1
|
Zhao Z, Liu J, Wu M, Yao X, Wang H, Liu X, He Z, Song X. A Soft, Adhesive Self-Healing Naked-Eye Strain/Stress Visualization Patch. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2307582. [PMID: 37781979 DOI: 10.1002/adma.202307582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 09/27/2023] [Indexed: 10/03/2023]
Abstract
Learning about the strain/stress distribution in a material is essential to achieve its mechanical stability and proper functionality. Conventional techniques such as universal testing machines only apply to static samples with standardized geometry in laboratory environment. Soft mechanical sensors based on stretchable conductors, carbon-filled composites, or conductive gels possess better adaptability, but still face challenges from complicated fabrication process, dependence on extra readout device, and limited strain/stress mapping ability. Inspired by the camouflage mechanism of cuttlefish and chameleons, here an innovative responsive hydrogel containing light-scattering "mechano-iridophores" is developed. Force induced reversible phase separation manipulates the dynamic generation of mechano-iridophores, serving as optical indicators of local deformation. Patch-shaped mechanical sensors made from the responsive hydrogel feature fast response time (<0.4 s), high spatial resolution (≈100 µm), and wide dynamic ranges (e.g., 10-150% strain). The intrinsic adhesiveness and self-healing material capability of sensing patches also ensure their excellent applicability and robustness. This combination of chemical and optical properties allows strain/stress distributions in target samples to be directly identified by naked eyes or smartphone apps, which is not yet achieved. The great advantages above are ideal for developing the next-generation mechanical sensors toward material studies, damage diagnosis, risk prediction, and smart devices.
Collapse
Affiliation(s)
- Zhi Zhao
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China
| | - Junjie Liu
- Department of Engineering Mechanics, Beijing University of Technology, Beijing, 100124, China
| | - Mengfei Wu
- Department of Engineering Mechanics, Beijing University of Technology, Beijing, 100124, China
| | - Xuan Yao
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China
| | - Haibin Wang
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China
| | - Xuemei Liu
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China
| | - Zhibin He
- Department of Vascular Surgery, Peking University People's Hospital, Beijing, 100044, China
| | - Xiaoyan Song
- Key Laboratory of Advanced Functional Materials, Education Ministry of China, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, China
| |
Collapse
|
2
|
Formulation Development of Doxycycline-Loaded Lipid Nanocarriers using Microfluidics by QbD Approach. J Pharm Sci 2023; 112:740-750. [PMID: 36170906 DOI: 10.1016/j.xphs.2022.09.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 11/24/2022]
Abstract
Liposomes have been used to improve therapeutic efficacy of drugs by increasing their bioavailability and altering biodistribution. The loading capacity of small molecules in liposomes remains a critical issue. Besides, the manufacturing process of liposomes requires multi-step procedures which hinders the clinical development. In this study, we developed a promising lipid-based nanocarriers (LN) delivery system for hydrophilic charged compounds using doxycycline (Doxy) as a model drug. This Doxy-loaded lipid nanocarrier (LN-Doxy) was fabricated by microfluidic technology. Design of experiments (DoE) was constructed to outline the interactions among the critical attributes of formulation, the parameters of microfluidic systems and excipient compositions. Response surface methodology (RSM) was furthered used for the optimization of LN-Doxy formulation. The LN-Doxy developed in this study showed high drug to lipid ratio and uniform distribution of particle size. Compared to Doxy solution, this LN-Doxy has reduced in vitro cellular toxicity and significant therapeutic efficacy which was verified in a peritonitis animal model. These results show the feasibility of using microfluidic technology combined with QbD approach to develop the LN formulation with high loading efficiency for ionizable hydrophilic drugs.
Collapse
|
3
|
Liu H, Prachyathipsakul T, Koyasseril-Yehiya TM, Le SP, Thayumanavan S. Molecular bases for temperature sensitivity in supramolecular assemblies and their applications as thermoresponsive soft materials. MATERIALS HORIZONS 2022; 9:164-193. [PMID: 34549764 PMCID: PMC8757657 DOI: 10.1039/d1mh01091c] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Thermoresponsive supramolecular assemblies have been extensively explored in diverse formats, from injectable hydrogels to nanoscale carriers, for a variety of applications including drug delivery, tissue engineering and thermo-controlled catalysis. Understanding the molecular bases behind thermal sensitivity of materials is fundamentally important for the rational design of assemblies with optimal combination of properties and predictable tunability for specific applications. In this review, we summarize the recent advances in this area with a specific focus on the parameters and factors that influence thermoresponsive properties of soft materials. We summarize and analyze the effects of structures and architectures of molecules, hydrophilic and lipophilic balance, concentration, components and external additives upon the thermoresponsiveness of the corresponding molecular assemblies.
Collapse
Affiliation(s)
- Hongxu Liu
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
| | | | | | - Stephanie P Le
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
| | - S Thayumanavan
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
- Department of Biomedical Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Molecular and Cellular Biology Program, University of Massachusetts, Amherst, Massachusetts 01003, USA
- Centre for Bioactive Delivery, Institute for Applied Life Science, University of Massachusetts, Amherst, Massachusetts 01003, USA
| |
Collapse
|
4
|
Su Z, Goodall B, Leitch JJ, Lipkowski J. Ion transport mechanism in gramicidin A channels formed in floating bilayer lipid membranes supported on gold electrodes. Electrochim Acta 2021. [DOI: 10.1016/j.electacta.2021.137892] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
|
5
|
Biocrude Production from Wheat Straw at Sub and Supercritical Hydrothermal Liquefaction. ENERGIES 2020. [DOI: 10.3390/en13123114] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this study, hydrothermal liquefaction (HTL) of wheat straw (WS) in sub (350 °C) and supercritical (400 °C) water with and without alkali catalyst was performed to investigate the potential of WS for the production of biocrude. The influences of temperature and catalyst were studied for the HTL products. Results showed that maximum biocrude yield (32.34 wt. %) with least solid residue (4.34 wt. %) was obtained at subcritical catalytic condition, whereas the carbon content was slightly higher in biocrude at supercritical. The higher heating value (HHV) for biocrude is around 35 MJ/kg for all four conditions. The major compounds in biocrude were observed as ketones, alcohols, acids, and hydrocarbons. At 350 °C, 44–55% of the carbon recovered into biocrude. The products were characterized in terms of elemental composition, higher heating values, organics, and inorganic compounds in different phases. To keep in consideration the scale-up of HTL process for continuous plant, aqueous phase from HTL was also recirculated which showed the fruitful outcomes by increasing the biocrude yield at each cycle.
Collapse
|
6
|
Çolak U, Durak H, Genel S. Hydrothermal liquefaction of Syrian mesquite (Prosopis farcta): Effects of operating parameters on product yields and characterization by different analysis methods. J Supercrit Fluids 2018. [DOI: 10.1016/j.supflu.2018.05.027] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
7
|
Hydrothermal conversion of biomass (Xanthium strumarium) to energetic materials and comparison with other thermochemical methods. J Supercrit Fluids 2018. [DOI: 10.1016/j.supflu.2018.07.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
8
|
Youssefian S, Rahbar N, Lambert CR, Van Dessel S. Variation of thermal conductivity of DPPC lipid bilayer membranes around the phase transition temperature. J R Soc Interface 2018; 14:rsif.2017.0127. [PMID: 28539484 PMCID: PMC5454301 DOI: 10.1098/rsif.2017.0127] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 04/26/2017] [Indexed: 01/28/2023] Open
Abstract
Given their amphiphilic nature and chemical structure, phospholipids exhibit a strong thermotropic and lyotropic phase behaviour in an aqueous environment. Around the phase transition temperature, phospholipids transform from a gel-like state to a fluid crystalline structure. In this transition, many key characteristics of the lipid bilayers such as structure and thermal properties alter. In this study, we employed atomistic simulation techniques to study the structure and underlying mechanisms of heat transfer in dipalmitoylphosphatidylcholine (DPPC) lipid bilayers around the fluid–gel phase transformation. To investigate this phenomenon, we performed non-equilibrium molecular dynamics simulations for a range of different temperature gradients. The results show that the thermal properties of the DPPC bilayer are highly dependent on the temperature gradient. Higher temperature gradients cause an increase in the thermal conductivity of the DPPC lipid bilayer. We also found that the thermal conductivity of DPPC is lowest at the transition temperature whereby one lipid leaflet is in the gel phase and the other is in the liquid crystalline phase. This is essentially related to a growth in thermal resistance between the two leaflets of lipid at the transition temperature. These results provide significant new insights into developing new thermal insulation for engineering applications.
Collapse
Affiliation(s)
- Sina Youssefian
- Civil and Environmental Engineering Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | - Nima Rahbar
- Civil and Environmental Engineering Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | - Christopher R Lambert
- Chemistry and Biochemistry Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| | - Steven Van Dessel
- Civil and Environmental Engineering Department, Worcester Polytechnic Institute, 100 Institute Road, Worcester, MA 01609, USA
| |
Collapse
|
9
|
Fluorescence Lifetime Distribution Brings Out Mechanisms Involving Biomolecules While Quantifying Population Heterogeneity. REVIEWS IN FLUORESCENCE 2017 2018. [DOI: 10.1007/978-3-030-01569-5_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
10
|
Abstract
Because membranes play a central role in regulating fluxes inward and outward from the cells, maintaining the appropriate structure of the membrane is crucial to maintain cellular integrity and functions. Microbes often face contrasted and fluctuating environmental conditions, to which they need to adapt or die. Membrane adaptation is achieved by a modification of the membrane lipid composition, a strategy termed homeoviscous adaptation. Homeoviscous adaptation in archaea involves strategies similar to that observed in bacteria and eucarya, such as the regulation of lipid chain length or saturation levels, as well as strategies specific to archaea, such as the regulation of the number of cycles along the isoprenoid chains or the regulation of the ratio between mono and bipolar lipids. Although not described yet described in hyperthermophilic bacteria, it is possible that these two strategies also apply to these latter organisms.
Collapse
|
11
|
Abstract
We review the combined effect of temperature and pressure on the structure, dynamics and phase behavior of lipid bilayers, differing in chain length, headgroup structure and composition as revealed by thermodynamic, spectroscopic and scattering experiments. The effect of additives, such as ions, cholesterol, and anaesthetics is discussed as well. Our data include also reports on the effect of pressure on the lateral organization of heterogeneous lipid membranes and lipid extracts from cellular membranes, as well as the influence of peptide and protein incorporation on the pressure-dependent structure and phase behavior of lipid membranes. Moreover, the effects of pressure on membrane protein function are summarized. Finally, we introduce pressure as a kinetic variable for studying the kinetics of various lipid phase transformations.
Collapse
Affiliation(s)
- Roland Winter
- Physical Chemistry I - Biophysical Chemistry, TU Dortmund University, Otto-Hahn Str. 6, D-44227, Dortmund, Germany,
| |
Collapse
|
12
|
Reddy PM, Chang CJ, Hsieh SR, Huang HC, Lee MC. Overview of the effect of monomers and green solvents on thermoresponsive copolymers: phase transition temperature and surface properties. RSC Adv 2015. [DOI: 10.1039/c5ra18246h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The thermoresponsive and surface properties of PNIPAM based copolymers were investigated in response to green solvents, ionic liquids.
Collapse
Affiliation(s)
- P. Madhusudhana Reddy
- Department of Chemical Engineering
- Feng Chia University
- Taichung 40724
- Republic of China
| | - Chi-Jung Chang
- Department of Chemical Engineering
- Feng Chia University
- Taichung 40724
- Republic of China
| | - Shih-Rong Hsieh
- Department of Surgery
- Taichung Veterans General Hospital
- Taichung 40705
- Republic of China
| | - Hsin-Chun Huang
- Department of Chemical Engineering
- Feng Chia University
- Taichung 40724
- Republic of China
| | - Ming-Ching Lee
- Department of Surgery
- Taichung Veterans General Hospital
- Taichung 40705
- Republic of China
| |
Collapse
|
13
|
In situ investigation of Geobacillus stearothermophilus spore germination and inactivation mechanisms under moderate high pressure. Food Microbiol 2014; 41:8-18. [DOI: 10.1016/j.fm.2014.01.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 11/21/2013] [Accepted: 01/10/2014] [Indexed: 01/18/2023]
|
14
|
Ion channel stability of Gramicidin A in lipid bilayers: Effect of hydrophobic mismatch. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:328-38. [DOI: 10.1016/j.bbamem.2013.10.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 09/20/2013] [Accepted: 10/03/2013] [Indexed: 11/18/2022]
|
15
|
Chaudhuri A, Haldar S, Sun H, Koeppe RE, Chattopadhyay A. Importance of indole N-H hydrogen bonding in the organization and dynamics of gramicidin channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:419-28. [PMID: 24148157 DOI: 10.1016/j.bbamem.2013.10.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 10/10/2013] [Accepted: 10/14/2013] [Indexed: 01/25/2023]
Abstract
The linear ion channel peptide gramicidin represents an excellent model for exploring the principles underlying membrane protein structure and function, especially with respect to tryptophan residues. The tryptophan residues in gramicidin channels are crucial for the structure and function of the channel. In order to test the importance of indole hydrogen bonding for the biophysical properties of gramicidin channels, we monitored the effect of N-methylation of gramicidin tryptophans, using a combination of steady state and time-resolved fluorescence approaches along with circular dichroism spectroscopy. We show here that in the absence of the hydrogen bonding ability of tryptophans, tetramethyltryptophan gramicidin (TM-gramicidin) is unable to maintain the single stranded, head-to-head dimeric channel conformation in membranes. Our results show that TM-gramicidin displays a red-shifted fluorescence emission maximum, lower red edge excitation shift (REES), and higher fluorescence intensity and lifetime, consistent with its nonchannel conformation. This is in agreement with the measured location (average depth) of the 1-methyltryptophans in TM-gramicidin using the parallax method. These results bring out the usefulness of 1-methyltryptophan as a fluorescent tool to examine the hydrogen bonding ability of tryptophans in proteins and peptides. We conclude that changes in the hydrogen bonding ability of tryptophans, along with coupled changes in peptide backbone structure induce the loss of single stranded β(6.3) helical dimer conformation. These results agree with earlier results from size-exclusion chromatography and single-channel measurements for TM-gramicidin, and confirm the importance of indole hydrogen bonding for the conformation and function of ion channels and membrane proteins.
Collapse
Affiliation(s)
- Arunima Chaudhuri
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | | | | | | | | |
Collapse
|
16
|
Widom JR, Lee W, Perdomo-Ortiz A, Rappoport D, Molinski TF, Aspuru-Guzik A, Marcus AH. Temperature-dependent conformations of a membrane supported zinc porphyrin tweezer by 2D fluorescence spectroscopy. J Phys Chem A 2013; 117:6171-84. [PMID: 23480874 PMCID: PMC3723700 DOI: 10.1021/jp400394z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We studied the equilibrium conformations of a zinc porphyrin tweezer composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4-butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of folded and extended conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17-85 °C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes.
Collapse
Affiliation(s)
- Julia R. Widom
- Department of Chemistry, Oregon Center for Optics, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403
| | - Wonbae Lee
- Department of Chemistry, Oregon Center for Optics, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403
| | | | - Dmitrij Rappoport
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Tadeusz F. Molinski
- Department of Chemistry and Biochemistry, and The Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California, 92093
| | - Alán Aspuru-Guzik
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138
| | - Andrew H. Marcus
- Department of Chemistry, Oregon Center for Optics, Institute of Molecular Biology, University of Oregon, Eugene, OR 97403
| |
Collapse
|
17
|
Bilayer Composition, Temperature, Speciation Effects and the Role of Bilayer Chain Ordering on Partitioning of Dexamethasone and its 21-Phosphate. Pharm Res 2013; 30:3154-69. [DOI: 10.1007/s11095-013-1143-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 07/01/2013] [Indexed: 10/26/2022]
|
18
|
Oger PM, Cario A. Adaptation of the membrane in Archaea. Biophys Chem 2013; 183:42-56. [PMID: 23915818 DOI: 10.1016/j.bpc.2013.06.020] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 06/25/2013] [Accepted: 06/25/2013] [Indexed: 12/11/2022]
Abstract
Microbes often face contrasted and fluctuating environmental conditions, to which they need to adapt or die. Because membranes play a central role in regulating fluxes inward and outward from the cells, maintaining the appropriate structure of the membrane is crucial to maintain cellular integrity and functions. This is achieved in bacteria and eucarya by a modification of the membrane lipid compositions, a strategy termed homeoviscous adaptation. We review here evidence for homeoviscous adaptation in Archaea, and discuss the limits of this strategy and our knowledge in this very peculiar domain of life.
Collapse
Affiliation(s)
- Philippe M Oger
- CNRS UMR 5276, Ecole Normale Supérieure de Lyon, 46 Allée d'Italie, 69364 Lyon cedex 07, France.
| | | |
Collapse
|
19
|
Seeliger J, Estel K, Erwin N, Winter R. Cosolvent effects on the fibrillation reaction of human IAPP. Phys Chem Chem Phys 2013; 15:8902-7. [DOI: 10.1039/c3cp44412k] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
20
|
Haldar S, Chaudhuri A, Gu H, Koeppe RE, Kombrabail M, Krishnamoorthy G, Chattopadhyay A. Membrane organization and dynamics of "inner pair" and "outer pair" tryptophan residues in gramicidin channels. J Phys Chem B 2012; 116:11056-64. [PMID: 22892073 PMCID: PMC3442126 DOI: 10.1021/jp304846f] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The linear ion channel peptide gramicidin serves as an excellent prototype for monitoring the organization, dynamics, and function of membrane-spanning channels. The tryptophan residues in gramicidin channels are crucial for establishing and maintaining the structure and function of the channel in the membrane bilayer. In order to address the basis of differential importance of tryptophan residues in the gramicidin channel, we monitored the effects of pairwise substitution of two of the four gramicidin tryptophans, the inner pair (Trp-9 and -11) and the outer pair (Trp-13 and -15), using a combination of steady state and time-resolved fluorescence approaches and circular dichroism spectroscopy. We show here that these double tryptophan gramicidin analogues adopt different conformations in membranes, suggesting that the conformational preference of double tryptophan gramicidin analogues is dictated by the positions of the tryptophans in the sequence. These results assume significance in the context of recent observations that the inner pair of tryptophans (Trp-9 and -11) is more important for gramicidin channel formation and channel conductance. These results could be potentially useful in analyzing the effect of tryptophan substitution on the functioning of ion channels and membrane proteins.
Collapse
Affiliation(s)
- Sourav Haldar
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
| | - Arunima Chaudhuri
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
| | - Hong Gu
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, U.S.A
| | - Roger E. Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, U.S.A
| | - Mamata Kombrabail
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India
| | - G. Krishnamoorthy
- Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India
| | - Amitabha Chattopadhyay
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad 500 007, India
| |
Collapse
|
21
|
Conformation of self-assembled porphyrin dimers in liposome vesicles by phase-modulation 2D fluorescence spectroscopy. Proc Natl Acad Sci U S A 2011; 108:16521-6. [PMID: 21940499 DOI: 10.1073/pnas.1017308108] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
By applying a phase-modulation fluorescence approach to 2D electronic spectroscopy, we studied the conformation-dependent exciton coupling of a porphyrin dimer embedded in a phospholipid bilayer membrane. Our measurements specify the relative angle and separation between interacting electronic transition dipole moments and thus provide a detailed characterization of dimer conformation. Phase-modulation 2D fluorescence spectroscopy (PM-2D FS) produces 2D spectra with distinct optical features, similar to those obtained using 2D photon-echo spectroscopy. Specifically, we studied magnesium meso tetraphenylporphyrin dimers, which form in the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine liposomes. Comparison between experimental and simulated spectra show that although a wide range of dimer conformations can be inferred by either the linear absorption spectrum or the 2D spectrum alone, consideration of both types of spectra constrain the possible structures to a "T-shaped" geometry. These experiments establish the PM-2D FS method as an effective approach to elucidate chromophore dimer conformation.
Collapse
|
22
|
Laredo T, Dutcher JR, Lipkowski J. Electric field driven changes of a gramicidin containing lipid bilayer supported on a Au(111) surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:10072-10087. [PMID: 21707110 DOI: 10.1021/la201625c] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Langmuir-Blodgett and Langmuir-Schaeffer methods were employed to deposit a mixed bilayer consisting of 90% of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 10% of gramicidin (GD), a short 15 residue ion channel forming peptide, onto a Au(111) electrode surface. This architecture allowed us to investigate the effect of the electrostatic potential applied to the electrode on the orientation and conformation of DMPC molecules in the bilayer containing the ion channel. The charge density data were determined from chronocoulometry experiments. The electric field and the potential across the membrane were determined through the use of charge density curves. The magnitudes of potentials across the gold-supported biomimetic membrane were comparable to the transmembrane potential acting on a natural membrane. The information regarding the orientation and conformation of DMPC and GD molecules in the bilayer was obtained from photon polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) measurements. The results show that the bilayer is adsorbed, in direct contact with the metal surface, when the potential across the interface is more positive than -0.4 V and is lifted from the gold surface when the potential across the interface is more negative than -0.4 V. This change in the state of the bilayer has a significant impact on the orientation and conformation of the phospholipid and gramicidin molecules. The potential induced changes in the membrane containing peptide were compared to the changes in the structure of the pure DMPC bilayer determined in earlier studies.
Collapse
Affiliation(s)
- Thamara Laredo
- Department of Chemistry, University of Guelph, Guelph, Ontario, N1G 2W1, Canada
| | | | | |
Collapse
|
23
|
Applications of pressure perturbation calorimetry in biophysical studies. Biophys Chem 2011; 156:13-23. [DOI: 10.1016/j.bpc.2010.12.010] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 12/29/2010] [Accepted: 12/29/2010] [Indexed: 10/18/2022]
|
24
|
Dzikovski BG, Borbat PP, Freed JH. Channel and nonchannel forms of spin-labeled gramicidin in membranes and their equilibria. J Phys Chem B 2011; 115:176-85. [PMID: 21142163 PMCID: PMC3076037 DOI: 10.1021/jp108105k] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Channel and nonchannel forms of gramicidin A (GA) were studied by ESR in various lipid environments using new mono- and double-spin-labeled compounds. For GA channels, we demonstrate here how pulse dipolar ESR can be used to determine the orientation of the membrane-traversing molecule relative to the membrane normal and to study subtle effects of lipid environment on the interspin distance in the spin-labeled gramicidin channel. To study nonchannel forms of gramicidin, pulse dipolar ESR was used first to determine interspin distances corresponding to monomers and double-helical dimers of spin-labeled GA molecules in the organic solvents trifluoroethanol and octanol. The same distances were then observed in membranes. Since detection of nonchannel forms in the membrane is complicated by aggregation, we suppressed any dipolar spectra from intermolecular interspin distances arising from the aggregates by using double-labeled GA in a mixture with excess unlabeled GA. In hydrophobic mismatching lipids (L(β) phase of DPPC), gramicidin channels dissociate into free monomers. The backbone structure of the monomeric form is similar to a monomeric unit of the channel dimer. In addition to channels and monomers, the double-helical conformation of gramicidin is present in some membrane environments. In the gel phase of saturated phosphatidylcholines, the fraction of double helices increases in the following order: DLPC < DMPC < DSPC < DPPC. The equilibrium DHD/monomer ratio in DPPC was determined. In membranes, the double-helical form is present only in aggregates. In addition, we studied the effect of N-terminal substitution in the GA molecule upon channel formation. This work demonstrates how pulsed dipolar ESR may be utilized to study complex equilibria of peptides in membranes.
Collapse
Affiliation(s)
- Boris G Dzikovski
- National Biomedical Center for Advanced ESR Technology, Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | | | | |
Collapse
|
25
|
Sellin D, Yan LM, Kapurniotu A, Winter R. Suppression of IAPP fibrillation at anionic lipid membranes via IAPP-derived amyloid inhibitors and insulin. Biophys Chem 2010; 150:73-9. [DOI: 10.1016/j.bpc.2010.01.006] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Revised: 01/20/2010] [Accepted: 01/21/2010] [Indexed: 12/01/2022]
|
26
|
Winter R. Exploring the Energy and Conformational Landscape of Biomolecules Under Extreme Conditions. ACTA ACUST UNITED AC 2010. [DOI: 10.1007/978-90-481-9258-8_47] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/27/2023]
|
27
|
Haldar S, Kombrabail M, Krishnamoorthy G, Chattopadhyay A. Monitoring membrane protein conformational heterogeneity by fluorescence lifetime distribution analysis using the maximum entropy method. J Fluoresc 2009; 20:407-13. [PMID: 19816758 DOI: 10.1007/s10895-009-0554-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 09/28/2009] [Indexed: 10/20/2022]
Abstract
Due to the inherent difficulty in crystallizing membrane proteins, approaches based on fluorescence spectroscopy have proved useful in elucidating their conformational characteristics. The ion channel peptide gramicidin serves as an excellent prototype for monitoring membrane protein conformation and dynamics due to a number of reasons. We have analyzed conformational heterogeneity in membrane-bound gramicidin using fluorescence lifetime distribution analysis of tryptophan residues by the maximum entropy method (MEM). MEM represents a model-free and robust approach for analyzing fluorescence lifetime distribution. In this paper, we show for the first time, that fluorescence lifetime distribution analysis using MEM could be a convenient approach to monitor conformational heterogeneity in membrane-bound gramicidin in particular and membrane proteins in general. Lifetime distribution analysis by MEM therefore provides a novel window to monitor conformational transitions in membrane proteins.
Collapse
Affiliation(s)
- Sourav Haldar
- Centre for Cellular and Molecular Biology, Council of Scientific and Industrial Research, Uppal Road, Hyderabad, 500 007, India
| | | | | | | |
Collapse
|
28
|
Pospiech EM, Geil B, Fujara F, Winter R. The Effect of Incorporation of Gramicidin on the Translational Lipid Diffusion in Bicontinuous Cubic Monoolein/Water Mesophases. Z PHYS CHEM 2009. [DOI: 10.1524/zpch.2009.6058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Abstract
The influence of incorporating the polypeptide gramicidin on the lateral mobility of the monoacylglyceride monoolein (MO) in its bicontinuous cubic lipid mesophases is studied applying static field gradient NMR. The effects of gramicidin on the topology, structure and phase behaviour of the system are characterized by small-angle x-ray scattering (SAXS) experiments. On the structural level the experiments show significant shifts in the boundaries of the various mesophases. Measurements of the translational dynamics are restricted to cubic mesophases, where the diffusion coefficients of lipid and additive are determined both by geometrical obstruction and by lipid-protein interaction effects.
Collapse
|
29
|
Dalisay DS, Quach T, Nicholas GN, Molinski TF. Amplification of the Cotton effect of a single chromophore through liposomal ordering-stereochemical assignment of plakinic acids I and J. Angew Chem Int Ed Engl 2009; 48:4367-71. [PMID: 19437515 DOI: 10.1002/anie.200900888] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A dramatic effect is observed when acyclic N-(2-naphthamides) of medium-chain 1-amino-2-methylalkanes are partially ordered with the help of liposomes: the Cotton effect arising from pi-pi* transitions of the terminal naphthamide chromophor is enormously enhanced. This effect was exploited to assign the configuration of new polyketide peroxides such as 1 from the sponge Plakortis halichondroides.
Collapse
Affiliation(s)
- Doralyn S Dalisay
- Department of Chemistry and Biochemistry and Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358, USA
| | | | | | | |
Collapse
|
30
|
Dalisay D, Quach T, Nicholas G, Molinski T. Amplification of the Cotton Effect of a Single Chromophore through Liposomal Ordering-Stereochemical Assignment of Plakinic Acids I and J. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200900888] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
31
|
Jeworrek C, Pühse M, Winter R. X-ray kinematography of phase transformations of three-component lipid mixtures: a time-resolved synchrotron X-ray scattering study using the pressure-jump relaxation technique. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:11851-11859. [PMID: 18767826 DOI: 10.1021/la801947v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
By using the pressure-jump relaxation technique in combination with time-resolved synchrotron small-angle X-ray diffraction (TRSAXS), the kinetics of lipid phase transformations of ternary lipid mixtures serving as model systems of heterogeneous raftlike membranes were investigated. To this end, we first established the temperature-pressure phase diagram of a model lipid raft mixture, 1,2-dioleoyl- sn-glycero-3-phosphatidylcholine (DOPC)/1,2-dipalmitoyl- sn-glycero-3-phosphatidylcholine (DPPC)/cholesterol (1:2:1), using Fourier transform infrared spectroscopy and SAXS, covering the pressure range from 1 bar to 10 kbar at temperatures in the range from 7 to 80 degrees C. We then studied the kinetics of interlamellar phase transitions of the ternary lipid system involving transitions from the fluidlike (liquid-disordered, l d) phase to the liquid-ordered (l o)/liquid-disordered (l d) two-phase coexistence region as well as between the two- and three-phase coexistence regions of the system, where also solid-ordered phases (s o) are involved. The phase transition from the all-fluid l d phase to the l o+l d two-phase coexistence region turns out to be rather rapid. Phases appear or disappear within the 25 ms time resolution of the technique, followed by a slow lattice relaxation process, which, depending on the pressure-jump amplitude, takes several seconds. Contrary to many one-component phospholipid phase transitions, the kinetics of the l d <--> l o+l d transition follows a similar time scale and mechanism for the pressurization and depressurization direction. A similar behavior is observed for the phase transition kinetics of the s o+l o+l d <--> l o+l d transformation and even for the s o+l o+l d <--> l d transformation, jumping across the l o+l d two-phase region. All transitions are fully reversible, and no intermediate states are populated. As indicated by the complex relaxation profiles observed, the overall rates observed seem to reflect the effect of coupling of various dynamical processes through the transformation, involving fast conformational changes in the sub-millisecond time regime and slow relaxation of the lattices growing, probably being largely controlled by the transport and redistribution of water into and in the new phases of the multilamellar vesicle assemblies.
Collapse
Affiliation(s)
- Christoph Jeworrek
- Dortmund University of Technology, Faculty of Chemistry, Physical Chemistry I - Biophysical Chemistry, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
| | | | | |
Collapse
|
32
|
Keerl M, Smirnovas V, Winter R, Richtering W. Copolymer Microgels from Mono- and Disubstituted Acrylamides: Phase Behavior and Hydrogen Bonds. Macromolecules 2008. [DOI: 10.1021/ma800785w] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Martina Keerl
- Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany, and Department of Chemistry, Physical Chemistry I, Dortmund University of Technology, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany
| | - Vytautas Smirnovas
- Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany, and Department of Chemistry, Physical Chemistry I, Dortmund University of Technology, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany
| | - Roland Winter
- Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany, and Department of Chemistry, Physical Chemistry I, Dortmund University of Technology, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany
| | - Walter Richtering
- Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52056 Aachen, Germany, and Department of Chemistry, Physical Chemistry I, Dortmund University of Technology, Otto-Hahn-Str. 6, D-44227 Dortmund, Germany
| |
Collapse
|
33
|
Lopes DHJ, Smirnovas V, Winter R. Islet amyloid polypeptide and high hydrostatic pressure: towards an understanding of the fibrillization process. ACTA ACUST UNITED AC 2008. [DOI: 10.1088/1742-6596/121/11/112002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
34
|
Radovan D, Smirnovas V, Winter R. Effect of pressure on islet amyloid polypeptide aggregation: revealing the polymorphic nature of the fibrillation process. Biochemistry 2008; 47:6352-60. [PMID: 18498175 DOI: 10.1021/bi800503j] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Type II diabetes mellitus is a disease which is characterized by peripheral insulin resistance coupled with a progressive loss of insulin secretion that is associated with a decrease in pancreatic islet beta-cell mass and the deposition of amyloid in the extracellular matrix of beta-cells, which lead to islet cell death. The principal component of the islet amyloid is a pancreatic hormone called islet amyloid polypeptide (IAPP). High-pressure coupled with FT-IR spectroscopic and AFM studies were carried out to elucidate further information about the aggregation pathway as well as the aggregate structures of IAPP. To this end, a comparative fibrillation study of IAPP fragments was carried out as well. As high hydrostatic pressure (HHP) is acting to weaken or even prevent hydrophobic self-organization and electrostatic interactions, application of HHP has been used as a measure to reveal the importance of these interactions in the fibrillation process of IAPP and its fragments. IAPP preformed fibrils exhibit a strong polymorphism with heterogeneous structures, a large population of which are rather sensitive to high hydrostatic pressure, thus indicating a high percentage of ionic and hydrophobic interactions and loose packing of these species. Conversely, fragments 1-19 and 1-29 are resistant to pressure treatment, suggesting more densely packed aggregate structures with less void volume and strong cooperative hydrogen bonding. Furthermore, the FT-IR data indicate that fragment 1-29 has intermolecular beta-sheet conformational properties different from those of fragment 1-19, the latter exhibiting polymorphic behavior with more disordered structures and less strongly hydrogen bonded fibrillar assemblies. The data also suggest that hydrophobic interactions and/or less efficient packing of amino acids 30-37 region leads to the marked pressure sensitivity observed for full-length IAPP.
Collapse
Affiliation(s)
- Diana Radovan
- Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, Dortmund University of Technology, D-44227 Dortmund, Germany
| | | | | |
Collapse
|
35
|
Abstract
The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been used extensively to study the organization, dynamics, and function of membrane-spanning channels. The tryptophan residues in gramicidin channels are crucial for maintaining the structure and function of the channel. We explored the structural basis for the reduction in channel conductance in the case of single-tryptophan analogs of gramicidin with three Trp --> hydrophobic substitutions using a combination of fluorescence approaches, which include red edge excitation shift and membrane penetration depth analysis, size-exclusion chromatography, and circular dichroism spectroscopy. We show here that the gramicidin analogs containing single-tryptophan residues adopt a mixture of nonchannel and channel conformations, as evident from analysis of membrane penetration depth, size-exclusion chromatography, and backbone circular dichroism data. These results are potentially useful in analyzing the effect of tryptophan substitution on the functioning of other ion channels and membrane proteins.
Collapse
|
36
|
Keerl M, Smirnovas V, Winter R, Richtering W. Interplay between hydrogen bonding and macromolecular architecture leading to unusual phase behavior in thermosensitive microgels. Angew Chem Int Ed Engl 2008; 47:338-41. [PMID: 18022987 DOI: 10.1002/anie.200703728] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Martina Keerl
- Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52056 Aachen, Germany
| | | | | | | |
Collapse
|
37
|
Keerl M, Smirnovas V, Winter R, Richtering W. Interplay between Hydrogen Bonding and Macromolecular Architecture Leading to Unusual Phase Behavior in Thermosensitive Microgels. Angew Chem Int Ed Engl 2008. [DOI: 10.1002/ange.200703728] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
38
|
Küsel A, Khattari Z, Schneggenburger PE, Banerjee A, Salditt T, Diederichsen U. Conformation and Interaction of ad,l-Alternating Peptide with a Bilayer Membrane: X-ray Reflectivity, CD, and FTIR Spectroscopy. Chemphyschem 2007; 8:2336-43. [DOI: 10.1002/cphc.200700477] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
39
|
Kelkar DA, Chattopadhyay A. The gramicidin ion channel: A model membrane protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2011-25. [PMID: 17572379 DOI: 10.1016/j.bbamem.2007.05.011] [Citation(s) in RCA: 264] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 05/09/2007] [Accepted: 05/10/2007] [Indexed: 02/07/2023]
Abstract
The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization, dynamics and function of membrane-spanning channels. In recent times, the availability of crystal structures of complex ion channels has challenged the role of gramicidin as a model membrane protein and ion channel. This review focuses on the suitability of gramicidin as a model membrane protein in general, and the information gained from gramicidin to understand lipid-protein interactions in particular. Special emphasis is given to the role and orientation of tryptophan residues in channel structure and function and recent spectroscopic approaches that have highlighted the organization and dynamics of the channel in membrane and membrane-mimetic media.
Collapse
Affiliation(s)
- Devaki A Kelkar
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | | |
Collapse
|
40
|
Kraineva J, Smirnovas V, Winter R. Effects of lipid confinement on insulin stability and amyloid formation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:7118-26. [PMID: 17523690 DOI: 10.1021/la700405y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We report on a study of insulin incorporation into cubic phases of mono-olein (MO), using synchrotron small-angle X-ray scattering and FT-IR spectroscopy. We studied the thermal stability and aggregation scenario of insulin as a function of protein concentration in the narrow water channels of the cubic lipid matrix and compared it with data for insulin unfolding and fibrillation in bulk water solutions. The concomitant effect of insulin entrapment on the structure and phase behavior of the lipid matrix itself was also examined. We show that the protein's unfolding behavior and stability are influenced by confinement due to geometrical limitations, and vice versa, the topological properties of the lipid matrix change as well. The addition of insulin already at concentrations as low as 0.1 wt % significantly alters the phase behavior of MO. Surprisingly, new cubic structures are induced by insulin incorporation into the lipid matrix. When insulin begins to partially unfold at higher temperatures, the structure of the new cubic phase changes and finally disappears around 60 degrees C, where the aggregation process sets in. The aggregation in cubo proceeds much faster and leads to the formation of medium-sized oligomers or clusters, while the formation of large fibrillar agglomerates, as observed for bulk insulin aggregation, is largely prohibited. Hence, the results yield valuable information about the use of cubic mesoporous lipid systems as a medium for long-term storage of insulin and aggregation-prone proteins in general. Furthermore, the results provide new insights into the effects of soft-matter confinement on protein aggregation and fibrillation, a situation usually met in natural cell environments.
Collapse
Affiliation(s)
- Julia Kraineva
- Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, University of Dortmund, Otto-Hahn Strasse 6, D-44227 Dortmund, Germany
| | | | | |
Collapse
|
41
|
Kelkar DA, Chattopadhyay A. Modulation of gramicidin channel conformation and organization by hydrophobic mismatch in saturated phosphatidylcholine bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:1103-13. [PMID: 17321493 DOI: 10.1016/j.bbamem.2007.01.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 01/18/2007] [Accepted: 01/22/2007] [Indexed: 11/25/2022]
Abstract
The matching of hydrophobic lengths of integral membrane proteins and the surrounding lipid bilayer is an important factor that influences both structure and function of integral membrane proteins. The ion channel gramicidin is known to be uniquely sensitive to membrane properties such as bilayer thickness and membrane mechanical properties. The functionally important carboxy terminal tryptophan residues of gramicidin display conformation-dependent fluorescence which can be used to monitor gramicidin conformations in membranes [S.S. Rawat, D.A. Kelkar, A. Chattopadhyay, Monitoring gramicidin conformations in membranes: a fluorescence approach, Biophys. J. 87 (2004) 831-843]. We have examined the effect of hydrophobic mismatch on the conformation and organization of gramicidin in saturated phosphatidylcholine bilayers of varying thickness utilizing the intrinsic conformation-dependent tryptophan fluorescence. Our results utilizing steady state and time-resolved fluorescence spectroscopic approaches, in combination with circular dichroism spectroscopy, show that gramicidin remains predominantly in the channel conformation and gramicidin tryptophans are at the membrane interfacial region over a range of mismatch conditions. Interestingly, gramicidin conformation shifts toward non-channel conformations in extremely thick gel phase membranes although it is not excluded from the membrane. In addition, experiments utilizing self quenching of tryptophan fluorescence indicate peptide aggregation in thicker gel phase membranes.
Collapse
Affiliation(s)
- Devaki A Kelkar
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | | |
Collapse
|
42
|
Lei S, Tero R, Misawa N, Yamamura S, Wan L, Urisu T. AFM characterization of gramicidin-A in tethered lipid membrane on silicon surface. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2006.07.091] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
43
|
Kelkar DA, Chattopadhyay A. Monitoring ion channel conformations in membranes utilizing a novel dual fluorescence quenching approach. Biochem Biophys Res Commun 2006; 343:483-8. [PMID: 16546136 DOI: 10.1016/j.bbrc.2006.02.163] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Accepted: 02/24/2006] [Indexed: 10/24/2022]
Abstract
The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization, dynamics, and function of membrane-spanning channels. We have analyzed the localization of the functionally important tryptophan residues of the membrane-bound channel and non-channel conformations of gramicidin utilizing a novel dual fluorescence quenching approach [G.A. Caputo, E. London, Biochemistry 42 (2003) 3265-3274]. In this paper, we show for the first time that the dual quenching approach is applicable to multiple tryptophan containing functional ion channel peptides such as gramicidin. Importantly, dual quenching is found to be sensitive to the membrane-bound conformations of this important model ion channel.
Collapse
Affiliation(s)
- Devaki A Kelkar
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | | |
Collapse
|
44
|
Nicolini C, Kraineva J, Khurana M, Periasamy N, Funari SS, Winter R. Temperature and pressure effects on structural and conformational properties of POPC/SM/cholesterol model raft mixtures--a FT-IR, SAXS, DSC, PPC and Laurdan fluorescence spectroscopy study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:248-58. [PMID: 16529710 DOI: 10.1016/j.bbamem.2006.01.019] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2005] [Revised: 01/24/2006] [Accepted: 01/26/2006] [Indexed: 11/17/2022]
Abstract
We report on the effects of temperature and pressure on the structure, conformation and phase behavior of aqueous dispersions of the model lipid "raft" mixture palmitoyloleoylphosphatidylcholine (POPC)/bovine brain sphingomyelin (SM)/cholesterol (Chol) (1:1:1). We investigated interchain interactions, hydrogen bonding, conformational and structural properties as well as phase transformations of this system using Fourier transform-infrared (FT-IR) spectroscopy, small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC) coupled with pressure perturbation calorimetry (PPC), and Laurdan fluorescence spectroscopy. The IR spectral parameters in combination with the scattering patterns from the SAXS measurements were used to detect structural and conformational transformations upon changes of pressure up to 7-9 kbar and temperature in the range from 1 to about 80 degrees C. The generalized polarization function (GP) values, obtained from the Laurdan fluorescence spectroscopy studies also reveal temperature and pressure dependent phase changes. DSC and PPC were used to detect thermodynamic properties accompanying the temperature-dependent phase changes. In combination with literature fluorescence spectroscopy and microscopy data, a tentative p,T stability diagram of the mixture has been established. The data reveal a broad liquid-order/solid-ordered (lo+so) two-phase coexistence region below 8+/-2 degrees C at ambient pressure. With increasing temperature, a lo+ld+so three-phase region is formed, which extends up to approximately 27 degrees C, where a liquid-ordered/liquid-disordered (lo+ld) immiscibility region is formed. Finally, above 48+/-2 degrees C, the POPC/SM/Chol (1:1:1) mixture becomes completely fluid-like (liquid-disordered, ld). With increasing pressure, all phase transition lines shift to higher temperatures. Notably, the lo+ld (+so) phase coexistence region, mimicking raft-like lateral phase separation in natural membranes, extends over a rather wide temperature range of about 40 degrees C, and a pressure range, which extends up to about 2 kbar for T=37 degrees C. Interestingly, in this pressure range, ceasing of membrane protein function in natural membrane environments has been observed for a variety of systems.
Collapse
Affiliation(s)
- Chiara Nicolini
- University of Dortmund, Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, Otto-Hahn-Strasse 6, D-44227 Dortmund, Germany
| | | | | | | | | | | |
Collapse
|
45
|
Eisenblätter J, Winter R. Pressure effects on the structure and phase behavior of DMPC-gramicidin lipid bilayers: a synchrotron SAXS and 2H-NMR spectroscopy study. Biophys J 2005; 90:956-66. [PMID: 16299078 PMCID: PMC1367120 DOI: 10.1529/biophysj.105.069799] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The influence of Gramicidin D (GD) incorporation on the structure and phase behavior of aqueous dispersions of DMPC lipid bilayers has been studied using small-angle x-ray scattering (SAXS) and (2)H-NMR spectroscopy. The experiments covered a temperature range from -10 degrees C to 60 degrees C and a pressure range of 0.001-4 kbar. Pressure was used to be able to tune the lipid bilayer conformational order and phase state and because high pressure is an important feature of certain natural biotopes. The data show that, depending on the GD concentration, the structure of the temperature- and pressure-dependent lipid phases is significantly altered by the insertion of the polypeptide, and a p,T-phase diagram could be obtained for intermediate GD concentrations. Upon gramicidin insertion, a rather narrow fluid-gel coexistence regions is formed. Two gel phases are induced which are different from those of the pure lipid bilayer system and which separate at low temperatures/high pressures. For both the temperature- and pressure-induced fluid-to-gel transition, a similar pseudocritical transitional behavior is observed, which is even more pronounced upon incorporation of the peptide.
Collapse
Affiliation(s)
- J Eisenblätter
- Department of Chemistry, Physical Chemistry I-Biophysical Chemistry, University of Dortmund, D-44227 Dortmund, Germany
| | | |
Collapse
|
46
|
Periasamy N, Winter R. The effects of temperature, pressure and peptide incorporation on ternary model raft mixtures--a Laurdan fluorescence spectroscopy study. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2005; 1764:398-404. [PMID: 16330267 DOI: 10.1016/j.bbapap.2005.10.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2005] [Revised: 10/14/2005] [Accepted: 10/17/2005] [Indexed: 11/21/2022]
Abstract
Recently, an increasing evidence accumulated for the existence of lipid microdomains, called lipid rafts, in cell membranes, which may play an important role in many important membrane-associated biological processes. Suitable model systems for studying biophysical properties of lipid rafts are lipid vesicles composed of three-component lipid mixtures, such as POPC/SM/cholesterol, which exhibit a rich phase diagram, including raft-like liquid-ordered/liquid-disordered phase coexistence regions. We explored the temperature, pressure and concentration-dependent phase behavior of such canonical model raft mixtures using the Laurdan fluorescence spectroscopic technique. Hydrostatic pressure has not only been used as a physical parameter for studying the stability and energetics of these systems, but also because high pressure is an important feature of certain natural membrane environments. We show that the liquid-disordered/liquid-ordered phase coexistence regions of POPC/SM/cholesterol model raft mixtures extends over a very wide temperature range of about 50 degrees C. Upon pressurization, an overall ordered membrane state is reached at pressures of approximately 1,000 bar at 20 degrees C, and of approximately 2,000 bar at 40 degrees C. Incorporation of 5 mol% gramicidin as a model ion channel slightly increases the overall order parameter profile in the l(o)+l(d) two-phase coexistence region, probably by selectively partitioning into l(d) domains, does not change the overall phase behavior, however. This behavior is in contrast to the effect of the peptide incorporation into simple, one-component phospholipid bilayer systems.
Collapse
Affiliation(s)
- Nagarajan Periasamy
- University of Dortmund, Physical Chemistry I-Biophysical Chemistry, D-44227 Dortmund, Germany
| | | |
Collapse
|
47
|
Dhoke MA, Ladha PJ, Boerio FJ, Lessard LB, Malinowska DH, Cuppoletti J, Wieczorek DS. Porous membranes for reconstitution of ion channels. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2005; 1716:117-25. [PMID: 16214106 DOI: 10.1016/j.bbamem.2005.09.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 08/26/2005] [Accepted: 09/06/2005] [Indexed: 11/25/2022]
Abstract
Functional biological synthetic composite (BSC) membranes were made using phospholipids, biological membrane proteins and permeable synthetic supports or membranes. Lipid bilayers were formed on porous polycarbonate (PC), polyethylene terephthalate (PETE) and poly (l-lactic acid) (PLLA) membranes and in 10-100 microm laser-drilled pores in a 96-well plastic plate as measured by increased resistance or decreased currents. Bilayers in 50 microm and smaller pores were stable for up to 4 h as measured by resistance changes or a current after gramicidin D reconstitution. Biological membrane transport reconstitution was then carried out. Using vesicles containing Kv1.5 K(+) channels, K(+) currents and decreased resistance were measured across bilayers in 50 microm pores in the plastic plate and PLLA membranes, respectively, which were inhibited by compound B, a Kv1.5 K(+) channel inhibitor. Functional reconstitution of Kv1.5 K(+) channels was successful. Incorporation of membrane proteins in functional form in stable permeable membrane-supported lipid bilayers is a simple technology to create BSC membranes that mimic biological function which is readily adaptable for high throughput screening.
Collapse
Affiliation(s)
- M A Dhoke
- Department of Materials Sciences and Engineering, University of Cincinnati, Cincinnati, OH 45221-0012, USA
| | | | | | | | | | | | | |
Collapse
|
48
|
Winter R, Dzwolak W. Exploring the temperature-pressure configurational landscape of biomolecules: from lipid membranes to proteins. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:537-563. [PMID: 15664898 DOI: 10.1098/rsta.2004.1507] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Hydrostatic pressure has been used as a physical parameter for studying the stability and energetics of biomolecular systems, such as lipid mesophases and proteins, but also because high pressure is an important feature of certain natural membrane environments and because the high-pressure phase behaviour of biomolecules is of biotechnological interest. By using spectroscopic and scattering techniques, the temperature- and pressure-dependent structure and phase behaviour of lipid systems, differing in chain configuration, headgroup structure and concentration, and proteins have been studied and are discussed. A thermodynamic approach is presented for studying the stability of proteins as a function of both temperature and pressure. The results demonstrate that combined temperature-pressure dependent studies can help delineate the free-energy landscape of proteins and hence help elucidate which features and thermodynamic parameters are essential in determining the stability of the native conformational state of proteins. We also introduce pressure as a kinetic variable. Applying the pressure jump relaxation technique in combination with time-resolved synchrotron X-ray diffraction and spectroscopic techniques, the kinetics of un/refolding of proteins has been studied. Finally, recent advances in using pressure for studying misfolding and aggregation of proteins will be discussed.
Collapse
Affiliation(s)
- R Winter
- University of Dortmund, Physical Chemistry I, Otto-Hahn Strasse 6, 44227 Dortmund, Germany.
| | | |
Collapse
|
49
|
Krishna G, Shutava T, Lvov Y. Lipid modified polyelectrolyte microcapsules with controlled diffusion. Chem Commun (Camb) 2005:2796-8. [PMID: 15928761 DOI: 10.1039/b415774e] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The lipid coating introduced directly on (polystyrene sulfonate/polyallylamine hydrochloride)5 polyelectrolyte microcapsule surfaces significantly reduces the permeability of capsule walls estimated by fluorescence recovery after photobleaching (FRAP).
Collapse
Affiliation(s)
- Gopal Krishna
- Institute for Micromanufacturing, Louisiana Tech University, 911 Hergot Ave, Ruston, LA 71272, USA
| | | | | |
Collapse
|
50
|
Feng ZV, Spurlin TA, Gewirth AA. Direct visualization of asymmetric behavior in supported lipid bilayers at the gel-fluid phase transition. Biophys J 2004; 88:2154-64. [PMID: 15596519 PMCID: PMC1305267 DOI: 10.1529/biophysj.104.052456] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We utilize in situ, temperature-dependent atomic force microscopy to examine the gel-fluid phase transition behavior in supported phospholipid bilayers constructed from 1,2-dimyristoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The primary gel-fluid phase transition at T(m) occurs through development of anisotropic cracks in the gel phase, which develop into the fluid phase. At approximately 5 degrees C above T(m), atomic force microscopy studies reveal the presence of a secondary phase transition in all three bilayers studied. The secondary phase transition occurs as a consequence of decoupling between the two leaflets of the bilayer due to enhanced stabilization of the lower leaflet with either the support or the water entrained between the support and the bilayer. Addition of the transmembrane protein gramicidin A or construction of a highly defected gel phase results in elimination of this decoupling and removal of the secondary phase transition.
Collapse
Affiliation(s)
- Z Vivian Feng
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | | | | |
Collapse
|