Porphyrin Fluorescence Dominates UV Photoemission of Folded Cytochrome <i>c</i>

Löwenich, Dennis; Kleinermanns, Karl

doi:10.1111/j.1751-1097.2007.00145.x

Cited by 8 publications

(9 citation statements)

References 22 publications

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“…This delayed haem population, also observed in its emission (see section 3), is concomitant with the Trp de-excitation and provides unambiguous evidence of a very efficient Trp-haem energy transfer, on the time scales of 350 and 700 fs. This is also in agreement with fluorescence QY measurements as a function of pH, , if we compare them to the radiative decay of ∼3 ns measured in aqueous solution …”

Section: Discussionsupporting

confidence: 87%

“…The UV fluorescence emission of Cyt c (300–450 nm) is expected to stem mainly from Trp residue. ,,, However, Löwenich et al reported a bimodal fluorescence, investigated through excitation-wavelength-dependent fluorescence spectroscopy . They claimed that upon excitation at 280 nm and at pH 7, the iron porphyrin contributes about 80% and tryptophan about 20% to the total fluorescence.…”

Section: Resultsmentioning

confidence: 99%

“…With lifetimes of 40 and 350 fs, respectively, we find that the emission quantum yield is the same for both the haem and the Trp moieties. Interestingly, L€ owenich et al 37 observed that upon excitation at 280 nm and at pH 7, the haem contributes about 80% and tryptophan about 20% to the total stationary fluorescence. This is not far from our aforementioned contributions of 72% and 28% of haem and Trp to the total absorption; therefore, a similar estimation for the QY is derived.…”

Section: ' Discussionmentioning

confidence: 99%

“…4,18,35,36 However, L€ owenich et al reported a bimodal fluorescence, investigated through excitation-wavelength-dependent fluorescence spectroscopy. 37 They claimed that upon excitation at 280 nm and at pH 7, the iron porphyrin contributes about 80% and tryptophan about 20% to the total fluorescence. They fitted the stationary emission spectrum of Cyt c with two broad Gaussians, respectively, centered at 355 nm for the Trp contribution and 370 nm for the haem contribution.…”

Section: ' Introductionmentioning

confidence: 99%

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Femtosecond UV Studies of the Electronic Relaxation Processes in Cytochrome c

et al. 2011

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We report on an experimental study with UV and visible ultrafast time-gated emission and transient absorption of the early photodynamics of horse heart Cytochrome c in both ferric and ferrous redox states. A clear separation in time and energy of tryptophan and haem emission is observed. Excitation of the haem via resonant energy transfer from the tryptophan residue is observed in the subsequent haem electronic relaxation. Different Trp-haem energy transfer time constants of the ferrous and ferric forms are obtained. An almost instantaneous relaxation to the lowest singlet excited state (corresponding to the so-called Q band) characterizes the earliest electronic dynamics of the haem, independent of excitation energy, while dark intermediate states govern the ground-state recovery. The information gathered in these two experiments and in the literature allows us to propose a simple scheme for the electronic relaxation leading to ligand dissociation.

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Section: Discussionsupporting

confidence: 87%

Section: Resultsmentioning

confidence: 99%

Section: ' Discussionmentioning

confidence: 99%

Section: ' Introductionmentioning

confidence: 99%

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Femtosecond UV Studies of the Electronic Relaxation Processes in Cytochrome c

et al. 2011

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“…35 The unfolding upon increasing urea concentration is characterized by a cooperative transition, N ↔ U, between the native (N) and unfolded conformations (U). 40 This equilibrium has been extensively characterized by different techniques including fluorescence 41 and circular dichroism (CD). 35,42 The stability of cyt c was accordingly analyzed here under the assumption of a simple N ↔ U equilibrium.…”

Section: Biomacromoleculesmentioning

confidence: 99%

Unfolding of Cytochromecupon Interaction with Azobenzene-Modified Copolymers

et al. 2012

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Hydrophilic or amphiphilic macromolecules are common organic matrices used to encapsulate and protect fragile drugs such as proteins. Polymer cargoes are in addition designed for remote control of protein delivery, upon imparting the macromolecules with stimuli-responsive properties, such as light-triggered polarity switches. The effect of interaction between polymers and proteins on the stability of the proteins is, however, rarely investigated. Here we studied the unfolding/folding equilibrium of cytochrome c (cyt c) under its oxidized or reduced forms, in the presence of various amphiphilic copolymers (by circular dichroism and intrinsic fluorescence measurements). As models of stimuli-responsive amphiphilic chains, we considered poly(acrylic acid) derivatives, modified to contain hydrophobic, light-responsive azobenzene moieties. These copolymers are, thus, capable to develop both ionic (under their sodium forms at pH > 8) and hydrophobic associations with the basic protein cyt c (isoelectric point of 10.0). In aqueous buffer upon increasing urea concentrations, cyt c underwent unfolding, at [urea] of 9-10 M, which was analyzed under the framework of the equilibrium between two states (native-unfolded). In the presence of polymers, the native folding of cyt c was preserved at low concentrations of urea (typically <4M). However, the presence of polymers facilitated unfolding, which occurred at urea concentrations lowered by 2-4 M as compared to unfolding in the absence of polymers (polymer/cyt c ratio of 1:1 g/g). The predominant contribution of coulombic interactions was shown by both the lack of significant impact of the amount of (neutral) azobenzene moieties in the copolymers and the disappearance of destabilization at ionic strength higher than 150 mM. In addition, stability was similar to that of an isolated cyt c, in the presence of a neutral chain bearing acryloyl(oligoethyleneoxide) units instead of the ionized sodium acrylate moieties. DSC measurements showed that in the presence of polymers, cyt c is thermally unfolded in aqueous buffer at temperatures lowered by >20 °C as compared to thermal unfolding in the absence of polymers. Upon exposure to UV light, properties of the polymers chains were perturbed in situ, upon cis/trans isomerization of the azobenzene groups. In polymers displaying a photoresponsive polarity and hydrophobicity switch (conventional azobenzene), the stability of cyt c was not affected by the exposure to light. In contrast, when photoionization occurred (using an hydroxyl-azobenzene whose pK(a) can be photoshifted), unfolding was initiated upon exposure to light. Altogether, these results show that coulombic binding is a predominant driving force that facilitates unfolding in water/urea solutions. In regard to the design of light-responsive systems for protein handling and control of folding, we conclude that remote control of the coulombic interaction upon photoionization of chromophores can be more efficient than the more conventional photomodulation of polarity.

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Alder‐Longo Method Derived Cationic Porphyrin‐Based Porous Polymer as Physical Antibacterial Agent for the Bacteria‐Infected Wound Synergy Therapy

Li,

Fu,

Chu

et al. 2024

ChemistrySelect

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The widespread of drug‐resistant genes has greatly exacerbated the difficulty for the effectively tre atment of diseases associated with bacterial infections. The ineffectiveness of antibiotics poses great challenges to the development of new antimicrobial agents, especially those does not cause bacterial resistance. Herein, a cation porous organic polymer (CPOP) denoted as BDPP, was facilely prepared via the Alder‐Longo method skipping the tedious porphyrin‐bearing monomer synthesis procedure. The repeated porphyrin units endowed excellent photoactivity with the porous skeletons, and the inherent cations significantly improved the binding ability of BDPP with the bacterial cell membrane. As a result, the as‐synthesized POPs could be used as a physical broad spectrum sterilization agent, amalgamating the cation and photothermal therapy to exert synergistic amplified antibacterial effects. In vivo assay demonstrated BDPP with good biocompatibility, could also significantly promote the healing of wounds with bacteria‐infection. This work paves a facile way for the rational construction of material‐based antibacterial agent for the bacteria inactivation.

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Porphyrin Fluorescence Dominates UV Photoemission of Folded Cytochrome c

Cited by 8 publications

References 22 publications

Femtosecond UV Studies of the Electronic Relaxation Processes in Cytochrome c

Femtosecond UV Studies of the Electronic Relaxation Processes in Cytochrome c

Unfolding of Cytochromecupon Interaction with Azobenzene-Modified Copolymers

Alder‐Longo Method Derived Cationic Porphyrin‐Based Porous Polymer as Physical Antibacterial Agent for the Bacteria‐Infected Wound Synergy Therapy

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