26
|
Semivrazhskaya O, Romero-Rivera A, Aroua S, Troyanov SI, Garcia-Borràs M, Stevenson S, Osuna S, Yamakoshi Y. Structures of Gd 3N@C 80 Prato Bis-Adducts: Crystal Structure, Thermal Isomerization, and Computational Study. J Am Chem Soc 2019; 141:10988-10993. [PMID: 31266302 DOI: 10.1021/jacs.9b05603] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The structures of two bis-ethylpyrrolidinoadducts of Gd3N@Ih-C80, obtained by regioselective 1,3-dipolar cycloadditions, were elucidated by single crystal X-ray, visible-near infrared (vis-NIR) spectra, studies on their thermal isomerization, and theoretical calculations. The structure of the minor-bis-adduct reveals a C2-symmetric carbon cage with [6,6][6,6]-addition sites and with an endohedral Gd3N cluster that is completely flattened. This is the first example of a crystal structure of Gd3N@Ih-C80 derivatives. The structure of the major-bis-adduct was inferred by the vis-NIR spectrum being corresponded to the structure of a previously reported major-bis-adduct of Y3N@Ih-C80 known to have an asymmetric [6,6][6,6]-structure. Based on experimental results showing that the minor-bis-adduct of Gd3N@Ih-C80 isomerized to the major-adduct, a possible second addition site was elucidated with support from density functional theory calculations.
Collapse
|
27
|
Yang Z, Jamieson CS, Xue XS, Garcia-Borràs M, Benton T, Dong X, Liu F, Houk K. Mechanisms and Dynamics of Reactions Involving Entropic Intermediates. TRENDS IN CHEMISTRY 2019. [DOI: 10.1016/j.trechm.2019.01.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
28
|
Huang X, Garcia-Borràs M, Miao K, Kan SBJ, Zutshi A, Houk KN, Arnold FH. A Biocatalytic Platform for Synthesis of Chiral α-Trifluoromethylated Organoborons. ACS CENTRAL SCIENCE 2019; 5:270-276. [PMID: 30834315 PMCID: PMC6396380 DOI: 10.1021/acscentsci.8b00679] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Indexed: 05/04/2023]
Abstract
There are few biocatalytic transformations that produce fluorine-containing molecules prevalent in modern pharmaceuticals. To expand the scope of biocatalysis for organofluorine synthesis, we have developed an enzymatic platform for highly enantioselective carbene B-H bond insertion to yield versatile α-trifluoromethylated (α-CF3) organoborons, an important class of organofluorine molecules that contain stereogenic centers bearing both CF3 and boron groups. In contrast to current "carbene transferase" enzymes that use a limited set of simple diazo compounds as carbene precursors, this system based on Rhodothermus marinus cytochrome c (Rma cyt c) can accept a broad range of trifluorodiazo alkanes and deliver versatile chiral α-CF3 organoborons with total turnovers up to 2870 and enantiomeric ratios up to 98.5:1.5. Computational modeling reveals that this broad diazo scope is enabled by an active-site environment that directs the alkyl substituent on the heme CF3-carbene intermediate toward the solvent-exposed face, thereby allowing the protein to accommodate diazo compounds with diverse structural features.
Collapse
|
29
|
García-Simón C, Monferrer A, Garcia-Borràs M, Imaz I, Maspoch D, Costas M, Ribas X. Size-selective encapsulation of C 60 and C 60-derivatives within an adaptable naphthalene-based tetragonal prismatic supramolecular nanocapsule. Chem Commun (Camb) 2019; 55:798-801. [PMID: 30570641 DOI: 10.1039/c8cc07886f] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A novel naphthalene-based 5·(BArF)8 capsule allows for the size-selective inclusion of C60 from fullerene mixtures. Its size selectivity towards C60 has been rationalized by its dynamic adaptability in solution that has been investigated by molecular dynamics. Additionally, 5·(BArF)8 encapsulates C60-derivatives such as C60-PCBM and N-methylpyrrolidine-C60. The latter can be separated from C60 since 5·(BArF)8 displays distinct affinity for them.
Collapse
|
30
|
Caddell Haatveit K, Garcia-Borràs M, Houk KN. Computational Protocol to Understand P450 Mechanisms and Design of Efficient and Selective Biocatalysts. Front Chem 2019; 6:663. [PMID: 30687699 PMCID: PMC6336901 DOI: 10.3389/fchem.2018.00663] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 12/20/2018] [Indexed: 11/13/2022] Open
Abstract
Cytochrome P450 enzymes have gained significant interest as selective oxidants in late-stage chemical synthesis. Their broad substrate scope enables them to be good candidates for their use in non-natural reactivity. Directed evolution evolves new enzyme biocatalysts that promote alternative reactivity for chemical synthesis. While directed evolution has proven useful in developing biocatalysts for specific purposes, this process is very time and labor intensive, and therefore not easily repurposed. Computational analysis of these P450 enzymes provides great insights into the broad substrate scope, the variety of reactions catalyzed, the binding specificity and the study of novel biosynthetic reaction mechanisms. By discovering new P450s and studying their reactivities, we uncover new insights into how this reactivity can be harnessed. We discuss a standard protocol using both DFT calculations and MD simulations to study a variety of cytochrome P450 enzymes. The approach entails theozyme models to study the mechanism and transition states via DFT calculations and subsequent MD simulations to understand the conformational poses and binding mechanisms within the enzyme. We discuss a few examples done in collaboration with the Tang and Sherman/Montgomery groups toward elucidating enzyme mechanisms and rationally designing new enzyme mutants as tools for selective C-H functionalization methods.
Collapse
|
31
|
Xue XS, Jamieson CS, Garcia-Borràs M, Dong X, Yang Z, Houk KN. Ambimodal Trispericyclic Transition State and Dynamic Control of Periselectivity. J Am Chem Soc 2019; 141:1217-1221. [DOI: 10.1021/jacs.8b12674] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
32
|
Li G, Garcia-Borràs M, Furst MJLJ, Ilie A, Fraaije MW, Houk KN, Reetz MT. Overriding Traditional Electronic Effects in Biocatalytic Baeyer-Villiger Reactions by Directed Evolution. J Am Chem Soc 2018; 140:10464-10472. [PMID: 30044629 PMCID: PMC6314816 DOI: 10.1021/jacs.8b04742] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Controlling the regioselectivity of Baeyer-Villiger (BV) reactions remains an ongoing issue in organic chemistry, be it by synthetic catalysts or enzymes of the type Baeyer-Villiger monooxygenases (BVMOs). Herein, we address the challenging problem of switching normal to abnormal BVMO regioselectivity by directed evolution using three linear ketones as substrates, which are not structurally biased toward abnormal reactivity. Upon applying iterative saturation mutagenesis at sites lining the binding pocket of the thermostable BVMO from Thermocrispum municipale DSM 44069 (TmCHMO) and using 4-phenyl-2-butanone as substrate, the regioselectivity was reversed from 99:1 (wild-type enzyme in favor of the normal product undergoing 2-phenylethyl migration) to 2:98 in favor of methyl migration when applying the best mutant. This also stands in stark contrast to the respective reaction using the synthetic reagent m-CPBA, which provides solely the normal product. Reversal of regioselectivity was also achieved in the BV reaction of two other linear ketones. Kinetic parameters and melting temperatures revealed that most of the evolved mutants retained catalytic activity, as well as thermostability. In order to shed light on the origin of switched regioselectivity in reactions of 4-phenyl-2-butanone and phenylacetone, extensive QM/MM and MD simulations were performed. It was found that the mutations introduced by directed evolution induce crucial changes in the conformation of the respective Criegee intermediates and transition states in the binding pocket of the enzyme. In mutants that destabilize the normally preferred migration transition state, a reversal of regioselectivity is observed. This conformational control of regioselectivity overrides electronic control, which normally causes preferential migration of the group that is best able to stabilize positive charge. The results can be expected to aid future protein engineering of BVMOs.
Collapse
|
33
|
Lewis RD, Garcia-Borràs M, Chalkley MJ, Buller AR, Houk KN, Kan SBJ, Arnold FH. Catalytic iron-carbene intermediate revealed in a cytochrome c carbene transferase. Proc Natl Acad Sci U S A 2018; 115:7308-7313. [PMID: 29946033 PMCID: PMC6048479 DOI: 10.1073/pnas.1807027115] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Recently, heme proteins have been discovered and engineered by directed evolution to catalyze chemical transformations that are biochemically unprecedented. Many of these nonnatural enzyme-catalyzed reactions are assumed to proceed through a catalytic iron porphyrin carbene (IPC) intermediate, although this intermediate has never been observed in a protein. Using crystallographic, spectroscopic, and computational methods, we have captured and studied a catalytic IPC intermediate in the active site of an enzyme derived from thermostable Rhodothermus marinus (Rma) cytochrome c High-resolution crystal structures and computational methods reveal how directed evolution created an active site for carbene transfer in an electron transfer protein and how the laboratory-evolved enzyme achieves perfect carbene transfer stereoselectivity by holding the catalytic IPC in a single orientation. We also discovered that the IPC in Rma cytochrome c has a singlet ground electronic state and that the protein environment uses geometrical constraints and noncovalent interactions to influence different IPC electronic states. This information helps us to understand the impressive reactivity and selectivity of carbene transfer enzymes and offers insights that will guide and inspire future engineering efforts.
Collapse
|
34
|
Mallinson SJB, Machovina MM, Silveira RL, Garcia-Borràs M, Gallup N, Johnson CW, Allen MD, Skaf MS, Crowley MF, Neidle EL, Houk KN, Beckham GT, DuBois JL, McGeehan JE. A promiscuous cytochrome P450 aromatic O-demethylase for lignin bioconversion. Nat Commun 2018; 9:2487. [PMID: 29950589 PMCID: PMC6021390 DOI: 10.1038/s41467-018-04878-2] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Accepted: 05/26/2018] [Indexed: 11/18/2022] Open
Abstract
Microbial aromatic catabolism offers a promising approach to convert lignin, a vast source of renewable carbon, into useful products. Aryl-O-demethylation is an essential biochemical reaction to ultimately catabolize coniferyl and sinapyl lignin-derived aromatic compounds, and is often a key bottleneck for both native and engineered bioconversion pathways. Here, we report the comprehensive characterization of a promiscuous P450 aryl-O-demethylase, consisting of a cytochrome P450 protein from the family CYP255A (GcoA) and a three-domain reductase (GcoB) that together represent a new two-component P450 class. Though originally described as converting guaiacol to catechol, we show that this system efficiently demethylates both guaiacol and an unexpectedly wide variety of lignin-relevant monomers. Structural, biochemical, and computational studies of this novel two-component system elucidate the mechanism of its broad substrate specificity, presenting it as a new tool for a critical step in biological lignin conversion.
Collapse
|
35
|
El Bakouri O, Postils V, Garcia-Borràs M, Duran M, Luis JM, Calvello S, Soncini A, Matito E, Feixas F, Solà M. Metal Cluster Electrides: A New Type of Molecular Electride with Delocalised Polyattractor Character. Chemistry 2018; 24:9853-9859. [DOI: 10.1002/chem.201800878] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Revised: 04/16/2018] [Indexed: 11/06/2022]
|
36
|
Serrano-Hervás E, Casadevall G, Garcia-Borràs M, Feixas F, Osuna S. Epoxide Hydrolase Conformational Heterogeneity for the Resolution of Bulky Pharmacologically Relevant Epoxide Substrates. Chemistry 2018; 24:12254-12258. [DOI: 10.1002/chem.201801068] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Indexed: 01/22/2023]
|
37
|
Gao SS, Zhang T, Garcia-Borràs M, Hung YS, Billingsley JM, Houk KN, Hu Y, Tang Y. Biosynthesis of Heptacyclic Duclauxins Requires Extensive Redox Modifications of the Phenalenone Aromatic Polyketide. J Am Chem Soc 2018; 140:6991-6997. [PMID: 29741874 DOI: 10.1021/jacs.8b03705] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Duclauxins are dimeric and heptacyclic fungal polyketides with notable bioactivities. We characterized the cascade of redox transformations in the biosynthetic pathway of duclauxin from Talaromyces stipitatus. The redox reaction sequence is initiated by a cupin family dioxygenase DuxM that performs an oxidative cleavage of the peri-fused tricyclic phenalenone and affords a transient hemiketal-oxaphenalenone intermediate. Additional redox enzymes then morph the oxaphenoalenone into either an anhydride or a dihydrocoumarin-containing monomeric building block that is found in dimeric duxlauxins. Oxidative coupling between the monomers to form the initial C-C bond was shown to be catalyzed by a P450 monooxygenase, although the enzyme responsible for the second C-C bond formation was not found in the pathway. Collectively, the number and variety of redox enzymes used in the duclauxin pathway showcase Nature's strategy to generate structural complexity during natural product biosynthesis.
Collapse
|
38
|
El Bakouri O, Garcia-Borràs M, Girón RM, Filippone S, Martín N, Solà M. On the regioselectivity of the Diels-Alder cycloaddition to C 60 in high spin states. Phys Chem Chem Phys 2018; 20:11577-11585. [PMID: 29417103 PMCID: PMC5932534 DOI: 10.1039/c7cp07965f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 01/24/2018] [Indexed: 11/21/2022]
Abstract
Controlling the regioselectivity in the exohedral functionalization of fullerenes and endohedral metallofullerenes is essential to produce specific desired fullerene derivatives. In this work, using density functional theory (DFT) calculations, we show that the regioselectivity of the Diels-Alder (DA) cycloaddition of cyclopentadiene to 2S+1C60 changes from the usual [6,6] addition in the singlet ground state to the [5,6] attack in high spin states of C60. Changes in the aromaticity of the five- and six-membered rings when going from singlet to high spin C60 provide a rationale to understand this regioselectivity change. Experimentally, however, we find that the DA cycloaddition of isoindene to triplet C60 yields the usual [6,6] adduct. Further DFT calculations and computational analysis give an explanation to this unanticipated experimental result by showing the presence of an intersystem crossing close to the formed triplet biradical intermediate.
Collapse
|
39
|
Newmister SA, Li S, Garcia-Borràs M, Sanders JN, Yang S, Lowell AN, Yu F, Smith JL, Williams RM, Houk KN, Sherman DH. Structural basis of the Cope rearrangement and cyclization in hapalindole biogenesis. Nat Chem Biol 2018; 14:345-351. [PMID: 29531360 PMCID: PMC5880276 DOI: 10.1038/s41589-018-0003-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 01/17/2018] [Indexed: 11/09/2022]
Abstract
Hapalindole alkaloids are a structurally diverse class of cyanobacterial natural products defined by their varied polycyclic ring systems and diverse biological activities. These complex metabolites are generated from a common biosynthetic intermediate by the Stig cyclases in three mechanistic steps: a rare Cope rearrangement, 6-exo-trig cyclization, and electrophilic aromatic substitution. Here we report the structure of HpiC1, a Stig cyclase that catalyzes the formation of 12-epi-hapalindole U in vitro. The 1.5-Å structure revealed a dimeric assembly with two calcium ions per monomer and with the active sites located at the distal ends of the protein dimer. Mutational analysis and computational methods uncovered key residues for an acid-catalyzed [3,3]-sigmatropic rearrangement, as well as specific determinants that control the position of terminal electrophilic aromatic substitution, leading to a switch from hapalindole to fischerindole alkaloids.
Collapse
|
40
|
Vidal S, Izquierdo M, Alom S, Garcia-Borràs M, Filippone S, Osuna S, Solà M, Whitby RJ, Martín N. Effect of incarcerated HF on the exohedral chemical reactivity of HF@C 60. Chem Commun (Camb) 2018; 53:10993-10996. [PMID: 28835947 DOI: 10.1039/c7cc05987f] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The first chemical modification on the brand new endohedral HF@C60 is reported. In particular, the isomerization from optically pure (2S,5S)-cis-pyrrolidino[3,4:1,2][60]fullerene 2b to (2S,5R)-trans-pyrrolidino[3,4:1,2][60]fullerene 2b has been studied and compared with empty C60 (2a) and endohedral H2O@C60 (3). The comparative study shows a kinetic order for the isomerization process of H2O@C60 > HF@C60 > C60, thus confirming the effect of the incarcerated species on the zwitterionic intermediate stability.
Collapse
|
41
|
Serrano-Hervás E, Garcia-Borràs M, Osuna S. Exploring the origins of selectivity in soluble epoxide hydrolase from Bacillus megaterium. Org Biomol Chem 2018; 15:8827-8835. [PMID: 29026902 PMCID: PMC5708342 DOI: 10.1039/c7ob01847a] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Epoxide hydrolase (EH) enzymes catalyze the hydration of racemic epoxides to yield their corresponding vicinal diols. In this work, the Bacillus megaterium epoxide hydrolase (BmEH)-mediated hydrolysis of racemic styrene oxide (rac-SO) and its para-nitro styrene oxide (rac-p-NSO) derivative are computationally investigated using density functional theory (DFT).
Epoxide hydrolase (EH) enzymes catalyze the hydration of racemic epoxides to yield their corresponding vicinal diols. These enzymes present different enantio- and regioselectivity depending upon either the substrate structure or the substitution pattern of the epoxide ring. In this study, we computationally investigate the Bacillus megaterium epoxide hydrolase (BmEH)-mediated hydrolysis of racemic styrene oxide (rac-SO) and its para-nitro styrene oxide (rac-p-NSO) derivative using density functional theory (DFT) and an active site cluster model consisting of 195 and 197 atoms, respectively. Full reaction mechanisms for epoxide ring opening were evaluated considering the attack at both oxirane carbons and considering two possible orientations of the substrate at the BmEH active site. Our results indicate that for both SO and p-NSO substrates the BmEH enantio- and regioselectivity is opposite to the inherent (R)-BmEH selectivity, the attack at the benzylic position (C1) of the (S)-enantiomer being the most favoured chemical outcome.
Collapse
|
42
|
Romero-Rivera A, Garcia-Borràs M, Osuna S. Role of Conformational Dynamics in the Evolution of Retro-Aldolase Activity. ACS Catal 2017; 7:8524-8532. [PMID: 29226011 PMCID: PMC5716449 DOI: 10.1021/acscatal.7b02954] [Citation(s) in RCA: 85] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 10/19/2017] [Indexed: 12/19/2022]
Abstract
![]()
Enzymes exist as
ensembles of conformations that are important
for function. Tuning these populations of conformational states through
mutation enables evolution toward additional activities. Here we computationally
evaluate the population shifts induced by distal and active site mutations
in a family of computationally designed and experimentally optimized
retro-aldolases. The conformational landscape of these enzymes was
significantly altered during evolution, as pre-existing catalytically
active conformational substates became major states in the most evolved
variants. We further demonstrate that key residues responsible for
these substate conversions can be predicted computationally. Significantly,
the identified residues coincide with those positions mutated in the
laboratory evolution experiments. This study establishes that distal
mutations that affect enzyme catalytic activity can be predicted computationally
and thus provides the enzyme (re)design field with a rational strategy
to determine promising sites for enhancing activity through mutation.
Collapse
|
43
|
Garcia-Borràs M, Houk KN, Jiménez-Osés G. Computational Design of Protein Function. COMPUTATIONAL TOOLS FOR CHEMICAL BIOLOGY 2017. [DOI: 10.1039/9781788010139-00087] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The computational design of enzymes is a tremendous challenge for both chemistry and biochemistry. The ability to design stable and functional biocatalysts that could operate under different conditions to perform chemical reactions without precedent in nature, allowing the large-scale production of chemicals à la carte, would revolutionise both synthetic, pharmacologic and materials chemistry. Despite the great advances achieved, this highly multidisciplinary area of research is still in its infancy. This chapter describes the ‘inside-out’ protocol for computational enzyme design and both the achievements and limitations of the current technology are highlighted. Furthermore, molecular dynamics simulations have proved to be invaluable in the enzyme design process, constituting an important tool for discovering elusive catalytically relevant conformations of the engineered or designed enzyme. As a complement to the ‘inside-out’ design protocol, different examples where hybrid QM/MM approaches have been directly applied to discover beneficial mutations in rational computational enzyme design are described.
Collapse
|
44
|
Fraley AE, Garcia-Borràs M, Tripathi A, Khare D, Mercado-Marin EV, Tran H, Dan Q, Webb GP, Watts KR, Crews P, Sarpong R, Williams RM, Smith JL, Houk KN, Sherman DH. Function and Structure of MalA/MalA', Iterative Halogenases for Late-Stage C-H Functionalization of Indole Alkaloids. J Am Chem Soc 2017; 139:12060-12068. [PMID: 28777910 PMCID: PMC5595095 DOI: 10.1021/jacs.7b06773] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Malbrancheamide is a dichlorinated fungal indole alkaloid isolated from both Malbranchea aurantiaca and Malbranchea graminicola that belongs to a family of natural products containing a characteristic bicyclo[2.2.2]diazaoctane core. The introduction of chlorine atoms on the indole ring of malbrancheamide differentiates it from other members of this family and contributes significantly to its biological activity. In this study, we characterized the two flavin-dependent halogenases involved in the late-stage halogenation of malbrancheamide in two different fungal strains. MalA and MalA' catalyze the iterative dichlorination and monobromination of the free substrate premalbrancheamide as the final steps in the malbrancheamide biosynthetic pathway. Two unnatural bromo-chloro-malbrancheamide analogues were generated through MalA-mediated chemoenzymatic synthesis. Structural analysis and computational studies of MalA' in complex with three substrates revealed that the enzyme represents a new class of zinc-binding flavin-dependent halogenases and provides new insights into a potentially unique reaction mechanism.
Collapse
|
45
|
Garcia-Borràs M, Osuna S, Luis JM, Solà M. Rationalizing the relative abundances of trimetallic nitride template-based endohedral metallofullerenes from aromaticity measures. Chem Commun (Camb) 2017; 53:4140-4143. [PMID: 28352903 PMCID: PMC5436040 DOI: 10.1039/c7cc01750b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 03/20/2017] [Indexed: 11/25/2022]
Abstract
The synthesis of endohedral metallofullerenes (EMFs) from a carbon soot sample of an arc discharge leads to a variety of EMFs that are obtained in different relative abundances. In the present work, we show that these abundances can be predicted from aromaticity calculations. In particular, we use the normalized Additive Local Aromaticity (ALAN) index. Our results show that the most abundant Sc3N-based and Y3N-based EMFs in fullerene soot are the most aromatic. This study reinforces the idea that aromaticity plays a key role in determining the stability of EMFs.
Collapse
|
46
|
Gao SS, Garcia-Borràs M, Barber JS, Hai Y, Duan A, Garg NK, Houk KN, Tang Y. Enzyme-Catalyzed Intramolecular Enantioselective Hydroalkoxylation. J Am Chem Soc 2017; 139:3639-3642. [PMID: 28240554 DOI: 10.1021/jacs.7b01089] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Hydroalkoxylation is a powerful and efficient method of forming C-O bonds and cyclic ethers in synthetic chemistry. In studying the biosynthesis of the fungal natural product herqueinone, we identified an enzyme that can perform an intramolecular enantioselective hydroalkoxylation reaction. PhnH catalyzes the addition of a phenol to the terminal olefin of a reverse prenyl group to give a dihydrobenzofuran product. The enzyme accelerates the reaction by 3 × 105-fold compared to the uncatalyzed reaction. PhnH belongs to a superfamily of proteins with a domain of unknown function (DUF3237), of which no member has a previously verified function. The discovery of PhnH demonstrates that enzymes can be used to promote the enantioselective hydroalkoxylation reaction and form cyclic ethers.
Collapse
|
47
|
Romero-Rivera A, Garcia-Borràs M, Osuna S. Computational tools for the evaluation of laboratory-engineered biocatalysts. Chem Commun (Camb) 2016; 53:284-297. [PMID: 27812570 PMCID: PMC5310519 DOI: 10.1039/c6cc06055b] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2016] [Accepted: 09/06/2016] [Indexed: 12/18/2022]
Abstract
Biocatalysis is based on the application of natural catalysts for new purposes, for which enzymes were not designed. Although the first examples of biocatalysis were reported more than a century ago, biocatalysis was revolutionized after the discovery of an in vitro version of Darwinian evolution called Directed Evolution (DE). Despite the recent advances in the field, major challenges remain to be addressed. Currently, the best experimental approach consists of creating multiple mutations simultaneously while limiting the choices using statistical methods. Still, tens of thousands of variants need to be tested experimentally, and little information is available on how these mutations lead to enhanced enzyme proficiency. This review aims to provide a brief description of the available computational techniques to unveil the molecular basis of improved catalysis achieved by DE. An overview of the strengths and weaknesses of current computational strategies is explored with some recent representative examples. The understanding of how this powerful technique is able to obtain highly active variants is important for the future development of more robust computational methods to predict amino-acid changes needed for activity.
Collapse
|
48
|
Li Y, Osuna S, Garcia-Borràs M, Qi X, Liu S, Houk KN, Lan Y. Reactivity of Single-Walled Carbon Nanotubes in the Diels-Alder Cycloaddition Reaction: Distortion-Interaction Analysis along the Reaction Pathway. Chemistry 2016; 22:12819-24. [PMID: 27465519 DOI: 10.1002/chem.201601799] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2016] [Indexed: 11/06/2022]
Abstract
Diels-Alder cycloaddition is one of the most powerful tools for the functionalization of single-walled carbon nanotubes (SWCNTs). Density functional theory at the B3-LYP level of theory has been used to investigate the reactivity of different-diameter SWCNTs (4-9,5) in Diels-Alder reactions with 1,3-butadiene; the reactivity was found to decrease with increasing SWCNT diameter. Distortion/interaction analysis along the whole reaction pathway was found to be a better way to explore the reactivity of this type of reaction. The difference in interaction energy along the reaction pathway is larger than that of the corresponding distortion energy. However, the distortion energy plots for these reactions show the same trend. Therefore, the formation of the transition state can be determined from the interaction energy. A lower interaction energy leads to an earlier transition state, which indicates a lower activation energy. The computational results also indicate that the original distortion of the SWCNTs leads to an increase in the reactivity of the SWCNTs.
Collapse
|
49
|
Zaleśny R, Garcia-Borràs M, Góra RW, Medved' M, Luis JM. On the physical origins of interaction-induced vibrational (hyper)polarizabilities. Phys Chem Chem Phys 2016; 18:22467-77. [PMID: 27465257 DOI: 10.1039/c6cp02500e] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This paper presents the results of a pioneering exploration of the physical origins of vibrational contributions to the interaction-induced electric properties of molecular complexes. In order to analyze the excess nuclear relaxation (hyper)polarizabilities, a new scheme was proposed which relies on the computationally efficient Bishop-Hasan-Kirtman method for determining the nuclear relaxation contributions to electric properties. The extension presented herein is general and can be used with any interaction-energy partitioning method. As an example, in this study we employed the variational-perturbational interaction-energy decomposition scheme (at the MP2/aug-cc-pVQZ level) and the extended transition state method by employing three exchange-correlation functionals (BLYP, LC-BLYP, and LC-BLYP-dDsC) to study the excess properties of the HCN dimer. It was observed that the first-order electrostatic contribution to the excess nuclear relaxation polarizability cancels with the negative exchange repulsion term out to a large extent, resulting in a positive value of Δα(nr) due to the contributions from the delocalization and the dispersion terms. In the case of the excess nuclear relaxation first hyperpolarizability, the pattern of interaction contributions is very similar to that for Δα(nr), both in terms of their sign as well as relative magnitude. Finally, our results show that the LC-BLYP and LC-BLYP-dDsC functionals, which yield smaller values of the orbital relaxation term than BLYP, are more successful in predicting excess properties.
Collapse
|
50
|
Martínez JP, Garcia-Borràs M, Osuna S, Poater J, Bickelhaupt FM, Solà M. Reaction Mechanism and Regioselectivity of the Bingel-Hirsch Addition of Dimethyl Bromomalonate to La@C2v -C82. Chemistry 2016; 22:5953-62. [PMID: 26991842 DOI: 10.1002/chem.201504668] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Indexed: 11/09/2022]
Abstract
We quantum chemically explore the thermodynamics and kinetics of all 65 possible mechanistic pathways of the Bingel-Hirsch addition of dimethyl bromomalonate to the endohedral metallofullerene La@C2v -C82 that result from the combination of 24 nonequivalent carbon atoms and 35 different bonds present in La@C2v -C82 by using dispersion-corrected DFT calculations. Experimentally, this reaction leads to four singly bonded derivatives and one fulleroid adduct. Of these five products, only the singly bonded derivative on C23 could be experimentally identified unambiguously. Our calculations show that La@C2v -C82 is not particularly regioselective under Bingel-Hirsch conditions. From the obtained results, however, it is possible to make a tentative assignment of the products observed experimentally. We propose that the observed fulleroid adduct results from the attack at bond 19 and that the singly bonded derivatives correspond to the C2, C19, C21, and C23 initial attacks. However, other possibilities cannot be ruled out completely.
Collapse
|