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Fontes FL, Rooker SA, Lynn-Barbe JK, Lyons MA, Crans DC, Crick DC. Pyrazinoic acid, the active form of the anti-tuberculosis drug pyrazinamide, and aromatic carboxylic acid analogs are protonophores. Front Mol Biosci 2024; 11:1350699. [PMID: 38414662 PMCID: PMC10896915 DOI: 10.3389/fmolb.2024.1350699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 01/16/2024] [Indexed: 02/29/2024] Open
Abstract
Pyrazinoic acid is the active form of pyrazinamide, a first-line antibiotic used to treat Mycobacterium tuberculosis infections. However, the mechanism of action of pyrazinoic acid remains a subject of debate, and alternatives to pyrazinamide in cases of resistance are not available. The work presented here demonstrates that pyrazinoic acid and known protonophores including salicylic acid, benzoic acid, and carbonyl cyanide m-chlorophenyl hydrazone all exhibit pH-dependent inhibition of mycobacterial growth activity over a physiologically relevant range of pH values. Other anti-tubercular drugs, including rifampin, isoniazid, bedaquiline, and p-aminosalicylic acid, do not exhibit similar pH-dependent growth-inhibitory activities. The growth inhibition curves of pyrazinoic, salicylic, benzoic, and picolinic acids, as well as carbonyl cyanide m-chlorophenyl hydrazone, all fit a quantitative structure-activity relationship (QSAR) derived from acid-base equilibria with R2 values > 0.95. The QSAR model indicates that growth inhibition relies solely on the concentration of the protonated forms of these weak acids (rather than the deprotonated forms). Moreover, pyrazinoic acid, salicylic acid, and carbonyl cyanide m-chlorophenyl hydrazone all caused acidification of the mycobacterial cytoplasm at concentrations that inhibit bacterial growth. Thus, it is concluded that pyrazinoic acid acts as an uncoupler of oxidative phosphorylation and that disruption of proton motive force is the primary mechanism of action of pyrazinoic acid rather than the inhibition of a classic enzyme activity.
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Affiliation(s)
- Fabio L. Fontes
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Steven A. Rooker
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Jamie K. Lynn-Barbe
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Michael A. Lyons
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
| | - Debbie C. Crans
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Department of Chemistry, Colorado State University, Fort Collins, CO, United States
| | - Dean C. Crick
- Program in Cell and Molecular Biology, Colorado State University, Fort Collins, CO, United States
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, United States
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Braasch-Turi MM, Koehn JT, Kostenkova K, Van Cleave C, Ives JW, Murakami HA, Crick DC, Crans DC. Electron Transport Lipids Fold Within Membrane-Like Interfaces. Front Chem 2022; 10:827530. [PMID: 35350775 PMCID: PMC8957872 DOI: 10.3389/fchem.2022.827530] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 01/07/2022] [Indexed: 12/23/2022] Open
Abstract
Lipoquinones, such as ubiquinones (UQ) and menaquinones (MK), function as essential lipid components of the electron transport system (ETS) by shuttling electrons and protons to facilitate the production of ATP in eukaryotes and prokaryotes. Lipoquinone function in membrane systems has been widely studied, but the exact location and conformation within membranes remains controversial. Lipoquinones, such as Coenzyme Q (UQ-10), are generally depicted simply as “Q” in life science diagrams or in extended conformations in primary literature even though specific conformations are important for function in the ETS. In this study, our goal was to determine the location, orientation, and conformation of UQ-2, a truncated analog of UQ-10, in model membrane systems and to compare our results to previously studied MK-2. Herein, we first carried out a six-step synthesis to yield UQ-2 and then demonstrated that UQ-2 adopts a folded conformation in organic solvents using 1H-1H 2D NOESY and ROESY NMR spectroscopic studies. Similarly, using 1H-1H 2D NOESY NMR spectroscopic studies, UQ-2 was found to adopt a folded, U-shaped conformation within the interface of an AOT reverse micelle model membrane system. UQ-2 was located slightly closer to the surfactant-water interface compared to the more hydrophobic MK-2. In addition, Langmuir monolayer studies determined UQ-2 resided within the monolayer water-phospholipid interface causing expansion, whereas MK-2 was more likely to be compressed out and reside within the phospholipid tails. All together these results support the model that lipoquinones fold regardless of the headgroup structure but that the polarity of the headgroup influences lipoquinone location within the membrane interface. These results have implications regarding the redox activity near the interface as quinone vs. quinol forms may facilitate locomotion of lipoquinones within the membrane. The location, orientation, and conformation of lipoquinones are critical for their function in generating cellular energy within membrane ETS, and the studies described herein shed light on the behavior of lipoquinones within membrane-like environments.
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Affiliation(s)
| | - Jordan T. Koehn
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
| | - Kateryna Kostenkova
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
| | - Cameron Van Cleave
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
| | - Jacob W. Ives
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
| | - Heide A. Murakami
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
| | - Dean C. Crick
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO, United States
- Microbiology, Immunology, and Pathology Department, Colorado State University, Fort Collins, CO, United States
| | - Debbie C. Crans
- Chemistry Department, Colorado State University, Fort Collins, CO, United States
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO, United States
- *Correspondence: Debbie C. Crans,
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Doucette KA, Chaiyasit P, Calkins DL, Martinez KN, Van Cleave C, Knebel CA, Tongraar A, Crans DC. The Interfacial Interactions of Glycine and Short Glycine Peptides in Model Membrane Systems. Int J Mol Sci 2020; 22:ijms22010162. [PMID: 33375246 PMCID: PMC7795424 DOI: 10.3390/ijms22010162] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/19/2020] [Accepted: 12/22/2020] [Indexed: 12/20/2022] Open
Abstract
The interactions of amino acids and peptides at model membrane interfaces have considerable implications for biological functions, with the ability to act as chemical messengers, hormones, neurotransmitters, and even as antibiotics and anticancer agents. In this study, glycine and the short glycine peptides diglycine, triglycine, and tetraglycine are studied with regards to their interactions at the model membrane interface of Aerosol-OT (AOT) reverse micelles via 1H NMR spectroscopy, dynamic light scattering (DLS), and Langmuir trough measurements. It was found that with the exception of monomeric glycine, the peptides prefer to associate between the interface and bulk water pool of the reverse micelle. Monomeric glycine, however, resides with the N-terminus in the ordered interstitial water (stern layer) and the C-terminus located in the bulk water pool of the reverse micelle.
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Affiliation(s)
- Kaitlin A. Doucette
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO 80523, USA;
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
| | - Prangthong Chaiyasit
- School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; (P.C.); (A.T.)
| | - Donn L. Calkins
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
| | - Kayli N. Martinez
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
| | - Cameron Van Cleave
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
| | - Callan A. Knebel
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
| | - Anan Tongraar
- School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand; (P.C.); (A.T.)
| | - Debbie C. Crans
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO 80523, USA;
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA; (D.L.C.); (K.N.M.); (C.V.C.); (C.A.K.)
- Correspondence: ; Tel.: +1-970-491-7635
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Van Cleave C, Murakami HA, Samart N, Koehn JT, Maldonado P, Kreckel HD, Cope EJ, Basile A, Crick DC, Crans DC. Location of menaquinone and menaquinol headgroups in model membranes. CAN J CHEM 2020. [DOI: 10.1139/cjc-2020-0024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Menaquinones are lipoquinones that consist of a headgroup (naphthoquinone, menadione) and an isoprenyl sidechain. They function as electron transporters in prokaryotes such as Mycobacterium tuberculosis. For these studies, we used Langmuir monolayers and microemulsions to investigate how the menaquinone headgroup (menadione) and the menahydroquinone headgroup (menadiol) interact with model membrane interfaces to determine if differences are observed in the location of these headgroups in a membrane. It has been suggested that the differences in the locations are mainly caused by the isoprenyl sidechain rather than the headgroup quinone-to-quinol reduction during electron transport. This study presents evidence that suggests the influence of the headgroup drives the movement of the oxidized quinone and the reduced hydroquinone to different locations within the interface. Utilizing the model membranes of microemulsions and Langmuir monolayers, it is determined whether or not there is a difference in the location of menadione and menadiol within the interface. Based on our findings, we conclude that the menadione and menadiol may reside in different locations within model membranes. It follows that if menaquinone moves within the cell membrane upon menaquinol formation, it is due at least in part, to the differences in the properties of headgroup interactions with the membrane in addition to the isoprenyl sidechain.
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Affiliation(s)
- Cameron Van Cleave
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Heide A. Murakami
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Nuttaporn Samart
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
- Department of Chemistry, Rajabhat Rajanagarindra University, Chachoengsao, Thailand
| | - Jordan T. Koehn
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Pablo Maldonado
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Heidi D. Kreckel
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Elana J. Cope
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Andrea Basile
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
| | - Dean C. Crick
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO 80523, USA
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, CO 80523, USA
| | - Debbie C. Crans
- Department of Chemistry, Colorado State University, Fort Collins, CO 80523, USA
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, CO 80523, USA
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5
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Koehn JT, Beuning CN, Peters BJ, Dellinger SK, Van Cleave C, Crick DC, Crans DC. Investigating Substrate Analogues for Mycobacterial MenJ: Truncated and Partially Saturated Menaquinones. Biochemistry 2019; 58:1596-1615. [DOI: 10.1021/acs.biochem.9b00007] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Crans DC, Koehn JT, Petry SM, Glover CM, Wijetunga A, Kaur R, Levina A, Lay PA. Hydrophobicity may enhance membrane affinity and anti-cancer effects of Schiff base vanadium(v) catecholate complexes. Dalton Trans 2019; 48:6383-6395. [PMID: 30941380 DOI: 10.1039/c9dt00601j] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Anti-cancer activities of vanadium compounds have generated recent interest because of a combination of desirable properties for chemotherapy, i.e., strong cytotoxicities, anti-metastatic activities and relatively low systemic toxicities. Certain hydrophobic vanadium(v) Schiff base/catecholate compounds, which as shown herein, have increased stability in aqueous media and affinity for membrane interfaces. Depending on their hydrophobicity, they may be able to enter cells intact. In this manuscript, two hydrophobic V(v) catecholate substituted analogues, [VO(Hshed)(cat)] and [VO(Hshed)(dtb)], (Hshed = N-(salicylideneaminato)-N'-(2-hydroxyethyl)-1,2-ethanediamine, cat = pyrocatechol, and dtb = 3,5-di(tert-butyl)catechol and the vanadium(v) precursor [V(O)2(Hshed)]) were synthesized for their ability to interact with membranes and their anti-cancer effects. Using 51V and 1H NMR spectroscopy, the presence and location of the free ligand, H2shed, and the three V(v) complexes were examined in a model membrane microemulsion system. The stability of the three complexes was measured in aqueous solution, cell media and an inhomogeneous microemulsion system. Our results demonstrated that free ligand H2shed and the intact V(v) complexes associated with the interface but that the V-complexes hydrolyzed to some extent because oxovanadates were observed by 51V NMR spectroscopy and decreasing complex by absorption spectroscopy in cell media. When determining the effects of V(v) catecholate complexes on bone cancer cells, the strongest effects were observed with the more stable hydrophobic complex [VO(Hshed)(dtb)] that was able to best associate and penetrate the model membrane system intact. These studies are consistent with the membrane permeability studies being a good predictor for in vitro cytotoxicity assays because [VO(Hshed)(dtb)] can pass through the cellular membrane intact, which may enhance its anti-cancer activities.
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Affiliation(s)
- Debbie C Crans
- Chemistry Department, Colorado State University, Fort Collins, Colorado 80523, USA.
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7
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Nazar MF, Yasir Siddique M, Saleem MA, Zafar M, Nawaz F, Ashfaq M, Khan AM, Abd Ur Rahman HM, Tahir MB, Mat Lazim A. Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:10603-10612. [PMID: 30109940 DOI: 10.1021/acs.langmuir.8b01775] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.
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Affiliation(s)
| | | | | | | | - Faisal Nawaz
- Department of Basic Sciences and Humanities , University of Engineering and Technology Lahore (Faisalabad Campus) , Faisalabad 54890 , Pakistan
| | | | - Asad Muhammad Khan
- Department of Chemistry , COMSATS Institute of Information Technology , Abbottabad 22060 , Pakistan
| | | | | | - Azwan Mat Lazim
- School of Chemical Sciences and Food Technology, Faculty of Science and Technology , University Kebangsaan Malaysia , Bangi 43600 , Selangor , Malaysia
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8
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Peters BJ, Van Cleave C, Haase AA, Hough JPB, Giffen-Kent KA, Cardiff GM, Sostarecz AG, Crick DC, Crans DC. Structure Dependence of Pyridine and Benzene Derivatives on Interactions with Model Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:8939-8951. [PMID: 29958493 PMCID: PMC6106790 DOI: 10.1021/acs.langmuir.8b01661] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Pyridine-based small-molecule drugs, vitamins, and cofactors are vital for many cellular processes, but little is known about their interactions with membrane interfaces. These specific membrane interactions of these small molecules or ions can assist in diffusion across membranes or reach a membrane-bound target. This study explores how minor differences in small molecules (isoniazid, benzhydrazide, isonicotinamide, nicotinamide, picolinamide, and benzamide) can affect their interactions with model membranes. Langmuir monolayer studies of dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylphosphatidylethanolamine (DPPE), in the presence of the molecules listed, show that isoniazid and isonicotinamide affect the DPPE monolayer at lower concentrations than the DPPC monolayer, demonstrating a preference for one phospholipid over the other. The Langmuir monolayer studies also suggest that nitrogen content and stereochemistry of the small molecule can affect the phospholipid monolayers differently. To determine the molecular interactions of the simple N-containing aromatic pyridines with a membrane-like interface, 1H one-dimensional NMR and 1H-1H two-dimensional NMR techniques were utilized to obtain information about the position and orientation of the molecules of interest within aerosol-OT (AOT) reverse micelles. These studies show that all six of the molecules reside near the AOT sulfonate headgroups and ester linkages in similar positions, but nicotinamide and picolinamide tilt at the water-AOT interface to varying degrees. Combined, these studies demonstrate that small structural changes of small N-containing molecules can affect their specific interactions with membrane-like interfaces and specificity toward different membrane components.
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Affiliation(s)
| | | | | | | | | | | | - Audra G Sostarecz
- Department of Chemistry , Monmouth College , Monmouth , Illinois 61462 , United States
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9
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Koehn J, Magallanes ES, Peters BJ, Beuning CN, Haase AA, Zhu MJ, Rithner CD, Crick DC, Crans DC. A Synthetic Isoprenoid Lipoquinone, Menaquinone-2, Adopts a Folded Conformation in Solution and at a Model Membrane Interface. J Org Chem 2018; 83:275-288. [PMID: 29168636 PMCID: PMC5759649 DOI: 10.1021/acs.joc.7b02649] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2017] [Indexed: 11/29/2022]
Abstract
Menaquinones (naphthoquinones, MK) are isoprenoids that play key roles in the respiratory electron transport system of some prokaryotes by shuttling electrons between membrane-bound protein complexes acting as electron acceptors and donors. Menaquinone-2 (MK-2), a truncated MK, was synthesized, and the studies presented herein characterize the conformational and chemical properties of the hydrophobic MK-2 molecule. Using 2D NMR spectroscopy, we established for the first time that MK-2 has a folded conformation defined by the isoprenyl side-chain folding back over the napthoquinone in a U-shape, which depends on the specific environmental conditions found in different solvents. We used molecular mechanics to illustrate conformations found by the NMR experiments. The measured redox potentials of MK-2 differed in three organic solvents, where MK-2 was most easily reduced in DMSO, which may suggest a combination of solvent effect (presumably in part because of differences in dielectric constants) and/or conformational differences of MK-2 in different organic solvents. Furthermore, MK-2 was found to associate with the interface of model membranes represented by Langmuir phospholipid monolayers and Aerosol-OT (AOT) reverse micelles. MK-2 adopts a slightly different U-shaped conformation within reverse micelles compared to within solution, which is in sharp contrast to the extended conformations illustrated in literature for MKs.
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Affiliation(s)
- Jordan
T. Koehn
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Estela S. Magallanes
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Benjamin J. Peters
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Cheryle N. Beuning
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Allison A. Haase
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Michelle J. Zhu
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Christopher D. Rithner
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Dean C. Crick
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
| | - Debbie C. Crans
- Chemistry
Department, Cell and Molecular Biology Program,
and Microbiology, Immunology,
and Pathology Department, Colorado State
University, Fort Collins, Colorado 80523, United States
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10
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Vermaas JV, Beckham GT, Crowley MF. Membrane Permeability of Fatty Acyl Compounds Studied via Molecular Simulation. J Phys Chem B 2017; 121:11311-11324. [PMID: 29040809 DOI: 10.1021/acs.jpcb.7b08233] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Interest in fatty acid-derived products as fuel and chemical precursors has grown substantially. Microbes can be genetically engineered to produce fatty acid-derived products that are able to cross host membranes and can be extracted into an applied organic overlay. This process is thought to be passive, with a rate dependent on the chemistry of the crossing compound. The relationship between the chemical composition and the energetics and kinetics of product accumulation within the overlay is not well understood. Through biased and unbiased molecular simulation, we compute the membrane permeability coefficients from production to extraction for different fatty acyl products, including fatty acids, fatty alcohols, fatty aldehydes, alkanes, and alkenes. These simulations identify specific interactions that accelerate the transit of aldehydes across the membrane bilayer relative to other oxidized products, specifically the lack of hydrogen bonds to the surrounding membrane environment. However, since extraction from the outer membrane leaflet into the organic phase is found to be rate limiting for the entire process, we find that fatty alcohols and fatty aldehydes would both manifest similar fluxes into a dodecane overlay under equivalent conditions, outpacing the accumulation of acids or alkanes into the organic phase. Since aldehydes are known to be highly reactive as well as toxic in high quantities, the findings suggest that indeed fatty alcohols are the optimal long-tail fatty acyl product for extraction.
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Affiliation(s)
- Josh V Vermaas
- Biosciences Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States
| | - Gregg T Beckham
- National Bioenergy Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States
| | - Michael F Crowley
- Biosciences Center, National Renewable Energy Laboratory , Golden, Colorado 80401, United States
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