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Müh F, Bothe A, Zouni A. Towards understanding the crystallization of photosystem II: influence of poly(ethylene glycol) of various molecular sizes on the micelle formation of alkyl maltosides. PHOTOSYNTHESIS RESEARCH 2024:10.1007/s11120-024-01079-5. [PMID: 38488943 DOI: 10.1007/s11120-024-01079-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/24/2024] [Indexed: 03/17/2024]
Abstract
The influence of poly(ethylene glycol) (PEG) polymers H-(O-CH2-CH2)p-OH with different average molecular sizes p on the micelle formation of n-alkyl-β-D-maltoside detergents with the number of carbon atoms in the alkyl chain ranging from 10 to 12 is investigated with the aim to learn more about the detergent behavior under conditions suitable for the crystallization of the photosynthetic pigment-protein complex photosystem II. PEG is shown to increase the critical micelle concentration (CMC) of all three detergents in the crystallization buffer in a way that the free energy of micelle formation increases linearly with the concentration of oxyethylene units (O-CH2-CH2) irrespective of the actual molecular weight of the polymer. The CMC shift is modeled by assuming for simplicity that it is dominated by the interaction between PEG and detergent monomers and is interpreted in terms of an increase of the transfer free energy of a methylene group of the alkyl chain by 0.2 kJ mol-1 per 1 mol L-1 increase of the concentration of oxyethylene units at 298 K. Implications of this effect for the solubilization and crystallization of protein-detergent complexes as well as detergent extraction from crystals are discussed.
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Affiliation(s)
- Frank Müh
- Institut für Theoretische Physik, Johannes Kepler Universität Linz, Altenberger Strasse 69, 4040, Linz, Austria.
| | - Adrian Bothe
- Institut für Molekularbiologie und Biophysik, ETH Zürich, HPK, Otto-Stern-Weg 5, CH-8093, Zurich, Switzerland
| | - Athina Zouni
- Institut für Biologie, Humboldt Universität zu Berlin, Leonor-Michaelis-Haus, Philippstrasse 13, 10095, Berlin, Germany
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Bothe A, Zouni A, Müh F. Refined definition of the critical micelle concentration and application to alkyl maltosides used in membrane protein research. RSC Adv 2023; 13:9387-9401. [PMID: 36968053 PMCID: PMC10031436 DOI: 10.1039/d2ra07440k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Accepted: 03/12/2023] [Indexed: 03/24/2023] Open
Abstract
The critical micelle concentration (CMC) of nonionic detergents is defined as the breaking point in the monomer concentration as a function of the total detergent concentration, identified by setting the third derivate of this function to zero. Combined with a mass action model for micelle formation, this definition yields analytic formulae for the concentration ratio of monomers to total detergent at the CMC and the relationship between the CMC and the free energy of micellization g mic. The theoretical breaking point is shown to coincide with the breaking point of the experimental titration curve, if the fluorescence enhancement of 8-anilino-1-naphthalene-sulfonic acid (ANS) or a similar probe dye is used to monitor micelle formation. Application to a series of n-alkyl-β-d-maltosides with the number of carbon atoms in the alkyl chain ranging from 8 to 12 demonstrates the good performance of a molecular thermodynamic model, in which the free energy of micellization is given by g mic = σΦ + g pack + g st. In this model, σ is a fit parameter with the dimension of surface tension, Φ represents the change in area of hydrophobic molecular surfaces in contact with the aqueous phase, and g pack and g st are contributions, respectively, from alkyl chain packing in the micelle interior and steric repulsion of detergent head groups. The analysis of experimental data from different sources shows that varying experimental conditions such as co-solutes in the aqueous phase can be accounted for by adapting only σ, if the co-solutes do not bind to the detergent to an appreciable extent. The model is considered a good compromise between theory and practicability to be applied in the context of in vitro investigations of membrane proteins.
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Affiliation(s)
- Adrian Bothe
- Institut für Biologie, Humboldt Universität zu Berlin Leonor-Michaelis-Haus, Philippstrasse 13 D-10095 Berlin Germany
| | - Athina Zouni
- Institut für Biologie, Humboldt Universität zu Berlin Leonor-Michaelis-Haus, Philippstrasse 13 D-10095 Berlin Germany
| | - Frank Müh
- Institut für Theoretische Physik, Johannes Kepler Universität Linz Altenberger Strasse 69 A-4040 Linz Austria
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Golub M, Hussein R, Ibrahim M, Hecht M, Wieland DCF, Martel A, Machado B, Zouni A, Pieper J. Solution Structure of the Detergent-Photosystem II Core Complex Investigated by Small-Angle Scattering Techniques. J Phys Chem B 2020; 124:8583-8592. [PMID: 32816484 DOI: 10.1021/acs.jpcb.0c07169] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Albeit achieving the X-ray diffraction structure of dimeric photosystem II core complexes (dPSIIcc) at the atomic resolution, the nature of the detergent belt surrounding dPSIIcc remains ambiguous. Therefore, the solution structure of the whole detergent-protein complex of dPSIIcc of Thermosynechococcus elongatus (T. elongatus) solubilized in n-dodecyl-ß-d-maltoside (ßDM) was investigated by a combination of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) with contrast variation. First, the structure of dPSIIcc was studied separately in SANS experiments using a contrast of 5% D2O. Guinier analysis reveals that the dPSIIcc solution is virtually free of aggregation in the studied concentration range of 2-10 mg/mL dPSIIcc, and characterized by a radius of gyration of 62 Å. A structure reconstitution shows that dPSIIcc in buffer solution widely retains the crystal structure reported by X-ray free electron laser studies at room temperature with a slight expansion of the entire protein. Additional SANS experiments on dPSIIcc samples in a buffer solution containing 75% D2O provide information about the size and shape of the whole detergent-dPSIIcc. The maximum position of P(r) function increases to 68 Å, i.e., it is about 6 Å larger than that of dPSIIcc only, thus indicating the presence of an additional structure. Thus, it can be concluded that dPSIIcc is surrounded by a monomolecular belt of detergent molecules under appropriate solubilization conditions. The homogeneity of the ßDM-dPSIIcc solutions was also verified using dynamic light scattering. Complementary SAXS experiments indicate the presence of unbound detergent micelles by a separate peak consistent with a spherical shape possessing a radius of about 40 Å. The latter structure also contributes to the SANS data but rather broadens the SANS curve artificially. Without the simultaneous inspection of SANS and SAXS data, this effect may lead to an apparent underestimation of the size of the PS II-detergent complex. The formation of larger unbound detergent aggregates in solution prior to crystallization may have a significant effect on the crystal formation or quality of the ßDM-dPSIIcc.
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Affiliation(s)
- Maksym Golub
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
| | - Rana Hussein
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Mohamed Ibrahim
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Max Hecht
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
| | | | - Anne Martel
- Institut Laue-Langevin, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Barbara Machado
- European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38043 Grenoble, France
| | - Athina Zouni
- Humboldt Universität zu Berlin, Philipp Str. 13, 10115 Berlin, Germany
| | - Jörg Pieper
- Institute of Physics, University of Tartu, Wilhelm Ostwald str. 1, 50411 Tartu, Estonia
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Müh F, Zouni A. Structural basis of light-harvesting in the photosystem II core complex. Protein Sci 2020; 29:1090-1119. [PMID: 32067287 PMCID: PMC7184784 DOI: 10.1002/pro.3841] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 02/06/2020] [Accepted: 02/06/2020] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) is a membrane-spanning, multi-subunit pigment-protein complex responsible for the oxidation of water and the reduction of plastoquinone in oxygenic photosynthesis. In the present review, the recent explosive increase in available structural information about the PSII core complex based on X-ray crystallography and cryo-electron microscopy is described at a level of detail that is suitable for a future structure-based analysis of light-harvesting processes. This description includes a proposal for a consistent numbering scheme of protein-bound pigment cofactors across species. The structural survey is complemented by an overview of the state of affairs in structure-based modeling of excitation energy transfer in the PSII core complex with emphasis on electrostatic computations, optical properties of the reaction center, the assignment of long-wavelength chlorophylls, and energy trapping mechanisms.
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Affiliation(s)
- Frank Müh
- Department of Theoretical Biophysics, Institute for Theoretical Physics, Johannes Kepler University Linz, Linz, Austria
| | - Athina Zouni
- Humboldt-Universität zu Berlin, Institute for Biology, Biophysics of Photosynthesis, Berlin, Germany
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Eslami H, Sedaghat P, Müller-Plathe F. Local bond order parameters for accurate determination of crystal structures in two and three dimensions. Phys Chem Chem Phys 2018; 20:27059-27068. [DOI: 10.1039/c8cp05248d] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Local order parameters for the characterization of liquid and different two- and three-dimensional crystalline structures are presented.
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Affiliation(s)
- Hossein Eslami
- Department of Chemistry
- College of Sciences
- Persian Gulf University
- Boushehr 75168
- Iran
| | - Parvin Sedaghat
- Department of Chemistry
- College of Sciences
- Persian Gulf University
- Boushehr 75168
- Iran
| | - Florian Müller-Plathe
- Eduard-Zintl-Institut für Anorganische und Physikalische Chemie
- Technische Universität Darmstadt
- 64287 Darmstadt
- Germany
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Meng X, Liu J, Yu X, Li J, Lu X, Shen T. Pluronic F127 and D-α-Tocopheryl Polyethylene Glycol Succinate (TPGS) Mixed Micelles for Targeting Drug Delivery across The Blood Brain Barrier. Sci Rep 2017; 7:2964. [PMID: 28592843 PMCID: PMC5462762 DOI: 10.1038/s41598-017-03123-y] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2017] [Accepted: 04/24/2017] [Indexed: 11/09/2022] Open
Abstract
A novel polymeric mixed micelle composed of Pluronic F127 and D-α-tocopheryl polyethylene glycol succinate (TPGS) was developed to improve the delivery of fluorescent dyes and protein across the blood brain barrier (BBB). Rhodamine 123 (Rho123) and DiR loaded mixed micelles, composed of Pluronic F127 and TPGS with proportion of 4:1 (FT), were prepared by thin-film hydration, and β-galactosidase (β-Gal) loaded FT mixed micelles were prepared by self-assembly. The brain-targeted capability of FT mixed micelles were evaluated both in vitro and in vivo. The FT mixed micelles showed that a average particle size of 20.03 nm, and a low CMC of 0.0031% in water. The in vitro release of Rho123 from Rho123 loaded FT mixed micelles (FT/Rho123) presented a sustained-release property. FT/Rho123 also showed higher efficiency for the accumulation in brain capillary endothelial cells (BCECs) and brain tissues. β-Gal, a model protein, was also delivered and accumulated efficiently in the brain by spontaneous loading in the FT mixed micelles. Therefore, the results indicated that F127/TPGS mixed micelles may be considered as an effective nanocarrier for the brain-targeted delivery of diagnostic and therapeutic drugs.
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Affiliation(s)
- Xin Meng
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, China
| | - Jiansheng Liu
- Department of Neurology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, 639 Zhizaoju Road, Shanghai, 200011, China
| | - Xiangrong Yu
- Department of Radiology, Zhuhai People's Hospital, Zhuhai Hospital of Jinan University, 79 Kangning Road, Zhuhai, 519000, China
| | - Jiajia Li
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, China
| | - Xiaotong Lu
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, China
| | - Teng Shen
- Department of Pharmaceutics, Key Laboratory of Smart Drug Delivery, Ministry of Education, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai, 201203, China. .,The Institutes of Integrative Medicine of Fudan University, 12 Wulumuqi Middle Road, Shanghai, 200040, China.
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