Technological Applications of Porphyrins and Related Compounds: Spintronics and Micro-/Nanomotors

The vital role played by porphyrins in cells and their use in therapeutic processes are well known. More recently, the technological applications of porphyrins have attracted the attention of researchers. Porphyrins have the property of half-metallic material, i.e., molecules that can host transition metals making feasible the production of spin-polarized electronic states at different channels. Therefore, porphyrins and hemeproteins are among the materials that have spin-filtering property to be applied in spintronics. Molecular spintronics is an emerging and highly relevant field due to their applications to the development of high-capacity information-storage devices and quantum computers. The catalytic properties of porphyrins and related compounds such as the hemeproteins are also applicable in the fabrication of micro-/nanomotors (MNMs). In this chapter, we describe the advances and future perspectives in the technological applications of porphyrins and related compounds in spintronic devices and micro-/nanomotors

Collagenase Activity of Bromelain Immobilized at Gold Nanoparticle Interfaces for Therapeutic Applications

Bromelain (Bro) is a multiprotein complex extracted from the pineapple plant Ananas comosus, composed of at least eight cysteine proteases. Bro has a wide range of applications in medicine and industry, where the stability of its active proteases is always a major concern. The present study describes the improvement of stability and gain of specific activity in the enzymatic content of Bro immobilized on gold nanoparticles (GNPs). GNPs were synthesized in situ using Bro as the reducing and stabilizing agents and characterized by surface plasmon resonance and transmission electron microscopy. Consistent with the structural changes observed by circular dichroism analysis, the association with GNPs affected enzyme activity. The active Bro immobilized on GNPs (NanoBro) remained stable under storage and gained thermal stability consistent with a thermophilic enzyme. Proteolytic assays were performed on type I collagen membranes using fluorescence spectroscopy of O-phthaldialdehyde (OPA), changes in the membrane superficial structure, and topography by scanning electron microscopy, FTIR, and scanning laser confocal microscopy. Another characteristic of the NanoBro observed was the significant increase in susceptibility to the inhibitory effect of E-64, indicating a gain in cysteine protease activity. The higher stability and specific activity of NanoBro contributed to the broadening and improvement of Bro applications

Structure and Catalysis of Fe(III) and Cu(II) Microperoxidase-11 Interacting with the Positively Charged Interfaces of Lipids

Numerous applications have been described for microperoxidases (MPs) such as in photoreceptors, sensing, drugs, and hydrogen evolution. The last application was obtained by replacing Fe(III), the native central metal, by cobalt ion and inspired part of the present study. Here, the Fe(III) of MP-11 was replaced by Cu(II) that is also a stable redox state in aerated medium, and the structure and activity of both MPs were modulated by the interaction with the positively charged interfaces of lipids. Comparative spectroscopic characterization of Fe(III) and Cu(II)MP-11 in the studied media demonstrated the presence of high and low spin species with axial distortion. The association of the Fe(III)MP-11 with CTAB and Cu(II)MP-11 with DODAB affected the colloidal stability of the surfactants that was recovered by heating. This result is consistent with hydrophobic interactions of MPs with DODAB vesicles and CTAB micelles. The hydrophobic interactions decreased the heme accessibility to substrates and the Fe(III) MP-11catalytic efficiency. Cu(II)MP-11 challenged by peroxides exhibited a cyclic Cu(II)/Cu(I) interconversion mechanism that is suggestive of a mimetic Cu/ZnSOD (superoxide dismutase) activity against peroxides. Hydrogen peroxide-activated Cu(II)MP-11 converted Amplex Red® to dihydroresofurin. This study opens more possibilities for technological applications of MPs

Intermediate Tyrosyl Radical and Amyloid Structure in Peroxide-Activated Cytoglobin.

We characterized the peroxidase mechanism of recombinant rat brain cytoglobin (Cygb) challenged by hydrogen peroxide, tert-butylhydroperoxide and by cumene hydroperoxide. The peroxidase mechanism of Cygb is similar to that of myoglobin. Cygb challenged by hydrogen peroxide is converted to a Fe4+ oxoferryl π cation, which is converted to Fe4+ oxoferryl and tyrosyl radical detected by direct continuous wave-electron paramagnetic resonance and by 3,5-dibromo-4-nitrosobenzene sulfonate spin trapping. When organic peroxides are used as substrates at initial reaction times, and given an excess of peroxide present, the EPR signals of the corresponding peroxyl radicals precede those of the direct tyrosyl radical. This result is consistent with the use of peroxide as a reducing agent for the recycling of Cygb high-valence species. Furthermore, we found that the Cygb oxidation by peroxides leads to the formation of amyloid fibrils. This result suggests that Cygb possibly participates in the development of degenerative diseases; our findings also support the possible biological role of Cygb related to peroxidase activity

EPR spectrum of resting Cygb and the spectral components obtained by simulation.

<p>The red line corresponds to simulation of the composite spectrum and the blue and green lines correspond to the high and low spin components, respectively. The g values of the low spin state component are: g1 = 3.228, g2 = 2.033 and g3 = 1.385 with rhombic distortion and for the high spin state the g values are: g1 = 6.062, g2 = 5.785 and g3 = 2.0409. The simulation was done by the software Symphonia. For EPR experiments, the protein concentration was of 1.2 mmol.L^-1. These results are representative of three independent replicates.</p

Formation of Cygb amyloid structure after challenge by peroxides.

<p>A), B) and C) show, respectively the epifluorescence images of Cygb control, control plus GSH and challenged by hydrogen peroxide obtained immediately (left panels) 24 h (right panels) after incubation and staining by thioflavine-T. For the low-vacuum SEM experiments, it was used 7 μmol.L^-1 cygb solution with 70 μmol.L^-1 peroxide solutions. For the epifluorescence experiments 70 μmol.L^-1 protein solution was incubated for 1 h with 700 μmol.L^-1 peroxide solution in the presence of thioflavin-T. For FTIR measurements, 7 μmol.L^-1 protein solution was incubated with 70 μmol.L^-1 peroxide solutions for 1 h. The results are representative of three independent experiments.</p

Interatoma of rat Cygb with hydrogen peroxide.

<p>The network shows, in each node, a protein predicted to have functional links with Cygb and hydrogen peroxide. Inside the figure the abbreviations are SOD1 (superoxide dismutase [Cu-Zn]), Hmox2 (heme oxygenase 2 [HO-2]), Mb (myoglobin), Mpo (myeloperoxidase), cat (catalase), Cygb (cytoglobin), Prdx1 (peroxyredoxin-1), Prdx5 (peroxyredoxin-5) and Srxn1 (Ab2-390). In the figure light green, cyan and magenta lines correspond, respectively, to textmining, databases and experiments supporting the relationship among the proteins and hydrogen peroxide.</p

Changes in the EA spectrum of Cygb during the reaction with hydrogen peroxide.

<p>A) Bleaching of Soret and Q bands of EA spectra of Cygb in the course of the reaction with hydrogen peroxide. The black line represents the EA spectrum of resting Cygb, red, green and blue lines corresponds to the spectra obtained at 30, 60 and 200 s after addition of hydrogen peroxide and indicated by the arrows. B) Normalized spectra of Cygb resting form and 200 s after hydrogen peroxide addition. C) Differential spectra of Cygb obtained 30 and 200 s after the addition of hydrogen peroxide The experiments of EA spectroscopy were performed using 65 μmol.L^-1 Cygb and 0.1 cm optical length. When present, the concentration of peroxide was 650 μmol.L^-1. These results are representative of three independent replicates.</p

Spectroscopic characteristics of Cygb.

<p>The upper panel shows the EA spectrum of Cygb and the respective inset the corresponding far-UV CD spectrum. The lower panel shows the CD (light gray line) and the MCD spectra of Cygb obtained by addition and subtraction of the original spectra obtained at positive and negative magnetic fields. MCD is shown at increasing magnetic fields and the respective inset shows the linear increase of Soret band intensity promoted by increasing the magnetic field. The experiments of EA spectroscopy were performed with 65 μmol.L^-1 Cygb using 0.1 cm optical length. The experiments of CD and MCD were performed using 20 μmol.L^-1 protein solution in 20 mmol.L^-1 phosphate buffer, pH 7.4. These results are representative of three independent replicates.</p