Induced CD and interaction of some porphyrin derivatives with α‐helical polypeptides in aqueous solutions

Abstract

Absorption spectra and induced CD have been measured on aqueous solutions of watersoluble porphyrins with a-helical poly (L-glutamic acid) or a-helical poly (L-lysine) a t different mixing ratios. For the former, porphyrin is porphine-meso-tetra (4-N-methylpyridinium) (TMpyP) , and for the latter, it is porphine-meso-tetra( 4-benzenesulfonate) (TPPS) or porphine-meso-tetra( 4-benzoate) ( T P P C ) . All the solutions of porphyrinpolypeptide systems show hypochromism in the Soret band and induced CD in the Soret region. The CD is characterized by a positive band at a shorter wavelength and a stronger negative band at a longer wavelength. The hypochromicity and the magnitude of molar ellipticities are much larger for the TPPSand TPPC-poly (L-lysine) systems than for the TMpyP-poly (L-glutamic acid) system. Porphyrin ions bind to the a-helix electrostatically, and the two components of the Soret transition of porphyrin are subject to dissymmetric perturbation. TMpyP ions bind to the a-helix at isolated sites, while TPPS ions and TPPC ions are in pairs on the a-helix, that is, two ions bind consecutively and dissymmetrically.In the TMpyP-poly (L-glutamic acid) system a single CD band is associated with each of the two components of the Soret transition, and these are of opposite sign. In the TPPSand TPPC-poly( L-lysine) systems, a pair of positive and negative CD bands is associated with each of the two components, thus giving apparently a single pair of CD bands with a shoulder, owing to partial overlapping.

Chiral memory and self-replication study of porphyrin and bilirubin aggregates formed on polypeptide matrices

“…The effect of the matrix average molecular weight can also be observed by UV-Vis absorption. It has been demonstrated [1] that the porphyrin supramolecular structure chirogenesis is manifested in a broader absorption and a decreased intensity of the porphyrin signals in the Soret region (hypochromic effect). Fig.…”

“…benzoato)porphyrin (TPPC) serve as porphyrin partners in the formation of binary complexes with positively charged polylysine [1,6,8]. The complex of polyglutamic acid and CuT4 has been well described [2,4,5,7] through the application of electronic circular dichroism (ECD) spectroscopy.…”

Spectroscopy for model heterogeneous asymmetric catalysis

“…Consequently, probing the optical activity of potential heterogeneous catalysts is a promising way to examine the effectiveness of chirality transfer. [71][72][73][74][75][76][77] In one of our recent contribution, we reported on the tunability of the effect in spin-coated films composed of achiral Rhodamine 110 laser dye and chiral 1,1′-bi-2-naphthol. We could show that by varying the partial concentration of the chiral component, the FIGURE 2 Illustration of a HeAC according to the asymmetrization approach that is suitable for model studies under controlled condition.…”

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

“…It is well known that secondary structure, which depends on intramolecular hydrogen bonds, is influenced by the physicochemical properties of solution [30] and polypeptide conformational changes have been described [14,[31][32][33][34]. Therefore, polypeptides can serve as polymeric spatially aligned matrices, which are able to imprint their geometric properties onto the interacting porphyrins [35][36][37][38][39][40]. A large induced ECD signal in the Soret region, which is characteristic for porphyrins, was observed in non-covalent complexes [37][38][39] as well as in covalent porphyrin-peptide conjugates [35].…”

“…Therefore, polypeptides can serve as polymeric spatially aligned matrices, which are able to imprint their geometric properties onto the interacting porphyrins [35][36][37][38][39][40]. A large induced ECD signal in the Soret region, which is characteristic for porphyrins, was observed in non-covalent complexes [37][38][39] as well as in covalent porphyrin-peptide conjugates [35]. The induction of porphyrin optical activity is not caused only by large macromolecules such as polypeptides but also by small chiral molecules, for example amino acids [41].…”