Spectra of Molecular Complexes of Porphyrins in Aqueous Solution^*

Abstract

The changes in the absorption and emission spectra of porphyrins in various molecular complexes in aqueous solution have been studied. These complexes are formed with a variety of molecules including large organic cations and planar neutral heterocyclic molecules. Spectral analysis by the method of continuous variation, the lack of isosbestic points, and a new analysis based on band widths all point to the formation of a series of complexes with several addends clustered about the porphyrin ring. Ionic and dispersion forces contribute to the stability of the complexes, but the water structure about these large hydrophobic molecules is an equally important factor. An estimate of the latter interaction based on interfacial tension is given.T he unique absorption spectra of the porphyrin pigments has allowed their identification and study throughout the biological realm. The large over-all variation of spectra with changes of structure has been used to identify these pigments. However, much information concerning the nonbonded or weakly bonded environment of these pigments remains untapped in minor spectral variations.In the course of experiments on the photoreactions of porphyrins, a marked effect of pyridinium salts (NAD' models) on the photochemistry was traced to the formation of complexes with the porphyrin. These complexes were found to occur with a wide class of compounds, many of biological importance. Their description is relevant to the problem of deciphering the effect of environment on porphyrin pigments in vivo. Moreover, some insight is gained into both the theory of porphyrin spectra and the binding of molecular complexes in aqueous solution. . This investigation was aided by a grant (GM 04922) from the U.S. Public Health Service.Abbreviation used in this work: NAD, nicotinamideadenine dinucleotide.The spectral changes, particularly the broadening of the Soret band and not of the red band I , are interpreted as a change in the nearly degenerate x and y components of the energy levels, and a model of the complex is derived.Studies at extreme dilution M), an analysis of the optical effects of aggregation on the spectra, and the absence of polarization of fluorescence all favor the view that the uroporphyrin is monomolecularly dispersed. A suggestion is made that such complexes occur in heme proteins as part of the phosphorylating mechanism and that the widespread occurrence of heterocyclic molecules in biological systems is related to the formation of complexes. otherwise stated, uroporphyrin isomer 111 or a mixture of isomers, mostly isomer 111, was used in this work. Most of the quaternary salts were synthesized in the laboratory and their melting points, analysis, and absorption spectra agreed with previously published data. Other compounds were the purest commercially available and were recrystallized when necessary, e.g., hexadecyltrimethylammonium bromide. The water was glass redistilled, and quantitative technique was used throughout. Absorption spectra were measured on a Cary Model 14 MR spectro...

Specific visible spectral changes induced by guanine binding to cytosine-derivatized porphyrin

“…Those interactions that withdraw electrons from the macrocycle tend to cause bathochromic shifts in the spectrum as noted by others [34][35][36]. For example, the binding of sugars to boronporphyrins [1] results in a change in the porphyrin spectrum.…”

“…The interaction of porphyrins with nucleic acids is of interest because of the usage of porphyrins in photodynamic therapy as well as their possible use in detecting genetic mutations. Changes in the absorbance spectra of porphyrins result from three possible interactions with porphyrins; first, interaction with a molecule(s) may induce stacking or porphyrin aggregation, resulting in spectral changes as a J-or H-type aggregate is formed [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]; second, the interaction with porphyrins may occur via co-facial/coplanar interaction, also resulting in spectral changes [34][35][36] and third, noncovalent interactions, such as hydrogen bonds of functionalized or derivatized porphyrins with another molecule [37] can result in spectral changes induced by electron redistribution in the porphyrin.…”

SINGLET OXYGEN GENERATION BY HEMATOPORPHYRIN IX, UROPORPHYRIN I and HEMATOPORPHYRIN DERIVATIVE AT 546 nm IN PHOSPHATE BUFFER and IN THE PRESENCE OF EGG PHOSPHATIDYLCHOLINE LIPOSOMES

“…The relatively high values of +A(Uro-I) in PB and PB7 indicate that aggregation is less important than with HP. [Uroporphyrin 111 has been shown to be monomeric in water solutions (Mauzerall, 1965).] The ratio: +A(Uro-I)/+A(HP) was measured as 1.55 with an ESR technique and 1.99 with the RNO method at pH 8.0 (Emiliani and Delmelle, 1983).…”

Simple Formation of an Abiotic Porphyrinogen in Aqueous Solution

“…By contrast, in N,N-dimethylformamide (DMF) or DMF/H 2 O (9:1), the B band appears at 427 nm and the Q bands are relatively sharp; the spectrum is nearly identical to that of the similarly substituted synthetic compound 2,7,12,8,13, (Kleinspehn et al 1966). Similar behavior in aqueous versus organic media is exhibited by coproporphyrin and other porphyrins that bear four or fewer alkyl carboxy groups (Mauzerall 1965;Brown et al 1976;Morales-Rojas and Yatsimirsky 1999). The broadened, blue-shifted spectrum in aqueous solution is a consequence of aggregation, most likely via hydrophobic stacking to form multimeric assemblies (Brown et al 1976).…”