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Sample records for zn-porphyrin tweezer host-guest

  1. Switchable host-guest systems on surfaces.

    PubMed

    Yang, Ying-Wei; Sun, Yu-Long; Song, Nan

    2014-07-15

    CONSPECTUS: For device miniaturization, nanotechnology follows either the "top-down" approach scaling down existing larger-scale devices or the "bottom-up' approach assembling the smallest possible building blocks to functional nanoscale entities. For synthetic nanodevices, self-assembly on surfaces is a superb method to achieve useful functions and enable their interactions with the surrounding world. Consequently, adaptability and responsiveness to external stimuli are other prerequisites for their successful operation. Mechanically interlocked molecules such as rotaxanes and catenanes, and their precursors, that is, molecular switches and supramolecular switches including pseudorotaxanes, are molecular machines or prototypes of machines capable of mechanical motion induced by chemical signals, biological inputs, light or redox processes as the external stimuli. Switching of these functional host-guest systems on surfaces becomes a fundamental requirement for artificial molecular machines to work, mimicking the molecular machines in nature, such as proteins and their assemblies operating at dynamic interfaces such as the surfaces of cell membranes. Current research endeavors in material science and technology are focused on developing either a new class of materials or materials with novel/multiple functionalities by shifting host-guest chemistry from solution phase to surfaces. In this Account, we present our most recent attempts of building monolayers of rotaxanes/pseudorotaxanes on surfaces, providing stimuli-induced macroscopic effects and further understanding on the switchable host-guest systems at interfaces. Biocompatible versions of molecular machines based on synthetic macrocycles, such as cucurbiturils, pillararenes, calixarenes, and cyclodextrins, have been employed to form self-assembled monolayers of gates on the surfaces of mesoporous silica nanoparticles to regulate the controlled release of cargo/drug molecules under a range of external stimuli, such as light, pH variations, competitive binding, and enzyme. Rotaxanes have also been assembled onto the surfaces of gold nanodisks and microcantilevers to realize active molecular plasmonics and synthetic molecular actuators for device fabrication and function. Pillararenes have been successfully used to control and aid the synthesis of gold nanoparticles, semiconducting quantum dots, and magnetic nanoparticles. The resulting organic-inorganic hydrid nanomaterials have been successfully used for controlled self-assembly, herbicide sensing and detection, pesticide removal, and so forth, taking advantage of the selective binding of pillarenes toward target molecules. Cyclodextrins have also been successfully functionalized onto the surface of gold nanoparticles to serve as recycling extractors for C60. Many interesting prototypes of nanodevices based on synthetic macrocycles and their host-guest chemistry have been constructed and served for different potential applications. This Account will be a summary of the efforts made mainly by us, and others, on the host-guest chemistry of synthetic macrocyclic compounds on the surfaces of different solid supports. PMID:24635353

  2. The Design of Molecular Hosts, Guests, and Their Complexes.

    ERIC Educational Resources Information Center

    Cram, Donald J.

    1988-01-01

    Describes the origins, definitions, tools, and principles of host-guest chemistry. Gives examples of chiral recognition in complexation, of partial transacylase mimics, of caviplexes, and of a synthetic molecular cell. (Author/RT)

  3. Aromatic amide and hydrazide foldamer-based responsive host-guest systems.

    PubMed

    Zhang, Dan-Wei; Zhao, Xin; Li, Zhan-Ting

    2014-07-15

    CONSPECTUS: In host-guest chemistry, a larger host molecule selectively and noncovalently binds to a smaller guest molecule or ion. Early studies of host-guest chemistry focused on the recognition of spherical metal or ammonium ions by macrocyclic hosts, such as cyclic crown ethers. In these systems, preorganization enables their binding sites to cooperatively contact and attract a guest. Although some open-chain crown ether analogues possess similar, but generally lower, binding affinities, the design of acyclic molecular recognition hosts has remained challenging. One of the most successful examples was rigid molecular tweezers, acyclic covalently bonded preorganized host molecules with open cavities that bind tightly as they stiffen. Depending on the length of the atomic backbones, hydrogen bonding-driven aromatic amide foldamers can form open or closed cavities. Through rational design of the backbones and the introduction of added functional groups, researchers can regulate the shape and size of the cavity. The directionality of hydrogen bonding and the inherent rigidity of aromatic amide units allow researchers to predict both the shape and size of the cavity of an aromatic amide foldamer. Therefore, researchers can then design guest molecules with structure that matches the cavity shape, size, and binding sites of the foldamer host. In addition, because hydrogen bonds are dynamic, researchers can design structures that can adapt to outside stimuli to produce responsive supramolecular architectures. In this Account, we discuss how aromatic amide and hydrazide foldamers induced by hydrogen bonding can produce responsive host-guest systems, based on research by our group and others. First we highlight the helical chirality induced as binding occurs in solution, which includes the induction of helicity by chiral guests in oligomeric and polymeric foldamers, the formation of diastereomeric complexes between chiral foldamer hosts and guests, and the induction of helical chirality by chiral guests into inherently flexible backbones. In addition, molecular or ion-pair guests can produce supramolecular helical chirality in the organogel state. Such structures exhibit remarkable time-dependence and a "Sergeants and Soldiers" effect that are not observed for other two-component organogels that have been reported. We further illustrate that the reversible folding behavior of an aromatic amide foldamer segment can modulate the switching behavior of donor-acceptor interaction-based [2]rotaxanes. Finally we show that a folded oligomer can induce folding in one or two attached intrinsically flexible oligomers, an example of a solvent-responsive intramolecular host-guest system. PMID:24673152

  4. Hybrid host-guest complexes: directing the supramolecular structure through secondary host-guest interactions.

    PubMed

    Streb, Carsten; McGlone, Thomas; Brcher, Oliver; Long, De-Liang; Cronin, Leroy

    2008-01-01

    A set of four hybrid host-guest complexes based on the inorganic crown ether analogue [H12W36O120]12- ({W36}) have been isolated and characterised. The cluster anion features a central rigid binding site made up of six terminal oxygen ligands and this motif allows the selective binding of a range of alkali and alkali-earth-metal cations. Here, the binding site was utilised to functionalise the metal oxide-based cavity by complexing a range of protonated primary amines within the recognition site. As a result, a set of four hybrid organic-inorganic host-guest complexes were obtained whereby the interactions are highly directed specifically within this cavity. The guest cations in these molecular assemblies range from the aromatic 2-phenethylamine (1) and 4-phenylbutylamine (2) to the bifunctional aromatic p-xylylene diamine (3) and the aliphatic, bifunctional 1,6-diaminohexane (4). Compounds 1-4 were structurally characterised by single-crystal X-ray diffraction, elemental analysis, flame atomic absorption spectroscopy, FTIR and bond valence sum calculations. This comparative study focuses on the supramolecular effects of the amine guest cations and investigates their structure-directing effects on the framework arrangement arising by locking the protonated amines within the cavity of the {W36} cluster. It was shown that parts of the organic guest cation protrude from the central binding cavity and the nature of this protruding organic "tail" directs the solid-state arrangement of compounds 1-4. Guest cations with a hydrophobic phenyl tail result in an antiparallel assembly of {W36} complexes arranged in a series of pillared layers. As a consequence, no direct supramolecular interactions between {W36} clusters are observed. In contrast, bifunctional guest cations with a secondary amino binding site act as molecular connectors and directly link two cluster units thus locking the supramolecular assembly in a tilted arrangement. This direct linking of {W36} anions results in the formation of an infinite supramolecular scaffold. PMID:18780383

  5. Host-Guest-Systems Based on Nanoporous Crystals

    NASA Astrophysics Data System (ADS)

    Laeri, Franco; Schuth, Ferdi; Simon, Ulrich; Wark, Michael

    2003-10-01

    Interest in nanoporous crystals as host-guest systems has risen dramatically over the past few years, such that this fascinating class of substances now plays an important role not only in material sciences, but also in numerous other disciplines, such as organic or supramolecular chemistry. With their unique characteristics, nanoporous crystals offer a wide range of possible applications: They are used as molecular sieves or membranes as well as catalytic converters. This work presents the very first overview of this exciting field. Readers will find everything they need to know about these unusual materials, with all their many attributes: Synthesis of host-guest systems Description of the structural and dynamic aspects Electronic and optical characteristics of the materials Possible applications. An indispensable reference for materials scientists as well as for catalytic and inorganic chemists, and all those working in the field.

  6. Viologen cyclophanes: redox controlled host-guest interactions.

    PubMed

    Berville, Mathilde; Karmazin, Lydia; Wytko, Jennifer A; Weiss, Jean

    2015-11-11

    Viologens can exist in three redox states varying from dicationic to neutral. This work emphasizes the control of the host-guest properties in bis-viologen cyclophanes. Two flexible cyclophanes were prepared by a cyclisation method sensitive to the odd/even number of carbons in the flexible chains linking two viologens. C5 and C7 cyclophanes were characterised by X-ray diffraction in their tetracationic state and their diradical dicationic state. In the presence of tetrathiafulvalene or methyl viologen as guests, inclusion complexes were obtained, including a mixed valence species. PMID:26356351

  7. Mass Spectrometric Detection of Nanoparticle HostGuest Interactions in Cells

    PubMed Central

    2015-01-01

    Synthetic hostguest chemistry is a versatile tool for biomedical applications. Characterization and detection of hostguest complexes in biological systems, however, is challenging due to the complexity of the biological milieu. Here, we describe and apply a mass spectrometric method to monitor the association and dissociation of nanoparticle (NP)-based hostguest interactions that integrates NP-assisted laser desorption/ionization (LDI) and matrix assisted laser desoption/ionization (MALDI) mass spectrometry. This LDI/MALDI approach reveals how NP surface functionality affects hostguest interactions in cells, information difficult to achieve using other techniques. PMID:24873526

  8. Regulating exocytosis of nanoparticles via host-guest chemistry.

    PubMed

    Kim, Chaekyu; Tonga, Gulen Yesilbag; Yan, Bo; Kim, Chang Soo; Kim, Sung Tae; Park, Myoung-Hwan; Zhu, Zhengjiang; Duncan, Bradley; Creran, Brian; Rotello, Vincent M

    2015-02-28

    Prolonged retention of internalized nanoparticulate systems inside cells improves their efficacy in imaging, drug delivery, and theranostic applications. Especially, regulating exocytosis of the nanoparticles is a key factor in the fabrication of effective nanocarriers for chemotherapeutic treatments but orthogonal control of exocytosis in the cellular environment is a major challenge. Herein, we present the first example of regulating exocytosis of gold nanoparticles (AuNPs), a model drug carrier, by using a simple host-guest supramolecular system. AuNPs featuring quaternary amine head groups were internalized into the cells through endocytosis. Subsequent in situ treatment of a complementary cucurbit[7]uril (CB[7]) to the amine head groups resulted in the AuNP-CB[7] complexation inside cells, rendering particle assembly. This complexation induced larger particle assemblies that remained sequestered in the endosomes, inhibiting exocytosis of the particles without any observed cytotoxicity. PMID:25569869

  9. Lanthanide-mediated supramolecular cages and host-guest interactions.

    PubMed

    El Aroussi, Badr; Gune, Laure; Pal, Prodipta; Hamacek, Josef

    2011-09-01

    The structure and thermodynamic properties of lanthanide complexes with a new tripodal ligand L2 have been elucidated using different physicochemical methods. At stoichiometric ratios, the tetrahedral three-dimensional complexes with lanthanide cations are formed in acetonitrile with good stabilities. Despite minor structural changes comparing to previously investigated tripodal ligands, the resulting assembly exhibits different features revealed with the crystal structure of [Eu(4)L2(4)](OH)(ClO(4))(11) (orthorhombic, Pbcn). Interestingly, the highly charged edifice contains an inner cage encapsulating a perchlorate anion. Such lanthanide mediated cage-like assemblies are rare, and may be of interest for different sensing applications. Indeed, the anionic guest can be exchanged with different anions. The related host-guest equilibria were investigated with NMR techniques. Various aspects of these reactions are qualitatively discussed. PMID:21797240

  10. Interfacial assembly of dendritic microcapsules with host-guest chemistry

    NASA Astrophysics Data System (ADS)

    Zheng, Yu; Yu, Ziyi; Parker, Richard M.; Wu, Yuchao; Abell, Chris; Scherman, Oren A.

    2014-12-01

    The self-assembly of nanoscale materials to form hierarchically ordered structures promises new opportunities in drug delivery, as well as magnetic materials and devices. Herein, we report a simple means to promote the self-assembly of two polymers with functional groups at a water-chloroform interface using microfluidic technology. Two polymeric layers can be assembled and disassembled at the droplet interface using the efficiency of cucurbit[8]uril (CB[8]) host-guest supramolecular chemistry. The microcapsules produced are extremely monodisperse in size and can encapsulate target molecules in a robust, well-defined manner. In addition, we exploit a dendritic copolymer architecture to trap a small hydrophilic molecule in the microcapsule skin as cargo. This demonstrates not only the ability to encapsulate small molecules but also the ability to orthogonally store both hydrophilic and hydrophobic cargos within a single microcapsule. The interfacially assembled supramolecular microcapsules can benefit from the diversity of polymeric materials, allowing for fine control over the microcapsule properties.

  11. Macroscopic switches constructed through host-guest chemistry.

    PubMed

    Sun, Yue; Ma, Junkai; Tian, Demei; Li, Haibing

    2016-03-17

    Molecular switch systems, having been extensively studied in the solution phase, have the ability to perform with good controllability and rapid-responsiveness, making them ideally suited for the design of molecular devices for drug delivery, and information or sensing functions. Inspired by a wide range of objects with visual changes, like Mimosa pudica towards external stimuli, in order to understand molecular switches well, they must be interfaced with the macroscopic world so that they can be directly realized by visual detectable changes even observed by the naked eye. This can be critical for fabricating intelligent microfluidics and laboratory-on-chip devices, that may have wide applications in the fields of biology and materials science. But to realize this objective, especially for fabricating macroscopic surface switches, unveiling host-guest weak interactions to achieve visual phenomena is still the greatest thrill. Thankfully, surface contact angles provide us with a wonderful method to further investigate the microscopic origin of the macroscopic changes. Therefore, interfacial modification becomes a paramount process. Macrocyclic compounds, encompassing an innovative concept to deal with reversible noncovalent interactions between macrocyclic hosts and suitable guests, are good candidates for surface functionalization. In this feature article, we discuss recent developments in macroscopic contact angle switches formed by different macrocyclic hosts and highlight the properties of these new functional surfaces and their potential applications. PMID:26905834

  12. A new topological parameter for monitoring subtle aggregation events in host-guest inclusion processes

    NASA Astrophysics Data System (ADS)

    Novato, Willian T. G.; De Almeida, Wagner B.; Dos Santos, Hlio F.

    2012-02-01

    Supramolecular complexes with cyclodextrin (CD) have been the subject of considerable research in the material and life sciences. The dynamics of systems are difficult to characterise, therefore, knowledge of the molecular features governing the host-guest equilibrium might aid in the design and practical application of the resulting inclusion complexes. In this Letter, we present a new topological parameter based on simple trigonometric considerations to be used to monitor subtle host-guest inclusion events along the molecular dynamics trajectory. The new topological descriptor, called vector-?, was applied to amphetamine@?/?-CD inclusion complexes, providing interesting insights on the host-guest equilibrium.

  13. Guest Chain ``Melting'' in Incommensurate Host-Guest Potassium

    NASA Astrophysics Data System (ADS)

    McBride, Emma; Munro, Keith; McMahon, Malcolm

    2013-06-01

    Upon increasing pressure the group-I elements transform from close-packed structures (bcc and fcc) to a series of low-symmetry complex structures. Residing in the middle of the group, potassium (K) has numerous structures in common with its neighbours, and, in fact, is remarkably structurally similar to sodium (Na) and rubidium (Rb). For example, the post-fcc transition in K is to a composite incommensurate host-guest structure (tI19), and the host structure of this phase is isostructural with that found in Na and Rb. Previously we have reported that below 16.7GPa, the Bragg peaks from the guest component of tI19-Rb broaden considerably, signalling a loss of the inter-chain correlation, or a ``melting'' of the chains. Furthermore, in tI19-Na above 125 GPa, the Bragg peaks from the guest component are also broadened, suggesting that the guest chains are also nearly ``melted.'' During studies of the melting curve of K, we observed that the guest peaks from tI19-K broaden dramatically on heating. Here we report single-crystal, quasi-single-crystal, and powder synchrotron x-ray diffraction measurements of tI19-K to 50 GPa and 800 K, which allowed a detailed study of this chain ``melting'' transition. The order-disorder transition is clearly visible over a 30 GPa pressure range, and there are significant changes in the gradient of the phase boundary, which may be influenced by the nature of the guest structure. Furthermore, data extending the melting curve will also be presented.

  14. Mechanism of host-guest complexation by cucurbituril.

    PubMed

    Mrquez, Csar; Hudgins, Robert R; Nau, Werner M

    2004-05-12

    The factors affecting host-guest complexation between the molecular container compound cucurbit[6]uril (CB6) and various guests in aqueous solution are studied, and a detailed complexation mechanism in the presence of cations is derived. The formation of the supramolecular complex is studied in detail for cyclohexylmethylammonium ion as guest. The kinetics and thermodynamics of complexation is monitored by NMR as a function of temperature, salt concentration, and cation size. The binding constants and the ingression rate constants decrease with increasing salt concentration and cation-binding constant, in agreement with a competitive binding of the ammonium site of the guest and the metal cation with the ureido carbonyl portals of CB6. Studies as a function of guest size indicate that the effective container volume of the CB6 cavity is approximately 105 A(3). It is suggested that larger guests are excluded for two reasons: a high activation barrier for ingression imposed by the tight CB6 portals and a destabilization of the complex due to steric repulsion inside. For example, in the case of the nearly spherical azoalkane homologues 2,3-diazabicyclo[2.2.1]hept-2-ene (DBH, volume ca. 96 A(3)) and 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO, volume ca. 110 A(3)), the former forms the CB6 complex promptly with a sizable binding constant (1300 M(-1)), while the latter does not form a complex even after several months at optimized complexation conditions. Molecular mechanics calculations are performed for several CB6/guest complexes. A qualitative agreement is found between experimental and calculated activation energies for ingression as a function of both guest size and state of protonation. The potential role of constrictive binding by CB6 is discussed. PMID:15125673

  15. A semiconducting organic radical cationic host-guest complex.

    PubMed

    Fahrenbach, Albert C; Sampath, Srinivasan; Late, Dattatray J; Barnes, Jonathan C; Kleinman, Samuel L; Valley, Nicholas; Hartlieb, Karel J; Liu, Zhichang; Dravid, Vinayak P; Schatz, George C; Van Duyne, Richard P; Stoddart, J Fraser

    2012-11-27

    The self-assembly and solid-state semiconducting properties of single crystals of a trisradical tricationic complex composed of the diradical dicationic cyclobis(paraquat-p-phenylene) (CBPQT(2(•+))) ring and methyl viologen radical cation (MV(•+)) are reported. An organic field effect transistor incorporating single crystals of the CBPQT(2(•+))⊂MV(•+) complex was constructed using lithographic techniques on a silicon substrate and shown to exhibit p-type semiconductivity with a mobility of 0.05 cm(2) V(-1) s(-1). The morphology of the crystals on the silicon substrate was characterized using scanning electron microscopy which revealed that the complexes self-assemble into "molecular wires" observable by the naked-eye as millimeter long crystalline needles. The nature of the recognition processes driving this self-assembly, radical-radical interactions between bipyridinium radical cations (BIPY(•+)), was further investigated by resonance Raman spectroscopy in conjunction with theoretical investigations of the vibrational modes, and was supported by X-ray structural analyses of the complex and its free components in both their radical cationic and dicationic redox states. These spectroscopic investigations demonstrate that the bond order of the BIPY(•+) radical cationic units of host and guest components is not changed upon complexation, an observation which relates to its conductivity in the solid-state. We envision the modularity inherent in this kind of host-guest complexation could be harnessed to construct a library of custom-made electronic organic materials tailored to fit the specific needs of a given electronic application. PMID:23078281

  16. Host-Guest Carbon Dots for Enhanced Optical Properties and Beyond

    PubMed Central

    Sun, Ya-Ping; Wang, Ping; Lu, Zhuomin; Yang, Fan; Meziani, Mohammed J.; LeCroy, Gregory E.; Liu, Yun; Qian, Haijun

    2015-01-01

    Carbon dots, generally small carbon nanoparticles with various forms of surface passivation, have achieved the performance level of semiconductor quantum dots in the green spectral region, but their absorption and fluorescence in red/near-IR are relatively weaker. Conceptually similar to endofullerenes, host-guest carbon dots were designed and prepared with red/near-IR dyes encapsulated as guest in the carbon nanoparticle core. Beyond the desired enhancement in optical properties, the host-guest configuration may significantly broaden the field of carbon dots. PMID:26196598

  17. Supramolecular Chemistry: Induced Circular Dichroism to Study Host-Guest Geometry

    ERIC Educational Resources Information Center

    Mendicuti, Francisco; Gonzalez-Alvarez, Maria Jose

    2010-01-01

    In this laboratory experiment, students obtain information about the structure of a host-guest complex from the interpretation of circular dichroism measurements. The value and sign of the induced circular dichroism (ICD) on an achiral chromophore guest when it complexes with a cyclodextrin can be related to the guest penetration and its

  18. Intracellular host-guest assembly of gold nanoparticles triggered by glutathione.

    PubMed

    Wang, Yin; Li, Huan; Jin, Qiao; Ji, Jian

    2016-01-11

    A simple method to achieve host-guest assembly of gold nanoparticles triggered by intracellular glutathione was demonstrated. The increased size of nanoparticles not only enhanced their retention time within cancer cells, but also induced apoptosis. This strategy may open an avenue for the development of smart nanocarriers for intracellular diagnosis and therapy. PMID:26548407

  19. Supramolecular Chemistry: Induced Circular Dichroism to Study Host-Guest Geometry

    ERIC Educational Resources Information Center

    Mendicuti, Francisco; Gonzalez-Alvarez, Maria Jose

    2010-01-01

    In this laboratory experiment, students obtain information about the structure of a host-guest complex from the interpretation of circular dichroism measurements. The value and sign of the induced circular dichroism (ICD) on an achiral chromophore guest when it complexes with a cyclodextrin can be related to the guest penetration and its…

  20. Engineering responsive polymer building blocks with host-guest molecular recognition for functional applications.

    PubMed

    Hu, Jinming; Liu, Shiyong

    2014-07-15

    CONSPECTUS: All living organisms and soft matter are intrinsically responsive and adaptive to external stimuli. Inspired by this fact, tremendous effort aiming to emulate subtle responsive features exhibited by nature has spurred the invention of a diverse range of responsive polymeric materials. Conventional stimuli-responsive polymers are constructed via covalent bonds and can undergo reversible or irreversible changes in chemical structures, physicochemical properties, or both in response to a variety of external stimuli. They have been imparted with a variety of emerging applications including drug and gene delivery, optical sensing and imaging, diagnostics and therapies, smart coatings and textiles, and tissue engineering. On the other hand, in comparison with molecular chemistry held by covalent bonds, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy for materials fabrication due to its facile accessibility, extraordinary reversibility and adaptivity, and potent applications in diverse fields. Typically involving more than one type of noncovalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic association, electrostatic interactions, van der Waals forces, and π-π stacking), host-guest recognition refers to the formation of supramolecular inclusion complexes between two or more entities connected together in a highly controlled and cooperative manner. The inherently reversible and adaptive nature of host-guest molecular recognition chemistry, stemming from multiple noncovalent interactions, has opened up a new platform to construct novel types of stimuli-responsive materials. The introduction of host-guest chemistry not only enriches the realm of responsive materials but also confers them with promising new applications. Most intriguingly, the integration of responsive polymer building blocks with host-guest recognition motifs will endow the former with further broadened responsiveness to external stimuli and accordingly more sophisticated functions. In this Account, we summarize recent progress in the field of responsive polymeric materials containing host-guest recognition motifs with selected examples and highlight their versatile functional applications, whereas small molecule-oriented host-guest supramolecular systems are excluded. We demonstrate how the introduction of host-guest chemistry into conventional polymer systems can modulate their responsive modes to external stimuli. Moreover, the responsive specificity and selectivity of polymeric systems can also be inherited from the host-guest recognition motifs, and these features provide extra advantages in terms of function integration. The following discussions are categorized in terms of design and functions, namely, host-guest chemistry toward the fabrication of responsive polymers and assemblies, optical sensing and imaging, drug and gene delivery, and self-healing materials. A concluding remark on future developments is also presented. We wish this prosperous field would incur more original and evolutionary ideas and benefit fundamental research and our daily life in a more convenient way. PMID:24742049

  1. Biological stimuli-responsive cyclodextrin-based host-guest nanosystems for cancer therapy.

    PubMed

    Dan, Zhaoling; Cao, Haiqiang; He, Xinyu; Zeng, Lijuan; Zou, Lili; Shen, Qi; Zhang, Zhiwen

    2015-04-10

    Stimuli-responsive nanosystems are of particular interest in cancer therapy, owing to their impressive capability to enable the on-demand drug release in response to specific biological stimuli in tumor microenvironments (such as pH, redox and enzyme, etc.). Cyclodextrin (CD)-based host-guest interactions provide a flexible and powerful platform for the development of multifunctional nanosystems. This article highlights the current progress of CD-based host-guest nanosystems (CHNs) with biological stimuli-responsive properties in cancer therapy. We summarize the composition, structure and design of various CHNs in response to specific stimuli in tumor, and focus on their performance in controlled drug delivery and cancer therapy. These recent advances make it a promising and intelligent drug delivery system to improve the anticancer efficacy. PMID:25639701

  2. Stimuli-responsive host-guest systems based on the recognition of cryptands by organic guests.

    PubMed

    Zhang, Mingming; Yan, Xuzhou; Huang, Feihe; Niu, Zhenbin; Gibson, Harry W

    2014-07-15

    CONSPECTUS: As the star compounds in host-guest chemistry, the syntheses of crown ethers proclaimed the birth of supramolecular chemistry. Crown ether-based host-guest systems have attracted great attention in self-assembly processes because of their good selectivity, high efficiency, and convenient responsiveness, enabling their facile application to the "bottom-up" approach for construction of functional molecular aggregates, such as artificial molecular machines, drug delivery materials, and supramolecular polymers. Cryptands, as preorganized derivatives of crown ethers, not only possess the above-mentioned properties but also have three-dimensional spatial structures and higher association constants compared with crown ethers. More importantly, the introduction of the additional arms makes cryptand-based host-guest systems responsive to more stimuli, which is crucial for the construction of adaptive or smart materials. In the past decade, we designed and synthesized crown ether-based cryptands as a new type of host for small organic guests with the purpose of greatly increasing the stabilities of the host-guest complexes and preparing mechanically interlocked structures and large supramolecular systems more efficiently while retaining or increasing their stimuli-responsiveness. Organic molecules such as paraquat derivatives and secondary ammonium salts have been widely used in the fabrication of functional supramolecular aggregates. Many host molecules including crown ethers, cyclodextrins, calixarenes, cucurbiturils, pillararenes, and cryptands have been used in the preparation of self-assembled structures with these guest molecules, but among them cryptands exhibit the best stabilities with paraquat derivatives in organic solvents due to their preorganization and additional and optimized binding sites. They enable the construction of sophisticated molecules or supramolecules in high yields, affording a very efficient way to fabricate stimuli-responsive functional supramolecular systems. This Account mainly focuses on the application of cryptands in the construction of mechanically interlocked molecules such as rotaxanes and catenanes, and stimuli-responsive host-guest systems such as molecular switches and supramolecular polymers due to their good host-guest properties. These cryptands are bicyclic derivatives of crown ethers, including dibenzo-24-crown-8, bis(m-phenylene)-26-crown-8, dibenzo-30-crown-10, and bis(m-phenylene)-32-crown-10. The length of the third arm has a very important influence on the binding strength of these cryptands with organic guests, because it affects not only the size fit between the host and the guest but also the distances and angles that govern the strengths of the noncovalent interactions between the host and the guest. For example, for bis(m-phenylene)-32-crown-10-based cryptands, a third arm of nine atoms is the best. The environmental responsiveness of these cryptand-based host-guest systems arises from either the crown ether units or the third arms. For example, a dibenzo-24-crown-8 unit introduces potassium cation responsiveness and an azobenzene group on the third arm imbues photoresponsiveness. We believe that studies on stimuli-responsive host-guest systems based on cryptands and organic guests will contribute significantly to future research on molecular devices, supramolecular polymers, and other functional supramolecular materials. PMID:24804805

  3. Nanoparticles functionalized with supramolecular host-guest systems for nanomedicine and healthcare.

    PubMed

    Wu, Zilong; Song, Nan; Menz, Ryan; Pingali, Bharadwaj; Yang, Ying-Wei; Zheng, Yuebing

    2015-05-01

    Synthetic macrocyclic host compounds can interact with suitable guest molecules via noncovalent interactions to form functional supramolecular systems. With the synergistic integration of the response of molecules and the unique properties at the nanoscale, nanoparticles functionalized with the host-guest supramolecular systems have shown great potentials for a broad range of applications in the fields of nanoscience and nanotechnology. In this review article, we focus on the applications of the nanoparticles functionalized with supramolecular host-guest systems in nanomedicine and healthcare, including therapeutic delivery, imaging, sensing and removal of harmful substances. A large number of examples are included to elucidate the working mechanisms, advantages, limitations and future developments of the nanoparticle-supramolecule systems in these applications. PMID:25996121

  4. Host-guest interaction of flavanone and 7-aminoflavone with C-Hexylpyrogallol[4]arene

    NASA Astrophysics Data System (ADS)

    Chandrasekaran, Sowrirajan; Enoch, Israel V. M. V.

    2014-11-01

    In this paper, we report the structures of the host-guest complexes of flavanone and 7-aminoflavone (guests) with C-Hexylpyrogallol[4]arene (host). The study of the host-guest binding is carried out using UV-Visible absorption, steady-state and time-resolved fluorescence, and 2D ROESY spectroscopy. The stoichiometry and the binding constant of the C-Hexylpyrogallol[4]arene-guest complexes are reported based on absorption and fluorescence titrations. Both flavanone and 7-aminoflavone form 1:1 complexes with the host with binding constant values of 1.71 × 104 mol-1 dm3 and 2.06 × 104 mol-1 dm3 respectively. Fluorescence quenching of the two flavonoids on complex formation occurs and the Stern-Volmer constants are reported. The mode of binding of flavanone and 7-aminoflavone with the host molecule is optimized with 2D ROESY and the structures of the inclusion complexes are proposed.

  5. Host-guest nanocomposites of multiwalled carbon nanotubes and ionic liquids with controllable composition.

    PubMed

    Ding, Yuxiao; Su, Dang Sheng

    2014-06-01

    It is widely believed that low-volatility is a defining characteristic of ionic liquids (ILs). Here we synthesize a series of host-guest nanocomposites containing multiwalled carbon nanotubes (MWCNTs) and ILs using the volatility of ILs under vacuum conditions. The nanocomposites with different IL contents can be easily obtained through simple physical methods. The interactions between IL and MWCNTs are thoroughly investigated. This new nanocomposite can be used both in carbon catalysis and IL catalysis. PMID:24623567

  6. Probing Conformational Changes of Ubiquitin by Host-Guest Chemistry Using Electrospray Ionization Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Lee, Jong Wha; Heo, Sung Woo; Lee, Shin Jung C.; Ko, Jae Yoon; Kim, Hyungjun; Kim, Hugh I.

    2013-01-01

    We report mechanistic studies of structural changes of ubiquitin (Ub) by host-guest chemistry with cucurbit[6]uril (CB[6]) using electrospray ionization mass spectrometry (ESI-MS) combined with circular dichroism spectroscopy and molecular dynamics (MD) simulation. CB[6] binds selectively to lysine (Lys) residues of proteins. Low energy collision-induced dissociation (CID) of the protein-CB[6] complex reveals CB[6] binding sites. We previously reported ( Anal. Chem. 2011, 83, 7916-7923) shifts in major charge states along with Ub-CB[6] complexes in the ESI-MS spectrum with addition of CB[6] to Ub from water. We also reported that CB[6] is present only at Lys6 or Lys11 in high charge state (+13) complex. In this study, we provide additional information to explain unique conformational change mechanisms of Ub by host-guest chemistry with CB[6] compared with solvent-driven conformational change of Ub. Additional CID study reveals that CB[6] is bound only to Lys48 and Lys63 in low charge state (+7) complex. MD simulation studies reveal that the high charge state complexes are attributed to the CB[6] bound to Lys11. The complexation prohibits salt bridge formation between Lys11 and Glu34 and induces conformational change of Ub. This results in formation of high charge state complexes in the gas phase. Then, by utilizing stronger host-guest chemistry of CB[6] with pentamethylenediamine, refolding of Ub via detaching CB[6] from the protein is performed. Overall, this study gives an insight into the mechanism of denatured Ub ion formation via host-guest interactions with CB[6]. Furthermore, this provides a direction for designing function-controllable supramolecular system comprising proteins and synthetic host molecules.

  7. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data. PMID:22653895

  8. Probing conformational changes of ubiquitin by host-guest chemistry using electrospray ionization mass spectrometry.

    PubMed

    Lee, Jong Wha; Heo, Sung Woo; Lee, Shin Jung C; Ko, Jae Yoon; Kim, Hyungjun; Kim, Hugh I

    2013-01-01

    We report mechanistic studies of structural changes of ubiquitin (Ub) by host-guest chemistry with cucurbit[6]uril (CB[6]) using electrospray ionization mass spectrometry (ESI-MS) combined with circular dichroism spectroscopy and molecular dynamics (MD) simulation. CB[6] binds selectively to lysine (Lys) residues of proteins. Low energy collision-induced dissociation (CID) of the protein-CB[6] complex reveals CB[6] binding sites. We previously reported (Anal. Chem. 2011, 83, 7916-7923) shifts in major charge states along with Ub-CB[6] complexes in the ESI-MS spectrum with addition of CB[6] to Ub from water. We also reported that CB[6] is present only at Lys(6) or Lys(11) in high charge state (+13) complex. In this study, we provide additional information to explain unique conformational change mechanisms of Ub by host-guest chemistry with CB[6] compared with solvent-driven conformational change of Ub. Additional CID study reveals that CB[6] is bound only to Lys(48) and Lys(63) in low charge state (+7) complex. MD simulation studies reveal that the high charge state complexes are attributed to the CB[6] bound to Lys(11). The complexation prohibits salt bridge formation between Lys(11) and Glu(34) and induces conformational change of Ub. This results in formation of high charge state complexes in the gas phase. Then, by utilizing stronger host-guest chemistry of CB[6] with pentamethylenediamine, refolding of Ub via detaching CB[6] from the protein is performed. Overall, this study gives an insight into the mechanism of denatured Ub ion formation via host-guest interactions with CB[6]. Furthermore, this provides a direction for designing function-controllable supramolecular system comprising proteins and synthetic host molecules. PMID:23247966

  9. The SAMPL4 hostguest blind prediction challenge: an overview

    PubMed Central

    Muddana, Hari S.; Fenley, Andrew T.

    2014-01-01

    Prospective validation of methods for computing binding affinities can help assess their predictive power and thus set reasonable expectations for their performance in drug design applications. Supramolecular hostguest systems are excellent model systems for testing such affinity prediction methods, because their small size and limited conformational flexibility, relative to proteins, allows higher throughput and better numerical convergence. The SAMPL4 prediction challenge therefore included a series of hostguest systems, based on two hosts, cucurbit[7]uril and octa-acid. Binding affinities in aqueous solution were measured experimentally for a total of 23 guest molecules. Participants submitted 35 sets of computational predictions for these hostguest systems, based on methods ranging from simple docking, to extensive free energy simulations, to quantum mechanical calculations. Over half of the predictions provided better correlations with experiment than two simple null models, but most methods underperformed the null models in terms of root mean squared error and linear regression slope. Interestingly, the overall performance across all SAMPL4 submissions was similar to that for the prior SAMPL3 hostguest challenge, although the experimentalists took steps to simplify the current challenge. While some methods performed fairly consistently across both hosts, no single approach emerged as consistent top performer, and the nonsystematic nature of the various submissions made it impossible to draw definitive conclusions regarding the best choices of energy models or sampling algorithms. Salt effects emerged as an issue in the calculation of absolute binding affinities of cucurbit[7]uril-guest systems, but were not expected to affect the relative affinities significantly. Useful directions for future rounds of the challenge might involve encouraging participants to carry out some calculations that replicate each others studies, and to systematically explore parameter options. PMID:24599514

  10. Porphyrinic supramolecular daisy chains incorporating pillar[5]arene-viologen host-guest interactions.

    PubMed

    Fathalla, Maher; Strutt, Nathan L; Sampath, Srinivasan; Katsiev, Khabiboulakh; Hartlieb, Karel J; Bakr, Osman M; Stoddart, J Fraser

    2015-07-01

    A porphyrin functionalised with pillar[5]arene and a viologen at its 5- and 15-meso positions assembles in a head-to-tail manner, producing linear supramolecular daisy chains in dichloromethane. At high concentrations, it forms an organogel which has been investigated by electron microscopy and rheological measurements, paving the way for the preparation of other functional supramolecular assemblies which harness viologen?pillararene host-guest interactions. PMID:26027650

  11. Microcalorimetric determination of thermodynamic parameters for ionophore-siderophore host-guest complex formation.

    PubMed

    Trzaska, S M; Toone, E J; Crumbliss, A L

    2000-03-20

    Thermodynamic parameters (delta H, delta S, and delta G) were determined by microcalorimetry in wet chloroform for host-guest assembly formation involving second-sphere complexation of the siderophore ferrioxamine B by crown ether (18-crown-6, cis-dicyclohexano-18-crown-6, benzo-18-crown-6) and cryptand (2.2.2 cryptand) hosts. Similar data were also collected for the same hosts with the pentylammonium ion guest, which corresponds to the pendant pentylamine side chain of ferroxamine B. Host-guest assembly formation constants (Ka) obtained from microcalorimetry agree with values obtained indirectly from chloroform/water extraction studies in those cases where comparable data are available. On the basis of a trend established by the pentylammonium guest, an enhanced stability relative to the crown ethers is observed for the assembly composed of ferrioxamine B and 2.2.2 cryptand that is due to entropic effects. Trends in delta H and delta S with changes in host and guest structure are discussed and attributed directly to host-guest complex formation, as solvation effects were determined to be insignificant (delta Cp = 0). PMID:12526393

  12. Highly emissive metal-organic framework composites by host-guest chemistry.

    PubMed

    Müller, Maike; Devaux, André; Yang, Cheng-Han; De Cola, Luisa; Fischer, Roland A

    2010-06-01

    The unique host-guest chemistry of metal-organic frameworks (MOFs) can be used to implement additional properties by loading the cavities with functional molecules or even nanoparticles. We describe the gas-phase loading of MOFs featuring either a three-dimensional (MOF-5, MOF-177 and UMCM-1) or one-dimensional channel system (MIL-53(Al)) with the highly emissive perylene derivative N,N-bis(2,6-dimethylphenyl)-3,4:9,10-perylene tetracarboxylic diimide (DXP) or an iridium complex, (2-carboxypyridyl)bis(3,5-difluoro-2-(2-pyridyl)phenyl)iridium(III) (FIrpic). The resulting host-guest composites show strong luminescence, with their optical properties being dominated by the guest species. DXP-loaded MOFs exhibit a high stability towards guest displacement by solvent molecules, while the interaction of FIrpic with the host is weaker. The emissive properties of intercalated DXP also indicate host-guest interactions such as caging effects, strong quenching of the MOF host emission, as well as aggregate formation. PMID:20473444

  13. Incommensurate host-guest structures in compressed elements: Hume—Rothery effects as origin

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2015-11-01

    Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atoms in their unit cell: tI11* in Bi, Sb, As, Ba, Sr, Sc and tI19* in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au3Cd5-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere-Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.

  14. Molecular dynamics of host-guest complexes of small gas molecules with calix[4]arenes.

    PubMed

    Adams, John E; Cox, Jack R; Christiano, Andrew J; Deakyne, Carol A

    2008-07-31

    The unexpected sorption of gases by a low-density p-tert-butylcalix[4]arene crystal polymorph raises fundamental questions about differential gas transport and sequestration in the organic solid state. To gain insight into the processes underlying these observations, we have used molecular dynamics simulations, augmented with calculations of potentials of mean force, to investigate the stability of isolated host-guest complexes and the relationship between the dynamics of these complexes and the dynamics of a solvated host molecule. Thermal fluctuations of the calixarenes themselves are found to be consistent with proposed mechanisms for gas entry into the host cavities, while relative host-guest stabilities correlate well with experimental absorption-desorption isotherms in some cases (CO2 and CH4) but not in others (C2H2). In these isolated systems, stable complexes characteristically form when the attractive interactions of the guest with the ring of negative charge density on the inner surface of the host cavity are not disrupted by thermal motion. The experimentally observed efficient uptake of gases such as C2H2 by the host crystals suggests, however, that stabilization of host-guest complexes in some systems may derive from dynamical constraints imposed by the crystal lattice. PMID:18593133

  15. Blind prediction of host-guest binding affinities: A new SAMPL3 challenge

    PubMed Central

    Muddana, Hari S.; Varnado, C. Daniel; Bielawski, Christopher W.; Urbach, Adam R.; Isaacs, Lyle; Geballe, Matthew T.; Gilson, Michael K.

    2012-01-01

    The computational prediction of protein-ligand binding affinities is of central interest in early-stage drug-discovery, and there is a widely recognized need for improved methods. Low molecular weight receptors and their ligands—i.e. host-guest systems – represent valuable test-beds for such affinity prediction methods, because their small size makes for fast calculations and relatively facile numerical convergence. The SAMPL3 community exercise included the first ever blind prediction challenge for host-guest binding affinities, through the incorporation of 11 new host-guest complexes. Ten participating research groups addressed this challenge with a variety of approaches. Statistical assessment indicates that, although most methods performed well at predicting some general trends in binding affinity, overall accuracy was not high, as all the methods suffered from either poor correlation or high RMS errors or both. There was no clear advantage in using explicit vs. implicit solvent models, any particular force field, or any particular approach to conformational sampling. In a few cases, predictions using very similar energy models but different sampling and/or free-energy methods resulted in significantly different results. The protonation states of one host and some guest molecules emerged as key uncertainties beyond the choice of computational approach. The present results have implications for methods development and future blind prediction exercises. PMID:22366955

  16. A responsive supramolecular polymer formed by orthogonal metal-coordination and cryptand-based host-guest interaction.

    PubMed

    Wei, Peifa; Xia, Binyuan; Zhang, Yanyan; Yu, Yihua; Yan, Xuzhou

    2014-04-18

    Herein, a cation responsive linear supramolecular polymer was constructed in an orthogonal fashion by unifying the themes of coordination-driven self-assembly and cryptand-based host-guest interaction. PMID:24609282

  17. Water-soluble host-guest system from ?-cyclodextrin as a fluorescent sensor for aluminium ions: synthesis and sensing studies.

    PubMed

    Liu, Z C; Zhu, W P; Chen, Y H; Li, Y X; Ding, Y J; Yang, W J; Li, K

    2015-10-01

    In this paper, a simple small molecule (L) based on 4-(diethylamino)-2-hydroxy-benzaldehyde and carbohydrazide has been synthesized and characterized. Moreover, under ultrasonic conditions, a host-guest system with ?-cyclodextrin and L was obtained. According to the hybridization process, the host-guest system showed excellent water solubility. The investigation of the fluorescence spectra revealed that the host-guest system exhibited a characteristic fluorescence behavior toward Al(3+) in a pure water environment. Upon addition of Al(3+), the host-guest system showed a strong blue fluorescence, which resulted from the fluorophore of L after the coordination of ?-CD-L and Al(3+) with a high binding constant (k = 3.1626 10(11) M(-1)). In addition, SEM images demonstrated that the host-guest system expressed good crystallization behavior. Fluorescence microscope images of onion epidermal cells with ?-CD-L-Al(3+) proved that the water-soluble host-guest system possessed a high ability for cell permeability. PMID:26328668

  18. Supramolecular polymers constructed from macrocycle-based host-guest molecular recognition motifs.

    PubMed

    Dong, Shengyi; Zheng, Bo; Wang, Feng; Huang, Feihe

    2014-07-15

    CONSPECTUS: Supramolecular polymers, fabricated via the combination of supramolecular chemistry and polymer science, are polymeric arrays of repeating units held together by reversible, relatively weak noncovalent interactions. The introduction of noncovalent interactions, such as hydrogen bonding, aromatic stacking interactions, metal coordination, and host-guest interactions, endows supramolecular polymers with unique stimuli responsiveness and self-adjusting abilities. As a result, diverse monomer structures have been designed and synthesized to construct various types of supramolecular polymers. By changing the noncovalent interaction types, numbers, or chemical structures of functional groups in these monomers, supramolecular polymeric materials can be prepared with tailored chemical and physical properties. In recent years, the interest in supramolecular polymers has been extended from the preparation of intriguing topological structures to the discoveries of potential applications as functional materials. Compared with traditional polymers, supramolecular polymers show some advantages in the fabrication of reversible or responsive materials. The development of supramolecular polymers also offers a platform to construct complex and sophisticated materials with a bottom-up approach. Macrocylic hosts, including crown ethers, cyclodextrins, calixarenes, cucurbiturils, and pillararenes, are the most commonly used building blocks in the fabrication of host-guest interaction-based supramolecular polymers. With the introduction of complementary guest molecules, macrocylic hosts demonstrate selective and stimuli-responsive host-guest complexation behaviors. By elaborate molecular design, the resultant supramolecular polymers can exhibit diverse structures based on the self-selectivity of host-guest interactions. The introduction of reversible host-guest interactions can further endow these supramolecular polymers with interesting and fascinating chemical/physical properties, including stimuli responsiveness, self-healing, and environmental adaptation. It has been reported that macrocycle-based supramolecular polymers can respond to pH change, photoirradition, anions, cations, temperature, and solvent. Macrocycle-based supramolecular polymers have been prepared in solution, in gel, and in the solid state. Furthermore, the solvent has a very important influence on the formation of these supramolecular polymers. Crown ether- and pillararene-based supramolecular polymers have mainly formed in organic solvents, such as chloroform, acetone, and acetonitrile, while cyclodextrin- and cucurbituril-based supramolecular polymerizations have been usually observed in aqueous solutions. For calixarenes, both organic solvents and water have been used as suitable media for supramolecular polymerization. With the development of supramolecular chemistry and polymer science, various methods, such as nuclear magnetic resonance spectroscopy, X-ray techniques, electron microscopies, and theoretical calculation and computer simulation, have been applied for characterizing supramolecular polymers. The fabrication of macrocycle-based supramolecular polymers has become a currently hot research topic. In this Account, we summarize recent results in the investigation of supramolecular polymers constructed from macrocycle-based host-guest molecular recognition motifs. These supramolecular polymers are classified based on the different macrocycles used in them. Their monomer design, structure control, stimuli-responsiveness, and applications in various areas are discussed, and future research directions are proposed. It is expected that the development of supramolecular polymers will not only change the way we live and work but also exert significant influence on scientific research. PMID:24684594

  19. Modular self-assembly, characterization, and host-guest chemistry of nanoscale organometallic architectures

    SciTech Connect

    Manna, J.; Kuehl, C.J.; Stang, P.J.; Muddiman, D.C.; Smith, R.D.

    1997-12-31

    The supramolecular synthesis and chemistry of organic macrocycles has been the focus of considerable study for over thirty years. In contrast, the chemistry of analogous inorganic and organometallic macrocycles is in it infancy; little is know about the stability, spectroscopic and physical properties, and chemistry of these species. We will report on the design of several unique supramolecular macrocycles and the characterization of these species by a range of spectroscopic techniques, including electrospray-ionization Fourier transform ion cyclotron resonance spectrometry. Preliminary data concerning the host-guest chemistry of these macrocycles will also be presented.

  20. Understanding a host-guest model system through ?Xe?NMR spectroscopic experiments and theoretical studies.

    PubMed

    Dubost, Emmanuelle; Dognon, Jean-Pierre; Rousseau, Bernard; Milanole, Galle; Dugave, Christophe; Boulard, Yves; Lonce, Estelle; Boutin, Cline; Berthault, Patrick

    2014-09-01

    Gaining an understanding of the nature of host-guest interactions in supramolecular complexes involving heavy atoms is a difficult task. Described herein is a robust simulation method applied to complexes between xenon and members of a cryptophane family. The calculated chemical shift of xenon caged in a H2O2 probe, as modeled by quantum chemistry with complementary-orbital, topological, and energy-decomposition analyses, is in excellent agreement with that observed in hyperpolarized (129)Xe?NMR spectra. This approach can be extended to other van der Waals complexes involving heavy atoms. PMID:25048162

  1. Measurements of host-guest interaction energies in a calixarene supramolecular complex

    NASA Astrophysics Data System (ADS)

    Caciuffo, R.; Galeazzi, R.; Horsewill, A. J.; Ikram, A.; Ugozzoli, F.

    1999-11-01

    We report the results of NMR relaxometry measurements on the p-tert-butyl-calix[4]arene and the p-tert-butyl-calix[4]arene(1:1)toluene supramolecular systems in the solid state. Relevant information on the dynamics of the p-tert-butyl groups of the host cage is obtained, and the variation produced by the toluene guest molecule in the activation energy characterizing the reorientation of the methyl groups is determined. This variation provides an estimate of the host-guest interaction energy, part of which is attributed to a noncovalent, attractive force between CH3 groups of the host and the ? system of the guest molecule.

  2. Supramolecular host-guest systems as frameworks for excitation energy transfer

    NASA Astrophysics Data System (ADS)

    Ibrahim, Moustafa Sh; Etaiw, Safaa El-din H.

    2002-01-01

    The antenna behavior of rhodamine 6G and methylene blue loaded novel host supramolecular frameworks is investigated. The geometrical constraints of these supramolecular hosts allows the cationic dye molecules encapsulating within the parallel channels to form novel host-guest systems. The cationic dyes are close together that self-quenching of electronic excitation energy can occur. The excitation energy transfer occurs from rhodamine 6G as a donor (D) to methylene blue as an acceptor (A) within supramolecular systems filled with a mixture of both dyes.

  3. Linear free energy relationships reveal structural changes in hydrogen-bonded host-guest interactions.

    PubMed

    McGrath, Jacqueline M; Pluth, Michael D

    2014-12-01

    Hydrogen bond strength in host-guest systems is modulated by many factors including preorganization, steric effects, and electronic effects. To investigate how electronic effects impact barbiturate binding in bifurcated Hamilton receptors, a library of receptors with differing electronic substituents was synthesized and (1)H NMR titrations were performed with diethyl barbital. The Hammett plot revealed a clear break between the different electronic substituents suggesting a change in binding conformation. The titration data were complimented with computational studies confirming the change in structure. PMID:25412431

  4. Linear Free Energy Relationships Reveal Structural Changes in Hydrogen-Bonded HostGuest Interactions

    PubMed Central

    2015-01-01

    Hydrogen bond strength in hostguest systems is modulated by many factors including preorganization, steric effects, and electronic effects. To investigate how electronic effects impact barbiturate binding in bifurcated Hamilton receptors, a library of receptors with differing electronic substituents was synthesized and 1H NMR titrations were performed with diethyl barbital. The Hammett plot revealed a clear break between the different electronic substituents suggesting a change in binding conformation. The titration data were complimented with computational studies confirming the change in structure. PMID:25412431

  5. Host-Guest Complexation Studied by Fluorescence Correlation Spectroscopy: AdamantaneCyclodextrin Inclusion

    PubMed Central

    Granadero, Daniel; Bordello, Jorge; Prez-Alvite, Maria Jesus; Novo, Mercedes; Al-Soufi, Wajih

    2010-01-01

    The host-guest complexation between an Alexa 488 labelled adamantane derivative and ?-cyclodextrin is studied by Fluorescence Correlation Spectroscopy (FCS). A 1:1 complex stoichiometry and a high association equilibrium constant of K = 5.2 104 M?1 are obtained in aqueous solution at 25 C and pH = 6. The necessary experimental conditions are discussed. FCS proves to be an excellent method for the determination of stoichiometry and association equilibrium constant of this type of complexes, where both host and guest are nonfluorescent and which are therefore not easily amenable to standard fluorescence spectroscopic methods. PMID:20162009

  6. Strategies for Using Host-Guest Chemistry in the Extractive Separations of Ionic Guests

    SciTech Connect

    Moyer, Bruce A.; Bonnesen, Peter V.; Custelcean, Radu; Delmau, Laetitia H.; Hay, Benjamin P.

    2005-09-12

    Host-guest chemistry has led to a new paradigm in extractive separations, generating new possibilities for efficient separations of ionic species to meet the challenging needs of industry. This account describes the approach the authors have recently undertaken, recent results, and future directions toward highly selective separations of anions based on host?guest chemistry principles. The material presented deals mainly with the genesis and discovery of new extractive systems, illustrating the potential of particular chemical concepts with examples of practical application. Major questions of interest concern the role of anions in extractive processes and factors underlying the recognition and transport of anions. Theoretical efforts explore the technique of molecular-design itself as embodied in the evolving HostDesigner program. Design calculations are capable of generating ranked candidate multifunctional ion receptors based on hydrogen-bond-donor groups having O?H and N?H donor functionalities. Efforts to synthesize candidate receptors together with studies of molecular structure and the thermodynamics of binding and transport provide a complete picture for understanding structure-function relationships and feedback for further molecular modeling. Extraction data are evaluated in a thermochemical context in which the solvent matrix, including use of anion-solvating lipophilic alcohols, plays a pivotal role. Applications are envisioned for the solution of many types of separations needs, and examples are taken mainly from the authors' own research as applied to treatment of radioactive wastes for disposal.

  7. Competitive host-guest interaction between ?-cyclodextrin polymer and pyrene-labeled probes for fluorescence analyses.

    PubMed

    Liu, Pei; Sun, Shan; Guo, Xiaochen; Yang, Xiaohai; Huang, Jin; Wang, Kemin; Wang, Qing; Liu, Jianbo; He, Leiliang

    2015-03-01

    We developed a novel homogeneous fluorescence analysis based on a novel competitive host-guest interaction (CHGI) mechanism between ?-cyclodextrin polymer (poly? CD) and pyrene-labeled probe for biochemical assay. Pyrene labeling with oligonucleotide strands can be recruited and reside in lipophilic cavities of poly? CD. This altered lipophilic microenvironment provides favored polarity for enhanced quantum efficiencies and extraordinarily increases the luminescence intensity of pyrene. However, with addition of complementary DNA, the pyrene-labeled probe formed double-strand DNA to hinder pyrene from entering the cavities of poly? CD. The release of pyrene from poly? CD, which are followed by fluorescence extinguishing, will provide the clear signal turn-off in the presence of target DNA. We also introduced Exodeoxyribonuclease I (Exo I) and Exodeoxyribonuclease III (Exo III) to improve the sensitivity of this system, and the following product of cleavage reaction, pyrene-nucleotide, could more easily host-guest interact with poly? CD and emit stronger fluorescence than pyrene-labeled probe. In addition, the successful detection of adenosine is also demonstrated by using the similar sensing scheme. Although this scheme might be easily interfered by some biomolecules in the real test sample, it holds promising potential for detecting a broad range of other types of aptamer-binding chemicals and biomolecules. PMID:25622804

  8. A Stimuli-Responsive Nanopore Based on a Photoresponsive Host-Guest System

    NASA Astrophysics Data System (ADS)

    Ying, Yi-Lun; Zhang, Junji; Meng, Fu-Na; Cao, Chan; Yao, Xuyang; Willner, Itamar; Tian, He; Long, Yi-Tao

    2013-04-01

    The open-close states of the ion channels in a living system are regulated by multiple stimuli such as ligand, pH, potential and light. Functionalizing natural channels by using synthetic chemistry would provide biological nanopores with novel properties and applications. Here we use para-sulfonato-calix[4]arene-based host-guest supramolecular system to develop artificial gating mechanisms aiming at regulating wild-type ?-HL commanded by both ligand and light stimuli. Using the gating property of ?-hemolysin, we studied the host-guest interactions between para-sulfonato-calix[4]arene and 4, 4'-dipyridinium-azobenzene at the single-molecule level. Subsequently, we have extended the application of this gating system to the real-time study of light-induced molecular shuttle based on para-sulfonato-calix[4]arene and 4, 4'-dipyridinium-azobenzene at the single-molecule level. These experiments provide a more efficient method to develop a general tool to analyze the individual motions of supramolecular systems by using commercially available ?-HL nanopores.

  9. Characterizing and Understanding Self-Assembling, Nanocapsule Host-Guest Systems

    NASA Astrophysics Data System (ADS)

    Whetstine, Jena L.

    Supramolecular, self-assembled nanocapsules have been shown to be capable of entrapping fluorescent guests. Previous solid- and solution-state research, focusing on hydrogen-bonded C-alkylpyrogallol[4]arenes (PgC 6)nanocapsules, have shed light on the host-guest-relationship potential of these materials. Investigations of these nanocapsules with different fluorophores were undertaken to better understand the guest properties (e.g., size, shape, molecular volume, and functionality) needed to facilitate robust encapsulation. In addition, another relatively new nanocapsule containing metal ions in place of some of the hydrogen bonds was also examined. UV-Visible absorption and steady-state and dynamic fluorescence spectroscopic techniques were used to examine the host-guest interactions between the capsule interior and the fluorescent reporter molecule pyrene butanol that became encapsulated in the PgC 6 nanocapsule. Solution-state spectroscopic data was compared with solid-state, single-crystal, X-ray crystallographic results. This work supported the hypothesis that the tail functionality of the encapsulated guest is a critical feature for encapsulation and potentially ensures the robustness of that association. The research laid the foundation for understanding how to achieve successful encapsulation of future entities. The work advanced the understanding of the goodness-of-fit criterion between guest and host for these PgC6 supramolecular, self-assemblies.

  10. Straightforward functionalization of breath figures: Simultaneous orthogonal host-guest and pH-responsive interfaces.

    PubMed

    Sanz de León, Alberto; Muñoz-Bonilla, Alexandra; Gallardo, Alberto; Fernandez-Mayoralas, Alfonso; Bernard, Julien; Rodríguez-Hernández, Juan

    2015-11-01

    Herein, we report the design and preparation of multireversible smart porous surfaces combining two different abilities. On the one hand, either neutral or negatively charged surfaces can be formed by formation/disruption of host-guest complexes. On the other hand, these surfaces have the capability of alternating negatively and positively charge upon complexation of a polycation. Moreover, these two functionalization steps were demonstrated to be reversible so that the initial surface can be recovered and employed again. For this purpose, first, a copolymer was prepared by polymerization of two different monomers, i.e. styrene (S) and a styrene modified with cyclodextrin (SCD) by click chemistry. Blends of this copolymer and polystyrene were employed to fabricate porous surfaces with controlled pore sizes and chemical distribution by the breath figures technique. More precisely, the cyclodextrin (CD) moieties, specifically located inside the holes of the surface, interact reversibly with adamantane end-terminated poly(acrylic acid) chain (Ada-PAA85). The latter served to establish electrostatic interaction with a polycation (poly-L-lysine, PLL), leading to positively charged surface. These interactions, both host-guest and electrostatic, can be inverted obtaining again the original surface, proving the full reversibility of the system. PMID:26196710

  11. Parameterization of an effective potential for protein-ligand binding from host-guest affinity data.

    PubMed

    Wickstrom, Lauren; Deng, Nanjie; He, Peng; Mentes, Ahmet; Nguyen, Crystal; Gilson, Michael K; Kurtzman, Tom; Gallicchio, Emilio; Levy, Ronald M

    2016-01-01

    Force field accuracy is still one of the "stalemates" in biomolecular modeling. Model systems with high quality experimental data are valuable instruments for the validation and improvement of effective potentials. With respect to protein-ligand binding, organic host-guest complexes have long served as models for both experimental and computational studies because of the abundance of binding affinity data available for such systems. Binding affinity data collected for cyclodextrin (CD) inclusion complexes, a popular model for molecular recognition, is potentially a more reliable resource for tuning energy parameters than hydration free energy measurements. Convergence of binding free energy calculations on CD host-guest systems can also be obtained rapidly, thus offering the opportunity to assess the robustness of these parameters. In this work, we demonstrate how implicit solvent parameters can be developed using binding affinity experimental data and the binding energy distribution analysis method (BEDAM) and validated using the Grid Inhomogeneous Solvation Theory analysis. These new solvation parameters were used to study protein-ligand binding in two drug targets against the HIV-1 virus and improved the agreement between the calculated and the experimental binding affinities. This work illustrates how benchmark sets of high quality experimental binding affinity data and physics-based binding free energy models can be used to evaluate and optimize force fields for protein-ligand systems. Copyright 2015 John Wiley & Sons, Ltd. PMID:26256816

  12. Light and host-guest inclusion mediated salmon sperm DNA/surfactant interactions.

    PubMed

    Lin, Yiyang; Zhang, Yudong; Qiao, Yan; Huang, Jianbin; Xu, Baocai

    2011-10-15

    DNA/cationic surfactant interaction is relevant from the viewpoint of gene therapy, where the complexation and resulting compaction are essential to protect DNA from nuclease, and to allow entry of DNA into cells. In this work, light input and host-guest inclusion controlled DNA complexation by a novel cationic surfactant 1-[6-(4-phenylazo-phenoxy)-hexyl]-3-methylimidazolium bromide (AzoC6Mim) is reported. The surfactant is covalently attached with an azobenzene group, which undergoes reversible photoisomerizations by changing light input. Under visible light, trans-AzoC6Mim can bind to salmon sperm DNA through electrostatic attraction and hydrophobic interaction, resulting into DNA compaction. Under UV light, although cis-AzoC6Mim still binds to DNA chain, DNA/surfactant complex is decompacted owing to the decrease of surfactant hydrophobicity. On the other hand, azobenzene group can form an inclusion complex with ?-CD through host-guest interaction, which removes AzoC6Mim from DNA chain and decompacts the DNA/surfactant complex. PMID:21802091

  13. Calculation of Host-Guest Binding Affinities Using a Quantum-Mechanical Energy Model

    PubMed Central

    Muddana, Hari S.; Gilson, Michael K.

    2012-01-01

    The prediction of protein-ligand binding affinities is of central interest in computer-aided drug discovery, but it is still difficult to achieve a high degree of accuracy. Recent studies suggesting that available force fields may be a key source of error motivate the present study, which reports the first mining minima (M2) binding affinity calculations based on a quantum mechanical energy model, rather than an empirical force field. We apply a semi-empirical quantum-mechanical energy function, PM6-DH+, coupled with the COSMO solvation model, to 29 host-guest systems with a wide range of measured binding affinities. After correction for a systematic error, which appears to derive from the treatment of polar solvation, the computed absolute binding affinities agree well with experimental measurements, with a mean error 1.6 kcal/mol and a correlation coefficient of 0.91. These calculations also delineate the contributions of various energy components, including solute energy, configurational entropy, and solvation free energy, to the binding free energies of these host-guest complexes. Comparison with our previous calculations, which used empirical force fields, point to significant differences in both the energetic and entropic components of the binding free energy. The present study demonstrates successful combination of a quantum mechanical Hamiltonian with the M2 affinity method. PMID:22737045

  14. Expansioncontraction of photoresponsive artificial muscle regulated by hostguest interactions

    PubMed Central

    Takashima, Yoshinori; Hatanaka, Shogo; Otsubo, Miyuki; Nakahata, Masaki; Kakuta, Takahiro; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2012-01-01

    The development of stimulus-responsive polymeric materials is of great importance, especially for the development of remotely manipulated materials not in direct contact with an actuator. Here we design a photoresponsive supramolecular actuator by integrating hostguest interactions and photoswitching ability in a hydrogel. A photoresponsive supramolecular hydrogel with ?-cyclodextrin as a host molecule and an azobenzene derivative as a photoresponsive guest molecule exhibits reversible macroscopic deformations in both size and shape when irradiated by ultraviolet light at 365?nm or visible light at 430?nm. The deformation of the supramolecular hydrogel depends on the incident direction. The selectivity of the incident direction allows plate-shaped hydrogels to bend in water. Irradiating with visible light immediately restores the deformed hydrogel. A light-driven supramolecular actuator with ?-cyclodextrin and azobenzene stems from the formation and dissociation of an inclusion complex by ultraviolet or visible light irradiation. PMID:23232400

  15. Driving Forces Controlling Host-Guest Recognition in Supercritical Carbon Dioxide Solvent.

    PubMed

    Ingrosso, Francesca; Altarsha, Muhannad; Dumarçay, Florence; Kevern, Gwendal; Barth, Danielle; Marsura, Alain; Ruiz-López, Manuel F

    2016-02-01

    The formation of supramolecular host-guest complexes is a very useful and widely employed tool in chemistry. However, supramolecular chemistry in non-conventional solvents such as supercritical carbon dioxide (scCO2 ), one of the most promising sustainable solvents, is still in its infancy. In this work, we explored a successful route to the development of green processes in supercritical CO2 by combining a theoretical approach with experiments. We were able to synthesize and characterize an inclusion complex between a polar aromatic molecule (benzoic acid) and peracetylated-β-cyclodextrin, which is soluble in the supercritical medium. This finding opens the way to wide, environmental friendly, applications of scCO2 in many areas of chemistry, including supramolecular synthesis, reactivity and catalysis, micro and nano-particle formation, molecular recognition, as well as enhanced extraction processes with increased selectivity. PMID:26784687

  16. Recognizing the Limited Applicability of Job Plots in Studying Host-Guest Interactions in Supramolecular Chemistry.

    PubMed

    Ulatowski, Filip; Dąbrowa, Kajetan; Bałakier, Tomasz; Jurczak, Janusz

    2016-03-01

    Continuous variation method, known as Job plot, is the most commonly applied method for the determination of stoichiometry of complex chemical entities for over 100 years. Although, the method was proven successful in the analysis of very stable metal-ligand complexes, we demonstrate that its use in supramolecular chemistry often provides false results. We support this statement with multiple simulations as well as cases studies of several real host-guest systems. We propose an alternative, general method relying on the analysis of residual distribution in titration data fitting. The latter method is more convenient compared to the Job plot and unlike it gives correct results in all real cases studied. PMID:26866984

  17. Chiral discrimination on the host-guest-complexation of resorc[4]arenes with quarternary amines.

    PubMed

    Mehdizadeh, Ahmad; Letzel, Matthias C; Klaes, Michael; Agena, Ceno; Mattay, Jochen

    2004-01-01

    The interaction of inherently chiral resorc[4]arenes with different chiral ammonium ions was measured by ESI-MS. For that purpose one enantiomer of the ammonium guests was labeled with deuterium to distinguish the enantiomers by their mass. We synthesized the ammonium salts by reaction of chiral primary amines with either CH3I or CD3I and analyzed the resulting ammonium iodides by NMR and optical rotation. The complexation experiments were performed by mixing the chiral host with various ratios of the unlabeled guest and its labeled enantiomer. By analysis of the integrals of the host-guest complexes we observed a chiral discrimination effect and a secondary isotope effect as well. PMID:15531798

  18. 3D nitrogen-doped graphene/β-cyclodextrin: host-guest interactions for electrochemical sensing

    NASA Astrophysics Data System (ADS)

    Liu, Jilun; Leng, Xuanye; Xiao, Yao; Hu, Chengguo; Fu, Lei

    2015-07-01

    Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity of host-guest interactions. Our 3D-NG was fabricated by a template-directed chemical vapour deposition (CVD) method, and it showed a large specific surface area, a high capacity for biomolecules and a high electron transfer efficiency. Thus, for the first time, we took 3D-NG as an electrode substrate for β-CD to establish a new type of biosensor. Using dopamine (DA) and acetaminophen (APAP) as representative guest molecules, our 3D-NG/β-CD biosensor shows extremely high sensitivities (5468.6 μA mM-1 cm-2 and 2419.2 μA mM-1 cm-2, respectively), which are significantly higher than those reported in most previous studies. The stable adsorption of β-CD on 3D-NG indicates potential applications in clinical detection and medical testing.Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity of host-guest interactions. Our 3D-NG was fabricated by a template-directed chemical vapour deposition (CVD) method, and it showed a large specific surface area, a high capacity for biomolecules and a high electron transfer efficiency. Thus, for the first time, we took 3D-NG as an electrode substrate for β-CD to establish a new type of biosensor. Using dopamine (DA) and acetaminophen (APAP) as representative guest molecules, our 3D-NG/β-CD biosensor shows extremely high sensitivities (5468.6 μA mM-1 cm-2 and 2419.2 μA mM-1 cm-2, respectively), which are significantly higher than those reported in most previous studies. The stable adsorption of β-CD on 3D-NG indicates potential applications in clinical detection and medical testing. Electronic supplementary information (ESI) available: The procedure for preparing the sensor, wide survey XPS, XRD patterns, the effect of scan rate, more CV data on the stability and selectivity, and a comparison with previous studies. See DOI: 10.1039/c5nr03109e

  19. Photoreversible [2] Catenane via the Host-Guest Interactions between a Palladium Metallacycle and ?-Cyclodextrin.

    PubMed

    Zhang, Dengqing; Nie, Yong; Saha, Manik Lal; He, Zuoli; Jiang, Long; Zhou, Zhixuan; Stang, Peter J

    2015-12-21

    We report the efficient preparation of an A2D2 (A = acceptor and D = donor) metallacycle 2 = [(en)2Pd2(1)2](NO3)4, using the coordination driven self-assembly of trans-azobenzene based bispyridyl ligand 1 and (en)Pd(NO3)2 (en = ethylenediamine). In the metallacycle, the trans-azobenzene units serve both as a structural element and as sites for subsequent host-guest chemistry with ?-cyclodextrin, leading to the formation of a [2] catenane 3. This catenation process is reversible and can be switched off and on in a photocontrollable manner via the trans-cis isomerization of the azobenzene units. PMID:26637012

  20. Networked-cage microcrystals for evaluation of host-guest interactions.

    PubMed

    Matsuzaki, Shohei; Arai, Tatsuhiko; Ikemoto, Koki; Inokuma, Yasuhide; Fujita, Makoto

    2014-12-31

    We have developed a new synthetic protocol for the preparation of a microcrystalline powder (median size: X50 = 25 ?m) of networked M6L4 cages 1a for the stationary phase of an affinity column on a greater than 50 g scale. Analogously to large single crystals 1b (X50 ? 0.5 mm), microcrystals 1a accommodate guest molecules tetrathiafulvalene (TTF) and fullerene (C60) at up to 32 and 35 wt %, respectively. Importantly, the host-guest interactions within networked cages could be evaluated in terms of the retention time from HPLC analysis by using microcrystals 1a as the stationary phase. In this way, favorable guests for networked cages 1 and even solution M6L4 cage 2 could easily be assessed by HPLC. PMID:25495652

  1. Host-guest inclusion system of artesunate with ?-cyclodextrin and its derivatives: Characterization and antitumor activity

    NASA Astrophysics Data System (ADS)

    Xie, Hudie; Yang, Bo; Wang, Fen; Zhao, Yulin

    2015-04-01

    Inclusion complexes between artesunate (ATS) and three cyclodextrins, namely ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD) and sulfobutyl ether-?-cyclodextrin (SBE-?-CD), were prepared by a suspension method. The complexes in both liquid and solid were characterized by phase-solubility diagram, nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD) and thermoanalysis. The results suggested that artesunate was partly encapsulated within the cyclodextrin cavity to form a 1:1 stoichiometry host-guest compound. Especially in the SBE-?-CD complex, displayed the greatest stability constant. Significant enhancement of water solubility and thermal stability of ATS in present of ?-CDs was shown. The calculated IC50 values indicated that the antitumor activities of inclusion complexes were better than that of ATS. Satisfactory aqueous solubility, along with high thermal stability of inclusion complexes will be potentially useful for their application on the formulation design of natural medicine.

  2. Spatially Controlled Out-of-Equilibrium Host-Guest System under Electrochemical Control.

    PubMed

    Krabbenborg, Sven O; Veerbeek, Janneke; Huskens, Jurriaan

    2015-06-26

    Self-assembly to create molecular and nanostructures is typically performed at the thermodynamic minimum. To achieve dynamic functionalities, such as adaptability, internal feedback, and self-replication, there is a growing focus on out-of-equilibrium systems. This report presents the dynamic self-assembly of an artificial host-guest system at an interface, under control by a dissipative electrochemical process using (electrical) energy, resulting in an out-of-equilibrium system exhibiting a supramolecular surface gradient. The gradient, its steepness, rate of formation, and complex surface composition after backfilling, as well as the surface compositions after switching between the different states of the system, are assessed and supported by modelling. Our method shows for the first time an artificial surface-confined out-of-equilibrium system. The electrochemical process parameters provide not only control over the system in time, but also in space. PMID:26031483

  3. Light-harvesting host-guest antenna materials for photonic devices

    NASA Astrophysics Data System (ADS)

    Calzaferri, Gion; Huber, Stefan; Devaux, Andr; Zabala Ruiz, Arantzazu; Li, Huanrong; Bossart, Olivia; Dieu, Le-Quyenh

    2006-04-01

    Dye-loaded zeolite L host-guest materials were already successfully used in the realisation of efficient light-harvesting antenna systems. A new hierarchy of structural order is introduced by arranging the zeolite L crystals into densely packed, oriented monolayers on a substrate. In device engineering, a high degree of supramolecular organisation is a prerequisite for achieving desired macroscopic properties. The methods we developed to synthesise such monolayers, to fill them with dyes and to terminate them with a luminescent stopcock will be discussed as well as their influence on the design of novel materials. By subsequent insertion of two different types of dye molecules in a zeolite L monolayer, the first unidirectional antenna system was realised. UV-VIS absorption as well as NIR luminescence spectroscopy was carried out on dye-loaded zeolite L monolayers. We also report a novel concept for the preparation of thin layer, silicon based solar cells.

  4. A universal strategy for aptamer-based nanopore sensing through host-guest interactions inside ?-hemolysin.

    PubMed

    Li, Ting; Liu, Lei; Li, Yuru; Xie, Jiani; Wu, Hai-Chen

    2015-06-22

    Nanopore emerged as a powerful single-molecule technique over the past two decades, and has shown applications in the stochastic sensing and biophysical studies of individual molecules. Here, we report a versatile strategy for nanopore sensing by employing the combination of aptamers and host-guest interactions. An aptamer is first hybridized with a DNA probe which is modified with a ferrocene?cucurbit[7]uril complex. The presence of analytes causes the aptamer-probe duplex to unwind and release the DNA probe which can quantitatively produce signature current events when translocated through an ?-hemolysin nanopore. The integrated use of magnetic beads can further lower the detection limit by approximately two to three orders of magnitude. Because aptamers have shown robust binding affinities with a wide variety of target molecules, our proposed strategy should be universally applicable for sensing different types of analytes with nanopore sensors. PMID:25966821

  5. Rational Design of Multifunctional Gold Nanoparticles via Host-Guest Interaction for Cancer-Targeted Therapy.

    PubMed

    Chen, Wei-Hai; Lei, Qi; Luo, Guo-Feng; Jia, Hui-Zhen; Hong, Sheng; Liu, Yu-Xin; Cheng, Yin-Jia; Zhang, Xian-Zheng

    2015-08-12

    A versatile gold nanoparticle-based multifunctional nanocomposite AuNP@CD-AD-DOX/RGD was constructed flexibly via host-guest interaction for targeted cancer chemotherapy. The pH-sensitive anticancer prodrug AD-Hyd-DOX and the cancer-targeted peptide AD-PEG8-GRGDS were modified on the surface of AuNP@CD simultaneously, which endowed the resultant nanocomposite with the capability to selectively eliminate cancer cells. In vitro studies indicated that the AuNP@CD-AD-DOX/RGD nanocomposite was preferentially uptaken by cancer cells via receptor-mediated endocytosis. Subsequently, anticancer drug DOX was released rapidly upon the intracellular trigger of the acid microenvirenment of endo/lysosomes, inducing apoptosis in cancer cells. As the ideal drug nanocarrier, the multifunctional gold nanoparticles with the active targeting and controllable intracellular release ability hold the great potential in cancer therapy. PMID:26192215

  6. Enzyme-free electrochemical immunosensor based on host-guest nanonets catalyzing amplification for procalcitonin detection.

    PubMed

    Shen, Wen-Jun; Zhuo, Ying; Chai, Ya-Qin; Yang, Zhe-Han; Han, Jing; Yuan, Ruo

    2015-02-25

    An enzyme-free electrochemical immunosensor based on the host-guest nanonets of N,N-bis(ferrocenoyl)-diaminoethane/?-cyclodextrins/poly(amidoamine) dendrimer-encapsulated Au nanoparticles (Fc-Fc/?-CD/PAMAM-Au) for procalcitonin (PCT) detection has been developed in this study. The signal probe was constructed as follows: amine-terminated ?-CD was adsorbed to PAMAM-Au first, and then the prepared Fc-Fc was recognized by the ?-CD to form stable host-guest nanonets. Next, secondary antibodies (Ab2) were attached into the formed netlike nanostructure of Fc-Fc/?-CD/PAMAM-Au by chemical absorption between PAMAM-Au and -NH2 of ?-CD. Herein, the PAMAM-Au act not only as nanocarriers for anchoring large amounts of the ?-CD and Ab2 but also as nanocatalysts to catalyze the oxidation of ascorbic acid (AA) for signal amplification. Moreover, the Fc-Fc could be stably immobilized by the hydrophobic inner cavity of ?-CD as well as improving solubility by the hydrophilic exterior of ?-CD. With the unique structure of two ferrocene units, Fc-Fc not only affords more electroactive groups to make the electrochemical response more sensitive but also plays a role of combining dispersive ?-CD-functionalized PAMAM-Au to form the netlike nanostructure. Furthermore, Fc-Fc exhibits good catalytic activity for AA oxidation. When the detection solution contained AA, the synergetic catalysis of PAMAM-Au and Fc-Fc to AA oxidation could be obtained, realizing enzyme-free signal amplification. The proposed immunosensor provided a linear range from 1.80 pg/mL to 500 ng/mL for PCT detection and a detection limit of 0.36 pg/mL under optimal experimental conditions. Moreover, the immunosensor has shown potential application in clinical detection of PCT. PMID:25629216

  7. Insights into Unfolded Proteins from the Intrinsic ?/? Propensities of the AAXAA Host-Guest Series.

    PubMed

    Towse, Clare-Louise; Vymetal, Jiri; Vondrasek, Jiri; Daggett, Valerie

    2016-01-19

    Various host-guest peptide series are used by experimentalists as reference conformational states. One such use is as a baseline for random-coil NMR chemical shifts. Comparison to this random-coil baseline, through secondary chemical shifts, is used to infer protein secondary structure. The use of these random-coil data sets rests on the perception that the reference chemical shifts arise from states where there is little or no conformational bias. However, there is growing evidence that the conformational composition of natively and nonnatively unfolded proteins fail to approach anything that can be construed as random coil. Here, we use molecular dynamics simulations of an alanine-based host-guest peptide series (AAXAA) as a model of unfolded and denatured states to examine the intrinsic propensities of the amino acids. We produced ensembles that are in good agreement with the experimental NMR chemical shifts and confirm that the sampling of the 20 natural amino acids in this peptide series is be far from random. Preferences toward certain regions of conformational space were both present and dependent upon the environment when compared under conditions typically used to denature proteins, i.e., thermal and chemical denaturation. Moreover, the simulations allowed us to examine the conformational makeup of the underlying ensembles giving rise to the ensemble-averaged chemical shifts. We present these data as an intrinsic backbone propensity library that forms part of our Structural Library of Intrinsic Residue Propensities to inform model building, to aid in interpretation of experiment, and for structure prediction of natively and nonnatively unfolded states. PMID:26789758

  8. Rotamerism-driven large magnitude host-guest binding change in a crown ether derivatized pyridinium-phenolate series.

    PubMed

    Ay, Emel; Hobeika, Nelly; Chaumeil, Hélène; Tschamber, Théophile; Jin, Ming; Versace, Davy-Louis; Malval, Jean-Pierre

    2016-03-17

    Two TICTOID-based pyridinium-phenolates bearing a crown ether macrocycle have been designed for the complexation of a potassium cation. The nucleophilicity of the intraannular phenolate -O(-) function can be strongly modulated by biaryl twisting. Such a structure/electronic transduction effect gives rise to a host-guest binding change by more than two orders of magnitude. PMID:26948128

  9. Crystal and molecular structures of ionophore-siderophore host-guest supramolecular assemblies relevant to molecular recognition.

    PubMed

    Dhungana, Suraj; White, Peter S; Crumbliss, Alvin L

    2003-12-01

    Ionophore-siderophore host-guest assemblies composed of 18-crown-6 and ferrioxamine B, benzo-18-crown-6 and ferrioxamine B, and cis-syn-cis-dicyclohexano-18-crown-6 and ferrioxamine B were successfully crystallized, and their structures were determined by single-crystal X-ray diffraction. All three crystal lattices also include solvated Mg(II) and perchlorate ions. The ionophore-siderophore host-guest assembly is noncovalently held together by a hydrogen bonding interaction between the pendant protonated amine in the second coordination sphere of ferrioxamine B and the hydrogen bond acceptor oxygen atoms in the crown ether. The crystals of 18-crown-6:ferrioxamine B host-guest assembly are monoclinic, with space group P2(1)/c, and four molecules per unit cell with dimensions a = 19.8327(11) A, b = 20.4111(11) A, c = 15.1698(8) A, and beta = 96.435(1) degrees. The crystals of benzo-18-crown-6:ferrioxamine B host-guest assembly are triclinic, with space group P(-)1, and two molecules per unit cell with dimensions a = 11.1747(10) A, b = 16.0580(15) A, c = 18.4175(17) A, alpha = 80.469(3) degrees, beta = 81.481(3) degrees and gamma = 70.212(2) degrees. The crystals of cis-syn-cis-dicyclohexano-18-crown-6:ferrioxamine B host-guest assembly are monoclinic, with space group P2(1)/c, and four molecules per unit cell with dimensions a = 20.1473(13) A, b = 21.5778(15) A, c = 14.8013(10) A, and beta = 94.586(2) degrees. The crystal structures of all three host-guest assemblies contain a racemic mixture of Lambda-N-cis, cis and Delta-N-cis, cis coordination isomers of ferrioxamine B. The crystal structures indicate that the steric rigidity of the benzo-18-crown-6 and cis-syn-cis-dicyclohexano-18-crown-6 cavity has a pronounced effect on the conformation of the crown ring and ultimately on the hydrogen bonding interactions between the crown ethers and ferrioxamine B. The structural parameters and the conformational features of the ferrioxamine B guests compare very well with each other and with those of the ferrioxamine B structure obtained in the absence of a host. Structural features relevant to siderophore molecular recognition are discussed. PMID:14640651

  10. Host-guest inclusion complex of mesalazine and ?-cyclodextrin and spectrofluorometric determination of mesalazine.

    PubMed

    Elbashir, Abdalla A; Altayib Alasha Abdalla, Fatima; Aboul-Enein, Hassan Y

    2015-06-01

    The supramolecular interaction of mesalazine (MSZ) and ?-cyclodextrin (?-CD) has been examined by ultraviolet-visible (UV-vis) light, infra-red (IR) light and fluorescence spectroscopy. The formation of an inclusion complex has been confirmed based on the changes of the spectral properties. MSZ-?-CD host-guest complex was formed in (1:1) stoichiometry and the inclusion constant (K?=?1.359??10(2) ?L?mol(-1) ) was ascertained by typical double reciprocal plots. Furthermore, the thermodynamic parameters (?G, ?H and ?S) of (MSZ-?-CD) were obtained. Based on the remarkable enhancement of the fluorescence intensity of MSZ produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of MSZ in aqueous solution in the presence of ?-CD was developed. The measurement of relative fluorescence intensity was carried with excitation at 330?nm and emission 493?nm. All variables affecting the reactions were studied and optimized. Beer's law was obeyed in the concentration range 0.1-0.45?g/mL. Absorbance was found to increase linearly with increasing concentration of MSZ, which is corroborated by the calculated correlation coefficient values of 0.99989. The molar absorptivity, Sandell's sensitivity, detection and quantification limits were calculated. The validity of the described methods was assessed, and the method was successfully applied to the determination of MSZ in its pharmaceutical formulation. In addition, a solid inclusion complex was synthesized by co-precipitation method. PMID:25204628

  11. Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

    2008-02-16

    Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

  12. Evaluation of Host-Guest Binding Thermodynamics of Model Cavities with Grid Cell Theory.

    PubMed

    Michel, Julien; Henchman, Richard H; Gerogiokas, Georgios; Southey, Michelle W Y; Mazanetz, Michael P; Law, Richard J

    2014-09-01

    A previously developed cell theory model of liquid water was used to evaluate the excess thermodynamic properties of confined clusters of water molecules. The results are in good agreement with reference thermodynamic integration calculations, suggesting that the model is adequate to probe the thermodynamic properties of water at interfaces or in cavities. Next, the grid cell theory (GCT) method was applied to elucidate the thermodynamic signature of nonpolar association for a range of idealized host-guest systems. Polarity and geometry of the host cavities were systematically varied, and enthalpic and entropic solvent components were spatially resolved for detailed graphical analyses. Perturbations in the thermodynamic properties of water molecules upon guest binding are restricted to the immediate vicinity of the guest in solvent-exposed cavities, whereas longer-ranged perturbations are observed in buried cavities. Depending on the polarity and geometry of the host, water displacement by a nonpolar guest makes a small or large enthalpic or entropic contribution to the free energy of binding. Thus, no assumptions about the thermodynamic signature of the hydrophobic effect can be made in general. Overall the results warrant further applications of GCT to more complex systems such as protein-ligand complexes. PMID:26588549

  13. Thermodynamics of host-guest interactions between fullerenes and a buckycatcher.

    PubMed

    Le, Vu H; Yanney, Michael; McGuire, Matthew; Sygula, Andrzej; Lewis, Edwin A

    2014-10-16

    (1)H NMR and isothermal titration calorimetry (ITC) experiments were employed to obtain reliable thermodynamic data for the formation of the 1:1 inclusion complexes of fullerenes C(60) and C(70) with the buckycatcher (C(60)H(28)). NMR measurements were done in toluene-d8 and chlorobenzene-d5 at 288, 298, and 308 K, while the ITC titrations were performed in toluene, chlorobenzene, o-dichlorobenzene, anisole, and 1,1,2,2-tetrachloroethane at temperatures from 278 to 323 K. The association constants, K(a), obtained with both techniques are in very good agreement. The thermodynamic data obtained by ITC indicate that generally the host-guest association is enthalpy-driven. Interestingly, the entropy contributions are, with rare exceptions, slightly stabilizing or close to zero. Neither ΔH nor ΔS is constant over the temperature range studied, and these thermodynamic functions exhibit classical enthalpy/entropy compensation. The ΔCp values calculated from the temperature dependence of the calorimetric ΔH values are negative for the association of both fullerenes with the buckycatcher in toluene. The negative ΔCp values are consistent with some desolvation of the host-cavity and the guest in the inclusion complexes, C(60)@C(60)H(28) and C(70)@C(60)H(28). PMID:25248285

  14. High Precision Measurement of Isotope Effects on Noncovalent Host-Guest Interactions

    SciTech Connect

    Mugridge, Jeffrey S.; Bergman, Robert G.; Raymond, Kenneth N.

    2009-06-23

    Isotope effects (IEs) are a powerful tool for examining the reactivity of, and interactions between, molecules. Recently, secondary IEs have been used to probe the nature of noncovalent interactions between guest and host molecules in supramolecular systems. While these studies can provide valuable insight into the specific interactions governing guest recognition and binding properties, IEs on noncovalent interactions are often very small and difficult to measure precisely. The Perrin group has developed an NMR titration method capable of determining ratios of equilibrium constants with remarkable precision. They have used this technique to study small, secondary equilibrium isotope effects (EIEs) on the acidity of carboxylic acids and phenols and on the basicity of amines, measuring differences down to thousandths of a pK{sub a} unit. It occurred to us that this titration method can in principle measure relative equilibrium constants for any process which is fast on the NMR timescale and for which the species under comparison are distinguishable by NMR. Here we report the application of this method to measure very small EIEs on noncovalent host-guest interactions in a supramolecular system.

  15. Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure.

    PubMed

    Spaulding, Dylan K; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

    2014-01-01

    New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis. PMID:25484135

  16. Redox-responsive supramolecular amphiphiles constructed via host-guest interactions for photodynamic therapy.

    PubMed

    Liu, Feng; Ma, Yufei; Xu, Lei; Liu, Lichao; Zhang, Weian

    2015-08-01

    A supramolecular photosensitizer delivery system has been established through the self-assembly of supramolecular amphiphiles constructed by the host-guest interaction between poly(ethylene glycol)-?-cyclodextrin (PEG-?-CD) and adamantane-terminated porphyrin derivatives bearing a disulfide bond (TPPC6-SS-Ada). TPPC6-SS-Ada/PEG-?-CD supramolecular amphiphiles can self-assemble into spherical micelles in water, and the assembled morphology was respectively characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Intracellular uptake and localization of supramolecular photosensitizers were further investigated by flow cytometry and confocal laser scanning microscopy (CLSM), and the result indicated that TPPC6-SS-Ada/PEG-?-CD micelles could be effectively up-taken by MCF-7 cells. Furthermore, the phototoxicity evaluated by an MTT assay showed that TPPC6-SS-Ada/PEG-?-CD micelles have very low dark toxicity but greater photo-toxicity compared to free porphyrin. Thus, TPPC6-SS-Ada/PEG-?-CD micelles would provide the potential application for photosensitizer delivery. PMID:26222037

  17. Supramolecular fishing for plasma membrane proteins using an ultrastable synthetic host-guest binding pair

    NASA Astrophysics Data System (ADS)

    Lee, Don-Wook; Park, Kyeng Min; Banerjee, Mainak; Ha, Sang Hoon; Lee, Taehoon; Suh, Kyungwon; Paul, Somak; Jung, Hyuntae; Kim, Jaeyoon; Selvapalam, Narayanan; Ryu, Sung Ho; Kim, Kimoon

    2011-02-01

    Membrane proteomics, the large-scale global analysis of membrane proteins, is often constrained by the efficiency of separating and extracting membrane proteins. Recent approaches involve conjugating membrane proteins with the small molecule biotin and using the receptor streptavidin to extract the labelled proteins. Despite the many advantages of this method, several shortcomings remain, including potential contamination by endogenously biotinylated molecules and interference by streptavidin during analytical stages. Here, we report a supramolecular fishing method for membrane proteins using the synthetic receptor-ligand pair cucurbit[7]uril-1-trimethylammoniomethylferrocene (CB[7]-AFc). CB[7]-conjugated beads selectively capture AFc-labelled proteins from heterogeneous protein mixtures, and AFc-labelling of cells results in the efficient capture of membrane proteins by these beads. The captured proteins can be recovered easily at room temperature by treatment with a strong competitor such as 1,1?-bis(trimethylammoniomethyl)ferrocene. This synthetic but biocompatible host-guest system may be a useful alternative to streptavidin-biotin for membrane proteomics as well as other biological and biotechnological applications.

  18. Thermodynamics of HostGuest Interactions between Fullerenes and a Buckycatcher

    PubMed Central

    2015-01-01

    1H NMR and isothermal titration calorimetry (ITC) experiments were employed to obtain reliable thermodynamic data for the formation of the 1:1 inclusion complexes of fullerenes C60 and C70 with the buckycatcher (C60H28). NMR measurements were done in toluene-d8 and chlorobenzene-d5 at 288, 298, and 308 K, while the ITC titrations were performed in toluene, chlorobenzene, o-dichlorobenzene, anisole, and 1,1,2,2-tetrachloroethane at temperatures from 278 to 323 K. The association constants, Ka, obtained with both techniques are in very good agreement. The thermodynamic data obtained by ITC indicate that generally the hostguest association is enthalpy-driven. Interestingly, the entropy contributions are, with rare exceptions, slightly stabilizing or close to zero. Neither ?H nor ?S is constant over the temperature range studied, and these thermodynamic functions exhibit classical enthalpy/entropy compensation. The ?Cp values calculated from the temperature dependence of the calorimetric ?H values are negative for the association of both fullerenes with the buckycatcher in toluene. The negative ?Cp values are consistent with some desolvation of the host-cavity and the guest in the inclusion complexes, C60@C60H28 and C70@C60H28. PMID:25248285

  19. Vesicular gold assemblies based on host-guest inclusion and its controllable release of doxorubicin.

    PubMed

    Ha, Wei; Kang, Yang; Peng, Shu-Lin; Ding, Li-Sheng; Zhang, Sheng; Li, Bang-Jing

    2013-12-13

    We have developed a kind of gold nanoparticle (AuNP) in which polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) are attached on the surface of a gold nanocrystal through the host-guest inclusion between adamantane groups (ADA) and ?-cyclodextrin (?-CD). The resulting AuNPs become amphiphilic in water above body temperature and self-assemble into vesicles. It is found that these vesicles can load doxorubicin (Dox) effectively. With a decrease in temperature, the PNIPAM shifted from hydrophobic to hydrophilic, causing Au vesicles to disassemble into stable small AuNPs, triggering the release of Dox. These hybrid vesicles, combining polymer functionality with the intriguing properties of AuNPs, can first release free Dox and AuNP/Dox at a site of a tumor through the application of either simple ice packs or deeply penetrating cryoprobes, then the AuNP/Dox can be taken in by tumor cells and destroy them like miniature munitions. Furthermore, these vesicles showed other therapeutic possibilities due to the presence of gold. We believe that the development of such multi-functional vesicles will provide new and therapeutically useful means for medical applications. PMID:24231410

  20. Vesicular gold assemblies based on host-guest inclusion and its controllable release of doxorubicin

    NASA Astrophysics Data System (ADS)

    Ha, Wei; Kang, Yang; Peng, Shu-Lin; Ding, Li-Sheng; Zhang, Sheng; Li, Bang-Jing

    2013-12-01

    We have developed a kind of gold nanoparticle (AuNP) in which polyethylene glycol (PEG) and poly(N-isopropylacrylamide) (PNIPAM) are attached on the surface of a gold nanocrystal through the host-guest inclusion between adamantane groups (ADA) and ?-cyclodextrin (?-CD). The resulting AuNPs become amphiphilic in water above body temperature and self-assemble into vesicles. It is found that these vesicles can load doxorubicin (Dox) effectively. With a decrease in temperature, the PNIPAM shifted from hydrophobic to hydrophilic, causing Au vesicles to disassemble into stable small AuNPs, triggering the release of Dox. These hybrid vesicles, combining polymer functionality with the intriguing properties of AuNPs, can first release free Dox and AuNP/Dox at a site of a tumor through the application of either simple ice packs or deeply penetrating cryoprobes, then the AuNP/Dox can be taken in by tumor cells and destroy them like miniature munitions. Furthermore, these vesicles showed other therapeutic possibilities due to the presence of gold. We believe that the development of such multi-functional vesicles will provide new and therapeutically useful means for medical applications.

  1. Host-guest complex of cypermethrin with ?-cyclodextrin: A spectroscopy and theoretical investigation

    NASA Astrophysics Data System (ADS)

    Li, Wei; Lu, Bitai; Chen, Feifei; Yang, Feng; Wang, Zhendong

    2011-03-01

    An inclusion complex of ?-CD with cypermethrin was synthesized. To reveal the host-guest interaction, UV-vis and Raman spectroscopic analysis in combination with DFT calculations at B3LYP/6-31G(d) level were performed on cypermethrin and its ?-CD inclusion complex. Upon examining the optimized geometry of inclusion complex, we find that the cypermethrin molecule inserts into the cavity of ?-CD from the larger opening, and the phenyl moiety is staying inside the cavity. Partial density of states spectra (PDOS) and natural bond orbital (NBO) analysis reveals that intermolecular hydrogen bond is main driving force of formation of inclusion complex. DFT calculations reproduce well the experimental spectra and the deviation is within 20 cm -1. Comparing the same vibrational modes of inclusion complex with those of free cypermethrin and ?-CD, we note that most of characteristic bands of free molecules present in the Raman spectrum of inclusion complex, but a small Raman shift of 2-13 cm -1 has been observed on the same mode. The presence of characteristic bands and the small Raman shifts affirm the weak interaction between cypermethrin and ?-CD. Calculated thermodynamic analysis reveals that the formation of ?-CD cypermethrin inclusion complex is a spontaneous and enthalpy-driven process.

  2. Hostguest complexes between cryptophane-C and chloromethanes revisited

    PubMed Central

    Takacs, Z; Soltesova, M; Kowalewski, J; Lang, J; Brotin, T; Dutasta, J-P

    2013-01-01

    Cryptophane-C is composed of two nonequivalent cyclotribenzylene caps, one of which contains methoxy group substituents on the phenyl rings. The two caps are connected by three OCH2CH2O linkers in an anti arrangement. Hostguest complexes of cryptophane-C with dichloromethane and chloroform in solution were investigated in detail by nuclear magnetic resonance techniques and density functional theory (DFT) calculations. Variable temperature proton and carbon-13 spectra show a variety of dynamic processes, such as guest exchange and host conformational transitions. The guest exchange was studied quantitatively by exchange spectroscopy measurements or by line-shape analysis. The conformational preferences of the guest-containing host were interpreted through cross-relaxation measurements, providing evidence of the gauche+2 and gauche?2 conformations of the linkers. In addition, the mobility of the chloroform guest inside the cavity was studied by carbon-13 relaxation experiments. Combining different types of evidence led to a detailed picture of molecular recognition, interpreted in terms of conformational selection. Copyright 2012 John Wiley & Sons, Ltd. PMID:23132654

  3. Pressure-induced chemistry in a nitrogen-hydrogen host-guest structure

    NASA Astrophysics Data System (ADS)

    Spaulding, Dylan K.; Weck, Gunnar; Loubeyre, Paul; Datchi, Fréderic; Dumas, Paul; Hanfland, Michael

    2014-12-01

    New topochemistry in simple molecular systems can be explored at high pressure. Here we examine the binary nitrogen/hydrogen system using Raman spectroscopy, synchrotron X-ray diffraction, synchrotron infrared microspectroscopy and visual observation. We find a eutectic-type binary phase diagram with two stable high-pressure van der Waals compounds, which we identify as (N2)6(H2)7 and N2(H2)2. The former represents a new type of van der Waals host-guest compound in which hydrogen molecules are contained within channels in a nitrogen lattice. This compound shows evidence for a gradual, pressure-induced change in bonding from van der Waals to ionic interactions near 50 GPa, forming an amorphous dinitrogen network containing ionized ammonia in a room-temperature analogue of the Haber-Bosch process. Hydrazine is recovered on decompression. The nitrogen-hydrogen system demonstrates the potential for new pressure-driven chemistry in high-pressure structures and the promise of tailoring molecular interactions for materials synthesis.

  4. Molecular Recognition: Use of Metal-Containing Molecular Clefts for Supramolecular Self-Assembly and Host-Guest Formation

    SciTech Connect

    Crowley, James D.; Bosnich, Brice

    2008-10-03

    Molecular clefts consisting of a rigid spacer linked to two parallel cofacially disposed terpy-M-X (M = Pd{sup 2+}, Pt{sup 2+}) units, which can vary in separation from 6.6 to 7.2 {angstrom}, have been used as molecular receptors and for self-assembly with linear and triangular linkers to produce rectangles and trigonal prisms, respectively. Aromatic molecules form multiple host-guest adducts with the molecular cleft receptors and with the rectangles and trigonal prisms. Planar complexes of Pt{sup 2+} also form host-guest adducts. The forces that control this molecular recognition, namely, {pi}-{pi} interactions, charge-induced dipole interactions, charge-charge forces, weak metal-metal interactions and solvation effects, are discussed and assigned to the various adducts.

  5. Host-guest Inclusion Complexes between Mitiglinide and the Naturally Occurring Cyclodextrins α, β, and γ: A Theoretical Approach

    PubMed Central

    Al Azzam, Khaldun Mohammad; Muhammad, Ermafatiha

    2015-01-01

    Purpose: The present study is aimed to study the host-guest inclusion complexation of the naturally occurring cyclodextrins (CDs), namely; (α-CD,β-CD, and γ-CD) with mitiglinide (MIT). Methods: Host-guest inclusion complexation was simulated using semi-empirical PM3 method. Results: The obtained results clearly indicate that the complexes formed are energetically favored in the presence of γ-CD (Ecomp = -17.884 kcal/mol) of the optimal configurations of (1:1) MIT/γ-CD inclusion complexes. Moreover, the results obtained reveal that the formation of more stable MIT/γ-CD complex compared to MIT/α-CD or MIT/β-CD complexes is primarily due to differences in intermolecular hydrogen bonding. Conclusion: The present theoretical results may be informative to scientists who are devoting themselves to developing effective methods for enhancing the drug solubility. PMID:26236670

  6. Host-guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes.

    PubMed

    Pérez-Mitta, Gonzalo; Albesa, Alberto G; Knoll, Wolfgang; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2015-10-14

    We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K(+) concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels. PMID:26365392

  7. Host-guest chemistry of mesoporous silicas: precise design of location, density and orientation of molecular guests in mesopores

    NASA Astrophysics Data System (ADS)

    Sohmiya, Minoru; Saito, Kanji; Ogawa, Makoto

    2015-10-01

    Mesoporous solids, which were prepared from inorganic-surfactant mesostructured materials, have been investigated due to their very large surface area and high porosity, pore size uniformity and variation, periodic pore arrangement and possible pore surface modification. Morphosyntheses from macroscopic morphologies such as bulk monolith and films, to nanoscopic ones, nanoparticles and their stable suspension, make mesoporous materials more attractive for applications and detailed characterization. This class of materials has been studied for such applications as adsorbents and catalysts, and later on, for optical, electronic, environmental and bio-related ones. This review summarizes the studies on the chemistry of mesoporous silica and functional guest species (host-guest chemistry) to highlight the present status and future applications of the host-guest hybrids.

  8. Exploring host-guest complexation mechanisms by a molecular dynamics/quantum mechanics/continuum solvent model approach

    NASA Astrophysics Data System (ADS)

    Ye, Renlong; Nie, Xuemei; Zhou, Yumei; Wong, Chung F.; Gong, Xuedong; Jiang, Wei; Tang, Weihua; Wang, Yan A.; Heine, Thomas; Zhou, Baojing

    2016-03-01

    We introduce a molecular dynamics/quantum mechanics/continuum solvent model (MD/QM/CSM) approach to investigate binding mechanisms of host-guest systems. The representative conformations of host, guest, and their complex generated from MD simulations at the molecular-mechanics level are used for binding free energy calculations based on a QM/CSM model. We use this approach to explore the binding mechanisms of β-cyclodextrin (β-CD) and 2, 6-di-methyl-β-CD (DM-β-CD) with various guest molecules. Our results suggest that solvent effects play a more important role in determining the relative binding affinities of DM-β-CD than those of β-CD mainly because the former is more flexible than the latter.

  9. Tunable nonlinear optical properties of PDA/Ag composite vesicles based on reversible host-guest interaction

    NASA Astrophysics Data System (ADS)

    Rao, Jinan; Jiang, Hao; Wang, Jin; Zou, Gang; Zhang, Qijin

    2012-06-01

    We develop a novel photo-responsive supramolecular system in which the aggregation and disaggregation of polydiacetylene/silver (PDA/Ag) composite vesicles is mediated by a reversible photo-responsive molecular recognition process. The PDA/Ag composite vesicles provide necessary nonlinear optical (NLO) properties, the host-guest interaction between azobenzene and ?-cyclodextrin get PDA/Ag composite vesicles sufficiently close to each other for providing the enhanced surface plasmon resonance and a corresponding NLO effect. NLO switching of PDA/Ag composite vesicles based on reversible host-guest interactions is realized by alternating visible and UV light irradiation, which may introduce a new way for preparation of smart NLO materials.

  10. Calculation of the absolute thermodynamic properties of association of host-guest systems from the intermolecular potential of mean force

    NASA Astrophysics Data System (ADS)

    Ghoufi, Aziz; Malfreyt, Patrice

    2006-12-01

    The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum.

  11. Calculation of the absolute thermodynamic properties of association of host-guest systems from the intermolecular potential of mean force.

    PubMed

    Ghoufi, Aziz; Malfreyt, Patrice

    2006-12-14

    The authors report calculations of the intermolecular potential of mean force (PMF) in the case of the host-guest interaction. The host-guest system is defined by a water soluble calixarene and a cation. With an organic cation such as the tetramethylammonium cation, the calixarene forms an insertion complex, whereas with the Lanthane cation, the supramolecular assembly is an outer-sphere complex. The authors apply a modified free energy perturbation method and the force constraint technique to establish the PMF profiles as a function of the separation distance between the host and guest. They use the PMF profile for the calculation of the absolute thermodynamic properties of association that they compare to the experimental values previously determined. They finish by giving some structural features of the insertion and outer-sphere complexes at the Gibbs free energy minimum. PMID:17176145

  12. Host-guest interactions mediated nano-assemblies using cyclodextrin-containing hydrophilic polymers and their biomedical applications.

    PubMed

    Zhang, Jianxiang; Ma, Peter X

    2010-08-01

    Supramolecular nanostructures assembled by polymeric amphiphiles have been intensively studied during the last two decades. Such nanocarriers may be engineered to possess on-demand bio-responsitivity for the prevention, diagnosis, and treatment of human diseases. The successful development of several nanoassembly-based polymer therapeutics further encouraged scientists to develop nano-vehicles to achieve controlled release, enhanced efficacy, improved specificity and reduced toxicity. Different from the abundant existing literatures on the hydrophobically or electrostatically driven self-assemblies and their therapeutic applications, this article reviews host-guest interaction mediated nanoassemblies, especially those constructed using cyclodextrins as the host entities. The excellent biocompatibility, complexation capacity, and chemical-sensitivity of cyclodextrin make cyclodextrin-containing polymers attractive to construct host-guest nanoassemblies. Such nanocarriers may be advantageous also because of the broad availability of cyclodextrins, their flexibility for structure/property modulation and their chemical-responsive characteristics. PMID:20725642

  13. Host-guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes

    NASA Astrophysics Data System (ADS)

    Pérez-Mitta, Gonzalo; Albesa, Alberto G.; Knoll, Wolfgang; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2015-09-01

    We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K+ concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels.We describe the use of asymmetric nanopores decorated with crown ethers for constructing robust signal-responsive chemical devices. The modification of single conical nanopores with 18-crown-6 units led to a nanodevice whose electronic readout, derived from the transmembrane ion current, can be finely tuned over a wide range of K+ concentrations. The electrostatic characteristics of the nanopore environment arising from host-guest ion-recognition processes taking place on the pore walls are responsible for tuning the transmembrane ionic transport and the rectification properties of the pore. This work illustrates the potential and versatility of host-guest chemistry, in combination with nanofluidic elements, as a key enabler to achieve addressable chemical nanodevices mimicking the ion transport properties and gating functions of specific biological channels. Electronic supplementary information (ESI) available: Experimental details of the preparation and characterization of the brush-modified nanopores. See DOI: 10.1039/c5nr04645a

  14. An ion signal responsive dynamic protein nano-spring constructed by high ordered host-guest recognition.

    PubMed

    Si, Chengye; Li, Jiaxi; Luo, Quan; Hou, Chunxi; Pan, Tiezheng; Li, Hongbin; Liu, Junqiu

    2016-02-01

    A protein self-assembly nano-spring was developed through host-guest interactions between cucurbit[8]uril and tripeptide FGG tags of fusion protein FGG-recoverin-GST. Fine control of the conformational changes of the Ca(2+)-responsive domain allows for a 50% stretch of the protein nano-spring as it switches from the contracted state to the extended state. PMID:26822329

  15. Modulating the rate of charge transport in a metal-organic framework thin film using host:guest chemistry.

    PubMed

    Hod, Idan; Farha, Omar K; Hupp, Joseph T

    2016-01-28

    Herein we demonstrate the use of host-guest chemistry to modulate rates of charge transport in metal-organic framework (MOF) films. The kinetics of site-to-site of charge hopping and, in turn, the overall redox conductivity, of a ferrocene-modified MOF can be altered by up to 30-fold by coupling electron exchange to the oxidation-state-dependent formation of inclusion complexes between cyclodextrin and channel-tethered metallocenes. PMID:26666952

  16. Temperature-Responsive Switch Constructed from an Anthracene-Functionalized Pillar[5]arene-Based Host-Guest System.

    PubMed

    Bi, Jiahai; Zeng, Xiangfei; Tian, Demei; Li, Haibing

    2016-03-01

    A monofunctionalized anthracene pillar[5]arene (MAP5) was designed and synthesized by a click reaction. MAP5 was bound to an ionic liquid through host-guest interactions to modify a gold interface. The bonding and release of MAP5 was readily and reversibly controlled by temperature regulation. The developed temperature-responsive switch at an interface can be used in memory storage, drug delivery, and sensing. PMID:26889706

  17. Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery.

    PubMed

    Zhu, Jing-Ling; Liu, Kerh Li; Wen, Yuting; Song, Xia; Li, Jun

    2016-01-01

    A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an ?-cyclodextrin (?-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-?-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin. PMID:26692041

  18. Tuning Emission Responses of a Triphenylamine Derivative in Host-Guest Complexes and an Unusual Dynamic Inclusion Phenomenon.

    PubMed

    Gangopadhyay, Monalisa; Mandal, Amal K; Maity, Arunava; Ravindranathan, Sapna; Rajamohanan, Pattuparambil R; Das, Amitava

    2016-01-15

    A newly synthesized triphenylamine derivative (1Cl3) shows significant differences in inclusion complex formation with two different macrocyclic hosts, cucurbit[7]uril (CB[7]) and ?-cyclodextrin (?-CD). Detailed investigations by NMR spectroscopy reveal that CB[7] forms a 1:3 host-guest complex ([13{CB[7]}]Cl3) in which three arms of 1Cl3 are bound to three host molecules. On the other hand, ?-CD forms a dynamic 1:1 inclusion complex ([1{?-CD}]Cl3) by binding to only one of the three arms of 1Cl3 at a given time. The formation of a 1:1 host-guest complex with ?-CD and 1:3 host-guest complex with CB[7] was also confirmed from the results of the isothermal titration calorimetric studies. Interestingly, 1Cl3 exhibits a rare dual emission property in solution at room temperature with the lower and higher energy bands arising from a locally excited state and an intramolecular charge-transfer transition, respectively. The difference in inclusion complex formation behavior of 1Cl3 with the two macrocyclic hosts results in the stabilization of different emission states in the two inclusion complexes. The fundamental difference in the electrostatic surface potentials, cavity polarities, and shapes of the two macrocyclic hosts could account for the formation of the different inclusion complexes with distinct luminescence responses. PMID:26649441

  19. Efficient solid-state host-guest light-emitting electrochemical cells based on cationic transition metal complexes

    NASA Astrophysics Data System (ADS)

    Su, Hai-Ching; Wu, Chung-Chih; Fang, Fu-Chuan; Wong, Ken-Tsung

    2006-12-01

    The authors demonstrate highly efficient solid-state light-emitting electrochemical cells (LECs) consisting of green-emitting [Ir(dFppy)2(SB)]+(PF6-) as the host and orange-emitting [Ir(ppy)2(SB)]+(PF6-) as the guest [where dFppy is 2-(2,4-difluorophenyl)pyridine, SB is 4,5-diaza-9,9'-spirobifluorene, and ppy is 2-phenylpyridine]. Photophysical studies show that with the optimized host-guest compositions, the emission is mainly from the guest and photoluminescence quantum yields are largely enhanced over those of pure host and guest films due to suppressed intermolecular interactions. Correspondingly, LECs based on such host-guest cationic complex systems show substantially enhanced quantum efficiencies (power efficiencies) of up to 10.4% (36.8lm/W), representing a 1.5 times enhancement compared to those of pure host and guest devices. Such results indicate that the host-guest system is essential and useful for achieving highly efficient solid-state LECs.

  20. Fluorescent Detection of Tadalafil Based on Competitive Host-Guest Interaction Using p-Sulfonated Calix[6]arene Functionalized Graphene.

    PubMed

    Yang, Long; Zhao, Hui; Li, Yucong; Ran, Xin; Deng, Guogang; Xie, Xiaoguang; Li, Can-Peng

    2015-12-01

    A competitive fluorescence method toward tadalafil detection has been developed based on host-guest recognition by selecting rhodamine B (RhB) and p-sulfonated calix[6]arene functionalized graphene (CX6-Gra) as the "reporter pair". Upon the presence of tadalafil to the performed CX6-Gra-RhB complex, the RhB molecules are displaced by tadalafil, leading to a "switch-on" fluorescence signal. The observed fluorescence signal can be used for quantitative detection of tadalafil ranging from 1.00 to 50.00 ?M with a detection limit of 0.32 ?M (S/N = 3). The inclusion complex of tadalafil and CX6 was studied by molecular docking and the results indicated that a 1:1 host-guest stoichiometry had the lowest ?G value of -7.18 kcal/mol. The docking studies demonstrated that the main forces including ?-? interactions, electrostatic interactions, and hydrophobic interactions should be responsible for the formation of this inclusion compound. The mechanism of the competitive host-guest interaction was clarified. The binding constant (K) of the tadalafil/CX6 complex was more than 5 times greater than that of RhB/CX6. PMID:26571350

  1. Characterization of self-assembled supramolecular [Ga4L6] host-guest complexes by electrospray ionization mass spectrometry.

    PubMed

    Andersen, Ulla N; Seeber, Georg; Fiedler, Dorothea; Raymond, Kenneth N; Lin, Dayin; Harris, Don

    2006-03-01

    Self-assembled supramolecular host-guest complexes have been characterized by electrospray ionization mass spectrometry. The spectra obtained by use of a Q-TOF instrument equipped with a Z-spray ion source show primarily the 3- and 4- charge states of the assemblies. The assemblies have the general formula [guest subset Ga4L6]11- where L represents the chelating bidentate catechol ligand 1,5-bis(2',3'-dihydroxy-benzamido)naphthalene and guests are tetramethyl ammonium (Me4N+), tetraethyl ammonium (Et4N+), tetra-n-propyl ammonium (Pr4N+) and decamethylcobaltocenium (Cp*2Co+) cations. For the first time, the mass spectrum of the empty assembly [Ga4L6]12- is reported. This article also reports that provided the electrospray ion source is capable of preserving noncovalent interactions, it is possible to observe host-guest complexes containing both weak binding guests as well as sterically demanding guests in the mass spectra. The present data suggest that electrospray mass spectrometry is a powerful tool for characterization of supramolecular host-guest complexes. PMID:16464607

  2. Fabrication of modular multifunctional delivery for antitumor drugs based on host-guest recognition.

    PubMed

    Chen, Li; Zhang, Zhe; Chen, Xiaofei; Yao, Xuemei; He, Chaoliang; Chen, Xuesi

    2015-05-01

    Herein, learning from the idea of the modular concept widely used in ship building, as a design approach that assembles some subdivided smaller modules to a specific ship, a new modular multifunctional drug delivery (MMDD) with excellent biocompatibility was directly prepared by a flexible host-guest interaction between pH-sensitive benzimidazole-graft-dextran (Dex-BM) and pre-synthesized multifunctional cyclodextrins. In this drug system, pH-sensitive Dex-BM acted as the main case and pre-synthesized multifunctional cyclodextrins were the changeable modules. To verify the feasibility of MMDD in cancer chemotherapy, doxorubicin (DOX) was used as a model drug. In vitro drug release experiments indicated that the drug released around 80% from DOX-loaded MMDD at pH 5.3, while approximately 40% of DOX released under the condition of pH 7.4. Moreover, the targeting antitumor activity of DOX-loaded MMDD was investigated in HeLa and HepG2 cells using MTT assays, confocal laser scanning microscopy and flow cytometer, which indicated that the targeted DOX-loaded MMDD provided an efficient drug delivery platform for inhibition of different cancer cells. Meantime, the incorporation of different functional modules into one system was also investigated, simultaneously exhibiting targeting and imaging property. These features suggest that this modular multifunctional drug delivery system can efficiently enhance the inhibition of cellular proliferation in vitro, and according to the needs in clinical treatment, some targeting and imaging molecules can be chosen. PMID:25749295

  3. UV photodissociation spectroscopy of cryogenically cooled gas phase host-guest complex ions of crown ethers.

    PubMed

    Inokuchi, Yoshiya; Haino, Takeharu; Sekiya, Ryo; Morishima, Fumiya; Dedonder, Claude; Fraud, Graldine; Jouvet, Christophe; Ebata, Takayuki

    2015-10-21

    The geometric and electronic structures of cold host-guest complex ions of crown ethers (CEs) in the gas phase have been investigated by ultraviolet (UV) fragmentation spectroscopy. As host CEs, we chose 15-crown-5 (15C5), 18-crown-6 (18C6), 24-crown-8 (24C8), and dibenzo-24-crown-8 (DB24C8), and as guests protonated-aniline (anilineH(+)) and protonated-dibenzylamine (dBAMH(+)) were chosen. The ions generated by an electrospray ionization (ESI) source were cooled in a quadrupole ion-trap (QIT) using a cryogenic cooler, and UV spectra were obtained by UV photodissociation (UVPD) spectroscopy. UV spectroscopy was complemented by quantum chemical calculations of the most probable complex structures. The UV spectrum of anilineH(+)CEs is very sensitive to the symmetry of CEs; anilineH(+)18C6 shows a sharp electronic spectrum similar to anilineH(+), while anilineH(+)15C5 shows a very broad structure with poor Franck-Condon factors. In addition, a remarkable cage effect in the fragmentation process after UV excitation was observed in both complex ions. In anilineH(+)CE complexes, the cage effect completely removed the dissociation channels of the anilineH(+) moiety. A large difference in the fragmentation yield between dBAMH(+)18C6 and dBAMH(+)24C8 was observed due to a large barrier for releasing dBAMH(+) from the axis of rotaxane in the latter complex. PMID:26095662

  4. A supramolecular host-guest carrier system for growth factors employing V(H)H fragments.

    PubMed

    Cabanas-Dans, Jordi; Rodrigues, Emilie Dooms; Landman, Ellie; van Weerd, Jasper; van Blitterswijk, Clemens; Verrips, Theo; Huskens, Jurriaan; Karperien, Marcel; Jonkheijm, Pascal

    2014-09-10

    A supramolecular strategy is presented for the assembly of growth factors employing His6-tagged single-domain antibodies (VHH). A combination of orthogonal supramolecular interactions of ?-cyclodextrin (?CD)-adamantyl (Ad) host-guest and N-nitrilotriacetic acid (NTA)-histidine (His) interactions was employed to generate reversible and homogeneous layers of growth factors. A single-domain antibody V(H)H fragment was identified to bind to the human bone morphogenetic protein-6 (hBMP6) growth factor and could be recombinantly expressed in E. coli. The V(H)H fragment was equipped with a C-terminal hexahistidine (His6) tether to facilitate the assembly on ?CD surfaces using a linker that contains an Ad group to bind to the ?CD receptors and an NTA moiety to interact with the His6-tag upon cocomplexation of Ni(2+) ions. After exploring the thermodynamic and kinetic stability of the V(H)H assemblies on ?CD surfaces using a variety of experimental techniques including microcontact printing (?CP), surface plasmon resonance (SPR), microscale thermophoresis (MST), and theoretical models for determining the thermodynamic behavior of the system, hBMP6 was assembled onto the V(H)H-functionalized surfaces. After analyzing the immobilized hBMP6 using immunostaining, the biological activity of hBMP6 was demonstrated in cell differentiation experiments. Early osteogenic differentiation was analyzed in terms of alkaline phosphatase (ALP) activity of KS483-4C3 mouse progenitor cells, and the results indicated that the reversibly immobilized growth factors were functionally delivered to the cells. In conclusion, the supramolecular strategy used here offers the necessary affinity, reversibility, and temporal control to promote biological function of the growth factors that were delivered by this strategy. PMID:25153343

  5. The synthesis and host-guest applications of synthetic receptor molecules

    NASA Astrophysics Data System (ADS)

    Osner, Zachary R.

    2011-12-01

    Host-guest chemistry involves the complimentary binding between two molecules. Host molecules have been synthesized to bind negative, positive, and neutral molecules such as proteins and enzymes, and have been used as optical sensors, electrochemical sensors, supramolecular catalysts, and in the pharmaceutical industry as anti-cancer agents.1 The field of nanoscience has exploited guest-host interactions to create optical sensors with colloidal gold and Dip-Pen nanolithography technologies. Gold nanoparticles, have been functionalized with DNA, and have been developed as a selective colorimetric detection system, that upon binding turns the solution from a red to blue in color.2 Cyclotriveratrylene (CTV) 1 is a common supramolecular scaffold that has been previously employed in guest-host chemistry, and the construction of CTV involves the cyclic trimerization of veratryl alcohol via the veratryl cation.3 Due to the rigid bowl shaped structure of CTV, CTV has been shown to act as a host molecule for fullerene-C60.4 Lectin binding receptor proteins are a specific class of proteins found in bacteria, viruses, plants, and animals that can bind to complimentary carbohydrates. It is these lectins that are believed to be responsible for cell-cell interactions and the formation of biofilms in pathenogenic bacteria.5 P. aeruginosa is a pathenogenic bacterium, shown to have a high resistance to many antibiotics, which can form biofilms in human lung tissue, causing respiratory tract infections in patients with compromised immune systems. 5 I will exploit guest-host interactions to create synthetic supramolecular and carbohydrate receptor molecules to that will be of use as biological sensing devices via self-assembled monolayers on solid surfaces and nanoparticle technologies. *Please refer to dissertation for references/footnotes.

  6. Prediction of SAMPL3 host-guest binding affinities: evaluating the accuracy of generalized force-fields.

    PubMed

    Muddana, Hari S; Gilson, Michael K

    2012-05-01

    We used the second-generation mining minima method (M2) to compute the binding affinities of the novel host-guest complexes in the SAMPL3 blind prediction challenge. The predictions were in poor agreement with experiment, and we conjectured that much of the error might derive from the force field, CHARMm with Vcharge charges. Repeating the calculations with other generalized force-fields led to no significant improvement, and we observed that the predicted affinities were highly sensitive to the choice of force-field. We therefore embarked on a systematic evaluation of a set of generalized force fields, based upon comparisons with PM6-DH2, a fast yet accurate semi-empirical quantum mechanics method. In particular, we compared gas-phase interaction energies and entropies for the host-guest complexes themselves, as well as for smaller chemical fragments derived from the same molecules. The mean deviations of the force field interaction energies from the quantum results were greater than 3 kcal/mol and 9 kcal/mol, for the fragments and host-guest systems respectively. We further evaluated the accuracy of force-fields for computing the vibrational entropies and found the mean errors to be greater than 4 kcal/mol. Given these errors in energy and entropy, it is not surprising in retrospect that the predicted binding affinities deviated from the experiment by several kcal/mol. These results emphasize the need for improvements in generalized force-fields and also highlight the importance of systematic evaluation of force-field parameters prior to evaluating different free-energy methods. PMID:22274835

  7. Prediction of SAMPL3 Host-Guest Binding Affinities: Evaluating the Accuracy of Generalized Force-Fields

    PubMed Central

    Muddana, Hari S.; Gilson, Michael K.

    2012-01-01

    We used the second-generation mining minima method (M2) to compute the binding affinities of the novel host-guest complexes in the SAMPL3 blind prediction challenge. The predictions were in poor agreement with experiment, and we conjectured that much of the error might derive from the force field, CHARMm with Vcharge charges. Repeating the calculations with other generalized force-fields led to no significant improvement, and we observed that the predicted affinities were highly sensitive to the choice of force-field. We therefore embarked on a systematic evaluation of a set of generalized force fields, based upon comparisons with PM6-DH2, a fast yet accurate semi-empirical quantum mechanics method. In particular, we compared gas-phase interaction energies and entropies for the host-guest complexes themselves, as well as for smaller chemical fragments derived from the same molecules. The mean deviations of the force field interaction energies from the quantum results were greater than 3 kcal/mol and 9 kcal/mol, for the fragments and host-guest systems respectively. We further evaluated the accuracy of force-fields for computing the vibrational entropies and found the mean errors to be greater than 4 kcal/mol. Given these errors in energy and entropy, it is not surprising in retrospect that the predicted binding affinities deviated from the experiment by several kcal/mol. These results emphasize the need for improvements in generalized force-fields and also highlight the importance of systematic evaluation of force-field parameters prior to evaluating different free-energy methods. PMID:22274835

  8. Smart protein biogate as a mediator to regulate competitive host-guest interaction for sensitive ratiometric electrochemical assay of prion

    PubMed Central

    Yu, Peng; Zhang, Xiaohua; Zhou, Jiawan; Xiong, Erhu; Li, Xiaoyu; Chen, Jinhua

    2015-01-01

    A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis. PMID:26531259

  9. Light-triggered capture and release of DNA and proteins by host-guest binding and electrostatic interaction.

    PubMed

    Moratz, Johanna; Samanta, Avik; Voskuhl, Jens; Mohan Nalluri, Siva Krishna; Ravoo, Bart Jan

    2015-02-16

    The development of an effective and general delivery method that can be applied to a large variety of structurally diverse biomolecules remains a bottleneck in modern drug therapy. Herein, we present a supramolecular system for the dynamic trapping and light-stimulated release of both DNA and proteins. Self-assembled ternary complexes act as nanoscale carriers, comprising vesicles of amphiphilic cyclodextrin, the target biomolecules and linker molecules with an azobenzene unit and a charged functionality. The non-covalent linker binds to the cyclodextrin by host-guest complexation with the azobenzene. Proteins or DNA are then bound to the functionalized vesicles through multivalent electrostatic attraction. The photoresponse of the host-guest complex allows a light-induced switch from the multivalent state that can bind the biomolecules to the low-affinity state of the free linker, thereby providing external control over the cargo release. The major advantage of this delivery approach is the wide variety of targets that can be addressed by multivalent electrostatic interaction, which we demonstrate on four types of DNA and six different proteins. PMID:25585879

  10. Tunable two-color luminescence and host-guest energy transfer of fluorescent chromophores encapsulated in metal-organic frameworks.

    PubMed

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-01-01

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner. PMID:24614015

  11. Tunable Two-color Luminescence and Host-guest Energy Transfer of Fluorescent Chromophores Encapsulated in Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Yan, Dongpeng; Tang, Yanqun; Lin, Heyang; Wang, Dan

    2014-03-01

    Co-assembly of chromophore guests with host matrices can afford materials which have photofunctionalities different from those of individual components. Compared with clay and zeolite materials, the use of metal-organic frameworks (MOFs) as a host structure for fabricating luminescent host-guest materials is still at an early stage. Herein, we report the incorporation of a laser dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran (DCM), into stilbene-based and naphthalene-based MOF systems. The resulting materials exhibit blue/red two-color emission, and the intensity ratio of blue to red fluorescence varies in different planes within the MOF crystal as detected by 3D confocal fluorescence microscopy. The observed changes in ratiometric fluorescence suggest the occurrence of energy transfer from MOF host to DCM molecules, which can be further confirmed by periodic density functional theoretical (DFT) calculations. Moreover, selective changes in luminescence behavior are observed on treating the guest@MOF samples with volatile organic compounds (methanol, acetone and toluene), indicating that these host-guest systems have potential applications as fluorescence sensors. It can be expected that by rational selection of MOF hosts and guest chromophores with suitable emissive colors and energy levels, a wide variety of multi-color luminescent and energy-transfer systems can readily be prepared in a similar manner.

  12. A targeted nanoglobular contrast agent from host-guest self-assembly for MR cancer molecular imaging.

    PubMed

    Zhou, Zhuxian; Han, Zhen; Lu, Zheng-Rong

    2016-04-01

    The clinical application of nanoparticular Gd(III) based contrast agents for tumor molecular MRI has been hindered by safety concerns associated with prolonged tissue retention, although they can produce strong tumor enhancement. In this study, a targeted well-defined cyclodextrin-based nanoglobular contrast agent was developed through self-assembly driven by host-guest interactions for safe and effective cancer molecular MRI. Multiple β-cyclodextrins attached POSS (polyhedral oligomeric silsesquioxane) nanoglobule was used as host molecule. Adamantane-modified macrocyclic Gd(III) contrast agent, cRGD (cyclic RGDfK peptide) targeting ligand and fluorescent probe was used as guest molecules. The targeted host-guest nanoglobular contrast agent cRGD-POSS-βCD-(DOTA-Gd) specifically bond to αvβ3 integrin in malignant 4T1 breast tumor and provided greater contrast enhancement than the corresponding non-targeted agent. The agent also provided significant fluorescence signal in tumor tissue. The histological analysis of the tumor tissue confirmed its specific and effective targeting to αvβ3 integrin. The targeted imaging agent has a potential for specific cancer molecular MR and fluorescent imaging. PMID:26874280

  13. Signal amplification for electrochemical immunosensing by in situ assembly of host-guest linked gold nanorod superstructure on immunocomplex.

    PubMed

    Lin, Dajie; Wu, Jie; Ju, Huangxian; Yan, Feng

    2013-07-15

    An amplification strategy for signal tracing was developed by introducing a host-guest binding reaction into the assembly process of gold nanorods (AuNRs) superstructure. The amplification pathway firstly used a thio-?-cyclodextrin (SH-?-CD) functionalized gold nanoparticles to label signal antibody, and then in situ assembled multi-layer SH-?-CD end-functionalized AuNRs to sandwich immunocomplex on immunosensor surface by using 4,4,4,4-(21H, 23H-porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) as a bridge to achieve simple and convenient host-guest reaction. The built end-to-end AuNRs superstructure showed excellent performance for the signal amplification in connection with the electrochemical biosensing by preoxidation and then voltammetric analysis of gold element. Using ?-fetoprotein as an analyte, the immunosensor was constructed by covalently binding capture antibody to chitosan-carbon nanotubes-poly(diallyldimethylammonium chloride) modified electrode. The superstructure rich in AuNRs brought an enhanced detection sensitivity of protein, which could detect ?-fetoprotein in a linear range from 0.5 pg mL(-1) to 0.5 ng mL(-1) with a detection limit down to 0.032 pg mL(-1). The immunoassay exhibited good stability and acceptable reproducibility and accuracy. The in situ superstructure assembly could be extended to other labeled recognition systems, providing a promising novel avenue for signal amplification and potential applications in bioanalysis and clinical diagnostics. PMID:23500363

  14. Host-guest interaction induced supramolecular amphiphilic star architecture and uniform nanovesicle formation for anticancer drug delivery

    NASA Astrophysics Data System (ADS)

    Zhu, Jing-Ling; Liu, Kerh Li; Wen, Yuting; Song, Xia; Li, Jun

    2016-01-01

    A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin.A star polymer of poly[(R,S)-3-hydroxybutyrate] (PHB) with adamantyl end-terminals extended from an α-cyclodextrin (α-CD) core is designed. It subsequently self-assembles to form controllable and uniform nanovesicles induced by host-guest interactions between heptakis(2,6-di-O-methyl)-β-CD and the adamantyl ends. The nanovesicles are suitable for loading and intracellular delivery of the anticancer drug doxorubicin. Electronic supplementary information (ESI) available: Polymer synthesis, characterization, preparation of drug-loaded nanovesicles, intracellular drug release and cytotoxicity assays, TEM and DLS measurements. See DOI: 10.1039/c5nr06744h

  15. Large scale affinity calculations of cyclodextrin host-guest complexes: Understanding the role of reorganization in the molecular recognition process

    PubMed Central

    Wickstrom, Lauren; He, Peng; Gallicchio, Emilio; Levy, Ronald M.

    2013-01-01

    Host-guest inclusion complexes are useful models for understanding the structural and energetic aspects of molecular recognition. Due to their small size relative to much larger protein-ligand complexes, converged results can be obtained rapidly for these systems thus offering the opportunity to more reliably study fundamental aspects of the thermodynamics of binding. In this work, we have performed a large scale binding affinity survey of 57 β-cyclodextrin (CD) host guest systems using the binding energy distribution analysis method (BEDAM) with implicit solvation (OPLS-AA/AGBNP2). Converged estimates of the standard binding free energies are obtained for these systems by employing techniques such as parallel Hamitionian replica exchange molecular dynamics, conformational reservoirs and multistate free energy estimators. Good agreement with experimental measurements is obtained in terms of both numerical accuracy and affinity rankings. Overall, average effective binding energies reproduce affinity rank ordering better than the calculated binding affinities, even though calculated binding free energies, which account for effects such as conformational strain and entropy loss upon binding, provide lower root mean square errors when compared to measurements. Interestingly, we find that binding free energies are superior rank order predictors for a large subset containing the most flexible guests. The results indicate that, while challenging, accurate modeling of reorganization effects can lead to ligand design models of superior predictive power for rank ordering relative to models based only on ligand-receptor interaction energies. PMID:25147485

  16. Smart protein biogate as a mediator to regulate competitive host-guest interaction for sensitive ratiometric electrochemical assay of prion

    NASA Astrophysics Data System (ADS)

    Yu, Peng; Zhang, Xiaohua; Zhou, Jiawan; Xiong, Erhu; Li, Xiaoyu; Chen, Jinhua

    2015-11-01

    A novel competitive host-guest strategy regulated by protein biogate was developed for sensitive and selective analysis of prion protein. The methylene blue (MB)-tagged prion aptamer (MB-Apt) was introduced to the multiwalled carbon nanotubes-β-cyclodextrins (MWCNTs-β-CD) composites-modified glassy carbon (GC) electrode through the host-guest interaction between β-CD and MB. In the absence of prion, MB-Apt could be displaced by ferrocenecarboxylic acid (FCA) due to its stronger binding affinity to β-CD, resulting in a large oxidation peak of FCA. However, in the presence of prion, the specific prion-aptamer interaction drove the formation of protein biogate to seal the cavity of β-CD, which hindered the guest displacement of MB by FCA and resulted in the oxidation peak current of MB (IMB) increased and that of FCA (IFCA) decreased. The developed aptasensor showed good response towards the target (prion protein) with a low detection limit of 160 fM. By changing the specific aptamers, this strategy could be easily extended to detect other proteins, showing promising potential for extensive applications in bioanalysis.

  17. A new supramolecular gel via host-guest complexation with cucurbit[8]uril and N-(4-diethylaminobenzyl)chitosan.

    PubMed

    Lin, Youwen; Li, Lifan; Li, Guangwen

    2013-01-30

    A novel supramolecular gel has been prepared via host-guest interaction between cucurbit[8]uril (Q[8]) and N-(4-diethylaminobenzyl)chitosan (EBCS). The structure of supramolecular gel has been characterized. The spectrum of (1)H NMR demonstrated the benzene ring of EBCS is reside inside the hydrophobic cavity of Q[8] and the host-guest interaction between Q[8] and EBCS was the main driving force for the formation of the supramolecular gel. The network structure of the xerogel of Q[8]/EBCS gel was observed by SEM. The Q[8]/EBCS gel system showed thermosensitive and pH-sensitive properties. The physical characterization by SEM, DSC, TG demonstrated the distinguished characters, which proved the formation of supramolecular gel instead of physical blending. The in vitro release study of the 5-fluorouracil-loaded supramolecular gel showed that sustained release profile in acidic condition, suggesting that Q[8]/EBCS gel could be a potential carrier for pH-sensitive drug controlled release system. PMID:23218316

  18. Responsive supramolecular polymer metallogel constructed by orthogonal coordination-driven self-assembly and host/guest interactions.

    PubMed

    Yan, Xuzhou; Cook, Timothy R; Pollock, J Bryant; Wei, Peifa; Zhang, Yanyan; Yu, Yihua; Huang, Feihe; Stang, Peter J

    2014-03-26

    An emerging strategy for the fabrication of advanced supramolecular materials is the use of hierarchical self-assembly techniques wherein multiple orthogonal interactions between molecular precursors can produce new species with attractive properties. Herein, we unify the spontaneous formation of metal-ligand bonds with the host/guest chemistry of crown ethers to deliver a 3D supramolecular polymer network (SPN). Specifically, we have prepared a highly directional dipyridyl donor decorated with a benzo-21-crown-7 moiety that undergoes coordination-driven self-assembly with a complementary organoplatinum acceptor to furnish hexagonal metallacycles. These hexagons subsequently polymerize into a supramolecular network upon the addition of a bisammonium salt due to the formation of [2]pseudorotaxane linkages between the crown ether and ammonium moieties. At high concentrations, the resulting 3D SPN becomes a gel comprising many cross-linked metallohexagons. Notably, thermo- and cation-induced gel-sol transitions are found to be completely reversible, reflecting the dynamic and tunable nature of such supramolecular materials. As such, these results demonstrate the structural complexity that can be obtained when carefully controlling multiple interactions in a hierarchical fashion, in this case coordination and host/guest chemistry, and the interesting dynamic properties associated with the materials thus obtained. PMID:24621148

  19. A pH-Responsive Host-guest Nanosystem Loading Succinobucol Suppresses Lung Metastasis of Breast Cancer

    PubMed Central

    Dan, Zhaoling; Cao, Haiqiang; He, Xinyu; Zhang, Zhiwen; Zou, Lili; Zeng, Lijuan; Xu, Yan; Yin, Qi; Xu, Minghua; Zhong, Dafang; Yu, Haijun; Shen, Qi; Zhang, Pengcheng; Li, Yaping

    2016-01-01

    Cancer metastasis is the leading reason for the high mortality of breast cancer. Herein, we report on a pH-responsive host-guest nanosystem of succinobucol (PHN) with pH-stimuli controlled drug release behavior to improve the therapeutic efficacy on lung metastasis of breast cancer. PHN was composed of the host polymer of β-cyclodextrin linked with multiple arms of N,N-diisopropylethylenediamine (βCD-DPA), the guest polymer of adamantyl end-capped methoxy poly(ethylene glycol) (mPEG-Ad), and the active agent of succinobucol. PHN comprises nanometer-sized homogenous spherical particles, and exhibits specific and rapid drug release in response to the intracellular acidic pH-stimuli. Then, the anti-metastatic efficacy of PHN is measured in metastatic 4T1 breast cancer cells, which effectively confirms the superior inhibitory effects on cell migration and invasion activities, VCAM-1 expression and cell-cell binding of RAW 264.7 to 4T1 cells. Moreover, PHN can be specifically delivered to the sites of metastatic nodules in lungs, and result in an obviously improved therapeutic efficacy on lung metastasis of breast cancer. Thereby, the pH-responsive host-guest nanosystem can be a promising drug delivery platform for effective treatment of cancer metastasis. PMID:26909117

  20. A pH-Responsive Host-guest Nanosystem Loading Succinobucol Suppresses Lung Metastasis of Breast Cancer.

    PubMed

    Dan, Zhaoling; Cao, Haiqiang; He, Xinyu; Zhang, Zhiwen; Zou, Lili; Zeng, Lijuan; Xu, Yan; Yin, Qi; Xu, Minghua; Zhong, Dafang; Yu, Haijun; Shen, Qi; Zhang, Pengcheng; Li, Yaping

    2016-01-01

    Cancer metastasis is the leading reason for the high mortality of breast cancer. Herein, we report on a pH-responsive host-guest nanosystem of succinobucol (PHN) with pH-stimuli controlled drug release behavior to improve the therapeutic efficacy on lung metastasis of breast cancer. PHN was composed of the host polymer of ?-cyclodextrin linked with multiple arms of N,N-diisopropylethylenediamine (?CD-DPA), the guest polymer of adamantyl end-capped methoxy poly(ethylene glycol) (mPEG-Ad), and the active agent of succinobucol. PHN comprises nanometer-sized homogenous spherical particles, and exhibits specific and rapid drug release in response to the intracellular acidic pH-stimuli. Then, the anti-metastatic efficacy of PHN is measured in metastatic 4T1 breast cancer cells, which effectively confirms the superior inhibitory effects on cell migration and invasion activities, VCAM-1 expression and cell-cell binding of RAW 264.7 to 4T1 cells. Moreover, PHN can be specifically delivered to the sites of metastatic nodules in lungs, and result in an obviously improved therapeutic efficacy on lung metastasis of breast cancer. Thereby, the pH-responsive host-guest nanosystem can be a promising drug delivery platform for effective treatment of cancer metastasis. PMID:26909117

  1. [Cs6 Cl][Fe24 Se26 ]: A Host-Guest Compound with Unique Fe-Se Topology.

    PubMed

    Valldor, Martin; Böhme, Bodo; Prots, Yurii; Borrmann, Horst; Adler, Peter; Schnelle, Walter; Watier, Yves; Kuo, Chang Yang; Pi, Tun-Wen; Hu, Zhiwei; Felser, Claudia; Tjeng, Liu Hao

    2016-03-18

    The novel host-guest compound [Cs6 Cl][Fe24 Se26 ] (I4/mmm; a=11.0991(9), c=22.143(2) Å) was obtained by reacting Cs2 Se, CsCl, Fe, and Se in closed ampoules. This is the first member of a family of compounds with unique Fe-Se topology, which consists of edge-sharing, extended fused cubane [Fe8 Se6 Se8/3 ] blocks that host a guest complex ion, [Cs6 Cl](5+) . Thus Fe is tetrahedrally coordinated and divalent with strong exchange couplings, which results in an ordered antiferromagnetic state below TN =221 K. At low temperatures, a distribution of hyperfine fields in the Mössbauer spectra suggests a structural distortion or a complex spin structure. With its strong Fe-Se covalency, the compound is close to electronic itinerancy and is, therefore, prone to exhibit tunable properties. PMID:26879367

  2. Host-Guest Chirality Interplay: A Mutually Induced Formation of a Chiral ZMOF and Its Double-Helix Polymer Guests.

    PubMed

    Luo, Xiaolong; Cao, Yu; Wang, Tao; Li, Guanghua; Li, Jiangang; Yang, Yonggang; Xu, Zhongxuan; Zhang, Jian; Huo, Qisheng; Liu, Yunling; Eddaoudi, Mohamed

    2016-01-27

    A novel homochiral zeolite-like metal-organic framework (ZMOF), [(Cu4I4) (dabco)2][Cu2(bbimb)]3DMF (JLU-Liu23, dabco =1,4-diazabicyclo[2.2.2]-octane, H2bbimb =1,3-bis(2-benzimidazol)benzene, DMF = N,N-dimethylformamide), has been successfully constructed to host unprecedented DNA-like [Cu2(bbimb)]n polymers with double-helicity. The host-guest chirality interplay permitted the induced formation of an unusual gyroid MOF with homochirality and helical channels in the framework for the first time, JLU-Liu23. Importantly, the enantiomeric pairs (23P, 23M) can be promoted and isolated in the presence of appropriate chiral inducing agents, affording enantioselective separation of chiral molecules as well as small gas molecules. PMID:26754145

  3. High Affinity Host-Guest FRET Pair for Single-Vesicle Content-Mixing Assay: Observation of Flickering Fusion Events.

    PubMed

    Gong, Bokyoung; Choi, Bong-Kyu; Kim, Jae-Yeol; Shetty, Dinesh; Ko, Young Ho; Selvapalam, Narayanan; Lee, Nam Ki; Kim, Kimoon

    2015-07-22

    Fluorescence-based single-vesicle fusion assays provide a powerful method for studying mechanisms underlying complex biological processes of SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor)-mediated vesicle fusion and neurotransmitter release. A crucial element of these assays is the ability of the fluorescent probe(s) to reliably detect key intermediate events of fusion pore opening and content release/mixing. Here, we report a new, reliable, and efficient single-vesicle content-mixing assay using a high affinity, fluorophore tagged host-guest pair, cucurbit[7]uril-Cy3 and adamantane-Cy5 as a fluorescence resonance energy transfer (FRET) pair. The power of these probes is demonstrated by the first successful observation of flickering dynamics of the fusion pore by in vitro assay using neuronal SNARE-reconstituted vesicles. PMID:26160008

  4. CO2 captured in zeolitic imidazolate frameworks: Raman spectroscopic analysis of uptake and host-guest interactions.

    PubMed

    Kontos, Athanassios G; Likodimos, Vlassis; Veziri, Charitomeni M; Kouvelos, Evangelos; Moustakas, Nikolaos; Karanikolos, Georgios N; Romanos, George Em; Falaras, Polycarpos

    2014-06-01

    Zeolitic imidazolate frameworks (ZIFs) exhibit enhanced selectivity and increased CO2 uptake due to the incorporation of functional imidazolate units in their structure as well as their extensive porosity and ring flexibility. In?situ Raman investigation of a representative host compound, ZIF-69, in practical CO2 pressure and temperature regimes (0-10?bar and 0-64?C) correlates well with corresponding macroscopic CO2 sorption data and shows clear clear spectroscopic evidence of CO2 uptake. Significant positive shift of the 159?cm(-1) phenyl bending mode of the benzimidazole moiety indicates weak hydrogen bonding with CO2 in the larger cavities of the ZIF matrix. Raman spectroscopy is shown to be an easy and sensitive tool for quantifying CO2 uptake, identifying weak host-guest interactions and elucidating CO2 sorption mechanism in ZIFs. PMID:24687911

  5. A novel, smart microsphere with K(+)-induced shrinking and aggregating properties based on a responsive host-guest system.

    PubMed

    Jiang, Ming-Yue; Ju, Xiao-Jie; Fang, Lu; Liu, Zhuang; Yu, Hai-Rong; Jiang, Lu; Wang, Wei; Xie, Rui; Chen, Qianming; Chu, Liang-Yin

    2014-01-01

    A novel type of smart microspheres with K(+)-induced shrinking and aggregating properties is designed and developed on the basis of a K(+)-recognition host-guest system. The microspheres are composed of cross-linked poly(N-isopropylacrylamide-co-acryloylamidobenzo-15-crown-5) (P(NIPAM-co-AAB15C5)) networks. Due to the formation of stable 2:1 "sandwich-type" host-guest complexes between 15-crown-5 units and K(+) ions, the P(NIPAM-co-AAB15C5) microspheres significantly exhibit isothermally and synchronously K(+)-induced shrinking and aggregating properties at a low K(+) concentration, while other cations (e.g., Na(+), H(+), NH4(+), Mg(2+), or Ca(2+)) cannot trigger such response behaviors. Effects of chemical compositions of microspheres on the K(+)-induced shrinking and aggregating behaviors are investigated systematically. The K(+)-induced aggregating sensitivity of the P(NIPAM-co-AAB15C5) microspheres can be enhanced by increasing the content of crown ether units in the polymeric networks; however, it is nearly not influenced by varying the monomer and cross-linker concentrations in the microsphere preparation. State diagrams of the dispersed-to-aggregated transformation of P(NIPAM-co-AAB15C5) microspheres in aqueous solutions as a function of temperature and K(+) concentration are constructed, which provide valuable information for tuning the dispersed/aggregated states of microspheres by varying environmental K(+) concentration and temperature. The microspheres with synchronously K(+)-induced shrinking and aggregating properties proposed in this study provide a brand-new model for designing novel targeted drug delivery systems. PMID:25325533

  6. Macrocyclic and lantern complexes of palladium(II) with bis(amidopyridine) ligands: synthesis, structure, and host-guest chemistry.

    PubMed

    Yue, Nancy L S; Eisler, Dana J; Jennings, Michael C; Puddephatt, Richard J

    2004-11-29

    The reactions of [PdCl2(NCPh)2] in a 1:1 ratio with the bis(amidopyridine) ligands LL=C6H3(5-R)(1,3-CONH-3-C5H4N)2 with R=H (1a) or R=t-Bu (1b) give the corresponding neutral dipalladium(II) macrocycles trans,trans-[Pd2Cl4(mu-LL)2], 2a and 2b, which crystallize from dimethylformamide with one or two solvent molecules as macrocycle guests. The reaction of [PdCl2(NCPh)2] with LL in a 1:2 ratio gave the cationic lantern complex [Pd2(mu-LL)4]Cl4, 3c (LL=1b), and the reaction in the presence of AgO2CCF3 gave the corresponding trifluoroacetate salts [Pd2(mu-LL)4](CF3CO2)4, 3a (LL=1a) and 3b (LL=1b). These lantern complexes exhibit a remarkable host-guest chemistry, as they can encapsulate cations, anions, and water molecules by interaction of the guest with either the electrophilic NH or the nucleophilic C=O substituents of the amide groups, which can be directed toward the center of the lantern through easy conformational change. The structures of several of these host-guest complexes were determined, and it was found that the cavity size and shape vary according to the ligand conformation, with Pd...Pd separations in the range from 9.45 to 11.95 A. Supramolecular ordering of the lanterns was observed in the solid state, through either hydrogen bonding or secondary bonding to the cationic palladium(II) centers. The selective inclusion by the lantern complexes of alkali metal ions in the sequence Na+ > K+ > Li+ was observed by ESI-MS. PMID:15554632

  7. Emergent ion-gated binding of cationic host-guest complexes within cationic M12L24 molecular flasks.

    PubMed

    Bruns, Carson J; Fujita, Daishi; Hoshino, Manabu; Sato, Sota; Stoddart, J Fraser; Fujita, Makoto

    2014-08-27

    "Molecular flasks" are well-defined supramolecular cages that can encapsulate one or more molecular guests within their cavities and, in so doing, change the physical properties and reactivities of the guests. Although molecular flasks are powerful tools for manipulating matter on the nanoscale, most of them are limited in their scope because of size restrictions. Recently, however, increasingly large and diverse supramolecular cages have become available with enough space in their cavities for larger chemical systems such as polymers, nanoparticles, and biomolecules. Here we report how a class of metallosupramolecular cages known as M12L24 polyhedra have been adapted to serve as nanometer-scale containers for solutions of a pseudorotaxane host-guest complex based on a tetracationic cyclophane host, cyclobis(paraquat-p-phenylene) (CBPQT(4+)), and a 1,5-dioxynaphthalene (DNP) guest. Remarkably, the hierarchical integration of pseudorotaxanes and M12L24 superhosts causes the system to express stimulus-responsive behavior, a property which can be described as emergent because neither the DNP?CBPQT(4+) nor the M12L24 assemblies exhibit this behavior independently. The DNP-containing M12L24 molecular flasks are effectively "sealed off" to CBPQT(4+) until ions are added as a stimulus to "open" them. The electrolyte stimulus reduces the electrostatic screening distance in solution, allowing favorable DNP?CBPQT(4+) host-guest interactions to overcome repulsive Coulombic interactions between the cationic M12L24 cages and CBPQT(4+) rings. This unusual example of ion-gated transport into chemical nanocontainers is reminiscent of transmembrane ion channels which act as gates to the cell, with the important difference that this system is reversible and operates at equilibrium. PMID:25046565

  8. Colorimetric and fluorescent nanofibrous film as a chemosensor for Hg(2+) in aqueous solution prepared by electrospinning and host-guest interaction.

    PubMed

    Wang, Wei; Li, Yapeng; Sun, Mingda; Zhou, Chen; Zhang, Yue; Li, Yaoxian; Yang, Qingbiao

    2012-02-15

    A fluorescent sensing film for Hg(2+) ions was fabricated by host-guest interaction and electrospinning. When the nanofibrous film was put into a solution of Hg(2+) ions, it gave rise to orange fluorescence, causing a clear color change from white to pink-red. PMID:22334338

  9. Host-guest complexation of di-cyclohexanocucurbit[6]uril and hexa-cyclohexanocucurbit[6]uril with alkyldiammonium ions: a comparative study.

    PubMed

    Fang, Guo-Sheng; Sun, Wen-Qi; Zhao, Wen-Xuan; Lin, Rui-Lian; Tao, Zhu; Liu, Jing-Xin

    2015-12-23

    The host-guest complexation of symmetrical di-cyclohexanocucurbit[6]uril (Cy2Q[6]) and hexa-cyclohexanocucurbit[6]uril (Cy6Q[6]) with a series of alkyldiammonium ions (H(3+)N(CH(2))nNH(3+), n = 2-8) has been studied both in solution and in the gas phase. (1)H NMR data indicate that all alkyldiammonium ions have inclusion interactions with both hosts except for the ethanediammonium ion. In addition, if the alkyl chain of the alkyldiammonium ion is longer than n = 5 methylene groups, compressed conformation may occur, which depends on the cavity shape of the hosts and the length of the alkyl chain. Isothermal titration calorimetry (ITC) studies point out that the host-guest complexations of both hosts with the latter five alkyldiammonium ions are enthalpically driven. The comparison of the thermodynamic data reveals that the enthalpies of the van der Waals interactions contribute more to the host-guest complexation enthalpy than the ion-dipole interactions. The enthalpic gain arises from the van der Waals interactions and the reduction of entropy upon the host-guest complexation is strongly affected by the cavity shape of the host. Gas phase structures of long alkyldiammonium guests within both hosts are completely different from those in aqueous solution. PMID:26551664

  10. Synthesis and Small Molecule Exchange Studies of a Magnesium Bisformate Metal-Organic Framework: An Experiment in Host-Guest Chemistry for the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Rood, Jeffrey A.; Henderson, Kenneth W.

    2013-01-01

    concepts of host-guest chemistry and size exclusion in porous metal-organic frameworks (MOFs). The experiment has been successfully carried out in both introductory and advanced-level inorganic chemistry laboratories. Students synthesized the porous MOF, alpha-Mg[subscript

  11. Synthesis and Small Molecule Exchange Studies of a Magnesium Bisformate Metal-Organic Framework: An Experiment in Host-Guest Chemistry for the Undergraduate Laboratory

    ERIC Educational Resources Information Center

    Rood, Jeffrey A.; Henderson, Kenneth W.

    2013-01-01

    concepts of host-guest chemistry and size exclusion in porous metal-organic frameworks (MOFs). The experiment has been successfully carried out in both introductory and advanced-level inorganic chemistry laboratories. Students synthesized the porous MOF, alpha-Mg[subscript…

  12. Visual determination of aliphatic diamines based on host-guest recognition of calix[4]arene derivatives capped gold nanoparticles.

    PubMed

    Chen, Yangyang; Zhang, Jiangjiang; Gao, Yanmin; Lee, Jaebeom; Chen, Hongxia; Yin, Yongmei

    2015-10-15

    Since amine compounds have been widespread pollutants in nature and they are extensively used in pharmaceutical industries and dye manufacturing, it is highly desirable to develop simple, effective and naked-eye available analytical methods for such aliphatic diamines determination. Calixarenes as macrocycles have drawn intensive interests for fields such as biomedicine, supramolecular chemistry and smart materials. Here, instead of the normal complicated modification strategy, a facile and efficient method for one-pot synthesis of calix[4]arene crown ether (CCE4) capped gold nanoparticles (AuNPs) is proposed. The as-prepared CCE4-AuNPs are not only high water dispersity and stability even after storage for 3 months, but also capable of host-guest recognition of diamines in aqueous systems. Size-selective encapsulation of amine group between CCE4 and diamines carry out the aggregation of CCE4-AuNPs. The determination of diamines such as hexamethylenediamine or spermine can be realized by the UV-vis absorbance change and visual color difference. PMID:26002014

  13. Self-assembly and host-guest interaction of metallomacrocycles using fluorescent dipyrazole linker with dimetallic clips.

    PubMed

    Ning, Guo-Hong; Yao, Liao-Yuan; Liu, Li-Xia; Xie, Ting-Zheng; Li, Yi-Zhi; Qin, Yu; Pan, Yuan-Jiang; Yu, Shu-Yan

    2010-09-01

    By employing diimine ligands coordinated dimetallic clips ([(bpy)2Pd2(NO3)2](NO3)2 or [(phen)2Pd2(NO3)2](NO3)2, where bpy = 2,2?-bipyridine, phen = 1,10-phenanthroline) as the corner and anthracene-, naphthalene-, and benzene-based dipyrazolate dianions as the linker, a series of positively charged metallomacrocycles ([M4L2]4+ or [M8L4]8+) have been synthesized through a directed self-assembly method in aqueous solution. Every macrocycle has a cavity to bind solvent molecules or anions. The structures were characterized by elemental analysis, 1H and 13C NMR, electrospray ionization mass spectrometry, and single crystal X-ray diffraction analysis for compound 1 x 4 PF6(-) (1 = {[(bpy)Pd]4L(1)2}4+), 3 x 4 PF6(-) x 8 CH3CN x H2O (3 = {[(bpy)Pd]4L(2)2}4+), and 7 x 4 PF6(-) x 6 H2O (7 = {[(bpy)Pd]4L(5)2}4+). The 1:1 host-guest complexation for anthracene-based dipyrazolate-bridged macrocycles with aromatic guests was investigated via UV-vis and fluorescent titration. PMID:20690696

  14. pH-Responsive Poly(ethylene glycol)/Poly(L-lactide) Supramolecular Micelles Based on Host-Guest Interaction.

    PubMed

    Zhang, Zhe; Lv, Qiang; Gao, Xiaoye; Chen, Li; Cao, Yue; Yu, Shuangjiang; He, Chaoliang; Chen, Xuesi

    2015-04-29

    pH-responsive supramolecular amphiphilic micelles based on benzimidazole-terminated poly(ethylene glycol) (PEG-BM) and β-cyclodextrin-modified poly(L-lactide) (CD-PLLA) were developed by exploiting the host-guest interaction between benzimidazole (BM) and β-cyclodextrin (β-CD). The dissociation of the supramolecular micelles was triggered in acidic environments. An antineoplastic drug, doxorubicin (DOX), was loaded into the supramolecular micelles as a model drug. The release of DOX from the supramolecular micelles was clearly accelerated as the pH was reduced from 7.4 to 5.5. The DOX-loaded PEG-BM/CD-PLLA supramolecular micelles displayed an enhanced intracellular drug-release rate in HepG2 cells compared to the pH-insensitive DOX-loaded PEG-b-PLLA counterpart. After intravenous injection into nude mice bearing HepG2 xenografts by the tail vein, the DOX-loaded supramolecular micelles exhibited significantly higher tumor inhibition efficacy and reduced systemic toxicity compared to free DOX. Furthermore, the DOX-loaded supramolecular micelles showed a blood clearance rate markedly lower than that of free DOX and comparable to that of the DOX-loaded PEG-b-PLLA micelles after intravenous injection into rats. Therefore, the pH-responsive PEG-BM/CD-PLLA supramolecular micelles hold potential as a smart nanocarrier for anticancer drug delivery. PMID:25856564

  15. Photofunctional host-guest hybrid materials and thin films of lanthanide complexes covalently linked to functionalized zeolite A.

    PubMed

    Hao, Ji-Na; Yan, Bing

    2014-02-21

    Eight host-guest assemblies of zeolite A (ZA) and their thin films have been synthesized. The assembly of zeolite A was prepared by first embedding lanthanide complexes (Eu(TTA)n or Tb(TAA)n) into the cages of zeolite A and then grafting lanthanide complexes (Eu(L) or Tb(L), L = bipy or phen) onto the surface of functionalized zeolite A via 3-(methacryloyloxy)propyltrimethoxysilane (?-MPS). The obtained organic-inorganic hybrid materials were investigated by means of XRD, FT-IR, SEM and luminescence spectroscopy. Firstly, the dependence of the crystal stability of zeolite A as the host of lanthanide complexes on the level of ion exchange was studied by XRD. The results indicated the degradation and partial collapse of zeolite A framework occurred upon doping with high amounts of lanthanide complexes into its channels. The integrity of zeolite A's framework was well maintained after fabrication through careful control of the ion-exchange extent. Secondly, the thin films of zeolite A assemblies obtained this way have the properties of homogeneous dense packing and a high degree of coverage of the crystals on the ITO glass, as shown in SEM images. Thirdly, the luminescence behavior of all the materials were investigated in detail. Among them, four white light-emitting materials from a three-component system that comprises a blue-emitting zeolite A matrix, a red-emitting europium complex and a green-emitting terbium complex were obtained. PMID:24336874

  16. Experimental results from host-guest complexes for the design of effectors in biological systems and of enzyme analogous catalysts.

    PubMed

    Schneider, H J; Eblinger, F; Sartorius, J; Rammo, J

    1996-01-01

    Strategies and results for the extraction of biologically important non-covalent binding increments from studies of synthetic host-guest complexes are described with selected examples. Systematic analyses of association constants and the corresponding complex conformation in solution allows us to assign specific values to different pairwise interactions, including salt bridges, amide-type hydrogen bonds, van der Waals effects, and metal ion interactions. A comparison of association constants between selected flexible and rigid ion pairs shows few differences, indicating that different entropy contributions either are small, or cancel with corresponding enthalpy changes, at least in weakly bound complexes. The supramolecular design of enzyme-analogous catalysts is illustrated with complexes containing, e.g. strongly bound yet still active Ln3+ ions, e.g. in an azacrown ether, and groups which support association with nucleic acids and can serve as nucleophiles. The experimentally observed hydrolysis rate enhancements with such artificial nucleases amount to 10(6) and more, both with phenyl phosphates and with ds-DNA. PMID:8877803

  17. Two-dimensional self-assemblies of telechelic organic compounds: structure and surface host-guest chemistry.

    PubMed

    Yan, Hui-Juan; Liu, Jia; Wang, Dong; Wan, Li-Jun

    2013-10-13

    Guiding the self-assembly of different types of functional molecules into well-defined structures on surfaces is beneficial for both fundamental surface and interface study and emerging application fields, especially molecular and organic electronics. This review focuses on understanding the two-dimensional self-assembly process of telechelic organics, which feature alkoxylene chains terminated with carboxyl groups. With the combined flexibility of alkyl chains and directionality of carboxyl groups, telechelic organics show unique assembly behaviour on two-dimensional surfaces. By increasing the length of the alkoxylene chains, the cavities in the nanoporous networks of telechelic trimesic acid (1,3,5-benzene tricarboxylic acid) derivatives change from hexagonal cavities to irregular cavities on a highly oriented pyrolytic graphite surface. The nanoporous networks provide a flexible host template for host-guest supramolecular chemistry because the cavities framed by the flexible alkoxylene chains can be changed in accordance with the sizes/shapes of the guest molecules. Furthermore, the terminal carboxylic group can form a hydrogen bond with another hydrogen bond partner, leading to multi-component structural motifs and hierarchical assemblies. The unique assembly behaviour of telechelic organics makes them promising structures as important building blocks for the design and construction of complex self-assembled nanoarchitectures. PMID:24000354

  18. Polymers with customizable optical and rheological properties based on an epoxy acrylate based host-guest system

    NASA Astrophysics Data System (ADS)

    Gleiβner, U.; Hobmaier, J.; Hanemann, T.

    2015-09-01

    We report an easy way to tune the optical refractive index and viscosity of an epoxy acrylate-based host-guest system which can be used for the fabrication of optical waveguides. This allows fast and precise modification of the material system for different replication methods like hot embossing, inkjet printing or spin coating. To modify the refractive index n, an electron-rich organic dopant such as phenanthrene is added to a commercially available reactive polymer based resin. Moreover, changes in viscosity can be achieved by using a comonomer with suitable properties like benzyl methacrylate (BMA). We used a commercially available UV-curable epoxy acrylate based polymer matrix to investigate both the influence of phenanthrene and of benzyl methacrylate. First, mixtures of the pure polymer and benzyl methacrylate with a ratio of 30, 50, and 80 wt% benzyl methacrylate were produced. Second, phenanthrene was added with 5 and 10 wt%, respectively. All components were mixed and then polymerized by UV-irradiation and with a thermal postcure. The viscosity of the mixtures decreased at 20C linearly from 1.5 Pas (30 wt%) to 8 mPas (80 wt%), whereas the refractive index decreased at the same time by a small amount from 1.570 to 1.568 (@589 nm, 20 C). By adding phenanthrene refractive index increased to a maximum of n = 1.586 (50 wt% BMA, 10 wt% phenanthrene). Abbe numbers for the compositions without phenanthrene ranged from 35 to 38.

  19. Enhanced photoelectrochemical water splitting efficiency of a hematite-ordered Sb:SnO2 host-guest system.

    PubMed

    Wang, Lei; Palacios-Padrs, Anna; Kirchgeorg, Robin; Tighineanu, Alexei; Schmuki, Patrik

    2014-02-01

    Host-guest systems such as hematite/SnO2 have attracted a great deal of interest as photoanodes for photoelectrochemical water splitting. In the present work we form an ordered porous tin oxide layer formed by self-organizing anodization of Sn films on a FTO substrate. Subsequently the anodic tin oxide nanostructure is doped with antimony (ATO) by a simple impregnation and annealing treatment, and then decorated with hematite using anodic deposition. Photoelectrochemical water splitting experiments show that compared to conventional SnO2 nanostructures, using a Sb doped nanochannel SnO2 as a host leads to a drastic increase of the water splitting photocurrent response up to 1.5 mA cm(-2) at 1.6 V (vs. RHE) in 1 M KOH under AM 1.5 (100 mW cm(-2) ) conditions compared to 0.04 mA cm(-2) for the non-Sb doped SnO2 scaffold. PMID:24449523

  20. Host-guest chemistry for tuning colloidal solubility, self-organization and photoconductivity of inorganic-capped nanocrystals.

    PubMed

    Bodnarchuk, Maryna I; Yakunin, Sergii; Piveteau, Laura; Kovalenko, Maksym V

    2015-01-01

    Colloidal inorganic nanocrystals (NCs), functionalized with inorganic capping ligands, such as metal chalcogenide complexes (MCCs), have recently emerged as versatile optoelectronic materials. As-prepared, highly charged MCC-capped NCs are dispersible only in highly polar solvents, and lack the ability to form long-range ordered NC superlattices. Here we report a simple and general methodology, based on host-guest coordination of MCC-capped NCs with macrocyclic ethers (crown ethers and cryptands), enabling the solubilization of inorganic-capped NCs in solvents of any polarity and improving the ability to form NC superlattices. The corona of organic molecules can also serve as a convenient knob for the fine adjustment of charge transport and photoconductivity in films of NCs. In particular, high-infrared-photon detectivities of up to 3.3 × 10(11) Jones with a fast response (3 dB cut-off at 3 kHz) at the wavelength of 1,200 nm were obtained with films of PbS/K3AsS4/decyl-18-crown-6 NCs. PMID:26647828

  1. Host-guest chemistry for tuning colloidal solubility, self-organization and photoconductivity of inorganic-capped nanocrystals

    NASA Astrophysics Data System (ADS)

    Bodnarchuk, Maryna I.; Yakunin, Sergii; Piveteau, Laura; Kovalenko, Maksym V.

    2015-12-01

    Colloidal inorganic nanocrystals (NCs), functionalized with inorganic capping ligands, such as metal chalcogenide complexes (MCCs), have recently emerged as versatile optoelectronic materials. As-prepared, highly charged MCC-capped NCs are dispersible only in highly polar solvents, and lack the ability to form long-range ordered NC superlattices. Here we report a simple and general methodology, based on host-guest coordination of MCC-capped NCs with macrocyclic ethers (crown ethers and cryptands), enabling the solubilization of inorganic-capped NCs in solvents of any polarity and improving the ability to form NC superlattices. The corona of organic molecules can also serve as a convenient knob for the fine adjustment of charge transport and photoconductivity in films of NCs. In particular, high-infrared-photon detectivities of up to 3.3 × 1011 Jones with a fast response (3 dB cut-off at 3 kHz) at the wavelength of 1,200 nm were obtained with films of PbS/K3AsS4/decyl-18-crown-6 NCs.

  2. Empirical and theoretical insights into the structural features and host-guest chemistry of M8L4 tube architectures.

    PubMed

    Meng, Wenjing; League, Aaron B; Ronson, Tanya K; Clegg, Jack K; Isley, William C; Semrouni, David; Gagliardi, Laura; Cramer, Christopher J; Nitschke, Jonathan R

    2014-03-12

    We demonstrate a general method for the construction of M8L4 tubular complexes via subcomponent self-assembly, starting from Cu(I) or Ag(I) precursors together with suitable elongated tetraamine and 2-formylpyridine subcomponents. The tubular architectures were often observed as equilibrium mixtures of diastereomers having two different point symmetries (D2d or D2 ⇄ D4) in solution. The equilibria between diastereomers were influenced through variation in ligand length, substituents, metal ion identity, counteranion, and temperature. In the presence of dicyanoaurate(I) and Au(I), the D4-symmetric hosts were able to bind linear Au(Au(CN)2)2(-) (with two different configurations) as the best-fitting guest. Substitution of dicyanoargentate(I) for dicyanoaurate(I) resulted in the formation of Ag(Au(CN)2)2(-) as the optimal guest through transmetalation. Density functional theory was employed to elucidate the host-guest chemistries of the tubes. PMID:24446911

  3. Visible light-driven water oxidation promoted by host-guest interaction between photosensitizer and catalyst with a high quantum efficiency.

    PubMed

    Li, Hua; Li, Fei; Zhang, Biaobiao; Zhou, Xu; Yu, Fengshou; Sun, Licheng

    2015-04-01

    A highly active supramolecular system for visible light-driven water oxidation was developed with cyclodextrin-modified ruthenium complex as the photosensitizer, phenyl-modified ruthenium complexes as the catalysts, and sodium persulfate as the sacrificial electron acceptor. The catalysts were found to form 1:1 host-guest adducts with the photosensitizer. Stopped-flow measurement revealed the host-guest interaction is essential to facilitate the electron transfer from catalyst to sensitizer. As a result, a remarkable quantum efficiency of 84% was determined under visible light irradiation in neutral aqueous phosphate buffer. This value is nearly 1 order of magnitude higher than that of noninteraction system, indicating that the noncovalent incorporation of sensitizer and catalyst is an appealing approach for efficient conversion of solar energy into fuels. PMID:25799114

  4. Molecular host-guest energy-transfer system with an ultralow amplified spontaneous emission threshold employing an ambipolar semiconducting host matrix.

    PubMed

    Toffanin, Stefano; Capelli, Raffaella; Hwu, Tsyr-Yuan; Wong, Ken-Tsung; Pltzing, Tobias; Frst, Michael; Muccini, Michele

    2010-01-14

    We report on the characteristics of a host-guest lasing system obtained by coevaporation of an oligo(9,9-diarylfluorene) derivative named T3 with the red-emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (DCM). We demonstrate that the ambipolar semiconductor T3 can be implemented as an active matrix in the realization of a host-guest system in which an efficient energy transfer takes place from the T3 matrix to the lasing DCM molecules. We performed a detailed spectroscopic study on the system by systematically varying the DCM concentration in the T3 matrix. Measurements of steady-state photoluminescence (PL), PL quantum yield (PLQY), time-resolved picosecond PL, and amplified spontaneous emission (ASE) threshold are used to optimize the acceptor concentration at which the ASE from DCM molecules takes place with the lowest threshold. The sample with a DCM relative deposition ratio of 2% shows an ASE threshold as low as 0.6 kW/cm(2) and a net optical gain measured by femtosecond time-resolved pump-and-probe spectroscopy as high as 77 cm(-1). The reference model system Alq(3):DCM sample measured in exactly the same experimental conditions presents an one-order-of-magnitude higher ASE threshold. The ASE threshold of T3:DCM is the lowest reported to date for a molecular host-guest energy-transfer system, which makes the investigated blend an appealing system for use as an active layer in lasing devices. In particular, the ambipolar charge transport properties of the T3 matrix and its field-effect characteristics make the host-guest system presented here an ideal candidate for the realization of electrically pumped organic lasers. PMID:19961197

  5. Synthesis, Structural Characterization, and Host-Guest Studies of Aminoquinonato-Bridged Re(I) Supramolecular Rectangles.

    PubMed

    Govindarajan, R; Nagarajaprakash, R; Manimaran, Bala

    2015-11-16

    Aminoquinonato bridged Re(I)-based metallarectangles have been constructed via an orthogonal bonding approach. Self-assembly of Re2(CO)10 and aminoquinone ligands in the presence of ditopic linear pyridyl ligands has resulted in the formation of metallarectangles of the general formula [{(CO)3Re(?-?(4)-L)Re(CO)3}2(?-N-L'-N)2] (1-4), wherein 1, L = 2,5-bis(n-butylamino)-1,4-benzoquinonato (bbbq) and N-L'-N = 4,4'-bipyridine (bpy); 2, L = 2,5-bis(phenethylamino)-1,4-benzoquinonato (bpbq) and N-L'-N = 4,4'-bipyridine; 3, L = 2,5-bis(n-butylamino)-1,4-benzoquinonato (bbbq) and N-L'-N = trans-1,2-bis(4-pyridyl)ethylene (bpe) and 4, L = 2,5-bis(phenethylamino)-1,4-benzoquinonato (bpbq) and N-L'-N = trans-1,2-bis(4-pyridyl)ethylene (bpe). Metallarectangles 1-4 have been characterized by elemental analysis, IR, NMR, and UV-vis absorption spectroscopic techniques. The molecular structures of 1 and 4 were determined by single-crystal X-ray diffraction methods. The molecular recognition capability of 1 and 3 with pyrene and triphenylene has been investigated using UV-vis absorption and emission spectroscopic techniques. The formation of host-guest complex has been further corroborated by the single-crystal X-ray structural evidence of carceplex system (3?pyrene)(DMF). PMID:26528890

  6. Dendrimeric ?-cyclodextrin/Gd(III) chelate supramolecular host-guest adducts as high-relaxivity MRI probes.

    PubMed

    Martinelli, Jonathan; Thangavel, Kalaivani; Tei, Lorenzo; Botta, Mauro

    2014-08-25

    We have synthesized a new macromolecular architecture, (PAMAM)-CD8 , which consists of eight ?-cyclodextrin units (?-CD) attached to a generation?1 poly(amidoamine) (PAMAM) dendrimer through a disulfide bond, which can be cleaved under reducing conditions. This system shows a pronounced hosting capability towards Gd(III) chelates functionalized with hydrophobic groups, thus leading to well-defined supramolecular adducts. (1)H?NMR relaxometric investigations were carried out to follow the formation of adducts with three Gd(III) chelates based on the ligand architectures of 6-amino-6-methylperhydro-1,4-diazepinetetraacetic acid (AAZTA) or 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) suitably functionalized with benzyl or adamantyl (Ad) pendant groups. In particular, the ditopic complex composed of two AAZTA chelating units connected to a central aromatic ring that bears an adamantyl group showed a strong affinity (ca.?10(6) ?M(-1)) for the CD units of the dendrimer, which is two orders of magnitude higher than toward human serum albumin (HSA). Remarkable relaxivity enhancements (i.e., up to 71% at 1?T and 25?C) were observed upon the formation of the macromolecular host-guest adducts due to a decrease in the molecular tumbling rate and fast water-exchange. Reduction experiments and competition studies between the paramagnetic dendrimer and HSA were carried out by relaxometric techniques. The results show that the metal complexes are not displaced by the protein, thus suggesting that this novel macromolecular probe is potentially suitable for applications in vivo. PMID:24827137

  7. Anomalous cage effect of the excited state dynamics of catechol in the 18-crown-6-catechol host-guest complex.

    PubMed

    Morishima, Fumiya; Kusaka, Ryoji; Inokuchi, Yoshiya; Haino, Takeharu; Ebata, Takayuki

    2015-02-12

    We determined the number of isomers and their structures for the 18-crown-6 (18C6)-catechol host-guest complex, and examined the effect of the complex formation on the S1 ((1)??*) dynamics of catechol under a supersonically cooled gas phase condition and in cyclohexane solution at room temperature. In the gas phase experiment, UV-UV hole-burning spectra of the 18C6-catechol 1:1 complex indicate that there are three stable isomers. For bare catechol, it has been reported that two adjacent OH groups have an intramolecular hydrogen (H) bond. The IR-UV double resonance spectra show two types of isomers in the 18C6-catechol 1:1 complex; one of the three 18C6-catechol 1:1 isomers has the intramolecular H-bond between the two OH groups, while in the other two isomers the intramolecular H-bond is broken and the two OH groups are H-bonded to oxygen atoms of 18C6. The complex formation with 18C6 substantially elongates the S1 lifetime from 7 ps for bare catechol and 2.0 ns for the catechol-H2O complex to 10.3 ns for the 18C6-catechol 1:1 complex. Density functional theory calculations of the 18C6-catechol 1:1 complex suggest that this elongation is attributed to a larger energy gap between the S1 ((1)??*) and (1)??* states than that of bare catechol or the catechol-H2O complex. In cyclohexane solution, the enhancement of the fluorescence intensity of catechol was found by adding 18C6, due to the formation of the 18C6-catechol complex in solution, and the complex has a longer S1 lifetime than that of catechol monomer. From the concentration dependence of the fluorescence intensity, we estimated the equilibrium constant K for the 18C6 + catechol ? 18C6-catechol reaction. The obtained value (log K = 2.3) in cyclohexane is comparable to those for alkali metal ions or other molecular ions, indicating that 18C6 efficiently captures catechol in solution. Therefore, 18C6 can be used as a sensitive sensor of catechol derivatives in solution with its high ability of fluorescence enhancement. PMID:25350575

  8. Cage effects on conformational preference and photophysics in the host-guest complex of benzenediols with 18-Crown-6.

    PubMed

    Morishima, Fumiya; Kusaka, Ryoji; Inokuchi, Yoshiya; Haino, Takeharu; Ebata, Takayuki

    2016-03-01

    The conformational preference and modification of photophysics of benzenediols, namely hydroquinone (HQ), resorcinol (RE) and catechol (CA), upon host-guest complex formation with 18-Crown-6 (18C6) have been investigated, under supersonically jet-cooled conditions. Laser induced fluorescence (LIF) and UV-UV hole-burning spectra indicate the presence of two conformers for HQ and RE and one conformer for CA. On the other hand, the number of isomers is reduced to one in the 18C6·HQ and 18C6·RE complexes, while the 18C6·CA complex has three stable isomers. The IR spectra of the OH stretching vibration reveal that the two OH groups are H-bonded in 18C6·CA and 18C6·RE. In 18C6·RE, RE adopts the highest energy conformation in the bare form. In 18C6·HQ, the H-bonding of one OH group affects the orientation of the other OH group. The complex formation changes the photophysics of the S1 state of the benzenediols in a different manner. In our previous work, we reported a remarkable S1 lifetime elongation in 18C6·CA complexes; the S1 lifetime of CA is elongated more than 1000 times longer (8 ps → 10.3 ns) in 18C6·CA (F. Morishima et al., J. Phys. Chem. B, 2015, 119, 2557-2565), which we called the "cage effect". In 18C6·RE, the increase of S1 lifetime is moderate: 4.0 ns (monomer) → 10.5 ns (complex). On the other hand, the S1 lifetime of HQ is shortened in 18C6·HQ: 2.6 ns (monomer) → 0.54 ns (complex). Density functional theory (DFT) calculations suggest that these behaviors are related to the S1 ((1)ππ*)-(1)πσ* energy gap, the character of the S2 state and the symmetry of benzenediol. These experimental results clearly show the potential ability of 18C6 to control the conformation and modification of the electronic structure of guest species. PMID:26924038

  9. Photoinduced charge carrier dynamics of Zn-porphyrin-TiO2 electrodes: the key role of charge recombination for solar cell performance.

    PubMed

    Imahori, Hiroshi; Kang, Soonchul; Hayashi, Hironobu; Haruta, Mitsutaka; Kurata, Hiroki; Isoda, Seiji; Canton, Sophie E; Infahsaeng, Yingyot; Kathiravan, Arunkumar; Pascher, Torbjörn; Chábera, Pavel; Yartsev, Arkady P; Sundström, Villy

    2011-04-28

    Time resolved absorption spectroscopy has been used to study photoinduced electron injection and charge recombination in Zn-porphyrin sensitized nanostructured TiO(2) electrodes. The electron transfer dynamics is correlated to the performance of dye sensitized solar cells based on the same electrodes. We find that the dye/semiconductor binding can be described with a heterogeneous geometry where the Zn-porphyrin molecules are attached to the TiO(2) surface with a distribution of tilt angles. The binding angle determines the porphyrin-semiconductor electron transfer distance and charge transfer occurs through space, rather than through the bridge connecting the porphyrin to the surface. For short sensitization times (1 h), there is a direct correlation between solar cell efficiency and amplitude of the kinetic component due to long-lived conduction band electrons, once variations in light harvesting (surface coverage) have been taken into account. Long sensitization time (12 h) results in decreased solar cell efficiency because of decreased efficiency of electron injection. PMID:20961148

  10. Theoretical exploration of the nanoscale host-guest interactions between [n]cycloparaphenylenes (n = 10, 8 and 9) and fullerene C??: from single- to three-potential well.

    PubMed

    Yuan, Kun; Zhou, Cai-Hua; Zhu, Yuan-Cheng; Zhao, Xiang

    2015-07-28

    The nanoscale host-guest interactions between [n]cycloparaphenylene ([n]CPP; n = 10, 8 and 9) nano-ring and fullerene C60 were explored theoretically. It is found that relatively small variations in the sizes of the [n]CPP host lead to very significant changes in encapsulation property toward the fullerene C60 guest. Expectedly, one stable inclusion-configuration of [10]CPP?C60 and one floating-configuration of [8]CPP?C60 are located on the potential surfaces of the two complexes, respectively. Unexpectedly, besides a floating-configuration (F-[9]CPP?C60), another stable inclusion-configuration (I-[9]CPP?C60) is also located on the potential surface of [9]CPP?C60 host-guest complex. Interaction energies and natural steric analysis show that these complexes are stabilized by balancing concave-convex ?-? attractive and steric repulsive host-guest interactions. In contrast, the steric repulsive energy (Es) between host and guest of I-[9]CPP?C60 is as high as 233.12 kJ mol(-1), which is much larger than those in other complexes. The movements of C60 guest through the cavities of [n]CPP host (n = 10, 8 and 9) are simulated by calculating the energy profile, and the results interestingly reveal that the encapsulation of C60 by [10]CPP is in the manner of a single-potential well, by [8]CPP in the manner of a double-potential well, and by [9]CPP in the special manner of a three-potential well. We predict that the movement of C60 guest through the cavity of [9]CPP host should be experimentally observable owing to the relatively low energy barrier (<50 kJ mol(-1), M06-2X/6-31G(d)). Charge population analysis shows that an obvious charge transfer between host and guest takes place during the formation of I-[9]CPP?C60, which is different from those during the formation of [8]CPP?C60, [10]CPP?C60 and F-[9]CPP?C60. Additionally, the host-guest interaction regions were detected and visualized in real space based on the electron density and reduced density gradient. PMID:26121936

  11. Supramolecular side-chain poly[2]pseudorotaxanes formed by orthogonal coordination-driven self-assembly and crown-ether-based host-guest interactions.

    PubMed

    Xing, Hao; Wei, Peifa; Yan, Xuzhou

    2014-06-01

    The themes of coordination-driven self-assembly, host-guest interactions, and supramolecular polymerization are unified in an orthogonal noninterfering fashion to deliver side-chain poly[2]pseudorotaxanes. Specifically, a bis(p-phenylene)-34-crown-10 derivative 1 bearing two pyridyl groups polymerizes into a side-chain poly[2]pseudorotaxane upon the addition of di-Pt(II) acceptor 4 in the presence of paraquat. Interestingly, by adding a competitive guest 3, the poly[2]pseudorotaxane can realize a conversion in one pot. PMID:24819441

  12. Supramolecular host-guest interaction of trityl-nitroxide biradicals with cyclodextrins: modulation of spin-spin interaction and redox sensitivity.

    PubMed

    Tan, Xiaoli; Song, Yuguang; Liu, Huiqiang; Zhong, Qinwen; Rockenbauer, Antal; Villamena, Frederick A; Zweier, Jay L; Liu, Yangping

    2016-01-27

    Supramolecular host-guest interactions of trityl-nitroxide (TN) biradicals CT02-VT, CT02-AT and CT02-GT with methyl-?-cyclodextrin (M-?-CD), hydroxypropyl-?-cyclodextrin (H-?-CD) and ?-cyclodextrin (?-CD) were investigated by EPR spectroscopy. In the presence of cyclodextrins (i.e., ?-CD, M-?-CD and H-?-CD), host-guest complexes of CT02-VT are formed where the nitroxide and linker parts possibly interact with the cyclodextrins' cavities. Complexation with cyclodextrins leads to suppression of the intramolecular through-space spin-spin exchange coupling in CT02-VT, thus allowing the determination of the through-bond spin-spin exchange coupling which was calculated to be 1.6 G using EPR simulations. Different types of cyclodextrins have different binding affinities with CT02-VT in the order of ?-CD (95 M(-1)) > M-?-CD (70 M(-1)) > H-?-CD (32 M(-1)). In addition, the effect of the linkers in TN biradicals on the host-guest interactions was also investigated. Among the three TN biradicals studied, CT02-VT has the highest association constant with one designated cyclodextrin derivative. On the other hand, the complexes of CT02-GT (?22 G) and CT02-AT (7.7-9.0 G) with cyclodextrins have much higher through-bond spin-spin exchange couplings than those of CT02-VT (1.6 G) due to the shorter linkers than those of CT02-VT. Furthermore, the stability of TN biradicals towards ascorbate was significantly enhanced after the complexation with CDs, with an almost 2-fold attenuation of the second-order rate constants for all the biradicals. Therefore, the supramolecular host-guest interactions with cyclodextrins will be an alternative method to modulate the magnitude of the spin-spin interactions and redox sensitivity of TN biradicals, and the resulting complexes are promising as highly efficient DNP polarizing agents as well as EPR redox probes. PMID:26700002

  13. Tuning excited-state proton transfer dynamics of a 3-hydroxychromone dye in supramolecular complexes via host-guest steric compatibility.

    PubMed

    Das, Ranjan; Duportail, Guy; Ghose, Avisek; Richert, Ludovic; Klymchenko, Andrey; Chakraborty, Sandipan; Yesylevskyy, Semen; Mely, Yves

    2014-01-14

    The photophysics of 2-(2'-benzofuryl)-3-hydroxychromone (BFHC) is remarkably modulated in its complexes with macrocyclic hosts such as ?-cyclodextrin (?-CD), hydroxypropyl-?-cyclodextrin (HP-?-CD) and methyl-?-cyclodextrin (M-?-CD). BFHC exhibits dual emission bands, attributable to excited normal (N*) and tautomer (T*) forms, where the latter originates from the former through an excited-state intramolecular proton transfer (ESIPT) reaction. Fluorescence lifetimes of the tautomer, along with the intensity ratio (IT*/IN*) of the dual emission bands, and the fluorescence quantum yield (?) of the dye, increase significantly in the order ?-CD < HP-?-CD < M-?-CD to indicate increasing hydrophobicity of the dye environment in the host CD cavity. In accordance with this increasing hydrophobicity of the dye environment, the ESIPT dynamics of BFHC becomes increasingly fast in the host cavity in the order ?-CD < HP-?-CD < M-?-CD. Binding constant data and molecular modeling studies indicate that the increasing order of the faster ESIPT dynamics originates from an increasingly tight host-guest spatial fit, which causes increasingly strong dehydration of the BFHC dye. Steric compatibility in size and shape between the host cavity and the guest, which modulates the tightness of the host-guest spatial fit and hence the extent of hydration, is a key factor for tuning the proton transfer dynamics since water molecules perturb the ESIPT reaction and quench the fluorescence of BFHC. PMID:24276115

  14. Influence of Equilibration Time in Solution on the Inclusion/Exclusion Topology Ratio of Host-Guest Complexes Probed by Ion Mobility and Collision-Induced Dissociation.

    PubMed

    Carroy, Glenn; Daxhelet, Charlotte; Lemaur, Vincent; De Winter, Julien; De Pauw, Edwin; Cornil, Jérôme; Gerbaux, Pascal

    2016-03-18

    Host-guest complexes are formed by the creation of multiple noncovalent bonds between a large molecule (the host) and smaller molecule(s) or ion(s) (the guest(s)). Ion-mobility separation coupled with mass spectrometry nowadays represents an ideal tool to assess whether the host-guest complexes, when transferred to the gas phase upon electrospray ionization, possess an exclusion or inclusion nature. Nevertheless, the influence of the solution conditions on the nature of the observed gas-phase ions is often not considered. In the specific case of inclusion complexes, kinetic considerations must be taken into account beside thermodynamics; the guest ingression within the host cavity can be characterized by slow kinetics, which makes the complexation reaction kinetically driven on the timescale of the experiment. This is particularly the case for the cucurbituril family of macrocyclic host molecules. Herein, we selected para-phenylenediamine and cucurbit[6]uril as a model system to demonstrate, by means of ion mobility and collision-induced dissociation measurements, that the inclusion/exclusion topology ratio varies as a function of the equilibration time in solution prior to the electrospray process. PMID:26880721

  15. ?-cyclodextrin-ferrocene host-guest complex multifunctional labeling triple amplification strategy for electrochemical immunoassay of subgroup J of avian leukosis viruses.

    PubMed

    Shang, Kun; Wang, Xindong; Sun, Bing; Cheng, Ziqiang; Ai, Shiyun

    2013-07-15

    A novel sandwich-type electrochemical immunosensor was fabricated for ultrasensitive detection of subgroup J of avian leukosis virus (ALVs-J) by employing ?-cyclodextrin-ferrocene (CD-Fc) host-guest complex multifunctional Fe3O4 nanospheres as labels and ?-cyclodextrin functional graphene sheets (CD-GS) nanocomposite as sensor platform. The sensitivity was greatly improved based on the triple amplification strategy. Firstly, the CD-GS improved the electron transfer rate as well as increasing the surface area to capture a large amount of primary antibodies (Ab1). Secondly, the CD on the Fe3O4 surface with strong recognition capability could form stable CD-Fc host-guest inclusion complex and provided larger free room for the conjugation of secondary antibodies (Ab2) and glucose oxidase (GOD). Finally, the conjugated GOD exhibited extraordinary electrochemical biocatalysis towards the reduction reaction of Fc(+) by glucose. Under the optimized conditions, the electrochemical immunosensor exhibited a wide working range from 10(2.27)-10(3.50) TCID50/mL (TCID50: 50% tissue culture infective dose) with a low detection limit of 10(2.19) TCID50/mL (S/N=3). The selectivity, reproducibility, and stability are acceptable. The assay was evaluated for real avian serum sample, receiving satisfactory results. This new type of triple amplification strategy may provide potential applications for the clinic application. PMID:23454341

  16. Ultrasensitive electrochemical immunoassay for CEA through host-guest interaction of ?-cyclodextrin functionalized graphene and Cu@Ag core-shell nanoparticles with adamantine-modified antibody.

    PubMed

    Gao, Jian; Guo, Zhankui; Su, Fengjie; Gao, Liang; Pang, Xuehui; Cao, Wei; Du, Bin; Wei, Qin

    2015-01-15

    A novel non-enzymatic immunoassay was designed for ultrasensitive electrochemical detection of carcino-embryonic antigen (CEA) using ?-cyclodextrin functionalized Cu@Ag (Cu@Ag-CD) core-shell nanoparticles as labels and ?-cyclodextrin functionalized graphene nanosheet (CD-GN) as sensor platform. CD-GN has excellent conductivity which promoted the electric transmission between base solution and electrode surface and enhanced sensitivity of immunosensor. In addition, owing to supramolecular recognition of CD-GN for the guest molecule, quite a few synthesized adamantine-modified primary antibodies (ADA-Ab1) were immobilized on the CD-GN by supramolecular host-guest interaction between CD and ADA. Cu@Ag-CD as a signal tag could be captured by ADA-modified secondary antibody (ADA-Ab2) through a host-guest interaction, leading to a large loading of Cu@Ag nanoparticles with high electrical conductivity and catalytic activity. The fabricated immunosensor exhibits excellent analytical performance for the measurement of CEA with wide range linear (0.0001-20 ng/mL), low detection limit (20 fg/mL), good sensitivity, reproducibility and stability, which provide an enormous application prospect in clinical diagnostics. PMID:25129508

  17. Selective host-guest interaction between metal ions and metal-organic frameworks using dynamic nuclear polarization enhanced solid-state NMR spectroscopy.

    PubMed

    Guo, Zhiyong; Kobayashi, Takeshi; Wang, Lin-Lin; Goh, Tian Wei; Xiao, Chaoxian; Caporini, Marc A; Rosay, Melanie; Johnson, Duane D; Pruski, Marek; Huang, Wenyu

    2014-12-01

    The host-guest interaction between metal ions (Pt(2+) and Cu(2+) ) and a zirconium metal-organic framework (UiO-66-NH2 ) was explored using dynamic nuclear polarization-enhanced (15) N{(1) H} CPMAS NMR spectroscopy supported by X-ray absorption spectroscopy and density functional calculations. The combined experimental results conclude that each Pt(2+) coordinates with two NH2 groups from the MOF and two Cl(-) from the metal precursor, whereas Cu(2+) do not form chemical bonds with the NH2 groups of the MOF framework. Density functional calculations reveal that Pt(2+) prefers a square-planar structure with the four ligands and resides in the octahedral cage of the MOF in either cis or trans configurations. PMID:25297002

  18. Efficient singlet-singlet energy transfer in a novel host-guest assembly composed of an organic cavitand, aromatic molecules, and a clay nanosheet.

    PubMed

    Ishida, Yohei; Kulasekharan, Revathy; Shimada, Tetsuya; Takagi, Shinsuke; Ramamurthy, V

    2013-02-12

    A supramolecular host-guest assembly composed of a cationic organic cavitand (host), neutral aromatic molecules (guests), and an anionic clay nanosheet has been prepared and demonstrated that in this arrangement efficient singlet-singlet energy transfer could take place. The novelty of this system is the use of a cationic organic cavitand that enabled neutral organic molecules to be placed on an anionic saponite nanosheet. Efficient singlet-singlet energy transfer between neutral pyrene and 2-acetylanthracene enclosed within a cationic organic cavitand (octa amine) arranged on a saponite nanosheet was demonstrated through steady-state and time-resolved emission studies. The high efficiency was realized from the suppression of aggregation, segregation, and self-fluorescence quenching. We believe that the studies presented here using a novel supramolecular assembly have expanded the types of molecules that could serve as candidates for efficient energy-transfer systems, such as in an artificial light-harvesting system. PMID:23360204

  19. Selective Host-Guest Interaction between Metal Ions and Metal-Organic Frameworks using Dynamic Nuclear Polarization Enhanced Solid-State NMR Spectroscopy

    SciTech Connect

    Guo, Zhiyong; Kobayashi, Takeshi; Wang, Lin-Lin; Goh, Tian Wei; Xiao, Chaoxian; Caporini, Marc A; Rosay, Melanie; Johnson, Duane D; Pruski, Marek; Huang, Wenyu

    2014-10-08

    The hostguest interaction between metal ions (Pt2+ and Cu2+) and a zirconium metalorganic framework (UiO-66-NH2) was explored using dynamic nuclear polarization-enhanced 15N{1H} CPMAS NMR spectroscopy supported by X-ray absorption spectroscopy and density functional calculations. The combined experimental results conclude that each Pt2+ coordinates with two NH2 groups from the MOF and two Cl? from the metal precursor, whereas Cu2+ do not form chemical bonds with the NH2 groups of the MOF framework. Density functional calculations reveal that Pt2+ prefers a square-planar structure with the four ligands and resides in the octahedral cage of the MOF in either cis or trans configurations.

  20. Fluorescent and colorimetric magnetic microspheres as nanosensors for Hg2+ in aqueous solution prepared by a sol-gel grafting reaction and host-guest interaction

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhang, Yue; Yang, Qingbiao; Sun, Mingda; Fei, Xiaoliang; Song, Yan; Zhang, Yingmu; Li, Yaoxian

    2013-05-01

    Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2+, and its detection limit measures up to the micromolar level in aqueous solution. Most importantly, magnetic measurements have shown that TFIC magnetic nanoparticles are superparamagnetic and they can be separated and collected easily using a commercial magnet. These results not only solve the limitations in practical sensing applications of nanosensors, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials.Fluorescent sensing TSRh6G-β-cyclodextrin fluorophore/adamantane-modified inclusion complex magnetic nanoparticles (TFIC MNPs) have been synthesized via the cooperation of a host-guest interaction and sol-gel grafting reaction. Powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and UV-visible absorption and emission spectroscopy have been employed to characterize the material. Fluorescence and UV-visible spectra have shown that the resultant multifunctional nanoparticle sensors exhibit selective `turn-on' type fluorescent enhancements and a clear color change from light brown to pink with Hg2+. Owing to a larger surface area and high permeability, TFIC MNPs exhibit remarkable selectivity and sensitivity for Hg2+, and its detection limit measures up to the micromolar level in aqueous solution. Most importantly, magnetic measurements have shown that TFIC magnetic nanoparticles are superparamagnetic and they can be separated and collected easily using a commercial magnet. These results not only solve the limitations in practical sensing applications of nanosensors, but also enable the fabrication of other multifunctional nanostructure-based hybrid nanomaterials. Electronic supplementary information (ESI) available: Synthetic procedures and characterization data for new compounds, fluorescence photographs and the curve of fluorescence intensity. See DOI: 10.1039/c3nr00580a

  1. Strategies for reducing dye aggregation in luminescent host-guest systems: Rhodamine 6G incorporated in new mesoporous sol-gel hosts

    NASA Astrophysics Data System (ADS)

    de Queiroz, Thiago B.; Botelho, Moema B. S.; De Boni, Leonardo; Eckert, Hellmut; de Camargo, Andrea S. S.

    2013-03-01

    Aiming at the design of new luminescent host-guest materials with minimized aggregation effects, two classes of sol-gel derived mesoporous materials were explored as hosts for Rhodamine 6G (Rh6G) dye: The first consists of pure (SiO2) and phenyl-modified silica (Ph0.17SiO1.915) xerogels, prepared via sol-gel reaction using an ionic liquid as catalytic agent. The second consists of mesoporous sodium aluminosilicate glasses with Si to Al ratio in the range of 6 ? Si/Al ? 9. Characterization through high resolution solid state NMR proved the successful obtention of the designed host matrices. Following Rh6G-loading in various concentrations, the resulting materials were characterized by their luminescence and excitation spectra, excited state lifetimes, and quantum yields. The dye doped silica xerogels presented high quantum yield values (up to 87%), with no substantial decrease in efficiency with increasing dye concentration. At suitable Rh6G contents, all the final materials presented laser action under 532 nm excitation from a Q-switched frequency doubled Nd:YAG laser. The phenyl silicate sample presents the highest laser photostability with a half-life of 6560 pulses, under 2 mJ/pulse pump power, and 10 Hz repetition rate. The laser experiments provided further insights on the photodegradation mechanisms of such organic species.

  2. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3

    NASA Astrophysics Data System (ADS)

    Miladi, Mahsan; Olaitan, Abayomi D.; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na+, K+, or Cs+)-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H]+ and [Z-PG-OCH3 + H]+ formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3]+) but no ND3 adducts were observed for [Z-PG + alkali metal]+ or [Z-PG + H - CO2]+. Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H]+ compared to [Z-PG + alkali metal]+ species. Molecular modeling and experimental MS results for [Z-PG + H]+ and [Z-PG + alkali metal]+ suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation.

  3. Simple Host?Guest Chemistry To Modulate the Process of Concentration and Crystallization of Membrane Proteins by Detergent Capture in a Microfluidic Device

    SciTech Connect

    Li, Liang; Nachtergaele, Sigrid; Seddon, Annela M.; Tereshko, Valentina; Ponomarenko, Nina; Ismagilov, Rustem F.

    2009-01-15

    This paper utilizes cyclodextrin-based host-guest chemistry in a microfluidic device to modulate the crystallization of membrane proteins and the process of concentration of membrane protein samples. Methyl-{beta}-cyclodextrin (MBCD) can efficiently capture a wide variety of detergents commonly used for the stabilization of membrane proteins by sequestering detergent monomers. Reaction Center (RC) from Blastochloris viridis was used here as a model system. In the process of concentrating membrane protein samples, MBCD was shown to break up free detergent micelles and prevent them from being concentrated. The addition of an optimal amount of MBCD to the RC sample captured loosely bound detergent from the protein-detergent complex and improved sample homogeneity, as characterized by dynamic light scattering. Using plug-based microfluidics, RC crystals were grown in the presence of MBCD, giving a different morphology and space group than crystals grown without MBCD. The crystal structure of RC crystallized in the presence of MBCD was consistent with the changes in packing and crystal contacts hypothesized for removal of loosely bound detergent. The incorporation of MBCD into a plug-based microfluidic crystallization method allows efficient use of limited membrane protein sample by reducing the amount of protein required and combining sparse matrix screening and optimization in one experiment. The use of MBCD for detergent capture can be expanded to develop cyclodextrin-derived molecules for fine-tuned detergent capture and thus modulate membrane protein crystallization in an even more controllable way.

  4. Mechanistic Insight into Receptor-Mediated Delivery of Cationic-β-Cyclodextrin:Hyaluronic Acid-Adamantamethamidyl Host:Guest pDNA Nanoparticles to CD44(+) Cells.

    PubMed

    Badwaik, Vivek; Liu, Linjia; Gunasekera, Dinara; Kulkarni, Aditya; Thompson, David H

    2016-03-01

    Targeted delivery is a key element for improving the efficiency and safety of nonviral vectors for gene therapy. We have recently developed a CD44 receptor targeted, hyaluronic acid-adamantamethamidyl based pendant polymer system (HA-Ad), capable of forming complexes with cationic β-cyclodextrins (CD-PEI(+)) and pDNA. Complexes formed using these compounds (HA-Ad:CD-PEI(+):pDNA) display high water solubility, good transfection efficiency, and low cytotoxicity. Spatial and dynamic tracking of the transfection complexes by confocal microscopy and multicolor flow cytometry techniques was used to evaluate the target specificity, subcellular localization, and endosomal escape process. Our data shows that cells expressing the CD44 receptor undergo enhanced cellular uptake and transfection efficiency with HA-Ad:CD-PEI(+):pDNA complexes. This transfection system, comprised noncovalent assembly of cyclodextrin:adamantamethamidyl-modified hyaluronic acid via host:guest interactions to condense pDNA, is a potentially useful tool for targeted delivery of nucleic acid therapeutics. PMID:26900622

  5. Isothermal titration calorimetry and 1H NMR studies on host-guest interaction of paeonol and two of its isomers with beta-cyclodextrin.

    PubMed

    Sun, De-Zhi; Li, Ling; Qiu, Xiao-Mei; Liu, Feng; Yin, Bao-Lin

    2006-06-19

    Thermodynamic parameters of inclusion complex of beta-cyclodextrin (beta-CD) with paeonol and two of its isomers in aqueous solution have been determined with nano-watt-order isothermal titration calorimetry (ITC) and the host-guest inclusion structure has been investigated by using 1H NMR spectra at 298.2 K. The analysis of thermodynamic data reveals that stoichiometry of beta-CD complex with paeonol (Pae) or acetovanillone (Ace) is 1:1 whereas the inclusion complex of beta-CD with 2-hydroxyl-5-methoxyacetophone (Hma) is in 1:1 coexistence with 2:1 stoichiometry. Further analysis indicates that formation of all the complexes is simultaneously driven by enthalpy and entropy, the inclusion complexation of Pae.beta-CD, Ace.beta-CD and Ham.beta-CD2 is predominantly driven by entropy while Ham.beta-CD by enthalpy. The 1H NMR spectra data provide clear evidence of the inclusion phenomena, which shows that the aromatic ring of the guest molecule insert itself into the torus from the narrow side of the cavity. PMID:16554127

  6. Azo-capped polysarcosine-b-polylysine as polypeptide gene vector: A new strategy to improve stability and easy optimization via host-guest interaction.

    PubMed

    Du, Jianwei; Tian, Ce; Liu, Yajie; Ling, Jun; Wang, Youxiang

    2015-06-01

    Polypeptide has been extensively researched in gene/drug delivery system due to the good biocompatibility. Herein, we synthesized total-polypeptide copolymers, i.e. Azo(azobenzene)-capped polysarcosine-b-polylysine (ASL) with narrow molecular weight distribution by ?-amino acid N-carboxyanhydride (NCA) polymerization. Although the molecular weight of PLL segment was only about 6 kDa, ASL could condense DNA effectively and form about 150 nm spherical nanoparticles at N/P ratio of 15. The surface charge was significantly reduced due to the shielding effect of polysarcosine (PSAR) shell. ASL/DNA PeptoPlexes showed good colloidal stability under physiological salt condition and complexation competition stability in the presence of counter polyanion, which might improve the circulation time in vivo. The tip design of azobenzene provided a facile way for ligand modification via host-guest interaction, which could be flexibly optimized by changing its functional tags responding to a request. Our data showed that the introduction of CD-R8 could promote the internalization of gene into cytoplasm and even nucleus owing to the membrane penetrating effect of R8. Cell culture experiments indicated as a total-polypeptide system, ASL showed good cellular viability and comparable gene transfection level as PLL with molecular weight of 50 kDa. Overall, PSAR served as an ideal alternative of PEG and this total-polypeptide system showed us a good direction for gene carrier design. PMID:25899841

  7. Chiral discrimination in host-guest supramolecular complexes. Understanding enantioselectivity and solid solution behaviors by using spectroscopic methods and chemical sensors.

    PubMed

    Grandeury, Arnaud; Condamine, Eric; Hilfert, Liane; Gouhier, Graldine; Petit, Samuel; Coquerel, Grard

    2007-06-28

    Diastereomeric host-guest associations formed between permethylated-beta-cyclodextrin (TMbeta-Cd) and the two enantiomers of p-bromophenylethanol (pBrPE) were characterized in aqueous solution by NMR spectroscopy, revealing similar inclusion geometries and weak binding constants, whatever the guest configuration. These features were confirmed by hydrogenation experiments, and do not allow to account for the ability of TMbeta-Cd to resolve racemic pBrPE by successive crystallizations [Grandeury, A.; Petit, S.; Gouhier, G.; Agasse, V.; Coquerel, G. Tetrahedron: Asymmetry 2003, 14, 2143-2152]. The analysis, by means of solid-state NMR, oxidation experiments, and solubility measurements, of the two crystalline phases containing known proportions of guest enantiomers revealed identical inclusion geometries in a given phase, irrespective of the enantiomeric composition. The corresponding solid solutions were further characterized by the determination of an isothermal section (40 degrees C) in the relevant ternary phase diagram. It appears from all these data that chiral resolution mechanisms in this system can only be envisaged in terms of nucleation conditions of each crystal form (with its specific inclusion geometry) and enantiomeric recognition at crystal solution interfaces during the growth of each crystal packing. PMID:17547451

  8. Host-Guest Interaction-Based Self-Engineering of Nano-Sized Vesicles for Co-Delivery of Genes and Anticancer Drugs.

    PubMed

    Yang, Bin; Dong, Xing; Lei, Qi; Zhuo, Renxi; Feng, Jun; Zhang, Xianzheng

    2015-10-01

    On the basis of host-guest interactions, this study reported a kind of linear-hyperbranched supramolecular amphiphile and its assembled vesicles for the combined achievement of drug encapsulation and DNA delivery. Amine-attached β-cyclodextrin-centered hyperbranched polyglycerol and linear adamantane-terminated octadecane were arranged to spontaneously interlink together and then self-assemble into nanoscale vesicles. As the model of a hydrophilic agent, DOX·HCl was demonstrated to be readily loaded into the hollow cavity of the vesicles. The drug release pattern could be controlled by adjusting the environmental acidity, favoring the intracellularly fast drug liberation in response to the cellular lysosomal microenvironment. The nanovesicles displayed superior serum-tolerant transgene ability and significantly lower cytotoxicity compared to those of PEI25K, the gold standard of gene delivery vectors. The drug-loaded nanovesicle can co-deliver DNA payloads into cells and allow the preferable accumulation of two payloads in nuclei. The drug encapsulation was found to have little influence on the transfection. This co-delivery vehicle presents a good example of rational design of cationic supramolecular vesicles for stimulus-responsive drug/DNA transport. PMID:26398113

  9. A 1H NMR Study of Host/Guest Supramolecular Complexes of a Curcumin Analogue with ?-Cyclodextrin and a ?-Cyclodextrin-Conjugated Gemini Surfactant.

    PubMed

    Poorghorban, Masoomeh; Karoyo, Abdalla H; Grochulski, Pawel; Verrall, Ronald E; Wilson, Lee D; Badea, Ildiko

    2015-08-01

    Host systems based on ?-cyclodextrin (?CD) were employed as pharmaceutical carriers to encapsulate a poorly soluble drug, curcumin analogue (NC 2067), in order to increase its water solubility. ?CD was chemically conjugated with an amphiphilic gemini surfactant with the ability to self-assemble and to form nanoscale supramolecular structures. The conjugated molecule, ?CDgemini surfactant (?CDg), was shown to be a promising drug delivery agent. In this report, its physicochemical properties were assessed in aqueous solution using 1D and 2D 1H NMR spectroscopy. The results showed that the apolar hydrocarbon domain of the gemini surfactant was self-included within the ?CD internal cavity. The host/guest complexes composed of native ?CD or ?CDg with NC 2067 were examined using 1D/2D ROESY NMR methods. The stoichiometry of ?CD/NC 2067 complex was estimated using Job's method via 1H NMR spectroscopy. The binding geometry of NC 2067 within ?CD was proposed using molecular docking and further supported by 1D and 2D ROESY NMR results. Addition of NC 2067 to ?CDg revealed minimal changes to the overall structure of the ?CDg system, in agreement with the formation of a ?CDg/NC 2067 ternary complex. PMID:26083126

  10. Regenerable fluorescent nanosensors for monitoring and recovering metal ions based on photoactivatable monolayer self-assembly and host-guest interactions.

    PubMed

    Wang, Wei; Wong, Nai-Kei; Sun, Mingda; Yan, Chunqiu; Ma, Siyuan; Yang, Qingbiao; Li, Yaoxian

    2015-04-29

    Efficient detection, removal, and recovery of heavy metal ions from aqueous environments represents a technologically challenging and ecologically urgent question in the face of increasing metal-related pollution and poisoning across the globe. Although small-molecule and entrapment-based nanoparticle sensors have been extensively explored for metal detection, neither of these extant strategies satisfies the critical needs for high-performance sensors that are inexpensive, efficient, and recyclable. Here we first report the development of a regenerable fluorescent nanosensor system for the selective and sensitive detection of multiple heavy metal ions, based on light-switchable monolayer self-assembly and host-guest interactions. The system exploits photocontrolled inclusion and exclusion responses of an ?-cyclodextrin (CD)-containing surface conjugated with photoisomerizable azobenzene as a supramolecular system that undergoes reversible assembly and disassembly. The metal nanosensors can be facilely fabricated and photochemically switched between three chemically distinct entities, each having an excellent capacity for selective detecting specific metal ions (namely, Cu(2+), Fe(3+), Hg(2+)) in a chemical system and in assays on actual water samples with interfering contaminants. PMID:25848888

  11. Supramolecular host-guest pseudocomb conjugates composed of multiple star polycations tied tunably with a linear polycation backbone for gene transfection.

    PubMed

    Hu, Y; Chai, M Y; Yang, W T; Xu, F J

    2013-06-19

    A series of novel supramolecular pseudocomb polycations (l-PGEA-Ad/CD-PGEAs) were synthesized by tying multiple low-molecular-weight ?-cyclodextrin (CD)-cored, ethanolamine-functionalized poly(glycidyl methacrylate) (PGEA) star polymers (CD-PGEAs) with an adamantine-modified linear PGEA (l-PGEA-Ad) backbone via the host-guest interaction. The pseudocomb carriers were studied in terms of their DNA binding capabilities, cytotoxicities, and gene transfection efficiencies in the HepG2 and HEK293 cell lines. The pseudocomb l-PGEA-Ad/CD-PGEAs exhibited better plasmid DNA-condensing abilities than their counterparts, CD-PGEA and l-PGEA. Meanwhile, the pseudocomb carriers displayed low cytotoxicity, similar to CD-PGEA and l-PGEA. Moreover, the gene transfection efficiencies of the pseudocomb carriers were much higher than those of CD-PGEA and l-PGEA at various PGEA nitrogen/DNA phosphate molar ratios. Such supramolecular preparation of pseudocomb gene carriers could provide a flexible approach for adjusting the structure and functionality of supramolecular polymers via the proper use of non-covalent interactions. PMID:23682960

  12. An ab initio study of the effect of host-guest interaction on thermal transport in Ba8Ga16Ge30

    NASA Astrophysics Data System (ADS)

    Tadano, Terumasa; Gohda, Yoshihiro; Tsuneyuki, Shinji

    2014-03-01

    Inorganic clathrate compounds are promising candidates for the next-generation thermoelectric devices because of their low lattice thermal-conductivities. In these materials, rattling vibrations of guest ions inside host cages are considered to play a significant role in reducing the lattice thermal-conductivity. In order to elucidate the microscopic mechanism of the reduction more clearly, we have performed first-principles analyses on a type-I clathrate Ba8Ga16Ge30. Firstly, we calculated harmonic and anharmonic force constants of the material using the direct-method. Then, phonon scattering probabilities are evaluated from the imaginary part of the phonon self-energy. Our analysis shows that host-guest interactions increase the scattering probability of acoustic modes by one order of magnitude, and also cause a 10-fold reduction in the lattice thermal-conductivity. In addition, we observe that phonon mean-free-paths are far larger than the separation of Ba atoms, indicating that Ba atoms cannot be considered as individual scattering centers.

  13. A neutral cluster cage with a tetrahedral [Pd12(II)L6] framework: crystal structures and hostguest studies.

    PubMed

    Gupta, Arvind K; Yadav, Ashok; Srivastava, Anant Kumar; Ramya, Kormathmadam Raghupathy; Paithankar, Harshad; Nandi, Shyamapada; Chugh, Jeetender; Boomishankar, Ramamoorthy

    2015-04-01

    A charge-neutral tetrahedral [(Pd3X)4L6] cage assembly built from a trinuclear polyhedral building unit (PBU), [Pd3X](3+), cis-blocked with an imido P(V) ligand, [(N(i)Pr)3PO](3-) (X(3-)), and oxalate dianions (L(2-)) is reported. Use of benzoate or ferrocene dicarboxylate anions, which do not offer wide-angle chelation as that of oxalate dianions, leads to smaller prismatic clusters instead of polyhedral cage assemblies. The porosity of the tetrahedral cage assembly was determined by gas adsorption studies, which show a higher uptake capacity for CO2 over N2 and H2. The tetrahedral cage was shown to encapsulate a wide range of neutral guest solvents from polar to nonpolar such as dimethyl sulfoxide, benzene, dichloromethane, chloroform, carbon tetrachloride, and cyclopentane as observed by mass spectral and single-crystal X-ray diffraction studies. The (1)H two-dimensional diffusion ordered spectroscopy NMR analysis shows that the host and guest molecules exhibit similar diffusion coefficients in all the studied host-guest systems. Further, the tetrahedral cage shows selective binding of benzene, CCl4, and cyclopentane among other solvents from their categories as evidenced from mass spectral analysis. A preliminary density functional theory analysis gave a highest binding energy for benzene among the other solvents that were structurally shown to be encapsulated at the intrinsic cavity of the tetrahedral cage. PMID:25781912

  14. Interferometer Control of Optical Tweezers

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2002-01-01

    This paper discusses progress in using spatial light modulators and interferometry to control the beam profile of an optical tweezers. The approach being developed is to use a spatial light modulator (SLM) to control the phase profile of the tweezers beam and to use a combination of the SLM and interferometry to control the intensity profile. The objective is to perform fine and calculable control of the moments and forces on a tip or tool to be used to manipulate and interrogate nanostructures. The performance of the SLM in generating multiple and independently controllable tweezers beams is also reported. Concurrent supporting research projects are mentioned and include tweezers beam scattering and neural-net processing of the interference patterns for control of the tweezers beams.

  15. Devil's lens optical tweezers.

    PubMed

    Pu, Jixiong; Jones, P H

    2015-04-01

    We demonstrate an optical tweezers using a laser beam on which is imprinted a focusing phase profile generated by a Devil's staircase fractal structure (Cantor set). We show that a beam shaped in this way is capable of stably trapping a variety of micron- and submicron-sized particles and calibrate the optical trap as a function of the control parameters of the fractal structure, and explain the observed variation as arising from radiation pressure exerted by unfocused parts of the beam in the region of the optical trap. Experimental results are complemented by calculation of the structure of the focus in the regime of high numerical aperture. PMID:25968658

  16. Competing noncovalent host-guest interactions and H/D exchange: reactions of benzyloxycarbonyl-proline glycine dipeptide variants with ND3.

    PubMed

    Miladi, Mahsan; Olaitan, Abayomi D; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-? and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ?. PMID:26289383

  17. Reduction in crystal symmetry of a solid solution: A neutron diffraction study at 15 K of the host/guest system asparagine/aspartic acid

    SciTech Connect

    Weisinger-Lewin, Y.; Frolow, F.; Lahav, M.; Leiserowitz, L. ); McMullan, R.K.; Koetzle, T.F. )

    1989-02-01

    It has been demonstrated, for the first time by diffraction methods, that a solid solution composed of host and guest molecules can exhibit a crystal symmetry lower than that of the host. The study proves that the symmetry of a solid solution is dependent not only upon the host crystal structure and the guest molecular structure but also upon the surface structure and symmetry of the host crystal. The crystal structures of (S)-asparagine monohydrate (D{sub 2}NCOCH{sub 2}CH(ND{sub 3})CO{sub 2} {times} D{sub 2}O) and of the solid solution (0.848:0.152) (S)-asparagine/(S)-aspartic acid (DO{sub 2}CCD{sub 2}CD(ND{sub 3})CO{sub 2}) monohydrate were refined by using neutron diffraction data obtained at 15 K. The space group of the pure host crystal is P2{sub 1}2{sub 1}2{sub 1} (Z = 4), whereas that of the host/guest crystal is monoclinic P12{sub 1}1 with two molecular sites per asymmetric unit. The ratios of guest/host occupancies of the two independent sites are 0.173:0.827 and 0.132:0.868. The reduction in symmetry is in accordance with the preferred adsorption of guest aspartic acid on the (010) crystal face at half of the orthorhombic, symmetry-related surface sites. Aspartic acid mimics, at the preferred (010) surface sites, molecular asparagine, participating in all hydrogen bonds. At the less-favored (010) surface sites a normal N-H{hor ellipsis}O(host) hydrogen bond is replaced by O(hydroxyl){hor ellipsis}O(host) repulsion between lone-pair electrons. 21 refs., 5 figs., 6 tabs.

  18. Spectroscopic and electrochemical properties of organic framework of macrocylic OONNOO-donor ligand with its metal organic framework: Host/guest stability measurements

    NASA Astrophysics Data System (ADS)

    Kumar, Rajiv; Singh, R. P.; Singh, R. P.

    2008-11-01

    In this study, we synthesized 1,2-di( o-aminophenoxy)ethane, as the starting material, used in the preparation of a novel hexadentate OONNOO-donor macrocyclic ligand-1,4,11,14-tetraoxo-7,8-diaza-5,6:9,10;15,16:19,20-terabezocyclododeca-8,17-iene. It has twenty membered organic framework (OF), which has been designed, synthesized and characterized. Our main findings of this paper are related to the organic framework of ligand, its capacity to digest the metal ions and the stability of metal organic framework (MOFs) with cobalt(II), nickel(II) and manganese(II). The authenticity of the used organic framework and its metal complexes have been detected and observed in solid state as well as in aqueous solutions. The main observations were made on the basis of physiochemical measurements viz.: elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, 1H NMR, 13C NMR, mass spectroscopy, electronic, ESR spectroscopy. In addition, the magnetic susceptibility and electrochemistry measurements have been made. The 1H NMR spectra suggest stereochemistry and proton movement interaction. Considering the used organic framework there are a lot of carbon atoms in the molecule reflected by the 13C NMR spectrum. All these observations gave a clear view to confirming the encapsulation; arrive at the composition, structure and geometry of encapsulated complexes. In simple words, it confirms the host/guest coordination and its stability. Electrochemical properties of the complexes have been investigated to confirm the various changes in oxidation state of metals with change in potentials with respect to current at different scan rate.

  19. Spectroscopic and electrochemical properties of organic framework of macrocylic OONNOO-donor ligand with its metal organic framework: host/guest stability measurements.

    PubMed

    Kumar, Rajiv; Singh, R P; Singh, R P

    2008-11-15

    In this study, we synthesized 1,2-di(o-aminophenoxy)ethane, as the starting material, used in the preparation of a novel hexadentate OONNOO-donor macrocyclic ligand-1,4,11,14-tetraoxo-7,8-diaza-5,6:9,10;15,16:19,20-terabezocyclododeca-8,17-iene. It has twenty membered organic framework (OF), which has been designed, synthesized and characterized. Our main findings of this paper are related to the organic framework of ligand, its capacity to digest the metal ions and the stability of metal organic framework (MOFs) with cobalt(II), nickel(II) and manganese(II). The authenticity of the used organic framework and its metal complexes have been detected and observed in solid state as well as in aqueous solutions. The main observations were made on the basis of physiochemical measurements viz.: elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, 1H NMR, 13C NMR, mass spectroscopy, electronic, ESR spectroscopy. In addition, the magnetic susceptibility and electrochemistry measurements have been made. The 1H NMR spectra suggest stereochemistry and proton movement interaction. Considering the used organic framework there are a lot of carbon atoms in the molecule reflected by the 13C NMR spectrum. All these observations gave a clear view to confirming the encapsulation; arrive at the composition, structure and geometry of encapsulated complexes. In simple words, it confirms the host/guest coordination and its stability. Electrochemical properties of the complexes have been investigated to confirm the various changes in oxidation state of metals with change in potentials with respect to current at different scan rate. PMID:18243048

  20. Are electron tweezers possible?

    PubMed

    Oleshko, Vladimir P; Howe, James M

    2011-11-01

    Positively answering the question in the title, we demonstrate in this work single electron beam trapping and steering of 20-300nm solid Al nanoparticles generated inside opaque submicron-sized molten Al-Si eutectic alloy spheres. Imaging of solid nanoparticles and liquid alloy in real time was performed using energy filtering in an analytical transmission electron microscope (TEM). Energy-filtering TEM combined with valence electron energy-loss spectroscopy enabled us to investigate in situ nanoscale transformations of the internal structure, temperature dependence of plasmon losses, and local electronic and optical properties under melting and crystallization of individual binary alloy particles. For particles below 20nm in size, enhanced vibrations of the dynamic solid-liquid interface due to instabilities near the critical threshold were observed just before melting. The obtained results indicate that focused electron beams can act as a tool for manipulation of metal nanoparticles by transferring linear and angular mechanical momenta. Such thermally assisted electron tweezers can be utilized for touchless manipulation and processing of individual nano-objects and potentially for fabrication of assembled nanodevices with atomic level sensitivity and lateral resolution provided by modern electron optical systems. This is by three orders of magnitude better than for light microscopy utilized in conventional optical tweezers. New research directions and potential applications of trapping and tracking of nano-objects by focused electron beams are outlined. PMID:21946000

  1. Optical Tweezer Assembly and Calibration

    NASA Technical Reports Server (NTRS)

    Collins, Timothy M.

    2004-01-01

    An Optical Tweezer, as the name implies, is a useful tool for precision manipulation of micro and nano scale objects. Using the principle of electromagnetic radiation pressure, an optical tweezer employs a tightly focused laser beam to trap and position objects of various shapes and sizes. These devices can trap micrometer and nanometer sized objects. An exciting possibility for optical tweezers is its future potential to manipulate and assemble micro and nano sized sensors. A typical optical tweezer makes use of the following components: laser, mirrors, lenses, a high quality microscope, stage, Charge Coupled Device (CCD) camera, TV monitor and Position Sensitive Detectors (PSDs). The laser wavelength employed is typically in the visible or infrared spectrum. The laser beam is directed via mirrors and lenses into the microscope. It is then tightly focused by a high magnification, high numerical aperture microscope objective into the sample slide, which is mounted on a translating stage. The sample slide contains a sealed, small volume of fluid that the objects are suspended in. The most common objects trapped by optical tweezers are dielectric spheres. When trapped, a sphere will literally snap into and center itself in the laser beam. The PSD s are mounted in such a way to receive the backscatter after the beam has passed through the trap. PSD s used with the Differential Interference Contrast (DIC) technique provide highly precise data. Most optical tweezers employ lasers with power levels ranging from 10 to 100 miliwatts. Typical forces exerted on trapped objects are in the pico-newton range. When PSDs are employed, object movement can be resolved on a nanometer scale in a time range of milliseconds. Such accuracy, however, can only by utilized by calibrating the optical tweezer. Fortunately, an optical tweezer can be modeled accurately as a simple spring. This allows Hook s Law to be used. My goal this summer at NASA Glenn Research Center is the assembly and calibration of an optical tweezer setup in the Instrumentation and Controls Division (5520). I am utilizing a custom LabVIEW Virtual Instrument program for data collection and microscope stage control. Helping me in my assignment are the following people: Mentor Susan Wrbanek (5520), Dr. Baha Jassemnejad (UCO) and Technicians Ken Weiland (7650) and James Williams (7650). Without their help, my task would not be possible.

  2. Undergraduate Construction of Optical Tweezers

    NASA Astrophysics Data System (ADS)

    Hubbell, Lawrence

    2012-10-01

    I will present a poster on the construction of optical tweezers. This will demonstrate the full process one must go through when working on a research project. First I sifted through the internet for papers and information pertaining to the tweezers. Afterwards I discussed the budget with the lab manager. Next I made purchases, however some items, such as the sample mount, needed to be custom made. These I built in the machine shop. Once the tweezers were operational I spent some time ensuring that the mirrors and lenses were adjusted just right, so that the trap performed at full strength. Finally, I used video data of the Brownian motion of trapped silica microspheres to get a reasonable estimate of the trapping stiffness with such particles. As a general note, all of this was done with the intent of leaving the tweezers for future use by other undergraduates. Because of this extra effort was taken to ensure the tweezers were as safe to use as possible. For this reason a visible LASER was chosen over an infrared LASER, in addition, the LASER was oriented parallel to the surface of the table in order to avoid stray upwards beams.

  3. Quantum noise in optical tweezers

    NASA Astrophysics Data System (ADS)

    Taylor, Michael A.; Bowen, Warwick P.

    2013-12-01

    Quantum enhanced sensitivity in optical tweezers based particle tracking was recently demonstrated. This has provided the necessary tool for quantum metrology to play an important role in biological measurements. Here we introduce the basic theory relevant to such optical tweezers experiments, and overview the significance of sub-shot noise limited sensitivity to practical experiments. In particular, biophysical experiments are subject to optical power constraints, which therefore limits the absolute sensitivity which is classically achievable. Quantum enhanced particle tracking can overcome this limit, and is therefore likely to play an important role in such biophysical experiments in the near future.

  4. Optical tweezers for confocal microscopy

    NASA Astrophysics Data System (ADS)

    Hoffmann, A.; Meyer zu Hrste, G.; Pilarczyk, G.; Monajembashi, S.; Uhl, V.; Greulich, K. O.

    2000-11-01

    In confocal laser scanning microscopes (CLSMs), lasers can be used for image formation as well as tools for the manipulation of microscopic objects. In the latter case, in addition to the imaging lasers, the light of an extra laser has to be focused into the object plane of the CLSM, for example as optical tweezers. Imaging as well as trapping by optical tweezers can be done using the same objective lens. In this case, z-sectioning for 3D imaging shifts the optical tweezers with the focal plane of the objective along the optical axis, so that a trapped object remains positioned in the focal plane. Consequently, 3D imaging of trapped objects is impossible without further measures. We present an experimental set-up keeping the axial trapping position of the optical tweezers at its intended position whilst the focal plane can be axially shifted over a distance of about 15 ?m. It is based on fast-moving correctional optics synchronized with the objective movement. First examples of application are the 3D imaging of chloroplasts of Elodea densa (Canadian waterweed) in a vigorous cytoplasmic streaming and the displacement of zymogen granules in pancreatic cancer cells (AR42 J).

  5. Colorimetric magnetic microspheres as chemosensor for Cu(2+) prepared from adamantane-modified rhodamine and β-cyclodextrin-modified Fe3O4@SiO2 via host-guest interaction.

    PubMed

    Zhang, Yue; Wang, Wei; Li, Qiang; Yang, Qingbiao; Li, Yaoxian; Du, Jianshi

    2015-08-15

    Adamantane-modified salicylrhodamine B and β-cyclodextrin-modified Fe3O4@SiO2 were assemblied by host-guest interactions which induced novel inclusion complex magnetic nanoparticles (SFIC MNPs) colorimetric sensitive for Cu(2+) being prepared. The MNPs exhibit a clear color change from colorless to pink selectively and sensitively with the addition of Cu(2+) in the experiments of UV-visible spectra, and the detection limit measures up to 5.99×10(-6)M in solutions of CH3CN-H2O =1:10. The SFIC magnetic nanoparticles are superparamagnetic according to magnetic measurements and can be separated and collected easily with a commercial magnet in nine seconds. In addition, the microspheres have also showed good ability of separating for other ions from aqueous solutions due to a large number of hydroxyl groups on the surface. PMID:25966377

  6. Host-Guest Inclusion Complexes between Amlodipine Enantiomers in the Biphasic Recognition Chiral Extraction System using Tartaric Acid and β-Cyclodextrin Derivatives as Positive Confirmation by using their Enantioselective Extraction

    PubMed Central

    Al Azzam, Khaldun M.; Abdallah, Hassan H.; Halim, Hairul N. Abdul; Ahmad, Maizatul Akmam; Shaibah, Hassan

    2015-01-01

    The current work reports an extended theoretical study from our previous experimental work for the enantioselective extraction of amlodipine enantiomers in a biphasic recognition chiral extraction system (BRCES) consisting of hydrophobic D-diisopropyl tartrate dissolved in organic phase (n-decanol) and hydrophilic hydroxypropyl-β-cyclodextrin (HP-β-CD) in aqueous phase (acetate buffer) which preferentially recognize the R-enantiomer and S-enantiomer, respectively. The calculations were simulated using a semi-empirical PM3 method as a part of the Gaussian09 software package and were used to optimize the structures of the hosts, guests, and host-guest complexes in the gas phase without any restrictions. It was found that HP-β-CD has the strongest recognition ability among the three β-CD derivatives studied, namely HP-β-CD, hydroxyethyl-β-cyclodextrin (HE-β-CD), and methylated-β-cyclodextrin (Me-β-CD), due to the large interaction energies (Ecomp = −14.3025 kcal/ mol), while D-diisopropyl tartrate has the strongest ability among the four tartaric acid derivatives studied namely; L-diisopropyl tartrate, D-diisopropyl tartrate, L-diethyl tartrate, and D-diethyl tartrate (Ecomp = −5.9964 kcal/ mol). The computational calculations for the enantioselective partitioning of amlodipine enantiomers rationalized the reasons for the different behaviors for this extraction. The present theoretical results may be informative to scientists who are devoting themselves to developing models for their experimental parts or for enhancing the hydrophobic drug solubility in drug delivery systems. PMID:26839848

  7. Optical tweezers technique and its applications

    NASA Astrophysics Data System (ADS)

    Guo, HongLian; Li, ZhiYuan

    2013-12-01

    Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

  8. Optoelectronic tweezers for medical diagnostics

    NASA Astrophysics Data System (ADS)

    Kremer, Clemens; Neale, Steven; Menachery, Anoop; Barrett, Mike; Cooper, Jonathan M.

    2012-01-01

    Optoelectronic tweezers (OET) allows the spatial patterning of electric fields through selected illumination of a photoconductive surface. This enables the manipulation of micro particles and cells by creating non-uniform electrical fields that then produce dielectrophoretic (DEP) forces. The DEP responses of cells differ and can produce negative or positive (repelled or attracted to areas of high electric field) forces. Therefore OET can be used to manipulate individual cells and separate different cell types from each other. Thus OET has many applications for medical diagnostics, demonstrated here with work towards diagnosing Human African Trypanosomiasis, also known as sleeping sickness.

  9. Fluorescence support in optical tweezers

    NASA Astrophysics Data System (ADS)

    Animas, J. G.; Arronte, M.; Flores, T.; Ponce, L.

    2013-11-01

    This paper presents the development of an installation for proves for characterization by fluorescence of micrometer and nanometer particles supported on the trapping and manipulation by optical trapping technique (optical tweezers). The system features an laser operating at 480 nm, CCD camera for image acquisition, Thor Labs micrometric table X, Y, Z for the movement of the sample and the trap in the visual field. The design includes the use of intensity modulated optical trap, with the option of being used in pulsed, opening up possibilities for the use of resonant phenomena optomechanical type for particle capture.

  10. Dynamical stabilisation in optical tweezers

    NASA Astrophysics Data System (ADS)

    Jones, Philip H.; Richards, Christopher J.; Smart, Thomas J.; Cubero, David

    2015-03-01

    We present a study of dynamical stabilisation of an overdamped, microscopic pendulum realised using optical tweezers. We first derive an analytical expression for the equilibrium dynamically stabilised pendulum position in a regime of high damping and high modulation frequency of the pendulum pivot. This model implies a threshold behavior for stabilisation to occur, and a continuous evolution of the angular position which, unlike the underdamped case, does not reach the fully inverted position. We then test the theoretical predictions using an optically trapped microparticle subject to fluid drag force, finding reasonable agreement with the threshold and equilibrium behavior at high modulation amplitude. Analytical theory and experiments are complemented by Brownian motion simulations.

  11. Optical tweezers to study viruses.

    PubMed

    Arias-Gonzalez, J Ricardo

    2013-01-01

    A virus is a complex molecular machine that propagates by channeling its genetic information from cell to cell. Unlike macroscopic engines, it operates in a nanoscopic world under continuous thermal agitation. Viruses have developed efficient passive and active strategies to pack and release nucleic acids. Some aspects of the dynamic behavior of viruses and their substrates can be studied using structural and biochemical techniques. Recently, physical techniques have been applied to dynamic studies of viruses in which their intrinsic mechanical activity can be measured directly. Optical tweezers are a technology that can be used to measure the force, torque and strain produced by molecular motors, as a function of time and at the single-molecule level. Thanks to this technique, some bacteriophages are now known to be powerful nanomachines; they exert force in the piconewton range and their motors work in a highly coordinated fashion for packaging the viral nucleic acid genome. Nucleic acids, whose elasticity and condensation behavior are inherently coupled to the viral packaging mechanisms, are also amenable to examination with optical tweezers. In this chapter, we provide a comprehensive analysis of this laser-based tool, its combination with imaging methods and its application to the study of viruses and viral molecules. PMID:23737055

  12. Microcrystal manipulation with laser tweezers

    SciTech Connect

    Wagner, Armin Duman, Ramona; Stevens, Bob; Ward, Andy

    2013-07-01

    Optical trapping has successfully been applied to select and mount microcrystals for subsequent X-ray diffraction experiments. X-ray crystallography is the method of choice to deduce atomic resolution structural information from macromolecules. In recent years, significant investments in structural genomics initiatives have been undertaken to automate all steps in X-ray crystallography from protein expression to structure solution. Robotic systems are widely used to prepare crystallization screens and change samples on synchrotron beamlines for macromolecular crystallography. The only remaining manual handling step is the transfer of the crystal from the mother liquor onto the crystal holder. Manual mounting is relatively straightforward for crystals with dimensions of >25 m; however, this step is nontrivial for smaller crystals. The mounting of microcrystals is becoming increasingly important as advances in microfocus synchrotron beamlines now allow data collection from crystals with dimensions of only a few micrometres. To make optimal usage of these beamlines, new approaches have to be taken to facilitate and automate this last manual handling step. Optical tweezers, which are routinely used for the manipulation of micrometre-sized objects, have successfully been applied to sort and mount macromolecular crystals on newly designed crystal holders. Diffraction data from CPV type 1 polyhedrin microcrystals mounted with laser tweezers are presented.

  13. Quantum limited particle sensing in optical tweezers

    SciTech Connect

    Tay, J.W.; Hsu, Magnus T. L.; Bowen, Warwick P.

    2009-12-15

    Particle sensing in optical tweezers systems provides information on the position, velocity, and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper, we show that quadrant detection is nonoptimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacies of both quadrant and spatial homodyne detection are shown. We demonstrate that 1 order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.

  14. Trapping N2 and CO2 on the Sub-Nano Scale in the Confined Internal Spaces of Open-Cage C60 Derivatives: Isolation and Structural Characterization of the Host-Guest Complexes.

    PubMed

    Futagoishi, Tsukasa; Murata, Michihisa; Wakamiya, Atsushi; Murata, Yasujiro

    2015-12-01

    An open-cage C60 tetraketone with a large opening was able to encapsulate N2 and CO2 molecules after its exposure to high pressures of N2 and CO2 gas. A subsequent selective reduction of one of the four carbonyl groups on the rim of the opening induced a contraction of the opening (?2) and trapped the guest molecules inside 2. The thus-obtained host-guest complexes N2 @2 and CO2 @2 could be isolated by recycling HPLC, and were found to be stable at room temperature. The molecular structures of N2 @2 and CO2 @2 were determined by single-crystal X-ray diffraction analyses, and revealed a short N?N triple bond for the encapsulated N2 , as well as an unsymmetric molecular structure for the encapsulated molecule of CO2 . The IR spectrum of CO2 @2 suggested that the rotation of the encapsulated molecule of CO2 is partially restricted, which was supported by DFT calculations. PMID:26473764

  15. Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

    PubMed Central

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

  16. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    .... (a) Identification. The tweezer-type epilator is an electrical device intended to remove hair. The energy provided at the tip of the tweezer used to remove hair may be radio frequency, galvanic...

  17. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... (a) Identification. The tweezer-type epilator is an electrical device intended to remove hair. The energy provided at the tip of the tweezer used to remove hair may be radio frequency, galvanic...

  18. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... (a) Identification. The tweezer-type epilator is an electrical device intended to remove hair. The energy provided at the tip of the tweezer used to remove hair may be radio frequency, galvanic...

  19. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... (a) Identification. The tweezer-type epilator is an electrical device intended to remove hair. The energy provided at the tip of the tweezer used to remove hair may be radio frequency, galvanic...

  20. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... (a) Identification. The tweezer-type epilator is an electrical device intended to remove hair. The energy provided at the tip of the tweezer used to remove hair may be radio frequency, galvanic...

  1. Magnetic Tweezers for the Measurement of Twist and Torque

    PubMed Central

    Lipfert, Jan; Lee, Mina; Ordu, Orkide; Kerssemakers, Jacob W. J.; Dekker, Nynke H.

    2014-01-01

    Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a conventional magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the conventional magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument. PMID:24894412

  2. Quantum computation architecture using optical tweezers

    SciTech Connect

    Weitenberg, Christof; Kuhr, Stefan; Moelmer, Klaus; Sherson, Jacob F.

    2011-09-15

    We present a complete architecture for scalable quantum computation with ultracold atoms in optical lattices using optical tweezers focused to the size of a lattice spacing. We discuss three different two-qubit gates based on local collisional interactions. The gates between arbitrary qubits require the transport of atoms to neighboring sites. We numerically optimize the nonadiabatic transport of the atoms through the lattice and the intensity ramps of the optical tweezer in order to maximize the gate fidelities. We find overall gate times of a few 100 {mu}s, while keeping the error probability due to vibrational excitations and spontaneous scattering below 10{sup -3}. The requirements on the positioning error and intensity noise of the optical tweezer and the magnetic field stability are analyzed and we show that atoms in optical lattices could meet the requirements for fault-tolerant scalable quantum computing.

  3. Tomographic phase microscopy using optical tweezers

    NASA Astrophysics Data System (ADS)

    Habaza, Mor; Gilboa, Barak; Roichman, Yael; Shaked, Natan T.

    2015-07-01

    We review our technique for tomographic phase microscopy with optical tweezers [1]. This tomographic phase microscopy approach enables full 3-D refractive-index reconstruction. Tomographic phase microscopy measures quantitatively the 3- D distribution of refractive-index in biological cells. We integrated our external interferometric module with holographic optical tweezers for obtaining quantitative phase maps of biological samples from a wide range of angles. The close-tocommon- path, off-axis interferometric system enables a full-rotation tomographic acquisition of a single cell using holographic optical tweezers for trapping and manipulating with a desired array of traps, while acquiring phase information of a single cell from all different angles and maintaining the native surrounding medium. We experimentally demonstrated two reconstruction algorithms: the filtered back-projection method and the Fourier diffraction method for 3-D refractive index imaging of yeast cells.

  4. Optical tweezers study life under tension

    NASA Astrophysics Data System (ADS)

    Fazal, Furqan M.; Block, Steven M.

    2011-06-01

    Optical tweezers have become one of the primary weapons in the arsenal of biophysicists, and have revolutionized the new field of single-molecule biophysics. Today's techniques allow high-resolution experiments on biological macromolecules that were mere pipe dreams only a decade ago.

  5. Optical tweezer micromanipulation of filamentous fungi.

    PubMed

    Wright, Graham D; Arlt, Jochen; Poon, Wilson C K; Read, Nick D

    2007-01-01

    Optical tweezers have been little used in experimental studies on filamentous fungi. We have built a simple, compact, easy-to-use, safe and robust optical tweezer system that can be used with brightfield, phase contrast, differential interference contrast and fluorescence optics on a standard research grade light microscope. We have used this optical tweezer system in a range of cell biology applications to trap and micromanipulate whole fungal cells, organelles within cells, and beads. We have demonstrated how optical tweezers can be used to: unambiguously determine whether hyphae are actively homing towards each other; move the Spitzenkrper and change the pattern of hyphal morphogenesis; make piconewton force measurements; mechanically stimulate hyphal tips; and deliver chemicals to localized regions of hyphae. Significant novel experimental findings from our study were that germ tubes generated significantly smaller growth forces than leading hyphae, and that both hyphal types exhibited growth responses to mechanical stimulation with optically trapped polystyrene beads. Germinated spores that had been optically trapped for 25min exhibited no deleterious effects with regard to conidial anastomosis tube growth, homing or fusion. PMID:16908207

  6. Aberrated optical tweezers for manipulation of microscopic objects

    NASA Astrophysics Data System (ADS)

    Mohanty, Samarendra K.; Gupta, Pradeep K.

    2007-02-01

    Microscopic objects can be manipulated in a more complex and effective way by use of static aberrated tweezers. We theoretically studied dynamics of interaction of Rayleigh particles with such asymmetric tweezers. Microscopic objects are pulled at the high intensity gradient end of the asymmetric tweezers, get accelerated and are ejected from the other end. Thus objects from two locations could be transported by two asymmetric line tweezers and mixed at another place where the low intensity gradient regions of the two beams meet. It is pertinent to note here that the speed of transport is determined by the laser beam power and the degree of asymmetry in the intensity profile. And since for a fixed asymmetry and laser power, the speed is dependent on the refractive index and size of the objects, sorting of these objects could be made possible. Sorting could be achieved either by scanning the asymmetric line tweezers across the sample or without scanning the stage by use of two asymmetric line tweezers. In the all-optical approach (use of two asymmetric line tweezers), we exploited the fact that when the speed of objects transported by one tweezers crossed a threshold value, these did not interact with the second tweezers and therefore moved undeviated; whereas slower moving objects were collected by the second tweezers and transported to a well-separated location.

  7. Exploring unconventional capabilities of holographic tweezers

    NASA Astrophysics Data System (ADS)

    Hernandez, R. J.; Pagliusi, P.; Provenzano, C.; Cipparrone, G.

    2011-06-01

    We report an investigation of manipulation and trapping capabilities of polarization holographic tweezers. A polarization gradient connected with a modulation of the ellipticity shows an optical force related to the polarization of the light that can influence optically isotropic particles. While in the case of birefringent particles an unconventional trapping in circularly polarized fringes is observed. A liquid crystal emulsion has been adopted to investigate the capabilities of the holographic tweezers. The unusual trapping observed for rotating bipolar nematic droplets has suggested the involvement of the lift hydrodynamic force responsible of the Magnus effect, originating from the peculiar optical force field. We show that the Magnus force which is ignored in the common approach can contribute to unconventional optohydrodynamic trapping and manipulation.

  8. Improved axial trapping with holographic optical tweezers.

    PubMed

    Pollari, Russell; Milstein, Joshua N

    2015-11-01

    Conventional optical tweezers suffer from several complications when applying axial forces to surface-tethered molecules. Aberrations from the refractive-index mismatch between an oil-immersion objective's medium and the aqueous trapping environment both shift the trap centre and degrade the trapping strength with focal depth. Furthermore, interference effects from back-scattered light make it difficult to use back-focal-plane interferometry for high-bandwidth position detection. Holographic optical tweezers were employed to correct for aberrations to achieve a constant axial stiffness and modulate artifacts from backscattered light. Once the aberrations are corrected for, the trap height can be precisely determined from either the back-scattered light or Brenner's formula. PMID:26561154

  9. Optoelectronic tweezers for microparticle and cell manipulation

    NASA Technical Reports Server (NTRS)

    Wu, Ming Chiang (Inventor); Chiou, Pei Yu (Inventor); Ohta, Aaron T. (Inventor)

    2009-01-01

    An optical image-driven light induced dielectrophoresis (DEP) apparatus and method are described which provide for the manipulation of particles or cells with a diameter on the order of 100 .mu.m or less. The apparatus is referred to as optoelectric tweezers (OET) and provides a number of advantages over conventional optical tweezers, in particular the ability to perform operations in parallel and over a large area without damage to living cells. The OET device generally comprises a planar liquid-filled structure having one or more portions which are photoconductive to convert incoming light to a change in the electric field pattern. The light patterns are dynamically generated to provide a number of manipulation structures that can manipulate single particles and cells or groups of particles/cells. The OET preferably includes a microscopic imaging means to provide feedback for the optical manipulation, such as detecting position and characteristics wherein the light patterns are modulated accordingly.

  10. Optoelectronic Tweezers for Microparticle and Cell Manipulation

    NASA Technical Reports Server (NTRS)

    Wu, Ming Chiang (Inventor); Chiou, Pei-Yu (Inventor); Ohta, Aaron T. (Inventor)

    2014-01-01

    An optical image-driven light induced dielectrophoresis (DEP) apparatus and method are described which provide for the manipulation of particles or cells with a diameter on the order of 100 micromillimeters or less. The apparatus is referred to as optoelectric tweezers (OET) and provides a number of advantages over conventional optical tweezers, in particular the ability to perform operations in parallel and over a large area without damage to living cells. The OET device generally comprises a planar liquid-filled structure having one or more portions which are photoconductive to convert incoming light to a change in the electric field pattern. The light patterns are dynamically generated to provide a number of manipulation structures that can manipulate single particles and cells or group of particles/cells. The OET preferably includes a microscopic imaging means to provide feedback for the optical manipulation, such as detecting position and characteristics wherein the light patterns are modulated accordingly.

  11. Independent trapping and manipulation of microparticles using dexterous acoustic tweezers

    SciTech Connect

    Courtney, Charles R. P.; Demore, Christine E. M.; Wu, Hongxiao; Cochran, Sandy; Grinenko, Alon; Wilcox, Paul D.; Drinkwater, Bruce W.

    2014-04-14

    An electronically controlled acoustic tweezer was used to demonstrate two acoustic manipulation phenomena: superposition of Bessel functions to allow independent manipulation of multiple particles and the use of higher-order Bessel functions to trap particles in larger regions than is possible with first-order traps. The acoustic tweezers consist of a circular 64-element ultrasonic array operating at 2.35 MHz which generates ultrasonic pressure fields in a millimeter-scale fluid-filled chamber. The manipulation capabilities were demonstrated experimentally with 45 and 90-μm-diameter polystyrene spheres. These capabilities bring the dexterity of acoustic tweezers substantially closer to that of optical tweezers.

  12. The Smallest Tweezers in the World

    ERIC Educational Resources Information Center

    Lewalle, Alexandre

    2008-01-01

    A pair of fine tweezers and a steady hand may well be enough to pick up a grain of sand, but what would you use to hold something hundreds of times smaller still, the size of only one micron? The answer is to use a device that is not mechanical in nature but that relies instead on the tiny forces that light exerts on small particles: "optical

  13. Interactive approach to optical tweezers control

    SciTech Connect

    Leach, Jonathan; Wulff, Kurt; Sinclair, Gavin; Jordan, Pamela; Courtial, Johannes; Thomson, Laura; Gibson, Graham; Karunwi, Kayode; Cooper, Jon; Laczik, Zsolt John; Padgett, Miles

    2006-02-10

    We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.

  14. The Smallest Tweezers in the World

    ERIC Educational Resources Information Center

    Lewalle, Alexandre

    2008-01-01

    A pair of fine tweezers and a steady hand may well be enough to pick up a grain of sand, but what would you use to hold something hundreds of times smaller still, the size of only one micron? The answer is to use a device that is not mechanical in nature but that relies instead on the tiny forces that light exerts on small particles: "optical…

  15. Digital holographic microscopy combined with optical tweezers

    NASA Astrophysics Data System (ADS)

    Cardenas, Nelson; Yu, Lingfeng; Mohanty, Samarendra K.

    2011-02-01

    While optical tweezers have been widely used for the manipulation and organization of microscopic objects in three dimensions, observing the manipulated objects along axial direction has been quite challenging. In order to visualize organization and orientation of objects along axial direction, we report development of a Digital holographic microscopy combined with optical tweezers. Digital holography is achieved by use of a modified Mach-Zehnder interferometer with digital recording of interference pattern of the reference and sample laser beams by use of a single CCD camera. In this method, quantitative phase information is retrieved dynamically with high temporal resolution, only limited by frame rate of the CCD. Digital focusing, phase-unwrapping as well as online analysis and display of the quantitative phase images was performed on a software developed on LabView platform. Since phase changes observed in DHOT is very sensitive to optical thickness of trapped volume, estimation of number of particles trapped in the axial direction as well as orientation of non-spherical objects could be achieved with high precision. Since in diseases such as malaria and diabetics, change in refractive index of red blood cells occurs, this system can be employed to map such disease-specific changes in biological samples upon immobilization with optical tweezers.

  16. Probing the Casimir force with optical tweezers

    NASA Astrophysics Data System (ADS)

    Ether, D. S., Jr.; Pires, L. B.; Umrath, S.; Martinez, D.; Ayala, Y.; Pontes, B.; Araújo, G. R. de S.; Frases, S.; Ingold, G.-L.; Rosa, F. S. S.; Viana, N. B.; Nussenzveig, H. M.; Neto, P. A. Maia

    2015-11-01

    We propose to use optical tweezers to probe the Casimir interaction between microspheres inside a liquid medium for geometric aspect ratios far beyond the validity of the widely employed proximity force approximation. This setup has the potential for revealing unprecedented features associated to the non-trivial role of the spherical curvatures. For a proof of concept, we measure femtonewton double-layer forces between polystyrene microspheres at distances above 400 nm by employing very soft optical tweezers, with stiffness of the order of fractions of a fN/nm. As a future application, we propose to tune the Casimir interaction between a metallic and a polystyrene microsphere in saline solution from attraction to repulsion by varying the salt concentration. With those materials, the screened Casimir interaction may have a larger magnitude than the unscreened one. This line of investigation has the potential for bringing together different fields including classical and quantum optics, statistical physics and colloid science, while paving the way for novel quantitative applications of optical tweezers in cell and molecular biology.

  17. Raman-tweezers spectroscopy of single biological cells and organelles

    NASA Astrophysics Data System (ADS)

    Li, Yongqing

    2004-11-01

    Raman tweezers, also called laser tweezers Raman spectroscopy (LTRS), is an instrument that combines optical tweezers and confocal Raman microscopy for simultaneous manipulation and analysis of single biological cells or organelles in a physiological solution without the need of introducing biochemical tags. The optical tweezers part of the LTRS system uses a tightly focused near-infrared beam to capture and immobilize a biological particle in a liquid medium by the gradient force. The Raman spectroscopy part can generate vibrational spectra of the trapped particle to provide composition and conformation information of molecules based on measuring molecular vibrations from the scattered light. In this talk, we will present the physical principle and instrumentation of optical tweezers and micro-Raman spectroscopy system. Applications in rapid detection and identification of microorganisms, sorting of living cells, and real-time measurement of the dynamical changes in biochemical properties of macromolecules within living cells, and detection of recombinant proteins in transgenic cells will be presented.

  18. Optical Tweezers Array and Nimble Tweezers Probe Generated by Spatial- Light Modulator

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Jassemnejad, Baha; Seibel, Robin E.; Weiland, Kenneth E.

    2003-01-01

    An optical tweezers is being developed at the NASA Glenn Research Center as a visiblelight interface between ubiquitous laser technologies and the interrogation, visualization, manufacture, control, and energization of nanostructures such as silicon carbide (SiC) nanotubes. The tweezers uses one or more focused laser beams to hold micrometer-sized particles called tools (sometimes called tips in atomic-force-microscope terminology). A strongly focused laser beam has an associated light-pressure gradient that is strong enough to pull small particles to the focus, in spite of the oppositely directed scattering force; "optical tweezers" is the common term for this effect. The objective is to use the tools to create carefully shaped secondary traps to hold and assemble nanostructures that may contain from tens to hundreds of atoms. The interaction between a tool and the nanostructures is to be monitored optically as is done with scanning probe microscopes. One of the initial efforts has been to create, shape, and control multiple tweezers beams. To this end, a programmable spatial-light modulator (SLM) has been used to modify the phase of a laser beam at up to 480 by 480 points. One program creates multiple, independently controllable tweezer beams whose shapes can be tailored by making the SLM an adaptive mirror in an interferometer (ref. 1). The beams leave the SLM at different angles, and an optical Fourier transform maps these beams to different positions in the focal plane of a microscope objective. The following figure shows two arrays of multiple beams created in this manner. The patterns displayed above the beam array control the intensity-to-phase transformation required in programming the SLM. Three of the seven beams displayed can be used as independently controllable beams.

  19. Investigating hydrodynamic synchronisation using holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Box, Stuart; Debono, Luke; Bruot, Nicolas; Kotar, Jurij; Cicuta, Pietro; Miles, Mervyn; Hanna, Simon; Phillips, David; Simpson, Stephen

    2014-09-01

    Coordinated motion at low Reynolds number is widely observed in biological micro-systems, but the underlying mechanisms are often unclear. A holographic optical tweezers system is used to experimentally study this phenomenon, by employing optical forces to drive a pair of coplanar microspheres in circular orbits with a constant tangential force. In this system synchronisation is caused by hydrodynamic forces arising from the motion of the two spheres. The timescales of their synchronisation from large initial phase differences are explored and found to be dependent on how stiffly the microspheres are confined to their circular orbits. These measured timescales show good agreement with numerical simulations.

  20. Micromechanics of Dipolar Chains Using Optical Tweezers

    NASA Technical Reports Server (NTRS)

    Furst, Eric M.; Gast, Alice P.

    1999-01-01

    Here we present our initial study of the micromechanical properties of dipolar chains and columns in a magnetorheological (MR) suspension. Using dual-trap optical tweezers, we are able to directly measure the deformation of the dipolar chains parallel and perpendicular to the applied magnetic field. We observe the field dependence of the mechanical properties such as resistance to deformation, chain reorganization, and rupturing of the chains. These forms of energy dissipation are important for understanding and tuning the yield stress and rheological behavior of an MR suspension.

  1. Reusable acoustic tweezers for disposable devices

    PubMed Central

    Guo, Feng; Xie, Yuliang; Li, Sixing; Lata, James; Ren, Liqiang; Mao, Zhangming; Ren, Baiyang; Wu, Mengxi; Ozcelik, Adem

    2015-01-01

    We demonstrate acoustic tweezers used for disposable devices. Rather than forming an acoustic resonance, we locally transmitted standing surface acoustic waves into a removable, independent polydimethylsiloxane (PDMS)-glass hybridized microfluidic superstrate device for micromanipulation. By configuring and regulating the displacement nodes on a piezoelectric substrate, cells and particles were effectively patterned and transported into said superstrate, accordingly. With the label-free and contactless nature of acoustic waves, the presented technology could offer a simple, accurate, low-cost, biocompatible, and disposable method for applications in the fields of point-of-care diagnostics and fundamental biomedical studies. PMID:26507411

  2. Topology optimization of the optical tweezers setup

    NASA Astrophysics Data System (ADS)

    Hwang, Sun-Uk; Lee, Yong-Gu

    2005-02-01

    Optical tweezers (OT) uses a focused laser beam to trap and move microscopic objects. The design of OT consists of laying out stationary and moving (or rotating) lenses and mirrors so that two design constraints are met at the objective back aperture (OBA): 1) the laser beam has to be pivoted around the center, and 2) the beam has to keep the same degree of overfilling. While these constraints are met, the objectives are to maximize the divergence/convergence angle and the beam rotation angle at the OBA. They are each accomplished by moving a lens or rotating a mirror, respectively. There are few known designs that give (claimed) good performances while satisfying above constraints. However, these designs are improvised inventions with no attempts in optimization. In this paper, we propose a new method for designing an optimized OT that achieves the best performance with given pool of optical elements. Our method, (Topology Optimization of the Optical Tweezers Setup) first divides the layout space into finite lattices and then distributes lenses and mirrors to appropriate lattices. Subsequently, whether the attempted configuration conforms to the constraints is tested. If the test is successful, the layout and its performance are recorded. At the end, the best performing layout is found. In this paper, we primarily concentrate on optimizing the positions of lens components. In the future, this approach will be generalized for more complicated configurations that include mirror components.

  3. Absolute calibration of forces in optical tweezers

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

    2014-07-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past 15 years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

  4. Touching the microworld with force-feedback optical tweezers.

    PubMed

    Pacoret, Cécile; Bowman, Richard; Gibson, Graham; Haliyo, Sinan; Carberry, David; Bergander, Arvid; Régnier, Stéphane; Padgett, Miles

    2009-06-01

    Optical tweezers are a powerful tool for micromanipulation and measurement of picoNewton sized forces. However, conventional interfaces present difficulties as the user cannot feel the forces involved. We present an interface to optical tweezers, based around a low-cost commercial force feedback device. The different dynamics of the micro-world make intuitive force feedback a challenge. We propose a coupling method using an existing optical tweezers system and discuss stability and transparency. Our system allows the user to perceive real Brownian motion and viscosity, as well as forces exerted during manipulation of objects by a trapped bead. PMID:19506679

  5. Potential-well model in acoustic tweezers.

    PubMed

    Kang, Shih-Tsung; Yeh, Chih-Kuang

    2010-06-01

    Standing-wave acoustic tweezers are popularly used for non-invasive and non-contact particle manipulation. Because of their good penetration in biological tissue, they also show promising prospects for in vivo applications. According to the concept of an optical vortex, we propose an acoustics-vortex- based trapping model of acoustic tweezers. A four-element 1-MHz planar transducer was used to generate 1-MHz sine waves at 1 MPa, with adjacent elements being driven with a pi/2-rad phase difference. Each element was a square with a side length of 5.08 mm, with kerfs initially set at 0.51 mm. An acoustic vortex constituting the spiral motion of an acoustic wave around the beam axis was created, with an axial null. Applying Gor'kov's theory in the Rayleigh regime yielded the potential energy and radiation force for use in subsequent analysis. In the transverse direction, the vortex structure behaved as a series of potential wells that tended to drive a suspended particle toward the beam axis. They were highly fragmented in the near field that is very close to the transducer where there was spiral interference, and well-constructed in the far field. We found that the significant trapping effect was only present between these two regions in the transverse direction--particles were free to move along the beam axis, and a repulsive force was observed in the outer acoustic vortex. Because the steepness of the potential gradient near an axial null dominates the trapping effect, the far field of the acoustic vortex is inappropriate for trapping. Particles too close to the transducer are not sufficiently trapped because of the fragmented potential pattern. We suggest that the ideal distance from the transducer for trapping particles is in front of one-fourth of the Rayleigh distance, based on the superposition of the wavefronts. The maximum trapping force acting on a 13-mum polystyrene sphere in the produced acoustic vortex was 50.0 pN, and it was possible to trap approximately 10(6) particles within a plane; the maximum repulsive force was 24.5 pN, and this was reduced to less than 13 pN by smoothing the outer gradient. Most stiff and dense particles can be used in this model. The presence of transverse trapping and the long working distance make the model useful for 2-D manipulation, particularly in in vivo applications. This paper details the trapping properties in the acoustic vortex and describes methods for improving the design of the transducer. The results obtained support the feasibility of the potential-well model of acoustic tweezers. PMID:20529720

  6. Plasmonic optical tweezers: A long arm and a tight grip

    NASA Astrophysics Data System (ADS)

    Tsuboi, Yasuyuki

    2016-01-01

    By taking advantage of the thermal gradient that is generated in plasmonic systems and by using an a.c. field, plasmonic tweezers can have a large radius of action and can trap and manipulate single nano-objects.

  7. Multiplexed spectroscopy with holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Cibula, Matthew A.; McIntyre, David H.

    2014-09-01

    We have developed a multiplexed holographic optical tweezers system with an imaging spectrometer to manipulate multiple optically trapped nanosensors and detect multiple fluorescence spectra. The system uses a spatial light modulator (SLM) to control the positions of infrared optical traps in the sample so that multiple nanosensors can be positioned into regions of interest. Spectra of multiple nanosensors are detected simultaneously with the application of an imaging spectrometer. Nanosensors are capable of detecting changes in their environment such as pH, ion concentration, temperature, and voltage by monitoring changes in the nanosensors' emitted fluorescence spectra. We use streptavidin labeled quantum dots bound to the surface of biotin labeled polystyrene microspheres to measure temperature changes by observing a corresponding shift in the wavelength of the spectral peak. The fluorescence is excited at 532 nm with a wide field source.

  8. Subpiconewton Dynamic Force Spectroscopy Using Magnetic Tweezers

    PubMed Central

    Kruithof, M.; Chien, F.; de Jager, M.; van Noort, J.

    2008-01-01

    We introduce a simple method for dynamic force spectroscopy with magnetic tweezers. This method allows application of subpiconewton force and twist control by calibration of the applied force from the height of the magnets. Initial dynamic force spectroscopy experiments on DNA molecules revealed a large hysteresis that is caused by viscous drag on the magnetic bead and will conceal weak interactions. When smaller beads are used, this hysteresis is sufficiently reduced to reveal intramolecular interactions at subpiconewton forces. Compared with typical quasistatic force spectroscopy, a significant reduction of measurement time is achieved, allowing the real-time study of transient structures and reaction intermediates. As a proof of principle, nucleosome-nucleosome interactions on a subsaturated chromatin fiber were analyzed. PMID:18065448

  9. Optical tweezers for studying taxis in parasites

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Fontes, A.; Stahl, C. V.; Pozzo, L. Y.; Ayres, D. C.; Almeida, D. B.; Farias, P. M. A.; Santos, B. S.; Santos-Mallet, J.; Gomes, S. A. O.; Giorgio, S.; Feder, D.; Cesar, C. L.

    2011-04-01

    In this work we present a methodology to measure force strengths and directions of living parasites with an optical tweezers setup. These measurements were used to study the parasites chemotaxis in real time. We observed behavior and measured the force of: (i) Leishmania amazonensis in the presence of two glucose gradients; (ii) Trypanosoma cruzi in the vicinity of the digestive system walls, and (iii) Trypanosoma rangeli in the vicinity of salivary glands as a function of distance. Our results clearly show a chemotactic behavior in every case. This methodology can be used to study any type of taxis, such as chemotaxis, osmotaxis, thermotaxis, phototaxis, of any kind of living microorganisms. These studies can help us to understand the microorganism sensory systems and their response function to these gradients.

  10. Stretching short DNA tethers using optical tweezers

    NASA Astrophysics Data System (ADS)

    Reihani, Nader; Bosanac, Lana; Hansen, Thomas M.; Oddershede, Lene B.

    2006-08-01

    With the evolution of single molecule techniques as force-scope optical tweezers, it has become possible to perform very accurate measurements of the elastic properties of biopolymers as e.g. DNA. Nucleic acid elasticity is important in the interaction of these molecules with proteins and protein complexes in the living cell. Most experimental and theoretical effort has been aimed at uncovering and understanding of the behavior of polymers with contour lengths significantly longer than their persistence length. The well-established Worm-Like-Chain model has been modified such that a satisfactory description of such long biopolymers is available. However, in many single molecule experiments, such as the unfolding of RNA stem-loops1 and RNA pseudoknots,2 one is dealing with biopolymers whose contour lengths are comparable to persistence lengths. A full understanding of such curves requires an understanding of the physics of short biopolymers. For such cases, theories are just beginning to emerge and there is hardly any experimental data available. We target this problem by optical tweezers quantitative force-extension measurements on short biopolymers. The biopolymers used are primarily double stranded DNA whose total length ( 300 nm) is comparable to their persistence length ( 50 nm). As a control of our equipment and methods, we also stretch longer dsDNA (1100 nm), the force-extension curves of which resemble those in literature. 3 For the short DNA the force-extension curves qualitatively resemble those predicted by WLC theories, but a reasonable fit can only be made if the persistence length is allowed to be a fitting parameter. If made a fitting parameter, the 'apparent persistence length' is found as 8.7+/-4 nm, a number which is significantly lower than the real physical value.

  11. Metal nanoparticle-functionalized DNA tweezers: from mechanically programmed nanostructures to switchable fluorescence properties.

    PubMed

    Shimron, Simcha; Cecconello, Alessandro; Lu, Chun-Hua; Willner, Itamar

    2013-08-14

    DNA tweezers are modified with two 10-nm sized Au NPs and one 5-nm sized Au NP. Upon treatment of the tweezers with fuel and antifuel nucleic acid strands, the switchable closure and opening of the tweezers proceed, leading to the control of programmed nanostructures of the tethered NPs. The tweezers are further modified with a single 10-nm sized nanoparticle, and a fluorophore unit (Cy3), positioned at different distinct sites of the tweezers. The reversible and cyclic fluorescence quenching or fluorescence enhancement phenomena, upon the dynamic opening/closure of the different tweezers, are demonstrated. PMID:23815358

  12. Laser tweezers Raman spectroscopy of single cells

    NASA Astrophysics Data System (ADS)

    Chen, De

    Raman scattering is an inelastic collision between the vibrating molecules inside the sample and the incident photons. During this process, energy exchange takes place between the photon and the scattering molecule. By measuring the energy change of the photon, the molecular vibration mode can be probed. The vibrational spectrum contains valuable information about the disposition of atomic nuclei and chemical bonds within a molecule, the chemical compositions and the interactions between the molecule and its surroundings. In this dissertation, laser tweezers Raman spectroscopy (LTRS) technique is applied for the analysis of biological cells and human cells at single cell level. In LTRS, an individual cell is trapped in aqueous medium with laser tweezers, and Raman scattering spectra from the trapped cell are recorded in real-time. The Raman spectra of these cells can be used to reveal the dynamical processes of cell growth, cell response to environment changes, and can be used as the finger print for the identification of a bacterial cell species. Several biophysical experiments were carried out using LTRS: (1) the dynamic germination process of individual spores of Bacillus thuringiensis was detected via Ca-DPA, a spore-specific biomarker molecule; (2) inactivation and killing of Bacillus subtilis spores by microwave irradiation and wet heat were studied at single cell level; (3) the heat shock activation process of single B. subtilis spores were analyzed, in which the reversible transition from glass-like state at low temperature to liquid-like state at high temperature in spore was revealed at the molecular level; (4) the kinetic processes of bacterial cell lysis of E. coli by lysozyme and by temperature induction of lambda phage were detected real-time; (5) the fixation and rehydration of human platelets were quantitatively evaluated and characterized with Raman spectroscopy method, which provided a rapid way to quantify the quality of freeze-dried therapeutic platelet products for long term preservation; (6) LTRS based depolarized Raman spectroscopy was developed and used to do bacterial cell identification of similar species. From these experiments, several new findings and conclusions have been obtained. (1) single spore dynamic germination was measured for the first time. The result showed the time-to-germinate of a single spore was stochastic and could be discrete. (2) the thermal nature of spore killing in solution by microwaves was identified, Spores killed directly by microwaves showed death marker in Raman spectrum; (3) The Ca-DPA inside the spore core of a spore would undergo a structure modification during heat shock, which was related to the spores' state transition from a glass-like to a rubbery-like state, this structure modification during heat shock was reversible; (4) the kinetic molecular processes of E. coli cell lysis by lysozyme and by temperature induction of bacterial phage were recorded for the first time. The different cellular processes of the lysis were revealed based on the two different mechanisms; (5) LTRS technique was successfully applied to characterize human platelet fixation; a major procedure for long term preservation of therapeutic human platelet products; (6) A depolarization laser tweezers Raman spectroscopy (DLTRS) technique was developed to enhance the ability to discriminate similar bacterial species.

  13. How safe is gamete micromanipulation by laser tweezers?

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Tromberg, Bruce J.; Tadir, Yona; Berns, Michael W.

    1998-04-01

    Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.

  14. Characterization of periodic cavitation in optical tweezers.

    PubMed

    Carmona-Sosa, Viridiana; Alba-Arroyo, José Ernesto; Quinto-Su, Pedro A

    2016-03-10

    Microscopic vapor explosions or cavitation bubbles can be generated repeatedly in optical tweezers with a microparticle that partially absorbs at the trapping laser wavelength. In this work we measure the size distribution and the production rate of cavitation bubbles for microparticles with a diameter of 3 μm using high-speed video recording and a fast photodiode. We find that there is a lower bound for the maximum bubble radius Rmax∼2  μm which can be explained in terms of the microparticle size. More than 94% of the measured Rmax are in the range between 2 and 6 μm, while the same percentage of the measured individual frequencies fi or production rates are between 10 and 200 Hz. The photodiode signal yields an upper bound for the lifetime of the bubbles, which is at most twice the value predicted by the Rayleigh equation. We also report empirical relations between Rmax, fi, and the bubble lifetimes. PMID:26974779

  15. Low frequency dynamical stabilisation in optical tweezers

    NASA Astrophysics Data System (ADS)

    Richards, Christopher J.; Smart, Thomas J.; Jones, Philip H.; Cubero, David

    2015-08-01

    It is well known that a rigid pendulum with minimal friction will occupy a stable equilibrium position vertically upwards when its suspension point is oscillated at high frequency. The phenomenon of the inverted pendulum was explained by Kapitza by invoking a separation of timescales between the high frequency modulation and the much lower frequency pendulum motion, resulting in an effective potential with a minimum in the inverted position. We present here a study of a microscopic optical analogue of Kapitza's pendulum that operates in different regimes of both friction and driving frequency. The pendulum is realized using a microscopic particle held in a scanning optical tweezers and subject to a viscous drag force. The motion of the optical pendulum is recorded and analyzed by digital video microscopy and particle tracking to extract the trajectory and stable orientation of the particle. In these experiments we enter the regime of low driving frequency, where the period of driving is comparable to the characteristic relaxation time of the radial motion of the pendulum with finite stiffness. In this regime we find stabilization of the pendulum at angles other than the vertical (downwards) is possible for modulation amplitudes exceeding a threshold value where, unlike the truly high frequency case studied previously, both the threshold amplitude and equilibrium position are found to be functions of friction. Experimental results are complemented by an analytical theory for induced stability in the low frequency driving regime with friction.

  16. Angular orientation of nanorods using nanophotonic tweezers.

    PubMed

    Kang, Pilgyu; Serey, Xavier; Chen, Yih-Fan; Erickson, David

    2012-12-12

    Near-field optical techniques have enabled the trapping, transport, and handling of nanoscopic materials much smaller than what can be manipulated with traditional optical tweezers. Here we extend the scope of what is possible by demonstrating angular orientation and rotational control of both biological and nonbiological nanoscale rods using photonic crystal nanotweezers. In our experiments, single microtubules (diameter 25 nm, length 8 ?m) and multiwalled carbon nanotubes (outer diameter 110-170 nm, length 5 ?m) are rotated by the optical torque resulting from their interaction with the evanescent field emanating from these devices. An angular trap stiffness of ? = 92.8 pNnm/rad(2)mW is demonstrated for the microtubules, and a torsional spring constant of 22.8 pNnm/rad(2)mW is measured for the nanotubes. We expect that this new capability will facilitate the development of high precision nanoassembly schemes and biophysical studies of bending strains of biomolecules. PMID:23145817

  17. Probing the Casimir force with optical tweezers

    NASA Astrophysics Data System (ADS)

    Maia Neto, Paulo; Ether, Diney; Pires, Luis; Ayala, Yareni; Rosa, Felipe; Umrath, Stefan; Ingold, Gert; Viana, Nathan; Nussenzveig, Moyses

    2015-03-01

    Optical tweezers (OT) are single-beam laser traps for neutral particles, usually applied to dielectric microspheres immersed in a fluid. The stiffness is proportional to the trapping beam power, and hence can be tuned to very small values, allowing one to measure femtonewton forces, once the device is carefully calibrated. We employ OT to measure the Casimir (or retarded van der Waals) force between polystyrene beads in ethanol, for distances between 50 nanometers and 1 micrometer. The spherical beads have diameters ranging from 3 to 7 micrometers. We find a rather large correction to the widely employed Proximity Force approximation (PFA), since the ratio between distances and sphere radii is much larger than the typical values probed in recent experiments. For the comparison with experimental data, we compute the Casimir force using the scattering approach applied to the spherical geometry, including the contribution of double-layer forces. We also present experimental results for the total force between a mercury microdroplet and a polystyrene bead immersed in ethanol, with similar distances and diameters. In short, we probe the Casimir force with different materials in a regime far from the validity of PFA, such that the spherical geometry plays a non-trivial role.

  18. A Plasma Tweezer Concept to De-spin an Asteroid

    NASA Astrophysics Data System (ADS)

    Vereen, Keon; Datta, Iman; You, Setthivoine

    2014-10-01

    The Plasma Tweezer is a new concept for controlled de-spinning and deflection of space bodies without mechanical contact. The method shoots plasma jets or beams at the target from a pair of plasma thrusters located at the end of each lever arm of a ``tweezer'' structure. The main spacecraft body is at the fulcrum point of the tweezer and the target is located between the thrusters. This arrangement cancels out the impulse of two plasma jets on the spacecraft and applies forces on opposite sides of the target. Careful timing and orientation of the jets can then provide the necessary forces to despin and redirect the target. This concept is more efficient than the Ion Beam Shepherd method [C. Bombardelli and J. Pelaez, J. Guid. Control Dyn. (2011)] because it does not require a secondary thruster to cancel momentum and can benefit from angular momentum stored in the spacecraft's initial spin stabilization.

  19. Mechanisms of HCV NS3 Helicase Monitored by Optical Tweezers

    PubMed Central

    Cheng, Wei

    2015-01-01

    As one of the essential enzymes for viral genome replication, the hepatitis C virus NS3 helicase is one of the best characterized RNA helicases to date in understanding the mechanistic cycles in a helicase-catalyzed strand separation reaction. Recently, single-molecule studies on NS3, in particular the use of optical tweezers with sub-base pair spatial resolution, have allowed people to examine the potential elementary steps of NS3 in unwinding the double-stranded RNA fueled by ATP binding and hydrolysis. In this chapter, I detail the essential technical elements involved in conducting a high-resolution optical tweezers study of NS3 helicase, starting from the purification of the recombinant helicase protein from E. coli to setting up a high-resolution single-molecule experiment using optical tweezers. PMID:25579590

  20. Optical tweezers based on near infrared diode laser

    NASA Astrophysics Data System (ADS)

    Grego, S.; Arimondo, Ennio; Frediani, Carlo

    1997-07-01

    Emission from a single-mode 100 mW diode laser at 840 nm is used to create optical tweezers: the trapping laser beam is introduced into a microscope and focused by the objective. The microscope also allows monitoring of the motion of the trapped particles. The optical tweezers were monitored with objectives having different numerical apertures between 0.65 and 1.3. The optical trapping of polystyrene spheres with a radius between 0.11 and 7.45 micrometers and of biological objects, the flagellated alga Tetraselmis, with typical dimensions of 8 X 8 X 13 micrometers 3 were studied. The efficiency of the optical tweezers has been characterized through a parameter Q and compared with theoretical models.

  1. Fast hologram computation and aberration control for holographic tweezers

    NASA Astrophysics Data System (ADS)

    Reicherter, M.; Haist, T.; Zwick, S.; Burla, A.; Seifert, L.; Osten, W.

    2005-08-01

    Holographic tweezers offer a very versatile tool in many trapping applications. Compared to tweezers working with acousto optical modulators or using the generalized phase contrast, holographic tweezers so far were relatively slow. The computation time for a hologram was much longer than the modulation frequency of the modulator. To overcome this drawback we present a method using modified algorithms which run on state of the art graphics boards and not on the CPU. This gives the potential for a fast manipulation of many traps, for cell sorting for example, as well as for a real-time aberration control. The control of aberrations which can vary spatially or temporally is relevant to many real world applications. This can be accomplished by applying an iterative approach based on image processing.

  2. Optical tweezers-assisted measurements of elastic light scattering

    NASA Astrophysics Data System (ADS)

    Kinnunen, M.; Tuorila, J.; Haapalainen, T.; Karmenyan, A.; Tuchin, V.; Myllyl, R.

    2014-01-01

    Optical tweezers have been used in biophysical studies for over twenty years. Typical application areas are force measurements of subcellular structures and cell biomechanics. Optical tweezers can also be used to manipulate the orientation of objects. Moreover, using various beam shapes, optical tweezers allow measuring light scattering from single and multiple objects by keeping particles and cells in place during the measurement. At single cell level, light scattering yields important information about the object being studied, including its size, shape and refractive index. Also dependent scattering can be studied. In this paper, we review experimental work conducted in this area by our group and show new results relating to optical clearing phenomena at single microparticle level.

  3. Optical tweezers force measurements to study parasites chemotaxis

    NASA Astrophysics Data System (ADS)

    de Thomaz, A. A.; Pozzo, L. Y.; Fontes, A.; Almeida, D. B.; Stahl, C. V.; Santos-Mallet, J. R.; Gomes, S. A. O.; Feder, D.; Ayres, D. C.; Giorgio, S.; Cesar, C. L.

    2009-07-01

    In this work, we propose a methodology to study microorganisms chemotaxis in real time using an Optical Tweezers system. Optical Tweezers allowed real time measurements of the force vectors, strength and direction, of living parasites under chemical or other kinds of gradients. This seems to be the ideal tool to perform observations of taxis response of cells and microorganisms with high sensitivity to capture instantaneous responses to a given stimulus. Forces involved in the movement of unicellular parasites are very small, in the femto-pico-Newton range, about the same order of magnitude of the forces generated in an Optical Tweezers. We applied this methodology to investigate the Leishmania amazonensis (L. amazonensis) and Trypanossoma cruzi (T. cruzi) under distinct situations.

  4. A mode-division-multiplexing single fiber optical tweezers

    NASA Astrophysics Data System (ADS)

    Zhao, Enming; Liu, Zhihai; Zhang, Yu; Zhang, Yaxun; Yang, Jun; Yuan, Libo

    2015-07-01

    We propose and demonstrate a mode division multiplexing single fiber optical tweezers. By using this tweezers, one can trap a yeast cell and then launch it away from the fiber tip with a certain speed to a certain position without moving the optical fiber in a single fiber optical trapping apparatus. We excite both LP01 and LP11 mode beams in a same normal communication fiber core to generate the optical launching force and trapping force by molding the fiber tip into a special tapered-tip shape. A yeast cell of 6?m diameter is trapped and then being launched away. We construct the optical trapping and launching potential wells by controlling the power of two mode beams. This micro particle directional launching function expands new features of fiber optical tweezers based on the normal communication fiber, providing for the possibility of more practical applications in the biomedical research fields.

  5. Atomic force microscopy combined with optical tweezers (AFM/OT)

    NASA Astrophysics Data System (ADS)

    Pierini, F.; Zembrzycki, K.; Nakielski, P.; Pawłowska, S.; Kowalewski, T. A.

    2016-02-01

    The role of mechanical properties is essential to understand molecular, biological materials, and nanostructures dynamics and interaction processes. Atomic force microscopy (AFM) is the most commonly used method of direct force evaluation, but due to its technical limitations this single probe technique is unable to detect forces with femtonewton resolution. In this paper we present the development of a combined atomic force microscopy and optical tweezers (AFM/OT) instrument. The focused laser beam, on which optical tweezers are based, provides us with the ability to manipulate small dielectric objects and to use it as a high spatial and temporal resolution displacement and force sensor in the same AFM scanning zone. We demonstrate the possibility to develop a combined instrument with high potential in nanomechanics, molecules manipulation and biological studies. AFM/OT equipment is described and characterized by studying the ability to trap dielectric objects and quantifying the detectable and applicable forces. Finally, optical tweezers calibration methods and instrument applications are given.

  6. Cellular viscoelasticity probed by active rheology in optical tweezers

    NASA Astrophysics Data System (ADS)

    Lyubin, Evgeny V.; Khokhlova, Maria D.; Skryabina, Maria N.; Fedyanin, Andrey A.

    2012-10-01

    A novel approach to probe viscoelastic properties of cells based on double trap optical tweezers is reported. Frequency dependence of the tangent of phase difference in the movement of the opposite erythrocyte edges while one of the edges is forced to oscillate by optical tweezers appeared to be highly dependent on the rigidity of the cellular membrane. Effective viscoelastic parameters characterizing red blood cells with different stiffnesses (normal and glutaraldehyde-fixed) are determined. It is shown that the photo-induced effects caused by laser trapping at the power level used in the experiments are negligible giving the possibility to use the offered technique for dynamic monitoring of soft materials viscoelastic properties.

  7. Marker-free cell discrimination by holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Schaal, F.; Warber, M.; Zwick, S.; van der Kuip, H.; Haist, T.; Osten, W.

    2009-06-01

    We introduce a method for marker-free cell discrimination based on optical tweezers. Cancerous, non-cancerous, and drug-treated cells could be distinguished by measuring the trapping forces using holographic optical tweezers. We present trapping force measurements on different cell lines: normal pre-B lymphocyte cells (BaF3; "normal cells"), their Bcr-Abl transformed counterparts (BaF3-p185; "cancer cells") as a model for chronic myeloid leukaemia (CML) and Imatinib treated BaF3-p185 cells. The results are compared with reference measurements obtained by a commercial flow cytometry system.

  8. Dynamic optical tweezers based assay for monitoring early drug resistance

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojing; Zhang, Yuquan; Min, Changjun; Zhu, Siwei; Feng, Jie; Yuan, X.-C.

    2013-06-01

    In this letter, a dynamic optical tweezers based assay is proposed and investigated for monitoring early drug resistance with Pemetrexed-resistant non-small cell lung cancer (NSCLC) cell lines. The validity and stability of the method are verified experimentally in terms of the physical parameters of the optical tweezers system. The results demonstrate that the proposed technique is more convenient and faster than traditional techniques when the capability of detecting small variations of the response of cells to a drug is maintained.

  9. Parallel trapping of multiwalled carbon nanotubes with optoelectronic tweezers

    PubMed Central

    Pauzauskie, Peter J.; Jamshidi, Arash; Valley, Justin K.; Satcher, Joe H.; Wu, Ming C.

    2009-01-01

    Here we report the use of optoelectronic tweezers and dynamic virtual electrodes to address multiwalled carbon nanotubes (MWCNTs) with trap stiffness values of approximately 50 fN??m. Both high-speed translation (>200 ?m?s) of individual-MWCNTs and two-dimensional trapping of MWCNT ensembles are achieved using 100,000 times less optical power density than single beam laser tweezers. Modulating the virtual electrodes intensity enables tuning of the MWCNT ensembles number density by an order of magnitude on the time scale of seconds promising a broad range of applications in MWCNT science and technology. PMID:19884988

  10. Fundamental constraints on particle tracking with optical tweezers

    NASA Astrophysics Data System (ADS)

    Taylor, Michael A.; Knittel, Joachim; Bowen, Warwick P.

    2013-02-01

    A general quantum limit to the sensitivity of particle position measurements is derived following the simple principle of the Heisenberg microscope. The value of this limit is calculated for particles in the Rayleigh and Mie scattering regimes, and with parameters which are relevant to optical tweezers experiments. The minimum power required to observe the zero-point motion of a levitating bead is also calculated, with the optimal particle diameter always smaller than the wavelength. We show that recent optical tweezers experiments are within two orders of magnitude of quantum limited sensitivity, suggesting that quantum optical resources may soon play an important role in high sensitivity tracking applications.

  11. Optical tweezers reveal how proteins alter replication

    NASA Astrophysics Data System (ADS)

    Chaurasiya, Kathy

    Single molecule force spectroscopy is a powerful method that explores the DNA interaction properties of proteins involved in a wide range of fundamental biological processes such as DNA replication, transcription, and repair. We use optical tweezers to capture and stretch a single DNA molecule in the presence of proteins that bind DNA and alter its mechanical properties. We quantitatively characterize the DNA binding mechanisms of proteins in order to provide a detailed understanding of their function. In this work, we focus on proteins involved in replication of Escherichia coli (E. coli ), endogenous eukaryotic retrotransposons Ty3 and LINE-1, and human immunodeficiency virus (HIV). DNA polymerases replicate the entire genome of the cell, and bind both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) during DNA replication. The replicative DNA polymerase in the widely-studied model system E. coli is the DNA polymerase III subunit alpha (DNA pol III alpha). We use optical tweezers to determine that UmuD, a protein that regulates bacterial mutagenesis through its interactions with DNA polymerases, specifically disrupts alpha binding to ssDNA. This suggests that UmuD removes alpha from its ssDNA template to allow DNA repair proteins access to the damaged DNA, and to facilitate exchange of the replicative polymerase for an error-prone translesion synthesis (TLS) polymerase that inserts nucleotides opposite the lesions, so that bacterial DNA replication may proceed. This work demonstrates a biophysical mechanism by which E. coli cells tolerate DNA damage. Retroviruses and retrotransposons reproduce by copying their RNA genome into the nuclear DNA of their eukaryotic hosts. Retroelements encode proteins called nucleic acid chaperones, which rearrange nucleic acid secondary structure and are therefore required for successful replication. The chaperone activity of these proteins requires strong binding affinity for both single- and double-stranded nucleic acids. We use single molecule DNA stretching to show that the nucleocapsid protein (NC) of the yeast retrotransposon Ty3, which is likely to be an ancestor of HIV NC, has optimal nucleic acid chaperone activity with only a single zinc finger. We also show that the chaperone activity of the ORF1 protein is responsible for successful replication of the mouse LINE-1 retrotransposon. LINE-1 is also 17% of the human genome, where it generates insertion mutations and alters gene expression. Retrotransposons such as LINE-1 and Ty3 are likely to be ancestors of retroviruses such as HIV. Human APOBEC3G (A3G) inhibits HIV-1 replication via cytidine deamination of the viral ssDNA genome, as well as via a distinct deamination-independent mechanism. Efficient deamination requires rapid on-off binding kinetics, but a slow dissociation rate is required for the proposed deaminase-independent mechanism. We resolve this apparent contradiction with a new quantitative single molecule method, which shows that A3G initially binds ssDNA with fast on-off rates and subsequently converts to a slow binding mode. This suggests that oligomerization transforms A3G from a fast enzyme to a slow binding protein, which is the biophysical mechanism that allows A3G to inhibit HIV replication. A complete understanding of the mechanism of A3G-mediated antiviral activity is required to design drugs that disrupt the viral response to A3G, enhance A3G packaging inside the viral core, and other potential strategies for long-term treatment of HIV infection. We use single molecule biophysics to explore the function of proteins involved in bacterial DNA replication, endogenous retrotransposition of retroelements in eukaryotic hosts such yeast and mice, and HIV replication in human cells. Our quantitative results provide insight into protein function in a range of complex biological systems and have wide-ranging implications for human health.

  12. Trapping and patterning of biological objects using photovoltaic tweezers

    NASA Astrophysics Data System (ADS)

    Jubera, M.; Elvira, I.; García-Cabañes, A.; Bella, J. L.; Carrascosa, M.

    2016-01-01

    Photovoltaic tweezers are a recently proposed technique for manipulation and patterning of micro- and nano-objects. It is based in the dielectrophoretic forces associated to the electric fields induced by illumination of certain ferroelectrics due to the bulk photovoltaic effect. The technique has been applied to the patterning of dielectric and metal micro- and nano-particles. In this work, we report the use of photovoltaic tweezers to pattern biological objects on LiNbO3:Fe. Specifically, spores and pollen grains and their nanometric fragments have been trapped and patterned. 1D and 2D arrangements have been achieved by deposition in air or from a hexane suspension. The quality of patterns obtained with nanometric fragments is even better than previous results using photovoltaic tweezers with inorganic micro- and nano-particles. In fact, 1D patterns with a period of 2 μm, almost half of the minimum reported period achieved with photovoltaic tweezers, have been obtained with pollen fragments.

  13. Reversible Guest Exchange Mechanisms in Supramolecular Host-GuestAssemblies

    SciTech Connect

    Pluth, Michael D.; Raymond, Kenneth N.

    2006-09-01

    Synthetic chemists have provided a wide array of supramolecular assemblies able to encapsulate guest molecules. The scope of this tutorial review focuses on supramolecular host molecules capable of reversibly encapsulating polyatomic guests. Much work has been done to determine the mechanism of guest encapsulation and guest release. This review covers common methods of monitoring and characterizing guest exchange such as NMR, UV-VIS, mass spectroscopy, electrochemistry, and calorimetry and also presents representative examples of guest exchange mechanisms. The guest exchange mechanisms of hemicarcerands, cucurbiturils, hydrogen-bonded assemblies, and metal-ligand assemblies are discussed. Special attention is given to systems which exhibit constrictive binding, a motif common in supramolecular guest exchange systems.

  14. Host-guest sensing by calixarenes on the surfaces.

    PubMed

    Kim, Hyun Jung; Lee, Min Hee; Mutihac, Lucia; Vicens, Jacques; Kim, Jong Seung

    2012-02-01

    The present critical review reports on recent developments of optical nanoparticles based on the association of gold, silver, silica and quantum dots and calixarenes. These hybrid organic-inorganic compounds characterized by a thick organic layer self-assembled on the surface of a core of mineral surface atoms take advantage of the supramolecular recognition of luminescent calixarenes to fabricate nanodevices of nanoparticle size, capable of detecting metal cations, polyaromatic hydrocarbons and pesticides. Also presented is an explanation of the involvement of such nanoparticles in biochemical systems. This critical review provides an overview of their preparation, the manner in which they are characterized, and their use (108 references). PMID:21870018

  15. Nanopatterning of a covalent organic framework host-guest system.

    PubMed

    Plas, Jan; Ivasenko, Oleksandr; Martsinovich, Natalia; Lackinger, Markus; De Feyter, Steven

    2015-12-15

    We have used a boroxine-based COF as a template for C60-fullerene self-assembly on graphite. Local removal of the COF by STM based nanomanipulation creates nanocorrals that may host other species. PMID:26514994

  16. Host-Guest Self-assembly in Block Copolymer Blends

    PubMed Central

    Park, Woon Ik; Kim, YongJoo; Jeong, Jae Won; Kim, Kyungho; Yoo, Jung-Keun; Hur, Yoon Hyung; Kim, Jong Min; Thomas, Edwin L.; Alexander-Katz, Alfredo; Jung, Yeon Sik

    2013-01-01

    Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their limited thin film morphologies. Here, we report that unusual and spontaneous positioning between host and guest BCP microdomains, even in the absence of H-bond linkages, can create hybridized morphologies that cannot be formed from a neat BCP. Our self-consistent field theory (SCFT) simulation results theoretically support that the precise registration of a spherical BCP microdomain (guest, B-b-C) at the center of a perforated lamellar BCP nanostructure (host, A-b-B) can energetically stabilize the blended morphology. As an exemplary application of the hybrid nanotemplate, a nanoring-type Ge2Sb2Te5 (GST) phase-change memory device with an extremely low switching current is demonstrated. These results suggest the possibility of a new pathway to construct more diverse and complex nanostructures using controlled blending of various BCPs. PMID:24217036

  17. Single-sided lateral-field and phototransistor-based optoelectronic tweezers

    NASA Technical Reports Server (NTRS)

    Ohta, Aaron (Inventor); Chiou, Pei-Yu (Inventor); Hsu, Hsan-Yin (Inventor); Jamshidi, Arash (Inventor); Wu, Ming-Chiang (Inventor); Neale, Steven L. (Inventor)

    2011-01-01

    Described herein are single-sided lateral-field optoelectronic tweezers (LOET) devices which use photosensitive electrode arrays to create optically-induced dielectrophoretic forces in an electric field that is parallel to the plane of the device. In addition, phototransistor-based optoelectronic tweezers (PhOET) devices are described that allow for optoelectronic tweezers (OET) operation in high-conductivity physiological buffer and cell culture media.

  18. Determination of motility forces on isolated chromosomes with laser tweezers

    NASA Astrophysics Data System (ADS)

    Khatibzadeh, Nima; Stilgoe, Alexander B.; Bui, Ann A. M.; Rocha, Yesenia; Cruz, Gladys M.; Loke, Vince; Shi, Linda Z.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

    2014-10-01

    Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064 nm laser trap. The minimum force required to move a single chromosome was determined to be ~0.8-5 pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ~0.01-0.02. These results confirm theoretical force calculations of ~0.1-12 pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5-15 µm in media with 1-7 cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens.

  19. Experiments with a rubidium condensate in an optical tweezer

    NASA Astrophysics Data System (ADS)

    Campbell, Gretchen; Boyd, Micah; Streed, Erik; Mun, Jongchul; Schneble, Dominik; Steinhauer, Jeff; Pritchard, David E.; Ketterle, Wolfgang

    2003-05-01

    We report on experiments with a rubidium Bose-Einstein condensate in an optical tweezer. The condensate is loaded into the focus of a red-detuned laser beam from a cloverleaf Ioffe-Pritchard magnetic trap to allow for translation into a glass at 73 cm distance from the production chamber. The tweezer is oriented perpendicular to the long axis of the condensate. Loading into this geometry is complicated by the large three-body loss and high mass of rubidium as compared to similar experiments in sodium, which have been performed recently in our group. We have explored methods to optimize the transfer efficiency and will report progress towards the transport and manipulation of the condensate

  20. A microscopic steam engine implemented in an optical tweezer

    NASA Astrophysics Data System (ADS)

    Quinto-Su, Pedro A.

    2014-12-01

    The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies.

  1. Mechanical force characterization in manipulating live cells with optical tweezers.

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

    Laser trapping with optical tweezers is a noninvasive manipulation technique and has received increasing attentions in biological applications. Understanding forces exerted on live cells is essential to cell biomechanical characterizations. Traditional numerical or experimental force measurement assumes live cells as ideal objects, ignoring their complicated inner structures and rough membranes. In this paper, we propose a new experimental method to calibrate the trapping and drag forces acted on live cells. Binding a micro polystyrene sphere to a live cell and moving the mixture with optical tweezers, we can obtain the drag force on the cell by subtracting the drag force on the sphere from the total drag force on the mixture, under the condition of extremely low Reynolds number. The trapping force on the cell is then obtained from the drag force when the cell is in force equilibrium state. Experiments on numerous live cells demonstrate the effectiveness of the proposed force calibration approach. PMID:21087769

  2. Force of single kinesin molecules measured with optical tweezers.

    PubMed

    Kuo, S C; Sheetz, M P

    1993-04-01

    Isometric forces generated by single molecules of the mechanochemical enzyme kinesin were measured with a laser-induced, single-beam optical gradient trap, also known as optical tweezers. For the microspheres used in this study, the optical tweezers was spring-like for a radius of 100 nanometers and had a maximum force region at a radius of approximately 150 nanometers. With the use of biotinylated microtubules and special streptavidin-coated latex microspheres as handles, microtubule translocation by single squid kinesin molecules was reversibly stalled. The stalled microtubules escaped optical trapping forces of 1.9 +/- 0.4 piconewtons. The ability to measure force parameters of single macromolecules now allows direct testing of molecular models for contractility. PMID:8469975

  3. A microscopic steam engine implemented in an optical tweezer.

    PubMed

    Quinto-Su, Pedro A

    2014-01-01

    The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies. PMID:25523395

  4. Probing DNA with micro- and nanocapillaries and optical tweezers

    NASA Astrophysics Data System (ADS)

    Steinbock, L. J.; Otto, O.; Skarstam, D. R.; Jahn, S.; Chimerel, C.; Gornall, J. L.; Keyser, U. F.

    2010-11-01

    We combine for the first time optical tweezer experiments with the resistive pulse technique based on capillaries. Quartz glass capillaries are pulled into a conical shape with tip diameters as small as 27 nm. Here, we discuss the translocation of ?-phage DNA which is driven by an electrophoretic force through the nanocapillary. The resulting change in ionic current indicates the folding state of single ?-phage DNA molecules. Our flow cell design allows for the straightforward incorporation of optical tweezers. We show that a DNA molecule attached to an optically trapped colloid is pulled into a capillary by electrophoretic forces. The detected electrophoretic force is in good agreement with measurements in solid-state nanopores.

  5. Determination of motility forces on isolated chromosomes with laser tweezers.

    PubMed

    Khatibzadeh, Nima; Stilgoe, Alexander B; Bui, Ann A M; Rocha, Yesenia; Cruz, Gladys M; Loke, Vince; Shi, Linda Z; Nieminen, Timo A; Rubinsztein-Dunlop, Halina; Berns, Michael W

    2014-01-01

    Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064 nm laser trap. The minimum force required to move a single chromosome was determined to be ? 0.8-5 pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ? 0.01-0.02. These results confirm theoretical force calculations of ? 0.1-12 pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5-15 m in media with 1-7 cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens. PMID:25359514

  6. Optical tweezers experiments for fibroblast cell growth stimulation

    NASA Astrophysics Data System (ADS)

    Avila, Remy; Medina-Villalobos, Norma; Tamariz, Elisa; Chiu, Roger; Lopez-Marn, Luz Mara.; Acosta, Anglica; Castao, Victor

    2014-05-01

    Optical tweezers constitute an increasingly used tool for the study of biomechanical properties of cells. Here we report experiments for the projection induction of NIH3T3 fibroblast cells, using a single-trap optical tweezers. The system is based on a 1064-nm, 50mW infrared gaussian laser beam, a 100x microscope objective with 1.25 numerical aperture and a temperature-controlled warming plate to maintain cell viability. Eighteen cells were exposed to the focussed laser beam in different cell zones and another 18 cells were observed without laser stimulation as a control population. The results show that the probability of lamelipodia growth increases on exposed cells by a factor 1.5.

  7. Manipulating ellipsoidal micro-particles by femtosecond vortex tweezers

    NASA Astrophysics Data System (ADS)

    Liu, Changxia; Guo, Zhongyi; Li, Yan; Wang, Xinshun; Qu, Shiliang

    2015-03-01

    We study the manipulation of the ellipsoidal micro-particles by the femtosecond vortex tweezer experimentally and theoretically. In our setup the micro-particles can be rotated stably by means of optical torque induced by the femtosecond optical whirl. In order to give insight into observed effects, we establish two adequate theoretical models: one is based upon assumption of full absorption and the other uses the ray tracing method. The numerical simulations agree well with the experimental results.

  8. Evidence for localized cell heating induced by infrared optical tweezers.

    PubMed Central

    Liu, Y; Cheng, D K; Sonek, G J; Berns, M W; Chapman, C F; Tromberg, B J

    1995-01-01

    The confinement of liposomes and Chinese hamster ovary (CHO) cells by infrared (IR) optical tweezers is shown to result in sample heating and temperature increases by several degrees centigrade, as measured by a noninvasive, spatially resolved fluorescence detection technique. For micron-sized spherical liposome vesicles having bilayer membranes composed of the phospholipid 1,2-diacyl-pentadecanoyl-glycero-phosphocholine (15-OPC), a temperature rise of approximately 1.45 +/- 0.15 degrees C/100 mW is observed when the vesicles are held stationary with a 1.064 microns optical tweezers having a power density of approximately 10(7) W/cm2 and a focused spot size of approximately 0.8 micron. The increase in sample temperature is found to scale linearly with applied optical power in the 40 to 250 mW range. Under the same trapping conditions, CHO cells exhibit an average temperature rise of nearly 1.15 +/- 0.25 degrees C/100 mW. The extent of cell heating induced by infrared tweezers confinement can be described by a heat conduction model that accounts for the absorption of infrared (IR) laser radiation in the aqueous cell core and membrane regions, respectively. The observed results are relevant to the assessment of the noninvasive nature of infrared trapping beams in micromanipulation applications and cell physiological studies. Images FIGURE 1 FIGURE 3 PMID:7612858

  9. Using Laser Tweezers For Manipulating Isolated Neurons In Vitro

    PubMed Central

    Clarke, Robert; Wang, Jianfeng; Townes-Anderson, Ellen

    2008-01-01

    In this paper and video, we describe the protocols used in our laboratory to study the targeting preferences of regenerating cell processes of adult retinal neurons in vitro. Procedures for preparing retinal cell cultures start with the dissection, digestion and trituration of the retina, and end with the plating of isolated retinal cells on dishes made especially for use with laser tweezers. These dishes are divided into a cell adhesive half and a cell repellant half. The cell adhesive side is coated with a layer of Sal-1 antibodies, which provide a substrate upon which our cells grow. Other adhesive substrates could be used for other cell types. The cell repellant side is coated with a thin layer of poly-HEMA. The cells plated on the poly-HEMA side of the dish are trapped with the laser tweezers, transported and then placed adjacent to a cell on the Sal-1 side to create a pair. Formation of cell groups of any size should be possible with this technique. "Laser-tweezers-controlled micromanipulation" means that the investigator can choose which cells to move, and the desired distance between the cells can be standardized. Because the laser beam goes through transparent surfaces of the culture dish, cell selection and placement are done in an enclosed, sterile environment. Cells can be monitored by video time-lapse and used with any cell biological technique required. This technique may help investigations of cell-cell interactions. PMID:19066536

  10. Using Laser Tweezers For Manipulating Isolated Neurons In Vitro.

    PubMed

    Clarke, Robert; Wang, Jianfeng; Townes-Anderson, Ellen

    2008-01-01

    In this paper and video, we describe the protocols used in our laboratory to study the targeting preferences of regenerating cell processes of adult retinal neurons in vitro. Procedures for preparing retinal cell cultures start with the dissection, digestion and trituration of the retina, and end with the plating of isolated retinal cells on dishes made especially for use with laser tweezers. These dishes are divided into a cell adhesive half and a cell repellant half. The cell adhesive side is coated with a layer of Sal-1 antibodies, which provide a substrate upon which our cells grow. Other adhesive substrates could be used for other cell types. The cell repellant side is coated with a thin layer of poly-HEMA. The cells plated on the poly-HEMA side of the dish are trapped with the laser tweezers, transported and then placed adjacent to a cell on the Sal-1 side to create a pair. Formation of cell groups of any size should be possible with this technique. "Laser-tweezers-controlled micromanipulation" means that the investigator can choose which cells to move, and the desired distance between the cells can be standardized. Because the laser beam goes through transparent surfaces of the culture dish, cell selection and placement are done in an enclosed, sterile environment. Cells can be monitored by video time-lapse and used with any cell biological technique required. This technique may help investigations of cell-cell interactions. PMID:19066536

  11. The study of optical trapping force from optical tweezers

    NASA Astrophysics Data System (ADS)

    Zhu, Yanying; Wang, Mingli

    2007-01-01

    Optical tweezers use the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometers to tens of micrometers. Since their introduction in 1986, the optical tweezers has become an important tool for research in the field of biology, physical chemistry and so on. So the study and measure of optical trapping forces are important currently, and those are also helpful for the development of optical tweezers. At present the theoretical model has been established about the calculation method of optical tweezers. This document shows a method of optical tweezers on axis. The optical trapping force was measured and estimated in experiment. The theoretical model of optical trapping force on axis is different with different size particle. One is Mie particle which size is much larger than the laser wavelength. We can calculate the optical trapping force by the theoretical model based on geometrical-optics. Another is Rayleigh particle which size is much smaller than the laser wavelength. We can calculate the optical trapping force by the theoretical model based on electromagnetics. A method was presented mainly about the calculation of optical trapping force on axis in this document. Under given parameters, the numerical simulation of the optical trapping force on particle was demonstrated. And the important impacts of the parameters were discussed including the radius of the beam waist, the laser wavelength, the laser power, particle radius and so on. Through the numerical simulation, they have the close relation between the different system parameters and the optical trapping force. The optical trap will change shallow along with the radius of the beam waist increasing. On the contrary, the optical trap will change deep along with the laser power increasing. They have a best optical trap scope between the laser wave length and the particle radius. Thus, we can choose the appropriate parameters in the experiment to obtain the best optical trapping force. We captured and moved a particle by a strongly focused beam of laser in experiment. In order to obtain the escaping speed, we control platform steadily and record the entire capture process through the CCD imaging system. Figuring out the escaping speed from the known two time interval and the granule displacement value, we can estimate the optical trapping force by Stocks formula.

  12. Construction of supramolecular hyperbranched polymers via the "tweezering directed self-assembly" strategy.

    PubMed

    Tian, Yu-Kui; Yang, Zhi-Shuai; Lv, Xiao-Qin; Yao, Ri-Sheng; Wang, Feng

    2014-08-28

    A bis-alkynylplatinum(II) terpyridine tweezer-alkynylgold(III) diphenylpyridine guest is shown to maintain the specific complexation in the presence of a B21C7-secondary ammonium salt recognition motif, which facilitates the formation of supramolecular hyperbranched polymers via the "tweezering directed self-assembly" strategy. PMID:25007971

  13. The simulation research of multi-core optical fiber near-field optical tweezers

    NASA Astrophysics Data System (ADS)

    Hou, Guohua; Liu, Zhihai

    2011-11-01

    In order to develop the near- field optical tweezers with perfect function , We design the near-field optical fiber optical tweezers basing on the multi-core of the optical fiber. Combining the total internal reflection and multi-core optical fiber, we form evanescent wave on the fiber water interface forming , and realize the capture of object .It can separate the near-field optical tweezers and its control from the microscopic observation system effectively, so It enhance the operability of near-field optical tweezers and the ability of active capture greatly. The Multi-core optical fiber constitutes the Near-field optical tweezers, the superposition of the coherent light from opposite transmission forms a area of capture. Interference effect makes light intensely, at the same time the capture space becomes more and more narrow. They can improve the capture function of the new generation of all-fiber near-field optical tweezers greatly. And we quantitatively calculating the optical trap force of the micron-grade particle. In this passage, there is a new progress in setting up the near field optical tweezers' model and the calculation method. Moreover, it improves the using value of the near field optical tweezers technology in the life sciences.

  14. A simple optical tweezers for trapping polystyrene particles

    NASA Astrophysics Data System (ADS)

    Shiddiq, Minarni; Nasir, Zulfa; Yogasari, Dwiyana

    2013-09-01

    Optical tweezers is an optical trap. For decades, it has become an optical tool that can trap and manipulate any particle from the very small size like DNA to the big one like bacteria. The trapping force comes from the radiation pressure of laser light which is focused to a group of particles. Optical tweezers has been used in many research areas such as atomic physics, medical physics, biophysics, and chemistry. Here, a simple optical tweezers has been constructed using a modified Leybold laboratory optical microscope. The ocular lens of the microscope has been removed for laser light and digital camera accesses. A laser light from a Coherent diode laser with wavelength ? = 830 nm and power 50 mW is sent through an immersion oil objective lens with magnification 100 and NA 1.25 to a cell made from microscope slides containing polystyrene particles. Polystyrene particles with size 3 ?m and 10 ?m are used. A CMOS Thorlabs camera type DCC1545M with USB Interface and Thorlabs camera lens 35 mm are connected to a desktop and used to monitor the trapping and measure the stiffness of the trap. The camera is accompanied by camera software which makes able for the user to capture and save images. The images are analyzed using ImageJ and Scion macro. The polystyrene particles have been trapped successfully. The stiffness of the trap depends on the size of the particles and the power of the laser. The stiffness increases linearly with power and decreases as the particle size larger.

  15. Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2002-01-01

    A new method to control microparticles was developed in-house at the NASA Glenn Research Center in support of the nanotechnology project under NASA's Aerospace Propulsion and Power Base Research Program. A prototype interferometer-controlled optical tweezers was constructed to manipulate scanning probe microscope (SPM) tips. A laser beam passed through a Mach-Zehnder interferometer, and a microscope objective then produced an optical trap from the coaxial beams. The trap levitated and generated the coarse motion of a 10-mm polystyrene sphere used to simulate a SPM tip. The interference between the beams provided fine control of the forces and moments on the sphere. The interferometer included a piezoelectric-scanned mirror to modulate the interference pattern. The 10-mm sphere was observed to oscillate about 1 mm as the mirror and fringe pattern oscillated. The prototype tweezers proved the feasibility of constructing a more sophisticated interferometer tweezers to hold and manipulate SPM tips. The SPM tips are intended to interrogate and manipulate nanostructures. A more powerful laser will be used to generate multiple traps to hold nanostructures and SPM tips. The vibrating mirror in the interferometer will be replaced with a spatial light modulator. The modulator will allow the optical phase distribution in one leg of the interferometer to be programmed independently at 640 by 480 points for detailed control of the forces and moments. The interference patterns will be monitored to measure the motion of the SPM tips. Neuralnetwork technology will provide fast analysis of the interference patterns for diagnostic purposes and for local or remote feedback control of the tips. This effort also requires theoretical and modeling support in the form of scattering calculations for twin coherent beams from nonspherical particles.

  16. Increasing trap stiffness with position clamping in holographic optical tweezers.

    PubMed

    Preece, Daryl; Bowman, Richard; Linnenberger, Anna; Gibson, Graham; Serati, Steven; Padgett, Miles

    2009-12-01

    We present a holographic optical tweezers system capable of position clamping multiple particles. Moving an optical trap in response to the trapped object's motion is a powerful technique for optical control and force measurement. We have now realised this experimentally using a Boulder Nonlinear Systems Spatial Light Modulator (SLM) with a refresh rate of 203Hz. We obtain a reduction of 44% in the variance of the bead's position, corresponding to an increase in effective trap stiffness of 77%. This reduction relies on the generation of holograms at high speed. We present software capable of calculating holograms in under 1ms using a graphics processor unit. PMID:20052197

  17. Translation and manipulation of silicon nanomembranes using holographic optical tweezers

    PubMed Central

    2011-01-01

    We demonstrate the use of holographic optical tweezers for trapping and manipulating silicon nanomembranes. These macroscopic free-standing sheets of single-crystalline silicon are attractive for use in next-generation flexible electronics. We achieve three-dimensional control by attaching a functionalized silica bead to the silicon surface, enabling non-contact trapping and manipulation of planar structures with high aspect ratios (high lateral size to thickness). Using as few as one trap and trapping powers as low as several hundred milliwatts, silicon nanomembranes can be rotated and translated in a solution over large distances. PMID:21867504

  18. Single optical tweezers based on elliptical core fiber

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Zhao, Li; Chen, Yunhao; Liu, Zhihai; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

    2016-04-01

    We propose and demonstrate a new single optical tweezers based on an elliptical core fiber, which can realize the trapped yeast cell rotation with a precise and simple control. Due to the elliptical shape of the fiber core, the LP11 mode beam can propagate stably. When we rotate the fiber tip, the LP11 mode beam will also rotate along with the fiber tip, which helps to realize the trapped micro-particle rotation. By using this method, we can easily realize the rotation of the trapped yeast cells, the rotating angle of the yeast cell is same as the elliptical core fiber tip.

  19. Continuous cell lysis in microfluidics through acoustic and optoelectronic tweezers

    NASA Astrophysics Data System (ADS)

    Witte, Christian; Kremer, Clemens; Cooper, Jonathan M.; Neale, Steven L.

    2013-03-01

    A versatile platform for efficient cell lysis using a combination of acoustic and electric fields in a microchannel is presented. Cell membrane disruption is triggered by electric fields inducing electroporation and then lysis. The principle of optoelectronic tweezers (OET) is applied to control the electric field strength and a surface acoustic wave transducer is attached to an OET chip to implement acoustic tweezing (AT). The system is characterized in terms of spatial control of electric fields, single cell precision and lysis times. Under continuous operation, a combination of AT and OET improves cell lysis significantly achieving for sample concentrations of 106 cell/ml lysis efficiencies of > 99%.

  20. Advances in magnetic tweezers for single molecule and cell biophysics.

    PubMed

    Kilinc, Devrim; Lee, Gil U

    2014-01-01

    Magnetic tweezers (MTW) enable highly accurate forces to be transduced to molecules to study mechanotransduction at the molecular or cellular level. We review recent MTW studies in single molecule and cell biophysics that demonstrate the flexibility of this technique. We also discuss technical advances in the method on several fronts, i.e., from novel approaches for the measurement of torque to multiplexed biophysical assays. Finally, we describe multi-component nanorods with enhanced optical and magnetic properties and discuss their potential as future MTW probes. PMID:24263142

  1. Optical tweezers: Characterization and systems approach to high bandwidth force estimation

    NASA Astrophysics Data System (ADS)

    Sehgal, Hullas

    In recent times, the hard boundaries between classical fields of sciences have almost disappeared. There is a cross-pollination of ideas between sciences, engineering and mathematics. This work investigates a modern tool of micro-manipulation of microscopic particles that is used primarily by bio-physicists and bio-chemists for single cell, single molecule studies. This tool called the Optical Tweezers can trap microscopic dielectric particles using radiation pressure of light. Optical tweezers is increasingly being used in bio-assays as it provides a means to observe bio-molecules non invasively and offers a spatial resolution in nanometers and force resolution in femto-Newtons at millisecond timescales. In this work, physics governing the operating principle behind optical tweezers is presented, followed by a step by step procedure to build an optical tweezers system having measurement and actuation capability along with a controller logic for feedback implementation. The working of optical tweezers system is presented using a spring mass damper model and the traditional methods of optical tweezers characterization are discussed. A comprehensive view of Optical tweezers is then presented from a system theoretic perspective, underlying the limitations of traditional methods of tweezers characterization that are based on the first principle. The role of feedback in Optical tweezers is presented along with the fundamental limitations that the plant model imposes on optical tweezers performance to be used as a force sensor for fast dynamics input force. The purpose of optical tweezers as a pico-newton force probe is emphasized and a classical controls based method to improve the bandwidth of force estimation using an ad-hoc approach of system inversion is presented. The efficacy of system inversion based method in improving the force probe capability of feedback enhanced optical tweezers is validated by experimental results. It is shown experimentally that the system inversion method results in an order of magnitude improvement in the bandwidth of external force estimation. Finally, a robust control strategy is presented, where the problem of estimation of high bandwidth force is casted as an H-infinity optimization problem along with other performance objectives. This strategy is then compared with the traditional method using PI-controllers and experimental results presented. The robust control strategy is found to further improve the ability of optical tweezers as a force sensor for fast changing force profile by approximately three times over the system inversion approach.

  2. Determination of motility forces on isolated chromosomes with laser tweezers

    PubMed Central

    Khatibzadeh, Nima; Stilgoe, Alexander B.; Bui, Ann A. M.; Rocha, Yesenia; Cruz, Gladys M.; Loke, Vince; Shi, Linda Z.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

    2014-01-01

    Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064 nm laser trap. The minimum force required to move a single chromosome was determined to be ≈0.8–5 pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ≈0.01–0.02. These results confirm theoretical force calculations of ≈0.1–12 pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5–15 µm in media with 1–7 cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens. PMID:25359514

  3. All-Optical Constant-Force Laser Tweezers

    PubMed Central

    Nambiar, Rajalakshmi; Gajraj, Arivalagan; Meiners, Jens-Christian

    2004-01-01

    Optical tweezers are a powerful tool for the study of single biomolecules. Many applications require that a molecule be held under constant tension while its extension is measured. We present two schemes based on scanning-line optical tweezers to accomplish this, providing all-optical alternatives to force-clamp traps that rely on electronic feedback to maintain constant-force conditions for the molecule. In these schemes, a laser beam is rapidly scanned along a line in the focal plane of the microscope objective, effectively creating an extended one-dimensional optical potential over distances of up to 8 μm. A position-independent lateral force acting on a trapped particle is created by either modulating the laser beam intensity during the scan or by using an asymmetric beam profile in the back focal plane of the microscope objective. With these techniques, forces of up to 2.69 pN have been applied over distances of up to 3.4 μm with residual spring constants of <26.6 fN/μm. We used these techniques in conjunction with a fast position measurement scheme to study the relaxation of λ-DNA molecules against a constant external force with submillisecond time resolution. We compare the results to predictions from the wormlike chain model. PMID:15345573

  4. Use of optical tweezers to probe epithelial mechanosensation

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    2010-01-01

    Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the ``ciliary hypothesis'' has been difficult due the spatially distributed nature of the mechanical disturbance-several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and actin cytoskeleton exist. I report initial data using optical tweezers to manipulate individual primary cilia in an attempt to elicit a mechanotransduction response-specifically, the release of intracellular calcium. The advantage of using laser tweezers over previous work is that the applied disturbance is highly localized. I find that stimulation of a primary cilium elicits a response, while stimulation of the apical surface membrane does not. These results lend support to the hypothesis that the primary cilium mediates transduction of mechanical strain into a biochemical response in renal epithelia.

  5. Precision Assembly of Complex Cellular Microenvironments using Holographic Optical Tweezers

    PubMed Central

    Kirkham, Glen R.; Britchford, Emily; Upton, Thomas; Ware, James; Gibson, Graham M.; Devaud, Yannick; Ehrbar, Martin; Padgett, Miles; Allen, Stephanie; Buttery, Lee D.; Shakesheff, Kevin

    2015-01-01

    The accurate study of cellular microenvironments is limited by the lack of technologies that can manipulate cells in 3D at a sufficiently small length scale. The ability to build and manipulate multicellular microscopic structures will facilitate a more detailed understanding of cellular function in fields such as developmental and stem cell biology. We present a holographic optical tweezers based technology to accurately generate bespoke cellular micro-architectures. Using embryonic stem cells, 3D structures of varying geometries were created and stabilized using hydrogels and cell-cell adhesion methods. Control of chemical microenvironments was achieved by the temporal release of specific factors from polymer microparticles positioned within these constructs. Complex co-culture micro-environmental analogues were also generated to reproduce structures found within adult stem cell niches. The application of holographic optical tweezers-based micromanipulation will enable novel insights into biological microenvironments by allowing researchers to form complex architectures with sub-micron precision of cells, matrices and molecules. PMID:25716032

  6. Micro-tweezers for studying vibrating carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Barnard, Arthur; Zhang, Mian; Lipson, Michal; McEuen, Paul

    2014-03-01

    Vibrational modes in suspended carbon nanotubes (CNTs) are incredibly soft, which makes them sensitive to small forces and a prime candidate as force sensors. This same property, combined with the stiffness of the CNT to stretching, makes them an unusual mechanical system characterized both by large thermally-activated fluctuations and strong nonlinear interactions between the resonance modes. How do these thermal fluctuations manifest themselves in the resonance behavior? To address this question, we developed an electrically-contacted micro-tweezer platform that is capable of lifting a pristine CNT off of its growth substrate, directly applying strain to the free-standing doubly-clamped CNT, and controlling its proximity to electrical gates and optical ring (microdisk) resonators for sensing. We measure both the mechanical resonance frequencies and quality factors of the CNT as a function of strain and temperature and compare these to recent predictions that account for the entropic effects of fluctuations on CNTs. In addition, we use these tweezers to couple a CNT to a high-Q optical resonator and demonstrate remarkably strong optomechanical coupling.

  7. A measurement of the maximal forces in plasmonic tweezers

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Dae; Choi, Jun-Hee; Lee, Yong-Gu

    2015-10-01

    Plasmonic tweezers that are designed to trap nanoscale objects create many new possibilities for single-molecule targeted studies. Numerous novel designs of plasmonic nanostructures are proposed in order to attain stronger forces and weaker laser intensity. Most experiments have consisted only of immobilization observations—that is, particles stick when the laser is turned on and fall away when the laser is turned off. Studies of the exertable forces were only theoretical. A few studies have experimentally measured trap stiffness. However, as far as we know, no studies have addressed maximal forces. In this paper, we present a new experimental design in which the motion of the trapped particle can be monitored in either parallel or orthogonal directions to the plasmonic structure’s symmetric axis. We measured maximal trapping force through such monitoring. Although stiffness would be useful for force-calibration or immobilization purposes, for which most plasmonic tweezers are used, we believe that the maximal endurable force is significant and thus, this paper presents this aspect.

  8. Invited article: a review of haptic optical tweezers for an interactive microworld exploration.

    PubMed

    Pacoret, Cécile; Régnier, Stéphane

    2013-08-01

    This paper is the first review of haptic optical tweezers, a new technique which associates force feedback teleoperation with optical tweezers. This technique allows users to explore the microworld by sensing and exerting picoNewton-scale forces with trapped microspheres. Haptic optical tweezers also allow improved dexterity of micromanipulation and micro-assembly. One of the challenges of this technique is to sense and magnify picoNewton-scale forces by a factor of 10(12) to enable human operators to perceive interactions that they have never experienced before, such as adhesion phenomena, extremely low inertia, and high frequency dynamics of extremely small objects. The design of optical tweezers for high quality haptic feedback is challenging, given the requirements for very high sensitivity and dynamic stability. The concept, design process, and specification of optical tweezers reviewed here are focused on those intended for haptic teleoperation. In this paper, two new specific designs as well as the current state-of-the-art are presented. Moreover, the remaining important issues are identified for further developments. The initial results obtained are promising and demonstrate that optical tweezers have a significant potential for haptic exploration of the microworld. Haptic optical tweezers will become an invaluable tool for force feedback micromanipulation of biological samples and nano- and micro-assembly parts. PMID:24007046

  9. Round-tip dielectrophoresis-based tweezers for single micro-object manipulation.

    PubMed

    Kodama, Taiga; Osaki, Toshihisa; Kawano, Ryuji; Kamiya, Koki; Miki, Norihisa; Takeuchi, Shoji

    2013-09-15

    In this paper, we present an efficient methodology to manipulate a single micro-object using round-tip positive dielectrophoresis-based tweezers. The tweezers consist of a glass needle with a round-tip and a pair of thin gold-film electrodes. The round-tip, which has a radius of 3m, is formed by melting a finely pulled glass needle and concentrates the electric field at the tip of the tweezers, which allows the individual manipulation of single micro-objects. The tweezers successfully captured, conveyed, and positioned single cell-sized liposomes with diameters of 5-23m, which are difficult to manipulate with conventional manipulation methodologies, such as optical tweezers or glass micropipettes, due to the similarities between their optical properties and those of the media, as well as the ease with which they are deformed or broken. We used Stokes' drag theory to experimentally evaluate the positive dielectrophoresis (pDEP) force generated by the tweezers as a function of the liposome size, the content of the surrounding media, and the applied AC voltage and frequency. The results agreed with the theoretically deduced pDEP force. Finally, we demonstrated the separation of labeled single cells from non-labeled cells with the tweezers. This device can be used as an efficient tool for precisely and individually manipulating biological micro-objects that are typically transparent and flexible. PMID:23570681

  10. Structure and dynamics of single DNA molecules manipulated by magnetic tweezers and or flow

    PubMed Central

    Leuba, Sanford H.; Wheeler, Travis B.; Cheng, Chao-Min; LeDuc, Philip R.; Fernández-Sierra, Mónica; Quiñones, Edwin

    2009-01-01

    Here we describe experiments which employ magnetic tweezers and or microfluidics to manipulate single DNA molecules. We describe the use of magnetic tweezers coupled to an inverted microscope as well as the use of a magnetic tweezers setup with an upright microscope. Using a chamber prepared via soft lithography, we also describe a microfluidic device for the manipulation of individual DNA molecules. Finally, we present some past successful examples of using these approaches to elucidate unique information about protein-nucleic acid interactions. PMID:19015032

  11. Investigation of shape memory of red blood cells using optical tweezers and quantitative phase microscopy

    NASA Astrophysics Data System (ADS)

    Cardenas, Nelson; Mohanty, Samarendra K.

    2012-03-01

    RBC has been shown to possess shape memory subsequent to shear-induced shape transformation. However, this property of RBC may not be generalized to all kinds of stresses. Here, we report our observation on the action of radiation pressure forces on RBC's shape memory using optical manipulation and quantitative phase microscopy (OMQPM). QPM, based on Mach-Zehnder interferrometry, allowed measurement of dynamic changes of shape of RBC in optical tweezers at different trapping laser powers. In high power near-infrared optical tweezers (>200mW), the RBC was found to deform significantly due to optical forces. Upon removal of the tweezers, hysteresis in recovering its original resting shape was observed. In very high power tweezers or long-term stretching events, shape memory was almost erased. This irreversibility of the deformation may be due to temperature rise or stress-induced phase transformation of lipids in RBC membrane.

  12. Automated transportation of single cells using robot-tweezer manipulation system.

    PubMed

    Hu, Songyu; Sun, Dong

    2011-08-01

    Manipulation of biological cells becomes increasingly important in biomedical engineering to address challenge issues in cell-cell interaction, drug discovery, and tissue engineering. Significant demand for both accuracy and productivity in cell manipulation highlights the need for automated cell transportation with integrated robotics and micro/nano manipulation technologies. Optical tweezers, which use highly focused low-power laser beams to trap and manipulate particles at micro/nanoscale, have emerged as an essential tool for manipulating single cells. In this article, we propose to use a robot-tweezer manipulation system to solve the problem of automatic transportation of biological cells, where optical tweezers function as special robot end effectors. Dynamics equation of the cell in optical tweezers is analyzed. A closed-loop controller is designed for transporting and positioning cells. Experiments are performed on live cells to demonstrate the effectiveness of the proposed approach in effective cell positioning. PMID:21764021

  13. Skewed brownian fluctuations in single-molecule magnetic tweezers.

    PubMed

    Burnham, Daniel R; De Vlaminck, Iwijn; Henighan, Thomas; Dekker, Cees

    2014-01-01

    Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements. PMID:25265383

  14. Use of Raman optical tweezers for cell cycle analysis.

    PubMed

    Ahlawat, Sunita; Chowdhury, Aniket; Uppal, Abha; Kumar, Nitin; Gupta, Pradeep Kumar

    2016-02-21

    We report the results of our investigations on the use of Raman optical tweezers for label free analysis of cells in different phases of their cell cycle. The studies performed on human colon adenocarcinoma (Colo-205) cells synchronized in G0/G1 and G2/M phases showed that the DNA Raman band at 783 cm(-1) in the Raman spectra of optically trapped cells can provide information about the DNA content in the nucleus of the cell without the need for the isolation of the nucleus. The histograms of intensity of this band among the cell populations were found to corroborate the results obtained from fluorescence image cytometry performed on DAPI stained cells. PMID:26738697

  15. Skewed Brownian Fluctuations in Single-Molecule Magnetic Tweezers

    PubMed Central

    Burnham, Daniel R.; De Vlaminck, Iwijn; Henighan, Thomas; Dekker, Cees

    2014-01-01

    Measurements in magnetic tweezers rely upon precise determination of the position of a magnetic microsphere. Fluctuations in the position due to Brownian motion allows calculation of the applied force, enabling deduction of the force-extension response function for a single DNA molecule that is attached to the microsphere. The standard approach relies upon using the mean of position fluctuations, which is valid when the microsphere axial position fluctuations obey a normal distribution. However, here we demonstrate that nearby surfaces and the non-linear elasticity of DNA can skew the distribution. Through experiment and simulations, we show that such a skewing leads to inaccurate position measurements which significantly affect the extracted DNA extension and mechanical properties, leading to up to two-fold errors in measured DNA persistence length. We develop a simple, robust and easily implemented method to correct for such mismeasurements. PMID:25265383

  16. Compact microscope-based 850-nm optical tweezers

    NASA Astrophysics Data System (ADS)

    Frediani, Carlo; Grego, S.; Guidoni, L.; Arimondo, Ennio

    1996-01-01

    Emission from a single mode 100 mW laser diode at 850 nm is used for realizing optical tweezers: the laser beam is introduced into a microscope and focused by the objective into the object plane. Injection of the beam into a 40X microscope objective has been studied and the position and the size of the waist measured. The trap performance was studied as a function of the dimensions of the trapped particles. Trapping of polystyrene latex spheres of different size (from 0.2 micrometer to 6 micrometer) was observed in different conditions of laser power and transverse velocity of the spheres. Biological objects, Tetraselmis, of large dimension (around 10 micrometer) were also studied. We demonstrate the existence of an optimal range of size of the particles to be trapped. Furthermore we measure minimum trapping power required for trapping and the maximum speed of the trapped objects as a function of the dimensions.

  17. Automated analysis of single cells using Laser Tweezers Raman Spectroscopy.

    PubMed

    Casabella, S; Scully, P; Goddard, N; Gardner, P

    2016-01-01

    In recent years, significant progress has been made into the label-free detection and discrimination of individual cancer cells using Laser Tweezers Raman Spectroscopy (LTRS). However, the majority of examples reported have involved manual trapping of cells, which is time consuming and may lead to different cell lines being analysed in discrete batches. A simple, low-cost microfluidic flow chamber is introduced which allows single cells to be optically trapped and analysed in an automated fashion, greatly reducing the level of operator input required. Two implementations of the flow chamber are discussed here; a basic single-channel device in which the fluid velocity is controlled manually, and a dual-channel device which permits the automated capture and analysis of multiple cell lines with no operator input. Results are presented for the discrimination of live epithelial prostate cells and lymphocytes, together with a consideration of the consequences of traditional 'batch analysis' typically used for LTRS of live cells. PMID:26587766

  18. Trapping particles using waveguide-coupled gold bowtie plasmonic tweezers.

    PubMed

    Lin, Pin-Tso; Chu, Heng-Yi; Lu, Tsan-Wen; Lee, Po-Tsung

    2014-12-21

    We propose and demonstrate a trapping configuration integrating coupled waveguides and gold bowtie structures to form near-field plasmonic tweezers. Compared with excitation from the top, waves coupled through the waveguide can excite specific bowties on the waveguide and trap particles precisely. Thus this scheme is more efficient and compact, and will assist the circuit design on a chip. With lightning rod and gap effects, the gold bowtie structures can generate highly concentrated resonant fields and induce trapping forces as strong as 652 pN W(-1) on particles with diameters as small as 20 nm. This trapping capability is investigated numerically and verified experimentally with observations of the transport, trapping, and release of particles in the system. PMID:25288366

  19. Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration

    NASA Astrophysics Data System (ADS)

    Hanes, Richard D. L.; Jenkins, Matthew C.; Egelhaaf, Stefan U.

    2009-08-01

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45, smaller angles give a full 2? phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.

  20. Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration

    SciTech Connect

    Hanes, Richard D. L.; Jenkins, Matthew C.; Egelhaaf, Stefan U.

    2009-08-15

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 deg., smaller angles give a full 2{pi} phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.

  1. Combined holographic-mechanical optical tweezers: construction, optimization, and calibration.

    PubMed

    Hanes, Richard D L; Jenkins, Matthew C; Egelhaaf, Stefan U

    2009-08-01

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 degrees, smaller angles give a full 2pi phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method. PMID:19725658

  2. Multi-beam bilateral teleoperation of holographic optical tweezers.

    PubMed

    Onda, Kazuhisa; Arai, Fumihito

    2012-02-13

    A multi-beam bilateral teleoperation system of holographic optical tweezers accelerated by a graphics processing unit is proposed and evaluated. This double-arm teleoperation system is composed of two haptic devices and two laser-trapped micro-beads. Each micro-bead is trapped and moved following the trajectory of each haptic device, and the forces to which the micro-beads are subjected, which are generated by Stokes drag, are measured and fed back to an operator via the haptic devices. This real-time telexistence was quantitatively evaluated based on the time response of the trapped beads and the fed-back forces. And the demonstration of touching red blood cells shows the effectiveness of this system for biomedical application. PMID:22418122

  3. Dynamic excitations in membranes induced by optical tweezers.

    PubMed Central

    Bar-Ziv, R; Moses, E; Nelson, P

    1998-01-01

    We present the phenomenology of transformations in lipid bilayers that are excited by laser tweezers. A variety of dynamic instabilities and shape transformations are observed, including the pearling instability, expulsion of vesicles, and more exotic ones, such as the formation of passages. Our physical picture of the laser-membrane interaction is based on the generation of tension in the bilayer and loss of surface area. Although tension is the origin of the pearling instability, it does not suffice to explain expulsion of vesicles, where we observe opening of giant pores and creeping motion of bilayers. We present a quantitative theoretical framework to understand most of the observed phenomenology. The main hypothesis is that lipid is pulled into the optical trap by the familiar dielectric effect, is disrupted, and finally is repackaged into an optically unresolvable suspension of colloidal particles. This suspension, in turn, can produce osmotic pressure and depletion forces, driving the observed transformations. PMID:9649388

  4. Mechanical properties of a giant liposome studied using optical tweezers

    NASA Astrophysics Data System (ADS)

    Shitamichi, Yoko; Ichikawa, Masatoshi; Kimura, Yasuyuki

    2009-09-01

    The mechanical properties of a micrometer-sized giant liposome are studied by deforming it from the inside using dual-beam optical tweezers. As the liposome is extended, its shape changes from a sphere to a lemon shape, and finally, a tubular part is generated. The surface tension σ and the bending rigidity κ of the lipid membrane are obtained from the measured force-extension curve. In a one-phase liposome, it was found that σ increases as the charged component increases but κ remains approximately constant. In a two-phase liposome, the characteristic deformation and the force-extension curve differ from those observed for the one-phase liposome.

  5. Optical tweezers for free-solution label-free single bio-molecule studies

    NASA Astrophysics Data System (ADS)

    Kotnala, Abhay; Al-Balushi, Ahmed A.; Gordon, Reuven

    2014-09-01

    Nanoaperture based trapping has developed as a significant tool among the various optical tweezer systems for trapping of very small particles down to the single nanometer range. The double nanohole aperture based trap provides a method for efficient, highly-sensitive, label-free, low-cost, free-solution single molecule trapping and detection. We use the double nanohole tweezer to understand biomolecular phenomena like protein unfolding, binding, structural conformation of DNA, protein-DNA interactions, and protein small molecule interactions.

  6. iTweezers: optical micromanipulation controlled by an Apple iPad

    NASA Astrophysics Data System (ADS)

    Bowman, R. W.; Gibson, G.; Carberry, D.; Picco, L.; Miles, M.; Padgett, M. J.

    2011-04-01

    The 3D interactive manipulation of multiple particles with holographic optical tweezers is often hampered by the control system. We use a multi-touch interface implemented on an Apple iPad to overcome many of the limitations of mouse-based control, and demonstrate an elegant and intuitive interface to multi-particle manipulation. This interface connects to the tweezers system hardware over a wireless network, allowing it to function as a remote monitor and control device.

  7. Measurement of interaction forces between red blood cells in aggregates by optical tweezers

    SciTech Connect

    Maklygin, A Yu; Priezzhev, A V; Karmenian, A; Nikitin, Sergei Yu; Obolenskii, I S; Lugovtsov, Andrei E; Kisun Li

    2012-06-30

    We have fabricated double-beam optical tweezers and demonstrated the possibility of their use for measuring the interaction forces between red blood cells (erythrocytes). It has been established experimentally that prolonged trapping of red blood cells in a tightly focused laser beam does not cause any visible changes in their shape or size. We have measured the interaction between red blood cells in the aggregate, deformed by optical tweezers.

  8. Extending the range for force calibration in magnetic tweezers.

    PubMed

    Daldrop, Peter; Brutzer, Hergen; Huhle, Alexander; Kauert, Dominik J; Seidel, Ralf

    2015-05-19

    Magnetic tweezers are a wide-spread tool used to study the mechanics and the function of a large variety of biomolecules and biomolecular machines. This tool uses a magnetic particle and a strong magnetic field gradient to apply defined forces to the molecule of interest. Forces are typically quantified by analyzing the lateral fluctuations of the biomolecule-tethered particle in the direction perpendicular to the applied force. Since the magnetic field pins the anisotropy axis of the particle, the lateral fluctuations follow the geometry of a pendulum with a short pendulum length along and a long pendulum length perpendicular to the field lines. Typically, the short pendulum geometry is used for force calibration by power-spectral-density (PSD) analysis, because the movement of the bead in this direction can be approximated by a simple translational motion. Here, we provide a detailed analysis of the fluctuations according to the long pendulum geometry and show that for this direction, both the translational and the rotational motions of the particle have to be considered. We provide analytical formulas for the PSD of this coupled system that agree well with PSDs obtained in experiments and simulations and that finally allow a faithful quantification of the magnetic force for the long pendulum geometry. We furthermore demonstrate that this methodology allows the calibration of much larger forces than the short pendulum geometry in a tether-length-dependent manner. In addition, the accuracy of determination of the absolute force is improved. Our force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates. PMID:25992733

  9. Investigation of inclined dual-fiber optical tweezers for 3D manipulation and force sensing.

    PubMed

    Liu, Yuxiang; Yu, Miao

    2009-08-01

    Optical tweezers provide a versatile tool in biological and physical researches. Optical tweezers based on optical fibers are more flexible and ready to be integrated when compared with those based on microscope objectives. In this paper, the three-dimensional (3D) trapping ability of an inclined dual-fiber optical tweezers is demonstrated. The trapping efficiency with respect to displacement is experimentally calibrated along two dimensions. The system is studied numerically using a modified ray-optics model. The spring constants obtained in the experiment are predicted by simulations. It is found both experimentally and numerically that there is a critical value for the fiber inclination angle to retain the 3D trapping ability. The inclined dual-fiber optical tweezers are demonstrated to be more robust to z-axis misalignment than the counter-propagating fiber optical tweezers, which is a special case of th former when the fiber inclination angle is 90 masculine. This inclined dual-fiber optical tweezers can serve as both a manipulator and a force sensor in integrated systems, such as microfluidic systems and lab-on-a-chip systems. PMID:19654770

  10. Aromatic interactions by molecular tweezers and clips in chemical and biological systems.

    PubMed

    Klrner, Frank-Gerrit; Schrader, Thomas

    2013-04-16

    Noncovalent interactions involving aromatic rings, such as ?-stacking and CH-?, occur throughout a range of fundamental processes including self-assembly and (bio)catalysis. Molecular clips and tweezers possess a central parallel or torus-shaped cavity with a surrounding belt of convergent aromatic rings; hence these structures exploit multiple aromatic interactions in a positively cooperative manner. Both clips and tweezers demonstrate selective binding of cationic or neutral guests that bear acceptor groups. The electrostatic surface potentials (ESP) explain this unexpected behavior: calculated ESPs were highly negative inside the tweezer or clip cavity, providing complementary profiles to the positive ESP plots of their preferred guest molecules. This Account presents more complex systems that use aromatic clips and tweezers to alter the reactivities of included guest species, to distinguish between guest enantiomers, and to interfere with biological processes such as enzymatic activity and protein aggregation. Napthalene tweezers show potential applications in organocatalysis. When pyridinium moieties are bound within the spacious cavity of naphthyl-spaced tweezers, the resulting complex significantly influences the first step of single-electron reductions of (bi)pyridinium salts. In addition, the environment within the tweezer cavity strongly accelerates the Menshutkin reaction (the alkylation of pyridine derivatives). Introduction of phosphonate, phosphate, or sulfate anions into the central aromatic bridge renders clips and tweezers water-soluble. Larger systems form extremely tight intertwined dimers that rely on the nonclassical hydrophobic effect for their stability. Smaller clips and tweezers with a simple benzene bridge remain monomeric in buffered aqueous solution and display a complementary binding profile. While the clips with parallel sidewalls prefer flat aromatic cations such as pyridinium salts, the torus-shaped tweezers bind to basic amino acids lysine and arginine via a threading process. These mutually exclusive binding modes make water-soluble clips and tweezers valuable tools for probing critical biological interactions with positively charged amino acid side chains and cofactors. Molecular clips and tweezers can be employed for the complete inhibition of dehydrogenases. The clip extracts NAD(+) from its Rossman fold, while the tweezer complexes access strategic lysine residues around the active site. Our new enzyme inhibitors recognize the protein surface and thus offer additional targets for medicinal chemistry. Finally, the ability of molecular tweezers to cap critical lysine residues can be used to interfere with the pathology of protein misfolding diseases such as Alzheimer's disease, because many of them involve noncovalent interactions with these critical residues during their early stages. When the key protein produces a ?-sheet-rich nucleus, this structure undergoes spontaneous polymerization into highly toxic oligomers, ultimately leading to mature fibrils. The benzene-spaced phosphate tweezer forms a specific complex with lysine residues 16 and 28 in A?42 and thus prevents the formation of misfolded oligomers rich in ?-sheets. This entirely new process-specific mechanism that prevents pathologic protein aggregation also operates in many other related amyloidogenic proteins. PMID:22725723

  11. Automated multi-parametric sorting of micron-sized particles via multi-trap laser tweezers

    NASA Astrophysics Data System (ADS)

    Kaputa, Daniel S.

    The capabilities of laser tweezers have rapidly expanded since the first demonstration by Ashkin and co-workers in 1970 of the ability to trap particles using optical energy. Laser tweezers have been used to measure piconewton forces in many biological and material science application, sort bacteria, measure DNA bond strength, and even perform microsurgery. The laser tweezers system developed for this dissertation foreshadows the next generation of laser tweezer systems that provide automated particle sorted based upon multiple criteria. Many laser tweezer sorting applications today entail the operator sorting cells from a bulk sample, one by one. This dissertation demonstrates the technologies of pattern recognition and image processing that allow for an entire microscope slide to be sorted without any operator intervention. We already live in an automated world where the cars we drive are built by machines instead of humans. The technology is there, and the only factors limiting the advancements of fully automated biological instrumentation is the lack of developers with the appropriate knowledge sets. This dissertation introduces the concept of sorting particles via a multi-parametric approach where several parameters such as size, fluorescence, and Raman spectra are used as sorting criteria. Since the advent of laser tweezers, several groups have demonstrated the ability to sort cells and other particle by size, or by fluorescence, or by any other parameter, but to our knowledge there does not exist a laser tweezer sorting system that can sort particles based upon multiple parameters. Sorting via a single parameter can be a severe limitation as the method lacks the robustness and class specificity that exists when sorting based upon multiple parameters. Simply put, it makes more sense to determine the worth of a baseball card by considering it's condition as well as it's age, rather then solely upon its condition. By adding another parameter such as the name of the player in the card, one can start collecting Babe Ruth rookie cards instead of mint condition cards of bench warmers. In the future, even better multi-parametric laser tweezer particle sorting systems will be developed that make use of pulsed radiation in order to stimulate nonlinear optical phenomena. This dissertation discusses the feasibility of combining a rapid, non-invasive chemical imaging technology called coherent anti-Stokes Raman scattering (CARS) with a laser tweezer sorting system. This would allow for the birth of a laser tweezer particle sorting system of unprecedented speed and chemical specificity the likes of which the world has not yet seen.

  12. Automatic real time evaluation of red blood cell elasticity by optical tweezers

    NASA Astrophysics Data System (ADS)

    Moura, Diógenes S.; Silva, Diego C. N.; Williams, Ajoke J.; Bezerra, Marcos A. C.; Fontes, Adriana; de Araujo, Renato E.

    2015-05-01

    Optical tweezers have been used to trap, manipulate, and measure individual cell properties. In this work, we show that the association of a computer controlled optical tweezers system with image processing techniques allows rapid and reproducible evaluation of cell deformability. In particular, the deformability of red blood cells (RBCs) plays a key role in the transport of oxygen through the blood microcirculation. The automatic measurement processes consisted of three steps: acquisition, segmentation of images, and measurement of the elasticity of the cells. An optical tweezers system was setup on an upright microscope equipped with a CCD camera and a motorized XYZ stage, computer controlled by a Labview platform. On the optical tweezers setup, the deformation of the captured RBC was obtained by moving the motorized stage. The automatic real-time homemade system was evaluated by measuring RBCs elasticity from normal donors and patients with sickle cell anemia. Approximately 150 erythrocytes were examined, and the elasticity values obtained by using the developed system were compared to the values measured by two experts. With the automatic system, there was a significant time reduction (60 × ) of the erythrocytes elasticity evaluation. Automated system can help to expand the applications of optical tweezers in hematology and hemotherapy.

  13. Numerical study of the properties of optical vortex array laser tweezers.

    PubMed

    Kuo, Chun-Fu; Chu, Shu-Chun

    2013-11-01

    Chu et al. constructed a kind of Ince-Gaussian modes (IGM)-based vortex array laser beams consisting of p x p embedded optical vortexes from Ince-Gaussian modes, IG(e)(p,p) modes [Opt. Express 16, 19934 (2008)]. Such an IGM-based vortex array laser beams maintains its vortex array profile during both propagation and focusing, and is applicable to optical tweezers. This study uses the discrete dipole approximation (DDA) method to study the properties of the IGM-based vortex array laser tweezers while it traps dielectric particles. This study calculates the resultant force exerted on the spherical dielectric particles of different sizes situated at the IGM-based vortex array laser beam waist. Numerical results show that the number of trapping spots of a structure light (i.e. IGM-based vortex laser beam), is depended on the relation between the trapped particle size and the structure light beam size. While the trapped particle is small comparing to the beam size of the IGM-based vortex array laser beams, the IGM-based vortex array laser beams tweezers are suitable for multiple traps. Conversely, the tweezers is suitable for single traps. The results of this study is useful to the future development of the vortex array laser tweezers applications. PMID:24216863

  14. Automatic real time evaluation of red blood cell elasticity by optical tweezers.

    PubMed

    Moura, Digenes S; Silva, Diego C N; Williams, Ajoke J; Bezerra, Marcos A C; Fontes, Adriana; de Araujo, Renato E

    2015-05-01

    Optical tweezers have been used to trap, manipulate, and measure individual cell properties. In this work, we show that the association of a computer controlled optical tweezers system with image processing techniques allows rapid and reproducible evaluation of cell deformability. In particular, the deformability of red blood cells (RBCs) plays a key role in the transport of oxygen through the blood microcirculation. The automatic measurement processes consisted of three steps: acquisition, segmentation of images, and measurement of the elasticity of the cells. An optical tweezers system was setup on an upright microscope equipped with a CCD camera and a motorized XYZ stage, computer controlled by a Labview platform. On the optical tweezers setup, the deformation of the captured RBC was obtained by moving the motorized stage. The automatic real-time homemade system was evaluated by measuring RBCs elasticity from normal donors and patients with sickle cell anemia. Approximately 150 erythrocytes were examined, and the elasticity values obtained by using the developed system were compared to the values measured by two experts. With the automatic system, there was a significant time reduction (60) of the erythrocytes elasticity evaluation. Automated system can help to expand the applications of optical tweezers in hematology and hemotherapy. PMID:26026527

  15. Dielectrophoretic Tweezers and Micropost Arrays for Cell and Particle Manipulation

    NASA Astrophysics Data System (ADS)

    Hunt, Tom; Lee, Hakho; Westervelt, Robert

    2005-03-01

    We describe a micromanipulator system that uses dielectrophoresis to capture and release cells or particles. Dielectrophoretic tweezers are capable of applying hundreds of piconewtons of force to micron scale objects suspended in liquid and precisely positioning objects in three dimensions. Metal electrodes on either side of a sharp pipette tip provide the electric field gradient necessary. This manipulation technique compliments our micropost array (1) for the manipulation of particles in a microfluidic system. We will discuss applications of dielectrophoresis using hybrid integrated circuit/microfluidic devices (2) with applications that include cell sorting and tissue assembly. This work made possible by a gift from Phillip Morris and the NSEC NSF grant PHY-0117795. 1. T. P. Hunt H. Lee and R. M. Westervelt, ``Addressable micropost array for the dielectrophoretic manipulation of particles in fluid," Appl. Phys. Lett. In Press. 2. H. Lee, et Al. ``An IC/ microfluidic hybrid microsystem for 2D magnetic manipulation of individual biological cells," To appear in IEEE ISSCC, Feb. 2005.

  16. Multiplexed single-molecule measurements with magnetic tweezers

    SciTech Connect

    Ribeck, Noah; Saleh, Omar A.

    2008-09-15

    We present a method for performing multiple single-molecule manipulation experiments in parallel with magnetic tweezers. We use a microscope with a low magnification, and thus a wide field of view, to visualize multiple DNA-tethered paramagnetic beads and apply an optimized image analysis routine to track the three-dimensional position of each bead simultaneously in real time. Force is applied to each bead using an externally applied magnetic field. Since variations in the field parameters are negligible across the field of view, nearly identical manipulation of all visible beads is possible. However, we find that the error in the position measurement is inversely proportional to the microscope's magnification. To mitigate the increased error caused by demagnification, we have developed a strategy based on tracking multiple fixed beads. Our system is capable of simultaneously manipulating and tracking up to 34 DNA-tethered beads at 60 Hz with {approx}1.5 nm resolution and with {approx}10% variation in applied force.

  17. Particle interaction measurements using laser tweezers optical trapping.

    SciTech Connect

    Koehler, Timothy P.; Brinker, C. Jeffrey; Brotherton, Christopher M.; Grillet, Anne M.; Molecke, Ryan A.

    2008-08-01

    Laser tweezers optical trapping provides a unique noninvasive capability to trap and manipulate particles in solution at the focal point of a laser beam passed through a microscope objective. Additionally, combined with image analysis, interaction forces between colloidal particles can be quantitatively measured. By looking at the displacement of particles within the laser trap due to the presence of a neighboring particle or looking at the relative diffusion of two particles held near each other by optical traps, interparticle interaction forces ranging from pico- to femto-Newtons can be measured. Understanding interaction forces is critical for predicting the behavior of particle dispersions including dispersion stability and flow rheology. Using a new analysis method proposed by Sainis, Germain, and Dufresne, we can simultaneously calculate the interparticle velocity and particle diffusivity which allows direct calculation of the interparticle potential for the particles. By applying this versatile tool, we measure difference in interactions between various phospholipid bilayers that have been coated onto silica spheres as a new type of solid supported liposome. We measure bilayer interactions of several cell membrane lipids under various environmental conditions such as pH and ionic strength and compare the results with those obtained for empty liposomes. These results provide insight into the role of bilayer fluctuations in liposome fusion, which is of fundamental interest to liposome based drug delivery schemes.

  18. Nano-funnels as electro-osmotic ``tweezers and pistons''

    NASA Astrophysics Data System (ADS)

    Wang, Yanqian; Panyukov, Sergey; Zhou, Jinsheng; Menard, Laurent D.; Ramsey, J. Michael; Rubinstien, Michael

    2014-03-01

    An electric field is used to force a DNA molecule into a nano-channel by compensating the free energy penalty that results from the reduced conformational entropy of the confined macromolecule. Narrow nano-channels require high critical electric fields to achieve DNA translocation, leading to short dwell times of DNA in these channels. We demonstrate that nano-funnels integrated with nano-channels reduce the free energy barrier and lower the critical electric field required for DNA translocation. A focused electric field within the funnel increases the electric force on the DNA, compresses the molecule, and increases the osmotic pressure at the nano-channel entrance. This ``electro-osmotic piston'' forces the molecule into the nano-channel at lower electric fields than those observed without the funnel. Appropirately designed nano-funnels can also function as tweezers that allow manipulation of the position of the DNA molecule. The predictions of our theory describing double-stranded DNA behavior in nano-funnel - nano-channel devices are consistent with experimental results. Thanks for the financial support from NSF (DMR-1309892, DMR-1121107, DMR-1122483), NIH (1-P50-HL107168, 1-P01-HL108808-01A1, R01HG02647), NHGRI and CF Foundation.

  19. Dispersive light-matter interaction in programmable optical tweezers

    NASA Astrophysics Data System (ADS)

    Sawyer, Bianca J.; Horvath, Milena S. J.; Deb, Amita B.; Kjørgaard, Niels

    2015-08-01

    We have developed a robust interrogation system using frequency modulation spectroscopy to measure the quantum state-dependent phase shift incurred on an off-resonant optical probe when transmitted by an atomic medium. Recently, our focus has been on extending this technique for the detection of Feshbach resonances in 87Rb atoms. Feshbach resonance is a mechanism which allows the atomic interaction strength to be precisely tuned via an external magnetic field. To access a Feshbach resonance atoms must be independently prepared in certain internal states, during which we utilize programmable optical tweezers to perform precise spatial micro-manipulation of the ensemble in laser "test-tubes." We use our dispersive probing system to identify the resonant magnetic field value in a sample with a dense "ball" geometry. An important design consideration for such a probing scheme is the three-dimensional mode-matching at the interface between light and the atomic sample when coupled by the dispersive interaction. We discuss challenges which dealing with this new geometry compared to the previously used prolate geometry, and consider the possibility of dipole-dipole interactions in our sample leading to cooperative light scattering processes.

  20. Probing DNA Helicase Kinetics with Temperature-Controlled Magnetic Tweezers

    PubMed Central

    Gollnick, Benjamin; Carrasco, Carolina; Zuttion, Francesca; Gilhooly, Neville S; Dillingham, Mark S; Moreno-Herrero, Fernando

    2015-01-01

    Motor protein functions like adenosine triphosphate (ATP) hydrolysis or translocation along molecular substrates take place at nanometric scales and consequently depend on the amount of available thermal energy. The associated rates can hence be investigated by actively varying the temperature conditions. In this article, a thermally controlled magnetic tweezers (MT) system for single-molecule experiments at up to 40 C is presented. Its compact thermostat module yields a precision of 0.1 C and can in principle be tailored to any other surface-coupled microscopy technique, such as tethered particle motion (TPM), nanopore-based sensing of biomolecules, or super-resolution fluorescence imaging. The instrument is used to examine the temperature dependence of translocation along double-stranded (ds)DNA by individual copies of the protein complex AddAB, a helicase-nuclease motor involved in dsDNA break repair. Despite moderately lower mean velocities measured at sub-saturating ATP concentrations, almost identical estimates of the enzymatic reaction barrier (around 2124 kBT) are obtained by comparing results from MT and stopped-flow bulk assays. Single-molecule rates approach ensemble values at optimized chemical energy conditions near the motor, which can withstand opposing loads of up to 14 piconewtons (pN). Having proven its reliability, the temperature-controlled MT described herein will eventually represent a routinely applied method within the toolbox for nano-biotechnology. PMID:25400244

  1. Manipulation of Suspended Single Cells by Microfluidics and Optical Tweezers

    PubMed Central

    Nve, Nathalie; Kohles, Sean S.; Winn, Shelley R.; Tretheway, Derek C.

    2010-01-01

    Chondrocytes and osteoblasts experience multiple stresses in vivo. The optimum mechanical conditions for cell health are not fully understood. This paper describes the optical and microfluidic mechanical manipulation of single suspended cells enabled by the ?PIVOT, an integrated micron resolution particle image velocimeter (?PIV) and dual optical tweezers instrument (OT). In this study, we examine the viability and trap stiffness of cartilage cells, identify the maximum fluid-induced stresses possible in uniform and extensional flows, and compare the deformation characteristics of bone and muscle cells. These results indicate cell photodamage of chondrocytes is negligible for at least 20 min for laser powers below 30 mW, a dead cell presents less resistance to internal organelle rearrangement and deforms globally more than a viable cell, the maximum fluid-induced shear stresses are limited to ~15 mPa for uniform flows but may exceed 1 Pa for extensional flows, and osteoblasts show no deformation for shear stresses up to 250 mPa while myoblasts are more easily deformed and exhibit a modulated response to increasing stress. This suggests that global and/or local stresses can be applied to single cells without physical contact. Coupled with microfluidic sensors, these manipulations may provide unique methods to explore single cell biomechanics. PMID:20824110

  2. Live cell lithography: using optical tweezers to create synthetic tissue.

    PubMed

    Mirsaidov, Utkur; Scrimgeour, Jan; Timp, Winston; Beck, Kaethe; Mir, Mustafa; Matsudaira, Paul; Timp, Gregory

    2008-12-01

    We demonstrate a new method for creating synthetic tissue that has the potential to capture the three-dimensional (3D) complexity of a multi-cellular organism with submicron precision. Using multiple laminar fluid flows in a microfluidic network, we convey cells to an assembly area where multiple, time-shared optical tweezers are used to organize them into a complex array. The cells are then encapsulated in a 30 microm x 30 microm x 45 microm volume of photopolymerizable hydrogel that mimicks an extra-cellular matrix. To extend the size, shape and constituency of the array without loss of viability, we then step to an adjacent location while maintaining registration with the reference array, and repeat the process. Using this step-and-repeat method, we formed a heterogeneous array of E. coli genetically engineered with a lac switch that is functionally linked to fluorescence reporters. We then induced the array using ligands through a microfluidic network and followed the space-time development of the fluorescence to evaluate viability and metabolic activity. PMID:19023484

  3. Parallel lipoplex folding pathways revealed using magnetic tweezers

    PubMed Central

    Sun, Zhiqiang; Tikhonova, Elena B.; Zgurskaya, Helen I.; Rybenkov, Valentin V.

    2012-01-01

    Lipid-coated DNA nanoparticles (lipoplexes) are a powerful gene delivery tool with promising therapeutic applications. The mechanism of lipoplex assembly remains poorly understood. We explored DNA packing by a cationic lipid DSTAP (distearoyl trimethylammonium-propane) using magnetic tweezers. DSTAP-induced DNA condensation occurred as a series of bursts with the mean step size of 60 nm to 80 nm. The pause time preceding the steps could be approximated as a bimodal distribution, which reveals at least two distinct condensation pathways. The rapidly condensed DNA was more resilient to force-induced decondensation. The proportion of the stable, fast-formed complexes decreased at high salt concentrations. A similar trend was observed in bulk experiments. Lipoplexes assembled at low salt concentration more efficiently shielded DNA from fluorescent dyes and DNase even after transfer to the high salt conditions. These data reveal that lipoplex folding occurs via two parallel pathways even at the single molecule level. The progress through the two pathways can be monitored in real time using single DNA manipulations. The relative efficiency of the two pathways can be varied by external conditions. PMID:22988939

  4. Membrane tether formation from outer hair cells with optical tweezers.

    PubMed

    Li, Zhiwei; Anvari, Bahman; Takashima, Masayoshi; Brecht, Peter; Torres, Jorge H; Brownell, William E

    2002-03-01

    Optical tweezers were used to characterize the mechanical properties of the outer hair cell (OHC) plasma membrane by pulling tethers with 4.5-microm polystyrene beads. Tether formation force and tether force were measured in static and dynamic conditions. A greater force was required for tether formations from OHC lateral wall (499 +/- 152 pN) than from OHC basal end (142 +/- 49 pN). The difference in the force required to pull tethers is consistent with an extensive cytoskeletal framework associated with the lateral wall known as the cortical lattice. The apparent plasma membrane stiffness, estimated under the static conditions by measuring tether force at different tether length, was 3.71 pN/microm for OHC lateral wall and 4.57 pN/microm for OHC basal end. The effective membrane viscosity was measured by pulling tethers at different rates while continuously recording the tether force, and estimated in the range of 2.39 to 5.25 pN x s/microm. The viscous force most likely results from the viscous interactions between plasma membrane lipids and the OHC cortical lattice and/or integral membrane proteins. The information these studies provide on the mechanical properties of the OHC lateral wall is important for understanding the mechanism of OHC electromotility. PMID:11867454

  5. Fiber based optical tweezers for simultaneous in situ force exertion and measurements in a 3D polyacrylamide gel compartment.

    PubMed

    Ti, Chaoyang; Thomas, Gawain M; Ren, Yundong; Zhang, Rui; Wen, Qi; Liu, Yuxiang

    2015-07-01

    Optical tweezers play an important role in biological applications. However, it is difficult for traditional optical tweezers based on objective lenses to work in a three-dimensional (3D) solid far away from the substrate. In this work, we develop a fiber based optical trapping system, namely inclined dual fiber optical tweezers, that can simultaneously apply and measure forces both in water and in a 3D polyacrylamide gel matrix. In addition, we demonstrate in situ, non-invasive characterization of local mechanical properties of polyacrylamide gel by measurements on an embedded bead. The fiber optical tweezers measurements agree well with those of atomic force microscopy (AFM). The inclined dual fiber optical tweezers provide a promising and versatile tool for cell mechanics study in 3D environments. PMID:26203364

  6. Fiber based optical tweezers for simultaneous in situ force exertion and measurements in a 3D polyacrylamide gel compartment

    PubMed Central

    Ti, Chaoyang; Thomas, Gawain M; Ren, Yundong; Zhang, Rui; Wen, Qi; Liu, Yuxiang

    2015-01-01

    Optical tweezers play an important role in biological applications. However, it is difficult for traditional optical tweezers based on objective lenses to work in a three-dimensional (3D) solid far away from the substrate. In this work, we develop a fiber based optical trapping system, namely inclined dual fiber optical tweezers, that can simultaneously apply and measure forces both in water and in a 3D polyacrylamide gel matrix. In addition, we demonstrate in situ, non-invasive characterization of local mechanical properties of polyacrylamide gel by measurements on an embedded bead. The fiber optical tweezers measurements agree well with those of atomic force microscopy (AFM). The inclined dual fiber optical tweezers provide a promising and versatile tool for cell mechanics study in 3D environments. PMID:26203364

  7. Temperature-Dependent Conformations of a Membrane Supported Zinc Porphyrin Tweezer by 2D Fluorescence Spectroscopy

    PubMed Central

    Widom, Julia R.; Lee, Wonbae; Perdomo-Ortiz, Alejandro; Rappoport, Dmitrij; Molinski, Tadeusz F.; Aspuru-Guzik, Aln; Marcus, Andrew H.

    2013-01-01

    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. PMID:23480874

  8. RBCs under optical tweezers as cellular motors and rockers: microfluidic applications

    NASA Astrophysics Data System (ADS)

    Mohanty, Samarendra; Mohanty, Khyati; Gupta, Pradeep

    2006-08-01

    Recently, we have reported self-rotation of normal red blood cells (RBC), suspended in hypertonic buffer, and trapped in unpolarized laser tweezers. Here, we report use of such an optically driven RBC-motor for microfluidic applications such as pumping/centrifugation of fluids. Since the speed of rotation of the RBC-motor was found to vary with the power of the trapping beam, the flow rate could be controlled by controlling the laser power. In polarized optical tweezers, preferential alignment of trapped RBC was observed. The aligned RBC (simulating a disk) in isotonic buffer, could be rotated in a controlled manner for use as a microfluidic valve by rotation of the plane of polarization of the trapping beam. The thickness of the discotic RBC could be changed by changing the osmolarity of the solution and thus the alignment torque on the RBC due to the polarization of the trapping beam could be varied. Further, in polarized tweezers, the RBCs in hypertonic buffer showed rocking motion while being in rotation. Here, the RBC rotated over a finite angular range, stopped for some time at a particular angle, and then started rotating till it was back to the aligned position and this cycle was found repetitive. This can be attributed to the fact that though the RBCs were found to experience an alignment torque to align with plane of polarization of the tweezers due to its form birefringence, it was smaller in magnitude as compared to the rotational torque due to its structural asymmetry in hypertonic solution. Changes in the laser power caused a transition from/to rocking to/from motor behavior of the RBC in a linearly polarized tweezers. By changing the direction of polarization caused by rotation of an external half wave plate, the stopping angle of rocking could be changed. Further, RBCs suspended in intermediate hypertonic buffer and trapped with polarized tweezers showed fluttering about the vertical plane.

  9. Calibration of a dual-trap optical tweezers for single molecule force spectroscopy study

    NASA Astrophysics Data System (ADS)

    Wang, Guoqing; Hu, Chunguang; Gao, Xiaoqing; Su, Chenguang; Wang, Sirong; Lei, Hai; Hu, Xiaodong; Li, Hongbin; Hu, Xiaotang

    2015-10-01

    Optical tweezers has shown its significant advantages in applying pico-Newton force on micro beads and handling them with nanometer-level precision, and becomes a powerful tool for single-molecule biology. Many excellent researching results in use of the optical tweezers have been reported. Most of them focus on the single-trap optical tweezers experiments. However, when a single-trap optical tweezers is applied to biological molecule, there is often an obvious noise from the sample chamber holder to which one end of the sample molecule is tethered. In contrast, a dual-trap optical tweezers can intrinsically avoid this problem because both ends of the sample tethered to microspheres are manipulated with two separate optical traps. In order to force the molecule precisely, it is of importance to do calibrations for both traps. Many approaches have been studied to obtain the stiffness and sensitivity of the trap, but those are not quite suitable for making calibration during experiment. Here, we use a modified method of power spectrum density (PSD) for the calibrations of the stiffness and sensitivity of the traps, which combines a sinusoidal motion of the sample stage. The main strength of the method is that the beads used for the calibration also can be used in experiment later. In addition, the calibration can be performed during experiment. Finally, an experiment using a dsDNA molecule to test the system is presented. The results show that the calibration approach for the dual-trap optical tweezers is efficient and accurate.

  10. Shape deformations of giant unilamellar vesicles with a laser tweezer array

    NASA Astrophysics Data System (ADS)

    Losert, Wolfgang; Poole, Cory; Bradford, Peter; English, Doug

    2004-10-01

    Vesicles are phospholipid bilayers that form a surface enclosing a volume of water or solution. They are of importance as model systems to study cells, as well as having practical applications such as containers for performing nanochemistry and facilitating drug delivery. Their properties have been studied for decades. Using a holographic laser tweezer array (LTA), which converts a single laser beam into many laser tweezer points, we stretch the vesicles in controlled ways from several points at once, measuring each force applied. Here, we present data on shape deformations of simple, spherical vesicles and on membrane fracture.

  11. Raman tweezers on bacteria: following the mechanisms of bacteriostatic versus bactericidal action

    NASA Astrophysics Data System (ADS)

    Bernatova, Silvie; Samek, Ota; Pilat, Zdenek; Sery, Mojmir; Jezek, Jan; Jakl, Petr; Siler, Martin; Krzyzanek, Vladislav; Zemanek, Pavel; Hola, Veronika; Dvorackova, Milada; Ruzicka, Filip

    2014-05-01

    Raman tweezers represents a unique method for identification of different microorganisms on the basis of Raman scattering. Raman tweezers allows us to fix and sterile manipulate with the trapped object and in the same time check the growth, viability, response to the external environment etc. by Raman signal evaluating. The investigations presented here include distinction of bacteria in general (staphylococcal cells), identification of bacteria strains (biofilm-positive and biofilm-negative) by using principal component analysis (PCA) and monitoring the influence of antibiotics.

  12. Dynamics of multiple trapping by a single-beam laser tweezer

    SciTech Connect

    Kaputa, Daniel S.; Kuzmin, Andrey N.; Kachynski, Aliaksandr V.; Cartwright, Alexander N.; Prasad, Paras N

    2005-07-01

    A multiple-trap single-beam scanning laser tweezer system was developed and characterized. Different stationary and mobile multiple-trap modes were generated for polystyrene beads in a water environment. Trapping efficiency and stability were investigated for several dynamic parameters such as transition time between the sites, waiting time on a single site, number of trapping sites, and IR laser power. Optimal parameters for efficient generation of complex arrays and matrices were determined. We demonstrate an example of a single laser beam multiple-trap application by measuring the trap's stiffness in water for our laser tweezer setup.

  13. Rate of growth pattern of yeast cells studied under optical tweezers

    NASA Astrophysics Data System (ADS)

    Charrunchon, Sookpichaya; Limtrakul, Jumras; Chattham, Nattaporn

    2013-06-01

    Cell growth and division has been of scientists' interest for over generations. Several mathematical models have been reported derived from conventional method of cell culture. Here we applied optical tweezers to guide cell division directionally. The patterns of Saccharonmyces bayanus yeast growth was studied under 1064 nm line optical tweezers generated by time-shared multiple optical traps. Yeast growth was found following the path of the generated laser patterns in linear, circular, square and L shapes, speculatively as a result of localized heating effect due to absorption at the focal point.

  14. Near-field enhanced optical tweezers utilizing femtosecond-laser nanostructured substrates

    NASA Astrophysics Data System (ADS)

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2015-11-01

    We present experimental evidence of plasmonic-enhanced optical tweezers, of polystyrene beads in deionized water in the vicinity of metal-coated nanostructures. The optical tweezers operate with a continuous wave near-infrared laser. We employ a Cu/Au bilayer that significantly improves dissipation of heat generated by the trapping laser beam and avoid de-trapping from heat convection currents. We investigate the improvement of the optical trapping force and the effective trapping quality factor, and observe an exponential distance dependence of the trapping force from the nanostructures, indicative of evanescent plasmonic enhancement.

  15. Single DNA molecule grafting and manipulation using a combined atomic force microscope and an optical tweezer

    NASA Astrophysics Data System (ADS)

    Shivashankar, G. V.; Libchaber, A.

    1997-12-01

    In this letter, we report on spatially selecting and grafting a DNA-tethered bead to an atomic force microscope (AFM) cantilever, using an optical tweezer. To quantify this technique, we measure force versus extension of a single DNA molecule using AFM. For such studies, we have developed a micromanipulation approach by combining an AFM, an optical tweezer, and visualization setup. The ability to select a single DNA polymer and specifically graft it to a localized position on a substrate opens up new possibilities in biosensors and bioelectronic devices.

  16. Mechanical and electrical properties of red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, A.; Barjas Castro, M. L.; Brando, M. M.; Fernandes, H. P.; Thomaz, A. A.; Huruta, R. R.; Pozzo, L. Y.; Barbosa, L. C.; Costa, F. F.; Saad, S. T. O.; Cesar, C. L.

    2011-04-01

    Optical tweezers are a very sensitive tool, based on photon momentum transfer, for individual, cell by cell, manipulation and measurements, which can be applied to obtain important properties of erythrocytes for clinical and research purposes. Mechanical and electrical properties of erythrocytes are critical parameters for stored cells in transfusion centers, immunohematological tests performed in transfusional routines and in blood diseases. In this work, we showed methods, based on optical tweezers, to study red blood cells and applied them to measure apparent overall elasticity, apparent membrane viscosity, zeta potential, thickness of the double layer of electrical charges and adhesion in red blood cells.

  17. Characterisation of coated aerosols using optical tweezers and neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Jones, S. H.; Ward, A.; King, M. D.

    2013-12-01

    Thin organic films are believed to form naturally on the surface of aerosols [1,2] and influence aerosol properties. Cloud condensation nuclei formation and chemical reactions such as aerosol oxidation are effected by the presence of thin films [3]. There is a requirement to characterise the physical properties of both the core aerosol and its organic film in order to fully understand the contribution of coated aerosols to the indirect effect. Two complementary techniques have been used to study the oxidation of thin organic films on the surface of aerosols; laser optical tweezers and neutron reflectometry. Micron sized polystyrene beads coated in oleic acid have been trapped in air using two counter propagating laser beams. Polystyrene beads are used as a proxy for solid aerosol. The trapped aerosol is illuminated with a white LED over a broadband wavelength range and the scattered light collected to produce a Mie spectrum [4]. Analysis of the Mie spectrum results in determination of the core polystyrene bead radius, the oleic acid film thickness and refractive index dispersion of the core and shell [5]. A flow of ozone gas can then be introduced into the aerosol environment to oxidise the thin film of oleic acid and the reaction followed by monitoring the changes in the Mie spectrum. The results demonstrate complete removal of the oleic acid film. We conclude that the use of a counter propagating optical trap combined with white light Mie spectroscopy can be used to study a range of organic films on different types of aerosols and their oxidation reactions. Neutron reflectometry has been used as a complementary technique to study the oxidation of monolayer films at the air-water interface in order to gain information on reaction kinetics. The oxidation of an oleic acid film at the air-water interface by the common tropospheric oxidant ozone has been studied using a Langmuir trough. Results indicate complete removal of the oleic acid film with ozone in agreement with the optical tweezers study, which confounds a previous study [6]. Findings also show complicated reaction kinetics that depend on the surface coverage of the film. Combining single particle studies using optical tweezing with macromolecular studies of thin films using neutron reflectometry provides a detailed atmospheric understanding of thin films on aerosols and their oxidation reactions. 1. Tervahattu H., Hartonen K., Kerminen V-H., Kupianen K., Aarnio P., Koskentalo T., Tuck A. and Vaida V., 2002, J. Geophys. Res. 107, 4053-4060. 2. Ellison G., Tuck A. and Vaida V., 1999, J. Geophys. Res. 104, 11633-11641. 3. King M.D., Thompson K.C., Ward A.D., 2004, JACS, 51, 16710-16711. 4. Ward A.D., Zhang M. and Hunt O., 2008, Opt. Express, 16, 16390-16403. 5. C.F. Bohren and D.R. Huffman, Absorption and Scattering of Light by Small Particles, (Wiley Scientific 1998). 6. King M.D., Rennie A.R., Thompson K.C., Fisher F.N., Dong C.C., Thomas R.K., Pfrang C., Hughes A.V., 2009, PCCP, 11, 7699-7707.

  18. Dynamic properties of bacterial pili measured by optical tweezers

    NASA Astrophysics Data System (ADS)

    Fallman, Erik G.; Andersson, Magnus J.; Schedin, Staffan S.; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

    2004-10-01

    The ability of uropathogenic Escherichia coli (UPEC) to cause urinary tract infections is dependent on their ability to colonize the uroepithelium. Infecting bacteria ascend the urethra to the bladder and then kidneys by attaching to the uroepithelial cells via the differential expression of adhesins. P pili are associated with pyelonephritis, the more severe infection of the kidneys. In order to find means to treat pyelonephritis, it is therefore of interest to investigate the properties P pili. The mechanical behavior of individual P pili of uropathogenic Escherichia coli has recently been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of ~1000 PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. We have earlier studied P pili regarding its stretching/elongation properties where we have found and characterized three different elongation regions, of which one constitute an unfolding of the quaternary (helical) structure of the PapA rod. It was shown that this unfolding takes place at an elongation independent force of 27 +/- 2 pN. We have also recently performed studies on its folding properties and shown that the unfolding/folding of the PapA rod is completely reversible. Here we present a study of the dynamical properties of the PapA rod. We show, among other things, that the unfolding force increases and that the folding force decreases with the speed of unfolding and folding respectively. Moreover, the PapA rod can be folded-unfolded a significant number of times without loosing its characteristics, a phenomenon that is believed to be important for the bacterium to keep close contact to the host tissue and consequently helps the bacterium to colonize the host tissue.

  19. Substrate-dependent cell elasticity measured by optical tweezers indentation

    NASA Astrophysics Data System (ADS)

    Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

    2016-01-01

    In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

  20. Mechanical properties of stored red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, Adriana; Alexandre de Thomaz, Andre; de Ysasa Pozzo, Liliana; de Lourdes Barjas-Castro, Maria; Brandao, Marcelo M.; Saad, Sara T. O.; Barbosa, Luiz Carlos; Cesar, Carlos Lenz

    2005-08-01

    We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity ? by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

  1. Molecular tweezers modulate 14-3-3 protein-protein interactions.

    PubMed

    Bier, David; Rose, Rolf; Bravo-Rodriguez, Kenny; Bartel, Maria; Ramirez-Anguita, Juan Manuel; Dutt, Som; Wilch, Constanze; Klrner, Frank-Gerrit; Sanchez-Garcia, Elsa; Schrader, Thomas; Ottmann, Christian

    2013-03-01

    Supramolecular chemistry has recently emerged as a promising way to modulate protein functions, but devising molecules that will interact with a protein in the desired manner is difficult as many competing interactions exist in a biological environment (with solvents, salts or different sites for the target biomolecule). We now show that lysine-specific molecular tweezers bind to a 14-3-3 adapter protein and modulate its interaction with partner proteins. The tweezers inhibit binding between the 14-3-3 protein and two partner proteins--a phosphorylated (C-Raf) protein and an unphosphorylated one (ExoS)--in a concentration-dependent manner. Protein crystallography shows that this effect arises from the binding of the tweezers to a single surface-exposed lysine (Lys214) of the 14-3-3 protein in the proximity of its central channel, which normally binds the partner proteins. A combination of structural analysis and computer simulations provides rules for the tweezers' binding preferences, thus allowing us to predict their influence on this type of protein-protein interactions. PMID:23422566

  2. Molecular tweezers modulate 14-3-3 protein-protein interactions

    NASA Astrophysics Data System (ADS)

    Bier, David; Rose, Rolf; Bravo-Rodriguez, Kenny; Bartel, Maria; Ramirez-Anguita, Juan Manuel; Dutt, Som; Wilch, Constanze; Klrner, Frank-Gerrit; Sanchez-Garcia, Elsa; Schrader, Thomas; Ottmann, Christian

    2013-03-01

    Supramolecular chemistry has recently emerged as a promising way to modulate protein functions, but devising molecules that will interact with a protein in the desired manner is difficult as many competing interactions exist in a biological environment (with solvents, salts or different sites for the target biomolecule). We now show that lysine-specific molecular tweezers bind to a 14-3-3 adapter protein and modulate its interaction with partner proteins. The tweezers inhibit binding between the 14-3-3 protein and two partner proteinsa phosphorylated (C-Raf) protein and an unphosphorylated one (ExoS)in a concentration-dependent manner. Protein crystallography shows that this effect arises from the binding of the tweezers to a single surface-exposed lysine (Lys214) of the 14-3-3 protein in the proximity of its central channel, which normally binds the partner proteins. A combination of structural analysis and computer simulations provides rules for the tweezers' binding preferences, thus allowing us to predict their influence on this type of protein-protein interactions.

  3. Optical tweezers with fluorescence detection for temperature-dependent microrheological measurements

    NASA Astrophysics Data System (ADS)

    Shundo, Atsuomi; Hori, Koichiro; Penaloza, David P.; Tanaka, Keiji

    2013-01-01

    We introduce a setup of optical tweezers, capable of carrying out temperature-dependent rheological measurements of soft materials. In our setup, the particle displacement is detected by imaging a bright spot due to fluorescence emitted from a dye-labeled particle against a dark background onto a quadrant photodiode. This setup has a relatively wide space around the sample that allows us to further accessorize the optical tweezers by a temperature control unit. The applicability of the setup was examined on the basis of the rheological measurements using a typical viscoelastic system, namely a worm-like micelle solution. The temperature and frequency dependences of the local viscoelastic functions of the worm-like micelle solution obtained by this setup were in good accordance with those obtained by a conventional oscillatory rheometer, confirming the capability of the optical tweezers as a tool for the local rheological measurements of soft materials. Since the optical tweezers measurements only require a tiny amount of sample (40 ?L), the rheological measurements using our setup should be useful for soft materials of which the available amount is limited.

  4. Listening to proteins and viruses with nanoaperture optical tweezers (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Gordon, Reuven

    2015-08-01

    This talk will present a nanoaperture tweezer approach to measure the acoustic spectra of viruses and single proteins. The approach, termed extraordinary optical Raman (EAR), shows promise for uncovering the structure and mechanical properties of nanoparticles as well as the effects of their interactions.

  5. High Spatiotemporal-Resolution Magnetic Tweezers: Calibration and Applications for DNA Dynamics.

    PubMed

    Dulin, David; Cui, Tao Ju; Cnossen, Jelmer; Docter, Margreet W; Lipfert, Jan; Dekker, Nynke H

    2015-11-17

    The observation of biological processes at the molecular scale in real time requires high spatial and temporal resolution. Magnetic tweezers are straightforward to implement, free of radiation or photodamage, and provide ample multiplexing capability, but their spatiotemporal resolution has lagged behind that of other single-molecule manipulation techniques, notably optical tweezers and AFM. Here, we present, to our knowledge, a new high-resolution magnetic tweezers apparatus. We systematically characterize the achievable spatiotemporal resolution for both incoherent and coherent light sources, different types and sizes of beads, and different types and lengths of tethered molecules. Using a bright coherent laser source for illumination and tracking at 6 kHz, we resolve 3 Å steps with a 1 s period for surface-melted beads and 5 Å steps with a 0.5 s period for double-stranded-dsDNA-tethered beads, in good agreement with a model of stochastic bead motion in the magnetic tweezers. We demonstrate how this instrument can be used to monitor the opening and closing of a DNA hairpin on millisecond timescales in real time, together with attendant changes in the hairpin dynamics upon the addition of deoxythymidine triphosphate. Our approach opens up the possibility of observing biological events at submillisecond timescales with subnanometer resolution using camera-based detection. PMID:26588570

  6. Noncontact microsurgery and micromanipulation of living cells with combined system femtosecond laser scalpel-optical tweezers

    NASA Astrophysics Data System (ADS)

    Il'ina, Inna V.; Sitnikov, Dmitry S.; Ovchinnikov, Andrey V.; Agranat, Mikhail B.; Khramova, Yulia V.; Semenova, Maria L.

    2012-06-01

    We report on the results of using self-developed combined laser system consisting of a femtosecond laser scalpel (Cr:Forsterite seed oscillator and a regenerative amplifier, 620 nm, 100 fs, 10 Hz) and optical tweezers (cw laser, 1064 nm) for performing noncontact laser-mediated polar body (PB) and trophectoderm (TE) biopsy of early mammalian embryos. To perform PB biopsy the femtosecond laser scalpel was initially used to drill an opening in the zona pellucida, and then the PB was extracted out of the zygote with the optical tweezers. Unlike PB biopsy, TE biopsy allows diagnosing maternally-derived as well as paternally-derived defects. Moreover, as multiple TE cells can be taken from the embryo, more reliable diagnosis can be done. TE biopsy was performed by applying laser pulses to dissect the desired amount of TE cells that had just left the zona pellucida during the hatching. Optical tweezers were then used to trap and move the dissected TE cells in a prescribed way. Laser power in optical tweezers and energy of femtosecond laser pulses were thoroughly optimized to prevent cell damage and obtain high viability rates. In conclusion, the proposed techniques of laser-based embryo biopsy enable accurate, contamination-free, simple and quick microprocessing of living cells.

  7. Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method

    NASA Astrophysics Data System (ADS)

    Cheng, Jianli; Vishnyakov, Aleksey; Neimark, Alexander V.

    2015-01-01

    Mechanisms of interactions between nanoparticles (NPs) and polymer brushes (PBs) are explored using dissipative particle dynamics simulations and an original "ghost tweezers" method that emulates lab experiments performed with optical or magnetic tweezers. The ghost tweezers method is employed to calculate the free energy of adhesion. Ghost tweezers represents a virtual harmonic potential, which tethers NP with a spring to a given anchor point. The average spring force represents the effective force of NP-PB interaction as a function of the NP coordinate. The free energy landscape of NP-PB interactions is calculated as the mechanical work needed to transfer NP from the solvent bulk to a particular distance from the substrate surface. With this technique, we explore the adhesion of bare and ligand-functionalized spherical NPs to polyisoprene natural rubber brush in acetone-benzene binary solvent. We examine two basic mechanisms of NP-PB interactions, NP adhesion at PB exterior and NP immersion into PB, which are governed by interplay between entropic repulsive forces and enthalpic attractive forces caused by polymer adsorption at the NP surface and ligand adsorption at the substrate. The relative free energies of the equilibrium adhesion states and the potential barriers separating these states are calculated at varying grafting density, NP size, and solvent composition.

  8. Red blood cell micromanipulation with elliptical laser beam profile optical tweezers in different osmolarity conditions

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Makropoulou, M.; Serafetinides, A. A.

    2011-07-01

    In this work optical tweezers with elliptical beam profiles have been developed in order to examine the effect of optical force on fresh red blood cells (RBC) in isotonic, hypertonic and hypotonic buffer solutions. Considering that the optical force depends essentially on the cell surface and the cytoplasmic refractive index, it is obvious that biochemical modifications associated with different states of the cell will influence its behaviour in the optical trap. Line optical tweezers were used to manipulate simultaneously more than one red blood cell. After we have been manipulated a RBC with an elliptical laser beam profile in an isotonic or hypertonic buffer, we noticed that it rotates by itself when gets trapped by optical tweezers and undergoes folding. Further shape deformations can be observed attributed to the competition between alignment and rotational torque which are transferred by laser light to the cell. In hypotonic buffer RBCs become spherical and do not rotate or fold since the resultant force due to rays emerging from diametrically opposite points of the cell leads to zero torque. Manipulation of fresh red blood cells in isotonic solution by line optical tweezers leads to folding and elongation of trapped RBCs. Membrane elasticity properties such as bending modulus can be estimated by measuring RBC's folding time in function with laser power.

  9. Research Advances: Nanoscale Molecular Tweezers; Cinnamon as Pesticide?; Recently Identified Dietary Sources of Antioxidants

    NASA Astrophysics Data System (ADS)

    King, Angela G.

    2004-12-01

    This Report from Other Journals surveys articles of interest to chemists that have been recently published in other science journals. Topics surveyed include reports that receptors have been designed to act as molecular tweezers; cinnamon has potential in the fight against mosquitoes; and high levels of antioxidants are found in some surprising foods. See Featured Molecules .

  10. Development of high frequency focused transducers for single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Sheng

    Contactless particle trapping and manipulation have found many potential applications in diverse fields, especially in biological and medical research. Among the various methods, optical tweezers is the most well-known and extensively investigated technique. However, there are some limitations for particle manipulation based on optical tweezers. Due to the conceptual similarity with the optical tweezers and recent advances in high frequency ultrasonic transducer, a single beam acoustic tweezer using high frequency (? 20 MHz) focused transducer has recently been considered, and its feasibility was theoretically and experimentally investigated. This dissertation mainly describes the development of high frequency focused ultrasonic transducers for single beam acoustic tweezers applications. Three different types of transducers were fabricated. First, a 60 MHz miniature focused transducer (<1 mm) was made using press-focusing technique. The single beam acoustic trapping experiment was performed to manipulate 15 microm polystyrene microspheres using this transducer. In vitro ultrasonic biomicroscopy imaging on the rabbit eye was also obtained with this device. Second approach is to build a 200 MHz self-focused ZnO transducer by sputtering ZnO film on a curved surface of the aluminum backing material. An individual 10 microm microsphere was effectively manipulated in two dimensions by this type of transducer. Another ultrahigh frequency focused transducer based on silicon lens design has also been developed, where a 330 MHz silicon lens transducer was fabricated and evaluated. Microparticle trapping experiment was carried out to demonstrate that silicon lens transducer can manipulate a single microsphere as small as 5 microm. The realization of single beam acoustic tweezers using high frequency focused transducers can offer wide range of applications in biomedical and chemical sciences including intercellular kinetics studies and cell stimulation. Additionally, we propose a simple and efficient approach to prepare xPMN-PT-(1-x)PZT (where x is 0.1, 0.3, 0.5, 0.7 and 0.9) composite films with controllable dielectric constant that offers better performance for high frequency ultrasonic transducer applications. A 200 MHz single element transducer utilizing 0.9PMN-PT-0.1PZT thin film was built. This type of xPMN-PT-(1-x)PZT film transducers may satisfy current needs of very high frequency biomedical applications, such as ultrasonic biomicroscopy or acoustic tweezers.

  11. Synthesis and Properties of Bis-Porphyrin Molecular Tweezers: Effects of Spacer Flexibility on Binding and Supramolecular Chirogenesis.

    PubMed

    Blom, Magnus; Norrehed, Sara; Andersson, Claes-Henrik; Huang, Hao; Light, Mark E; Bergquist, Jonas; Grennberg, Helena; Gogoll, Adolf

    2015-01-01

    Ditopic binding of various dinitrogen compounds to three bisporphyrin molecular tweezers with spacers of varying conformational rigidity, incorporating the planar enediyne (1), the helical stiff stilbene (2), or the semi-rigid glycoluril motif fused to the porphyrins (3), are compared. Binding constants Ka = 10?-10? M(-1) reveal subtle differences between these tweezers, that are discussed in terms of porphyrin dislocation modes. Exciton coupled circular dichroism (ECCD) of complexes with chiral dinitrogen guests provides experimental evidence for the conformational properties of the tweezers. The results are further supported and rationalized by conformational analysis. PMID:26703562

  12. Fullerene recognition with molecular tweezers made up of efficient buckybowls: a dispersion-corrected DFT study.

    PubMed

    Josa, Daniela; Rodrguez-Otero, Jess; Cabaleiro-Lago, Enrique M

    2015-05-28

    In 2007, Sygula and co-workers introduced a novel type of molecular tweezers with buckybowl pincers that have attracted the substantial interest of researchers due to their ideal architecture for recognizing fullerenes by concave-convex ????? interactions (A. Sygula et al., J. Am. Chem. Soc., 2007, 129, 3842). Although in recent years some modifications have been performed on these original molecular tweezers to improve their ability for catching fullerenes, very few improvements were achieved to date. For that reason, in the present work a series of molecular tweezers have been devised and their supramolecular complexes with C60 studied at the B97-D2/TZVP//SCC-DFTB-D and B97-D2/TZVP levels. Three different strategies have been tested: (1) changing the corannulene pincers to other buckybowls, (2) replacing the tetrabenzocyclooctatetraene tether by a buckybowl, and (3) adding methyl groups on the molecular tweezers. According to the results, all the three approaches are effective, in such a way that a combination of the three strategies results in buckycatchers with complexation energies (with C60) up to 2.6 times larger than that of the original buckycatcher, reaching almost -100 kcal mol(-1). The B97-D2/TZVP//SCC-DFTB-D approach can be a rapid screening tool for testing new molecular tweezers. However, since this approach does not reproduce correctly the deformation energy and this energy represents an important contribution to the total complexation energy of complexes, subsequent higher-level re-optimization is compulsory to achieve reliable results (the full B97-D2/TZVP level is used herein). This re-optimization could be superfluous when quite rigid buckycatchers are studied. PMID:25805299

  13. An Improved Optical Tweezers Assay for Measuring the Force Generation of Single Kinesin Molecules

    PubMed Central

    Nicholas, Matthew P.; Rao, Lu; Gennerich, Arne

    2014-01-01

    Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments. PMID:24633799

  14. 2D multiforce optical tweezers to investigate cell adhesion strengthening in living cells

    NASA Astrophysics Data System (ADS)

    Emiliani, Valentina; Sanvitto, Daniele; Durieux, Christiane

    2006-04-01

    We present the multi trap optical tweezers system that enables to generate two-dimensional dynamical configurations of focal spot where the trapping force of each element can be individually changed. We apply the system to investigate how substrate rigidity affects the strength of the integrin-extracellular matrix adhesion in living cells. Adhesion sites of different rigidity are mimicked by simultaneously attaching on cell cortex beads held by optical traps of different stiffness. We monitor the effect induced by the local rigidity on cell adhesion by looking at vinculin recruitment in GFP-Vin transfected HeLa cell. To this end the optical tweezers system is inserted in an epifluorescence inverted microscope.

  15. Identification of individual biofilm-forming bacterial cells using Raman tweezers

    NASA Astrophysics Data System (ADS)

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral "Raman fingerprints" obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

  16. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers.

    PubMed

    Gao, Hongbo; Metz, Jeremy; Teanby, Nick A; Ward, Andy D; Botchway, Stanley W; Coles, Benjamin; Pollard, Mark R; Sparkes, Imogen

    2016-01-01

    Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes. PMID:26518344

  17. DNA as a Metrology Standard for Length and Force Measurements with Optical Tweezers

    PubMed Central

    Rickgauer, John Peter; Fuller, Derek N.; Smith, Douglas E.

    2006-01-01

    Optical tweezers have broad applications in studies of structures and processes in molecular and cellular biophysics. Use of optical tweezers for quantitative molecular-scale measurement requires careful calibration in physical units. Here we show that DNA molecules may be used as metrology standards for force and length measurements. Analysis of DNA molecules of two specific lengths allows simultaneous determination of all essential measurement parameters. We validate this biological-calibration method experimentally and with simulated data, and show that precisions in determining length scale factor (∼0.2%), length offset (∼0.03%), force scale factor (∼2%), and compliance of the traps (∼3%) are limited only by current measurement variation, much of which arises from polydispersity of the microspheres (∼2%). We find this procedure to be simpler and more convenient than previous methods, and suggest that it provides an easily replicated standard that can insure uniformity of measurements made in different laboratories. PMID:16963512

  18. Probing the structural dynamics of proteins and nucleic acids with optical tweezers.

    PubMed

    Ritchie, Dustin B; Woodside, Michael T

    2015-10-01

    Conformational changes are an essential feature of most molecular processes in biology. Optical tweezers have emerged as a powerful tool for probing conformational dynamics at the single-molecule level because of their high resolution and sensitivity, opening new windows on phenomena ranging from folding and ligand binding to enzyme function, molecular machines, and protein aggregation. By measuring conformational changes induced in a molecule by forces applied by optical tweezers, new insight has been gained into the relationship between dynamics and function. We discuss recent advances from studies of how structure forms in proteins and RNA, including non-native structures, fluctuations in disordered proteins, and interactions with chaperones assisting native folding. We also review the development of assays probing the dynamics of complex protein-nucleic acid and protein-protein assemblies that reveal the dynamic interactions between biomolecular machines and their substrates. PMID:26189090

  19. Low cost optical tweezers systems using double coil driving stepping motor to controlling sample stage

    NASA Astrophysics Data System (ADS)

    Laowattanatham, N.; Cheamanunkul, N.; Plaipichit, S.; Buranasiri, P.; Nuansri, R.

    2013-06-01

    In this research, the low cost optical tweezers systems using X-Y stage has been developed by using 5-phase stepping motor. By using sequential double coil driving, we can obtain the driving torque larger than using the single coil driving. The moving scale is fine resolution at 0.2 micrometer. The overall systems based on microcontroller PIC18F458 and joystick controller with LabView graphical user interface (GUI). The mechanical damping has been included in the system for decreasing the vibrational noise. By using this method, our optical tweezers system is cheaper than the other commercial system that has been used the piezoelectric driving, and still has the same efficiency.

  20. Enantioselective recognitions of chiral molecular tweezers containing imidazoliums for amino acids.

    PubMed

    Su, Xiaoyu; Luo, Kui; Xiang, Qingxiang; Lan, Jingbo; Xie, Rugang

    2009-05-01

    Two kinds of novel chiral molecular tweezers containing imidazoliums were synthesized from L-alanine, L-phenylalanine, and L-glutamic acid. They are constructed by the chiral imidazolium pincers and two different spacers which are 1,3-bis (bromomethyl)benzene and 2,6-bis(bromomethyl)pyridine, respectively. The enantioselective recognition of L- and D-amino acid derivatives by these molecular tweezers was investigated by UV spectroscopic titration experiments and good enantioselectivities were obtained, which are highly sensitive to whether the spacer has the binding site and the pincers has the other aromatic rings besides imidazolium ring. The host molecular 3b.2PF6- showed remarkable enantioselectivity for N-Boc protected histidine methyl ester, affording K(L)/K(D) of 5.10. PMID:18698646

  1. Identification of individual biofilm-forming bacterial cells using Raman tweezers.

    PubMed

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment. PMID:25734616

  2. Luminescent nanoparticle trapping with far-field optical fiber-tip tweezers.

    PubMed

    Decombe, Jean-Baptiste; Valdivia-Valero, Francisco J; Dantelle, Graldine; Lemnager, Godefroy; Gacoin, Thierry; Colas des Francs, Grard; Huant, Serge; Fick, Jochen

    2016-02-25

    We report stable and reproducible trapping of luminescent dielectric YAG:Ce(3+) nanoparticles with sizes down to 60 nm using far-field dual fiber tip optical tweezers. The particles are synthesized by a specific glycothermal route followed by an original protected annealing step, resulting in significantly enhanced photostability. The tweezers properties are analyzed by studying the trapped particles residual Brownian motion using video or reflected signal records. The trapping potential is harmonic in the transverse direction to the fiber axis, but reveals interference fringes in the axial direction. Large trapping stiffness of 35 and 2 pN ?m(-1) W(-1) is measured for a fiber tip-to-tip distance of 3 ?m and 300 nm and 60 nm particles, respectively. The forces acting on the nanoparticles are discussed within the dipolar approximation (gradient and scattering force contributions) or exact calculations using the Maxwell Stress Tensor formalism. Prospects for trapping even smaller particles are discussed. PMID:26883602

  3. Luminescent nanoparticle trapping with far-field optical fiber-tip tweezers

    NASA Astrophysics Data System (ADS)

    Decombe, Jean-Baptiste; Valdivia-Valero, Francisco J.; Dantelle, Géraldine; Leménager, Godefroy; Gacoin, Thierry; Colas Des Francs, Gérard; Huant, Serge; Fick, Jochen

    2016-02-01

    We report stable and reproducible trapping of luminescent dielectric YAG:Ce3+ nanoparticles with sizes down to 60 nm using far-field dual fiber tip optical tweezers. The particles are synthesized by a specific glycothermal route followed by an original protected annealing step, resulting in significantly enhanced photostability. The tweezers properties are analyzed by studying the trapped particles residual Brownian motion using video or reflected signal records. The trapping potential is harmonic in the transverse direction to the fiber axis, but reveals interference fringes in the axial direction. Large trapping stiffness of 35 and 2 pN μm-1 W-1 is measured for a fiber tip-to-tip distance of 3 μm and 300 nm and 60 nm particles, respectively. The forces acting on the nanoparticles are discussed within the dipolar approximation (gradient and scattering force contributions) or exact calculations using the Maxwell Stress Tensor formalism. Prospects for trapping even smaller particles are discussed.

  4. Neural Network for Image-to-Image Control of Optical Tweezers

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Anderson, Robert C.; Weiland, Kenneth E.; Wrbanek, Susan Y.

    2004-01-01

    A method is discussed for using neural networks to control optical tweezers. Neural-net outputs are combined with scaling and tiling to generate 480 by 480-pixel control patterns for a spatial light modulator (SLM). The SLM can be combined in various ways with a microscope to create movable tweezers traps with controllable profiles. The neural nets are intended to respond to scattered light from carbon and silicon carbide nanotube sensors. The nanotube sensors are to be held by the traps for manipulation and calibration. Scaling and tiling allow the 100 by 100-pixel maximum resolution of the neural-net software to be applied in stages to exploit the full 480 by 480-pixel resolution of the SLM. One of these stages is intended to create sensitive null detectors for detecting variations in the scattered light from the nanotube sensors.

  5. Design of a high-quality optical conjugate structure in optical tweezers.

    PubMed

    Hu, Chunguang; An, Ran; Zhang, Chengwei; Lei, Hai; Hu, Xiaodong; Li, Hongbin; Hu, Xiaotang

    2015-02-20

    We propose an approach to realize a high-quality optical conjugate of a piezo-driven mirror (PM) in optical tweezers. Misalignments between the optical beam and the steering center of the PM are analyzed mathematically. The decentrations in different directions cause different changes, either a position change of the conjugate plane or a spot variation of the beam during PM steering. On the other hand, these misalignment-introduced problems provide the information to check the assembling errors. Thus a wanted conjugate plane of the PM can be effectively and precisely achieved according to the detection signals. This approach is also available to deal with multifactor coupling error. At the end, the procedure for error analysis is given by testing homebuilt optical tweezers. PMID:25968206

  6. Optical tweezers and surface plasmon resonance combination system based on the high numerical aperture lens

    NASA Astrophysics Data System (ADS)

    Shan, Xuchen; Zhang, Bei; Lan, Guoqiang; Wang, Yiqiao; Liu, Shugang

    2015-11-01

    Biology and medicine sample measurement takes an important role in the microscopic optical technology. Optical tweezer has the advantage of accurate capture and non-pollution of the sample. The SPR(surface plasmon resonance) sensor has so many advantages include high sensitivity, fast measurement, less consumption of sample and label-free detection of biological sample that the SPR sensing technique has been used for surface topography, analysis of biochemical and immune, drug screening and environmental monitoring. If they combine, they will play an important role in the biological, chemical and other subjects. The system we propose use the multi-axis cage system, by using the methods of reflection and transmiss ion to improve the space utilization. The SPR system and optical tweezer were builtup and combined in one system. The cage of multi-axis system gives full play to its accuracy, simplicity and flexibility. The size of the system is 20 * 15 * 40 cm3 and thus the sample can be replaced to switch between the optical tweezers system and the SPR system in the small space. It means that we get the refractive index of the sample and control the particle in the same system. In order to control the revolving stage, get the picture and achieve the data stored automatically, we write a LabVIEW procedure. Then according to the data from the back focal plane calculate the refractive index of the sample. By changing the slide we can trap the particle as optical tweezer, which makes us measurement and trap the sample at the same time.

  7. A feasibility study of in vivo applications of single beam acoustic tweezers.

    PubMed

    Li, Ying; Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K Kirk

    2014-10-27

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system. PMID:25422525

  8. A feasibility study of in vivo applications of single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Li, Ying; Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk

    2014-10-01

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system.

  9. A feasibility study of in vivo applications of single beam acoustic tweezers

    SciTech Connect

    Li, Ying Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk

    2014-10-27

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system.

  10. Time-shared optical tweezers with a microlens array for dynamic microbead arrays.

    PubMed

    Tanaka, Yoshio; Wakida, Shin-Ichi

    2015-10-01

    Dynamic arrays of microbeads and cells offer great flexibility and potential as platforms for sensing and manipulation applications in various scientific fields, especially biology and medicine. Here, we present a simple method for assembling and manipulating dense dynamic arrays based on time-shared scanning optical tweezers with a microlens array. Three typical examples, including the dynamic and simultaneous bonding of microbeads in real-time, are demonstrated. The optical design and the hardware setup for our approach are also described. PMID:26504619

  11. Time-shared optical tweezers with a microlens array for dynamic microbead arrays

    PubMed Central

    Tanaka, Yoshio; Wakida, Shin-ichi

    2015-01-01

    Dynamic arrays of microbeads and cells offer great flexibility and potential as platforms for sensing and manipulation applications in various scientific fields, especially biology and medicine. Here, we present a simple method for assembling and manipulating dense dynamic arrays based on time-shared scanning optical tweezers with a microlens array. Three typical examples, including the dynamic and simultaneous bonding of microbeads in real-time, are demonstrated. The optical design and the hardware setup for our approach are also described. PMID:26504619

  12. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    NASA Astrophysics Data System (ADS)

    Chen, La; Offenhusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 0.1 mm2, a force of up to 400 pN can be applied on a 2.8 ?m superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  13. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    SciTech Connect

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-15

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  14. An integral imaging method for depth extraction with lens array in an optical tweezer system

    NASA Astrophysics Data System (ADS)

    Wang, Shulu; Liu, Wei-Wei; Wang, Anting; Li, Yinmei; Ming, Hai

    2014-10-01

    In this paper, a new integral imaging method is proposed for depth extraction in an optical tweezer system. A mutual coherence algorithm of stereo matching are theoretically analyzed and demonstrated feasible by virtual simulation. In our design, optical tweezer technique is combined with integral imaging in a single microscopy system by inserting a lens array into the optical train. On one hand, the optical tweezer subsystem is built based on the modulated light field from a solid laser, and the strong focused beam forms a light trap to capture tiny specimens. On the other hand, through parameters optimization, the microscopic integral imaging subsystem is composed of a microscope objective, a lens array (150x150 array with 0.192mm unit size and 9mm focal length) and a single lens reflex (SLR). Pre-magnified by the microscope objective, the specimens formed multiple images through the lens array. A single photograph of a series of multiple sub-images has recorded perspective views of the specimens. The differences between adjacent sub-images have been analyzed for depth extraction with the mutual coherence algorithm. The experimental results show that the axial resolution can reach to 1?m -1 and lateral resolution can reach to 2 ?m -1.

  15. Combining optical tweezers and patch clamp for studies of cell membrane electromechanics

    NASA Astrophysics Data System (ADS)

    Qian, Feng; Ermilov, Sergey; Murdock, David; Brownell, William E.; Anvari, Bahman

    2004-09-01

    We have designed and implemented a novel experimental setup which combines optical tweezers with patch-clamp apparatus to investigate the electromechanical properties of cellular plasma membranes. In this system, optical tweezers provide measurement of forces at piconewton scale, and the patch-clamp technique allows control of the cell transmembrane potential. A micron-size bead trapped by the optical tweezers is brought in contact with the membrane of a voltage-clamped cell, and subsequently moved away to form a plasma membrane tether. Bead displacement from the trapping center is monitored by a quadrant photodetector for dynamic measurements of tether force. Fluorescent beads and the corresponding fluorescence imaging optics are used to eliminate the shadow of the cell projected on the quadrant photodetector. Salient information associated with the mechanical properties of the membrane tether can thus be obtained. A unique feature of this setup is that the patch-clamp headstage and the manipulator for the recording pipette are mounted on a piezoelectric stage, preventing relative movements between the cell and the patch pipette during the process of tether pulling. Tethers can be pulled from the cell membrane at different holding potentials, and the tether force response can be measured while changing transmembrane potential. Experimental results from mammalian cochlear outer hair cells and human embryonic kidney cells are presented.

  16. Optical nanofiber integrated into an optical tweezers for particle manipulation and in-situ fiber probing

    NASA Astrophysics Data System (ADS)

    Gusachenko, Ivan; Frawley, Mary C.; Truong, Viet. G.; Nic Chormaic, Sle

    2014-09-01

    Precise control of particle positioning is desirable in many optical propulsion and sorting applications. Here, we develop an integrated platform for particle manipulation consisting of a combined optical nanofiber and optical tweezers system. Individual silica microspheres were introduced to the nanofiber at arbitrary points using the optical tweezers, thereby producing pronounced dips in the fiber transmission. We show that such consistent and reversible transmission modulations depend on both particle and fiber diameter, and may be used as a reference point for in-situ nanofiber or particle size measurement. Therefore we combine SEM size measurements with nanofiber transmission data to provide calibration for particle-based fiber assessment. We also demonstrate how the optical tweezers can be used to create a `particle jet' to feed a supply of microspheres to the nanofiber surface, forming a particle conveyor belt. This integrated optical platform provides a method for selective evanescent field manipulation of micron-sized particles and facilitates studies of optical binding and light-particle interaction dynamics.

  17. Amyloid ?-Protein Assembly: The Effect of Molecular Tweezers CLR01 and CLR03

    PubMed Central

    2015-01-01

    The early oligomerization of amyloid ?-protein (A?) has been shown to be an important event in the pathology of Alzheimers disease (AD). Designing small molecule inhibitors targeting A? oligomerization is one attractive and promising strategy for AD treatment. Here we used ion mobility spectrometry coupled to mass spectrometry (IMS-MS) to study the different effects of the molecular tweezers CLR01 and CLR03 on A? self-assembly. CLR01 was found to bind to A? directly and disrupt its early oligomerization. Moreover, CLR01 remodeled the early oligomerization of A?42 by compacting the structures of dimers and tetramers and as a consequence eliminated higher-order oligomers. Unexpectedly, the negative-control derivative, CLR03, which lacks the hydrophobic arms of the tweezer structure, was found to facilitate early A? oligomerization. Our study provides an example of IMS as a powerful tool to study and better understand the interaction between small molecule modulators and A? oligomerization, which is not attainable by other methods, and provides important insights into therapeutic development of molecular tweezers for AD treatment. PMID:25751170

  18. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications.

    PubMed

    Zacchia, Nicholas A; Valentine, Megan T

    2015-05-01

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy. PMID:26026529

  19. Single-cell optoporation and transfection using femtosecond laser and optical tweezers

    PubMed Central

    Waleed, Muhammad; Hwang, Sun-Uk; Kim, Jung-Dae; Shabbir, Irfan; Shin, Sang-Mo; Lee, Yong-Gu

    2013-01-01

    In this paper, we demonstrate a new single-cell optoporation and transfection technique using a femtosecond Gaussian laser beam and optical tweezers. Tightly focused near-infrared (NIR) femtosecond laser pulse was employed to transiently perforate the cellular membrane at a single point in MCF-7 cancer cells. A distinct technique was developed by trapping the microparticle using optical tweezers to focus the femtosecond laser precisely on the cell membrane to puncture it. Subsequently, an external gene was introduced in the cell by trapping and inserting the same plasmid-coated microparticle into the optoporated cell using optical tweezers. Various experimental parameters such as femtosecond laser exposure power, exposure time, puncture hole size, exact focusing of the femtosecond laser on the cell membrane, and cell healing time were closely analyzed to create the optimal conditions for cell viability. Following the insertion of plasmid-coated microparticles in the cell, the targeted cells exhibited green fluorescent protein (GFP) under the fluorescent microscope, hence confirming successful transfection into the cell. This new optoporation and transfection technique maximizes the level of selectivity and control over the targeted cell, and this may be a breakthrough method through which to induce controllable genetic changes in the cell. PMID:24049675

  20. Acoustic tweezers for studying intracellular calcium signaling in SKBR-3 human breast cancer cells.

    PubMed

    Hwang, Jae Youn; Yoon, Chi Woo; Lim, Hae Gyun; Park, Jin Man; Yoon, Sangpil; Lee, Jungwoo; Shung, K Kirk

    2015-12-01

    Extracellular matrix proteins such as fibronectin (FNT) play crucial roles in cell proliferation, adhesion, and migration. For better understanding of these associated cellular activities, various microscopic manipulation tools have been used to study their intracellular signaling pathways. Recently, it has appeared that acoustic tweezers may possess similar capabilities in the study. Therefore, we here demonstrate that our newly developed acoustic tweezers with a high-frequency lithium niobate ultrasonic transducer have potentials to study intracellular calcium signaling by FNT-binding to human breast cancer cells (SKBR-3). It is found that intracellular calcium elevations in SKBR-3 cells, initially occurring on the microbead-contacted spot and then eventually spreading over the entire cell, are elicited by attaching an acoustically trapped FNT-coated microbead. Interestingly, they are suppressed by either extracellular calcium elimination or phospholipase C (PLC) inhibition. Hence, this suggests that our acoustic tweezers may serve as an alternative tool in the study of intracellular signaling by FNT-binding activities. PMID:26150401

  1. Quantitation of Malaria Parasite-Erythrocyte Cell-Cell Interactions Using Optical Tweezers

    PubMed Central

    Crick, Alex J.; Theron, Michel; Tiffert, Teresa; Lew, Virgilio L.; Cicuta, Pietro; Rayner, Julian C.

    2014-01-01

    Erythrocyte invasion by Plasmodium falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria. Invasion has been studied intensively, but our cellular understanding has been limited by the fact that it occurs very rapidly: invasion is generally complete within 1 min, and shortly thereafter the merozoites, at least in in vitro culture, lose their invasive capacity. The rapid nature of the process, and hence the narrow time window in which measurements can be taken, have limited the tools available to quantitate invasion. Here we employ optical tweezers to study individual invasion events for what we believe is the first time, showing that newly released P. falciparum merozoites, delivered via optical tweezers to a target erythrocyte, retain their ability to invade. Even spent merozoites, which had lost the ability to invade, retain the ability to adhere to erythrocytes, and furthermore can still induce transient local membrane deformations in the erythrocyte membrane. We use this technology to measure the strength of the adhesive force between merozoites and erythrocytes, and to probe the cellular mode of action of known invasion inhibitory treatments. These data add to our understanding of the erythrocyte-merozoite interactions that occur during invasion, and demonstrate the power of optical tweezers technologies in unraveling the blood-stage biology of malaria. PMID:25140419

  2. New biodiagnostics based on optical tweezers: typing red blood cells, and identification of drug resistant bacteria

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Wen; Lin, Chuen-Fu; Wang, Shyang-Guang; Lee, Yi-Chieh; Chiang, Chung-Han; Huang, Min-Hui; Lee, Yi-Hsiung; Vitrant, Guy; Pan, Ming-Jeng; Lee, Horng-Mo; Liu, Yi-Jui; Baldeck, Patrice L.; Lin, Chih-Lang

    2013-09-01

    Measurements of optical tweezers forces on biological micro-objects can be used to develop innovative biodiagnostics methods. In the first part of this report, we present a new sensitive method to determine A, B, D types of red blood cells. Target antibodies are coated on glass surfaces. Optical forces needed to pull away RBC from the glass surface increase when RBC antigens interact with their corresponding antibodies. In this work, measurements of stripping optical forces are used to distinguish the major RBC types: group O Rh(+), group A Rh(+) and group B Rh(+). The sensitivity of the method is found to be at least 16-folds higher than the conventional agglutination method. In the second part of this report, we present an original way to measure in real time the wall thickness of bacteria that is one of the most important diagnostic parameters of bacteria drug resistance in hospital diagnostics. The optical tweezers force on a shell bacterium is proportional to its wall thickness. Experimentally, we determine the optical tweezers force applied on each bacteria family by measuring their escape velocity. Then, the wall thickness of shell bacteria can be obtained after calibrating with known bacteria parameters. The method has been successfully applied to indentify, from blind tests, Methicillinresistant Staphylococcus aureus (MRSA), including VSSA (NCTC 10442), VISA (Mu 50), and heto-VISA (Mu 3)

  3. Measurement of macrophage adhesion using optical tweezers with backward-scattered detection

    NASA Astrophysics Data System (ADS)

    Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

    2010-08-01

    Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 ?m diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

  4. The Use of Raman Tweezers and Chemometric Analysis to Discriminate the Urological Cell Lines, PC-3, LNCaP, BPH and MGH-U1

    NASA Astrophysics Data System (ADS)

    Harvey, T. J.; Hughes, C.; Ward, A. D.; Gazi, E.; Faria, E. Correia; Clarke, N. W.; Brown, M.; Snook, R.; Gardner, P.

    2008-11-01

    Here we report on investigations into using Raman optical tweezers to analyse both live and chemically fixed prostate and bladder cells. Spectra were subjected to chemometric analysis to discriminate and classify the cell types based on their spectra. Subsequent results revealed the potential of Raman tweezers as a potential clinical diagnostic tool.

  5. Novel tunable dynamic tweezers using dark-bright soliton collision control in an optical add/drop filter.

    PubMed

    Teeka, Chat; Jalil, Muhammad Arif; Yupapin, Preecha P; Ali, Jalil

    2010-12-01

    We propose a novel system of the dynamic optical tweezers generated by a dark soliton in the fiber optic loop. A dark soliton known as an optical tweezer is amplified and tuned within the microring resonator system. The required tunable tweezers with different widths and powers can be controlled. The analysis of dark-bright soliton conversion using a dark soliton pulse propagating within a microring resonator system is analyzed. The dynamic behaviors of soliton conversion in add/drop filter is also analyzed. The control dark soliton is input into the system via the add port of the add/drop filter. The dynamic behavior of the dark-bright soliton conversion is observed. The required stable signal is obtained via a drop and throughput ports of the add/drop filter with some suitable parameters. In application, the trapped light/atom and transportation can be realized by using the proposed system. PMID:21266312

  6. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    SciTech Connect

    Chen, La; Offenhusser, Andreas; Krause, Hans-Joachim

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 ?m superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particles position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  7. Preliminary study for the development of a tweezers-type coincidence detector for tumor detection

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiichi; Higashi, Tatsuya; Matsumoto, Keiichi; Senda, Michio

    2005-08-01

    We have conducted a preliminary study for development of a tweezer-type coincidence detector for tumor detection in procedures such as FDG-guided surgery. The detector consists of a pair of LSO scintillators, optical fibers, a pair of photo-multiplier tubes (PMTs), and a coincidence circuit. Because the LSO scintillators are located on the tips of tweezers, a target organ such as a lymph node or the colon can be positioned between them. The size of a single LSO was 3.7 mm3.7 mm10 mm, and the scintillation photons are transferred to the PMTs via 2-mm-diameter, 1-m long optical fibers. The results show that the light loss due to the fiber was significant but there was sufficient light to observe the photo-peak of the 511-keV gamma photons. Sensitivity response function perpendicular to the detector has a full-width at half-maximum (FWHM) of 2.5 mm, while that parallel to the detector has a FWHM of 5.5 mm. Background counts due to the natural radioisotope in 176Lu can be observed when the distance between these two scintillators is small. Results also show that the absolute sensitivity was 0.057% at the center of the detector when the two LSOs were 10 mm apart and that the optical fiber was insensitive to bending up to a radius of 10 cm. From these results, we conclude that the proposed tweezers-type coincidence detector could be some interest for tumor detection using FDG, such as that in radio-guided surgery.

  8. Optical macro-tweezers: trapping of highly motile micro-organisms

    NASA Astrophysics Data System (ADS)

    Thalhammer, G.; Steiger, R.; Bernet, S.; Ritsch-Marte, M.

    2011-04-01

    Optical micromanipulation stands for contact-free handling of microscopic particles by light. Optical forces can manipulate non-absorbing objects in a large range of sizes, e.g., from biological cells down to cold atoms. Recently much progress has been made going from the micro- down to the nanoscale. Less attention has been paid to going the other way, trapping increasingly large particles. Optical tweezers typically employ a single laser beam tightly focused by a microscope objective of high numerical aperture to stably trap a particle in three dimensions (3D). As the particle size increases, stable 3D trapping in a single-beam trap requires scaling up the optical power, which eventually induces adverse biological effects. Moreover, the restricted field of view of standard optical tweezers, dictated by the use of high NA objectives, is particularly unfavorable for catching actively moving specimens. Both problems can be overcome by traps with counter-propagating beams. Our 'macro-tweezers' are especially designed to trap highly motile organisms, as they enable three-dimensional all-optical trapping and guiding in a volume of 2 × 1 × 2 mm3. Here we report for the first time the optical trapping of large actively swimming organisms, such as for instance Euglena protists and dinoflagellates of up to 70 µm length. Adverse bio-effects are kept low since trapping occurs outside high intensity regions, e.g., focal spots. We expect our approach to open various possibilities in the contact-free handling of 50-100 µm sized objects that could hitherto not be envisaged, for instance all-optical holding of individual micro-organisms for taxonomic identification, selective collecting or tagging.

  9. Development of a novel Raman tweezers setup for single-cell studies

    NASA Astrophysics Data System (ADS)

    Ramser, Kerstin K.; Logg, Katarina I.; Goksor, Mattias; Enger, Jonas; Kall, Mikael; Hanstorp, Dag

    2003-06-01

    It has recently been shown that the combination of Raman spectroscopy and optical tweezers constitute a powerful tool for biological studies. Raman spectra of single cells immobilized in a sterile surrounding can then be recorded without the risk of surface-induced morphological cell changes. Further, the complete cellular environment can be changed while measuring dynamics in real time. We here introduce a novel Raman tweezers set-up ideal for resonance Raman studies of single cells. The system differs from earlier set-ups in that two separate laser beams, used for trapping and Raman excitation, are combined in a double-microscope configuration. This has the advantage that the wavelength and power of the trapping and probe beam can be adjusted individually, for example in order to optimize the functionality of the set-up or to record resonance Raman profiles from the same trapped cell. Further, the tweezers can be removed from the system without affecting the spectrometer configuration. Trapping is achieved by tightly focusing IR diode laser radiation (830 nm) through an inverted oil immersion objective with high numerical aperture (NA = 1.25), while Raman scattering is excited by the lines of an ArKr ion-laser. The backscattered Raman signal is collected by a single-grating spectrometer equipped with a microscope and a 60x water-immersion objective (NA = 0.9). The functionality of the system is demonstrated by measurements of trapped single functional erythrocytes using differen excitation lines (488, 514.5 568.2 nm) in resonance with the heme moiety and by studying the spectral evolution during illumination.

  10. Laser-induced fusion of human embryonic stem cells with optical tweezers

    NASA Astrophysics Data System (ADS)

    Chen, Shuxun; Cheng, Jinping; Kong, Chi-Wing; Wang, Xiaolin; Han Cheng, Shuk; Li, Ronald A.; Sun, Dong

    2013-07-01

    We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

  11. Laser microbeams and optical tweezers: how they work and why they work

    NASA Astrophysics Data System (ADS)

    Greulich, Karl-Otto; Monajembashi, Shamci

    1996-01-01

    Laser microbeams and optical tweezers work by focusing lasers into a microscope. The energy density of a laser with a beam cross section of 1 cm2 can be condensed by almost nine orders of magnitude and focused into a volume of less than 1 femtoliter. When a comparably soft nitrogen laser pulse with 1 (mu) Joule total energy is focused to the diffraction limit, intensities above 1 Terawatt per cm2 and local temperatures above 100,000 Kelvin can be obtained. Probably a physical microplasma is generated where the laser pulse hits directly. This is the case even for comparably transparent biological objects, provided the plasma threshold can be reached. Since the heat is generated in a very small volume only, it can dissipate into the environment within a few tens of nanoseconds. This is faster than biological macromolecules can denature. Therefore, the laser microbeam interacts very locally with biological matter. In contrast to laser microbeams, optical tweezers use continuous infrared lasers of only moderate power at wavelengths with only small absorption by biological material. In such cases, the generation of heat is less prevalent and light pressure and gradient forces can be exploited to move microscopic particles. In the very inhomogeneous electric field of a highly focused laser, dielectric objects such as macromolecules, biological subcellular structures, cells or nonliving microspheres are, under suitable conditions, pulled towards the focus and are fixed there similarly as they would be fixed by micromechanical tweezers. This is true for particles with dimensions much smaller than the wavelength of the light used for trapping Rayleigh particles) as well as for particles much larger (Mie particles). Theoretical treatment of the Rayleigh particles assumes that they are linear dipoles. In contrast, many biological objects can be treated as Mie particles, where the basis for force generation is the interaction of the electromagnetic field of light with induced currents. Since Mie particles are large enough, ray optics can be used to explain the interplay of the different forces involved in optical trapping. Both, laser microbeams and optical tweezers (or synonymously 'single beam gradient laser traps') work most economically when the aperture of the microscope objective is just fully illuminated. Trapping effects are largest when the effective refractive index is between 1.1 and 1.6 -- a condition which is often satisfied with biological material.

  12. Nano-bio-optomechanics: nanoaperture tweezers probe single nanoparticles, proteins, and their interactions

    NASA Astrophysics Data System (ADS)

    Gordon, Reuven

    2015-09-01

    Nanoparticles in the single digit nanometer range can be easily isolated and studied with low optical powers using nanoaperture tweezers. We have studied individual proteins and their interactions with small molecules, DNA and antibodies. Recently, using the fluctuations of the trapped object, we have pioneered a new way to "listen" to the vibrations of nanoparticles in the 100 GHz - 1 THz range; the approach is called extraordinary acoustic Raman (EAR). EAR gives unprecedented low frequency spectra of individual proteins in solution, allowing for identification and analysis, as well as probing their role in biological functions. We have also used EAR to study the elastic properties, shape and size of various individual nanoparticles.

  13. Template stripped double nanohole in a gold film for nano-optical tweezers.

    PubMed

    Zehtabi-Oskuie, Ana; Zinck, Aurora A; Gelfand, Ryan M; Gordon, Reuven

    2014-12-12

    Double nanohole (DNH) laser tweezers can optically trap and manipulate objects such as proteins, nanospheres, and other nanoparticles; however, precise fabrication of those DNHs has been expensive with low throughput. In this work, template stripping was used to pattern DNHs with gaps as small as 7 nm, in optically thick Au films. These DNHs were used to trap streptavidin as proof of operation. The structures were processed multiple times from the same template to demonstrate reusability. Template stripping is a promising method for high-throughput, reproducible, and cost efficient fabrication of DNH apertures for optical trapping. PMID:25407447

  14. Template stripped double nanohole in a gold film for nano-optical tweezers

    NASA Astrophysics Data System (ADS)

    Zehtabi-Oskuie, Ana; Zinck, Aurora A.; Gelfand, Ryan M.; Gordon, Reuven

    2014-12-01

    Double nanohole (DNH) laser tweezers can optically trap and manipulate objects such as proteins, nanospheres, and other nanoparticles; however, precise fabrication of those DNHs has been expensive with low throughput. In this work, template stripping was used to pattern DNHs with gaps as small as 7 nm, in optically thick Au films. These DNHs were used to trap streptavidin as proof of operation. The structures were processed multiple times from the same template to demonstrate reusability. Template stripping is a promising method for high-throughput, reproducible, and cost efficient fabrication of DNH apertures for optical trapping.

  15. Simultaneous Single-Molecule Force and Fluorescence Sampling of DNA Nanostructure Conformations Using Magnetic Tweezers.

    PubMed

    Kemmerich, Felix E; Swoboda, Marko; Kauert, Dominik J; Grieb, M Svea; Hahn, Steffen; Schwarz, Friedrich W; Seidel, Ralf; Schlierf, Michael

    2016-01-13

    We present a hybrid single-molecule technique combining magnetic tweezers and Frster resonance energy transfer (FRET) measurements. Through applying external forces to a paramagnetic sphere, we induce conformational changes in DNA nanostructures, which are detected in two output channels simultaneously. First, by tracking a magnetic bead with high spatial and temporal resolution, we observe overall DNA length changes along the force axis. Second, the measured FRET efficiency between two fluorescent probes monitors local conformational changes. The synchronized orthogonal readout in different observation channels will facilitate deciphering the complex mechanisms of biomolecular machines. PMID:26632021

  16. Measuring stall forces in vivo with optical tweezers through light momentum changes

    NASA Astrophysics Data System (ADS)

    Mas, J.; Farr, A.; Lpez-Quesada, C.; Fernndez, X.; Martn-Badosa, E.; Montes-Usategui, M.

    2011-10-01

    The stall forces of processive molecular motors have been widely studied previously in vitro. Even so, in vivo experiments are required for determining the actual performance of each molecular motor in its natural environment. We report the direct measurement of light momentum changes in single beam optical tweezers as a suitable technique for measuring forces inside living cells, where few alternatives exist. The simplicity of this method, which does not require force calibration for each trapped object, makes it convenient for measuring the forces involved in fast dynamic biological processes such us intracellular traffic. Here we present some measurements of the stall force of processive molecular motors inside living Allium cepa cells.

  17. Laser-induced fusion of human embryonic stem cells with optical tweezers

    SciTech Connect

    Chen Shuxun; Wang Xiaolin; Sun Dong; Cheng Jinping; Han Cheng, Shuk; Kong, Chi-Wing; Li, Ronald A.

    2013-07-15

    We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

  18. Optoelectronic Tweezers as a Tool for Parallel Single-Cell Manipulation and Stimulation

    PubMed Central

    Valley, Justin K.; Ohta, Aaron T.; Hsu, Hsan-Yin; Neale, Steven L.; Jamshidi, Arash; Wu, Ming C.

    2010-01-01

    Optoelectronic tweezers (OET) is a promising approach for the parallel manipulation of single cells for a variety of biological applications. By combining the manipulation capabilities of OET with other relevant biological techniques (such as cell lysis and electroporation), one can realize a true parallel, single-cell diagnostic and stimulation tool. Here, we demonstrate the utility of the OET device by integrating it onto single-chip systems capable of performing in-situ, electrode-based electroporation/lysis, individual cell, light-induced lysis, and light-induced electroporation. PMID:20543904

  19. Temporal response of biological cells to high-frequency optical jumping and vibrating tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Lingyao; Sheng, Yunlong

    2014-09-01

    We analyzed the temporal responses of biological cells in the jumping and vibrating optical tweezers for tugging, wiggling and stretching the cells with the finite element method. Some new concepts were established, which might be investigated in the future experiments, such as the jumping of local stress and local strain, independently on the recovery time of the viscoelastic material and on the jumping frequency, the energy dissipation in the hysteresis cycles, the cytoplasm fluid field and its interaction with the cell membrane. The cell was modeled with full 3D structure and viscoelastic continuum materials.

  20. Mechanical analysis of the optical tweezers in time-sharing regime.

    PubMed

    Yu, Lingyao; Sheng, Yunlong

    2014-04-01

    Time-sharing optical tweezers is a versatile technique to realize multiple traps for manipulating biological cells and macromolecules. It has been based on an intuitive hypothesis that the trapped viscoelastic object does not "sense" blinking of the optical beam. We present a quantitative analysis using mechanical modeling and numerical simulation, showing that the local stress and strain are jumping all the time and at all locations with the jumping amplitude independent of the recovery time of the viscoelastic material and the jumping frequency. Effects of the stress and strain jumping on the object deformation and the internal energy dissipation are analyzed. PMID:24718171

  1. Microfluidic integrated optoelectronic tweezers for single-cell preparation and analysis.

    PubMed

    Huang, Kuo-Wei; Wu, Yi-Chien; Lee, Ji-Ann; Chiou, Pei-Yu

    2013-09-21

    We report a novel microfluidic integrated optoelectronic tweezers (OET) platform for single-cell sample preparation and analysis. Integration of OET and microfluidics is achieved by embedding single-wall carbon nanotube (SWNT) electrodes into multilayer PDMS structures. This integrated platform allows users to selectively pick up individual cells from a population with light beams based on their optical signatures such as size, shape, and fluorescence, and transport them into isolated chambers using light induced dielectrophoretic forces. Isolated cells can be encapsulated into nanoliter liquid plugs and transported out of the platform for downstream molecule analysis using standard commercial instruments. PMID:23884358

  2. High-resolution, long-term characterization of bacterial motility using optical tweezers

    PubMed Central

    Min, Taejin L.; Mears, Patrick J.; Chubiz, Lon M.; Rao, Christopher V.; Golding, Ido; Chemla, Yann R.

    2009-01-01

    We present a single-cell motility assay, which allows the quantification of bacterial swimming in a well-controlled environment, for durations of up to an hour and with a temporal resolution higher than the flagellar rotation rates of ~100 Hz. The assay is based on an instrument combining optical tweezers, light and fluorescence microscopy, and a microfluidic chamber. Using this device we characterized the long-term statistics of the run-tumble time series in individual Escherichia coli cells. We also quantified higher-order features of bacterial swimming, such as changes in velocity and reversals of swimming direction. PMID:19801991

  3. Plasmon-exciton interactions on single thermoresponsive platforms demonstrated by optical tweezers.

    PubMed

    Hormeo, Silvia; Basts, Neus G; Pietsch, Andrea; Weller, Horst; Arias-Gonzalez, J R; Jurez, Beatriz H

    2011-11-01

    Optical and hydrodynamic-size studies on single bare thermo-responsive microspheres, and microspheres covered either with Au nanoparticles, CdSe/CdS quantum dots, or a combination of both have been performed by optical tweezers. The photothermal heating of water in the focal region boosts the shrinkage of the microspheres, an effect that is intensified in the presence of Au nanoparticles. In contrast, bigger microspheres are measured when they are covered with quantum dots. Plasmon-exciton interactions are observable in the trap in the combined Au and quantum dots hybrid systems. PMID:22003895

  4. Optical determination of motility forces in human spermatozoa with laser tweezers

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Svaasand, Lars O.; Tadir, Yona; Tromberg, Bruce J.; Berns, Michael W.

    1996-12-01

    Laser tweezers may act as optical force transducers. We report on the determination of intrinsic motility forces of human spermatozoa by employing an 800 nm optical trap. The cellular forces were calculated from calibrated trapping forces. The determination of trapping forces based on a hydrodynamic model for ellipsoidal specimens, the measurement of the minimum laser power required to confine a single cell in the trap, and the calculation of viscus forces during the movement of optically trapped sperm heads through a laminar fluid. A mean motility force of 44 plus or minus 24 pN was calculated for spermatozoa of healthy donors.

  5. A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

    PubMed Central

    2016-01-01

    Summary This review summarizes part of the author’s research in the area of supramolecular chemistry, beginning with his early life influences and early career efforts in molecular recognition, especially molecular tweezers. Although designed to complex DNA, these hosts proved more applicable to the field of host–guest chemistry. This early experience and interest in intercalation ultimately led to the current efforts to develop small molecule therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples. PMID:26877815

  6. Fast acoustic tweezers for the two-dimensional manipulation of individual particles in microfluidic channels

    NASA Astrophysics Data System (ADS)

    Tran, S. B. Q.; Marmottant, P.; Thibault, P.

    2012-09-01

    This paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very controlled manner by the two-dimensional drifting of a standing wave array, using a slight frequency modulation of two ultrasound emitters around their resonance. These acoustic tweezers allow any type of motion at velocities up to few 10 mm/s, while the device transparency is adapted for optical studies. The possibility of automation provides a critical step in the development of lab-on-a-chip cell sorters and it should find applications in biology, chemistry, and engineering domains.

  7. Photovoltaic tweezers an emergent tool for applications in nano and bio-technology

    NASA Astrophysics Data System (ADS)

    Carrascosa, M.; Garca-Cabaes, A.; Jubera, M.; Elvira, I.; Burgos, H.; Bella, J. L.; Agull-Lpez, F.; Muoz-Martnez, J. F.; Alczar, A.

    2015-05-01

    An overview of the work recently conducted by our group on the development and applications of photovoltaic tweezers is presented. It includes the analysis of the physical basis of the method and the main achievements in its experimental implementation. Particular attention will be paid to the main potential applications and first demonstrations of its use in nano- and bio-technology. Specifically: i) fabrication of metallic nanoestructures for plasmonic applications, ii) development of diffractive components, iii) manipulation and patterning (1D and 2D) of various types of bio-objects (spores or pollen) and iv) effects of PV fields of LiNbO3 in tumour cells.

  8. Polymeric optical fiber tweezers as a tool for single cell micro manipulation and sensing

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Soppera, O.; Guerreiro, A.; Jorge, P. A...

    2015-09-01

    In this paper a new type of polymeric fiber optic tweezers for single cell manipulation is reported. The optical trapping of a yeast cell using a polymeric micro lens fabricated by guided photo polymerization at the fiber tip is demonstrated. The 2D trapping of the yeast cells is analyzed and maximum optical forces on the pN range are calculated. The experimental results are supported by computational simulations using a FDTD method. Moreover, new insights on the potential for simultaneous sensing and optical trapping, are presented.

  9. Programmable manipulation of motile cells in optoelectronic tweezers using a grayscale image

    NASA Astrophysics Data System (ADS)

    Choi, Wonjae; Nam, Seong-Won; Hwang, Hyundoo; Park, Sungsu; Park, Je-Kyun

    2008-10-01

    This paper describes a grayscale optoelectronic tweezers (OET) which allows adjustment of the electric field strength at each position of OET. A grayscale light image was used to pattern vertical electric field strength on an OET. As an electric field depends on the brightness at each point, the brighter light patterns generate the stronger electric field in the OET. Its feasibility for application to cell manipulation was demonstrated by aligning highly motile protozoan cells in vertical direction. Depending on the brightness of each pixel, the behaviors of aligned cells varied due to the different electric field strength to each cell.

  10. Highly ordered alignment of a vinyl polymer by host-guest cross-polymerization

    NASA Astrophysics Data System (ADS)

    Distefano, Gaetano; Suzuki, Hirohito; Tsujimoto, Masahiko; Isoda, Seiji; Bracco, Silvia; Comotti, Angiolina; Sozzani, Piero; Uemura, Takashi; Kitagawa, Susumu

    2013-04-01

    Chain alignment can significantly influence the macroscopic properties of a polymeric material, but no general and versatile methodology has yet been reported to obtain highly ordered crystalline packing of polymer chains, with high stability. Here, we disclose a strategy that relies on ‘ordered crosslinks’ to produce polymeric materials that exhibit a crystalline arrangement. Divinyl crosslinkers (2,5-divinyl-terephthalate) were first embedded, as substitutional ligands, into the structure of a porous coordination polymer (PCP), [Cu(terephthalate)triethylenediamine0.5]n. A representative vinyl monomer, styrene, was subsequently polymerized inside the channels of the host PCP. The polystyrene chains that form within the PCP channels also crosslink with the divinyl species. This bridges together the polymer chains of adjacent channels and ensures that, on selective removal of the PCP, the polymer chains remain aligned. Indeed, the resulting material exhibits long-range order and is stable to thermal and solvent treatments, as demonstrated by X-ray powder diffraction and transmission electron microscopy.

  11. Fluorescence detecting of paraquat using host-guest chemistry with cucurbit[8]uril

    NASA Astrophysics Data System (ADS)

    Sun, Shiguo; Li, Fusheng; Liu, Fengyu; Wang, Jitao; Peng, Xiaojun

    2014-01-01

    Paraquat (PQ) is one of the most widely used herbicides in the world, which has a good occupational safety record when used properly. While, it presents high mortality index after intentional exposure. Accidental deaths and suicides from PQ ingestion are relatively common in developing countries with an estimated 300,000 deaths occurring in the Asia-Pacific region alone each year, and there are no specific antidotes. Good predictors of outcome and prognosis may be plasma and urine testing within the first 24 h of intoxication. A fluorescence enhancement of approximately 30 times was seen following addition of PQ to a solution of the supramolecular compound 2MB@CB[8], which comprised two methylene blue (MB) molecules within one cucurbit[8]uril (CB[8]) host molecule. The fluorescence intensity was linearly proportional to the amount of PQ added over the concentration range 2.4 × 10-10 M-2.5 × 10-4 M. The reaction also occurred in living cells and within live mice.

  12. Host-guest interactions in fluorinated polymer electrolytes: A 7Li-13C NMR study

    NASA Astrophysics Data System (ADS)

    Mustarelli, P.; Quartarone, E.; Capiglia, C.; Tomasi, C.; Ferloni, P.; Magistris, A.

    1999-08-01

    Gel-type electrolytes based on fluorinated polymers are of interest for electrochemical devices. We present a 7Li-13C solid-state NMR and modulated differential scanning calorimetry (MDSC) study of gel electrolytes based on a copolymer poly(vinylidene fluoride) (PVdF)-hexafluoropropylene (HFP) activated with a nonaqueous solution ethylene carbonate (EC)-propylene carbonate (PC)-LiN(CF3SO2)2. We show that the narrowing of the Li lineshape is decoupled from the glass transition. The behavior of the longitudinal relaxation times, T1, confirms that the host polymer matrix simply behaves like a quasiinert cage for the solution. These results are confirmed by 13C NMR at the magic angle (MAS) data, which show that the presence of the polymer does not significantly affect the chemical shift changes induced in the EC/PC carbons by the imide salt.

  13. Host-guest encapsulation of materials by assembled virus protein cages

    NASA Astrophysics Data System (ADS)

    Douglas, Trevor; Young, Mark

    1998-05-01

    Self-assembled cage structures of nanometre dimensions can be used as constrained environments for the preparation of nanostructured materials, and the encapsulation of guest molecules, with potential applications in drug delivery and catalysis. In synthetic systems the number of subunits contributing to cage structures is typically rather small,. But the protein coats of viruses (virions) commonly comprise hundreds of subunits that self-assemble into a cage for transporting viral nucleic acids. Many virions, moreover, can undergo reversible structural changes that open or close gated pores to allow switchable access to their interior. Here we show that such a virion - that of the cowpea chlorotic mottle virus - can be used as a host for the synthesis of materials. We report the mineralization of two polyoxometalate species (paratungstate and decavanadate) and the encapsulation of an anionic polymer inside this virion, controlled by pH-dependent gating of the virion's pores. The diversity in size and shape of such virus particles make this a versatile strategy for materials synthesis and molecular entrapment.

  14. Self-assembly and host-guest chemistry of a 3.5-nm coordination nanotube.

    PubMed

    Yamaguchi, Takumi; Tashiro, Shohei; Tominaga, Masahide; Kawano, Masaki; Ozeki, Tomoji; Fujita, Makoto

    2007-04-01

    Upon complexation with Pd(II) ions, precisely designed strandlike ligands with two tris(3,5-pyridine) units at both terminals were assembled, with the aid of a linear template molecule, into a discrete tubular complex with a length of 3.5 nm. The high stability and the well-defined structure of the coordination nanotube were revealed by NMR spectroscopy, cold-spray ionization MS, and single-crystal X-ray analysis. Guest lengths were discriminated by the tube: When the association of strandlike guest molecules, in which two biphenylene units are linked with an (OCH2CH2)n linker, were compared, the tube selectively recognized an appropriate guest whose length was comparable to that of the tube. Tetrathiafulvalene (TTF)-terminated linear guests were directly oxidized to TTF2+ in the tube, but reduced stepwise via TTF+ outside the tube. PMID:17441183

  15. Discovery of a non classic host guest complexation mode in a ?-cyclodextrin/propionic acid model.

    PubMed

    Rutenberg, R; Leitus, G; Fallik, E; Poverenov, E

    2016-02-11

    A non-classic complexation mode was discovered upon spectroscopic, thermodynamic, crystallographic and computational studies of a ?-cyclodextrin/propionic acid complex. A "fully immersed" complexation phenomenon, where both the guest's hydrophobic and polar moieties are located inside the host and are stabilized by it, was found and calculated as the most favorable configuration. PMID:26744749

  16. Anion- and Spacer-Directed Host-Guest Complexes of Bipyridine with Pyrogallol[4]arene.

    PubMed

    Patil, Rahul S; Kumari, Harshita; Barnes, Charles L; Atwood, Jerry L

    2015-07-13

    New oval-shaped capsular and bilayer-type hydrogen-bonded arrangements of C-propyl-ol-pyrogallol[4]arene (PgC3-OH) with bipyridine-type spacer complexes are reported here. These complexes are engineered by virtue of derivatization of C-alkyl tails of pyrogallol[4]arene and the use of divergent spacer ligands. Complexes of PgC3-OH, PgC3-OH with bpy (4,4'-bipyridine) and PgC3-OH with bpa (1,2-bis(4-pyridyl)acetylene) have bilayer type arrangements; however, the use of hydrogen chloride causes protonation of bpy molecule, which is then entrapped flat within an offset oval-shaped dimeric hydrogen-bonded PgC3-OH nanocapsule. The presence of chloride anion in the crystal lattice controls the geometry of the resultant nanoassembly. PMID:26046450

  17. Responsive Double Network Hydrogels of Interpenetrating DNA and CB[8] Host-Guest Supramolecular Systems.

    PubMed

    Li, Chuang; Rowland, Matthew J; Shao, Yu; Cao, Tianyang; Chen, Chun; Jia, Haoyang; Zhou, Xu; Yang, Zhongqiang; Scherman, Oren A; Liu, Dongsheng

    2015-06-01

    A supramolecular double network hydrogel is presented by physical interpenetration of DNA and cucurbit[8]uril networks. In addition to exhibiting an increase in strength and thermal stability, the double network hydrogel possesses excellent properties such as stretchability, ductility, shear-thinning, and thixotropy. Moreover, it is enzymatically responsive to both nuclease and cellulase, as well as small molecules, showing great potential as a new soft material scaffold. PMID:25899855

  18. Design and comparison of exchange spectroscopy approaches to cryptophane-xenon host-guest kinetics

    NASA Astrophysics Data System (ADS)

    Korchak, Sergey; Kilian, Wolfgang; Schröder, Leif; Mitschang, Lorenz

    2016-04-01

    Exchange spectroscopy is used in combination with a variation of xenon concentration to disentangle the kinetics of the reversible binding of xenon to cryptophane-A. The signal intensity of either free or crytophane-bound xenon decays in a manner characteristic of the underlying exchange reactions when the spins in the other pool are perturbed. Three experimental approaches, including the well-known Hyper-CEST method, are shown to effectively entail a simple linear dependence of the signal depletion rate, or of a related quantity, on free xenon concentration. This occurs when using spin pool saturation or inversion followed by free exchange. The identification and quantification of contributions to the binding kinetics is then straightforward: in the depletion rate plot, the intercept at the vanishing free xenon concentration represents the kinetic rate coefficient for xenon detachment from the host by dissociative processes while the slope is indicative of the kinetic rate coefficient for degenerate exchange reactions. Comparing quantified kinetic rates for hyperpolarized xenon in aqueous solution reveals the high accuracy of each approach but also shows differences in the precision of the numerical results and in the requirements for prior knowledge. Because of their broad range of applicability the proposed exchange spectroscopy experiments can be readily used to unravel the kinetics of complex formation of xenon with host molecules in the various situations appearing in practice.

  19. Enhanced imine synthesis in water: from surfactant-mediated catalysis to host-guest mechanisms.

    PubMed

    Meguellati, Kamel; Fallah-Araghi, Ali; Baret, Jean-Christophe; El Harrak, Abdeslam; Mangeat, Thomas; Marques, Carlos M; Griffiths, Andrew D; Ladame, Sylvain

    2013-12-14

    An environment-responsive and fluorogenic reaction is reported and used as a model system to demonstrate experimentally three mechanisms of enhanced imine synthesis in water using either surfactants (below and above their CMC) or double-stranded DNA (acting as a reaction host). PMID:24162811

  20. Does Size Really Matter? The Steric Isotope Effect in a Supramolecular Host?Guest Exchange Reaction

    SciTech Connect

    Mugridge, Jeffrey; Bergman, Robert; Raymond, Kenneth

    2010-01-29

    Isotope effects (IEs), which arise from differences in zero point energies (ZPEs) between a parent and isotopically substituted bond, have been used extensively by chemists to probe molecular interactions and reactivity. Due to the anharmonicity of the C-H/D vibrational potential energy function and the lower ZPE of a C-D bond, the average C-D bond length is typically {approx}0.005 {angstrom} shorter than an equivalent C-H bond. It is this difference in size that is often invoked to explain the observation of secondary, inverse kinetic isotope effects (KIEs) in chemical processes which proceed through a sterically strained transition state. This so-called 'steric isotope effect' (SIE) has been observed in processes such as the racemization of ortho-substituted biphenyls[6] and phenanthrenes, ring flipping of cyclophanes, and more recently in the deslipping of rotaxanes, where substitution of the sterically less demanding deuterium for protium results in rate accelerations for these processes. Herein, we use deuterium substitution in a cationic guest molecule to probe the sensitivity limits of the guest exchange process from a highly-charged supramolecular host.

  1. Comprehensive Benchmark of Association (Free) Energies of Realistic Host-Guest Complexes.

    PubMed

    Sure, Rebecca; Grimme, Stefan

    2015-08-11

    The S12L test set for supramolecular Gibbs free energies of association ?Ga (Grimme, S. Chem. Eur. J. 2012, 18, 9955-9964) is extended to 30 complexes (S30L), featuring more diverse interaction motifs, anions, and higher charges (-1 up to +4) as well as larger systems with up to 200 atoms. Various typical noncovalent interactions like hydrogen and halogen bonding, ?-? stacking, nonpolar dispersion, and CH-? and cation-dipolar interactions are represented by "real" complexes. The experimental Gibbs free energies of association (?Ga exp) cover a wide range from -0.7 to -24.7 kcal mol-1. In order to obtain a theoretical best estimate for ?Ga, we test various dispersion corrected density functionals in combination with quadruple-? basis sets for calculating the association energies in the gas phase. Further, modern semiempirical methods are employed to obtain the thermostatistical corrections from energy to Gibbs free energy, and the COSMO-RS model with several parametrizations as well as the SMD model are used to include solvation contributions. We investigate the effect of including counterions for the charged systems (S30L-CI), which is found to overall improve the results. Our best method combination consists of PW6B95-D3 (for neutral and charged systems) or ?B97X-D3 (for systems with counterions) energies, HF-3c thermostatistical corrections, and Gibbs free energies of solvation obtained with the COSMO-RS 2012 parameters for nonpolar solvents and 2013-fine for water. This combination gives a mean absolute deviation for ?Ga of only 2.4 kcal mol-1 (S30L) and 2.1 kcal mol-1 (S30L-CI), with a mean deviation of almost zero compared to experiment. Regarding the relative Gibbs free energies of association for the 13 pairs of complexes which share the same host, the correct trend in binding affinities could be reproduced except for two cases. The MAD compared to experiment amounts to 1.2 kcal mol-1, and the MD is almost zero. The best-estimate theoretical corrections are used to back-correct the experimental ?Ga values in order to get an empirical estimate for the "experimental", zero-point vibrational energy exclusive, gas phase binding energies. These are then utilized to benchmark the performance of various "lowcost" quantum chemical methods for noncovalent interactions in large systems. The performance of other common DFT methods as well as the use of semiempirical methods for structure optimizations is discussed. PMID:26574460

  2. Efficient host-guest energy transfer in polycationic cyclophane-perylene diimide complexes in water.

    PubMed

    Ryan, Sen T J; Del Barrio, Jess; Ghosh, Indrajit; Biedermann, Frank; Lazar, Alexandra I; Lan, Yang; Coulston, Roger J; Nau, Werner M; Scherman, Oren A

    2014-06-25

    We report the self-assembly of a series of highly charged supramolecular complexes in aqueous media composed of cyclobis(4,4'-(1,4-phenylene)bispyridine-p-phenylene)tetrakis(chloride) (ExBox) and three dicationic perylene diimides (PDIs). Efficient energy transfer (ET) is observed between the host and guests. Additionally, we show that our hexacationic complexes are capable of further complexation with neutral cucurbit[7]uril (CB[7]), producing a 3-polypseudorotaxane via the self-assembly of orthogonal recognition moieties. ExBox serves as the central ring, complexing to the PDI core, while two CB[7]s behave as supramolecular stoppers, binding to the two outer quaternary ammonium motifs. The formation of the 3-polypseudorotaxane results in far superior photophysical properties of the central PDI unit relative to the binary complexes at stoichiometric ratios. Lastly, we also demonstrate the ability of our binary complexes to act as a highly selective chemosensing ensemble for the neurotransmitter melatonin. PMID:24893200

  3. Solution and air stable host/guest architectures from a single layer covalent organic framework.

    PubMed

    Cui, D; MacLeod, J M; Ebrahimi, M; Perepichka, D F; Rosei, F

    2015-11-01

    We show that the surface-supported two-dimensional covalent organic framework (COF) known as COF-1 can act as a host architecture for C60 fullerene molecules, predictably trapping the molecules under a range of conditions. The fullerenes occupy the COF-1 lattice at the solution/solid interface, and in dried films of the COF-1/fullerene network that can be synthesized through either drop-deposition of fullerene solution or by a dipstick-type synthesis in which the surface-supported COF-1 is briefly dipped into the fullerene solution. PMID:26417872

  4. Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability

    NASA Astrophysics Data System (ADS)

    Zhou, Shu-Ya; Ma, Shui-Xian; Cheng, Hui-Lin; Yang, Li-Juan; Chen, Wen; Yin, Yan-Qing; Shi, Yi-Min; Yang, Xiao-Dong

    2014-01-01

    The inclusion complexation behavior, characterization and binding ability of pinocembrin with ?-cyclodextrin (?-CD) and its derivative 2-hydroxypropyl-?-cyclodextrin (HP?CD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

  5. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    PubMed Central

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, NoSoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-01-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. PMID:26067060

  6. Tunable elastic modulus of nanoparticle monolayer films by host-guest chemistry.

    PubMed

    Jeong, Youngdo; Chen, Yu-Cheng; Turksoy, Merve K; Rana, Subinoy; Tonga, Gulen Yesilbag; Creran, Brian; Sanyal, Amitav; Crosby, Alfred J; Rotello, Vincent M

    2014-08-01

    The elastic modulus of an ultrathin nanoparticle (NP) monolayer film is tuned by modulating the binding strength between the NPs on a molecular level. NP monolayer films constructed by crosslinking NPs of different binding affinities are fabricated at oil/water interfaces. By inducing buckling patterns on these films, the correlation between the binding affinity of the NPs and the elastic modulus is investigated. PMID:24889993

  7. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, Nosoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-06-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions.

  8. Metallacycle-catalyzed SNAr reaction in water: supramolecular inhibition by means of hostguest complexation.

    PubMed

    Lpez-Vidal, Eva M; Fernndez-Mato, Antonio; Garca, Marcos D; Prez-Lorenzo, Moiss; Peinador, Carlos; Quintela, Jos M

    2014-02-01

    The performance of a Pt(II) diazapyrenium-based metallacycle as a reusable substoichiometric catalyst for the SNAr reaction between halodinitrobenzenes and sodium azide at rt in aqueous media is reported. The results suggest that the catalytic effect is promoted by the association of the azide to the diazapyrenium cationic subunits of the catalyst. The findings demonstrate that the formation of an inclusion complex between pyrene and the metallacycle has a regulatory effect over the system, resulting in allosteric-like inhibition of the SNAr reaction. PMID:24444092

  9. Supramolecular hydrogels from in situ host-guest inclusion between chemically modified cellulose nanocrystals and cyclodextrin.

    PubMed

    Lin, Ning; Dufresne, Alain

    2013-03-11

    When grafted ?-cyclodextrin is used as targeting sites, Pluronic polymers have been introduced on the surface of cellulose nanocrystals by means of inclusion interaction between ?-cyclodextrin and hydrophobic segment of the polymer. Because of the steric stabilization effect, surface poly(ethylene glycol) chains facilitate the dispersion and compatibility of nanocrystals, which also enhance the loading levels of nanocrystals in the hydrogel system. Meanwhile, uncovered poly(ethylene glycol) segments render the participating inclusion of ?-cyclodextrin for the architecture of in situ hydrogels. Surface grafting and inclusion reactions were proved by solid (13)C NMR and FTIR. Grafting efficiency of ?-cyclodextrin and inclusion efficiency of Pluronic on the surface of nanocrystals were confirmed by UV spectroscopy and elemental analysis. A significant enhancement of the structural and thermal stability of in situ hydrogels with high loading levels of modified nanocrystals (>5.77 wt %) was observed by rheological analysis. Further study reveals the performance and behavior of hydrogels under a different pH environment. Finally, in situ hydrogels were used as drug carrier for in vitro release of doxorubicin and exhibit the behavior of prolonged drug release with special release kinetics. PMID:23347071

  10. Light-harvesting host-guest antenna materials for solar energy conversion devices

    NASA Astrophysics Data System (ADS)

    Huber, Stefan; Calzaferri, Gion

    2006-04-01

    In natural photosynthesis, light is absorbed by photonic antenna systems consisting of a few hundred chlorophyll molecules. These devices allow fast energy transfer from an electronically excited molecule to an unexcited neighbour molecule in such a way that the excitation energy reaches the reaction centre with high probability. Trapping occurs there. The anisotropic arrangement of the chlorophyll molecules is important for efficient energy migration. In natural antennae the formation of aggregates is prevented by fencing the chlorophyll molecules in polypeptide cages. A similar approach is possible by enclosing dyes inside a microporous material and by choosing conditions such that the cavities are able to uptake only monomers but not aggregates. In most of our experiments we have been using zeolite L as a host because it was found to be very versatile. Its crystals are of cylindrical shape and consist of an extended one-dimensional tube system. They can be prepared in wide size range. We have filled the individual tubes with successive chains of different dye molecules and we have shown that photonic antenna materials can be prepared. Moreover, fluorescent dye molecules can be bound covalently to the channel entrances. Dependent on the spectral properties of these stopcock molecules, the electronic excitation energy is transported radiationless to the stopcock fixed at the ends of the nanochannels or injected from the stopcock to the dyes inside the zeolite. The radiationless energy migration is in competition with spontaneous emission, thermal deactivation, quenching, and photochemically induced degradation. Fast energy migration is therefore crucial for an efficient antenna material. - The supramolecular organization of the dyes inside the channels is a first stage of organization. It allows light harvesting within the volume of a dye-loaded zeolite L crystal and radiationless transport to both ends of the cylinder or from the ends to the centre. The second stage of organization is the coupling to an external acceptor or donor stopcock fluorophore at the ends of the zeolite L channels, which can trap or inject electronic excitation energy. The third stage of organization is the coupling to an external device via a stopcock intermediate. The wide-ranging tunability of these highly organized materials offers fascinating new possibilities for exploring excitation energy transfer phenomena, and challenges for developing new photonic devices for solar energy conversion and storage.

  11. Cooperative assembly of discrete stacked aggregates driven by supramolecular host-guest complexation.

    PubMed

    Baslio, Nuno; Pieiro, ngel; Da Silva, Jos P; Garca-Ro, Luis

    2013-09-20

    p-Sulfonatocalix[4]arene (SC4) interacts with the aromatic dye crystal violet (CV) to form complexes with stoichiometries ranging from SC4:CV = 1:1 up to 1:5 both in solution and in the gas phase. While the 1:1 complex is of the inclusion type, as frequently observed for other guests, in the higher-order complexes the CV molecules interact with SC4 in a peripheral manner. The formation of such complexes is driven by ionic interactions established between the dye and the calixarene and by CV-CV stacking interactions. The application of an advanced fitting procedure made possible a quantitative analysis of the UV-vis data and allowed the determination of the stepwise binding constants. This unprecedented approach provides evidence that the formation of the highest-order complexes occurs through a cooperative mechanism. Moreover, the development of a quantitative analytical model enables the possibility of using this type of system for water-soluble sensing assays, as is also exemplified in the present work. PMID:23962101

  12. Host-guest Interaction Mediated Polymeric Assemblies: Multifunctional Nanoparticles for Drug and Gene Delivery

    PubMed Central

    Zhang, Jianxiang; Sun, Hongli; Ma, Peter X

    2010-01-01

    Novel core-shell structured nano-assemblies are assembled by a ?-cyclodextrin containing positively charged host polymer and a hydrophobic guest polymer. The hydrophobic core of this type of assemblies serves as a nano-container to load and release the hydrophobic drugs, while the positively charged hydrophilic shell is able to condense the plasmid DNA and achieve its transfection/expression in osteoblast cells. These assemblies may be used as a new generation of multi-functional nano-carriers for simultaneous drug delivery and gene therapy. PMID:20112968

  13. Insights into the Complexity of Weak Intermolecular Interactions Interfering in Host-Guest Systems.

    PubMed

    Zhang, Dawei; Chatelet, Bastien; Serrano, Eloisa; Perraud, Olivier; Dutasta, Jean-Pierre; Robert, Vincent; Martinez, Alexandre

    2015-10-01

    The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation-? and anion-? interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron-poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion-pair recognition. Wavefunction calculations highlight how short- and long-range interactions interfere in this recognition process, suggesting that a disruption of anion-? interactions can occur in the presence of a co-bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions. PMID:26401973

  14. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes.

    PubMed

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, NoSoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-01-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. PMID:26067060

  15. Optical Detection of Aqueous Phase Analytes via Host-Guest Interactions on a Lipid Membrane Surface

    SciTech Connect

    Sasaki, D.Y.; Waggoner, T.A.

    1999-01-11

    The organization and assembly of molecules in cellular membranes is orchestrated through the recognition and binding of specific chemical signals. A simplified version of the cellular membrane system has been developed using a synthetically prepared membrane receptor incorporated into a biologically derived lipid bilayer. Through an interplay of electrostatic and van der Wards interactions, aggregation or dispersion of molecular components could be executed on command using a specific chemical signal. A pyrene fluorophore was used as an optical probe to monitor the aggregational state of the membrane receptors in the bilayer matrix. The pyrene excimer emission to monomer emission (E/M) intensity ratio gave a relative assessment of the local concentration of receptors in the membrane. Bilayers were prepared with receptors selective for the divalent metal ions of copper, mercury, and lead. Addition of the metal ions produced a rapid dispersion of aggregated receptor components at nano- to micro-molar concentrations. The process was reversible by sequestering the metal ions with EDTA. Receptors for proteins and polyhistidine were also prepared and incorporated into phosphatidylcholine lipid bilayers. In this case, the guest molecules bound to the membrane through multiple points of interaction causing aggregation of initially dispersed receptor molecules. The rapid, selective, and sensitive fluorescence optical response of these lipid assemblies make them attractive in sensor applications for aqueous phase metal ions and polypeptides.

  16. Binary Crystallized Supramolecular Aerogels Derived from Host-Guest Inclusion Complexes.

    PubMed

    Wang, Jin; Zhang, Xuetong

    2015-11-24

    Aerogels with low density and high porosity show outstanding properties such as large surface area and low thermal and acoustic conductivity. However, great challenges remain to convert hydrophilic polymer based hydrogels to corresponding aerogels. Here, we report a structurally new type of aerogels, supramolecular aerogels (SMAs), derived from supramolecular hydrogels formed by self-assembling of poly(ethylene glycol) and ?-/?-cyclodextrin. The SMAs posses a characteristic binary crystallized nanosheet structure due to their supramolecular cross-linking nature, and their specific surface areas and nanosheet structures are tunable. Furthermore, we demonstrated application of the aerogels as solid-solid phase change materials with tunable latent heat, reversible melting-crystallization cycle while keeping the microstructure of the SMAs unchanged. PMID:26513140

  17. Rationally designed cooperatively enhanced receptors to magnify host-guest binding in water.

    PubMed

    Gunasekara, Roshan W; Zhao, Yan

    2015-01-21

    When disengaged interactions within a receptor are turned on by its guest, these intrahost interactions will contribute to the overall binding energy. Although such receptors are common in biology, their synthetic mimics are rare and difficult to design. By engineering conflictory requirements between intrareceptor electrostatic and hydrophobic interactions, we enabled complementary guests to eliminate the "electrostatic frustration" within the host and turn on the intrahost interactions. The result was a binding constant of Ka >10(5) M(-1) from ammonium-carboxylate salt bridges that typically function poorly in water. These cooperatively enhanced receptors displayed excellent selectivity in binding, despite a large degree of conformational flexibility in the structure. PMID:25531747

  18. Luminescent cation sensors: from host-guest chemistry, supramolecular chemistry to reaction-based mechanisms.

    PubMed

    Yeung, Margaret Ching-Lam; Yam, Vivian Wing-Wah

    2015-07-01

    Other than traditional cation detection strategies, which are solely based on the ion-receptor complementarity, the extension of the concept of supramolecular chemistry and the mechanisms of irreversible analyte-specific reactions have also been integrated into the design of luminescent probes for the detection of cation in view of the exploration of highly sensitive and selective sensors. In this highlight, a versatile range of organic and organometallic architectures with cation-sensing capabilities based on the above mechanisms will be discussed. PMID:25588608

  19. Optical detection of aqueous phase analytes via host-guest interactions on a lipid membrane surface

    NASA Astrophysics Data System (ADS)

    Sasaki, Darryl Y.; Waggoner, Tina Y.

    1999-06-01

    The organization and assembly of molecules in cellular membranes is orchestrated through the recognition and binding of specific chemical signals. A simplified version of the cellular membrane system has been developed using a synthetically prepared membrane receptor incorporated into a biologically derived lipid bilayer. Through an interplay of electrostatic and van der Waals interactions, aggregation or dispersion of molecular components could be executed on command using a specific chemical signal. A pyrene fluorophore was used as an optical probe to monitor the aggregational state of the membrane receptors in the bilayer matrix. The pyrene excimer emission to monomer emission (E/M) intensity ratio gave a relative assessment of the local concentration of receptors in the membrane. Bilayers were prepared with receptors selective for the divalent metal ions of copper, mercury, and lead. Addition of the metal ions produced a rapid dispersion of aggregated receptor components at nano- to micro-molar concentrations. The process was reversible by sequestering the metal ions with EDTA. Receptors for proteins and polyhistidine were also prepared and incorporated into phosphatidylcholine lipid bilayers. In this case, the guest molecules bound to the membrane through multiple points of interaction causing aggregation of initially dispersed receptor molecules. The rapid, selective, and sensitive fluorescence optical response of these lipid assemblies make them attractive in sensor applications for aqueous phase metal ions and polypeptides.

  20. Host-guest interactions in Fe(III)-trimesate MOF nanoparticles loaded with doxorubicin.

    PubMed

    Anand, Resmi; Borghi, Francesco; Manoli, Francesco; Manet, Ilse; Agostoni, Valentina; Reschiglian, Pierluigi; Gref, Ruxandra; Monti, Sandra

    2014-07-24

    Doxorubicin (DOX) entrapment in porous Fe(III)-trimesate metal organic frameworks (MIL-100(Fe)) nanoparticles was investigated in neutral Tris buffer via UV-vis absorption, circular dichroism (CD), and fluorescence. The binding constants and the absolute spectra of the DOX-MIL-100(Fe) complexes were determined via absorption and fluorescence titrations. A binding model where DOX associates as monomer to the dehydrated Fe3O (OH)(H2O)2 [(C6H3)(CO2)3]2 structural unit in 1:1 stoichiometry, with apparent association constant of (1.1 to 1.8) × 10(4) M(-1), was found to reasonably fit the experimental data. Spectroscopic data indicate that DOX binding occurs via the formation of highly stable coordination bonds between one or both deprotonated hydroxyl groups of the aglycone moiety and coordinatively unsaturated Fe(III) centers. Complete quenching of the DOX fluorescence and remarkable thermal and photochemical stability were observed for DOX incorporated in the MIL-100(Fe) framework. PMID:24960194

  1. Posaconazole/hydroxypropyl-β-cyclodextrin host-guest system: Improving dissolution while maintaining antifungal activity.

    PubMed

    Tang, Peixiao; Ma, Xiaoli; Wu, Di; Li, Shanshan; Xu, Kailin; Tang, Bin; Li, Hui

    2016-05-20

    This study aimed to prepare and characterize the inclusion complex between posaconazole (POS) and hydroxypropyl-β-cyclodextrin (HP-β-CD). Phase solubility study was conducted to investigate the drug/CD interaction in solution, including the stoichiometry and apparent stability constant. The solid complex (HP-β-CD-POS) obtained was characterized through Fourier transform infrared spectroscopy, powder X-ray diffraction, (1)H and ROESY 2D nuclear magnetic resonance, differential scanning calorimetry, and scanning electron microscopy. These approaches confirmed the formation of the inclusion complex. The HP-β-CD-POS inclusion complex exhibited better water solubility and higher dissolution rate than the free POS did; the water solubility of POS was increased by 82 times and almost 90% of the loaded drug dissolved after 10min in the dissolution media. In addition, preliminary in vitro antifungal susceptibility testing revealed that HP-β-CD-POS maintains a high level of antifungal activities. Therefore, the HP-β-CD complex may be useful in the delivery of posaconazole. PMID:26917368

  2. Efficient synthesis and host-guest properties of a new class of calix[6]azacryptands.

    PubMed

    Gac, Stphane Le; Zeng, Xianshun; Girardot, Camille; Jabin, Ivan

    2006-11-24

    Two members of a new class of calix[6]azacryptands, namely, calix[6]tampo and calix[6]tamb, have been synthesized through an efficient [1 + 1] macrocyclization reaction--reduction sequence. One of them has been obtained in a remarkably high overall yield from the known X(6)H(3)Me(3). In comparison to all the other calix[6]azacryptands, they possess unique conformational properties since they present a rigidified cone conformation with a partial filling of the cavity by the methoxy groups. In contrast to calix[6]tampo, the fully protonated derivative of calix[6]tamb behaves as a remarkable molecular receptor toward polar neutral guests. NMR studies have shown that the intracavity binding process is governed by a conformational flip of the aromatic walls of the calixarene core. PMID:17109555

  3. Characterization of folic acid/native cyclodextrins host-guest complexes in solution

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena; Zimnicka, Magdalena; Wszelaka-Rylik, Małgorzata; Troć, Anna

    2016-04-01

    The complexation of folic acid (FA) with native cyclodextrins was studied and this process was used for the comparison of 1H NMR, ITC and ESIMS for the evaluation of association constants. The stability increases in the series: α-cyclodextrin/FA < γ-cyclodextrin/FA < β-cyclodextrin/FA. 1H NMR and ITC gave comparable results in regard to association constant values, while results obtained for MS were considerably higher due to different interactions (electrostatic instead of hydrophobic) responsible for the stabilization of the complexes. The dimerization of FA in water was also studied, as well as its impact on the process of complexation with native cyclodextrins.

  4. A novel single fiber optical tweezers based on light-induced thermal effect

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Liu, Zhihai; Liang, Peibo; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

    2015-07-01

    We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10?m) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.

  5. Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer.

    PubMed

    Galinskiy, Ivan; Isaksson, Oscar; Salgado, Israel Rebolledo; Hautefeuille, Mathieu; Mehlig, Bernhard; Hanstorp, Dag

    2015-10-19

    We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counter-propagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets. PMID:26480368

  6. Measuring integrated cellular mechanical stress response at focal adhesions by optical tweezers

    NASA Astrophysics Data System (ADS)

    Bordeleau, François; Bessard, Judicael; Marceau, Normand; Sheng, Yunlong

    2011-09-01

    The ability of cells to sustain mechanical stress is largely modulated by the cytoskeleton. We present a new application of optical tweezers to study cell's mechanical properties. We trap a fibronectin-coated bead attached to an adherent H4II-EC3 rat hepatoma cell in order to apply the force to the cell surface membrane. The bead position corresponding to the cell's local mechanical response at focal adhesions is measured with a quadrant detector. We assessed the cell response by tracking the evolution of the equilibrium force for 40 cells selected at random and selected a temporal window to assess the cell initial force expression at focal adhesions. The mean value of the force within this time window over 40 randomly selected bead/cell bounds was 52.3 pN. Then, we assessed the responses of the cells with modulation of the cytoskeletons, namely the ubiquitous actin-microfilaments and microtubules, plus the differentiation-dependent keratin intermediate filaments. Notably, a destabilization of the first two networks led to around 50 and 30% reductions in the mean equilibrium forces, respectively, relative to untreated cells, whereas a loss of the third one yielded a 25% increase. The differences in the forces from untreated and treated cells are resolved by the optical tweezers experiment.

  7. Application of laser tweezers Raman spectroscopy techniques to the monitoring of single cell response to stimuli

    NASA Astrophysics Data System (ADS)

    Chan, James W.; Liu, Rui; Matthews, Dennis L.

    2012-06-01

    Laser tweezers Raman spectroscopy (LTRS) combines optical trapping with micro-Raman spectroscopy to enable label-free biochemical analysis of individual cells and small biological particles in suspension. The integration of the two technologies greatly simplifies the sample preparation and handling of suspension cells for spectroscopic analysis in physiologically meaningful conditions. In our group, LTRS has been used to study the effects of external perturbations, both chemical and mechanical, on the biochemistry of the cell. Single cell dynamics can be studied by performing longitudinal studies to continuously monitor the response of the cell as it interacts with its environment. The ability to carry out these measurements in-vitro makes LTRS an attractive tool for many biomedical applications. Here, we discuss the use of LTRS to study the response of cancer cells to chemotherapeutics and bacteria cells to antibiotics and show that the life cycle and apoptosis of the cells can be detected. These results show the promise of LTRS for drug discovery/screening, antibiotic susceptibility testing, and chemotherapy response monitoring applications. In separate experiments, we study the response of red blood cells to the mechanical forces imposed on the cell by the optical tweezers. A laser power dependent deoxygenation of the red blood cell in the single beam trap is reported. Normal, sickle cell, and fetal red blood cells have a different behavior that enables the discrimination of the cell types based on this mechanochemical response. These results show the potential utility of LTRS for diagnosing and studying red blood cell diseases.

  8. Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria

    NASA Astrophysics Data System (ADS)

    Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

    2011-04-01

    The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force from the laser tweezers were measured. Human (Homo sapiens), dog (Canis lupis familiaris) and drill (Mandrillus leucophaeus) sperm were treated with DiOC6(3) to measure the membrane potential in the mitochondria-rich sperm midpieces. Sperm from all three species exhibited an increase in fluorescence when treated with the DiOC6(3). When a cyanide inhibitor (CCCP) of aerobic respiration was applied, sperm of all three species exhibited a reduction in fluorescence to pre-dye levels. With respect to VCL and escape force, the CCCP had no effect on dog or human sperm, suggesting a major reliance upon anaerobic respiration (glycolysis) for ATP in these two species. Based on the preliminary study on drill sperm, CCCP caused a drop in the VCL, suggesting potential reliance on both glycolysis and aerobic respiration for motility. The results demonstrate that optical trapping in combination with DiOC6(3) is an effective way to study sperm motility and energetics.

  9. Analysis of cell mechanics in single vinculin-deficient cells using a magnetic tweezer

    NASA Technical Reports Server (NTRS)

    Alenghat, F. J.; Fabry, B.; Tsai, K. Y.; Goldmann, W. H.; Ingber, D. E.

    2000-01-01

    A magnetic tweezer was constructed to apply controlled tensional forces (10 pN to greater than 1 nN) to transmembrane receptors via bound ligand-coated microbeadswhile optically measuring lateral bead displacements within individual cells. Use of this system with wild-type F9 embryonic carcinoma cells and cells from a vinculin knockout mouse F9 Vin (-/-) revealed much larger differences in the stiffness of the transmembrane integrin linkages to the cytoskeleton than previously reported using related techniques that measured average mechanical properties of large cell populations. The mechanical properties measured varied widely among cells, exhibiting an approximately log-normal distribution. The median lateral bead displacement was 2-fold larger in F9 Vin (-/-) cells compared to wild-type cells whereas the arithmetic mean displacement only increased by 37%. We conclude that vinculin serves a greater mechanical role in cells than previously reported and that this magnetic tweezer device may be useful for probing the molecular basis of cell mechanics within single cells. Copyright 2000 Academic Press.

  10. Formation of an artificial blood vessel: adhesion force measurements with optical tweezers

    NASA Astrophysics Data System (ADS)

    Knoener, Gregor; Campbell, Julie H.; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina

    2004-10-01

    We are investigating the formation of a tissue capsule around a foreign body. This tissue capsule can be used as an autologous graft for the replacement of diseased blood vessels or for bypass surgery. The graft is grown in the peritoneal cavity of the recipient and the formation starts with the adhesion of cells to the foreign body. We identify the cell type and measure the adhesion of these cells to foreign materials using optical tweezers. Cell adhesion to macroscopic samples and microspheres is investigated. No difference in the adhesion force was measurable for polyethylene, silicon and Tygon on a scale accessible to optical tweezers. The density of adherent cells was found to vary strongly, being highest on polyethylene. The mean rupture forces for cell-microsphere adhesion ranged from 24 to 39 pN and changed upon preadsorption of bovine serum albumin. For plain microspheres, the highest mean rupture force was found for PMMA, which also showed the highest adhesion probability for the cell-microsphere interaction.

  11. A combined double-tweezers and wavelength-tunable laser nanosurgery microscope

    NASA Astrophysics Data System (ADS)

    Zhu, Qingyuan; Parsa, Shahab; Shi, Linda Z.; Harsono, Marcellinus; Wakida, Nicole M.; Berns, Michael W.

    2009-08-01

    In two previous studies we have conducted combined laser subcellular microsurgery and optical trapping on chromosomes in living cells1, 2. In the latter study we used two separate microscopes, one for the trap and one for the laser scissors, thus requiring that we move the cell specimen between microscopes and relocate the irradiated cells. In the former paper we combined the 1064 nm laser trap and the 532 nm laser scissors into one microscope. However, in neither study did we have multiple traps allowing for more flexibility in application of the trapping force. In the present paper we describe a combined laser scissors and tweezers microscope that (1) has two trapping beams (both moveable via rapid scanning mirrors (FSM- 300, Newport Corp.), (2) uses a short pulsed tunable 200 fs 710-990 nm Ti:Sapphire laser for laser microsurgery, and (3) also has the option to use a 337 nm 4 ns UV laser for subcellular surgery. The two laser tweezers and either of the laser ablation beams can be used in a cell surgery experiment. The system is integrated into the robotic-controlled RoboLase system3. Experiments on mitotic chromosomes of rat kangaroo PTK2 cells are described.

  12. A study of red blood cell deformability in diabetic retinopathy using optical tweezers

    NASA Astrophysics Data System (ADS)

    Smart, Thomas J.; Richards, Christopher J.; Bhatnagar, Rhythm; Pavesio, Carlos; Agrawal, Rupesh; Jones, Philip H.

    2015-08-01

    Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus (DM) in which high blood sugar levels cause swelling, leaking and occlusions in the blood vessels of the retina, often resulting in a loss of sight. The microvascular system requires red blood cells (RBCs) to undergo significant cellular deformation in order to pass through vessels whose diameters are significantly smaller than their own. There is evidence to suggest that DM impairs the deformability of RBCs, and this loss of deformability has been associated with diabetic kidney disease (or nephropathy) - another microvascular complication of DM. However, it remains unclear whether reduced deformability of RBCs correlates with the presence of DR. Here we present an investigation into the deformability of RBCs in patients with diabetic retinopathy using optical tweezers. To extract a value for the deformability of RBCs we use a dual-trap optical tweezers set-up to stretch individual RBCs. RBCs are trapped directly (i.e. without micro-bead handles), so rotate to assume a `side-on' orientation. Video microscopy is used to record the deformation events, and shape analysis software is used to determine parameters such as initial and maximum RBC length, allowing us to calculate the deformability for each RBC. A small decrease in deformability of diabetes cells subject to this stretching protocol is observed when compared to control cells. We also report on initial results on three dimensional imaging of individual RBCs using defocussing microscopy.

  13. In situ microparticle analysis of marine phytoplankton cells with infrared laser-based optical tweezers

    NASA Astrophysics Data System (ADS)

    Sonek, G. J.; Liu, Y.; Iturriaga, R. H.

    1995-11-01

    We describe the application of infrared optical tweezers to the in situ microparticle analysis of marine phytoplankton cells. A Nd:YAG laser (lambda=3D 1064 nm) trap is used to confine and manipulate single Nannochloris and Synechococcus cells in an enriched seawater medium while spectral fluorescence and Lorenz-Mie backscatter signals are simultaneously acquired under a variety of excitation and trapping conditions. Variations in the measured fluorescence intensities of chlorophyll a (Chl a) and phycoerythrin pigments in phytoplankton cells are observed. These variations are related, in part, to basic intrasample variability, but they also indicate that increasing ultraviolet-exposure time and infrared trapping power may have short-term effects on cellular physiology that are related to Chl a photobleaching and laser-induced heating, respectively. The use of optical tweezers to study the factors that affect marine cell physiology and the processes of absorption, scattering, and attenuation by individual cells, organisms, and particulate matter that contribute to optical closure on a microscopic scale are also described. (c)1995 Optical Society of America

  14. Simulation of heart infarction by laser microbeams and induction of arrhythmias by optical tweezers

    NASA Astrophysics Data System (ADS)

    Perner, Birgit; Monajembashi, Shamci; Rapp, Alexander; Wollweber, Leo; Greulich, Karl Otto

    2004-10-01

    Laser microbeam and optical tweezers were used for micromanipulation of a heart tissue model consisting of embryonic chicken cardiomyocytes and bibroblasts. Using the laser microbeam a would was created, i.e. a sort of artificial heart infarction was generated. The first steps of wound repair were observed by live cell imaging. A complete filling of teh would primarily by migrating fibroblasts but not by cardiomyocytes was detected 18 hours after wounding. In another set of experiments erythrocyte mediated force application (EMFA) by optical tweezers was applied for optomechanical manipulatoin of cardiomyocytes and fibroblasts. Here we demonstrate induction of dramatic distrubances of calcium waves in a group of synchronously beating cardiomyocytes by an optomechanical input that results in cellular deformation. Surprisingly, it was found that putatively non-excitable fibroblasts respond to this mechanical stress with calcium oscillations. The results reported here indicate that the induction of artificial heart infarction can provide insights into healing processes after mycardial injury. EMFA is capable to examine effects of myocardial overload and to provide important information about processes triggered by mechanical stress on the level of single or very few cells. As a perspective, the preseneted techniques may be used to study the influence of drugs on wound healing and coordination of beating in the heart.

  15. Natural user interface as a supplement of the holographic Raman tweezers

    NASA Astrophysics Data System (ADS)

    Tomori, Zoltan; Kanka, Jan; Kesa, Peter; Jakl, Petr; Sery, Mojmir; Bernatova, Silvie; Antalik, Marian; Zemnek, Pavel

    2014-09-01

    Holographic Raman tweezers (HRT) manipulates with microobjects by controlling the positions of multiple optical traps via the mouse or joystick. Several attempts have appeared recently to exploit touch tablets, 2D cameras or Kinect game console instead. We proposed a multimodal "Natural User Interface" (NUI) approach integrating hands tracking, gestures recognition, eye tracking and speech recognition. For this purpose we exploited "Leap Motion" and "MyGaze" low-cost sensors and a simple speech recognition program "Tazti". We developed own NUI software which processes signals from the sensors and sends the control commands to HRT which subsequently controls the positions of trapping beams, micropositioning stage and the acquisition system of Raman spectra. System allows various modes of operation proper for specific tasks. Virtual tools (called "pin" and "tweezers") serving for the manipulation with particles are displayed on the transparent "overlay" window above the live camera image. Eye tracker identifies the position of the observed particle and uses it for the autofocus. Laser trap manipulation navigated by the dominant hand can be combined with the gestures recognition of the secondary hand. Speech commands recognition is useful if both hands are busy. Proposed methods make manual control of HRT more efficient and they are also a good platform for its future semi-automated and fully automated work.

  16. Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering

    SciTech Connect

    Ott, Dino; Oddershede, Lene B.; Reihani, S. Nader S.

    2014-05-15

    In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts.

  17. Laser scanning confocal microscopy and laser tweezers based experiments to understand dentine-bacteria interactions

    NASA Astrophysics Data System (ADS)

    Peng, Sum Chee; Mohanty, Samarendra; Gupta, P. K.; Kishen, Anil

    2007-02-01

    Failure of endodontic treatment is commonly due to Enterococcal infection. In this study influence of chemical treatments of type-I collagen membrane by chemical agents commonly used in endodontic treatment on Enterococcus faecalis cell adherence was evaluated. In order to determine the change in number of adhering bacteria after chemical treatment, confocal laser scanning microscopy was used. For this, overnight culture of E faecalis in All Culture broth was applied to chemically treated type-I collagen membrane. It was found that Ca(OH) II treated groups had statistically significant (p value=0.05) increase in population of bacteria adherence. The change in adhesion force between bacteria and collagen was determined by using optical tweezers (1064 nm). For this experiment, Type-I collagen membrane was soaked for 5 mins in a media that contained 50% all culture media and 50% saturated Ca(OH) II . The membrane was spread on the coverslip, on which diluted bacterial suspension was added. The force of laser tweezers on the bacteria was estimated at different trap power levels using viscous drag method and trapping stiffness was calculated using Equipartition theorem method. Presence of Ca(OH) II was found to increase the cell-substrate adherence force from 0.38pN to >2.1pN. Together, these experiments show that it was highly probable that the increase in adherence to collagen was due to a stronger adhesion in the presence of Ca (OH) II.

  18. Application of optical tweezers and excimer laser to study protoplast fusion

    NASA Astrophysics Data System (ADS)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

  19. Holographic optical tweezers: microassembling of shape-complementary 2PP building blocks

    NASA Astrophysics Data System (ADS)

    Ksouri, Sarah Isabelle; Mattern, Manuel; Khler, Jannis; Aumann, Andreas; Zyla, Gordon; Ostendorf, Andreas

    2014-09-01

    Based on an ongoing trend in miniaturization and due to the increased complexity in MEMS-technology new methods of assembly need to be developed. Recent developments show that particularly optical forces are suitable to meet the requirements. The unique advantages of optical tweezers (OT) are attractive due to their contactless and precise manipulation forces. Spherical as well as non-spherical shaped pre-forms can already be assembled arbitrarily by using appropriate beam profiles generated by a spatial light modulator (SLM), resulting in a so called holographic optical tweezer (HOT) setup. For the fabrication of shape-complementary pre-forms, a two-photon-polymerization (2PP) process is implemented. The purpose of the process combination of 2PP and HOT is the development of an optical microprocessing platform for assembling arbitrary building blocks. Here, the optimization of the 2PP and HOT processes is described in order to allow the fabrication and 3D assembling of interlocking components. Results include the analysis of the dependence of low and high qualities of 2PP microstructures and their manufacturing accuracy for further HOT assembling processes. Besides, the applied detachable interlocking connections of the 2PP building blocks are visualized by an application example. In the long-term a full optical assembly method without applying any mechanical forces can thus be realized.

  20. Counter-propagating dual-trap optical tweezers based on linear momentum conservation

    SciTech Connect

    Ribezzi-Crivellari, M.; Huguet, J. M.; Ritort, F.

    2013-04-15

    We present a dual-trap optical tweezers setup which directly measures forces using linear momentum conservation. The setup uses a counter-propagating geometry, which allows momentum measurement on each beam separately. The experimental advantages of this setup include low drift due to all-optical manipulation, and a robust calibration (independent of the features of the trapped object or buffer medium) due to the force measurement method. Although this design does not attain the high-resolution of some co-propagating setups, we show that it can be used to perform different single molecule measurements: fluctuation-based molecular stiffness characterization at different forces and hopping experiments on molecular hairpins. Remarkably, in our setup it is possible to manipulate very short tethers (such as molecular hairpins with short handles) down to the limit where beads are almost in contact. The setup is used to illustrate a novel method for measuring the stiffness of optical traps and tethers on the basis of equilibrium force fluctuations, i.e., without the need of measuring the force vs molecular extension curve. This method is of general interest for dual trap optical tweezers setups and can be extended to setups which do not directly measure forces.

  1. A modular assembling platform for manufacturing of microsystems by optical tweezers

    NASA Astrophysics Data System (ADS)

    Ksouri, Sarah Isabelle; Aumann, Andreas; Ghadiri, Reza; Prfer, Michael; Baer, Sebastian; Ostendorf, Andreas

    2013-09-01

    Due to the increased complexity in terms of materials and geometries for microsystems new assembling techniques are required. Assembling techniques from the semiconductor industry are often very specific and cannot fulfill all specifications in more complex microsystems. Therefore, holographic optical tweezers are applied to manipulate structures in micrometer range with highest flexibility and precision. As is well known non-spherical assemblies can be trapped and controlled by laser light and assembled with an additional light modulator application, where the incident laser beam is rearranged into flexible light patterns in order to generate multiple spots. The complementary building blocks are generated by a two-photon-polymerization process. The possibilities of manufacturing arbitrary microstructures and the potential of optical tweezers lead to the idea of combining manufacturing techniques with manipulation processes to "microrobotic" processes. This work presents the manipulation of generated complex microstructures with optical tools as well as a storage solution for 2PP assemblies. A sample holder has been developed for the manual feeding of 2PP building blocks. Furthermore, a modular assembling platform has been constructed for an `all-in-one' 2PP manufacturing process as a dedicated storage system. The long-term objective is the automation process of feeding and storage of several different 2PP micro-assemblies to realize an automated assembly process.

  2. Optical tweezers and cell biomechanics in macro- and nano-scale

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexander A.; Makropoulou, Mersini; Spyratou, Ellas

    2013-03-01

    The mechanical properties of cells, as well as their dysfunction, have been implicated in many aspects of human physiology and patho-physiology. Hence, new biophysical techniques, as optical tweezers, are of great importance for biomechanical measurements in both cells and cell simulators (e.g. liposomes). Liposomes are used, among other applications, as drug delivery nanosystems in cancer therapy. In this work, experimental measurements of the optical forces exerted by line optical tweezers on trapped cells (erythrocytes) and liposomes, using the dielectrophoresis method for calibration, are presented. Folding and elongation of trapped red blood cells was observed, in the direction of the electric field of incident beam, while, upon removal of the optical trap, the red blood cells were observed to unfold to their original biconcave shape. By measuring the folding and unfolding times, membrane elasticity properties such as bending modulus were estimated. Shear and bending modulus of liposomes were also estimated by measuring the liposome deformations, induced by optical forces along the beam long axis. The optical force is quasi-linearly increased with the increase of liposome diameter. In the elasticity regime, when the laser was turned off, the liposome acquired gradually its initial shape without any hysteresis.

  3. Probing Mechanical Properties of Jurkat Cells under the Effect of ART Using Oscillating Optical Tweezers

    PubMed Central

    2015-01-01

    Acute lymphoid leukemia is a common type of blood cancer and chemotherapy is the initial treatment of choice. Quantifying the effect of a chemotherapeutic drug at the cellular level plays an important role in the process of the treatment. In this study, an oscillating optical tweezer was employed to characterize the frequency-dependent mechanical properties of Jurkat cells exposed to the chemotherapeutic agent, artesunate (ART). A motion equation for a bead bound to a cell was applied to describe the mechanical characteristics of the cell cytoskeleton. By comparing between the modeling results and experimental results from the optical tweezer, the stiffness and viscosity of the Jurkat cells before and after the ART treatment were obtained. The results demonstrate a weak power-law dependency of cell stiffness with frequency. Furthermore, the stiffness and viscosity were increased after the treatment. Therefore, the cytoskeleton cell stiffness as the well as power-law coefficient can provide a useful insight into the chemo-mechanical relationship of drug treated cancer cells and may serve as another tool for evaluating therapeutic performance quantitatively. PMID:25928073

  4. Measuring integrated cellular mechanical stress response at focal adhesions by optical tweezers.

    PubMed

    Bordeleau, Franois; Bessard, Judicael; Marceau, Normand; Sheng, Yunlong

    2011-09-01

    The ability of cells to sustain mechanical stress is largely modulated by the cytoskeleton. We present a new application of optical tweezers to study cell's mechanical properties. We trap a fibronectin-coated bead attached to an adherent H4II-EC3 rat hepatoma cell in order to apply the force to the cell surface membrane. The bead position corresponding to the cell's local mechanical response at focal adhesions is measured with a quadrant detector. We assessed the cell response by tracking the evolution of the equilibrium force for 40 cells selected at random and selected a temporal window to assess the cell initial force expression at focal adhesions. The mean value of the force within this time window over 40 randomly selected bead?cell bounds was 52.3 pN. Then, we assessed the responses of the cells with modulation of the cytoskeletons, namely the ubiquitous actin-microfilaments and microtubules, plus the differentiation-dependent keratin intermediate filaments. Notably, a destabilization of the first two networks led to around 50 and 30% reductions in the mean equilibrium forces, respectively, relative to untreated cells, whereas a loss of the third one yielded a 25% increase. The differences in the forces from untreated and treated cells are resolved by the optical tweezers experiment. PMID:21950914

  5. Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

    2012-09-01

    Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level.

  6. Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis

    NASA Astrophysics Data System (ADS)

    Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

    2006-08-01

    The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

  7. Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments

    PubMed Central

    Janissen, Richard; Berghuis, Bojk A.; Dulin, David; Wink, Max; vanLaar, Theo; Dekker, Nynke H.

    2014-01-01

    Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy. PMID:25140010

  8. In situ calibrating optical tweezers with sinusoidal-wave drag force method

    NASA Astrophysics Data System (ADS)

    Li, Di; Zhou, Jin-Hua; Hu, Xin-Yao; Zhong, Min-Cheng; Gong, Lei; Wang, Zi-Qiang; Wang, Hao-Wei; Li, Yin-Mei

    2015-11-01

    We introduce a corrected sinusoidal-wave drag force method (SDFM) into optical tweezers to calibrate the trapping stiffness of the optical trap and conversion factor (CF) of photodetectors. First, the theoretical analysis and experimental result demonstrate that the correction of SDFM is necessary, especially the error of no correction is up to 11.25% for a bead of 5 ?m in diameter. Second, the simulation results demonstrate that the SDFM has a better performance in the calibration of optical tweezers than the triangular-wave drag force method (TDFM) and power spectrum density method (PSDM) at the same signal-to-noise ratio or trapping stiffness. Third, in experiments, the experimental standard deviations of calibration of trapping stiffness and CF with the SDFM are about less than 50% of TDFM and PSDM especially at low laser power. Finally, the experiments of stretching DNA verify that the in situ calibration with the SDFM improves the measurement stability and accuracy. Project supported by the National Natural Science Foundation of China (Grant Nos.11302220, 11374292, and 31100555) and the National Basic Research Program of China (Grant No.2011CB910402).

  9. Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells

    SciTech Connect

    Chang Yiren; Hsu Long; Chi Sien

    2006-06-01

    Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system.

  10. Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy

    PubMed Central

    Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit

    2015-01-01

    Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase–polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase–alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the observed different affinities determined for AlgE4-polymannuronic acid (poly-M) and AlgE4-polyalternating alginate (poly-MG) macromolecular pairs these data give important contribution to the growing understanding of the mechanisms underlying the processive mode of these enzymes. PMID:26496653

  11. Accurate measurement of force and displacement with optical tweezers using DNA molecules as metrology standards.

    PubMed

    delToro, Damian; Smith, Douglas E

    2014-04-01

    Optical tweezers facilitate measurement of piconewton-level forces and nanometer-level displacements and have broad applications in biophysics and soft matter physics research. We have shown previously that DNA molecules can be used as metrology standards to define such measurements. Force-extension measurements on two DNA molecules of different lengths can be used to determine four necessary measurement parameters. Here, we show that the accuracy of determining these parameters can be improved by more than 7-fold by incorporating measurements of the DNA overstretching transition and using a multi-step data analysis procedure. This method results in very robust and precise fitting of DNA force-extension measurements to the worm-like chain model. We verify the accuracy through independent measurements of DNA stretching, DNA unzipping, and microsphere contact forces. PMID:25316922

  12. Accurate measurement of force and displacement with optical tweezers using DNA molecules as metrology standards

    NASA Astrophysics Data System (ADS)

    delToro, Damian; Smith, Douglas E.

    2014-04-01

    Optical tweezers facilitate measurement of piconewton-level forces and nanometer-level displacements and have broad applications in biophysics and soft matter physics research. We have shown previously that DNA molecules can be used as metrology standards to define such measurements. Force-extension measurements on two DNA molecules of different lengths can be used to determine four necessary measurement parameters. Here, we show that the accuracy of determining these parameters can be improved by more than 7-fold by incorporating measurements of the DNA overstretching transition and using a multi-step data analysis procedure. This method results in very robust and precise fitting of DNA force-extension measurements to the worm-like chain model. We verify the accuracy through independent measurements of DNA stretching, DNA unzipping, and microsphere contact forces.

  13. Freely orbiting magnetic tweezers to directly monitor changes in the twist of nucleic acids

    PubMed Central

    Lipfert, Jan; Wiggin, Matthew; Kerssemakers, Jacob W.J.; Pedaci, Francesco; Dekker, Nynke H.

    2011-01-01

    The double-stranded nature of DNA links its replication, transcription and repair to rotational motion and torsional strain. Magnetic tweezers (MT) are a powerful single-molecule technique to apply both forces and torques to individual DNA or RNA molecules. However, conventional MT do not track rotational motion directly and constrain the free rotation of the nucleic acid tether. Here we present freely orbiting MT (FOMT) that allow the measurement of equilibrium fluctuations and changes in the twist of tethered nucleic acid molecules. Using a precisely aligned vertically oriented magnetic field, FOMT enable tracking of the rotation angle from straight forward (x,y)-position tracking and permits the application of calibrated stretching forces, without biasing the tether's free rotation. We utilize FOMT to measure the force-dependent torsional stiffness of DNA from equilibrium rotational fluctuations and to follow the assembly of recombination protein A filaments on DNA. PMID:21863006

  14. Evaluating cell matrix mechanics using an integrated nonlinear optical tweezer-confocal imaging system

    NASA Astrophysics Data System (ADS)

    Peng, Berney; Alonzo, Carlo A. C.; Xia, Lawrence; Speroni, Lucia; Georgakoudi, Irene; Soto, Ana M.; Sonnenschein, Carlos; Cronin-Golomb, Mark

    2013-09-01

    Biomechanics plays a central role in breast epithelial morphogenesis. In this study we have used 3D cultures in which normal breast epithelial cells are able to organize into rounded acini and tubular ducts, the main structures found in the breast tissue. We have identified fiber organization as a main determinant of ductal organization. While bulk rheological properties of the matrix seem to play a negligible role in determining the proportion of acini versus ducts, local changes may be pivotal in shape determination. As such, the ability to make microscale rheology measurements coupled with simultaneous optical imaging in 3D cultures can be critical to assess the biomechanical factors underlying epithelial morphogenesis. This paper describes the inclusion of optical tweezers based microrheology in a microscope that had been designed for nonlinear optical imaging of collagen networks in ECM. We propose two microrheology methods and show preliminary results using a gelatin hydrogel and collagen/Matrigel 3D cultures containing mammary gland epithelial cells.

  15. Interrogating the activities of conformational deformed enzyme by single-molecule fluorescence-magnetic tweezers microscopy.

    PubMed

    Guo, Qing; He, Yufan; Lu, H Peter

    2015-11-10

    Characterizing the impact of fluctuating enzyme conformation on enzymatic activity is critical in understanding the structure-function relationship and enzymatic reaction dynamics. Different from studying enzyme conformations under a denaturing condition, it is highly informative to manipulate the conformation of an enzyme under an enzymatic reaction condition while monitoring the real-time enzymatic activity changes simultaneously. By perturbing conformation of horseradish peroxidase (HRP) molecules using our home-developed single-molecule total internal reflection magnetic tweezers, we successfully manipulated the enzymatic conformation and probed the enzymatic activity changes of HRP in a catalyzed H2O2-amplex red reaction. We also observed a significant tolerance of the enzyme activity to the enzyme conformational perturbation. Our results provide a further understanding of the relation between enzyme behavior and enzymatic conformational fluctuation, enzyme-substrate interactions, enzyme-substrate active complex formation, and protein folding-binding interactions. PMID:26512103

  16. Double nanohole optical tweezers visualize protein p53 suppressing unzipping of single DNA-hairpins.

    PubMed

    Kotnala, Abhay; Gordon, Reuven

    2014-06-01

    Here we report on the use of double-nanohole (DNH) optical tweezers as a label-free and free-solution single-molecule probe for protein-DNA interactions. Using this approach, we demonstrate the unzipping of individual 10 base pair DNA-hairpins, and quantify how tumor suppressor p53 protein delays the unzipping. From the Arrhenius behavior, we find the energy barrier to unzipping introduced by p53 to be 2 10(-20) J, whereas cys135ser mutant p53 does not show suppression of unzipping, which gives clues to its functional inability to suppress tumor growth. This transformative approach to single molecule analysis allows for ultra-sensitive detection and quantification of protein-DNA interactions to revolutionize the fight against genetic diseases. PMID:24940547

  17. Extended linear detection range for optical tweezers using image-plane detection scheme

    NASA Astrophysics Data System (ADS)

    Hajizadeh, Faegheh; Masoumeh Mousavi, S.; Khaksar, Zeinab S.; Reihani, S. Nader S.

    2014-10-01

    Ability to measure pico- and femto-Newton range forces using optical tweezers (OT) strongly relies on the sensitivity of its detection system. We show that the commonly used back-focal-plane detection method provides a linear response range which is shorter than that of the restoring force of OT for large beads. This limits measurable force range of OT. We show, both theoretically and experimentally, that utilizing a second laser beam for tracking could solve the problem. We also propose a new detection scheme in which the quadrant photodiode is positioned at the plane optically conjugate to the object plane (image plane). This method solves the problem without need for a second laser beam for the bead sizes that are commonly used in force spectroscopy applications of OT, such as biopolymer stretching.

  18. Mechanism of termination of bacteriophage DNA packaging investigated with optical tweezers

    NASA Astrophysics Data System (ADS)

    delToro, Damian J.; Smith, Douglas E.

    2012-10-01

    The genomes of many dsDNA viruses are replicated by a mechanism that produces a long concatemer of multiple genomes. These viruses utilize multifunctional molecular motor complexes referred to as "terminases" that can excise a unit genome length of DNA and package it into preformed viral shells. Remarkably, the terminase motor can initiate packaging at the appropriate start point, translocate DNA, sense when a sufficient length has been packaged, and then switch into a mode where it arrests and cleaves the DNA to release a filled virus particle. We have recently developed an improved method to measure single phage lambda DNA packaging using dual-trap optical tweezers and pre-stalled motor-DNA-procapsid complexes. We are applying this method to test proposed mechanisms for the sensor that triggers termination; specifically a velocity-monitor model vs. energy-monitor model vs. capsid-filling monitor model.

  19. Mechanical tweezer action by self-tightening knots in surfactant nanotubes

    PubMed Central

    Lobovkina, Tatsiana; Dommersnes, Paul; Joanny, Jean-Francois; Bassereau, Patricia; Karlsson, Mattias; Orwar, Owe

    2004-01-01

    Entanglements and trefoil knots on surfactant nanotubes in the liquid phase were produced by a combination of network self-organization and micromanipulation. The resulting knots are self-tightening, and the tightening is driven by minimization of surface free energy of the surfactant membrane material. The formation of the knot and the steady-state knot at quasi-equilibrium can be directly followed and localized by using fluorescence microscopy. Knots on nanotubes can be used as nanoscale mechanical tweezers for trapping and manipulation of single nano- and micrometer-sized high-aspect ratio objects. Furthermore, we demonstrate that by controlling the surface tension, objects captured by a knot can be transported along given trajectories defined by the nanotube axes. PMID:15141081

  20. Raman tweezers provide the fingerprint of cells supporting the late stages of KSHV reactivation.

    PubMed

    Dyson, Ossie F; Ford, Patrick W; Chen, De; Li, Yong-Qing; Akula, Shaw M

    2009-08-01

    Kaposi's sarcoma-associated herpesvirus (KSHV) has both latent and lytic phases of replication. The molecular switch that triggers a reactivation is still unclear. Cells from the S phase of the cell cycle provide apt conditions for an active reactivation. In order to specifically delineate the Raman spectra of cells supporting KSHV reactivation, we followed a novel approach where cells were sorted based on the state of infection (latent versus lytic) by a flow cytometer and then analysed by the Raman tweezers. The Raman bands at 785, 813, 830, 1095 and 1128 cm(-1) are specifically altered in cells supporting KSHV reactivation. These five peaks make up the Raman fingerprint of cells supporting KSHV reactivation. The physiological relevance of the changes in these peaks with respect to KSHV reactivation is discussed in the following report. PMID:18752634

  1. Observation of a Single-Beam Gradient Force Acoustical Trap for Elastic Particles: Acoustical Tweezers

    NASA Astrophysics Data System (ADS)

    Baresch, Diego; Thomas, Jean-Louis; Marchiano, Régis

    2016-01-01

    We demonstrate the trapping of elastic particles by the large gradient force of a single acoustical beam in three dimensions. Acoustical tweezers can push, pull and accurately control both the position and the forces exerted on a unique particle. Forces in excess of 1 micronewton were exerted on polystyrene beads in the submillimeter range. A beam intensity less than 50 W /cm2 was required, ensuring damage-free trapping conditions. The large spectrum of frequencies covered by coherent ultrasonic sources provides a wide variety of manipulation possibilities from macroscopic to microscopic length scales. Our observations could open the way to important applications, in particular, in biology and biophysics at the cellular scale and for the design of acoustical machines in microfluidic environments.

  2. 3D Manipulation of Protein Microcrystals with Optical Tweezers for X-ray Crystallography

    NASA Astrophysics Data System (ADS)

    Hikima, T.; Hashimoto, K.; Murakami, H.; Ueno, G.; Kawano, Y.; Hirata, K.; Hasegawa, K.; Kumasaka, T.; Yamamoto, M.

    2013-03-01

    In some synchrotron facilities such as SPring-8, X-ray microbeams have been utilized for protein crystallography, allowing users to collect diffraction data from a protein microcrystal. Usually, a protein crystal is picked up manually from a crystallization droplet. However it is very difficult to manipulate the protein microcrystals which are very small and fragile against a shock and changes of temperature and solvent condition. We have been developing an automatic system applying the optical tweezers with two lensed fiber probes to manipulate the fragile protein microcrystal. The system succeeded in trapping a crystal and levitating it onto the cryoloop in the solvent. X-ray diffraction measurement for the manipulated protein microcrystals indicated that laser irradiation and trap with 1064nm wavelength hardly affected the result of X-ray structural analysis.

  3. Calibrating oscillation response of a piezo-stage using optical tweezers.

    PubMed

    Zhou, Jin-Hua; Li, Di; Hu, Xin-Yao; Zhong, Min-Cheng; Wang, Zi-Qiang; Gong, Lei; Liu, Wei-Wei; Li, Yin-Mei

    2015-09-21

    In optical tweezers, a piezo-stage (PZT) is widely used to precisely position samples for force clamp, calibrating optical trap and stretching DNA. For a trapped bead in solution, the oscillation response of PZT is vital for all kinds of applications. A coupling ratio, actual amplitude to nominal amplitude, can be calibrated by power spectral density during sinusoidal oscillations. With oscillation frequency increasing, coupling ratio decreases in both x- and y-directions, which is also confirmed by the calibration with light scattering of scanning two aligned beads on slide. Those oscillation responses are related with deformability of chamber and the intrinsic characteristics of PZT. If we take nominal amplitude as actual amplitude for sinusoidal oscillations at 50 Hz, the amplitude is overestimated ~2 times in x-direction and ~3 times in y-direction. That will lead to huge errors for subsequent calibrations. PMID:26406617

  4. Interrogating the activities of conformational deformed enzyme by single-molecule fluorescence-magnetic tweezers microscopy

    PubMed Central

    Guo, Qing; He, Yufan; Lu, H. Peter

    2015-01-01

    Characterizing the impact of fluctuating enzyme conformation on enzymatic activity is critical in understanding the structurefunction relationship and enzymatic reaction dynamics. Different from studying enzyme conformations under a denaturing condition, it is highly informative to manipulate the conformation of an enzyme under an enzymatic reaction condition while monitoring the real-time enzymatic activity changes simultaneously. By perturbing conformation of horseradish peroxidase (HRP) molecules using our home-developed single-molecule total internal reflection magnetic tweezers, we successfully manipulated the enzymatic conformation and probed the enzymatic activity changes of HRP in a catalyzed H2O2amplex red reaction. We also observed a significant tolerance of the enzyme activity to the enzyme conformational perturbation. Our results provide a further understanding of the relation between enzyme behavior and enzymatic conformational fluctuation, enzymesubstrate interactions, enzymesubstrate active complex formation, and protein foldingbinding interactions. PMID:26512103

  5. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-01

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  6. Modeling of a single red blood cell thermal reaction exposed to infrared laser tweezers

    NASA Astrophysics Data System (ADS)

    Seteikin, A.; Krasnikov, I.; Bernhardt, I.

    2013-02-01

    Continuous-wave laser micro-beams are generally used as diagnostic tools in laser scanning microscopes or in the case of near-infrared (NIR) micro-beams, as optical traps for cell manipulation and force characterization. Because single beam traps are created with objectives of high numerical aperture, typical trapping intensities and photon flux densities are in the order of 106 W/cm2 and 103 cm-2s-1, respectively. The main idea of our theoretical study was to investigate the thermal reaction of RBCs irradiated by laser micro-beam. The study is supported by the fact that many experiments have been carried out with RBCs in laser NIR tweezers. In the present work it has been identified that the laser affects a RBC with a density of absorbed energy at approximately 107 J/cm3, which causes a temperature rise in the cell of about 7 - 12 C.

  7. Optical tweezers as a force sensor for separating dielectrophoresis and AC electroosmosis forces

    NASA Astrophysics Data System (ADS)

    Wang, Jingyu; Ou-Yang, H. Daniel

    2010-08-01

    Forces experienced by colloidal particles in an AC electric field such as dielectrophoresis (DEP) and AC electro-osmosis (ACEO) have been widely investigated for their application in microfluidic devices. In order to provide a more complete theoretical basis for such AC electrokinetic mechanisms, we propose a method to quantify the two forces upon one individual particle using optical tweezers as a force transducer and lock-in phase sensitive detection technique to allow high selectivity. Using this method, we isolated the ACEO force from the DEP force for charged polystyrene sphere in deionized (DI) water. ACEO free DEP crossover frequencies and a comprehensive 2D-mapping of the frequency dependent ACEO forces are presented in this paper.

  8. Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film

    PubMed Central

    Zhu, Benpeng; Xu, Jiong; Li, Ying; Wang, Tian; Xiong, Ke; Lee, Changyang; Yang, Xiaofei; Shiiba, Michihisa; Takeuchi, Shinichi; Zhou, Qifa; Shung, K. Kirk

    2016-01-01

    Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d33 = 270pC/N and kt = 0.51) was employed for SBAT applications and a press-focusing technology was introduced. The obtained SBAT, acting at an operational frequency of 50MHz, a low f-number (∼0.9), demonstrated the capability to trap and manipulate a micro-particle sized 10μm in the distilled water. These results suggest that such a device has great potential as a manipulator for a wide range of biomedical and chemical science applications. PMID:27014504

  9. Composite SERS-based satellites navigated by optical tweezers for single cell analysis.

    PubMed

    Stetciura, Inna Y; Yashchenok, Alexey; Masic, Admir; Lyubin, Evgeny V; Inozemtseva, Olga A; Drozdova, Maria G; Markvichova, Elena A; Khlebtsov, Boris N; Fedyanin, Andrey A; Sukhorukov, Gleb B; Gorin, Dmitry A; Volodkin, Dmitry

    2015-08-01

    Herein, we have designed composite SERS-active micro-satellites, which exhibit a dual role: (i) effective probes for determining cellular composition and (ii) optically movable and easily detectable markers. The satellites were synthesized by the layer-by-layer assisted decoration of silica microparticles with metal (gold or silver) nanoparticles and astralen in order to ensure satellite SERS-based microenvironment probing and satellite recognition, respectively. A combination of optical tweezers and Raman spectroscopy can be used to navigate the satellites to a certain cellular compartment and probe the intracellular composition following cellular uptake. In the future, this developed approach may serve as a tool for single cell analysis with nanometer precision due to the multilayer surface design, focusing on both extracellular and intracellular studies. PMID:26040199

  10. Haptic guidance for improved task performance in steering microparticles with optical tweezers.

    PubMed

    Basdogan, Cagatay; Kiraz, Alper; Bukusoglu, Ibrahim; Varol, Ayd?n; Do?anay, Sultan

    2007-09-01

    We report the manipulation of 4-5 mum diameter polymer microspheres floating in water using optical tweezers (OT) and a haptic device (i.e. force-reflecting robotic arm). Trapped microspheres are steered using the end-effector of a haptic device that is virtually coupled to an XYZ piezo-scanner controlling the movements of the fluid bed. To help with the manipulations, we first calculate a collision-free path for the particle and then display artificial guidance forces to the user through the haptic device to keep him/her on this path during steering. Experiments conducted with 8 subjects show almost two-fold improvements in the average path error and average speed under the guidance of haptic feedback. PMID:19547521

  11. Rapid feedback control and stabilization of an optical tweezers with a budget microcontroller

    NASA Astrophysics Data System (ADS)

    Nino, Daniel; Wang, Haowei; Milstein, Joshua N.

    2014-09-01

    Laboratories ranging the scientific disciplines employ feedback control to regulate variables within their experiments, from the flow of liquids within a microfluidic device to the temperature within a cell incubator. We have built an inexpensive, yet fast and rapidly deployed, feedback control system that is straightforward and flexible to implement from a commercially available Arduino Due microcontroller. This is in comparison with the complex, time-consuming and often expensive electronics that are commonly implemented. As an example of its utility, we apply our feedback controller to the task of stabilizing the main trapping laser of an optical tweezers. The feedback controller, which is inexpensive yet fast and rapidly deployed, was implemented from hacking an open source Arduino Due microcontroller. Our microcontroller based feedback system can stabilize the laser intensity to a few tenths of a per cent at 200 kHz, which is an order of magnitude better than the laser's base specifications, illustrating the utility of these devices.

  12. Measurement of PLGA-NP interaction with single smooth muscle cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Gu, Ling; Mondal, Argha; Homayoni, Homa; Nguyen, Kytai; Mohanty, Samarendra

    2012-10-01

    For intervention of cardiovascular diseases, biodegradable and biocompatible, poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP) are emerging as agents of choice for controlled and targeted drug delivery. Therefore development of PLGA-NP with optimal physico-chemical properties will allow efficient binding and thus delivery of drug to targeted cells under various patho-physiological conditions. The force kinetics and its dependence on size of the NPs will be crucial for designing the NPs. Since optical tweezers allow non-contact, highly sensitive force measurement with high spatial and temporal resolution, we utilized it for studying interaction forces between magnetic PLGA nanoparticles with smooth muscle cells (SMC). In order to investigate effect of size, interaction force for 200 to 1100nm PLGA NP was measured. For similar interaction duration, the force was found to be higher with increase in size. The rupture force was found to depend on time of interaction of SMC with NPs.

  13. Optical tweezers assisted imaging of the Z-ring in Escherichia coli: measuring its radial width

    NASA Astrophysics Data System (ADS)

    Carmon, G.; Kumar, P.; Feingold, M.

    2014-01-01

    Using single-beam, oscillating optical tweezers we can trap and rotate rod-shaped bacterial cells with respect to the optical axis. This technique allows imaging fluorescently labeled three-dimensional sub-cellular structures from different, optimized viewpoints. To illustrate our method we measure D, the radial width of the Z-ring in unconstricted Escherichia coli. We use cells that express FtsZ-GFP and have their cytoplasmic membrane stained with FM4-64. In a vertically oriented cell, both the Z-ring and the cytoplasmic membrane images appear as symmetric circular structures that lend themselves to quantitative analysis. We found that D ≅ 100 nm, much larger than expected.

  14. The efficiency of fiber optical tweezers for cell manipulation using distinct fabrication methods

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Soppera, O.; Viegas, J.; Guerreiro, A.; Jorge, P. A. S.

    2015-03-01

    In this work, the trapping efficiency of new fiber optical tweezers structures fabricated using photo polymerization and focused ion beam milling techniques is evaluated. The first fabrication methods may present limited capabilities on the tailoring of the structures, and therefore limited operation features. On the other hand, with focused ion beam milling a vast myriad of structures may be accurately fabricated, and contrarily to conventional fabrication methods, more specialized manipulation tools can be developed. In this regard, the performance of FOT for the trapping of yeast cells using spherical lenses (photo polymerization) and spiral phase lenses (FIB) will be presented. In addition, finite difference time domain (FDTD) simulations of the full vectorial optical propagation through the designed structures and the corresponding calculation of the optical forces are presented and different designs are evaluated.

  15. Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers

    PubMed Central

    Samadi, Akbar; Zhang, Chensong; Chen, Joseph; Reihani, S. N. S.; Chen, Zhigang

    2014-01-01

    We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the killing time of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision. PMID:25657879

  16. Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers.

    PubMed

    Samadi, Akbar; Zhang, Chensong; Chen, Joseph; Reihani, S N S; Chen, Zhigang

    2015-01-01

    We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the "killing time" of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision. PMID:25657879

  17. Analysis of the influence of manufacturing and alignment related errors on an optical tweezer system

    NASA Astrophysics Data System (ADS)

    Kampmann, R.; Sinzinger, S.

    2014-12-01

    In this work we present the design process as well as experimental results of an optical system for trapping particles in air. For positioning applications of micro-sized objects onto a glass wafer we developed a highly efficient optical tweezer. The focus of this paper is the iterative design process where we combine classical optics design software with a ray optics based force simulation tool. Thus we can find the best compromise which matches the optical systems restrictions with stable trapping conditions. Furthermore we analyze the influence of manufacturing related tolerances and errors in the alignment process of the optical elements on the optical forces. We present the design procedure for the necessary optical elements as well as experimental results for the aligned system.

  18. Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film

    NASA Astrophysics Data System (ADS)

    Zhu, Benpeng; Xu, Jiong; Li, Ying; Wang, Tian; Xiong, Ke; Lee, Changyang; Yang, Xiaofei; Shiiba, Michihisa; Takeuchi, Shinichi; Zhou, Qifa; Shung, K. Kirk

    2016-03-01

    Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d33 = 270pC/N and kt = 0.51) was employed for SBAT applications and a press-focusing technology was introduced. The obtained SBAT, acting at an operational frequency of 50MHz, a low f-number (˜0.9), demonstrated the capability to trap and manipulate a micro-particle sized 10μm in the distilled water. These results suggest that such a device has great potential as a manipulator for a wide range of biomedical and chemical science applications.

  19. Optoelectronic tweezers for the measurement of the relative stiffness of erythrocytes

    NASA Astrophysics Data System (ADS)

    Neale, Steven L.; Mody, Nimesh; Selman, Colin; Cooper, Jonathan M.

    2012-10-01

    In this paper we describe the first use of Optoelectronic Tweezers (OET), an optically controlled micromanipulation method, to measure the relative stiffness of erythrocytes in mice. Cell stiffness is an important measure of cell health and in the case of erythrocytes, the most elastic cells in the body, an increase in cell stiffness can indicate pathologies such as type II diabetes mellitus or hypertension (high blood pressure). OET uses a photoconductive device to convert an optical pattern into and electrical pattern. The electrical fields will create a dipole within any polarisable particles in the device, such as cells, and non-uniformities of the field can be used to place unequal forces onto each side of the dipole thus moving the particle. In areas of the device where there are no field gradients, areas of constant illumination, the force on each side of the dipole will be equal, keeping the cell stationary, but as there are opposing forces on each side of the cell it will be stretched. The force each cell will experience will differ slightly so the stretching will depend on the cells polarisability as well as its stiffness. Because of this a relative stiffness rather than absolute stiffness is measured. We show that with standard conditions (20Vpp, 1.5MHz, 10mSm-1 medium conductivity) the cell's diameter changes by around 10% for healthy mouse erythrocytes and we show that due to the low light intensities required for OET, relative to conventional optical tweezers, multiple cells can be measured simultaneously.

  20. Protection of primary neurons and mouse brain from Alzheimer’s pathology by molecular tweezers

    PubMed Central

    Attar, Aida; Ripoli, Cristian; Riccardi, Elisa; Maiti, Panchanan; Li Puma, Domenica D.; Liu, Tingyu; Hayes, Jane; Jones, Mychica R.; Lichti-Kaiser, Kristin; Yang, Fusheng; Gale, Greg D.; Tseng, Chi-hong; Tan, Miao; Xie, Cui-Wei; Straudinger, Jeffrey L.; Klärner, Frank-Gerrit; Schrader, Thomas; Frautschy, Sally A.; Grassi, Claudio

    2012-01-01

    Alzheimer’s disease is a devastating cureless neurodegenerative disorder affecting >35 million people worldwide. The disease is caused by toxic oligomers and aggregates of amyloid β protein and the microtubule-associated protein tau. Recently, the Lys-specific molecular tweezer CLR01 has been shown to inhibit aggregation and toxicity of multiple amyloidogenic proteins, including amyloid β protein and tau, by disrupting key interactions involved in the assembly process. Following up on these encouraging findings, here, we asked whether CLR01 could protect primary neurons from Alzheimer’s disease-associated synaptotoxicity and reduce Alzheimer’s disease–like pathology in vivo. Using cell culture and brain slices, we found that CLR01 effectively inhibited synaptotoxicity induced by the 42-residue isoform of amyloid β protein, including ∼80% inhibition of changes in dendritic spines density and long-term potentiation and complete inhibition of changes in basal synaptic activity. Using a radiolabelled version of the compound, we found that CLR01 crossed the mouse blood–brain barrier at ∼2% of blood levels. Treatment of 15-month-old triple-transgenic mice for 1 month with CLR01 resulted in a decrease in brain amyloid β protein aggregates, hyperphosphorylated tau and microglia load as observed by immunohistochemistry. Importantly, no signs of toxicity were observed in the treated mice, and CLR01 treatment did not affect the amyloidogenic processing of amyloid β protein precursor. Examining induction or inhibition of the cytochrome P450 metabolism system by CLR01 revealed minimal interaction. Together, these data suggest that CLR01 is safe for use at concentrations well above those showing efficacy in mice. The efficacy and toxicity results support a process-specific mechanism of action of molecular tweezers and suggest that these are promising compounds for developing disease-modifying therapy for Alzheimer’s disease and related disorders. PMID:23183235