Resonance Rayleigh scattering study of the interaction of bleomycinA_5 with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in batho- chromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum condi- tions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Resonance Rayleigh scattering study of the interaction of bleomycinA<Subscript>5</Subscript> with nucleic acids and its analytical application

The interaction of bleomycinA5 with nucleic acids has been investigated by using resonance Rayleigh scattering (RRS), molecular absorption and fluorescence spectra. The result shows that in near pH 2.2 buffer medium and absence of any metal ions, nucleic acids are capable of binding with bleomycinA5 (BLMA5) to form complexes which can remarkably enhance the RRS intensity and result in bathochromic and hyperchromic molecular absorption of nucleic acids and fluorescence quenching of bleomycinA5. The RRS spectral characteristics for the binding products of bleomycinA5 with various DNA and RNA are similar, and the maximum RRS peaks are at 301 nm for ctDNA and sDNA, 370 nm for hsDNA, 310 nm for RNAtypeVI and RNAtypeIII, respectively. The increments of RRS intensity are greatly different in which DNA enhances greatly and RNA enhances lightly. In this work, the optimum conditions of the interaction and some influencing factors have been investigated. The reaction mechanism and a binding model for the interaction of BLMA5 with the nucleic acids are discussed. In addition, a highly sensitive, simple and rapid new method for the determination of DNA has been developed. The detection limits (3σ) are 5.7 ng/mL for ctDNA, 7.4 ng/mL for sDNA and 9.2 ng/mL for hsDNA, respectively. The method can be applied to determination of trace amounts of DNA.     

Studies on the Binding Mode of Pinacyanol Chloride to Nucleic Acids

The interaction of pinacyanol chloride(PC) with nucleic acids has been investigated by a series of experiments.Extensive hypochromism,appreciable peak shifts,isosbestic points and new peaks of the product of binding to nucleic acids in the spectra were observed.They showed that the interaction between PC and nucleic acids occurred.The results from absorption spectra of DNA,DNA melting,electrophoresis and fluorescence polarization studies have indicated that PC binds to DNA in nonintercalative way.Consistent with the nonintercalation,the studies of fluorescence titration and absorption titration specified that the binding of PC to nucleic acids occurred by an outside stacking binding,in which nucleic acids served for acting templates,The fact that the new absorption peaks of bound PC at ca,485nm are just close to the absorption bands of Haggregate of PC at high concentrations without DNA further supports the outside stacking binding mode,In addition,other evidence indicated that the interaction between PC and nucleic acids is not purely electrostatic.     

Acidichromism of indolinospirooxazines in isopropanol

1,3,3-tnmethyl-spiro[mdolino-2,3'-[2H]naphtho[2,1-b] [1,4]oxazine(SP1) and 1,3,3-trimen-thyl-9-methoxy-spiro[indolino2,3'-[2H]naphtho[2,1-b] [ 1,4]oxazine] (SP2) react with hydrochloric acid to form the complex SP HCl in isopropanol solution at room temperature The absorption maxima of these complexes are 440 and 463 nm respectively In acidic media,the opening form of spirooxazine can react with hydrochloric acid to form the complex PMC HCl via zwittenon form The absorption spectra of PMC HCl are obviously hypsochromic shifted compared with the reported spectra of the complex in neutral media In the mean time,the thermal stability of the complex is increased.The first order kinetics for the decoloration process of the acidichromic product of the opening form was determined and the lifetimes of these products are 180 and 200 s,respectively.     

Photophysical Properties of the Asymmetric Pentaazadentate Porphyrin-like Macrocycles

The linear correlations of Hammett constants with the 0-0 transition energies, and the ratios of the oscillator strength are used to probe the conjugation interactions between π-electron of macrocy-cles and metal ion of complexes with the substituents on m-position of benzene ring for the asymmetric pen-taazadentate porphyrin-like compounds. The absorption and fluorescence spectra appear on λmax> 750 nm and 769 nm near-IR regions respectively. The quantum yields and lifetimes of fluorescence are about 10-2and less than 1 ns respectively. The T1--Tn transient absorption spectra appear on 487-496 nm and thequantum yields for generating singlet oxygen are as high as 0. 86.     

Microwave Synthesis, Characterization and DNA-binding Properties of a New Cobalt（ Ⅱ ） Complex with 2,6-Bis（benzimidazol-2-yl）pyridine

A new cobalt(Ⅱ) complex with tridentate ligand 2, 6-bis (benzimidazol-2-yl)pyridine has been synthesized by microwave irradiation method and characterized by elemental analysis,electrochemical and spectral methods. The binding of the complex with calf thymus DNA has also been investigated by absorption and fluorescence spectra.     

A STUDY ON THE SPECTRUM CHARACTER AND PHOTOSTABILIZATION ABILITY OF A NOVEL UV-ABSORBER-DIBENZOYL METHANE

The absorption and fluorescence spectra of dibenzoyl methane have been studied. From the absorption spectra it was found that there are two peaks locating at 252 nm and 340 nm, respectively, similar to that of o-hydroxy benzophenone which can form intra-molecular hydrogen bond. Besides, an uncommonly large Stoke's shift of fluorescence can be observed in fluorescence spectra. The photostabilizing effects of dibenzoyl methane and UV-531 on the photodegradation of poly (cis-1, 4-butadiene) in solution have been investigated and compared. A possible mechanism was discussed.     

Resonance Rayleigh scattering spectrum for the chelate of lanthanum(Ⅲ) with sodium tanshinon ⅡA silate and its analytical application

In a pH 3.6―5.0 HAc-NaAc buffer solution, when sodium tanshinon ⅡA silate (STSⅡA) reacts with La(Ⅲ) to form a chelate, the resonance Rayleigh scattering (RRS) intensity can be en-hanced greatly and a new RRS spectrum will appear. The maximum RRS peak is located at 306 nm and the RRS intensity is proportional to the concentration of STSⅡA in a certain range. The method is very sensitive and the detection limit for STSⅡA (3σ/K) is 82.12 ng·mL?1. The optimum reaction condi-tions and the effect of coexisting substances have been investigated. A new, simple and fast method for the determination of STSⅡA based on RRS method is developed. It can be applied to the deter-mination of STSⅡA in the synthesis samples and Nuoxinkang injection. Combined with infrared ab-sorption and NMR spectra, the structure of the chelate and the reasons of RRS enhancement are also discussed.     

Spectral studies of the interaction between sanguinarine and guanosine

The interaction between sanguinarine and guanosine was investigated by using UV-vis and fluorescence spectra at pH 7.2. The binding of sanguinarine to guanosine was substantiated by the hypochromism and bathochromism in the absorption spectra and the emission quenching in fluorescence spectra. The fluorescence lifetime results, the varieties of the fluorophore absorption spectra and the decrease of the binding constant with the increasing temperature all indicate that the fluorescence quenching is static. The ratio and constant of the binding cytidine to sanguinarine are 2 and 6.44 × 10^7, respectively. The result shows that the binding of sanguinarine to guanosine is not only exothermic but also entropy-driven with △H=-8.53kJ/mol, AS = 0.12 kJ/（molK）, and AG =-44.57 kJ/mol at 298.15 K.     

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.     

Electronic spectroscopy and photochromic mechanism of bis-Schiff bases, N, N''''-bis(2-hydroxy-1-naphthylidene)-1,4-phenyldiamine

The steady state and transient state absorption spectra and fluorescence spectra of N,N'-bis(2-hy-droxy-1-napbthylidcne)-1,4-phenyldiamme ( BNP ) in cyclohexane and acetonitrile were determined.The pho-tochromic mechanism was discussed In nonpolar solvents,BNP exists mainly in the enol form and has the absorption maximum in the UV region In polar solvents,however,both the enol and proton transfer tautomer are formed,but the farmer is the main one Fluorescence emissions result from the excited state of proton transfer product.     

Photochemical reaction between magnesium tetraphenyl porphyrin and oxygen

The photochemical reaction of magnesium tetraphenyl porphyrin （MgTPP） with O2 was studied in CH2Cl2 by steady-state fluorescence, UV-vis absorption, FTIR and MALDI-TOF MS measurements. These spectra indicate that O2 can react with MgTPP excited by irradiation, forming the stable 1：1 coordinated adduct of MgTPP-O2. In the adduct, the oxygen atoms of O2 may insert in the Mg-N bonds in MgTPP and bind with the nitrogen atoms of MgTPP to form N-O-Mg bonds.     

STUDY ON THE NANOSECOND TRANSIENT ABSORPTION SPECTRA OF HYPOCRELLIN A

In this paper, the nanosecond transient absorption spectra and the fluorescence spectraof Hypocrellin A(HA) are examined in solvents of varying polarity. There are three absorp-tion bands in dilute HA solutions: Ⅰa, Ⅱa are defined as the triplet-triplet absorption ofHA, the band Ⅲa is supposed to be the absorption of the solvent--sepatated ion pair (SSIP).In more concentrated solutions, only the absorption of SSIP was observed. The effects ofsolvent polarity on transient absorption spectra and fluorescence spectra of HA and the effectof oxygen on the intensities of the fluorescence of HA are discussed. Then a reasonablemechanism for the photolysis of HA is proposed.     

Study on the interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate by the resonance Rayleigh scattering, second-order scattering and frequency doubling scattering spectra and its analytical application

The interaction between palladium(II)-chlorpromazine hydrochloride and sodium tungstate was investigated by ultravioletvisible absorption,resonance Rayleigh scattering(RRS),second-order scattering(SOS)and frequency doubling scattering (FDS)spectroscopy.In pH 5.3 Britton-Robinson(BR)buffer medium,chlorpromazine hydrochloride(CPZ)reacted with Pd(II) to form 2:1 cationic chelate,which further reacted with Na2WO4 to form a 1:1 ternary ion-association complex ([Pd(CPZ)2]·WO4).As a result,the signal intensities o...     

Synthesis,Crystal Structures,DNA Cleavage and DNA-binding Studies of Ho(Ⅲ) and Er(Ⅲ)Complexes Based on Macrocyclic Schiff Base

Two novel macrocyclic Schiff base complexes [LnL(PhCOO)(CH_3OH)](ClO_4)_2·(CH_3OH)_2(Ln =Ho, 1; Ln = Er, 2), in which L denotes the macrocyclic ligand, were synthesized via condensation of 2,6-diformyl-4-methyl-phenol and 1,3-diamino-2-propanol by employing benzoate as the second ligand. Their crystal structures were determined by X-ray diffraction, which showed that both complexes belong to a monoclinic system with space group P2_(1/c). The coordination polyhedron displayed a distorted bicapped trigonal prism with the coordination number of eight. Both complexes efficiently cleaved supercoiled DNA to its nicked circular form. The UV-vis absorption results and ethidium bromide(EB) fluorescence spectra indicated that the complexes bind to CT-DNA in an intercalative mode, with K_(sq) values to be 11830 and 10560, respectively.     

Study on the absorption and fluorescence and resonance Rayleigh scattering spectra of Cu (II)-fluoroquinolone chelates with erythrosine and their applications

In pH 4.2-5.0 Britton-Robinson buffer solution medium, fluoroquinolone antibiotics (FLQs), such as ciprofloxacin (CIP), norfloxacin (NOR), ofloxacin (OF), levofloxacin (LEV), lomefloxacin (LOM), and sparfloxacin (SPA), react with Cu (II) to form chelate cations, which further bind with erythrosine to form the ion association complexes. They can result in the changes of the absorption spectra. Simultane- ously, erythrosine fades obviously and the maximum fading wavelength is located at 526 nm. The fad- ing reactions have high sensitivities. Thus, new spectrophotometries of determination for these drugs are developed. The ion-association reactions result in the quenching of fluorescence, which also have high sensitivities. The detection limits for six antibiotics are in the range of 7.1-12.2 μg·L?1. Furthermore, the reactions can result in the enhancement of resonance Rayleigh scattering (RRS). The maximum scattering peaks of six ion-association complexes are located at 566 nm, and there are two small RRS peaks at 333 nm and 287 nm. The detection limits for fluoroquinolone antibiotics are in the range of 1.70 -3.10 μg·L?1 for RRS method. Among the above three methods, the RRS method has the highest sen- sitivity. In this work, we investigated the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions, and the properties of the analytical chemistry. In addi- tion, the mechanism of reactions were discussed by density function theory (DFT) and AM1 methods.     

1-Pyrenecarboxaldehyde thiosemicarbazone:A novel fluorescent molecular sensor towards mercury(Ⅱ) ion

<正>A novel and simple fluorescent molecular sensor,1-pyrenecarboxaldehyde thiosemicarbazone(Hpytsc),was synthesized.Its higher sensitivity and selectivity to mercury(Ⅱ) ion were studied through absorption and emission channels.The UV-vis spectra show that the increasing mercury(Ⅱ) ion concentrations result in the decreasing absorption intensity.The fluorescence monomer emission of Hpytsc is enhanced upon binding mercury(Ⅱ) ion,which should be due to the 1:1 complex formation between Hpytsc and metal ion.     

Effect of the position of substitution on the electronic properties of nitrophenyl derivatives of fulleropyrrolidines:Fundamental understanding toward raising LUMO energy of fullerene electron-acceptor

A series of substituted para-, meta- and ortho-nitrophenyl derivatives of fulleropyrrolidine were synthesized to investigate the effects of the position of substitution on electronic properties by using steady-state absorption and fluorescence spectra, combined with DFT calculations. The results confirmed that the position of substitution has little effect on absorption and fluorescence spectra, whereas a significant effect was observed on their LUMO energy levels. The theoretical calculations revealed that the LUMO energy of the ortho-nitrophenyl substituted derivative was increased 0.1 eV above those ofpara- and meta-substitution. The prominent effect ofortho-substitution was attributed to the through-space orbital interaction between spatially closed electron-withdrawing nitro group and fullerene cage. These findings could provide fundamental insights in raising LUMO levels of C6o-based electron acceptor materials and an alternative strategy to increase open circuit voltage Voc in polymer solar cells.     

Quantum chemical study on excited states and charge transfer of oxazolo[4,5-b]-pyridine derivatives

The excitedstate intramolecular charge transfer of four oxazolo[4,5-b]pyridine derivatives with different electron donating and electron withdrawing groups was investigated using the time-dependent density functional theory. The vertical excitation energies and the electronic structures were explored. Their distinct properties of absorption and fluorescence spectra in solvent phase were explained according to the electronic coupling matrix elements calculated by the Mulliken-Hush theory. The sub-stituent on the oxazolo[4,5-b]pyridines will remarkably change their spectra properties and increase the first excited-state dipole moments. The effect of protonation on the absorption and fluorescence spectra was also investigated systematically. Our study suggests that the present method is feasible to explain charge transfer excitation and predict the properties of absorption and emission spectra in the studied systems.     

Photochemical reaction of magnesium tetraphenyl porphyrin with sulfur dioxide

<正>The photochemical reaction of magnesium tetraphenyl porphyrin(MgTPP) with sulfur dioxide(SO_2) was investigated in dichloromethane(CH_2Cl_2) by steady-state fluorescence,UV-vis absorption,MS,and XRD spectroscopic techniques.These spectra showed that under irradiation MgTPP reacted with SO_2 to form 1:1 molecular adduct at first step.During the process of keeping irradiation and maintaining the flow of SO_2,SO_2 was reduced into S~(2-) by MgTPP and the results were detected using MS and XRD techniques.Understanding the photochemical reaction of MgTPP with SO_2 is of key interest in elucidating fundamental photochemical reaction mechanisms associated with this class of chlorophyll in the presence of SO_2.