1
|
SpeedyGenesXL: an Automated, High-Throughput Platform for the Preparation of Bespoke Ultralarge Variant Libraries for Directed Evolution. Methods Mol Biol 2022; 2461:67-83. [PMID: 35727444 DOI: 10.1007/978-1-0716-2152-3_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Directed evolution of proteins is a highly effective strategy for tailoring biocatalysts to a particular application, and is capable of engineering improvements such as kcat, thermostability and organic solvent tolerance. It is recognized that large and systematic libraries are required to navigate a protein's vast and rugged sequence landscape effectively, yet their preparation is nontrivial and commercial libraries are extremely costly. To address this, we have developed SpeedyGenesXL, an automated, high-throughput platform for the production of wild-type genes, Boolean OR, combinatorial, or combinatorial-OR-type libraries based on the SpeedyGenes methodology. Together this offers a flexible platform for library synthesis, capable of generating many different bespoke, diverse libraries simultaneously.
Collapse
|
2
|
Machado LFM, Dixon N. Directed Evolution of Transcription Factor-Based Biosensors for Altered Effector Specificity. Methods Mol Biol 2022; 2461:175-193. [PMID: 35727451 DOI: 10.1007/978-1-0716-2152-3_12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Transcription factor-based biosensors are important tools in Synthetic Biology for the sensing of industrially valuable molecules and clinically important metabolites, therefore presenting applications in the bioremediation, industrial biotechnology, and biomedical fields. The directed evolution of allosteric transcription factors (aTFs) with the aim of altering effector specificity has the potential for the development of new biosensors to detect natural and nonnatural molecules, expanding the scope of available aTF-based biosensors. In this chapter, we delineate a general method for the directed evolution of aTFs. The theory of library design is discussed, along with the detailed methodology for an improved transformation of combined libraries, and the experimental search space by counterselection using fluorescence-activated cell sorting (FACS) is presented.
Collapse
|
3
|
Currin A, Parker S, Robinson CJ, Takano E, Scrutton NS, Breitling R. The evolving art of creating genetic diversity: From directed evolution to synthetic biology. Biotechnol Adv 2021; 50:107762. [PMID: 34000294 PMCID: PMC8299547 DOI: 10.1016/j.biotechadv.2021.107762] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Revised: 04/21/2021] [Accepted: 04/25/2021] [Indexed: 12/31/2022]
Abstract
The ability to engineer biological systems, whether to introduce novel functionality or improved performance, is a cornerstone of biotechnology and synthetic biology. Typically, this requires the generation of genetic diversity to explore variations in phenotype, a process that can be performed at many levels, from single molecule targets (i.e., in directed evolution of enzymes) to whole organisms (e.g., in chassis engineering). Recent advances in DNA synthesis technology and automation have enhanced our ability to create variant libraries with greater control and throughput. This review highlights the latest developments in approaches to create such a hierarchy of diversity from the enzyme level to entire pathways in vitro, with a focus on the creation of combinatorial libraries that are required to navigate a target's vast design space successfully to uncover significant improvements in function.
Collapse
Affiliation(s)
- Andrew Currin
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom.
| | - Steven Parker
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Christopher J Robinson
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Eriko Takano
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nigel S Scrutton
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Rainer Breitling
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom.
| |
Collapse
|
4
|
Qu G, Li A, Acevedo‐Rocha CG, Sun Z, Reetz MT. Die zentrale Rolle der Methodenentwicklung in der gerichteten Evolution selektiver Enzyme. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201901491] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Ge Qu
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
| | - Aitao Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-resources Hubei Key Laboratory of Industrial Biotechnology College of Life Sciences Hubei University 368 Youyi Road Wuchang Wuhan 430062 China
| | | | - Zhoutong Sun
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
| | - Manfred T. Reetz
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim Deutschland
- Department of Chemistry, Hans-Meerwein-Straße 4 Philipps-Universität 35032 Marburg Deutschland
| |
Collapse
|
5
|
Qu G, Li A, Acevedo‐Rocha CG, Sun Z, Reetz MT. The Crucial Role of Methodology Development in Directed Evolution of Selective Enzymes. Angew Chem Int Ed Engl 2020; 59:13204-13231. [PMID: 31267627 DOI: 10.1002/anie.201901491] [Citation(s) in RCA: 233] [Impact Index Per Article: 58.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Indexed: 12/14/2022]
Affiliation(s)
- Ge Qu
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
| | - Aitao Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-resources Hubei Key Laboratory of Industrial Biotechnology College of Life Sciences Hubei University 368 Youyi Road Wuchang Wuhan 430062 China
| | | | - Zhoutong Sun
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
| | - Manfred T. Reetz
- Tianjin Institute of Industrial Biotechnology Chinese Academy of Sciences 32 West 7th Avenue, Tianjin Airport Economic Area Tianjin 300308 China
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim Germany
- Department of Chemistry, Hans-Meerwein-Strasse 4 Philipps-University 35032 Marburg Germany
| |
Collapse
|
6
|
F M Machado L, Currin A, Dixon N. Directed evolution of the PcaV allosteric transcription factor to generate a biosensor for aromatic aldehydes. J Biol Eng 2019; 13:91. [PMID: 31798685 PMCID: PMC6882365 DOI: 10.1186/s13036-019-0214-z] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 10/16/2019] [Indexed: 12/27/2022] Open
Abstract
Background Transcription factor-based biosensors are useful tools for the detection of metabolites and industrially valuable molecules, and present many potential applications in biotechnology and biomedicine. However, the most common approach to develop biosensors relies on employing a limited set of naturally occurring allosteric transcription factors (aTFs). Therefore, altering the ligand specificity of aTFs towards the detection of new effectors is an important goal. Results Here, the PcaV repressor, a member of the MarR aTF family, was used to develop a biosensor for the detection of hydroxyl-substituted benzoic acids, including protocatechuic acid (PCA). The PCA biosensor was further subjected to directed evolution to alter its ligand specificity towards vanillin and other closely related aromatic aldehydes, to generate the Van2 biosensor. Ligand recognition of Van2 was explored in vitro using a range of biochemical and biophysical analyses, and extensive in vivo genetic-phenotypic analysis was performed to determine the role of each amino acid change upon biosensor performance. Conclusions This is the first study to report directed evolution of a member of the MarR aTF family, and demonstrates the plasticity of the PCA biosensor by altering its ligand specificity to generate a biosensor for aromatic aldehydes.
Collapse
Affiliation(s)
- Leopoldo F M Machado
- 1Manchester Institute of Biotechnology (MIB), The University of Manchester, M1 7DN, Manchester, UK.,2Department of Chemistry, The University of Manchester, M1 7DN, Manchester, UK
| | - Andrew Currin
- 1Manchester Institute of Biotechnology (MIB), The University of Manchester, M1 7DN, Manchester, UK.,2Department of Chemistry, The University of Manchester, M1 7DN, Manchester, UK.,3SYNBIOCHEM, The University of Manchester, M1 7DN, Manchester, UK
| | - Neil Dixon
- 1Manchester Institute of Biotechnology (MIB), The University of Manchester, M1 7DN, Manchester, UK.,2Department of Chemistry, The University of Manchester, M1 7DN, Manchester, UK.,3SYNBIOCHEM, The University of Manchester, M1 7DN, Manchester, UK
| |
Collapse
|
7
|
Currin A, Kwok J, Sadler JC, Bell EL, Swainston N, Ababi M, Day P, Turner NJ, Kell DB. GeneORator: An Effective Strategy for Navigating Protein Sequence Space More Efficiently through Boolean OR-Type DNA Libraries. ACS Synth Biol 2019; 8:1371-1378. [PMID: 31132850 PMCID: PMC7007284 DOI: 10.1021/acssynbio.9b00063] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Directed evolution requires the creation of genetic diversity and subsequent screening or selection for improved variants. For DNA mutagenesis, conventional site-directed methods implicitly utilize the Boolean AND operator (creating all mutations simultaneously), producing a combinatorial explosion in the number of genetic variants as the number of mutations increases. We introduce GeneORator, a novel strategy for creating DNA libraries based on the Boolean logical OR operator. Here, a single library is divided into many subsets, each containing different combinations of the desired mutations. Consequently, the effect of adding more mutations on the number of genetic combinations is additive (Boolean OR logic) and not exponential (AND logic). We demonstrate this strategy with large-scale mutagenesis studies, using monoamine oxidase-N ( Aspergillus niger) as the exemplar target. First, we mutated every residue in the secondary structure-containing regions (276 out of a total 495 amino acids) to screen for improvements in kcat. Second, combinatorial OR-type libraries permitted screening of diverse mutation combinations in the enzyme active site to detect activity toward novel substrates. In both examples, OR-type libraries effectively reduced the number of variants searched up to 1010-fold, dramatically reducing the screening effort required to discover variants with improved and/or novel activity. Importantly, this approach enables the screening of a greater diversity of mutation combinations, accessing a larger area of a protein's sequence space. OR-type libraries can be applied to any biological engineering objective requiring DNA mutagenesis, and the approach has wide ranging applications in, for example, enzyme engineering, antibody engineering, and synthetic biology.
Collapse
Affiliation(s)
- Andrew Currin
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Jane Kwok
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Joanna C. Sadler
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Elizabeth L. Bell
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Neil Swainston
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Maria Ababi
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PL, United Kingdom
- School of Computer Science, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Philip Day
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Nicholas J. Turner
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| | - Douglas B. Kell
- Manchester Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM), Manchester Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
- School of Chemistry, The University of Manchester, Manchester M13 9PL, United Kingdom
| |
Collapse
|
8
|
Novel synthetic nucleotides of notifiable dengue (1-4), Japanese encephalitis, yellow fever and Zika flaviviruses. Future Sci OA 2018; 5:FSO353. [PMID: 30652021 PMCID: PMC6331751 DOI: 10.4155/fsoa-2018-0081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 09/27/2018] [Indexed: 11/30/2022] Open
Abstract
Aim: To produce synthetic nucleotides of notifiable dengue virus (1–4 types), Japanese encephalitis, yellow fever and Zika flaviviruses. These notifiable flaviviruses, particularly dengue and Zika, are problematic mosquito-borne infections in the Philippines, as well as in those countries with tropical and subtropical climates. Method: An algorithmic design formulation of overlap extension – polymerase chain reaction (OE-PCR) was performed to propagate 50–60 oligomer lengths of select notifiable flaviviral RNAs to DNA nucleotides via the two-step process of OE-PCR. Result: Algorithmic OE-PCR design formulation efficiently produced 253–256 bp of notifiable flaviviruses. Comparing the newly designed algorithmic OE-PCR with existing executable programs demonstrated it to be efficient and useful in generating accurate sequences of synthetic flaviviral nucleotides. Conclusion: The efficiently and accurately produced novel synthetic nucleotides of notifiable dengue virus 1–4, Japanese encephalitis, yellow fever and Zika flaviviruses using OE-PCR is useful in understanding the dynamics of flaviviral species and holds potential for the development of synthetic nucleotide-based immunogens. Dengue virus (1–4), Japanese encephalitis and Zika fevers are notable mosquito-borne infections that continue to be problematic in the Philippines and its southeast Asian neighbors. Flaviviral yellow fever affects other tropical countries. This study aimed to effectively and efficiently synthesize flaviviral nucleotides through a predictively accurate algorithmic overlap extension-polymerase chain reaction design. The cost-saving arithmetic formulation has enabled the advanced production of 253–256 bp flaviviral nucleotide lengths. The newly synthesized and sequenced products are now ready for further experimentation and open the door for immunological exploration.
Collapse
|
9
|
Sadler JC, Currin A, Kell DB. Ultra-high throughput functional enrichment of large monoamine oxidase (MAO-N) libraries by fluorescence activated cell sorting. Analyst 2018; 143:4747-4755. [PMID: 30199078 PMCID: PMC6156879 DOI: 10.1039/c8an00851e] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 07/17/2018] [Indexed: 12/16/2022]
Abstract
Directed evolution enables the improvement and optimisation of enzymes for particular applications and is a valuable tool for biotechnology and synthetic biology. However, studies are often limited in their scope by the inability to screen very large numbers of variants to identify improved enzymes. One class of enzyme for which a universal, operationally simple ultra-high throughput (>106 variants per day) assay is not available is flavin adenine dinucleotide (FAD) dependent oxidases. The current high throughput assay involves a visual, colourimetric, colony-based screen, however this is not suitable for very large libraries and does not enable quantification of the relative fitness of variants. To address this, we describe an optimised method for the sensitive detection of oxidase activity within single Escherichia coli (E. coli) cells, using the monoamine oxidase from Aspergillus niger, MAO-N, as a model system. In contrast to other methods for the screening of oxidase activity in vivo, this method does not require cell surface expression, emulsion formation or the addition of an extracellular peroxidase. Furthermore, we show that fluorescence activated cell sorting (FACS) of large libraries derived from MAO-N under the assay conditions can enrich the library in functional variants at much higher rates than via the colony-based method. We demonstrate its use for directed evolution by identifying a new mutant of MAO-N with improved activity towards a novel secondary amine substrate. This work demonstrates, for the first time, an ultra-high throughput screening methodology widely applicable for the directed evolution of FAD dependent oxidases in E. coli.
Collapse
Affiliation(s)
- Joanna C. Sadler
- School of Chemistry
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- The Manchester Institute of Biotechnology
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- Centre for the Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM)
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
.
;
;
; http://dbkgroup.org/@dbkell
| | - Andrew Currin
- School of Chemistry
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- The Manchester Institute of Biotechnology
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- Centre for the Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM)
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
.
;
;
; http://dbkgroup.org/@dbkell
| | - Douglas B. Kell
- School of Chemistry
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- The Manchester Institute of Biotechnology
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
- Centre for the Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM)
, The University of Manchester
,
131 Princess St
, Manchester M1 7DN
, UK
.
;
;
; http://dbkgroup.org/@dbkell
| |
Collapse
|
10
|
Currin A, Dunstan MS, Johannissen LO, Hollywood KA, Vinaixa M, Jervis AJ, Swainston N, Rattray NJW, Gardiner JM, Kell DB, Takano E, Toogood HS, Scrutton NS. Engineering the "Missing Link" in Biosynthetic (-)-Menthol Production: Bacterial Isopulegone Isomerase. ACS Catal 2018; 8:2012-2020. [PMID: 29750129 PMCID: PMC5937688 DOI: 10.1021/acscatal.7b04115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/15/2018] [Indexed: 12/28/2022]
Abstract
![]()
The
realization of a synthetic biology approach to microbial (1R,2S,5R)-(−)-menthol (1) production relies on the identification
of a gene encoding an isopulegone isomerase (IPGI), the only enzyme
in the Mentha piperita biosynthetic
pathway as yet unidentified. We demonstrate that Δ5-3-ketosteroid
isomerase (KSI) from Pseudomonas putida can act as an IPGI, producing (R)-(+)-pulegone
((R)-2) from (+)-cis-isopulegone (3). Using a robotics-driven semirational
design strategy, we identified a key KSI variant encoding four active
site mutations, which confer a 4.3-fold increase in activity over
the wild-type enzyme. This was assisted by the generation of crystal
structures of four KSI variants, combined with molecular modeling
of 3 binding to identify key active site residue targets.
The KSI variant was demonstrated to function efficiently within cascade
biocatalytic reactions with downstream Mentha enzymes pulegone reductase and (−)-menthone:(−)-menthol
reductase to generate 1 from 3. This study
introduces the use of a recombinant IPGI, engineered to function efficiently
within a biosynthetic pathway for the production of 1 in microorganisms.
Collapse
|
11
|
Abstract
Directed evolution has emerged as one of the most effective protein engineering methods in basic research as well as in applications in synthetic organic chemistry and biotechnology. The successful engineering of protein activity, allostery, binding affinity, expression, folding, fluorescence, solubility, substrate scope, selectivity (enantio-, stereo-, and regioselectivity), and/or stability (temperature, organic solvents, pH) is just limited by the throughput of the genetic selection, display, or screening system that is available for a given protein. Sometimes it is possible to analyze millions of protein variants from combinatorial libraries per day. In other cases, however, only a few hundred variants can be screened in a single day, and thus the creation of smaller yet smarter libraries is needed. Different strategies have been developed to create these libraries. One approach is to perform mutational scanning or to construct "mutability landscapes" in order to understand sequence-function relationships that can guide the actual directed evolution process. Herein we provide a protocol for economically constructing scanning mutagenesis libraries using a cytochrome P450 enzyme in a high-throughput manner. The goal is to engineer activity, regioselectivity, and stereoselectivity in the oxidative hydroxylation of a steroid, a challenging reaction in synthetic organic chemistry. Libraries based on mutability landscapes can be used to engineer any fitness trait of interest. The protocol is also useful for constructing gene libraries for deep mutational scanning experiments.
Collapse
Affiliation(s)
- Carlos G Acevedo-Rocha
- Department of Biocatalysis, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany.
- Department of Chemistry, Philipps-Universität Marburg, Marburg, 35032, Germany.
- Biosyntia ApS, 2100, Copenhagen, Denmark.
| | - Matteo Ferla
- Department of Biochemistry, Oxford University, Oxford, OX1 3QU, UK
| | - Manfred T Reetz
- Department of Biocatalysis, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim an der Ruhr, Germany
- Department of Chemistry, Philipps-Universität Marburg, Marburg, 35032, Germany
| |
Collapse
|