(II)TMPyP) and Co(II) meso-tetrakis (4-N-methyl-pyridiniumyl) porphyrin (Co(II)TMPyP) are investigated, and their interactions with calf thymus DNA (ctDNA) are studied by UV-vis, fluorescence and resonance light scattering (RLS) and based on the changes of UV-vis spectra, fluorescence and RLS spectra, the intrinsic binding constants of Cu(II)TMPyP/Co(II)TMPyP with ctDNA are obtained in the case of phosphate buffer solution (pH 7.2), respectively. According to the experimental results, it can be inferred that the interaction model of Cu(II)TMPyP with ctDNA is intercalative binding, while Co(II)TMPyP is the long-range assembly on the molecular surface of ctDNA.     

Uncharged water-soluble Co(II)-porphyrin: a receptor for aromatic alpha-amino acids

Changes in the UV-vis spectra and induced circular dichroism (ICD) signals observed, in correspondence with the porphyrin Soret region, for aqueous solutions of achiral 5,10,15,20-tetrakis{p-[omega-methoxy poly(oxy-ethylene)]phenyl}porphyrin cobalt (II) (Co-P) and aromatic alpha-L-amino acids (Trp and Phe) give direct evidence for the coordination between the Co-P and amino acids. Considering that Co-P, besides the Co atom (one-fixation-point system), does not contain in the molecule active ligand groups and that no ICD signals have been observed in the case of Co-P/Ala, it has been concluded that hydrophobic interactions or stacking interactions between the aromatic rings of the porphyrin and those of Trp or Phe, acting as further amino acid (AA) fixation points, can strongly reduce the mobility of the chiral guest, thus permitting the generation of ICD signals. The effects of changes of both pH (in the range 2-9) and amino acid structure on the ICD phenomenon have also been investigated. In particular, the following have been observed: (i) strong ICD signals for all of the Co-P/N-acetyl amino acid aqueous solutions at pH 7, (ii) an unexpected ICD band with a bisignate form for the Co-P/Ala solution at pH 9 after long aging, and (iii) an opposite ICD signal when alpha-D-Phe and alpha-D-Trp enantiomers have been used. The data reported in this paper show how the binding mechanism between receptor and AAs changes by modulating properly the pH or the molecular structures and indicate that in these aqueous solutions the coordination Co-N is not the fundamental mechanism giving rise to the formation of the complexes and that the binding can be driven by hydrophobic interactions. These occurrences, through the analysis of the spectroscopic response (and, in particular, the form of the ICD band), can allow the recognition of AAs.     

Synthesis of Calix[6]arene-Porphyrin Receptors and Study on their Catalytic Performance in Epoxidation of Styrene

The artificial receptors with multiple recognition site had been synthesized by linking two unsymmetrical monofunctionalized porphyrin to p-tert-butyl calix[6]-arene via two flexible chain, followed by inserting metal ion into the porphyrin species.The structures (see Fig 1) of these calix[6]arene-diporphyrins and their metal complexes were confirmed by UV-vis spectra, IR spectra, mass spectra, ¹NMR spectra(600 MHz) and/or ¹³C NMR. Their conformations were investigated preliminarily by UV-vis spectra and computer simulation. In constrast with the correspounding porphyrin monomer, the soret bond of calix[6]arene-diporphyrins in UV-vis spectra showed hypsochromic shift. This phenomenon suggested that two porphyrin rings maintain a face to face parallel conformation, as confirmed by computer simulation that showed the conformation energy is the lowest as two porphyrin rings hold such a conformation. Besides, simplicity of the ¹NMR spectra indicates that the conformation of calix[6]arene-diporphyrin possesses high symmetry. Therefore,the calix[6]arene must be cone conformation.     

Synthesis of a phosphorus-containing hybrid porphyrin

A phosphorus-containing hybrid porphyrin was successfully prepared via the BF3-promoted dehydrative condensation between sigma4-phosphatripyrrane and 2,5-bis[hydroxy(phenyl)methyl]thiophene. The NMR and UV-vis absorption spectra, electrochemical measurements, and DFT calculations revealed that the sigma3-P,N2,S-hybrid porphyrin exhibits high aromaticity as an 18pi-electron system in terms of both geometric and magnetic criteria. [structure: see text]     

Adduct of magnesium tetraphenylporphyrin with aniline for colorimetric detection of SO2

Adduct of magnesium tetraphenylporphyrin（MgTPP） with aniline for colorimetric detection of SO₂ was investigated in CH₂C1₂ by steady-state fluorescence and UV-vis absorption spectroscopic techniques.The UV-vis spectra showed that the increasing aniline concentrations resulted in red shift of 3 nm for MgTPP Soret absorption band.Once introduced,SO₂ competes with MgTPP for aniline,which eventually leads to the release of MgTPP and changes in the solution color/absorption.The fluorescence spectra suggested that MgTPP interacted with aniline to form 1:1 molecular adducts,and showed that the binding of MgTPP with aniline with the binding constants of 1.58-1.64 is not only endothermal but entropy-driven withΔH = 1.622 kJ mol^-1, AS = 9.389 J mor^-1 K^-1,and AG = -1.585 kJ mol^-1 at T= 298.15 K.     

Study on the interaction of new water-soluble porphyrin with DNA

A porphyrin meso-tetrakis{[4-(1-pyridyl)propoxy]phenyl}porphyrin (TPyPP) and its Ni complex (TPyPP(Ni)) have been synthesized and characterized by 1H NMR, UV-vis spectra. The interaction of two porphyrins with calf thymus-DNA (CT-DNA) has been explored by UV-vis, fluorescence and circular dichroic spectroscopy and viscosity measurements. The results suggest that these porphyrins can bind to DNA by the same binding mode. TPyPP outside binds by self-stack with DNA both at low drug load r (=[porphyrin]/[DNA]) and high drug load. Though TPyPP(Ni) has center metal nickel, binding mode with DNA has little difference compared with TPyPP, dominating out-binding mode with different direction along DNA. The binding constants of the TPyPP and TPyPP(Ni) to DNA were 4.65 x 10(5) M(-1) and 3.2 x 10(5) M(-1), respectively. A colored precipitate was found after time in two porphyrin's viscosity measurement. The reasonable interpretation is the porphyrins with alkyl connected N-position of pyridine can strongly interact with the anionic phosphates of DNA and lead to hydrophobic complex.     

Synthesis of an anion receptor for acetate based on the frame of ferrocene

An anion receptor was synthesized with ferrocene as binding frame. Anion recognition can be monitored by anion complexation-induced changes in UV-vis absorption spectra. Interaction between the receptor and acetate was described on the basis of ¹H NMR experiments.     

Anion chelation-induced porphyrin protonation and its application for chloride anion sensing

The protonation of a simple meso-tetraphenylporphyrin in an organic-aqueous system was found to be induced by the counteranions. During the process of protonation, the counteranion of the proton sources binds with the porphyrin core and thus promotes the complexation of the porphyrin and protons. The interaction of porphyrin and anion was characterized by fluorescence, UV-visible, cyclic voltammetry, (1)H NMR, and IR. Moreover, it could be exploited in selective fluorescent sensing of Cl(-). The sensing mechanism was based on extraction of protons from the aqueous phase into the organic phase by free base porphyrin and simultaneous coextraction of Cl(-), which promoted porphyrin protonation, and hence resulted in significant changes of the porphyrin fluorescence spectra. Selectivity trends turned out to be dependent upon the lipophilicity of anion and the binding affinity and structure complementarity between the protonated porphyrin and anions. The fluorescence enhancement of the porphyrin band at 684 nm showed modest selectivity for Cl(-) and NO(3)(-).     

Diastereochemically controlled porphyrin dimer formation on a DNA duplex scaffold

DNA-porphyrin conjugates were designed and synthesized for the preparation of the conformationally controlled porphyrin dimer structures constructed on a d(GCGTATACGC)2. Porphyrin derivatives were introduced to the central TATpA sequence where p represents the phosphoramidate for the attachment of the free-base porphyrin (FbP) and zinc-coordinated porphyrin (ZnP), which allows contact of the two porphyrins in the minor groove. The porphyrin dimers were characterized using CD, UV-vis, steady-state, and time-resolved fluorescence spectroscopies, indicating that the porphyrins form face-to-face conformations. Also the co-facial conformation was confirmed by comparison with spectra of the non-self-complementary duplex containing one porphyrin moiety. Introduction of zinc into porphyrin moiety destabilized the duplex formation. Two diastereomers showed different thermal stabilities and affected the conformations of porphyrin dimers. The temperature-dependent assembly and the conformational change of the porphyrin dimer on the duplex DNA were observed in the UV-vis spectra, indicating that the dynamic movement of the porphyrin dimer occurs on the duplex. The results indicate that the porphyrin dimers of DNA-FbP conjugates are overlapped clockwise and are located in the minor groove of the usual B-form DNA backbone. The interaction and conformation of two porphyrin moieties are controlled by the following three factors: (1) temperature change during and after formation of the duplex porphyrins at lower temperature; (2) diastereochemistry of the phosphoramidates where porphyrins are connected via a linker; and (3) zinc ion coordination that destabilizes the interaction of porphyrins as well duplex formation.     

Spectroscopic, morphological, and mechanistic investigation of the solvent-promoted aggregation of porphyrins modified in meso-positions by glucosylated steroids

Solvent-driven aggregation of a series of porphyrin derivatives was studied by UV/Vis and circular dichroism spectroscopy. The porphyrins are characterised by the presence in the meso positions of steroidal moieties further conjugated with glucosyl groups. The presence of these groups makes the investigated macrocycles amphiphilic and soluble in aqueous solvent, namely, dimethyl acetamide/water. Aggregation of the macrocycles is triggered by a change in bulk solvent composition leading to formation of large architectures that express supramolecular chirality, steered by the presence of the stereogenic centres on the periphery of the macrocycles. The aggregation behaviour and chiroptical features of the aggregates are strongly dependent on the number of moieties decorating the periphery of the porphyrin framework. In particular, experimental evidence indicates that the structure of the steroid linker dictates the overall chirality of the supramolecular architectures. Moreover, the porphyrin concentration strongly affects the aggregation mechanism and the CD intensities of the spectra. Notably, AFM investigations reveal strong differences in aggregate morphology that are dependent on the nature of the appended functional groups, and closely in line with the changes in aggregation mechanism. The suprastructures formed at lower concentration show a network of long fibrous structures spanning over tens of micrometres, whereas the aggregates formed at higher concentration have smaller rod-shaped structures that can be recognised as the result of coalescence of smaller globular structures. The fully steroid substituted derivative forms globular structures over the whole concentration range explored. Finally, a rationale for the aggregation phenomena was given by semiempirical calculations at the PM6 level.     

PHOTOINDUCED DEGRADATION AND MODIFICATION OF PHOTOFRIN II IN CELLS in vitro

Abstract— Human cells of the line NHIK 3025 were incubated with Photofrin II (PII) and exposed to light. Fluorescence- and absorption spectra of PII in the cells were measured. Light exposure resulted in a degradation of PII in the cells and changes in the shape of the fluorescence spectra. These changes are probably partly due to a photochemical modification of PII and to a relocalization of PII in the cells. Notably, a destruction of binding sites for PII on or close to proteins was caused by the light exposure. The rate of the light-induced decay of the porphyrin fluorescence intensity was only slightly increasing with the PII concentration, indicating that each porphyrin molecule is mainly degraded by photoproducts originating from itself. On the other hand, the rate of the degradation of porphyrin binding sites on the proteins increased with increasing PII concentrations.
The excitation spectrum of PII in cells has a peak at285–290 nm attributed to energy transfer from proteins to porphyrins located close to the proteins. The intensity of this peak relative to the intensity of the Soret band increases with decreasing porphyrin concentrations. This might indicate that some of the binding sites close to proteins have a higher affinity for the porphyrin than binding sites at longer distances from the proteins.     

Optochemical sensing of hydrogen chloride gas using meso-tetramesitylporphyrin deposited glass plate

Meso-tetramesitylporphyrin (MTMP) deposited glass plate (solid state sensor) was used to sense hydrogen chloride (HCl) gas based on optochemical method. Exposure of the solid state sensor to HCl vapor results in the formation of protonated meso-tetramesitylporphyrin (PMTMP). UV-vis and fluorescence spectral techniques were used to study the protonation of MTMP in dichloromethane-methanol mixture. The optical spectra of MTMP show an intense Soret band at 418 nm with a 14 nm red shift upon protonation by HCl. Ab-initio calculations were carried out to visualize the effect of protonation on planarity and stability of the porphyrin ring. The solid state sensor was characterized by UV-vis spectral technique. The sensor exhibits characteristic Soret and Q bands for the deposited MTMP with slight red shift when compared to MTMP in dichloromethane. The concentration of gaseous HCl was monitored from the changes in the absorbance of Soret band of PMTMP at 452 nm. The detection limit of the solid state sensor towards gaseous HCl was found to be 0.03 ppm. The present solid state sensor was highly stable for several months.     

Foldamer-based pyridine-fullerene tweezer receptors for enhanced binding of zinc porphyrin

This paper reports the design and synthesis of a new series of hydrogen bonding-mediated foldamer-derived tweezer receptors that are used for efficient complexation of zinc porphyrin guest. One end of the rigidified aromatic amide backbone is incorporated with one fullerene unit, while another end is connected to one pyridine or imidazole unit. The ¹H NMR, UV-vis, and fluorescent investigations in chloroform revealed that, due to the intramolecular hydrogen bonding-driven preorganized folded conformation, the fullerene and pyridine units of the receptors are located with suitable spatial separation and consequently able to co-complex zinc porphyrin with remarkably increased stability. In contrast, the imidazole-incorporated receptor displays a weakened binding affinity possibly due to structural mismatching and large steric hindrance. The association constants of the complexes of the new receptors with zinc porphyrin have been determined.     

Formation of higher-order structures of chiral poly(ethynylpyridine)s depending on size, temperature, and saccharide recognition

Amphiphilic 2,6-pyridylene ethynylene "meta-ethynylpyridine" polymers having chiral oligo(oxyethylene) side chains were developed as hosts for saccharide recognition. The polymers were prepared via a Sonogashira reaction and fractionated by gel permeation chromatography (GPC). They showed circular dichroism (CD) activity due to their higher-order chiral helical structures, and their CD and UV-vis spectra changed depending on not only saccharide recognition but also molecular size, temperature, and metal cation recognition.     

Synthesis of an Anionic Receptor Based on Phenylhydrazone Group and Its Recognition Property for Acetate

A colorimetric anion receptor was synthesized by a simple method where the phenylhydrazone moiety was need as binding sites. The anion recognition via hydrogen-bonding interactions can be easily monitored by anion complexation induced changes in UV-vis absorption spectra. Moreover, the hydrogen bond formation between the phenylhydrazone N-H and acetate or fluoride anion was described on the basis of ^1H NMR experiments.     

Single sensor for multiple analytes: chromogenic detection of I and fluorescent detection of Fe

A novel receptor, designed with a combination of oxygen and nitrogen-binding sites for metal ions and hydrogen bond donor sites for anion binding, was synthesized. The receptor has been explored for the selective detection of I⁻ against a range of physiologically relevant anions and cations through changes in its UV-vis spectra. On the other hand, receptor-binding selectivity for Fe³⁺ over a wide linear concentration range was observed through changes in the emission spectra. This is the first Letter of a sensor capable of detecting both I⁻ and Fe³⁺ using two different detection modes.     

两种卟啉化合物在Ag溶胶表面的紫外-可见吸收光谱和表面增强拉曼散射光谱研究

表面增强拉曼散射(SERS)自1974年被Fleischmann等^[1]发现以来,日益受到人们的重视.通过SERS谱图分析,可以获得物质结构及其与基体作用的信息.由于SERS可使拉曼信号增强10⁵~10⁶倍^[2],并且在某些情况下银胶还能使表面吸附质的荧光猝灭^[3,4], SERS常用来检测一些普通拉曼光谱难以检测的样品和考察界面络合物的形成.     

Conformational Re‐engineering of Porphyrins as Receptors with Switchable N−H⋅⋅⋅X‐Type Binding Modes

The selectivity and functional variability of porphyrin cofactors are typically based on substrate binding of metalloporphyrins wherein the pyrrole nitrogen units only serve to chelate the metal ions. Yet, using the porphyrin inner core system for other functions is possible through conformational engineering. As a first step towards porphyrin “enzyme‐like” active centers, a structural and spectroscopic study of substrate binding to the inner core porphyrin system shows that a highly saddle‐distorted porphyrin with peripheral amino receptor groups ( 1 , 2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetrakis(2‐aminophenyl)porphyrin) coordinates analytes in a switchable manner dependent on the acidity of the solution. The supramolecular ensemble exhibits exceptionally high affinity to and selectivity for the pyrophosphate anion (2.26±0.021)×10⁹ m ^?1. ¹H NMR spectroscopic studies provided insight into the likely mode of binding and the characterization of atropisomers, all four of which were also studied by X‐ray crystallography.     

Interaction of water-soluble cationic porphyrin with anionic surfactant

The interaction of a cationic water-soluble porphyrin, 5,10,15,20-tetrakis [4-(3-pyridiniumpropoxy)phenyl]porphyrin tetrakisbromide (TPPOC3Py), with anionic surfactant, sodium dodecyl sulfate (SDS), in aqueous solution has been studied by means of UV-vis, (1)H NMR, fluorescence, circular dichroism (CD) spectra and dynamic laser light scattering (DLLS), and it reveals that TPPOC3Py forms porphyrin-surfactant complexes (aggregates), including ordered structures J- and H-aggregates, induced by association with surfactant monomers below the SDS critical micelle concentration (cmc), and forms micellized monomer upon the cmc, respectively. The position of TPPOC3Py in the micelle is determined, which is not in the micelle core instead of intercalated among the SDS chains, most likely with the pyridinium group extending into the polar headgroup region of the micelle.     

Modular fluorescence sensors for saccharides

Modular and modular polymer supported fluorescence photoinduced electron transfer (PET) sensors 2 and 3 with two boronic acid receptor units, a pyren-1-yl fluorophore, and hexamethylene linker show selective saccharide binding in aqueous methanolic solution at pH 8.21.