Design and Evaluation of Artificial Hybrid Photoredox Biocatalysts

Article abstract of DOI:10.1002/cbic.202000362

A pair of 9-mesityl-10-phenyl acridinium (Mes?Acr⁺) photoredox catalysts were synthesized with an iodoacetamide handle for cysteine bioconjugation. Covalently tethering of the synthetic Mes?Acr⁺ cofactors with a small panel of thermo

Full text of DOI:10.1002/cbic.202000362

Combining Chemistry and Biology
Accepted Article
Title: Design and Evaluation of Artificial Hybrid Photoredox Biocatalysts
Authors: Timothy Daniel Schwochert, Cole Cruz, John W. Watters,
Evan W. Reynolds, David A. Nicewicz, and Eric Brustad
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: ChemBioChem 10.1002/cbic.202000362
Link to VoR: https://doi.org/10.1002/cbic.202000362
01/2020

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
Design and Evaluation of Artificial Hybrid Photoredox
Biocatalysts
Timothy D. Schwochert[a], Cole L. Cruz[a], John W. Watters[a], Evan W. Reynolds[a], David A. Nicewicz[a],
Eric M. Brustad[a],[b]
[a]
T. D. Schwochert, Dr. C. L. Cruz, J. W. Watters, Prof. D. A. Nicewicz, Prof. E. M. Brustad
Department of Chemistry
University of North Carolina at Chapel Hill
125 South Road CB 3290, Chapel Hill, NC 27599 (USA)
[b]
Current address:
Illumina, Inc.
5200 Illumina Way, San Diego, CA 82130
E-mail: ebrustad@illumina.com
Supporting information for this article is given via a link at the end of the document.
A
pair of 9-mesityl-10-phenyl acridinium (Mes-Acr+)
example, photoredox catalysis has shown increased application
for chemical synthesis due to its broad utility in bond activation
via mechanisms that are often orthogonal or complementary to
traditional transition metal chemistry.[12,13] Photoredox
Abstract:
photoredox catalysts were synthesized with an iodoacetamide handle
for cysteine bioconjugation. Covalently tethering of the synthetic Mes-
Acr+ cofactors with a small panel of thermostable protein scaffolds
resulted in twelve newly reported artificial enzymes. The unique
chemical and structural environment of the protein hosts had a
measurable effect on the photophysical properties and photocatalytic
activity of the cofactors. The constructed Mes-Acr+ hybrid enzymes
were found to be active photoinduced electron transfer catalysts,
controllably oxidizing a variety of aryl sulphides when irradiated with
visible light and possessed activities that correlated with the
photophysical characterization data. Catalytic performance was found
to be dependent on multiple factors including the Mes-Acr+ cofactor,
the protein scaffold, the location of cofactor immobilization, and the
substrate. This work provides a framework toward adapting synthetic
photoredox catalysts into artificial cofactors and includes important
considerations for future bioengineering efforts.
transformations operate through photoinduced electron transfer
(PET) events, which facilitate the generation of highly reactive
intermediates at ambient temperature bypassing thermal
barriers and permitting access to unique reactivity patterns.
Intriguingly, nature already employs a number of photoexcitable
chromophores that initiate light-driven single electron redox
pathways in order to drive and regulate a variety of biological
processes. Select examples include the use of chlorophyll and
carotenoids in photosynthesis[14] and flavins in reversible light-
activated signal transduction pathways.[15] However, the
functions of most photoexcitable proteins in biology are highly
specific, rendering their broad-scoped application as synthetic
photoredox catalysts quite challenging.
Despite the limited synthetic utility of natural light-harvesting
proteins, Hyster and coworkers have recently identified
promiscuous photoredox activity in non-light activated enzymes
that bind chromophoric cofactors, including nicotinamide-[16] and
flavin-dependent oxidoreductases.[17] This work takes advantage
of the excited-state synthetic potential of the natural cofactors in
conjunction with the enzyme’s substrate binding cavities, which
enables substrate access, binding, and orientation in proximity
to the chromophore. Although, due to the limited structural and
electronic diversity of photoactivatable cofactors in nature, the
synthetic repertoire accessible to these systems is inherently
restricted.[18] On the other hand, there is a wealth of diversity
among reported synthetic photoredox catalysts which can be
tuned to have a broad range of redox potentials and
Introduction
Nature supplements the reactivity of enzymes through the
recruitment of small molecule cofactors that impart chemical
functionality not available to native amino acids. Inspired by this
resourcefulness, protein engineers have expanded the breadth
of enzyme catalysis by designing hybrid systems that combine
the unique reactivity of synthetic catalysts - as artificial cofactors
- with the control and structural complexity endowed by
biomolecular scaffolds.[1-3] The selection of artificial cofactors for
bioengineering applications has historically been guided by the
field of small molecule homogenous catalysis, most notably
centered on transition metal catalysis due to the rich and diverse
chemistries enabled by these complexes.[4,5] Importantly, the
properties of the protein-bound metal catalysts can be tuned by
proximal and distal amino acids to enhance turnover,
wavelengths for excitation.[12,13] We believe the adaptation of
these synthetic photoredox catalysts as artificial cofactors will
provide a general and systematic approach to expand light-
driven biocatalysis with the potential to generate diverse new-to-
nature chemical reactivities.
There have been a number of reports describing the
immobilization of photocatalysts onto protein scaffolds to serve
as mediators for controlling the redox state of natural
stereoselectivity, stability, and activity in water.[6,7] Furthermore,
this marriage of chemical ingenuity and protein engineering has
led to the development of artificial metalloenzymes capable of
performing a number of new-to-nature chemical
cofactors.[19,20] However, the direct use of photoredox catalysts
to carry out biocatalytic transformations on small molecules is
underexplored. Lewis and colleagues reported the first example
of a hybrid enzyme appended to a non-natural photoredox
cofactor.[21] In their design, a cyclooctyne-modified Fukuzumi
catalyst was immobilized within an engineered cavity of prolyl
peptidase via click reaction to an unnatural amino acid side
transformations.[8,9]
Based on the success of artificial metalloenzyme engineering,
there is growing interest in expanding the scope of artificial
cofactors to encompass other catalytic modalities.[10,11] For
1
This article is protected by copyright. All rights reserved.

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
chain. The hybrid photo-enzyme showed improved photostability
for the cofactor due to immobilization within the hydrophobic
interior of the protein cavity. However, diminished photocatalytic
oxygenase activity was observed compared to the free cofactor.
Beyond this report, there are no other examples of the
accommodate the Mes-Acr+ cofactors (see supplemental
methods). We chose to explore multiple protein scaffolds
because it has been shown that the identity of scaffold can have
a substantial effect on the properties of the synthetic
cofactors.[6,26] Furthermore, varying the attachment residue
within the same scaffold can also vary the behavior of a bound
catalyst.[27] By screening multiple scaffolds for the Mes-Acr+
cofactors and a pair of cysteine conjugation residues for each
scaffold, we surmised this would increase our chances to
observe context dependent interactions between the host and
cofactor. We restricted our scaffold search to proteins from
thermophilic organisms, as these proteins generally possess
high thermostability and provide promising initial platforms for
further mutation and design. We selected three protein scaffolds,
all from the thermophile Thermotoga Maritima (Tm), which
include an aspartate dehydrogenase (AspDH),
construction of artificial cofactors as a means to directly install
PET activity into enzymes for small molecule synthesis.
Results and Discussion
We set out with the goal of designing a set of novel artificial
photoredox cofactors which could be linked to a variety of
protein scaffolds. In recent years, the organic dye 9-mesityl-10-
phenyl acirindium (Mes-Acr+) has emerged as a powerful excited
state oxidant, catalyzing a diverse array of photoredox
transformations when irradiated with visible light.[13,22-23] Due to
its utility, multiple generations of the organic Mes-Acr+ catalysts
with different properties have emerged such as 1a and 2a
(Figure 1A).[24,25] The more recently developed 2a is decorated
with a pair of methyl groups on the acridinium core which have
been shown to improve catalyst stability and performance in
select applications. Based on these precedents, we
phosphoribosylamine-glycine ligase (GARS), and
folylpolyglutamate synthase (FPGS). All three proteins possess
large cavities to accomodate the photocatalyst (Figure 1b).
Following inspection of the amino acid residues within the cavity
interiors, we chose two different residue positions in all three
scaffolds for cysteine mutagenesis to covalently attach 1b and
2b (Figure 1B). In the preparation and design of host proteins, it
was important to note that Tm(AspDH) and Tm(FPGS) both
contain one or more endogenous cysteines, none of which
participate in disulfide bonds. Accordingly, these native
cysteines were mutated to a valine or serine prevent
heterogeneous cofactor attachment. Ultimately, covalent
attachment of these engineered scaffolds with 1b and 2b
through cysteine alkylation (see supplemental methods) resulted
in a small library of twelve artificial enzymes. Bioconjugation of
artificial cofactors was confirmed via high resolution mass
spectrometry (Table S1, Figure S1 and S2).
hypothesized Mes-Acr+ could serve well as an artificial cofactor
and would hopefully retain its powerful light-driven catalytic
properties in a protein environment. Two Mes-Acr+ cofactor
derivatives (1b & 2b) were synthesized with an iodoacetamide
handle for covalent anchoring to a host protein via cysteine
alkylation (Figure 1A, see supplemental methods).
With the new artificial Mes-Acr+ conjugates in hand, we first
examined their photophysical properties in buffered solution. We
believe this initial characterization to be an important first step in
the analysis of photoactive cofactors as the ground and excited
state behavior of the catalyst ultimately govern the catalyst’s
photoredox activity. UV/Vis experiments surveying for alterations
in the ground state revealed no significant changes in the
absorbance profile of 1b and 2b when bound to the protein
scaffolds with the exception of moderate red shifting of 1 - 2 nm
for both cofactors (Figure S3). In all experiments, protein-bound
cofactors were compared with the parent 1a and 2a Mes-Acr+
catalysts in lieu of the iodoacetamide derivatives because heavy
atoms such as iodine can influence photochemical and
photophysical properties.[28]
The steady state fluorescence and excited state lifetimes (τf) for
the enzyme library were then analyzed as these metrics can
have an effect on excited state electron transfer. Reductions in
quantum yield of fluorescence (Φf) or τf in the absence of
substrate can indicate static and dynamic quenching
respectively, both inefficient pathways drawing away from the
desired electron transfer iniating catalysis. With respect to Φf
(Table S2), one protein scaffold, AspDH, increased fluorescence
emission of 1a when irradiated with 425 nm light. For both
cofactor attachment positions (T223C & S226C) of the scaffold,
Φf was increased 2-2.5 fold (Figure 2). Both Tm(GARS) and
Tm(FPGS) caused a notable reduction (2 – 3 fold) in Φf for 1,
indicating some degree of scaffold-induced quenching.
Tm(AspDH) is unique in that it does not contain tryptophan
residues, an aromatic side chain that can induce quenching on
protein-conjugated fluorophores that may contribute to the
descreased fluorescence observed in Tm(GARS) and
Tm(FPGS). These results show that the structural environment
of the protein catavity can impose distinct photophysical
properities on the artificial cofactor.
Figure 1. (A) Mes-Acr+ catalysts and artificial cofactors synthesized with an
iodoacetamide handle for covalent attachment to the protein scaffold.
(B) Biomolecules from T. Maritima selected for artificial cofactor
immobilization. Engineered cysteines in scaffold cavities for covalent
attachment of cofactors are shown as spheres (left). Protein concavities for
artificial cofactor active sites are shown in grey (right). PDB id’s for scaffolds,
AspDH: (1J5P), GARS: (1VKZ), FPGS: (1O5Z).
In order to select protein hosts for these novel artificial cofactors,
we scanned the Protein Data Base for biomolecular scaffolds
with concavities in their tertiary structure that would sufficiently
2
This article is protected by copyright. All rights reserved.

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
Figure 2. (A) Steady state fluorescence emission spectra of unbound and protein bound Mes-Acr+ catalysts when irradiated with 425 nm light in relative
fluorescence units. (B) Tables showing ratio of unbound Mes-Acr+ Φf to protein scaffold bound 1b or 2b and fluorescence lifetimes (in ns) Mes-Acr+ catalysts
measured at 510 nm by time-correlated single photon counting, λexcitation = 444 nm. Emission spectra and lifetime data were both collected at 20µM Mes-Acr+
derivatives in 25 mM Tris buffer pH 7.5 with 10% acetonitrile under the same instrument parameters.
To test if the excited state of our artificial enzymes could
controllably oxidize aryl thioethers with atmospheric O2, the
enzymes were irradiated with 450 nm LEDs in the presence of a
model substrate, thioanisole (Figure 3).
Interestingly, the trend of increasing emission did not carry over
for cofactor 2b as all protein scaffolds and all cofactor
attachment positions resulted in attenuated Φf (Figure 2A).
However, in the case of 2b and consistent with catalyst 1b,
Tm(AspDH) showed the least perturbation of catalyst
flourescence. Unbound Mes-Acr+ 2a was shown to be a much
more emissive species than 1a and may be less sensitive to
quenching effects of the buffered aqueous environment (Figure
2A). The Tm(AspDH) scaffold still permitted the most emissive
form of protein-conjugated 2b with ~60-70% Φf when compared
to the unbound cofactor followed by Tm(GARS) and then
Tm(FPGS).
Nearly all of the scaffolds and variants increased yield of the
desired methyl phenyl sulfoxide for both artificial cofactors 1b
and 2b when compared to the unbound catalysts. The Mes-Acr+
catalyst 2 also outperformed 1 in all reactions, whether free or
bound to a protein scaffold. Tm(AspDH)T223C-2b was an
efficient sulfoxidation catalyst and yielded 85% of the desired
sulfoxide product compared to a 55 % yield observed with the
free cofactor, 2a. Both these results correlated well with the
photophysical characterization data as 2a and the Tm(AspDH)
conjugates consistently provided the most desirable excited
state properties for PET. In addition, no over oxidation of the
sulfoxide to the sulfone was observed by GCMS analysis (Figure
S2).
To further characterize the excited state of our constructed
enzymes, τf was measured using time-correlated single photon
counting experiments (Figure 2B and Figures S4). The
fluorescence plots were fit to multi-exponential decays,
highlighting the complicated excited-state behavior of these
species in the aqueous buffers.[21,29] A small increase of 1-2
nanoseconds (ns) in τf was measured across all scaffolds for 1b
indicating relaxation-pathways may be weakly mitigated when
bound to the tested scaffolds. Conversely, when 2b is attached
to the protein scaffolds τf was measured to be lower across a
range of 0.2 to 3 ns in comparison to 2a with Tm(AspDH)
showing a slight reduction in lifetime.
Control experiments showed that both light and the presence of
catalyst were necessary for product formation (Figure 3). To
further probe the mechanism of the reaction, a Stern-Volmer
analysis was performed on the Tm(AspDH)-2b variants with
thioanisole as a quencher.The excited state was quenched in a
linear manner across a range of thioanisole concentrations for
free and bound cofactors, indicative of a mechanism proceeding
through PET (Figure S6).
The suite of 12 hybrid enzymes were then evaluated as
photoredox catalysts in the oxidation of aryl thioethers to
sulfoxides (see supplemental methods and Figure S5).
Sulfoxidation reactions are generally performed through two
electron chemical oxidation requiring stoichiometric amounts of
a sacrificial oxidant and run the risk of overoxidation to the
sulfone.[30] Due to this, photocatalytic methods using O2 to trap
radical intermediates have been explored as alternatives and
offer greener and potentially more controllable processes.[31]
Based on these initial results, a small set of 10 aryl thioethers
were then analyzed as sulfoxidation substrates for the two
variants of Tm(AspDH) conjugated to 2b, the more reactive
cofactor (Figure 4). Electron withdrawing and donating groups
on the arenes were tolerated as well as ethyl and benzyl aryl
thioethers. No general trends were observed with respect to the
protein variant and free catalyst. In most cases, comparable
yield or a modest increase in yield were observed for the protein
bound catalyst. Decreased yield was observed for chloro- and
nitro-substituted thioethers 9 and 11. Some notable
improvements in product turnover were observed in specific
cases. Notably, in the case of napthyl-substituted substrate 7,
the free cofactor provide only 24 % yield for the sulfoxide
product, whereas, Tm(AspDH)T223C-2b increased the reaction
yield to 81 %. However, Tm(AspDH)T226C-2b, only increased
product yield to 39 %. Chiral analysis of the sulfoxide products
revealed that none of the tested scaffolds resulted in observable
enantiomeric enrichment (Figure S3). Taken together, these
results show that the hybrid Mes-Acr+ enzymes displayed a
range of efficiencies in mediating photoinduced sulfoxidation and
the activity is not only substrate dependent but also varies
across the cofactors and scaffolds tested.
Figure 3. Screen of Mes-Acr+ catalysts and hybrid enzymes in the
photoinduced oxidation of thioansiole with yields shown in the heat map
above. n.d. = not detected.
3
This article is protected by copyright. All rights reserved.

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
Acknowledgements
This work was supported by a National Science Foundation
(NSF) Career Award (CHE-1552718). This research made use
of instrumentation funded by the UNC EFRC: Center for Solar
Fuels, an Energy Frontier Research Center supported by the
U.S. Department of Energy, Office of Science, Office of Basic
Energy Sciences, under award number DE-SC0001011.
Keywords: Artificial Cofactors • Biocatalysis • Artificial Enzyme •
Photoredox Catalysis • Sulfoxidation
[1]
[2]
[3]
M. E. Wilson, G. M. Whitesides, J. Am. Chem. Soc. 1978, 100, 306–
307.
S. Abe, J. Niemeyer, M. Abe, Y. Takezawa, T. Ueno, T. Hikage, G.
Erker, Y. Watanabe, J. Am. Chem. Soc. 2008, 130, 10512–10514.
I. S. Hassan, A. N. Ta, M. W. Danneman, N. Semakul, M. Burns, C. H.
Basch, V. N. Dippon, B. R. McNaughton, T. Rovis, J. Am. Chem. Soc.
2019, 141, 4815–4819.
[4]
F. Schwizer, Y. Okamoto, T. Heinisch, Y. Gu, M. M. Pellizzoni, V.
Lebrun, R. Reuter, V. Köhler, J. C. Lewis, T. R. Ward, Chem. Rev.
2018, 118, 142–231.
[5]
[6]
H. J. Davis, T. R. Ward, ACS Cent. Sci. 2019, 5, 1120–1136.
H. M. Key, P. Dydio, D. S. Clark, J. F. Hartwig, Nature 2016, 534, 534–
537.
[7]
[8]
G. Sreenilayam, E. J. Moore, V. Steck, R. Fasan, ACS Catal. 2017, 7,
7629–7633.
H. Yang, A. M. Swartz, H. J. Park, P. Srivastava, K. Ellis-Guardiola, D.
M. Upp, G. Lee, K. Belsare, Y. Gu, C. Zhang, et al., Nature Chemistry
2018, 10, 318–324.
Figure 4. Sulfoxidation of aryl-substitued thioethers catalyzed by Mes-Acr+ 2a
and best scaffold hit Tm(AspDH) with 2b.
[9]
T. K. Hyster, L. Knörr, T. R. Ward, T. Rovis, Science 2012, 338, 500–
503.
[10] C. J. Seel, T. Gulder, ChemBioChem 2019, 20, 1871–1897.
[11] L. Zhang, J. Yuan, Y. Xu, Y.-H. P. Zhang, X. Qian, Chem. Commun.
2016, 52, 6471–6474.
[12] M. H. Shaw, J. Twilton, D. W. C. MacMillan, J. Org. Chem. 2016, 81,
6898–6926.
Conclusion
In summary, we report the preparation, characterization, and
application of twelve novel artificial photoredox enzymes. Two
derivatives of the organic photoredox catalyst, 9-mesityl-10-
phenyl acirindium (Mes-Acr+), were synthesized and covalently
tethered to three thermostable protein scaffolds at two different
anchoring sites each. The photophysical properties of each of
the bound Mes-Acr+ catalysts were analyzed and compared
alongside the free cofactor in solution. It was found that the
identity of the protein scaffold can have a measurable effect on
the quantum yield of fluorescence and excited state lifetime of
the chromophore, both important properties for applications in
photoredox catalysis. Reaction screening of the Mes-Acr+-
modified protein scaffolds revealed all are active photoenzymes,
but the performance of these catalysts towards light-driven
sulfoxidation is dependent on multiple factors including the
artificial cofactor, the protein scaffold, the location of cofactor
immobilization, and the reaction substrate. It is likely that a
single protein scaffold will not be sufficient to serve as a general
platform for catalysis and that there is significant benefit in
generating a library of hybrid protein scaffolds for reaction
screening. The field of engineering artificial photoredox cofactors
is still very young and we anticipate that the general design
strategy presented herein as well as the specific Mes-Acr+
cofactors and protein scaffolds in this study will be informative
for future artificial biocatalysis developments.
[13] N. A. Romero, D. A. Nicewicz, Chem. Rev. 2016, 116, 10075–10166.
[14] H. A. Frank, R. J. Cogdell, Photochemistry and Photobiology 1996, 63,
257–264.
[15] J. M. Christie, Annu. Rev. Plant Biol. 2007, 58, 21–45.
[16] M. A. Emmanuel, N. R. Greenberg, D. G. Oblinsky, T. K. Hyster, Nature
2016, 540, 414–417.
[17] B. A. Sandoval, A. J. Meichan, T. K. Hyster, J. Am. Chem. Soc. 2017,
139, 11313–11316.
[18] L. Schmermund, V. Jurkaš, F. F. Özgen, G. D. Barone, H. C.
Büchsenschütz, C. K. Winkler, S. Schmidt, R. Kourist, W. Kroutil, ACS
Catal. 2019, 9, 4115–4144.
[19] N.-H. Tran, N. Huynh, T. Bui, Y. Nguyen, P. Huynh, M. E. Cooper, L. E.
Cheruzel, Chem. Commun. 2011, 47, 11936–11938.
[20] V. Sosa, M. Melkie, C. Sulca, J. Li, L. Tang, J. Li, J. Faris, B. Foley, T.
Banh, M. Kato, et al., ACS Catal. 2018, 8, 2225–2229.
[21] Y. Gu, K. Ellis‐Guardiola, P. Srivastava, J. C. Lewis, ChemBioChem
2015, 16, 1880–1883.
[22] P. D. Morse, D. A. Nicewicz, Chem. Sci. 2014, 6, 270–274.
[23] L. Wang, F. Wu, J. Chen, D. A. Nicewicz, Y. Huang, Angewandte
Chemie International Edition 2017, 56, 6896–6900.
[24] K. Ohkubo, K. Mizushima, R. Iwata, K. Souma, N. Suzuki, S. Fukuzumi,
Chem. Commun. 2010, 46, 601–603.
[25] D. J. Wilger, J.-M. M. Grandjean, T. R. Lammert, D. A. Nicewicz, Nature
Chemistry 2014, 6, 720–726.
[26] H. M. Key, P. Dydio, Z. Liu, J. Y.-E. Rha, A. Nazarenko, V.
Seyedkazemi, D. S. Clark, J. F. Hartwig, ACS Cent. Sci. 2017, 3, 302–
308.
[27] R. R. Davies, H. Kuang, D. Qi, A. Mazhary, E. Mayaan, M. D.
Distefano, Bioorganic & Medicinal Chemistry Letters 1999, 9, 79–84.
[28] Lakowicz, J. R. Principles of Fluorescence Spectroscopy, 3rd ed.;
Springer: New York, 2006.
[29] G. Jones, D. Yan, J. Hu, J. Wan, B. Xia, V. I. Vullev, J. Phys. Chem. B
2007, 111, 6921–6929.
4
This article is protected by copyright. All rights reserved.

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
[30] S. Velusamy, A. V. Kumar, R. Saini, T. Punniyamurthy, Tetrahedron
Letters 2005, 46, 3819–3822.
[31] X. Gu, X. Li, Y. Chai, Q. Yang, P. Li, Y. Yao, Green Chem. 2013, 15,
357–361.
5
This article is protected by copyright. All rights reserved.

10.1002/cbic.202000362
ChemBioChem
FULL PAPER
Entry for the Table of Contents
Insert graphic for Table of Contents here. ((Please ensure your graphic is in one of following formats))
((max. width: 11.5 cm; max. height: 2.5 cm))
Please delete this box prior to submission
Shining Light on Enzymes. Here we report the design and evaluation of two artificial organic photoredox cofactors in the context of
multiple protein scaffold hosts. The ground and excited-state properties of the free and scaffold-bound cofactors were measured, as
the photophysical properties govern the photocatalytic activity. The engineered artificial enzymes were found to be active excited-
state oxidants, acting on a range of aryl sulfides.
((The Table of Contents text should give readers a short preview of the main theme of the research and results included in the paper
to attract their attention into reading the paper in full. The Table of Contents text should be different from the abstract and should
be no more than 450 characters including spaces.))
6
This article is protected by copyright. All rights reserved.