pH-controlled self-assembling of meso-tetrakis(4-sulfonatophenyl)porphyrin-chitosan complexes.

Solid meso-tetrakis(4-sulfonatophenyl)porphyrin (TPPS(4))-chitosan supramolecular complexes were prepared by addition of porphyrin to an aqueous solution of chitosan at pH values. The precipitates obtained were assigned as 1 (pH 6.8) and 2 (pH 2.5) and characterized by spectroscopic, thermal, and microscopic methods. Spectroscopic investigation confirmed the presence of TPPS(4) and chitosan in both products and that the porphyrin is highly self-associated. H-type (stacked) of TPPS(4) aggregation was proposed for 1 and J-type (tilted) for 2. Thermal analysis revealed different pyrolysis routes of the complexes depending on their structural diversity. Light microscopic analysis indicated fibrous and lamellar microstructures, respectively, for 1 and 2. SEM and AFM analysis showed that both complexes consist of compact nanostructures; their size and interconnection is different for 1 and 2. Based on structural inferences, self-assembling hierarchy models were proposed for both of the TPPS(4)-chitosan supramolecular complexes.

Interaction of meso-tetrakis(4-sulphonatophenyl)porphine with chitosan in aqueous solutions.

Interaction of meso-tetrakis(4-sulphonatophenyl)porphine (TPPS4) with chitosan (Mr approximately 400 kDa, N-acetyls approximately 20 mol.%) was studied in aqueous solutions. UV-vis absorption and circular dichroism (CD) spectroscopic titration of 10 micromol l-1 TPPS4 with chitosan demonstrated that an addition of the polysaccharide at appropriate concentrations and pH values induce and support self-aggregation of the macrocycles. The mode of aggregation was strongly dependent on pH: stacking (H-type) aggregates predominated at weak acidic conditions (pH 4.8-6.8) and tilted (J-type) aggregates at pH 2.5. At the intermediate pH value (3.6) both types of TPPS4 aggregates were detected. High amount of chitosan (>0.05 mmol l-1 of GlcN) disrupts H-aggregates forming monomeric porphyrin-chitosan complexes (pH 3.6-6.8), while J-aggregates (pH 2.5) are stable even at very high chitosan concentrations. CD titration experiments confirmed the formation of optically active species of TPPS4 in the presence of chitosan. The complex nature of CD bands assigned to both types of porphyrin aggregates indicated the occurrence of several chiral macrocyclic species dependently on pH value and chitosan concentration.

Optical sensing system for ATP using porphyrin-alkaloid conjugates.

Tetrabrucin-porphyrin as a sensor for ATP was designed and tested; selectivity for ATP was proved in the presence of ADP and AMP.

In vitro interaction of macrocyclic photosensitizers with intact mitochondria: a spectroscopic study.

Six water-soluble macrocyclic photosensitizers, the members of two groups of expanded porphyrins (metallotexaphyrins and free-base sapphyrins) containing hydrophilic substituents and meso-tetra(4-sulfonatophenyl)-porphyrin, were tested by UV-Vis absorption and resonance Raman spectroscopy in the in vitro binding experiments with intact mitochondria isolated from swine liver. Studied macrocycles showed markedly different affinity to mitochondria. The highest uptake was observed for sapphyrin-sugar conjugate and metallotexaphyrins. Sapphyrin-polyamine conjugates exhibit something less affinity to mitochondria, while the porphyrin of anionic character showed very low mitochondrial uptake. Obtained spectroscopic results confirm that the binding process altered the self-aggregation degree of expanded porphyrins.

Biodistribution assessment of a lutetium(III) texaphyrin analogue in tumor-bearing mice using NIR Fourier-transform Raman spectroscopy.

The use of near-infrared (NIR)-excited Fourier-transform (FT) Raman spectroscopy as a technique for evaluating the extent of photosensitizer localization in tumor (human pancreatic adenocarcinomas)-bearing mice has been tested using lutetium(III) texaphyrin analogue Lu-T2B2Tex. The complex was injected subcutaneously in the form of three injections given during the course of 3 days. The kinetics of biodistribution were then followed over a time scale of 1-6 days. The NIR-FT-Raman spectra of tissue samples obtained from the xenographic tumor, muscle, heart, brain, liver, spleen, kidney and blood were recorded and used to identify the presence of Lu-T2B2Tex in these tissues. Five Raman sensitizer markers were used to estimate the relative content of Lu-T2B2Tex in tumor at various postinjection times. UV-Visible (Vis) absorption spectroscopic detection of this sensitizer in tissue extracts was applied as a conventional method. Both spectroscopic methods were in good agreement with each other and confirm that Lu-T2B2Tex localizes well in tumor tissue. Maximal drug content was observed 3 days after the final injection. This time delay seems to be optimal for tumor irradiation in photodynamic therapy.

The complexation of metal cations by D-galacturonic acid: a spectroscopic study.

Solid complexes of D-galacturonic acid (GalA) with cobalt(II), copper(II), nickel(II) and oxovanadium(IV) (1-4) were prepared and characterised. The metal-to-ligand molar ratio was 1:2 for complexes 1-3 and 1:1 for complex 4. The alpha- and beta-anomers of GalA were detected in all the complexes in solid state and in solutions. An addition of small amounts of the paramagnetic complexes to the D2O solution of pure ligand led to NMR line broadening of some 1H and 13C nuclei. This broadening was sensitive to the anomeric state of GalA in the case of complexes 1 and 4. NMR and vibrational spectroscopic data indicate the formation of carboxylate complexes of all the cations, while noncarboxylic oxygens are also involved into the metal bonding in some cases. VCD spectra of complexes 1-4 in D2O and Me2SO-d6 solutions confirm that GalA carboxylic group may participate in the formation of optically active species around the metal cation. Possible ways of GalA coordination by metal cations of this study were proposed and discussed.

Biolocalisation and photochemical properties of two novel macrocyclic photosensitisers: a spectroscopic study.

Biolocalisation and photochemical properties of novel macrocyclic photosensitisers, guanidiniocarbonyl-substituted tetraphenylporphyrin (1) and sugar-substituted sapphyrin (2) were investigated by spectroscopic methods. Both photosensitisers absorb in far visible region and showed good tumour localisation. Photosensitiser 2 demonstrated significantly larger absolute and relative to normal tissue (T/N) amount in tumour (330 microg g(-1) wet tissue, T/N=19.0) than photosensitiser 1 did (13 microg g(-1) wet tissue, T/N=2.1). According to iodometric and uric acid assays, compound 1 produced large amount of 1O2 (phidelta=0.60-0.68), while compound 2 showed non-significant 1O2 production (phidelta=0.04). The electronic spectroscopic study confirms that only photosensitiser 1 is able to mediate photooxidation of model compounds (BSA, poly(Trp), Tyr, Trp, and GMP) after light irradiation. Pour photochemical activity of compound 2 was explained by its self-aggregation. Raman spectroscopic study indicated that monomerised photosensitiser 2 effectively damaged BSA and calf thymus DNA after light excitation at the conditions of high excess of these macromolecules.

The function of the blood aqueous barrier in eyes with emulsified silicone oil.

PURPOSE: To evaluate the function of the blood aqueous barrier(BAB) in the eyes with silicone oil emulsification (SOE). METHODS: Protein concentrations, expressed in albumin equivalents,were determined in aqueous humor of the eyes with SOE in 11 consecutive patients by means of proton nuclear magnetic resonance (1H NMR) spectroscopy. Correlations with various clinical factors were studied. RESULTS: Normal function of the BAB (albumin equivalents 1mg/ml and less was found in 8 eyes (73%) independently on underlying disease, early postoperative reaction after pars plana vitrectomy with SO implantation, degree of SOE and late postoperative complications. Increased permeability of the BAB (albumin equivalents equal 2, 3 and 6.5 mg/ml) was found in 3 eyes (27%) with recent acute complication (retinal detachment after SO removal in 2 eyes, and secondary angle closure glaucoma in 1 eye). CONCLUSION: SOE in vivo was associated with increased permeability of the BAB in the minority of the eyes. Other factors should be studied to explain the variability of SOE. 1H NMR spectroscopy might be a valuable method for the study of SOE.

Interactions of cyclodextrins with aromatic compounds studied by vibrational circular dichroism spectroscopy.

The host/guest complexation between cyclodextrins (CDs) and aromatic compounds was studied by vibrational circular dichroism (VCD) spectroscopy in mid-IR region. Benzoic acid, 4-aminobenzoic acid, and 2,6-naphthalene-dicarboxylic acid acting as the guests with aromatic skeleton, cause the significant changes in VCD patterns of CD, which indicate that the secondary hydroxyl groups of the CDs are involved in the host/guest complexation. In addition, the intensities and dissymmetry factors (deltaA/A) of the VCD bands, which belong to skeletal CD vibrations, depend on the sizes of the guest molecules. Our results indicate that the formation of the CD inclusion complexes can be followed by VCD spectroscopy.

Molecular structure of guanine-quartet supramolecular assemblies in a gel-state based on a DFT calculation of infrared and vibrational circular dichroism spectra.

The infrared (IR) and vibrational circular dichroism (VCD) spectra of guanosine-5'-hydrazide ( G-1), a powerful hydrogelator, have been measured and analyzed on the basis of ab initio modeling. B3LYP/6-31G** DFT calculations predict that G-1, forming a clear solution in deuterated DMSO, is present in monomeric form in this solvent, whereas strong gelation in a phosphate buffer is due to the formation of a guanine-quartet structure, ( G-1)4, in which the four G-1 are linked by hydrogen-bonded guanine moieties and stabilized by an alkali metal cation. The B3LYP/6-31G** IR and VCD spectra of the nearly planar G-quartet, whose structure is slightly distorted from the C4h symmetry, in which the G-bases interact via four Hoogsteen-type hydrogen bonds and a sodium cation is positioned in the middle of the G-quartet, are in very good agreement with the experimental spectra, indicating that this structure is the predominant structure in the gel state. The geometric parameters are discussed. This study is the first to use IR and VCD spectroscopies coupled with DFT calculations to elucidate the structure of a supramolecular species in a gel state and shows the VCD spectroscopy as a powerful method for investigating the structure of complex supramolecular self-assemblies where the use of other structural methods is limited.

Investigation of guanosine-quartet assemblies by vibrational and electronic circular dichroism spectroscopy, a novel approach for studying supramolecular entities.

The self-assembly of guanosine-5'-hydrazide G-1 in D(2)O, in the presence and absence of sodium cations, has been investigated by chiroptical techniques: electronic (ECD) and the newly introduced vibrational (VCD) circular dichroism spectroscopy. Using a combination of ECD and VCD with other methods such as IR, electron microscopy, and electrospray ionization mass spectrometry (ESI-MS) it was found that G-1 produces long-range chiral aggregates consisting of G-quartets, (G-1)(4), subsequently stacked into columns, [(G-1)(4)](n), induced by binding of metal cations between the (G-1)(4) species. This process, accompanied by gelation of the sample, is highly efficient in the presence of an excess of sodium cations, leading to aggregates with strong quartet-quartet interaction. Thermally induced conformational changes and conformational stability of guanosine-5'-hydrazide assemblies were studied by chiroptical techniques and the melting temperature of the hydrogels formed was obtained. The temperature-dependent experiments indicate that the long-range supramolecular aggregates are dissociated by increasing temperature into less ordered species, monomers, or other intermediates in equilibrium, as indicated by MS experiments.

Circular dichroism spectroscopic study of non-covalent interactions of poly-L-glutamic acid with a porphyrin derivative in aqueous solutions.

The interactions of poly-L-glutamic acid and a cationic porphyrin derivative in aqueous solutions were studied by the combination of vibrational circular dichroism (VCD) and electronic circular dichroism (ECD) spectroscopies. It was found that non-covalent interactions between both agents influence the structure of the polymeric matrix and the guest porphyrins and vice versa, but the physico-chemical properties of the solutions, especially the pH and the relative permittivity of the solvent, play a key role in the structure of the polypeptide part of the formed complexes. It was shown that the interaction with porphyrins prevents the precipitation of poly-L-glutamic acid in aqueous solution at acidic pH. In special conditions, the porphyrins attached to the polypeptide probably possess face-to-face interaction as demonstrated by the enhancement of the characteristic ECD signal and the appearance of sidebands on its short and long wavelength sides.

Extraction of p-hydroxyacetophenone and catechin from Norway spruce needles. Comparison of different extraction solvents.

The phenolic compounds p-hydroxyacetophenone and catechin have been extracted from Norway spruce needles with pure methanol, 80 and 50% (v/v) aqueous methanol, pure acetonitrile, 80% (v/v) aqueous acetonitrile, and pure water. Extraction efficiency of the individual solvents was compared. Although 80% aqueous methanol is the solvent most frequently used for extraction of soluble phenolic compounds from needles, it was found that pure methanol is a more suitable extraction solvent. Surprisingly, a two-step procedure based on the extraction of crushed needles with water then re-extraction with methanol proved a good alternative to direct extraction with methanol. Extraction of uncrushed spruce needles might indicate that relatively more p-hydroxyacetophenone than catechin was located in the surface layer of the needle.

Surface plasmon resonance and Raman scattering effects studied for layers deposited on Spreeta sensors.

The possibility to detect and prospectively to characterize deposited organic layers directly on Spreeta sensors by Fourier transform Raman spectroscopy was studied. A special holder of sensors that enabled measurement of FT Raman spectra was developed. The effects of various angles of incidence of the laser beam on the sensor surface were studied with respect to the intensity of Raman spectra and to the risks of artifacts. No effect of measurement of FT Raman spectra on SPR functionality of sensors was proven. The key role of the surface morphology of the sensing gold layer on repeatability of SPR curves and the possibility to check the surface by optical microscopy was demonstrated.

Vibrational circular dichroism spectroscopy study of paroxetine and femoxetine precursors.

The solution structures of (3R,4S)- and (3S,4R)- 4-(4-fluorophenyl)-3-hydroxylmethyl- 1-methylpiperidine, which are intermediates in the synthesis of the two pharmaceuticals paroxetine and femoxetine, were studied by vibrational circular dichroism (VCD) spectroscopy. In addition, six derivatives with different substituents attached to the C3 atom were prepared and their VCD and absorption spectra discussed with the aid of ab initio simulations. The VCD spectra were found to be sensitive to the geometry changes. In addition, a subtle variation caused by intermolecular aggregation was apparent in the spectra. The VCD technique can be applied for structural analysis of chiral pharmaceuticals in solutions.

Conformational flexibility of Corey lactone derivatives indicated by absorption and vibrational circular dichroism spectra.

Infrared absorption and vibrational circular dichroism (VCD) spectra of four Corey lactone derivatives (diol, benzoate, p-phenylbenzoate, and bisbenzoate) were measured and analyzed on the basis of ab initio computations. The analysis interpreted most of the spectral features as well as the differences among individual compounds. Despite the common rigid lactone residue, conformational behaviors and spectral features of the derivatives were found to be different, because of hydrogen bonding and solvent effects. Recognition of common molecular parts in the spectra of different molecules increases the potential of using VCD for monitoring the purity of intermediates in chiral syntheses. For the derivatives, a conserved spectral component corresponding to the lactone skeleton could be identified on the basis of theoretical analysis but was relatively weak in intensity.

(3R,4S)-4-(4-Fluorophenyl)-3-hydroxymethyl-1-methylpiperidine: conformation and structure monitoring by vibrational circular dichroism.

Absorption and vibrational circular dichroism (VCD) spectra of the title compound, a common intermediate in synthesis of many pharmaceuticals, were measured and analyzed in order to determine its absolute configuration and prevailing conformations. The analysis was combined with a systematic conformer search based on relative energies as well as with comparison of experimental and computed NMR shifts. The spectra were interpreted on the basis of ab initio simulations. The results indicate that the compound adopts exclusively a chair conformation of the piperidine ring with all the fluorophenyl, hydroxymethyl, and methyl substituents attached in equatorial positions. A limited rotation of the hydroxymethyl group is most consistent with the observed VCD pattern. VCD parameters were found significantly more sensitive to conformational changes than absorption or NMR. Concentration dependence of the absorption spectra indicated aggregation in concentrated solutions, but involved hydrogen bonds probably do not influence molecular conformation.