8 research outputs found
Photocatalytic Generation of Oxygen Radicals by the Water-Soluble Bacteriochlorophyll Derivative WST11, Noncovalently Bound to Serum Albumin
In Situ Grafting of Silica Nanoparticle Precursors with Covalently Attached Bioactive Agents to Form PVA-Based Materials for Sustainable Active Packaging
Sustainable antibacterial–antioxidant films were prepared using in situ graftings of silica nanoparticle (SNP) precursors with covalently attached bioactive agents benzoic acid (ba) or curcumin (cur) on polyvinyl alcohol (PVA). The modified PVA-SNP, PVA-SNP-ba and PVA-SNP-cur films were characterized using spectroscopic, physicochemical and microscopic methods. The prepared films showed excellent antibacterial and antioxidant activity, and increased hydrophobicity providing protection from undesired moisture. The PVA-SNP-ba films completely prevented the growth of the foodborne human pathogen Listeria innocua, whereas PVA-SNP-cur resulted in a 2.5 log reduction of this bacteria. The PVA-SNP-cur and PVA-SNP-ba films showed high antioxidant activity of 15.9 and 14.7 Mm/g TEAC, respectively. The described approach can serve as a generic platform for the formation of PVA-based packaging materials with tailor-made activity tuned by active substituents on silica precursors. Application of such biodegradable films bearing safe bioactive agents can be particularly valuable for advanced sustainable packaging materials in food and medicine
Transparent Gold as a Platform for Adsorbed Protein Spectroelectrochemistry: Investigation of Cytochrome <i>c</i> and Azurin
The majority of protein spectroelectrochemical methods
utilize
a diffusing, chemical mediator to exchange electrons between the electrode
and the protein. In such methods, electrochemical potential control
is limited by mediator choice and its ability to interact with the
protein of interest. We report an approach for unmediated, protein
spectroelectrochemistry that overcomes this limitation by adsorbing
protein directly to thiol self-assembled monolayer (SAM) modified,
thin (10 nm), semitransparent gold. The viability of the method is
demonstrated with two diverse and important redox proteins: cytochrome <i>c</i> and azurin. Fast, reversible electrochemical signals comparable
to those previously reported for these proteins on ordinary disk gold
electrodes were observed. Although the quantity of protein in a submonolayer
adsorbed at an electrode is expected to be insufficient for detection
of UV–vis absorption bands based on bulk extinction coefficients,
excellent spectra were detected for each of the proteins in the adsorbed
state. Furthermore, AFM imaging confirmed that only a single layer
of protein was adsorbed to the electrode. We hypothesize that interaction
of the relatively broad gold surface plasmon with the proteins’
electronic transitions results in surface signal enhancement of the
molecular transitions of between 8 and 112 times, allowing detection
of the proteins at much lower than expected concentrations. Since
many other proteins are known to interact with gold SAMs and the technical
requirements for implementation of these experiments are simple, this
approach is expected to be very generally applicable to exploring
mechanisms of redox proteins and enzymes as well as development of
sensors and other redox protein based applications
Submolecular Gates Self-Assemble for Hot-Electron Transfer in Proteins
Redox
reactions play key roles in fundamental biological processes.
The related spatial organization of donors and acceptors is assumed
to undergo evolutionary optimization facilitating charge mobilization
within the relevant biological context. Experimental information from
submolecular functional sites is needed to understand the organization
strategies and driving forces involved in the self-development of
structure–function relationships. Here we exploit chemically
resolved electrical measurements (CREM) to probe the atom-specific
electrostatic potentials (ESPs) in artificial arrays of bacteriochlorophyll
(BChl) derivatives that provide model systems for photoexcited (hot)
electron donation and withdrawal. On the basis of computations we
show that native BChl’s in the photosynthetic reaction center
(RC) self-assemble at their ground-state as aligned gates for functional
charge transfer. The combined computational and experimental results
further reveal how site-specific polarizability perpendicular to the
molecular plane enhances the hot-electron transport. Maximal transport
efficiency is predicted for a specific, ∼5 Å, distance
above the center of the metalized BChl, which is in remarkably close
agreement with the distance and mutual orientation of corresponding
native cofactors. These findings provide new metrics and guidelines
for analysis of biological redox centers and for designing charge
mobilizing machines such as artificial photosynthesis