pH-Driven Ordering Transitions in Liquid Crystal Induced by Conformational Changes of Cardiolipin

Sidiq, Sumyra; Verma, Indu; Pal, Santanu Kumar

doi:10.1021/acs.langmuir.5b00798

Cited by 27 publications

(22 citation statements)

References 53 publications

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“…Anisotropic optical properties arising from the orientational ordering of LC molecules in bulk nematic phases produce birefringence patterns that depend on the mode of molecular orientation along the surface. As a consequence, birefringence has been exploited for biosensing by using thin nematic LC films in which the orientational ordering is responsive to the presence of foreign molecules at the aqueous/LC interface . Recently, there has been increasing interest in developing emulsion‐based homogeneous and mobile nematic LC droplets that are immiscible with the continuous aqueous phase.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Sequestration of Proteins into Liquid Crystalline Microdroplets

Naveenkumar

Mann

Sharma

2018

Adv Materials Inter

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In this work a facile method for fabricating protein‐sequestered liquid crystal (LC) emulsion droplets based on the uptake of surface‐engineered protein–polymer surfactant (PS) core–shell bioconjugates is described. Uptake of myoglobin‐PS, bovine serum albumin‐PS, Zn‐porphyrin myoglobin‐PS, horseradish peroxidase‐PS, and glucose oxidase‐PS occurs without structural or functional degradation, and gives rise to sequestration within the interior or at the surface of 4‐cyano‐4′‐pentylbiphenyl (5CB) nematic droplets depending on the surface modification of the protein‐PS bioconjugates. Differences in uptake behavior are used to achieve the spontaneous positional assembly of multiple proteins in the LC phase, and the use of spatially separated glucose oxidase‐PS and horseradish peroxidase‐PS bioconjugates is demonstrated to produce 5CB based droplets capable of housing an enzyme cascade reaction. This method opens a pathway for the development of bioactive liquid crystal droplets and can have potential applications in the optical sensing of biomolecular substrates.

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Section: Introductionmentioning

confidence: 99%

Spontaneous Sequestration of Proteins into Liquid Crystalline Microdroplets

Naveenkumar

Mann

Sharma

2018

Adv Materials Inter

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“…More recently, support for disparate pK a values of CL phosphates has come on many fronts. For instance, surface force measurements suggest that at neutral pH, the fraction of ionized CL phosphates decreases with increasing molar concentrations of CL [54], Fourier transform infrared (FTIR) spectroscopy measurements support two widely separated pK a values [55], and liquid crystal-detected ordering transitions indicate monoanionic CL species at intermediate pH values [56]. Moreover, molecular dynamics simulations support the feasibility of intramolecular hydrogen bonding within the CL headgroup [57–60].…”

Section: Introductionmentioning

confidence: 99%

The ionization properties of cardiolipin and its variants in model bilayers

Sathappa¹,

Alder²

2016

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The anionic phospholipid cardiolipin has an unusual dimeric structure with a two-phosphate headgroup and four acyl chains. Cardiolipin is present in energy-transducing membranes that maintain electrochemical gradients, including most bacterial plasma membranes and the mitochondrial inner membrane, where it mediates respiratory complex assembly and activation, among many other roles. Dysfunctional biogenesis of cardiolipin is implicated in the pathogenesis of several diseases including Barth syndrome. Because cardiolipin is a dominant anionic lipid in energy-conserving membranes, its headgroup is a major contributor to surface charge density and the bilayer electrostatic profile. However, the proton dissociation behavior of its headgroup remains controversial. In one model, the pKa values of the phosphates differ by several units and the headgroup exists as a monoanion at physiological pH. In another model, both phosphates ionize as strong acids with low pKa values and the headgroup exists in dianionic form at physiological pH. Using independent electrokinetic and spectroscopic approaches, coupled with analysis using Gouy–Chapman–Stern formalism, we have analyzed the ionization properties of cardiolipin within biologically relevant lipid bilayer model systems. We show that both phosphates of the cardiolipin headgroup show strong ionization behavior with low pKa values. Moreover, cardiolipin variants lacking structural features proposed to be required to maintain disparate pKa values – namely the secondary hydroxyl on the central glycerol or a full complement of four acyl chains – were shown to have ionization behavior identical to intact cardiolipin. Hence, these results indicate that within the physiological pH range, the cardiolipin headgroup is fully ionized as a dianion. We discuss the implications of these results with respect to the role of cardiolipin in defining membrane surface potential, activating respiratory complexes, and modulating membrane curvature.

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“…Thus, the study of the different conformers of the CL is potentially important for therapeutical and clinical point of view. In this study, we were interested to use the intrinsic cooperative behavior associated with the long-range orientational order of the LC phase as a probe to study the different polymorphic behaviors of CL.We investigate the interfacial phenomena occurring at aqueous-LC interfaces that trigger an orientational ordering transition of the LC in the presence of CL by varying pH (Sidiq et al, 2015). …”

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confidence: 99%

Liquid Crystal Biosensors: New Approaches

Sidiq¹

2016

Proceedings of the Indian National Science Academy

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This review describes recent advances in the area of research involving the interfacial design of liquid crystal (LC) based biosensors. The first advance revolves around the design and modulation of LC based interfaces for developing LC based stimuli responsive materials. For example, designing nanostructured thin films of LC-based colloidal gels exhibit the sensitivity and specificity with the added benefits of mechanical robustness and processability and can be used to report adsorption of biological and synthetic amphiphiles at aqueous-LC interfaces. In addition, a new pathway for the easy formation of spontaneous uniform LC droplets has been reported that provides a high spatial resolution of micrometers with a very high sensitivity. A second development has focused on the investigations of the ordering of LCs at aqueous interfaces for qualitative and quantitative understanding of important biomolecular interactions for bedside diagnostics and laboratory applications. These important biomolecular interactions include: (i) protein endotoxin interactions as these lead to divergent effects on lipopolysaccharide (LPS)-induced responses, (ii) pH induced conformation change of cardiolipin (CL) which is known to affect a range of cellular processes and (iii) endotoxin interactions with bacterial cell wall components.Thirdly this study involves design of LC based sensors that hold promise to act as a marker for cells and cell based interactions. Overall, this review illustrates new approaches for developing LC based stimuli responsive materials that are anticipated with fundamental understanding of biomolecular interactions and provide a gateway for further advances involving LCs. Keywords IntroductionBiomolecular interactions govern the affinity and specificity of complex formation and determine their biological function which could be of enormous scientific and practical importance. The pre-requisite to understand biomolecular function in the context of life and metabolism, it is necessary to analyze interactions of biomolecules by each other. A promising approach to study these interactions is to use liquid crystalline (LC) materials since it is advantageous as many biological systems, including cell membranes, phospholipids, cholesterols, DNA and so forth, exist in LC phases (Stewart, 2003; Steward, 2004). Recently, LCs have been explored for the design of interfaces that mediate desired interactions with biological systems (Lowe and Abbott, 2012). LC materials allow label-free observations of biological phenomena as the orientational properties of LCs enable the amplification and the transduction of biologically relevant binding events at nanostructured surfaces into optical outputs visible by naked eye (Brake et al., 2003a; Lin et al., 2011;Brake and Abbott, 2002; Brake et al., 2003b; Lockwood et al., 2005; Price and Schwartz, 2008;Brake et al., 2005; Lockwood et al., 2006;Sivakumar et al., 2009;Gupta et al., 2009; Park and Abbott, 2008; Hu and Jang, 2012;Bai et al., 2014; Khan and Park, 2014;Sadati et al....

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pH-Driven Ordering Transitions in Liquid Crystal Induced by Conformational Changes of Cardiolipin

Cited by 27 publications

References 53 publications

Spontaneous Sequestration of Proteins into Liquid Crystalline Microdroplets

Spontaneous Sequestration of Proteins into Liquid Crystalline Microdroplets

The ionization properties of cardiolipin and its variants in model bilayers

Liquid Crystal Biosensors: New Approaches

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