Sample records for zn-porphyrin tweezer host-guest

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

    E-print Network

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

    2014-12-16

    microdroplet, the interfacial assembly of pre-formed polymeric materials to form multi-layer amphiphilic microcapsules has not yet been demon- strated. Supramolecular host-guest chemistry has been ap- plied in the preparation of various self... , J., Loh, X. J., Das, D., Lee, T.- C., and Scherman, O. A. Supramolecular peptide amphiphile vesicles through host-guest complexa- tion. Angew. Chem. Int. Ed. 51, 9633–7 (2012). [17] Kim, E., Kim, D., Jung, H., Lee, J., Paul, S., Selvapalam, N., Yang...

  2. Reversibly tunable upconversion luminescence by host-guest chemistry.

    PubMed

    Taniguchi, Takaaki; Murakami, Tomoaki; Funatsu, Asami; Hatakeyama, Kazuto; Koinuma, Michio; Matsumoto, Yasumichi

    2014-09-01

    Tuning upconversion (UPC) luminescence using external stimuli and fields, as well as chemical reactions, is expected to lead to novel and efficient optical sensors. Herein, highly tunable UPC luminescence was achieved through a host-guest chemistry approach. Specifically, interlayer ion exchange reactions reversibly tuned the emission intensity and green-red color of Er/Yb-codoped A2La2Ti3O10 layered perovskite, where A corresponds to proton and alkali metal ions, enabling the visualization of host-guest interactions and reactions. PMID:25122035

  3. 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.

  4. Redox-responsive self-healing materials formed from host–guest polymers

    Microsoft Academic Search

    Masaki Nakahata; Yoshinori Takashima; Hiroyasu Yamaguchi; Akira Harada

    2011-01-01

    Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host

  5. 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

  6. Supramolecular chemistry at interfaces: host-guest interactions for fabricating multifunctional biointerfaces.

    PubMed

    Yang, Hui; Yuan, Bin; Zhang, Xi; Scherman, Oren A

    2014-07-15

    CONSPECTUS: Host-guest chemistry can greatly improve the selectivity of biomolecule-ligand binding on account of recognition-directed interactions. In addition, functional structures and the actuation of supramolecular assemblies in molecular systems can be controlled efficiently through various host-guest chemistry. Together, these highly selective, strong yet dynamic interactions can be exploited as an alternative methodology for applications in the field of programmable and controllable engineering of supramolecular soft materials through the reversible binding between complementary components. Many processes in living systems such as biotransformation, transportation of matter, and energy transduction begin with interfacial molecular recognition, which is greatly influenced by various external stimuli at biointerfaces. Detailed investigations about the molecular recognition at interfaces can result in a better understanding of life science, and further guide us in developing new biomaterials and medicines. In order to mimic complicated molecular-recognition systems observed in nature that adapt to changes in their environment, combining host-guest chemistry and surface science is critical for fabricating the next generation of multifunctional biointerfaces with efficient stimuli-responsiveness and good biocompatibility. In this Account, we will summarize some recent progress on multifunctional stimuli-responsive biointerfaces and biosurfaces fabricated by cyclodextrin- or cucurbituril-based host-guest chemistry and highlight their potential applications including drug delivery, bioelectrocatalysis, and reversible adsorption and resistance of peptides, proteins, and cells. In addition, these biointerfaces and biosurfaces demonstrate efficient response toward various external stimuli, such as UV light, pH, redox chemistry, and competitive guests. All of these external stimuli can aid in mimicking the biological stimuli evident in complex biological environments. We begin by reviewing the current state of stimuli-responsive supramolecular assemblies formed by host-guest interactions, discussing how to transfer host-guest chemistry from solution onto surfaces required for fabricating multifunctional biosurfaces and biointerfaces. Then, we present different stimuli-responsive biosurfaces and biointerfaces, which have been prepared through a combination of cyclodextrin- or cucurbituril-based host-guest chemistry and various surface technologies such as self-assembled monolayers or layer-by-layer assembly. Moreover, we discuss the applications of these biointerfaces and biosurfaces in the fields of drug release, reversible adsorption and release of some organic molecules, peptides, proteins, and cells, and photoswitchable bioelectrocatalysis. In addition, we summarize the merits and current limitations of these methods for fabricating multifunctional stimuli-responsive biointerfaces in a dynamic noncovalent manner. Finally, we present possible strategies for future designs of stimuli-responsive multifunctional biointerfaces and biosurfaces by combining host-guest chemistry with surface science, which will lead to further critical development of supramolecular chemistry at interfaces. PMID:24766328

  7. Supramolecular polymers constructed by orthogonal self-assembly based on host-guest and metal-ligand interactions.

    PubMed

    Wei, Peifa; Yan, Xuzhou; Huang, Feihe

    2015-02-01

    Supramolecular polymers constructed by orthogonal self-assembly based on host-guest and metal-ligand interactions are attracting increasing attention currently because of their interesting properties and potential applications. Host-guest interactions impart these polymers with good selectivity and convenient enviro-responsiveness, and metal-ligand interactions endow them with various coordination geometries, strong yet tunable coordination binding abilities, as well as magnetic, redox, photophysical, and electrochromic properties. Therefore, supramolecular polymers constructed by orthogonal host-guest and metal-ligand interactions have wide applications in the fields of soft matter, fluorescence sensing, heterocatalysis, electronics, gas storage, etc. In this critical review, we will address the recent development of supramolecular polymeric systems involving metal-ligand interactions and host-guest molecular recognition. Specifically, we classify the related supramolecular polymers depending on the types of macrocyclic hosts, and highlight their intriguing properties originating from the elegant combination of host-guest complexation and metal centers. PMID:25423355

  8. 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…

  9. Supramolecular host-guest interaction for labeling and detection of cellular biomarkers.

    PubMed

    Agasti, Sarit S; Liong, Monty; Tassa, Carlos; Chung, Hyun Jung; Shaw, Stanley Y; Lee, Hakho; Weissleder, Ralph

    2012-01-01

    Be my guest: A supramolecular host-guest interaction is utilized for highly efficient bioorthogonal labeling of cellular targets. Antibodies labeled with a cyclodextrin host molecule bind to adamantane-labeled magnetofluorescent nanoparticles (see picture) and provide an amplifiable strategy for biomarker detection that can be adapted to different diagnostic techniques such as molecular profiling or magnetic cell sorting. PMID:22113923

  10. An efficient multiple healing conductive composite via host-guest inclusion.

    PubMed

    Zhang, Da-Li; Ju, Xin; Li, Luo-Hao; Kang, Yang; Gong, Xiao-Lei; Li, Bang-Jing; Zhang, Sheng

    2015-03-26

    A self-healable conductive composite is developed by combining the small molecules and nanotubes through host-guest interactions. This material shows uniform conductivity, microwave absorption and humidity sensing properties, and can be rapidly healed to over 90% electrical and mechanical properties with the aid of water multiple times. In addition, the produced material is also remouldable and recyclable. PMID:25761433

  11. 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 ?-? 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

  12. 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

  13. Redox-responsive self-healing materials formed from host–guest polymers

    PubMed Central

    Nakahata, Masaki; Takashima, Yoshinori; Yamaguchi, Hiroyasu; Harada, Akira

    2011-01-01

    Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing ?-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol?gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces. PMID:22027591

  14. 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

  15. The SAMPL4 host–guest 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 host–guest 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 host–guest 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 host–guest 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 host–guest 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

  16. Supramolecular Host-Guest Chemistry of Heterocyclic V-Shaped Molecules

    NASA Astrophysics Data System (ADS)

    Bishop, Roger

    The host-guest inclusion properties of heterocyclic molecules that utilise C 2-symmetric V-shaped building blocks in their construction are reviewed. Such compounds are classified here according to the molecular structures of these building blocks. Salient features of the crystal structures of the resulting inclusion compounds are described and the f unctions of their key supramolecular synthons are analysed. Concepts underpinning the deliberate design and synthesis of new host molecules of this type are explained and then put into practice.

  17. 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

  18. Host-guest interaction manipulated self-assembly of pyridinium-tailored naphthalene.

    PubMed

    Wang, Peiyi; Lin, Yuan; Smith, Mark; Feng, Sheng; Song, Baoan; Yang, Song; Hu, Jun

    2014-10-14

    Host–guest interactions are employed to manipulate the assembled morphology of an amphiphile, 2-NP, which contains an electron-rich naphthalene group and an electron-deficient pyridinium cation linked with a flexible alkyl arm. By encapsulating the pyridinium and the naphthalene group of 2-NP into the cavity of cucurbit[8]uril (CB[8]), fluorescence-enhanced microsheets were formed. PMID:25162071

  19. 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

  20. 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

  1. 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

  2. Reversible Phase Transfer of Nanoparticles Based on Photoswitchable Host–Guest Chemistry

    PubMed Central

    2015-01-01

    An azobenzene-containing surfactant was synthesized for the phase transfer of ?-cyclodextrin (?-CD)-capped gold nanoparticles between water and toluene phases by host–guest chemistry. With the use of the photoisomerization of azobenzene, the reversible phase transfer of gold nanoparticles was realized by irradiation with UV and visible light. Furthermore, the phase transfer scheme was applied for the quenching of a reaction catalyzed by gold nanoparticles, as well as the recovery and recycling of the gold nanoparticles from aqueous solutions. This work will have significant impact on materials transfer and recovery in catalysis and biotechnological applications. PMID:24524295

  3. Electron collection in host-guest nanostructured hematite photoanodes for water splitting: the influence of scaffold doping density.

    PubMed

    Kondofersky, Ilina; Dunn, Halina K; Müller, Alexander; Mandlmeier, Benjamin; Feckl, Johann M; Fattakhova-Rohlfing, Dina; Scheu, Christina; Peter, Laurence M; Bein, Thomas

    2015-03-01

    Nanostructuring has proven to be a successful strategy in overcoming the trade-off between light absorption and hole transport to the solid/electrolyte interface in hematite photoanodes for water splitting. The suggestion that poor electron (majority carrier) collection hinders the performance of nanostructured hematite electrodes has led to the emergence of host-guest architectures in which the absorber layer is deposited onto a transparent high-surface-area electron collector. To date, however, state of the art nanostructured hematite electrodes still outperform their host-guest counterparts, and a quantitative evaluation of the benefits of the host-guest architecture is still lacking. In this paper, we examine the impact of host-guest architectures by comparing nanostructured tin-doped hematite electrodes with hematite nanoparticle layers coated onto two types of conducting macroporous SnO2 scaffolds. Analysis of the external quantum efficiency spectra for substrate (SI) and electrolyte side (EI) illumination reveals that the electron diffusion length in the host-guest electrodes based on an undoped SnO2 scaffold is increased substantially relative to the nanostructured hematite electrode without a supporting scaffold. Nevertheless, electron collection is still incomplete for EI illumination. By contrast, an electron collection efficiency of 100% is achieved by fabricating the scaffold using antimony-doped SnO2, showing that the scaffold conductivity is crucial for the device performance. PMID:25562687

  4. Tunable polymer brush/Au NPs hybrid plasmonic arrays based on host-guest interaction.

    PubMed

    Fang, Liping; Li, Yunfeng; Chen, Zhaolai; Liu, Wendong; Zhang, Junhu; Xiang, Siyuan; Shen, Huaizhong; Li, Zibo; Yang, Bai

    2014-11-26

    The fabrication of versatile gold nanoparticle (Au NP) arrays with tunable optical properties by a novel host-guest interaction are presented. The gold nanoparticles were incorporated into polymer brushes by host-guest interaction between ?-cyclodextrin (?-CD) ligand of gold nanoparticles and dimethylamino group of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA). The gold nanoparticle arrays were prepared through the template of PDMAEMA brush patterns which were fabricated combining colloidal lithography and surface-initiated atom-transfer radical polymerization (SI-ATRP). The structure parameters of gold nanoparticle patterns mediated by polymer brushes such as height, diameters, periods and distances, could be easily tuned by tailoring the etching time or size of colloidal spheres in the process of colloidal lithography. The change of optical properties induced by different gold nanoparticle structures was demonstrated. The direct utilization of PDMAEMA brushes as guest avoids a series of complicated modification process and the PDMAEMA brushes can be grafted on various substrates, which broaden its applications. The prepared gold naoparticle arrays are promising in applications of nanosensors, memory storage and surface enhanced spectroscopy. PMID:25347749

  5. Crystal structures of three host-guest complexes of methylsubstituted cucurbit[6]urils and anthracene derivatives

    NASA Astrophysics Data System (ADS)

    Chen, Ze-Hua; Zhou, Fa-Geng; Zhang, Yun-Qian; Zhu, Qian-Jiang; Xue, Sai-Feng; Tao, Zhu

    2009-07-01

    Three host-guest complexes of methylsubstituted cucurbit[6]urils host and anthracene derivatives guests were synthesized and structurally characterized by single crystal X-ray diffractions and 1H NMR technique. The hosts are dodecamethylcucurbit[6]uril (DDMeQ[6]), ?,?',?,?'-tetramethylcucurbit[6]uril (TMeQ[6]), and hexa-methylsubstituted cucurbituril (HSMeQ[6]) made from 3a-methyl-glycoluril. The guests are 9,10-bis[ N-(aminoethylene)aminomethyl]anthracene (AN1), 9,10-bis[ N-(aminopropylene) aminomethyl]anthracene (AN2) and 9,10-bis[ N-(aminobutylene)aminomethyl]anthracene (AN3). The crystal structures show the compounds 1-3 with stoichiometry of {DDMeQ[6]-AN1} 2+2NO 3-24H 2O ( 1), {TMeQ[6]-AN2} 2+4NO 3- 2H 3O +10H 2O ( 2) and {2HSMeQ[6]-AN3} 2+2Cl -25H 2O ( 3) respectively, and the formation of an exclusion or inclusion host-guest complex is dependent on the length of the substituted alkyl chains on the anthracene.

  6. Encapsulation of a rhodamine dye within a bile acid binding protein: toward water processable functional bio host-guest materials.

    PubMed

    Tomaselli, Simona; Giovanella, Umberto; Pagano, Katiuscia; Leone, Giuseppe; Zanzoni, Serena; Assfalg, Michael; Meinardi, Francesco; Molinari, Henriette; Botta, Chiara; Ragona, Laura

    2013-10-14

    New strategies are requested for the preparation of bioinspired host-guest complexes to be employed in technologically relevant applications, as sensors and optoelectronic devices. We report here a new approach employing a single monomeric protein as host for the strongly fluorescent rhodamine dye. The selected protein, belonging to the intracellular lipid binding protein family, fully encapsulates one rhodamine molecule inside its cavity forming a host-guest complex stabilized by H and ?-hydrogen bonds, a salt bridge, and favorable hydrophobic contacts, as revealed by the NMR derived structural model. The protein-dye solutions are easily processable and form homogeneous thin films exhibiting excellent photophysical and morphological properties, as derived from photoluminescence and AFM data. The obtained results represent the proof of concept of the viability of this bio host-guest system for the development of bioinspired optoelectronic devices. PMID:24032431

  7. 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

  8. Steering molecular organization and host-guest interactions using two-dimensional nanoporous coordination systems

    NASA Astrophysics Data System (ADS)

    Stepanow, Sebastian; Lingenfelder, Magalí; Dmitriev, Alexandre; Spillmann, Hannes; Delvigne, Erik; Lin, Nian; Deng, Xiaobin; Cai, Chengzhi; Barth, Johannes V.; Kern, Klaus

    2004-04-01

    Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C60 guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions.

  9. Tuning temperature responsive poly(2-alkyl-2-oxazoline)s by supramolecular host-guest interactions.

    PubMed

    de la Rosa, Victor R; Nau, Werner M; Hoogenboom, Richard

    2015-02-24

    A poly[(2-ethyl-2-oxazoline)-ran-(2-nonyl-2-oxazoline)] random copolymer was synthesized and its thermoresponsive behavior in aqueous solution modulated by the addition of different supramolecular host molecules. The macrocycles formed inclusion complexes with the nonyl aliphatic side-chains present in the copolymer, increasing its cloud point temperature. The extent of this temperature shift was found to depend on the cavitand concentration and on the strength of the host-guest complexation. The cloud point temperature could be tuned in an unprecedented wide range of 30 K by supramolecular interactions. Since the temperature-induced breakage of the inclusion complexes constitutes the driving force for the copolymer phase transition, the shift in cloud point temperature could be utilized to estimate the association constant of the nonyl side chains with the cavitands. PMID:25621735

  10. Self-healing polymer materials constructed by macrocycle-based host-guest interactions.

    PubMed

    Yang, Xianpeng; Yu, Haojie; Wang, Li; Tong, Rongbai; Akram, Muhammad; Chen, Yongsheng; Zhai, Xiaoting

    2015-02-01

    Self-healing polymers, which can spontaneously recover themselves after being ruptured, result in enhanced lifetimes for materials and open up a fascinating direction in material science. Macrocycle-based host-guest interactions, one of the most crucial non-covalent interactions, play a key role in self-healing material fabrication. This review aims to highlight the very recent and important progress made in the area of self-healing polymer materials by focusing on cyclodextrins (CDs), crown ethers, cucurbit[n]urils (CBs), calix[n]arenes and pillar[n]arenes with special guest groups and tailored structures. In addition, we also propose future research directions and hope that this review can in a way reflect the current situation and future trends in this developing area. PMID:25614350

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

    NASA Astrophysics Data System (ADS)

    Calzaferri, Gion; Huber, Stefan; Devaux, André; 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.

  12. 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

  13. Optimization of the host-guest system within an OLED using different models of mobility

    NASA Astrophysics Data System (ADS)

    Adames Prada, Rosana; Ardila Vargas, Angel Miguel

    2014-12-01

    To optimize the host-guest system of organic light emitting devices (OLEDs), it were performed simulations by doping a small molecule organic semiconductor (acting as host) with the transition organometallic complex known as Ir(ppy)2(acac) (acting as a guest). The simulation was carried out using simOLED with different mobility models: the Pool-Frenkel Model (PFM), the Extended Gaussian Disorder Model (EGDM) and Extended Correlated Disorder Model (ECDM), with the aim to determine the magnitude of some parameters like temperature, applied electric field, film thickness and charge carrier density that improve the electrical and optical properties of OLEDs with a more simplified structure like ITO/CBP/CBP:Ir(ppy)2(acac)/TPBi/LiF/Al.

  14. Host-guest interactions between a nonmicellized amphiphilic invertible polymer and insoluble cyclohexasilane in acetonitrile.

    PubMed

    Kohut, Ananiy; Kudina, Olena; Dai, Xuliang; Schulz, Douglas L; Voronov, Andriy

    2011-09-01

    Host-guest interactions between cyclohexasilane (Si(6)H(12)) and amphiphilic invertible macromolecules based on PEG and sebacic acid in acetonitrile (neither a solvent for cyclohexasilane nor a support for the micellization of amphiphilic invertible macromolecules) have been investigated. Despite the extended conformation of the macromolecules and the absence of self-assembled polymeric domains, a macromolecular amphiphilicity itself contributes to localizing Si(6)H(12) by AIP and thus enables Lewis acid-base interactions between Si(6)H(12) and the AIP carbonyl groups. The obtained results demonstrate an interesting phenomenon in that insoluble Si(6)H(12) can be localized by AIP macromolecules in a medium that does not support the formation of polymeric domains. PMID:21797281

  15. Free Energy, Entropy, and Induced Fit in Host-Guest Recognition: Calculations with the Second-Generation Mining

    E-print Network

    Chang, Chia-en "Angelina"

    barbiturate receptor. The computed standard free energies of binding for the 12 binding reactions agree and encapsulation, and enantioselective synthesis. These systems also represent elegant, simplified models, termed M2, to analyze the binding reactions of 12 host-guest complexes in an organic solvent

  16. 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

  17. Cyclic Tetranuclear and Hexanuclear Palladium(II) Complexes and Their Host-Guest Chemistry

    PubMed Central

    Walmsley, Judith A.; Zhu, Shourong; Matilla, Antonio; Donowick, Tiffanee G.; Cramp, Jessica E.; Tercero, Jose Manuel; Dalrymple, Tatyana

    2008-01-01

    Cyclic tetrameric complexes have been prepared by the reaction of Pd(en)Cl2 or Pd(dapol)Cl2, or their nitrato analogs, with Na2(5?GMP) in aqueous solution, where en = 1,2-diaminoethane, dapol = 1,3-diamino-2-propanol, 5?-GMP = guanosine 5?-monophosphate. Addition of certain small molecules containing hydrophobic groups resulted in the expansion of the tetramer to a cyclic hexamer with strong bonding of one guest per hexameric host. At pH 5-6, the guest molecule can be a cation, anion, or neutral, and those species containing trimetylsilyl and t-butyl groups bonded the most strongly. The size of the central cavity of the [Pd(en)(5?GMP)]6 host has been estimated to be 5.2 ?. Formation of the host-guest complex caused a large upfield shift (??) of 2.5-2.9 ppm in the 1H NMR spectrum of the most highly affected guest protons, which were those in closest proximity to the guanine nucleobases. NOESY spectra were used to determine the interaction sites between the host and the guest. Apparent association constants determined at 26 °C and pD 5.4 for the [Pd(en)(5?GMP)]6-DSS and [Pd(en)(5?GMP)]6 -t-butanol systems, where DSS is 3-(trimethylsilyl)-1-propanesulfonate anion, were 1.36 ± 0.11 × 104 and 2.74 ± 0.95 × 104 M?3/2, respectively. The Pd(dapol)-5?GMP system forms hexameric host-guest complexes, similar in nature to those of the Pd(en)-5?-GMP system. The molecular and crystal structures of Pd(dapol)Cl2 are also reported. PMID:17924617

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

    SciTech Connect

    Crowley, James D.; Bosnich, Brice (UC)

    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.

  19. 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 ?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, C(60)@C(60)H(28) and C(70)@C(60)H(28). PMID:25248285

  20. 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.

  1. 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.

  2. Regulation of folding and photochromic reactivity of terarylenes through a host-guest interaction.

    PubMed

    Nakashima, Takuya; Fujii, Ryosuke; Kawai, Tsuyoshi

    2011-09-19

    The photochromic reactivity of terarylenes is integrated with molecular folding that is controlled through a host-guest interaction. A thieno[3,2,b]pyridine unit is introduced into a photochromic terarylene structure as an aryl unit to form a guest-interacting site. Thienopyridine-containing terarylenes showed solvent-dependent photochromic reactivity in solution. A terarylene moiety that contains two thienopyridyl units showed significantly high photocoloration reactivity as high as 88% of photocyclization quantum yield in methanol, whereas that value was only 24% in hexane. A temperature-dependent (1)H NMR spectroscopic study in different solvents indicated an interconversion between photochromic-reactive and unreactive conformations. In methanol, the intermolecular interaction between terarylene species and the solvent molecule slows the rate of interconversion and increases the population of the photochromic-active form, whereas the unreactive conformation is dominant in hexane. Crystal-structural studies demonstrated the perfect regulation of molecular folding between a photochromic-active form and an unreactive conformation by changing the solvents for recrystallization. Single crystals prepared from solutions in methanol showed reversible photochromic reactivity, whereas recrystallization from solutions in hexane did not show this reactivity. X-ray crystallographic studies of single crystals from solutions in methanol demonstrated that the photochromic molecules bind a solvent methanol molecule at the guest-interacting site to regulate the molecular conformation into a photochromic-active form in collaboration with specific intramolecular interactions, whereas crystals from solutions in hexane possess the photochromic-unreactive conformation. PMID:21932234

  3. Steering molecular organization and host-guest interactions using two-dimensional nanoporous coordination systems.

    PubMed

    Stepanow, Sebastian; Lingenfelder, Magalí; Dmitriev, Alexandre; Spillmann, Hannes; Delvigne, Erik; Lin, Nian; Deng, Xiaobin; Cai, Chengzhi; Barth, Johannes V; Kern, Klaus

    2004-04-01

    Metal-organic coordination networks (MOCNs) have attracted wide interest because they provide a novel route towards porous materials that may find applications in molecular recognition, catalysis, gas storage and separation. The so-called rational design principle-synthesis of materials with predictable structures and properties-has been explored using appropriate organic molecular linkers connecting to metal nodes to control pore size and functionality of open coordination networks. Here we demonstrate the fabrication of surface-supported MOCNs comprising tailored pore sizes and chemical functionality by the modular assembly of polytopic organic carboxylate linker molecules and iron atoms on a Cu(100) surface under ultra-high-vacuum conditions. These arrays provide versatile templates for the handling and organization of functional species at the nanoscale, as is demonstrated by their use to accommodate C(60) guest molecules. Temperature-controlled studies reveal, at the single-molecule level, how pore size and chemical functionality determine the host-guest interactions. PMID:15004551

  4. Enhanced host-guest electrochemical recognition of herbicide MCPA using a ?-cyclodextrin carbon nanotube sensor.

    PubMed

    Rahemi, V; Vandamme, J J; Garrido, J M P J; Borges, F; Brett, C M A; Garrido, E M P J

    2012-09-15

    An electrochemical sensor for the determination of the chlorophenoxy herbicide MCPA has been developed, based on a combination of multi-walled carbon nanotubes with incorporated ?-cyclodextrin and a polyaniline film modified glassy carbon electrode. The proposed molecular host-guest recognition based sensor has a high electrochemical sensitivity for the determination of MCPA. The electrochemical behaviour of MCPA at the chemically modified electrode was investigated in detail by cyclic voltammetry. The results indicate that the ?-CD/MWCNT modified glassy carbon electrode exhibits efficient electrocatalytic oxidation of MCPA with high sensitivity, stability and lifetime. The analytical characteristics of this film were used for the quantitative determination of MCPA in natural waters. Cyclic voltammetry in phosphate buffer solution at pH 6.0, allowed the development of a method to determine MCPA, without any previous steps of extraction, clean-up, or derivatization, in the range of 10-100 ?mol L(-1), with a detection limit of 0.99 ?mol L(-1) in water. The results were statistically compared with those obtained through an established high-performance liquid chromatography technique, no significant differences having been found between the two methods. PMID:22967554

  5. 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.

  6. 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

  7. 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.

  8. Cyclodextrin-modified zeolites: host-guest surface chemistry for the construction of multifunctional nanocontainers.

    PubMed

    Szarpak-Jankowska, Anna; Burgess, Christine; De Cola, Luisa; Huskens, Jurriaan

    2013-10-25

    The functionalization of nanoporous zeolite?L crystals with ?-cyclodextrin (CD) has been demonstrated. The zeolite surface was first modified with amino groups by using two different aminoalkoxysilanes. Then, 1,4-phenylene diisothiocyanate was reacted with the amino monolayer and used to bind CD heptamine by using its remaining isothiocyanate groups. The use of the different aminoalkoxysilanes, 3-aminopropyl dimethylethoxysilane (APDMES) and 3-aminopropyl triethoxysilane (APTES), led to drastic differences in uptake and release properties. Thionine was found to be absorbed and released from amino- and CD-functionalized zeolites when APDMES was used, whereas functionalization by APTES led to complete blockage of the zeolite channels. Fluorescence microscopy showed that the CD groups covalently attached to the zeolite crystals could bind adamantyl-modified dyes in a specific and reversible manner. This strategy allowed the specific immobilization of His-tagged proteins by using combined host-guest and His-tag-Ni-nitrilotriacetic acid (NTA) coordination chemistry. Such multifunctional systems have the potential for encapsulation of drug molecules inside the zeolite pores and non-covalent attachment of other (for example, targeting) ligand molecules on its surface. PMID:24038376

  9. 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.

  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?µg/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. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25204628

  11. Proteasome-cytochrome c interactions: a model system for investigation of proteasome host-guest interactions.

    PubMed

    Huffman, Holly A; Sadeghi, Mehrnoosh; Seemuller, Erika; Baumeister, Wolfgang; Dunn, Michael F

    2003-07-29

    Owing to its high thermal stability and structural simplicity, the archaebacterium Thermoplasma Acidophilum 20S proteasome was selected for mechanistic studies in this work. This oligomeric enzyme complex consists of a barrel-shaped 20S core (approximately 700kDa) comprised of four stacked seven-membered rings with a alpha(7)beta(7)beta(7)alpha(7) subunit structure situated around a 7-fold symmetry axis. The hollow interior of the proteasome has three large interconnected chambers with narrow (13 A diameter) entrances from solution located at either end of the barrel. The 14 beta-subunit proteolytic sites are located on the inner surface of the central chamber. Herein, we demonstrate that unfolded horse heart ferricytochrome c (Cyt c) is a novel chromophoric probe for investigation of the mechanism of proteasome action. Under conditions of temperature and denaturant which unfold Cyt c but do not alter the thermophilic proteasome, Cyt c is extensively cleaved by the proteasome. Ten peptides were isolated and sequenced from the proteasome digest. Analysis of the cleavage products established that unfolded Cyt c and its covalently attached heme prosthetic group are translocated to the central chamber where proteolysis occurs. In the presence of site-specific inhibitors of the proteasome, we demonstrate that unfolded cytochrome c can be sequestered inside the proteasome complex. Upon cooling, a quasistable host-guest complex is formed. Analysis of the complex via UV/visible spectroscopy and mass spectrometry gave evidence that the sequestered Cyt c is essentially intact within the inhibited proteasome. High-performance liquid chromatography data show that (1) complexes with an apparent stoichiometry of approximately one Cyt c per proteasome can be formed and (2) when inhibition is removed from the complex, a rapid turnover of the sequestered Cyt c occurs. PMID:12873127

  12. Host-Guest Interactions between Calixarenes and Cp2NbCl2

    PubMed Central

    Morales, Alexis; Santana, Alberto; Althoff, Gerhard; Melendez, Enrique

    2011-01-01

    The possible inclusion complexes of Cp2NbCl2 into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, 1H NMR solution and solid state 13C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp2NbCl2. Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp2NbCl2, a band between 500–850 cm?1 characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp2NbCl2) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp2NbCl2(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp2NbCl2(OH). Solid State 13C CP MAS NMR and solution 1H NMR spectroscopies together with ab-initio results showed that Cp2NbCl2 is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution 1H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp2NbCl2 in CDCl3 solution. Cp2NbCl2 is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp2NbCl2 into the cavity. PMID:21709809

  13. 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

  14. 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.

  15. Host-guest interactions in amylose inclusion complexes: photochemistry of surfactant stilbenes in helical cavities of amylose

    SciTech Connect

    Hui, Y.; Russell, J.C.; Whitten, D.G.

    1983-03-09

    A series of substituted stilbenes, S/sub n/, in which the stilbene chromophore is incorporated into a surfactant molecule, has been synthesized. It has been found that these stilbenes are sensitive structural probes for organized media. The behavior of three of the surfactant stiblenes in the presence of amylose in aqueous dimethyl sulfoxide is described. The results reveal several interesting features of amylose host-guest interaction, including a clear indication that, at least for the stilbenes, the guest is held in a reasonably constrained site similar to that provided by various bilayer structures.

  16. Self-assembled monolayers of alpha-cyclodextrin derivatives on gold and their host-guest behavior.

    PubMed

    Perl, András; Kumprecht, Lukás; Kraus, Tomás; Armspach, Dominique; Matt, Dominique; Reinhoudt, David N; Huskens, Jurriaan

    2009-02-01

    Various sulfur-modified alpha-cyclodextrin (alpha-CD) derivatives formed ordered monolayers on gold surfaces as confirmed by water contact angle goniometry, electrochemistry, X-ray photoelectron spectroscopy, and atomic force microscopy measurements. Self-assembled monolayers (SAMs) of the adsorbates showed high polarity, uniform monolayer arrangement, and low charge transfer resistance. Electrochemical capacitance measurements were used to determine the binding affinity of aliphatic carboxylic acid salts with four, six, and eight carbon atoms. The nonmethylated cyclodextrin host-guest pairs showed 1-2 orders of magnitude higher binding constants on surfaces than in solution. PMID:19125561

  17. 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 ?-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

  18. Multiaddressable molecular rectangles with reversible host-guest interactions: modulation of pH-controlled guest release and capture.

    PubMed

    Chan, Alan Kwun-Wa; Lam, Wai Han; Tanaka, Yuya; Wong, Keith Man-Chung; Yam, Vivian Wing-Wah

    2015-01-20

    A series of multiaddressable platinum(II) molecular rectangles with different rigidities and cavity sizes has been synthesized by endcapping the U-shaped diplatinum(II) terpyridine moiety with various bis-alkynyl ligands. The studies of the host-guest association with various square planar platinum(II), palladium(II), and gold(III) complexes and the related low-dimensional gold(I) complexes, most of which are potential anticancer therapeutics, have been performed. Excellent guest confinement and selectivity of the rectangular architecture have been shown. Introduction of pH-responsive functionalities to the ligand backbone generates multifunctional molecular rectangles that exhibit reversible guest release and capture on the addition of acids and bases, indicating their potential in controlled therapeutics delivery on pH modulation. The reversible host-guest interactions are found to be strongly perturbed by metal-metal and ?-? interactions and to a certain extent, electrostatic interactions, giving rise to various spectroscopic changes depending on the nature of the guest molecules. Their binding mode and thermodynamic parameters have been determined by 2D NMR and van't Hoff analysis and supported by computational study. PMID:25568083

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

    PubMed Central

    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

  20. 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.

  1. 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

  2. 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

  3. Organic light-emitting diodes for lighting: High color quality by controlling energy transfer processes in host-guest-systems

    NASA Astrophysics Data System (ADS)

    Weichsel, Caroline; Reineke, Sebastian; Furno, Mauro; Lüssem, Björn; Leo, Karl

    2012-02-01

    Exciton generation and transfer processes in a multilayer organic light-emitting diode (OLED) are studied in order to realize OLEDs with warm white color coordinates and high color-rendering index (CRI). We investigate a host-guest-system containing four phosphorescent emitters and two matrix materials with different transport properties. We show, by time-resolved spectroscopy, that an energy back-transfer from the blue emitter to the matrix materials occurs, which can be used to transport excitons to the other emitter molecules. Furthermore, we investigate the excitonic and electronic transfer processes by designing suitable emission layer stacks. As a result, we obtain an OLED with Commission Internationale de lÉclairage (CIE) coordinates of (0.444;0.409), a CRI of 82, and a spectrum independent of the applied current. The OLED shows an external quantum efficiency of 10% and a luminous efficacy of 17.4 lm/W at 1000 cd/m2.

  4. Luminescent hybrid materials based on zeolite L crystals and lanthanide complexes: host-guest assembly and ultraviolet-visible excitation.

    PubMed

    Chen, Lei; Yan, Bing

    2014-10-15

    Several kinds of host-guest hybrid materials have been synthesized employing a ship in a bottle method by loading 9-hydroxy-2-methylphenalenone (MHPO) or 9-hydroxyphenalen (HPNP) from gas phase into the nanochannels of Ln(3+)-exchanged zeolite L (ZL) crystals (Ln=Gd or Eu). The resulting hybrids without lanthanide ions, MHPO-ZL, HPNP-ZL and the hybrids with lanthanide ions Ln-MHPO-ZL and Ln-HPNP-ZL are characterized with FT-IR, UV-vis DRS and photoluminescence spectroscopy. The photoluminescence properties of these hybrid materials have been analyzed and discussed, exhibiting the luminescence of Eu(3+) and ligands under the excitation at ultraviolet-visible region. These results provide useful data and can be expected to have potential application in the practical fields. PMID:24815195

  5. 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

  6. Self-assembly behavior of a linear-star supramolecular amphiphile based on host-guest complexation.

    PubMed

    Wang, Juan; Wang, Xing; Yang, Fei; Shen, Hong; You, Yezi; Wu, Decheng

    2014-11-01

    A star polymer, ?-cyclodextrin-poly(l-lactide) (?-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (?-CD-PLLA@Azo-PEG) based on the host-guest interaction between ?-CD and azobenzene moieties. This linear-star supramolecular amphiphilic copolymer further self-assembled into a variety of morphologies, including sphere-like micelle, carambola-like micelle, naan-like micelle, shuttle-like lamellae, tube-like fiber, and random curled-up lamellae, by tuning the length of hydrophilic or hydrophobic chains. The variation of morphology was closely related to the topological structure and block ratio of the supramolecular amphiphiles. These self-assembly structures could disassemble upon an ultraviolet (UV) light irradiation. PMID:25310380

  7. Luminescent hybrid materials based on zeolite L crystals and lanthanide complexes: Host-guest assembly and ultraviolet-visible excitation

    NASA Astrophysics Data System (ADS)

    Chen, Lei; Yan, Bing

    2014-10-01

    Several kinds of host-guest hybrid materials have been synthesized employing a ship in a bottle method by loading 9-hydroxy-2-methylphenalenone (MHPO) or 9-hydroxyphenalen (HPNP) from gas phase into the nanochannels of Ln3+-exchanged zeolite L (ZL) crystals (Ln = Gd or Eu). The resulting hybrids without lanthanide ions, MHPO-ZL, HPNP-ZL and the hybrids with lanthanide ions Ln-MHPO-ZL and Ln-HPNP-ZL are characterized with FT-IR, UV-vis DRS and photoluminescence spectroscopy. The photoluminescence properties of these hybrid materials have been analyzed and discussed, exhibiting the luminescence of Eu3+ and ligands under the excitation at ultraviolet-visible region. These results provide useful data and can be expected to have potential application in the practical fields.

  8. A self-assembled conformational switch: a host-guest stabilized triple stem molecular beacon via a photoactivated and thermal regeneration mode.

    PubMed

    He, Leiliang; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Zhao, Fang; Huang, Jin; Liu, Jianbo

    2014-07-25

    We present a novel strategy for construction of a conformational switch of a molecular beacon based on the combination of nucleic acid (DNA) self-assembly and reversible host-guest inclusion interaction. With the functionalized probe, the nucleic acid hybridization process can be easily controlled with a photoactivated and thermal regeneration mode. PMID:24903573

  9. Selectivity and Stoichiometry Boosting of -Cyclodextrin in Cationic/Anionic Surfactant Systems: When Host-Guest Equilibrium Meets Biased Aggregation Equilibrium

    E-print Network

    Huang, Jianbin

    Selectivity and Stoichiometry Boosting of -Cyclodextrin in Cationic/Anionic Surfactant Systems, 2009; ReVised Manuscript ReceiVed: December 28, 2009 Cationic surfactant/anionic surfactant/ -CD ternary aqueous systems provide a platform for the coexistence of the host-guest ( -CD/surfactant

  10. 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

  11. 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

  12. Tuning the host-guest interactions in a phosphine coordination polymer through different types of post-synthetic modification.

    PubMed

    Nuñez, Ana J; Chang, Maxwell S; Ibarra, Ilich A; Humphrey, Simon M

    2014-01-01

    The porous Phosphine Coordination Material, PCM-10 contains abundant free P(III) donor sites that can be subjected to a variety of post-synthetic modifications. The diverse P(III)/P(V) organic reactivity and coordination chemistry available to aryl phosphines have been exploited to decorate the pores of PCM-10, allowing for an extensive structure-function study. Polar P?O moieties, charged P(+)-CH3 phosphonium species with exchangeable coanions (I(-), F(-), BF4(-), and PF6(-)) and P-AuCl groups have been successfully post-synthetically incorporated. These modifications directly affect the strength of the resulting host-guest interactions, as demonstrated by comparative sorption studies of CO2, H2, and other gases in the solid-state. Broad tunability of the enthalpy of CO2 adsorption is observed: incorporation of BF4(-) ions inside the pores of PCM-10 results in 24% enhancement of the isosteric adsorption enthalpy of CO2 compared to the parent material, while F(-) anions induce a 36% reduction. Meanwhile, AuCl-decorated PCM-10 shows a high H2 sorption capacity of 4.72 wt % at 77 K and 1.0 bar, versus only 0.63 wt % in the unmodified material. PMID:24359324

  13. Core-shell superparamagnetic Fe3O4@?-CD composites for host-guest adsorption of polychlorinated biphenyls (PCBs).

    PubMed

    Wang, Manlin; Liu, Peng; Wang, Yu; Zhou, Dongmei; Ma, Chen; Zhang, Dongju; Zhan, Jinhua

    2015-06-01

    The effective recognition and enrichment of trace polychlorinated biphenyls (PCBs) in the environment are currently challenging issues due to human health concerns. In this paper, a surface absorptive layer coating superparamagnetic Fe3O4 nanoparticles for PCBs enrichment were prepared. This protocol involved the synthesis of Fe3O4 particles through a solvothermal reaction and the covering of a silica layer bonded ?-cyclodextrin (?-CD) over Fe3O4 via a sol-gel process to construct core-shell Fe3O4@?-CD composites. ?-CD was linked covalently to Fe3O4 nanoparticles to generate the binding sites, enhancing the stability of Fe3O4 nanoparticles in water. Meanwhile, superparamagnetic Fe3O4 core could be rapidly separated from matrix to simplify time-consuming washing extraction. The adsorption capacity of Fe3O4@?-CD composites to PCB28 and PCB52 in aqueous solutions was investigated. To estimate the theoretical binding site number of Fe3O4@?-CD, the obtained binding data were replotted according to Scatchard equation. The host-guest interaction between ?-CD and PCBs were further examined with density functional theory (DFT) calculations. It provides theoretical evidence of ?-CD as host molecule has a higher binding amount towards PCB-28 than PCB-52 on the basis of their optimized geometries and calculated complexation energies. The nanomaterial reported herein is an ideal candidate for various applications, including the recognition and removal of environmentally deleterious substances. PMID:25687400

  14. Fluorimetric determination of sulphaguanidine and sulphamethoxazole by host-guest complexation in beta-cyclodextrin and partial least squares calibration.

    PubMed

    Diez, N Mora; de la Peña, A Muñoz; García, M C Mahedero; Gil, D Bohoyo; Cañada-Cañada, F

    2007-05-01

    The host-guest inclusion complexes of sulphamethoxazole (SMTX) and sulphaguanidine (SGN) with beta-cyclodextrin, in aqueous solutions, have been investigated. A 1:1 stoichiometry of the complexes was established, the association constants were calculated by different methods, and the influence of several chemical variables on the complexation processes were established. According to the results obtained, a spectrofluorimetric method for the determination of these sulphonamides has been proposed. The individual and binary mixtures of both sulphonamides have been determined in human urine samples, at representative therapeutic ranges, by application of a first-order multivariate calibration partial least squares (PLS-1) model. The calibration set was designed with 9 samples, containing different concentrations of the two sulphonamides, and 8 blank urine samples, with the aim of modelling the variability of the background. The concentration ranges for the sulphonamides were up to 0.5 microg mL(-1) for SMTX and 1.0 microg mL(-1) for SGN. Figures of merit as selectivity, analytical sensitivity and limit of detection (LOD) were also calculated. The proposed procedure was validated by comparing the obtained results with a HPLC method, with satisfactory results for the assayed method. PMID:17393284

  15. Host-guest interactions in the confined geometries formed from molecular aggregates of push-pull molecules.

    PubMed

    K, Rohini; Swathi, R S

    2013-07-18

    We have considered push-pull molecules, aminonitroacetylene and aminonitrodiacetylene (O2N-(C?C)n-NH2; n = 1 and 2) as the basic units to design a series of molecular aggregates containing favorable hydrogen bonding interactions. Linear, closed, and stacked geometries of dimers, trimers, tetramers, and pentamers formed from these molecules are found to have very good stabilization energies due to the strong hydrogen bonding abilities of the terminal -NO2 and -NH2 groups. The closed hydrogen-bonded assemblies can act as supramolecular hosts for accommodating some molecules and ions as guests. We have been able to find substantial host-guest interaction energies for the complexes of the hydrogen-bonded closed assemblies with some highly reactive molecules like hexahydro-1,3,5-trinitro-s-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), pentafluoroethane (R-125), and difluoromethane (R-32). Further investigations on the interaction of the ions Li(+), Na(+), K(+), Mg(2+), Ca(2+), Al(3+), F(-), Cl(-), and Br(-) with the monomers as well as the oligomers reveal the formation of strong ion-? complexes, unlike the conventional weak ion-? complexes found in similar acetylenic systems without the end groups. This opens up the possibility of tuning the nature of ionic interactions in ?-systems by varying the terminal groups. PMID:23772692

  16. 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

  17. Theoretical prediction of the host-guest interactions between novel photoresponsive nanorings and C60 : A strategy for facile encapsulation and release of fullerene.

    PubMed

    Yuan, Kun; Dang, Jing-Shuang; Guo, Yi-Jun; Zhao, Xiang

    2015-03-30

    A series of photoresponsive-group-containing nanorings hosts with 12?14 Å in diameter is designed by introducing different number of azo groups as the structural composition units. And the host-guest interactions between fullerene C60 and those nanoring hosts were investigated theoretically at M06-2X/6-31G(d)//M06-L/MIDI! and wB97X-D/6-31G(d) levels. Analysis on geometrical characteristics and host-guest binding energies revealed that the designed nanoring molecule (labeled as 7) which is composed by seven azo groups and seven phenyls is the most feasible host for encapsulation of C60 guest among all candidates. Moreover, inferring from the simulated UV-vis-NIR spectroscopy, the C60 guest could be facilely released from the cavity of the host 7 via configuration transformation between trans-form and cis-form of the host under the 563 nm photoirradiation. Additionally, the frontier orbital features, weak interaction regions, infrared, and NMR spectra of the C60 @7 host-guest complex have also been investigated theoretically. © 2015 Wiley Periodicals, Inc. PMID:25594162

  18. The influence of host-guest inclusion complex formation on the biotransformation of cortisone acetate Delta(1)-dehydrogenation.

    PubMed

    Ma, Yin-Hu; Wang, Min; Fan, Zhi; Shen, Yan-Bing; Zhang, Li-Ting

    2009-11-01

    An intensive and systematic investigation had been carried out on the Delta(1)-dehydrogenation of cortisone acetate (CA) to prednisone acetate (PA) by Arthrobacter simplex TCCC 11037 in the presence of native and modified beta-cyclodextrins (beta-CDs). The biotransformation was improved through the formation of the host-guest inclusion complex between CA and CDs in aqueous solution. The inclusion complexes of CDs with CA were investigated by means of phase solubility, 2D NMR spectroscopy and differential scanning calorimetry (DSC). The structural difference of CDs resulted in the stoichiometric differences between the complexes, the RM-beta-CD-CA, SBE-beta-CD-CA, HP-beta-CD-CA complexes were 1:1 whereas beta-CD-CA gave both 1:1 and 2:1 complexes, of which the 2:1 complex decreased the soluble CA concentration and inhibited the dissociation of beta-CD-CA in aqueous solution. The increase in solubility of CA was in the order of RM-beta-CD>SBE-beta-CD>HP-beta-CD>beta-CD. RM-beta-CD-CA, SBE-beta-CD-CA and HP-beta-CD-CA exhibited the higher biotransformation rate in comparison with native beta-CD. And the solubilization of CDs for CA in aqueous medium plays a key role in the biotransformation process. The article focuses on the various factors influencing the substrate water solubility, complex stability and biotransformation of CA through the addition of CDs in order to solve many problems associated with the process of drug delivery and biotransformation of different novel steroids. PMID:19744560

  19. A surprising host-guest relationship between 1,2-dichloroethane and the cesium complex of tetrabenzo-24-crown-8

    SciTech Connect

    Levitskaia, T.G.; Bryan, J.C.; Sachleben, R.A.; Lamb, J.D.; Moyer, B.A.

    2000-02-02

    The structure of the complex [Cs(tetrabenzo-24-crown-8)(1,2-dichloroethane){sub 2}](NO{sub 3}){sm{underscore}bullet}H{sub 2}O was shown by X-ray crystallography to involve an unprecedented bidentate coordination of two 1,2-dichloroethane solvent molecules to the Cs{sup +} cation via the four chlorine atoms. The coordination of the solvent molecules occurs within two clefts between facing benzo groups, one pair of benzo groups related to the other pair by an improper noncrystallographic 90{degree} rotation. Resembling the seam on a tennis ball, the crown ether envelops the metal cation within a cagelike arrangement of eight crown ether oxygen atoms. Good geometric and electronic complimentarily characterizes the apparent host-guest relationship between the cleft environment and the solvent molecules. The complete encapsulation of the cation by the crown ether and two solvent molecules explains well the speciation behavior observed in liquid-liquid extraction of CsNO{sub 3} or CsClO{sub 4} from aqueous solution to 1,2-dichloroethane solutions of the alkylated analogues 4,4{double{underscore}prime}- or 4,5{double{underscore}prime}-bis(tert-octylbenzo)dibenzo-24-crown-8. In the extraction process studied at 25 C, simple 1:1 metal/crown complexes form in the solvent phase, as modeled by the program SXLSQI. The complex cation and counteranion are present both as ion-pairs, postulated to be ligand-separated ion-pairs as suggested by the crystal structure, and as dissociated ions. In agreement with a theoretical treatment of ion-pairing, the ion-pairs possess unusually low stability and exhibit no discrimination between the anions, largely ascribed to the large effective radius of the complex metal cation. Values of log K{sub f} corresponding to the formation of the complex cations Cs[bis(tert-octylbenzo)-dibenzo-24-crown-8]{sup +} in 1,2-dichloroethane at 25 C average 10.5 {+-} 0.2 for both positional isomers of the crown ether and for their 3:2 mixture. Overall, these results provide insight into the role of clefts as host environments for inclusion of neutral molecules and show how even solvent molecules with exceptionally weak donor-acceptor properties may participate in supramolecular assemblies. In addition, the results are unique in enabling a clear assessment of the effect of the encapsulation of the metal cation on the ion-pairing tendency of the metal complex and implications for anion selectivity.

  20. 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

  1. 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

  2. Host-guest energetic nanocomposites based on self-assembly of multi-nitro organic molecules in nanochannels of mesoporous materials

    NASA Astrophysics Data System (ADS)

    Cai, Huaqiang; Yang, Rongji; Yang, Guangcheng; Huang, Hui; Nie, Fude

    2011-07-01

    Host-guest energetic nanocomposites have been synthesized by self-assembly of the high energy density compound HNIW in nanometer-scale channels of an ordered mesoporous material SBA-15. The complete impregnation of HNIW can be achieved in acetone solvent at ambient temperature, and the maximum amount was around 70 wt%. Structural characterizations were systematically provided by XRD, TEM, N2 adsorption, TG, 13C solid-state NMR and FT-IR. The tendency of multi-nitro organic molecules to self-assemble when the solvent evaporated has been described. Hydrogen bond interactions were considered as the main driving force, so the choices of matched host matrix and guest organic compounds were pivotal for implementing this process. The thermal properties of nanocomposites were measured by DSC analysis. Compared with pure HNIW and a physical mixture, the decomposition peak temperature of the confined crystals decreased about 11 °C, while the total amount of heat released slightly increased. This strategy can also be expanded to other similar host-guest systems.

  3. Characterization of the host–guest complex of a curcumin analog with ?-cyclodextrin and ?-cyclodextrin–gemini surfactant and evaluation of its anticancer activity

    PubMed Central

    Poorghorban, Masoomeh; Das, Umashankar; Alaidi, Osama; Chitanda, Jackson M; Michel, Deborah; Dimmock, Jonathan; Verrall, Ronald; Grochulski, Pawel; Badea, Ildiko

    2015-01-01

    Background Curcumin analogs, including the novel compound NC 2067, are potent cytotoxic agents that suffer from poor solubility, and hence, low bioavailability. Cyclodextrin-based carriers can be used to encapsulate such agents. In order to understand the interaction between the two molecules, the physicochemical properties of the host–guest complexes of NC 2067 with ?-cyclodextrin (CD) or ?-cyclodextrin–gemini surfactant (CDgemini surfactant) were investigated for the first time. Moreover, possible supramolecular structures were examined in order to aid the development of new drug delivery systems. Furthermore, the in vitro anticancer activity of the complex of NC 2067 with CDgemini surfactant nanoparticles was demonstrated in the A375 melanoma cell line. Methods Physicochemical properties of the complexes formed of NC 2067 with CD or CDgemini surfactant were investigated by synchrotron-based powder X-ray diffraction, Fourier-transform infrared spectroscopy, and thermogravimetric analysis. Synchrotron-based small- and wide-angle X-ray scattering and size measurements were employed to assess the supramolecular morphology of the complex formed by NC 2067 with CDgemini surfactant. Lastly, the in vitro cell toxicity of the formulations toward A375 melanoma cells at various drug-to-carrier mole ratios were measured by cell viability assay. Results Physical mixtures of NC 2067 and CD or CDgemini surfactant showed characteristics of the individual components, whereas the complex of NC 2067 and CD or CDgemini surfactant presented new structural features, supporting the formation of the host–guest complexes. Complexes of NC 2067 with CDgemini surfactants formed nanoparticles having sizes of 100–200 nm. NC 2067 retained its anticancer activity in the complex with CDgemini surfactant for different drug-to-carrier mole ratios, with an IC50 (half-maximal inhibitory concentration) value comparable to that for NC 2067 without the carrier. Conclusion The formation of host–guest complexes of NC 2067 with CD or CDgemini surfactant has been confirmed and hence the CDgemini surfactant shows good potential to be used as a delivery system for anticancer agents. PMID:25609956

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

    SciTech Connect

    Guo, Zhiyong [Iowa State University; Kobayashi, Takeshi [Ames Laboratory; Wang, Lin-Lin [Ames Laboratory; Goh, Tian Wei [Iowa State University; Xiao, Chaoxian [Iowa State University; Caporini, Marc A [Bruker BioSpin Corporation; Rosay, Melanie [Bruker BioSpin Corporation; Johnson, Duane D [Ames Laboratory; Pruski, Marek [Ames Laboratory; Huang, Wenyu [Ames Laboratory

    2014-10-08

    The host–guest interaction between metal ions (Pt2+ and Cu2+) and a zirconium metal–organic 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.

  5. Large and fast single-crystal resistive humidity sensitivity of metal pnictide halides containing van der Waals host-guest interactions.

    PubMed

    Jiang, Xiao-Ming; Yan, Zhi-Bo; Liu, Dan; Wang, Ke-Feng; Guo, Guo-Cong; Li, Shao-Zhen; Liu, Jun-Ming

    2014-10-01

    Two new metal pnictide halides, (Hg(9.75)As(5.5))(GaCl4)3 and (Hg13Sb8)(ZnBr4)4, have been prepared by solid-state reactions. Their structures feature 3D cationic host frameworks built of mercury pnictide polyhedra and form 1D tunnels filled with discrete guest halide polyanions; the guests and hosts are assembled by van der Waals interactions. Both complexes exhibit good single-crystal humidity sensitivity, with a humidity sensitivity factor as big as three orders of magnitude, a quick resistance response, fast recovery, and good reproducibility. This study provide a new way to design promising resistive humidity detectors by introducing van der Waals host-guest interactions into their structures. PMID:25110860

  6. Nanoscale Molecular Tweezers

    NSDL National Science Digital Library

    The featured molecules for this month are drawn from the "Research Advances" column by Angela G. King, and represent some of the structures from the research on molecular tweezers (published in J. Am. Chem. Soc. 2004, 126, 8124). The structures below are based on the figure on page 1690 showing two types of receptors that switch between U and W shapes upon coordination of soft metal cations, acting in the manner of mechanical tweezers. When viewing these molecules in Chime you must render in ball and stick or space filling modes in order to see the incorporated metal ions. In several cases the torsion angles connecting the anthracene substituents to the rest of the molecule are not well defined and have been drawn as either coplanar or orthogonal to the central ring system. At a moderate level of theory, the torsion angle in those instances where it has been set to 90° displays a broad minimum ranging for 50?130°.

  7. Hardware manual of dexterous tweezers(1/25) Hardware manual of dexterous tweezers

    E-print Network

    Fearing, Ron

    Hardware manual of dexterous tweezers(1/25) Hardware manual of dexterous tweezers Version 0 ..................................................................... 23 #12;Hardware manual of dexterous tweezers(2/25) 1 Overview The prototype tweezers for micro stage X stage Y stageX finger Y finger #12;Hardware manual of dexterous tweezers(3/25) 2 Setup outline 2

  8. 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, Géraldine; Petit, Samuel; Coquerel, Gérard

    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

  9. Anion Binding Properties of Alkynylplatinum(II) Complexes with Amide-Functionalized Terpyridine: Host–Guest Interactions and Fluoride Ion-Induced Deprotonation**

    PubMed Central

    Yeung, Margaret Ching-Lam; Chu, Ben Wai-Kin; Yam, Vivian Wing-Wah

    2014-01-01

    Molecular sensors able to detect ions are of interest due to their potential application in areas such as pollutant sequestration. Alkynylplatinum(II) terpyridine complexes with an amide-based receptor moiety have been synthesized and characterized. Their anion binding properties based on host–guest interactions have been examined with the use of UV-vis absorption and emission spectral titration studies. Spectral changes were observed for both complexes upon the addition of spherical and nonspherical anions. Their titration profiles were shown to be in good agreement with theoretical results predicting a 1:1 binding model, and the binding constants were determined from the experimental data. Drastic color changes from yellow to orange–red were observed for one of the complexes upon titration with fluoride (F?) ion in acetone. These changes were ascribed to the deprotonation of the amide functionalities induced by F? ion, and this was confirmed by the restoration of spectral changes upon addition of trifluoroacetic acid to the F? ion–complex mixture as well as by electrospray ionization mass spectrometry (ESI-MS) data. PMID:25478312

  10. Theoretical investigation of enantioselectivity of cage-like supramolecular assembly: The insights into the shape complementarity and host-guest interaction.

    PubMed

    Ootani, Yusuke; Akinaga, Yoshinobu; Nakajima, Takahito

    2015-03-15

    Enantioselectivity in the aza-Cope rearrangement of a guest molecule encapsulated in a cage-like supramolecular assembly [Ga4 L6 ](12-) [L?=?1,5-bis(2',3'-dihydroxybenzamido)naphthalene] is investigated using density functional theory and ab initio molecular orbital calculations. Reaction pathways leading to R- and S-enantiomers encapsulated in the [Ga4 L6 ](12-) are explored. The reaction barriers and the stabilities of the prochiral structures differed in the [Ga4 L6 ](12-) , resulting that the product with an R structure is favorably produced in the ?-structure [Ga4 L6 ](12-) . The large energy difference in the prochiral structures in the [Ga4 L6 ](12-) was attributed to the deformation of the bulky substituent. The host-guest interaction energy raises the reaction barrier for the product with an S structure. The previous study suggested that the different stability of the prochiral substrates in the assembly was the origin of the enantioselectivity, and the suggestion is supported by our computational finding. In addition, our results show that the difference in the reaction barriers also importantly contributes to the enantioselectivity. © 2015 Wiley Periodicals, Inc. PMID:25565267

  11. 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. (UC)

    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.

  12. Formation of 1:1 and 2:1 host-guest inclusion complexes of ?-cyclodextrin with cycloalkanols: A 1H and 13C NMR spectroscopic study

    NASA Astrophysics Data System (ADS)

    Akita, Tomoki; Yoshikiyo, Keisuke; Yamamoto, Tatsuyuki

    2014-09-01

    Binding constants (Ka's) for the formation of inclusion complexes of ?-cyclodextrin (?-CD) with cycloalkanols (c-CnOH; n = 4-8) were determined by means of 1H and 13C NMR titration, under two different conditions: (i) only 1:1 host-guest inclusion complexes are formed when the guest is in excess; (ii) the formation of 2:1 inclusion complexes occurs only after that of 1:1 inclusion complexes, when the host is in excess. The results of this work showed that ?-CD can include c-C4OH or c-C5OH only when the molar ratio is 1:1; larger ring-sized cycloalkanols such as c-C6OH, c-C7OH or c-C8OH can be included only when the molar ratio is 2:1. These findings, together with those obtained for the four derivatives of ?-CD, per-6-O-methyl-?-CD, per-2-O-methyl-?-CD, per-3-O-methyl-?-CD, and per-2,6-di-O-methyl-?-CD, suggested that ?-CD forms 2:1 inclusion complexes with c-C6OH, c-C7OH or c-C8OH in a tail-to-tail manner, in which the secondary hydroxy sides of the two CD molecules face each other. Two-dimensional ROESY measurements confirmed our results.

  13. Study of host-guest interactions in benzodiazacoronands by means of solid state NMR spectroscopy, X-ray diffraction and quantum mechanical computations.

    PubMed

    Nowicka, Katarzyna; Bujacz, Anna; Paluch, Piotr; Sobczuk, Adam; Jeziorna, Agata; Ciesielski, W?odzimierz; Bujacz, Grzegorz D; Jurczak, Janusz; Potrzebowski, Marek J

    2011-04-14

    In this work we present solid state data for five host-guest complexes formed by N-(4,19-dioxo-2,8,15,21-tetraoxa-5,18-diazatricyclohexacosa-1(25),9(14),10,12,22(26),23-hexaen-26-yl)-benzamide (1) belonging to the group of benzodiazacoronands, achiral compounds for which chiral crystals were found (J. Kalisiak and J. Jurczak, Cryst. Growth Des., 2006, 6, 20). The X-ray structure was resolved for four of them. It was found that 1 crystallizes in P2(1)/c, P1 and P2(1)/n achiral space groups. Differentiation of molecular packing and the presence of guest molecules within the crystal lattice were analyzed with solid state NMR. An attempt was made to correlate changes in (13)C ?(ii) and (15)N ?(ii) chemical shift tensor values, obtained from analysis of spinning sidebands of 1D and 2D (2D PASS) NMR spectra, with changes in the strength of hydrogen bonding. Quantum mechanical DFT GIAO calculations of NMR shielding parameters carried out on structures with coordinates taken from XRD were employed for signals assignment and verification of structural constraints. PMID:21384038

  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. A study on the versatility of metallacycles in host-guest chemistry: interactions in halide-centered hexanuclear copper(II) pyrazolate complexes.

    PubMed

    Ponce-Vargas, Miguel; Muñoz-Castro, Alvaro

    2014-07-14

    Hexanuclear copper(II) pyrazolate complexes have shown the ability to encapsulate different halide ions, leading to [trans-Cu6{?-3,5-(CF3)2pz}6(?-OH)6X](-) (X = F, Cl, Br, I). They offer an interesting case study for variation in local properties at host binding sites, due to the presence of a six membered ring involving Cu(II) centers considered as the borderline Lewis acid according to the Pearson Hard and Soft Acids and Bases (HSAB) principle. Here, we describe the host-guest interactions via relativistic density functional calculations, involving the graphical description of local dipole and quadrupole moments, energy decomposition analysis, non-covalent indices, and magnetic behavior. The observed variation in the copper local dipole and quadrupole moments suggests that a metallacycle host offers great advantages in comparison to their organic counterparts, prompted by the versatility of the metallic centers to modulate the surrounding electron density accordingly. According to our results, the contribution of ion-dipole forces in the halide-centered series decreases from 95.0% to 77.0% from the fluoride to the iodide complex, whereas the contribution of higher order interactions such as quadrupole-dipole and quadrupole-quadrupole, goes from 5.0% to 23.0% towards a softer guest. In addition, the through-the-space magnetic response of trans-Cu6{?-3,5-(CF3)2pz}6(?-OH)6, reveals a noteworthy aromatic structure, which is driven by the superexchange through the ligands leading to a singlet ground state. PMID:24866754

  16. On chip shapeable optical tweezers

    PubMed Central

    Renaut, C.; Cluzel, B.; Dellinger, J.; Lalouat, L.; Picard, E.; Peyrade, D.; Hadji, E.; de Fornel, F.

    2013-01-01

    Particles manipulation with optical forces is known as optical tweezing. While tweezing in free space with laser beams was established in the 1980s, integrating the optical tweezers on a chip is a challenging task. Recent experiments with plasmonic nanoantennas, microring resonators, and photonic crystal nanocavities have demonstrated optical trapping. However, the optical field of a tweezer made of a single microscopic resonator cannot be shaped. So far, this prevents from optically driven micromanipulations. Here we propose an alternative approach where the shape of the optical trap can be tuned by the wavelength in coupled nanobeam cavities. Using these shapeable tweezers, we present micromanipulation of polystyrene microspheres trapped on a silicon chip. These results show that coupled nanobeam cavities are versatile building blocks for optical near-field engineering. They open the way to much complex integrated tweezers using networks of coupled nanobeam cavities for particles or bio-objects manipulation at a larger scale. PMID:23887310

  17. 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.

  18. 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.

  19. Advantages of holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Reicherter, Marcus; Liesener, Jan; Haist, Tobias; Tiziani, Hans J.

    2003-10-01

    In the last decade optical tweezers became an important tool in microbiology. However, the setup becomes very complex if more than one trap needs to be moved. Holographic tweezers offer a very simple and cost efficient way of manipulating several traps independently in all three dimensions with an accuracy of less 100 nm. No mechanically moving parts are used therefore making them less vulnerable to vibration. They use computer-generated holograms (CGHs) written into a spatial light modulator (SLM) to control the position of each trap in space and to manipulate their shape. The ability to change the shape of the optical trap makes it possible to adapt the light field to a specific particle shape or in the case of force measurements to adjust the trapping potential. Furthermore the SLM can be used to correct for aberrations within the optical setup.

  20. 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.

  1. Absolute calibration of optical tweezers

    SciTech Connect

    Viana, N.B.; Mazolli, A.; Maia Neto, P.A.; Nussenzveig, H.M.; Rocha, M.S.; Mesquita, O.N. [LPO-COPEA and Instituto de Fisica, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, 21941-590 (Brazil); Departamento de Fisica, Instituto de Ciencias ExatasUniversidade Federal de Minas Gerais, Belo Horizonte, MG, 30123-970 (Brazil)

    2006-03-27

    As a step toward absolute calibration of optical tweezers, a first-principles theory of trapping forces with no adjustable parameters, corrected for spherical aberration, is experimentally tested. Employing two very different setups, we find generally very good agreement for the transverse trap stiffness as a function of microsphere radius for a broad range of radii, including the values employed in practice, and at different sample chamber depths. The domain of validity of the WKB ('geometrical optics') approximation to the theory is verified. Theoretical predictions for the trapping threshold, peak position, depth variation, multiple equilibria, and 'jump' effects are also confirmed.

  2. Quantum limited particle sensing in optical tweezers

    SciTech Connect

    Tay, J.W. [Jack Dodd Centre for Photonics and Ultracold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); Hsu, Magnus T. L. [School of Mathematics and Physics, University of Queensland, St. Lucia, Queensland 4072 (Australia); Bowen, Warwick P. [Jack Dodd Centre for Photonics and Ultracold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); School of Mathematics and Physics, University of Queensland, St. Lucia, Queensland 4072 (Australia)

    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.

  3. 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

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

    E-print Network

    Ritort, Felix

    Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy Keir C Neuman1 & Attila Nagy2 Single-molecule force spectroscopy has emerged as a powerful tool and displacement generated by single molecules ranging from cells to proteins. Although there is an ever

  5. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...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 (direct current), or a combination of radio...

  6. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...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 (direct current), or a combination of radio...

  7. "Red Tweezers": Fast, customisable hologram generation for optical tweezers

    NASA Astrophysics Data System (ADS)

    Bowman, Richard W.; Gibson, Graham M.; Linnenberger, Anna; Phillips, David B.; Grieve, James A.; Carberry, David M.; Serati, Steven; Miles, Mervyn J.; Padgett, Miles J.

    2014-01-01

    Holographic Optical Tweezers (HOT) are a versatile way of manipulating microscopic particles in 3D. However, their ease of use has been hampered by the computational load of calculating the holograms, resulting in an unresponsive system. We present a program for generating these holograms on a consumer Graphics Processing Unit (GPU), coupled to an easy-to-use interface in LabVIEW (National Instruments). This enables a HOT system to be set up without writing any additional code, as well as providing a platform enabling the fast generation of other holograms. The GPU engine calculates holograms over 300 times faster than the same algorithm running on a quad core CPU. The hologram algorithm can be altered on-the-fly without recompiling the program, allowing it to be used to control Spatial Light Modulators in any situation where the hologram can be calculated in a single pass. The interface has also been rewritten to take advantage of new features in LabVIEW 2010. It is designed to be easily modified and extended to integrate with hardware other than our own.

  8. Optical tweezers: light for manipulating microscopic world

    NASA Astrophysics Data System (ADS)

    Dasgupta, Raktim

    2012-05-01

    Optical tweezers make use of a tightly focused laser beam to trap, move, guide, rotate and even sort microscopic objects solely with light. Although the basic laser tweezers, making use of a TEM00 laser beam to create a single trap point, have proved to be useful for any applications in areas ranging from physics to biology, a major breakthrough in this field came as the use of computer generated holograms enabled researchers to create multiple trap sites from single laser source (holographic optical tweezers). Coupled with microfluidic techniques, holographic optical tweezers have promised development of optical techniques for high throughput sorting of different cell types under a single micro-chip platform. The holographic methods have also helped the use of specialized laser beams like Laguerre-Gaussian beams instead of the conventional laser beam for interesting applications like orienting/rotating the trapped objects or trapping cells with minimum photodamage. Further, combining optical tweezers with Raman spectroscopy is becoming increasingly popular for studying single cell biochemistry as use of optical forces to immobilize the cells under investigations not only avoids the negative effects of fixing the cells onto substrate but also improve the quality of the recorded spectra. These advanced optical trapping techniques as outlined above along with some illustrative biophotonics applications have been explored.

  9. Quantum computation architecture using optical tweezers

    SciTech Connect

    Weitenberg, Christof [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Kuhr, Stefan [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); University of Strathclyde, Department of Physics, SUPA, Glasgow G4 0NG (United Kingdom); Moelmer, Klaus; Sherson, Jacob F. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

    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.

  10. Designing single-beam multitrapping acoustical tweezers.

    PubMed

    Silva, Glauber T; Baggio, André L

    2015-02-01

    The concept of a single-beam acoustical tweezer device which can simultaneously trap microparticles at different points is proposed and demonstrated through computational simulations. The device employs an ultrasound beam produced by a circular focused transducer operating at 1 MHz in water medium. The ultrasound beam exerts a radiation force that may tweeze suspended microparticles in the medium. Simulations show that the acoustical tweezer can simultaneously trap microparticles in the pre-focal zone along the beam axis, i.e. between the transducer surface and its geometric focus. As acoustical tweezers are fast becoming a key instrument in microparticle handling, the development of acoustic multitrapping concept may turn into a useful tool in engineering these devices. PMID:25304994

  11. A force calibration standard for magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Köber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.

    2014-12-01

    To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below ˜1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.

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

    SciTech Connect

    Courtney, Charles R. P., E-mail: c.r.p.courtney@bath.ac.uk [Department of Mechanical Engineering, University of Bath, Bath (United Kingdom); Demore, Christine E. M.; Wu, Hongxiao; Cochran, Sandy [Institute of Medical Science and Technology, University of Dundee, Dundee (United Kingdom); Grinenko, Alon; Wilcox, Paul D.; Drinkwater, Bruce W. [Department of Mechanical Engineering, University of Bristol, Bristol (United Kingdom)

    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-?m-diameter polystyrene spheres. These capabilities bring the dexterity of acoustic tweezers substantially closer to that of optical tweezers.

  13. Quantum-noise quenching in atomic tweezers

    SciTech Connect

    Zippilli, Stefano [Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Theoretische Physik, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany); Fachbereich Physik and Research Center OPTIMAS, Technische Universitaet Kaiserslautern, D-67663 Kaiserslautern (Germany); Mohring, Bernd; Schleich, Wolfgang [Institut fuer Quantenphysik, Universitaet Ulm, D-89081 Ulm (Germany); Lutz, Eric [Department of Physics, University of Augsburg, D-86135 Augsburg (Germany); Morigi, Giovanna [Departament de Fisica, Universitat Autonoma de Barcelona, E-08193 Bellaterra (Spain); Theoretische Physik, Universitaet des Saarlandes, D-66041 Saarbruecken (Germany)

    2011-05-15

    The efficiency of extracting single atoms or molecules from an ultracold bosonic reservoir is theoretically investigated for a protocol based on lasers, coupling the hyperfine state in which the atoms form a condensate to another stable state, in which the atom experiences a tight potential in the regime of collisional blockade, the quantum tweezers. The transfer efficiency into the single-atom ground state of the tight trap is fundamentally limited by the collective modes of the condensate, which are thermally and dynamically excited. The noise due to these excitations can be quenched for sufficiently long laser pulses, thereby achieving high efficiencies. These results show that this protocol can be applied to initializing a quantum register based on tweezer traps for neutral atoms.

  14. 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.

  15. 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.

  16. 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…

  17. Measuring storage and loss moduli using optical tweezers: broadband microrheology

    E-print Network

    Manlio Tassieri; Graham M. Gibson; R. M. L. Evans; Alison M. Yao; Rebecca Warren; Miles J. Padgett; Jonathan M. Cooper

    2009-10-07

    We present an experimental procedure to perform broadband microrheological measurements with optical tweezers. A generalised Langevin equation is adopted to relate the time-dependent trajectory of a particle in an imposed flow to the frequency-dependent moduli of the complex fluid. This procedure allows us to measure the material linear viscoelastic properties across the widest frequency range achievable with optical tweezers.

  18. Single-Molecule Magnetic Tweezers Studies of Type IB Topoisomerases

    E-print Network

    Dekker, Nynke

    .2). Above the flow cell, a pair of permanent magnets or an electromagnet is suspended on a motorized stageChapter 7 Single-Molecule Magnetic Tweezers Studies of Type IB Topoisomerases Jan Lipfert, Daniel A the application of single-molecule force spectroscopy techniques to the study of topoisomerases. Magnetic tweezers

  19. 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.

  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. 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.

  2. Optical capsule and tweezer array for molecular motor use.

    PubMed

    Yupapin, Preecha P; Kulsirirat, Kathawut; Techithdeera, Wicharn

    2013-09-01

    A generation of optical capsules and tweezers within a modified optical add-drop filter known as PANDA ring resonator with a new concept is proposed. By using dark and bright solitons, the orthogonal tweezers can be formed within the system and observed simultaneously at the output ports. Under the resonant condition, the optical capsules and tweezers generated by dark and bright soliton pair corresponding to the left-hand and right-hand rotating solitons (tweezers) can be generated. When a soliton is interacted by an object, an angular momentum of either bright or dark tweezers is imparted to the object, in which two possible spin states known as tweezer spins are exhibited. Furthermore, an array of molecular capsules and spins, i.e., trapped molecules can be generated and detected by using the proposed system, which can be used to form large scale tweezer or capsule spins. In application, the trapped molecules can be moved and rotated securely to the required destinations, which can be useful for many applications, especially, in medical diagnosis, therapy and surgery. PMID:23955778

  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. Optical tweezers calibration with Bayesian inference

    NASA Astrophysics Data System (ADS)

    Türkcan, Silvan; Richly, Maximilian U.; Le Gall, Antoine; Fiszman, Nicolas; Masson, Jean-Baptiste; Westbrook, Nathalie; Perronet, Karen; Alexandrou, Antigoni

    2014-09-01

    We present a new method for calibrating an optical-tweezer setup that is based on Bayesian inference1. This method employs an algorithm previously used to analyze the confined trajectories of receptors within lipid rafts2,3. The main advantages of this method are that it does not require input parameters and is insensitive to systematic errors like the drift of the setup. Additionally, it exploits a much larger amount of the information stored in the recorded bead trajectory than standard calibration approaches. The additional information can be used to detect deviations from the perfect harmonic potential or detect environmental influences on the bead. The algorithm infers the diffusion coefficient and the potential felt by a trapped bead, and only requires the bead trajectory as input. We demonstrate that this method outperforms the equipartition method and the power-spectrum method in input information required (bead radius and trajectory length) and in output accuracy. Furthermore, by inferring a higher order potential our method can reveal deviations from the assumed second-order potential. More generally, this method can also be used for magnetic-tweezer calibration.

  5. Quantitative modeling and optimization of magnetic tweezers.

    PubMed

    Lipfert, Jan; Hao, Xiaomin; Dekker, Nynke H

    2009-06-17

    Magnetic tweezers are a powerful tool to manipulate single DNA or RNA molecules and to study nucleic acid-protein interactions in real time. Here, we have modeled the magnetic fields of permanent magnets in magnetic tweezers and computed the forces exerted on superparamagnetic beads from first principles. For simple, symmetric geometries the magnetic fields can be calculated semianalytically using the Biot-Savart law. For complicated geometries and in the presence of an iron yoke, we employ a finite-element three-dimensional PDE solver to numerically solve the magnetostatic problem. The theoretical predictions are in quantitative agreement with direct Hall-probe measurements of the magnetic field and with measurements of the force exerted on DNA-tethered beads. Using these predictive theories, we systematically explore the effects of magnet alignment, magnet spacing, magnet size, and of adding an iron yoke to the magnets on the forces that can be exerted on tethered particles. We find that the optimal configuration for maximal stretching forces is a vertically aligned pair of magnets, with a minimal gap between the magnets and minimal flow cell thickness. Following these principles, we present a configuration that allows one to apply > or = 40 pN stretching forces on approximately 1-microm tethered beads. PMID:19527664

  6. Exploring the mechanome with optical tweezers and single molecule fluorescence

    E-print Network

    Brau, Ricardo R. (Ricardo Rafael), 1979-

    2008-01-01

    The combination of optical tweezers and single molecule fluorescence into an instrument capable of making combined, coincident measurements adds an observable dimension that allows for the examination of the localized ...

  7. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type epilator. (a) Identification. The...

  8. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type epilator. (a) Identification. The...

  9. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Therapeutic Devices § 878.5360 Tweezer-type epilator. (a) Identification. The...

  10. 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

  11. Measuring storage and loss moduli using optical tweezers: broadband microrheology.

    PubMed

    Tassieri, Manlio; Gibson, Graham M; Evans, R M L; Yao, Alison M; Warren, Rebecca; Padgett, Miles J; Cooper, Jonathan M

    2010-02-01

    We present an experimental procedure to perform broadband microrheological measurements with optical tweezers. A generalized Langevin equation is adopted to relate the time-dependent trajectory of a particle in an imposed flow to the frequency-dependent moduli of the complex fluid. This procedure allows us to measure the material linear viscoelastic properties across the widest frequency range achievable with optical tweezers. PMID:20365652

  12. Universal axial fluctuations in optical tweezers.

    PubMed

    Ribezzi-Crivellari, Marco; Alemany, Anna; Ritort, Felix

    2015-03-01

    Optical tweezers (OTs) allow the measurement of fluctuations at the nanoscale, in particular fluctuations in the end-to-end distance in single molecules. Fluctuation spectra can yield valuable information, but they can easily be contaminated by instrumental effects. We identify axial fluctuations, i.e., fluctuations of the trapped beads in the direction of light propagation, as one of these instrumental effects. Remarkably, axial fluctuations occur on a characteristic timescale similar to that of conformational (folding) transitions, which may lead to misinterpretation of the experimental results. We show that a precise measurement of the effect of force on both axial and conformational fluctuations is crucial to disentangle them. Our results on axial fluctuations are captured by a simple and general formula valid for all OT setups and provide experimentalists with a general strategy to distinguish axial fluctuations from conformational transitions. PMID:25723436

  13. 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.

  14. Eukaryotic membrane tethers revisited using magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Hosu, Basarab G.; Sun, Mingzhai; Marga, Françoise; Grandbois, Michel; Forgacs, Gabor

    2007-06-01

    Membrane nanotubes, under physiological conditions, typically form en masse. We employed magnetic tweezers (MTW) to extract tethers from human brain tumor cells and compared their biophysical properties with tethers extracted after disruption of the cytoskeleton and from a strongly differing cell type, Chinese hamster ovary cells. In this method, the constant force produced with the MTW is transduced to cells through super-paramagnetic beads attached to the cell membrane. Multiple sudden jumps in bead velocity were manifest in the recorded bead displacement-time profiles. These discrete events were interpreted as successive ruptures of individual tethers. Observation with scanning electron microscopy supported the simultaneous existence of multiple tethers. The physical characteristics, in particular, the number and viscoelastic properties of the extracted tethers were determined from the analytic fit to bead trajectories, provided by a standard model of viscoelasticity. Comparison of tethers formed with MTW and atomic force microscopy (AFM), a technique where the cantilever-force transducer is moved at constant velocity, revealed significant differences in the two methods of tether formation. Our findings imply that extreme care must be used to interpret the outcome of tether pulling experiments performed with single molecular techniques (MTW, AFM, optical tweezers, etc). First, the different methods may be testing distinct membrane structures with distinct properties. Second, as soon as a true cell membrane (as opposed to that of a vesicle) can attach to a substrate, upon pulling on it, multiple nonspecific membrane tethers may be generated. Therefore, under physiological conditions, distinguishing between tethers formed through specific and nonspecific interactions is highly nontrivial if at all possible.

  15. 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.

  16. 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.

  17. Sorting out bacterial viability with optical tweezers.

    PubMed

    Ericsson, M; Hanstorp, D; Hagberg, P; Enger, J; Nyström, T

    2000-10-01

    We have developed a method, using laser, optical tweezers and direct microscopic analysis of reproductive potential and membrane integrity, to assess single-cell viability in a stationary-phase Escherichia coli population. It is demonstrated here that a reduction in cell integrity, determined by using the fluorescent nucleic acid stain propidium iodide, correlated well with a reduction in cell proliferating potential during the stationary-phase period studied. Moreover, the same cells that exhibited reduced integrity were found to be the ones that failed to divide upon nutrient addition. A small but significant number of the intact cells (496 of 7,466 [6.6%]) failed to replicate. In other words, we did not find evidence for the existence of a large population of intact but nonculturable cells during the stationary-phase period studied but it is clear that reproductive ability can be lost prior to the loss of membrane integrity. In addition, about 1% of the stationary-phase cells were able to divide only once upon nutrient addition, and in a few cases, only one of the two cells produced by division was able to divide a second time, indicating that localized cell deterioration, inherited by only one of the daughters, may occur. The usefulness of the optical trapping methodology in elucidating the mechanisms involved in stationary-phase-induced bacterial death and population heterogeneity is discussed. PMID:10986260

  18. 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.

  19. Magneto-optical tweezers built around an inverted microscope

    SciTech Connect

    Claudet, Cyril; Bednar, Jan

    2005-06-10

    We present a simple experimental setup of magneto-optical tweezers built around an inverted microscope. Two pairs of coils placed around the focal point of the objective generate a planar-rotating magnetic field that is perpendicular to the stretching direction. This configuration allows us to control the rotary movement of a paramagnetic bead trapped in the optical tweezers. The mechanical design is universal and can be simply adapted to any inverted microscope and objective. The mechanical configuration permits the use of a rather large experimental cell and the simple assembly and disassembly of the magnetic attachment.

  20. Magneto-optical tweezers built around an inverted microscope.

    PubMed

    Claudet, Cyril; Bednar, Jan

    2005-06-10

    We present a simple experimental setup of magneto-optical tweezers built around an inverted microscope. Two pairs of coils placed around the focal point of the objective generate a planar-rotating magnetic field that is perpendicular to the stretching direction. This configuration allows us to control the rotary movement of a paramagnetic bead trapped in the optical tweezers. The mechanical design is universal and can be simply adapted to any inverted microscope and objective. The mechanical configuration permits the use of a rather large experimental cell and the simple assembly and disassembly of the magnetic attachment. PMID:16007842

  1. Tunable optical tweezers for wavelength-dependent measurements

    PubMed Central

    Hester, Brooke; Campbell, Gretchen K.; López-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

    2012-01-01

    Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them. PMID:22559522

  2. 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.

  3. 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 electrode’s intensity enables tuning of the MWCNT ensemble’s 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

  4. A new real non-invasive single fiber tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Yu; Liu, Zhihai; Yang, Jun; Yuan, Libo

    2012-02-01

    A new real non-invasive two-core single fiber optical tweezers is proposed and fabricated by fiber grinding and polishing technology. The yeast cells trapping performance of this special designed truncated cone tip fiber probe is demonstrated and investigated. The distributions of the optical field emerging from the truncated cone fiber tip are simulated by Beam Prop Method. Both axial and transverse trapping forces are calculated by FDTD method. This new optical tweezers can realize truly non-invasive remote trapping and manipulating bio-cells.

  5. 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.

  6. 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.

  7. Ultrahigh Frequency Lensless Ultrasonic Transducers for Acoustic Tweezers Application

    PubMed Central

    Hsu, Hsiu-Sheng; Li, Ying; Lee, Changyang; Lin, Anderson; Zhou, Qifa; Kim, Eun Sok; Shung, Kirk Koping

    2014-01-01

    Similar to optical tweezers, a tightly focused ultrasound microbeam is needed to manipulate microparticles in acoustic tweezers. The development of highly sensitive ultrahigh frequency ultrasonic transducers is crucial for trapping particles or cells with a size of a few microns. As an extra lens would cause excessive attenuation at ultrahigh frequencies, two types of 200-MHz lensless transducer design were developed as an ultrasound microbeam device for acoustic tweezers application. Lithium niobate single crystal press-focused (PF) transducer and zinc oxide self-focused transducer were designed, fabricated and characterized. Tightly focused acoustic beams produced by these transducers were shown to be capable of manipulating single microspheres as small as 5 ?m two-dimensionally within a range of hundreds of micrometers in distilled water. The size of the trapped microspheres is the smallest ever reported in the literature of acoustic PF devices. These results suggest that these lensless ultrahigh frequency ultrasonic transducers are capable of manipulating particles at the cellular level and that acoustic tweezers may be a useful tool to manipulate a single cell or molecule for a wide range of biomedical applications. PMID:23042219

  8. Supplementary information for: Electromagnetic Torque Tweezers: A Versatile Approach

    E-print Network

    Dekker, Nynke

    tweezers experimental configuration In the eMTT, electromagnets are combined with a permanent magnet assembly. The permanent magnet assembly consists of a stack of three individual cylindrical magnets and permanent magnet assembly is mounted onto a manual xy-stage (9064-XY, Newport) to facilitate alignment

  9. 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.

  10. 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.

  11. Optical tweezers experiments for fibroblast cell growth stimulation

    NASA Astrophysics Data System (ADS)

    Avila, Remy; Medina-Villalobos, Norma; Tamariz, Elisa; Chiu, Roger; Lopez-Marín, Luz María.; Acosta, Angélica; Castaño, 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.

  12. Construction of an optical tweezer for nanometer scale rheology

    NASA Astrophysics Data System (ADS)

    Raghu, A.; Ananthamurthy, Sharath

    2005-10-01

    The optical tweezer is a versatile set-up that can be employed in a wide variety of studies investigating the microscopic properties of materials. In particular, this set-up has in recent times been gainfully employed in probing rheological properties of materials that exhibit viscoelasticity. These measurements can provide data at the micro and nanometer scales, not normally accessible by rheometers that are used for measurements on bulk samples. In this work we describe a single laser beam optical tweezer set-up, which is built around an inverted open microscope. The trapped polystyrene particle bead's deviation from the trap potential minimum is monitored by laser back-scattering technique and the bead position measured by a quadrant photodiode detector. Additionally, a provision is made for video microscopic studies on dispersed beads using a CCD camera. A single particle microrheological experiment that can be performed using the set-up is described with relevant calculations.

  13. 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

  14. 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.

  15. Optical tweezers for mechanical control over DNA in a nanopore.

    PubMed

    Keyser, Ulrich F

    2012-01-01

    The translocation of long-chain molecules, such as DNA or peptides, through membranes is an integral process for the function of living cells. During the translocation process, a number of interactions of electrostatic or hydrophobic nature govern the translocation velocity. Most of these interactions remain largely unexplored on the single-molecule level due to a lack of suitable instrumentation. We have shown that a combination of optical tweezers, single solid-state nanopores, and electrophysiological ionic current detection can provide further insight into the behavior of polymers in confinement. Here, we describe the experimental procedures necessary for manipulation of single biopolymers in a single nanopore not only by electrical fields, but also through mechanical forces using optical tweezers. PMID:22528261

  16. 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

  17. 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.

  18. Cluster formation in ferrofluids induced by holographic optical tweezers.

    PubMed

    Masajada, Jan; Bacia, Marcin; Drobczy?ski, S?awomir

    2013-10-01

    Holographic optical tweezers were used to show the interaction between a strongly focused laser beam and magnetic nanoparticles in ferrofluid. When the light intensity was high enough, magnetic nanoparticles were removed from the beam center and formed a dark ring. The same behavior was observed when focusing vortex or Bessel beams. The interactions between two or more separated rings of magnetic nanoparticles created by independent optical traps were also observed. PMID:24081086

  19. Multiplying optical tweezers force using a micro-lever

    E-print Network

    Boyer, Edmond

    Multiplying optical tweezers force using a micro-lever Chih-Lang Lin1* , Yi-Hsiung Lee2 , Yi-Jui Liu2,3 , Jiann-Lih Hwang2 , Chin-Te Lin,4 Tien-Tung Chung4 , and Patrice L. Baldeck 1,5 1 Inst-driven micro-lever fabricated to multiply optical forces using the two-photon polymerization 3D

  20. 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.

  1. 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

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

    E-print Network

    Park, Woon Ik

    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 ...

  3. 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.

  4. 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

  5. An easier way to improve the trapping performance of optical tweezers by donut-shaped beam

    Microsoft Academic Search

    Che-Liang Tsai; Hang-Ping Huang; Long Hsu; Ken-Yuh Hsu

    2010-01-01

    In optical tweezers, it can be comprehended that the larger the inclination angle between the condensed laser beam and the optical axis contributes more to axial trapping force, while the central part of laser beam with smaller inclination angle contributes more transverse trapping force. Therefore donut-shaped beam is used to improve the problem of lessaxial trapping for common optical tweezers.

  6. Robotic manipulation of human red blood cells with optical tweezers for cell property characterization

    Microsoft Academic Search

    Youhua Tan; Dong Sun; Wenhao Huang; Jinping Cheng; Shuk Han Cheng

    2010-01-01

    Cell manipulation has received considerable attentions in recent years. Most of cell manipulations are performed manually without guarantee of high precision and high throughput. This paper reports our latest research on integrating robotics technologies into optical tweezers system for manipulation and biomechanical characterization of human red blood cells (RBCs). We first demonstrate the effectiveness of the robot-tweezers system in manipulation

  7. A general method for manipulating DNA sequences from any organism with optical tweezers

    E-print Network

    Ritort, Felix

    A general method for manipulating DNA sequences from any organism with optical tweezers Derek N sequences from any organism with optical tweezers. Molecules are produced from either genomic or cloned DNA method for manipulating DNA sequences from any organism. Here we describe and char- acterize

  8. Recognition of sequence-information in synthetic copolymer chains by a conformationally-constrained tweezer molecule.

    PubMed

    Colquhoun, Howard M; Zhu, Zhixue; Cardin, Christine J; Drew, Michael G B; Gan, Yu

    2009-01-01

    A novel type of tweezer molecule containing electron-rich 2-pyrenyloxy arms has been designed to exploit intramolecular hydrogen bonding in stabilising a preferred conformation for supramolecular complexation to complementary sequences in aromatic copolyimides. This tweezer-conformation is demonstrated by single-crystal X-ray analyses of the tweezer molecule itself and of its complex with an aromatic diimide model-compound. In terms of its ability to bind selectively to polyimide chains, the new tweezer molecule shows very high sensitivity to sequence effects. Thus, even low concentrations of tweezer relative to diimide units (< 2.5 mol %) are sufficient to produce dramatic, sequence-related splittings of the pyromellitimide proton NMR resonances. These induced resonance-shifts arise from ring-current shielding of pyromellitimide protons by the pyrenyloxy arms of the tweezer-molecule, and the magnitude of such shielding is a function of the tweezer-binding constant for any particular monomer sequence. Recognition of both short-range and long-range sequences is observed, the latter arising from cumulative ring-current shielding of diimide protons by tweezer molecules binding at multiple adjacent sites on the copolymer chain. PMID:20334103

  9. Single and dual fiber nano-tip optical tweezers: trapping and analysis

    E-print Network

    Paris-Sud XI, Université de

    Single and dual fiber nano-tip optical tweezers: trapping and analysis Jean-Baptiste Decombe tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping-position adjustment," Opt. Lett. 38, 2617­2620 (2013). 15. S. K. Mondal, S. S. Pal, and P. Kapur, "Optical fiber nano

  10. An automated and user-friendly optical tweezers for biomolecular investigations

    NASA Astrophysics Data System (ADS)

    Rathi, Pranav

    Optical tweezers are not new to biological applications but building a tweezers which is versatile, automated, precise, stable and user-friendly is quite challenging. Such a tweezers usually require not only a hefty budget but vast understanding of engineering of optomechanical systems. I describe in this dissertation a versatile, automated, precise, stable and user-friendly optical tweezers that we developed for biomolecular investigations under limited budget. I describe automation and control improvements along with newly-developed surface detection software. I also describe cost-effective optomechanical devices used in tweezers with potential for broader application. Finally, I present new results of single-molecule force spectroscopy of DNA overstretching as a function of water isotope type. Single DNA unzipping is also presented as a proof of concept.

  11. MatLab program for precision calibration of optical tweezers

    NASA Astrophysics Data System (ADS)

    Toli?-Nørrelykke, Iva Marija; Berg-Sørensen, Kirstine; Flyvbjerg, Henrik

    2004-06-01

    Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the ( x, y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum. First, cross-talk between channels in 2D position measurements is tested for, and eliminated if detected. Then, the Lorentzian power spectrum that results from the Einstein-Ornstein-Uhlenbeck theory, is fitted to the low-frequency part of the experimental spectrum in order to obtain an initial guess for parameters to be fitted. Finally, a more complete theory is fitted, a theory that optionally accounts for the frequency dependence of the hydrodynamic drag force and hydrodynamic interaction with a nearby cover slip, for effects of finite sampling frequency (aliasing), for effects of anti-aliasing filters in the data acquisition electronics, and for unintended "virtual" filtering caused by the position detection system. Each of these effects can be left out or included as the user prefers, with user-defined parameters. Several tests are applied to the experimental data during calibration to ensure that the data comply with the theory used for their interpretation: Independence of x- and y-coordinates, Hooke's law, exponential distribution of power spectral values, uncorrelated Gaussian scatter of residual values. Results are given with statistical errors and covariance matrix. Program summaryTitle of program: tweezercalib Catalogue identifier: ADTV Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Program Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV Computer for which the program is designed and others on which it has been tested: General computer running MatLab (MathWorks Inc.). Programming language used: MatLab (MathWorks Inc.). Uses "Optimization Toolbox" and "Statistics Toolbox". Memory required to execute with typical data: Of order 4 times the size of the data file. High speed storage required: None No. of lines in distributed program, including test data, etc.: 133 183 No. of bytes in distributed program, including test data, etc.: 1 043 674 Distribution format: tar gzip file Nature of physical problem: Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system. Method of solution: Elimination of cross-talk between quadrant photo-diode's output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects: Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for "virtual filtering" caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting. Statistical support for fit is given, with several plots suitable for inspection of consistency and quality of data and fit. Restrictions on the complexity of the problem: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate: The sampling rate should be well above the characteristic frequency of the trap,

  12. 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.

  13. Direct measurement of colloidal interactions with holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Polin, Marco

    This thesis describes experimental studies of colloidal interactions. After a brief introduction to some essential aspects of colloidal physics in Chapter 1, and to optical tweezers and digital video microscopy in Chapter 2, we present in Chapter 3 an analysis of the hydrodynamic interactions among colloidal particles. We propose a simple model for the hydrodynamic interactions among sufficiently separated colloidal particles, and prove its validity analyzing the vibrations of a one dimensional lattice of colloidal particles held by holographic optical tweezers. This model predicts a crossover from highly overdamped lattice vibrations, to propagating modes for systems having a sufficient number of particles. In Chapter 4 we study the equilibrium structure of highly deionized colloidal dispersions sedimented on a bounding surface. The particles in these systems develop an identical charge, and interact with an effective electrostatic interaction predicted to be purely repulsive. Several previous experiments, however, report a long ranged attractive component in the effective potential, but only for sufficiently low ionic concentrations. We present evidence for a qualitative dependence of the effective interparticle forces on the bounding surface's chemistry, with the attraction disappearing altogether when the bounding surface is coated with a thin layer of gold. We interpret this as evidence of the influence that ionizable groups on the glass surface have on the interactions among sedimented colloidal particles. We conclude by introducing in Chapter 5 a new method to measure directly the effective interaction among two colloidal particles. This method, based on the analysis of the diffusion of pairs of colloids along a line tweezer, is both local and fast, and it does not require a separate calibration for the line potential. It is strictly valid even in presence of light induced colloidal interactions, which have been a concern in previous experiments. We test the validity of our analysis using both simulations and experiments.

  14. Stabilization of distribution of radiation energy in optical tweezers wand

    NASA Astrophysics Data System (ADS)

    Derzhypolskyi, A.; Melenevskyi, D.; Gnatovskyi, O.; Negriyko, A.

    2008-05-01

    Considered is a correlation method of forming of specified distribution of radiation energy over the target, particularly in the optical tweezers wand. The method exploits an interaction of beforehand spatially modulated in phase wand beam with synthesized hologram specific to the modulation. The specified energy distribution is obtained as the convolution of the required field distribution and of cross-correlation function of the ideal wand beam and the real one. Because of beams wave fronts modulation the result of such a convolution is weakly dependent on the difference of the ideal and the real beams. Examined is the possibility of dynamic operation mode involving the spatial light modulation (SLM) device.

  15. Moving average process underlying the holographic-optical-tweezers experiments

    NASA Astrophysics Data System (ADS)

    ?lezak, Jakub; Drobczy?ski, S?awomir; Weron, Karina; Masajada, Jan

    2013-12-01

    We study statistical properties of the recordings which contain time-dependent positions of a bead trapped in optical tweezers. Analysis of such a time series indicates that the commonly accepted model, i.e., the autoregressive process of first order, is not sufficient to fit the data. We show a presence of the first-order moving average part in the dynamical model of the system. We explain origin of this part as an influence of the high frequency CCD camera on the measurements. The proposed autoregressive moving average model appears to reflect perfectly all statistical features of the high-frequency recording data.

  16. Multi-functional optical tweezers using computer-generated holograms

    NASA Astrophysics Data System (ADS)

    Liesener, J.; Reicherter, M.; Haist, T.; Tiziani, H. J.

    2000-11-01

    Optical tweezers are capable of trapping microscopic particles by photon momentum transfer. The use of dynamic computer-generated holograms for beam shaping allows a high flexibility in terms of trap characteristics and features. We use a liquid crystal display (LCD) to display the holograms. Efficiency losses caused by the periodic electrode structure of the LCD have been clearly reduced by use of an optically addressed spatial light modulator. We realized multiple traps, which can hold and move at least seven silica spheres independently in real time. We also demonstrate the controllability of trapped particles in three dimensions without the need for mechanical elements in the setup.

  17. Hybrid optical tweezers for dynamic micro-bead arrays

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshio; Tsutsui, Shogo; Ishikawa, Mitsuru; Kitajima, Hiroyuki

    2011-08-01

    Dynamic micro-bead arrays offer great flexibility and potential as sensing tools in various scientific fields. Two optical trapping techniques, the GPC method using a spatial light modulator and a mechanical scanning method using galvano mirrors, are combined in a hybrid optical tweezers system to handle dynamic micro-bead arrays. This system provides greater versatility while the GPC method creates massive micro-bead arrays in a 2D space, where the trapped beads can be manipulated smoothly and very quickly in a 3D space using the mechanical scanning method. Four typical examples are demonstrated in real time.

  18. Stiffer optical tweezers through real-time feedback control

    NASA Astrophysics Data System (ADS)

    Wallin, Anders E.; Ojala, Heikki; Hæggström, Edward; Tuma, Roman

    2008-06-01

    Using real-time re-programmable signal processing we connect acousto-optic steering and back-focal-plane interferometric position detection in optical tweezers to create a fast feedback controlled instrument. When trapping 3?m latex beads in water we find that proportional-gain position-clamping increases the effective lateral trap stiffness ˜13-fold. A theoretical power spectrum for bead fluctuations during position-clamped trapping is derived and agrees with the experimental data. The loop delay, ˜19?s in our experiment, limits the maximum achievable effective trap stiffness.

  19. 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

  20. Imaging microscopic viscosity with confocal scanning optical tweezers

    NASA Astrophysics Data System (ADS)

    Nemet, Boaz A.; Shabtai, Yossef; Cronin-Golomb, Mark

    2002-02-01

    The techniques of confocal microscopy and optical tweezers have shown themselves to be powerful tools in biological and medical research. We combine these methods to develop a minimally invasive instrument that is capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around biopolymer-producing cells, 100 × 100 images can be taken with 0.5-?m spatial resolution in 3 min. An image of the viscosity distribution around a pullulan-producing cell of Aureobasidium pullulans is shown as an example.

  1. Forming Three-Dimensional Colloidal Structures Using Holographic Optical Tweezers

    E-print Network

    C. R. Knutson; J. Plewa

    2005-08-05

    A method for forming permanent three dimensional structures from colloidal particles using holographic optical trapping is described. Holographic optical tweezers (HOT) are used to selectively position charge stabilized colloidal particles within a flow cell. Once the particles are in the desired location an electrolyte solution is pumped into the cell which reduces the Debye length and induces aggregation caused by the van der Waals attraction. This technique allows for the formation of three dimensional structures both on and away from the substrate that can be removed from solution without the aid of critical point drying. This technique is inexpensive, fast, and versatile as it relies on forces acting on almost all colloidal suspensions.

  2. 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 ? and the bending rigidity ? of the lipid membrane are obtained from the measured force-extension curve. In a one-phase liposome, it was found that ? increases as the charged component increases but ? 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.

  3. 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%.

  4. Molecular Basis for Preventing ?-Synuclein Aggregation by a Molecular Tweezer*

    PubMed Central

    Acharya, Srabasti; Safaie, Brian M.; Wongkongkathep, Piriya; Ivanova, Magdalena I.; Attar, Aida; Klärner, Frank-Gerrit; Schrader, Thomas; Loo, Joseph A.; Bitan, Gal; Lapidus, Lisa J.

    2014-01-01

    Recent work on ?-synuclein has shown that aggregation is controlled kinetically by the rate of reconfiguration of the unstructured chain, such that the faster the reconfiguration, the slower the aggregation. In this work we investigate this relationship by examining ?-synuclein in the presence of a small molecular tweezer, CLR01, which binds selectively to Lys side chains. We find strong binding to multiple Lys within the chain as measured by fluorescence and mass-spectrometry and a linear increase in the reconfiguration rate with concentration of the inhibitor. Top-down mass-spectrometric analysis shows that the main binding of CLR01 to ?-synuclein occurs at the N-terminal Lys-10/Lys-12. Photo-induced cross-linking of unmodified proteins (PICUP) analysis shows that under the conditions used for the fluorescence analysis, ?-synuclein is predominantly monomeric. The results can be successfully modeled using a kinetic scheme in which two aggregation-prone monomers can form an encounter complex that leads to further oligomerization but can also dissociate back to monomers if the reconfiguration rate is sufficiently high. Taken together, the data provide important insights into the preferred binding site of CLR01 on ?-synuclein and the mechanism by which the molecular tweezer prevents self-assembly into neurotoxic aggregates by ?-synuclein and presumably other amyloidogenic proteins. PMID:24567327

  5. 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 ?m. 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 ?m with residual spring constants of <26.6 fN/?m. We used these techniques in conjunction with a fast position measurement scheme to study the relaxation of ?-DNA molecules against a constant external force with submillisecond time resolution. We compare the results to predictions from the wormlike chain model. PMID:15345573

  6. 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

  7. 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.

  8. Calibration of optical tweezers based on an autoregressive model.

    PubMed

    Wang, Zi-Qiang; Zhou, Jin-Hua; Zhong, Min-Cheng; Li, Di; Li, Yin-Mei

    2014-07-14

    The power spectrum density (PSD) has long been explored for calibrating optical tweezers stiffness. Fast Fourier Transform (FFT) based spectral estimator is typically used. This approach requires a relatively longer data acquisition time to achieve adequate spectral resolution. In this paper, an autoregressive (AR) model is proposed to obtain the Spectrum Density using a limited number of samples. According to our method, the arithmetic model has been established with burg arithmetic, and the final prediction error criterion has been used to select the most appropriate order of the AR model, the power spectrum density has been estimated based the AR model. Then, the optical tweezers stiffness has been determined with the simple calculation from the power spectrum. Since only a small number of samples are used, the data acquisition time is significantly reduced and real-time stiffness calibration becomes feasible. To test this calibration method, we study the variation of the trap stiffness as a function of the parameters of the data length and the trapping depth. Both of the simulation and experiment results have showed that the presented method returns precise results and outperforms the conventional FFT method when using a limited number of samples. PMID:25090511

  9. Orthogonal actuation of a supramolecular double-porphyrin tweezer.

    PubMed

    Schmittel, Michael; Samanta, Soumen K

    2010-09-01

    A supramolecular three-component double-porphyrin tweezer (PT) is prepared quantitatively using heteroleptic complex formation along the HETTAP methodology. Insertion of guest molecules, such as DABCO or pyrazine, into the coupled porphyrin cavities of PT leads to an actuation of the double-porphyrin tweezer function. Evidence from (1)H NMR, VT NMR, and UV-vis titration suggests a rapid association/dissociation of the DABCO molecules at the central porphyrin. Upon addition of an equimolar mixture of DABCO and pyrazine to PT, a dynamic five-component self-assembled structure was furnished exclusively. (1)H NMR and K(assoc) values validate the greater stability of the heteroloaded PT-(DABCO)(py) system in comparison to the two homoloaded systems, PT-(DABCO)(2) and PT-(py)(2). The higher stability of PT-(DABCO)(py) seems to be the result of charge transfer from DABCO to the vacant pi* orbital of pyrazine across the porphyrin plane. PMID:20677818

  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. Design and construction of a space-borne optical tweezer apparatus

    NASA Astrophysics Data System (ADS)

    Resnick, Andrew

    2001-11-01

    A compact optical tweezer package has been developed for use on a microscope to be flown on the International Space Station as part of a series of experiments in colloid crystallization. A brief introduction to the principles of single-beam optical tweezer operation will be presented, after which a detailed system layout will be shown. Special design requirements due to the spaceflight nature of the hardware will also be discussed. The tweezer apparatus is capable of trapping many particles through use of a two-axis acousto-optical deflector. The trap strength is sufficient to perform the required science (50 pN at ?n=0.2). The trap beam behaves approximately as a diffraction limited single mode Gaussian beam of numerical aperture, NA=1.4, as shown through spot size measurements and confocal-type images of the focal region. This is the first time optical tweezers will be deployed in a microgravity environment.

  12. Interrogating Biology with Force: Single Molecule High-Resolution Measurements with Optical Tweezers

    PubMed Central

    Capitanio, Marco; Pavone, Francesco S.

    2013-01-01

    Single molecule force spectroscopy methods, such as optical and magnetic tweezers and atomic force microscopy, have opened up the possibility to study biological processes regulated by force, dynamics of structural conformations of proteins and nucleic acids, and load-dependent kinetics of molecular interactions. Among the various tools available today, optical tweezers have recently seen great progress in terms of spatial resolution, which now allows the measurement of atomic-scale conformational changes, and temporal resolution, which has reached the limit of the microsecond-scale relaxation times of biological molecules bound to a force probe. Here, we review different strategies and experimental configurations recently developed to apply and measure force using optical tweezers. We present the latest progress that has pushed optical tweezers’ spatial and temporal resolution down to today’s values, discussing the experimental variables and constraints that are influencing measurement resolution and how these can be optimized depending on the biological molecule under study. PMID:24047980

  13. Coherence and Raman Sideband Cooling of a Single Atom in an Optical Tweezer

    E-print Network

    Thompson, J. D.

    We investigate quantum control of a single atom in a tightly focused optical tweezer trap. We show that inevitable spatially varying polarization gives rise to significant internal-state decoherence but that this effect ...

  14. Microrheology with Optical Tweezers of gel-like materials 'is not an option'!

    E-print Network

    Tassieri, Manlio

    2015-01-01

    Optical tweezers have been successfully adopted as exceptionally sensitive transducers for microrheology studies of complex 'fluids'. Despite the general trend, a similar approach cannot be adopted for microrheology studies of 'gel-like' materials, e.g. living cells.

  15. Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State

    NASA Astrophysics Data System (ADS)

    Kaufman, A. M.; Lester, B. J.; Regal, C. A.

    2012-10-01

    We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.

  16. TweezPal - Optical tweezers analysis and calibration software

    NASA Astrophysics Data System (ADS)

    Osterman, Natan

    2010-11-01

    Optical tweezers, a powerful tool for optical trapping, micromanipulation and force transduction, have in recent years become a standard technique commonly used in many research laboratories and university courses. Knowledge about the optical force acting on a trapped object can be gained only after a calibration procedure which has to be performed (by an expert) for each type of trapped objects. In this paper we present TweezPal, a user-friendly, standalone Windows software tool for optical tweezers analysis and calibration. Using TweezPal, the procedure can be performed in a matter of minutes even by non-expert users. The calibration is based on the Brownian motion of a particle trapped in a stationary optical trap, which is being monitored using video or photodiode detection. The particle trajectory is imported into the software which instantly calculates position histogram, trapping potential, stiffness and anisotropy. Program summaryProgram title: TweezPal Catalogue identifier: AEGR_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGR_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 44 891 No. of bytes in distributed program, including test data, etc.: 792 653 Distribution format: tar.gz Programming language: Borland Delphi Computer: Any PC running Microsoft Windows Operating system: Windows 95, 98, 2000, XP, Vista, 7 RAM: 12 Mbytes Classification: 3, 4.14, 18, 23 Nature of problem: Quick, robust and user-friendly calibration and analysis of optical tweezers. The optical trap is calibrated from the trajectory of a trapped particle undergoing Brownian motion in a stationary optical trap (input data) using two methods. Solution method: Elimination of the experimental drift in position data. Direct calculation of the trap stiffness from the positional variance. Calculation of 1D optical trapping potential from the positional distribution of data points. Trap stiffness calculation by fitting a parabola to the trapping potential. Presentation of X-Y positional density for close inspection of the 2D trapping potential. Calculation of the trap anisotropy. Running time: Seconds

  17. 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.

  18. Dynamic holographic optical tweezers using a twisted-nematic liquid crystal display

    Microsoft Academic Search

    Guangfu Wang; Cheng Wen; Anpei Ye

    2006-01-01

    In this paper, we realize dynamic holographic optical tweezers (HOT) using a commercial twisted-nematic liquid crystal display (TN-LCD) removed from a video projector, and manipulate multiple particles simultaneously. After measuring the parameters of the TN-LCD, we find that it is not suited to work as a phase-only modulator for infrared optical tweezers because of the small range of its phase

  19. 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.

  20. Operational Regimes and Physics Present in Optoelectronic Tweezers

    PubMed Central

    Valley, Justin K.; Jamshidi, Arash; Ohta, Aaron T.; Hsu, Hsan-Yin; Wu, Ming C.

    2008-01-01

    Optoelectronic tweezers (OET) are a powerful light-based technique for the manipulation of micro- and nanoscopic particles. In addition to an optically patterned dielectrophoresis (DEP) force, other light-induced electrokinetic and thermal effects occur in the OET device. In this paper, we present a comprehensive theoretical and experimental investigation of various fluidic, optical, and electrical effects present during OET operation. These effects include DEP, light-induced ac electroosmosis, electrothermal flow, and buoyancy-driven flow. We present finite-element modeling of these effects to establish the dominant mode for a given set of device parameters and bias conditions. These results are confirmed experimentally and present a comprehensive outline of the operational regimes of the OET device. PMID:19079767

  1. 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

  2. Combined holographic-mechanical optical tweezers: Construction, optimisation and calibration

    E-print Network

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

    2009-07-21

    A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers set-up. This provides great flexibility as the SLM creates an array of traps which can be moved smoothly and quickly with the GMM. To optimise 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.

  3. Simultaneous measurements of electrophoretic and dielectrophoretic forces using optical tweezers

    E-print Network

    Giuseppe Pesce; Giulia Rusciano; Gianluigi Zito; Antonio Sasso

    2015-03-16

    Herein, charged microbeads handled with optical tweezers are used as a sensitive probe for simultaneous measurements of electrophoretic and dielectrophoretic forces. We first determine the electric charge carried by a single bead by keeping it in a predictable uniform electric field produced by two parallel planar electrodes, then, we examine same bead's response in proximity to a tip electrode. In this case, besides electric forces, the bead simultaneously experiences non-negligible dielectrophoretic forces produced by the strong electric field gradient. The stochastic and deterministic motions of the trapped bead are theoretically and experimentally analysed in terms of the autocorrelation function. By fitting the experimental data, we are able to extract simultaneously the spatial distribution of electrophoretic and dielectrophoretic forces around the tip. Our approach can be used for determining actual, total force components in the presence of high-curvature electrodes or metal scanning probe tips.

  4. Using Optical Tweezers to Study Cell Mechanics during Airway Reopening

    NASA Astrophysics Data System (ADS)

    Yalcin, Huseyin; Wang, Jing; Ghadiali, Samir; Ou-Yang, H. Daniel

    2006-03-01

    Patients suffering from the acute respiratory distress syndrome (ARDS) must be mechanically ventilated in order to survive. However, these ventilation protocols may generate injurious hydrodynamic stresses especially during low tidal volume (VT) ventilation when the flow of micron-sized air bubbles displace the surrounding liquid. In-vitro studies in our lab revealed that microbubble flows can severally damage lung epithelial cells (EC). The degree of injury was elevated for sub-confluent monolayers in small channel heights. Under these conditions, the micromechanics of individual EC may influence the degree of cellular injury. To investigate the role of cell mechanics, we used an oscillating Optical Tweezers (OT) technique to measure the intrinsic mechanical properties of EC before and after the flow of microbubbles. Knowledge of how the EC's micromechanical properties influence cell viability may lead to the development of novel treatment therapies that enhance the EC's ability to withstand injurious hydrodynamic stresses during ventilation treatment.

  5. Peculiarities of RBC aggregation studied by double trap optical tweezers

    NASA Astrophysics Data System (ADS)

    Khokhlova, Maria D.; Lyubin, Evgeny V.; Zhdanov, Alexander G.; Rykova, Sofia Yu.; Krasnova, Tatyana N.; Sokolova, Irina A.; Fedyanin, Andrey A.

    2010-04-01

    Aggregation peculiarities of red blood cells (RBCs) in autologous plasma are studied using double trap optical tweezers technique. The positions of RBCs are controlled with submicrometer accuracy by two optical traps formed by strongly focused laser beams (?=1064 nm). Quantitative measurements of interaction forces between RBCs in pair aggregates are performed. Depending on the RBCs aggregation force, four different end-points of disaggregation induced by optical trap movement are revealed. Analysis of experimental force dependence on the distance between two RBCs during disaggregation is in a good agreement with the model of ring-shaped interaction surfaces of RBCs in pair aggregate. Aggregation velocities measured are shown to be strongly different for healthy and pathologic (System Lupus Erythematosis - SLE) blood samples.

  6. Optimization of holographic optical tweezers for multiplexed fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Cibula, Matthew; McIntyre, David

    2012-10-01

    We are developing a multiplexed spectroscopy technique that employs holographic optical tweezers to trap and excite multiple sensor particles. Our goal is to develop a lab-on-a-chip measurement platform for monitoring pH and other ion concentrations with high spatial resolution in a microfluidic device or within biological cells. To ensure efficient use of the available laser power required to trap multiple particles, we address three aspects of the spatial light modulator (SLM) used in the holographic technique. We measure and optimize the input and output polarizations used before and after the birefringent SLM. We reduce optical aberrations by adding appropriate Zernike polynomials to the computed hologram. We optimize the diffraction efficiency of the SLM by adjusting the gray scale input-to-output table to account for the nonlinear phase response of the SLM.

  7. 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

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

    SciTech Connect

    Hanes, Richard D. L.; Jenkins, Matthew C.; Egelhaaf, Stefan U. [Condensed Matter Physics Laboratory, Heinrich-Heine University, 40225 Duesseldorf (Germany)

    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.

  9. Dissociation of ligand-receptor complexes using magnetic tweezers.

    PubMed

    Danilowicz, Claudia; Greenfield, Derek; Prentiss, Mara

    2005-05-15

    We present a new tool for measuring ligand-receptor complex bonds at the single-molecule level using magnetic tweezers. Our apparatus allows massively parallel (100-1000) measurements on many single complexes perturbed by constant forces. Compared to other single-molecule techniques, our method is simple, inexpensive, robust, and widely compatible with other techniques. We immobilized specific receptor molecules on the surface of superparamagnetic beads and corresponding ligand molecules on a fixed surface. The beads were allowed to contact the surface so that ligand-receptor binding occurred. A permanent magnet then generated a constant force that pulled the receptors away from the ligands. The rates at which bound species separated at various forces allowed us to characterize the potential energy landscape of the bond and extrapolate bulk solution kinetic rates and transition-state distances. These values agreed with those obtained using bulk and single-molecule methods. PMID:15889889

  10. Near-field-magnetic-tweezer manipulation of single DNA molecules.

    PubMed

    Yan, Jie; Skoko, Dunja; Marko, John F

    2004-07-01

    We have developed an instrument for micromanipulation of single DNA molecules end labeled with 3-microm-diameter paramagnetic particles. A small, permanent magnet that can be moved as close as 10 microm to the particle being manipulated can generate forces in excess of 200 pN, significantly larger than obtained in other recent "magnetic-tweezer" studies. Our instrument generates these forces in the focal plane of a microscope objective, allowing straightforward real-time observation of molecule extension with a position resolution of approximately 30 nm. We show how our magnetic manipulation system can be combined with manipulation and force measurement using glass micropipettes to allow rapid switching between measurements in fixed-force and fixed-extension ensembles. We demonstrate the use of our system to study formation of DNA loops by an enzyme which strongly binds two copies of a specific 6-base-pair sequence. PMID:15324086

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

    PubMed

    Klärner, 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

  12. Computer-automated program for calibration of optical tweezers

    NASA Astrophysics Data System (ADS)

    Taylor, C. D.; Foley, T. W.; Chang, A. N.; Mowa, S.; Burris, J. L.; Hester, B. C.

    2012-10-01

    An optical tweezers (OT) system uses focused laser light to contain and manipulate nano-scale to micro-scale particles. Trap stiffness is the quantitative measurement of the ability to trap a particle. For some techniques, this measurement depends on an accurate knowledge of the particle's position in time. A position sensing detector (PSD) is used to track particle motion by detecting laser light from the trapping region. The PSD outputs voltages corresponding to the x- and y-coordinates of particle motion, providing a means of knowing the location of the particle in time. An OT system requires a calibration to convert the measured voltages into accurate distances. This process is time-consuming and frequently needs to be repeated, however, with the growing availability of computer-aided data acquisition and control, the complete process can now be automated, reducing time spent by researchers and increasing level of accuracy of future measurements. We have developed a program written in LabVIEW that will, after initialization, 1) via image processing, calibrate the pixel size of the camera, 2) calibrate the optical tweezer position detector by controlling a motorized mirror to move a trapped bead through a detection laser with simultaneous position detector signal measurements, 3) re-align the trap beam and the detection beam by motorized mirror control, 4) measure position data for the same trapped particle being illuminated by the detection beam, and 5) analyze the position signal via the power spectrum method and equipartition method to give two trap stiffness values for comparison. Previous automated calibration methods require additional and sometimes costly equipment as well as some precalibration of stage motion or pixel size. Here, the user only needs to input the known size of the bead (provided by the manufacturer) into the program, insert their prepared slide into their microscope, input some parameters and make selections, and click "start" in order to achieve experimental values of the camera and position detector calibrations, as well as trap stiffness. We intend to implement many other calibration techniques that require additional equipment, but have designed this initial system for use in a standard position-detection-capable OT setup as long as it has a digital camera and motorized mirror that can be controlled with LabVIEW.

  13. Mapping force of interaction between PLGA nanoparticle with cell membrane using optical tweezers

    NASA Astrophysics Data System (ADS)

    Chhajed, Suyash; Gu, Ling; Homayoni, Homa; Nguyen, Kytai; Mohanty, Samarendra

    2011-03-01

    Drug delivery using magnetic (Fe3O4) Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles is finding increasing usage in therapeutic applications due to its biodegradability, biocompatibility and targeted localization. Since optical tweezers allow non-contact, highly sensitive force measurement, we utilized optical tweezers for studying interaction forces between the Fe3O4-PLGA nanoparticles with prostate cancer PC3 cells. Presence of Fe3O4 within the PLGA shell allowed efficient trapping of these nanoparticles in near-IR optical tweezers. The conglomerated PLGA nanoparticles could be dispersed by use of the optical tweezers. Calibration of trapping stiffness as a function of laser beam power was carried out using equipartition theorem method, where the mean square displacement was measured with high precision using time-lapse fluorescence imaging of the nanoparticles. After the trapped PLGA nanoparticle was brought in close vicinity of the PC3 cell membrane, displacement of the nanoparticle from trap center was measured as a function of time. In short time scale (< 30sec), while the force of interaction was within 0.2 pN, the force increased beyond 1pN at longer time scales (˜ 10 min). We will present the results of the time-varying force of interactions between PLGA nanoparticles with PC3 cells using optical tweezers.

  14. Wavefront analysis and optimization from conventional liquid crystal displays for low-cost holographic optical tweezers and digital holographic microscopy

    Microsoft Academic Search

    Andreas Weber; Valentin Ortega Clavero; Werner Schröder

    2011-01-01

    In different study fields the manipulation and imaging of micro-sized particles is essential. The use of holographic optical tweezers (HOT) and digital holographic microscopy (DHM) facilitates this task in a non-mechanical way by providing the proper computer generated hologram and the required amount of light. Electrically addressed spatial light modulators (EASLM) found in holographic optical tweezers are typically of the

  15. Near-field-magnetic-tweezer manipulation of single DNA molecules Jie Yan, Dunja Skoko, and John F. Marko

    E-print Network

    Croquette, Vincent

    with 3- m-diameter paramagnetic particles. A small, permanent magnet that can be moved as close as 10 m in other recent "magnetic-tweezer" studies. Our instrument generates these forces in the focal plane include optical trapping (OT), glass microfibers (GM), magnetic tweezers (MT), and atomic-force microscopy

  16. Triaxial Atomic Force Microscope Contact-Free Tweezers for Nanoassembly

    PubMed Central

    Brown, Keith A; Westervelt, Robert M

    2010-01-01

    We propose a Traixial Atomic Force Microscope (AFM) Contact-free Tweezer (TACT) for the controlled assembly of nanoparticles suspended in a liquid. The TACT overcomes four major challenges faced in nanoassembly: (1) The TACT can hold and position a single nanoparticle with spatial accuracy smaller than the nanoparticle size (~ 5 nm). (2) The nanoparticle is held away from the surface of the TACT by negative dielectrophoresis (nDEP) to prevent van der Waals forces from sticking it to the TACT. (3) The TACT holds nanoparticles in a trap that is size-matched to the particle and surrounded by a repulsive region so that it will only trap a single particle at a time. (4) The trap can hold a semiconductor nanoparticle in water with a trapping energy greater than thermal energy. For example, a 5 nm radius silicon nanoparticle is held with 10 kBT at room temperature. We propose methods for using the TACT as a nanoscale pick-and-place tool to assemble semiconductor quantum dots, biological molecules, semiconductor nanowires, and carbon nanotubes. PMID:19713582

  17. Optical tweezers as manufacturing and characterization tool in microfluidics

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Ghadiri, R.; Ksouri, S. I.; Gurevich, E. L.; Ostendorf, A.

    2014-09-01

    Pumping and mixing of small volumes of liquid samples are basic processes in microfluidic applications. Among the number of different principles for active transportation of the fluids microrotors have been investigated from the beginning. The main challenge in microrotors, however, has been the driving principle. In this work a new approach for a very simple magnetic driving principle has been realized. More precisely, we take advantage of optical grippers to fabricate various microrotors and introduce an optical force method to characterize the fluid flow generated by rotating the structures through magnetic actuation. The microrotors are built of silica and magnetic microspheres which are initially coated with Streptavidin or Biotin molecules. Holographic optical tweezers (HOT) are used to trap, to position, and to assemble the microspheres with the chemical interaction of the biomolecules leading to a stable binding. Using this technique, complex designs of microrotors can be realized. The magnetic response of the magnetic microspheres enables the rotation and control of the structures through an external magnetic field. The generated fluid flow around the microrotor is measured optically by inserting a probe particle next to the rotor. While the probe particle is trapped by optical forces the flow force leads to a displacement of the particle from the trapping position. This displacement is directly related to the flow velocity and can be measured and calibrated. Variations of the microrotor design and rotating speed lead to characteristic flow fields.

  18. Compact microscope-based optical tweezers system for molecular manipulation

    NASA Astrophysics Data System (ADS)

    Sischka, Andy; Eckel, Rainer; Toensing, Katja; Ros, Robert; Anselmetti, Dario

    2003-11-01

    A compact single beam optical tweezers system for force measurements and manipulation of individual double-stranded deoxyribonucleic acid (DNA) molecules was integrated into a commercial inverted optical microscope. A maximal force of 150 pN combined with a force sensitivity of less than 0.5 pN allows measurements of elastic properties of single molecules which complements and overlaps the force regime accessible with atomic force microscopy (AFM). The manipulation and measurement performance of this system was tested with individual ?-DNA molecules and renders new aspects of dynamic forces phenomena with higher precision in contrast to AFM studies. An integrated liquid handling system with a fluid cell allows investigation of the force response of individual DNA molecules in the presence of DNA binding agents. Comparison of YOYO-1-, ethidium bromide intercalated DNA, and distamycin-A complexed DNA revealed accurate and reproducible differences in the force response to an external load. This opens the possibility to use it as a single molecule biosensor to investigate DNA binding agents and even to identify molecular binding mechanisms.

  19. Probing DNA helicase kinetics with temperature-controlled magnetic tweezers.

    PubMed

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

    2015-03-01

    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 21-24 kB T) 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

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

    PubMed Central

    Nève, 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

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

    PubMed Central

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

    2002-01-01

    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

  2. Silicon photonics for functional on-chip optical tweezers devices and circuits

    NASA Astrophysics Data System (ADS)

    Cai, Hong; Wang, Jiawei; Poon, Andrew W.

    2013-02-01

    Silicon photonics using waveguide- and microresonator-based devices are finding technologically important applications in the field of optofluidics. By integrating microfluidic channels on top of silicon-based planar devices, silicon photonic devices can function as on-chip optical tweezers to manipulate micro/nanoparticles. In this paper, we will highlight our recent progress in the field of optofluidics using silicon nitride devices for on-chip optical manipulation including the experimental demonstrations of: (i) planar optical tweezers using waveguide junctions with and without tapers, (ii) microparticle buffering and dropping on microring resonator devices upon linearly polarized light and (iii) microparticle trapping and assembling on circular microdisk resonators. Such devices can function as basic building blocks for "optical tweezers circuits" in lab-on-chip applications.

  3. Tweezers for parahydrogen: a metal-free probe of nonequilibrium nuclear spin states of H? molecules.

    PubMed

    Zhivonitko, Vladimir V; Telkki, Ville-Veikko; Chernichenko, Konstantin; Repo, Timo; Leskelä, Markku; Sumerin, Victor; Koptyug, Igor V

    2014-01-15

    To date, only metal-containing hydrogenation catalysts have been utilized for producing substantial NMR signal enhancements by means of parahydrogen-induced polarization (PHIP). Herein, we show that metal-free compounds known as molecular tweezers are useful in this respect. It is shown that ansa-aminoborane tweezers QCAT provided (20-30)-fold signal enhancements of parahydrogen-originating hydrogens in (1)H NMR spectra. Nuclear polarization transfer from the polarized hydrogens to (11)B nuclei leads to a 10-fold enhancement in the (11)B NMR spectrum. Moreover, our results indicate that dihydrogen activation by QCAT and CAT tweezers is carried out in a pairwise manner, and PHIP can be used for understanding the activation mechanism in metal-free catalytic systems in general. PMID:24359087

  4. Optical manipulation and rotation of liquid crystal drops using high-index fiber-optic tweezers

    NASA Astrophysics Data System (ADS)

    Abedin, Kazi Sarwar; Kerbage, Charles; Fernandez-Nieves, Alberto; Weitz, David A.

    2007-08-01

    We report an optical fiber tweezer based on high-index material for trapping and optical manipulation of microscale particles in water. The use of a high-index material increases the trapping force with respect to the more common silica, through tighter focusing of light. We demonstrate the potential of this simple and versatile device by trapping and rotating nematic liquid crystal drops. We monitor the rotation of the drop by detecting light modulation observed with the same fiber using backscattered light, which exhibits modulation in intensity due to the rotation of the drop; this further extends the capabilities of the fiber tweezers.

  5. Characterisation of Au nanorod dynamics in optical tweezers via localised surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Andres-Arroyo, Ana; Kemp, Scott; Toe, Wen Jun; Wang, Fan; Coleman, Victoria; Reece, Peter J.

    2014-09-01

    We present a study of the trapping properties of Au nanorods of different aspect ratios in an optical tweezers and comparison with other characterization techniques like transmission electron microscope (TEM) imaging and dynamic light scattering (DLS). This study provides information on the dynamics and orientation of Au nanorods inside an optical trap based on a time study of their localised surface plasmon resonance (LSPR) features. The results indicate that the orientation of the Au nanorods trapped in our optical tweezers varies with time and LSPR spectra can provide information on the angle of the nanorod with respect to the direction of propagation of the trapping laser.

  6. Advanced optical tweezers for the study of cellular and molecular biomechanics.

    PubMed

    Brouhard, Gary J; Schek, Henry T; Hunt, Alan J

    2003-01-01

    Optical tweezers are an important tool for studying cellular and molecular biomechanics. We present a robust optical tweezers device with advanced features including: multiple optical traps, acousto-optic trap steering, and back focal plane interferometry position detection. We integrate these features into an upright microscope, with no compromise to its capabilities (differential interference contrast microscopy, fluorescence microscopy, etc.). Acousto-optic deflectors (AODs) steer each beam and can create multiple time-shared traps. Position detection, force calibrations and AOD performance are presented. The system can detect subnanometer displacements and forces below 0.1 pN. PMID:12617534

  7. 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.

  8. Mechanical and electrical properties of red blood cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, A.; Barjas Castro, M. L.; Brandão, 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.

  9. 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.

  10. Near-field enhanced optical tweezers utilizing femtosecond-laser nanostructured substrates

    E-print Network

    Kotsifaki, Domna G; Lagoudakis, Pavlos G

    2015-01-01

    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 (CW) 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, the effective trapping quality factor, and observe an exponential distance dependence of the trapping force from the nanostructures, expected from the evanescent plasmon field.

  11. Single and dual fiber nano-tip optical tweezers: trapping and analysis

    E-print Network

    Decombe, Jean-Baptiste; Fick, Jochen

    2013-01-01

    An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

  12. 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.

  13. Molecular tweezers for hydrogen: synthesis, characterization, and reactivity.

    PubMed

    Sumerin, Victor; Schulz, Felix; Atsumi, Michiko; Wang, Cong; Nieger, Martin; Leskelä, Markku; Repo, Timo; Pyykkö, Pekka; Rieger, Bernhard

    2008-10-29

    The first ansa-aminoborane N-TMPN-CH2C6H4B(C6F5)2 (where TMPNH is 2,2,6,6-tetramethylpiperidinyl) which is able to reversibly activate H2 through an intramolecular mechanism is synthesized. This new substance makes use of the concept of molecular tweezers where the active N and B centers are located close to each other so that one H2 molecule can fit in this void and be activated. Because of the fixed geometry of this ansa-ammonium-borate it forms a short N-H...H-B dihydrogen bond of 1.78 A as determined by X-ray analysis. Therefore, the bound hydrogen can be released above 100 degrees C. In addition, the short H...H contact and the N-H...H (154 degrees) and B-H...H (125 degrees) angles show that the dihydrogen interaction in N-TMPNH-CH2C6H4BH(C6F5)2 is partially covalent in nature. As a basis for discussing the mechanism, quantum chemical calculations are performed and it is found that the energy needed for splitting H2 can arise from the Coulomb attraction between the resulting ionic fragments, or "Coulomb pays for Heitler-London". The air- and moisture-stable N-TMPNH-CH2C6H4BH(C6F5)2 is employed in the catalytic reduction of nonsterically demanding imines and enamines under mild conditions (110 degrees C and 2 atm of H2) to give the corresponding amines in high yields. PMID:18826306

  14. 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.

  15. 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.

  16. TweezPal Optical tweezers analysis and calibration software Natan Osterman1

    E-print Network

    Osterman, Natan

    TweezPal ­ Optical tweezers analysis and calibration software Natan Osterman1 J. Stefan Institute and calibration software Authors: Natan Osterman Program title: TweezPal Licensing provisions: CPC non-profit use two 1 E-mail address: natan.osterman@ijs.si 1 #12;methods. Solution method: Elimination

  17. Quantitation of Malaria Parasite-Erythrocyte Cell-Cell Interactions Using Optical Tweezers

    E-print Network

    Cicuta, Pietro

    Article Quantitation of Malaria Parasite-Erythrocyte Cell-Cell Interactions Using Optical Tweezers falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria in unraveling the blood-stage biology of malaria. BACKGROUND Most cases of severe and fatal malaria in humans

  18. 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.

  19. Force Spectroscopy with Dual-Trap Optical Tweezers: Molecular Stiffness Measurements and Coupled Fluctuations Analysis

    PubMed Central

    Ribezzi-Crivellari, M.; Ritort, F.

    2012-01-01

    Dual-trap optical tweezers are often used in high-resolution measurements in single-molecule biophysics. Such measurements can be hindered by the presence of extraneous noise sources, the most prominent of which is the coupling of fluctuations along different spatial directions, which may affect any optical tweezers setup. In this article, we analyze, both from the theoretical and the experimental points of view, the most common source for these couplings in dual-trap optical-tweezers setups: the misalignment of traps and tether. We give criteria to distinguish different kinds of misalignment, to estimate their quantitative relevance and to include them in the data analysis. The experimental data is obtained in a, to our knowledge, novel dual-trap optical-tweezers setup that directly measures forces. In the case in which misalignment is negligible, we provide a method to measure the stiffness of traps and tether based on variance analysis. This method can be seen as a calibration technique valid beyond the linear trap region. Our analysis is then employed to measure the persistence length of dsDNA tethers of three different lengths spanning two orders of magnitude. The effective persistence length of such tethers is shown to decrease with the contour length, in accordance with previous studies. PMID:23199920

  20. 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 .

  1. Mechanical characterization of human red blood cells by robotic manipulation with optical tweezers

    Microsoft Academic Search

    Youhua Tan; Dong Sun; Wenhao Huang; Hanxiong Li

    2009-01-01

    Human red blood cells (RBCs) are responsible to transport oxygen and carbon dioxide for human bodies. The physiological functions of RBCs are greatly influenced by their mechanical properties. Any alteration of the cell mechanics may cause human diseases. In this paper, to understand the correlation between the cell properties and their osmotic environments, robotic manipulation technology with optical tweezers is

  2. Two-dimensional transport and transfer of a single atomic qubit in optical tweezers

    E-print Network

    Loss, Daniel

    that these manipulations of the external degrees of freedom preserve the coherence of the qubit, and do not induce any. An attractive architecture is a large set of physically independent qubits arranged in three spatial regions­6 . Furthermore, we transfer a qubit between two tweezers, and show that this manipulation also preserves

  3. Measurement of adhesive forces between bacteria and protein-coated surfaces using optical tweezers

    Microsoft Academic Search

    Kathryn H. Simpson; Gabriela Bowden; Magnus Hook; Bahman Anvari

    2002-01-01

    Bacterial adhesion is a primary cause of failure in implanted medical devices. Bacteria commonly found in device-related infections, such as S. aureus, have multiple cell surface adhesins which mediate specific adhesion to molecules found in extracellular matrix and blood plasma. Adhesins recognizing fibrinogen, fibronectin, collagen, and elastin molecules have been isolated in S. aureus. We have used optical tweezers to

  4. Nonlinear Stabilization of a Spherical Particle Trapped in an Optical Tweezer Aruna Ranaweera

    E-print Network

    Sontag, Eduardo

    Nonlinear Stabilization of a Spherical Particle Trapped in an Optical Tweezer Aruna Ranaweera-5070 Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106-9560 Abstract-- We describe the nonlinear equations of mo- tion of a spherical particle trapped in an optical

  5. Electromagnetic Torque Tweezers: A Versatile Approach for Measurement of Single-Molecule Twist and Torque

    E-print Network

    Dekker, Nynke

    of freedom. Here we present electromagnetic torque tweezers (eMTT) that combine permanent and electromagnets degrees of freedom: for example, current MTT instruments employ permanent magnets that control bothMTT combine permanent and electromagnets to enable the application of a wide range of stretching forces (from

  6. Quantitative Modeling and Optimization of Magnetic Tweezers Jan Lipfert, Xiaomin Hao, and Nynke H. Dekker*

    E-print Network

    Dekker, Nynke

    , and the simplicity and robustness of the experimental implementation. Both permanent magnets and electromagnets can complication compared to the use of permanent magnets. At the same time, electromagnets poten- tially allow one to apply more complex magnetic field patterns, compared to permanent magnets. Electromagnetic tweezers make

  7. Quantitative Guidelines for Force Calibration through Spectral Analysis of Magnetic Tweezers Data

    E-print Network

    Dekker, Nynke

    tweezers experiments. INTRODUCTION Recently, single-molecule techniques such as atomic force microscopy, The Netherlands ABSTRACT Single-molecule techniques are powerful tools that can be used to study the kinetics to control the force applied to a single molecule and thereby facilitate the investigation of real

  8. Optical tweezers in concentrated colloidal dispersions : Manipulating and imaging individual particles

    NASA Astrophysics Data System (ADS)

    Vossen, Dirk Leo Joep

    2004-11-01

    Using a laser beam that is focused down to a diffraction-limited spot, particles with a size ranging from several nanometers up to tens of micrometers can be trapped and manipulated. This technique, known as optical tweezers or optical trapping, has been used in a wide variety of (interdisciplinary) fields and its use is expanding fast. Recent improvements allow for new exciting and promising applications. First an introduction to the technique of optical tweezers is given and the setup that combines optical tweezers with confocal microscopy is described. By time-sharing a single laser beam, hundreds of optical traps can be created and changed dynamically. Independent three-dimensional trapping and imaging of individual particles is possible because two microscope objectives are used, one below and one above the sample. We demonstrate that large two-dimensional patterns of colloidal particles can be created using optical tweezers by positioning particles on a coated surface. These structures of colloidal particles can subsequently be used as masks for colloidal lithography. These masks can be modified further using ion beam deformation or, alternatively, chemical methods. Large arrays of metal nanoparticles with sizes in the range of tens of nanometers have been created using these techniques. Using our setup we have also studied crystallization and melting in colloidal dispersions. A single optical trap was used on collections of particles to crystallize two- and three-dimensional colloidal dispersions. With specially synthesized mixtures of core-shell colloidal particles it is now possible to manipulate individual articles selectively inside concentrated dispersions. Arrays of optical tweezers were used to trap core-shell particles that act as nuclei for homogeneous and heterogeneous nucleation in concentrated colloidal dispersions. We show a single particle driven through a three-dimensional colloidal crystal.

  9. Using optical tweezers, single molecule fluorescence and the ZIF268 protein-DNA system to probe mechanotransduction mechanisms

    E-print Network

    Lee, Peter, S.M. Massachusetts Institute of Technology

    2006-01-01

    Optical tweezers instruments use laser radiation pressure to trap microscopic dielectric beads. With the appropriate chemistry, such a bead can be attached to a single molecule as a handle, permitting the application of ...

  10. 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.

  11. 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.

  12. Femtosecond optical tweezers for in-situ control of two-photon fluorescence.

    PubMed

    Agate, B; Brown, C; Sibbett, W; Dholakia, K

    2004-06-28

    We perform a comparison of optical tweezing using continuous wave (cw) and femtosecond lasers. Measurement of the relative Q-values in the femtosecond and cw regimes shows that femtosecond optical tweezers are just as effective as cw optical tweezers. We also demonstrate simultaneous optical tweezing and in-situ control of two-photon fluorescence (at 400nm) from dye-doped polymer microspheres. By switching the 800 nm tweezing laser source between femtosecond and cw regimes, we turned the fluorescent signal from the tweezed particle on and off while maintaining an equivalent tweezing action. Femtosecond lasers can thus be used for optical tweezing and simultaneously utilized to induce nonlinear multi-photon processes such as two-photon excitation or even photoporation. PMID:19483818

  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. 3D Raman sideband cooling of single atoms in an optical tweezer trap

    NASA Astrophysics Data System (ADS)

    Thompson, Jeff; Tiecke, Tobias; Vuletic, Vladan; Lukin, Mikhail

    2012-06-01

    We have cooled a single atom in an optical tweezer trap very close to its three-dimensional ground state. An atom loaded with an initial temperature of around 110 uK has radial and axial occupation numbers of nr= 23 and na= 170; after cooling, we achieve final occupation numbers of nr< 0.1 and na=7.5. The principal technical challenge we encountered was effective magnetic field gradients arising from distortions of the dipole trap polarization in the optical tweezer focus, which we will discuss in some detail. Additionally, we will present ongoing work on two fronts: using the tightly localized atom to sense optical fields on the nanometer-scale, and bringing the atom close to nanoscale optical waveguides and can ities with the goal of achieving strong atom-photon interactions.

  15. 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; R?ži?ka, 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

  16. Analysis of Cell Mechanics in Single Vinculin-Deficient Cells Using a Magnetic Tweezer

    Microsoft Academic Search

    Francis J. Alenghat; Ben Fabry; Kenneth Y. Tsai; Wolfgang H. Goldmann; Donald E. Ingber

    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

  17. 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 ?m, 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.

  18. A feasibility study of in vivo applications of single beam acoustic tweezers

    SciTech Connect

    Li, Ying, E-mail: yli582@usc.edu; Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk [NIH Transducer Resource Center and Department of Biomedical Engineering, University of Southern California, Los Angeles, California 90089-1111 (United States)

    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 ?m, 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.

  19. Micromanipulation and physiological monitoring of cells using two-photon excited fluorescence in cw laser tweezers

    NASA Astrophysics Data System (ADS)

    Sonek, Gregory J.; Liu, Yagang; Berns, Michael W.; Tromberg, Bruce J.

    1996-05-01

    We report the observation of two-photon fluorescence excitation and cell confinement, simultaneously, in a continuous-wave (cw) single-beam gradient force optical trap, and demonstrate its use as an in-situ probe to study the physiological state of an optically confined cell sample. At the wavelength of 1064 nm, a single focused gaussian laser beam is used to simultaneously confine, and excite visible fluorescence from, a human sperm cell that has been tagged with propidium iodide, a exogenous fluorescent dye that functions as a viability assay of cellular physiological state. The intensity at the dye peak emission wavelength of 620 nm exhibits a near-square-law dependence on incident trapping beam photon laser power, a behavior consistent with a two-photon absorption process. In addition, for a sperm cell held stationary in the optical tweezers for a period of several minutes at a constant trapping power, red fluorescence emission was observed to increase the time, indicating that the cell has gradually transitioned between a live and dead state. Two-photon excited fluorescence was also observed in chinese hamster ovary cells that were confined by cw laser tweezers and stained with either propidium iodide or Snarf, a pH-sensitive dye probe. These results suggest that, for samples suitably tagged with fluorescent probes and vital stains, optical tweezers can be used to generate their own in-situ diagnostic optical probes of cellular viability or induced photodamage, via two-photon processes.

  20. Microrheology of non mulberry silk varieties by optical tweezer and video microscopy based techniques

    E-print Network

    Yogesha; Raghu A; Siddaraju G N; G Subramanya; Somashekar R; Sharath Ananthamurthy

    2011-02-15

    We have carried out a comparative study of the microrheological properties of silk fibroin solutions formed from a variety of silks indigenous to the Indian subcontinent. We present the measured viscoelastic moduli of Tasar silk fibroin solution using both a single and dual optical tweezer at 0.16% and 0.25% (w/v). The bandwidth of the measurements carried out using optical tweezers is extended down to the lower frequency regime by a video microscopy measurement. Further, we have measured the viscoelastic moduli of Eri and Muga varieties of silk fibroin solutions at a higher concentration (1.00% w/v) limiting the tool of measurement to video microscopy, as the reduced optical transparencies of these solutions at higher concentration preclude an optical tweezer based investigation. The choice of a higher concentration of fibroin solution of the latter silk varieties is so as to enable a comparison of the shear moduli obtained from optical methods with their corresponding fibre stiffness obtained from wide angle X-ray scattering data. We report a correlation between the microstructure and microrheological parameters of these silk varieties for the concentration of fibroin solutions studied.

  1. 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, Síle

    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.

  2. Amyloid ?-Protein Assembly: The Effect of Molecular Tweezers CLR01 and CLR03.

    PubMed

    Zheng, Xueyun; Liu, Deyu; Klärner, Frank-Gerrit; Schrader, Thomas; Bitan, Gal; Bowers, Michael T

    2015-04-01

    The early oligomerization of amyloid ?-protein (A?) has been shown to be an important event in the pathology of Alzheimer's 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

  3. Micro-rheology and interparticle interactions in aerosols probed with optical tweezers

    NASA Astrophysics Data System (ADS)

    Reid, Jonathan P.; Power, Rory M.; Cai, Chen; Simpson, Stephen H.

    2014-09-01

    Using optical tweezers for micro-rheological investigations of a surrounding fluid has been routinely demonstrated. In this work, we will demonstrate that rheological measurements of the bulk and surface properties of aerosol particles can be made directly using optical tweezers, providing important insights into the phase behavior of materials in confined environments and the rate of molecular diffusion in viscous phases. The use of holographic optical tweezers to manipulate aerosol particles has become standard practice in recent years, providing an invaluable tool to investigate particle dynamics, including evaporation/ condensation kinetics, chemical aging and phase transformation. When combined with non-linear Raman spectroscopy, the size and refractive index of a particle can be determined with unprecedented accuracy <+/- 0.05%). Active control of the relative positions of pairs of particles can allow studies of the coalescence of particles, providing a unique opportunity to investigate the bulk and surface properties that govern the hydrodynamic relaxation in particle shape. In particular, we will show how the viscosity and surface tension of particles can be measured directly in the under-damped regime at low viscosity. In the over-damped regime, we will show that viscosity measurements can extend close to the glass transition, allowing measurements over an impressive dynamic range of 12 orders of magnitude in relaxation timescale and viscosity. Indeed, prior to the coalescence event, we will show how the Brownian trajectories of trapped particles can yield important and unique insights into the interactions of aerosol particles.

  4. Practical lab tool for living cells based on microstereolithography and multiple dynamic holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Monneret, Serge; Belloni, Federico; Marguet, Didier

    2006-02-01

    Recent studies have shown that the cell is mechanically differentiated both spatially and temporally, leading to a regional approach in cell behaviour essays. Most experiments are based on spatially-controlled contacts between microbeads and cells. We here propose an apparatus based on holographic optical tweezers to put on a target cell a two- or three-dimensional custom-built pattern of beads, with respect to the target cell shape, with both temporal and spatial dynamic control of each contact. In order to avoid disturbance or contact from the excess beads with the target cell, we keep the beads under isolated condition, by placing them in a confinement chamber made by microstereolithography. Our system exploits a digital display to project binary images on a photocurable resin surface, and induce space-resolved photopolymerisation reactions, constructing three-dimensional micro structures with complex shapes, including reservoirs for the filling, outlets, and confinement chambers. Combination of microfluidics, holographic optical tweezers and one supplementary single manually steerable optical tweezers leads to several experimental procedures allowing the sequential or parallel deposition of beads onto a target, with both a spatial and temporal control.

  5. Dislocation reactions, grain boundaries, and irreversibility in two-dimensional lattices using topological tweezers

    PubMed Central

    Irvine, William T. M.; Hollingsworth, Andrew D.; Grier, David G.; Chaikin, Paul M.

    2013-01-01

    Dislocations, disclinations, and grain boundaries are topological excitations of crystals that play a key role in determining out-of-equilibrium material properties. In this article we study the kinetics, creation, and annihilation processes of these defects in a controllable way by applying “topological tweezers,” an array of weak optical tweezers which strain the lattice by weakly pulling on a collection of particles without grabbing them individually. We use topological tweezers to deterministically control individual dislocations and grain boundaries, and reversibly create and destroy dislocation pairs in a 2D crystal of charged colloids. Starting from a perfect lattice, we exert a torque on a finite region and follow the complete step-by-step creation of a disoriented grain, from the creation of dislocation pairs through their reactions to form a grain boundary and their reduction of elastic energy. However, when the grain is rotated back to its original orientation the dislocation reactions do not retrace. Rather, the process is irreversible; the grain boundary expands instead of collapsing. PMID:24009341

  6. Stretching of red blood cells by optical tweezers quantified by digital holographic microscopy

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    Red blood cells (RBC) possess unique viscoelastic characteristics which allow them to pass through capillaries narrower than their size. Measurement of viscoelastic property of cells (e.g. RBC) in low-force regime is of high significance as it represents conditions of membrane fluctuation in response to physiological conditions. Estimation of visco-elastic properties of RBC requires measurement of extent of deformation in RBC subjected to known force. Optical tweezers, being gentle and absolutely sterile, are emerging as the tool of choice for application of localized force on cells. However, stretching of RBC in very low force regime has not been quantified. Further, though deformations in transverse directions have been measured, vertical deformations due to stretching of cells cannot be quantified by classical microscopic images. Here, we report realization of offaxis digital holographic microscopy (DHM) for highly sensitive axial changes in RBC shape due to stretching by optical tweezers without attaching microscopic beads. The RBC was stretched in axial direction with nanometer precision by change of divergence of the trapping beam. The obtained deformation patterns were compared with the axial position of the tweezers focus. Since the pathophysiology of progression of diseases like malaria and cancer is reflected in the biophysical (both mechanical and material) properties of the cells, it is possible to identify the changes by simultaneous measurement of refractive index and elasticity using this approach.

  7. Differential detection of dual traps improves the spatial resolution of optical tweezers

    PubMed Central

    Moffitt, Jeffrey R.; Chemla, Yann R.; Izhaky, David; Bustamante, Carlos

    2006-01-01

    The drive toward more sensitive single-molecule manipulation techniques has led to the recent development of optical tweezers capable of resolving the motions of biological systems at the subnanometer level, approaching the fundamental limit set by Brownian fluctuations. One successful approach has been the dual-trap optical tweezers, in which the system of study is held at both ends by microspheres in two separate optical traps. We present here a theoretical description of the Brownian limit on the spatial resolution of such systems and verify these predictions by direct measurement in a Brownian noise-limited dual-trap optical tweezers. We find that by detecting the positions of both trapped microspheres, correlations in their motions can be exploited to maximize the resolving power of the instrument. Remarkably, we show that the spatial resolution of dual optical traps with dual-trap detection is always superior to that of more traditional, single-trap designs, despite the added Brownian noise of the second trapped microsphere. PMID:16751267

  8. Chromosomal analysis and identification based on optical tweezers and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Ojeda, Jenifer F.; Xie, Changan; Li, Yong-Qing; Bertrand, Fred E.; Wiley, John; McConnell, Thomas J.

    2006-06-01

    The ability to identify specific chromosomes with certainty has been established by the development of several cytogenetic techniques based on staining. Here, we report the use of a new optical technique, laser tweezers and Raman spectroscopy (LTRS), to capture and manipulate chromosomes in order to obtain their spectral patterns for molecular analysis without the need for staining. The purpose of this study was to obtain Raman spectroscopy patterns for chromosomes number 1, 2, and 3 and to test if the Raman spectroscopy pattern could be used to distinguish these three chromosomes. In our experiment, optical tweezers were used to capture the individual chromosomes and the Raman spectral patterns were collected for the trapped chromosomes. Then, the captured chromosome was manipulated with the optical tweezers and moved to another chamber through a micro - channel, in which the chromosomes were G banded for positive identification as chromosome number 1, 2, or 3. Generalized discriminate analysis (GDA) was used to compare the Raman signatures. This analysis revealed that chromosomes 1, 2, and 3 could be distinguished and identified based on their Raman spectra. Development of this approach will lead to more rapid automatic methods for chromosome analysis and identification without the use of prior staining. Moreover, the Raman spectral patterns may lend themselves to more detailed analysis of chromosomal structure than is currently available with standard staining protocols. Such analysis may some day be useful for rapid, automated screening and diagnosis for certain cancers.

  9. 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

  10. Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-print Network

    Sharma, Shobhona

    Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes This article has been.1088/0957-4484/21/24/245102 Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes Hema Ramachandran1 , A K fragmentation of the bundles. Thus, microbubbles may be used for scavenging, transporting and dispersal

  11. 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

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. The self-orientation of mammalian cells in optical tweezers—the importance of the nucleus

    NASA Astrophysics Data System (ADS)

    Perney, Nicolas M. B.; Horak, Peter; Hanley, Neil A.; Melvin, Tracy

    2012-04-01

    Here we present the first evidence showing that eukaryotic cells can be stably trapped in a single focused Gaussian beam with an orientation that is defined by the nucleus. A mammalian eukaryotic cell (in suspension) is trapped and is re-oriented in the focus of a linearly polarized Gaussian beam with a waist of dimension smaller than the radius of the nucleus. The cell reaches a position relative to the focus that is dictated by the nucleus and nuclear components. Our studies illustrate that the force exerted by the optical tweezers at locations within the cell can be predicted theoretically; the data obtained in this way is consistent with the experimental observations.

  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. Laser-induced fusion of human embryonic stem cells with optical tweezers

    SciTech Connect

    Chen Shuxun; Wang Xiaolin; Sun Dong [Department of Mechanical and Biomedical Engineering, City University of Hong Kong (Hong Kong); Cheng Jinping; Han Cheng, Shuk [Department of Biology and Chemistry, City University of Hong Kong (Hong Kong); Kong, Chi-Wing [Stem Cell and Regenerative Medicine Consortium, and Departments of Medicine and Physiology, LKS Faculty of Medicine, University of Hong Kong (Hong Kong); Li, Ronald A. [Stem Cell and Regenerative Medicine Consortium, and Departments of Medicine and Physiology, LKS Faculty of Medicine, University of Hong Kong (Hong Kong); Center of Cardiovascular Research, Mount Sinai School of Medicine, New York, New York 10029 (United States)

    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.

  20. 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.

  1. 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.

  2. 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.

  3. Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments.

    PubMed

    Janissen, Richard; Berghuis, Bojk A; Dulin, David; Wink, Max; van Laar, Theo; Dekker, Nynke H

    2014-10-01

    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

  4. Counter-propagating dual-trap optical tweezers based on linear momentum conservation.

    PubMed

    Ribezzi-Crivellari, M; Huguet, J M; Ritort, F

    2013-04-01

    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. PMID:23635178

  5. 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; Zemánek, 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.

  6. Holographic optical tweezers: microassembling of shape-complementary 2PP building blocks

    NASA Astrophysics Data System (ADS)

    Ksouri, Sarah Isabelle; Mattern, Manuel; Köhler, 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.

  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. Investigation of the mechanical property of individual cell using axial optical tweezers

    NASA Astrophysics Data System (ADS)

    Dy, Mary-Clare; Sugiura, Tadao; Minato, Kotaro

    2013-02-01

    Optical tweezers is a technique that can trap and manipulate small objects using a highly focused laser beam. Because optical tweezers can also be used to measure small forces, it has been extensively used for the measurement of the mechanical forces of cells. Previous research works typically study particle manipulation and cell force measurement in the lateral direction, hence excluding valuable insights about the axial mechanical properties of cells. Other works that investigate axial cell force measurements utilize spatial light modulators and other devices that are expensive and complicate the setup. Thus, in our study, we designed a simple scheme that can axially manipulate particles by adjusting the position of one lens, called L1-lens, in our setup. Image processing techniques were utilized to determine the changes in the axial particle translation, providing nanometer sensitivity. We investigated the capability of our system using two different-sized particles and results show that for a given L1-lens default position and movement, a 2-micron particle and a 4.26-micron particle were moved axially for 7.68 µm and 4.83 µm, respectively. Axial trapping stiffness was also measured for the stated bead sizes in different magnification. Using the computed trapping sti_ness, we will investigate the axial reactive forces of cells.

  9. Counter-propagating dual-trap optical tweezers based on linear momentum conservation

    SciTech Connect

    Ribezzi-Crivellari, M.; Huguet, J. M. [Small Biosystems Lab, Dept. de Fisica Fonamental, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona (Spain); Ritort, F. [Small Biosystems Lab, Dept. de Fisica Fonamental, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona (Spain); Ciber-BBN de Bioingenieria, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid (Spain)

    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.

  10. Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy

    PubMed Central

    Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

    2012-01-01

    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. PMID:23020384

  11. Observation of a single-beam gradient force acoustical trap for elastic particles: acoustical tweezers

    E-print Network

    Diego Baresch; Jean-Louis Thomas; Régis Marchiano

    2014-11-07

    The ability to manipulate matter precisely is critical for the study and development of a large variety of systems. Optical tweezers are excellent tools to handle particles ranging in size from a few micrometers to hundreds of nanometers but become inefficient and damaging on larger objects. We demonstrate for the first reported time the trapping of elastic particles by the large gradient force of a single acoustical beam in three dimensions. We show that at equal power, acoustical forces overtake by 8 orders of magnitude that of optical ones on macroscopic objects. Acoustical tweezers can push, pull and accurately control both the position of the particle and the forces exerted under damage-free conditions. The large spectrum of frequencies covered by coherent ultrasonic sources will provide a wide variety of manipulation possibilities from macro- to microscopic length scales. We believe our observations improve the prospects for wider use of non-contact manipulation in biology, biophysics, microfluidics and robotics and bridge the gap that had remained to the macroscopic scale.

  12. 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; van Laar, 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

  13. Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering

    SciTech Connect

    Ott, Dino; Oddershede, Lene B., E-mail: oddershede@nbi.dk [Niels Bohr Institute (NBI), University of Copenhagen, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Reihani, S. Nader S. [Department of Physics, Sharif University of Technology, 11369-9161 Tehran (Iran, Islamic Republic of)

    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.

  14. Optical properties of red blood cells: an optical tweezer based analysis

    NASA Astrophysics Data System (ADS)

    Nagesh, B. V.; Lakkegowda, Yogesha; Pratibha, R.; Praveen, P.; Bhattacharya, Sarbari; Ananthamurthy, Sharath

    2014-03-01

    A microscopic object finds an equilibrium orientation under a laser tweezer such that a maximum of its volume lies in the region of highest electric field. Furthermore, birefringent microscopic objects show no rotational diffusion after reorienting under a linearly polarized optical trap and also are seen to follow the plane of polarization when the latter is changed using a half wave plate. We observe that a healthy human Red Blood Cell (RBC) reproduces these observations in an optical tweezer, which confirms it to be birefringent. Polarization microscopy based measurements reveal that the birefringence is confined to the cell's dimple region and the mean value of retardation for polarized green light (? = 546nm) is 9 +/- 1.5nm. We provide a simple geometrical model that attributes the birefringence to the nature of arrangement of the phospholipid molecules of the bilayer. This predicts the observed variation in the measured birefringence, from the dimple to the rim of the cell which we further show, can serve to demarcate the extent of the dimple region. This points to the value of birefringence measurements in revealing cell membrane contours. . We extend this technique to understand the birefringence of a chicken RBC, an oblate shaped cell, wherein the slow axis is identified to be coincident with the long axis of the cell. Further, we observe the birefringence to be confined to the edges of the cell. Experiments to probe the optomechanical response of the chicken RBC are in progress.

  15. Development of a two-photon polymerization and optical tweezers microscope for fabrication and manipulation of microstructures

    NASA Astrophysics Data System (ADS)

    Ingle, Ninad; Mohanty, Samarendra K.

    2011-03-01

    We report development of a two-photon polymerization (TPP) microscope, for micro-fabrication of microstructures, which is capable of optical manipulation by use of optical tweezers. The system is based on an inverted Nikon microscope with a tunable Ti: Sapphire femto-second (fs) laser coupled to the upper back port. While in modelocked condition, nanoparticles and wires were fabricated in photo-polymerizable synthetic materials using TPP. By axial positioning of the focused TPP laser beam, 1D-structures (for use as wave guide) were fabricated at desired height above the surface of the substrate. In the mode lock-OFF condition the same tunable laser microbeam was employed as optical tweezers to the hold the nanostructures and manipulate them even in highly viscous medium before immobilizing. Size of the TPP induced structure was found to depend on the fs laser intensity and exposure. Further, by shaping the fs laser beam to line pattern, linear 1D structures could be fabricated without scanning the beam or stage, which remain aligned along the line intensity profile due to anisotropic trapping force of the line tweezers in X and Y-directions. Use of optical tweezers with two-photon polymerization not only allowed in-situ corrective positioning of the polymerized structures, but also the integration of fluorescent microspheres (resonator/detector) with polymerized waveguide.

  16. Dynamic Excitations in Membranes Induced by Optical Tweezers Roy Bar-Ziv,* Elisha Moses,* and Philip Nelson#

    E-print Network

    Moses, Elisha

    and water, with laser tweezers as the energy source. Artificial membrane vesicles made of lipids ("lipo ABSTRACT We present the phenomenology of transformations in lipid bilayers that are excited by laser picture of the laser-membrane interaction is based on the generation of tension in the bilayer and loss

  17. Parallel optical tweezers with combining a diffractive optical element and a spatial light modulator for photonic DNA memory

    Microsoft Academic Search

    MingJie Zheng; Naoya Tate; Yusuke Ogura; Jun Tanida

    2007-01-01

    To overcome the restriction of the density of optical memory systems due to diffraction limit, we have been studying photonic DNA memory, which utilizes photonic technologies and the DNA computing methodology. Our scheme is on the basis of local DNA reaction using laser irradiation and transportation of DNA using parallel optical tweezers with fabricating DNA clusters by attaching DNA onto

  18. NAP1-Assisted Nucleosome Assembly on DNA Measured in Real Time by Single-Molecule Magnetic Tweezers

    E-print Network

    Dekker, Cees

    NAP1-Assisted Nucleosome Assembly on DNA Measured in Real Time by Single-Molecule Magnetic Tweezers-assisted nucleosome formation are not well understood. We study NAP1 (nucleosome assembly protein 1) assisted-to-end length when NAP1 and core histones (CH) are added to the dsDNA. We characterize the formation of complete

  19. Real-time observation of ultrafast electron injection at graphene-Zn porphyrin interfaces.

    PubMed

    Masih, Dilshad; Aly, Shawkat M; Usman, Anwar; Alarousu, Erkki; Mohammed, Omar F

    2015-04-14

    We report on the ultrafast interfacial electron transfer (ET) between zinc(ii) porphyrin (ZnTMPyP) and negatively charged graphene carboxylate (GC) using state-of-the-art femtosecond laser spectroscopy with broadband capabilities. The steady-state interaction between GC and ZnTMPyP results in a red-shifted absorption spectrum, providing a clear indication for the binding affinity between ZnTMPyP and GC via electrostatic and ?-? stacking interactions. Ultrafast transient absorption (TA) spectra in the absence and presence of three different GC concentrations reveal (i) the ultrafast formation of singlet excited ZnTMPyP*, which partially relaxes into a long-lived triplet state, and (ii) ET from the singlet excited ZnTMPyP* to GC, forming ZnTMPyP?(+) and GC?(-), as indicated by a spectral feature at 650-750 nm, which is attributed to a ZnTMPyP radical cation resulting from the ET process. PMID:25751714

  20. Fluorescence detecting of paraquat using host-guest chemistry with cucurbit[8]uril

    PubMed Central

    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. PMID:24389647

  1. Tailoring the optical and rheological properties of an epoxy acrylate based host-guest system

    NASA Astrophysics Data System (ADS)

    Gleißner, Uwe; Hanemann, Thomas

    2014-05-01

    Polymers with individually adjusted optical and rheological properties are gaining more and more importance in industrial applications like in information technology. To modify the refractive index n, an electron-rich organic dopant is added to a commercially available polymer based resin. Changes in viscosity for applications like ink-jet printing can be achieved by using a comonomer with suitable properties. Therefore we used a commercially available epoxy acrylate based UV-curable polymer matrix to investigate the influence of ethylene glycol dimethacrylate (EGDMA) on viscosity and phenanthrene on refractive index. Refractive index was measured at a wavelength of 589 nm and 20 °C using an Abbe refractometer. As a result the change in viscosity decreased linearly from 47 Pa·s to 4 mPa·s which is a more suitable region for inkjet printing. However, the refractive index decreased at the same time from 1.548 to 1.514. Adding phenanthrene the refractive index increased linearly from 1.548 up to 1.561. It was shown that both, viscosity and refractive index can be successfully adjusted in a wide range depending on desired properties.

  2. Radial basis function networks in host–guest interactions: instant and accurate formation constant calculations

    Microsoft Academic Search

    Yannis L Loukas

    2000-01-01

    The application of the second most popular artificial neural networks (ANN), namely, the radial basis function (RBF) networks, have been developed for obtaining sufficient quantitative structure-formation relationships (QSFR) with improved accuracy. To this end, a data set of 17 barbiturates as guests complexing to ?- and ?-cyclodextrins (CDs) was examined using RBF and generalized regression neural networks (GRNN) as function

  3. 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.

  4. Host-Guest Interaction Mediated Polymeric Core-Shell Assemblies: Versatile Nanocarriers for Drug Delivery

    PubMed Central

    Zhang, Jianxiang; Ma, Peter X.

    2009-01-01

    Novel hydrophilic-hydrophilic block copolymer with one block containing ?-cyclodextrin was synthesized. Core-shell structured nano-assemblies with chemical sensitivity could be constructed by this copolymer in the presence of hydrophobic compounds. By selecting appropriate guest components, polyion complex micelles could also be assembled. These results suggest the potential versatile applications of this type of copolymers in pharmaceutics, nanomedicine, and nano-biotechnology. PMID:19101966

  5. 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.

  6. Ce Zr Al O system with host guest interactions: Peculiarities of the optical properties

    NASA Astrophysics Data System (ADS)

    Frolova, Elena V.; Ivanovskaya, Marya I.; Hlushonak, Henadz K.

    2006-05-01

    The structural composition and optical properties of glassy Ce-Zr-Al-O samples obtained by a totally inorganic modification of the sol-gel technique were investigated by XRD, FTIR, ESR, UV-Vis, PL and XPS. EPR data indicate the appearance of the Ce 3+-defects that are considered as coordinately unsaturated ions in contact with oxygen vacancies—[Ce 3+ - VO] ( g? = 1.962-1.967, g? = 1.938-1.940, assigned to 4f 1 state, with concentration ˜2 × 10 18 spin/g). The significant PL intensity rising at elevated temperature was related to a spontaneous increase of the Ce 3+ concentration in sol-gel samples under thermal dehydration. Also, an unexpected formation of intra-band-gap states during thermal treatment of xero-gels was manifested in UV-Vis and XPS spectra. These intra-band-gap states are attributed to the oxygen-related defects that contribute to the PL signal.

  7. 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.

  8. 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.

  9. A Novel Approach to Molecular Recognition Surface of Magnetic Nanoparticles Based on Host–Guest Effect

    PubMed Central

    2009-01-01

    A novel route has been developed to prepared ?-cyclodextrin (?-CD) functionalized magnetic nanoparticles (MNPs). The MNPs were first modified with monotosyl-poly(ethylene glycol) (PEG) silane and then tosyl units were displaced by amino-?-CD through the nucleophilic substitution reaction. The monotosyl-PEG silane was synthesized by modifying a PEG diol to form the corresponding monotosyl-PEG, followed by a reaction with 3-isocyanatopropyltriethoxysilane (IPTS). The success of the synthesis of the monotosyl-PEG silane was confirmed with1H NMR and Fourier transform infrared (FTIR) spectroscopy. The analysis of FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of ?-CD onto MNPs. Transmission electron microscopy (TEM) indicated that the ?-CD functionalized MNPs were mostly present as individual nonclustered units in water. The number of ?-CD molecules immobilized on each MNP was about 240 according to the thermogravimetric analysis (TGA) results. The as-prepared ?-CD functionalized MNPs were used to detect dopamine with the assistance of a magnet. PMID:20596347

  10. A study of supramolecular host-guest interaction of dothiepin and doxepin drugs with cyclodextrin macrocycles

    NASA Astrophysics Data System (ADS)

    Rajendiran, N.; Sankaranarayanan, R. K.; Saravanan, J.

    2014-06-01

    Inclusion complexation behavior of dothiepin (DOT) and doxepin (DOX) with two cyclodextrins (?-CD and ?-CD) were studied by absorption, fluorescence, time resolved fluorescence, scanning electron microscope (SEM), transmission electron microscope (TEM), Fourier transformation infrared spectroscopy (FT-IR), differential scanning colorimetry (DSC), powder X-ray diffraction (PXRD), proton nuclear magnetic resonance (1H NMR) and molecular modeling methods. Absorption and fluorescence spectral studies reveal that both drugs form different types of inclusion complexes with ?-CD and ?-CD. DOT and DOX exhibit short life time in aqueous medium (DOT ? 2.29 ns, DOX ? 1.89 ns) and higher in CD medium (DOT:?-CD ? 3.45 ns, DOT:?-CD ? 4.84 ns, DOX:?-CD ? 3.55 ns and DOT:?-CD ? 4.33 ns). The supramolecular structure of the nano-sized sphere and agglomerate was established by TEM. Alkyl chain and aromatic ring protons of the drug molecule are entrapped in the CD nanocavities. The significant proton chemical shifts give evidence for expected inclusion complex formation. PM3 calculations suggest that the alkyl chain encapsulation is most energetically favored in ?-CD. The positive free energy and entropy changes indicated that both inclusion complexation processes are non-spontaneous and entropy driven.

  11. Supramolecular solubilization of cyclodextrin-modified carbon nano-onions by host-guest interactions.

    PubMed

    Wajs, Ewelina; Molina-Ontoria, Agustín; Nielsen, Thorbjørn Terndrup; Echegoyen, Luis; Fragoso, Alex

    2015-01-13

    Small carbon nano-onions (CNOs, 6-12 shells) were prepared in high yields and functionalized with carboxylic groups by chemical oxidation and reacted with ?CD-NH2 to yield CNOs decorated with ?CDs. A biocompatibile dextran polymer with graphted ferrocene groups was employed for the supramolecular self-assembly on the ?CD-CNO surfaces. The ?CDs act as hosts and the polymer ferrocene groups as guests (Fc-Dex) by the formation of inclusion complexes. After their assembly these nanostructures were soluble in aqueous solutions. The resulting product was characterized by transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and FT-IR and Raman spectroscopies. Moreover, the deposition of successive layers on the surface of the particles was monitored using DLS measurements and zeta potentials. Through-space interactions between the Fc moieties and the CNO cores and the influence of an additional dextran-?CD outer layer were measured electrochemically. PMID:25496567

  12. 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

  13. Single-molecule manipulation of double-stranded DNA using optical tweezers: Interaction studies of DNA with RecA and YOYO-1

    Microsoft Academic Search

    Martin L. Bennink; Orlando D. Scharer; Ronald Kanaar; Kumiko Sakata-Sogawa; Juleon M. Schins; Johannes S. Kanger; Grooth de Bart G; Jan Greve

    1999-01-01

    By using optical tweezers and a specially designed flow cell with an integrated glass micropipette, we constructed a setup similar to that of Smith et al. (Science 271:795-799, 1996) in which an individual double-stranded DNA (dsDNA) molecule can be captured between two polystyrene beads. The first bead is immobilized by the optical tweezers and the second by the micropipette. Movement

  14. Optical Tweezers as a Micromechanical Tool for Studying Defects in 2D Colloidal Crystals

    E-print Network

    Sungcheol Kim; Lichao Yu; Stephanie Huang; Alexandros Pertsinidis; Xinsheng Sean Ling

    2011-08-09

    This paper reports on some new results from the analyses of the video microscopy data obtained in a prior experiment on two-dimensional (2D) colloidal crystals. It was reported previously that optical tweezers can be used to create mono- and di-vacancies in a 2D colloidal crystal. Here we report the results on the creation of a vacancy-interstitial pair, as well as tri-vacancies. It is found that the vacancy-interstitial pair can be long-lived, but they do annihilate each other. The behavior of tri-vacancies is most intriguing, as it fluctuates between a configuration of bound pairs of dislocations and that of a locally amorphous state. The relevance of this observation to the issue of the nature of 2D melting is discussed.

  15. 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.

  16. Comparison of T-matrix calculation methods for scattering by cylinders in optical tweezers.

    PubMed

    Qi, Xiaoqiong; Nieminen, Timo A; Stilgoe, Alexander B; Loke, Vincent L Y; Rubinsztein-Dunlop, Halina

    2014-08-15

    The T-matrix method, or the T-matrix formulation of scattering, is a framework for mathematically describing the scattering properties of an object as a linear relationship between expansion coefficients of the incident and scattering fields in a basis of vector spherical wave functions (VSWFs). A variety of methods can be used to calculate the T-matrix. We explore the applicability of the extended boundary condition method (EBCM) and point matching (PM) method to calculate the T-matrix for scattering by cylinders in optical tweezers and hence the optical force acting on them. We compare both methods with the discrete-dipole approximation (DDA) to measure their accuracy for different sizes and aspect ratios (ARs) for Rayleigh and wavelength-size cylinders. We determine range of sizes and ARs giving errors below 1% and 10%. These results can help researchers choose the most efficient method to calculate the T-matrix for nonspherical particles with acceptable accuracy. PMID:25121885

  17. Robert Feulgen Prize Lecture. Laser tweezers and multiphoton microscopes in life sciences.

    PubMed

    König, K

    2000-08-01

    Near infrared (NIR) laser microscopy enables optical micromanipulation, piconewton force determination, and sensitive fluorescence studies by laser tweezers. Otherwise, fluorescence images with high spatial and temporal resolution of living cells and tissues can be obtained via non-resonant fluorophore excitation with multiphoton NIR laser scanning microscopes. Furthermore, NIR femtosecond laser pulses at TW/cm2 intensities can be used to realize non-invasive contact-free surgery of nanometer-sized structures within living cells and tissues. Applications of these novel versatile NIR laser-based tools for the determination of motility forces, coenzyme and chlorophyll imaging, three-dimensional multigene detection, non-invasive optical sectioning of tissues ("optical biopsy"), functional protein imaging, and nanosurgery of chromosomes are described. PMID:11052257

  18. Fast digital hologram generation and adaptive force measurement in liquid-crystal-display-based holographic tweezers

    NASA Astrophysics Data System (ADS)

    Reicherter, Marcus; Zwick, Susanne; Haist, Tobias; Kohler, Christian; Tiziani, Hans; Osten, Wolfgang

    2006-02-01

    Computer-generated holograms in conjunction with spatial light modulators (SLMs) offer a way to dynamically generate holograms that are adapted to specific tasks. To use the full dynamic capability of the SLM, the hologram computation should be very fast. We present a method that uses the highly parallel architecture of a consumer graphics board to compute analytical holograms in video real time. A precice characterization of the SLM (Holoeye LC-R-2500) and the adaption of its settings to our near-infrared application is necessary to guarantee an efficient hologram reconstruction. The benefits of a fast computation of adapted holograms and the application of an efficient SLM are demonstrated by measuring the trapping forces of holographic tweezers.

  19. Fast digital hologram generation and adaptive force measurement in liquid-crystal-display-based holographic tweezers.

    PubMed

    Reicherter, Marcus; Zwick, Susanne; Haist, Tobias; Kohler, Christian; Tiziani, Hans; Osten, Wolfgang

    2006-02-10

    Computer-generated holograms in conjunction with spatial light modulators (SLMs) offer a way to dynamically generate holograms that are adapted to specific tasks. To use the full dynamic capability of the SLM, the hologram computation should be very fast. We present a method that uses the highly parallel architecture of a consumer graphics board to compute analytical holograms in video real time. A precice characterization of the SLM (Holoeye LC-R-2500) and the adaption of its settings to our near-infrared application is necessary to guarantee an efficient hologram reconstruction. The benefits of a fast computation of adapted holograms and the application of an efficient SLM are demonstrated by measuring the trapping forces of holographic tweezers. PMID:16512530

  20. 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

  1. Magnetic tweezers measurements of the nanomechanical properties of DNA in the presence of drugs

    PubMed Central

    Salerno, Domenico; Brogioli, Doriano; Cassina, Valeria; Turchi, Diana; Beretta, Giovanni Luca; Seruggia, Davide; Ziano, Roberto; Zunino, Franco

    2010-01-01

    Herein, we study the nanomechanical characteristics of single DNA molecules in the presence of DNA binders, including intercalating agents (ethidium bromide and doxorubicin), a minor groove binder (netropsin) and a typical alkylating damaging agent (cisplatin). We have used magnetic tweezers manipulation techniques, which allow us to measure the contour and persistence lengths together with the bending and torsional properties of DNA. For each drug, the specific variations of the nanomechanical properties induced in the DNA have been compared. We observed that the presence of drugs causes a specific variation in the DNA extension, a shift in the natural twist and a modification of bending dependence on the imposed twist. By introducing a naive model, we have justified an anomalous correlation of torsion data observed in the presence of intercalators. Finally, a data analysis criterion for discriminating between different molecular interactions among DNA and drugs has been suggested. PMID:20601682

  2. 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.

  3. 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.

  4. 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.

  5. Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers

    NASA Astrophysics Data System (ADS)

    Frusawa, Hiroshi; Matsumoto, Youei

    2014-02-01

    To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission.

  6. Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers

    PubMed Central

    Frusawa, Hiroshi; Matsumoto, Youei

    2014-01-01

    To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission. PMID:24509866

  7. 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.

  8. 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.

  9. Reverse DNA translocation through a solid-state nanopore by magnetic tweezers

    PubMed Central

    Peng, Hongbo; Ling, Xinsheng Sean

    2009-01-01

    Voltage-driven DNA translocation through nanopores has attracted wide interest for many potential applications in molecular biology and biotechnology. However, it is intrinsically difficult to control the DNA motion in standard DNA translocation processes in which a strong electric field is required in drawing DNA into the pore, but it also leads to uncontrollable fast DNA translocation. Here we explore a new type of DNA translocation. We dub it ‘reverse DNA translocation’, in which the DNA is pulled through a nanopore mechanically by a magnetic bead, driven by a magnetic-field gradient. This technique is compatible with simultaneous ionic current measurements and is suitable for multiple nanopores, paving the way for large scale applications. We report the first experiment of reverse DNA translocation through a solid-state nanopore using magnetic tweezers. PMID:19420602

  10. 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.

  11. 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

  12. Floating electrode optoelectronic tweezers: Light-driven dielectrophoretic droplet manipulation in electrically insulating oil medium

    PubMed Central

    Park, Sungyong; Pan, Chenlu; Wu, Ting-Hsiang; Kloss, Christoph; Kalim, Sheraz; Callahan, Caitlin E.; Teitell, Michael; Chiou, Eric P.Y.

    2008-01-01

    We report an optical actuation mechanism, floating electrode optoelectronic tweezers (FEOET). FEOET enables light-driven transport of aqueous droplets immersed in electrically insulating oil on a featureless photoconductive glass layer with direct optical images. We demonstrate that a 681 ?m de-ionized water droplet immersed in corn oil medium is actuated by a 3.21 ?W laser beam with an average intensity as low as 4.08 ?W?mm2 at a maximum speed of 85.1 ?m?s on a FEOET device. FEOET provides a promising platform for massively parallel droplet manipulation with optical images on low cost, silicon-coated glass. The FEOET device structure, fabrication, working principle, numerical simulations, and operational results are presented in this letter. PMID:19479046

  13. Imaging microscopic fluid viscosity and velocity fields using confocal scanning optical tweezers

    NASA Astrophysics Data System (ADS)

    Nemet, Boaz A.; Harnik, Nili; Cronin-Golomb, Mark

    2002-05-01

    Confocal microscopy and optical tweezers were combined to develop a minimally invasive instrument capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around bipolymer producing cells. An image of the viscosity distribution around a pullulan producing cell of Aureobasidium pullulans is shown as an example. We present results from experiments supporting a linearized model for the motion of a trapped bead in an oscillating harmonic potential. Fluid velocity measurements are tested by comparing to an independent video based measurement. We apply the technique to obtain a 2-D map of the flow past a microscopic wedge and compare to a theoretical solution for the stream lines assuming potential flow. Since the velocity is measured simultaneously with the trap relaxation time, it requires practically no calibration and is independent of the trap stiffness and the particle size.

  14. Double nanohole optical tweezers visualize protein p53 suppressing unzipping of single DNA-hairpins

    PubMed Central

    Kotnala, Abhay; Gordon, Reuven

    2014-01-01

    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

  15. Micro- and nano-particle trapping using fibered optical nano-tweezers

    NASA Astrophysics Data System (ADS)

    Decombe, Jean-Baptiste; Dantelle, Géraldine; Gacoin, Thierry; Valdivia-Valero, Francisco J.; Colas des Francs, Gérard; Huant, Serge; Fick, Jochen

    2014-09-01

    We present the stable trapping of luminescent 300-nm cerium-doped YAG particles in aqueous suspension using a dual fiber tip optical tweezers. The particles were elaborated using a specific glycothermal synthesis route together with an original protected annealing step. We obtained harmonic trap potentials in the direction transverse to the optical fiber axes. In the longitudinal direction, the potential shows some sub-structure revealed by two peaks in the distribution statistics with a distance of about half the wavelength of the trapping laser. We calculated intensity normalized trapping stiffness of 36 pN•?m-1W-1. These results are compared to previous work of microparticle trapping and discussed thanks to numerical simulations based on finite element method.

  16. Coherence and Raman Sideband Cooling of a Single Atom in an Optical Tweezer

    NASA Astrophysics Data System (ADS)

    Thompson, J. D.; Tiecke, T. G.; Zibrov, A. S.; Vuleti?, V.; Lukin, M. D.

    2013-03-01

    We investigate quantum control of a single atom in a tightly focused optical tweezer trap. We show that inevitable spatially varying polarization gives rise to significant internal-state decoherence but that this effect can be mitigated by an appropriately chosen magnetic bias field. This enables Raman sideband cooling of a single atom close to its three-dimensional ground state (vibrational quantum numbers n¯x=n¯y=0.01, n¯z=8) even for a trap beam waist as small as w=900nm. The small atomic wave packet with ?x=?y=24nm and ?z=270nm represents a promising starting point for future hybrid quantum systems where atoms are placed in close proximity to surfaces.

  17. Coherence and Raman sideband cooling of a single atom in an optical tweezer.

    PubMed

    Thompson, J D; Tiecke, T G; Zibrov, A S; Vuleti?, V; Lukin, M D

    2013-03-29

    We investigate quantum control of a single atom in a tightly focused optical tweezer trap. We show that inevitable spatially varying polarization gives rise to significant internal-state decoherence but that this effect can be mitigated by an appropriately chosen magnetic bias field. This enables Raman sideband cooling of a single atom close to its three-dimensional ground state (vibrational quantum numbers n(x)=n(y)=0.01, n(z)=8) even for a trap beam waist as small as w=900??nm. The small atomic wave packet with ?x=?y=24??nm and ?z=270??nm represents a promising starting point for future hybrid quantum systems where atoms are placed in close proximity to surfaces. PMID:23581312

  18. High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments.

    PubMed

    Lin, Jun; Valentine, Megan T

    2012-05-01

    We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to ?4.5 ?m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ?1 kPa. PMID:22667631

  19. High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments

    SciTech Connect

    Lin Jun [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States); Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106 (United States); Valentine, Megan T. [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States)

    2012-05-15

    We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to {approx}4.5 {mu}m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as {approx}1 kPa.

  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 ? 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 ? 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 ? 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 ? 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 ? 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

  1. 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.

  2. Cone and rod cells have different target preferences in vitro as revealed by optical tweezers

    PubMed Central

    Clarke, Robert J.; Högnason, Kormákur; Brimacombe, Michael

    2008-01-01

    Purpose When neural circuits are damaged in adulthood, regenerating and sprouting processes must distinguish appropriate targets to recreate the normal circuitry. We tested the ability of adult nerve cells to target specific cells in culture using the retina as a model system. Methods Under sterile culture conditions, retinal cells, isolated from tiger salamander retina, were micromanipulated with optical tweezers to create pairs of first-order photoreceptor cells with second- or third-order retinal neurons. The development of cell contact and presynaptic varicosities, the direction and amount of neuritic growth, and nerve cell polarity were assessed after seven days in vitro. Cultures were labeled for rod opsin to distinguish rod from cone cells and for the alpha subunit of the trimeric G protein Go (Go?) to identify cone-dominated and mixed rod-cone ON bipolar cells. Results Quantitative analysis of growth demonstrated that target preferences were cell-specific: Cone cells preferred second-order bipolar cells, whereas rod cells grew toward third-order neurons, which include amacrine and ganglion cells. In addition, when rod cells grew toward bipolar cells, they chose an abnormally high number of Go?-positive bipolar cells. These growth patterns were not affected by tweezers manipulation or the amount of growth. Cell orientation of the photoreceptor also did not affect preferences: Cells oriented away from dendritic processes could reorient their axonal pole toward the target cell. Conclusions Cone cells preferred normal partners, and rod cells preferred novel partners. These intrinsic preferences indicate that adult nerve cells can have differing capacities for targeting even if they come from the same cell class. Further, these differences may help explain the patterns of photoreceptor sprouting seen in retinal degeneration in which rod, but not cone, cells invade the inner retinal layers where third-order neurons are located. PMID:18432315

  3. 3D manipulation and visualization of in-vitro cells by optical tweezers and digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Merola, F.; Miccio, L.; Memmolo, P.; Di Caprio, G.; Coppola, G.; Netti, P.; Ferraro, P.

    2014-03-01

    We present the possibility to trap cells (mouse fibroblasts, bovine spermatozoa and diatoms), to manage their position and to induce rotation, by using optical tweezers. The aim is to place them in desired positions, in order to record holographic images in a microscope configuration. Then we are able to recover the 3D shape and to calculate the biovolume of the cells starting from the reconstructed quantitative phase maps (QPMs).

  4. Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces

    NASA Astrophysics Data System (ADS)

    Khokhlova, Maria D.; Lyubin, Eugeny V.; Zhdanov, Alexander G.; Rykova, Sophia Yu.; Sokolova, Irina A.; Fedyanin, Andrey A.

    2012-02-01

    Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level.

  5. Combining Optical Tweezers, Single-Molecule Fluorescence Microscopy, and Microfluidics for Studies of DNA–Protein Interactions

    Microsoft Academic Search

    Peter Gross; Géraldine Farge; Erwin J. G. Peterman; Gijs J. L. Wuite

    2010-01-01

    The technically challenging field of single-molecule biophysics has established itself in the last decade by granting access to detailed information about the fate of individual biomolecules, unattainable in traditional biochemical assays. The appeal of single-molecule methods lies in the directness of the information obtained from individual biomolecules. Technological improvements in single-molecule methods have made it possible to combine optical tweezers,

  6. Tracking of single quantum dot labeled EcoRV sliding along DNA manipulated by double optical tweezers.

    PubMed

    Biebricher, Andreas; Wende, Wolfgang; Escudé, Christophe; Pingoud, Alfred; Desbiolles, Pierre

    2009-04-22

    Fluorescence microscopy provides a powerful method to directly observe single enzymes moving along a DNA held in an extended conformation. In this work, we present results from single EcoRV enzymes labeled with quantum dots which interact with DNA manipulated by double optical tweezers. The application of quantum dots facilitated accurate enzyme tracking without photobleaching whereas the tweezers allowed us to precisely control the DNA extension. The labeling did not affect the biochemical activity of EcoRV checked by directly observing DNA digestion on the single molecule level. We used this system to demonstrate that during sliding, the enzyme stays in close contact with the DNA. Additionally, slight overstretching of the DNA resulted in a significant decrease of the 1D diffusion constant, which suggests that the deformation changes the energy landscape of the sliding interaction. Together with the simplicity of the setup, these results demonstrate that the combination of optical tweezers with fluorescence tracking is a powerful tool for the study of enzyme translocation along DNA. PMID:19383444

  7. Drug-DNA interactions at single molecule level: A view with optical tweezers

    NASA Astrophysics Data System (ADS)

    Paramanathan, Thayaparan

    Studies of small molecule--DNA interactions are essential for developing new drugs for challenging diseases like cancer and HIV. The main idea behind developing these molecules is to target and inhibit the reproduction of the tumor cells and infected cells. We mechanically manipulate single DNA molecule using optical tweezers to investigate two molecules that have complex and multiple binding modes. Mononuclear ruthenium complexes have been extensively studied as a test for rational drug design. Potential drug candidates should have high affinity to DNA and slow dissociation kinetics. To achieve this, motifs of the ruthenium complexes are altered. Our collaborators designed a dumb-bell shaped binuclear ruthenium complex that can only intercalate DNA by threading through its bases. Studying the binding properties of this complex in bulk studies took hours. By mechanically manipulating a single DNA molecule held with optical tweezers, we lower the barrier to thread and make it fast compared to the bulk experiments. Stretching single DNA molecules with different concentration of drug molecules and holding it at a constant force allows the binding to reach equilibrium. By this we can obtain the equilibrium fractional ligand binding and length of DNA at saturated binding. Fitting these results yields quantitative measurements of the binding thermodynamics and kinetics of this complex process. The second complex discussed in this study is Actinomycin D (ActD), a well studied anti-cancer agent that is used as a prototype for developing new generations of drugs. However, the biophysical basis of its activity is still unclear. Because ActD is known to intercalate double stranded DNA (dsDNA), it was assumed to block replication by stabilizing dsDNA in front of the replication fork. However, recent studies have shown that ActD binds with even higher affinity to imperfect duplexes and some sequences of single stranded DNA (ssDNA). We directly measure the on and off rates by stretching the DNA molecule to a certain force and holding it at constant force while adding the drug and then while washing off the drug. Our finding resolves the long lasting controversy of ActD binding modes, clearly showing that both the dsDNA binding and ssDNA binding converge to the same single mode. The result supports the hypothesis that the primary characteristic of ActD that contributes to its biological activity is its ability to inhibit cellular replication by binding to transcription bubbles and causing cell death.

  8. Blind predictions of DNA and RNA tweezers experiments with force and torque.

    PubMed

    Chou, Fang-Chieh; Lipfert, Jan; Das, Rhiju

    2014-08-01

    Single-molecule tweezers measurements of double-stranded nucleic acids (dsDNA and dsRNA) provide unprecedented opportunities to dissect how these fundamental molecules respond to forces and torques analogous to those applied by topoisomerases, viral capsids, and other biological partners. However, tweezers data are still most commonly interpreted post facto in the framework of simple analytical models. Testing falsifiable predictions of state-of-the-art nucleic acid models would be more illuminating but has not been performed. Here we describe a blind challenge in which numerical predictions of nucleic acid mechanical properties were compared to experimental data obtained recently for dsRNA under applied force and torque. The predictions were enabled by the HelixMC package, first presented in this paper. HelixMC advances crystallography-derived base-pair level models (BPLMs) to simulate kilobase-length dsDNAs and dsRNAs under external forces and torques, including their global linking numbers. These calculations recovered the experimental bending persistence length of dsRNA within the error of the simulations and accurately predicted that dsRNA's "spring-like" conformation would give a two-fold decrease of stretch modulus relative to dsDNA. Further blind predictions of helix torsional properties, however, exposed inaccuracies in current BPLM theory, including three-fold discrepancies in torsional persistence length at the high force limit and the incorrect sign of dsRNA link-extension (twist-stretch) coupling. Beyond these experiments, HelixMC predicted that 'nucleosome-excluding' poly(A)/poly(T) is at least two-fold stiffer than random-sequence dsDNA in bending, stretching, and torsional behaviors; Z-DNA to be at least three-fold stiffer than random-sequence dsDNA, with a near-zero link-extension coupling; and non-negligible effects from base pair step correlations. We propose that experimentally testing these predictions should be powerful next steps for understanding the flexibility of dsDNA and dsRNA in sequence contexts and under mechanical stresses relevant to their biology. PMID:25102226

  9. Probing the micro-rheological properties of aerosol particles using optical tweezers

    NASA Astrophysics Data System (ADS)

    Power, Rory M.; Reid, Jonathan P.

    2014-07-01

    The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability.

  10. Probing the micro-rheological properties of aerosol particles using optical tweezers.

    PubMed

    Power, Rory M; Reid, Jonathan P

    2014-07-01

    The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >10(12) Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability. PMID:24994710

  11. Blind Predictions of DNA and RNA Tweezers Experiments with Force and Torque

    PubMed Central

    Chou, Fang-Chieh; Lipfert, Jan; Das, Rhiju

    2014-01-01

    Single-molecule tweezers measurements of double-stranded nucleic acids (dsDNA and dsRNA) provide unprecedented opportunities to dissect how these fundamental molecules respond to forces and torques analogous to those applied by topoisomerases, viral capsids, and other biological partners. However, tweezers data are still most commonly interpreted post facto in the framework of simple analytical models. Testing falsifiable predictions of state-of-the-art nucleic acid models would be more illuminating but has not been performed. Here we describe a blind challenge in which numerical predictions of nucleic acid mechanical properties were compared to experimental data obtained recently for dsRNA under applied force and torque. The predictions were enabled by the HelixMC package, first presented in this paper. HelixMC advances crystallography-derived base-pair level models (BPLMs) to simulate kilobase-length dsDNAs and dsRNAs under external forces and torques, including their global linking numbers. These calculations recovered the experimental bending persistence length of dsRNA within the error of the simulations and accurately predicted that dsRNA's “spring-like” conformation would give a two-fold decrease of stretch modulus relative to dsDNA. Further blind predictions of helix torsional properties, however, exposed inaccuracies in current BPLM theory, including three-fold discrepancies in torsional persistence length at the high force limit and the incorrect sign of dsRNA link-extension (twist-stretch) coupling. Beyond these experiments, HelixMC predicted that ‘nucleosome-excluding’ poly(A)/poly(T) is at least two-fold stiffer than random-sequence dsDNA in bending, stretching, and torsional behaviors; Z-DNA to be at least three-fold stiffer than random-sequence dsDNA, with a near-zero link-extension coupling; and non-negligible effects from base pair step correlations. We propose that experimentally testing these predictions should be powerful next steps for understanding the flexibility of dsDNA and dsRNA in sequence contexts and under mechanical stresses relevant to their biology. PMID:25102226

  12. Haptic Manipulation of Microspheres Using Optical Tweezers Under the Guidance of Artificial Force Fields

    E-print Network

    Bukusoglu, Ibrahim; Kiraz, Alper; Kurt, Adnan

    2007-01-01

    Using optical tweezers and a haptic device, microspheres having diameters ranging from 3 to 4 um (floating in a fluid solution) are manipulated in order to form patterns of coupled optical microresonators by assembling the spheres via chemical binding. For this purpose, biotin-coated microspheres trapped by a laser beam are steered and chemically attached to an immobilized streptavidin-coated sphere (i.e. anchor sphere) one by one using an XYZ piezo scanner controlled by a haptic device. The positions of all spheres in the scene are detected using a CCD camera and a collision-free path for each manipulated sphere is generated using the potential field approach. The forces acting on the manipulated particle due to the viscosity of the fluid and the artificial potential field are scaled and displayed to the user through the haptic device for better guidance and control during steering. In addition, a virtual fixture is implemented such that the desired angle of approach and strength are achieved during the bind...

  13. Calibration of optical tweezers with positional detection in the back focal plane

    SciTech Connect

    Tolic-Noerrelykke, Simon F.; Schaeffer, Erik; Howard, Jonathon; Pavone, Francesco S.; Juelicher, Frank; Flyvbjerg, Henrik [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany) and European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy) and Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden (Germany); European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany); Isaac Newton Institute for Mathematical Sciences, Cambridge CB3 0EH (United Kingdom); Biosystems Department, Risoe National Laboratory, DK-4000 Roskilde (Denmark) and Danish Polymer Centre, Risoe National Laboratory, DK-4000 Roskilde (Denmark)

    2006-10-15

    We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.

  14. Dynamic translocation of ligand-complexed DNA through solid-state nanopores with optical tweezers

    NASA Astrophysics Data System (ADS)

    Sischka, Andy; Spiering, Andre; Khaksar, Maryam; Laxa, Miriam; König, Janine; Dietz, Karl-Josef; Anselmetti, Dario

    2010-11-01

    We investigated the threading and controlled translocation of individual lambda-DNA (?-DNA) molecules through solid-state nanopores with piconewton force sensitivity, millisecond time resolution and picoampere ionic current sensitivity with a set-up combining quantitative 3D optical tweezers (OT) with electrophysiology. With our virtually interference-free OT set-up the binding of RecA and single peroxiredoxin protein molecules to ?-DNA was quantitatively investigated during dynamic translocation experiments where effective forces and respective ionic currents of the threaded DNA molecule through the nanopore were measured during inward and outward sliding. Membrane voltage-dependent experiments of reversible single protein/DNA translocation scans yield hysteresis-free, asymmetric single-molecule fingerprints in the measured force and conductance signals that can be attributed to the interplay of optical trap and electrostatic nanopore potentials. These experiments allow an exact localization of the bound protein along the DNA strand and open fascinating applications for label-free detection of DNA-binding ligands, where structural and positional binding phenomena can be investigated at a single-molecule level.

  15. Angular and position stability of a nanorod trapped in an optical tweezers.

    PubMed

    Bareil, Paul B; Sheng, Yunlong

    2010-12-01

    We analyze the trap stiffness and trapping force potential for a nano-cylinder trapped in the optical tweezers against its axial and lateral shift and tilt associated to the natural Brownian motion. We explain the physical properties of the optical trapping by computing and integrating the radiation stress distribution on the nano-cylinder surfaces using the T-matrix approach. Our computation shows that the force stiffness to the lateral shift is several times higher than that to the axial shift of the nano-cylinder, and lateral torque due to the stress on the side-face is 1-2 orders of magnitude higher than that on the end-faces of a nano-cylinder with the aspect ratio of 2 - 20. The torque due to the stress on the nano-cylinder surface is 2-3 orders of magnitude higher than the spin torque. We explain why a nano-cylinder of low aspect ratio is trapped and aligned normal to the trapping beam axis. PMID:21164989

  16. Measuring the viscosity of embryonic epithelia in vivo by magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Ma, Xiaoyan; Angarita, M. Paula; Frierson, Mershard; Sheldon, Drew; Hutson, M. Shane

    2011-03-01

    During early development, sheets of epithelial cells are reshaped by cellular forces. Several recent investigations in fruit fly (Drosophila) embryos have used laser microsurgery and video force microscopy to measure these forces; however, these measurements are actually limited to force/viscosity ratios because the effective viscosity of epithelial cells in a living embryo is largely unknown. This effective viscosity may vary spatially within the embryo and temporally as development progresses. To address this issue, we use microinjection, magnetic tweezers and confocal microscopy to measure the effective viscosity of epithelial cells in fruit fly embryos in vivo. We inject fluorescent magnetic beads (2-?m diameter) into GFP-labeled embryos at the multi-nuclear syncytial blastoderm stage. The beads are pulled to embryo's surface by a permanent magnet and become engulfed by individual epithelial cells during cellularization. During later stages of development, we supply current pulses to an electromagnet to apply force pulses to the beads with a magnitude of ˜100 pN. The effective viscosity is inferred from the movement of these beads as tracked by confocal microscopy. We will report initial results on amnioserosa cells during dorsal closure.

  17. Measurements of the force fields within an acoustic standing wave using holographic optical tweezers

    SciTech Connect

    Bassindale, P. G.; Drinkwater, B. W. [Faculty of Engineering, Queens building, University of Bristol, Bristol BS8 1TR (United Kingdom); Phillips, D. B. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Barnes, A. C. [Department of Physics, H.H.Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

    2014-04-21

    Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5??m silica micro-sphere was used to characterise a 6.8?MHz standing wave, ??=?220??m, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2?nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.

  18. Horizontal Magnetic Tweezers for Micromanipulation of Single DNA-Protein Complexes

    NASA Astrophysics Data System (ADS)

    McAndrew, C.; Sarkar, A.; Mehl, P.

    2011-03-01

    We report on the development of a new magnetic force transducer or "tweezer" that can apply pico-Newton forces on single DNA molecules in the focus plane. Since the changes in DNA's end-to-end extension are coplanar with the pulling force, there is no need to continually refocus. The DNA constructs (?-DNA end labeled with a 3?m polystyrene bead and a 2.8?m paramagnetic sphere) and appropriate buffer are introduced to a custom built 400?L to 650?L closed cell. This closed cell isolates our sample and produces low-noise force and extension measurements. This chamber rests on a stage fixed to a three axis micromanipulator. Entering the flat chamber are two micropipettes, a 2.5?m id pipette for aspirating the polystyrene bead and a 20?m id pipette for injecting proteins of interest. The suction and the injection pipettes are rigidly mounted to a hydraulic, three-axis micromanipulator. DNA-bead constructs, once introduced to the chamber, can be located by moving the stage over the objective. We have shown that we can easily and reputably find, capture, and manipulate single molecules of DNA within a force range of 0.1pN to 100pN.

  19. Optical tweezers reveal relationship between microstructure and nanoparticle penetration of pulmonary mucus.

    PubMed

    Kirch, Julian; Schneider, Andreas; Abou, Bérengère; Hopf, Alexander; Schaefer, Ulrich F; Schneider, Marc; Schall, Christian; Wagner, Christian; Lehr, Claus-Michael

    2012-11-01

    In this study, the mobility of nanoparticles in mucus and similar hydrogels as model systems was assessed to elucidate the link between microscopic diffusion behavior and macroscopic penetration of such gels. Differences in particle adhesion to mucus components were strongly dependent on particle coating. Particles coated with 2 kDa PEG exhibited a decreased adhesion to mucus components, whereas chitosan strongly increased the adhesion. Despite such mucoinert properties of PEG, magnetic nanoparticles of both coatings did not penetrate through native respiratory mucus, resisting high magnetic forces (even for several hours). However, model hydrogels were, indeed, penetrated by both particles in dependency of particle coating, obeying the theory of particle mobility in an external force field. Comparison of penetration data with cryogenic scanning EM images of mucus and the applied model systems suggested particularly high rigidity of the mucin scaffold and a broad pore size distribution in mucus as reasons for the observed particle immobilization. Active probing of the rigidity of mucus and model gels with optical tweezers was used in this context to confirm such properties of mucus on the microscale, thus presenting the missing link between micro- and macroscopical observations. Because of high heterogeneity in the size of the voids and pores in mucus, on small scales, particle mobility will depend on adhesive or inert properties. However, particle translocation over distances larger than a few micrometers is restricted by highly rigid structures within the mucus mesh. PMID:23091027

  20. The ?PIVOT: an integrated particle image velocimeter and optical tweezers instrument for microenvironment investigations

    PubMed Central

    Nève, N; Lingwood, J K; Zimmerman, J; Kohles, S S; Tretheway, D C

    2008-01-01

    A novel instrument to manipulate and characterize the mechanical environment in and around microscale objects in a fluidic environment has been developed by integrating two laser-based techniques: micron-resolution particle image velocimetry (?PIV) and optical tweezers (OT). This instrument, the ?PIVOT, enables a new realm of microscale studies, yet still maintains the individual capabilities of each optical technique. This was demonstrated with individual measurements of optical trap stiffness (?70 pN ?m?1 for a 20 ?m polystyrene sphere and a linear relationship between trap stiffness and laser power) and fluid velocities within 436 nm of a microchannel wall. The integrated device was validated by comparing computational flow predictions to the measured velocity profile around a trapped particle in either a uniform flow or an imposed, gravity-driven microchannel flow (R2 = 0.988, RMS error = 13.04 ?m s?1). Interaction between both techniques is shown to be negligible for 15 ?m to 35 ?m diameter trapped particles subjected to fluid velocities from 50 ?m s?1 to 500 ?m s?1 even at the highest laser power (1.45 W). The integrated techniques will provide a unique perspective toward understanding microscale phenomena including single-cell biomechanics, non-Newtonian fluid mechanics and single particle or particle–particle hydrodynamics. PMID:18953424

  1. Optical tweezers based measurement of PLGA-NP interaction with prostate cancer cells

    NASA Astrophysics Data System (ADS)

    Blesener, Thea; Mondal, Argha; Menon, Jyothi U.; Nguyen, Kytai T.; Mohanty, Samarendra

    2013-02-01

    In order to quantify the binding capacities of polymeric, biodegradable and biocompatible poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), conjugated with either R11 peptides or Folic Acid, the strength by detach from prostate cancer cells (PCCs) was measured via optical tweezers based measurements. Specific nanoparticle drug delivery eliminates the previously used diffuse, full-body application of potent cancer drugs by localizing drug delivery to malignant cells. Precise monitoring of NP position in the trap near the PCC membrane using a fluorescence imaging based method enabled calibration of the trap stiffness and subsequent force measurements. By defining the force with which the many diverse conjugates and coatings of different types of NPs bind the vast array of cancer cell types, chemotherapeutic drugs can be delivered in a specific manner with the optimal particle and corresponding conjugates. Further, and most significantly, the rupture force measurements will reveal whether or not targeted nanoparticles can overcome the force of blood attempting to pull the particle from designated cells. Our preliminary study revealed that the binding between PLGA-NPs and prostate cancer cells is enhanced by coating with folic acid or R11 peptides. These conjugates increase the force required to detach the particle thus allowing particles to overcome drag force of the blood in prostate capillary systems.

  2. Optical tweezers reveal a dynamic mechanical response of cationic peptide-DNA complexes

    NASA Astrophysics Data System (ADS)

    Lee, Amy; Zheng, Tai; Sucayan, Sarah; Chou, Szu-Ting; Tricoli, Lucas; Hustedt, Jason; Kahn, Jason; Mixson, A. James; Seog, Joonil

    2013-03-01

    Nonviral carriers have been developed to deliver nucleic acids by forming nanoscale complexes; however, there has been limited success in achieving high transfection efficiency. Our hypothesis is that a factor affecting gene delivery efficiency is the mechanical response of the condensed complex. To begin to test this hypothesis, we directly measured the mechanical properties of DNA-carrier complexes using optical tweezers. Histidine-lysine (HK) polymer, Asparagine-lysine (NK) polymer and poly-L-lysine were used to form complexes with a single DNA molecule. As carriers were introduced, a sudden decrease in DNA extension occurrs at a force level which is defined as critical force (Fc). Fc is carrier and concentration dependent. Pulling revealed reduction in DNA extension length for HK-DNA complexes. The characteristics of force profiles vary by agent and can be dynamically manipulated by changes in environmental conditions such as ionic strength of the buffer as well as pH. Heparin can remove cationic reagents which are otherwise irreversibly bound to DNA. The implications for optimizing molecular interactions to enhance transfection efficiency will be discussed.

  3. Force measuring optical tweezers system for long time measurements of P pili stability

    NASA Astrophysics Data System (ADS)

    Andersson, Magnus; Fällman, Erik; Uhlin, Bernt Eric; Axner, Ove

    2006-02-01

    A force-measuring optical tweezers instrumentation and long time measurements of the elongation and retraction of bacterial fimbriae from Uropathogenic E. coli (UPEC) under strain are presented. The instrumentation is presented in some detail. Special emphasis is given to measures taken to reduce the influence of noise and drifts in the system and from the surrounding, which makes long term force measurements possible. Individual P pili from UPEC bacteria were used as a biological model system for repetitive unfolding and refolding cycles of bacterial fimbriae under equilibrium conditions. P pili have evolved into a three-dimensional helix-like structure, the PapA rod, that can be successively and significantly elongated and/or unfolded when exposed to external forces. The instrumentation is used for characterization of the force-vs.-elongation response of the PapA rod of individual P pili, with emphasis on the long time stability of the forced unfolding and refolding of the helical structure of the PapA rod. The results show that the PapA rod is capable of withstanding extensive strain, leading to a complete unfolding of the helical structure, repetitive times during the life cycle of a bacterium without any noticeable alteration of the mechanical properties of the P pili. This function is believed to be importance for UPEC bacteria in vivo since it provides a close contact to a host cell (which is an initial step of invasion) despite urine cleaning attempts.

  4. Cell manipulation tool with combined microwell array and optical tweezers for cell isolation and deposition

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolin; Gou, Xue; Chen, Shuxun; Yan, Xiao; Sun, Dong

    2013-07-01

    Isolation from rare cells and deposition of sorted cells with high accuracy for further study are critical to a wide range of biomedical applications. In the current paper, we report an automated cell manipulation tool with combined optical tweezers and a uniquely designed microwell array, which functions for recognition, isolation, assembly, transportation and deposition of the interesting cells. The microwell array allows the passive hydrodynamic docking of cells, while offering the opportunity to inspect the interesting cell phenotypes with high spatio-temporal resolution based on the flexible image processing technique. In addition, dynamic and parallel cell manipulation in three dimensions can realize the target cell levitation from microwell and pattern assembly with multiple optical traps. Integrated with the programmed motorized stage, the optically levitated and assembled cells can be transported and deposited to the predefined microenvironment, so the tool can facilitate the integration of other on-chip functionalities for further study without removing these isolated cells from the chip. Experiments on human embryonic stem cells and yeast cells are performed to demonstrate the effectiveness of the proposed cell manipulation tool. Besides the application to cell isolation and deposition, three other biological applications with this tool are also presented.

  5. Application of vertical-cavity laser-based optical tweezers for particle manipulation in microfluidic channels

    NASA Astrophysics Data System (ADS)

    Kroner, Andrea; Schneck, Carolin; Rinaldi, Fernando; Rösch, Rudolf; Michalzik, Rainer

    2008-04-01

    The combination of microfluidics and optical manipulation offers new possibilities for particle handling and sorting on a single-cell level in the field of biophotonics. We present particle manipulation in microfluidics based on vertical-cavity surface-emitting lasers (VCSELs) which constitute a new low-cost, high beam quality nanostructured laser source for optical trapping, additionally allowing easy formation of small-sized, two-dimensional laser arrays. Single devices as well as densely packed linear VCSEL arrays with a pitch of only 24 ?m are fabricated. Microfluidic channels with widths of 50 to 150 ?m forming T- and Y-junctions are made of PDMS using common soft-lithography. With a single laser, selected polystyrene particles are trapped in the inlet channel and transferred to the desired outlet branch by moving the chip relatively to the optical trap. In a second approach, a tilted, linear laser array is introduced into the setup, effectively forming an optical lattice. While passing the continuously operating tweezers array, particles are not fully trapped, but deflected by each single laser beam. Therefore, non-mechanical particle separation in microfluidics is achieved. We also show the route to ultra-miniaturization of the system avoiding any external optics. Simulations of an integrated particle deflection and sorting scheme as well as first fabrication steps for the integrated optical trap are presented.

  6. Combined optical tweezers and laser dissector for controlled ablation of functional connections in neural networks

    NASA Astrophysics Data System (ADS)

    Difato, Francesco; Dal Maschio, Marco; Marconi, Emanuele; Ronzitti, Giuseppe; Maccione, Alessandro; Fellin, Tommasso; Berdondini, Luca; Chieregatti, Evelina; Benfenati, Fabio; Blau, Axel

    2011-05-01

    Regeneration of functional connectivity within a neural network after different degrees of lesion is of utmost clinical importance. To test pharmacological approaches aimed at recovering from a total or partial damage of neuronal connections within a circuit, it is necessary to develop a precise method for controlled ablation of neuronal processes. We combined a UV laser microdissector to ablate neural processes in vitro at single neuron and neural network level with infrared holographic optical tweezers to carry out force spectroscopy measurements. Simultaneous force spectroscopy, down to the sub-pico-Newton range, was performed during laser dissection to quantify the tension release in a partially ablated neurite. Therefore, we could control and measure the damage inflicted to an individual neuronal process. To characterize the effect of the inflicted injury on network level, changes in activity of neural subpopulations were monitored with subcellular resolution and overall network activity with high temporal resolution by concurrent calcium imaging and microelectrode array recording. Neuronal connections have been sequentially ablated and the correlated changes in network activity traced and mapped. With this unique combination of electrophysiological and optical tools, neural activity can be studied and quantified in response to controlled injury at the subcellular, cellular, and network level.

  7. A model for inertial particle trapping locations in hydrodynamic tweezers arrays

    NASA Astrophysics Data System (ADS)

    House, Tyler A.; Lieu, Valerie H.; Schwartz, Daniel T.

    2014-04-01

    We present a model for the trapping of particles with finite inertia in the microscale viscous steady streaming flow of hydrodynamic tweezers. Devices containing a square array and an offset array of cylindrical posts of radius 25 µm were fabricated. As water is oscillated at small amplitude (s < 5 µm) and audible frequency (5000 Hz), highly symmetric microeddies form causing the fluid and particles suspended in the fluid to transport through the device. We image the flows by using 0.5 µm radius fluorescent polystyrene particles, and demonstrate trapping with larger 5 µm radius polystyrene particles. The streaming flow fields are simulated numerically using a fast analytic-numeric approach, and inertial particle motion is determined using the well-known Maxey-Riley equation for small Stokes number (St) particle motion. The St-dependent period-averaged particle velocity is used to describe the effects of inertia on particle trapping locations. We find the St-dependence of trapping location depends on the underlying symmetry of the flow. Only traps located near eddy centers are affected by particle inertia.

  8. Dynamic deformation of a soft particle in dual-trap optical tweezers

    NASA Astrophysics Data System (ADS)

    Rancourt-Grenier, Sebastien; Wei, Ming-Tzo; Bai, Jar-Jin; Chiou, Arthur; Bareil, Paul; Duval, Pierre-Luc; Sheng, Yunlong

    2010-08-01

    A dual-trap optical tweezers is used for deforming the red blood cell (RBC) in suspension and studying its elasticity. The radiation force is applied directly to the cell without physical contact. The 3D radiation stress distribution was computed by ray tracing, the generalized Lorentz-Mie theory with the T-matrix and the FDTD via the Maxwell stress tensor. The 3D deformation of the cells was computed with the elastic membrane theory. The calculated deformation can fit to experimental data resulting in cell's elasticity coefficient. The static approach is valid only for small deformation (5- 10%). For a large deformation such as that of the RBC, we consider re-distribution of the radiation stress on the morphologically deformed cell. This stress re-distribution in turn induces subsequent deformation of the deformed cell and new stress re-distribution. The recursive process continues until a final equilibrium state is achieved. This iterative computation was implemented with the finite element method using the COMSOLTM multi-physics models. The deformation results can fit to the experimental data for cell's deformation up to 20%.

  9. Removal forces and adhesion properties of Saccharomyces cerevisiae on glass substrates probed by optical tweezer.

    PubMed

    Castelain, Mickaël; Pignon, Frédéric; Piau, Jean-Michel; Magnin, Albert; Mercier-Bonin, Muriel; Schmitz, Philippe

    2007-10-01

    In agroindustry, the hygiene of solid surfaces is of primary importance in order to ensure that products are safe for consumers. To improve safety, one of the major ways consists in identifying and understanding the mechanisms of microbial cell adhesion to nonporous solid surfaces or filtration membranes. In this paper we investigate the adhesion of the yeast cell Saccharomyces cerevisiae (about 5 mum in diameter) to a model solid surface, using well-defined hydrophilic glass substrates. An optical tweezer device developed by Piau [J. Non-Newtonian Fluid Mech. 144, 1 (2007)] was applied to yeast cells in contact with well-characterized glass surfaces. Two planes of observation were used to obtain quantitative measurements of removal forces and to characterize the corresponding mechanisms at a micrometer length scale. The results highlight various adhesion mechanisms, depending on the ionic strength, contact time, and type of yeast. The study has allowed to show a considerable increase of adhering cells with the ionic strength and has provided a quantitative measurement of the detachment forces of cultured yeast cells. Force levels are found to grow with ionic strength and differences in mobility are highlighted. The results clearly underline that a microrheological approach is essential for analyzing the adhesion mechanisms of biological systems at the relevant local scales. PMID:17919057

  10. Studying red blood cell agglutination by measuring membrane viscosity with optical tweezers

    NASA Astrophysics Data System (ADS)

    Fernandes, Heloise P.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Barjas-Castro, Maria L.; Cesar, Carlos L.

    2007-09-01

    The red blood cell (RBC) viscoelastic membrane contains proteins and glycoproteins embedded in a fluid lipid bilayer that are responsible for cell agglutination. Manipulating RBCs rouleaux with a double optical tweezers, we observed that the cells slide easily one over the others but are strongly connected by their edges. An explanation for this behavior could be the fact that when the cells slide one over the others, proteins are dragged through the membrane. It confers to the movement a viscous characteristic that is dependent of the velocity between the RBCs and justifies why is so easy to slide them apart. Therefore, in a first step of this work, by measuring the force as a function of the relative velocity between two cells, we confirmed this assumption and used this viscous characteristic of the RBC rouleaux to determine the apparent membrane viscosity of the cell. As this behavior is related to the proteins interactions, we can use the apparent membrane viscosity to obtain a better understanding about cell agglutination. Methods related to cell agglutination induced by antigen-antibody interactions are the basis of most of tests used in transfusion centers. Then, in a second step of this work, we measured the apparent membrane viscosity using antibodies. We observed that this methodology is sensitive to different kinds of bindings between RBCs. Better comprehension of the forces and bindings between RBCs could improve the sensibility and specificity of the hemagglutination reactions and also guides the development of new potentiator substances.

  11. Removal forces and adhesion properties of Saccharomyces cerevisiae on glass substrates probed by optical tweezer

    NASA Astrophysics Data System (ADS)

    Castelain, Mickaël; Pignon, Frédéric; Piau, Jean-Michel; Magnin, Albert; Mercier-Bonin, Muriel; Schmitz, Philippe

    2007-10-01

    In agroindustry, the hygiene of solid surfaces is of primary importance in order to ensure that products are safe for consumers. To improve safety, one of the major ways consists in identifying and understanding the mechanisms of microbial cell adhesion to nonporous solid surfaces or filtration membranes. In this paper we investigate the adhesion of the yeast cell Saccharomyces cerevisiae (about 5?m in diameter) to a model solid surface, using well-defined hydrophilic glass substrates. An optical tweezer device developed by Piau [J. Non-Newtonian Fluid Mech. 144, 1 (2007)] was applied to yeast cells in contact with well-characterized glass surfaces. Two planes of observation were used to obtain quantitative measurements of removal forces and to characterize the corresponding mechanisms at a micrometer length scale. The results highlight various adhesion mechanisms, depending on the ionic strength, contact time, and type of yeast. The study has allowed to show a considerable increase of adhering cells with the ionic strength and has provided a quantitative measurement of the detachment forces of cultured yeast cells. Force levels are found to grow with ionic strength and differences in mobility are highlighted. The results clearly underline that a microrheological approach is essential for analyzing the adhesion mechanisms of biological systems at the relevant local scales.

  12. Electrical tweezer for highly parallelized electrorotation measurements over a wide frequency bandwidth.

    PubMed

    Rohani, Ali; Varhue, Walter; Su, Yi-Hsuan; Swami, Nathan S

    2014-07-01

    Electrorotation (ROT) is a powerful tool for characterizing the dielectric properties of cells and bioparticles. However, its application has been somewhat limited by the need to mitigate disruptions to particle rotation by translation under positive DEP and by frictional interactions with the substrate. While these disruptions may be overcome by implementing particle positioning schemes or field cages, these methods restrict the frequency bandwidth to the negative DEP range and permit only single particle measurements within a limited spatial extent of the device geometry away from field nonuniformities. Herein, we present an electrical tweezer methodology based on a sequence of electrical signals, composed of negative DEP using 180-degree phase-shifted fields for trapping and levitation of the particles, followed by 90-degree phase-shifted fields over a wide frequency bandwidth for highly parallelized electrorotation measurements. Through field simulations of the rotating electrical field under this wave-sequence, we illustrate the enhanced spatial extent for electrorotation measurements, with no limitations to frequency bandwidth. We apply this methodology to characterize subtle modifications in morphology and electrophysiology of Cryptosporidium parvum with varying degrees of heat treatment, in terms of shifts in the electrorotation spectra over the 0.05-40 MHz region. Given the single particle sensitivity and the ability for highly parallelized electrorotation measurements, we envision its application toward characterizing heterogeneous subpopulations of microbial and stem cells. PMID:24668830

  13. An Interactive Virtual Reality Simulation for Nanoparticle Manipulation for Nanoassembly using Optical Tweezers

    NSDL National Science Digital Library

    Bhavaraju, Krishna

    Nanotechnology and nano devices is believed to be one of the most promising steps that science is taking to the future. This paper proposes virtual reality (VR) as a tool to simulate nano particle manipulation using optical tweezers towards achieving nano- assembly for effectively handling issues such as difficulty in viewing, perceiving and controlling the nano-scale objects. The nano simulation is modeled, using virtual reality, displaying all the forces acting on nano particle during the manipulation. The simulation is developed for particles that belong to Rayleigh region and, represents interactions of OT (a laser beam) with the nano particle. The laser beam aimed on to the nano particle traps the particle by applying optical forces. The trapped particle is then moved by moving the laser beam. The proposed VR based simulation tool with its capabilities can be easily extended and used for creating an open system framework by connecting it to a real OT setup to control nano particles manipulation. In addition, a feedback system can be build to increase of precision of movement.

  14. Measurements of the force fields within an acoustic standing wave using holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Bassindale, P. G.; Phillips, D. B.; Barnes, A. C.; Drinkwater, B. W.

    2014-04-01

    Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pNpp) and streaming forces (<0.2 pN) were measured. A 5 ?m silica micro-sphere was used to characterise a 6.8 MHz standing wave, ? = 220 ?m, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2 nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.

  15. Guest encapsulation and coronene-C60 exchange in supramolecular zinc porphyrin tweezers, grids and prisms.

    PubMed

    Samanta, Soumen K; Schmittel, Michael

    2013-05-21

    Using a variant of the HETPHEN concept, heteroleptic 2D and 3D metallosupramolecular structures, such as tweezer T, grid G and tetragonal prism P, were fabricated quantitatively and characterised by (1)H NMR, (13)C NMR, (1)H-(1)H COSY, DOSY as well as ESI-MS. All structures encapsulate C60, with P showing the highest binding affinity (Kassoc = 3.3 × 10(6) M(-1)). The association constant increases along the series T < G < P, most likely due to the enhanced structural rigidity and better coplanarity of the two zinc porphyrin units. In contrast to T and G, the tetragonal prism P shows notable encapsulation of coronene (Kassoc = 1.1 × 10(4) M(-1)). In T and G, on the other hand, complexation of coronene is kinetically inhibited by the bulky mesityl rings at the porphyrin periphery. As illustrated in the facile displacement of coronene by C60 in coronene@P to furnish C60@P, P behaves as a flexible and guest-adaptive host. PMID:23440088

  16. Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers.

    PubMed

    Cai, Chen; Stewart, David J; Reid, Jonathan P; Zhang, Yun-Hong; Ohm, Peter; Dutcher, Cari S; Clegg, Simon L

    2015-01-29

    Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate retrievals of component vapor pressures and hygroscopic response through examining correlated variations in size and composition for binary droplets containing water and a single organic component. Measurements are reported for a homologous series of dicarboxylic acids, maleic acid, citric acid, glycerol, or 1,2,6-hexanetriol. An assessment of the inherent uncertainties in such measurements when measuring only particle size is provided to confirm the value of such a correlational approach. We also show that the method of molar refraction provides an accurate characterization of the compositional dependence of the refractive index of the solutions. In this method, the density of the pure liquid solute is the largest uncertainty and must be either known or inferred from subsaturated measurements with an error of <±2.5% to discriminate between different thermodynamic treatments. PMID:25522920

  17. Optical tweezers reveal force plateau and internal friction in PEG-induced DNA condensation.

    PubMed

    Ojala, Heikki; Ziedaite, Gabija; Wallin, Anders E; Bamford, Dennis H; Hæggström, Edward

    2014-03-01

    The simplified artificial environments in which highly complex biological systems are studied do not represent the crowded, dense, salty, and dynamic environment inside the living cell. Consequently, it is important to investigate the effect of crowding agents on DNA. We used a dual-trap optical tweezers instrument to perform force spectroscopy experiments at pull speeds ranging from 0.3 to 270 ?m/s on single dsDNA molecules in the presence of poly(ethylene glycol) (PEG) and monovalent salt. PEG of sizes 1,500 and 4,000 Da condensed DNA, and force-extension data contained a force plateau at approximately 1 pN. The level of the force plateau increased with increasing pull speed. During slow pulling the dissipated work increased linearly with pull speed. The calculated friction coefficient did not depend on amount of DNA incorporated in the condensate, indicating internal friction is independent of the condensate size. PEG300 had no effect on the dsDNA force-extension curve. The force plateau implies that condensation induced by crowding agents resembles condensation induced by multivalent cations. PMID:24477280

  18. Modeling highly focused laser beam in optical tweezers with the vector Gaussian beam in the T-matrix method.

    PubMed

    Bareil, Paul B; Sheng, Yunlong

    2013-01-01

    The vector Gaussian beam with high-order corrections is used to describe accurately the laser beam up to numerical aperture NA=1.20 in the optical tweezers for trapping nanoparticles. The beam is then expanded in the T-matrix method into the vector spherical wave function (VSWF) series using the point matching method with a new selection of the matching points. The errors in the beam description and in the VSWF expansion are much lower than those that occur in the paraxial Gaussian beam model. PMID:23455996

  19. Proof-of-principle for simple microshelter-assisted buffer exchange in laser tweezers: interaction of hypericin with single cells.

    PubMed

    Omar, Moktar A; Miskovsky, Pavol; Bánó, Gregor

    2014-05-01

    Microshelters (i.e. thin dead-end side-arms of fluid channels) are used to aid buffer exchange in optical tweezers experiments. The basic idea is to transfer trapped objects into microshelters during the buffer exchange process. Particles "hidden" in microshelters become insensitive to extreme flow conditions in the main fluid channel, which minimizes the requirements for the applied flow system. The construction scheme of a simple microshelter system is described. The concept has been tested by fluorescence measurements on hypericin interaction with trapped yeast cells in different environments. PMID:24632728

  20. Experimental phase diagram of negatively supercoiled DNA measured by magnetic tweezers and fluorescence

    NASA Astrophysics Data System (ADS)

    Vlijm, Rifka; Mashaghi, Alireza; Bernard, Stéphanie; Modesti, Mauro; Dekker, Cees

    2015-02-01

    The most common form of DNA is the well-known B-structure of double-helix DNA. Many processes in the cell, however, exert force and torque, inducing structural changes to the DNA that are vital to biological function. Virtually all DNA in cells is in a state of negative supercoiling, with a DNA structure that is complex. Using magnetic tweezers combined with fluorescence imaging, we here study DNA structure as a function of negative supercoiling at the single-molecule level. We classify DNA phases based on DNA length as a function of supercoiling, down to a very high negative supercoiling density ? of -2.5, and forces up to 4.5 pN. We characterize plectonemes using fluorescence imaging. DNA bubbles are visualized by the binding of fluorescently labelled RPA, a eukaryotic single-strand-binding protein. The presence of Z-DNA, a left-handed form of DNA, is probed by the binding of Z?77, the minimal binding domain of a Z-DNA-binding protein. Without supercoiling, DNA is in the relaxed B-form. Upon going toward negative supercoiling, plectonemic B-DNA is being formed below 0.6 pN. At higher forces and supercoiling densities down to about -1.9, a mixed state occurs with plectonemes, multiple bubbles and left-handed L-DNA. Around ? = -1.9, a buckling transition occurs after which the DNA end-to-end length linearly decreases when applying more negative turns, into a state that we interpret as plectonemic L-DNA. By measuring DNA length, Z?77 binding, plectoneme and ssDNA visualisation, we thus have mapped the co-existence of many DNA structures and experimentally determined the DNA phase diagram at (extreme) negative supercoiling.The most common form of DNA is the well-known B-structure of double-helix DNA. Many processes in the cell, however, exert force and torque, inducing structural changes to the DNA that are vital to biological function. Virtually all DNA in cells is in a state of negative supercoiling, with a DNA structure that is complex. Using magnetic tweezers combined with fluorescence imaging, we here study DNA structure as a function of negative supercoiling at the single-molecule level. We classify DNA phases based on DNA length as a function of supercoiling, down to a very high negative supercoiling density ? of -2.5, and forces up to 4.5 pN. We characterize plectonemes using fluorescence imaging. DNA bubbles are visualized by the binding of fluorescently labelled RPA, a eukaryotic single-strand-binding protein. The presence of Z-DNA, a left-handed form of DNA, is probed by the binding of Z?77, the minimal binding domain of a Z-DNA-binding protein. Without supercoiling, DNA is in the relaxed B-form. Upon going toward negative supercoiling, plectonemic B-DNA is being formed below 0.6 pN. At higher forces and supercoiling densities down to about -1.9, a mixed state occurs with plectonemes, multiple bubbles and left-handed L-DNA. Around ? = -1.9, a buckling transition occurs after which the DNA end-to-end length linearly decreases when applying more negative turns, into a state that we interpret as plectonemic L-DNA. By measuring DNA length, Z?77 binding, plectoneme and ssDNA visualisation, we thus have mapped the co-existence of many DNA structures and experimentally determined the DNA phase diagram at (extreme) negative supercoiling. Electronic supplementary information (ESI) available: See DOI: 10.1039/c4nr04332d

  1. Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

    PubMed Central

    Raghunathan, Krishnan; Milstein, Joshua N.; Meiners, Jens -Christian

    2011-01-01

    Single-molecule techniques for stretching DNA of contour lengths less than a kilobase are fraught with experimental difficulties. However, many interesting biological events such as histone binding and protein-mediated looping of DNA1,2, occur on this length scale. In recent years, the mechanical properties of DNA have been shown to play a significant role in fundamental cellular processes like the packaging of DNA into compact nucleosomes and chromatin fibers3,4. Clearly, it is then important to understand the mechanical properties of short stretches of DNA. In this paper, we provide a practical guide to a single-molecule optical tweezing technique that we have developed to study the mechanical behavior of DNA with contour lengths as short as a few hundred basepairs. The major hurdle in stretching short segments of DNA is that conventional optical tweezers are generally designed to apply force in a direction lateral to the stage5,6, (see Fig. 1). In this geometry, the angle between the bead and the coverslip, to which the DNA is tethered, becomes very steep for submicron length DNA. The axial position must now be accounted for, which can be a challenge, and, since the extension drags the microsphere closer to the coverslip, steric effects are enhanced. Furthermore, as a result of the asymmetry of the microspheres, lateral extensions will generate varying levels of torque due to rotation of the microsphere within the optical trap since the direction of the reactive force changes during the extension. Alternate methods for stretching submicron DNA run up against their own unique hurdles. For instance, a dual-beam optical trap is limited to stretching DNA of around a wavelength, at which point interference effects between the two traps and from light scattering between the microspheres begin to pose a significant problem. Replacing one of the traps with a micropipette would most likely suffer from similar challenges. While one could directly use the axial potential to stretch the DNA, an active feedback scheme would be needed to apply a constant force and the bandwidth of this will be quite limited, especially at low forces. We circumvent these fundamental problems by directly pulling the DNA away from the coverslip by using a constant force axial optical tweezers7,8. This is achieved by trapping the bead in a linear region of the optical potential, where the optical force is constant-the strength of which can be tuned by adjusting the laser power. Trapping within the linear region also serves as an all optical force-clamp on the DNA that extends for nearly 350 nm in the axial direction. We simultaneously compensate for thermal and mechanical drift by finely adjusting the position of the stage so that a reference microsphere stuck to the coverslip remains at the same position and focus, allowing for a virtually limitless observation period. PMID:22025209

  2. Mechanical properties of neuronal growth cone membranes studied by tether formation with laser optical tweezers.

    PubMed Central

    Dai, J.; Sheetz, M. P.

    1995-01-01

    Many cell phenomena involve major morphological changes, particularly in mitosis and the process of cell migration. For cells or neuronal growth cones to migrate, they must extend the leading edge of the plasma membrane as a lamellipodium or filopodium. During extension of filopodia, membrane must move across the surface creating shear and flow. Intracellular biochemical processes driving extension must work against the membrane mechanical properties, but the forces required to extend growth cones have not been measured. In this paper, laser optical tweezers and a nanometer-level analysis system were used to measure the neuronal growth cone membrane mechanical properties through the extension of filopodia-like tethers with IgG-coated beads. Although the probability of a bead attaching to the membrane was constant irrespective of treatment; the probability of forming a tether with a constant force increased dramatically with cytochalasin B or D and dimethylsulfoxide (DMSO). These are treatments that alter the organization of the actin cytoskeleton. The force required to hold a tether at zero velocity (F0) was greater than forces generated by single molecular motors, kinesin and myosin; and F0 decreased with cytochalasin B or D and DMSO in correlation with the changes in the probability of tether formation. The force of the tether on the bead increased linearly with the velocity of tether elongation. From the dependency of tether force on velocity of tether formation, we calculated a parameter related to membrane viscosity, which decreased with cytochalasin B or D, ATP depletion, nocodazole, and DMSO. These results indicate that the actin cytoskeleton affects the membrane mechanical properties, including the force required for membrane extension and the viscoelastic behavior. Images FIGURE 4 PMID:7756561

  3. Effect of salicylate on outer hair cell plasma membrane viscoelasticity: studies using optical tweezers

    NASA Astrophysics Data System (ADS)

    Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

    2004-06-01

    The plasma membrane (PM) of mammalian outer hair cells (OHCs) generates mechanical forces in response to changes in the transmembrane electrical potential. The resulting change in the cell length is known as electromotility. Salicylate (Sal), the anionic, amphipathic derivative of aspirin induces reversible hearing loss and decreases electromotile response of the OHCs. Sal may change the local curvature and mechanical properties of the PM, eventually resulting in reduced electromotility or it may compete with intracellular monovalent anions, particularly Cl-, which are essential for electromotility. In this work we have used optical tweezers to study the effects of Sal on viscoelastic properties of the OHC PM when separated from the underlying composite structures of the cell wall. In this procedure, an optically trapped microsphere is brought in contact with PM and subsequently pulled away to form a tether. We measured the force exerted on the tether as a function of time during the process of tether growth at different pulling rates. Effective tether viscosity, steady-state tethering force extrapolated to zero pulling rate, and the time constant for tether growth were estimated from the measurements of the instantaneous tethering force. The time constant for the tether growth measured for the OHC basal end decreased 1.65 times after addition of 10 mM Sal, which may result from an interaction between Sal and cholesterol, which is more prevalent in the PM of OHC basal end. The time constants for the tether growth calculated for the OHC lateral wall and control human embryonic kidney cells as well as the other calculated viscoelastic parameters remained the same after Sal perfusion, favoring the hypothesis of competitive inhibition of electromotility by salicylate.

  4. Optical tweezers for single molecule force spectroscopy on bacterial adhesion organelles

    NASA Astrophysics Data System (ADS)

    Andersson, Magnus; Axner, Ove; Uhlin, Bernt Eric; Fällman, Erik

    2006-08-01

    Instrumentation and methodologies for single molecule force spectroscopy on bacterial adhesion organelles by the use of force measuring optical tweezers have been developed. A thorough study of the biomechanical properties of fimbrial adhesion organelles expressed by uropathogenic E. coli, so-called pili, is presented. Steady-state as well as dynamic force measurements on P pili, expressed by E. coli causing pyelonephritis, have revealed, among other things, various unfolding and refolding properties of the helical structure of P pili, the PapA rod. Based on these properties an energy landscape model has been constructed by which specific biophysical properties of the PapA rod have been extracted, e.g. the number of subunits, the length of a single pilus, bond lengths and activation energies for bond opening and closure. Moreover, long time repetitive measurements have shown that the rod can be unfolded and refolded repetitive times without losing its intrinsic properties. These properties are believed to be of importance for the bacteria's ability to maintain close contact with host cells during initial infections. The results presented are considered to be of importance for the field of biopolymers in general and the development of new pharmaceuticals towards urinary tract infections in particular. The results show furthermore that the methodology can be used to gain knowledge of the intrinsic biomechanical function of adhesion organelles. The instrumentation is currently used for characterization of type 1 pili, expressed by E. coli causing cystitis, i.e. infections in the bladder. The first force spectrometry investigations of these pili will be presented.

  5. Force Mapping during the Formation and Maturation of Cell Adhesion Sites with Multiple Optical Tweezers

    PubMed Central

    Schwingel, Melanie; Bastmeyer, Martin

    2013-01-01

    Focal contacts act as mechanosensors allowing cells to respond to their biomechanical environment. Force transmission through newly formed contact sites is a highly dynamic process requiring a stable link between the intracellular cytoskeleton and the extracellular environment. To simultaneously investigate cellular traction forces in several individual maturing adhesion sites within the same cell, we established a custom-built multiple trap optical tweezers setup. Beads functionalized with fibronectin or RGD-peptides were placed onto the apical surface of a cell and trapped with a maximum force of 160 pN. Cells form adhesion contacts around the beads as demonstrated by vinculin accumulation and start to apply traction forces after 30 seconds. Force transmission was found to strongly depend on bead size, surface density of integrin ligands and bead location on the cell surface. Highest traction forces were measured for beads positioned on the leading edge. For mouse embryonic fibroblasts, traction forces acting on single beads are in the range of 80 pN after 5 minutes. If two beads were positioned parallel to the leading edge and with a center-to-center distance less than 10 µm, traction forces acting on single beads were reduced by 40%. This indicates a spatial and temporal coordination of force development in closely related adhesion sites. We also used our setup to compare traction forces, retrograde transport velocities, and migration velocities between two cell lines (mouse melanoma and fibroblasts) and primary chick fibroblasts. We find that maximal force development differs considerably between the three cell types with the primary cells being the strongest. In addition, we observe a linear relation between force and retrograde transport velocity: a high retrograde transport velocity is associated with strong cellular traction forces. In contrast, migration velocity is inversely related to traction forces and retrograde transport velocity. PMID:23372781

  6. Determination of fluid viscosity and femto Newton forces of Leishmania amazonensis using optical tweezers

    NASA Astrophysics Data System (ADS)

    Fontes, Adriana; Giorgio, Selma; de Castro, Archimedes, Jr.; Neto, Vivaldo M.; de Y. Pozzo, Liliana; de Thomaz, Andre A.; Barbosa, Luiz C.; Cesar, Carlos L.

    2005-08-01

    The displacements of a polystyrene microsphere trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences such as the measurement of forces of living microorganisms or the viscosity of local fluids. The technique we used allowed us to measure forces on the 200 femto Newtons to 4 pico Newtons range of the protozoa Leishmania amazonensis, responsible for a serious tropical disease. These observations can be used to understand the infection mechanism and chemotaxis of these parasites. The same technique was used to measure viscosities of few microliters sample with agreement with known samples better than 5%. To calibrate the force as a function of the microsphere displacement we first dragged the microsphere in a fluid at known velocity for a broad range of different optical and hydrodynamical parameters. The hydrodynamical model took into account the presence of two walls and the force depends on drag velocity, fluid viscosity and walls proximities, while the optical model in the geometric optics regime depends on the particle and fluid refractive indexes and laser power. To measure the high numerical (NA) aperture laser beam power after the objective we used an integration sphere to avoid the systematic errors of usual power meters for high NA beams. After this careful laser power measurement we obtained an almost 45 degrees straight line for the plot of the optical force (calculated by the particle horizontal displacement) versus hydrodynamic force (calculated by the drag velocity) under variation of all the parameters described below. This means that hydrodynamic models can be used to calibrate optical forces, as we have done for the parasite force measurement, or vice-versa, as we did for the viscosity measurements.

  7. Quantitative High-Resolution Sensing of DNA Hybridization Using Magnetic Tweezers with Evanescent Illumination

    PubMed Central

    Oliver, Piercen M.; Park, Jin Seon; Vezenov, Dmitri

    2012-01-01

    We applied the combined approach of evanescent nanometry and force spectroscopy using magnetic tweezers to quantify the degree of hybridization of a single synthetic single-stranded DNA oligomer to a resolution approaching a single-base. In this setup, the 200 nucleotide long DNA was covalently attached to the surface of an optically transparent solid support at one end and to the surface of a superparamagnetic fluorescent microsphere (force probe) at the other end. The force was applied to the probes using an electromagnet. The end-to-end molecular distance (i.e. out-of-image-plane position of the force probe) was determined from the intensity of the probe fluorescent image observed with total-internal reflectance microscopy. An equation of state for single stranded DNA molecules under tension (extensible freely jointed chain) was used to derive the penetration depth of the evanescent field and to calibrate the magnetic properties of the force probes. The parameters of the magnetic response of the force probes obtained from the equation of state remained constant when changing the penetration depth, indicating a robust calibration procedure. The results of such a calibration were also confirmed using independently measured probe-surface distances for probes mounted onto cantilevers of an atomic force microscope. Upon hybridization of the complementary 50 nucleotide-long oligomer to the surface-bound 200-mer, the changes in the force-distance curves were consistent with the quantitative conversion of 25% of the original single-stranded DNA to its double-stranded form, which was modeled as an elastic rod. The method presented here for quantifying the hybridization state of the single DNA molecules has potential for determining the degree of hybridization of individual molecules in a single molecule array with high accuracy. PMID:21103547

  8. Single-cell adhesion probed in-situ using optical tweezers: A case study with Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Castelain, Mickaël; Rouxhet, Paul G.; Pignon, Frédéric; Magnin, Albert; Piau, Jean-Michel

    2012-06-01

    A facile method of using optical trapping to measure cell adhesion forces is presented and applied to the adhesion of Saccharomyces cerevisiae on glass, in contact with solutions of different compositions. Trapping yeast cells with optical tweezers (OT) is not perturbed by cell wall deformation or cell deviation from a spherical shape. The trapping force calibration requires correction not only for the hydrodynamic effect of the neighboring wall but also for spherical aberrations affecting the focal volume and the trap stiffness. Yeast cells trapped for up to 5 h were still able to undergo budding but showed an increase of doubling time. The proportion of adhering cells showed the expected variation according to the solution composition. The detachment force varied in the same way. This observation and the fact that the detachment stress was exerted parallel to the substrate surface point to the role of interactions involving solvated macromolecules. Both the proportion of adhering cells and the removal force showed a distribution which, in our experimental conditions, must be attributed to a heterogeneity of surface properties at the cell level or at the subcellular scale. As compared with magnetic tweezers, atomic force microscopy, and more conventional ways of studying cell adhesion (shear-flow cells), OT present several advantages that are emphasized in this paper.

  9. Wavefront analysis and optimization from conventional liquid crystal displays for low-cost holographic optical tweezers and digital holographic microscopy

    NASA Astrophysics Data System (ADS)

    Weber, Andreas; Ortega Clavero, Valentin; Schröder, Werner

    2011-05-01

    In different study fields the manipulation and imaging of micro-sized particles is essential. The use of holographic optical tweezers (HOT) and digital holographic microscopy (DHM) facilitates this task in a non-mechanical way by providing the proper computer generated hologram and the required amount of light. Electrically addressed spatial light modulators (EASLM) found in holographic optical tweezers are typically of the reflective liquid crystal on silicon (LCoS) type which can achieve a phase shift of more than 2? but they are expensive. Similar components like transmissive twisted nematic liquid crystal displays (TN-LCD) are produced in large quantities, their optical characteristics improve rapidly and they are inexpensive. Under certain circumstances these devices can be used instead of expensive spatial light modulators. Consumer grade objectives are not always well corrected for spherical aberration. In that case conventional liquid crystal displays can also compensate these undesired optical effects. For this purpose software-corrected computer generated holograms are calculated. Procedures to analyze and compensate different parameters of a conventional low-cost liquid crystal display, e.g. phase shift evaluation and aberration correction of objectives by Zernike polynomials approximation are explained. The applied software compensation of the computer generated hologram has shown significant improvement of the focus quality. An important price reduction of holographic devices could be achieved by replacing special optical elements if correction algorithms for conventional liquid crystal displays are provided.

  10. [Laser tweezers Raman spectroscopy analysis of cold-adapted aromatic hydrocarbons-degradating strains isolated from Antarctic Sea].

    PubMed

    Wang, Yi-Bin; Miao, Jin-Lai; He, Bi-Juan; Liang, Qiang; Liu, Fang-Ming; Zheng, Zhou

    2011-02-01

    Laser tweezers Raman spectroscopy can help with observing and studying individual cells or organelles in a natural state for a relatively long period. In the present experiment, Laser tweezers Raman spectroscopy (LTRS) was used as a tool to report physiological metabolism such as cells growth and nucleic acid, proteins, lipid and glucose of a single active cold-adapted Aromatic hydrocarbons-degradating strains isolated from Antarctic Sea. After the Raman spectrum was collected and analyzed, the findings are as follows: Raman spectrum identified the components of a single cold-adapted Aromatic hydrocarbons-degradating strain and there were more proteins and carbohydrate produced during the Planococcus sp. NJ41 and Shewanella sp. NJ49 growth and degradation; but there was more lipid than the proteins produced during the Pseudoalteromonas sp. NJ289 growth and degradation; the amount of proteins produced by the strains corresponds with the production of degradation rate-limiting enzyme, and was also related to the capacity of low-temperature degradation of aromatic hydrocarbons. PMID:21510394

  11. Physiological monitoring of optically trapped cells: assessing the effects of confinement by 1064-nm laser tweezers using microfluorometry.

    PubMed Central

    Liu, Y; Sonek, G J; Berns, M W; Tromberg, B J

    1996-01-01

    We report the results of microfluorometric measurements of physiological changes in optically trapped immotile Chinese hamster ovary cells (CHOs) and motile human sperm cells under continuous-wave (CW) and pulsed-mode trapping conditions at 1064 nm. The fluorescence spectra derived from the exogenous fluorescent probes laurdan, acridine orange, propidium iodide, and Snarf are used to assess the effects of optical confinement with respect to temperature, DNA structure, cell viability, and intracellular pH, respectively. In the latter three cases, fluorescence is excited via a two-photon process, using a CW laser trap as the fluorescence excitation source. An average temperature increase of < 0.1 +/- 0.30 degrees C/100 mW is measured for cells when held stationary with CW optical tweezers at powers of up to 400 mW. The same trapping conditions do not appear to alter DNA structure or cellular pH. In contrast, a pulsed 1064-nm laser trap (100-ns pulses at 40 microJ/pulse and average power of 40 mW) produced significant fluorescence spectral alterations in acridine orange, perhaps because of thermally induced DNA structural changes or laser-induced multiphoton processes. The techniques and results presented herein demonstrate the ability to perform in situ monitoring of cellular physiology during CW and pulsed laser trapping, and should prove useful in studying mechanisms by which optical tweezers and microbeams perturb metabolic function and cellular viability. PMID:8889192

  12. Cell-scaffold adhesion dynamics measured in first seconds predicts cell growth on days scale - optical tweezers study.

    PubMed

    Podlipec, Rok; Štrancar, Janez

    2015-04-01

    Understanding the cell-biomaterial interface from the very first contact is of crucial importance for their successful implementation and function in damaged tissues. However, the lack of bio- and mechano-analytical methods to investigate and probe the initial processes on the interface, especially in 3D, raises the need for applying new experimental techniques. In our study, optical tweezers combined with confocal fluorescence microscopy were optimized to investigate the initial cell-scaffold contact and to investigate its correlation with the material-dependent cell growth. By the optical tweezers-induced cell manipulation accompanied by force detection up to 100 pN and position detection by fluorescence microscopy, accurate adhesion dynamics and strength analysis was implemented, where several attachment sites were formed on the interface in the first few seconds. More importantly, we have shown that dynamics of cell adhesion on scaffold surfaces correlates with cell growth on the days scale, which indicates that the first seconds of the contact could markedly direct further cell response. Such a contact dynamics analysis on 3D scaffold surfaces, applied for the first time, can thus serve to predict scaffold biocompatibility. PMID:25764169

  13. Axial and transverse acoustic radiation forces on a fluid sphere placed arbitrarily in Bessel beam standing wave tweezers

    SciTech Connect

    Mitri, F.G., E-mail: mitri@chevron.com

    2014-03-15

    The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere’s radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study. -- Highlights: •The axial and transverse forces on a fluid sphere in acoustical Bessel beams tweezers are evaluated. •The attraction or repulsion to an equilibrium position in the standing wave field is examined. •Potential applications are in particle manipulation using standing waves.

  14. Journal of the Korean Physical Society, Vol. 48, February 2006, pp. S222S225 Rotation of Irregularly Shaped Liposome Using Optical Tweezers

    E-print Network

    Pak, Hyuk Kyu

    with a laser beam in 1970 [1], op- tical tweezers have been widely used in trapping and ma- nipulating microscopic materials, such as colloidal par- ticles, red blood cells, and artificially synthesized lipo], a 1064 nm Nd:YVO4 laser (TEM00, Golden Light Co., HSR70) is used as a laser source. The laser light

  15. PHYSICAL REVIEW A 82, 023623 (2010) Measurement of the atom number distribution in an optical tweezer using single-photon counting

    E-print Network

    Boyer, Edmond

    tweezers [2] or of magnetic traps [3], double- well potential geometries [4], and optical lattices (e], or in arrays of magnetic microtraps [14]. For all these applications, the knowledge of the distribution atomic cloud can be measured by usual optical techniques, such as laser-induced fluorescence

  16. Monitoring Dynamic Protein Expression in Single Living E. Coli. Bacterial Cells by Laser Tweezers Raman Spectroscopy

    SciTech Connect

    Chan, J W; Winhold, H; Corzett, M H; Ulloa, J M; Cosman, M; Balhorn, R; Huser, T

    2007-01-09

    Laser tweezers Raman spectroscopy (LTRS) is a novel, nondestructive, and label-free method that can be used to quantitatively measure changes in cellular activity in single living cells. Here, we demonstrate its use to monitor changes in a population of E. coli cells that occur during overexpression of a protein, the extracellular domain of myelin oligodendrocyte glycoprotein (MOG(1-120)) Raman spectra were acquired of individual E. coli cells suspended in solution and trapped by a single tightly focused laser beam. Overexpression of MOG(1-120) in transformed E. coli Rosetta-Gami (DE3)pLysS cells was induced by addition of isopropyl thiogalactoside (IPTG). Changes in the peak intensities of the Raman spectra from a population of cells were monitored and analyzed over a total duration of three hours. Data was also collected for concentrated purified MOG(1-120) protein in solution, and the spectra compared with that obtained for the MOG(1-120) expressing cells. Raman spectra of individual, living E. coli cells exhibit signatures due to DNA and protein molecular vibrations. Characteristic Raman markers associated with protein vibrations, such as 1257 cm{sup -1}, 1340 cm{sup -1}, 1453 cm{sup -1} and 1660 cm{sup -1}, are shown to increase as a function of time following the addition of IPTG. Comparison of these spectra and the spectra of purified MOG protein indicates that the changes are predominantly due to the induction of MOG protein expression. Protein expression was found to occur mostly within the second hour, with a 470% increase relative to the protein expressed in the first hour. A 230% relative increase between the second and third hour indicates that protein expression begins to level off within the third hour. It is demonstrated that LTRS has sufficient sensitivity for real-time, nondestructive, and quantitative monitoring of biological processes, such as protein expression, in single living cells. Such capabilities, which are not currently available in flow cytometry, open up new possibilities for analyzing cellular processes occurring in single microbial and eukaryotic cells.

  17. Measuring nanoscale interactions and dynamics of DNA-grafted colloids with line optical tweezers

    NASA Astrophysics Data System (ADS)

    Biancaniello, Paul Louis

    Much of the excitement regarding nanotechnology stems from the idea of "bottom-up" self-assembly: the possibility of spontaneously growing complex structures or devices out of molecular scale components rather than using conventional microfabrication. Realizing such goals requires a reliable method for inducing specific interactions between multiple particle species. The preferred method for inducing such interactions is to use hybridization, the sequence-specific assembly of single stranded DNA grafted onto the particles into double strands. Linking bridges of DNA can either glue two objects together strongly or cause them to weakly and reversibly adhere. While the strong adhesion limit has been studied, the weak reversible interactions required for equilibrium self-assembly and annealing remain poorly characterized, hindering experimental and theoretical progress. All previous attempts to assemble non-DNA objects using DNA interactions have created highly disordered aggregates rather than the hoped for crystal-like structures. Here we report the first direct measurements of such DNA-induced colloidal interactions, as well as the first colloidal crystals assembled using them. The pair interactions measured with our optical tweezer method can be modeled in detail by well-known statistical physics and chemistry, boding well for their application to directed self-assembly. The microspheres' binding dynamics, however, have a surprising power-law scaling that can significantly slow annealing and crystallization. We separated effects due to multiple bridge kinetics from those due to individual DNA hybridization by adjusting the microspheres' DNA surface density. The process of DNA hybridization requires the traversing of a multitude of intermediate steps to get from two random coil oligonucleotides to a tidy duplex DNA. We probed the nature of these intermediate states by measuring the lifetime distribution of single 16-bp duplexes subject to thermal dissociation under effectively zero tension. Unlike comparable single molecule experiments performed at finite tension, we find an unusual stretched exponential lifetime distribution, suggesting that thermal dissociation proceeds via a number of competing intermediate pathways. Similar measurements with higher DNA density indicate that multiple-bridged states are highly unstable, indicating that the duplexes are extremely force sensitive. Our power-law kinetics are a likely consequence of the exquisite force sensitivity and nonexponential dissociation kinetics of the DNA bridges.

  18. Development of optical-based array devices using imaging fiber bundles: Optical tweezer arrays, nanoscale arrays, and microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Tam, Jenny M.

    The work in this dissertation describes the development of imaging fiber-based array devices, specifically the fabrication and application of an optical tweezer array, a fiber-based nanoarray, and a nanotip array. With regards for the fabrication of an optical tweezer array, this thesis describes how fiber bundles have been used as a method to create multiple beams, which are used as optical traps. By coupling a single beam into an imaging fiber bundle, the light energy is distributed across the face of the fiber bundle. Each illuminated individual fiber in the array propagates light to the distal face of the bundle, where light focusing elements at the end of each fiber focus the laser light and form optical traps. These optical traps are capable of capturing and arraying microspheres in parallel. The number of optical traps is determined by the number of fibers in the optical fiber bundle and is capable of creating a dense array (˜104 traps/mm2) of optical tweezers. This dissertation also describes the fabrication of fiber bundle-based nanoarrays with two different size formats---one with 700 nm array elements and one with 300 nm array elements. These arrays have an ultra-high packing density in that they contain 1 x 106 or 4.5 x 10 6 array elements/mm2. Current fiber bundle-based arrays have micron feature sizes and a high packing density, up to 5 x 10 4 fibers/mm2. These nanoarrays have feature sizes at least 4 times smaller than the micron-sized arrays used and contain up to 4.5 x 106 fibers/mm2. Nanofiber bundles were chemically etched to create nanowells into which sensors were deposited. The number of sensor elements in these arrays provides enough sensing positions such that they could be used to screen an entire genome while also moving towards the concept of a universal array. In addition, this high density of sensors allows for a large number of replicates, leading to an improvement in the signal to noise ratio. An improvement on creating nanoapertures that was originally developed by Paul Pantano, a former postdoctoral fellow in the Walt lab, is also discussed in this thesis. The original technique employed a mechanical puller that heated and pulled a fiber bundle, which was then polished and etched to create nanowells. Although effective, the technique was difficult to reproduce. (Abstract shortened by UMI.)

  19. Molecular cleft or tweezer compounds derived from trioxabicyclo[3.3.1]nonadiene diisocyanate and diacid dichloride

    PubMed Central

    Smounig, Ralf; Belaj, Ferdinand; Kvaskoff, David

    2015-01-01

    Summary The structures of two derivatives of the bisdioxine diisocyanate 1, the bisurea 4 and the biscarbamate 5, are established by X-ray crystallography and DFT calculations. These compounds possess endo,endo structures, in the case of the bisurea 4 with two nearly parallel pendant chains. The X-ray structures are reproduced very well by DFT calculations. Similar endo,endo conformations are calculated for the bisamide crown ether derivatives 7, where two proximate and nearly parallel crown ether units endow the molecules with a claw-like molecular cleft or tweezer structure as evidenced by an enhanced ability to extract some alkali, alkaline earth and rare earth metal ions. PMID:25670985

  20. A FRET-based DNA nano-tweezer technique for the imaging analysis of specific mRNA.

    PubMed

    Funabashi, Hisakage; Shigeto, Hajime; Nakatsuka, Keisuke; Kuroda, Akio

    2015-02-21

    A DNA nano-tweezer (DNA-NT) structure-based target mRNA detection probe, which uses fluorescence resonance energy transfer (FRET) as a detection signal and works as a single molecule, has been developed. This FRET-paired fluorescent dye-modified DNA-NT, self-assembled from three single-stranded DNAs, alters its structure from open to closed states and produces a FRET signal in response to in vitro transcripts of Hes-1 mRNA. Our results showed that the FRET-based DNA-NT detected both GLUT1 mRNA as a pre-fixed target mRNA model and Hes-1 mRNA as a model expressed inside a living cell. These results confirm the feasibility of using the FRET-based DNA-NT for imaging analysis of target mRNA. PMID:25529369

  1. Using optical tweezers for measuring the interaction forces between human bone cells and implant surfaces: System design and force calibration

    SciTech Connect

    Andersson, Martin; Madgavkar, Ashwin; Stjerndahl, Maria; Wu, Yanrong; Tan, Weihong; Duran, Randy; Niehren, Stefan; Mustafa, Kamal; Arvidson, Kristina; Wennerberg, Ann [Department of Chemistry, University of Florida, Gainesville, Florida 32611 (United States); Molecular Machines and Industries GmbH, Breslauerstrasse 2, 85386 Eching (Germany); Center for Clinical Dental Research, University of Bergen, N-5009 Bergen (Norway); Department of Prosthodontics/Dental Material Science, University of Goeteborg, S-40530 Goeteborg, Sweden and Department of Biomaterials, University of Goeteborg, S-40530 Goeteborg (Sweden)

    2007-07-15

    Optical tweezers were used to study the interaction and attachment of human bone cells to various types of medical implant materials. Ideally, the implant should facilitate cell attachment and promote migration of the progenitor cells in order to decrease the healing time. It is therefore of interest, in a controlled manner, to be able to monitor the cell adhesion process. Results from such studies would help foresee the clinical outcome of integrating medical implants. The interactions between two primary cell culture models, human gingival fibroblasts and bone forming human osteoblast cells, and three different implant materials, glass, titanium, and hydroxyapatite, were studied. A novel type of optical tweezers, which has a newly designed quadrant detector and a powerful 3 W laser was constructed and force calibrated using two different methods: one method in which the stiffness of the optical trap was obtained by monitoring the phase lag between the trap and the moved object when imposing a forced oscillation on the trapped object and another method in which the maximum trapping force was derived from the critical velocity at which the object escapes the trap. Polystyrene beads as well as cells were utilized for the calibrations. This is the first time that cells have been used directly for these types of force calibrations and, hence, direct measurements of forces exerted on cells can be performed, thus avoiding the difficulties often encountered when translating the results obtained from cell measurements to the calibrations obtained with reference materials. This more straightforward approach represents an advantage in comparison to established methods.

  2. Parallel optical tweezers with combining a diffractive optical element and a spatial light modulator for photonic DNA memory

    NASA Astrophysics Data System (ADS)

    Zheng, MingJie; Tate, Naoya; Ogura, Yusuke; Tanida, Jun

    2007-09-01

    To overcome the restriction of the density of optical memory systems due to diffraction limit, we have been studying photonic DNA memory, which utilizes photonic technologies and the DNA computing methodology. Our scheme is on the basis of local DNA reaction using laser irradiation and transportation of DNA using parallel optical tweezers with fabricating DNA clusters by attaching DNA onto beads. This paper reports on a new dynamic optical tweezers system, which combines a spatial light modulator (SLM) and a diffractive optical element (DOE) for manipulating DNA clusters. With this combination, real-time programmable manipulation of DNA clusters is achievable in a large spatial range. We also can choose simple patterns for the SLM, and decrease computation cost. In this experiment, a laser beam (633nm wavelength) illuminates a SLM (Hamamatsu Photonics K. K.; PPM8267), which is imaged on an 80-lp/mm transmission-type grating, then the beam is focused with a water immersible objective lens (x 100, NA 1). Simple blazed-phase patterns have different grating constants that are perpendicular to that of the grating are displayed on the SLM. We succeeded in lifting up three 6-micron-diameter polystyrene beads on a glass slide with light spots duplicated by the grating, then transporting the beads in three dimensions simultaneously with changing the grating constants on the SLM. We demonstrated that a same manipulation was implemented at different positions by duplicating a pattern that was generated when only using the SLM. This is usable in implementing a same operation for different data at multiple positions with a single instruction. The promising applications of the method include a nano-scale image memory with encryption.

  3. Using optical tweezers for measuring the interaction forces between human bone cells and implant surfaces: System design and force calibration

    NASA Astrophysics Data System (ADS)

    Andersson, Martin; Madgavkar, Ashwin; Stjerndahl, Maria; Wu, Yanrong; Tan, Weihong; Duran, Randy; Niehren, Stefan; Mustafa, Kamal; Arvidson, Kristina; Wennerberg, Ann

    2007-07-01

    Optical tweezers were used to study the interaction and attachment of human bone cells to various types of medical implant materials. Ideally, the implant should facilitate cell attachment and promote migration of the progenitor cells in order to decrease the healing time. It is therefore of interest, in a controlled manner, to be able to monitor the cell adhesion process. Results from such studies would help foresee the clinical outcome of integrating medical implants. The interactions between two primary cell culture models, human gingival fibroblasts and bone forming human osteoblast cells, and three different implant materials, glass, titanium, and hydroxyapatite, were studied. A novel type of optical tweezers, which has a newly designed quadrant detector and a powerful 3W laser was constructed and force calibrated using two different methods: one method in which the stiffness of the optical trap was obtained by monitoring the phase lag between the trap and the moved object when imposing a forced oscillation on the trapped object and another method in which the maximum trapping force was derived from the critical velocity at which the object escapes the trap. Polystyrene beads as well as cells were utilized for the calibrations. This is the first time that cells have been used directly for these types of force calibrations and, hence, direct measurements of forces exerted on cells can be performed, thus avoiding the difficulties often encountered when translating the results obtained from cell measurements to the calibrations obtained with reference materials. This more straightforward approach represents an advantage in comparison to established methods.

  4. Using optical tweezers to examine the chemotactic force to a single inflammatory cell--eosinophil stimulated by chemoattractants prepared from Toxocara Canis larvae

    NASA Astrophysics Data System (ADS)

    Shih, Po-Chen; Su, Yi-Jr; Chen, Ke-Min; Jen, Lin-Ni; Liu, Cheng-tzu; Hsu, Long

    2005-08-01

    Granulocytes are a group of white blood cells belonging to the innate immune system in human and in murine in which eosinophils play an important role in worm infection-induced inflammation. The migration of these cells is well characterized and has been separated into four steps: rolling, adhesion, transendothelial migration, and chemotaxis, however, the physical characteristics of the chemotactic force to eosinophils from worm component remain largely unknown. Note that optical tweezers are featured in the manipulation of a single cell and the measurement of biological forces. Therefore, we propose to use optical tweezers to examine the chemotactic force to a eosinophil from a T. canis lavae preparation in terms of distance during the migration of eosinophil.

  5. Remarkably efficient photocurrent generation based on a [60]fullerene-triosmium cluster/Zn-porphyrin/boron-dipyrrin triad SAM.

    PubMed

    Lee, Chang Yeon; Jang, Jae Kwon; Kim, Chul Hoon; Jung, Jaehoon; Park, Bo Keun; Park, Jihee; Choi, Wonyong; Han, Young-Kyu; Joo, Taiha; Park, Joon T

    2010-05-17

    A new artificial photosynthetic triad array, a [60]fullerene-triosmium cluster/zinc-porphyrin/boron-dipyrrin complex (1, Os(3)C(60)/ZnP/Bodipy), has been prepared by decarbonylation of Os(3)(CO)(8)(CN(CH(2))(3)Si(OEt)(3))(mu(3)-eta(2):eta(2):eta(2)-C(60)) (6) with Me(3)NO/MeCN and subsequent reaction with the isocyanide ligand CNZnP/Bodipy (5) containing zinc porphyrin (ZnP) and boron dipyrrin (Bodipy) moieties. Triad 1 has been characterized by various spectroscopic methods (MS, NMR, IR, UV/Vis, photoluminescence, and transient absorption spectroscopy). The electrochemical properties of 1 in chlorobenzene (CB) have been examined by cyclic voltammetry; the general feature of the cyclic voltammogram of 1 is nine reversible one-electron redox couples, that is, the sum of those of 5 and 6. DFT has been applied to study the molecular and electronic structures of 1. On the basis of fluorescence-lifetime measurements and transient absorption spectroscopic data, 1 undergoes an efficient energy transfer from Bodipy to ZnP and a fast electron transfer from ZnP to C(60); the detailed kinetics involved in both events have been elucidated. The SAM of triad 1 (1/ITO; ITO=indium-tin oxide) has been prepared by immersion of an ITO electrode in a CB solution of 1 and diazabicyclo-octane (2:1 equiv), and characterized by UV/Vis absorption spectroscopy, water contact angle, X-ray photoelectron spectroscopy, and cyclic voltammetry. The photoelectrochemical properties of 1/ITO have been investigated by a standard three-electrode system in the presence of an ascorbic acid sacrificial electron donor. The quantum yield of the photoelectrochemical cell has been estimated to be 29 % based on the number of photons absorbed by the chromophores. Our triad 1 is unique when compared to previously reported photoinduced electron-transfer arrays, in that C(60) is linked by pi bonding with little perturbation of the C(60) electron delocalization. PMID:20401879

  6. Host-guest inclusion system of scutellarein with 2-hydroxypropyl-beta-cyclodextrin: preparation, characterization, and anticancer activity.

    PubMed

    Wang, Fen; Yang, Bo; Zhao, Yulin; Liao, Xiali; Gao, Chuanzhu; Jiang, Ruijian; Han, Bin; Yang, Jian; Liu, Man; Zhou, Rongguang

    2014-01-01

    The inclusion complexation behavior of scutellarein (SCUE) with 2-hydroxypropyl-?-cyclodextrin (HP-?-CD) has been investigated in both solution and in the solid state. SCUE/HP-?-CD solid system was prepared by suspension method. The formation of SCUE/HP-?-CD complex in aqueous solution was demonstrated by fluorescence spectroscopy, and the Job plot showed a maximum at a molar fraction of 0.5, indicating 1:1 inclusion complexation between SCUE and HP-?-CD. However, SCUE/HP-?-CD inclusion complex was characterized by means of XRD, DSC, (1)H, and two-dimensional NMR. Through the complexation between HP-?-CD and SCUE, the water solubility and antitumor activity of SCUE were obviously increased. This satisfactory water solubility and high antitumor activity of the SCUE/HP-?-CD complex will be potentially useful for its application on human colon cancer chemotherapies. PMID:24555409

  7. Host-guest inclusion system of norathyriol with ?-cyclodextrin and its derivatives: preparation, characterization, and anticancer activity.

    PubMed

    Han, Bin; Yang, Bo; Yang, Xuemin; Zhao, Yulin; Liao, Xiali; Gao, Chuanzhu; Wang, Fen; Jiang, Ruijian

    2014-06-01

    The characterization, binding ability and inclusion complexation behavior of the inclusion complexes of norathyriol with ?-cyclodextrin (?-CD) and its derivatives such as hydroxypropyl-?-cyclodextrin (HP?CD), sulfobutyl ether ?-cyclodextrin (SBE?CD) and mono (6-ethylene-diamino-6-deoxy)-?-cyclodextrin (EN?CD) were investigated in both solution and solid state by means of femtosecond spectroscopy, (1)H and 2D nuclear magnetic resonance, powder X-ray diffraction. The results showed that the aqueous solubility of the complexes was much higher than that of norathyriol. The cytotoxicity of complexes on human colon cancer cell lines HT-29, SW480, Lovo and HCT116 indicated that the antitumor activities of the complexes were better than that of norathyriol. This high antitumor activity, along with the satisfactory aqueous solubility of the complexes, will be potentially useful for their application on cancer chemotherapies. PMID:24508024

  8. The host-guest complex between cone-25,26:27,28-bis(methylenedioxy)calix[4]arene and dichloromethane.

    PubMed

    Dielemann, Cedric; Matt, Dominique; Jones, Peter G; Thönnessen, Holger

    2003-05-01

    The title compound, 25,26:27,28-bis(methylenedioxy)pentacyclo[19.3.1.1(3,7).1(9,13).1(15,19)]octacosa-1(25)3,5,7(28),9,11,13(27),15,17,19(26),21,23-dodecaene dichloromethane solvate, C(30)H(24)O(4).CH(2)Cl(2), possesses crystallographic twofold symmetry in both components. The calixarene shows a pinched cone conformation with an elliptical cavity, in which the guest dichloromethane solvent molecule is accommodated. The contact distance between guest and host (H.ring centroid = 2.44 A) is extremely short. PMID:12743405

  9. Location of MTBE and toluene in the channel system of the zeolite mordenite: Adsorption and host-guest interactions

    NASA Astrophysics Data System (ADS)

    Arletti, Rossella; Martucci, Annalisa; Alberti, Alberto; Pasti, Luisa; Nassi, Marianna; Bagatin, Roberto

    2012-10-01

    This paper reports a study of the location of Methyl Tertiary Butyl Ether (MTBE) and toluene molecules adsorbed in the pores of the organophylic zeolite mordenite from an aqueous solution. The presence of these organic molecules in the zeolite channels was revealed by structure refinement performed by the Rietveld method. About 3 molecules of MTBE and 3.6 molecules of toluene per unit cell were incorporated into the cavities of mordenite, representing 75% and 80% of the total absorption capacity of this zeolite. In both cases a water molecule was localized inside the side pocket of mordenite. The saturation capacity determined by the adsorption isotherms, obtained by batch experiments, and the weight loss given by thermogravimetric (TG) analyses were in very good agreement with these values. The interatomic distances obtained after the structural refinements suggest MTBE could be connected to the framework through a water molecule, while toluene could be bonded to framework oxygen atoms. The rapid and high adsorption of these hydrocarbons into the organophylic mordenite zeolite makes this cheap and environmental friendly material a suitable candidate for the removal of these pollutants from water.

  10. Free-energy perturbation and quantum mechanical study of SAMPL4 octa-acid host-guest binding energies.

    PubMed

    Mikulskis, Paulius; Cioloboc, Daniela; Andreji?, Milica; Khare, Sakshi; Brorsson, Joakim; Genheden, Samuel; Mata, Ricardo A; Söderhjelm, Pär; Ryde, Ulf

    2014-04-01

    We have estimated free energies for the binding of nine cyclic carboxylate guest molecules to the octa-acid host in the SAMPL4 blind-test challenge with four different approaches. First, we used standard free-energy perturbation calculations of relative binding affinities, performed at the molecular-mechanics (MM) level with TIP3P waters, the GAFF force field, and two different sets of charges for the host and the guest, obtained either with the restrained electrostatic potential or AM1-BCC methods. Both charge sets give good and nearly identical results, with a mean absolute deviation (MAD) of 4 kJ/mol and a correlation coefficient (R (2)) of 0.8 compared to experimental results. Second, we tried to improve these predictions with 28,800 density-functional theory (DFT) calculations for selected snapshots and the non-Boltzmann Bennett acceptance-ratio method, but this led to much worse results, probably because of a too large difference between the MM and DFT potential-energy functions. Third, we tried to calculate absolute affinities using minimised DFT structures. This gave intermediate-quality results with MADs of 5-9 kJ/mol and R (2) = 0.6-0.8, depending on how the structures were obtained. Finally, we tried to improve these results using local coupled-cluster calculations with single and double excitations, and non-iterative perturbative treatment of triple excitations (LCCSD(T0)), employing the polarisable multipole interactions with supermolecular pairs approach. Unfortunately, this only degraded the predictions, probably because of a mismatch between the solvation energies obtained at the DFT and LCCSD(T0) levels. PMID:24700414

  11. Modular, homochiral, porous coordination polymers: rational design, enantioselective guest exchange sorption and ab initio calculations of host-guest interactions.

    PubMed

    Dybtsev, Danil N; Yutkin, Maxim P; Samsonenko, Denis G; Fedin, Vladimir P; Nuzhdin, Alexey L; Bezrukov, Andrey A; Bryliakov, Konstantin P; Talsi, Evgeniy P; Belosludov, Rodion V; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki; Subbotin, Oleg S; Belosludov, Vladimir R

    2010-09-10

    Two new, homochiral, porous metal-organic coordination polymers [Zn(2)(ndc){(R)-man}(dmf)]?3DMF and [Zn(2)(bpdc){(R)-man}(dmf)]?2DMF (ndc=2,6-naphthalenedicarboxylate; bpdc=4,4'-biphenyldicarboxylate; man=mandelate; dmf=N,N'-dimethylformamide) have been synthesized by heating Zn(II) nitrate, H(2)ndc or H(2)bpdc and chiral (R)-mandelic acid (H(2)man) in DMF. The colorless crystals were obtained and their structures were established by single-crystal X-ray diffraction. These isoreticular structures share the same topological features as the previously reported zinc(II) terephthalate lactate [Zn(2)(bdc){(S)-lac}(dmf)]?DMF framework, but have larger pores and opposite absolute configuration of the chiral centers. The enhanced pores size results in differing stereoselective sorption properties: the new metal-organic frameworks effectively and stereoselectively (ee up to 62?%) accommodate bulkier guest molecules (alkyl aryl sulfoxides) than the parent [Zn(2)(bdc){(S)-lac}(dmf)]?DMF, while the latter demonstrates decent enantioselectivity toward precursor of chiral anticancer drug sulforaphane, CH(3)SO(CH(2))(4)OH. The new homochiral porous metal-organic coordination polymers are capable of catalyzing a highly selective oxidation of bulkier sulfides (2-NaphSMe (2-C(10)H(7)SMe) and PhSCH(2)Ph) that could not be achieved by the smaller-pore [Zn(2)(bdc){(S)-lac}(dmf)]?DMF. The sorption of different guest molecules (both R and S isomers) into the chiral pores of [Zn(2)(bdc){(S)-lac}(dmf)]?DMF was modeled by using ab initio calculations that provided a qualitative explanation for the observed sorption enantioselectivity. The high stereo-preference is accounted for by the presence of coordinated inner-pore DMF molecule that forms a weak C-H...O bond between the DMF methyl group and the (S)-PhSOCH(3) sulfinyl group. PMID:20730747

  12. Synthesis, Characterization, and Preliminary Host-Guest Binding Studies of Porphyrinic Molecular Squares Featuring fac-Tricarbonylrhenium(I) Chloro Corners

    E-print Network

    -3 Depending on cavity size and overall charge, selected molecular squares are capable of functioning comparatively long-lived metal-to-bridging-ligand charge-transfer (MLCT) excited states. The available square In the presence of appropriate guests, these can adopt complementary tub-shaped geometries. Compound 1

  13. Tuning the surface activity of gemini amphiphile by the host-guest interaction of cucurbit[7]uril.

    PubMed

    Wang, Guangtong; Kang, Yuetong; Tang, Bohan; Zhang, Xi

    2015-01-13

    This research is aimed to develop an effective supramolecular route for tuning the surface activity of the surfactant. To this end, cationic gemini amphiphiles and cucurbit[7]uril (CB[7]) were complexed in water, and each hydrophobic chain of the gemini amphiphiles was bound with a CB[7]. The steric hindrance of CB[7] prevented the two hydrophobic chains from getting closed to each other, leading a significant change of surface activity. Before supramolecular complexation, the surface activity of the gemini amphiphile is relatively high, which can generate the foams easily. However, the foam generated by gemini amphiphile can be destructed by adding CB[7], suggesting that the suface activity is lowed after the supramolecular complexation. The surface activity can recover after adding 1-adamantanamine hydrochloride, which has a stronger ability to bind CB[7]. Therefore, a controllable foaming and defoaming process can be realized. It is highly anticipated that supramolecular chemistry for tuning amphiphilicity of surfactants may find application in the fields that fast foaming and defoaming are needed. PMID:25489870

  14. Variational Implicit-Solvent Modeling of Host-Guest Binding: A Case Study on Cucurbit[7]uril

    E-print Network

    Li, Bo

    in the high-affinity binding of #12;the B2 bicyclo[2.2.2]octane derivative to CB[7]. For the unbound host, we[n]uril hosts thanks to its good balance between the number of water molecules confined in the host cavity[2.2.2]octane derivative (B2), is a highly suitable candidate for the development of computational

  15. In vivo X-ray elemental imaging of single cell model organisms manipulated by laser-based optical tweezers.

    PubMed

    Vergucht, Eva; Brans, Toon; Beunis, Filip; Garrevoet, Jan; De Rijcke, Maarten; Bauters, Stephen; Deruytter, David; Vandegehuchte, Michiel; Van Nieuwenhove, Ine; Janssen, Colin; Burghammer, Manfred; Vincze, Laszlo

    2015-01-01

    We report on a radically new elemental imaging approach for the analysis of biological model organisms and single cells in their natural, in vivo state. The methodology combines optical tweezers (OT) technology for non-contact, laser-based sample manipulation with synchrotron radiation confocal X-ray fluorescence (XRF) microimaging for the first time. The main objective of this work is to establish a new method for in vivo elemental imaging in a two-dimensional (2D) projection mode in free-standing biological microorganisms or single cells, present in their aqueous environment. Using the model organism Scrippsiella trochoidea, a first proof of principle experiment at beamline ID13 of the European Synchrotron Radiation Facility (ESRF) demonstrates the feasibility of the OT XRF methodology, which is applied to study mixture toxicity of Cu-Ni and Cu-Zn as a result of elevated exposure. We expect that the new OT XRF methodology will significantly contribute to the new trend of investigating microorganisms at the cellular level with added in vivo capability. PMID:25762511

  16. Mechanical characterization of protein L in the low-force regime by electromagnetic tweezers/evanescent nanometry.

    PubMed

    Liu, Ruchuan; Garcia-Manyes, Sergi; Sarkar, Atom; Badilla, Carmen L; Fernández, Julio M

    2009-05-01

    Mechanical manipulation at the single molecule level of proteins exhibiting mechanical stability poses a technical challenge that has been almost exclusively approached by atomic force microscopy (AFM) techniques. However, due to mechanical drift limitations, AFM techniques are restricted to experimental recordings that last less than a minute in the high-force regime. Here we demonstrate a novel combination of electromagnetic tweezers and evanescent nanometry that readily captures the forced unfolding trajectories of protein L at pulling forces as low as 10-15 pN. Using this approach, we monitor unfolding and refolding cycles of the same polyprotein for a period of time longer than 30 min. From such long-lasting recordings, we obtain ensemble averages of unfolding step sizes and rates that are consistent with single-molecule AFM data obtained at higher stretching forces. The unfolding kinetics of protein L at low stretching forces confirms and extends the observations that the mechanical unfolding rate is exponentially dependent on the pulling force within a wide range of stretching forces spanning from 13 pN up to 120 pN. Our experiments demonstrate a novel approach for the mechanical manipulation of single proteins for extended periods of time in the low-force regime. PMID:19413987

  17. In vivo X-ray elemental imaging of single cell model organisms manipulated by laser-based optical tweezers

    NASA Astrophysics Data System (ADS)

    Vergucht, Eva; Brans, Toon; Beunis, Filip; Garrevoet, Jan; de Rijcke, Maarten; Bauters, Stephen; Deruytter, David; Vandegehuchte, Michiel; van Nieuwenhove, Ine; Janssen, Colin; Burghammer, Manfred; Vincze, Laszlo

    2015-03-01

    We report on a radically new elemental imaging approach for the analysis of biological model organisms and single cells in their natural, in vivo state. The methodology combines optical tweezers (OT) technology for non-contact, laser-based sample manipulation with synchrotron radiation confocal X-ray fluorescence (XRF) microimaging for the first time. The main objective of this work is to establish a new method for in vivo elemental imaging in a two-dimensional (2D) projection mode in free-standing biological microorganisms or single cells, present in their aqueous environment. Using the model organism Scrippsiella trochoidea, a first proof of principle experiment at beamline ID13 of the European Synchrotron Radiation Facility (ESRF) demonstrates the feasibility of the OT XRF methodology, which is applied to study mixture toxicity of Cu-Ni and Cu-Zn as a result of elevated exposure. We expect that the new OT XRF methodology will significantly contribute to the new trend of investigating microorganisms at the cellular level with added in vivo capability.

  18. Optical tweezers studies of viral DNA packaging: Motor function and DNA confinement in Bacteriophages phi29, lambda, and T4

    NASA Astrophysics Data System (ADS)

    Smith, Douglas

    2007-03-01

    In the assembly of many viruses a powerful molecular motor translocates the genome into a pre-assembled capsid. We use optical tweezers to directly measure translocation of a single DNA molecule into the viral capsid. Improved techniques allow us to measure initiation and early stages of packaging. With phi29 the DNA terminal protein was found to cause large variations in the starting point of packaging. Removal of this protein results in terminal initiation, permitting more accurate assessment of motor function and DNA confinement forces. We investigated the role of electrostatic repulsion by varying ionic screening of the DNA. The observed trends are in accord with those theoretically expected considering counter-ion competition; however the forces are larger than expected in comparison with recent theories and DNA ejection measurements. We have recently succeeded in extending our methods to study two other phages: lambda and T4. These systems have unique structural and functional features, presenting an opportunity for comparative studies in this family of molecular motors. Initial measurements show that lambda and T4 translocate DNA several times faster than the phi29 motor, but are more sensitive to applied load.

  19. Trapping and two-photon fluorescence excitation of microscopic objects using ultrafast single-fiber optical tweezers

    NASA Astrophysics Data System (ADS)

    Mishra, Yogeshwar N.; Ingle, Ninad; Mohanty, Samarendra K.

    2011-10-01

    Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample.

  20. In vivo X-ray elemental imaging of single cell model organisms manipulated by laser-based optical tweezers

    PubMed Central

    Vergucht, Eva; Brans, Toon; Beunis, Filip; Garrevoet, Jan; De Rijcke, Maarten; Bauters, Stephen; Deruytter, David; Vandegehuchte, Michiel; Van Nieuwenhove, Ine; Janssen, Colin; Burghammer, Manfred; Vincze, Laszlo

    2015-01-01

    We report on a radically new elemental imaging approach for the analysis of biological model organisms and single cells in their natural, in vivo state. The methodology combines optical tweezers (OT) technology for non-contact, laser-based sample manipulation with synchrotron radiation confocal X-ray fluorescence (XRF) microimaging for the first time. The main objective of this work is to establish a new method for in vivo elemental imaging in a two-dimensional (2D) projection mode in free-standing biological microorganisms or single cells, present in their aqueous environment. Using the model organism Scrippsiella trochoidea, a first proof of principle experiment at beamline ID13 of the European Synchrotron Radiation Facility (ESRF) demonstrates the feasibility of the OT XRF methodology, which is applied to study mixture toxicity of Cu-Ni and Cu-Zn as a result of elevated exposure. We expect that the new OT XRF methodology will significantly contribute to the new trend of investigating microorganisms at the cellular level with added in vivo capability. PMID:25762511

  1. Axial and transverse acoustic radiation forces on a fluid sphere placed arbitrarily in Bessel beam standing wave tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2014-03-01

    The axial and transverse radiation forces on a fluid sphere placed arbitrarily in the acoustical field of Bessel beams of standing waves are evaluated. The three-dimensional components of the time-averaged force are expressed in terms of the beam-shape coefficients of the incident field and the scattering coefficients of the fluid sphere using a partial-wave expansion (PWE) method. Examples are chosen for which the standing wave field is composed of either a zero-order (non-vortex) Bessel beam, or a first-order Bessel vortex beam. It is shown here, that both transverse and axial forces can push or pull the fluid sphere to an equilibrium position depending on the chosen size parameter ka (where k is the wave-number and a the sphere's radius). The corresponding results are of particular importance in biophysical applications for the design of lab-on-chip devices operating with Bessel beams standing wave tweezers. Moreover, potential investigations in acoustic levitation and related applications in particle rotation in a vortex beam may benefit from the results of this study.

  2. Disrupting Self-Assembly and Toxicity of Amyloidogenic Protein Oligomers by “Molecular Tweezers” - from the Test Tube to Animal Models

    PubMed Central

    Attar, Aida; Bitan, Gal

    2014-01-01

    Despite decades of research, therapy for diseases caused by abnormal protein folding and aggregation (amyloidoses) is limited to treatment of symptoms and provides only temporary and moderate relief to sufferers. The failure in developing successful disease-modifying drugs for amyloidoses stems from the nature of the targets for such drugs – primarily oligomers of amyloidogenic proteins, which are distinct from traditional targets, such as enzymes or receptors. The oligomers are metastable, do not have well-defined structures, and exist in dynamically changing mixtures. Therefore, inhibiting the formation and toxicity of these oligomers likely will require out-of-the-box thinking and novel strategies. We review here the development of a strategy based on targeting the combination of hydrophobic and electrostatic interactions that are key to the assembly and toxicity of amyloidogenic proteins using lysine (K)-specific “molecular tweezers” (MTs). Our discussion includes a survey of the literature demonstrating the important role of K residues in the assembly and toxicity of amyloidogenic proteins and the development of a lead MT derivative called CLR01, from an inhibitor of protein aggregation in vitro to a drug candidate showing effective amelioration of disease symptoms in animal models of Alzheimer’s and Parkinson’s diseases. PMID:23859557

  3. Mechanical unfolding of human telomere G-quadruplex DNA probed by integrated fluorescence and magnetic tweezers spectroscopy

    PubMed Central

    Long, Xi; Parks, Joseph W.; Bagshaw, Clive R.; Stone, Michael D.

    2013-01-01

    Single-molecule techniques facilitate analysis of mechanical transitions within nucleic acids and proteins. Here, we describe an integrated fluorescence and magnetic tweezers instrument that permits detection of nanometer-scale DNA structural rearrangements together with the application of a wide range of stretching forces to individual DNA molecules. We have analyzed the force-dependent equilibrium and rate constants for telomere DNA G-quadruplex (GQ) folding and unfolding, and have determined the location of the transition state barrier along the well-defined DNA-stretching reaction coordinate. Our results reveal the mechanical unfolding pathway of the telomere DNA GQ is characterized by a short distance (<1 nm) to the transition state for the unfolding reaction. This mechanical unfolding response reflects a critical contribution of long-range interactions to the global stability of the GQ fold, and suggests that telomere-associated proteins need only disrupt a few base pairs to destabilize GQ structures. Comparison of the GQ unfolded state with a single-stranded polyT DNA revealed the unfolded GQ exhibits a compacted non-native conformation reminiscent of the protein molten globule. We expect the capacity to interrogate macromolecular structural transitions with high spatial resolution under conditions of low forces will have broad application in analyses of nucleic acid and protein folding. PMID:23303789

  4. Magnetic Tweezers-Based 3D Microchannel Electroporation for High-Throughput Gene Transfection in Living Cells.

    PubMed

    Chang, Lingqian; Howdyshell, Marci; Liao, Wei-Ching; Chiang, Chi-Ling; Gallego-Perez, Daniel; Yang, Zhaogang; Lu, Wu; Byrd, John C; Muthusamy, Natarajan; Lee, L James; Sooryakumar, Ratnasingham

    2014-12-01

    A novel high-throughput magnetic tweezers-based 3D microchannel electroporation system capable of transfecting 40 000 cells/cm(2) on a single chip for gene therapy, regenerative medicine, and intracellular detection of target mRNA for screening cellular heterogeneity is reported. A single cell or an ordered array of individual cells are remotely guided by programmable magnetic fields to poration sites with high (>90%) cell alignment efficiency to enable various transfection reagents to be delivered simultaneously into the cells. The present technique, in contrast to the conventional vacuum-based approach, is significantly gentler on the cellular membrane yielding >90% cell viability and, moreover, allows transfected cells to be transported for further analysis. Illustrating the versatility of the system, the GATA2 molecular beacon is delivered into leukemia cells to detect the regulation level of the GATA2 gene that is associated with the initiation of leukemia. The uniform delivery and a sharp contrast of fluorescence intensity between GATA2 positive and negative cells demonstrate key aspects of the platform for gene transfer, screening and detection of targeted intracellular markers in living cells. PMID:25469659

  5. Laser microbeams for DNA damage induction, optical tweezers for the search on blood pressure relaxing drugs: contributions to ageing research

    NASA Astrophysics Data System (ADS)

    Grigaravicius, P.; Monajembashi, S.; Hoffmann, M.; Altenberg, B.; Greulich, K. O.

    2009-08-01

    One essential cause of human ageing is the accumulation of DNA damages during lifetime. Experimental studies require quantitative induction of damages and techniques to visualize the subsequent DNA repair. A new technique, the "immuno fluorescent comet assay", is used to directly visualize DNA damages in the microscope. Using DNA repair proteins fluorescently labeled with green fluorescent protein, it could be shown that the repair of the most dangerous DNA double strand breaks starts with the inaccurate "non homologous end joining" pathway and only after 1 - 1 ½ minutes may switch to the more accurate "homologous recombination repair". One might suggest investigating whether centenarians use "homologous recombination repair" differently from those ageing at earlier years and speculate whether it is possible, for example by nutrition, to shift DNA repair to a better use of the error free pathway and thus promote healthy ageing. As a complementary technique optical tweezers, and particularly its variant "erythrocyte mediated force application", is used to simulate the effects of blood pressure on HUVEC cells representing the inner lining of human blood vessels. Stimulating one cell induces in the whole neighbourhood waves of calcium and nitric oxide, known to relax blood vessels. NIFEDIPINE and AMLODIPINE, both used as drugs in the therapy of high blood pressure, primarily a disease of the elderly, prolong the availability of nitric oxide. This partially explains their mode of action. In contrast, VERAPAMILE, also a blood pressure reducing drug, does not show this effect, indicating that obviously an alternative mechanism must be responsible for vessel relaxation.

  6. Dependence of bacteriophage ?29 DNA packaging on ionic conditions studied by optical tweezers manipulation of single DNA molecules

    NASA Astrophysics Data System (ADS)

    Fuller, Derek N.; Rickgauer, John P.; Grimes, Shelley; Jardine, Paul J.; Anderson, Dwight L.; Smith, Douglas E.

    2006-08-01

    The bacteriophage ?29 portal motor is capable of packaging the ?29, 19.3 Kbp, genome to high density into its preformed capsid. The packaging process must overcome the forces due to confining the highly negative charge of the DNA to a small volume, as well as the forces due to bending the DNA on length scales smaller than one persistence length. Both of these energetic considerations can be modulated by the ionic nature of the buffer DNA packaging occurs in. To measure the effects of DNA charge shielding on the packaging process, we studied the dynamics of DNA packaging by optical tweezers in a variety of different ionic conditions. We looked at the effects monovalent, divalent, and trivalent cations have on the motor function and its dependence on external force and, we observed the rate of DNA packaging at nominal force as a function of capsid filling. Specifically, we varied the concentrations of Na +, Mg +2, and cobalt hexamine in the solution bathing the bacteriophage during packaging to see what effects, if any, these cations have. From these measurements, we present an inferred internal force as a function of percent filling of the bacteriophage capsid in a variety of ionic environments. Preliminary analysis suggests the ionic environment can modulate internal pressure, with the presence of higher valence cations better shielding the packaged DNA resulting in lower internal pressures.

  7. Disrupting self-assembly and toxicity of amyloidogenic protein oligomers by "molecular tweezers" - from the test tube to animal models.

    PubMed

    Attar, Aida; Bitan, Gal

    2014-01-01

    Despite decades of research, therapy for diseases caused by abnormal protein folding and aggregation (amyloidoses) is limited to treatment of symptoms and provides only temporary and moderate relief to sufferers. The failure in developing successful disease-modifying drugs for amyloidoses stems from the nature of the targets for such drugs - primarily oligomers of amyloidogenic proteins, which are distinct from traditional targets, such as enzymes or receptors. The oligomers are metastable, do not have well-defined structures, and exist in dynamically changing mixtures. Therefore, inhibiting the formation and toxicity of these oligomers likely will require out-of-the-box thinking and novel strategies. We review here the development of a strategy based on targeting the combination of hydrophobic and electrostatic interactions that are key to the assembly and toxicity of amyloidogenic proteins using lysine (K)-specific "molecular tweezers" (MTs). Our discussion includes a survey of the literature demonstrating the important role of K residues in the assembly and toxicity of amyloidogenic proteins and the development of a lead MT derivative called CLR01, from an inhibitor of protein aggregation in vitro to a drug candidate showing effective amelioration of disease symptoms in animal models of Alzheimer's and Parkinson's diseases. PMID:23859557

  8. NAP1-Assisted Nucleosome Assembly on DNA Measured in Real Time by Single-Molecule Magnetic Tweezers

    PubMed Central

    Vlijm, Rifka; Smitshuijzen, Jeremy S. J.; Lusser, Alexandra; Dekker, Cees

    2012-01-01

    While many proteins are involved in the assembly and (re)positioning of nucleosomes, the dynamics of protein-assisted nucleosome formation are not well understood. We study NAP1 (nucleosome assembly protein 1) assisted nucleosome formation at the single-molecule level using magnetic tweezers. This method allows to apply a well-defined stretching force and supercoiling density to a single DNA molecule, and to study in real time the change in linking number, stiffness and length of the DNA during nucleosome formation. We observe a decrease in end-to-end length when NAP1 and core histones (CH) are added to the dsDNA. We characterize the formation of complete nucleosomes by measuring the change in linking number of DNA, which is induced by the NAP1-assisted nucleosome assembly, and which does not occur for non-nucleosomal bound histones H3 and H4. By rotating the magnets, the supercoils formed upon nucleosome assembly are removed and the number of assembled nucleosomes can be counted. We find that the compaction of DNA at low force is about 56 nm per assembled nucleosome. The number of compaction steps and associated change in linking number indicate that NAP1-assisted nucleosome assembly is a two-step process. PMID:23050009

  9. A new technique for high sensitive detection of rotational motion in optical tweezers by a differential measurement of backscattered intensity

    NASA Astrophysics Data System (ADS)

    Roy, Basudev; Bera, Sudipta K.; Mondal, Argha; Banerjee, Ayan

    2014-09-01

    Asymmetric particles, such as biological cells, often experience torque under optical tweezers due to birefringence or unbalanced scattering forces, which makes precise determination of the torque crucial for calibration and control of the particles. The estimate of torque relies on the accurate measurement of rotational motion, which has been achieved by various techniques such as measuring the intensity fluctuations of the forward scattered light, or the polarization component orthogonal to the trapping light polarization in plasmonic nanoparticles and vaterite crystals. Here we present a simple yet high sensitive technique to measure rotation of such an asymmetric trapped particle by detecting the light backscattered onto a quadrant photodiode, and subtracting the signals along the two diagonals of the quadrants. This automatically suppresses the common mode translational signal obtained by taking the difference signal of the adjacent quadrants, while amplifying the rotational signal. Using this technique, we obtain a S/N of 200 for angular displacement of a trapped micro-rod by 5 degrees, which implies a sensitivity of 50 mdeg with S/N of 2. The technique is thus independent of birefringence and polarization properties of the asymmetric particle and depends only on the scattering cross-section.

  10. Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers

    SciTech Connect

    Mitri, F.G. [Mayo Clinic College of Medicine, Department of Physiology and Biomedical Engineering, Ultrasound Research Laboratory, 200 First Street SW, Rochester, MN 55905 (United States)], E-mail: mitri@ieee.org

    2008-07-15

    Starting from the exact acoustic scattering from a sphere immersed in an ideal fluid and centered along the propagation axis of a standing or quasi-standing zero-order Bessel beam, explicit partial-wave representations for the radiation force are derived. A standing or a quasi-standing acoustic field is the result of propagating two equal or unequal amplitude zero-order Bessel beams, respectively, along the same axis but in opposite sense. The Bessel beam is characterized by the half-cone angle {beta} of its plane wave components, such that {beta} = 0 represents a plane wave. It is assumed here that the half-cone angle {beta} for each of the counter-propagating acoustic Bessel beams is equal. Fluid, elastic and viscoelastic spheres immersed in water are treated as examples. Results indicate the capability of manipulating spherical targets based on their mechanical and acoustical properties. This condition provides an impetus for further designing acoustic tweezers operating with standing or quasi-standing Bessel acoustic waves. Potential applications include particle manipulation in micro-fluidic lab-on-chips as well as in reduced gravity environments.

  11. Fast characterisation of cell-derived extracellular vesicles by nanoparticles tracking analysis, cryo-electron microscopy, and Raman tweezers microspectroscopy

    PubMed Central

    Tatischeff, Irène; Larquet, Eric; Falcón-Pérez, Juan M.; Turpin, Pierre-Yves; Kruglik, Sergei G.

    2012-01-01

    The joint use of 3 complementary techniques, namely, nanoparticle tracking analysis (NTA), cryo-electron microscopy (Cryo-EM) and Raman tweezers microspectroscopy (RTM), is proposed for a rapid characterisation of extracellular vesicles (EVs) of various origins. NTA is valuable for studying the size distribution and concentration, Cryo-EM is outstanding for the morphological characterisation, including observation of vesicle heterogeneity, while RTM provides the global chemical composition without using any exogenous label. The capabilities of this approach are evaluated on the example of cell-derived vesicles of Dictyostelium discoideum, a convenient general model for eukaryotic EVs. At least 2 separate species differing in chemical composition (relative amounts of DNA, lipids and proteins, presence of carotenoids) were found for each of the 2 physiological states of this non-pathogenic microorganism, that is, cell growth and starvation-induced aggregation. These findings demonstrate the specific potency of RTM. In addition, the first Raman spectra of human urinary exosomes are reported, presumably constituting the primary step towards Raman characterisation of EVs for the purpose of human diseases diagnoses. PMID:24009887

  12. A method for an approximate determination of a polymer-rich-domain concentration in phase-separated poly(N-isopropylacrylamide) aqueous solution by means of confocal Raman microspectroscopy combined with optical tweezers.

    PubMed

    Shoji, Tatsuya; Nohara, Riku; Kitamura, Noboru; Tsuboi, Yasuyuki

    2015-01-01

    The paper demonstrates that a confocal Raman microspectroscope combined with optical tweezers is a promising technique to estimate polymer concentration in polymer-rich domain in phase-separated-aqueous polymer solution. The sample polymer is poly-(N-isopropylacrylamide) (PNIPAM) that is well-known as a representative thermo-responsive polymer. Optical tweezers can selectively trap the polymer-rich domain at the focal point in non-contact and non-intrusive modes. Such situation allows us to determine polymer concentration in the domain, which has been unclear due to a lack of appropriate analytical technique. It is applicable for a variety of other thermo-responsive polymers. PMID:25479874

  13. Molecular hydrogen tweezers: structure and mechanisms by neutron diffraction, NMR, and deuterium labeling studies in solid and solution.

    PubMed

    Schulz, Felix; Sumerin, Victor; Heikkinen, Sami; Pedersen, Björn; Wang, Cong; Atsumi, Michiko; Leskelä, Markku; Repo, Timo; Pyykkö, Pekka; Petry, Winfried; Rieger, Bernhard

    2011-12-21

    The mechanism of reversible hydrogen activation by ansa-aminoboranes, 1-N-TMPH-CH(2)-2-[HB(C(6)F(5))(2)]C(6)H(4) (NHHB), was studied by neutron diffraction and thermogravimetric mass-spectroscopic experiments in the solid state as well as with NMR and FT-IR spectroscopy in solution. The structure of the ansa-ammonium borate NHHB was determined by neutron scattering, revealing a short N-H···H-B dihydrogen bond of 1.67 Å. Moreover, this intramolecular H-H distance was determined in solution to be also 1.6-1.8 Å by (1)H NMR spectroscopic T(1) relaxation and 1D NOE measurements. The X-ray B-H and N-H distances deviated from the neutron and the calculated values. The dynamic nature of the molecular tweezers in solution was additionally studied by multinuclear and variable-temperature NMR spectroscopy. We synthesized stable, individual isotopic isomers NDDB, NHDB, and NDHB. NMR measurements revealed a primary isotope effect in the chemical shift difference (p)?(1)H(D) = ?(NH) - ?(ND) (0.56 ppm), and hence supported dihydrogen bonding. The NMR studies gave strong evidence that the structure of NHHB in solution is similar to that in the solid state. This is corroborated by IR studies providing clear evidence for the dynamic nature of the intramolecular dihydrogen bonding at room temperature. Interestingly, no kinetic isotope effect was detected for the activation of deuterium hydride by the ansa-aminoborane NB. Theoretical calculations attribute this to an "early transition state". Moreover, 2D NOESY NMR measurements support fast intermolecular proton exchange in aprotic CD(2)Cl(2) and C(6)D(6). PMID:22087634

  14. Determining the binding mode and binding affinity constant of tyrosine kinase inhibitor PD153035 to DNA using optical tweezers

    SciTech Connect

    Cheng, Chih-Ming [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Lee, Yuarn-Jang [Section of Infectious Diseases, Department of Internal Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan (China)] [Section of Infectious Diseases, Department of Internal Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Wang, Wei-Ting [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Hsu, Chien-Ting [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China) [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Tsai, Jing-Shin [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Wu, Chien-Ming [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China)] [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Ou, Keng-Liang [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China) [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2011-01-07

    Research highlights: {yields} PD153035 is a DNA intercalator and intercalation occurs only under very low salt concentration. {yields} The minimum distance between adjacent bound PD153035 {approx} 11 bp. {yields} Binding affinity constant for PD153035 is 1.18({+-}0.09) x 10{sup 4} (1/M). {yields} The change of binding free energy of PD153035-DNA interaction is -5.49 kcal mol{sup -1} at 23 {+-} 0.5 {sup o}C. -- Abstract: Accurately predicting binding affinity constant (K{sub A}) is highly required to determine the binding energetics of the driving forces in drug-DNA interactions. Recently, PD153035, brominated anilinoquinazoline, has been reported to be not only a highly selective inhibitor of epidermal growth factor receptor but also a DNA intercalator. Here, we use a dual-trap optical tweezers to determining K{sub A} for PD153035, where K{sub A} is determined from the changes in B-form contour length (L) of PD153035-DNA complex. Here, L is fitted using a modified wormlike chain model. We found that a noticeable increment in L in 1 mM sodium cacodylate was exhibited. Furthermore, our results showed that K{sub A} = 1.18({+-}0.09) x 10{sup 4} (1/M) at 23 {+-} 0.5 {sup o}C and the minimum distance between adjacent bound PD153035 {approx} 11 bp. We anticipate that by using this approach we can determine the complete thermodynamic profiles due to the presence of DNA intercalators.

  15. Leishmania amazonensis chemotaxis under glucose gradient studied by the strength and directionality of forces measured with optical tweezers

    NASA Astrophysics Data System (ADS)

    de Ysasa Pozzo, Liliana; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz Carlos; Ayres, Diana Copi; Giorgio, Selma; Cesar, Carlos Lenz

    2007-02-01

    Chemotaxis is the mechanism microorganisms use to sense the environment surrounding them and to direct their movement towards attractive, or away from the repellent, chemicals. The biochemical sensing is almost the only way for communication between unicellular organisms. Prokaryote and Eukaryote chemotaxis has been mechanically studied mainly by observing the directionality and timing of the microorganisms movements subjected to a chemical gradient, but not through the directionality and strength of the forces it generates. To observe the vector force of microorganisms under a chemical gradient we developed a system composed of two large chambers connected by a tiny duct capable to keep the chemical gradient constant for more than ten hours. We also used the displacements of a microsphere trapped in an Optical Tweezers as the force transducer to measure the direction and the strength of the propulsion forces of flagellum of the microorganism under several gradient conditions. A 9?m diameter microsphere particle was trapped with a Nd:YAG laser and its movement was measured through the light scattered focused on a quadrant detector. We observed the behavior of the protozoa Leishmania amazonensis (eukaryote) under several glucose gradients. This protozoa senses the gradient around it by swimming in circles for three to five times following by tumbling, and not by the typical straight swimming/tumbling of bacteria. Our results also suggest that force direction and strength are also used to control its movement, not only the timing of swimming/tumbling, because we observed a higher force strength clearly directed towards the glucose gradient.

  16. To Study the Effect of Paclitaxel on the Cytoplasmic Viscosity of Murine Macrophage Immune Cell RAW 264.7 Using Self-Developed Optical Tweezers System

    NASA Astrophysics Data System (ADS)

    Chen, Ying-chun; Wu, Chien-ming

    2012-12-01

    In recent years, optical tweezers have become one of the tools to measure the mechanical properties of living cells. In this study, we first constructed an optical tweezers to investigate the cytoplasmic viscosity of immune cells. In addition to measuring viscosity of cells in a normal condition, we also treated cells with anti-cancer drug, Paclitaxel, and in order to study its effect on the cytoplasmic viscosity. The results showed that the viscosity decreased dramatically during the first 3 h. After 3 h, the change started to slow down and it remained nearly flat by the end of the experiment. In addition, we used the confocal laser scanning microscope to observe the cytoskeleton of the cell after drug treatment for 3 and 5 h, respectively, and found that actin filaments were disrupted and that the nucleus had disintegrated in some drug-treated cells, similar to the process of apoptosis. This study presents a new way for measuring the changes in cytoplasmic viscosity, and to determine if a cell is going into apoptosis as a result of a drug treatment.

  17. Safety and pharmacological characterization of the molecular tweezer CLR01 – a broad-spectrum inhibitor of amyloid proteins’ toxicity

    PubMed Central

    2014-01-01

    Background The “molecular tweezer” CLR01 is a broad-spectrum inhibitor of abnormal protein self-assembly, which acts by binding selectively to Lys residues. CLR01 has been tested in several in vitro and in vivo models of amyloidoses all without signs of toxicity. With the goal of developing CLR01 as a therapeutic drug for Alzheimer’s disease and other amyloidoses, here we studied its safety and pharmacokinetics. Methods Toxicity studies were performed in 2-m old wild-type mice. Toxicity was evaluated by serum chemical analysis, histopathology analysis, and qualitative behavioral analysis. Brain penetration studies were performed using radiolabeled CLR01 in both wild-type mice and a transgenic mouse model of Alzheimer’s disease at 2-m, 12-m, and 22-m of age. Brain levels were measured from 0.5?-?72 h post administration. Results Examination of CLR01’s effect on tubulin polymerization, representing normal protein assembly, showed disruption of the process only when 55-fold excess CLR01 was used, supporting the compound’s putative “process-specific” mechanism of action. A single-injection of 100 mg/kg CLR01 in mice – 2,500-fold higher than the efficacious dose reported previously, induced temporary distress and liver injury, but no mortality. Daily injection of doses up to 10 mg/kg did not produce any signs of toxicity, suggesting a high safety margin. The brain penetration of CLR01 was found to be 1?-?3% of blood levels depending on age. Though CLR01 was almost completely removed from the blood by 8 h, unexpectedly, brain levels of CLR01 remained steady over 72 h. Conclusion Estimation of brain levels compared to amyloid ?-protein concentrations reported previously suggest that the stoichiometry obtained in vitro and in vivo is similar, supporting the mechanism of action of CLR01. The favorable safety margin of CLR01, together with efficacy shown in multiple animal models, support further development of CLR01 as a disease-modifying agent for amyloidoses. PMID:24735982

  18. Physiological Monitoring of Optically Trapped Cells: Studying the Effects of Confinement by 1064 NM Lazer Tweezers Using Microfluorometry

    NASA Astrophysics Data System (ADS)

    Liu, Yagang

    A novel technique that combines microfluorometric detection and optical laser trapping has been developed for in-situ assessing the physiological state of an optically trapped biological sample. This optical diagnostic technique achieves high sensitivity (>30 dB signal -to-noise ratio) and high spatial resolution (~ 1 ?m) over a broad spectral range (>400 nm). The fluorescence spectra derived from exogenous fluorescent probes, including laurdan, acridine orange, propidium iodide and Snarf, are used to assess the effects of optical confinement with respect to temperature, DNA structure, cell viability, and intracellular pH, respectively. In the latter three cases, fluorescence is excited via a two-photon absorption process, using the cw laser trap itself as the fluorescence excitation source. This enables the cw near infrared laser trapping beam to be used simultaneously as an optical diagnostic probe as well as an optical micromanipulator. Using microfluorometry, a temperature increase of less than several degrees centigrade was measured for test samples, including liposomes, Chinese hamster ovary (CHO) cells and human sperm cells that were held stationary by 1064 nm optical tweezers having a power density of ~10^7 W/cm^2. Additional physiological monitoring experiments indicated that there is no observable denaturation of DNA, or change of intracellular pH under typical continuous wave laser trapping conditions (P <= 400 mW). Under some circumstances, however, it was possible to achieve a decrease in cell viability with cw trapping, as monitored by a live/dead vital stain. In comparison, significant DNA denaturation and cellular physiological changes (e.g. cell death) were observed when a Q-switched pulsed laser at a threshold of ~30mu J/pulse was used as trapping source. These results generally support the conclusion that cw laser trapping at 1064 nm wavelength is a safe, non-invasive process and should prove to be of great value for understanding the mechanisms of laser microirradiation effects on living cells held stationary in a near-infrared trapping beam.

  19. Barriers for lateral diffusion of transferrin receptor in the plasma membrane as characterized by receptor dragging by laser tweezers: fence versus tether

    PubMed Central

    1995-01-01

    Our previous results indicated that the plasma membrane of cultured normal rat kidney fibroblastic cell is compartmentalized for diffusion of receptor molecules, and that long-range diffusion is the result of successive intercompartmental jumps (Sako, Y. and Kusumi, A. 1994. J. Cell Biol. 125:1251-1264). In the present study, we characterized the properties of intercompartmental boundaries by tagging transferrin receptor (TR) with either 210-nm-phi latex or 40-nm-phi colloidal gold particles, and by dragging the particle-TR complexes laterally along the plasma membrane using laser tweezers. Approximately 90% of the TR- particle complexes showed confined-type diffusion with a microscopic diffusion coefficient (Dmicro) of approximately 10(-9) cm2/s and could be dragged past the intercompartmental boundaries in their path by laser tweezers at a trapping force of 0.25 pN for gold-tagged TR and 0.8 pN for latex-tagged TR. At lower dragging forces between 0.05 and 0.1 pN, particle-TR complexes tended to escape from the laser trap at the boundaries, and such escape occurred in both the forward and backward directions of dragging. The average distance dragged was half of the confined distance of TR, which further indicates that particle- TR complexes escape at the compartment boundaries. Since variation in the particle size (40 and 210 nm, the particles are on the extracellular surface of the plasma membrane) hardly affects the diffusion rate and behavior of the particle-TR complexes at the compartment boundaries, and since treatment with cytochalasin D or vinblastin affects the movements of TR (Sako and Kusumi as cited above), argument has been advanced that the boundaries are present in the cytoplasmic domain. Rebound of the particle-TR complexes when they escape from the laser tweezers at the compartment boundaries suggests that the boundaries are elastic structures. These results are consistent with the proposal that the compartment boundaries consist of membrane skeleton or a membrane-associated part of the cytoskeleton (membrane skeleton fence model). Approximately 10% of TR exhibited slower diffusion (Dmicro approximately 10(-10)-10(-11) cm2/s) and binding to elastic structures. PMID:7790354

  20. The complex folding behavior of HIV-1-protease monomer revealed by optical-tweezer single-molecule experiments and molecular dynamics simulations.

    PubMed

    Caldarini, M; Sonar, P; Valpapuram, I; Tavella, D; Volonté, C; Pandini, V; Vanoni, M A; Aliverti, A; Broglia, R A; Tiana, G; Cecconi, C

    2014-12-01

    We have used optical tweezers and molecular dynamics simulations to investigate the unfolding and refolding process of a stable monomeric form of HIV-1-protease (PR). We have characterized the behavior under tension of the native state (N), and that of the ensemble of partially folded (PF) conformations the protein visits en route to N, which collectively act as a long-lived state controlling the slow kinetic phase of the folding process. Our results reveal a rich network of unfolding events, where the native state unfolds either in a two-state manner or by populating an intermediate state I, while the PF state unravels through a multitude of pathways, underscoring its structural heterogeneity. Refolding of mechanically denatured HIV-1-PR monomers is also a multiple-pathway process. Molecular dynamics simulations allowed us to gain insight into possible conformations the protein adopts along the unfolding pathways, and provide information regarding possible structural features of the PF state. PMID:25194276

  1. Hydrodynamic slip on DNA observed by optical tweezers-controlled translocation experiments with solid-state and lipid-coated nanopores.

    PubMed

    Galla, Lukas; Meyer, Andreas J; Spiering, Andre; Sischka, Andy; Mayer, Michael; Hall, Adam R; Reimann, Peter; Anselmetti, Dario

    2014-07-01

    We use optical tweezers to investigate the threading force on a single dsDNA molecule inside silicon-nitride nanopores between 6 and 70 nm in diameter, as well as lipid-coated solid-state nanopores. We observe a strong increase of the threading force for decreasing nanopore size that can be attributed to a significant reduction in the electroosmotic flow (EOF), which opposes the electrophoresis. Additionally, we show that the EOF can also be reduced by coating the nanopore wall with an electrically neutral lipid bilayer, resulting in an 85% increase in threading force. All experimental findings can be described by a quantitative theoretical model that incorporates a hydrodynamic slip effect on the DNA surface with a slip length of 0.5 nm. PMID:24935198

  2. Identification of stepped changes of binding affinity during interactions between the disintegrin rhodostomin and integrin ?IIb?3 in living cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Hsieh, Chia-Fen; Chang, Bo-Jui; Pai, Chyi-Huey; Chen, Hsuan-Yi; Chi, Sien; Hsu, Long; Tsai, Jin-Wu; Lin, Chi-Hung

    2004-10-01

    Integrin receptors serve as both mechanical links and signal transduction mediators between the cell and its environment. Experimental evidence demonstrates that conformational changes and lateral clustering of the integrin proteins may affect their binding to ligands and regulate downstream cellular responses; however, experimental links between the structural and functional correlations of the ligand-receptor interactions are not yet elucidated. In the present report, we utilized optical tweezers to measure the dynamic binding between the snake venom rhodostomin, coated on a microparticle and functioned as a ligand, and the membrane receptor integrin alpha(IIb)beta(3) expressed on a Chinese Hamster Ovary (CHO) cell. A progressive increase of total binding affinity was found between the bead and CHO cell in the first 300 sec following optical tweezers-guided contact. Further analysis of the cumulative data revealed the presence of "unit binding force" presumably exerted by a single rhodostomin-integrin pair. Interestingly, two such units were found. Among the measurements of less total binding forces, presumably taken at the early stage of ligand-receptor interactions, a unit of 4.15 pN per molecule pair was derived. This unit force dropped to 2.54 pN per molecule pair toward the later stage of interactions when the total binding forces were relatively large. This stepped change of single molecule pair binding affinity was not found when mutant rhodostomin proteins were used as ligands (a single unit of 1.81 pN per pair was found). These results were interpreted along with the current knowledge about the conformational changes of integrins during the "molecule activation" process.

  3. Holographic optical tweezers

    Microsoft Academic Search

    Gabriel C. Spalding; Johannes Courtial; Roberto Di Leonardo

    The craze for miniaturization has swept o'er most every nation, but should a hand e'er so slightly tremble no micro-machine can it assemble: and so all those really small bits leave the technicians in ts

  4. optical tweezers tractor beams

    E-print Network

    ; force/extension) cell membrane mech props molecular motors (kinesin stepping on microtubules) In vitro fertilization; sperm cell motility optical scissors (chromosomes dissection + manipulation) In vivo..? K

  5. Three-component noncovalent assembly consisting of a central tetrakis-4-pyridyl porphyrin and two lateral gable-like bis-Zn porphyrins.

    PubMed

    Beyler, Maryline; Heitz, Valérie; Sauvage, Jean-Pierre; Ventura, Barbara; Flamigni, Lucia; Rissanen, Kari

    2009-09-01

    A pentaporphyrinic assembly was formed in one step, quantitatively, from a gable like zinc(II) bis-porphyrin and a free-base meso-tetrakis(4-pyridyl)porphyrin, because of the formation of four zinc-nitrogen coordination bonds. The X-ray crystal structure obtained shows a symmetrical structure, the free-base porphyrin being located at the center of a square formed by the four zinc atoms of the two zinc(II) bis-porphyrins. The two phenanthrolines connecting the zinc porphyrins are respectively above and below the plane of the central free-base porphyrin because of favorable CH-pi interactions between several porphyrinic assemblies within the crystal. Spectrophotometric and spectrofluorimetric titrations and studies reveal a high association constant for the porphyrinic assembly in the order of 10(14) M(-2). As expected, energy transfer from the zinc porphyrin component to the central free-base porphyrin quenches the fluorescence of the zinc porphyrin components whereas no sensitization of the emission of the free-base porphyrin was observed. Hypotheses on this unusual behavior are discussed. PMID:19670879

  6. Investigating Molecular Level Stress-Strain Relationships in Entangled F-Actin Networks by Combined Force-Measuring Optical Tweezers and Fluorescence Microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Kent; Henze, Dean; Robertson-Anderson, Rae M.

    2013-03-01

    Actin is an important cytoskeletal protein involved in cell structure and motility, cancer invasion and metastasis, and muscle contraction. The intricate viscoelastic properties of filamentous actin (F-actin) networks allow for the many dynamic roles of actin, thus warranting investigation. Exploration of this unique stress-strain/strain-rate relationship in complex F-actin networks can also improve biomimetic materials engineering. Here, we use optical tweezers with fluorescence microscopy to study the viscoelastic properties of F-actin networks on the microscopic level. Optically trapped microspheres embedded in various F-actin networks are moved through the network using a nanoprecision piezoelectric stage. The force exerted on the microspheres by the F-actin network and subsequent force relaxation are measured, while a fraction of the filaments in the network are fluorescent-labeled to observe filament deformation in real-time. The dependence of the viscoelastic properties of the network on strain rates and amplitudes as well as F-actin concentration is quantified. This approach provides the much-needed link between induced force and deformation over localized regimes (tens of microns) and down to the single molecule level.

  7. The active digestion of uniparental chloroplast DNA in a single zygote of Chlamydomonas reinhardtii is revealed by using the optical tweezer

    PubMed Central

    Nishimura, Yoshiki; Misumi, Osami; Matsunaga, Sachihiro; Higashiyama, Tetsuya; Yokota, Akiho; Kuroiwa, Tsuneyoshi

    1999-01-01

    The non-Mendelian inheritance of organelle genes is a phenomenon common to almost all eukaryotes, and in the isogamous alga Chlamydomonas reinhardtii, chloroplast (cp) genes are transmitted from the mating type positive (mt+) parent. In this study, the preferential disappearance of the fluorescent cp nucleoids of the mating type negative (mt?) parent was observed in living young zygotes. To study the change in cpDNA molecules during the preferential disappearance, the cpDNA of mt+ or mt? origin was labeled separately with bacterial aadA gene sequences. Then, a single zygote with or without cp nucleoids was isolated under direct observation by using optical tweezers and investigated by nested PCR analysis of the aadA sequences. This demonstrated that cpDNA molecules are digested completely during the preferential disappearance of mt? cp nucleoids within 10 min, whereas mt+ cpDNA and mitochondrial DNA are protected from the digestion. These results indicate that the non-Mendelian transmission pattern of organelle genes is determined immediately after zygote formation. PMID:10535964

  8. Optoelectronic Tweezers Integrated with Lens-free Holographic Microscopy for Wide-field Interactive Cell and Particle Manipulation on a Chip

    PubMed Central

    Huang, Kuo-Wei; Su, Ting-Wei; Ozcan, Aydogan; Chiou, Pei-Yu

    2013-01-01

    We demonstrate an optoelectronic tweezer (OET) coupled to a lensfree holographic microscope for real-time interactive manipulation of cells and micro-particles over a large field-of-view (FOV). This integrated platform can record the holographic images of cells and particles over the entire active area of a CCD sensor array, perform digital image reconstruction to identify target cells, dynamically track the positions of cells and particles, and project light beams to trigger light-induced dielectrophoretic forces to pattern and sort cells on a chip. OET technology has been previously shown capable of performing parallel single cell manipulation over a large area. However, its throughput has been bottlenecked by the number of cells that can be imaged within the limited FOV of a conventional microscope objective lens. Integrating lensfree holographic imaging with OET solves this fundamental FOV barrier, while also creating a compact on-chip cell/particle manipulation platform. Using this unique platform, we have successfully demonstrated real-time interactive manipulation of thousands of single cells and micro-particles over an ultra-large area of e.g., 240 mm2 (i.e. 17.96 mm × 13.52 mm). PMID:23661233

  9. (15)N and (13)C group-selective techniques extend the scope of STD NMR detection of weak host-guest interactions and ligand screening.

    PubMed

    Kövér, Katalin E; Wéber, Edit; Martinek, Tamás A; Monostori, Eva; Batta, Gyula

    2010-10-18

    Saturation transfer difference (STD) is a valuable tool for studying the binding of small molecules to large biomolecules and for obtaining detailed information on the binding epitopes. Here, we demonstrate that the proposed (15)N/(13)C variants of group-selective, "GS-STD" experiments provide a powerful approach to mapping the binding epitope of a ligand even in the absence of efficient spin diffusion within the target protein. Therefore, these experimental variants broaden the scope of STD studies to smaller and/or more-dynamic targets. The STD spectra obtained in four different experimental setups (selective (1)H STD, (15)N GS-STD, (13)C(Ar) and (13)C(aliphatic) GS-STD approaches) revealed that the signal-intensity pattern of the difference spectra is affected by both the type and the spatial distribution of the excited "transmitter" atoms, as well as by the efficiency of the spin-diffusion-mediated magnetization transfer. The performance of the experiments is demonstrated on a system by using the lectin, galectin-1 and its carbohydrate ligand, lactose. PMID:20878964

  10. Biosynthesis of ketomycin. (II) biomimetic model for beta-lactamase catalysis: host-guest interactions in cyclodextrin-penicillin inclusion complex

    SciTech Connect

    Mak, H.W.

    1986-01-01

    The antibiotic ketomycin is formed from shikimic acid via chorismic acid and prephenic acid. Phenylalanine and 2',5'-dihydrophenylalanine derived from shikimic acid are not intermediates in the biosynthesis. Degradation of ketomycin derived from (1,6-/sup 14/C)shikimic acid showed that prephenic acid is converted into ketomycin with stereospecific discrimination between the two enantiotopic edges of the ring, the pro-S-R edge giving rise to the C-2', C-3' side of the cyclohexane ring of ketomycin. The resistance of pathogenic bacteria to the action of ..beta..-lactam antibiotics is mainly ascribed to their ability to produce ..beta..-lactamase to cleave the ..beta..-lactam ring. It is essential to understand the molecular nature of ..beta..-lactamase-penicillin recognition for designing and formulating more effective ..beta..-lactam antibiotics. A biomimetic study of ..beta..-lactamase is therefore initiated. To meet the requirements of hydrophobic and serine protease characteristics of ..beta..-lactamase, ..cap alpha..-cyclodextrin is chosen as a biomimetic model for ..beta..-lactamase. The structural specificity and the chemical dynamics of ..cap alpha..-cyclodextrin-phenoxymethyl penicillin inclusion complex in solid state and in solution have been determined by IR and NMR spectroscopy. The spectral results strongly indicate that the phenyl portion of the phenoxymethyl penicillin forms a stable inclusion complex with the hydrophobic cavity of ..cap alpha..-cyclodextrin in solution as well as in the solid state. Kinetic studies followed by /sup 1/HNMR and HPLC analyses under alkaline condition have shown that the ..cap alpha..-cyclodextrin mimics the catalytic function of serine of ..beta..-lactamase in the stereospecific hydrolysis of the ..beta..-lactam ring of phenoxymethyl penicillin.

  11. Host-Guest Chemistry of a Bis-Calix[4]pyrrole Derivative Containing a trans/cis-Switchable Azobenzene Unit with Several Aliphatic Bis-Carboxylates.

    PubMed

    Cafeo, Grazia; Kohnke, Franz H; Mezzatesta, Giovanni; Profumo, Aldo; Rosano, Camillo; Villari, Antonino; White, Andrew J P

    2015-03-27

    The azobenzene unit used as a photochemically and thermally switchable linker in the assembly of a bis-calix[4]pyrrole receptor provides a means to modulate the binding of bis-carboxylates of significant biological importance in cancer research. Conversely, the complexation of different bis-anionic guests has significant kinetic effects on both the photochemical and thermal trans/cis isomerization of the azobenzene unit. PMID:25708864

  12. Mass spectrometric behavior of functionalized calix[4]arenes: the screening ability of host–guest complex formation with amino acid methyl esters

    Microsoft Academic Search

    Andrei Medvedovici; Florin Albu; Abdelwaheb Hamdi; Rachid Souane; Lidia Kim; Lucia Mutihac; Jacques Vicens

    The ESI–MS and MS\\/MS behavior of functionalized calix[4]arenes (1–5) has been studied in both positive and negative-ion mode. Liquid chromatography coupled to ESI–MS has been successfully used\\u000a for separation of the byproducts issuing from the functionalization pathways, through the application of a simple reversed\\u000a phase mechanism. The ability of (1–5) to host methyl esters of amino acids, tyrosine, tryptophan, phenylalanine,

  13. Ternary europium mesoporous polymeric hybrid materials Eu({beta}-diketonate){sub 3}pvpd-SBA-15(16): host-guest construction, characterization and photoluminescence

    SciTech Connect

    Gu Yanjing [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China); Yan Bing, E-mail: byan@tongji.edu.cn [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China); Li Yanyan [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China)

    2012-06-15

    Novel organic-inorganic mesoporous luminescent polymeric hybrid materials containing europium(III) complexes incorporated to mesoporous silica SBA-15/SBA-16 have been prepared by simple physical doping (impregnation) methods, followed by the addition polymerization reaction of the monomer 4-vinylpyridine (vpd) extending along the mesoporous channels. The precursor europium(III) complexes are synthesized by {beta}-diketonate ({beta}-diketonate=2-thenoyltrifluoroacetonate (tta), hexafluoroacetylacetonate (hfac), trifluoroacetylacetonate (taa)) and monomer 4-vinylpyridine (vpd) coordinated to Eu{sup 3+}, and SBA-15/SBA-16 are obtained via a sol-gel process. After the physical doping and the polymerization reaction, the final ternary materials Eu({beta}-diketonate){sub 3}pvpd-SBA-15/Eu({beta}-diketonate){sub 3}pvpd-SBA-16 ({beta}-diketonate=tta, hfac, taa) are received. The physical properties and espeically the photoluminescence of these hybrids are characterized, and the XRD and BET results reveal that all of these hybrid materials have uniformity in the mesostructure. The detailed luminescence investigation on all the materials show that Eu(tta){sub 3}pvpd-SBA-16 have the highest luminescence intensity and the materials with taa ligands have longer lifetimes. - Grapical abstract: Luminescent mesoporous polymeric hybrid materials containing europium complexes hydrogen bonding to silica SBA-15/SBA-16 followed by the addition polymerization reaction of 4-vinylpyridine (vpd) extending along the mesoporous channels. Highlights: Black-Right-Pointing-Pointer Functional mesoporous with simple impregnation method. Black-Right-Pointing-Pointer New lanthanide mesoporous hybrids with polymer ligands. Black-Right-Pointing-Pointer Luminescence in visible region.

  14. Insights into the effects of 2:1 "sandwich-type" crown-ether/metal-ion complexes in responsive host-guest systems.

    PubMed

    Yu, Hai-Rong; Hu, Jia-Qi; Lu, Xiao-Hua; Ju, Xiao-Jie; Liu, Zhuang; Xie, Rui; Wang, Wei; Chu, Liang-Yin

    2015-01-29

    In-depth investigations of the specific ion-responsive characteristics based on 2:1 "sandwich" structures and effects of crown ether cavity sizes on the metal-ion/crown-ether complexation are systematically performed with a series of PNIPAM-based responsive copolymers containing similar contents of crown ether units with different cavity dimensions (12-crown-4 (12C4), 15-crown-5 (15C5), 18-crown-6 (18C6)). The lower critical solution temperature (LCST) values of copolymers in deionized water shift to lower temperatures gradually when the crown ether contents increase or the ring sizes decrease from 18C6 to 12C4. With increasing the concentrations of alkali metal ions (Na(+), K(+), Cs(+)) or the contents of pendent crown ether groups, the copolymers with different crown ether cavity sizes exhibit higher selectivity and sensitivity to corresponding cations. Importantly, the ion sensitivities of the copolymers in response to corresponding alkali metal ions increase dramatically with an increase in the crown ether cavity size. Interestingly, a linear relationship between the crown ether cavity size and the diameter of corresponding cation for the formation of stable 2:1 "sandwich" complexes is found for the first time, from which the size of metal ions or other guests that able to form 2:1 "sandwich" complexes with crown ethers can be deduced. The results in this work are valuable and useful for further developments and practical applications of various crown-ether-based smart materials. PMID:25562507

  15. Interplay of hole transfer and host-guest interaction in a molecular dyad and triad: ensemble and single-molecule spectroscopy and sensing applications.

    PubMed

    Wu, Xiangyang; Liu, Fang; Wells, Kym L; Tan, Serena L J; Webster, Richard D; Tan, Howe-Siang; Zhang, Dawei; Xing, Bengang; Yeow, Edwin K L

    2015-02-16

    A new molecular dyad consisting of a Cy5 chromophore and ferrocene (Fc) and a triad consisting of Cy5, Fc, and ?-cyclodextrin (CD) are synthesized and their photophysical properties investigated at both the ensemble and single-molecule levels. Hole transfer efficiency from Cy5 to Fc in the dyad is reduced upon addition of CD. This is due to an increase in the Cy5-Fc separation (r) when the Fc is encapsulated in the macrocyclic host. On the other hand, the triad adopts either a Fc-CD inclusion complex conformation in which hole transfer quenching of the Cy5 by Fc is minimal or a quasi-static conformation with short r and rapid charge transfer. Single-molecule fluorescence measurements reveal that r is lengthened when the triad molecules are deposited on a glass substrate. By combining intramolecular charge transfer and competitive supramolecular interaction, the triad acts as an efficient chemical sensor to detect different bioactive analytes such as amantadine hydrochloride and sodium lithocholate in aqueous solution and synthetic urine. PMID:25538048

  16. Two steps forward, one step back: determining XPD helicase mechanism by single-molecule fluorescence and high-resolution optical tweezers.

    PubMed

    Spies, Maria

    2014-08-01

    XPD-like helicases constitute a prominent DNA helicase family critical for many aspects of genome maintenance. These enzymes share a unique structural feature, an auxiliary domain stabilized by an iron-sulphur (FeS) cluster, and a 5'-3' polarity of DNA translocation and duplex unwinding. Biochemical analyses alongside two single-molecule approaches, total internal reflection fluorescence microscopy and high-resolution optical tweezers, have shown how the unique structural features of XPD helicase and its specific patterns of substrate interactions tune the helicase for its specific cellular function and shape its molecular mechanism. The FeS domain forms a duplex separation wedge and contributes to an extended DNA binding site. Interactions within this site position the helicase in an orientation to unwind the duplex, control the helicase rate, and verify the integrity of the translocating strand. Consistent with its cellular role, processivity of XPD is limited and is defined by an idiosyncratic stepping kinetics. DNA duplex separation occurs in single base pair steps punctuated by frequent backward steps and conformational rearrangements of the protein-DNA complex. As such, the helicase in isolation mainly stabilizes spontaneous base pair opening and exhibits a limited ability to unwind stable DNA duplexes. The presence of a cognate ssDNA binding protein converts XPD into a vigorous helicase by destabilizing the upstream dsDNA as well as by trapping the unwound strands. Remarkably, the two proteins can co-exist on the same DNA strand without competing for binding. The current model of the XPD unwinding mechanism will be discussed along with possible modifications to this mechanism by the helicase interacting partners and unique features of such bio-medically important XPD-like helicases as FANCJ (BACH1), RTEL1 and CHLR1 (DDX11). PMID:24560558

  17. Two steps forward, one step back: determining XPD helicase mechanism by single-molecule fluorescence and high-resolution optical tweezers

    PubMed Central

    Spies, Maria

    2014-01-01

    XPD-like helicases constitute a prominent DNA helicase family critical for many aspects of genome maintenance. These enzymes share a unique structural feature, an auxiliary domain stabilized by an iron-sulphur (FeS) cluster, and a 5?-3? polarity of DNA translocation and duplex unwinding. Biochemical analyses alongside two single-molecule approaches, total internal reflection fluorescence microscopy and high-resolution optical tweezers, have shown how the unique structural features of XPD helicase and its specific patterns of substrate interactions tune the helicase for its specific cellular function and shape its molecular mechanism. The FeS domain forms a duplex separation wedge and contributes to an extended DNA binding site. Interaction within this site position the helicase in an orientation to unwind the duplex, control the helicase rate, and verify the integrity of the translocating strand. Consistent with its cellular role, processivity of XPD is limited and is defined by an idiosyncratic stepping kinetics. DNA duplex separation occurs in single base pair steps punctuated by frequent backward steps and conformational rearrangements of the protein-DNA complex. As such, the helicase in isolation mainly stabilizes spontaneous base pair opening and exhibits a limited ability to unwind stable DNA duplexes. The presence of a cognate ssDNA binding protein converts XPD into a vigorous helicase by destabilizing the upstream dsDNA as well as by trapping the unwound strands. Remarkably, the two proteins can co-exist on the same DNA strand without competing for binding. The current model of the XPD unwinding mechanism will be discussed along with possible modifications to this mechanism by the helicase interacting partners and unique features of such bio-medically important XPD-like helicases as FANCJ (BACH1), RTEL1 and CHLR1 (DDX11). PMID:24560558

  18. Stretching DNA with optical tweezers.

    PubMed Central

    Wang, M D; Yin, H; Landick, R; Gelles, J; Block, S M

    1997-01-01

    Force-extension (F-x) relationships were measured for single molecules of DNA under a variety of buffer conditions, using an optical trapping interferometer modified to incorporate feedback control. One end of a single DNA molecule was fixed to a coverglass surface by means of a stalled RNA polymerase complex. The other end was linked to a microscopic bead, which was captured and held in an optical trap. The DNA was subsequently stretched by moving the coverglass with respect to the trap using a piezo-driven stage, while the position of the bead was recorded at nanometer-scale resolution. An electronic feedback circuit was activated to prevent bead movement beyond a preset clamping point by modulating the light intensity, altering the trap stiffness dynamically. This arrangement permits rapid determination of the F-x relationship for individual DNA molecules as short as -1 micron with unprecedented accuracy, subjected to both low (approximately 0.1 pN) and high (approximately 50 pN) loads: complete data sets are acquired in under a minute. Experimental F-x relationships were fit over much of their range by entropic elasticity theories based on worm-like chain models. Fits yielded a persistence length, Lp, of approximately 47 nm in a buffer containing 10 mM Na1. Multivalent cations, such as Mg2+ or spermidine 3+, reduced Lp to approximately 40 nm. Although multivalent ions shield most of the negative charges on the DNA backbone, they did not further reduce Lp significantly, suggesting that the intrinsic persistence length remains close to 40 nm. An elasticity theory incorporating both enthalpic and entropic contributions to stiffness fit the experimental results extremely well throughout the full range of extensions and returned an elastic modulus of approximately 1100 pN. Images FIGURE 1 FIGURE 2 PMID:9138579

  19. Magnetic tweezers for DNA micromanipulation

    Microsoft Academic Search

    Charbel Haber; Denis Wirtz

    2000-01-01

    We detail the design of an electromagnetic assembly capable of generating a constant magnetic field superimposed to a large magnetic field gradient (between 40 and 100 T\\/m), which was uniform over a large gap (between 1.5 and 2 cm). Large gaps allowed the use of wide high numerical-aperture lenses to track microspheres attached to DNA molecules with an inverted light

  20. Host–guest-driven color change in water: influence of cyclodextrin on the structure of a copper complex of poly((4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl)methacrylamide-co-dimethylacrylamide)

    PubMed Central

    Retzmann, Nils; Maatz, Gero

    2014-01-01

    Summary In the present work we report the synthesis of poly((4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl)methacrylamide-co-dimethylacrylamide) and its reversible optical and complex-forming properties due to copper and cyclodextrin (CD) interactions. Color changing effects are characterized by UV–vis spectroscopy and the supramolecular behavior is investigated by dynamic light scattering experiments. PMID:25383119

  1. Processing carbon nanotubes with holographic optical tweezers

    E-print Network

    Grier, David

    , and perhaps even individual nanotubes, can be transported at high speeds, deposited onto substrates, untangled processing with light. © 2012 Optical Society of America OCIS codes: (140.7010) Trapping; (090.1760) Computer of aligned carbon nanotubes via laser trimming,'' Nanotechnology 14, 433--437 (2003). 16. L. A. Nagahara, I

  2. Processing carbon nanotubes with holographic optical tweezers

    E-print Network

    Grier, David

    nanotubes, can be transported at high speeds, deposited onto substrates, untangled, and selectively ablated. © 2012 Optical Society of America OCIS codes: (140.7010) Trapping; (090.1760) Computer holography; (120, "Large area patterned arrays of aligned carbon nanotubes via laser trimming," Nanotechnology 14, 433

  3. Iptycene-derived crown ether hosts for molecular recognition and self-assembly.

    PubMed

    Han, Ying; Meng, Zheng; Ma, Ying-Xian; Chen, Chuan-Feng

    2014-07-15

    CONSPECTUS: Synthetic macrocyclic hosts have played key roles in the development of host-guest chemistry. Crown ethers are a class of macrocyclic molecules with unique flexible structures. They have served as the first generation of synthetic hosts, and researchers have extensively studied them in molecular recognition. However, the flexible structures of simple crown ethers and their relatively limited modes of complexation with guests have limited the further applications of these molecules. In recent years, researchers have moved toward fabricating interlocking molecules, supramolecular polymers, and other assemblies with specific structures and properties. Therefore, researchers have developed more complex crown ether-based macrocyclic hosts with multicavity structures and multicomplexation modes that provide more diverse and sophisticated host-guest systems. In this Account, we summarize our research on the synthesis and characterization of iptycene-derived crown ether hosts, their use as host molecules, and their applications in self-assembled complexes. Iptycenes including triptycenes and pentiptycenes are a class of aromatic compounds with unique rigid three-dimensional structures. As a result, they are promising building blocks for the synthesis of novel macrocyclic hosts and the construction of novel self-assembled complexes with specific structures and properties. During the last several years, we have designed and synthesized a new class of iptycene-derived crown ether hosts including macrotricyclic polyethers, molecular tweezer-like hosts, and tritopic tris(crown ether) hosts, which are all composed of rigid iptycene building blocks linked by flexible crown ether chains. We have examined the complexation behavior of these hosts with different types of organic guest molecules. Unlike with conventional crown ethers, the combination of iptycene moieties and crown ether chains provides the iptycene-derived crown ether hosts with complexation properties that differ based on the structure of the guests. The rigid iptycene moieties within these synthetic host molecules both maintain their inherent three-dimensional cavities and generate multicavity structures. The flexible crown ether chains allow the iptycene-derived hosts to adjust their conformations as they encapsulate guest molecules. Moreover, the expanded complexation properties also allow the host-guest systems based on the iptycene-derived crown ethers to respond to multiple external stimuli, resulting in a variety of supramolecular assemblies. Finally, we also describe the construction of mechanically interlocked self-assemblies, molecular switches/molecular machines, and supramolecular polymers using these new host molecules. We expect that the unique structural features and diverse complexation properties of these iptycene-derived crown ether hosts will lead to increasing interest in this field and in supramolecular chemistry overall. PMID:24877894

  4. Interfacial Interactions Pertinent to Single-Molecule and Solar-Energy Applications

    E-print Network

    Upadhyayula, Srigokul

    2013-01-01

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

  5. Synthesis and characterization of transition metal clusters: From the isolation of ligand-stabilized solid fragments to the tuning of magnetic anisotropy and host-guest selectivity, and, Approaches to science teaching: Development of an observation instrument with a measurement model based on item response theory

    Microsoft Academic Search

    Allan George Hee

    2004-01-01

    Part I. The work presented herein describes efforts to develop general techniques for the synthesis of transition metal clusters and the manipulation of their properties. In Chapter 2, it is demonstrated that a modified metal atom reactor allows for the vaporization, passivation, and isolation of metal-chalcogenide clusters from their parent binary solids. Among the clusters produced by this method were

  6. Synthesis and characterization of transition metal clusters: From the isolation of ligand-stabilized solid fragments to the tuning of magnetic anisotropy and host-guest selectivity, and, Approaches to science teaching: Development of an observation instrument with a measurement model based on item response theory

    NASA Astrophysics Data System (ADS)

    Hee, Allan George

    Part I. The work presented herein describes efforts to develop general techniques for the synthesis of transition metal clusters and the manipulation of their properties. In Chapter 2, it is demonstrated that a modified metal atom reactor allows for the vaporization, passivation, and isolation of metal-chalcogenide clusters from their parent binary solids. Among the clusters produced by this method were Cr6S8(PEt3)6, Fe4S 4(PEt3)4, Co6S8(PEt 3)6, Cu6S4(PEt3)6, Cu12S6(PEt3)8, and Cu26Se 13(PEt3)14. To create single-molecule magnets with higher demagnetization barriers, we are developing metal-cyanide systems which exhibit highly adjustable magnetic behavior. Chapter 3 reports an attempt to introduce magnetic anisotropy into a MnCr6 cluster. Replacement of CrIII with Mo III resulted in the assembly of K[(Me3tacn)6MnMo 6(CN)18](ClO4)3 (Me3tacn = N,N',N? -trimethyl-1,4,7-triazacyclononane)---the first well-documented example of a cyano-bridged single-molecule magnet. Recently, it was demonstrated that replacing Me3tacn with the less sterically hindering tach (tach = cis,cis-1,3,5-triaminocyclohexane) in the face-centered cubic cluster [(tach)8Cr8Ni 6(CN)24]Br12 provides greater access to the cluster cavity. Chapter 4 describes my efforts to probe the selectivity of this cluster toward inclusion of various guests. Part II. Successful implementation of student-centered curricula reforms requires the creation of a measurement instrument for monitoring whether the curricula are being used as intended. The creation and development of an observation instrument would greatly contribute to this effort. To develop a theoretically sound construct map, it is necessary to review the literature and conduct our own investigations of approaches to science teaching. Chapter 2 presents the findings of these investigations and their contributions to our understanding of the construct. Using these findings, the Science Teaching Observation Protocol (STOP) was created and designed to measure two subconstructs: intentions and strategies. Chapter 3 details the first pilot test of STOP and analysis of the collected data. In Chapter 4, the theoretical shortcomings of the instrument are analyzed and discussed. Modified versions of the intention and strategy subconstruct maps are presented.

  7. Host-Guest Behavior of a Heavy-Atom Heterocycle Re4(CO)16(?-SbPh2)2(?-H)2 Obtained from a Palladium-Assisted Ring Opening Dimerization of Re2(CO)8(?-SbPh2)(?-H).

    PubMed

    Adams, Richard D; Pearl, William C; Wong, Yuen Onn; Hall, Michael B; Walensky, Justin R

    2015-04-01

    The heavy-atom heterocycle Pd[Re2(CO)8(?-SbPh2)(?-H)]2 (5) has been synthesized by the palladium-catalyzed ring-opening cyclodimerization of the three-membered heterocycle Re2(CO)8(?-SbPh2)(?-H) (3). The Pd atom occupies the center of the ring. The Pd atom in 5 can be removed reversibly to yield the palladium-free heterocycle [Re2(CO)8((?-SbPh2)(?-H)]2 (6). PMID:25756937

  8. A focal spot with variable intensity distribution for optical tweezers

    NASA Astrophysics Data System (ADS)

    Hao, X.; Kuang, C. F.; Li, Y. H.; Liu, X.

    2013-04-01

    An optical setup that can generate a focused light spot, with its shape tunable from a very sharp peak-centered beam to a donut-shaped dark-centered beam, is always desired in optical tweezing. This setup is now realized by incorporating an image inverting interferometer (III) and a helical phase element into a radially polarized beam generator, which enables the trapping and control of a large variety of particles with a single optical tweezing system. The performance of this system is investigated theoretically.

  9. Forces due to pulsed beams in optical tweezers: linear effects.

    PubMed

    Preez-Wilkinson, Nathaniel du; Stilgoe, Alexander B; Alzaidi, Thuraya; Rubinsztein-Dunlop, Halina; Nieminen, Timo A

    2015-03-23

    We present a method for the precise calculation of optical forces due to a tightly-focused pulsed laser beam using generalized Lorenz-Mie theory or the T-matrix method. This method can be used to obtain the fields as a function of position and time, allowing the approximate calculation of weak non-linear effects, and provides a reference calculation for validation of calculations including non-linear effects. We calculate forces for femtosecond pulses of various widths, and compare with forces due to a continuous wave (CW) beam. The forces are similar enough so that the continuous beam case provides a useful approximation for the pulsed case, with trap parameters such as the radial spring constant usually differing by less than 1% for pulses of 100 fs or longer. For large high-index (e.g., polystyrene, with n = 1.59) particles, the difference can be as large as 3% for 100 fs pulses, and up to 8% for 25 fs pulses. A weighted average of CW forces for individual spectral components of the pulsed beam provides a simple improved approximation, which we use to illustrate the physical principles responsible for the differences between pulsed and CW beams. PMID:25837064

  10. Trapping volume control in optical tweezers using cylindrical vector beams.

    PubMed

    Skelton, S E; Sergides, M; Saija, R; Iatì, M A; Maragó, O M; Jones, P H

    2013-01-01

    We present the result of an investigation into the optical trapping of spherical microparticles using laser beams with a spatially inhomogeneous polarization direction [cylindrical vector beams (CVBs)]. We perform three-dimensional tracking of the Brownian fluctuations in the position of a trapped particle and extract the trap spring constants. We characterize the trap geometry by the aspect ratio of spring constants in the directions transverse and parallel to the beam propagation direction and evaluate this figure of merit as a function of polarization angle. We show that the additional degree of freedom present in CVBs allows us to control the optical trap strength and geometry by adjusting only the polarization of the trapping beam. Experimental results are compared with a theoretical model of optical trapping using CVBs derived from electromagnetic scattering theory in the T-matrix framework. PMID:23282827

  11. Tools to study the kinesin mechanome using optical tweezers

    E-print Network

    González Rubio, Ricardo, S.M. Massachusetts Institute of Technology

    2009-01-01

    Molecular motors play an important role in driving some of the most complex and important tasks in biological systems, ranging from transcribing RNA from a DNA template (Polymerases) to muscle contraction (Myosin) and ...

  12. Effects of viscosity on sperm motility studied with optical tweezers

    E-print Network

    Chen, Zhongping

    such as sperm cryopreser- vation, in-vitro fertilization (IVF), and artificial insemination (AI). Factors quality and fertilization capacity.1 The ability to evaluate sperm motility is important in areas have a major impact on its motility and its subsequent ability to reach and fertilize the egg

  13. Single beam optical vortex tweezers with tunable orbital angular momentum

    SciTech Connect

    Gecevi?ius, Mindaugas; Drevinskas, Rokas, E-mail: rd1c12@orc.soton.ac.uk; Beresna, Martynas; Kazansky, Peter G. [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2014-06-09

    We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.

  14. With microscope and tweezers: the worm from MIT's perspective

    Microsoft Academic Search

    Jon A. Rochlis; Mark W. Eichin

    1989-01-01

    The actions taken by a group of computer scientists at MIT during the worm invasion represents a study of human response to a crisis. The authors also relate the experiences and reactions of other groups throughout the country, especially in terms of how they interacted with the MIT team.

  15. Single and dual fiber nanotip optical tweezers: trapping and analysis

    E-print Network

    Paris-Sud XI, Université de

    . Picard, F. d. Fornel, and E. Hadji, ``Assembly of microparticles by optical trapping with a photonic crystal nanocavity,'' Appl. Phys. Lett. 100, 101103 (2012). 4. K. Wang, E. Schonbrun, P. Steinvurzel nanoparticles using plasmonic dipole antennas,'' Nano Lett. 10, 1006--1011 (2010). 6. Y. Tanaka and K. Sasaki

  16. Multispectral optical tweezers for molecular diagnostics of single biological cells

    E-print Network

    Wu, Shin-Tson

    , suspended in a 10mM Hepes buffer with 5% glucose for mitochondria tagging http://www.chemistry.nmsu.edu/Instrumentation/fluorescence_Std_4.html #12;Fluorescence imaging Imaging mitochondria in yeast cell Only ~3 mitochondria: anaerobic

  17. Solar sails, optical tweezers, and other light-driven machines

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud

    2011-10-01

    Electromagnetic waves carry energy, linear momentum, and angular momentum. When light (or other electromagnetic radiation) interacts with material media, both energy and momentum are usually exchanged. The force and torque experienced by material bodies in their interactions with the electromagnetic field are such that the energy as well as the linear and angular momenta of the overall system (i.e., the system of field plus matter) are conserved. Radiation forces are now used routinely to trap and manipulate small objects such as glass or plastic micro-beads and biological cells, to drive micro- and nanomachines, and to contemplate interstellar travel with the aid of solar sails. We discuss the properties of the electromagnetic field that enable such wide-ranging applications.

  18. Absolute position total internal reflection microscopy with an optical tweezer.

    PubMed

    Liu, Lulu; Woolf, Alexander; Rodriguez, Alejandro W; Capasso, Federico

    2014-12-30

    A noninvasive, in situ calibration method for total internal reflection microscopy (TIRM) based on optical tweezing is presented, which greatly expands the capabilities of this technique. We show that by making only simple modifications to the basic TIRM sensing setup and procedure, a probe particle's absolute position relative to a dielectric interface may be known with better than 10 nm precision out to a distance greater than 1 ?m from the surface. This represents an approximate 10× improvement in error and 3× improvement in measurement range over conventional TIRM methods. The technique's advantage is in the direct measurement of the probe particle's scattering intensity vs. height profile in situ, rather than relying on assumptions, inexact system analogs, or detailed knowledge of system parameters for calibration. To demonstrate the improved versatility of the TIRM method in terms of tunability, precision, and range, we show our results for the hindered near-wall diffusion coefficient for a spherical dielectric particle. PMID:25512542

  19. Using optical tweezers to study protein-DNA interactions

    NASA Astrophysics Data System (ADS)

    Smith, Douglas E.; Gemmen, Gregory J.; Millin, Rachel; Rickgauer, John P.; Schweitzer, Allan L.; Fuller, Derek N.

    2005-08-01

    Mechanical manipulation of single DNA molecules can provide novel information about protein-DNA interactions. Here we review two examples studied by our group. First, we have studied the forced unraveling of nucleosomes assembled on heterogeneous DNA using core histones, the histone chaperone NAP-1, and ATP-dependent chromatin assembly and remodeling factor (ACF). We measure abrupt events releasing ~55 to 95 base pairs of DNA, which are attributable to non-equilibrium unraveling of individual nucleosomes. Wide variations observed in the unraveling force and sudden DNA re-wrapping events may have an important regulatory influence on DNA directed biochemical processes. Second, we have studied the mechanics and dynamics of single DNA looping and cleavage by "two-site" restriction enzymes. Cleavage is measured as a function of DNA tension, incubation time, and enzyme concentration, distinguishing enzymes that require DNA looping from ones that do not. Forced disruption of fixed DNA loops formed in the absence of Mg2+ is observed, allowing the distribution of number of loops, loop length, and disruption force to be measured as a function of time, DNA tension, and ionic conditions.

  20. Two-photon fluorescence diagnostics of femtosecond laser tweezers

    PubMed Central

    Kumar De, Arijit; Roy, Debjit; Goswami, Debabrata

    2013-01-01

    We show how two-photon fluorescence signal can be used as an effective detection scheme for trapping particles of any size in comparison to methods using back-scattered light. Development of such a diagnostic scheme allows us a direct observation of trapping a single nanoparticle, which shows new directions to spectroscopy at the single-molecule level in solution. PMID:23814313

  1. Use tweezers to grasp the tick at the surface of

    E-print Network

    you Remove a Tick: Lone Star tick Contact your local county Extension office at: Take protective tick, found in North Central and North Eastern U.S., is a tick that has been found to cause Lyme disease. Other ticks include the Lone Star and Rocky Mountain tick. LYME DISEASE Occurs 3 to 30 days after

  2. Cleaved fiber optic double nanohole optical tweezers for trapping nanoparticles.

    PubMed

    Gelfand, Ryan M; Wheaton, Skylar; Gordon, Reuven

    2014-11-15

    We demonstrate the trapping of single 20 and 40 nm polystyrene spheres at the cleaved end of a fiber optic with a double nanohole aperture in gold and without any microscope optics. An optical transmission increase of 15% indicates a trapping event for the 40 nm particle, and the jump is 2% for the 20 nm particle. This modular technique can be used to replace those used with current optical trapping setups that require complicated free space optics and frequent calibration, with one that is modular and requires no free space optics. This simple arrangement with the potential for fiber translation is of interest for future biosensor and optical nano-pipette devices. PMID:25490482

  3. Spontaneous Expulsion of Giant Lipid Vesicles Induced by Laser Tweezers

    E-print Network

    Roy Bar-Ziv; J. David Moroz; Elisha Moses; Philip Nelson

    1996-10-08

    Irradiation of a giant unilamellar lipid bilayer vesicle with a focused laser spot leads to a tense pressurized state which persists indefinitely after laser shutoff. If the vesicle contains another object it can then be gently and continuously expelled from the tense outer vesicle. Remarkably, the inner object can be almost as large as the parent vesicle; its volume is replaced during the exit process. We offer a qualitative theoretical model to explain these and related phenomena. The main hypothesis is that the laser trap pulls in lipid and ejects it in the form of submicron objects, whose osmotic activity then drives the expulsion.

  4. Self-Sorting of cyclic peptide homodimers into a heterodimeric assembly featuring an efficient photoinduced intramolecular electron-transfer process.

    PubMed

    Aragay, Gemma; Ventura, Barbara; Guerra, Arcadio; Pintre, Inmaculada; Chiorboli, Claudio; García-Fandiño, Rebeca; Flamigni, Lucia; Granja, Juan R; Ballester, Pablo

    2014-03-17

    We describe the thermodynamic characterisation of the self-sorting process experienced by two homodimers assembled by hydrogen-bonding interactions through their cyclopeptide scaffolds and decorated with Zn-porphyrin and fullerene units into a heterodimeric assembly that contains one electron-donor (Zn–porphyrin) and one electron-acceptor group (fullerene). The fluorescence of the Zn-porphyrin unit is strongly quenched upon heterodimer formation. This phenomenon is demonstrated to be the result of an efficient photoinduced electron-transfer (PET) process occurring between the Zn-porphyrin and the fullerene units of the heterodimeric system. The recombination lifetime of the charge-separated state of the heterodimer complex is in the order of 180 ns. In solution, both homo- and heterodimers are present as a mixture of three regioisomers: two staggered and one eclipsed. At the concentration used for this study, the high stability constant determined for the heterodimer suggests that the eclipsed conformer is the main component in solution. The application of the bound-state scenario allowed us to calculate that the heterodimer exists mainly as the eclipsed regioisomer (75-90 %). The attractive interaction that exists between the donor and acceptor chromophores in the heterodimeric assembly favours their arrangement in close contact. This is confirmed by the presence of charge-transfer bands centred at 720 nm in the absorption spectrum of the heterodimer. PET occurs in approximately 75% of the chromophores after excitation of both Zn-porphyrin and fullerene chromophores. Conversely, analogous systems, reported previously, decorated with extended tetrathiafulvalene and fullerene units showed a PET process in a significantly reduced extent (33%). We conclude that the strength (stability constant (K) x effective molarity (EM)) of the intramolecular interaction established between the two chromophores in the Zn-porphyrin/fullerene cyclopeptide-based heterodimers controls the regioisomeric distribution and regulates the high extent to which the PET process takes place in this system. PMID:24677609

  5. High-conductance surface-anchoring of a mechanically flexible platform-based porphyrin complex

    NASA Astrophysics Data System (ADS)

    Hauptmann, Nadine; Groß, Lynn; Buchmann, Kristof; Scheil, Katharina; Schütt, Christian; Otte, Franziska L.; Herges, Rainer; Herrmann, Carmen; Berndt, Richard

    2015-01-01

    The conductances of molecular model junctions comprising a triazatriangulenium platform with or without an ethynyl spacer and an upright Zn-porphyrin are probed with a low-temperature scanning probe microscope. The platform alone is found to be highly conductive. The ethynyl-linked Zn-porphyrin moiety reduces the conductance by three orders of magnitude and leads to an unexpected, non-monotonous variation of the force that was measured simultaneously at the tip of the microscope. Density functional theory calculations show that this variation results from an induced tilting of the porphyrin.

  6. Molecular recognition of curcumin (Indian Ayurvedic medicine) by the supramolecular probe, p-t-butyl calix(8)arene

    NASA Astrophysics Data System (ADS)

    Meenakshi, C.; Jayabal, P.; Ramakrishnan, V.

    2014-06-01

    The thermodynamic property of the host-guest complexes formed between the curcumin, component of Indian Ayurvedic medicine turmeric, a drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene has been used as a host molecule and curcumin as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(8)arene with curcumin. The stochiometry of the host-guest complexes formed and the binding constant were determined. An interesting 1:1 and 4:1 stochiometric host-guest complexes were formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed.

  7. From metallic cluster-based ceramics to nematic hybrid liquid crystals: a double supramolecular approach.

    PubMed

    Nayak, Susanta K; Amela-Cortes, Maria; Roiland, Claire; Cordier, Stéphane; Molard, Yann

    2015-03-01

    We describe a new supramolecular approach combining host-guest and electrostatic interactions to design hybrid materials containing polyanionic bulky inorganic compounds and showing liquid crystalline properties. PMID:25646896

  8. Purification of C60 and C70 by selective complexation with calixarenes

    Microsoft Academic Search

    Jerry L. Atwood; George A. Koutsantonis; Colin L. Raston

    1994-01-01

    MOLECULAR complexation of fullerenes in host-guest complexes has the potential to afford efficient large-scale purification of fullerenes1. This method would avoid the losses inherent in the chromatographic techniques currently in use, which arise from irreversible absorption on the stationary phase2. Several host-guest interactions have been reported for C60, including the formation of complexes with 1,4-hydroquinone3,4, azacrown compounds5, certain water-soluble macrocycles

  9. Interactions of cyclodextrins with aromatic compounds studied by vibrational circular dichroism spectroscopy

    Microsoft Academic Search

    Vladim??r Setni?ka; Marie Urbanová; Vladim??r Král; Karel Volka

    2002-01-01

    The host\\/guest complexation between cyclodextrins (CDs) and aromatic compounds was studied by vibrational circular dichroism (VCD) spectroscopy in mid-IR region. Benzoic acid, 4-aminobenzoic acid, and 2,6-naphthalenedicarboxylic acid acting as the guests with aromatic skeleton, cause the significant changes in VCD patterns of CD, which indicate that the secondary hydroxyl groups of the CDs are involved in the host\\/guest complexation. In

  10. With Microscope and Tweezers: An Analysis of the Internet Virus of November 1988

    Microsoft Academic Search

    Mark W. Eichin; Jon A. Rochlis

    1989-01-01

    In early November 1988 the Internet, a collection of networksconsisting of 60,000 host computers implementingthe TCP\\/IP protocol suite, was attacked by a virus, a programwhichbroke into computers on the network and whichspread from one machine to another. This paper is a detailedanalysis of the virus programitself, as well as the reactionsof the besieged Internet community. We discuss thestructure of the

  11. Three-Dimensional Optical Trapping of a Plasmonic Nanoparticle using Low Numerical Aperture Optical Tweezers

    PubMed Central

    Brzobohatý, Oto; Šiler, Martin; Trojek, Jan; Chvátal, Lukáš; Karásek, Vít?zslav; Paták, Aleš; Pokorná, Zuzana; Mika, Filip; Zemánek, Pavel

    2015-01-01

    It was previously believed that larger metal nanoparticles behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, several groups have recently reported successful optical trapping of gold and silver particles as large as 250?nm. We offer a possible explanation based on the fact that metal nanoparticles naturally occur in various non-spherical shapes and their optical properties differ significantly due to changes in localized plasmon excitation. We demonstrate experimentally and support theoretically three-dimensional confinement of large gold nanoparticles in an optical trap based on very low numerical aperture optics. We showed theoretically that the unique properties of gold nanoprisms allow an increase of trapping force by an order of magnitude at certain aspect ratios. These results pave the way to spatial manipulation of plasmonic nanoparticles using an optical fibre, with interesting applications in biology and medicine. PMID:25630432

  12. Spectrin-Level Modeling of the Cytoskeleton and Optical Tweezers Stretching of the Erythrocyte

    E-print Network

    Dao, Ming

    (Mohandas and Evans, 1994) in such cases as sickle cell anemia (Platt, 1995) and malaria (Cooke et al., 2001-dimensional computational study of whole-cell equilibrium shape and deformation of human red blood cell (RBC) using spectrin. INTRODUCTION The deformation of the human erythrocyte or red blood cell (RBC) has been the topic of detailed

  13. Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity

    PubMed Central

    2013-01-01

    Recently, optical tweezing has been used to provide a method for microrheology addressed to measure the rheological properties of small volumes of samples. In this work, we corroborate this emerging field of microrheology by using these optical methods for the characterization of polyelectrolyte solutions with very low viscoelasticity. The influence of polyelectrolyte (i.e., polyacrylamide, PAM) concentration, specifically its aging, of the salt concentration is shown. The close agreement of the technique with classical bulk rheological measurements is demonstrated, illustrating the advantages of the technique. PMID:23786307

  14. Evidence for non-equilibrium dynamics in viral DNA packaging from optical tweezers measurements

    NASA Astrophysics Data System (ADS)

    Berndsen, Zachary T.; Keller, Nicholas; Smith, Douglas E.

    2013-09-01

    In many viruses molecular motors generate large forces to package DNA to high densities. The dynamics and energetics of this process is a subject of wide debate and is of interest as a model for studying confined polymer physics in general. Here we present preliminary results showing that DNA in bacteriophage phi29 undergoes nonequilibrium conformational dynamics during packaging with a relaxation time >60,000x longer than for free DNA and >3000x longer than reported for DNA confined in nanochannels. Nonequilibrium dynamics significantly increases the load on the motor, causes heterogeneity in the rates of packaging, and causes frequent pausing in motor translocation.

  15. Real-time nonlinear correction of back-focal-plane detection in optical tweezers

    NASA Astrophysics Data System (ADS)

    Aggarwal, Tanuj; Salapaka, Murti

    2010-12-01

    Photodiode based detection of laser trapped beads using forward scattered light is a frequently employed technique for position measurement. There is a nonlinear relationship between photodiode outputs and bead position but for small displacements linear approximation holds well. Traditionally, the nonlinearity is compensated by normalizing the photodiode's position signal with the intensity signal and then using a polynomial fit in the range where voltage to position mapping is one to one. In this article, this range is extended by using the intensity signal as an independent input along with the two position signals. A map from the input signals to the actual position values is obtained. This mapping is one-to-one for a larger range that results in an increased detection range. An artificial neural network that facilitates implementation is employed for this purpose. This scheme is implemented on a Field Programmable Gate Array based data acquisition and control hardware with closed loop bandwidth of 50 kHz. Detection of the order of 350 nm from the center of detection laser is demonstrated for a 500 nm diameter bead compared to 180 nm achieved by a polynomial fit.

  16. Real-time nonlinear correction of back-focal-plane detection in optical tweezers.

    PubMed

    Aggarwal, Tanuj; Salapaka, Murti

    2010-12-01

    Photodiode based detection of laser trapped beads using forward scattered light is a frequently employed technique for position measurement. There is a nonlinear relationship between photodiode outputs and bead position but for small displacements linear approximation holds well. Traditionally, the nonlinearity is compensated by normalizing the photodiode's position signal with the intensity signal and then using a polynomial fit in the range where voltage to position mapping is one to one. In this article, this range is extended by using the intensity signal as an independent input along with the two position signals. A map from the input signals to the actual position values is obtained. This mapping is one-to-one for a larger range that results in an increased detection range. An artificial neural network that facilitates implementation is employed for this purpose. This scheme is implemented on a Field Programmable Gate Array based data acquisition and control hardware with closed loop bandwidth of 50 kHz. Detection of the order of 350 nm from the center of detection laser is demonstrated for a 500 nm diameter bead compared to 180 nm achieved by a polynomial fit. PMID:21198012

  17. Active Microrheology of Networks Composed of Semiflexible Polymers I. Computer Simulation of Magnetic Tweezers

    E-print Network

    N. Ter-Oganessian; D. A. Pink; B. Quinn; A. Boulbitch

    2005-03-23

    We have simulated the motion of a bead subjected to a constant force while embedded in a network of semiflexible polymers which can represent actin filaments. We find that the bead displacement obeys the power law x ~ t^alfa. After the initial stage characterized by the exponent alfa=0.75 we find a new regime with alfa=0.5. The response in this regime is linear in force and scales with the polymer concentration as c^(-1.4). We find that the polymers pile up ahead of the moving bead, while behind it the polymer density is reduced. We show that the force resisting the bead motion is due to steric repulsion exerted by the polymers on the front hemisphere of the bead.

  18. Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers

    Microsoft Academic Search

    Andreas R. Bausch; Winfried Möller; Erich Sackmann

    1999-01-01

    We measured the viscoelastic properties of the cytoplasm of J774 macrophages with a recently developed microrheometer. Ferromagnetic beads (1.3?m in diameter) were used to determine the local viscoelastic moduli. Step-force pulses were applied to the magnetic beads and the displacement was observed by single particle tracking. By analyzing the creep response curves in terms of a triphasic mechanical equivalent circuit,

  19. Condensation of hydrodynamically stretched DNA using single-molecule fluorescence imaging and optical tweezers

    NASA Astrophysics Data System (ADS)

    Theofanidou, Eirini; Su, Tsueu Ju; Arlt, Jochen; Dryden, David T. F.; Hossack, William J.; Crain, Jason; Poon, Wilson C. K.

    2004-10-01

    We have observed a latency time of the order 10 s in the spermidine-induced condensation of YOYO-1-labelled DNA in flow. Higher flow speeds, longer DNA and higher salt all led to an increase in the latency time. We propose that two effects may be relevant to these observations (1) the competition between spermidine and YOYO-1 for DNA binding sites, and (2) the bending of DNA upon spermidine binding, so that flow-induced straightening of the DNA weakens spermidine's affinity for DNA. Moreover, literature data on the mechanical properties of condensed DNA chains suggest that the hydrodynamic drag forces in our experiments should indeed significantly perturb condensation kinetics.

  20. Raman tweezers in microfluidic systems for analysis and sorting of living cells

    NASA Astrophysics Data System (ADS)

    Pilát, Zdenëk; Ježek, Jan; Ka?ka, Jan; Zemánek, Pavel

    2014-03-01

    We have devised an analytical and sorting system combining optical trapping with Raman spectroscopy in microfluidic environment in order to identify and sort biological objects, such as living cells of various prokaryotic and eukaryotic organisms. Our main objective was to create a robust and universal platform for non-contact sorting of microobjects based on their Raman spectral properties. This approach allowed us to collect information about the chemical composition of the objects, such as the presence and composition of lipids, proteins, or nucleic acids without using artificial chemical probes such as fluorescent markers. The non-destructive and non-contact nature of this optical analysis and manipulation allowed us to separate individual living cells of our interest in a sterile environment and provided the possibility to cultivate the selected cells for further experiments. We used differently treated cells of algae to test and demonstrate the function of our analytical and sorting system. The devised system could find its use in many medical, biotechnological, and biological applications.