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Sample records for zn-porphyrin tweezer host-guest

  1. CD-sensitive Zn-porphyrin tweezer host-guest complexes, part 1: MC/OPLS-2005 computational approach for predicting preferred interporphyrin helicity.

    PubMed

    Petrovic, Ana G; Chen, Yihui; Pescitelli, Gennaro; Berova, Nina; Proni, Gloria

    2010-01-01

    This article describes a computational study on dimeric zinc porphyrin tweezer complexes with primary/secondary amines and secondary alcohols that validates the use of Optimized Potential for Liquid Simulations (OPLS-2005) as the lead computational choice for assisting the tweezer methodology in the absolute configurational assignment of organic compounds. A supramolecular, microscale approach known as the tweezer method has been widely applied in the past decade for determining the absolute configuration of chiral substrates that are difficult to study by other readily available methods. The method relies on a host/guest complexation mechanism between a porphyrin tweezer moiety and a substrate, after its conversion into a bidentate conjugate. The formation of 1:1 complexes is a stereodifferentiating process: upon complexation, the originally achiral tweezer adopts a preferential interporphyrin helicity, dictated by the absolute configuration of the chiral substrate. By correctly predicting the sign of the interporphyrin helicity in the complex, OPLS-2005 provides a correlation between the observed circular dichroism (CD) signal and the absolute configuration of the substrate. It also offers a great degree of insight into the structural factors responsible for chiral recognition and the amplitude of exciton couplets. Moreover, the preferential binding sites between the Zn-tweezer and secondary amine conjugates were revealed by using the new computational approach.

  2. Bulky melamine-based Zn-porphyrin tweezer as a CD probe of molecular chirality.

    PubMed

    Petrovic, Ana G; Vantomme, Ghislaine; Negrón-Abril, Yashira L; Lubian, Elisa; Saielli, Giacomo; Menegazzo, Ileana; Cordero, Roselynn; Proni, Gloria; Nakanishi, Koji; Carofiglio, Tommaso; Berova, Nina

    2011-10-01

    The transfer of chirality from a guest molecule to an achiral host is the subject of significant interest especially when, upon chiral induction, the chiroptical response of the host/guest complex can effectively report the absolute configuration (AC) of the guest. For more than a decade, dimeric metalloporphyrin hosts (tweezers) have been successfully applied as chirality probes for determination of the AC for a wide variety of chiral synthetic compounds and natural products. The objective of this study is to investigate the utility of a new class of melamine-bridged Zn-porphyrin tweezers as sensitive AC reporters. A combined approach based on an experimental CD analysis and a theoretical prediction of the prevailing interporphyrin helicity demonstrates that these tweezers display favorable properties for chiral recognition. Herein, we discuss the application of the melamine-bridged tweezer to the chiral recognition of a diverse set of chiral guests, such as 1,2-diamines, α-amino-esters and amides, secondary alcohols, and 1,2-amino-alcohols. The bulky periphery and the presence of a rigid porphyrin linkage lead, in some cases, to a more enhanced CD sensitivity than that reported earlier with other tweezers.

  3. Host-guest interactions of phosphorescent molecular tweezers based on an alkynylplatinum(II) terpyridine system with polyaromatic hydrocarbons.

    PubMed

    Tanaka, Yuya; Wong, Keith Man-Chung; Yam, Vivian Wing-Wah

    2013-01-02

    Host-guest interactions of a molecular tweezer complex 1 with various planar organic molecules including polyaromatic hydrocarbons (PAHs) were investigated by 1D and 2D (1)H NMR spectroscopy, UV/Vis absorption and emission titration studies. 2D and DOSY NMR spectroscopies support the sandwiched binding mode based on 1:1 host-guest interactions. The binding constants (K(S)) of complex 1 for various PAHs were determined by NMR titration studies and the values were found to span up to an order of 10(4)  M(-1) for coronene to no observable interaction for benzene, indicating that the π-surface area is important for such host-guest interactions. The substituent effect on the host-guest interaction based on the guest series of 9-substituted anthracenes was also studied. In general, a stronger interaction was observed for the anthracene guest with electron-donating groups, although steric and π-conjugation factors cannot be completely excluded. The photophysical responses of complex 1 upon addition of various PAHs were measured by UV/Vis and emission titration studies. The UV/Vis absorption spectra were found to show a drop in absorbance of the metal-to-ligand charge-transfer (MLCT) and ligand-to-ligand charge-transfer (LLCT) admixture band upon addition of various guest molecules to 1, whereas the emission behavior was found to change differently depending on the guest molecules, showing emission enhancement and/or quenching. It was found that emission quenching occurred either via energy transfer or electron transfer pathway or both, while emission enhancement was caused by the increase in rigidity of complex 1 as a result of host-guest interaction.

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

    ERIC Educational Resources Information Center

    Cram, Donald J.

    1988-01-01

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

  5. Emerging Supramolecular Therapeutic Carriers Based on Host-Guest Interactions.

    PubMed

    Karim, Anis Abdul; Dou, Qingqing; Li, Zibiao; Loh, Xian Jun

    2016-05-06

    Recent advances in host-guest chemistry have significantly influenced the construction of supramolecular soft biomaterials. The highly selective and non-covalent interactions provide vast possibilities of manipulating supramolecular self-assemblies at the molecular level, allowing a rational design to control the sizes and morphologies of the resultant objects as carrier vehicles in a delivery system. In this Focus Review, the most recent developments of supramolecular self-assemblies through host-guest inclusion, including nanoparticles, micelles, vesicles, hydrogels, and various stimuli-responsive morphology transition materials are presented. These sophisticated materials with diverse functions, oriented towards therapeutic agent delivery, are further summarized into several active domains in the areas of drug delivery, gene delivery, co-delivery and site-specific targeting deliveries. Finally, the possible strategies for future design of multifunctional delivery carriers by combining host-guest chemistry with biological interface science are proposed.

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

    PubMed

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

    2014-07-15

    CONSPECTUS: In host-guest chemistry, a larger host molecule selectively and noncovalently binds to a smaller guest molecule or ion. Early studies of host-guest chemistry focused on the recognition of spherical metal or ammonium ions by macrocyclic hosts, such as cyclic crown ethers. In these systems, preorganization enables their binding sites to cooperatively contact and attract a guest. Although some open-chain crown ether analogues possess similar, but generally lower, binding affinities, the design of acyclic molecular recognition hosts has remained challenging. One of the most successful examples was rigid molecular tweezers, acyclic covalently bonded preorganized host molecules with open cavities that bind tightly as they stiffen. Depending on the length of the atomic backbones, hydrogen bonding-driven aromatic amide foldamers can form open or closed cavities. Through rational design of the backbones and the introduction of added functional groups, researchers can regulate the shape and size of the cavity. The directionality of hydrogen bonding and the inherent rigidity of aromatic amide units allow researchers to predict both the shape and size of the cavity of an aromatic amide foldamer. Therefore, researchers can then design guest molecules with structure that matches the cavity shape, size, and binding sites of the foldamer host. In addition, because hydrogen bonds are dynamic, researchers can design structures that can adapt to outside stimuli to produce responsive supramolecular architectures. In this Account, we discuss how aromatic amide and hydrazide foldamers induced by hydrogen bonding can produce responsive host-guest systems, based on research by our group and others. First we highlight the helical chirality induced as binding occurs in solution, which includes the induction of helicity by chiral guests in oligomeric and polymeric foldamers, the formation of diastereomeric complexes between chiral foldamer hosts and guests, and the induction of

  7. Host-guest chemistry in two-dimensional supramolecular networks.

    PubMed

    Teyssandier, Joan; Feyter, Steven De; Mali, Kunal S

    2016-09-20

    Nanoporous supramolecular networks physisorbed on solid surfaces have been extensively used to immobilize a variety of guest molecules. Host-guest chemistry in such two-dimensional (2D) porous networks is a rapidly expanding field due to potential applications in separation technology, catalysis and nanoscale patterning. Diverse structural topologies with high crystallinity have been obtained to capture molecular guests of different sizes and shapes. A range of non-covalent forces such as hydrogen bonds, van der Waals interactions, coordinate bonds have been employed to assemble the host networks. Recent years have witnessed a surge in the activity in this field with the implementation of rational design strategies for realizing controlled and selective guest capture. In this feature article, we review the development in the field of surface-supported host-guest chemistry as studied by scanning tunneling microscopy (STM). Typical host-guest architectures studied on solid surfaces, both under ambient conditions at the solution-solid interface as well as those formed at the ultrahigh vacuum (UHV)-solid interface, are described. We focus on isoreticular host networks, hosts functionalized pores and dynamic host-guest systems that respond to external stimuli.

  8. Supramolecular host guest complexes based on cyclodextrin diphenylhexatriene

    NASA Astrophysics Data System (ADS)

    Rabara, L.; Aranyosiova, M.; Velic, D.

    2006-07-01

    Supramolecular host-guest complex cyclodextrin-diphenylhexatriene as a model of noncovalent binding is studied by means of time-of-flight secondary ion mass spectrometry. Cyclodextrin and diphenylhexatriene are in forms of β-cyclodextrin (C 42H 70O 35) and 1,6-diphenyl-1,3,5-hexatriene (C 18H 16), respectively. The whole intact supramolecular host-guest 1:1 complex between cyclodextrin and diphenylhexatriene is observed in cationized forms with Na at 1389.5 m/ z and with K at 1405.5 m/ z. The focus is on the higher ratio complexes, where the complexes of cyclodextrin-diphenylhexatriene with ratios of 1:2 and 2:1 are observed in cationized forms with Na at 1622 and at 2524 m/ z, and with K at 1638 and 2541 m/ z, respectively. These complexes are assumed to be basic building blocks of cyclodextrin-diphenylhexatriene nanowire structure.

  9. Charge Transport by Superexchange in Molecular Host-Guest Systems

    NASA Astrophysics Data System (ADS)

    Symalla, Franz; Friederich, Pascal; Massé, Andrea; Meded, Velimir; Coehoorn, Reinder; Bobbert, Peter; Wenzel, Wolfgang

    2016-12-01

    Charge transport in disordered organic semiconductors is generally described as a result of incoherent hopping between localized states. In this work, we focus on multicomponent emissive host-guest layers as used in organic light-emitting diodes (OLEDs), and show using multiscale ab initio based modeling that charge transport can be significantly enhanced by the coherent process of molecular superexchange. Superexchange increases the rate of emitter-to-emitter hopping, in particular if the emitter molecules act as relatively deep trap states, and allows for percolation path formation in charge transport at low guest concentrations.

  10. Supramolecular Recognition Forces: An Examination of Weak Metal-Metal Interactions in Host-Guest Formation

    SciTech Connect

    Crowley, James D.; Steele, Ian M.; Bosnich, B.

    2008-10-03

    Molecular receptors consisting of two parallel-disposed terpy-M-Cl units (M = Pd{sup 2+}, Pt{sup 2+}) are used to form host-guest adducts with aromatic molecules and with neutral square-planar Pt{sup 2+} complexes. Host-guest formation is controlled by several factors including {pi}-{pi} interactions and, in some cases, weak Pt-Pt interactions between the host and the guest. This latter interaction was examined by comparing the host-guest stability of adducts formed by isoelectronic Pt{sup 2+} and Au{sup 3+} complexes with the Pt{sup 2+} receptor. Consistently, the former is more stable.

  11. A Photoresponsive Orthogonal Supramolecular Complex Based on Host-Guest Interactions.

    PubMed

    Wang, Dongsheng; Wagner, Manfred; Saydjari, Andrew K; Mueller, Julius; Winzen, Svenja; Butt, Hans-Jürgen; Wu, Si

    2017-02-21

    We synthesized a novel green-light-responsive tetra-ortho-isopropoxy-substituted azobenzene (ipAzo). Cis-ipAzo forms a strong host-guest complex with γ-cyclo dextrin (γ-CD) whereas trans-ipAzo binds weakly. This new photoresponsive host-guest interaction is reverse to the well-known azobenzene (Azo)/α-cyclodextrin (α-CD) complex, which is strong only between trans-Azo and α-CD. By combining the UV-light-responsive Azo/α-CD and green-light-responsive ipAzo/γ-CD host-guest complexes, a photoresponsive orthogonal supramolecular system is developed.

  12. Highly Flexible, Tough, and Self-Healing Supramolecular Polymeric Materials Using Host-Guest Interaction.

    PubMed

    Nakahata, Masaki; Takashima, Yoshinori; Harada, Akira

    2015-09-23

    Flexible, tough, and self-healable polymeric materials are promising to be a solution to the energy problem by substituting for conventional heavy materials. A fusion of supramolecular chemistry and polymer chemistry is a powerful method to create such intelligent materials. Here, a supramolecular polymeric material using multipoint molecular recognition between cyclodextrin (CD) and hydrophobic guest molecules at polymer side chain is reported. A transparent, flexible, and tough hydrogel (host-guest gel) is formed by a simple preparation procedure. The host-guest gel shows self-healing property in both wet state and dry state due to reversible nature of host-guest interaction. The practical utility of the host-guest gel as a scratch curable coating is demonstrated.

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

    NASA Astrophysics Data System (ADS)

    McBride, Emma; Munro, Keith; McMahon, Malcolm

    2013-06-01

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

  14. Calculating binding free energies of host-guest systems using the AMOEBA polarizable force field.

    PubMed

    Bell, David R; Qi, Rui; Jing, Zhifeng; Xiang, Jin Yu; Mejias, Christopher; Schnieders, Michael J; Ponder, Jay W; Ren, Pengyu

    2016-11-09

    Molecular recognition is of paramount interest in many applications. Here we investigate a series of host-guest systems previously used in the SAMPL4 blind challenge by using molecular simulations and the AMOEBA polarizable force field. The free energy results computed by Bennett's acceptance ratio (BAR) method using the AMOEBA polarizable force field ranked favorably among the entries submitted to the SAMPL4 host-guest competition [Muddana, et al., J. Comput.-Aided Mol. Des., 2014, 28, 305-317]. In this work we conduct an in-depth analysis of the AMOEBA force field host-guest binding thermodynamics by using both BAR and the orthogonal space random walk (OSRW) methods. The binding entropy-enthalpy contributions are analyzed for each host-guest system. For systems of inordinate binding entropy-enthalpy values, we further examine the hydrogen bonding patterns and configurational entropy contribution. The binding mechanism of this series of host-guest systems varies from ligand to ligand, driven by enthalpy and/or entropy changes. Convergence of BAR and OSRW binding free energy methods is discussed. Ultimately, this work illustrates the value of molecular modelling and advanced force fields for the exploration and interpretation of binding thermodynamics.

  15. Light-Switchable Self-Healing Hydrogel Based on Host-Guest Macro-Crosslinking.

    PubMed

    Yang, Qiaofeng; Wang, Ping; Zhao, Chuanzhuang; Wang, Wenqin; Yang, Jingfa; Liu, Qiao

    2017-03-01

    A self-healing hydrogel is prepared by crosslinking acrylamide with a host-guest macro-crosslinker assembled from poly(β-cyclodextrin) nanogel and azobenzeneacrylamide. The photoisomerizable azobenzene moiety can change its binding affinity with β-cyclodextrin, therefore the crosslinking density and rheology property of the hydrogel can be tuned with light stimulus. The hydrogel can repair its wound autonomously through the dynamic host-guest interaction. In addition, the wounded hydrogel will lose its ability of self-healing when exposed to ultraviolet light, and the self-healing behavior can be recovered upon the irradiation of visible light. The utilizing of host-guest macro-crosslinking approach manifests the as-prepared hydrogel reversible and light-switchable self-healing property, which would broaden the potential applications of self-healing polymers.

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

    PubMed Central

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

    2015-01-01

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

  17. Supramolecular chemistry 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

  18. 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…

  19. 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

    2012-01-09

    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.

  20. Determination of association constant of host-guest supramolecular complex (molecular recognition of carbamazepine, antiseizure drug, with calix(4)arene).

    PubMed

    Meenakshi, C; Jayabal, P; Ramakrishnan, V

    2015-12-05

    The thermodynamic property of the host-guest, inclusion complex formed between p-t-butyl calix(4)arene which is a supramolecule, and the antiseizure drug, carbamazepine was studied. p-t-Butyl calix(4)arene has been used as a host molecule and carbamazepine as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(4)arene with carbamazepine. The stochiometry of the host-guest complexes formed and the association constant were determined. An interesting 1:2 stochiometric host-guest complex was 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. Molecular dimension of the host molecule plays a vital role in the formation of the host-guest stochiometric complexes.

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

    PubMed

    Wei, Peifa; Yan, Xuzhou; Huang, Feihe

    2015-02-07

    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.

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

    PubMed

    Hu, Jinming; Liu, Shiyong

    2014-07-15

    CONSPECTUS: All living organisms and soft matter are intrinsically responsive and adaptive to external stimuli. Inspired by this fact, tremendous effort aiming to emulate subtle responsive features exhibited by nature has spurred the invention of a diverse range of responsive polymeric materials. Conventional stimuli-responsive polymers are constructed via covalent bonds and can undergo reversible or irreversible changes in chemical structures, physicochemical properties, or both in response to a variety of external stimuli. They have been imparted with a variety of emerging applications including drug and gene delivery, optical sensing and imaging, diagnostics and therapies, smart coatings and textiles, and tissue engineering. On the other hand, in comparison with molecular chemistry held by covalent bonds, supramolecular chemistry built on weak and reversible noncovalent interactions has emerged as a powerful and versatile strategy for materials fabrication due to its facile accessibility, extraordinary reversibility and adaptivity, and potent applications in diverse fields. Typically involving more than one type of noncovalent interactions (e.g., hydrogen bonding, metal coordination, hydrophobic association, electrostatic interactions, van der Waals forces, and π-π stacking), host-guest recognition refers to the formation of supramolecular inclusion complexes between two or more entities connected together in a highly controlled and cooperative manner. The inherently reversible and adaptive nature of host-guest molecular recognition chemistry, stemming from multiple noncovalent interactions, has opened up a new platform to construct novel types of stimuli-responsive materials. The introduction of host-guest chemistry not only enriches the realm of responsive materials but also confers them with promising new applications. Most intriguingly, the integration of responsive polymer building blocks with host-guest recognition motifs will endow the former with

  3. Synthesis, optical and electrochemical properties of Zn-porphyrin for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Kotteswaran, S.; Pandian, M. Senthil; Ramasamy, P.

    2016-05-01

    Zn-Porphyrin dye has been synthesized by the reaction between aldehydes and pyrrole. The dye structure was confirmed by 1H NMR, 13C NMR spectrum. The functional group of the dye molecule was confirmed by FTIR spectrum. The UV-Vis-NIR absorption spectrum of Zn-Porphyrin in DMF solution was recorded in spectrophotometer. The UV-Vis NIR spectrum of dye exhibits a strong Soret band and Q-band. Cyclic Voltammograms were obtained with three electrode systems: Pt as counter electrode, saturated calomel used as a reference electrode and glassy carbon as working electrode at a scan rate of 100 mV/s. The curves recorded the oxidation of 0.5 mM compound Zn-Porphyrin in a dichloromethane solution containing 0.1M TBAP as supporting electrolyte, reveal two successive quasi reversible redox couples with the first anodic and cathodic peak potentials of -0.2 V and -1 V. The second anodic and cathodic peak potentials are 0.82 V and 0.01 V respectively.

  4. Cyclodextrin-based host-guest supramolecular nanoparticles for delivery: from design to applications.

    PubMed

    Hu, Qi-Da; Tang, Gu-Ping; Chu, Paul K

    2014-07-15

    CONSPECTUS: Efficient assembly in host-guest interactions is crucial to supramolecular nanotechnology. Cyclodextrins (CDs), which possess a hydrophilic exterior surface and hydrophobic interior cavity on the truncated cone, improve the biocompatibility of nanodelivery systems, and hence, supramolecular approaches utilizing CDs can improve and expand the design and applications of functional delivery systems. Owing to good inclusion ability, αCD and βCD are commonly used in the design and construction of supramolecular structures. In this Account, we describe the design strategies to adopt CDs in host-guest delivery systems. Modification of CDs with polymers is popular in current research due to the potential benefits rendered by cationic protection and improved capability. While the process has only minor influence on the host characteristics of the CD cavity, the interaction between the CD and the guest moiety imparts new attributes to the nanosystems with guest-decorated functional groups such as adamantyl poly(ethylene glycol) (PEG) for coating protection, hybrid guests for conformational flexibility, and adamantyl prodrugs for drug delivery. Some specific agents form inclusion complexes with the polymerized βCDs directly and core-shell nanoparticles with hydrophobic cores and are usually created to carry insoluble drugs while the hydrophilic shells offer protection. These unique designs provide the means to practically adapt special characteristics for additional functions or co-delivery. In order to be accepted clinically, delivery systems need to possess extra functions such as controlled particle size, biodegradability, controlled release, and targeted delivery to overcome the hurdles in delivery. These features can be added to biomaterials by self-assembly of functional groups facilitated by the host-guest interactions. Size control by hybridization of switchable polymer compartments in supramolecular structures contributes to the biodistribution utility

  5. 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

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

    PubMed

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

    2015-05-01

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

  7. 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.

  8. Host-guest complexation of cucurbit[8]uril with two enantiomers

    NASA Astrophysics Data System (ADS)

    Gao, Zhong-Zheng; Lin, Rui-Lian; Bai, Dong; Tao, Zhu; Liu, Jing-Xin; Xiao, Xin

    2017-03-01

    Host-guest complexation of cucurbit[8]uril (Q[8]) with two enantiomers, D-3-(2-naphthyl)-alanine (D-NA) and L-3-(2-naphthyl)-alanine (L-NA), has been fully investigated. Experimental data indicate that double guests reside within the cavity of Q[8] in both aqueous solution and solid state, generating highly stable homoternary complexes D-NA2@Q[8] and L-NA2@Q[8].

  9. Host-guest complexation of cucurbit[8]uril with two enantiomers

    PubMed Central

    Gao, Zhong-Zheng; Lin, Rui-Lian; Bai, Dong; Tao, Zhu; Liu, Jing-Xin; Xiao, Xin

    2017-01-01

    Host-guest complexation of cucurbit[8]uril (Q[8]) with two enantiomers, D-3-(2-naphthyl)-alanine (D-NA) and L-3-(2-naphthyl)-alanine (L-NA), has been fully investigated. Experimental data indicate that double guests reside within the cavity of Q[8] in both aqueous solution and solid state, generating highly stable homoternary complexes D-NA2@Q[8] and L-NA2@Q[8]. PMID:28300189

  10. Electrochemiluminescence aptasensor for adenosine triphosphate detection using host-guest recognition between metallocyclodextrin complex and aptamer.

    PubMed

    Chen, Hong; Chen, Qiong; Zhao, Yingying; Zhang, Fan; Yang, Fan; Tang, Jie; He, Pingang

    2014-04-01

    A sensitive and label-free electrochemiluminescence (ECL) aptasensor for the detection of adenosine triphosphate (ATP) was successfully designed using host-guest recognition between a metallocyclodextrin complex, i.e., tris(bipyridine)ruthenium(II)-β-cyclodextrin [tris(bpyRu)-β-CD], and an ATP-binding aptamer. In the protocol, the NH2-terminated aptamer was immobilized on a glassy carbon electrode (GCE) by a coupling interaction. After host-guest recognition between tris(bpyRu)-β-CD and aptamer, the tris(bpyRu)-β-CD/aptamer/GCE produced a strong ECL signal as a result of the photoactive properties of tris(bpyRu)-β-CD. However, in the presence of ATP, the ATP/aptamer complex was formed preferentially, which restricted host-guest recognition, and therefore less tris(bpyRu)-β-CD was attached to the GCE surface, resulting in an obvious decrease in the ECL intensity. Under optimal determination conditions, an excellent logarithmic linear relationship between the ECL decrease and ATP concentration was obtained in the range 10.0-0.05 nM, with a detection limit of 0.01 nM at the S/N ratio of 3. The proposed ECL-based ATP aptasensor exhibited high sensitivity and selectivity, without time-consuming signal-labeling procedures, and is considered to be a promising model for detection of aptamer-specific targets.

  11. 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

  12. Defined Host-Guest Chemistry on Nanocarbon for Sustained Inhibition of Cancer.

    PubMed

    Ostadhossein, Fatemeh; Misra, Santosh K; Mukherjee, Prabuddha; Ostadhossein, Alireza; Daza, Enrique; Tiwari, Saumya; Mittal, Shachi; Gryka, Mark C; Bhargava, Rohit; Pan, Dipanjan

    2016-08-22

    Signal transducer and activator of transcription factor 3 (STAT-3) is known to be overexpressed in cancer stem cells. Poor solubility and variable drug absorption are linked to low bioavailability and decreased efficacy. Many of the drugs regulating STAT-3 expression lack aqueous solubility; hence hindering efficient bioavailability. A theranostics nanoplatform based on luminescent carbon particles decorated with cucurbit[6]uril is introduced for enhancing the solubility of niclosamide, a STAT-3 inhibitor. The host-guest chemistry between cucurbit[6]uril and niclosamide makes the delivery of the hydrophobic drug feasible while carbon nanoparticles enhance cellular internalization. Extensive physicochemical characterizations confirm successful synthesis. Subsequently, the host-guest chemistry of niclosamide and cucurbit[6]uril is studied experimentally and computationally. In vitro assessments in human breast cancer cells indicate approximately twofold enhancement in IC50 of drug. Fourier transform infrared and fluorescence imaging demonstrate efficient cellular internalization. Furthermore, the catalytic biodegradation of the nanoplatforms occur upon exposure to human myeloperoxidase in short time. In vivo studies on athymic mice with MCF-7 xenograft indicate the size of tumor in the treatment group is half of the controls after 40 d. Immunohistochemistry corroborates the downregulation of STAT-3 phosphorylation. Overall, the host-guest chemistry on nanocarbon acts as a novel arsenal for STAT-3 inhibition.

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

    NASA Astrophysics Data System (ADS)

    Degtyareva, V. F.

    2015-11-01

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

  14. Sunlight induced cycloaddition and host-guest property of self-assembled organometallic macrocycles based on a versatile building block.

    PubMed

    Wu, Tong; Weng, Lin-Hong; Jin, Guo-Xin

    2012-05-11

    Organometallic rectangle 1 which undergoes [2+2] cycloaddition upon irradiation with sunlight and organometallic prism 3 which displayed interesting host-guest property were self-assembled based on a versatile building block.

  15. Triple-helix propensity of hydroxyproline and fluoroproline: comparison of host-guest and repeating tripeptide collagen models.

    PubMed

    Persikov, Anton V; Ramshaw, John A M; Kirkpatrick, Alan; Brodsky, Barbara

    2003-09-24

    Peptide models have proved important in defining the structural features of the collagen triple-helix. Some models are based on multiple repeats of a given tripeptide unit, while a host-guest design includes an individual tripeptide unit substituted within a constant repeating Pro-Hyp-Gly framework. In the present study, proline, hydroxyproline, and fluoroproline residues are incorporated in X- or Y-positions of a guest triplet in the host-guest peptide design. All host-guest peptides, including Hyp-Pro-Gly, formed stable triple-helices, even though a triple-helix cannot be formed by (Hyp-Pro-Gly)10. The order of stability Pro-Hyp-Gly > Pro-Pro-Gly > Hyp-Pro-Gly remains the same in all models, while the Pro-Flp-Gly is very stabilizing in a repeating context but destabilizing in a host-guest context. The range of thermal stabilities and calorimetric enthalpies is very small among the five host-guest peptides, consistent with the concept that the effect of one Xaa-Yaa-Gly tripeptide unit in the host-guest system would be less than the much larger variations when there are 10 repeating units. However, a simple additive model based on host-guest peptides predicts a greater stability than experimentally observed. The difference in stability contributions of the same tripeptide unit in host-guest versus repeating tripeptide systems illustrates the impact of sequence environment on stability, and factors that play a role include ring puckering as a consequence of electron inductive effects, residual monomer structure, and native state hydration networks.

  16. 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

  17. Overview of the SAMPL5 host-guest challenge: Are we doing better?

    NASA Astrophysics Data System (ADS)

    Yin, Jian; Henriksen, Niel M.; Slochower, David R.; Shirts, Michael R.; Chiu, Michael W.; Mobley, David L.; Gilson, Michael K.

    2017-01-01

    The ability to computationally predict protein-small molecule binding affinities with high accuracy would accelerate drug discovery and reduce its cost by eliminating rounds of trial-and-error synthesis and experimental evaluation of candidate ligands. As academic and industrial groups work toward this capability, there is an ongoing need for datasets that can be used to rigorously test new computational methods. Although protein-ligand data are clearly important for this purpose, their size and complexity make it difficult to obtain well-converged results and to troubleshoot computational methods. Host-guest systems offer a valuable alternative class of test cases, as they exemplify noncovalent molecular recognition but are far smaller and simpler. As a consequence, host-guest systems have been part of the prior two rounds of SAMPL prediction exercises, and they also figure in the present SAMPL5 round. In addition to being blinded, and thus avoiding biases that may arise in retrospective studies, the SAMPL challenges have the merit of focusing multiple researchers on a common set of molecular systems, so that methods may be compared and ideas exchanged. The present paper provides an overview of the host-guest component of SAMPL5, which centers on three different hosts, two octa-acids and a glycoluril-based molecular clip, and two different sets of guest molecules, in aqueous solution. A range of methods were applied, including electronic structure calculations with implicit solvent models; methods that combine empirical force fields with implicit solvent models; and explicit solvent free energy simulations. The most reliable methods tend to fall in the latter class, consistent with results in prior SAMPL rounds, but the level of accuracy is still below that sought for reliable computer-aided drug design. Advances in force field accuracy, modeling of protonation equilibria, electronic structure methods, and solvent models, hold promise for future improvements.

  18. Host-guest interaction and structural ordering in polymeric nanoassemblies: Influence of molecular design.

    PubMed

    Antoniuk, Iurii; Plazzotta, Beatrice; Wintgens, Véronique; Volet, Gisèle; Nielsen, Thorbjørn T; Pedersen, Jan Skov; Amiel, Catherine

    2017-02-24

    Host-guest nanoassemblies made from spontaneous self-association of host and guest polymers in aqueous solutions have been studied. The specific motivation behind this work was to clarify the impact of the molecular design of the polymers on the interactions between them and on the inner structure of the resulting nanoassemblies. The polymers were composed of a dextran backbone, functionalized with either pendant β-cyclodextrin (CD) or adamantyl (Ada). Those groups were connected to the backbone either directly or with hydrophilic polyethylene glycol (PEG) spacers. To study the impact of those spacers we have proposed a synthetic pathway to new guest polymers. The latter relied on the use of thiol-substituted dextrans as a scaffold, which is subsequently transformed into PEG-Ada grafted guest polymers via nucleophile-mediated thiol-click reaction. Surface plasmon resonance (SPR) studies evidenced strong mutual affinities between the host and guest polymers and showed that the stoichiometry was close to the ideal one (CD/Ada = 1/1) when PEG spacers were introduced. The structure of the nanoassemblies was studied by a combination of dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS). The nature of the individual host or guest polymers has a strong impact on the size and internal structure of the resulting nanoassemblies. The presence of PEG spacers in the polymers led to smaller and less compact nanoassemblies, as evidenced by their large correlation length values (4-20nm compared to 2nm without PEG spacers). At the same time, all types of nanoassemblies appear to have radial density distribution with denser cores and pending polymer chains at the periphery. This study, centered on the influence of the molecular design on the host-guest interactions and structural ordering in polymeric nanoassemblies, will help to tailor host-guest nanoassemblies with attractive drug delivery profiles.

  19. Praseodymium(III)-based bis-metallacalix[4]arene with host-guest behaviour.

    PubMed

    Xu, Gong-Feng; Gamez, Patrick; Teat, Simon J; Tang, Jinkui

    2010-05-14

    The reaction of Pr(NO(3))(3).6H(2)O with the ligand 2-hydroxy-N-(2'-hydroxyethyl)-3-methoxybenzamide (H(3)L) in MeOH-MeCN generates the nonanuclear compound [Pr(9)(H(2)L)(8)(OH)(10)(NO(3))(8)](NO(3))(H(2)O)(2)(CH(3)CN) (), whose single-crystal X-ray structure reveals the presence of metallacalix[4]arene cavities that host guest molecules. The crystal packing of the antiferromagnetic Pr(9) cluster shows an intricate network of hydrogen bonds producing a one-dimensional supramolecular chain.

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

    SciTech Connect

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

    1997-12-31

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

  1. An electron-transfer photochromic crystalline MOF accompanying photoswitchable luminescence in a host-guest system.

    PubMed

    Liu, Yu-Shuang; Luo, Yu-Hui; Li, Li; Zhang, Hong

    2017-03-23

    A new electron transfer type photoactive host-guest supramolecule was constructed by introducing (CH3)2NH2(+) cations to the MOF framework. The resulting compound 1 exhibits reversible photochromic property without using photochromic components, resulting from photoinduced electron-transfer between the electron-rich anionic framework and the electron-deficient guest ions. In addition, a photoluminescence "on/off switch" occurs during the coloration-decoloration process. The raw materials are non-poisonous and harmless, hence compound 1 may be more cost-effective, clean, and harmless to the heath than existing photochromic materials.

  2. Host-Guest Assembly of a Molecular Reporter with Chiral Cyanohydrins for Assignment of Absolute Stereochemistry.

    PubMed

    Gholami, Hadi; Anyika, Mercy; Zhang, Jun; Vasileiou, Chrysoula; Borhan, Babak

    2016-06-27

    The absolute stereochemistry of cyanohydrins, derived from ketones and aldehydes, is obtained routinely, in a microscale and derivatization-free manner, upon their complexation with Zn-MAPOL, a zincated porphyrin host with a binding pocket comprised of a biphenol core. The host-guest complex leads to observable exciton-coupled circular dichroism (ECCD), the sign of which is easily correlated to the absolute stereochemistry of the bound cyanohydrin. A working model, based on the ECCD signal of cyanohydrins with known configuration, is proposed.

  3. Dual-responsive colloidal microcapsules based on host-guest interaction on solid templates.

    PubMed

    Li, Guangyu; Dong, Zhirui; Zhu, Yuting; Tong, Weijun; Gao, Changyou

    2016-08-01

    Colloidal microcapsules (MCs) have received considerable attention in the fields of microencapsulation, drug delivery as well as microreactors due to their unique nanoparticles-composed structure. In this study, dual-responsive colloidal MCs based on host-guest interaction were successfully fabricated via a layer-by-layer assembly method on sacrificial solid templates. Ferrocene-modified polyethylenimine (PEI-Fc) and cyclodextrin-modified polystyrene nanoparticles (PS-CD NPs) were used as building blocks for assembly. The colloidal MCs could be disassembled into nano-components upon addition of competitive adamantane (Ad) molecules or in the solution with a pH lower than 4.

  4. 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

    2015-03-04

    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.

  5. Host-Guest Engineering of Coordination Polymers for Highly Tunable Luminophores Based on Charge Transfer Emissions.

    PubMed

    Zhao, Bei; Li, Na; Wang, Xi; Chang, Ze; Bu, Xian-He

    2017-01-25

    Aiming at the targeted construction of coordination polymer luminophores, the engineering of host-guest architectures with charge transfer based emissions is performed by utilizing the interactions between the electron-deficient 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine (tpt) and electron-rich polycyclic aromatic hydrocarbons (PAHs) motifs as acceptors and donors, respectively. Through guest modulation of a prototype coordination polymer [Cd(tpt)(1,4-pda)(H2O)2]·(tpt)·(H2O)2 (1) (1,4-H2pda = 1,4-phenylenediacetic acid), a series of coordination polymers with different PAHs as guests, [Cd2(tpt)2(1,4-pda)2]·guest (2-5) (guest = triphenylene for 2, pyrene for 3, coronene for 4, and perylene for 5), are successfully fabricated. Distinct from 1, coordination polymers 2-5 reveal unique bilayer structures with PAHs interlayer and good stability, owing to the enhanced stacking interactions between tpt motifs and PAH guests. Moreover, their emissions cover a wide range of wavelength due to the effective guest to host charge transfer interactions between donor and acceptor motifs. Their readily tunable host-guest charge transfer based emissions make them good candidates as potential luminophores.

  6. Obtaining control of cell surface functionalizations via Pre-targeting and Supramolecular host guest interactions

    NASA Astrophysics Data System (ADS)

    Rood, Mark T. M.; Spa, Silvia J.; Welling, Mick M.; Ten Hove, Jan Bart; van Willigen, Danny M.; Buckle, Tessa; Velders, Aldrik H.; van Leeuwen, Fijs W. B.

    2017-01-01

    The use of mammalian cells for therapeutic applications is finding its way into modern medicine. However, modification or “training” of cells to make them suitable for a specific application remains complex. By envisioning a chemical toolbox that enables specific, but straight-forward and generic cellular functionalization, we investigated how membrane-receptor (pre)targeting could be combined with supramolecular host-guest interactions based on β-cyclodextrin (CD) and adamantane (Ad). The feasibility of this approach was studied in cells with membranous overexpression of the chemokine receptor 4 (CXCR4). By combining specific targeting of CXCR4, using an adamantane (Ad)-functionalized Ac-TZ14011 peptide (guest; KD = 56 nM), with multivalent host molecules that entailed fluorescent β-CD-Poly(isobutylene-alt-maleic-anhydride)-polymers with different fluorescent colors and number of functionalities, host-guest cell-surface modifications could be studied in detail. A second set of Ad-functionalized entities enabled introduction of additional surface functionalities. In addition, the attraction between CD and Ad could be used to drive cell-cell interactions. Combined we have shown that supramolecular interactions, that are based on specific targeting of an overexpressed membrane-receptor, allow specific and stable, yet reversible, surface functionalization of viable cells and how this approach can be used to influence the interaction between cells and their surroundings.

  7. Direct Measurement of Electron Transfer in Nanoscale Host-Guest Systems: Metallocenes in Carbon Nanotubes.

    PubMed

    McSweeney, Robert L; Chamberlain, Thomas W; Baldoni, Matteo; Lebedeva, Maria A; Davies, E Stephen; Besley, Elena; Khlobystov, Andrei N

    2016-09-12

    Electron-transfer processes play a significant role in host-guest interactions and determine physicochemical phenomena emerging at the nanoscale that can be harnessed in electronic or optical devices, as well as biochemical and catalytic systems. A novel method for qualifying and quantifying the electronic doping of single walled carbon nanotubes (SWNTs) using electrochemistry has been developed that establishes a direct link between these experimental measurements and ab initio DFT calculations. Metallocenes such as cobaltocene and methylated ferrocene derivatives were encapsulated inside SWNTs (1.4 nm diameter) and cyclic voltammetry (CV) was performed on the resultant host-guest systems. The electron transfer between the guest molecules and the host SWNTs is measured as a function of shift in the redox potential (E1/2 ) of Co(II) /Co(I) , Co(III) /Co(II) and Fe(III) /Fe(II) . Furthermore, the shift in E1/2 is inversely proportional to the nanotube diameter. To quantify the amount of electron transfer from the guest molecules to the SWNTs, a novel method using coulometry was developed, allowing the mapping of the density of states and the Fermi level of the SWNTs. Correlated with theoretical calculations, coulometry provides an accurate indication of n/p-doping of the SWNTs.

  8. Host-Guest Complexes of Carboxylated Pillar[n]arenes With Drugs.

    PubMed

    Wheate, Nial J; Dickson, Kristie-Ann; Kim, Ryung Rae; Nematollahi, Alireza; Macquart, René B; Kayser, Veysel; Yu, Guocan; Church, W Bret; Marsh, Deborah J

    2016-12-01

    Pillar[n]arenes are a new family of nanocapsules that have shown application in a number of areas, but because of their poor water solubility their biomedical applications are limited. Recently, a method of synthesizing water-soluble pillar[n]arenes was developed. In this study, carboxylated pillar[n]arenes (WP[n], n = 6 or 7) have been examined for their ability to form host-guest complexes with compounds relevant to drug delivery and biodiagnostic applications. Both pillar[n]arenes form host-guest complexes with memantine, chlorhexidine hydrochloride, and proflavine by (1)H nuclear magnetic resonance and modeling. Binding is stabilized by hydrophobic effects within the cavities, and hydrogen bonding and electrostatic interactions at the portals. Encapsulation within WP[6] results in the complete and efficient quenching of proflavine fluorescence, giving rise to "on" and "off" states that have potential in biodiagnostics. The toxicity of the pillar[n]arenes was examined using in vitro growth assays with the OVCAR-3 and HEK293 cell lines. The pillar[n]arenes are relatively nontoxic to cells except at high doses and after prolonged continuous exposure. Overall, the results show that there could be a potentially large range of medical applications for carboxylated pillar[n]arene nanocapsules.

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

    PubMed

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

    2015-11-01

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

  10. Obtaining control of cell surface functionalizations via Pre-targeting and Supramolecular host guest interactions.

    PubMed

    Rood, Mark T M; Spa, Silvia J; Welling, Mick M; Ten Hove, Jan Bart; van Willigen, Danny M; Buckle, Tessa; Velders, Aldrik H; van Leeuwen, Fijs W B

    2017-01-06

    The use of mammalian cells for therapeutic applications is finding its way into modern medicine. However, modification or "training" of cells to make them suitable for a specific application remains complex. By envisioning a chemical toolbox that enables specific, but straight-forward and generic cellular functionalization, we investigated how membrane-receptor (pre)targeting could be combined with supramolecular host-guest interactions based on β-cyclodextrin (CD) and adamantane (Ad). The feasibility of this approach was studied in cells with membranous overexpression of the chemokine receptor 4 (CXCR4). By combining specific targeting of CXCR4, using an adamantane (Ad)-functionalized Ac-TZ14011 peptide (guest; KD = 56 nM), with multivalent host molecules that entailed fluorescent β-CD-Poly(isobutylene-alt-maleic-anhydride)-polymers with different fluorescent colors and number of functionalities, host-guest cell-surface modifications could be studied in detail. A second set of Ad-functionalized entities enabled introduction of additional surface functionalities. In addition, the attraction between CD and Ad could be used to drive cell-cell interactions. Combined we have shown that supramolecular interactions, that are based on specific targeting of an overexpressed membrane-receptor, allow specific and stable, yet reversible, surface functionalization of viable cells and how this approach can be used to influence the interaction between cells and their surroundings.

  11. Obtaining control of cell surface functionalizations via Pre-targeting and Supramolecular host guest interactions

    PubMed Central

    Rood, Mark T. M.; Spa, Silvia J.; Welling, Mick M.; ten Hove, Jan Bart; van Willigen, Danny M.; Buckle, Tessa; Velders, Aldrik H.; van Leeuwen, Fijs W. B.

    2017-01-01

    The use of mammalian cells for therapeutic applications is finding its way into modern medicine. However, modification or “training” of cells to make them suitable for a specific application remains complex. By envisioning a chemical toolbox that enables specific, but straight-forward and generic cellular functionalization, we investigated how membrane-receptor (pre)targeting could be combined with supramolecular host-guest interactions based on β-cyclodextrin (CD) and adamantane (Ad). The feasibility of this approach was studied in cells with membranous overexpression of the chemokine receptor 4 (CXCR4). By combining specific targeting of CXCR4, using an adamantane (Ad)-functionalized Ac-TZ14011 peptide (guest; KD = 56 nM), with multivalent host molecules that entailed fluorescent β-CD-Poly(isobutylene-alt-maleic-anhydride)-polymers with different fluorescent colors and number of functionalities, host-guest cell-surface modifications could be studied in detail. A second set of Ad-functionalized entities enabled introduction of additional surface functionalities. In addition, the attraction between CD and Ad could be used to drive cell-cell interactions. Combined we have shown that supramolecular interactions, that are based on specific targeting of an overexpressed membrane-receptor, allow specific and stable, yet reversible, surface functionalization of viable cells and how this approach can be used to influence the interaction between cells and their surroundings. PMID:28057918

  12. 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 π-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.

  13. Hydrogen bonding assemblies in host guest complexes with 18-crown-6

    NASA Astrophysics Data System (ADS)

    Fonari, M. S.; Simonov, Yu. A.; Kravtsov, V. Ch.; Lipkowski, J.; Ganin, E. V.; Yavolovskii, A. A.

    2003-02-01

    Recent X-ray crystal structural data for two novel 1:2 host-guest complexes of 18-crown-6 with neutral organic molecules, thiaamide hydrazide of 2-aminobenzoic acid and thiaamide hydrazide of 4-amino-1,2,5-thiadiazole-3-carbonic acid are reported. The supramolecular structures of these two and five relative complexes are discussed from the point of view of participation of donor groups in coordination with the crown ether, and donor and acceptor groups in the self-assembly of the guest molecules. Guest molecules have incorporated amine and hydrazine moieties as proton donors and carbonyl oxygen and sulfur (in thiadiazole and in thiaamine moieties) as proton acceptors. The guest-guest interactions appeared to be crucial in the final architecture.

  14. Host-Guest Strategy to Reversibly Control a Chloride Carrier Process with Cyclodextrins.

    PubMed

    Gravel, Julien; Kempf, Julie; Schmitzer, Andreea

    2015-12-14

    Herein, we report a reversible modular chloride transport process based on host-guest competitive interactions between an imidazolium-based chloride carrier and beta-cyclodextrin. We report evidence for the formation of the supramolecular complex between 1,3-bis(2-(adamantan-1-yl)ethyl)imidazolium bis(trifluorometyl-sulfonyl)imide with two β-cyclodextrins. Through fluorescence assays in liposomes and black lipid membrane experiments, we demonstrate that the formation of the supramolecular complex results in the inhibition of the chloride transport. We show that the chloride transport process can be entirely restored in the presence of competitive adamantyl-functionalized guests. This is the first example of an entirely reversible modular chloride transport process in phospholipid bilayers involving a mobile carrier transporter and cyclodextrin supramolecular complex.

  15. 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 μm) 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.

  16. Laser Spectroscopic Study of Cold Gas-Phase Host-Guest Complexes of Crown Ethers.

    PubMed

    Ebata, Takayuki; Inokuchi, Yoshiya

    2016-06-01

    The structure, molecular recognition, and inclusion effect on the photophysics of guest species are investigated for neutral and ionic cold host-guest complexes of crown ethers (CEs) in the gas phase. Here, the cold neutral host-guest complexes are produced by a supersonic expansion technique and the cold ionic complexes are generated by the combination of electrospray ionization (ESI) and a cryogenically cooled ion trap. The host species are 3n-crown-n (3nCn; n = 4, 5, 6, 8) and (di)benzo-3n-crown-n ((D)B3nCn; n = 4, 5, 6, 8). For neutral guests, we have chosen water and aromatic molecules, such as phenol and benzenediols, and as ionic species we have chosen alkali-metal ions (M(+) ). The electronic spectra and isomer-specific vibrational spectra for the complexes are observed with various laser spectroscopic methods: laser-induced fluorescence (LIF); ultraviolet-ultraviolet hole-burning (UV-UV HB); and IR-UV double resonance (IR-UV DR) spectroscopy. The obtained spectra are analyzed with the aid of quantum chemical calculations. We will discuss how the host and guest species change their flexible structures for forming best-fit stable complexes (induced fitting) and what kinds of interactions are operating for the stabilization of the complexes. For the alkali metal ion•CE complexes, we investigate the solvation effect by attaching water molecules. In addition to the ground-state stabilization problem, we will show that the complexation leads to a drastic effect on the excited-state electronic structure and dynamics of the guest species, which we call a "cage-like effect".

  17. Host-guest complexation of [60]fullerenes and porphyrins enabled by "click chemistry".

    PubMed

    Ho, Khanh-Hy Le; Hijazi, Ismail; Rivier, Lucie; Gautier, Christelle; Jousselme, Bruno; de Miguel, Gustavo; Romero-Nieto, Carlos; Guldi, Dirk M; Heinrich, Benoit; Donnio, Bertrand; Campidelli, Stéphane

    2013-08-19

    Herein the synthesis, characterization, and organization of a first-generation dendritic fulleropyrrolidine bearing two pending porphyrins are reported. Both the dendron and the fullerene derivatives were synthesized by Cu(I) -catalyzed alkyne-azide cycloaddition (CuAAC). The electron-donor-acceptor conjugate possesses a shape that allows the formation of supramolecular complexes by encapsulation of C60 within the jaws of the two porphyrins of another molecule. The interactions between the two photoactive units (i.e., C60 and Zn-porphyrin) were confirmed by cyclic voltammetry as well as by steady-state and time-resolved spectroscopy. For example, a shift of about 85 mV was found for the first reduction of C60 in the electron-donor-acceptor conjugate compared with the parent molecules, which indicates that C60 is included in the jaws of the porphyrin. The fulleropyrrolidine compound exhibits a rich polymorphism, which was corroborated by AFM and SEM. In particular, it was found to form supramolecular fibrils when deposited on substrates. The morphology of the fibrils suggests that they are formed by several rows of fullerene-porphyrin complexes.

  18. Dynamic Cross-Linking of Polymeric Binders Based on Host-Guest Interactions for Silicon Anodes in Lithium Ion Batteries.

    PubMed

    Kwon, Tae-woo; Jeong, You Kyeong; Deniz, Erhan; AlQaradawi, Siham Y; Choi, Jang Wook; Coskun, Ali

    2015-11-24

    We report supramolecular cross-linking of polymer binders via dynamic host-guest interactions between hyperbranched β-cyclodextrin polymer and a dendritic gallic acid cross-linker incorporating six adamantane units for high-capacity silicon anodes. Calorimetric analysis in the solution phase indicates that the given host-guest complexation is a highly spontaneous and enthalpically driven process. These findings are further verified by carrying out gelation experiments in both aqueous and organic media. The dynamic cross-linking process enables intimate silicon-binder interaction, structural stability of electrode film, and controlled electrode-electrolyte interface, yielding enhanced cycling performance. Control experiments using both α, γ-CDp with different cavity sizes and a guest molecule incorporating a single adamantane unit verified that the enhanced cycle life originates from the host-guest interaction between β-cyclodextrin and adamantane. The impact of the dynamic cross-linking is maximized at an optimal stoichiometry between the two components. Importantly, the present investigation proves that the molecular-level tuning of the host-guest interactions can be translated directly to the cycling performance of silicon anodes.

  19. Gas/solvent-induced transformation and expansion of a nonporous solid to 1:1 host guest form

    SciTech Connect

    Thallapally, Praveen K.; McGrail, B. Peter; Dalgarno, Scott J.; Atwood, Jerry L.

    2008-07-01

    Herein we report the gas (CO2, N2O and propane) and solvent (CS2 and acetone) induced transformation and expansion of guest free thermodynamic form of a p-tert-butylcalix [4]arene to 1:1 host guest form.

  20. Blinded predictions of host-guest standard free energies of binding in the SAMPL5 challenge

    NASA Astrophysics Data System (ADS)

    Bosisio, Stefano; Mey, Antonia S. J. S.; Michel, Julien

    2017-01-01

    In the context of the SAMPL5 blinded challenge standard free energies of binding were predicted for a dataset of 22 small guest molecules and three different host molecules octa-acids (OAH and OAMe) and a cucurbituril (CBC). Three sets of predictions were submitted, each based on different variations of classical molecular dynamics alchemical free energy calculation protocols based on the double annihilation method. The first model ( model A) yields a free energy of binding based on computed free energy changes in solvated and host-guest complex phases; the second ( model B) adds long range dispersion corrections to the previous result; the third ( model C) uses an additional standard state correction term to account for the use of distance restraints during the molecular dynamics simulations. Model C performs the best in terms of mean unsigned error for all guests (MUE 3.2 < 3.4 < 3.6 {kcal} {mol}^{-1}—95 % confidence interval) for the whole data set and in particular for the octa-acid systems (MUE 1.7 < 1.9 < 2.1 {kcal} {mol}^{-1}). The overall correlation with experimental data for all models is encouraging (R^2 0.65 < 0.70<0.75). The correlation between experimental and computational free energy of binding ranks as one of the highest with respect to other entries in the challenge. Nonetheless the large MUE for the best performing model highlights systematic errors, and submissions from other groups fared better with respect to this metric.

  1. Prediction of SAMPL4 host-guest binding affinities using funnel metadynamics

    NASA Astrophysics Data System (ADS)

    Hsiao, Ya-Wen; Söderhjelm, Pär

    2014-04-01

    Accurately predicting binding affinities between ligands and macromolecules has been a much sought-after goal. A tremendous amount of resources can be saved in the pharmaceutical industry through accurate binding-affinity prediction and hence correct decision-making for the drug discovery processes. Owing to the structural complexity of macromolecules, one of the issues in binding affinity prediction using molecular dynamics is the adequate sampling of the conformational space. Recently, the funnel metadynamics method (Limongelli et al. in Proc Natl Acad Sci USA 110:6358, 2013) was developed to enhance the sampling of the ligand at the binding site as well as in the solvated state, and offer the possibility to predict the absolute binding free energy. We apply funnel metadynamics to predict host-guest binding affinities for the cucurbit[7]uril host as part of the SAMPL4 blind challenge. Using total simulation times of 300-400 ns per ligand, we show that the errors due to inadequate sampling are below 1 kcal/mol. However, despite the large investment in terms of computational time, the results compared to experiment are not better than a random guess. As we obtain differences of up to 11 kcal/mol when switching between two commonly used force fields (with automatically generated parameters), we strongly believe that in the pursuit of accurate binding free energies a more careful force-field parametrization is needed to address this type of system.

  2. 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 β-cyclodextrin (β-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.

  3. Host-Guest Binding-Site-Tunable Self-Assembly of Stimuli-Responsive Supramolecular Polymers.

    PubMed

    Yao, Hao; Qi, Miao; Liu, Yuyang; Tian, Wei

    2016-06-13

    Despite the remarkable progress made in controllable self-assembly of stimuli-responsive supramolecular polymers (SSPs), a basic issue that has not been consideration to date is the essential binding site. The noncovalent binding sites, which connect the building blocks and endow supramolecular polymers with their ability to respond to stimuli, are expected to strongly affect the self-assembly of SSPs. Herein, the design and synthesis of a dual-stimuli thermo- and photoresponsive Y-shaped supramolecular polymer (SSP2) with two adjacent β-cyclodextrin/azobenzene (β-CD/Azo) binding sites, and another SSP (SSP1) with similar building blocks, but only one β-CD/Azo binding site as a control, are described. Upon gradually increasing the polymer solution temperature or irradiating with UV light, SSP2 self-assemblies with a higher binding-site distribution density; exhibits a flower-like morphology, smaller size, and more stable dynamic aggregation process; and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies. The host-guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies. This work is beneficial for precisely controlling the structural parameters and controlled release function of SSP self-assemblies.

  4. 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.

  5. 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.

  6. The Delicate Balance of Preorganisation and Adaptability in Multiply Bonded Host-Guest Complexes.

    PubMed

    von Krbek, Larissa K S; Achazi, Andreas J; Schoder, Stefan; Gaedke, Marius; Biberger, Tobias; Paulus, Beate; Schalley, Christoph A

    2017-02-24

    Rigidity and preorganisation are believed to be required for high affinity in multiply bonded supramolecular complexes as they help reduce the entropic penalty of the binding event. This comes at the price that such rigid complexes are sensitive to small geometric mismatches. In marked contrast, nature uses more flexible building blocks. Thus, one might consider putting the rigidity/high-affinity notion to the test. Multivalent crown/ammonium complexes are ideal for this purpose as the monovalent interaction is well understood. A series of divalent complexes with different spacer lengths and rigidities has thus been analysed to correlate chelate cooperativities and spacer properties. Too long spacers reduce chelate cooperativity compared to exactly matching ones. However, in contrast to expectation, flexible guests bind with chelate cooperativities clearly exceeding those of rigid structures. Flexible spacers adapt to small geometric host-guest mismatches. Spacer-spacer interactions help overcome the entropic penalty of conformational fixation during binding and a delicate balance of preorganisation and adaptability is at play in multivalent complexes.

  7. 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.

  8. Sustained Small Molecule Delivery from Injectable Hyaluronic Acid Hydrogels through Host-Guest Mediated Retention

    PubMed Central

    Mealy, Joshua E.; Rodell, Christopher B.; Burdick, Jason A.

    2015-01-01

    Self-assembled and injectable hydrogels have many beneficial properties for the local delivery of therapeutics; however, challenges still exist in the sustained release of small molecules from these highly hydrated networks. Host-guest chemistry between cyclodextrin and adamantane has been used to create supramolecular hydrogels from modified polymers. Beyond assembly, this chemistry may also provide increased drug retention and sustained release through the formation of inclusion complexes between drugs and cyclodextrin. Here, we engineered a two-component system from adamantane-modified and β-cyclodextrin (CD)-modified hyaluronic acid (HA), a natural component of the extracellular matrix, to produce hydrogels that are both injectable and able to sustain the release of small molecules. The conjugation of cyclodextrin to HA dramatically altered its affinity for hydrophobic small molecules, such as tryptophan. This interaction led to lower molecule diffusivity and the release of small molecules for up to 21 days with release profiles dependent on CD concentration and drug-CD affinity. There was significant attenuation of release from the supramolecular hydrogels (~20% release in 24h) when compared to hydrogels without CD (~90% release in 24h). The loading of small molecules also had no effect on hydrogel mechanics or self-assembly properties. Finally, to illustrate this controlled delivery approach with clinically used small molecule pharmaceuticals, we sustained the release of two widely used drugs (i.e., doxycycline and doxorubicin) from these hydrogels. PMID:26693019

  9. 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.

  10. 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 β-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.

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

    PubMed

    Ghoufi, Aziz; Malfreyt, Patrice

    2006-12-14

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

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

    SciTech Connect

    Crowley, James D.; Bosnich, Brice

    2008-10-03

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

  13. Spectral and electrochemical study of host-guest inclusion complex between 2,4-dinitrophenol and β-cyclodextrin.

    PubMed

    Srinivasan, K; Stalin, T; Sivakumar, K

    2012-08-01

    The formation of host-guest inclusion complex of 2,4-dinitrophenol (2,4-DNP) with nano-hydrophobic cavity of β-cyclodextrin (β-CD) in solution phase was studied by UV-visible spectrophotometer and electrochemical method (cyclic voltammetry, CV). The prototropic behaviors of 2,4-DNP with and without β-CD and the ground state acidity constant (pK(a)) of host-guest inclusion complex (2,4-DNP-β-CD) were studied. The binding constant of inclusion complex at 303K was calculated using Benesi-Hildebrand plot and thermodynamic parameter (ΔG) was also calculated. The solid inclusion complex formation between β-CD and 2,4-DNP was confirmed by (1)H NMR, FT-IR, XRD and SEM analysis. A schematic representation of this inclusion process is proposed by molecular docking studies using PatchDock server.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2016-01-21

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

  16. Host-guest architectures with a surface confined imine covalent organic framework as two-dimensional host networks.

    PubMed

    Sun, Jiang; Zhou, Xin; Lei, Shengbin

    2016-07-05

    A two-dimensional covalent organic framework (2D COF), synthesized on a highly oriented pyrolytic graphite (HOPG) surface with benzene-1,3,5-tricarbaldehyde and p-phenylenediamine as the precursors, is used as a host to accommodate three guest molecules, coronene, copper phthalocyanine (CuPc), and fluorine-substituted copper phthalocyanine (F16CuPc). The host-guest interaction and dynamic behavior were investigated by scanning tunneling microscopy and density functional theory.

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

    PubMed

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

    2016-01-28

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

  18. Mechanism of host-guest complex formation and identification of intermediates through NMR titration and diffusion NMR spectroscopy.

    PubMed

    Lamm, Jan-Hendrik; Niermeier, Philipp; Mix, Andreas; Chmiel, Jasmin; Neumann, Beate; Stammler, Hans-Georg; Mitzel, Norbert W

    2014-07-21

    The formation of host-guest (H-G) complexes between 1,8-bis[(diethylgallanyl)ethynyl]anthracene (H) and the N-heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host-guest structures in solution were compared with those of tailor-made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host-guest species and equilibria. With increasing concentrations of the pyridine guest, the equilibrium H2⇄H2κ(1)-G1⇄HG2 is observed (in the second step a host dimer coordinates one guest molecule); for pyrimidine the equilibrium H2→H1κ(2)-G1⇄HG2 is observed (the formation of a 1:1 aggregate is the second step).

  19. All organic host-guest crystals based on a dumb-bell-shaped conjugated host for light harvesting through resonant energy transfer.

    PubMed

    Winkler, Reingard; Berger, Ricarda; Manca, Marianna; Hulliger, Jürg; Weber, Edwin; Loi, Maria A; Botta, Chiara

    2012-01-16

    Together we glow: Fully organic host-guest crystals with two dyes inserted in their parallel nanochannels display broad emission in the visible range thanks to resonant energy transfer. The conjugated host crystal provides light harvesting in the UV region.

  20. A thermochromic thin film based on host-guest interactions in a layered double hydroxide.

    PubMed

    Wang, Xinrui; Lu, Jun; Shi, Wenying; Li, Feng; Wei, Min; Evans, David G; Duan, Xue

    2010-01-19

    Optically transparent thin films with thermochromic properties have been fabricated by means of cointercalation of different molar ratios of 4-(4-anilinophenylazo)benzenesulfonate (AO5) and sodium dodecylbenzene sulfonate (SDS) into the galleries of a ZnAl layered double hydroxide (LDH). The X-ray diffraction (XRD) patterns of these thin films show that they are assembled in a highly c-oriented manner, and the basal spacing ranges from 2.95 to 2.63 nm with varying AO5/SDS molar ratio. The preferential orientation of AO5 in the galleries of 10% AO5-LDH (AO5/SDS = 10:90, molar percentage) was evaluated by the fluorescence polarization technique; the results show that AO5 anions are accommodated between sheets of ZnAl-LDH as monomeric units with a tilt angle Psi (defined as the angle between the transition dipole moment of the AO5 anion with respect to the normal to the LDH layer) of 74 degrees. It was found that the composite film exhibits marked thermochromic behavior (light yellow <==> reddish-orange) in the temperature range of 35-65 degrees C, which is reversible over a number of heating-cooling cycles. It has been demonstrated that the thermochromic behavior results from tautomerism of interlayer AO5 and furthermore that both the host-guest and guest-guest interactions are key factors, since pristine AO5 shows no thermochromic performance. The 10% AO5-LDH film shows the highest thermochromic efficiency of all the films examined. Furthermore, a reversible contraction and expansion of the LDH basal spacing was also observed for this thin film over the same temperature range.

  1. Reduced activity of alkaline phosphatase due to host-guest interactions with humic superstructures.

    PubMed

    Mazzei, Pierluigi; Oschkinat, Hartmut; Piccolo, Alessandro

    2013-11-01

    Nuclear Magnetic Resonance (NMR) spectroscopy was applied to directly study the interactions between the alkaline phosphatase enzyme (AP) and two different humic acids from a volcanic soil (HA-V) and a Lignite deposit (HA-L). Addition of humic matter to enzyme solutions caused signals broadening in (1)H-NMR spectra, and progressive decrease and increase of enzyme relaxation (T1 and T2) and correlation (τC) times, respectively. Spectroscopic changes were explained with formation of ever larger weakly-bound humic-enzyme complexes, whose translational and rotational motion was increasingly restricted. NMR diffusion experiments also showed that the AP diffusive properties were progressively reduced with formation of large humic-enzyme complexes. The more hydrophobic HA-L affected spectral changes more than the more hydrophilic HA-V. (1)H-NMR spectra also showed the effect of progressively greater humic-enzyme complexes on the hydrolysis of an enzyme substrate, the 4-nitrophenyl phosphate disodium salt hexahydrate (p-NPP). While AP catalysis concomitantly decreased NMR signals of p-NPP and increased those of nitrophenol, addition of humic matter progressively and significantly slowed down the rate of change for these signals. In agreement with the observed spectral changes, the AP catalytic activity was more largely inhibited by HA-L than by HA-V. Contrary to previous studies, in which humic-enzyme interactions were only indirectly assumed from changes in spectrophotometric behavior of enzyme substrates, the direct measurements of AP behavior by NMR spectroscopy indicated that humic materials formed weakly-bound host-guest complexes with alkaline phosphatase, and the enzyme catalytic activity was thereby significantly inhibited. These results suggest that the role of extracellular enzymes in soils may be considerably reduced when they come in contact with organic matter dissolved in the soil solution.

  2. 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.

  3. Computational Calorimetry: High-Precision Calculation of Host-Guest Binding Thermodynamics.

    PubMed

    Henriksen, Niel M; Fenley, Andrew T; Gilson, Michael K

    2015-09-08

    We present a strategy for carrying out high-precision calculations of binding free energy and binding enthalpy values from molecular dynamics simulations with explicit solvent. The approach is used to calculate the thermodynamic profiles for binding of nine small molecule guests to either the cucurbit[7]uril (CB7) or β-cyclodextrin (βCD) host. For these systems, calculations using commodity hardware can yield binding free energy and binding enthalpy values with a precision of ∼0.5 kcal/mol (95% CI) in a matter of days. Crucially, the self-consistency of the approach is established by calculating the binding enthalpy directly, via end point potential energy calculations, and indirectly, via the temperature dependence of the binding free energy, i.e., by the van't Hoff equation. Excellent agreement between the direct and van't Hoff methods is demonstrated for both host-guest systems and an ion-pair model system for which particularly well-converged results are attainable. Additionally, we find that hydrogen mass repartitioning allows marked acceleration of the calculations with no discernible cost in precision or accuracy. Finally, we provide guidance for accurately assessing numerical uncertainty of the results in settings where complex correlations in the time series can pose challenges to statistical analysis. The routine nature and high precision of these binding calculations opens the possibility of including measured binding thermodynamics as target data in force field optimization so that simulations may be used to reliably interpret experimental data and guide molecular design.

  4. Host-Guest Self-Assembly Toward Reversible Thermoresponsive Switching for Bacteria Killing and Detachment.

    PubMed

    Shi, Zhen-Qiang; Cai, Yu-Ting; Deng, Jie; Zhao, Wei-Feng; Zhao, Chang-Sheng

    2016-09-14

    A facile method to construct reversible thermoresponsive switching for bacteria killing and detachment was currently developed by host-guest self-assembly of β-cyclodextrin (β-CD) and adamantane (Ad). Ad-terminated poly(N-isopropylacrylamide) (Ad-PNIPAM) and Ad-terminated poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (Ad-PMT) were synthesized via atom transfer radical polymerization, and then assembled onto the surface of β-CD grafted silicon wafer (SW-CD) by simply immersing SW-CD into a mixed solution of Ad-PNIPAM and Ad-PMT, thus forming a thermoresponsive surface (SW-PNIPAM/PMT). Atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), and water contact angle (WCA) analysis were used to characterize the surface of SW-PNIPAM/PMT. The thermoresponsive bacteria killing and detachment switch of the SW-PNIPAM/PMT was investigated against Staphyloccocus aureus. The microbiological experiments confirmed the efficient bacteria killing and detachment switch across the lower critical solution temperature (LCST) of PNIPAM. Above the LCST, the Ad-PNIPAM chains on the SW-PNIPAM/PMT surface were collapsed to expose Ad-PMT chains, and then the exposed Ad-PMT would kill the attached bacteria. While below the LCST, the previously collapsed Ad-PNIPAM chains became more hydrophilic and swelled to cover the Ad-PMT chains, leading to the detachment of bacterial debris. Besides, the proposed method to fabricate stimuli-responsive surfaces with reversible switches for bacteria killing and detachment is facile and efficient, which creates a new route to extend the application of such smart surfaces in the fields requiring long-term antimicrobial treatment.

  5. Electronic and magnetic functions of nanographene-based host-guest system

    NASA Astrophysics Data System (ADS)

    Enoki, Toshiaki

    2009-03-01

    The electronic structure of nanographene having open edges crucially depends on its edge shape. According to theoretical predictions, nanographene has nonbonding π-electron state (edge state) localized in zigzag edges. We investigated the electronic structure of graphene edges, the magnetism of the edge-state spins in nanographene and the effect of host-guest interaction on the magnetism. For magnetic investigations, we employed nanoporous activated carbon fiber (ACF) having a 3D disordered network of nanographite domains, each of which is a stack of 3-4 nanographene sheets. STM/STS investigations of hydrogen-terminated graphene edges confirm the presence of edge states around zigzag edges, in good agreement with theoretical works. The feature of the edge state depends on the detailed geometry of the edge structures. The magnetism of nanographene in ACF has a ferrimagnetism feature with a net magnetic moment, for which the cooperation of ferromagnetic intra-zigzag-edge and ferromagntic/antiferromagnetic inter-zigzag-edge interactions is responsible. Heat-treatment, which induces an insulator-metal transition, brings about spin glass state of the edge-state spins in the vicinity of the transition. Physisorption of guest species such as water, organic molecules, rare gas in the ACF nanopores generates a high-spin/low-spin magnetic switching phenomenon, in which a discontinuous reduction of the magnetic moment takes place. This is explained in terms of the strengthening of the inter-graphene-sheet antiferromagnetic interaction, which is induced by the mechanical compression of nanographite domains by the condensed guest molecules. The magnetic oxygen molecules physisorbed in the nanopores work seriously to decrease the magnetoresistance in ACF as a consequence of the interaction between the oxygen molecule spins and edge-state spins.

  6. Examination of cucurbit[7]uril and its host-guest complexes by diffusion nuclear magnetic resonance.

    PubMed

    Wheate, Nial J; Kumar, P G Anil; Torres, Allan M; Aldrich-Wright, Janice R; Price, William S

    2008-02-28

    The self-diffusion of cucurbit[7]uril (CB[7]) and its host-guest complexes in D2O has been examined using pulsed gradient spin-echo nuclear magnetic resonance spectroscopy. CB[7] diffuses freely at a concentration of 2 mM with a diffusion coefficient (D) of 3.07 x 10(-10) m(2) s(-1). At saturation (3.7 mM), CB[7] diffuses more slowly (D = 2.82 x 10(-10) m(2) s(-1)) indicating that it partially self-associates. At concentrations between 2 and 200 mM, CsCl has no effect on the diffusion coefficient of CB[7] (1 mM). Conversely, CB[7] (2 mM) significantly affects the diffusion of 133Cs+ (1 mM), decreasing its diffusion coefficient from 1.86 to 0.83 x 10(-9) m(2) s(-1). Similar changes in the rate of diffusion of other alkali earth metal cations are observed upon the addition of CB[7]. The diffusion coefficient of 23Na+ changes from 1.26 to 0.90 x 10(-9) m(2) s(-1) and 7Li+ changes from 3.40 to 3.07 x 10(-9) m(2) s(-1). In most cases, encapsulation of a variety of inorganic and organic guests within CB[7] decreases their rates of diffusion in D2O. For instance, the diffusion coefficient of the dinuclear platinum complex trans-[[PtCl(NH3)2}2mu-dpzm](2+) (where dpzm is 4,4'-dipyrazolylmethane) decreases from 4.88 to 2.95 x 10(-10) m(2) s(-1) upon encapsulation with an equimolar concentration of CB[7].

  7. A Multistate Molecular Switch Based on the 6,8-Rearrangement in Bromo-apigeninidin Operated with pH and Host-Guest Inputs.

    PubMed

    Basílio, Nuno; Cruz, Luís; de Freitas, Victor; Pina, Fernando

    2016-07-28

    The equilibrium between 6- and 8-bromo-apigeninidin is quantitatively displaced toward the formation of the former in the presence of cucurbit[7]uril because of the selective recognition of the 6-bromo isomer by the host. This phenomenon permits us to conceive a unidirectional multistate switch addressed with host-guest inputs and enables the reversible activation and deactivation of the 6-/8-bromo-apigeninidin dynamic molecular multistate through coupled host-guest and pH inputs.

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

    PubMed

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

    2015-10-07

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

  9. Solvent-controlled 2D host-guest (2,7,12-trihexyloxytruxene/coronene) molecular nanostructures at organic liquid/solid interface investigated by scanning tunneling microscopy.

    PubMed

    Liu, Jia; Zhang, Xu; Yan, Hui-Juan; Wang, Dong; Wang, Jie-Yu; Pei, Jian; Wan, Li-Jun

    2010-06-01

    The two-dimensional (2D) self-assembled networks of 2,7,12-trihexyloxytruxene (Tr) are shown to accommodate coronene guest molecules on highly oriented pyrolytic graphite (HOPG) surfaces. The host-guest structures are revealed by scanning tunneling microscopy (STM) at liquid/solid interfaces. The effect of solvents on the host-guest structures is intensively investigated in different solvents such as 1,2,4-trichlorobenzene (TCB), 1-phenyloctane, 1-octanol, and tetradecane. In contrast to the similar 2D hexagonal self-assembly of Tr host template on HOPG in different solvents, the formation of host-guest nanostructures of coronene in Tr 2D network strongly depend on the polarity of the solvents. The thermodynamic equilibrium during the host-guest assembly process is discussed, and the solvent-guest interaction is proposed as a main contributor for the observed solvent effect in the 2D host-guest self-assembly process. The results are significant to surface host-guest chemistry and nanopatterning.

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

    PubMed Central

    Muddana, Hari S.; Gilson, Michael K.

    2012-01-01

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

  11. 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 π-π 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.

  12. Dynamic interplay between spin-crossover and host-guest function in a nanoporous metal-organic framework material.

    SciTech Connect

    Southon, P. D.; Liu, L.; Fellows, E. A.; Price, D. J.; Halder, G. J.; Chapman, K. W.; Moubaraki, B.; Murray, K. S.; Letard, J.F.; Kepert, C. J.; Univ. Sydney; Monash Univ.; Universite Bordeaux

    2009-01-01

    The nanoporous metal-organic framework [Fe(pz)Ni(CN){sub 4}], 1 (where pz is pyrazine), exhibits hysteretic spin-crossover at ambient conditions and is robust to the adsorption and desorption of a wide range of small molecular guests, both gases (N{sub 2}, O{sub 2}, CO{sub 2}) and vapors (methanol, ethanol, acetone, acetonitrile, and toluene). Through the comprehensive analysis of structure, host-guest properties, and spin-crossover behaviors, it is found that this pillared Hofmann system uniquely displays both guest-exchange-induced changes to spin-crossover and spin-crossover-induced changes to host-guest properties, with direct dynamic interplay between these two phenomena. Guest desorption and adsorption cause pronounced changes to the spin-crossover behavior according to a systematic trend in which larger guests stabilize the high-spin state and therefore depress the spin-crossover temperature of the host lattice. When stabilizing the alternate spin state of the host at any given temperature, these processes directly stimulate the spin-crossover process, providing a chemisensing function. Exploitation of the bistability of the host allows the modification of adsorption properties at a fixed temperature through control of the host spin state, with each state shown to display differing chemical affinities to guest sorption. Guest desorption then adsorption, and vice versa, can be used to switch between spin states in the bistable temperature region, adding a guest-dependent memory effect to this system.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    PubMed Central

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

    2013-01-01

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

  15. Sequential energy and charge transfer processes in mixed host-guest complexes of subphthalocyanine, porphyrin and phthalocyanine chromophores.

    PubMed

    Menting, Roel; Ng, Dennis K P; Röder, Beate; Ermilov, Eugeny A

    2012-11-14

    Porphyrins, phthalocyanines and subphthalocyanines are three attractive classes of chromophores with intriguing properties making them suitable for the design of artificial photosynthetic systems. The assembly of these components by a supramolecular approach is of particular interest as it provides a facile means to build multi-chromophoric arrays with various architectures and tuneable photophysical properties. In this paper, we show the formation of mixed host-guest supramolecular complexes that consist of a β-cyclodextrin-conjugated subphthalocyanine, a tetrasulfonated porphyrin and a series of silicon(IV) phthalocyanines substituted axially with two β-cyclodextrins via different spacers. We found that the three components form supramolecular complexes held by host-guest interactions in aqueous solution. Upon excitation of the subphthalocyanine part of the complex, the excitation energy is delivered to the phthalocyanine unit via excitation energy transfer and the porphyrin chromophore acts as an energy transfer bridge enabling this process. It was shown that photo-induced charge transfer also takes place. A sequential electron transfer process from the porphyrin unit to the phthalocyanine moiety and subsequently from the subphthalocyanine moiety to the porphyrin unit takes place, and the probability of this process is controlled by the linker between β-cyclodextrin and phthalocyanine. The lifetime of the charge-separated state was found to be 1.7 ns by transient absorption spectroscopy.

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

    PubMed Central

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    PubMed Central

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

    2015-01-01

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

  19. Do CH-Anion and Anion-π Interactions Alter the Mechanism of 2:1 Host-Guest Complexation in Arylethynyl Monourea Anion Receptors?

    PubMed

    Eytel, Lisa M; Gilbert, Annie K; Görner, Paul; Zakharov, Lev N; Johnson, Darren W; Haley, Michael M

    2017-03-23

    Selective tuning of arylethynyl urea scaffolds for anionic guests requires an understanding of preferred binding motifs of the host-guest interaction. To investigate the binding preference of receptors without a pre-organized binding pocket, two electron-deficient phenylacetylene receptors with a single urea moiety have been prepared and were found to bind halides as 2:1 host-guest complexes that feature key CH-anion or anion-π interactions. These supporting interactions also appear to influence the mechanism of the 2:1 binding event.

  20. Spectrofluorimetric study of host-guest complexation of ibuprofen with β-cyclodextrin and its analytical application

    NASA Astrophysics Data System (ADS)

    Manzoori, Jamshid L.; Amjadi, Mohammad

    2003-03-01

    The characteristics of host-guest complexation between β-cyclodextrin (β-CD) and two forms of ibuprofen (protonated and deprotonated) were investigated by fluorescence spectrometry. 1:1 stoichiometries for both complexes were established and their association constants at different temperatures were calculated by applying a non-linear regression method to the change in the fluorescence of ibuprofen that brought about by the presence of β-CD. The thermodynamic parameters (Δ H, Δ S and Δ G) associated with the inclusion process were also determined. Based on the obtained results, a sensitive spectrofluorimetric method for the determination of ibuprofen was developed with a linear range of 0.1-2 μg ml -1 and a detection limit of 0.03 μg ml -1. The method was applied satisfactorily to the determination of ibuprofen in pharmaceutical preparations.

  1. 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

    2014-11-04

    A star polymer, β-cyclodextrin-poly(l-lactide) (β-CD-PLLA), and a linear polymer, azobenzene-poly(ethylene glycol) (Azo-PEG), could self-assemble into a supramolecular amphiphilic copolymer (β-CD-PLLA@Azo-PEG) based on the host-guest interaction between β-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.

  2. Surface modification of cellulose fiber via supramolecular assembly of biodegradable polyesters by the aid of host-guest inclusion complexation.

    PubMed

    Zhao, Qiang; Wang, Shufang; Cheng, Xinjian; Yam, Richard C M; Kong, Deling; Li, Robert K Y

    2010-05-10

    In this article, we report a novel surface modification method for cellulose fiber that is based on supramolecular assembly. Beta-cyclodextrin (beta-CD) was first covalently grafted onto the fiber surface. Then poly(epsilon-caprolactone) (PCL) oligomers having both ends capped with adamantane motifs (i.e., PCL-AD) were immobilized to the cellulose fiber surface through the host-guest inclusion complexation between beta-CD and AD motif. FTIR-ATR and XPS analyses confirmed the successful assembly of PCL-ADs, which was further supported by the increasing trend of weight gain with the concentration of CDs on the fiber surface. Contact angle and TGA measurements reflect the enhanced hydrophobicity and thermal stability of the cellulose fiber as a consequence of this modification. The morphologies of the cellulose fiber before and after the assembly process have also been compared by SEM.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  5. Analysis of the phosphorescent dye concentration dependence of triplet-triplet annihilation in organic host-guest systems

    NASA Astrophysics Data System (ADS)

    Zhang, L.; van Eersel, H.; Bobbert, P. A.; Coehoorn, R.

    2016-10-01

    Using a novel method for analyzing transient photoluminescence (PL) experiments, a microscopic description is obtained for the dye concentration dependence of triplet-triplet annihilation (TTA) in phosphorescent host-guest systems. It is demonstrated that the TTA-mechanism, which could be a single-step dominated process or a diffusion-mediated multi-step process, can be deduced for any given dye concentration from a recently proposed PL intensity analysis. A comparison with the results of kinetic Monte Carlo simulations provides the TTA-Förster radius and shows that the TTA enhancement due to triplet diffusion can be well described in a microscopic manner assuming Förster- or Dexter-type energy transfer.

  6. A synthetic host-guest system achieves avidin-biotin affinity by overcoming enthalpy-entropy compensation.

    PubMed

    Rekharsky, Mikhail V; Mori, Tadashi; Yang, Cheng; Ko, Young Ho; Selvapalam, N; Kim, Hyunuk; Sobransingh, David; Kaifer, Angel E; Liu, Simin; Isaacs, Lyle; Chen, Wei; Moghaddam, Sarvin; Gilson, Michael K; Kim, Kimoon; Inoue, Yoshihisa

    2007-12-26

    The molecular host cucurbit[7]uril forms an extremely stable inclusion complex with the dicationic ferrocene derivative bis(trimethylammoniomethyl)ferrocene in aqueous solution. The equilibrium association constant for this host-guest pair is 3 x 10(15) M(-1) (K(d) = 3 x 10(-16) M), equivalent to that exhibited by the avidin-biotin pair. Although purely synthetic systems with larger association constants have been reported, the present one is unique because it does not rely on polyvalency. Instead, it achieves its extreme affinity by overcoming the compensatory enthalpy-entropy relationship usually observed in supramolecular complexes. Its disproportionately low entropic cost is traced to extensive host desolvation and to the rigidity of both the host and the guest.

  7. Spatial, Hysteretic, and Adaptive Host-Guest Chemistry in a Metal-Organic Framework with Open Watson-Crick Sites.

    PubMed

    Cai, Hong; Li, Mian; Lin, Xiao-Rong; Chen, Wei; Chen, Guang-Hui; Huang, Xiao-Chun; Li, Dan

    2015-09-01

    Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site-specific recognition takes advantage of cooperative spatial effects, as in local folding in protein-DNA binding. Herein, we report a new nucleobase-tagged metal-organic framework (MOF), namely ZnBTCA (BTC=benzene-1,3,5-tricarboxyl, A=adenine), in which the exposed Watson-Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson-Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host-guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine-thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed.

  8. Fluorometric detection of cholesterol based on β-cyclodextrin functionalized carbon quantum dots via competitive host-guest recognition.

    PubMed

    Sun, Qian; Fang, Siying; Fang, Yafen; Qian, Zhaosheng; Feng, Hui

    2017-05-15

    A sensitive and selective fluorescent method for detection of cholesterol based on β-cyclodextrin functionalized carbon quantum dots (β-CD-CQD) nanoprobe through competitive host-guest recognition has been developed. The bright fluorescence of β-CD-CQD nanoprobe can be effectively quenched by the introduction of a very small amount of p-nitrophenol, and strong quenching ability of p-nitrophenol to the probe was identified. This efficient fluorescence quenching as a static quenching is due to the formation of nonfluorescent complex between β-CD-CQD and p-nitrophenol induced by host-guest interaction between them. Cholesterol, as a more suited guest molecule of β-cyclodextrin, can form an inclusion complex with β-cyclodextrin with a much greater binding constant than p-nitrophenol. As a result, the presence of cholesterol causes a replacement of guest molecule of β-CD moiety in the probe through a competitive way, and the inclusion of cholesterol in the probe as the removal of p-nitropheonl induces significant fluorescence enhancement. The fluorescence recovery can be achieved by continuous addition of cholesterol. In terms of this relationship between enhanced fluorescence and concentration of cholesterol, a quantitative measurement for cholesterol based on β-CD-CQD nanoprobe has been established. Under the optimized detection conditions, this method shows good analytical performance in detection of cholesterol with lowest detection limit of 0.7±0.1µM and a relatively wide linear scope of 110µM. Specificity test and complex matrix test show that this method possesses excellent selectivity to cholesterol, and complex matrix such as serum does not exert apparent influence on the analytical performance, which enables its use in practical serum samples.

  9. Host-Guest Chemistry in Integrated Porous Space Formed by Molecular Self-Assembly at Liquid-Solid Interfaces.

    PubMed

    Iritani, Kohei; Tahara, Kazukuni; De Feyter, Steven; Tobe, Yoshito

    2017-02-23

    Host-guest chemistry in two-dimensional (2D) space, that is, physisorbed monolayers of a single atom or a single molecular thickness on surfaces, has become a subject of intense current interest because of perspectives for various applications in molecular-scale electronics, selective sensors, and tailored catalysis. Scanning tunneling microscopy has been used as a powerful tool for the visualization of molecules in real space on a conducting substrate surface. For more than a decade, we have been investigating the self-assembly of a series of triangle-shaped phenylene-ethynylene macrocycles called dehydrobenzo[12]annulenes (DBAs). These molecules are substituted with six alkyl chains and are capable of forming hexagonal porous 2D molecular networks via van der Waals interactions between interdigitated alkyl chains at the interface of organic solvents and graphite. The dimension of the nanoporous space or nanowell formed by the self-assembly of DBAs can be controlled from 1.6 to 4.7 nm by simply changing the alkyl chain length from C6 to C20. Single molecules as well as homoclusters and heteroclusters are capable of coadsorbing within the host matrix using shape- and size-complementarity principles. Moreover, on the basis of the versatility of the DBA molecules that allows chemical modification of the alkyl chain terminals, we were able to decorate the interior space of the nanoporous networks with functional groups such as azobenzenedicarboxylic acid for photoresponsive guest adsorption/desorption or fluoroalkanes and tetraethylene glycol groups for selective guest binding by electrostatic interactions and zinc-porphyrin units for complexation with a guest by charge-transfer interactions. In this Feature Article, we describe the general aspects of molecular self-assembly at liquid/solid interfaces, followed by the formation of programmed porous molecular networks using rationally designed molecular building blocks. We focus on our own work involving host-guest

  10. Binding Enthalpy Calculations for a Neutral Host-Guest Pair Yield Widely Divergent Salt Effects across Water Models

    PubMed Central

    Gao, Kaifu; Yin, Jian; Henriksen, Niel M.; Fenley, Andrew T.; Gilson, Michael K.

    2015-01-01

    Dissolved salts are a part of the physiological milieu and can significantly influence the kinetics and thermodynamics of varied biomolecular processes, such as binding and catalysis, so it is important for molecular simulations to reliably describe their effects. The present study uses a simple, non-ionized host-guest model system to study the sensitivity of computed binding enthalpies to the choice of water and salt models. Molecular dynamics simulations of a cucurbit[7]uril host with a neutral guest molecule show striking differences in the salt dependency of the binding enthalpy across four water models, TIP3P, SPC/E, TIP4P-Ew and OPC, with additional sensitivity to the choice of parameters for sodium and chloride. In particular, although all of the models predict that binding will be less exothermic with increasing NaCl concentration, the strength of this effect varies by 7 kcal/mol across models. The differences appear to result primarily from differences in the number of sodium ions displaced from the host on binding the guest, rather than from differences in the enthalpy associated with this displacement; and it is the electrostatic energy that contributes most to the changes in enthalpy with increasing salt concentration. That a high sensitivity of salt effects to the choice of water model is observed for the present host-guest system, despite its being non-ionized, raises issues regarding the selection and adjustment of water models for use with biological macromolecules, especially as these typically possess multiple ionized groups which can interact relatively strongly with ions in solution. PMID:26574247

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

    PubMed

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

    2014-01-01

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

  12. Binding enthalpy calculations for a neutral host-guest pair yield widely divergent salt effects across water models.

    PubMed

    Gao, Kaifu; Yin, Jian; Henriksen, Niel M; Fenley, Andrew T; Gilson, Michael K

    2015-10-13

    Dissolved salts are a part of the physiological milieu and can significantly influence the kinetics and thermodynamics of various biomolecular processes, such as binding and catalysis; thus, it is important for molecular simulations to reliably describe their effects. The present study uses a simple, nonionized host-guest model system to study the sensitivity of computed binding enthalpies to the choice of water and salt models. Molecular dynamics simulations of a cucurbit[7]uril host with a neutral guest molecule show striking differences in the salt dependency of the binding enthalpy across four water models, TIP3P, SPC/E, TIP4P-Ew, and OPC, with additional sensitivity to the choice of parameters for sodium and chloride. In particular, although all of the models predict that binding will be less exothermic with increasing NaCl concentration, the strength of this effect varies by 7 kcal/mol across models. The differences appear to result primarily from differences in the number of sodium ions displaced from the host upon binding the guest rather than from differences in the enthalpy associated with this displacement, and it is the electrostatic energy that contributes most to the changes in enthalpy with increasing salt concentration. That a high sensitivity of salt affecting the choice of water model, as observed for the present host-guest system despite it being nonionized, raises issues regarding the selection and adjustment of water models for use with biological macromolecules, especially as these typically possess multiple ionized groups that can interact relatively strongly with ions in solution.

  13. 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.

  14. Factors Affecting the Formation of 2:1 Host:Guest Inclusion Complexes of 2-[(R-Phenyl)amine]-1,4-naphthalenediones (PAN) in β- and γ-Cyclodextrins.

    PubMed

    Jankowski, Christopher K; Lamouroux, Christine; Jiménez-Estrada, Manuel; Arseneau, Sebastien; Wagner, Brian D

    2016-11-18

    The molecular hosts cyclodextrins form inclusion complexes with a wide variety of guests, resulting in complexes with various host:guest stoichiometries. In the case of a series of 19 1,4-naphthoquinolines as guests with either β- or γ-cyclodextrin studied using electrospray mass spectroscopy, in most cases only 1:1 complexes were observed, with 2:1 host:guest complexes observed in just 6 out of 38 host:guest combinations. It is shown that these higher-order complexes were observed only in the case of small (or no) electronically withdrawing substituents, and were much less likely in the case of the larger γ-cyclodextrin host. The size and electronic properties of the substituents involved shows that both steric and electronic factors must be taken into account in predicting which cyclodextrin host:guest stoichiometries will be stable enough to form (or once formed, be robust enough to be observed in the ESI-MS experiments). It is clear that the prediction of host-guest stoichiometry for a specific host-guest pair is complicated, and involves a subtle interplay of both electronic and steric factors. However, there are definite trends, which can be used to help predict host:guest stoichiometry for a given host-guest pair.

  15. Study of the counter anions in the host-guest chemistry of cucurbit[8]uril and 1-ethyl-1'-benzyl-4,4'-bipyridinium.

    PubMed

    Ji, Hailong; Liu, Fengyu; Sun, Shiguo

    2013-01-01

    A series of 1-ethyl-1'-benzyl-4,4'-bipyridinium compounds with different counter anions (BEV-X2, where the X is Cl, Br, I, PF6, ClO4) were synthesized. By using of NMR, MS, electrochemistry, Na2S2O4-induced redox chemistry, and UV-Vis, the role of the different counter anions in the host-guest chemistry of cucurbit[8]uril (CB[8]) was studied for the first time. The result demonstrated that BEV-X2 can form a 1 : 1 host-guest complex with CB[8] in water. Theoretical calculation further suggested that the viologen region was threaded through the cavity of CB[8], while the corresponding counter anions were located outside the cavity. Some difference can be observed on UV-Vis titration and Na2S2O4-induced redox chemistry, which showed that the counter anions have some effect on the host-guest chemistry. All these provide new insights into CB[8] host-guest system.

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

    ERIC Educational Resources Information Center

    Rood, Jeffrey A.; Henderson, Kenneth W.

    2013-01-01

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

  17. Photonic hybrid crystals constructed from in situ host-guest nanoconfinement of a light-emitting complex in metal-organic framework pores

    NASA Astrophysics Data System (ADS)

    Chaudhari, Abhijeet K.; Ryder, Matthew R.; Tan, Jin-Chong

    2016-03-01

    We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and substantiated further via theoretical molecular orbital calculations revealing the plausible host-guest charge transfer mechanism involved. Evidence suggests that its photophysical properties are not only strongly determined by the host-guest co-operative bonding interactions within the environment of the confined MOF nanocage, but also can be engineered to manipulate its emission color chromaticity or to shield light-sensitive emitting guests against rapid photochemical degradation.We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and

  18. Supra-dendron Gelator Based on Azobenzene-Cyclodextrin Host-Guest Interactions: Photoswitched Optical and Chiroptical Reversibility.

    PubMed

    Xie, Fan; Ouyang, Guanghui; Qin, Long; Liu, Minghua

    2016-12-12

    A novel amphiphilic dendron (AZOC8 GAc) with three l-glutamic acid units and an azobenzene moiety covalently linked by an alkyl spacer has been designed. The compound formed hydrogels with water at very low concentration and self-assembled into chiral-twist structures. The gel showed a reversible macroscopic volume phase transition in response to pH variations and photo-irradiation. During the photo-triggered changes, although the gel showed complete reversibility in its optical absorptions, only an incomplete chiroptical property change was achieved. On the other hand, the dendron could form a 1:1 inclusion complex through a host-guest interaction with α-cyclodextrin (α-CD), designated as supra-dendron gelator AZOC8 GAc/α-CD. The supra-dendron showed similar gelation behavior to that of AZOC8 GAc, but with enhanced photoisomerization-transition efficiency and chiroptical switching capacity, which was completely reversible in terms of both optical and chiroptical performances. The self-assembly of the supra-dendron is a hierarchical or multi-supramolecular self-assembling process. This work has clearly illustrated that the hierarchical and multi-supramolecular self-assembling system endows the supramolecular nanostructures or materials with superior reversible optical and chiroptical switching.

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

    PubMed

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

    2014-02-01

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

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

    PubMed

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

    2015-12-09

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

  1. Predicting paramagnetic 1H NMR chemical shifts and state-energy separations in spin-crossover host-guest systems.

    PubMed

    Isley, William C; Zarra, Salvatore; Carlson, Rebecca K; Bilbeisi, Rana A; Ronson, Tanya K; Nitschke, Jonathan R; Gagliardi, Laura; Cramer, Christopher J

    2014-06-14

    The behaviour of metal-organic cages upon guest encapsulation can be difficult to elucidate in solution. Paramagnetic metal centres introduce additional dispersion of signals that is useful for characterisation of host-guest complexes in solution using nuclear magnetic resonance (NMR). However, paramagnetic centres also complicate spectral assignment due to line broadening, signal integration error, and large changes in chemical shifts, which can be difficult to assign even for known compounds. Quantum chemical predictions can provide information that greatly facilitates the assignment of NMR signals and identification of species present. Here we explore how the prediction of paramagnetic NMR spectra may be used to gain insight into the spin crossover (SCO) properties of iron(II)-based metal organic coordination cages, specifically examining how the structure of the local metal coordination environment affects SCO. To represent the tetrahedral metal-organic cage, a model system is generated by considering an isolated metal-ion vertex: fac-ML3(2+) (M = Fe(II), Co(II); L = N-phenyl-2-pyridinaldimine). The sensitivity of the (1)H paramagnetic chemical shifts to local coordination environments is assessed and utilised to shed light on spin crossover behaviour in iron complexes. Our data indicate that expansion of the metal coordination sphere must precede any thermal SCO. An attempt to correlate experimental enthalpies of SCO with static properties of bound guests shows that no simple relationship exists, and that effects are likely due to nuanced dynamic response to encapsulation.

  2. Host-guest inclusion complex of propafenone hydrochloride with α- and β-cyclodextrins: Spectral and molecular modeling studies

    NASA Astrophysics Data System (ADS)

    Siva, S.; Thulasidhasan, J.; Rajendiran, N.

    2013-11-01

    Host-guest inclusion complexes of cyclodextrins (CDs) with a potential cardiovascular drug propafenone hydrochloride (PFO), were prepared and characterized using absorption, fluorescence, time-resolved fluorescence, SEM, FT-IR, DSC, 1H NMR, XRD and PM3 methods. The spectral studies suggested the phenyl ring along with carbonyl group is present inside of CD cavity. Solvent studies revealed that the normal Stokes shifted band originates from the locally excited state and the large Stokes shifted band occurs due to the emission from ICT. Nanosecond time-resolved studies indicated that PFO exhibits biexponential decay in water and triexponential decay in CD, indicating the formation of 1:1 inclusion complex. The results from solid state studies showed important modifications in the physicochemical properties of free PFO. The ΔH, ΔG and ΔS of the complexation process were determined and it was found that the complexation processes were spontaneous. Investigations of thermodynamic and electronic properties confirmed the stability of the inclusion complex.

  3. Self-Assembly PEGylation Retaining Activity (SPRA) Technology via a Host-Guest Interaction Surpassing Conventional PEGylation Methods of Proteins.

    PubMed

    Hirotsu, Tatsunori; Higashi, Taishi; Abu Hashim, Irhan Ibrahim; Misumi, Shogo; Wada, Koki; Motoyama, Keiichi; Arima, Hidetoshi

    2017-02-06

    Polyethylene glycol (PEG) modification (PEGylation) is one of the best approaches to improve the stabilities and blood half-lives of protein drugs; however, PEGylation dramatically reduces the bioactivities of protein drugs. Here, we present "self-assembly PEGylation retaining activity" (SPRA) technology via a host-guest interaction between PEGylated β-cyclodextrin (PEG-β-CyD) and adamantane-appended (Ad) proteins. PEG-β-CyD formed stable complexes with Ad-insulin and Ad-lysozyme to yield SPRA-insulin and SPRA-lysozyme, respectively. Both SPRA-proteins showed high stability against heat and trypsin digest, comparable with that of covalently PEGylated protein equivalents. Importantly, the SPRA-lysozyme possessed ca. 100% lytic activity, whereas the activity of the covalently PEGylated lysozyme was ca. 23%. Additionally, SPRA-insulin provided a prolonged and peakless blood glucose profile when compared with insulin glargine. It also showed no loss of activity. In contrast, the covalently PEGylated insulin showed a negligible hypoglycemic effect. These findings indicate that SPRA technology has potential as a generic method, surpassing conventional PEGylation methods for proteins.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    PubMed

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

    2015-10-15

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

  6. Synchronous spectrofluorimetric study of the supramolecular host-guest interaction of β-cyclodextrin with propranolol: A comparative study

    NASA Astrophysics Data System (ADS)

    Bani-Yaseen, Abdulilah Dawoud

    2015-09-01

    The objective of this work is to assess the use of constant-wavelength synchronous fluorescence spectroscopy (SFS) in comparison to conventional fluorescence spectroscopy (CFS) for the investigation of the supramolecular host-guest interaction of β-CD with propranolol (PPL) in aqueous solutions. Scanning for the optimal Δλ at which the SFS can be performed in the presence of β-CD was examined. The results obtained revealed three distinguishable shapes for PPL using SFS that can be represented by three different Δλ values, namely 10, 40, and 100 nm. However, the effect of the β-CD concentration on the fluorescence intensity of PPL was examined using CFS and SFS of PPL at a Δλ of 10 and 100 nm. The change in the fluorescence intensity was used to calculate the equilibrium constant (Keq) for the formation of the β-CD:PPL inclusion complex by applying the Benesi-Hildebrand method. Keq values of 108, 112, and 117 M-1 were obtained using SFS with a Δλ of 10 and 100 nm, and CFS, respectively. Further, the SFS method was successfully employed to examine the iodide quenching effect on the fluorescence intensity of PPL, where the results obtained revealed a Stern-Volmer quenching constant of 42.8 M-1, which is in good agreement with results obtained using CFS. All results obtained using the SFS method were compared with the results obtained using the CFS method.

  7. A size, shape and concentration controlled self-assembling structure with host-guest recognition at the liquid-solid interface studied by STM

    NASA Astrophysics Data System (ADS)

    Shen, Mengqi; Luo, Zhouyang; Zhang, Siqi; Wang, Shuai; Cao, Lili; Geng, Yanfang; Deng, Ke; Zhao, Dahui; Duan, Wubiao; Zeng, Qingdao

    2016-06-01

    In the present investigation, we reported the fabrication of host networks formed by two newly prepared phenanthrene-butadiynylene macrocycles (PBMs) at the liquid-solid interface. Size, shape and concentration controlled experiments have been performed to investigate the PBMs/coronene (COR) host-guest system with the structural polymorphism phenomenon. Initially, PBM1 could form a regular linear network structure and PBM2 form a well-ordered nanoporous network structure. When the COR molecules were introduced, the self-assembled structure of PBM1 remained unchanged, while COR could be entrapped into the cavities of the PBM2 nanoporous network, and the co-assembly of the PBM2/COR host-guest systems underwent a structural transformation with the increase of concentration of COR. Scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular nanoarrays controlled by the solution concentration.In the present investigation, we reported the fabrication of host networks formed by two newly prepared phenanthrene-butadiynylene macrocycles (PBMs) at the liquid-solid interface. Size, shape and concentration controlled experiments have been performed to investigate the PBMs/coronene (COR) host-guest system with the structural polymorphism phenomenon. Initially, PBM1 could form a regular linear network structure and PBM2 form a well-ordered nanoporous network structure. When the COR molecules were introduced, the self-assembled structure of PBM1 remained unchanged, while COR could be entrapped into the cavities of the PBM2 nanoporous network, and the co-assembly of the PBM2/COR host-guest systems underwent a structural transformation with the increase of concentration of COR. Scanning tunneling microscopy (STM) measurements and density functional theory (DFT) calculations are utilized to reveal the formation mechanism of the molecular nanoarrays controlled by the solution

  8. Thermal-cycling-induced spectral diffusion and thermal barriers in anisole-doped cyclohexane, an unusual multiphase host-guest system.

    PubMed

    Somoza, Mark M; Friedrich, Josef

    2006-09-28

    The host-guest system of anisole incorporated into a cyclohexane matrix was investigated in a series of hole-burning experiments. This system is unusual in that cyclohexane can freeze into coexisting solid phases. The hole-burning experiments support the existence of two crystalline phases and one disordered phase. A second surprising characteristic of this system is that the quasi-line absorption features of the spectra appear inverted at low temperature because of unexpected dominance of fluorescence and phosphorescence.

  9. Selective Host-Guest Co-crystallization of Pyridine-Functionalized Tetraphenylethylenes with Phthalic Acids and Multicolor Emission of the Co-crystals.

    PubMed

    Feng, Hai-Tao; Xiong, Jia-Bin; Luo, Jun; Feng, Wen-Fang; Yang, Desuo; Zheng, Yan-Song

    2017-01-12

    Tetraphenylethylene (TPE) and its derivatives are the most typical and most widely studied organic compounds showing aggregation-induced emission (AIE). Due to their propeller-like structures, V-like clefts exist between the aryl rings, which make them promising host compounds. However, such a possibility is seldom explored. Herein, it is reported that TPE derivatives bearing two or four pyridine rings at the para positions of the phenyl rings (TPE-Pys) can selectively include triangular (Δ-like) m-phthalic acid from a mixture of o-, m-, and p-phthalic acids due to their shape complementary to form host-guest co-crystals, which showed redder emission than the TPE-Pys themselves. The emission of co-crystals 1-5 could be reversibly switched between yellow and red by alternating exposure to HCl and ammonia vapor. The host-guest co-crystals not only exhibited great potential for selectively recognizing and separating m-phthalic acid and as multicolor emission materials, but are also suitable for use as secret ink due to their reversible color change on varying the host-guest interactions.

  10. Photonic hybrid crystals constructed from in situ host-guest nanoconfinement of a light-emitting complex in metal-organic framework pores.

    PubMed

    Chaudhari, Abhijeet K; Ryder, Matthew R; Tan, Jin-Chong

    2016-03-28

    We report the concept underpinning the facile nanoconfinement of a bulky luminous guest molecule in the pores of a metal-organic framework (MOF) host, which yields a hybrid host ⊃ guest nanomaterial with tunable opto-electronic characteristics and enhanced photostability. Utilizing an in situ host-guest confinement strategy enabled by molecular self-assembly, we show that the highly emitting ZnQ [Zn-(bis-8-hydroxyquinoline)] guest complexes could be rapidly encapsulated within the sodalite nanocages of zeolitic imidazolate framework (ZIF-8) host crystals. The nature of optical and electronic transitions phenomena of the guest-encapsulated ZIF-8 ⊃ ZnQ has been elucidated by means of fluorescence and absorption spectroscopy measurements, and substantiated further via theoretical molecular orbital calculations revealing the plausible host-guest charge transfer mechanism involved. Evidence suggests that its photophysical properties are not only strongly determined by the host-guest co-operative bonding interactions within the environment of the confined MOF nanocage, but also can be engineered to manipulate its emission color chromaticity or to shield light-sensitive emitting guests against rapid photochemical degradation.

  11. 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.

  12. Perylene Bisimide Cyclophanes with High Binding Affinity for Large Planar Polycyclic Aromatic Hydrocarbons: Host-Guest Complexation versus Self-Encapsulation of Side Arms.

    PubMed

    Spenst, Peter; Sieblist, Andreas; Würthner, Frank

    2017-01-31

    Binding of guest molecules with high affinity and selectivity requires well-designed hosts to provide optimized interactions in the host-guest complexes. Herein we report the design and synthesis of new cyclophanes 2PBI(2,6-iPr)2 and 2PBI(2,6-Ph)2 based on core-disubstituted perylene bisimide (PBI) chromophores bearing two phenoxy bay-substituents that evoke almost planar PBI scaffolds. This strategy afforded the new cyclophanes with conformationally rigid cavities to ensure strong binding to stiff planar polycyclic aromatic hydrocarbons (PAHs). Our detailed host-guest binding studies with different PAHs by UV/Vis and fluorescence titration experiments revealed record binding strengths for PAHs with binding constants of up to 1.6×10(6)  m(-1) in chloroform at room temperature. One- and two-dimensional NMR experiments and solvent-dependent titration studies revealed self-encapsulation of the side arms of PBI bay-substituents into the cavities that attained high fluorescence quantum yields of these cyclophanes close to unity by preventing the interaction of PBI subunits in the excited states. The binding constants and Gibbs free energies of host-guest complexations disclosed significant effects of PBI bay-substituents and core twist on the binding affinity of the cyclophanes.

  13. A fluorometric assay for alkaline phosphatase activity based on β-cyclodextrin-modified carbon quantum dots through host-guest recognition.

    PubMed

    Tang, Cong; Qian, Zhaosheng; Huang, Yuanyuan; Xu, Jiamin; Ao, Hang; Zhao, Meizhi; Zhou, Jin; Chen, Jianrong; Feng, Hui

    2016-09-15

    A convenient, reliable and highly sensitive assay for alkaline phosphatase (ALP) activity in the real-time manner is developed based on β-cyclodextrin-modified carbon quantum dots (β-CD-CQDs) nanoprobe through specific host-guest recognition. Carbon quantum dots were first functionalized with 3-aminophenyl boronic acid to produce boronic acid-functionalized CQDs, and then further modified with hydropropyl β-cyclodextrins (β-CD) through B-O bonds to form β-CD-CQDs nanoprobe. p-Nitrophenol phosphate disodium salt is used as the substrate of ALP, and can hydrolyze to p-nitrophenol under the catalysis of ALP. The resulting p-nitrophenol can enter the cavity of β-CD moiety in the nanoprobe due to their specific host-guest recognition, where photoinduced electron transfer process between p-nitrophenol and CQDs takes place to efficiently quench the fluorescence of the probe. The correlation between quenched fluorescence and ALP level can be used to establish quantitative evaluation of ALP activity in a broad range from 3.4 to 100.0U/L with the detection limit of 0.9U/L. This assay shows a high sensitivity to ALP even in the presence of a very high concentration of glucose. This study demonstrates a good electron donor/acceptor pair, which can be used to design general detection strategy through PET process, and also broadens the application of host-guest recognition for enzymes detection in clinical practice.

  14. Synthesis of Air-Stable Cyclopentadienyl Fe(CO)2 (Fp) Polymers by a Host-Guest Interaction of Cyclodextrin with Air-Sensitive Fp Pendant Groups.

    PubMed

    Zhou, Na; Peng, Liao; Salgado, Shehan; Yuan, Jinying; Wang, Xiaosong

    2017-03-13

    Host-guest chemistry is used to address the challenge of the synthesis of air-stable polymers containing air-sensitive metal complexes. The complexation of the CpFe(CO)2 (Fp) pendent group with cyclodextrin (CD) molecules created air-stable poly(Fp-methylstyrene) P(CD/FpMSt). This CD complexation resulted in dimerization of the adjacent Fp groups, which was characterized by NMR, FTIR, and cyclic voltammetry (CV) analyses. P(CD/FpMSt) was soluble in DMSO and remained stable even the solution was exposed to air for months. The host-guest chemistry accounted for the improved stability, because the Fp groups decomposed upon removal of the CD molecules using competing guest molecules. The CD-complexed polymer showed light-trigged properties, including CO release and antimicrobial activity. Host-guest chemistry of air-sensitive organometallic complexes is therefore a promising technique that can be used to broaden the scope of metal-containing polymers (MCPs) with processable novel functions.

  15. Host-guest interaction of adamantine with a β-cyclodextrin-functionalized AuPd bimetallic nanoprobe for ultrasensitive electrochemical immunoassay of small molecules.

    PubMed

    Wang, Lisong; Lei, Jianping; Ma, Rongna; Ju, Huangxian

    2013-07-02

    A modular labeling strategy was presented for electrochemical immunoassay via supramolecular host-guest interaction between β-cyclodextrin (β-CD) and adamantine (ADA). An ADA-labeled antibody (ADA-Ab) was synthesized via amidation, and the number of ADA moieties loaded on a single antibody was calculated to be ~7. The β-CD-functionalized gold-palladium bimetallic nanoparticles (AuPd-CD) were synthesized in aqueous solution via metal-S chemistry and characterized with transmission electron microscopy and X-ray photoelectron spectra. After the ADA-Ab was bound to the antigen-modified electrode surface with a competitive immunoreaction, AuPd-CD as a signal tag was immobilized onto the immunosensor by a host-guest interaction, leading to a large loading of AuPd nanoparticles. The highly efficient electrocatalysis by AuPd nanoparticles for NaBH4 oxidation produced an ultrasensitive response to chloramphenicol as a model of a small molecule antigen. The immunoassay method showed a wide linear range from 50 pg/mL to 50 μg/mL and a detection limit of 4.6 pg/mL. The specific recognition of antigen by antibody resulted in good selectivity for the proposed method. The host-guest interaction strategy provided a universal labeling approach for the ultrasensitive detection of small molecule targets.

  16. Host-guest kinetic interactions between HP-β-cyclodextrin and drugs for prediction of bitter taste masking.

    PubMed

    Guo, Zhen; Wu, Fei; Singh, Vikramjeet; Guo, Tao; Ren, Xiaohong; Yin, Xianzhen; Shao, Qun; York, Peter; Patterson, Laurence H; Zhang, Jiwen

    2017-03-20

    Cyclodextrins (CD) are widely used bitter taste masking agents, for which the binding equilibrium constant (K) for the drug-CD complex is a conventional parameter for quantitating the taste masking effects. However, some exceptions have been reported to the expected relationship between K and bitterness reduction and the relationship between kinetic parameters of a drug-CD interaction, including association rate constant (Ka) and disassociation rate constant (Kd), and taste masking remains unexplored. In this study, based upon a database of kinetic parameters of drugs-HP-β-CD generated by Surface Plasmon Resonance Imaging for 485 drugs, the host-guest kinetic interactions between drugs and HP-β-CD for prediction of taste masking effects have been investigated. The taste masking effects of HP-β-CD for 13 bitter drugs were quantitatively determined using an electronic gustatory system (α-Astree e-Tongue). Statistical software was used to establish a model based on Euclidean distance measurements, Ka and Kd of the bitter drugs/HP-β-CD-complexes (R(2)=0.96 and P<0.05). Optimized parameters, Ka(3), Kd, KaKd, Kd(3), Ka(2) and Ka/Kd with notable influence, were obtained by stepwise regression from 12 parameters derived from Ka, Kd and K (Ka/Kd). 10-fold cross-validation was used to verify the reliability of the model (correlation coefficient of 0.84, P<0.05). The established model indicated a relationship between Ka, Kd, K and taste masking by HP-β-CD and was successful in predicting the extent of taste masking by HP-β-CD of 44 bitter drugs, which was in accordance with the literature reported. In conclusion, the relationship between kinetics of drug-CD interactions and taste masking was established and providing a new strategy for predicting the cyclodextrin mediated bitter taste masking.

  17. A concept for the removal of microplastics from the marine environment with innovative host-guest relationships.

    PubMed

    Herbort, Adrian Frank; Schuhen, Katrin

    2017-04-01

    Environmental pollution caused by inert anthropogenic stressors such as microplastics in aquatic media is constantly increasing. Through the proliferating use of plastic products in daily life, more and more plastic particles enter waters as primary microplastics. Even though large scale plastic items such as plastic bottles and bags represent the highest percentage of plastic waste, their degeneration also generates microparticles and nanoparticles (secondary microplastics). Modern sewage treatment plants require innovative ideas in order to deal with this man-made problem. State-of-the-art technology offers approaches to minimise the amount of microplastics in aquatic systems. These technologies, however, are either insufficient or very costly, as well as time-consuming in both cases. The conceptual idea presented here is to apply innovative inorganic-organic hybrid silica gels which provide a cost-effective and straightforward approach. Currently, the synthesis of preorganised bioinspired compounds is advancing in order to produce functionalised hybrid silica gels in a further step. These gels have the ability to remove stressors such as microplastics from waste water. By means of the sol-gel process, bioinspired silane compounds are currently being permuted to macromolecules and examined with respect to their properties as fixation and filter material in order to remove the hydrophobic anthropogenic stressors sustainably. Here, the reproduction of biological systems plays a significant role. In particular in material sciences, this approach is becoming increasingly important. Among other concepts, new biomimetic molecules form the basis for the investigation of innovative host-guest relationships for anthropogenic stressors in the environment and their implementation in technical processes.

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  19. Experimental and theoretical charge density distribution in a host-guest system: synthetic terephthaloyl receptor complexed to adipic acid.

    PubMed

    Nguyen, Thanh Ha; Howard, Sian T; Hanrahan, Jane R; Groundwater, Paul W; Platts, James A; Hibbs, David E

    2012-06-14

    The experimental charge density distributions in a host-guest complex have been determined. The host, 1,4-bis[[(6-methylpyrid-2-yl)amino]carbonyl]benzene (1) and guest, adipic acid (2). The molecular geometries of 1 and 2 are controlled by the presence in the complex of intermolecular hydrogen bonding interactions and the presence in the host 1 of intramolecular hydrogen bonding motifs. This system therefore serves as an excellent model for studying noncovalent interactions and their effects on structure and electron density, and the transferability of electron distribution properties between closely related molecules. For the complex, high resolution X-ray diffraction data created the basis for a charge density refinement using a pseudoatomic multipolar expansion (Hansen-Coppens formalism) against extensive low-temperature (T = 100 K) single-crystal X-ray diffraction data and compared with a selection of theoretical DFT calculations on the same complex. The molecules crystallize in the noncentrosymmetric space group P2(1)2(1)2(1) with two independent molecules in the asymmetric unit. A topological analysis of the resulting density distribution using the atoms in molecules methodology is presented along with multipole populations, showing that the host and guest structures are relatively unaltered by the geometry changes on complexation. Three separate refinement protocols were adopted to determine the effects of the inclusion of calculated hydrogen atom anisotropic displacement parameters on hydrogen bond strengths. For the isotropic model, the total hydrogen bond energy differs from the DFT calculated value by ca. 70 kJ mol(-1), whereas the inclusion of higher multipole expansion levels on anisotropic hydrogen atoms this difference is reduced to ca. 20 kJ mol(-l), highlighting the usefulness of this protocol when describing H-bond energetics.

  20. Host-guest interactions between cyclodextrins and surfactants with functional groups at the end of the hydrophobic tail.

    PubMed

    Martín, Victoria Isabel; Ostos, Francisco José; Angulo, Manuel; Márquez, Antonio M; López-Cornejo, Pilar; López-López, Manuel; Carmona, Ana Teresa; Moyá, María Luisa

    2017-04-01

    The aim of this work was to investigate the influence of the incorporation of substituents at the end of the hydrophobic tail on the binding of cationic surfactants to α-, β-, and γ-cyclodextrins. The equilibrium binding constants of the 1:1 inclusion complexes formed follow the trend K1(α-CD)>K1(β-CD)≫K1(γ-CD), which can be explained by considering the influence of the CD cavity volume on the host-guest interactions. From the comparison of the K1 values obtained for dodecyltriethylammonium bromide, DTEAB, to those estimated for the surfactants with the substituents, it was found that the incorporation of a phenoxy group at the end of the hydrocarbon tail does not affect K1, and the inclusion of a naphthoxy group has some influence on the association process, slightly diminishing K1. This makes evident the importance of the contribution of hydrophobic interactions to the binding, the length of the hydrophobic chain being the key factor determining K1. However, the presence of the aromatic rings does influence the location of the host and the guest in the inclusion complexes. The observed NOE interactions between the aromatic protons and the CD protons indicate that the aromatic rings are partially inserted within the host cavity, with the cyclodextrin remaining close to the aromatic rings, which could be partially intercalated in the host cavity. To the authors' knowledge this is the first study on the association of cyclodextrins with monomeric surfactants incorporating substituents at the end of the hydrophobic tail.

  1. 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)ππ*) 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)ππ*) and (1)πσ* 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

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

    PubMed

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

    2016-03-18

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

  3. Host-Guest Chemistry between Perylene Diimide (PDI) Derivatives and 18-Crown-6: Enhancement in Luminescence Quantum Yield and Electrical Conductivity.

    PubMed

    Lasitha, P; Prasad, Edamana

    2016-07-18

    Perylene diimide (PDI) derivatives exhibit a high propensity for aggregation, which causes the aggregation-induced quenching of emission from the system. Host-guest chemistry is one of the best-known methods for preventing aggregation through the encapsulation of guest molecules. Herein we report the use of 18-crown-6 (18-C-6) as a host system to disaggregate suitably substituted PDI derivatives in methanol. 18-C-6 formed complexes with amino-substituted PDIs in methanol, which led to disaggregation and enhanced emission from the systems. Furthermore, the embedding of the PDI⋅18-C-6 complexes in poly(vinyl alcohol) (PVA) films generated remarkably high emission quantum yields (60-70 %) from the PDI derivatives. More importantly, the host-guest systems were tested for their ability to conduct electricity in PVA films. The electrical conductivities of the self-assembled systems in PVA were measured by electrochemical impedance spectroscopy (EIS) and the highest conductivity observed was 2.42×10(-5)  S cm(-1) .

  4. Facile fabrication of narrowly-distributed polymeric micelles via host-guest inclusion complexation of hyperbranched polymers and cyclodextrin and its two-dimensional self-assembly.

    PubMed

    Sun, Xiaoyi; Huang, Wei; Zhou, Yongfeng; Yan, Deyue

    2010-10-14

    A novel narrowly-distributed (ND) polymeric micelle obtained in combination with host-guest recognition and self-assembly is reported. First, the adamantyl-terminated hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO-AD) was synthesized by esterification of hyperbranched poly[3-ethyl-3-(hydroxymethyl)oxetane] (HBPO) with 1-adamantanecarbonyl chloride. Then the ND polymeric core-shell micelles, with the hydrophobic HBPO-AD cores and hydrophilic beta-cyclodextrin (β-CD) shells, were prepared via host-guest inclusion complexation of HBPO-AD and β-CD. The resultant polymer micelles were well characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Interestingly, after annealing at a temperature above the glass transition temperature (T(g)) for a certain time, the polymeric micelles can further self-assemble and fuse into two-dimensional (2D) sheets. The TEM, SEM and atomic force microscopy (AFM) characterization validate that the sheets are formed through stacking and fusion of tightly packed nanoparticles. In addition, the formation mechanism of polymeric complex micelles and 2D sheets has also been discussed.

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

    PubMed

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

    2013-07-15

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

  6. Host-guest chemistry in the gas phase: selected fragmentations of CB[6]-peptide complexes at lysine residues and its utility to probe the structures of small proteins.

    PubMed

    Heo, Sung Woo; Choi, Tae Su; Park, Kyung Man; Ko, Young Ho; Kim, Seung Bin; Kim, Kimoon; Kim, Hugh I

    2011-10-15

    The gas phase host-guest chemistry between cucurbit[6]uril (CB[6]) and peptide is investigated using electrospray ionization mass spectrometry (ESI-MS). CB[6] exhibits a high preference to interacting with a Lys residue in a peptide forming a CB[6]-peptide complex. Collisionally activated CB[6] complexes of peptides yield a common highly selective fragment product at m/z 549.2, corresponding to the doubly charged CB[6] complex of 5-iminiopentylammonium (5IPA). The process involves the formation of an internal iminium ion, which results from further fragments to an a-type ion from a y-type ion, and the resulting 5IPA ion threads through CB[6]. Numerous peptides are investigated to test the generality of the observed unique host-guest chemistry of CB[6]. Its potential utility in probing protein structures is demonstrated using CB[6] complexes of ubiquitin. Low-energy collision induced dissociation yields CB[6] complex fragments, and further MS(n) spectra reveal details of the CB[6] binding sites, which allow us to deduce the protein structure in the solution phase. The mechanisms and energetics of the observed reactions are evaluated using density functional theory calculations.

  7. Femtosecond Optical Tweezers

    NASA Astrophysics Data System (ADS)

    Peng, Jiahui; Wang, Lei; Sokolov, Alexei

    2004-10-01

    Optical tweezers has drawn much attention of people since recent years, which shows great advantages on biological applications due to quite straightforward ideas and simple configurations. Optical tweezers rely upon the extremely high gradient in the electric field produced near the beam waist of a tightly focused laser beam, which creates a force sufficient to trap micron-sized dielectric particles in three dimensions.(J.E. Molloy and M.J. Padgett, Light, Action: Optical Tweezers, Contemporary P)hysics, 43 241 (2002). We applied a femtosecond laser on optical tweezers as light source and got successfully ``optical trapping'' and ``optical tweezers.'' Further, due to the characters of short pulse width and extremely high intensity of laser, femtosecond optical tweezers may direct us to new optics field. Under such strong intensity many non-linear optical phenomena could be observable, such like optical Kerr effect, stimulated Raman effect and so on. Our work will shows that it may be applied into the recently proposed FAST CAR (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Spectroscopy) by M. Scully et. al.(M. O. Scully, G. W. Kattawar, R. P. Lucht, T. Opatrny, H. Pilloff, A. Rebane, A. V. Sokolov, and M. S. Zubairy, ``FAST CARS: Engineering a Laser Spectroscopic Technique for Rapid Identification of Bacterial Spores,'' Proceedings of NASE (2002).)

  8. Automation of optical tweezers

    NASA Astrophysics Data System (ADS)

    Hsieh, Tseng-Ming; Chang, Bo-Jui; Hsu, Long

    2000-07-01

    Optical tweezers is a newly developed instrument, which makes possible the manipulation of micro-optical particles under a microscope. In this paper, we present the automation of an optical tweezers which consists of a modified optical tweezers, equipped with two motorized actuators to deflect a 1 W argon laser beam, and a computer control system including a joystick. The trapping of a single bead and a group of lactoacidofilus was shown, separately. With the aid of the joystick and two auxiliary cursers superimposed on the real-time image of a trapped bead, we demonstrated the simple and convenient operation of the automated optical tweezers. By steering the joystick and then pressing a button on it, we assign a new location for the trapped bead to move to. The increment of the motion 0.04 (mu) m for a 20X objective, is negligible. With a fast computer for image processing, the manipulation of the trapped bead is smooth and accurate. The automation of the optical tweezers is also programmable. This technique may be applied to accelerate the DNA hybridization in a gene chip. The combination of the modified optical tweezers with the computer control system provides a tool for precise manipulation of micro particles in many scientific fields.

  9. Removal of sulfamethoxazole sulfonamide antibiotic from water by high silica zeolites: a study of the involved host-guest interactions by a combined structural, spectroscopic, and computational approach.

    PubMed

    Blasioli, Sonia; Martucci, Annalisa; Paul, Geo; Gigli, Lara; Cossi, Maurizio; Johnston, Cliff T; Marchese, Leonardo; Braschi, Ilaria

    2014-04-01

    Sulfonamide antibiotics are persistent pollutants present in surface and subsurface waters in both agricultural and urban environments. Sulfonamides are of particular concern in the environment because they are known to induce high levels of bacterial resistance. Adsorption of sulfamethoxazole sulfonamide antibiotic into three high silica zeolites (Y, mordenite, and ZSM-5) with pore opening sizes comparable to sulfamethoxazole dimensions is reported. Sulfamethoxazole was almost completely removed from water by zeolite Y and MOR in a few minutes. Adsorption onto ZSM-5 showed an increased kinetics with increasing temperature. Antibiotic sorption was largely irreversible with little antibiotic desorbed. Sulfamethoxazole incorporation and localization into the pore of each zeolite system was defined along with medium-weak and cooperative host-guest interactions in which water molecules play a certain role only in zeolite Y and mordenite.

  10. NMR, surface tension and conductance study to investigate host-guest inclusion complexes of three sequential ionic liquids with β-cyclodextrin in aqueous media

    NASA Astrophysics Data System (ADS)

    Barman, Siti; Ekka, Deepak; Saha, Subhadeep; Roy, Mahendra Nath

    2016-08-01

    Host-guest inclusion complexes of three sequential cationic room temperature surface active ionic liquids, benzyltrialkylammonium chloride [(C6H5CH2)N(CnH2n+1)3Cl; where n = 1, 2, 4] with β-cyclodextrin in aqueous media have been studied using surface tension, conductance and NMR spectroscopy. All the studies have suggested that the hydrophobic benzyl group of ionic liquids is encapsulated inside into the cavity of β-cyclodextrin and played a crucial role in supporting the formation of inclusion complexes. The variation of the thermodynamic parameters with guest size, shape is used to draw inferences about contributions to the overall binding by means of the driving forces, viz., hydrophobic effect, steric hindrance, van der Waal force, and electrostatic force.

  11. On the characterization of host-guest complexes: surface tension, calorimetry, and molecular dynamics of cyclodextrins with a non-ionic surfactant.

    PubMed

    Piñeiro, Angel; Banquy, Xavier; Pérez-Casas, Silvia; Tovar, Edgar; García, Abel; Villa, Alessandra; Amigo, Alfredo; Mark, Alan E; Costas, Miguel

    2007-05-03

    Three host-guest systems have been characterized using surface tension (sigma), calorimetry, and molecular dynamics simulations (MD). The hosts were three native cyclodextrins (CD) and the guest the non-ionic carbohydrate surfactant octyl-beta-d-glucopyranoside. It is shown that, for any host-guest system, a rough screening of the most probable complex stoichiometries can be obtained in a model free form, using only calorimetric data. The sigma data were analyzed using a model that includes a newly proposed adsorption isotherm. The equilibrium constants for several stoichiometries were simultaneously obtained through fitting the sigma data. For alpha- and beta-CD, the predominant species is 1:1 and to a lesser extent 2:1, disregarding the existence of the 1:2. For gamma-CD, the 1:2 species dominates, the other two being also present. In an attempt to confirm these results, 10 ns MD simulations for each CD were performed using seven different starting conformations. The MD stable conformations agree with the results found from the experimental data. In one case, the spontaneous dissociation-formation of a complex was observed. Analysis of the trajectories indicates that hydrophobic interactions are primarily responsible for the formation and stability of the inclusion complexes. For the 2:1 species, intermolecular H-bonds between CD molecules result in a tight packed structure where their original truncated cone shape is lost in favor of a cylindrical geometry. Together, the results clearly demonstrate that the often used assumption of considering only a 1:1 species is inappropriate.

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  13. Fluorescent Cross-Linked Supramolecular Polymer Constructed by Orthogonal Self-Assembly of Metal-Ligand Coordination and Host-Guest Interaction.

    PubMed

    Qian, Xiaomin; Gong, Weitao; Li, Xiaopeng; Fang, Le; Kuang, Xiaojun; Ning, Guiling

    2016-05-10

    A new host molecule consists of four terpyridine groups as the binding sites with zinc(II) ion and a copillar[5]arene incorporated in the center as a spacer to interact with guest molecule was designed and synthesized. Due to the 120 ° angle of the rigid aromatic segment, a cross-linked dimeric hexagonal supramolecular polymer was therefore generated as the result of the orthogonal self-assembly of metal-ligand coordination and host-guest interaction. UV/Vis spectroscopy, (1) H NMR spectroscopy, viscosity and dynamic light-scattering techniques were employed to characterize and understand the cross-linking process with the introduction of zinc(II) ion and guest molecule. More importantly, well-defined morphology of the self-assembled supramolecular structure can be tuned by altering the adding sequence of the two components, that is, the zinc(II) ion and the guest molecule. In addition, introduction of a competitive ligand suggested the dynamic nature of the supramolecular structure.

  14. Dual absorber Fe2O3/WO3 host-guest architectures for improved charge generation and transfer in photoelectrochemical applications

    NASA Astrophysics Data System (ADS)

    Müller, Alexander; Kondofersky, Ilina; Folger, Alena; Fattakhova-Rohlfing, Dina; Bein, Thomas; Scheu, Christina

    2017-01-01

    In this study the influence of the spatial distribution and of different nanostructures of WO3 and Fe2O3 in the dual absorber system Fe2O3/WO3 was systematically investigated for the first time. WO3 was applied as a scaffold and/or as a surface treatment to mesoporous Fe2O3 films. Both approaches strongly increased the performance compared to the individual photoabsorbers. By combining a host guest architecture with a surface treatment, current densities of about 0.7 mA cm‑2 at 1.23 V versus reversible hydrogen electrode under AM 1.5 illumination with an incident photon-to-current efficiency of 17% at 350 nm were achieved without the use of further catalysts. We could identify several beneficial interactions between Fe2O3 and WO3. WO3 strongly scatters visible light, resulting in increased absorption by Fe2O3 and higher current densities. We also determined a cathodic shift in the onset potential to 0.8 V and increased transfer rates of up to 88%. This combination of beneficial effects proves the viability of the presented device architecture.

  15. Resolving the problem of trapped water in binding cavities: prediction of host-guest binding free energies in the SAMPL5 challenge by funnel metadynamics

    NASA Astrophysics Data System (ADS)

    Bhakat, Soumendranath; Söderhjelm, Pär

    2017-01-01

    The funnel metadynamics method enables rigorous calculation of the potential of mean force along an arbitrary binding path and thereby evaluation of the absolute binding free energy. A problem of such physical paths is that the mechanism characterizing the binding process is not always obvious. In particular, it might involve reorganization of the solvent in the binding site, which is not easily captured with a few geometrically defined collective variables that can be used for biasing. In this paper, we propose and test a simple method to resolve this trapped-water problem by dividing the process into an artificial host-desolvation step and an actual binding step. We show that, under certain circumstances, the contribution from the desolvation step can be calculated without introducing further statistical errors. We apply the method to the problem of predicting host-guest binding free energies in the SAMPL5 blind challenge, using two octa-acid hosts and six guest molecules. For one of the hosts, well-converged results are obtained and the prediction of relative binding free energies is the best among all the SAMPL5 submissions. For the other host, which has a narrower binding pocket, the statistical uncertainties are slightly higher; longer simulations would therefore be needed to obtain conclusive results.

  16. A combined treatment of hydration and dynamical effects for the modeling of host-guest binding thermodynamics: the SAMPL5 blinded challenge

    NASA Astrophysics Data System (ADS)

    Pal, Rajat Kumar; Haider, Kamran; Kaur, Divya; Flynn, William; Xia, Junchao; Levy, Ronald M.; Taran, Tetiana; Wickstrom, Lauren; Kurtzman, Tom; Gallicchio, Emilio

    2017-01-01

    As part of the SAMPL5 blinded experiment, we computed the absolute binding free energies of 22 host-guest complexes employing a novel approach based on the BEDAM single-decoupling alchemical free energy protocol with parallel replica exchange conformational sampling and the AGBNP2 implicit solvation model specifically customized to treat the effect of water displacement as modeled by the Hydration Site Analysis method with explicit solvation. Initial predictions were affected by the lack of treatment of ionic charge screening, which is very significant for these highly charged hosts, and resulted in poor relative ranking of negatively versus positively charged guests. Binding free energies obtained with Debye-Hückel treatment of salt effects were in good agreement with experimental measurements. Water displacement effects contributed favorably and very significantly to the observed binding affinities; without it, the modeling predictions would have grossly underestimated binding. The work validates the implicit/explicit solvation approach employed here and it shows that comprehensive physical models can be effective at predicting binding affinities of molecular complexes requiring accurate treatment of conformational dynamics and hydration.

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  18. Predicting binding affinities of host-guest systems in the SAMPL3 blind challenge: the performance of relative free energy calculations

    NASA Astrophysics Data System (ADS)

    König, Gerhard; Brooks, Bernard R.

    2012-05-01

    Relative free energy calculations based on molecular dynamics simulations are combined with available experimental binding free energies to predict unknown binding affinities of acyclic Cucurbituril complexes in the blind SAMPL3 competition. The predictions yield root mean square errors between 2.6 and 3.2 kcal/mol for seven host-guest systems. Those deviations are comparable to results for solvation free energies of small organic molecules. However, the standard deviations found in our simulations range from 0.4 to 2.4 kcal/mol, which indicates the need for better sampling. Three different approaches are compared. Bennett's Acceptance Ratio Method and thermodynamic integration based on the trapezoidal rule with 12 λ-points exhibit a root mean square error of 2.6 kcal/mol, while thermodynamic integration with Simpson's rule and 11 λ-points leads to a root mean square error of 3.2 kcal/mol. In terms of absolute median errors, Bennett's Acceptance Ratio Method performs better than thermodynamic integration with the trapezoidal rule (1.7 vs. 2.9 kcal/mol). Simulations of the deprotonated forms of the guest molecules exhibit a poorer correspondence to experimental results with a root mean square error of 5.2 kcal/mol. In addition, a decrease of the buffer concentration by approximately 20 mM in the simulations raises the root mean square error to 3.8 kcal/mol.

  19. Host-guest chemistry in the gas phase: complex formation with 18-crown-6 enhances helicity of alanine-based peptides.

    PubMed

    Ko, Jae Yoon; Heo, Sung Woo; Lee, Joon Ho; Oh, Han Bin; Kim, Hyungjun; Kim, Hugh I

    2011-12-15

    The gas-phase helix propensities of alanine-based polypeptides are studied with different locations of a Lys residue and host-guest interactions with 18-Crown-6 (18C6). A series of model peptides Ac-Ala(9-n)-LysH(+)-Ala(n) (n = 0, 1, 3, 5, 7, and 9) is examined alone and with 18C6 using traveling wave ion mobility mass spectrometry combined with molecular dynamics (MD) simulations. The gas-phase helices are observed from the peptides whose Lys residue is located close to the C-terminus so that the Lys exerts its capping effect on the C-terminal carbonyl groups. The peptides, which interact with 18C6 in the gas phase, show enhanced helical propensities. The enhanced helicity of the peptide in the complex is attributed by isolation of the Lys butylammonium group from the helix backbone and the interaction of methylene groups of 18C6, which possess localized positive partial charges, with C-terminal carbonyl groups serving as a cap to stabilize the helix.

  20. Sensitive fluorescence detection of ATP based on host-guest recognition between near-infrared β-Cyclodextrin-CuInS2 QDs and aptamer.

    PubMed

    Hu, Tianyu; Na, Weidan; Yan, Xu; Su, Xingguang

    2017-04-01

    We have developed a near-infrared (NIR) fluorescent aptamer-based sensor for sensitive detection of adenosine-5'-triphosphate (ATP) by using a ATP-binding aptamer and β-Cyclodextrin-CuInS2 quantum dots (β-CD-CuInS2 QDs). The fluorescence of β-CD-CuInS2 QDs has a slight enhancement with the addition of ATP-binding aptamer due to the host-guest recognition between aptamer and β-CD. When ATP is added, it will bind to aptamer to form G-quadruplexes. Aptamer-ATP complexes can enter into the hydrophobic cavities of β-CD and result in great enhancement of the fluorescence intensity. Under the optimum conditions, the fluorescence intensity of β-CD-CuInS2 QDs is proportional to the concentration of ATP, which shows a good linear response toward ATP concentration range of 6-1200μmolL(-1), the detection limit for ATP is 3μmolL(-1). The present assay shows a good selectivity for ATP over other biologically important proteins, and it is applied to the determination of ATP in human serum sample with satisfactory results.

  1. Q-dots and Q-wires in the microporous and mesoporous zeolite as matrix host-guest and guest-guest interaction

    NASA Astrophysics Data System (ADS)

    Tel'biz, German M.; Shvets, Olexyi V.; Brodyn, Michail S.; Vozny, Volodymyr L.

    2001-04-01

    We report here on the development of host-guest and guest-guest interaction in course of preparation procedures semiconductor clusters (CdS, PbI2), in zeolite (FAU,LTL) matrix. Optical properties of practically unexplored PbI2/zeolite LTL system have been investigated. Both in absorption (reconstructed from diffuse reflection via Kubelka-Munk function) and luminescence spectra the features were observed at energies much exceeding the excitation resonance energy Eex in bulk PbI2. This is considered as an indication of size quantization through the unambiguous attribution of the respective transitions requires further studies, including theoretical ones. For the samples with relatively high PbI2 content the narrow emission peak only slightly blue-shifted from Eex was observed and attributed to long clusters formed inside the main channels of zeolite LTL lattice and possible retaining the layer structure of bulk PbI2. The gradual disappearance of this peak during the storage of samples in the air is explained by assuming that originally formed long clusters undergo fragmentation into smaller species.

  2. Predicting binding affinities of host-guest systems in the SAMPL3 blind challenge: the performance of relative free energy calculations.

    PubMed

    König, Gerhard; Brooks, Bernard R

    2012-05-01

    Relative free energy calculations based on molecular dynamics simulations are combined with available experimental binding free energies to predict unknown binding affinities of acyclic Cucurbituril complexes in the blind SAMPL3 competition. The predictions yield root mean square errors between 2.6 and 3.2 kcal/mol for seven host-guest systems. Those deviations are comparable to results for solvation free energies of small organic molecules. However, the standard deviations found in our simulations range from 0.4 to 2.4 kcal/mol, which indicates the need for better sampling. Three different approaches are compared. Bennett's Acceptance Ratio Method and thermodynamic integration based on the trapezoidal rule with 12 λ-points exhibit a root mean square error of 2.6 kcal/mol, while thermodynamic integration with Simpson's rule and 11 λ-points leads to a root mean square error of 3.2 kcal/mol. In terms of absolute median errors, Bennett's Acceptance Ratio Method performs better than thermodynamic integration with the trapezoidal rule (1.7 vs. 2.9 kcal/mol). Simulations of the deprotonated forms of the guest molecules exhibit a poorer correspondence to experimental results with a root mean square error of 5.2 kcal/mol. In addition, a decrease of the buffer concentration by approximately 20 mM in the simulations raises the root mean square error to 3.8 kcal/mol.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  4. Core-shell structured nanoassemblies based on β-cyclodextrin containing block copolymer and poly(β-benzyl L-aspartate) via host-guest complexation

    PubMed Central

    Zhang, Jianxiang; Ma, Peter X

    2011-01-01

    Double hydrophilic copolymers (PEG-b-PCDs) with one PEG block and another block containing β-cyclodextrin (β-CD) units were synthesized by macromolecular substitution reaction. Via a dialysis procedure, complex assemblies with a core-shell structure were prepared using PEG-b-PCDs in the presence of a hydrophobic homopolymer poly(β-benzyl L-aspartate) (PBLA). The hydrophobic PBLA resided preferably in the cores of assemblies, while the extending PEG chains acted as the outer shell. Host-guest interaction between β-CD and hydrophobic benzyl group was found to mediate the formation of the assemblies, where PEG-b-PCD and PBLA served as the host and guest macromolecules, respectively. The particle size of the assemblies could be modulated by the composition of the host PEG-b-PCD copolymer. The molecular weight of the guest polymer also had a significant effect on the size of the assemblies. The assemblies prepared from the host and guest polymer pair were stable during a long-term storage. These assemblies could also be successfully reconstituted after freeze-drying. The assemblies may therefore be used as novel nanocarriers for the delivery of hydrophobic drugs. PMID:22046058

  5. Cyclen dithiocarbamate-functionalized silver nanoparticles as a probe for colorimetric sensing of thiram and paraquat pesticides via host-guest chemistry

    NASA Astrophysics Data System (ADS)

    Rohit, Jigneshkumar V.; Kailasa, Suresh Kumar

    2014-11-01

    We have developed a simple and rapid colorimetric method for on-site analysis of thiram and paraquat using cyclen dithiocarbamate-functionalized silver nanoparticles (CN-DTC-Ag NPs) as a colorimetric probe. The synthesized CN-DTC-Ag NPs were characterized by UV-Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy, dynamic light scattering, and transmission electron microscopic techniques. The CN-DTC molecules provide good supramolecular self assembly on the surfaces of Ag NPs to encapsulate thiram and paraquat selectively via "host-guest" chemistry, resulting in red-shift in surface plasmon resonance peak of CN-DTC-Ag NPs from 396 to 530 nm and 510 nm and color change from yellow to pink for thiram and to orange for paraquat, which can be naked-eye detected. The present method shows good linearity in the range of 10.0-20.0 µM and of 50.0-250 µM with limits of detection 2.81 × 10-6 M and 7.21 × 10-6 M for thiram and paraquat, respectively. This method was proved as a promising tool for on-site and real-time monitoring of thiram and paraquat in environmental water, potato, and wheat samples.

  6. 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.

  7. The SAMPL5 host-guest challenge: computing binding free energies and enthalpies from explicit solvent simulations by the attach-pull-release (APR) method

    NASA Astrophysics Data System (ADS)

    Yin, Jian; Henriksen, Niel M.; Slochower, David R.; Gilson, Michael K.

    2017-01-01

    The absolute binding free energies and binding enthalpies of twelve host-guest systems in the SAMPL5 blind challenge were computed using our attach-pull-release (APR) approach. This method has previously shown good correlations between experimental and calculated binding data in retrospective studies of cucurbit[7]uril (CB7) and β-cyclodextrin (βCD) systems. In the present work, the computed binding free energies for host octa acid (OA or OAH) and tetra-endo-methyl octa-acid (TEMOA or OAMe) with guests are in good agreement with prospective experimental data, with a coefficient of determination (R2) of 0.8 and root-mean-squared error of 1.7 kcal/mol using the TIP3P water model. The binding enthalpy calculations achieve moderate correlations, with R2 of 0.5 and RMSE of 2.5 kcal/mol, for TIP3P water. Calculations using the newly developed OPC water model also show good performance. Furthermore, the present calculations semi-quantitatively capture the experimental trend of enthalpy-entropy compensation observed, and successfully predict guests with the strongest and weakest binding affinity. The most populated binding poses of all twelve systems, based on clustering analysis of 750 ns molecular dynamics (MD) trajectories, were extracted and analyzed. Computational methods using MD simulations and explicit solvent models in a rigorous statistical thermodynamic framework, like APR, can generate reasonable predictions of binding thermodynamics. Especially with continuing improvement in simulation force fields, such methods hold the promise of making substantial contributions to hit identification and lead optimization in the drug discovery process.

  8. Amplified fluorescence detection of adenosine via catalyzed hairpin assembly and host-guest interactions between β-cyclodextrin polymer and pyrene.

    PubMed

    Huang, Haihua; Yang, Xiaohai; Wang, Kemin; Wang, Qing; Guo, Qiuping; Huang, Jin; Liu, Jianbo; Song, Chunxia

    2016-04-21

    Nowadays, enzyme-free nucleic acid-based signal amplification strategies are frequently utilized in the design of biosensors due to their excellent sensitivity. Developing more extended analytical methods is fundamental for basic studies in the biological and biomedical fields. Herein, we introduce an enzyme-free amplified detection strategy for the small molecule adenosine. The approach is based on adenosine-aptamer binding triggered catalyzed hairpin assembly and host-guest interactions between β-cyclodextrin polymer (β-CDP) and pyrene. Two hairpin probes (probe H1 and probe H2) and an aptamer-trigger/inhibitor duplex probe were employed in the system and the pyrene-labeled probe H1 was chosen as the signal unit. In the absence of adenosine, the aptamer-trigger was inhibited by the inhibitor strand. The hairpin probes were in the closed hairpin formation without activation of the trigger strand. Pyrene labeled at the 5'-termini of the single-stranded stem of probe H1 could be easily trapped in the hydrophobic cavity of β-CDP because of weak steric hindrance, leading to a significant fluorescence enhancement. Once the hairpin assembly was catalyzed by the adenosine-aptamer binding event, a hybridized DNA duplex H1/H2 was created continuously. Pyrene labeled at the 5'-termini of the DNA duplex H1/H2 finds it difficult to enter the cavity of β-CDP due to steric hindrance, leading to a weaker fluorescence signal. Thus, the target could be detected by this simple mix-and-detect amplification method without a need for expensive and perishable protein enzymes. As low as 42 nM of adenosine was detected by this assay, which is comparable to that of some reported colorimetric methods. Meanwhile, the proposed method was further successfully applied to detect adenosine in human serum samples, showing great potential for adenosine detection from complex fluids.

  9. Gate-opening gas adsorption and host-guest interacting gas trapping behavior of porous coordination polymers under applied AC electric fields.

    PubMed

    Kosaka, Wataru; Yamagishi, Kayo; Zhang, Jun; Miyasaka, Hitoshi

    2014-09-03

    The gate-opening adsorption behavior of the one-dimensional chain compound [Ru2(4-Cl-2-OMePhCO2)4(phz)] (1; 4-Cl-2-OMePhCO2(-) = 4-chloro-o-anisate; phz = phenazine) for various gases (O2, NO, and CO2) was electronically monitored in situ by applying ac electric fields to pelletized samples attached to a cryostat, which was used to accurately control the temperature and gas pressure. The gate-opening and -closing transitions induced by gas adsorption/desorption, respectively, were accurately monitored by a sudden change in the real part of permittivity (ε'). The transition temperature (TGO) was also found to be dependent on the applied temperature and gas pressure according to the Clausius-Clapeyron equation. This behavior was also observed in the isostructural compound [Rh2(4-Cl-2-OMePhCO2)4(phz)] (2), which exhibited similar gate-opening adsorption properties, but was not detected in the nonporous gate-inactive compound [Ru2(o-OMePhCO2)4(phz)] (3). Furthermore, the imaginary part of permittivity (ε″) effectively captured the electronic perturbations of the samples induced by the introduced guest molecules. Only the introduction of NO resulted in the increase of the sample's electronic conductivity for 1 and 3, but not for 2. This behavior indicates that electronic host-guest interactions were present, albeit very weak, at the surface of sample 1 and 3, i.e., through grain boundaries of the sample, which resulted in perturbation of the conduction band of this material's framework. This technique involving the in situ application of ac electric fields is useful not only for rapidly monitoring gas sorption responses accompanied by gate-opening/-closing structural transitions but also potentially for the development of molecular framework materials as chemically driven electronic devices.

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

    PubMed

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

    2008-11-15

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

  11. Are electron tweezers possible?

    PubMed

    Oleshko, Vladimir P; Howe, James M

    2011-11-01

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

  12. Optical tweezers on biaxial crystal

    NASA Astrophysics Data System (ADS)

    Angelsky, Oleg V.; Maksimyak, Andrew P.; Maksimyak, Peter P.

    2009-10-01

    In this paper, we propose optical tweezers based on a biaxial crystal. To control the movement of opaque particles, we use the shift polarization interferometer. The results of experimental study of laser tweezers are shown. We demonstrates movement of a microparticle of toner using singular-optical trap, rotate a particle due to orbital momentum, conversion of two traps when changing the plane of polarizer transmission and converging of two traps.

  13. On the fly estimation of host-guest binding free energies using the movable type method: participation in the SAMPL5 blind challenge

    NASA Astrophysics Data System (ADS)

    Bansal, Nupur; Zheng, Zheng; Cerutti, David S.; Merz, Kenneth M.

    2017-01-01

    We review our performance in the SAMPL5 challenge for predicting host-guest binding affinities using the movable type (MT) method. The challenge included three hosts, acyclic Cucurbit[2]uril and two octa-acids with and without methylation at the entrance to their binding cavities. Each host was associated with 6-10 guest molecules. The MT method extrapolates local energy landscapes around particular molecular states and estimates the free energy by Monte Carlo integration over these landscapes. Two blind submissions pairing MT with variants of the KECSA potential function yielded mean unsigned errors of 1.26 and 1.53 kcal/mol for the non-methylated octa-acid, 2.83 and 3.06 kcal/mol for the methylated octa-acid, and 2.77 and 3.36 kcal/mol for Cucurbit[2]uril host. While our results are in reasonable agreement with experiment, we focused on particular cases in which our estimates gave incorrect results, particularly with regard to association between the octa-acids and an adamantane derivative. Working on the hypothesis that differential solvation effects play a role in effecting computed binding affinities for the parent octa-acid and the methylated octa-acid and that the ligands bind inside the pockets (rather than on the surface) we devised a new solvent accessible surface area term to better quantify solvation energy contributions in MT based studies. To further explore this issue a, molecular dynamics potential of mean force (PMF) study indicates that, as found by our docking calculations, the stable binding mode for this ligand is inside (rather than surface bound) the octa-acid cavity whether the entrance is methylated or not. The PMF studies also obtained the correct order for the methylation-induced change in binding affinities and associated the difference, to a large extent to differential solvation effects. Overall, the SAMPL5 challenge yielded in improvements our solvation modeling and also demonstrated the need for thorough validation of input data

  14. Theoretical exploration of the nanoscale host-guest interactions between [n]cycloparaphenylenes (n = 10, 8 and 9) and fullerene C₆₀: from single- to three-potential well.

    PubMed

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

    2015-07-28

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

  15. Optical Tweezer Assembly and Calibration

    NASA Technical Reports Server (NTRS)

    Collins, Timothy M.

    2004-01-01

    An Optical Tweezer, as the name implies, is a useful tool for precision manipulation of micro and nano scale objects. Using the principle of electromagnetic radiation pressure, an optical tweezer employs a tightly focused laser beam to trap and position objects of various shapes and sizes. These devices can trap micrometer and nanometer sized objects. An exciting possibility for optical tweezers is its future potential to manipulate and assemble micro and nano sized sensors. A typical optical tweezer makes use of the following components: laser, mirrors, lenses, a high quality microscope, stage, Charge Coupled Device (CCD) camera, TV monitor and Position Sensitive Detectors (PSDs). The laser wavelength employed is typically in the visible or infrared spectrum. The laser beam is directed via mirrors and lenses into the microscope. It is then tightly focused by a high magnification, high numerical aperture microscope objective into the sample slide, which is mounted on a translating stage. The sample slide contains a sealed, small volume of fluid that the objects are suspended in. The most common objects trapped by optical tweezers are dielectric spheres. When trapped, a sphere will literally snap into and center itself in the laser beam. The PSD s are mounted in such a way to receive the backscatter after the beam has passed through the trap. PSD s used with the Differential Interference Contrast (DIC) technique provide highly precise data. Most optical tweezers employ lasers with power levels ranging from 10 to 100 miliwatts. Typical forces exerted on trapped objects are in the pico-newton range. When PSDs are employed, object movement can be resolved on a nanometer scale in a time range of milliseconds. Such accuracy, however, can only by utilized by calibrating the optical tweezer. Fortunately, an optical tweezer can be modeled accurately as a simple spring. This allows Hook s Law to be used. My goal this summer at NASA Glenn Research Center is the assembly and

  16. 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.

  17. Plasmon nano-optical tweezers

    NASA Astrophysics Data System (ADS)

    Juan, Mathieu L.; Righini, Maurizio; Quidant, Romain

    2011-06-01

    Conventional optical tweezers, formed at the diffraction-limited focus of a laser beam, have become a powerful and flexible tool for manipulating micrometre-sized objects. Extending optical trapping down to the nanometre scale would open unprecedented opportunities in many fields of science, where such nano-optical tweezers would allow the ultra-accurate positioning of single nano-objects. Among the possible strategies, the ability of metallic nanostructures to control light at the subwavelength scale can be exploited to engineer such nano-optical traps. This Review summarizes the recent advances in the emerging field of plasmon-based optical trapping and discusses the details of plasmon tweezers along with their potential applications to bioscience and quantum optics.

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

    PubMed

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

    2015-01-15

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

  19. Optical tweezers: 20 years on.

    PubMed

    McGloin, David

    2006-12-15

    In 1986, Arthur Ashkin and colleagues published a seminal paper in Optics Letters, 'Observation of a single-beam gradient force optical trap for dielectric particles' which outlined a technique for trapping micrometre-sized dielectric particles using a focused laser beam, a technology which is now termed optical tweezers. This paper will provide a background in optical manipulation technologies and an overview of the applications of optical tweezers. It contains some recent work on the optical manipulation of aerosols and concludes with a critical discussion of where the future might lead this maturing technology.

  20. Optical tweezers for confocal microscopy

    NASA Astrophysics Data System (ADS)

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

    2000-11-01

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

  1. Bright Fluorescence and Host-Guest Sensing with a Nanoscale M₄L₆ Tetrahedron Accessed by Self-Assembly of Zinc-Imine Chelate Vertices and Perylene Bisimide Edges.

    PubMed

    Frischmann, Peter D; Kunz, Valentin; Würthner, Frank

    2015-06-15

    A highly luminescent Zn4L6 tetrahedron is reported with 3.8 nm perylene bisimide edges and hexadentate Zn(II)-imine chelate vertices. Replacing Fe(II) and monoamines commonly utilized in subcomponent self-assembly with Zn(II) and tris(2-aminoethyl)amine provides access to a metallosupramolecular host with the rare combination of structural integrity at concentrations <10(-7) mol L(-1) and an exceptionally high fluorescence quantum yield of Φ(em) =0.67. Encapsulation of multiple perylene or coronene guest molecules is accompanied by strong luminescence quenching. We anticipate this self-assembly strategy may be generalized to improve access to brightly fluorescent coordination cages tailored for host-guest light-harvesting, photocatalysis, and sensing.

  2. Synthesis and solid-state study of supramolecular host-guest assemblies: Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] dichalcogenides.

    PubMed

    Potrzebowski, Marek J; Potrzebowski, Wojciech M; Jeziorna, Agata; Ciesielski, Wlodzimierz; Gajda, Jarosław; Bujacz, Grzegorz D; Chruszcz, Maksymilian; Minor, Wladek

    2008-06-20

    A complementary approach for studying structural details of complex solid materials formed by symmetrical and unsymmetrical dichalcogenides, which employs both X-ray diffraction (XRD) and solid-state NMR (SS NMR), is presented. The new diagnostic technique allows reversible crystallographic space group change and very subtle distortion of host geometry to be followed during guest migration in the crystal lattice. Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)]thiophosphoryl selenenyl sulfide, a representative of wheel-and-axle host (WAAH) molecules, can be synthesized in the solid state by grinding and gentle heating of disulfide 1 and diselenide 2. Full characterization of disulfide 1 in the solid phase has been reported (J. Org. Chem. 1995, 60, 2549). In the current work, the synthesis and both XRD and SS NMR studies of the isostructural diselenide substrate 2 are presented. A (31)P cross polarization magic angle spinning experiment is employed to follow the progress of synthesis of selenenyl sulfide 3 in the solid state. It is concluded that selenenyl sulfide exists in equilibrium with disulfide and diselenide in a 1:1:1 ratio in both the liquid and the powdered solid. A mixture of isostructural dichalcogenides crystallized from different solvents form three-component host-guest inclusion complexes with columnar architecture. In the host-guest complex of diselenide 2 with toluene (space group C2), columns of host molecules are in parallel orientations along all the axes, whereas in the structures of diselenide 2 with propan-2-ol and propan-1-ol (space group P3 2), the columns of host molecules lay along the 3-fold symmetry axis. Thermal processes effecting structural changes in the host lattice and the kinetics of reversible guest molecule diffusion were investigated using SS NMR spectroscopy. Finally, the Se/S scrambling phenomenon and limitations in the X-ray structure refinement of organic compounds containing selenium and sulfur in chains

  3. 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.

    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.

  4. Optoelectronic tweezers for medical diagnostics

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  5. Ultrafast charge transfer and radiationless relaxations from higher excited state (S 2) of directly linked Zn-porphyrin (ZP)-acceptor dyads: investigations into fundamental problems of exciplex chemistry

    NASA Astrophysics Data System (ADS)

    Mataga, Noboru; Taniguchi, Seiji; Chosrowjan, Haik; Osuka, Atsuhiro; Yoshida, Naoya

    2003-12-01

    We have investigated photoinduced electron transfer and related processes from the higher excited electronic state (S 2) of Zn-porphyrin-imide acceptor directly linked supramolecular systems (ZP-I) designed especially for the critical studies of the energy gap law (EGL) of the charge separation (CS) from the S 2 state and solvent effects upon EGL. We have confirmed the modification of the EGL by change of solvent polarity from acetonitrile (ACN), tetrahydrofuran (THF) to toluene (Tol) and methyl-cyclohexane (MCH), from rather typical bell-shaped one in ACN to that with less prominent normal region and prominent inverted region with moderate slope extending over wider range of -Δ GCS values in nonpolar solvent MCH. We have demonstrated that these solvent effects upon EGL affect delicately various radiationless relaxation processes from S 2 state. We have examined also effects of the hydrogen bonding solvent ethanol (EtOH) on the EGL for CS and found very specific effect controlling the CS reaction and related processes.

  6. Microcrystal manipulation with laser tweezers

    SciTech Connect

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

    2013-07-01

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

  7. Molecular clips and tweezers hosting neutral guests.

    PubMed

    Hardouin-Lerouge, Marie; Hudhomme, Piétrick; Sallé, Marc

    2011-01-01

    Intense current interest in supramolecular chemistry is devoted to the construction of molecular assemblies displaying controlled molecular motion associated to recognition. On this ground, molecular clips and tweezers have focused an increasing attention. This tutorial review points out the recent advances in the construction of always more sophisticated molecular clips and tweezers, illustrating their remarkably broad structural variety and focusing on their binding ability towards neutral guests. A particular attention is brought to recent findings in dynamic molecular tweezers whose recognition ability can be regulated by external stimuli. Porphyrin-based systems will not be covered here as this very active field has been recently reviewed.

  8. Quantum limited particle sensing in optical tweezers

    SciTech Connect

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

    2009-12-15

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

  9. Observation of the properties of a single unit of a limited CDW structure in a Pt(II)/Pt(IV) host-guest binary system based on a square-shaped complex.

    PubMed

    Hirahara, Eri; Takaishi, Shinya; Yamashita, Masahiro

    2009-09-01

    A macrocyclic tetranuclear platinum(II) complex [Pt(en)(4,4'-bpy)](4)(NO(3))(8) (1(NO(3))(8); en = ethylenediamine, 4,4'-bpy = 4,4'-bipyridine) and a mononuclear platinum(IV) complex [Pt(en)(2)Br(2)]Br(2) (2Br(2)) formed two kinds of Pt(II)/Pt(IV) mixed valence assemblies when reacted: a discrete host-guest complex 12Br(10) (3) and an extended 1-D zigzag sheet 1(2)(3)Br(8)(NO(3))(6) (4). Single crystal X-ray analysis showed that the dimensions of the assemblies could be stoichiometrically controlled. Resonance Raman spectra suggested the presence of an intervalence interaction, which is typically observed for quasi-1-D halogen-bridged M(II)/M(IV) complexes. The intervalence interaction indicates the presence of an isolated {Pt(II)X-Pt(IV)-XPt(II)} moiety in the structure of 4. On the basis of electronic spectra and polarized reflectance measurements, we conclude that 4 exhibits intervalence charge transfer (IVCT) bands. A Kramers-Kronig transformation was carried out to obtain an optical conductivity spectrum, and two sub-bands corresponding to slightly different Pt(II)-Pt(IV) distances were observed.

  10. Steerable optical tweezers for ultracold atom studies.

    PubMed

    Roberts, K O; McKellar, T; Fekete, J; Rakonjac, A; Deb, A B; Kjærgaard, N

    2014-04-01

    We report on the implementation of an optical tweezer system for controlled transport of ultracold atoms along a narrow, static confinement channel. The tweezer system is based on high-efficiency acousto-optic deflectors and offers two-dimensional control over beam position. This opens up the possibility for tracking the transport channel when shuttling atomic clouds along it, forestalling atom spilling. Multiple clouds can be tracked independently by time-shared tweezer beams addressing individual sites in the channel. The deflectors are controlled using a multichannel direct digital synthesizer, which receives instructions on a submicrosecond time scale from a field-programmable gate array. Using the tweezer system, we demonstrate sequential binary splitting of an ultracold 87Rb cloud into 2(5) clouds.

  11. Optical tweezers based on polarization interferometer

    NASA Astrophysics Data System (ADS)

    Angelsky, Oleg V.; Maksimyak, Andrew P.; Maksimyak, Peter P.; Dominikov, Mykola M.

    2013-06-01

    In this paper, we propose optical tweezers based on a biaxial crystal. To control the movement of opaque particles, we use the shift polarization interferometer. The results of experimental study of laser tweezers are shown. We demonstrates movement of a microparticle of toner using singular-optical trap, rotate a particle due to orbital momentum, conversion of two traps when changing the plane of polarizer transmission and converging of two traps.

  12. 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

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

    PubMed

    Neuman, Keir C; Nagy, Attila

    2008-06-01

    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. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

  14. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

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

  15. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

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

  16. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

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

  17. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

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

  18. 21 CFR 878.5360 - Tweezer-type epilator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

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

  19. "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.

  20. Magnetic tweezers for the measurement of twist and torque.

    PubMed

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

    2014-05-19

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

  1. Quantum computation architecture using optical tweezers

    SciTech Connect

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

    2011-09-15

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

  2. Micro-objective manipulated with optical tweezers

    SciTech Connect

    Sasaki, M.; Kurosawa, T.; Hane, K.

    1997-02-01

    A microscope is described that uses a {mu}m-sized ball lens, which is here termed micro-objective, manipulated with optical tweezers to image the side view of the arbitrary region of a sample. Since this micro-objective is small in size, it can go into a concave region to produce a local image of the inside which the conventional microscope cannot observe. Preliminary results show good lens performance from the micro-objective when combined with optical tweezers. {copyright} {ital 1997 American Institute of Physics.}

  3. Origin and Future of Plasmonic Optical Tweezers

    PubMed Central

    Huang, Jer-Shing; Yang, Ya-Tang

    2015-01-01

    Plasmonic optical tweezers can overcome the diffraction limits of conventional optical tweezers and enable the trapping of nanoscale objects. Extension of the trapping and manipulation of nanoscale objects with nanometer position precision opens up unprecedented opportunities for applications in the fields of biology, chemistry and statistical and atomic physics. Potential applications include direct molecular manipulation, lab-on-a-chip applications for viruses and vesicles and the study of nanoscale transport. This paper reviews the recent research progress and development bottlenecks and provides an overview of possible future directions in this field. PMID:28347051

  4. Molecular tweezers targeting transthyretin amyloidosis.

    PubMed

    Ferreira, Nelson; Pereira-Henriques, Alda; Attar, Aida; Klärner, Frank-Gerrit; Schrader, Thomas; Bitan, Gal; Gales, Luís; Saraiva, Maria João; Almeida, Maria Rosário

    2014-04-01

    Transthyretin (TTR) amyloidoses comprise a wide spectrum of acquired and hereditary diseases triggered by extracellular deposition of toxic TTR aggregates in various organs. Despite recent advances regarding the elucidation of the molecular mechanisms underlying TTR misfolding and pathogenic self-assembly, there is still no effective therapy for treatment of these fatal disorders. Recently, the "molecular tweezers", CLR01, has been reported to inhibit self-assembly and toxicity of different amyloidogenic proteins in vitro, including TTR, by interfering with hydrophobic and electrostatic interactions known to play an important role in the aggregation process. In addition, CLR01 showed therapeutic effects in animal models of Alzheimer's disease and Parkinson's disease. Here, we assessed the ability of CLR01 to modulate TTR misfolding and aggregation in cell culture and in an animal model. In cell culture assays we found that CLR01 inhibited TTR oligomerization in the conditioned medium and alleviated TTR-induced neurotoxicity by redirecting TTR aggregation into the formation of innocuous assemblies. To determine whether CLR01 was effective in vivo, we tested the compound in mice expressing TTR V30M, a model of familial amyloidotic polyneuropathy, which recapitulates the main pathological features of the human disease. Immunohistochemical and Western blot analyses showed a significant decrease in TTR burden in the gastrointestinal tract and the peripheral nervous system in mice treated with CLR01, with a concomitant reduction in aggregate-induced endoplasmic reticulum stress response, protein oxidation, and apoptosis. Taken together, our preclinical data suggest that CLR01 is a promising lead compound for development of innovative, disease-modifying therapy for TTR amyloidosis.

  5. Synergetic effect of host-guest chemistry and spin crossover in 3D Hofmann-like metal-organic frameworks [Fe(bpac)M(CN)4] (M=Pt, Pd, Ni).

    PubMed

    Bartual-Murgui, Carlos; Salmon, Lionel; Akou, Amal; Ortega-Villar, Norma A; Shepherd, Helena J; Muñoz, M Carmen; Molnár, Gábor; Real, José Antonio; Bousseksou, Azzedine

    2012-01-09

    The synthesis and characterization of a series of three-dimensional (3D) Hofmann-like clathrate porous metal-organic framework (MOF) materials [Fe(bpac)M(CN)(4)] (M=Pt, Pd, and Ni; bpac=bis(4-pyridyl)acetylene) that exhibit spin-crossover behavior is reported. The rigid bpac ligand is longer than the previously used azopyridine and pyrazine and has been selected with the aim to improve both the spin-crossover properties and the porosity of the corresponding porous coordination polymers (PCPs). The 3D network is composed of successive {Fe[M(CN)(4)]}(n) planar layers bridged by the bis-monodentate bpac ligand linked in the apical positions of the iron center. The large void between the layers, which represents 41.7% of the unit cell, can accommodate solvent molecules or free bpac ligand. Different synthetic strategies were used to obtain a range of spin-crossover behaviors with hysteresis loops around room temperature; the samples were characterized by magnetic susceptibility, calorimetric, Mössbauer, and Raman measurements. The complete physical study reveals a clear relationship between the quantity of included bpac molecules and the completeness of the spin transition, thereby underlining the key role of the π-π stacking interactions operating between the host and guest bpac molecules within the network. Although the inclusion of the bpac molecules tends to increase the amount of active iron centers, no variation of the transition temperature was measured. We have also investigated the ability of the network to accommodate the inclusion of molecules other than water and bpac and studied the synergy between the host-guest interaction and the spin-crossover behavior. In fact, the clathration of various aromatic molecules revealed specific modifications of the transition temperature. Finally, the transition temperature and the completeness of the transition are related to the nature of the metal associated with the iron center (Ni, Pt, or Pd) and also to the

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    SciTech Connect

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

    2014-04-14

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

  9. Optoelectronic tweezers for microparticle and cell manipulation

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  10. Optoelectronic Tweezers for Microparticle and Cell Manipulation

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  11. Exploring unconventional capabilities of holographic tweezers

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  12. The Smallest Tweezers in the World

    ERIC Educational Resources Information Center

    Lewalle, Alexandre

    2008-01-01

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

  13. Tweezers for Chimeras in Small Networks

    NASA Astrophysics Data System (ADS)

    Omelchenko, Iryna; Omel'chenko, Oleh E.; Zakharova, Anna; Wolfrum, Matthias; Schöll, Eckehard

    2016-03-01

    We propose a control scheme which can stabilize and fix the position of chimera states in small networks. Chimeras consist of coexisting domains of spatially coherent and incoherent dynamics in systems of nonlocally coupled identical oscillators. Chimera states are generally difficult to observe in small networks due to their short lifetime and erratic drifting of the spatial position of the incoherent domain. The control scheme, like a tweezer, might be useful in experiments, where usually only small networks can be realized.

  14. Fractal zone plate beam based optical tweezers

    PubMed Central

    Cheng, Shubo; Zhang, Xinyu; Ma, Wenzhuo; Tao, Shaohua

    2016-01-01

    We demonstrate optical manipulation with an optical beam generated by a fractral zone plate (FZP). The experimental results show that the FZP beam can simultaneously trap multiple particles positioned in different focal planes of the FZP beam, owing to the multiple foci and self-reconstruction property of the FZP beam. The FZP beam can also be used to construct three-dimensional optical tweezers for potential applications. PMID:27678305

  15. New approaches in the design of magnetic tweezers-current magnetic tweezers

    NASA Astrophysics Data System (ADS)

    Bessalova, Valentina; Perov, Nikolai; Rodionova, Valeria

    2016-10-01

    The main advantages of the magnetic tweezers are the low price and simplicity of use. However the range of their application is reduced due to shortcomings like, for example, the remanent induction of the core and interaction between ferromagnetic cores. We present the new design of magnetic tweezers-Current Magnetic Tweezers (CMT) that allow particle manipulation by means of the magnetic field generated by the electric currents flowing through the non-magnetic wires. Arranging wires in different geometric shapes allows the particle movement either in two or three dimensions. Forces acting on the magnetic particles with the magnetic moment of 2·10-11 A m2 at distances up to 1 mm had been experimentally measured. It is established that a current of about 1 A at a 1 mm distance generates force of (approximately) 3 pN which is consistent with theoretical estimates.

  16. The Smallest Tweezers in the World

    NASA Astrophysics Data System (ADS)

    Lewalle, Alexandre

    2008-11-01

    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 tweezers." In recent years, this technique has become central to nanotechnology for the manipulation of small particles, even individual molecules. It is also an ideal illustration of how classroom physics is applied to cutting-edge research, combining concepts such as the vector nature of momentum and force, Newton's laws, optics, the wave-particle duality of light, and thermodynamics. The physics behind optical tweezers has many layers of complexity, but it can be reduced to a basic principle: the conservation of momentum. This paper guides the reader through a much simplified demonstration of this "tweezing effect" using a question-answer approach, leaving the reader with the choice to treat each step as a problem exercise.

  17. 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.

  18. Reusable acoustic tweezers for disposable devices

    PubMed Central

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

    2015-01-01

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

  19. 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.

  20. Investigating the potential applications of a Raman tweezer system

    NASA Astrophysics Data System (ADS)

    Wray, John Casey

    This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (e=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman spectra obtained from optically trapped samples of polystyrene fluorescent orange, amine-modified latex beads. In addition, I explored the Raman spectra of bulk cytochrome c mixed with or injected onto Ag aggregates for SERs enhancement.

  1. Subpiconewton dynamic force spectroscopy using magnetic tweezers.

    PubMed

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

    2008-03-15

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

  2. 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.

  3. 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

  4. 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.

  5. Systems approach to identification of feedback enhanced optical tweezers

    NASA Astrophysics Data System (ADS)

    Sehgal, Hullas; Aggarwal, Tanuj; Salapaka, Murti V.

    2008-08-01

    Feedback enhanced optical tweezers, based on Proportional and Integral (PI) control, are routinely used for increasing the stiffness of optical traps. Digital implementation of PI controller, using DSP or FPGA, enables easy maneuverability of feedback gains. In this paper, we report occurrence of a peak in the thermal noise power spectrum of the trapped bead as the proportional gain is cranked up, which imposes a limit on how stiff a trap can be made using position feedback. We explain the reasons for the deviant behavior in the power spectrum and present a mathematical formula to account for the anomaly, which is in very good agreement with the experimental observations. Further, we present a new method to do the closed loop system identification of feedback enhanced optical tweezers by applying a frequency chirp. The system model thus obtained greatly predicts the closed loop behavior of our feedback based optical tweezers system.

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

    NASA Astrophysics Data System (ADS)

    Vereen, Keon; Datta, Iman; You, Setthivoine

    2014-10-01

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

  7. Magnetic tweezers for manipulation of magnetic particles in single cells

    NASA Astrophysics Data System (ADS)

    Ebrahimian, H.; Giesguth, M.; Dietz, K.-J.; Reiss, G.; Herth, S.

    2014-02-01

    Magnetic tweezers gain increasing interest for applications in biology. Here, a setup of magnetic tweezers is introduced using micropatterned conducting lines on transparent glass slides. Magnetic particles of 1 μm diameter were injected in barley cell vacuoles using a microinject system under microscopic control. Time dependent tracking of the particles after application of a magnetic field was used to determine the viscosity of vacuolar sap in vivo relative to water and isolated vacuolar fluid. The viscosity of vacuolar sap in cells was about 2-fold higher than that of extracted vacuolar fluid and 5 times higher than that of water.

  8. Control and manipulation of cold atoms in optical tweezers

    NASA Astrophysics Data System (ADS)

    Muldoon, Cecilia; Brandt, Lukas; Dong, Jian; Stuart, Dustin; Brainis, Edouard; Himsworth, Matthew; Kuhn, Axel

    2012-07-01

    Neutral atoms trapped by laser light are among the most promising candidates for storing and processing information in a quantum computer or simulator. The application certainly calls for a scalable and flexible scheme for addressing and manipulating the atoms. We have now made this a reality by implementing a fast and versatile method to dynamically control the position of neutral atoms trapped in optical tweezers. The tweezers result from a spatial light modulator (SLM) controlling and shaping a large number of optical dipole-force traps. Trapped atoms adapt to any change in the potential landscape, such that one can rearrange and randomly access individual sites within atom-trap arrays.

  9. 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.

  10. Tunable optical tweezers for wavelength-dependent measurements.

    PubMed

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

    2012-04-01

    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.

  11. Optical tweezers reveal how proteins alter replication

    NASA Astrophysics Data System (ADS)

    Chaurasiya, Kathy

    Single molecule force spectroscopy is a powerful method that explores the DNA interaction properties of proteins involved in a wide range of fundamental biological processes such as DNA replication, transcription, and repair. We use optical tweezers to capture and stretch a single DNA molecule in the presence of proteins that bind DNA and alter its mechanical properties. We quantitatively characterize the DNA binding mechanisms of proteins in order to provide a detailed understanding of their function. In this work, we focus on proteins involved in replication of Escherichia coli (E. coli ), endogenous eukaryotic retrotransposons Ty3 and LINE-1, and human immunodeficiency virus (HIV). DNA polymerases replicate the entire genome of the cell, and bind both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) during DNA replication. The replicative DNA polymerase in the widely-studied model system E. coli is the DNA polymerase III subunit alpha (DNA pol III alpha). We use optical tweezers to determine that UmuD, a protein that regulates bacterial mutagenesis through its interactions with DNA polymerases, specifically disrupts alpha binding to ssDNA. This suggests that UmuD removes alpha from its ssDNA template to allow DNA repair proteins access to the damaged DNA, and to facilitate exchange of the replicative polymerase for an error-prone translesion synthesis (TLS) polymerase that inserts nucleotides opposite the lesions, so that bacterial DNA replication may proceed. This work demonstrates a biophysical mechanism by which E. coli cells tolerate DNA damage. Retroviruses and retrotransposons reproduce by copying their RNA genome into the nuclear DNA of their eukaryotic hosts. Retroelements encode proteins called nucleic acid chaperones, which rearrange nucleic acid secondary structure and are therefore required for successful replication. The chaperone activity of these proteins requires strong binding affinity for both single- and double-stranded nucleic

  12. Assembling silver nanowires using optoelectronic tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Shuailong; Cooper, Jonathan M.; Neale, Steve L.

    2016-03-01

    Light patterned dielectrophoresis or optoelectronic tweezers (OET) has been proved to be an effective micromanipulation technology for cell separation, cell sorting and control of cell interactions. Apart from being useful for cell biology experiments, the capability of moving small objects accurately also makes OET an attractive technology for other micromanipulation applications. In particular, OET has the potential to be used for efficiently and accurately assembling small optoelectronic/electronic components into circuits. This approach could produce a step change in the size of the smallest components that are routinely assembled; down from the current smallest standard component size of 400×200 μm (0402 metric) to components a few microns across and even nanostructured components. In this work, we have demonstrated the use of OET to manipulate conductive silver nanowires into different patterns. The silver nanowires (typical diameter: 60 nm; typical length: 10 μm) were suspended in a 15 mS/m solution of KCL in water and manipulated by positive dielectrophoresis force generated by OET. A proof-of-concept demonstration was also made to prove the feasibility of using OET to manipulate silver nanowires to form a 150-μm-long conductive path between two isolated electrodes. It can be seen that the resistance between two electrodes was effectively brought down to around 700 Ω after the silver nanowires were assembled and the solution evaporated. Future work in this area will focus on increasing the conductivity of these tracks, encapsulating the assembled silver nanowires to prevent silver oxidation and provide mechanical protection, which can be achieved via 3D printing and inkjet printing technology.

  13. Airy acoustical-sheet spinner tweezers

    NASA Astrophysics Data System (ADS)

    Mitri, F. G.

    2016-09-01

    The Airy acoustical beam exhibits parabolic propagation and spatial acceleration, meaning that the propagation bending angle continuously increases before the beam trajectory reaches a critical angle where it decays after a propagation distance, without applying any external bending force. As such, it is of particular importance to investigate its properties from the standpoint of acoustical radiation force, spin torque, and particle dynamics theories, in the development of novel particle sorting techniques and acoustically mediated clearing systems. This work investigates these effects on a two-dimensional (2D) circular absorptive structure placed in the field of a nonparaxial Airy "acoustical-sheet" (i.e., finite beam in 2D), for potential applications in surface acoustic waves and acousto-fluidics. Based on the characteristics of the acoustic field, the beam is capable of manipulating the circular cylindrical fluid cross-section and guides it along a transverse or parabolic trajectory. This feature of Airy acoustical beams could lead to a unique characteristic in single-beam acoustical tweezers related to acoustical sieving, filtering, and removal of particles and cells from a section of a small channel. The analysis developed here is based on the description of the nonparaxial Airy beam using the angular spectrum decomposition of plane waves in close association with the partial-wave series expansion method in cylindrical coordinates. The numerical results demonstrate the ability of the nonparaxial Airy acoustical-sheet beam to pull, propel, or accelerate a particle along a parabolic trajectory, in addition to particle confinement in the transverse direction of wave propagation. Negative or positive radiation force and spin torque causing rotation in the clockwise or the anticlockwise direction can occur depending on the nondimensional parameter ka (where k is the wavenumber and a is the radius) and the location of the cylinder in the beam. Applications in

  14. Synthesis, structure, and properties of a series of chiral tweezer-diamine complexes consisting of an achiral zinc(II) bisporphyrin host and chiral diamine guest: induction and rationalization of supramolecular chirality.

    PubMed

    Brahma, Sanfaori; Ikbal, Sk Asif; Rath, Sankar Prasad

    2014-01-06

    We report here the synthesis, structure, and spectroscopic properties of a series of supramolecular chiral 1:1 tweezer-diamine complexes consisting of an achiral Zn(II) bisporphyrin (Zn2DPO) host and five different chiral diamine guests, namely, (R)-diaminopropane (DAP), (1S,2S)-diaminocyclohexane (CHDA), (S)-phenylpropane diamine (PPDA), (S)-phenyl ethylenediamine (PEDA), and (1R,2R)-diphenylethylene diamine (DPEA). The solid-state structures are preserved in solution, as reflected in their (1)H NMR spectra, which also revealed the remarkably large upfield shifts of the NH2 guest protons with the order Zn2DPO·DAP > Zn2DPO·CHDA > Zn2DPO·PPDA> Zn2DPO·PEDA ≫ Zn2DPO·DPEA, which happens to be the order of binding constants of the respective diamines with Zn2DPO. As the bulk of the substituent at the chiral center of the guest ligand increases, the Zn-Nax distance of the tweezer-diamine complex also increases, which eventually lowers the binding of the guest ligand toward the host. Also, the angle between the two porphyrin rings gradually increases with increasing bulk of the guest in order to accommodate the guest within the bisporphyrin cavity with minimal steric clash. The notably high amplitude bisignate CD signal response by Zn2DPO·DAP, Zn2DPO·CHDA, and Zn2DPO·PPDA can be ascribed to the complex's high stability and the formation of a unidirectional screw as observed in the X-ray structures of the complexes. A relatively lower value of CD amplitude shown by Zn2DPO·PEDA is due to the lower stability of the complex. The projection of the diamine binding sites of the chiral guest would make the two porphyrin macrocycles oriented in either a clockwise or anticlockwise direction in order to minimize host-guest steric clash. In sharp contrast, Zn2DPO·DPEA shows a very low amplitude bisignate CD signal due to the presence of both left- (dictated by the pre-existing chirality of (1R,2R)-DPEA) and right-handed screws (dictated by the steric differentiation at

  15. Trapping and patterning of biological objects using photovoltaic tweezers

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  16. 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 μm 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

  17. Spin dynamics and Kondo physics in optical tweezers

    NASA Astrophysics Data System (ADS)

    Lin, Yiheng; Lester, Brian J.; Brown, Mark O.; Kaufman, Adam M.; Long, Junling; Ball, Randall J.; Isaev, Leonid; Wall, Michael L.; Rey, Ana Maria; Regal, Cindy A.

    2016-05-01

    We propose to use optical tweezers as a toolset for direct observation of the interplay between quantum statistics, kinetic energy and interactions, and thus implement minimum instances of the Kondo lattice model in systems with few bosonic rubidium atoms. By taking advantage of strong local exchange interactions, our ability to tune the spin-dependent potential shifts between the two wells and complete control over spin and motional degrees of freedom, we design an adiabatic tunneling scheme that efficiently creates a spin-singlet state in one well starting from two initially separated atoms (one atom per tweezer) in opposite spin state. For three atoms in a double-well, two localized in the lowest vibrational mode of each tweezer and one atom in an excited delocalized state, we plan to use similar techniques and observe resonant transfer of two-atom singlet-triplet states between the wells in the regime when the exchange coupling exceeds the mobile atom hopping. Moreover, we argue that such three-atom double-tweezers could potentially be used for quantum computation by encoding logical qubits in collective spin and motional degrees of freedom. Current address: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.

  18. Plasmon enhanced optical tweezers with gold-coated black silicon

    NASA Astrophysics Data System (ADS)

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2016-05-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects.

  19. Plasmon enhanced optical tweezers with gold-coated black silicon

    PubMed Central

    Kotsifaki, D. G.; Kandyla, M.; Lagoudakis, P. G.

    2016-01-01

    Plasmonic optical tweezers are a ubiquitous tool for the precise manipulation of nanoparticles and biomolecules at low photon flux, while femtosecond-laser optical tweezers can probe the nonlinear optical properties of the trapped species with applications in biological diagnostics. In order to adopt plasmonic optical tweezers in real-world applications, it is essential to develop large-scale fabrication processes without compromising the trapping efficiency. Here, we develop a novel platform for continuous wave (CW) and femtosecond plasmonic optical tweezers, based on gold-coated black silicon. In contrast with traditional lithographic methods, the fabrication method relies on simple, single-step, maskless tabletop laser processing of silicon in water that facilitates scalability. Gold-coated black silicon supports repeatable trapping efficiencies comparable to the highest ones reported to date. From a more fundamental aspect, a plasmon-mediated efficiency enhancement is a resonant effect, and therefore, dependent on the wavelength of the trapping beam. Surprisingly, a wavelength characterization of plasmon-enhanced trapping efficiencies has evaded the literature. Here, we exploit the repeatability of the recorded trapping efficiency, offered by the gold-coated black silicon platform, and perform a wavelength-dependent characterization of the trapping process, revealing the resonant character of the trapping efficiency maxima. Gold-coated black silicon is a promising platform for large-scale parallel trapping applications that will broaden the range of optical manipulation in nanoengineering, biology, and the study of collective biophotonic effects. PMID:27195446

  20. Multipoint viscosity measurements in microfluidic channels using optical tweezers.

    PubMed

    Keen, Stephen; Yao, Alison; Leach, Jonathan; Di Leonardo, Roberto; Saunter, Chris; Love, Gordon; Cooper, Jonathan; Padgett, Miles

    2009-07-21

    We demonstrate the technique of multipoint viscosity measurements incorporating the accurate calibration of micron sized particles. We describe the use of a high-speed camera to measure the residual motion of particles trapped in holographic optical tweezers, enabling us to calculate the fluid viscosity at multiple points across the field-of-view of the microscope within a microfluidic system.

  1. Unraveling chromatin structure using magnetic tweezers

    NASA Astrophysics Data System (ADS)

    van Noort, John

    2010-03-01

    The compact, yet dynamic organization of chromatin plays an essential role in regulating gene expression. Although the static structure of chromatin fibers has been studied extensively, the controversy about the higher order folding remains. The compaction of eukaryotic DNA into chromatin has been implicated in the regulation of all DNA processes. To understand the relation between gene regulation and chromatin structure it is essential to uncover the mechanisms by which chromatin fibers fold and unfold. We used magnetic tweezers to probe the mechanical properties of individual nucleosomes and chromatin fibers consisting of a single, well-defined array of 25 nucleosomes. From these studies five major features appeared upon forced extension of chromatin fibers: the elastic stretching of chromatin's higher order structure, the breaking of internucleosomal contacts, unwrapping of the first turn of DNA, unwrapping of the second turn of DNA, and the dissociation of histone octamers. These events occur sequentially at the increasing force. Neighboring nucleosomes stabilize DNA folding into a nucleosome relative to isolated nucleosomes. When an array of nucleosomes is folded into a 30 nm fiber, representing the first level of chromatin condensation, the fiber stretched like a Hookian spring at forces up to 4 pN. Together with a nucleosome-nucleosome stacking energy of 14 kT this points to a solenoid as the underlying topology of the 30 nm fiber. Surprisingly, linker histones do not affect the length or stiffness of the fibers, but stabilize fiber folding up to forces of 7 pN. The stiffness of the folded chromatin fiber points at histone tails that mediate nucleosome stacking. Fibers with a nucleosome repeat length of 167 bp instead of 197 bp are significantly stiffer, consistent with a two-start helical arrangement. The extensive thermal breathing of the chromatin fiber that is a consequence of the observed high compliance provides a structural basis for understanding the

  2. Development and biological applications of optical tweezers and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Xie, Chang'an

    Optical tweezers is a three-dimensional manipulation tool that employs a gradient force that originates from the single highly focused laser beam. Raman spectroscopy is a molecular analytical tool that can give a highly unique "fingerprint" for each substance by measuring the unique vibrations of its molecules. The combination of these two optical techniques offers a new tool for the manipulation and identification of single biological cells and microscopic particles. In this thesis, we designed and implemented a Laser-Tweezers-Raman-Spectroscopy (LTRS) system, also called the Raman-tweezers, for the simultaneous capture and analysis of both biological particles and non-biological particles. We show that microparticles can be conveniently captured at the focus of a laser beam and the Raman spectra of trapped particles can be acquired with high quality. The LTRS system overcomes the intrinsic Brownian motion and cell motility of microparticles in solution and provides a promising tool for in situ identifying suspicious agents. In order to increase the signal to noise ratio, several schemes were employed in LTRS system to reduce the blank noise and the fluorescence signal coming from analytes and the surrounding background. These techniques include near-infrared excitation, optical levitation, confocal microscopy, and frequency-shifted Raman difference. The LTRS system has been applied for the study in cell biology at the single cell level. With the built Raman-tweezers system, we studied the dynamic physiological processes of single living cells, including cell cycle, the transcription and translation of recombinant protein in transgenic yeast cells and the T cell activation. We also studied cell damage and associated biochemical processes in optical traps, UV radiations, and evaluated heating by near-infrared Raman spectroscopy. These studies show that the Raman-tweezers system is feasible to provide rapid and reliable diagnosis of cellular disorders and can be

  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. Cyclodextrins in analytical chemistry: host-guest type molecular recognition.

    PubMed

    Szente, Lajos; Szemán, Julianna

    2013-09-03

    Cyclodextrins are utilized in many diverse fields of analytical chemistry, due to their propensity to form reversible inclusion complexes and recognize analytes selectively. This Feature shows how these nanocavities can serve analysts in sample preparation, sensitivity and selectivity improvement, enantio-separation, creating single-molecule sensors, and automatizing DNA sequencing.

  5. 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.

  6. Simultaneous calibration of optical tweezers spring constant and position detector response.

    PubMed

    Le Gall, Antoine; Perronet, Karen; Dulin, David; Villing, André; Bouyer, Philippe; Visscher, Koen; Westbrook, Nathalie

    2010-12-06

    We demonstrate a fast and direct calibration method for systems using a single laser for optical tweezers and particle position detection. The method takes direct advantage of back-focal-plane interferometry measuring not an absolute but a differential position, i.e. the position of the trapped particle relative to the center of the optical tweezers. Therefore, a fast step-wise motion of the optical tweezers yields the impulse response of the trapped particle. Calibration parameters such as the detector's spatial and temporal response and the spring constant of the optical tweezers then follow readily from fitting the measured impulse response.

  7. Nanoscopy of bacterial cells immobilized by holographic optical tweezers

    PubMed Central

    Diekmann, Robin; Wolfson, Deanna L.; Spahn, Christoph; Heilemann, Mike; Schüttpelz, Mark; Huser, Thomas

    2016-01-01

    Imaging non-adherent cells by super-resolution far-field fluorescence microscopy is currently not possible because of their rapid movement while in suspension. Holographic optical tweezers (HOTs) enable the ability to freely control the number and position of optical traps, thus facilitating the unrestricted manipulation of cells in a volume around the focal plane. Here we show that immobilizing non-adherent cells by optical tweezers is sufficient to achieve optical resolution well below the diffraction limit using localization microscopy. Individual cells can be oriented arbitrarily but preferably either horizontally or vertically relative to the microscope's image plane, enabling access to sample sections that are impossible to achieve with conventional sample preparation and immobilization. This opens up new opportunities to super-resolve the nanoscale organization of chromosomal DNA in individual bacterial cells. PMID:27958271

  8. 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 λ-phage DNA which is driven by an electrophoretic force through the nanocapillary. The resulting change in ionic current indicates the folding state of single λ-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.

  9. Synthesis and Characterization of Carbazole-Linked Porphyrin Tweezers.

    PubMed

    Chang, Yi; Michelin, Clément; Bucher, Léo; Desbois, Nicolas; Gros, Claude P; Piant, Sébastien; Bolze, Frédéric; Fang, Yuanyuan; Jiang, Xiaoqin; Kadish, Karl M

    2015-08-17

    Herein the synthesis, spectroscopic characterization, two-photon absorption and electrochemical properties of 3,6-disubstituted carbazole tweezers is reported. A dimer resulting from a Glaser homocoupling was isolated during a Sonogashira coupling reaction between a diethynyl-carbazole spacer and a 5-bromo-triarylporphyrin and the properties of this original compound were compared with the 3,6-disubstituted carbazole bisporphyrin tweezers. The dyads reported herein present a two-photon absorption maximum at 920 nm with two-photon absorption cross-section in the 1200 GM range. Despite a strong linear absorption in the Soret region and moderate fluorescence quantum yield, they both lead to a high brightness reaching 30 000 M(-1)  cm(-1) .

  10. A guide to magnetic tweezers and their applications

    NASA Astrophysics Data System (ADS)

    Sarkar, Rupa; Rybenkov, Valentin

    2016-12-01

    Magnetic force spectroscopy is a rapidly developing single molecule technique that found numerous applications at the interface of physics and biology. Since the invention of the first magnetic tweezers, a number of modifications were incorporated into the approach that helped relieve the limitations of the original design and amplified its strengths. Inventive molecular biology solutions further advanced the technique by expanding its possible applications. In its present form, the method can be applied to single molecules and live cells without resorting to intense sample irradiation, can be easily multiplexed, accommodates multiple DNAs, displays impressive resolution, and allows a remarkable ease in stretching and twisting macromolecules. In this review, we describe the architecture of magnetic tweezers, key requirements to the experimental design and analysis of data, and outline several applications of the method that illustrate its versatility.

  11. 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.

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

    PubMed

    Quinto-Su, Pedro A

    2014-12-19

    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.

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

    PubMed

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

    2014-10-31

    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.

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

    PubMed

    Wu, Yanhua; Sun, Dong; Huang, Wenhao

    2011-02-24

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

  15. Sensing interactions in the microworld with optical tweezers

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    Optical Tweezers have become a widespread tool in Cell Biology, microengineering and other fields requiring delicate micromanipulation. But for those sensitive tasks, it remains difficult to handle objects without damaging them. As the precision in position and force measurement increase, the richness of information cannot be fully exploited with simple interfaces such as a mouse or a common joystick. For this reason, we propose a haptic force-feedback optical tweezer command and a force-feedback system controlled by one hand. The system combines accurate force measurement using a fast camera and the coupling of these measured forces with a human operator. The overall transparency allows even the feeling of the Brownian motion.

  16. Active-passive calibration of optical tweezers in viscoelastic media.

    PubMed

    Fischer, Mario; Richardson, Andrew C; Reihani, S Nader S; Oddershede, Lene B; Berg-Sørensen, Kirstine

    2010-01-01

    In order to use optical tweezers as a force measuring tool inside a viscoelastic medium such as the cytoplasm of a living cell, it is crucial to perform an exact force calibration within the complex medium. This is a nontrivial task, as many of the physical characteristics of the medium and probe, e.g., viscosity, elasticity, shape, and density, are often unknown. Here, we suggest how to calibrate single beam optical tweezers in a complex viscoelastic environment. At the same time, we determine viscoelastic characteristics such as friction retardation spectrum and elastic moduli of the medium. We apply and test a method suggested [M. Fischer and K. Berg-Sørensen, J. Opt. A, Pure Appl. Opt. 9, S239 (2007)], a method which combines passive and active measurements. The method is demonstrated in a simple viscous medium, water, and in a solution of entangled F-actin without cross-linkers.

  17. Multispectral optical tweezers for molecular diagnostics of single biological cells

    NASA Astrophysics Data System (ADS)

    Butler, Corey; Fardad, Shima; Sincore, Alex; Vangheluwe, Marie; Baudelet, Matthieu; Richardson, Martin

    2012-03-01

    Optical trapping of single biological cells has become an established technique for controlling and studying fundamental behavior of single cells with their environment without having "many-body" interference. The development of such an instrument for optical diagnostics (including Raman and fluorescence for molecular diagnostics) via laser spectroscopy with either the "trapping" beam or secondary beams is still in progress. This paper shows the development of modular multi-spectral imaging optical tweezers combining Raman and Fluorescence diagnostics of biological cells.

  18. Measurement of angular momentum flux in optical tweezers

    NASA Astrophysics Data System (ADS)

    Rubinsztein-Dunlop, Halina; Asavei, Theodor; Preece, Daryl; Stilgoe, Alexander B.; Heckenberg, Norman R.; Nieminen, Timo A.

    2011-03-01

    It is well established that a light beam can carry angular momentum and therefore when using optical tweezers it is possible to exert torques to twist or rotate microscopic objects. Both spin and orbital angular momentum can be transferred. This transfer can be achieved using birefringent particles exposed to a Gaussian circularly polarized beam. In this case, a transfer of spin angular momentum will occur. The change in spin, and hence the torque, can be readily measured optically. On the other hand, it is much more challenging to measure orbital angular momentum and torque. Laguerre-Gauss mode decomposition, as used for orbital angular momentum encoding for quantum communication, and rotational frequency shift can be used, and are effective methods in a macro-environment. However, the situation becomes more complicated when a measurement is done on microscale, especially with highly focused laser beams. We review the methods for the measurement of the angular momentum of light in optical tweezers, and the challenges faced when measuring orbital angular momentum. We also demonstrate one possible simple method for a quantitative measurement of the orbital angular momentum in optical tweezers.

  19. Magnetic tweezers: micromanipulation and force measurement at the molecular level.

    PubMed Central

    Gosse, Charlie; Croquette, Vincent

    2002-01-01

    Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators. PMID:12023254

  20. Electromagnetic tweezers with independent force and torque control

    NASA Astrophysics Data System (ADS)

    Jiang, Chang; Lionberger, Troy A.; Wiener, Diane M.; Meyhofer, Edgar

    2016-08-01

    Magnetic tweezers are powerful tools to manipulate and study the mechanical properties of biological molecules and living cells. In this paper we present a novel, bona fide electromagnetic tweezer (EMT) setup that allows independent control of the force and torque applied via micrometer-sized magnetic beads to a molecule under study. We implemented this EMT by combining a single solenoid that generates force (f-EMT) with a set of four solenoids arranged into a symmetric quadrupole to generate torque (τ-EMT). To demonstrate the capability of the tweezers, we attached optically asymmetric Janus beads to single, tethered DNA molecules. We show that tension in the piconewton force range can be applied to single DNA molecules and the molecule can simultaneously be twisted with torques in the piconewton-nanometer range. Furthermore, the EMT allows the two components to be independently controlled. At various force levels applied to the Janus bead, the trap torsional stiffness can be continuously changed simply by varying the current magnitude applied to the τ-EMT. The flexible and independent control of force and torque by the EMT makes it an ideal tool for a range of measurements where tensional and torsional properties need to be studied simultaneously on a molecular or cellular level.

  1. Theory of optical-tweezers forces near a plane interface

    NASA Astrophysics Data System (ADS)

    Dutra, R. S.; Neto, P. A. Maia; Nussenzveig, H. M.; Flyvbjerg, H.

    2016-11-01

    Optical-tweezers experiments in molecular and cell biology often take place near the surface of the microscope slide that defines the bottom of the sample chamber. There, as elsewhere, force measurements require force-calibrated tweezers. In bulk, one can calculate the tweezers force from first principles, as recently demonstrated. Near the surface of the microscope slide, this absolute calibration method fails because it does not account for reverberations from the slide of the laser beam scattered by the trapped microsphere. Nor does it account for evanescent waves arising from total internal reflection of wide-angle components of the strongly focused beam. In the present work we account for both of these phenomena. We employ Weyl's angular spectrum representation of spherical waves in terms of real and complex rays and derive a fast-converging recursive series of multiple reflections that describes the reverberations, including also evanescent waves. Numerical simulations for typical setup parameters evaluate these effects on the optical force and trap stiffness, with emphasis on axial trapping. Results are in good agreement with available experimental data. Thus, absolute calibration now applies to all situations encountered in practice.

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

    PubMed

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

    2014-08-28

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

  3. Linear microrheology with optical tweezers of living cells 'is not an option'!

    PubMed

    Tassieri, Manlio

    2015-08-07

    Optical tweezers have been successfully adopted as exceptionally sensitive transducers for microrheology studies of complex fluids. Despite the general trend, in this article I explain why a similar approach should not be adopted for microrheology studies of living cells. This conclusion is acheived on the basis of statistical mechanics principles that indicate the unsuitability of optical tweezers for such purpose.

  4. pH-stimulated concurrent mechanical activation of two DNA "tweezers". A "SET-RESET" logic gate system.

    PubMed

    Elbaz, Johann; Wang, Zhen-Gang; Orbach, Ron; Willner, Itamar

    2009-12-01

    A DNA tweezer consisting of C-rich arms is kept in the "closed" form by hybridization of the arms with a nucleic acid cross-linker. At acidic pH (pH = 5.2), the arms are stabilized through the formation of the i-motif, C-quadruplex structures, releasing the cross-linking nucleic acid and transforming the tweezer to its "opened" state. At neutral pH (pH = 7.2), the C-quadruplex structures are dissociated, resulting in the capturing of the cross-linking nucleic acid and the closure of the tweezer. By the reversible treatment of the tweezer at pH = 5.2 and at pH = 7.2, the tweezer system is cycled between the open and closed states, respectively, followed by a FRET process between a fluorophore-quencher pair that labels the tweezer. Also the concurrent activation of two DNA tweezers by pH stimuli is described. The pH-induced opening of one tweezer (tweezer A) by the formation of C-quadruplex (pH = 5.2) and the release of the cross-linking nucleic acid result in the closure of a second tweezer (tweezer B) by the hybridization of the released strand with the arms of tweezer B. The dissociation of the C-quadruplex structures (pH = 7.2) results in the favored translocation of the cross-linking nucleic acid from tweezer B to A. By the cycling of the pH of the system between pH = 5.2 and pH = 7.2, the concurrent opening and closure of the two tweezers are accomplished. The two tweezers system performs a SET-RESET logic gate operation, where the pH stimuli act as inputs.

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

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.

    2002-01-01

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

  6. 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 λ = 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 μm and 10 μm 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.

  7. Analysis of micro-fluidic tweezers in the Stokes regime

    NASA Astrophysics Data System (ADS)

    Zhao, Longhua; Ding, Yang

    2016-11-01

    Nanowire fluidic tweezers have been developed to capture and manipulate micro objects. The fluidic trapping force and the fluid field are important to achieve accurate control, but have not been fully understood yet. Utilizing singularity method, we construct the exact velocity field to analyze flows induced by a spheroid nanowire tumbling in the Stokes regime. To further explore the trapping, we analyze the trajectories of rigid or deformable microspheres near the tumbling nanowire using regularized Stokeslet method. The fluid structure, the trapping phenomenon and mechanism, and precise relation about trapping with the geometry will be presented. YD is sponsored by the Recruitment Program of Global Young Experts (China).

  8. Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments

    SciTech Connect

    Amenitsch, H.; Rappolt, M.; Sartori, B.; Laggner, P.; Cojoc, D.; Ferrari, E.; Garbin, V.; Di Fabrizio, E.; Burghammer, M.; Riekel, Ch.

    2007-01-19

    In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 {mu}m large cluster). Further we have performed a scanning diffraction experiment with a 1 micrometer beam to demonstrate the fixing capabilities and to confirm the size of the liposome cluster by X-ray diffraction.

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

    PubMed

    Kilinc, Devrim; Lee, Gil U

    2014-01-01

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

  10. Single molecule studies of helicases with magnetic tweezers.

    PubMed

    Hodeib, Samar; Raj, Saurabh; Manosas, M; Zhang, Weiting; Bagchi, Debjani; Ducos, Bertrand; Allemand, Jean-François; Bensimon, David; Croquette, Vincent

    2016-08-01

    Helicases are a broad family of enzymes that perform crucial functions in DNA replication and in the maintenance of DNA and RNA integrity. A detailed mechanical study of helicases on DNA and RNA is possible using single molecule manipulation methods. Among those, magnetic tweezers (or traps) present a convenient, moderate throughput assay (tens of enzymes can be monitored simultaneously) that allow for high resolution (single base-pair) studies of these enzymes in various conditions and on various substrates (double and single stranded DNA and RNA). Here we discuss various implementation of the basic assay relevant for these studies.

  11. Optical tweezers studies of transcription by eukaryotic RNA polymerases.

    PubMed

    Lisica, Ana; Grill, Stephan W

    2017-02-21

    Transcription is the first step in the expression of genetic information and it is carried out by large macromolecular enzymes called RNA polymerases. Transcription has been studied for many years and with a myriad of experimental techniques, ranging from bulk studies to high-resolution transcript sequencing. In this review, we emphasise the advantages of using single-molecule techniques, particularly optical tweezers, to study transcription dynamics. We give an overview of the latest results in the single-molecule transcription field, focusing on transcription by eukaryotic RNA polymerases. Finally, we evaluate recent quantitative models that describe the biophysics of RNA polymerase translocation and backtracking dynamics.

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

    NASA Astrophysics Data System (ADS)

    Sehgal, Hullas

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

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

    PubMed

    Pacoret, Cécile; Régnier, Stéphane

    2013-08-01

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

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

    PubMed

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

    2013-09-15

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

  15. Developments of pulse laser assist optical tweezers (PLAT) for in vivo manipulation

    NASA Astrophysics Data System (ADS)

    Maeda, Saki; Sugiura, Tadao; Minato, Kotaro

    2011-02-01

    Optical tweezers is a technique to trap and to manipulate micron sized objects under a microscope by radiation pressure force exerted by a laser beam. Optical tweezers has been utilized for single-molecular measurements of force exerted by molecular interactions and for cell palpation. To extend applications of optical tweezers we have developed a novel optical tweezers system combined with a pulse laser. We utilize a pulsed laser (Q-switched Nd: YAG laser, wavelength of 1064 nm) to assist manipulations by conventional optical tweezers achieved by a continuous wave (CW) laser. The pulsed laser beam is introduced into the same optics for conventional optical tweezers. In principle, instantaneous radiation force is proportional to instantaneous power of laser beam. As a result, pulsed laser beam generates strong instantaneous force on an object to be manipulated. If the radiation force becomes strong enough to get over an obstacle structure and/or to be released from adhesion, the object will be free from these difficulties. We have named this technique as Pulse Laser beam Assisted optical Tweezers (PLAT). We have successfully demonstrated to manipulate objects surface on a living cell for "in vivo manipulation."

  16. 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.

  17. Multiplexed single-molecule force proteolysis measurements using magnetic tweezers.

    PubMed

    Adhikari, Arjun S; Chai, Jack; Dunn, Alexander R

    2012-07-25

    The generation and detection of mechanical forces is a ubiquitous aspect of cell physiology, with direct relevance to cancer metastasis(1), atherogenesis(2) and wound healing(3). In each of these examples, cells both exert force on their surroundings and simultaneously enzymatically remodel the extracellular matrix (ECM). The effect of forces on ECM has thus become an area of considerable interest due to its likely biological and medical importance(4-7). Single molecule techniques such as optical trapping(8), atomic force microscopy(9), and magnetic tweezers(10,11) allow researchers to probe the function of enzymes at a molecular level by exerting forces on individual proteins. Of these techniques, magnetic tweezers (MT) are notable for their low cost and high throughput. MT exert forces in the range of ~1-100 pN and can provide millisecond temporal resolution, qualities that are well matched to the study of enzyme mechanism at the single-molecule level(12). Here we report a highly parallelizable MT assay to study the effect of force on the proteolysis of single protein molecules. We present the specific example of the proteolysis of a trimeric collagen peptide by matrix metalloproteinase 1 (MMP-1); however, this assay can be easily adapted to study other substrates and proteases.

  18. Multiplying optical tweezers force using a micro-lever.

    PubMed

    Lin, Chih-Lang; Lee, Yi-Hsiung; Lin, Chin-Te; Liu, Yi-Jui; Hwang, Jiann-Lih; Chung, Tien-Tung; Baldeck, Patrice L

    2011-10-10

    This study presents a photo-driven micro-lever fabricated to multiply optical forces using the two-photon polymerization 3D-microfabrication technique. The micro-lever is a second class lever comprising an optical trapping sphere, a beam, and a pivot. A micro-spring is placed between the short and long arms to characterize the induced force. This design enables precise manipulation of the micro-lever by optical tweezers at the micron scale. Under optical dragging, the sphere placed on the lever beam moves, resulting in torque that induces related force on the spring. The optical force applied at the sphere is approximately 100 to 300 pN, with a laser power of 100 to 300 mW. In this study, the optical tweezers drives the micro-lever successfully. The relationship between the optical force and the spring constant can be determined by using the principle of leverage. The arm ratio design developed in this study multiplies the applied optical force by 9. The experimental results are in good agreement with the simulation of spring property.

  19. 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

  20. Use of optical tweezers to probe epithelial mechanosensation.

    PubMed

    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.

  1. Inducing trauma into neuroblastoma cells and synthetic neural networks using optical tweezers

    NASA Astrophysics Data System (ADS)

    Schneider, Patrick William

    The laser tweezers have become a very useful tool in the fields of physics, chemistry, and biology. My intent is to use the laser tweezers to induce trauma into neuroblastoma cells, cells that resemble neural cells when treated with retinoic acid, to try to surmise what happens when neural cells and networks are disrupted or destroyed. The issues presented will deal with the obtaining, maintenance, and differentiation of the cells, as well as the inner operations of the laser tweezers themselves, and what kind of applications it has been applied to, as well as to my work in this project.

  2. Optical tweezers assisted quantitative phase imaging led to thickness mapping of red blood cells

    NASA Astrophysics Data System (ADS)

    Cardenas, Nelson; Mohanty, Samarendra K.

    2013-07-01

    Quantitative phase microscopy (QPM) allows dynamic mapping of optical path length of microscopic samples with high temporal and axial resolution. However, decoupling of the geometric thickness from the refractive index in phase measurements is challenging. Here, we report use of optical tweezers combined with QPM for decoupling geometric thickness from the refractive index. This is demonstrated by orienting the microscopic sample (red blood cell) by optical tweezers and imaging the phase at various orientations. Since optical tweezers can orient wide variety of micro and nanoscopic objects, this integrated method can be employed to accurately determine their physical properties.

  3. A simple method for evaluating the trapping performance of acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Li, Ying; Lee, Changyang; Ho Lam, Kwok; Kirk Shung, K.

    2013-02-01

    The purpose of this paper is to present a rapid and simple method to evaluate the trapping performance of high frequency focused ultrasonic transducers for acoustic tweezer applications. The method takes into consideration the friction between the particle to be trapped and the surface that it resides on. As a result it should be more reliable and accurate than the methods proposed previously. The trapping force produced by a 70-MHz press-focused transducer was measured to evaluate the performance of this approach. This method demonstrates its potential in optimizing the excitation conditions for acoustic tweezer applications and the design of acoustic tweezers.

  4. A simple method for evaluating the trapping performance of acoustic tweezers.

    PubMed

    Li, Ying; Lee, Changyang; Ho Lam, Kwok; Kirk Shung, K

    2013-02-25

    The purpose of this paper is to present a rapid and simple method to evaluate the trapping performance of high frequency focused ultrasonic transducers for acoustic tweezer applications. The method takes into consideration the friction between the particle to be trapped and the surface that it resides on. As a result it should be more reliable and accurate than the methods proposed previously. The trapping force produced by a 70-MHz press-focused transducer was measured to evaluate the performance of this approach. This method demonstrates its potential in optimizing the excitation conditions for acoustic tweezer applications and the design of acoustic tweezers.

  5. 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

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

    PubMed

    Hu, Songyu; Sun, Dong

    2011-08-01

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

  7. Manipulation and spectroscopy of a single particle by use of white-light optical tweezers

    NASA Astrophysics Data System (ADS)

    Li, Peng; Shi, Kebin; Liu, Zhiwen

    2005-01-01

    We demonstrate, for the first time to our knowledge, three-dimensional (3D) trapping and manipulation of microscopic objects by use of supercontinuum white light generated from photonic crystal fibers. Furthermore, we show that the supercontinuum white-light optical tweezers used have the unique capability to perform optical scattering spectroscopy of a single 3D trapped object over a broad wavelength range. These novel tweezers can potentially open a promising avenue toward simultaneous manipulation and characterization of microscopic objects.

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

    NASA Astrophysics Data System (ADS)

    Bak, Jimmy; Jørgensen, Thomas M.

    2007-05-01

    The authors of the work: ‘Chromosomal analysis and identification based on optical tweezers and raman spectroscopy’ [Opt. Express 14, 5385 (2006], claim that they have been able to identify and differentiate between three human chromosomes with an optical-tweezer Raman Spectroscopic experimental (LTRS) set-up. The results and conclusions as they are presented in the paper are questionable, however, when the spectral data and data analysis are studied in greater detail.

  9. 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.

  10. 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 (λ=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.

  11. Probing multiscale mechanics of collagen with optical tweezers

    NASA Astrophysics Data System (ADS)

    Shayegan, Marjan; Rezaei, Naghmeh; Lam, Norman H.; Altindal, Tuba; Wieczorek, Andrew; Forde, Nancy R.

    2013-09-01

    How the molecular structure of the structural, extracellular matrix protein collagen correlates with its mechanical properties at different hierarchical structural levels is not known. We demonstrate the utility of optical tweezers to probe collagen's mechanical response throughout its assembly hierarchy, from single molecule force-extension measurements through microrheology measurements on solutions of collagen molecules, collagen fibrillar gels and gelatin. These experiments enable the determination of collagen's flexibility, mechanics, and timescales and strengths of interaction at different levels of hierarchy, information critical to developing models of how collagen's physiological function and stability are influenced by its chemical composition. By investigating how the viscoelastic properties of collagen are affected by the presence of telopeptides, protein domains that strongly influence fibril formation, we demonstrate that these play a role in conferring transient elasticity to collagen solutions.

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

    PubMed

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

    2016-01-21

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

  13. Kinect the dots: 3D control of optical tweezers

    NASA Astrophysics Data System (ADS)

    Shaw, Lucy; Preece, Daryl; Rubinsztein-Dunlop, Halina

    2013-07-01

    Holographically generated optical traps confine micron- and sub-micron sized particles close to the center of focused light beams. They also provide a way of trapping multiple particles and moving them in three dimensions. However, in many systems the user interface is not always advantageous or intuitive especially for collaborative work and when depth information is required. We discuss and evaluate a set of multi-beam optical tweezers that utilize off the shelf gaming technology to facilitate user interaction. We use the Microsoft Kinect sensor bar as a way of getting the user input required to generate arbitrary optical force fields and control optically trapped particles. We demonstrate that the system can also be used for dynamic light control.

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

    SciTech Connect

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

    2009-08-15

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

  15. Dynamic excitations in membranes induced by optical tweezers.

    PubMed Central

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

    1998-01-01

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

  16. 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.

  17. The effect of immersion oil in optical tweezers.

    PubMed

    Mahmoudi, Ali; Reihani, S Nader S

    2011-08-01

    Optimized optical tweezers are of great importance for biological micromanipulation. In this paper, we present a detailed electromagnetic-based calculation of the spatial intensity distribution for a laser beam focused through a high numerical aperture objective when there are several discontinuities in the optical pathway of the system. For a common case of 3 interfaces we have shown that 0.01 increase in the refractive index of the immersion medium would shift the optimal trapping depth by 3-4 μm (0.2-0.6 μm) for aqueous (air) medium. For the first time, We have shown that the alteration of the refractive index of the immersion medium can be also used in aerosol trapping provided that larger increase in the refractive index is considered.

  18. Investigating collagen self-assembly with optical tweezers microrheology

    NASA Astrophysics Data System (ADS)

    Forde, Nancy; Shayegan, Marjan; Altindal, Tuba

    Collagen is the fundamental structural protein in vertebrates. Assembled from individual triple-helical proteins to make strong fibres, collagen is a beautiful example of a hierarchical self-assembling system. Using optical tweezers to perform microrheology measurements, we explore the dynamics of interactions between collagens responsible for their self-assembly and examine the development of heterogeneous mechanics during assembly into fibrillar gels. Telopeptides, short non-helical regions that flank the triple helix, have long been known to facilitate fibril self-assembly. We find that their removal not only slows down fibril nucleation but also results in a significant frequency-dependent reduction in the elastic modulus of collagens in solution. We interpret these results in terms of a model in which telopeptides facilitate transient intermolecular interactions, which enhance network connectivity in solution and lead to more rapid assembly in fibril-forming conditions. Current address: Department of Physics, McGill University.

  19. Extending the Range for Force Calibration in Magnetic Tweezers

    PubMed Central

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

    2015-01-01

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

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

    PubMed

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

    2015-05-19

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

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

    PubMed

    Liu, Yuxiang; Yu, Miao

    2009-08-03

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

  2. MatLab program for precision calibration of optical tweezers

    NASA Astrophysics Data System (ADS)

    Tolić-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

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

    NASA Astrophysics Data System (ADS)

    Kaputa, Daniel S.

    The capabilities of laser tweezers have rapidly expanded since the first demonstration by Ashkin and co-workers in 1970 of the ability to trap particles using optical energy. Laser tweezers have been used to measure piconewton forces in many biological and material science application, sort bacteria, measure DNA bond strength, and even perform microsurgery. The laser tweezers system developed for this dissertation foreshadows the next generation of laser tweezer systems that provide automated particle sorted based upon multiple criteria. Many laser tweezer sorting applications today entail the operator sorting cells from a bulk sample, one by one. This dissertation demonstrates the technologies of pattern recognition and image processing that allow for an entire microscope slide to be sorted without any operator intervention. We already live in an automated world where the cars we drive are built by machines instead of humans. The technology is there, and the only factors limiting the advancements of fully automated biological instrumentation is the lack of developers with the appropriate knowledge sets. This dissertation introduces the concept of sorting particles via a multi-parametric approach where several parameters such as size, fluorescence, and Raman spectra are used as sorting criteria. Since the advent of laser tweezers, several groups have demonstrated the ability to sort cells and other particle by size, or by fluorescence, or by any other parameter, but to our knowledge there does not exist a laser tweezer sorting system that can sort particles based upon multiple parameters. Sorting via a single parameter can be a severe limitation as the method lacks the robustness and class specificity that exists when sorting based upon multiple parameters. Simply put, it makes more sense to determine the worth of a baseball card by considering it's condition as well as it's age, rather then solely upon its condition. By adding another parameter such as the name of

  4. Fiber optical tweezers for microscale and nanoscale particle manipulation and force sensing

    NASA Astrophysics Data System (ADS)

    Liu, Yuxiang

    2011-12-01

    Optical tweezers have been an important tool in biology and physics for studying single molecules and colloidal systems. Most of current optical tweezers are built with microscope objectives, which are: i) expensive, ii) bulky and hard to integrate, iii) sensitive to environmental fluctuations, iv) limited in terms of working distances from the substrate, and v) rigid with the requirements on the substrate (transparent substrate made with glass and with a fixed thickness). These limitations of objective-based optical tweezers prevent them from being miniaturized. Fiber optical tweezers can provide a solution for cost reduction and miniaturization, and these optical tweezers can be potentially used in microfluidic systems. However, the existing fiber optical tweezers have the following limitations: i) low trapping efficiency due to weakly focused beams, ii) lack of the ability to control the positions of multiple particles simultaneously, and iii) limited functionalities. The overall objective of this dissertation work is to further the fundamental understanding of fiber optical tweezers through experimental study and modeling, and to develop novel fiber optical tweezers systems to enhance the capability and functionalities of fiber optical tweezers as microscale and nanoscale manipulators/sensors. The contributions of this dissertation work are summarized as follows. i) An enhanced understanding of the inclined dual-fiber optical tweezers (DFOTs) system has been achieved. Stable three dimensional (3D) optical trapping of a single micron-sized particle has been experimentally demonstrated. This is the first time that the trapping efficiency has been calibrated and the stiffness of the trap has been obtained in the experiments, which has been carried out by using two methods: the drag force method and power spectrum analysis. Such calibration enables the system to be used as a picoNewton-level force sensor in addition to a particle manipulator. The influence of

  5. Quantitative guidelines for force calibration through spectral analysis of magnetic tweezers data.

    PubMed

    te Velthuis, Aartjan J W; Kerssemakers, Jacob W J; Lipfert, Jan; Dekker, Nynke H

    2010-08-09

    Single-molecule techniques are powerful tools that can be used to study the kinetics and mechanics of a variety of enzymes and their complexes. Force spectroscopy, for example, can be used to control the force applied to a single molecule and thereby facilitate the investigation of real-time nucleic acid-protein interactions. In magnetic tweezers, which offer straightforward control and compatibility with fluorescence measurements or parallel tracking modes, force-measurement typically relies on the analysis of positional fluctuations through video microscopy. Significant errors in force estimates, however, may arise from incorrect spectral analysis of the Brownian motion in the magnetic tweezers. Here we investigated physical and analytical optimization procedures that can be used to improve the range over which forces can be reliably measured. To systematically probe the limitations of magnetic tweezers spectral analysis, we have developed a magnetic tweezers simulator, whose outcome was validated with experimental data. Using this simulator, we evaluate methods to correctly perform force experiments and provide guidelines for correct force calibration under configurations that can be encountered in typical magnetic tweezers experiments.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

    Kuo, Chun-Fu; Chu, Shu-Chun

    2013-11-04

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

  8. 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

    2015-03-18

    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 k(B)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.

  9. Improved antireflection coated microspheres for biological applications of optical tweezers

    NASA Astrophysics Data System (ADS)

    Ferro, Valentina; Sonnberger, Aaron; Abdosamadi, Mohammad K.; McDonald, Craig; Schäffer, Erik; McGloin, David

    2016-09-01

    The success of optical tweezers in cellular biology1 is in part due to the wide range of forces that can be applied, from femto- to hundreds of pico-Newtons; nevertheless extending the range of applicable forces to the nanoNewton regime opens access to a new set of phenomena that currently lie beyond optical manipulation. A successful approach to overcome the conventional limits on trapping forces involves the optimization of the trapped probes. Jannasch et al.2 demonstrated that an anti-reflective shell of nanoporous titanium dioxide (aTiO2, nshell = 1.75) on a core particle made out of titanium dioxide in the anatase phase (cTiO2, ncore = 2.3) results in trappable microspheres capable to reach forces above 1 nN. Here we present how the technique can be further improved by coating the high refractive index microspheres with an additional anti-reflective shell made out of silica (SiO2). This external shell not only improves the trap stability for microspheres of different sizes, but also enables the use of functionalization techniques already established for commercial silica beads in biological experiments. We are also investigating the use of these new microspheres as probes to measure adhesion forces between intercellular adhesion molecule 1 (ICAM-1) and lymphocyte function-associated antigen 1 (LFA-1) in effector T-Cells and will present preliminary results comparing standard and high-index beads.

  10. A holographic optical tweezers module for the International Space Station

    NASA Astrophysics Data System (ADS)

    Shane, J.; Serati, R.; Masterson, H.; Serati, Steve

    2016-09-01

    The International Space Station (ISS) is an unparalleled laboratory for studying colloidal suspensions in microgravity. The first colloidal experiments on the ISS involved passive observation of suspended particles, and current experiments are now capable of observation under controlled environmental conditions; for example, under heating or under externally applied magnetic or electric fields. Here, we describe the design of a holographic optical tweezers (HOT) module for the ISS, with the goal of giving ISS researchers the ability to actively control 3D arrangements of particles, allowing them to initialize and perform repeatable experiments. We discuss the design's modifications to the basic HOT module hardware to allow for operation in a high-vibration, microgravity environment. We also discuss the module's planned particle tracking and routing capabilities, which will enable the module to remotely perform pre-programmed colloidal and biological experiments. The HOT module's capabilities can be expanded or upgraded through software alone, providing a unique platform for optical trapping researchers to test new tweezing beam configurations and routines in microgravity.

  11. Application of laser tweezers to passive microrheology of collagen solutions

    NASA Astrophysics Data System (ADS)

    Shayegan, Marjan; Forde, Nancy R.

    2009-05-01

    Rheology is the field that can describe both viscous and elastic properties of a material in response to applied force or deformation. Passive microrheology (PMR) is a technique in which motion of a particle arising from thermal fluctuations is measured on nanometer length scales. One experimental approach to PMR uses optical tweezers, which trap and probe μm-sized particles, located within the material, at a high bandwidth. In this study, viscoelastic properties of solutions of collagen are characterized. To do this, we have probed the power spectral density of fluctuations of 1-μm-diameter microspheres optically trapped in acidic solutions of varying concentration of collagen type I (0, 0.5, and 1 mg/ml). The results show evidence that the behaviour of the solutions becomes increasingly non-Newtonian at high protein concentration. We attribute this to the presence of the viscoelastic polymer. This introduces frequency dependence to the complex modulus of the solution which is used to characterize the elasticity and viscosity of these systems.

  12. Use of shape induced birefringence for rotation in optical tweezers

    NASA Astrophysics Data System (ADS)

    Asavei, Theodor; Nieminen, Timo A.; Heckenberg, Norman R.; Rubinsztein-Dunlop, Halina

    2010-08-01

    Since a light beam can carry angular momentum (AM) it is possible to use optical tweezers to exert torques to twist or rotate microscopic objects. The alignment torque exerted on an elongated particle in a polarized light field represents a possible torque mechanism. In this situation, although some exchange of orbital angular momentum occurs, scattering calculations show that spin dominates, and polarization measurements allow the torque to be measured with good accuracy. This phenomenon can be explained by considering shape birefringence with an induced polarizability tensor. Another example of a shape birefringent object is a microsphere with a cylindrical cavity. Its design is based on the fact that due to its symmetry a sphere does not rotate in an optical trap, but one could break the symmetry by designing an object with a spherical outer shape with a non spherical cavity inside. The production of such a structure can be achieved using a two photon photo-polymerization technique. We show that using this technique, hollow spheres with varying sizes of the cavity can be successfully constructed. We have been able to demonstrate rotation of these spheres with cylindrical cavities when they are trapped in a laser beam carrying spin angular momentum. The torque efficiency achievable in this system can be quantified as a function of a cylinder diameter. Because they are biocompatible and easily functionalized, these structures could be very useful in work involving manipulation, control and probing of individual biological molecules and molecular motors.

  13. Bio-syncretic tweezers actuated by microorganisms: modeling and analysis.

    PubMed

    Zhang, C; Xie, S X; Wang, W X; Xi, N; Wang, Y C; Liu, L Q

    2016-09-28

    Advancements in micro-/nano-technology have led to the development of micro-manipulators. However, some challenges remain; for instance, the efficiency, precision and flexibility of micro-manipulators restrain their applications. This paper proposes a bio-tweezer system to flexibly manipulate micro-objects with bio-actuation via local light-induced high-concentration microorganisms in two different manipulation modes: light-spot induced mode and geometric shape-induced mode. Depending on the shape of micro-objects, either 2-dimensional translation or 1-dimensional rotation can be achieved. Based on the Langevin equation, a mathematical model considering both hydrodynamics and mimicked Brownian motion is proposed to analyze the bio-manipulation performance of the microorganisms; the model was validated by experiments to translate micro-particles in a two-dimensional plane and to rotate a micro-gear structure around its axis. This paper will aid in the development of micro-manipulators and the quantitative understanding of micro-/nano-manipulation actuated by microorganisms.

  14. Magnetic tweezers force calibration for molecules that exhibit conformational switching

    NASA Astrophysics Data System (ADS)

    Jacobson, David R.; Saleh, Omar A.

    2016-09-01

    High spatial and temporal resolution magnetic tweezers experiments allow for the direct calibration of pulling forces applied to short biomolecules. In one class of experiments, a force is applied to a structured RNA or protein to induce an unfolding transition; when the force is maintained at particular values, the molecule can exhibit conformational switching between the folded and unfolded states or between intermediate states. Here, we analyze the degree to which common force calibration approaches, involving the fitting of model functions to the Allan variance or power spectral density of the bead trajectory, are biased by this conformational switching. We find significant effects in two limits: that of large molecular extension changes between the two states, in which alternative fitting functions must be used, and that of very fast switching kinetics, in which the force calibration cannot be recovered due to the slow diffusion time of the magnetic bead. We use simulations and high-resolution RNA hairpin data to show that most biophysical experiments do not occur in either of these limits.

  15. Probing DNA Helicase Kinetics with Temperature‐Controlled Magnetic Tweezers

    PubMed Central

    Gollnick, Benjamin; Carrasco, Carolina; Zuttion, Francesca; Gilhooly, Neville S.; Dillingham, Mark S.

    2015-01-01

    Motor protein functions like adenosine triphosphate (ATP) hydrolysis or translocation along molecular substrates take place at nanometric scales and consequently depend on the amount of available thermal energy. The associated rates can hence be investigated by actively varying the temperature conditions. In this article, a thermally controlled magnetic tweezers (MT) system for single‐molecule experiments at up to 40 °C is presented. Its compact thermostat module yields a precision of 0.1 °C and can in principle be tailored to any other surface‐coupled microscopy technique, such as tethered particle motion (TPM), nanopore‐based sensing of biomolecules, or super‐resolution fluorescence imaging. The instrument is used to examine the temperature dependence of translocation along double‐stranded (ds)DNA by individual copies of the protein complex AddAB, a helicase‐nuclease motor involved in dsDNA break repair. Despite moderately lower mean velocities measured at sub‐saturating ATP concentrations, almost identical estimates of the enzymatic reaction barrier (around 21–24 k B 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

  16. Particle interaction measurements using laser tweezers optical trapping.

    SciTech Connect

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

    2008-08-01

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

  17. Temperature control and measurement with tunable femtosecond optical tweezers

    NASA Astrophysics Data System (ADS)

    Mondal, Dipankar; Goswami, Debabrata

    2016-09-01

    We present the effects of wavelength dependent temperature rise in a femtosecond optical tweezers. Our experiments involve the femtosecond trapping laser tunable from 740-820 nm at low power 25 mW to cause heating in the trapped volume within a homogeneous solution of sub micro-molar concentration of IR dye. The 780 nm high repetition rate laser acts as a resonant excitation source which helps to create the local heating effortlessly within the trapping volume. We have used both position autocorrelation and equipartion theorem to evaluate temperature at different wavelength having different absorption coefficient. Fixing the pulse width in the temporal domain gives constant bandwidth at spatial domain, which makes our system behave as a tunable temperature rise device with high precision. This observation leads us to calculate temperature as well as viscosity within the vicinity of the trapping zone. A mutual energy transfer occurs between the trapped bead and solvents that leads to transfer the thermal energy of solvents into the kinetic energy of the trap bead and vice-versa. Thus hot solvated molecules resulting from resonant and near resonant excitation of trapping wavelength can continuously dissipate heat to the trapped bead which will be reflected on frequency spectrum of Brownian noise exhibited by the bead. Temperature rise near the trapping zone can significantly change the viscosity of the medium. We observe temperature rise profile according to its Gaussian shaped absorption spectrum with different wavelength.

  18. Manipulating and assembling metallic beads with Optoelectronic Tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Shuailong; Juvert, Joan; Cooper, Jonathan M.; Neale, Steven L.

    2016-09-01

    Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10‑9 N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction.

  19. 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

  20. Manipulating and assembling metallic beads with Optoelectronic Tweezers

    PubMed Central

    Zhang, Shuailong; Juvert, Joan; Cooper, Jonathan M.; Neale, Steven L.

    2016-01-01

    Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10−9 N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction. PMID:27599445

  1. Toward automated formation of microsphere arrangements using multiplexed optical tweezers

    NASA Astrophysics Data System (ADS)

    Rajasekaran, Keshav; Bollavaram, Manasa; Banerjee, Ashis G.

    2016-09-01

    Optical tweezers offer certain advantages such as multiplexing using a programmable spatial light modulator, flexibility in the choice of the manipulated object and the manipulation medium, precise control, easy object release, and minimal object damage. However, automated manipulation of multiple objects in parallel, which is essential for efficient and reliable formation of micro-scale assembly structures, poses a difficult challenge. There are two primary research issues in addressing this challenge. First, the presence of stochastic Langevin force giving rise to Brownian motion requires motion control for all the manipulated objects at fast rates of several Hz. Second, the object dynamics is non-linear and even difficult to represent analytically due to the interaction of multiple optical traps that are manipulating neighboring objects. As a result, automated controllers have not been realized for tens of objects, particularly with three dimensional motions with guaranteed collision avoidances. In this paper, we model the effect of interacting optical traps on microspheres with significant Brownian motions in stationary fluid media, and develop simplified state-space representations. These representations are used to design a model predictive controller to coordinate the motions of several spheres in real time. Preliminary experiments demonstrate the utility of the controller in automatically forming desired arrangements of varying configurations starting with randomly dispersed microspheres.

  2. 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.

  3. Calibration of holographic optical tweezers for force measurements on biomaterials

    NASA Astrophysics Data System (ADS)

    van der Horst, Astrid; Forde, Nancy

    2009-05-01

    Holographic optical tweezers (HOTs) modify the phase of a laser beam to create and dynamically position multiple optical traps independently in 3D; refractive micrometer-sized particles can be held in these traps to function as probing handles. HOTs offer the flexibility needed to probe the mechanics of complex systems such as cells or protein networks. Thus far, however, HOTs have not found wide use in biophysics, in large part due to lack of evidence as to how exerted forces vary as the positions of HOT traps are changed. To perform quantitative force measurements, parameters such as trap stiffness, range of trap steering, and minimum step size are of key importance. We find for our HOT setup that stiffness does not change significantly over a range of ˜25μm. In addition, we control and detect, using high-speed (>kHz) camera imaging, trap displacements to ˜1nm. Our results suggest that after full characterization HOTs can be successfully employed in quantitative experiments on biomaterials, e.g., probing elastomeric properties of structural protein networks.

  4. 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

  5. Calibration of femtosecond optical tweezers as a sensitive thermometer

    NASA Astrophysics Data System (ADS)

    Mondal, Dipankar; Goswami, Debabrata

    2015-08-01

    We present cumulative perturbation effects of femtosecond laser pulses on an optical tweezer. Our experiments involve a dual wavelength high repetition rate femtosecond laser, one at the non-heating wavelength of 780 nm while the other at 1560 nm to cause heating in the trapped volume under low power (100-800 μW) conditions. The 1560 nm high repetition rate laser acts as a resonant excitation source for the vibrational combination band of the hydroxyl group (OH) of water, which helps create the local heating effortlessly within the trapping volume. With such an experimental system, we are the first to observe direct effect of temperature on the corner frequency deduced from power spectrum. We can, thus, control and measure temperature precisely at the optical trap. This observation has lead us to calculate viscosity as well as temperature in the vicinity of the trapping zone. These experimental results also support the well-known fact that the nature of Brownian motion is the response of the optically trapped bead from the temperature change of surroundings. Temperature rise near the trapping zone can significantly change the viscosity of the medium. However, we notice that though the temperature and viscosity are changing as per our corner frequency calculations, the trap stiffness remains the same throughout our experiments within the temperature range of about 20 K.

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

    PubMed

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

    2015-07-01

    Optical tweezers play an important role in biological applications. However, it is difficult for traditional optical tweezers based on objective lenses to work in a three-dimensional (3D) solid far away from the substrate. In this work, we develop a fiber based optical trapping system, namely inclined dual fiber optical tweezers, that can simultaneously apply and measure forces both in water and in a 3D polyacrylamide gel matrix. In addition, we demonstrate in situ, non-invasive characterization of local mechanical properties of polyacrylamide gel by measurements on an embedded bead. The fiber optical tweezers measurements agree well with those of atomic force microscopy (AFM). The inclined dual fiber optical tweezers provide a promising and versatile tool for cell mechanics study in 3D environments.

  7. Thermal gradient induced tweezers for the manipulation of particles and cells

    NASA Astrophysics Data System (ADS)

    Chen, Jiajie; Cong, Hengji; Loo, Fong-Chuen; Kang, Zhiwen; Tang, Minghui; Zhang, Haixi; Wu, Shu-Yuen; Kong, Siu-Kai; Ho, Ho-Pui

    2016-11-01

    Optical tweezers are a well-established tool for manipulating small objects. However, their integration with microfluidic devices often requires an objective lens. More importantly, trapping of non-transparent or optically sensitive targets is particularly challenging for optical tweezers. Here, for the first time, we present a photon-free trapping technique based on electro-thermally induced forces. We demonstrate that thermal-gradient-induced thermophoresis and thermal convection can lead to trapping of polystyrene spheres and live cells. While the subject of thermophoresis, particularly in the micro- and nano-scale, still remains to be fully explored, our experimental results have provided a reasonable explanation for the trapping effect. The so-called thermal tweezers, which can be readily fabricated by femtosecond laser writing, operate with low input power density and are highly versatile in terms of device configuration, thus rendering high potential for integration with microfluidic devices as well as lab-on-a-chip systems.

  8. Thermal gradient induced tweezers for the manipulation of particles and cells

    PubMed Central

    Chen, Jiajie; Cong, Hengji; Loo, Fong-Chuen; Kang, Zhiwen; Tang, Minghui; Zhang, Haixi; Wu, Shu-Yuen; Kong, Siu-Kai; Ho, Ho-Pui

    2016-01-01

    Optical tweezers are a well-established tool for manipulating small objects. However, their integration with microfluidic devices often requires an objective lens. More importantly, trapping of non-transparent or optically sensitive targets is particularly challenging for optical tweezers. Here, for the first time, we present a photon-free trapping technique based on electro-thermally induced forces. We demonstrate that thermal-gradient-induced thermophoresis and thermal convection can lead to trapping of polystyrene spheres and live cells. While the subject of thermophoresis, particularly in the micro- and nano-scale, still remains to be fully explored, our experimental results have provided a reasonable explanation for the trapping effect. The so-called thermal tweezers, which can be readily fabricated by femtosecond laser writing, operate with low input power density and are highly versatile in terms of device configuration, thus rendering high potential for integration with microfluidic devices as well as lab-on-a-chip systems. PMID:27853191

  9. Manipulation of cells with laser microbeam scissors and optical tweezers: a review

    NASA Astrophysics Data System (ADS)

    Greulich, Karl Otto

    2017-02-01

    The use of laser microbeams and optical tweezers in a wide field of biological applications from genomic to immunology is discussed. Microperforation is used to introduce a well-defined amount of molecules into cells for genetic engineering and optical imaging. The microwelding of two cells induced by a laser microbeam combines their genetic outfit. Microdissection allows specific regions of genomes to be isolated from a whole set of chromosomes. Handling the cells with optical tweezers supports investigation on the attack of immune systems against diseased or cancerous cells. With the help of laser microbeams, heart infarction can be simulated, and optical tweezers support studies on the heartbeat. Finally, laser microbeams are used to induce DNA damage in living cells for studies on cancer and ageing.

  10. Optical disassembly of cellular clusters by tunable ‘tug-of-war’ tweezers

    PubMed Central

    Bezryadina, Anna S; Preece, Daryl C; Chen, Joseph C; Chen, Zhigang

    2016-01-01

    Bacterial biofilms underlie many persistent infections, posing major hurdles in antibiotic treatment. Here we design and demonstrate ‘tug-of-war’ optical tweezers that can facilitate the assessment of cell–cell adhesion—a key contributing factor to biofilm development, thanks to the combined actions of optical scattering and gradient forces. With a customized optical landscape distinct from that of conventional tweezers, not only can such ‘tug-of-war’ tweezers stably trap and stretch a rod-shaped bacterium in the observing plane, but, more importantly, they can also impose a tunable lateral force that pulls apart cellular clusters without any tethering or mechanical movement. As a proof of principle, we examined a Sinorhizobium meliloti strain that forms robust biofilms and found that the strength of intercellular adhesion depends on the growth medium. This technique may herald new photonic tools for optical manipulation and biofilm study, as well as other biological applications. PMID:27818838

  11. Thermal gradient induced tweezers for the manipulation of particles and cells.

    PubMed

    Chen, Jiajie; Cong, Hengji; Loo, Fong-Chuen; Kang, Zhiwen; Tang, Minghui; Zhang, Haixi; Wu, Shu-Yuen; Kong, Siu-Kai; Ho, Ho-Pui

    2016-11-17

    Optical tweezers are a well-established tool for manipulating small objects. However, their integration with microfluidic devices often requires an objective lens. More importantly, trapping of non-transparent or optically sensitive targets is particularly challenging for optical tweezers. Here, for the first time, we present a photon-free trapping technique based on electro-thermally induced forces. We demonstrate that thermal-gradient-induced thermophoresis and thermal convection can lead to trapping of polystyrene spheres and live cells. While the subject of thermophoresis, particularly in the micro- and nano-scale, still remains to be fully explored, our experimental results have provided a reasonable explanation for the trapping effect. The so-called thermal tweezers, which can be readily fabricated by femtosecond laser writing, operate with low input power density and are highly versatile in terms of device configuration, thus rendering high potential for integration with microfluidic devices as well as lab-on-a-chip systems.

  12. Temperature-dependent conformations of a membrane supported zinc porphyrin tweezer by 2D fluorescence spectroscopy.

    PubMed

    Widom, Julia R; Lee, Wonbae; Perdomo-Ortiz, Alejandro; Rappoport, Dmitrij; Molinski, Tadeusz F; Aspuru-Guzik, Alán; Marcus, Andrew H

    2013-07-25

    We studied the equilibrium conformations of a zinc porphyrin tweezer composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4-butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of folded and extended conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17-85 °C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes.

  13. RBCs under optical tweezers as cellular motors and rockers: microfluidic applications

    NASA Astrophysics Data System (ADS)

    Mohanty, Samarendra; Mohanty, Khyati; Gupta, Pradeep

    2006-08-01

    Recently, we have reported self-rotation of normal red blood cells (RBC), suspended in hypertonic buffer, and trapped in unpolarized laser tweezers. Here, we report use of such an optically driven RBC-motor for microfluidic applications such as pumping/centrifugation of fluids. Since the speed of rotation of the RBC-motor was found to vary with the power of the trapping beam, the flow rate could be controlled by controlling the laser power. In polarized optical tweezers, preferential alignment of trapped RBC was observed. The aligned RBC (simulating a disk) in isotonic buffer, could be rotated in a controlled manner for use as a microfluidic valve by rotation of the plane of polarization of the trapping beam. The thickness of the discotic RBC could be changed by changing the osmolarity of the solution and thus the alignment torque on the RBC due to the polarization of the trapping beam could be varied. Further, in polarized tweezers, the RBCs in hypertonic buffer showed rocking motion while being in rotation. Here, the RBC rotated over a finite angular range, stopped for some time at a particular angle, and then started rotating till it was back to the aligned position and this cycle was found repetitive. This can be attributed to the fact that though the RBCs were found to experience an alignment torque to align with plane of polarization of the tweezers due to its form birefringence, it was smaller in magnitude as compared to the rotational torque due to its structural asymmetry in hypertonic solution. Changes in the laser power caused a transition from/to rocking to/from motor behavior of the RBC in a linearly polarized tweezers. By changing the direction of polarization caused by rotation of an external half wave plate, the stopping angle of rocking could be changed. Further, RBCs suspended in intermediate hypertonic buffer and trapped with polarized tweezers showed fluttering about the vertical plane.

  14. Pulse laser assist optical tweezers (PLAT) with long-duration pulse laser

    NASA Astrophysics Data System (ADS)

    Maeda, Saki; Sugiura, Tadao; Minato, Kotaro

    2011-07-01

    Optical tweezers is a technique to trap and to manipulate micron sized objects under a microscope by radiation pressure force exerted by a laser beam. Optical tweezers has been utilized for single-molecular measurements of force exerted by molecular interactions and for cell palpation. To extend applications of optical tweezers we have developed a novel optical tweezers system combined with a pulse laser. We utilize a pulse laser (Q-switched Nd: YAG laser, wavelength of 1064 nm) to assist manipulations by conventional optical tweezers with a continuous wave (CW) laser. The pulse laser beam is introduced into the same optics for conventional optical tweezers. In principle, instantaneous radiation force is proportional to instantaneous power of laser beam. As a result, pulse laser beam generates strong instantaneous force on an object to be manipulated. If the radiation force becomes strong enough to get over an obstacle structure and/or to be released from adhesion, the object will be free from these difficulties. We investigate the effect of pulse laser assistance with changing pulse duration of the laser. We report optimum pulse duration of 100 ns to 200 ns deduced from motion analysis of a particle in a beam spot. Our goal is to realize in-vivo manipulation and operation of a cell. For this purpose we need to reduce light energy of pulse laser beam and to avoid laser induced breakdown caused by strong light field. So we have developed a pulse laser with 160-ns pulse duration and have confirmed that availability on manipulation of living cells.

  15. Two-particle quantum interference in tunnel-coupled optical tweezers.

    PubMed

    Kaufman, A M; Lester, B J; Reynolds, C M; Wall, M L; Foss-Feig, M; Hazzard, K R A; Rey, A M; Regal, C A

    2014-07-18

    The quantum statistics of atoms is typically observed in the behavior of an ensemble via macroscopic observables. However, quantum statistics modifies the behavior of even two particles. Here, we demonstrate near-complete control over all the internal and external degrees of freedom of two laser-cooled (87)Rb atoms trapped in two optical tweezers. This controllability allows us to observe signatures of indistinguishability via two-particle interference. Our work establishes laser-cooled atoms in optical tweezers as a promising route to bottom-up engineering of scalable, low-entropy quantum systems.

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

    SciTech Connect

    Kotsifaki, D. G. Kandyla, M.; Lagoudakis, P. G.

    2015-11-23

    We present experimental evidence of plasmonic-enhanced optical tweezers, of polystyrene beads in deionized water in the vicinity of metal-coated nanostructures. The optical tweezers operate with a continuous wave near-infrared laser. We employ a Cu/Au bilayer that significantly improves dissipation of heat generated by the trapping laser beam and avoid de-trapping from heat convection currents. We investigate the improvement of the optical trapping force and the effective trapping quality factor, and observe an exponential distance dependence of the trapping force from the nanostructures, indicative of evanescent plasmonic enhancement.

  17. 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.

  18. Manipulating multiparticles simultaneously with tapered-tip single fiber optical tweezers

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

    We present a single-core tapered-tip single fiber optical tweezers, which can trap multi-particle simultaneously. In order to test and verify its new function, finite difference time domain (FDTD) method is used to calculate and simulate. The relationship between the trapping force and the particle-parameters, such as the size, refractive index and others of particle are studied. By experimental validation, the tapered-tip single optic fiber tweezers can trap Particle 2nd after the Particle 1st trapped firmly, but can not trap Particle 3rd, which just verifies the theoretical simulation results to be right.

  19. 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

  20. Investigating intermolecular forces associated with thrombus initiation using optical tweezers

    NASA Astrophysics Data System (ADS)

    Arya, Maneesh; Lopez, Jose A.; Romo, Gabriel M.; Dong, Jing-Fei; McIntire, Larry V.; Moake, Joel L.; Anvari, Bahman

    2002-05-01

    Thrombus formation occurs when a platelet membrane receptor, glycoprotein (GP) Ib-IX-V complex, binds to its ligand, von Willebrand factor (vWf), in the subendothelium or plasma. To determine which GP Ib-IX-V amino acid sequences are critical for bond formation, we have used optical tweezers to measure forces involved in the binding of vWf to GP Ib-IX-V variants. Inasmuch as GP Ib(alpha) subunit is the primary component in human GP Ib-IX-V complex that binds to vWf, and that canine GP Ib(alpha) , on the other hand, does not bind to human vWf, we progressively replaced human GP Ib(alpha) amino acid sequences with canine GP Ib(alpha) sequences to determine the sequences essential for vWf/GP Ib(alpha) binding. After measuring the adhesive forces between optically trapped, vWf-coated beads and GP Ib(alpha) variants expressed on mammalian cells, we determined that leucine- rich repeat 2 of GP Ib(alpha) was necessary for vWf/GP Ib-IX- V bond formation. We also found that deletion of the N- terminal flanking sequence and leucine-rich repeat 1 reduced adhesion strength to vWf but did not abolish binding. While divalent cations are known to influence binding of vWf, addition of 1mM CaCl2 had no effect on measured vWf/GP Ib(alpha) bond strengths.

  1. 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.

  2. 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 μ 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.

  3. Substrate-dependent cell elasticity measured by optical tweezers indentation

    NASA Astrophysics Data System (ADS)

    Yousafzai, Muhammad S.; Ndoye, Fatou; Coceano, Giovanna; Niemela, Joseph; Bonin, Serena; Scoles, Giacinto; Cojoc, Dan

    2016-01-01

    In the last decade, cell elasticity has been widely investigated as a potential label free indicator for cellular alteration in different diseases, cancer included. Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. In this paper, we propose a simple approach to perform cell indentation at pN forces by axially moving the cell against a trapped microbead. The elastic modulus is calculated using the Hertz-model. Besides the axial component, the setup also allows us to examine the lateral cell-bead interaction. This technique has been applied to measure the local elasticity of HBL-100 cells, an immortalized human cell line, originally derived from the milk of a woman with no evidence of breast cancer lesions. In addition, we have studied the influence of substrate stiffness on cell elasticity by performing experiments on cells cultured on two substrates, bare and collagen-coated, having different stiffness. The mean value of the cell elastic modulus measured during indentation was 26±9 Pa for the bare substrate, while for the collagen-coated substrate it diminished to 19±7 Pa. The same trend was obtained for the elastic modulus measured during the retraction of the cell: 23±10 Pa and 13±7 Pa, respectively. These results show the cells adapt their stiffness to that of the substrate and demonstrate the potential of this setup for low-force probing of modifications to cell mechanics induced by the surrounding environment (e.g. extracellular matrix or other cells).

  4. Red blood cell micromanipulation with elliptical laser beam profile optical tweezers in different osmolarity conditions

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Makropoulou, M.; Serafetinides, A. A.

    2011-07-01

    In this work optical tweezers with elliptical beam profiles have been developed in order to examine the effect of optical force on fresh red blood cells (RBC) in isotonic, hypertonic and hypotonic buffer solutions. Considering that the optical force depends essentially on the cell surface and the cytoplasmic refractive index, it is obvious that biochemical modifications associated with different states of the cell will influence its behaviour in the optical trap. Line optical tweezers were used to manipulate simultaneously more than one red blood cell. After we have been manipulated a RBC with an elliptical laser beam profile in an isotonic or hypertonic buffer, we noticed that it rotates by itself when gets trapped by optical tweezers and undergoes folding. Further shape deformations can be observed attributed to the competition between alignment and rotational torque which are transferred by laser light to the cell. In hypotonic buffer RBCs become spherical and do not rotate or fold since the resultant force due to rays emerging from diametrically opposite points of the cell leads to zero torque. Manipulation of fresh red blood cells in isotonic solution by line optical tweezers leads to folding and elongation of trapped RBCs. Membrane elasticity properties such as bending modulus can be estimated by measuring RBC's folding time in function with laser power.

  5. Applying torque to the Escherichia coli flagellar motor using magnetic tweezers

    PubMed Central

    van Oene, Maarten M.; Dickinson, Laura E.; Cross, Bronwen; Pedaci, Francesco; Lipfert, Jan; Dekker, Nynke H.

    2017-01-01

    The bacterial flagellar motor of Escherichia coli is a nanoscale rotary engine essential for bacterial propulsion. Studies on the power output of single motors rely on the measurement of motor torque and rotation under external load. Here, we investigate the use of magnetic tweezers, which in principle allow the application and active control of a calibrated load torque, to study single flagellar motors in Escherichia coli. We manipulate the external load on the motor by adjusting the magnetic field experienced by a magnetic bead linked to the motor, and we probe the motor’s response. A simple model describes the average motor speed over the entire range of applied fields. We extract the motor torque at stall and find it to be similar to the motor torque at drag-limited speed. In addition, use of the magnetic tweezers allows us to force motor rotation in both forward and backward directions. We monitor the motor’s performance before and after periods of forced rotation and observe no destructive effects on the motor. Our experiments show how magnetic tweezers can provide active and fast control of the external load while also exposing remaining challenges in calibration. Through their non-invasive character and straightforward parallelization, magnetic tweezers provide an attractive platform to study nanoscale rotary motors at the single-motor level. PMID:28266562

  6. Listening to proteins and viruses with nanoaperture optical tweezers (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Gordon, Reuven

    2015-08-01

    This talk will present a nanoaperture tweezer approach to measure the acoustic spectra of viruses and single proteins. The approach, termed extraordinary optical Raman (EAR), shows promise for uncovering the structure and mechanical properties of nanoparticles as well as the effects of their interactions.

  7. High Spatiotemporal-Resolution Magnetic Tweezers: Calibration and Applications for DNA Dynamics

    PubMed Central

    Dulin, David; Cui, Tao Ju; Cnossen, Jelmer; Docter, Margreet W.; Lipfert, Jan; Dekker, Nynke H.

    2015-01-01

    The observation of biological processes at the molecular scale in real time requires high spatial and temporal resolution. Magnetic tweezers are straightforward to implement, free of radiation or photodamage, and provide ample multiplexing capability, but their spatiotemporal resolution has lagged behind that of other single-molecule manipulation techniques, notably optical tweezers and AFM. Here, we present, to our knowledge, a new high-resolution magnetic tweezers apparatus. We systematically characterize the achievable spatiotemporal resolution for both incoherent and coherent light sources, different types and sizes of beads, and different types and lengths of tethered molecules. Using a bright coherent laser source for illumination and tracking at 6 kHz, we resolve 3 Å steps with a 1 s period for surface-melted beads and 5 Å steps with a 0.5 s period for double-stranded-dsDNA-tethered beads, in good agreement with a model of stochastic bead motion in the magnetic tweezers. We demonstrate how this instrument can be used to monitor the opening and closing of a DNA hairpin on millisecond timescales in real time, together with attendant changes in the hairpin dynamics upon the addition of deoxythymidine triphosphate. Our approach opens up the possibility of observing biological events at submillisecond timescales with subnanometer resolution using camera-based detection. PMID:26588570

  8. 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 .

  9. Stress response in Caenorhabditis elegans caused by optical tweezers: wavelength, power, and time dependence.

    PubMed Central

    Leitz, Guenther; Fällman, Erik; Tuck, Simon; Axner, Ove

    2002-01-01

    Optical tweezers have emerged as a powerful technique for micromanipulation of living cells. Although the technique often has been claimed to be nonintrusive, evidence has appeared that this is not always the case. This work presents evidence that near-infrared continuous-wave laser light from optical tweezers can produce stress in Caenorhabditis elegans. A transgenic strain of C. elegans, carrying an integrated heat-shock-responsive reporter gene, has been exposed to laser light under a variety of illumination conditions. It was found that gene expression was most often induced by light of 760 nm, and least by 810 nm. The stress response increased with laser power and irradiation time. At 810 nm, significant gene expression could be observed at 360 mW of illumination, which is more than one order of magnitude above that normally used in optical tweezers. In the 700-760-nm range, the results show that the stress response is caused by photochemical processes, whereas at 810 nm, it mainly has a photothermal origin. These results give further evidence that the 700-760-nm wavelength region is unsuitable for optical tweezers and suggest that work at 810 nm at normal laser powers does not cause stress at the cellular level. PMID:11916877

  10. Inversion of product selectivity in an enzyme-inspired metallosupramolecular tweezer catalyzed epoxidation reaction†

    PubMed Central

    Ulmann, Pirmin A.; Braunschweig, Adam B.; Lee, One-Sun; Wiester, Michael J.

    2014-01-01

    This study describes a heteroligated, hemilabile PtII–P,S tweezer coordination complex that combines a chiral Jacobsen–Katsuki MnIII-salen epoxidation catalyst with an amidopyridine receptor, which leads to an inversion of the major epoxide product compared to catalysts without a recognition group. PMID:20448966

  11. Multifunctional single beam acoustic tweezer for non-invasive cell/organism manipulation and tissue imaging

    PubMed Central

    Lam, Kwok Ho; Li, Ying; Li, Yang; Lim, Hae Gyun; Zhou, Qifa; Shung, Koping Kirk

    2016-01-01

    Non-contact precise manipulation of single microparticles, cells, and organisms has attracted considerable interest in biophysics and biomedical engineering. Similar to optical tweezers, acoustic tweezers have been proposed to be capable of manipulating microparticles and even cells. Although there have been concerted efforts to develop tools for non-contact manipulation, no alternative to complex, unifunctional tweezer has yet been found. Here we report a simple, low-cost, multifunctional single beam acoustic tweezer (SBAT) that is capable of manipulating an individual micrometer scale non-spherical cell at Rayleigh regime and even a single millimeter scale organism at Mie regime, and imaging tissue as well. We experimentally demonstrate that the SBAT with an ultralow f-number (f# = focal length/aperture size) could manipulate an individual red blood cell and a single 1.6 mm-diameter fertilized Zebrafish egg, respectively. Besides, in vitro rat aorta images were collected successfully at dynamic foci in which the lumen and the outer surface of the aorta could be clearly seen. With the ultralow f-number, the SBAT offers the combination of large acoustic radiation force and narrow beam width, leading to strong trapping and high-resolution imaging capabilities. These attributes enable the feasibility of using a single acoustic device to perform non-invasive multi-functions simultaneously for biomedical and biophysical applications. PMID:27874052

  12. Multifunctional single beam acoustic tweezer for non-invasive cell/organism manipulation and tissue imaging

    NASA Astrophysics Data System (ADS)

    Lam, Kwok Ho; Li, Ying; Li, Yang; Lim, Hae Gyun; Zhou, Qifa; Shung, Koping Kirk

    2016-11-01

    Non-contact precise manipulation of single microparticles, cells, and organisms has attracted considerable interest in biophysics and biomedical engineering. Similar to optical tweezers, acoustic tweezers have been proposed to be capable of manipulating microparticles and even cells. Although there have been concerted efforts to develop tools for non-contact manipulation, no alternative to complex, unifunctional tweezer has yet been found. Here we report a simple, low-cost, multifunctional single beam acoustic tweezer (SBAT) that is capable of manipulating an individual micrometer scale non-spherical cell at Rayleigh regime and even a single millimeter scale organism at Mie regime, and imaging tissue as well. We experimentally demonstrate that the SBAT with an ultralow f-number (f# = focal length/aperture size) could manipulate an individual red blood cell and a single 1.6 mm-diameter fertilized Zebrafish egg, respectively. Besides, in vitro rat aorta images were collected successfully at dynamic foci in which the lumen and the outer surface of the aorta could be clearly seen. With the ultralow f-number, the SBAT offers the combination of large acoustic radiation force and narrow beam width, leading to strong trapping and high-resolution imaging capabilities. These attributes enable the feasibility of using a single acoustic device to perform non-invasive multi-functions simultaneously for biomedical and biophysical applications.

  13. 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

  14. Adhesion of nanoparticles to polymer brushes studied with the ghost tweezers method.

    PubMed

    Cheng, Jianli; Vishnyakov, Aleksey; Neimark, Alexander V

    2015-01-21

    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.

  15. RBC aggregation dynamics in autologous plasma and serum studied with double-channel optical tweezers

    NASA Astrophysics Data System (ADS)

    Lee, Kisung; Danilina, Anna; Potkin, Anton; Kinnunen, Matti; Priezzhev, Alexander; Meglinski, Igor

    2016-04-01

    Red blood cells aggregating and disaggregating forces were measured in the autologous plasma and serum using the double-channeled optical tweezers. A significant, three-fold decrease of the both forces was observed in the serum compared to the plasma. The results of this study help to better assess the RBC aggregation mechanism.

  16. Development of high frequency focused transducers for single beam acoustic tweezers

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiu-Sheng

    Contactless particle trapping and manipulation have found many potential applications in diverse fields, especially in biological and medical research. Among the various methods, optical tweezers is the most well-known and extensively investigated technique. However, there are some limitations for particle manipulation based on optical tweezers. Due to the conceptual similarity with the optical tweezers and recent advances in high frequency ultrasonic transducer, a single beam acoustic tweezer using high frequency (≥ 20 MHz) focused transducer has recently been considered, and its feasibility was theoretically and experimentally investigated. This dissertation mainly describes the development of high frequency focused ultrasonic transducers for single beam acoustic tweezers applications. Three different types of transducers were fabricated. First, a 60 MHz miniature focused transducer (<1 mm) was made using press-focusing technique. The single beam acoustic trapping experiment was performed to manipulate 15 microm polystyrene microspheres using this transducer. In vitro ultrasonic biomicroscopy imaging on the rabbit eye was also obtained with this device. Second approach is to build a 200 MHz self-focused ZnO transducer by sputtering ZnO film on a curved surface of the aluminum backing material. An individual 10 microm microsphere was effectively manipulated in two dimensions by this type of transducer. Another ultrahigh frequency focused transducer based on silicon lens design has also been developed, where a 330 MHz silicon lens transducer was fabricated and evaluated. Microparticle trapping experiment was carried out to demonstrate that silicon lens transducer can manipulate a single microsphere as small as 5 microm. The realization of single beam acoustic tweezers using high frequency focused transducers can offer wide range of applications in biomedical and chemical sciences including intercellular kinetics studies and cell stimulation. Additionally, we

  17. Oscillating optical tweezer-based 3-D confocal microrheometer for investigating the intracellular micromechanics and structures

    NASA Astrophysics Data System (ADS)

    Ou-Yang, H. D.; Rickter, E. A.; Pu, C.; Latinovic, O.; Kumar, A.; Mengistu, M.; Lowe-Krentz, L.; Chien, S.

    2005-08-01

    Mechanical properties of living biological cells are important for cells to maintain their shapes, support mechanical stresses and move through tissue matrix. The use of optical tweezers to measure micromechanical properties of cells has recently made significant progresses. This paper presents a new approach, the oscillating optical tweezer cytorheometer (OOTC), which takes advantage of the coherent detection of harmonically modulated particle motions by a lock-in amplifier to increase sensitivity, temporal resolution and simplicity. We demonstrate that OOTC can measure the dynamic mechanical modulus in the frequency range of 0.1-6,000 Hz at a rate as fast as 1 data point per second with submicron spatial resolution. More importantly, OOTC is capable of distinguishing the intrinsic non-random temporal variations from random fluctuations due to Brownian motion; this capability, not achievable by conventional approaches, is particular useful because living systems are highly dynamic and often exhibit non-thermal, rhythmic behavior in a broad time scale from a fraction of a second to hours or days. Although OOTC is effective in measuring the intracellular micromechanical properties, unless we can visualize the cytoskeleton in situ, the mechanical property data would only be as informative as that of "Blind men and the Elephant". To solve this problem, we take two steps, the first, to use of fluorescent imaging to identify the granular structures trapped by optical tweezers, and second, to integrate OOTC with 3-D confocal microscopy so we can take simultaneous, in situ measurements of the micromechanics and intracellular structure in living cells. In this paper, we discuss examples of applying the oscillating tweezer-based cytorheometer for investigating cultured bovine endothelial cells, the identification of caveolae as some of the granular structures in the cell as well as our approach to integrate optical tweezers with a spinning disk confocal microscope.

  18. Fullerene recognition with molecular tweezers made up of efficient buckybowls: a dispersion-corrected DFT study.

    PubMed

    Josa, Daniela; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

    2015-05-28

    In 2007, Sygula and co-workers introduced a novel type of molecular tweezers with buckybowl pincers that have attracted the substantial interest of researchers due to their ideal architecture for recognizing fullerenes by concave-convex π∙∙∙π interactions (A. Sygula et al., J. Am. Chem. Soc., 2007, 129, 3842). Although in recent years some modifications have been performed on these original molecular tweezers to improve their ability for catching fullerenes, very few improvements were achieved to date. For that reason, in the present work a series of molecular tweezers have been devised and their supramolecular complexes with C60 studied at the B97-D2/TZVP//SCC-DFTB-D and B97-D2/TZVP levels. Three different strategies have been tested: (1) changing the corannulene pincers to other buckybowls, (2) replacing the tetrabenzocyclooctatetraene tether by a buckybowl, and (3) adding methyl groups on the molecular tweezers. According to the results, all the three approaches are effective, in such a way that a combination of the three strategies results in buckycatchers with complexation energies (with C60) up to 2.6 times larger than that of the original buckycatcher, reaching almost -100 kcal mol(-1). The B97-D2/TZVP//SCC-DFTB-D approach can be a rapid screening tool for testing new molecular tweezers. However, since this approach does not reproduce correctly the deformation energy and this energy represents an important contribution to the total complexation energy of complexes, subsequent higher-level re-optimization is compulsory to achieve reliable results (the full B97-D2/TZVP level is used herein). This re-optimization could be superfluous when quite rigid buckycatchers are studied.

  19. A new iterative Fourier transform algorithm for optimal design in holographic optical tweezers

    NASA Astrophysics Data System (ADS)

    Memmolo, P.; Miccio, L.; Merola, F.; Ferraro, P.; Netti, P. A.

    2012-06-01

    We propose a new Iterative Fourier Transform Algorithm (IFTA) capable to suppress ghost traps and noise in Holographic Optical Tweezers (HOT), maintaining a high diffraction efficiency in a computational time comparable with the others iterative algorithms. The process consists in the planning of the suitable ideal target of optical tweezers as input of classical IFTA and we show we are able to design up to 4 real traps, in the field of view imaged by the microscope objective, using an IFTA built on fictitious phasors, located in strategic positions in the Fourier plane. The effectiveness of the proposed algorithm is evaluated both for numerical and optical reconstructions and compared with the other techniques known in literature.

  20. Identification of individual biofilm-forming bacterial cells using Raman tweezers.

    PubMed

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral “Raman fingerprints” obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

  1. Evolution of Nanoflowers and Nanospheres of Zinc Bisporphyrinate Tweezers at the Air/water Interface.

    PubMed

    Xie, Fan; Zhuo, Congcong; Hu, Chuanjiang; Liu, Ming Hua

    2017-03-22

    While the sophisticated Langmuir and Langmuir-Blodgett technique facilitates the fabrication of uniform ultrathin monolayer and films, it is also revealed as a powerful tool for the bottom-up constructions of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked Zinc bis-porphyrinate tweezers using the Langmuir and Langmuir-Blodgett (LB) technique. It was found that both the two tweezer type Zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates by the vertical lifting method. The atomic force microscope (AFM) revealed that at the initial spreading stage the compound formed flat disk-like domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

  2. Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating

    NASA Astrophysics Data System (ADS)

    Kuo, Ju-Nan; Chen, Kuan-Yu

    2010-11-01

    In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

  3. Exact Theory of Optical Tweezers and Its Application to Absolute Calibration.

    PubMed

    Dutra, Rafael S; Viana, Nathan B; Neto, Paulo A Maia; Nussenzveig, H Moysés

    2017-01-01

    Optical tweezers have become a powerful tool for basic and applied research in cell biology. Here, we describe an experimentally verified theory for the trapping forces generated by optical tweezers based on first principles that allows absolute calibration. For pedagogical reasons, the steps that led to the development of the theory over the past 15 years are outlined. The results are applicable to 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. Protocols for implementing absolute calibration are given, explaining how to measure all required experimental parameters, and including a link to an applet for stiffness calculations.

  4. Neural Network for Image-to-Image Control of Optical Tweezers

    NASA Technical Reports Server (NTRS)

    Decker, Arthur J.; Anderson, Robert C.; Weiland, Kenneth E.; Wrbanek, Susan Y.

    2004-01-01

    A method is discussed for using neural networks to control optical tweezers. Neural-net outputs are combined with scaling and tiling to generate 480 by 480-pixel control patterns for a spatial light modulator (SLM). The SLM can be combined in various ways with a microscope to create movable tweezers traps with controllable profiles. The neural nets are intended to respond to scattered light from carbon and silicon carbide nanotube sensors. The nanotube sensors are to be held by the traps for manipulation and calibration. Scaling and tiling allow the 100 by 100-pixel maximum resolution of the neural-net software to be applied in stages to exploit the full 480 by 480-pixel resolution of the SLM. One of these stages is intended to create sensitive null detectors for detecting variations in the scattered light from the nanotube sensors.

  5. Design of Fresnel Lens-Type Multi-Trapping Acoustic Tweezers

    PubMed Central

    Tu, You-Lin; Chen, Shih-Jui; Hwang, Yean-Ren

    2016-01-01

    In this paper, acoustic tweezers which use beam forming performed by a Fresnel zone plate are proposed. The performance has been demonstrated by finite element analysis, including the acoustic intensity, acoustic pressure, acoustic potential energy, gradient force, and particle distribution. The acoustic tweezers use an ultrasound beam produced by a lead zirconate titanate (PZT) transducer operating at 2.4 MHz and 100 Vpeak-to-peak in a water medium. The design of the Fresnel lens (zone plate) is based on air reflection, acoustic impedance matching, and the Fresnel half-wave band (FHWB) theory. This acoustic Fresnel lens can produce gradient force and acoustic potential wells that allow the capture and manipulation of single particles or clusters of particles. Simulation results strongly indicate a good trapping ability, for particles under 150 µm in diameter, in the minimum energy location. This can be useful for cell or microorganism manipulation. PMID:27886050

  6. Thermophoretic Tweezers for Low-Power and Versatile Manipulation of Biological Cells.

    PubMed

    Lin, Linhan; Peng, Xiaolei; Wei, Xiaoling; Mao, Zhangming; Xie, Chong; Zheng, Yuebing

    2017-03-28

    Optical manipulation of biological cells and nanoparticles is significantly important in life sciences, early disease diagnosis, and nanomanufacturing. However, low-power and versatile all-optical manipulation has remained elusive. Herein, we have achieved light-directed versatile thermophoretic manipulation of biological cells at an optical power 100-1000 times lower than that of optical tweezers. By harnessing the permittivity gradient in the electric double layer of the charged surface of the cell membrane, we succeed at the low-power trapping of suspended biological cells within a light-controlled temperature gradient field. Furthermore, through dynamic control of optothermal potentials using a digital micromirror device, we have achieved arbitrary spatial arrangements of cells at a resolution of ∼100 nm and precise rotation of both single and assemblies of cells. Our thermophoretic tweezers will find applications in cellular biology, nanomedicine, and tissue engineering.

  7. Studying taxis in real time using optical tweezers: applications for Leishmania amazonensis parasites.

    PubMed

    Pozzo, L Y; Fontes, A; de Thomaz, A A; Santos, B S; Farias, P M A; Ayres, D C; Giorgio, S; Cesar, C L

    2009-01-01

    Beads trapped by an optical tweezers can be used as a force transducer for measuring forces of the same order of magnitude as typical forces induced by flagellar motion. We used an optical tweezers to study chemotaxis by observing the force response of a flagellated microorganism when placed in a gradient of attractive chemical substances. This report shows such observations for Leishmania amazonensis, responsible for leishmaniasis, a serious disease. We quantified the movement of this protozoan for different gradients of glucose. We were able to observe both the strength and the directionality of the force. The characterization of the chemotaxis of these parasites can help to understand the mechanics of infection and improve the treatments employed for this disease. This methodology can be used to quantitatively study the taxis of any kind of flagellated microorganisms under concentration gradients of different chemical substances, or even other types of variable gradients such as temperature and pressure.

  8. Design of Fresnel Lens-Type Multi-Trapping Acoustic Tweezers.

    PubMed

    Tu, You-Lin; Chen, Shih-Jui; Hwang, Yean-Ren

    2016-11-23

    In this paper, acoustic tweezers which use beam forming performed by a Fresnel zone plate are proposed. The performance has been demonstrated by finite element analysis, including the acoustic intensity, acoustic pressure, acoustic potential energy, gradient force, and particle distribution. The acoustic tweezers use an ultrasound beam produced by a lead zirconate titanate (PZT) transducer operating at 2.4 MHz and 100 Vpeak-to-peak in a water medium. The design of the Fresnel lens (zone plate) is based on air reflection, acoustic impedance matching, and the Fresnel half-wave band (FHWB) theory. This acoustic Fresnel lens can produce gradient force and acoustic potential wells that allow the capture and manipulation of single particles or clusters of particles. Simulation results strongly indicate a good trapping ability, for particles under 150 µm in diameter, in the minimum energy location. This can be useful for cell or microorganism manipulation.

  9. 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

  10. Identification of individual biofilm-forming bacterial cells using Raman tweezers

    NASA Astrophysics Data System (ADS)

    Samek, Ota; Bernatová, Silvie; Ježek, Jan; Šiler, Martin; Šerý, Mojmir; Krzyžánek, Vladislav; Hrubanová, Kamila; Zemánek, Pavel; Holá, Veronika; Růžička, Filip

    2015-05-01

    A method for in vitro identification of individual bacterial cells is presented. The method is based on a combination of optical tweezers for spatial trapping of individual bacterial cells and Raman microspectroscopy for acquisition of spectral "Raman fingerprints" obtained from the trapped cell. Here, Raman spectra were taken from the biofilm-forming cells without the influence of an extracellular matrix and were compared with biofilm-negative cells. Results of principal component analyses of Raman spectra enabled us to distinguish between the two strains of Staphylococcus epidermidis. Thus, we propose that Raman tweezers can become the technique of choice for a clearer understanding of the processes involved in bacterial biofilms which constitute a highly privileged way of life for bacteria, protected from the external environment.

  11. 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.

  12. Red blood cell membrane viscoelasticity, agglutination and zeta potential measurements with double optical tweezers

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

    The red blood cell (RBC) viscoelastic membrane contains proteins and glycolproteins embedded in, or attached, to a fluid lipid bilayer and are negatively charged, which creates a repulsive electric (zeta) potential between the cells and prevents their aggregation in the blood stream. There are techniques, however, to decrease the zeta potential to allow cell agglutination which are the basis of most of the tests of antigen-antibody interactions in blood banks. This report shows the use of a double optical tweezers to measure RBC membrane viscosity, agglutination and zeta potential. In our technique one of the optical tweezers trap a silica bead that binds strongly to a RBC at the end of a RBCs rouleaux and, at the same time, acts as a pico-Newton force transducer, after calibration through its displacement from the equilibrium position. The other optical tweezers trap the RBC at the other end. To measure the membrane viscosity the optical force is measured as a function of the velocity between the RBCs. To measure the adhesion the tweezers are slowly displaced apart until the RBCs disagglutination happens. The RBC zeta potential is measured in two complimentary ways, by the force on the silica bead attached to a single RBC in response to an applied electric field, and the conventional way, by the measurement of terminal velocity of the RBC after released from the optical trap. These two measurements provide information about the RBC charges and, also, electrolytic solution properties. We believe this can improve the methods of diagnosis in blood banks.

  13. Optical tweezers and surface plasmon resonance combination system based on the high numerical aperture lens

    NASA Astrophysics Data System (ADS)

    Shan, Xuchen; Zhang, Bei; Lan, Guoqiang; Wang, Yiqiao; Liu, Shugang

    2015-11-01

    Biology and medicine sample measurement takes an important role in the microscopic optical technology. Optical tweezer has the advantage of accurate capture and non-pollution of the sample. The SPR(surface plasmon resonance) sensor has so many advantages include high sensitivity, fast measurement, less consumption of sample and label-free detection of biological sample that the SPR sensing technique has been used for surface topography, analysis of biochemical and immune, drug screening and environmental monitoring. If they combine, they will play an important role in the biological, chemical and other subjects. The system we propose use the multi-axis cage system, by using the methods of reflection and transmiss ion to improve the space utilization. The SPR system and optical tweezer were builtup and combined in one system. The cage of multi-axis system gives full play to its accuracy, simplicity and flexibility. The size of the system is 20 * 15 * 40 cm3 and thus the sample can be replaced to switch between the optical tweezers system and the SPR system in the small space. It means that we get the refractive index of the sample and control the particle in the same system. In order to control the revolving stage, get the picture and achieve the data stored automatically, we write a LabVIEW procedure. Then according to the data from the back focal plane calculate the refractive index of the sample. By changing the slide we can trap the particle as optical tweezer, which makes us measurement and trap the sample at the same time.

  14. Light-induced rotations of chiral birefringent microparticles in optical tweezers

    PubMed Central

    Donato, M. G.; Mazzulla, A.; Pagliusi, P.; Magazzù, A.; Hernandez, R. J.; Provenzano, C.; Gucciardi, P. G.; Maragò, O. M.; Cipparrone, G.

    2016-01-01

    We study the rotational dynamics of solid chiral and birefringent microparticles induced by elliptically polarized laser light in optical tweezers. We find that both reflection of left circularly polarized light and residual linear retardance affect the particle dynamics. The degree of ellipticity of laser light needed to induce rotations is found. The experimental results are compared with analytical calculations of the transfer of angular moment from elliptically polarized light to chiral birefringent particles. PMID:27601200

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

    SciTech Connect

    Li, Ying Lee, Changyang; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk

    2014-10-27

    Tools that are capable of manipulating micro-sized objects have been widely used in such fields as physics, chemistry, biology, and medicine. Several devices, including optical tweezers, atomic force microscope, micro-pipette aspirator, and standing surface wave type acoustic tweezers have been studied to satisfy this need. However, none of them has been demonstrated to be suitable for in vivo and clinical studies. Single beam acoustic tweezers (SBAT) is a technology that uses highly focused acoustic beam to trap particles toward the beam focus. Its feasibility was first theoretically and experimentally demonstrated by Lee and Shung several years ago. Since then, much effort has been devoted to improving this technology. At present, the tool is capable of trapping a microparticle as small as 1 μm, as well as a single red blood cell. Although in comparing to other microparticles manipulating technologies, SBAT has advantages of providing stronger trapping force and deeper penetration depth in tissues, and producing less tissue damage, its potential for in vivo applications has yet been explored. It is worth noting that ultrasound has been used as a diagnostic tool for over 50 years and no known major adverse effects have been observed at the diagnostic energy level. This paper reports the results of an initial attempt to assess the feasibility of single beam acoustic tweezers to trap microparticles in vivo inside of a blood vessel. The acoustic intensity of SBAT under the trapping conditions that were utilized was measured. The mechanical index and thermal index at the focus of acoustic beam were found to be 0.48 and 0.044, respectively, which meet the standard of commercial diagnostic ultrasound system.

  16. Amyloid β-Protein Assembly: The Effect of Molecular Tweezers CLR01 and CLR03

    PubMed Central

    2015-01-01

    The early oligomerization of amyloid β-protein (Aβ) has been shown to be an important event in the pathology of Alzheimer’s disease (AD). Designing small molecule inhibitors targeting Aβ 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 Aβ self-assembly. CLR01 was found to bind to Aβ directly and disrupt its early oligomerization. Moreover, CLR01 remodeled the early oligomerization of Aβ42 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 Aβ oligomerization. Our study provides an example of IMS as a powerful tool to study and better understand the interaction between small molecule modulators and Aβ oligomerization, which is not attainable by other methods, and provides important insights into therapeutic development of molecular tweezers for AD treatment. PMID:25751170

  17. Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

    PubMed

    Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

    2016-09-05

    Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

  18. Stable optical trapping and sensitive characterization of nanostructures using standing-wave Raman tweezers

    NASA Astrophysics Data System (ADS)

    Wu, Mu-Ying; Ling, Dong-Xiong; Ling, Lin; Li, William; Li, Yong-Qing

    2017-02-01

    Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints.

  19. Stable optical trapping and sensitive characterization of nanostructures using standing-wave Raman tweezers

    PubMed Central

    Wu, Mu-ying; Ling, Dong-xiong; Ling, Lin; Li, William; Li, Yong-qing

    2017-01-01

    Optical manipulation and label-free characterization of nanoscale structures open up new possibilities for assembly and control of nanodevices and biomolecules. Optical tweezers integrated with Raman spectroscopy allows analyzing a single trapped particle, but is generally less effective for individual nanoparticles. The main challenge is the weak gradient force on nanoparticles that is insufficient to overcome the destabilizing effect of scattering force and Brownian motion. Here, we present standing-wave Raman tweezers for stable trapping and sensitive characterization of single isolated nanostructures with a low laser power by combining a standing-wave optical trap with confocal Raman spectroscopy. This scheme has stronger intensity gradients and balanced scattering forces, and thus can be used to analyze many nanoparticles that cannot be measured with single-beam Raman tweezers, including individual single-walled carbon nanotubes (SWCNT), graphene flakes, biological particles, SERS-active metal nanoparticles, and high-refractive semiconductor nanoparticles. This would enable sorting and characterization of specific SWCNTs and other nanoparticles based on their increased Raman fingerprints. PMID:28211526

  20. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    SciTech Connect

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-15

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  1. Quantitation of malaria parasite-erythrocyte cell-cell interactions using optical tweezers.

    PubMed

    Crick, Alex J; Theron, Michel; Tiffert, Teresa; Lew, Virgilio L; Cicuta, Pietro; Rayner, Julian C

    2014-08-19

    Erythrocyte invasion by Plasmodium falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria. Invasion has been studied intensively, but our cellular understanding has been limited by the fact that it occurs very rapidly: invasion is generally complete within 1 min, and shortly thereafter the merozoites, at least in in vitro culture, lose their invasive capacity. The rapid nature of the process, and hence the narrow time window in which measurements can be taken, have limited the tools available to quantitate invasion. Here we employ optical tweezers to study individual invasion events for what we believe is the first time, showing that newly released P. falciparum merozoites, delivered via optical tweezers to a target erythrocyte, retain their ability to invade. Even spent merozoites, which had lost the ability to invade, retain the ability to adhere to erythrocytes, and furthermore can still induce transient local membrane deformations in the erythrocyte membrane. We use this technology to measure the strength of the adhesive force between merozoites and erythrocytes, and to probe the cellular mode of action of known invasion inhibitory treatments. These data add to our understanding of the erythrocyte-merozoite interactions that occur during invasion, and demonstrate the power of optical tweezers technologies in unraveling the blood-stage biology of malaria.

  2. Scanning a DNA Molecule for Bound Proteins Using Hybrid Magnetic and Optical Tweezers

    PubMed Central

    van Loenhout, Marijn T. J.; De Vlaminck, Iwijn; Flebus, Benedetta; den Blanken, Johan F.; Zweifel, Ludovit P.; Hooning, Koen M.; Kerssemakers, Jacob W. J.; Dekker, Cees

    2013-01-01

    The functional state of the genome is determined by its interactions with proteins that bind, modify, and move along the DNA. To determine the positions and binding strength of proteins localized on DNA we have developed a combined magnetic and optical tweezers apparatus that allows for both sensitive and label-free detection. A DNA loop, that acts as a scanning probe, is created by looping an optically trapped DNA tether around a DNA molecule that is held with magnetic tweezers. Upon scanning the loop along the λ-DNA molecule, EcoRI proteins were detected with ∼17 nm spatial resolution. An offset of 33±5 nm for the detected protein positions was found between back and forwards scans, corresponding to the size of the DNA loop and in agreement with theoretical estimates. At higher applied stretching forces, the scanning loop was able to remove bound proteins from the DNA, showing that the method is in principle also capable of measuring the binding strength of proteins to DNA with a force resolution of 0.1 pN/. The use of magnetic tweezers in this assay allows the facile preparation of many single-molecule tethers, which can be scanned one after the other, while it also allows for direct control of the supercoiling state of the DNA molecule, making it uniquely suitable to address the effects of torque on protein-DNA interactions. PMID:23755219

  3. Design and optimization of arrays of neodymium iron boron-based magnets for magnetic tweezers applications

    NASA Astrophysics Data System (ADS)

    Zacchia, Nicholas A.; Valentine, Megan T.

    2015-05-01

    We present the design methodology for arrays of neodymium iron boron (NdFeB)-based magnets for use in magnetic tweezers devices. Using finite element analysis (FEA), we optimized the geometry of the NdFeB magnet as well as the geometry of iron yokes designed to focus the magnetic fields toward the sample plane. Together, the magnets and yokes form a magnetic array which is the basis of the magnetic tweezers device. By systematically varying 15 distinct shape parameters, we determined those features that maximize the magnitude of the magnetic field gradient as well as the length scale over which the magnetic force operates. Additionally, we demonstrated that magnetic saturation of the yoke material leads to intrinsic limitations in any geometric design. Using this approach, we generated a compact and light-weight magnetic tweezers device that produces a high field gradient at the image plane in order to apply large forces to magnetic beads. We then fabricated the optimized yoke and validated the FEA by experimentally mapping the magnetic field of the device. The optimization data and iterative FEA approach outlined here will enable the streamlined design and construction of specialized instrumentation for force-sensitive microscopy.

  4. 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.

  5. Acoustic tweezers via sub–time-of-flight regime surface acoustic waves

    PubMed Central

    Collins, David J.; Devendran, Citsabehsan; Ma, Zhichao; Ng, Jia Wei; Neild, Adrian; Ai, Ye

    2016-01-01

    Micrometer-scale acoustic waves are highly useful for refined optomechanical and acoustofluidic manipulation, where these fields are spatially localized along the transducer aperture but not along the acoustic propagation direction. In the case of acoustic tweezers, such a conventional acoustic standing wave results in particle and cell patterning across the entire width of a microfluidic channel, preventing selective trapping. We demonstrate the use of nanosecond-scale pulsed surface acoustic waves (SAWs) with a pulse period that is less than the time of flight between opposing transducers to generate localized time-averaged patterning regions while using conventional electrode structures. These nodal positions can be readily and arbitrarily positioned in two dimensions and within the patterning region itself through the imposition of pulse delays, frequency modulation, and phase shifts. This straightforward concept adds new spatial dimensions to which acoustic fields can be localized in SAW applications in a manner analogous to optical tweezers, including spatially selective acoustic tweezers and optical waveguides. PMID:27453940

  6. Mechanics of the human red blood cell deformed by optical tweezers*1

    NASA Astrophysics Data System (ADS)

    Dao, M.; Lim, C. T.; Suresh, S.

    2003-11-01

    The mechanical deformation characteristics of living cells are known to influence strongly their chemical and biological functions and the onset, progression and consequences of a number of human diseases. The mechanics of the human red blood cell (erythrocyte) subjected to large deformation by optical tweezers forms the subject of this paper. Video photography of the cell deformed in a phosphate buffered saline solution at room temperature during the imposition of controlled stretching forces, in the tens to several hundreds picoNewton range, is used to assess experimentally the deformation characteristics. The mechanical responses of the cell during loading and upon release of the optical force are then analysed to extract the elastic properties of the cell membrane by recourse to several different constitutive formulations of the elastic and viscoelastic behavior within the framework of a fully three-dimensional finite element analysis. A parametric study of various geometric, loading and structural factors is also undertaken in order to develop quantitative models for the mechanics of deformation by means of optical tweezers. The outcome of the experimental and computational analyses is then compared with the information available on the mechanical response of the red blood cell from other independent experimental techniques. Potential applications of the optical tweezers method described in this paper to the study of mechanical deformation of living cells under different stress states and in response to the progression of some diseases are also highlighted.

  7. Measurement of macrophage adhesion using optical tweezers with backward-scattered detection

    NASA Astrophysics Data System (ADS)

    Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

    2010-08-01

    Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 μm diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

  8. New biodiagnostics based on optical tweezers: typing red blood cells, and identification of drug resistant bacteria

    NASA Astrophysics Data System (ADS)

    Chen, Jia-Wen; Lin, Chuen-Fu; Wang, Shyang-Guang; Lee, Yi-Chieh; Chiang, Chung-Han; Huang, Min-Hui; Lee, Yi-Hsiung; Vitrant, Guy; Pan, Ming-Jeng; Lee, Horng-Mo; Liu, Yi-Jui; Baldeck, Patrice L.; Lin, Chih-Lang

    2013-09-01

    Measurements of optical tweezers forces on biological micro-objects can be used to develop innovative biodiagnostics methods. In the first part of this report, we present a new sensitive method to determine A, B, D types of red blood cells. Target antibodies are coated on glass surfaces. Optical forces needed to pull away RBC from the glass surface increase when RBC antigens interact with their corresponding antibodies. In this work, measurements of stripping optical forces are used to distinguish the major RBC types: group O Rh(+), group A Rh(+) and group B Rh(+). The sensitivity of the method is found to be at least 16-folds higher than the conventional agglutination method. In the second part of this report, we present an original way to measure in real time the wall thickness of bacteria that is one of the most important diagnostic parameters of bacteria drug resistance in hospital diagnostics. The optical tweezers force on a shell bacterium is proportional to its wall thickness. Experimentally, we determine the optical tweezers force applied on each bacteria family by measuring their escape velocity. Then, the wall thickness of shell bacteria can be obtained after calibrating with known bacteria parameters. The method has been successfully applied to indentify, from blind tests, Methicillinresistant Staphylococcus aureus (MRSA), including VSSA (NCTC 10442), VISA (Mu 50), and heto-VISA (Mu 3)

  9. Acoustic tweezers for studying intracellular calcium signaling in SKBR-3 human breast cancer cells.

    PubMed

    Hwang, Jae Youn; Yoon, Chi Woo; Lim, Hae Gyun; Park, Jin Man; Yoon, Sangpil; Lee, Jungwoo; Shung, K Kirk

    2015-12-01

    Extracellular matrix proteins such as fibronectin (FNT) play crucial roles in cell proliferation, adhesion, and migration. For better understanding of these associated cellular activities, various microscopic manipulation tools have been used to study their intracellular signaling pathways. Recently, it has appeared that acoustic tweezers may possess similar capabilities in the study. Therefore, we here demonstrate that our newly developed acoustic tweezers with a high-frequency lithium niobate ultrasonic transducer have potentials to study intracellular calcium signaling by FNT-binding to human breast cancer cells (SKBR-3). It is found that intracellular calcium elevations in SKBR-3 cells, initially occurring on the microbead-contacted spot and then eventually spreading over the entire cell, are elicited by attaching an acoustically trapped FNT-coated microbead. Interestingly, they are suppressed by either extracellular calcium elimination or phospholipase C (PLC) inhibition. Hence, this suggests that our acoustic tweezers may serve as an alternative tool in the study of intracellular signaling by FNT-binding activities.

  10. Determining the structure-mechanics relationships of dense microtubule networks with confocal microscopy and magnetic tweezers-based microrheology.

    PubMed

    Yang, Yali; Valentine, Megan T

    2013-01-01

    The microtubule (MT) cytoskeleton is essential in maintaining the shape, strength, and organization of cells. Its spatiotemporal organization is fundamental for numerous dynamic biological processes, and mechanical stress within the MT cytoskeleton provides an important signaling mechanism in mitosis and neural development. This raises important questions about the relationships between structure and mechanics in complex MT structures. In vitro, reconstituted cytoskeletal networks provide a minimal model of cell mechanics while also providing a testing ground for the fundamental polymer physics of stiff polymer gels. Here, we describe our development and implementation of a broad tool kit to study structure-mechanics relationships in reconstituted MT networks, including protocols for the assembly of entangled and cross-linked MT networks, fluorescence imaging, microstructure characterization, construction and calibration of magnetic tweezers devices, and mechanical data collection and analysis. In particular, we present the design and assembly of three neodymium iron boron (NdFeB)-based magnetic tweezers devices optimized for use with MT networks: (1) high-force magnetic tweezers devices that enable the application of nano-Newton forces and possible meso- to macroscale materials characterization; (2) ring-shaped NdFeB-based magnetic tweezers devices that enable oscillatory microrheology measurements; and (3) portable magnetic tweezers devices that enable direct visualization of microscale deformation in soft materials under applied force.

  11. Three-dimensional image and spatial spectrum analysis of behavior of small animal erythrocytes in optical tweezers

    NASA Astrophysics Data System (ADS)

    Chen, Hui Chi; Shen, Wen-Tai; Kong, Yu-Han; Chuang, Chun-Hao

    2008-02-01

    Because of the softness of membrane, erythrocytes (red blood cell, RBC) have different shapes while being immersed in buffer with different osmotic pressure. While affecting by different viruses and illnesses, RBC may change its shape, or its membrane may become rigid. Moreover, RBC will ford and stretch when it is trapped by optical tweezers. Therefore, the behaviors of RBC in optical tweezers raise more discussion. In this report, we set up an optical tweezers to trap RBC of small animals like feline and canine. By adding a long working distance objective to collect the side-viewing image, a 3-D image system was constructed to detect the motion of trapped RBC. To improve the image quality for side-view, an aperture and narrow glass plate were used. From the video of these images and their spatial spectrum, the shape of trapped RBC was studied.

  12. The design and biological applications of dual-beam oscillating optical tweezer-based imaging cytorheometer

    NASA Astrophysics Data System (ADS)

    Ou-Yang, H. D.; Wang, J.

    2006-08-01

    Because of its non-invasive nature, optical tweezers have emerged as a popular tool for the studies of complex fluids and biological cells and tissues. The capabilities of optical tweezer-based experimental instruments continue to evolve for better and broader applications, through new apparatus designs and integrations with microscopic imaging techniques. In this paper, we present the design, calibration and applications of a powerful microrheometer that integrates a novel high temporal and spatial resolution dual-beam oscillating optical tweezer-based cytorheometer (DOOTC) with spinning disk confocal microscopy. The oscillating scheme detects the position of micron-size probe particles via a phase-sensitive lock-in amplifier to greatly enhance sensitivity. The dual-beam scheme ensures that the cytorheometer is insensitive to sample specimen background parameter variances, and thus enables the investigation of micromechanical properties of biological samples, which are intrinsically inhomogeneous. The cytorheometer system is demonstrated to be capable of measuring dynamic local mechanical moduli in the frequency range of 0.1-150 Hz at up to 2 data point per second and with nanometer spatial resolutions, while visualizing and monitoring structural properties in situ. We report the results of system applications in the studies of bovine skin gelatin gel, purified microtubule assemblies, and human alveolar epithelial cells. The time evolution of the storage moduli G' and the loss moduli G'' of the gel is recorded for undisturbed gel-forming process with high temporal resolution. The micromechanical modulus G* of polymerized microtubule network as a function of frequency are shown to be both inhomogeneous and anisotropic consistent with local structures revealed by confocal imaging. The mechanical properties of A549 human lung cells as a function of temperature will be reported showing significant decrease in cell stiffness at higher temperature.

  13. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads

    SciTech Connect

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-15

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm{sup 2}, a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle’s position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  14. Optical macro-tweezers: trapping of highly motile micro-organisms

    NASA Astrophysics Data System (ADS)

    Thalhammer, G.; Steiger, R.; Bernet, S.; Ritsch-Marte, M.

    2011-04-01

    Optical micromanipulation stands for contact-free handling of microscopic particles by light. Optical forces can manipulate non-absorbing objects in a large range of sizes, e.g., from biological cells down to cold atoms. Recently much progress has been made going from the micro- down to the nanoscale. Less attention has been paid to going the other way, trapping increasingly large particles. Optical tweezers typically employ a single laser beam tightly focused by a microscope objective of high numerical aperture to stably trap a particle in three dimensions (3D). As the particle size increases, stable 3D trapping in a single-beam trap requires scaling up the optical power, which eventually induces adverse biological effects. Moreover, the restricted field of view of standard optical tweezers, dictated by the use of high NA objectives, is particularly unfavorable for catching actively moving specimens. Both problems can be overcome by traps with counter-propagating beams. Our 'macro-tweezers' are especially designed to trap highly motile organisms, as they enable three-dimensional all-optical trapping and guiding in a volume of 2 × 1 × 2 mm3. Here we report for the first time the optical trapping of large actively swimming organisms, such as for instance Euglena protists and dinoflagellates of up to 70 µm length. Adverse bio-effects are kept low since trapping occurs outside high intensity regions, e.g., focal spots. We expect our approach to open various possibilities in the contact-free handling of 50-100 µm sized objects that could hitherto not be envisaged, for instance all-optical holding of individual micro-organisms for taxonomic identification, selective collecting or tagging.

  15. Magnetic tweezers with high permeability electromagnets for fast actuation of magnetic beads.

    PubMed

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-04-01

    As a powerful and versatile scientific instrument, magnetic tweezers have been widely used in biophysical research areas, such as mechanical cell properties and single molecule manipulation. If one wants to steer bead position, the nonlinearity of magnetic properties and the strong position dependence of the magnetic field in most magnetic tweezers lead to quite a challenge in their control. In this article, we report multi-pole electromagnetic tweezers with high permeability cores yielding high force output, good maneuverability, and flexible design. For modeling, we adopted a piece-wise linear dependence of magnetization on field to characterize the magnetic beads. We implemented a bi-linear interpolation of magnetic field in the work space, based on a lookup table obtained from finite element simulation. The electronics and software were custom-made to achieve high performance. In addition, the effects of dimension and defect on structure of magnetic tips also were inspected. In a workspace with size of 0.1 × 0.1 mm(2), a force of up to 400 pN can be applied on a 2.8 μm superparamagnetic bead in any direction within the plane. Because the magnetic particle is always pulled towards a tip, the pulling forces from the pole tips have to be well balanced in order to achieve control of the particle's position. Active video tracking based feedback control is implemented, which is able to work at a speed of up to 1 kHz, yielding good maneuverability of the magnetic beads.

  16. 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.

  17. Raman tweezers spectroscopy study of free radical induced oxidative stress leading to eryptosis

    NASA Astrophysics Data System (ADS)

    Barkur, Surekha; Bankapur, Aseefhali; Chidangil, Santhosh

    2016-11-01

    Raman tweezers spectroscopy study of effect of free radicals was carried out on erythrocytes. We prepared hydroxyl radicals using Fenton reaction (which yields hydroxyl radicals). Raman spectra were acquired from single, trapped erythrocytes after supplementing with these free radicals. The changes in the Raman bands such as 1211 cm-1, 1224 cm-1, 1375 cm-1 indicate deoxygenation of red blood cells (RBCs). Our study shows that free radicals can induce oxidative stress on erythrocytes. The changes in the Raman spectra as well as shape of erythrocytes indicate that oxidative stress can trigger eryptosis in erythrocytes.

  18. Temporal response of three-dimensional biological cells to high-frequency optical jumping tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Lingyao; Sheng, Yunlong

    2015-01-01

    We analyzed the temporal responses of biological cells in the jumping optical tweezers for tugging, wiggling, and stretching the cells in the time-sharing regime with the finite-element method. We showed that the jumping of local stress and local strain is independently omnipresent on the recovery time of the viscoelastic material and the jumping frequency of the load. We demonstrated that the elongation of a three-dimensional (3-D) viscoelastic object under a jumping load cannot be evaluated using the one-dimensional spring-dashpot material model without considering its 3-D structure.

  19. Temporal response of biological cells to high-frequency optical jumping and vibrating tweezers

    NASA Astrophysics Data System (ADS)

    Yu, Lingyao; Sheng, Yunlong

    2014-09-01

    We analyzed the temporal responses of biological cells in the jumping and vibrating optical tweezers for tugging, wiggling and stretching the cells with the finite element method. Some new concepts were established, which might be investigated in the future experiments, such as the jumping of local stress and local strain, independently on the recovery time of the viscoelastic material and on the jumping frequency, the energy dissipation in the hysteresis cycles, the cytoplasm fluid field and its interaction with the cell membrane. The cell was modeled with full 3D structure and viscoelastic continuum materials.

  20. Simultaneous Single-Molecule Force and Fluorescence Sampling of DNA Nanostructure Conformations Using Magnetic Tweezers.

    PubMed

    Kemmerich, Felix E; Swoboda, Marko; Kauert, Dominik J; Grieb, M Svea; Hahn, Steffen; Schwarz, Friedrich W; Seidel, Ralf; Schlierf, Michael

    2016-01-13

    We present a hybrid single-molecule technique combining magnetic tweezers and Förster resonance energy transfer (FRET) measurements. Through applying external forces to a paramagnetic sphere, we induce conformational changes in DNA nanostructures, which are detected in two output channels simultaneously. First, by tracking a magnetic bead with high spatial and temporal resolution, we observe overall DNA length changes along the force axis. Second, the measured FRET efficiency between two fluorescent probes monitors local conformational changes. The synchronized orthogonal readout in different observation channels will facilitate deciphering the complex mechanisms of biomolecular machines.

  1. Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions.

    PubMed

    Lee, Kisung; Kinnunen, Matti; Khokhlova, Maria D; Lyubin, Evgeny V; Priezzhev, Alexander V; Meglinski, Igor; Fedyanin, Andrey A

    2016-03-01

    Kinetics of optical tweezers (OT)-induced spontaneous aggregation and disaggregation of red blood cells (RBCs) were studied at the level of cell doublets to assess RBC interaction mechanics. Measurements were performed under in vitro conditions in plasma and fibrinogen and fibrinogen + albumin solutions. The RBC spontaneous aggregation kinetics was found to exhibit different behavior depending on the cell environment. In contrast, the RBC disaggregation kinetics was similar in all solutions qualitatively and quantitatively, demonstrating a significant contribution of the studied proteins to the process. The impact of the study on assessing RBC interaction mechanics and the protein contribution to the reversible RBC aggregation process is discussed.

  2. Optical tweezers study of red blood cell aggregation and disaggregation in plasma and protein solutions

    NASA Astrophysics Data System (ADS)

    Lee, Kisung; Kinnunen, Matti; Khokhlova, Maria D.; Lyubin, Evgeny V.; Priezzhev, Alexander V.; Meglinski, Igor; Fedyanin, Andrey A.

    2016-03-01

    Kinetics of optical tweezers (OT)-induced spontaneous aggregation and disaggregation of red blood cells (RBCs) were studied at the level of cell doublets to assess RBC interaction mechanics. Measurements were performed under in vitro conditions in plasma and fibrinogen and fibrinogen + albumin solutions. The RBC spontaneous aggregation kinetics was found to exhibit different behavior depending on the cell environment. In contrast, the RBC disaggregation kinetics was similar in all solutions qualitatively and quantitatively, demonstrating a significant contribution of the studied proteins to the process. The impact of the study on assessing RBC interaction mechanics and the protein contribution to the reversible RBC aggregation process is discussed.

  3. The Cryptococcus neoformans capsule: lessons from the use of optical tweezers and other biophysical tools

    PubMed Central

    Pontes, Bruno; Frases, Susana

    2015-01-01

    The fungal pathogen Cryptococcus neoformans causes life-threatening infections in immunocompromised individuals, representing one of the leading causes of morbidity and mortality in AIDS patients. The main virulence factor of C. neoformans is the polysaccharide capsule; however, many fundamental aspects of capsule structure and function remain poorly understood. Recently, important capsule properties were uncovered using optical tweezers and other biophysical techniques, including dynamic and static light scattering, zeta potential and viscosity analysis. This review provides an overview of the latest findings in this emerging field, explaining the impact of these findings on our understanding of C. neoformans biology and resistance to host immune defenses. PMID:26157436

  4. A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

    PubMed Central

    2016-01-01

    Summary This review summarizes part of the author’s research in the area of supramolecular chemistry, beginning with his early life influences and early career efforts in molecular recognition, especially molecular tweezers. Although designed to complex DNA, these hosts proved more applicable to the field of host–guest chemistry. This early experience and interest in intercalation ultimately led to the current efforts to develop small molecule therapeutic agents for myotonic dystrophy using a rational design approach that heavily relies on principles of supramolecular chemistry. How this work was influenced by that of others in the field and the evolution of each area of research is highlighted with selected examples. PMID:26877815

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

    SciTech Connect

    Chen Shuxun; Wang Xiaolin; Sun Dong; Cheng Jinping; Han Cheng, Shuk; Kong, Chi-Wing; Li, Ronald A.

    2013-07-15

    We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

  6. 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

  7. Effect of Surface Layer on Electromechanical Stability of Tweezers and Cantilevers Fabricated from Conductive Cylindrical Nanowires

    NASA Astrophysics Data System (ADS)

    Keivani, Maryam; Koochi, Ali; Sedighi, Hamid M.; Abadyan, Mohamadreza; Farrokhabadi, Amin; Shahedin, Abed Moheb

    2016-12-01

    Herein, the impact of surface layer on the stability of nanoscale tweezers and cantilevers fabricated from nanowires with cylindrical cross section is studied. A modified continuum based on the Gurtin-Murdoch surface elasticity is applied for incorporating the presence of surface layer. Considering the cylindrical geometry of the nanowire, the presence of the Coulomb attraction and dispersion forces are incorporated in the derived formulations. Three different approaches, i.e. numerical differential quadrature method (DQM), an approximated homotopy perturbation method (HPM) and developing lumped parameter model (LPM) have been employed to solve the governing equations. The impact of surface layer on the instability of the system is demonstrated.

  8. Measuring stall forces in vivo with optical tweezers through light momentum changes

    NASA Astrophysics Data System (ADS)

    Mas, J.; Farré, A.; López-Quesada, C.; Fernández, X.; Martín-Badosa, E.; Montes-Usategui, M.

    2011-10-01

    The stall forces of processive molecular motors have been widely studied previously in vitro. Even so, in vivo experiments are required for determining the actual performance of each molecular motor in its natural environment. We report the direct measurement of light momentum changes in single beam optical tweezers as a suitable technique for measuring forces inside living cells, where few alternatives exist. The simplicity of this method, which does not require force calibration for each trapped object, makes it convenient for measuring the forces involved in fast dynamic biological processes such us intracellular traffic. Here we present some measurements of the stall force of processive molecular motors inside living Allium cepa cells.

  9. Quantitative characterization for dielectrophoretic behavior of biological cells using optical tweezers

    NASA Astrophysics Data System (ADS)

    Park, In Soo; Hee Park, Se; Woo Lee, Sang; Sung Yoon, Dae; Kim, Beop-Min

    2014-02-01

    We report a method to precisely quantify dielectrophoretic (DEP) forces and cutoff frequencies (fc) of viable and nonviable yeast cells. The method consists of a two-step process in which generated DEP forces act upon a cell through a micro-electrode device, followed by direct measurement of DEP forces using optical tweezers. DEP behaviors of viable and nonviable yeast cells are monitored as a function of AC frequency. We believe that the proposed method can be used as a powerful platform for cell-based assays to characterize the DEP behavior of various cell types including cancer and normal cells.

  10. Polymeric optical fiber tweezers as a tool for single cell micro manipulation and sensing

    NASA Astrophysics Data System (ADS)

    Rodrigues Ribeiro, R. S.; Soppera, O.; Guerreiro, A.; Jorge, P. A...

    2015-09-01

    In this paper a new type of polymeric fiber optic tweezers for single cell manipulation is reported. The optical trapping of a yeast cell using a polymeric micro lens fabricated by guided photo polymerization at the fiber tip is demonstrated. The 2D trapping of the yeast cells is analyzed and maximum optical forces on the pN range are calculated. The experimental results are supported by computational simulations using a FDTD method. Moreover, new insights on the potential for simultaneous sensing and optical trapping, are presented.

  11. 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.

  12. Applications of Optical Tweezers and an Integrated Force Measurement Module for Biomedical Research

    DTIC Science & Technology

    2000-07-01

    away from the bead trapped in the tweezers by moving the DC motor -driven microscope stage rightward. The bead (A) and its diffraction pattern (B...the cell by moving the DC motor -driven stage rightward at a constant velocity of -I micron/sec. There was a membrane tether (not shown at this focal...motion driven by the DC - motor . Using fluid flow assay, we estimated that the maximal force our experimental configuration could exert was -12pN on a

  13. Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation.

    PubMed

    Jordan, Pamela; Cooper, Jon; McNay, Graeme; Docherty, Frances; Graham, Duncan; Smith, W; Sinclair, Gavin; Padgett, Miles

    2005-05-30

    Silica particles were partially coated with silver, and a suitable chromophore, such that they could be simultaneously trapped within an optical tweezers system, and emit a surface-enhanced resonance Raman scattering (SERRS) response. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The con fi guration has clear applications in providing apparatus that can simultaneously manipulate a particle whilst obtaining surface sensitive sensory information.

  14. Host-guest interaction of ZnBDC-MOF + doxorubicin: A theoretical and experimental study

    NASA Astrophysics Data System (ADS)

    Vasconcelos, Iane B.; Wanderley, Kaline A.; Rodrigues, Nailton M.; da Costa, Nivan B.; Freire, Ricardo O.; Junior, Severino A.

    2017-03-01

    The incorporation of drugs in biodegradable polymeric particles is one of many processes that controllably and significantly increase their release and action. In this paper, we describe the synthesis and physicochemical characterization of ZnBDC-MOF + doxorubicin (DOXO@ZnBDC) and the system's effectiveness in the sustained release of the drug doxorubicin. An experimental and theoretical study is presented of the interaction between the [Zn(BDC)(H2O)2]n MOF and the drug doxorubicin (DOXO). The synthesis was characterized by elemental analysis and X-ray powder diffraction (XRPD). The experimental incorporation was accomplished and analyzed by Fourier transform infrared spectroscopy (FTIR), XRPD and UV-Vis (ultraviolet-visible) spectrophotometry. Based on an analysis of the doxorubicin release profile, our results suggest that the drug delivery system showed slower release than other systems under development. Studies of cytotoxicity by the MTT method showed good results for the system developed with antineoplastic doxorubicin, and together with the other results of this study, suggest the successful development of a MOF-based drug delivery system.

  15. Design and comparison of exchange spectroscopy approaches to cryptophane-xenon host-guest kinetics.

    PubMed

    Korchak, Sergey; Kilian, Wolfgang; Schröder, Leif; Mitschang, Lorenz

    2016-04-01

    Exchange spectroscopy is used in combination with a variation of xenon concentration to disentangle the kinetics of the reversible binding of xenon to cryptophane-A. The signal intensity of either free or crytophane-bound xenon decays in a manner characteristic of the underlying exchange reactions when the spins in the other pool are perturbed. Three experimental approaches, including the well-known Hyper-CEST method, are shown to effectively entail a simple linear dependence of the signal depletion rate, or of a related quantity, on free xenon concentration. This occurs when using spin pool saturation or inversion followed by free exchange. The identification and quantification of contributions to the binding kinetics is then straightforward: in the depletion rate plot, the intercept at the vanishing free xenon concentration represents the kinetic rate coefficient for xenon detachment from the host by dissociative processes while the slope is indicative of the kinetic rate coefficient for degenerate exchange reactions. Comparing quantified kinetic rates for hyperpolarized xenon in aqueous solution reveals the high accuracy of each approach but also shows differences in the precision of the numerical results and in the requirements for prior knowledge. Because of their broad range of applicability the proposed exchange spectroscopy experiments can be readily used to unravel the kinetics of complex formation of xenon with host molecules in the various situations appearing in practice.

  16. Supramolecular chiral host-guest nanoarchitecture induced by the selective assembly of barbituric acid derivative enantiomers

    NASA Astrophysics Data System (ADS)

    Sun, Xiaonan; Silly, Fabien; Maurel, Francois; Dong, Changzhi

    2016-10-01

    Barbituric acid derivatives are prochiral molecules, i.e. they are chiral upon adsorption on surfaces. Scanning tunneling microscopy reveals that barbituric acid derivatives self-assemble into a chiral guest-host supramolecular architecture at the solid-liquid interface on graphite. The host nanoarchitecture has a sophisticated wavy shape pattern and paired guest molecules are nested insides the cavities of the host structure. Each unit cell of the host structure is composed of both enantiomers with a ratio of 1:1. Furthermore, the wavy patterns of the nanoarchitecture are formed from alternative appearance of left- and right-handed chiral building blocks, which makes the network heterochiral. The functional guest-host nanoarchitecture is the result of two-dimensional chiral amplification from single enantiomers to organizational heterochiral supramolecular self-assembly.

  17. Origin of White Electroluminescence in Graphene Quantum Dots Embedded Host/Guest Polymer Light Emitting Diodes

    PubMed Central

    Kyu Kim, Jung; Bae, Sukang; Yi, Yeonjin; Jin Park, Myung; Jin Kim, Sang; Myoung, NoSoung; Lee, Chang-Lyoul; Hee Hong, Byung; Hyeok Park, Jong

    2015-01-01

    Polymer light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nano-material without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. PMID:26067060

  18. 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.

  19. 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

  20. Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability

    NASA Astrophysics Data System (ADS)

    Zhou, Shu-Ya; Ma, Shui-Xian; Cheng, Hui-Lin; Yang, Li-Juan; Chen, Wen; Yin, Yan-Qing; Shi, Yi-Min; Yang, Xiao-Dong

    2014-01-01

    The inclusion complexation behavior, characterization and binding ability of pinocembrin with β-cyclodextrin (β-CD) and its derivative 2-hydroxypropyl-β-cyclodextrin (HPβCD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

  1. Host-Guest Interaction between Herbicide Oxadiargyl and Hydroxypropyl-β-Cyclodextrin

    PubMed Central

    Benfeito, Sofia; Borges, Fernanda; Garrido, E. Manuela

    2013-01-01

    In the face of a growing human population and increased urbanization, the demand for pesticides will simply rise. Farmers must escalate yields on increasingly fewer farm acres. However, the risks of pesticides, whether real or perceived, may force changes in the way these chemicals are used. Scientists are working toward pest control plans that are environmentally sound, effective, and profitable. In this context the development of new pesticide formulations which may improve application effectiveness, safety, handling, and storage can be pointed out as a solution. As a contribution to the area, the microencapsulation of the herbicide oxadiargyl (OXA) in (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was performed. The study was conducted in different aqueous media (ultrapure water and in different pH buffer solutions). In all cases an increment of the oxadiargyl solubility as a function of the HP-β-CD concentration that has been related to the formation of an inclusion complex was verified. UV-Vis and NMR experiments allowed concluding that the stoichiometry of the OXA/HP-β-CD complex formed is 1 : 1. The gathered results can be regarded as an important step for its removal from industrial effluents and/or to increase the stabilizing action, encapsulation, and adsorption in water treatment plants. PMID:24396310

  2. Characterization of folic acid/native cyclodextrins host-guest complexes in solution

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena; Zimnicka, Magdalena; Wszelaka-Rylik, Małgorzata; Troć, Anna

    2016-04-01

    The complexation of folic acid (FA) with native cyclodextrins was studied and this process was used for the comparison of 1H NMR, ITC and ESIMS for the evaluation of association constants. The stability increases in the series: α-cyclodextrin/FA < γ-cyclodextrin/FA < β-cyclodextrin/FA. 1H NMR and ITC gave comparable results in regard to association constant values, while results obtained for MS were considerably higher due to different interactions (electrostatic instead of hydrophobic) responsible for the stabilization of the complexes. The dimerization of FA in water was also studied, as well as its impact on the process of complexation with native cyclodextrins.

  3. Posaconazole/hydroxypropyl-β-cyclodextrin host-guest system: Improving dissolution while maintaining antifungal activity.

    PubMed

    Tang, Peixiao; Ma, Xiaoli; Wu, Di; Li, Shanshan; Xu, Kailin; Tang, Bin; Li, Hui

    2016-05-20

    This study aimed to prepare and characterize the inclusion complex between posaconazole (POS) and hydroxypropyl-β-cyclodextrin (HP-β-CD). Phase solubility study was conducted to investigate the drug/CD interaction in solution, including the stoichiometry and apparent stability constant. The solid complex (HP-β-CD-POS) obtained was characterized through Fourier transform infrared spectroscopy, powder X-ray diffraction, (1)H and ROESY 2D nuclear magnetic resonance, differential scanning calorimetry, and scanning electron microscopy. These approaches confirmed the formation of the inclusion complex. The HP-β-CD-POS inclusion complex exhibited better water solubility and higher dissolution rate than the free POS did; the water solubility of POS was increased by 82 times and almost 90% of the loaded drug dissolved after 10 min in the dissolution media. In addition, preliminary in vitro antifungal susceptibility testing revealed that HP-β-CD-POS maintains a high level of antifungal activities. Therefore, the HP-β-CD complex may be useful in the delivery of posaconazole.

  4. Supramolecular control in carbohydrate epimerization: discovery of a new anion host-guest system.

    PubMed

    Dong, Hai; Rahm, Martin; Brinck, Tore; Ramström, Olof

    2008-11-19

    A new anion-carbohydrate recognition system is described. Pyranosides with axial protons in 1-, 3-, and 5-position proved efficient, forming relatively strong complexes between the anion and the B-face of the carbohydrate. This system could furthermore be used in supramolecular control in Lattrell-Dax epimerization reactions, leading to either activation or deactivation effects.

  5. Host-guest molecular interactions in vanillin/amylose inclusion complexes.

    PubMed

    Rodríguez, Silvio D; Bernik, Delia L

    2013-08-01

    The interaction of 4-hydroxy-3-methoxybenzaldehyde (vanillin) and Hylon VII due to the formation of an inclusion complex is studied using Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and circular dichroism (CD). The results confirm the close interaction among the different functional groups of vanillin and its host. In addition, a second case study was carried out with an amylose from a different source (100% amylose [APT III]). As a result, remarkable differences were found in the vanillin complexation capability of this amylose, which is only shown in solution by circular dichroism spectroscopy studies through a clear Cotton effect. This finding confirms the value of using CD studies, which shows that, depending on the amylose source, inclusion complexes can be found in solution, or both in solution and the coexisting precipitates, as shown using other techniques, such as X-ray diffraction (XRD) or differential scanning calorimetry (DSC). Moreover, solubility assays and complexation of both starches with iodine and subsequent absorption spectroscopy studies gives more information regarding the possible source of the starch encapsulation capability. Thus, Hylon VII shows higher capacity as vanillin encapsulant than APT III, showing the formation of inclusion complexes both in solution and solid phase, whereas APT III complexes are only perceivable in solution.

  6. Insights into the Complexity of Weak Intermolecular Interactions Interfering in Host-Guest Systems.

    PubMed

    Zhang, Dawei; Chatelet, Bastien; Serrano, Eloisa; Perraud, Olivier; Dutasta, Jean-Pierre; Robert, Vincent; Martinez, Alexandre

    2015-10-05

    The recognition properties of heteroditopic hemicryptophane hosts towards anions, cations, and neutral pairs, combining both cation-π and anion-π interaction sites, were investigated to probe the complexity of interfering weak intermolecular interactions. It is suggested from NMR experiments, and supported by CASSCF/CASPT2 calculations, that the binding constants of anions can be modulated by a factor of up to 100 by varying the fluorination sites on the electron-poor aromatic rings. Interestingly, this subtle chemical modification can also reverse the sign of cooperativity in ion-pair recognition. Wavefunction calculations highlight how short- and long-range interactions interfere in this recognition process, suggesting that a disruption of anion-π interactions can occur in the presence of a co-bound cation. Such molecules can be viewed as prototypes for examining complex processes controlled by the competition of weak interactions.

  7. Carbohydrate Nanotechnology: Hierarchical Assemblies and Information Processing from Oligosaccharide-Synthetic Lectin Host-Guest

    DTIC Science & Technology

    2014-09-17

    8. PERFORMING ORGANIZATION REPORT NUMBER RESEARCH ADMINISTRATION – CORAL GABLES 1551 BRECIA AVE RM 100A CORAL GABLES FL 33146-2503...Braunschweig a.braunschweig@miami.edu Phone: (305) 284-2516 Department of Chemistry University of Miami 1301 Memorial Drive Coral Gables, FL

  8. 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.

  9. Comparison of host-guest Langmuir-Blodgett multilayer formation by two different amphiphilic cyclodextrins

    SciTech Connect

    Parazak, D.P.; Khan, A.R.; D`Souza, V.T.; Stine, K.J.

    1996-08-07

    We report here our results for Langmuir monolayers of the derivatives of cyclodextrin shown: hexakis(6-deoxy-6-dodecylamino)-{alpha}-cyclodextrin (1a), heptakis(6-deoxy-6-dodecylamino)-{beta}-cyclodextrin (1b), and heptakis(6-deoxy-6-dodecylthio)-{beta}-cyclodextrin (2b ), which was found to be partially substituted. Langmuir films of these derivatives were examined using {Pi}-A isotherm measurements and Brewster angle microscopy. Langmuir-Blodgett (LB) multilayer films of these derivatives were deposited from subphases containing p-nitrophenol to determine the extent of incorporation of the guest molecule in the LB film. The transfer ratios of the film exhibited a noteworthy evolution with the transfer pressure. The variation in the extent of guest molecule incorporation is discussed and compared with the binding behavior in solution of unmodified cyclodextrins. 29 refs., 4 figs.

  10. Efficient host-guest energy transfer in polycationic cyclophane-perylene diimide complexes in water.

    PubMed

    Ryan, Seán T J; Del Barrio, Jesús; Ghosh, Indrajit; Biedermann, Frank; Lazar, Alexandra I; Lan, Yang; Coulston, Roger J; Nau, Werner M; Scherman, Oren A

    2014-06-25

    We report the self-assembly of a series of highly charged supramolecular complexes in aqueous media composed of cyclobis(4,4'-(1,4-phenylene)bispyridine-p-phenylene)tetrakis(chloride) (ExBox) and three dicationic perylene diimides (PDIs). Efficient energy transfer (ET) is observed between the host and guests. Additionally, we show that our hexacationic complexes are capable of further complexation with neutral cucurbit[7]uril (CB[7]), producing a 3-polypseudorotaxane via the self-assembly of orthogonal recognition moieties. ExBox serves as the central ring, complexing to the PDI core, while two CB[7]s behave as supramolecular stoppers, binding to the two outer quaternary ammonium motifs. The formation of the 3-polypseudorotaxane results in far superior photophysical properties of the central PDI unit relative to the binary complexes at stoichiometric ratios. Lastly, we also demonstrate the ability of our binary complexes to act as a highly selective chemosensing ensemble for the neurotransmitter melatonin.

  11. Solution and air stable host/guest architectures from a single layer covalent organic framework.

    PubMed

    Cui, D; MacLeod, J M; Ebrahimi, M; Perepichka, D F; Rosei, F

    2015-11-28

    We show that the surface-supported two-dimensional covalent organic framework (COF) known as COF-1 can act as a host architecture for C60 fullerene molecules, predictably trapping the molecules under a range of conditions. The fullerenes occupy the COF-1 lattice at the solution/solid interface, and in dried films of the COF-1/fullerene network that can be synthesized through either drop-deposition of fullerene solution or by a dipstick-type synthesis in which the surface-supported COF-1 is briefly dipped into the fullerene solution.

  12. 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 (α-CD and β-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 α-CD and β-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:α-CD ∼ 3.45 ns, DOT:β-CD ∼ 4.84 ns, DOX:α-CD ∼ 3.55 ns and DOT:β-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 α-CD. The positive free energy and entropy changes indicated that both inclusion complexation processes are non-spontaneous and entropy driven.

  13. 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.

  14. Host-guest encapsulation of materials by assembled virus protein cages

    NASA Astrophysics Data System (ADS)

    Douglas, Trevor; Young, Mark

    1998-05-01

    Self-assembled cage structures of nanometre dimensions can be used as constrained environments for the preparation of nanostructured materials, and the encapsulation of guest molecules, with potential applications in drug delivery and catalysis. In synthetic systems the number of subunits contributing to cage structures is typically rather small,. But the protein coats of viruses (virions) commonly comprise hundreds of subunits that self-assemble into a cage for transporting viral nucleic acids. Many virions, moreover, can undergo reversible structural changes that open or close gated pores to allow switchable access to their interior. Here we show that such a virion - that of the cowpea chlorotic mottle virus - can be used as a host for the synthesis of materials. We report the mineralization of two polyoxometalate species (paratungstate and decavanadate) and the encapsulation of an anionic polymer inside this virion, controlled by pH-dependent gating of the virion's pores. The diversity in size and shape of such virus particles make this a versatile strategy for materials synthesis and molecular entrapment.

  15. Anion- and Spacer-Directed Host-Guest Complexes of Bipyridine with Pyrogallol[4]arene.

    PubMed

    Patil, Rahul S; Kumari, Harshita; Barnes, Charles L; Atwood, Jerry L

    2015-07-13

    New oval-shaped capsular and bilayer-type hydrogen-bonded arrangements of C-propyl-ol-pyrogallol[4]arene (PgC3-OH) with bipyridine-type spacer complexes are reported here. These complexes are engineered by virtue of derivatization of C-alkyl tails of pyrogallol[4]arene and the use of divergent spacer ligands. Complexes of PgC3-OH, PgC3-OH with bpy (4,4'-bipyridine) and PgC3-OH with bpa (1,2-bis(4-pyridyl)acetylene) have bilayer type arrangements; however, the use of hydrogen chloride causes protonation of bpy molecule, which is then entrapped flat within an offset oval-shaped dimeric hydrogen-bonded PgC3-OH nanocapsule. The presence of chloride anion in the crystal lattice controls the geometry of the resultant nanoassembly.

  16. Highly ordered alignment of a vinyl polymer by host-guest cross-polymerization.

    PubMed

    Distefano, Gaetano; Suzuki, Hirohito; Tsujimoto, Masahiko; Isoda, Seiji; Bracco, Silvia; Comotti, Angiolina; Sozzani, Piero; Uemura, Takashi; Kitagawa, Susumu

    2013-04-01

    Chain alignment can significantly influence the macroscopic properties of a polymeric material, but no general and versatile methodology has yet been reported to obtain highly ordered crystalline packing of polymer chains, with high stability. Here, we disclose a strategy that relies on 'ordered crosslinks' to produce polymeric materials that exhibit a crystalline arrangement. Divinyl crosslinkers (2,5-divinyl-terephthalate) were first embedded, as substitutional ligands, into the structure of a porous coordination polymer (PCP), [Cu(terephthalate)triethylenediamine0.5]n. A representative vinyl monomer, styrene, was subsequently polymerized inside the channels of the host PCP. The polystyrene chains that form within the PCP channels also crosslink with the divinyl species. This bridges together the polymer chains of adjacent channels and ensures that, on selective removal of the PCP, the polymer chains remain aligned. Indeed, the resulting material exhibits long-range order and is stable to thermal and solvent treatments, as demonstrated by X-ray powder diffraction and transmission electron microscopy.

  17. 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

    2015-01-01

    Small carbon nano-onions (CNOs, 6-12 shells) were prepared in high yields and functionalized with carboxylic groups by chemical oxidation and reacted with βCD-NH2 to yield CNOs decorated with βCDs. A biocompatibile dextran polymer with graphted ferrocene groups was employed for the supramolecular self-assembly on the βCD-CNO surfaces. The βCDs 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-βCD outer layer were measured electrochemically.

  18. Host-guest chemistry with water-soluble gold nanoparticle supraspheres

    NASA Astrophysics Data System (ADS)

    Wang, Yizhan; Zeiri, Offer; Raula, Manoj; Le Ouay, Benjamin; Stellacci, Francesco; Weinstock, Ira A.

    2016-11-01

    The uptake of molecular guests, a hallmark of the supramolecular chemistry of cages and containers, has yet to be documented for soluble assemblies of metal nanoparticles. Here we demonstrate that gold nanoparticle-based supraspheres serve as a host for the hydrophobic uptake, transport and subsequent release of over two million organic guests, exceeding by five orders of magnitude the capacities of individual supramolecular cages or containers and rivalling those of zeolites and metal-organic frameworks on a mass-per-volume basis. The supraspheres are prepared in water by adding hexanethiol to polyoxometalate-protected 4 nm gold nanoparticles. Each 200 nm assembly contains hydrophobic cavities between the estimated 27,400 gold building blocks that are connected to one another by nanometre-sized pores. This gives a percolated network that effectively absorbs large numbers of molecules from water, including 600,000, 2,100,000 and 2,600,000 molecules (35, 190 and 234 g l‑1) of para-dichorobenzene, bisphenol A and trinitrotoluene, respectively.

  19. Application of optical tweezers and excimer laser to study protoplast fusion

    NASA Astrophysics Data System (ADS)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

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

    SciTech Connect

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

    2013-04-15

    We present a dual-trap optical tweezers setup which directly measures forces using linear momentum conservation. The setup uses a counter-propagating geometry, which allows momentum measurement on each beam separately. The experimental advantages of this setup include low drift due to all-optical manipulation, and a robust calibration (independent of the features of the trapped object or buffer medium) due to the force measurement method. Although this design does not attain the high-resolution of some co-propagating setups, we show that it can be used to perform different single molecule measurements: fluctuation-based molecular stiffness characterization at different forces and hopping experiments on molecular hairpins. Remarkably, in our setup it is possible to manipulate very short tethers (such as molecular hairpins with short handles) down to the limit where beads are almost in contact. The setup is used to illustrate a novel method for measuring the stiffness of optical traps and tethers on the basis of equilibrium force fluctuations, i.e., without the need of measuring the force vs molecular extension curve. This method is of general interest for dual trap optical tweezers setups and can be extended to setups which do not directly measure forces.

  1. Measuring integrated cellular mechanical stress response at focal adhesions by optical tweezers

    NASA Astrophysics Data System (ADS)

    Bordeleau, François; Bessard, Judicael; Marceau, Normand; Sheng, Yunlong

    2011-09-01

    The ability of cells to sustain mechanical stress is largely modulated by the cytoskeleton. We present a new application of optical tweezers to study cell's mechanical properties. We trap a fibronectin-coated bead attached to an adherent H4II-EC3 rat hepatoma cell in order to apply the force to the cell surface membrane. The bead position corresponding to the cell's local mechanical response at focal adhesions is measured with a quadrant detector. We assessed the cell response by tracking the evolution of the equilibrium force for 40 cells selected at random and selected a temporal window to assess the cell initial force expression at focal adhesions. The mean value of the force within this time window over 40 randomly selected bead/cell bounds was 52.3 pN. Then, we assessed the responses of the cells with modulation of the cytoskeletons, namely the ubiquitous actin-microfilaments and microtubules, plus the differentiation-dependent keratin intermediate filaments. Notably, a destabilization of the first two networks led to around 50 and 30% reductions in the mean equilibrium forces, respectively, relative to untreated cells, whereas a loss of the third one yielded a 25% increase. The differences in the forces from untreated and treated cells are resolved by the optical tweezers experiment.

  2. A combined double-tweezers and wavelength-tunable laser nanosurgery microscope

    NASA Astrophysics Data System (ADS)

    Zhu, Qingyuan; Parsa, Shahab; Shi, Linda Z.; Harsono, Marcellinus; Wakida, Nicole M.; Berns, Michael W.

    2009-08-01

    In two previous studies we have conducted combined laser subcellular microsurgery and optical trapping on chromosomes in living cells1, 2. In the latter study we used two separate microscopes, one for the trap and one for the laser scissors, thus requiring that we move the cell specimen between microscopes and relocate the irradiated cells. In the former paper we combined the 1064 nm laser trap and the 532 nm laser scissors into one microscope. However, in neither study did we have multiple traps allowing for more flexibility in application of the trapping force. In the present paper we describe a combined laser scissors and tweezers microscope that (1) has two trapping beams (both moveable via rapid scanning mirrors (FSM- 300, Newport Corp.), (2) uses a short pulsed tunable 200 fs 710-990 nm Ti:Sapphire laser for laser microsurgery, and (3) also has the option to use a 337 nm 4 ns UV laser for subcellular surgery. The two laser tweezers and either of the laser ablation beams can be used in a cell surgery experiment. The system is integrated into the robotic-controlled RoboLase system3. Experiments on mitotic chromosomes of rat kangaroo PTK2 cells are described.

  3. Optical tweezers and cell biomechanics in macro- and nano-scale

    NASA Astrophysics Data System (ADS)

    Serafetinides, Alexander A.; Makropoulou, Mersini; Spyratou, Ellas

    2013-03-01

    The mechanical properties of cells, as well as their dysfunction, have been implicated in many aspects of human physiology and patho-physiology. Hence, new biophysical techniques, as optical tweezers, are of great importance for biomechanical measurements in both cells and cell simulators (e.g. liposomes). Liposomes are used, among other applications, as drug delivery nanosystems in cancer therapy. In this work, experimental measurements of the optical forces exerted by line optical tweezers on trapped cells (erythrocytes) and liposomes, using the dielectrophoresis method for calibration, are presented. Folding and elongation of trapped red blood cells was observed, in the direction of the electric field of incident beam, while, upon removal of the optical trap, the red blood cells were observed to unfold to their original biconcave shape. By measuring the folding and unfolding times, membrane elasticity properties such as bending modulus were estimated. Shear and bending modulus of liposomes were also estimated by measuring the liposome deformations, induced by optical forces along the beam long axis. The optical force is quasi-linearly increased with the increase of liposome diameter. In the elasticity regime, when the laser was turned off, the liposome acquired gradually its initial shape without any hysteresis.

  4. 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.

  5. Binding mechanism of PicoGreen to DNA characterized by magnetic tweezers and fluorescence spectroscopy.

    PubMed

    Wang, Ying; Schellenberg, Helene; Walhorn, Volker; Toensing, Katja; Anselmetti, Dario

    2017-03-01

    Fluorescent dyes are broadly used in many biotechnological applications to detect and visualize DNA molecules. However, their binding to DNA alters the structural and nanomechanical properties of DNA and, thus, interferes with associated biological processes. In this work we employed magnetic tweezers and fluorescence spectroscopy to investigate the binding of PicoGreen to DNA at room temperature in a concentration-dependent manner. PicoGreen is an ultrasensitive quinolinium nucleic acid stain exhibiting hardly any background signal from unbound dye molecules. By means of stretching and overwinding single, torsionally constrained, nick-free double-stranded DNA molecules, we acquired force-extension and supercoiling curves which allow quantifying DNA contour length, persistence length and other thermodynamical binding parameters, respectively. The results of our magnetic tweezers single-molecule binding study were well supported through analyzing the fluorescent spectra of stained DNA. On the basis of our work, we could identify a concentration-dependent bimodal binding behavior, where, apparently, PicoGreen associates to DNA as an intercalator and minor-groove binder simultaneously.

  6. In situ microparticle analysis of marine phytoplankton cells with infrared laser-based optical tweezers

    NASA Astrophysics Data System (ADS)

    Sonek, G. J.; Liu, Y.; Iturriaga, R. H.

    1995-11-01

    We describe the application of infrared optical tweezers to the in situ microparticle analysis of marine phytoplankton cells. A Nd:YAG laser (lambda=3D 1064 nm) trap is used to confine and manipulate single Nannochloris and Synechococcus cells in an enriched seawater medium while spectral fluorescence and Lorenz-Mie backscatter signals are simultaneously acquired under a variety of excitation and trapping conditions. Variations in the measured fluorescence intensities of chlorophyll a (Chl a) and phycoerythrin pigments in phytoplankton cells are observed. These variations are related, in part, to basic intrasample variability, but they also indicate that increasing ultraviolet-exposure time and infrared trapping power may have short-term effects on cellular physiology that are related to Chl a photobleaching and laser-induced heating, respectively. The use of optical tweezers to study the factors that affect marine cell physiology and the processes of absorption, scattering, and attenuation by individual cells, organisms, and particulate matter that contribute to optical closure on a microscopic scale are also described. (c)1995 Optical Society of America

  7. Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria

    NASA Astrophysics Data System (ADS)

    Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

    2011-04-01

    The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force from the laser tweezers were measured. Human (Homo sapiens), dog (Canis lupis familiaris) and drill (Mandrillus leucophaeus) sperm were treated with DiOC6(3) to measure the membrane potential in the mitochondria-rich sperm midpieces. Sperm from all three species exhibited an increase in fluorescence when treated with the DiOC6(3). When a cyanide inhibitor (CCCP) of aerobic respiration was applied, sperm of all three species exhibited a reduction in fluorescence to pre-dye levels. With respect to VCL and escape force, the CCCP had no effect on dog or human sperm, suggesting a major reliance upon anaerobic respiration (glycolysis) for ATP in these two species. Based on the preliminary study on drill sperm, CCCP caused a drop in the VCL, suggesting potential reliance on both glycolysis and aerobic respiration for motility. The results demonstrate that optical trapping in combination with DiOC6(3) is an effective way to study sperm motility and energetics.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

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

    SciTech Connect

    Ott, Dino; Oddershede, Lene B.; Reihani, S. Nader S.

    2014-05-15

    In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts.

  13. A modular assembling platform for manufacturing of microsystems by optical tweezers

    NASA Astrophysics Data System (ADS)

    Ksouri, Sarah Isabelle; Aumann, Andreas; Ghadiri, Reza; Prüfer, Michael; Baer, Sebastian; Ostendorf, Andreas

    2013-09-01

    Due to the increased complexity in terms of materials and geometries for microsystems new assembling techniques are required. Assembling techniques from the semiconductor industry are often very specific and cannot fulfill all specifications in more complex microsystems. Therefore, holographic optical tweezers are applied to manipulate structures in micrometer range with highest flexibility and precision. As is well known non-spherical assemblies can be trapped and controlled by laser light and assembled with an additional light modulator application, where the incident laser beam is rearranged into flexible light patterns in order to generate multiple spots. The complementary building blocks are generated by a two-photon-polymerization process. The possibilities of manufacturing arbitrary microstructures and the potential of optical tweezers lead to the idea of combining manufacturing techniques with manipulation processes to "microrobotic" processes. This work presents the manipulation of generated complex microstructures with optical tools as well as a storage solution for 2PP assemblies. A sample holder has been developed for the manual feeding of 2PP building blocks. Furthermore, a modular assembling platform has been constructed for an `all-in-one' 2PP manufacturing process as a dedicated storage system. The long-term objective is the automation process of feeding and storage of several different 2PP micro-assemblies to realize an automated assembly process.

  14. A study of red blood cell deformability in diabetic retinopathy using optical tweezers

    NASA Astrophysics Data System (ADS)

    Smart, Thomas J.; Richards, Christopher J.; Bhatnagar, Rhythm; Pavesio, Carlos; Agrawal, Rupesh; Jones, Philip H.

    2015-08-01

    Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus (DM) in which high blood sugar levels cause swelling, leaking and occlusions in the blood vessels of the retina, often resulting in a loss of sight. The microvascular system requires red blood cells (RBCs) to undergo significant cellular deformation in order to pass through vessels whose diameters are significantly smaller than their own. There is evidence to suggest that DM impairs the deformability of RBCs, and this loss of deformability has been associated with diabetic kidney disease (or nephropathy) - another microvascular complication of DM. However, it remains unclear whether reduced deformability of RBCs correlates with the presence of DR. Here we present an investigation into the deformability of RBCs in patients with diabetic retinopathy using optical tweezers. To extract a value for the deformability of RBCs we use a dual-trap optical tweezers set-up to stretch individual RBCs. RBCs are trapped directly (i.e. without micro-bead handles), so rotate to assume a `side-on' orientation. Video microscopy is used to record the deformation events, and shape analysis software is used to determine parameters such as initial and maximum RBC length, allowing us to calculate the deformability for each RBC. A small decrease in deformability of diabetes cells subject to this stretching protocol is observed when compared to control cells. We also report on initial results on three dimensional imaging of individual RBCs using defocussing microscopy.

  15. Optical Tweezers as a New Biomedical Tool to Measure Zeta Potential of Stored Red Blood Cells

    PubMed Central

    Silva, Carlos A. L.; Fernandes, Heloise P.; Filho, Milton M.; Lucena, Sheyla C.; Costa, Ana Maria D. N.; Cesar, Carlos L.; Barjas-Castro, Maria L.; Santos, Beate S.; Fontes, Adriana

    2012-01-01

    During storage, red blood cells (RBCs) for transfusion purposes suffer progressive deterioration. Sialylated glycoproteins of the RBC membrane are responsible for a negatively charged surface which creates a repulsive electrical zeta potential. These charges help prevent the interaction between RBCs and other cells, and especially among each RBCs. Reports in the literature have stated that RBCs sialylated glycoproteins can be sensitive to enzymes released by leukocyte degranulation. Thus, the aim of this study was, by using an optical tweezers as a biomedical tool, to measure the zeta potential in standard RBCs units and in leukocyte reduced RBC units (collected in CPD-SAGM) during storage. Optical tweezers is a sensitive tool that uses light for measuring cell biophysical properties which are important for clinical and research purposes. This is the first study to analyze RBCs membrane charges during storage. In addition, we herein also measured the elasticity of RBCs also collected in CPD-SAGM. In conclusion, the zeta potential decreased 42% and cells were 134% less deformable at the end of storage. The zeta potential from leukodepleted units had a similar profile when compared to units stored without leukoreduction, indicating that leukocyte lyses were not responsible for the zeta potential decay. Flow cytometry measurements of reactive oxygen species suggested that this decay is due to membrane oxidative damages. These results show that measurements of zeta potentials provide new insights about RBCs storage lesion for transfusion purposes. PMID:22363729

  16. Measurement of particle motion in optical tweezers embedded in a Sagnac interferometer.

    PubMed

    Galinskiy, Ivan; Isaksson, Oscar; Salgado, Israel Rebolledo; Hautefeuille, Mathieu; Mehlig, Bernhard; Hanstorp, Dag

    2015-10-19

    We have constructed a counterpropagating optical tweezers setup embedded in a Sagnac interferometer in order to increase the sensitivity of position tracking for particles in the geometrical optics regime. Enhanced position determination using a Sagnac interferometer has previously been described theoretically by Taylor et al. [Journal of Optics 13, 044014 (2011)] for Rayleigh-regime particles trapped in an antinode of a standing wave. We have extended their theory to a case of arbitrarily-sized particles trapped with orthogonally-polarized counter-propagating beams. The working distance of the setup was sufficiently long to optically induce particle oscillations orthogonally to the axis of the tweezers with an auxiliary laser beam. Using these oscillations as a reference, we have experimentally shown that Sagnac-enhanced back focal plane interferometry is capable of providing an improvement of more than 5 times in the signal-to-background ratio, corresponding to a more than 30-fold improvement of the signal-to-noise ratio. The experimental results obtained are consistent with our theoretical predictions. In the experimental setup, we used a method of optical levitator-assisted liquid droplet delivery in air based on commercial inkjet technology, with a novel method to precisely control the size of droplets.

  17. Optical Tweezers Studies on Notch: Single-molecule Interaction Strength is Independent of Ligand Endocytosis

    PubMed Central

    Shergill, Bhupinder; Meloty-Kapella, Laurence; Musse, Abdiwahab A.; Weinmaster, Gerry; Botvinick, Elliot

    2012-01-01

    SUMMARY Notch signaling controls diverse cellular processes critical to development and disease. Cell surface ligands bind Notch on neighboring cells yet require endocytosis to activate signaling. The role ligand endocytosis plays in Notch activation has not been established. Here we integrate optical tweezers with cell biological and biochemical methods to test the prevailing model that ligand endocytosis facilitates recycling to enhance ligand interactions with Notch necessary to trigger signaling. Specifically, single-molecule measurements indicate that interference of ligand endocytosis and/or recycling does not alter the force required to rupture bonds formed between cells expressing the Notch ligand Delta-like1 (Dll1) and laser-trapped Notch1-beads. Together, our analyses eliminate roles for ligand endocytosis and recycling in Dll1-Notch1 interactions, and indicate that recycling indirectly affects signaling by regulating the accumulation of cell-surface ligand. Importantly, our study demonstrates the utility of optical tweezers to test a role for ligand endocytosis in generating cell-mediated mechanical force. PMID:22658935

  18. A novel single fiber optical tweezers based on light-induced thermal effect

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.

  19. Understanding local forces in electrophoretic ink systems: utilizing optical tweezers to explore electrophoretic display devices

    NASA Astrophysics Data System (ADS)

    Wei, David L.; Dickinson, Mark R.; Smith, N.; Gleeson, Helen F.

    2016-09-01

    Optical tweezers can be used as a valuable tool to characterize electrophoretic display (EPD) systems. EPDs are ubiquitous with e-readers and are becoming a commonplace technology where reflective, low-power displays are required; yet the physics of some features crucial to their operation remains poorly defined. We utilize optical tweezers as a tool to understand the motion of charged ink particles within the devices and show that the response of optically trapped electrophoretic particles can be used to characterize electric fields within these devices. This technique for mapping the force can be compared to simulations of the electric field in our devices, thus demonstrating that the electric field itself is the sole governor of the particle motion in an individual-particle regime. By studying the individual-particle response to the electric field, we can then begin to characterize particle motion in `real' systems with many particles. Combining optical tweezing with particle tracking techniques, we can investigate deviations in many particle systems from the single-particle case.

  20. Design of hybrid optical tweezers system for controlled three-dimensional micromanipulation

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshio; Tsutsui, Shogo; Kitajima, Hiroyuki

    2013-04-01

    Three-dimensional (3D) micro/nano-manipulation using optical tweezers is a significant technique for various scientific fields ranging from biology to nanotechnology. For the dynamic handling of multiple/individual micro-objects in a true 3D working space, we present an improved hybrid optical tweezers system consisting of two multibeam techniques. These two techniques include the generalized phase contrast method with a spatial light modulator and the time-shared scanning method with a two-axis steering mirror and an electrically focus-tunable lens. Unlike our previously reported system that could only handle micro-objects in a two and half dimensional working space, the present system has high versatility for controlled manipulation of multiple micro-objects in a true 3D working space. The controlled rotation of five beads forming a pentagon, that of four beads forming a tetrahedron about arbitrary axes, and the fully automated assembly and subsequent 3D translation of micro-bead arrays are successfully demonstrated as part of the 3D manipulation experiment.

  1. 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.

  2. Optical trapping of a spherically symmetric sphere in the ray-optics regime: a model for optical tweezers upon cells

    SciTech Connect

    Chang Yiren; Hsu Long; Chi Sien

    2006-06-01

    Since their invention in 1986, optical tweezers have become a popular manipulation and force measurement tool in cellular and molecular biology. However, until recently there has not been a sophisticated model for optical tweezers on trapping cells in the ray-optics regime. We present a model for optical tweezers to calculate the optical force upon a spherically symmetric multilayer sphere representing a common biological cell. A numerical simulation of this model shows that not only is the magnitude of the optical force upon a Chinese hamster ovary cell significantly three times smaller than that upon a polystyrene bead of the same size, but the distribution of the optical force upon a cell is also much different from that upon a uniform particle, and there is a 30% difference in the optical trapping stiffness of these two cases. Furthermore, under a small variant condition for the refractive indices of any adjacent layers of the sphere, this model provides a simple approximation to calculate the optical force and the stiffness of an optical tweezers system.

  3. Energy Landscape of Alginate-Epimerase Interactions Assessed by Optical Tweezers and Atomic Force Microscopy

    PubMed Central

    Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit

    2015-01-01

    Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase–polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase–alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the

  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. Optically-driven red blood cell rotor in linearly polarized laser tweezers

    NASA Astrophysics Data System (ADS)

    Khan, Manas; Mohanty, Samarendra K.; Sood, A. K.

    2005-11-01

    We have constructed a dual trap optical tweezers set-up around an inverted microscope where both the traps can be independently controlled and manipulated in all the three dimensions. Here we report our observations on rotation of red blood cells (RBCs) in a linearly polarized optical trap. Red blood cells deform and become twisted in hypertonic phosphate buffer saline and when trapped, experience an unbalanced radiation pressure force. The torque generated from the unbalanced force causes the trapped RBC to rotate. Addition of Ca^{++} ions in the solution, keeping the osmolarity same, makes the cell membranes stiffer and the cells deform less. Thus the speed of rotation of the red blood cells can be controlled, as less deformation and in turn less asymmetry in shape produces less torque under the radiation pressure resulting in slower rotation at the same laser power.

  6. Inhibition of Huntingtin Exon-1 Aggregation by the Molecular Tweezer CLR01.

    PubMed

    Vöpel, Tobias; Bravo-Rodriguez, Kenny; Mittal, Sumit; Vachharajani, Shivang; Gnutt, David; Sharma, Abhishek; Steinhof, Anne; Fatoba, Oluwaseun; Ellrichmann, Gisa; Nshanian, Michael; Heid, Christian; Loo, Joseph A; Klärner, Frank-Gerrit; Schrader, Thomas; Bitan, Gal; Wanker, Erich E; Ebbinghaus, Simon; Sanchez-Garcia, Elsa

    2017-04-13

    Huntington's disease is a neurodegenerative disorder associated with the expansion of the polyglutamine tract in the exon-1 domain of the huntingtin protein (htt(e1)). Above a threshold of 37 glutamine residues, htt(e1) starts to aggregate in a nucleation-dependent manner. A 17-residue N-terminal fragment of htt(e1) (N17) has been suggested to play a crucial role in modulating the aggregation propensity and toxicity of htt(e1). Here we identify N17 as a potential target for novel therapeutic intervention using the molecular tweezer CLR01. A combination of biochemical experiments and computer simulations shows that binding of CLR01 induces structural rearrangements within the htt(e1) monomer and inhibits htt(e1) aggregation, underpinning the key role of N17 in modulating htt(e1) toxicity.

  7. Detection of doxorubicin-induced apoptosis of leukemic T-lymphocytes by laser tweezers Raman spectroscopy

    PubMed Central

    Moritz, Tobias J.; Taylor, Douglas S.; Krol, Denise M.; Fritch, John; Chan, James W.

    2010-01-01

    Laser tweezers Raman spectroscopy (LTRS) was used to acquire the Raman spectra of leukemic T lymphocytes exposed to the chemotherapy drug doxorubicin at different time points over 72 hours. Changes observed in the Raman spectra were dependent on drug exposure time and concentration. The sequence of spectral changes includes an intensity increase in lipid Raman peaks, followed by an intensity increase in DNA Raman peaks, and finally changes in DNA and protein (phenylalanine) Raman vibrations. These Raman signatures are consistent with vesicle formation, cell membrane blebbing, chromatin condensation, and the cytoplasm of dead cells during the different stages of drug-induced apoptosis. These results suggest the potential of LTRS as a real-time single cell tool for monitoring apoptosis, evaluating the efficacy of chemotherapeutic treatments, or pharmaceutical testing. PMID:21258536

  8. Micro-particle manipulation by single beam acoustic tweezers based on hydrothermal PZT thick film

    PubMed Central

    Zhu, Benpeng; Xu, Jiong; Li, Ying; Wang, Tian; Xiong, Ke; Lee, Changyang; Yang, Xiaofei; Shiiba, Michihisa; Takeuchi, Shinichi; Zhou, Qifa; Shung, K. Kirk

    2016-01-01

    Single-beam acoustic tweezers (SBAT), used in laboratory-on-a-chip (LOC) device has promising implications for an individual micro-particle contactless manipulation. In this study, a freestanding hydrothermal PZT thick film with excellent piezoelectric property (d33 = 270pC/N and kt = 0.51) was employed for SBAT applications and a press-focusing technology was introduced. The obtained SBAT, acting at an operational frequency of 50MHz, a low f-number (∼0.9), demonstrated the capability to trap and manipulate a micro-particle sized 10μm in the distilled water. These results suggest that such a device has great potential as a manipulator for a wide range of biomedical and chemical science applications. PMID:27014504

  9. Studies of cochlear outer hair cell membrane mechanics using optical tweezers

    NASA Astrophysics Data System (ADS)

    Murdock, David R.; Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

    2003-06-01

    An optical tweezers system was used to study the mechanical characteristics of outer hair cell (OHC) and human embryonic kidney (HEK) cell plasma membranes. The effect of the cationic amphipath chlorpromazine (CPZ) on the equilibrium tethering force, (Feq) force relaxation time constant,(τ) and effective membrane viscosity (ηeff) was measured. The Feq for the OHC lateral wall plasma membrane was ~60 pN and was unchanged by addition of CPZ. A significantly greater τ value was observed in CPZ-treated OHCs (30.5 +/- 12.6 s) than in control OHCs (19.0 +/- 13.2 s). The Feq and τ values for control HEK cells were >60% lower than the respective OHC values but increased by ~3 times following CPZ addition. Effective viscosity ranged between 1.49-1.81 pN•s/μm for CPZ-treated OHCs. This represents a decrease from reported control OHC membrane viscosities.

  10. Optical tweezers study of viscoelastic properties in the outer hair cell plasma membrane

    NASA Astrophysics Data System (ADS)

    Murdock, David R.; Ermilov, Sergey A.; Qian, Feng; Brownell, William E.; Anvari, Bahman

    2004-06-01

    An optical tweezers system was used to study the mechanical characteristics of the outer hair cell (OHC) lateral wall by forming plasma membrane tethers. A 2nd order generalized Kelvin model was applied to describe the viscoelastic behavior of OHC membrane tethers. The measured parameters included equilibrium tethering force, (Feq), force relaxation times (τ), stiffness values (κ), and coefficients of friction (μ). An analysis of force relaxation in membrane tethers indicated that the force decay is a biphasic process containing both an elastic and a viscous phase. In general, we observed an overall negative trend in the measured parameters upon application of the cationic amphipath chlorpromazine (CPZ). CPZ was found to cause up to a 40 pN reduction in Feq in OHCs. A statistically significant reduction in relaxation times and coefficients of friction was also observed, suggesting an increase in rate of force decay and a decrease in plasma membrane viscosity.

  11. 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

  12. Optical levitation and manipulation of stuck particles with pulsed optical tweezers.

    PubMed

    Ambardekar, Amol Ashok; Li, Yong-Qing

    2005-07-15

    We report on optical levitation and manipulation of microscopic particles that are stuck on a glass surface with pulsed optical tweezers. An infrared pulse laser at 1.06 microm was used to generate a large gradient force (up to 10(-9) N) within a short duration (approximately 45 micros) that overcomes the adhesive interaction between the particles and the glass surface. Then a low-power continuous-wave diode laser at 785 nm was used to capture and manipulate the levitated particle. We have demonstrated that both stuck dielectric and biological micrometer-sized particles, including polystyrene beads, yeast cells, and Bacillus cereus bacteria, can be levitated and manipulated with this technique. We measured the single-pulse levitation efficiency for 2.0 microm polystyrene beads as a function of the pulse energy and of the axial displacement from the stuck particle to the pulsed laser focus, which was as high as 88%.

  13. Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis

    PubMed Central

    Ferraro, Davide; Champ, Jérôme; Teste, Bruno; Serra, Marco; Malaquin, Laurent; Viovy, Jean-Louis; de Cremoux, Patricia; Descroix, Stephanie

    2016-01-01

    The development of precision medicine, together with the multiplication of targeted therapies and associated molecular biomarkers, call for major progress in genetic analysis methods, allowing increased multiplexing and the implementation of more complex decision trees, without cost increase or loss of robustness. We present a platform combining droplet microfluidics and magnetic tweezers, performing RNA purification, reverse transcription and amplification in a fully automated and programmable way, in droplets of 250nL directly sampled from a microtiter-plate. This platform decreases sample consumption about 100 fold as compared to current robotized platforms and it reduces human manipulations and contamination risk. The platform’s performance was first evaluated on cell lines, showing robust operation on RNA quantities corresponding to less than one cell, and then clinically validated with a cohort of 21 breast cancer samples, for the determination of their HER2 expression status, in a blind comparison with an established routine clinical analysis. PMID:27157697

  14. Characterization of the mechanical properties of HL-1 cardiomyocytes with high throughput magnetic tweezers

    SciTech Connect

    Chen, La; Maybeck, Vanessa; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-08-03

    We characterized the mechanical properties of cardiomyocyte-like HL-1 cells using our recently developed multi-pole magnetic tweezers. With the optimized design, both high force and high throughput are achieved at the same time. Force up to 100 pN can be applied on a 1 μm diameter superparamagnetic bead in a workspace with 60 μm radius, which is encircled symmetrically by 3 sharp magnetic tips. By adjusting the coil currents, both the strength and direction of force can be controlled. The result shows that both viscosity and shear elastic modulus of HL-1 cells exhibit an approximately log-normal distribution. The cells became stiffer as they matured, consistent with a transition from proliferating cells to contractile muscle tissue. Moreover, the mechanical properties of HL-1 cells show high heterogeneity, which agrees well with their physiological structure.

  15. 3D Manipulation of Protein Microcrystals with Optical Tweezers for X-ray Crystallography

    NASA Astrophysics Data System (ADS)

    Hikima, T.; Hashimoto, K.; Murakami, H.; Ueno, G.; Kawano, Y.; Hirata, K.; Hasegawa, K.; Kumasaka, T.; Yamamoto, M.

    2013-03-01

    In some synchrotron facilities such as SPring-8, X-ray microbeams have been utilized for protein crystallography, allowing users to collect diffraction data from a protein microcrystal. Usually, a protein crystal is picked up manually from a crystallization droplet. However it is very difficult to manipulate the protein microcrystals which are very small and fragile against a shock and changes of temperature and solvent condition. We have been developing an automatic system applying the optical tweezers with two lensed fiber probes to manipulate the fragile protein microcrystal. The system succeeded in trapping a crystal and levitating it onto the cryoloop in the solvent. X-ray diffraction measurement for the manipulated protein microcrystals indicated that laser irradiation and trap with 1064nm wavelength hardly affected the result of X-ray structural analysis.

  16. Identification of volume phase transition of a single microgel particle using optical tweezers

    NASA Astrophysics Data System (ADS)

    Karthickeyan, D.; Gupta, Deepak K.; Tata, B. V. R.

    2016-10-01

    Poly (N-isopropyl acrylamide-co-acrylic acid) (PNIPAM-co-Aac) microgel particles are pH responsive and exhibit volume phase transition (VPT) upon variation of pH. Dynamic light scattering (DLS) is used conventionally to identify VPT and requires a dilute suspension with particle concentration ˜107 particles cm-3 and if particles are polydisperse in nature, DLS data interpretation is relatively difficult. Here we show that optical tweezers allow one to measure the VPT of a single microgel particle by measuring the optical trap stiffness, κ of trapped particle as a function of pH. We report here a sudden change in κ at VPT, which is shown to arise from a sudden decrease in particle diameter with a concomitant increase in the refractive index of the particle at VPT.

  17. Optical tweezers based active microrheology of sodium polystyrene sulfonate (NaPSS).

    PubMed

    Chiang, Chia-Chun; Wei, Ming-Tzo; Chen, Yin-Quan; Yen, Pei-Wen; Huang, Yi-Chiao; Chen, Jun-Yeh; Lavastre, Olivier; Guillaume, Husson; Guillaume, Darsy; Chiou, Arthur

    2011-04-25

    We used oscillatory optical tweezers to investigate the microrheological properties of Sodium polystyrene sulfonate (NaPSS; Mw = 70 kDa) polymer solutions with different concentrations from 0.001 mM to 10 mM in terms of elastic modulus G'(ω) and loss modulus G"(ω) as a function of angular frequency (ω) in the range of 6 rad/s to 6000 rad/s. The viscoelastic properties (including zero-shear-rate viscosity, crossing frequency and transition frequency) as a function of polymer concentration, deduced from our primary data, reveal the subtle structural changes in the polymer solutions as the polymer concentration increases from dilute to semi-dilute regimes, passing through the critical micelle formation concentration and the polymer overlapping concentration. The experimental results are consistent with the Maxwell model in some regime, and with the Rouse model in other, indicating the transient network character and the micelles formation in different regimes.

  18. Surface modes of a sessile water drop: An optical tweezer based study

    NASA Astrophysics Data System (ADS)

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S.

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  19. Surface modes of a sessile water drop: an optical tweezer based study.

    PubMed

    Ghosh, Shankar; Sharma, Prerna; Bhattacharya, S

    2007-11-01

    A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained.

  20. Controlled modulation of laser beam and dynamic patterning of colloidal particles using optical tweezers

    NASA Astrophysics Data System (ADS)

    Singh, Brijesh Kumar; Singh Mehta, Dalip; Kumar, Ranjeet; Senthilkumaran, Paramasivam

    2016-02-01

    We present controlled generation of complex-structured beam profiles using diffractive optical element and demonstrate multiple dynamic trapping of colloidal particles. The phase element is programmed to generate various tailored optical fields having structures, similar to that of number three, spiral, and circle but in a tractable manner. Thus, the generated spatially tailored optical fields are confined to focal volume in optical tweezers. This enabled real-time trapping of multiple microscopic objects whereby its transverse organization was controlled in a dynamic manner from one structure to another with the help of spatial light modulator. Such a controlled beam shaping finds potential applications in biophotonics, super resolution imaging, and measurement of biophysical parameters, cell sorting, and micro-manipulation of colloidal particles.

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

    PubMed

    Thompson, J D; Tiecke, T G; Zibrov, A S; Vuletić, 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 δx=δy=24  nm and δz=270  nm represents a promising starting point for future hybrid quantum systems where atoms are placed in close proximity to surfaces.

  2. Stretching single DNA molecules to demonstrate high-force capabilities of holographic optical tweezers.

    PubMed

    Farré, Arnau; van der Horst, Astrid; Blab, Gerhard A; Downing, Benjamin P B; Forde, Nancy R

    2010-04-01

    The well calibrated force-extension behaviour of single double-stranded DNA molecules was used as a standard to investigate the performance of phase-only holographic optical tweezers at high forces. Specifically, the characteristic overstretch transition at 65 pN was found to appear where expected, demonstrating (1) that holographic optical trap calibration using thermal fluctuation methods is valid to high forces; (2) that the holographic optical traps are harmonic out to >250 nm of 2.1 mum particle displacement; and (3) that temporal modulations in traps induced by the spatial light modulator (SLM) do not affect the ability of optical traps to hold and steer particles against high forces. These studies demonstrate a new high-force capability for holographic optical traps achievable by SLM technologies.

  3. Study of a colloidal sphere near flat walls using oscillating optical tweezers

    NASA Astrophysics Data System (ADS)

    Ha, Chungil; Ou-Yang, H. Daniel; Pak, Hyuk Kyu

    2009-11-01

    We study the dynamics of a micron-sized colloidal sphere in two cases; one is for a particle near a single flat wall and the other is for a particle confined between two parallel flat walls. In this geometry, the force felt by a moving particle is quite different from that of a moving particle in unbounded space. Even though the presence of wall(s) complicates the flow field surrounding the colloidal sphere, the dynamics of a colloidal sphere near flat walls provides a model system with which to understand the phenomenon of more complex systems whose boundaries can be modeled as effective walls.[1] In this work, hydrodynamic interactions of colloidal sphere with nearby plat wall(s) are studied by using oscillating optical tweezers and compared with known theories and other experimental results using different techniques.

  4. Evaluating cell matrix mechanics using an integrated nonlinear optical tweezer-confocal imaging system

    NASA Astrophysics Data System (ADS)

    Peng, Berney; Alonzo, Carlo A. C.; Xia, Lawrence; Speroni, Lucia; Georgakoudi, Irene; Soto, Ana M.; Sonnenschein, Carlos; Cronin-Golomb, Mark

    2013-09-01

    Biomechanics plays a central role in breast epithelial morphogenesis. In this study we have used 3D cultures in which normal breast epithelial cells are able to organize into rounded acini and tubular ducts, the main structures found in the breast tissue. We have identified fiber organization as a main determinant of ductal organization. While bulk rheological properties of the matrix seem to play a negligible role in determining the proportion of acini versus ducts, local changes may be pivotal in shape determination. As such, the ability to make microscale rheology measurements coupled with simultaneous optical imaging in 3D cultures can be critical to assess the biomechanical factors underlying epithelial morphogenesis. This paper describes the inclusion of optical tweezers based microrheology in a microscope that had been designed for nonlinear optical imaging of collagen networks in ECM. We propose two microrheology methods and show preliminary results using a gelatin hydrogel and collagen/Matrigel 3D cultures containing mammary gland epithelial cells.

  5. 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.

  6. Microfluidic platform combining droplets and magnetic tweezers: application to HER2 expression in cancer diagnosis

    NASA Astrophysics Data System (ADS)

    Ferraro, Davide; Champ, Jérôme; Teste, Bruno; Serra, Marco; Malaquin, Laurent; Viovy, Jean-Louis; de Cremoux, Patricia; Descroix, Stephanie

    2016-05-01

    The development of precision medicine, together with the multiplication of targeted therapies and associated molecular biomarkers, call for major progress in genetic analysis methods, allowing increased multiplexing and the implementation of more complex decision trees, without cost increase or loss of robustness. We present a platform combining droplet microfluidics and magnetic tweezers, performing RNA purification, reverse transcription and amplification in a fully automated and programmable way, in droplets of 250nL directly sampled from a microtiter-plate. This platform decreases sample consumption about 100 fold as compared to current robotized platforms and it reduces human manipulations and contamination risk. The platform’s performance was first evaluated on cell lines, showing robust operation on RNA quantities corresponding to less than one cell, and then clinically validated with a cohort of 21 breast cancer samples, for the determination of their HER2 expression status, in a blind comparison with an established routine clinical analysis.

  7. Implementation and Tuning of an Optical Tweezers Force-Clamp Feedback System.

    PubMed

    Bugiel, Michael; Jannasch, Anita; Schäffer, Erik

    2017-01-01

    Feedback systems can be used to control the value of a system variable. In optical tweezers, active feedback is often implemented to either keep the position or tension applied to a single biomolecule constant. Here, we describe the implementation of the latter: an optical force-clamp setup that can be used to study the motion of processive molecular motors under a constant load. We describe the basics of a software-implemented proportional-integral-derivative (PID) controller, how to tune it, and how to determine its optimal feedback rate. Limitations, possible feed-forward applications, and extensions into two- and three-dimensional optical force clamps are discussed. The feedback is ultimately limited by thermal fluctuations and the compliance of the involved molecules. To investigate a particular mechanical process, understanding the basics and limitations of the feedback system will be helpful for choosing the proper feedback hardware, for optimizing the system parameters, and for the design of the experiment.

  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. Use of optoelectronic tweezers in manufacturing—accurate solder bead positioning

    NASA Astrophysics Data System (ADS)

    Zhang, Shuailong; Liu, Yongpeng; Juvert, Joan; Tian, Pengfei; Navarro, Jean-Claude; Cooper, Jonathan M.; Neale, Steven L.

    2016-11-01

    In this work, we analyze the use of optoelectronic tweezers (OETs) to manipulate 45 μm diameter Sn62Pb36Ag2 solder beads with light-induced dielectrophoresis force and we demonstrate high positioning accuracy. It was found that the positional deviation of the solder beads increases with the increase of the trap size. To clarify the underlying mechanism, simulations based on the integration of the Maxwell stress tensor were used to study the force profiles of OET traps with different sizes. It was found that the solder beads felt a 0.1 nN static friction or stiction force due to electrical forces pulling them towards the surface and that this force is not dependent on the size of the trap. The stiction limits the positioning accuracy; however, we show that by choosing a trap that is just larger than the solder bead sub-micron positional accuracy can be achieved.

  10. Semi-automated sorting using holographic optical tweezers remotely controlled by eye/hand tracking camera

    NASA Astrophysics Data System (ADS)

    Tomori, Zoltan; Keša, Peter; Nikorovič, Matej; Kaůka, Jan; Zemánek, Pavel

    2016-12-01

    We proposed the improved control software for the holographic optical tweezers (HOT) proper for simple semi-automated sorting. The controller receives data from both the human interface sensors and the HOT microscope camera and processes them. As a result, the new positions of active laser traps are calculated, packed into the network format and sent to the remote HOT. Using the photo-polymerization technique, we created a sorting container consisting of two parallel horizontal walls where one wall contains "gates" representing a place where the trapped particle enters into the container. The positions of particles and gates are obtained by image analysis technique which can be exploited to achieve the higher level of automation. Sorting is documented on computer game simulation and the real experiment.

  11. An active one-particle microrheometer: incorporating magnetic tweezers to total internal reflection microscopy.

    PubMed

    Gong, Xiangjun; Hua, Li; Wu, Chi; Ngai, To

    2013-03-01

    We present a novel microrheometer by incorporating magnetic tweezers in the total internal reflection microscopy (TIRM) that enables measuring of viscoelastic properties of materials near solid surface. An evanescent wave generated by a solid∕liquid interface in the TIRM is used as the incident light source in the microrheometer. When a probe particle (of a few micrometers diameter) moves near the interface, it can interact with the evanescent field and reflect its position with respect to the interface by the scattered light intensity. The exponential distance dependence of the evanescent field, on the one hand, makes this technique extremely sensitive to small changes from z-fluctuations of the probe (with a resolution of several nanometers), and on the other, it does not require imaging of the probe with high lateral resolution. Another distinct advantage is the high sensitivity in determining the z position of the probe in the absence of any labeling. The incorporated magnetic tweezers enable us to effectively manipulate the distance of the embedded particle from the interface either by a constant or an oscillatory force. The force ramp is easy to implement through a coil current ramp. In this way, the local viscous and elastic properties of a given system under different confinements can therefore be measured by resolving the near-surface particle motion. To test the feasibility of applying this microrheology to soft materials, we measured the viscoelastic properties of sucrose and poly(ethylene glycol) solutions and compared the results to bulk rheometry. In addition, we applied this technique in monitoring the structure and properties of deformable microgel particles near the flat surface.

  12. 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.

  13. Application of optical tweezers using DOE and SLM to control of beads with information-DNA for photonic DNA computing

    NASA Astrophysics Data System (ADS)

    Zheng, M. J.; Ogura, Y.; Tanida, J.

    2008-03-01

    We have proposed photonic DNA computing as a new parallel computing paradigm, in which optical techniques are used to manipulate information-coded DNA. In this paper, we present a parallel transportation of multiple beads bound with hairpin-structure DNA using a dynamic optical tweezers system which combines a spatial light modulator (SLM) with a diffractive optical element (DOE). This system provides and effective method for parallel manipulations of DNA-bound beads at multiple positions. In the experiments, three 2.8-μm-diameter beads bound with hairpin DNA were trapped and transported in 1 μm of step by switching of the SLM patterns. The results demonstrate that the dynamic holographic optical tweezers system with combination of the DOE and the SLM is useful in spatially parallel processing required for photonic DNA computing.

  14. Tethered anthracene pair as molecular tweezers for post-production separation of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Anderson, Ankoma; Yang, Fengchun; Cao, Li; Li, Huaping; Meziani, Mohammed J.; Sun, Ya-Ping

    2016-07-01

    As-produced single-walled carbon nanotubes (SWNTs) are metallic and semiconducting mixtures. An anthracene mono-derivative with a long alkyl tail and a molecule with a tethered pair of anthracene species (bis-anthracene) in a ;molecular tweezers;-like configuration were synthesized and evaluated for the separation of SWNTs. While the mono-derivative was incapable of the noncovalent functionalization-solubilization, the bis-anthracene was found to be very effective. The results suggest that molecular tweezers of a tethered pair of planar aromatic species can be coupled with the selection of a suitable solvent or solvent mixture for effective and efficient post-production separation of metallic and semiconducting SWNTs.

  15. Towards nano-optical tweezers with graphene plasmons: Numerical investigation of trapping 10-nm particles with mid-infrared light

    PubMed Central

    Zhang, Jianfa; Liu, Wenbin; Zhu, Zhihong; Yuan, Xiaodong; Qin, Shiqiao

    2016-01-01

    Graphene plasmons are rapidly emerging as a versatile platform for manipulating light at the deep subwavelength scale. Here we show numerically that strong optical near-field forces can be generated under the illumination of mid-IR light when dielectric nanoparticles are located in the vicinity of a nanostructured graphene film. These near-field forces are attributed to the excitation of the graphene’s plasmonic mode. The optical forces can generate an efficient optical trapping potential for a 10-nm-diameter dielectric particle when the light intensity is only about about 4.4 mW/μm2 and provide possibilities for a new type of plasmonic nano-tweezers. Graphene plasmonic tweezers can be potentially exploited for optical manipulation of nanometric biomolecules and particles. Moreover, the optical trapping/tweezing can be combined with biosensing and provide a versatile platform for studing biology and chemistry with mid-IR light. PMID:27905527

  16. An inspection of force reduction in high force electromagnetic tweezers made of FeCo-V foil by laser cutting

    NASA Astrophysics Data System (ADS)

    Chen, La; Offenhäusser, Andreas; Krause, Hans-Joachim

    2015-09-01

    One of the main goals in the design of magnetic tweezers is to obtain a high force output. In general, the force can be enhanced by adopting materials with high saturation magnetization and by using small sharp structures as magnetic pole tips. However, the practically achieved saturation forces are usually lower than predicted values. In this article, we inspect this issue in detail both by experiments and simulations. Our results show that the observed force reduction can be ascribed to two factors: magnetic performance deterioration near the cutting edges of the tips and a 3D geometrical effect. The high power laser used in cutting causes segregation and morphological roughness near the cutting edge. Moreover, the geometry of the magnetic tips plays an important role regarding the force behavior. As a matter of fact, there is a trade-off among high force, maneuverability, throughput, and manufacturing issues in practical design of magnetic tweezers.

  17. Towards nano-optical tweezers with graphene plasmons: Numerical investigation of trapping 10-nm particles with mid-infrared light

    NASA Astrophysics Data System (ADS)

    Zhang, Jianfa; Liu, Wenbin; Zhu, Zhihong; Yuan, Xiaodong; Qin, Shiqiao

    2016-12-01

    Graphene plasmons are rapidly emerging as a versatile platform for manipulating light at the deep subwavelength scale. Here we show numerically that strong optical near-field forces can be generated under the illumination of mid-IR light when dielectric nanoparticles are located in the vicinity of a nanostructured graphene film. These near-field forces are attributed to the excitation of the graphene’s plasmonic mode. The optical forces can generate an efficient optical trapping potential for a 10-nm-diameter dielectric particle when the light intensity is only about about 4.4 mW/μm2 and provide possibilities for a new type of plasmonic nano-tweezers. Graphene plasmonic tweezers can be potentially exploited for optical manipulation of nanometric biomolecules and particles. Moreover, the optical trapping/tweezing can be combined with biosensing and provide a versatile platform for studing biology and chemistry with mid-IR light.

  18. Measurement of Macrophage Adhesion at Various pH Values by Optical Tweezers with Backward-Scattered Detection

    NASA Astrophysics Data System (ADS)

    Yi-Jr Su,; Long Hsu,

    2010-07-01

    Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 μm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 μm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection.

  19. Measurement of Macrophage Adhesion at Various pH Values by Optical Tweezers with Backward-Scattered Detection

    NASA Astrophysics Data System (ADS)

    Su, Yi-Jr; Hsu, Long

    2010-07-01

    Optical tweezers have emerged as a powerful tool with broad applications in biology and physics. In force-measuring applications, the trapped bead position is usually accurately determined by forward-scattered detection. The current study discusses both backward-scattered detection and forward-scattered detection related to the linear detection range for a 3 µm bead and the distance between the two laser system focuses, confirming the optimum positions of the two focuses. The result indicates that the linear detection range of backward-scattered detection is longer than the forward-scattered one. Finally, this work investigates real-time adhesion force measurements between human macrophages and 3 µm trapped beads coated with lipopolysaccharides at various pH values by optical tweezers with backward-scattered detection.

  20. 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.