Study on the interaction of 5-pyridine-10,15,20-tris-(p-chlorophenyl)porphyrin with cyclodextrins and DNA by spectroscopy.

The interaction of 5-pyridine-10,15,20-tris-(p-chlorophenyl)porphyrin (PyTPP) with beta-CD and TM-beta-CD were examined by UV-vis absorption, fluorescence and (1)H NMR spectroscopy. PyTPP prefers to form the 1:1 inclusion complex with TM-beta-CD but hardly form inclusion complex with beta-CD. An inclusion constant (K) for the formation of PyTPP-TM-beta-CD inclusion complex has been evaluated to be 4.4x10(3)L/mol from the absorbance changes. This K value is nearly the same as that 4.5x10(3)L/mol obtained from the fluorescence intensity changes. Compared to beta-CD, the inclusion ability of TM-beta-CD with PyTPP is stronger. It indicates that the hydrophobic effect plays an important role in the inclusion procedure. The mechanism of inclusion interaction was carried out by 1H NMR technique. Furthermore, the interaction of PyTPP with DNA is shown here. It can bind DNA by out-side stacking along the DNA helix but not by intercalation because of the high electron density in the porphyrin core. The binding constant and binding number of PyTPP to DNA are 4.3x10(3) and 1.3, respectively. The interaction of PyTPP with DNA was further carried out in the presence of TM-beta-CD. The significant decrease of the binding constant and binding number were observed and the interaction of porphyrin-bound DNA has been inhibited, which was due to the fact that PyTPP inter into the cavity of TM-beta-CD and influence binding affinity of PyTPP to DNA.

Electrochemical studies of the interaction of Basic Brown G with DNA and determination of DNA.

A new method of electrochemical probe has been proposed for the determination of Herring Sperm DNA (DNA) based on its interaction with Basic Brown G (BBG). The electrochemical behavior of interaction of BBG with DNA was investigated on Hg electrode. In 0.1molL(-1) NH(3)-NH(4)Cl buffer solution (pH 8.0), BBG can be reduced on Hg electrode with a well-defined voltammetric peak at -0.67V (versus SCE). In the presence of DNA, the reduction peak current of BBG decreases and the peak potential shifts to a more positive potential without the appearance of new peak. The study shows that a new BBG-DNA complex is formed by linear sweep voltammetry (LSV) and spectrophotometry. The decrease of the second order derivative of reductive peak current (Delta i(")(p)) of BBG is proportional to the concentration of DNA in the range of 0.10-36microg mL(-1). Limit of detection of DNA is 0.04microg mL(-1). DNA of Hepatitis B Virus in serum samples was determined satisfactorily. Additionally, the binding mechanism was preliminarily discussed. The mode of interaction between BBG and DNA was found to be intercalation binding.

Study on the supramolecular systems of 5-(2-hydroxy phenyl)-10,15,20-tris (4-methoxy phenyl) porphyrin with cyclodextrins.

In neutral phosphate buffer solutions of pH 7.4, the inclusive complexation of 5-(2-hydroxy phenyl)-10,15,20-tris(4-methoxy phenyl) porphyrin (o-HTPP) with alpha-cyclodextrin (alpha-CD), beta-CD, heptakis (2,3,6-tri-O-methyl)-beta-CD (TM-beta-CD), SBE-beta-CD, HP-beta-CD and gamma-CD has been examined by means of UV-vis and fluorescence spectroscopy. The formation of inclusion complexes has been confirmed on the base of changes of spectroscopy properties. The o-HTPP forms 1:2 inclusion complexes with TM-beta-CD and 1:1 inclusion complexes with the other five cyclodextrins. The formation constants (K) of o-HTPP for the formation of the inclusion complexes have been estimated from the absorbance and fluorescence intensity changes in neutral phosphate buffer solutions. The K value (2.89x10(7)), which is the formation constant for the formation of the 1:2 inclusion supramolecular, is nearly 10(4) times than those of the 1:1 inclusion complexes. Compared to the other five cyclodextrins, the strongest inclusion ability of TM-beta-CD can be explained that the hydrogen bond plays significant role in the inclusion process. UV-vis experiments also showed that the cavity of TM-beta-CD causes the transform of the state of o-HTPP. In addition (1)H NMR data and 2D-ROSEY NMR spectra support the inclusion conformation of the o-HTPP-CD supramolecular system, indicating the interaction mechanism of inclusion processes.

Electroanalytical method for TPPS4, the interaction of TPPS4 with BSA and the influence of CDs on it by fluorescence spectroscopy.

AIM: To establish a simple, rapid and accurate electroanalytical method for water soluble porphyrin meso-tetrakis-(4-sulfonatophenyl) porphyrin (TPPS4); to clarify the reaction between water soluble porphyrins and bovine serum albumin (BSA); and to determine the interaction of TPPS4 with BSA in the absence of presence of cyclodextrins (CDs), separately. METHODS: Three methods including LSV, UV spectroscopy and fluorescence spectroscopy had been employed to the relevant experiments. The way of employing three methods at the same time could make the experiment results more reliable. RESULTS: In the supporting electrolyte of NaH2 PO4-Na2 HPO4 (pH 7.18), a sensitive reduction peak of TPPS4 was found by linear sweep voltammetry (LSV), the peak potential (Ep) was -0.70 V (vs SCE). The relationship between the second derivative peak of LSV (ip") and the concentration of TPPS4 was linear from 1.0 x 10(-7) mol x L(-1) to 1.0 x 10(-5) mol x L(-1), the square of correlation coefficients (r2) were 0.998 3 and 0.999 3, respectively. The relative standard deviation (RSD) was 0.56% (n = 5). The mean recovery of TPPS4 was 99.59%. In NH4Cl-NH3 x H2O buffers (pH 9.05), it was proved that BSA and TPPS4 could interact with each other and form 1 : 1 TPPS4-BSA supramolecular system. Moreover, the interaction between TPPS4 and BSA had been investigated by adding cyclodextrins (CDs). The interaction of TPPS4 with BSA was facilitated both by hydroxypropyl-beta-CD (HP-beta-CD) and sulforbutylether-beta-CD (SBE-beta-CD). CONCLUSION: An electroanalytical method for TPPS4 has been established by LSV. The porphyrin drugs included by CDs could react with protein existing inside the human body easier. The consequences of this article also show that CDs will play important role in controlling and releasing the porphyrin drugs.

Study on the interaction of bovine serum albumin with acid cyanine 5R and its application in analysis.

A supramolecular complex of bovine serum albumin (BSA) with acid cyanine 5R (AC 5R, C.I. acid blue 113, C.I.: 26360) has been shown to form in Tris-HCl buffer solution (pH 7.42) by linear sweep voltammetry (LSV), fluorimetry, and spectrophotometry. The binding ratio and binding constant of BSA with AC 5R have been detected by LSV and fluorimetry. The binding mechanism is also preliminarily discussed. In Tris-HCl buffer solution (pH 7.42), AC 5R can easily be reduced on the mercury electrode, and it has a well-defined LSV peak current (Ip) and peak potential (Ep) at -0.65 V (vs. SCE). In the presence of BSA, the Ip of AC 5R decreases, and the peak potential (Ep) shifts to a more positive potential. The decrease of the second-order derivative of reductive peak current (deltaIp'') of AC 5R is proportional to the logarithm of BSA concentration in the range of 1.54 x 10(-8) mol x L(-1)-1.54 x 10(-5) mol x L(-1) (r = 0.9931-0.9977). The limit of detection of BSA is 9.0 x 10(-9) mol x L(-1). The relative standard deviation is 1.83% (n = 10), and the standard recovery is 97.5%-104.8%. This method can be used to determine BSA concentration on the basis of the interaction of BSA with AC 5R.

[Thermodynamics studies on the reaction characteristics of hemoporphyrin with human serum albumin].

The quenching reaction of hemoporphyrin with human serum albumin (HSA) was studied by using fluorescence spectraand absorption spectra. The formation constants of them were analyzed at different temperature according to Stem-Volmer equation and double-reciprocal equation, which are smaller at high temperature than at low temperature. The binding site was calculated (r = 4.36) by Foster energy transfer mechanism, and the thermodynamic parameters were obtained. H-bond and Van der Waals are two main reactions between HP and HSA.

[Molecular recognitions of purines by hematoporphyrin and metalloporphyrin receptors].

The present paper studies the interactions of purines and porphyrin by fluorescence, UV, and NMR spectra. The optimal conditions (acidity and ion intensity) of the interaction of purines and hematoporphyrin and metalloporphyrin were investigated in detail. The result shows that hematoporphyrin and metalloporphyrin exhibit significant recognition of purines. The binding constants of metalloporphyrin: K(Ni(II)-HP) > K(Co(II)-HP) > K(Zn(II)-HP) > K(Cu(II)-HP) in pH 11.2 Kolthoff buffer solution. The mechanism of recognition was further discussed. Recognition is achieved by cooperative functions of three recognition groups (metalloporphyrin) and two recognition groups (hematoporphyrin).

Electroanalytical method of TCPP and its supramolecular system with cyclodextrins.

In this paper, electroanalytical method of tetrakis (4-carboxylphenyl) porphyrin (TCPP) has been established. In a supporting electrolyte of KH(2)PO(4)-Na(2)HPO(4) (pH 7.0), a sensitive second derivative reduction peak of TCPP was found by single-sweep oscillopolarography. The potential peak is -0.70V (versus SCE).The relationship between peak height and the concentration of TCPP is linear from 1x10(-7) to 2x10(-5)moll(-1), the relative standard deviation (R.S.D.) was 0.41% (n=8), and the recovery of TCPP varied from 95.8-105.4%.The interaction of cyclodextrins (CD) with TCPP in NH(3)-NH(4)Cl (pH 8.0) has been studied by polarography. The TCPP can form the 1:1 inclusion complex with beta-CD, gamma-CD, hydroxylpropyl-beta-CD, sulfurbutylether-beta-CD and trimethyl-beta-CD. "Current method" has been used to determine the formation constants of TCPP with five CDs. The result shows that the inclusion ability of hydroxylpropyl-beta-CD is very strong. Moreover, modified beta-CD has stronger inclusion capacity than native beta-CD. The formation constant of TCPP with gamma-CD is much greater than that of TCPP with beta-CD, because the gamma-CD has a bigger cavity that can match with the size of the meso-phenyl of TCPP. The supramolecular data will provide useful information for further application of TCPP.

Porphyrin binding to DNA investigated by cyclodextrin supramolecular system.

The interactive mode of meso-tetrakis- (4- N-trimethylaminobenzyl) porphyrin (TAPP) with DNA has been investigated by the cyclodextrin (CD)-porphyrin supramolecular system. The binding of TAPP with DNA is inhibited by the anion CD derivative, sulfurbutyl-beta-cyclodextrin (SB-beta-CD); however, the neutral CD cannot influence the binding. As for the inclusion procedure of the CDs-TAPP system, the (1)H-NMR data suggests that the hydrophobic segment of TAPP enters into the cavity of CD, which means that the hydrophobic part of TAPP is not the binding site in the TAPP-DNA interaction. Therefore, the binding model cannot be the intercalation and is not related to the grooves of DNA. In addition, experimental data show that the charge attraction, which exists in the inclusion procedure of SB-beta-CD and TAPP hampers the binding of TAPP with DNA. The negative groups of SB-beta-CD compete with the phosphate groups of the DNA backbone, and have an attraction to the positive groups of TAPP. This competitive attraction supports the theory that the binding mode of TAPP with DNA is "electrostatic binding". Furthermore, there are two binding sites between one TAPP molecule and one DNA standard. We produce a possible binding structure (a suprahelical structure of DNA) for this TAPP-DNA complex. This structure is in good agreement with the literature.