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1

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

PubMed

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

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

2008-01-01

2

Energy transfer and conformational dynamics in Zn-porphyrin dendrimers  

NASA Astrophysics Data System (ADS)

The energy transfer within a series of Zn-porphyrin appended dendrimers was studied by means of time-resolved fluorescence anisotropy. We show that the energy transfer process between the Zn-porphyrin units in the dendrimers is limited to a maximum of four porphyrin units. At 200 K, the energy transfer process takes place on a 100-ps time scale, and can be modeled by Förster theory. Our results at room temperature further show that the porphyrin units are very mobile within the dendrimer, exhibiting rotational dynamics similar to that of a monomeric building block.

Larsen, Jane; Andersson, Johan; Polívka, Tomáš; Sly, Joseph; Crossley, Maxwell J.; Sundström, Villy; Åkesson, Eva

2005-02-01

3

Host-Guest Interactions in ExBox4+  

E-print Network

The host-guest interaction between benzene or azine with the newly synthesized ExBox4+ complex is studied with the help of DFT. The solvent phase interaction energy is found to decrease with gradual substitution of methine group of guest benzene ring with N atom in the resultant azine@ExBox4+ complex. The nature of bonding interaction is studied with the help of newly developed NCI plot program package along with energy decomposition analysis (EDA) and charge decomposition analysis (CDA). The interaction is mostly pi-type van der Waals interaction.

Das, Ranjita

2014-01-01

4

A new photo-switchable "on-off" host-guest system.  

PubMed

A new photo-switchable "on-off" host-guest system comprising cucurbit[7]uril (CB[7]) and a photoresponsive cinnamamide derivative (trans-(3-phenyl-acryloylamino)-acetic acid, E-1) is studied. The cinnamamide derivative and CB[7] forms a stable 1 : 1 host-guest complex (CB[7]·E-1) with a high binding constant (K = 2.1 × 10(4) M(-1)). Irradiation of UV light (300 nm) to an aqueous solution of CB[7]·E-1 induces the E- to Z-conformational change of the cinnamamide derivative, which then leads to the dissociation of the complex as evidenced by UV-visible and (1)H-NMR spectroscopy. The reverse process, photo-induced host-guest complex formation between CB[7] and Z-1 is achieved by irradiation of UV light at 254 nm. The photo-switchable "on-off" host-guest system shows high reversibility and switching efficiency, which makes it potentially useful in designing photoresponsive gating systems. PMID:21455508

Kim, Youngkook; Ko, Young Ho; Jung, Minseon; Selvapalam, Narayanan; Kim, Kimoon

2011-09-01

5

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

ERIC Educational Resources Information Center

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…

Mendicuti, Francisco; Gonzalez-Alvarez, Maria Jose

2010-01-01

6

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

PubMed

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

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

2014-07-15

7

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

8

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

PubMed

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

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

2012-07-01

9

Theranostic systems assembled in situ on demand by host-guest chemistry  

Microsoft Academic Search

Theranostic systems have been explored extensively for a diagnostic therapy in the forms of polymer conjugates, implantable devices, and inorganic nanoparticles. In this work, we report theranostic systems in situ assembled by host-guest chemistry responding to a request. As a model theranostic system on demand, cucurbit[6]uril-conjugated hyaluronate (CB[6]-HA) was synthesized and decorated with FITC-spermidine (spmd) and\\/or formyl peptide receptor like

Hyuntae Jung; Kyeng Min Park; Jeong-A. Yang; Eun Ju Oh; Don-Wook Lee; Sung Ho Ryu; Sei Kwang Hahn; Kimoon Kim

2011-01-01

10

Reversible single-chain selective point folding via cyclodextrin driven host-guest chemistry in water.  

PubMed

In the present communication we introduce a new platform technology for the reversible folding of single polymer chains in aqueous environment on the basis of cyclodextrin (CD) host-guest chemistry and controlled radical polymerization protocols. The single-chain folding of adamantyl-?-CD ?-?-functionalized poly(N,N-dimethylacrylamide) and its reversion at elevated temperatures were monitored by DLS and nuclear Overhauser enhancement spectroscopy (NOESY). PMID:24850295

Willenbacher, Johannes; Schmidt, Bernhard V K J; Schulze-Suenninghausen, David; Altintas, Ozcan; Luy, Burkhard; Delaittre, Guillaume; Barner-Kowollik, Christopher

2014-07-01

11

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

PubMed Central

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

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

2012-01-01

12

Chemical-responsive control of lower critical solution temperature behavior by pillar[10]arene-based host-guest interactions.  

PubMed

A new water-soluble thermoresponsive pillar[10]arene with tri(ethylene oxide) groups was synthesized and its cloud point could be reversibly controlled based on a chemical-responsive host-guest system. PMID:25252148

Chi, Xiaodong; Xue, Min

2014-10-14

13

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

PubMed

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

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

2014-07-15

14

Selective host-guest interactions of a transformable coordination capsule/tube with fullerenes.  

PubMed

An M2L4 coordination capsule or an M2L2 coordination tube was selectively formed by the combination of Hg(II) hinges and bent bispyridine ligands. The two structures reversibly interconvert at room temperature in response to modulation of the metal-to-ligand ratio and exhibit different host-guest interaction behavior. The capsule alone encapsulates large spherical molecules, fullerenes C60 and C70, and the bound guests are released upon capsule-to-tube transformation by the simple addition of metal ions. PMID:24590625

Kishi, Norifumi; Akita, Munetaka; Yoshizawa, Michito

2014-04-01

15

Reversible phase transfer of nanoparticles based on photoswitchable host-guest chemistry.  

PubMed

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

Peng, Lu; You, Mingxu; Wu, Cuichen; Han, Da; Öçsoy, Ismail; Chen, Tao; Chen, Zhuo; Tan, Weihong

2014-03-25

16

Investigation on a host-guest inclusion system by ?-cyclodextrin derivative and its analytical application.  

PubMed

The host-guest inclusion system of ethyl substituted ?-cyclodextrin (DE-?-CD) with mangiferin (MA) was investigated by fluorescence spectra in solution. The results showed that the MA was encapsulated in the DE-?-CD's cavity to form a 2:1 stoichiometry host-guest inclusion complex (DE-?-CD/MA) and the inclusion constant (K=3.04×10(6)L(2)/mol(2)) was confirmed by the typical double reciprocal plots. Furthermore, several experimental conditions were optimized in order to obtain the maximum fluorescence signal. In addition, the thermodynamic parameters, Gibbs free energy (?G°), enthalpy change (?H°) and entropy change (?S°) of DE-?-CD/MA were obtained by the Van't Hoff equation. A spectrofluorimetric method for the determination of MA in solution in the presence of DE-?-CD was developed based on the remarkable enhancement of the fluorescence intensity of MA. The linear range was 2.00×10(-8)-7.00×10(-6)mol/L and the detection limit was 4.05×10(-9)mol/L. The proposed method was successfully applied to the analysis of MA in serum with the satisfactory result. PMID:21273073

Huang, Lizhen; He, Jiang; Lu, Ruihua; Ge, Xia; Guo, Jingjing

2011-02-15

17

Cytomimetic large-scale vesicle aggregation and fusion based on host-guest interaction.  

PubMed

Herein, we have shown a large-scale cell-mimetic (cytomimetic) aggregation process by using cell-sized polymer vesicles as the building blocks and intervesicular host-guest molecular recognition interactions as the driving force. We first prepared the hyperbranched polymer vesicles named branched polymersomes (BPs) around 5-10 ?m through the aqueous self-assembly of a hyperbranched multiarm copolymer of HBPO-star-PEO [HBPO = hyperbranched poly(3-ethyl-3-oxetanemethanol); PEO = poly(ethylene oxide)]. Subsequently, adamantane-functionalized BPs (Ada-BPs) or ?-cyclodextrin-functionalized BPs (CD-BPs) were prepared through the coassembly of HBPO-star-PEO and Ada-modified HBPO-star-PEO (HBPO-star-PEO-Ada), or of HBPO-star-PEO and CD-modified HBPO-star-PEO (HBPO-star-PEO-CD), respectively. Macroscopic vesicle aggregates were obtained by mixing CD-BPs and Ada-BPs. The intervesicular host-guest recognition interactions between ?-CD units in CD-BPs and Ada units in Ada-BPs, which were proved by (1)H nuclear Overhauser effect spectroscopy (NOESY) spectrum and the fluorescence probe method, are responsible for the vesicle aggregation. Additionally, the vesicle fusion events happened frequently in the process of vesicle aggregation, which were certified by double-labeling fluorescent assay, real-time observation, content mixing assay, and component mixing assay. PMID:22129210

Jin, Haibao; Liu, Yong; Zheng, Yongli; Huang, Wei; Zhou, Yongfeng; Yan, Deyue

2012-01-31

18

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

PubMed

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

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

2013-10-14

19

Host-guest interactions between molecular clips and multistate systems based on flavylium salts.  

PubMed

Flavylium salts contain the basic structure and show a pH-dependent sequence of reactions identical to natural anthocyanins, which are responsible for most of the red and blue colors of flowers and fruits. In this work we investigated the effect of the water-soluble molecular clips C1 and C2 substituted by hydrogen phosphate or sulfate groups on the stability and reactions of the flavylium salts 1-4 by the use of UV-vis absorption, fluorescence, and NMR spectroscopy as well as of the time-resolved pH jump and flash photolysis methods. Clip C1 forms highly stable host-guest complexes with the flavylium salts 1 and 2 and the quinoidal base 3A in methanol. The binding constants were determined by fluorometric titration to be log K = 4.1, 4.7, and 5.6, respectively. Large complexation-induced (1)H NMR shifts of guest signals, Delta delta(max), indicate that in the case of the flavylium salts 1 and 2 the pyrylium ring and in the case of the quinoidal base 3A the o-hydroxyquinone ring are preferentially bound inside the clip cavity. Due to the poor solubility of these host-guest complexes in water, the association constants could be only determined in highly diluted aqueous solution by UV-vis titration experiments for the complex formation of clip C1 with the flavylium salt 3AH(+) at pH = 2 and the quinoidal base 3A at pH = 5.3 to be log K = 4.9 for both complexes. Similar results were obtained for the formation of the complexes of the sulfate-substituted clip C2 with flavylium salt 4AH(+) and its quinoidal base 4A which are slightly better soluble in water (log K = 4.3 and 4.0, respectively). According to the kinetic analysis (performed by using the methods mentioned above) the thermally induced trans-cis chalcone isomerization (4Ct --> 4Cc) and the H(2)O addition to flavylium cation 4AH(+) followed by H(+) elimination leading to hemiketal 4B are both retarded in the presence of clip C2, whereas the photochemically induced trans-cis isomerization (4Ct --> 4Cc) is not affected by clip C2. The results presented here are explained with dominating hydrophobic interactions between the molecular clips and the flavylium guest molecules. The other potential interactions (ion-ion, cation-pi, pi-pi, and CH-pi), which certainly determine the structures of these host-guest complexes to a large extent, seem to be of minor importance for their stability. PMID:19485378

Gomes, Raquel; Parola, A Jorge; Bastkowski, Frank; Polkowska, Jolanta; Klärner, Frank-Gerrit

2009-07-01

20

Expansion-contraction of photoresponsive artificial muscle regulated by host-guest interactions  

PubMed Central

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

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

2012-01-01

21

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

NASA Astrophysics Data System (ADS)

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

Adames Prada, Rosana; Ardila Vargas, Angel Miguel

2014-12-01

22

Host-guest complexation of oxicam NSAIDs with beta-cyclodextrin.  

PubMed

Spectroscopic and molecular modeling techniques have been employed to study the interaction of the oxicam group of nonsteroidal antiinflammatory drugs (NSAIDs) with a polysaccharide such as beta-cyclodextrin (beta-cd). beta-cd is a good drug delivery system and is known to reduce harmful side effects of these drugs in the gastrointestinal tract and to increase their clinical efficacy. A detailed understanding of such host-guest interaction helps in designing a better drug delivery system coupled with increased therapeutic potential. However, there exists a controversy as to which prototropic form of piroxicam, a drug belonging to the oxicam group, becomes encapsulated in the host and also the stoichiometry of binding. In this study, we have revisited that controversy using steady state fluorescence, absorption, fluorescence anisotropy measurements, and molecular modeling techniques. In addition, we have for the first time studied the interactions of two other oxicam drugs, viz. tenoxicam and meloxicam, with beta-cd in aqueous solution. In all cases the neutral forms of these drugs were incorporated in the beta-cd cavity with a binding stoichiometry of 1:1 host : guest. The values of the binding constants for piroxicam, meloxicam, and tenoxicam with beta-cyclodextrin are 134 +/- 21, 114 +/- 15, and 115 +/- 13 M(-1), respectively. Molecular modeling studies show that the minimum energy configuration gives favorable interaction energy between the host and the guest in the complex with 1:1 stoichiometry when the conjugated rings of the drugs are inside the hydrophobic bucket-like cavity of beta-cd and the third ring is exposed to the solvent. PMID:15372483

Banerjee, Rona; Chakraborty, Hirak; Sarkar, Munna

2004-11-01

23

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

PubMed Central

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

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

2008-01-01

24

The formation of host-guest complexes between surfactants and cyclodextrins.  

PubMed

Cyclodextrins are able to act as host molecules in supramolecular chemistry with applications ranging from pharmaceutics to detergency. Among guest molecules surfactants play an important role with both fundamental and practical applications. The formation of cyclodextrin/surfactant host-guest compounds leads to an increase in the critical micelle concentration and in the solubility of surfactants. The possibility of changing the balance between several intermolecular forces, and thus allowing the study of, e.g., dehydration and steric hindrance effects upon association, makes surfactants ideal guest molecules for fundamental studies. Therefore, these systems allow for obtaining a deep insight into the host-guest association mechanism. In this paper, we review the influence on the thermodynamic properties of CD-surfactant association by highlighting the effect of different surfactant architectures (single tail, double-tailed, gemini and bolaform), with special emphasis on cationic surfactants. This is complemented with an assessment of the most common analytical techniques used to follow the association process. The applied methods for computation of the association stoichiometry and stability constants are also reviewed and discussed; this is an important point since there are significant discrepancies and scattered data for similar systems in the literature. In general, the surfactant-cyclodextrin association is treated without reference to the kinetics of the process. However, there are several examples where the kinetics of the process can be investigated, in particular those where volumes of the CD cavity and surfactant (either the tail or in special cases the head group) are similar in magnitude. This will also be critically reviewed. PMID:24011696

Valente, Artur J M; Söderman, Olle

2014-03-01

25

Molecular tweezers with varying anions: a comparative study.  

PubMed

Selective binding of the phosphate-substituted molecular tweezer 1a to protein lysine residues was suggested to explain the inhibition of certain enzymes and the aberrant aggregation of amyloid petide A?42 or ?-synuclein, which are assumed to be responsible for Alzheimer's and Parkinson's disease, respectively. In this work we systematically investigated the binding of four water-soluble tweezers 1a-d (substituted by phosphate, methanephosphonate, sulfate, or O-methylenecarboxylate groups) to amino acids and peptides containing lysine or arginine residues by using fluorescence spectroscopy, NMR spectroscopy, and isothermal titration calorimetry (ITC). The comparison of the experimental results with theoretical data obtained by a combination of QM/MM and ab initio(1)H NMR shift calculations provides clear evidence that the tweezers 1a-c bind the amino acid or peptide guest molecules by threading the lysine or arginine side chain through the tweezers' cavity, whereas in the case of 1d the guest molecule is preferentially positioned outside the tweezer's cavity. Attractive ionic, CH-?, and hydrophobic interactions are here the major binding forces. The combination of experiment and theory provides deep insight into the host-guest binding modes, a prerequisite to understanding the exciting influence of these tweezers on the aggregation of proteins and the activity of enzymes. PMID:23750919

Dutt, Som; Wilch, Constanze; Gersthagen, Thomas; Talbiersky, Peter; Bravo-Rodriguez, Kenny; Hanni, Matti; Sánchez-García, Elsa; Ochsenfeld, Christian; Klärner, Frank-Gerrit; Schrader, Thomas

2013-07-01

26

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

SciTech Connect

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.

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

2008-07-01

27

Thermodynamics of Host-Guest Interactions between Fullerenes and a Buckycatcher.  

PubMed

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

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

2014-10-16

28

Coupled-cluster interaction energies for 200-atom host-guest systems.  

PubMed

We have developed a method to calculate interaction energies of large systems (such as host-guest or even protein-ligand systems) at the local coupled-cluster with singles, doubles, and perturbative triples level, and with extrapolation to the limit of a complete basis set. The method is based on the polarizable multipole interactions with supermolecular pairs molecular fractionation approach, which combines a pairwise quantum-mechanical evaluation of the short-range interactions with a polarizable multipole treatment of many-body effects. The method is tested for nine guest molecules binding to an octa-acid host (in total 198-207 atoms), as part of the SAMPL4 blind challenge. From the test calculations, the accuracy of the approach is found to be 10 kJ?mol(-1) or better. Comparison with dispersion-corrected density functional theory reveals that the latter underestimates the dispersion contribution for this type of system, which leads to a difference in the ranking of the ligands. PMID:25262989

Andreji?, Milica; Ryde, Ulf; Mata, Ricardo A; Söderhjelm, Pär

2014-10-20

29

Supramolecular hybrid hydrogel based on host-guest interaction and its application in drug delivery.  

PubMed

In this work, we developed a simple, novel method for constructing gold nanocomposite supramolecular hybrid hydrogels for drug delivery, in which gold nanocrystals were utilized as building blocks. First, methoxypoly(ethylene glycol) thiol (mPEG-SH, molecular weight (MW) = 5 K) capped gold nanocrystals (nanospheres and nanorods) were prepared via a facile one-step ligand-exchange procedure. Then, the homogeneous supramolecular hybrid hydrogels were formed, after adding ?-cyclodextrin (?-CD) into PEG-modified gold nanocrystal solutions, due to the host-guest inclusion. Both gold nanoparticles and inclusion complexes formed between ?-CD and PEG chain provided the supra-cross-links, which are beneficial to the gelation formation. The resulting hybrid hydrogels were fully characterized by a combination of techniques including X-ray diffraction, rheology studies, and scanning electron microscopy. Meanwhile, the hybrid hydrogel systems demonstrated unique reversible gel-sol transition properties at a certain temperature caused by the temperature-responsive reversible supramolecular assembly. The drug delivery applications of such hybrid hydrogels were further investigated in which doxorubicin was selected as a model drug for in vitro release, cytotoxicity, and intracellular release studies. We believe that the development of such hybrid hydrogels will provide new and therapeutically useful means for medical applications. PMID:25372156

Yu, Jing; Ha, Wei; Sun, Jian-Nan; Shi, Yan-Ping

2014-11-26

30

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

PubMed

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

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

2012-09-15

31

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

32

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

SciTech Connect

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.

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

2008-02-16

33

Laser spectroscopic study of cold host-guest complexes of crown ethers in the gas phase.  

PubMed

A laser spectroscopic study on the structure and dynamics of cold host-guest inclusion complexes of crown ethers (CEs) with various neutral and ionic species in the gas phase is presented. The complexes with neutral guest species are formed by using supersonic free jets, and those with ionic species are generated with electrospray ionization combined with a cold 22-pole ion trap. For CEs, various sizes of 3n-crown-n ethers (n=4, 5, 6, and 8) and their benzene-substituted species are used. For the guest species, water, methanol, ammonia, acetylene, and phenol are employed as neutral guest species, and for charged guest species, alkali metal cations are chosen. The electronic and vibrational spectra of the complexes are measured by using various laser spectroscopic methods; electronic spectra for the neutral complexes are measured by laser-induced fluorescence. Discrimination of different species such as conformers is performed by ultraviolet-ultraviolet hole-burning spectroscopy. The vibrational spectra of selected species are observed by infrared-ultraviolet double-resonance (IR-UV DR) spectroscopy. For the ionic complexes, ultraviolet photodissociation and IR-UV DR spectroscopy are applied. The complex structures are determined by comparing the observed spectra with those of possible structures obtained by density functional theory calculations. How the host CEs change their conformation or which conformer prefers to form unique inclusion complexes are discussed. These results reveal the key interactions for forming special complexes leading to molecular recognition. PMID:23203940

Inokuchi, Yoshiya; Kusaka, Ryoji; Ebata, Takayuki; Boyarkin, Oleg V; Rizzo, Thomas R

2013-03-18

34

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

NASA Astrophysics Data System (ADS)

The formation of host-guest inclusion complex of 2,4-dinitrophenol (2,4-DNP) with nano-hydrophobic cavity of ?-cyclodextrin (?-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 ?-CD and the ground state acidity constant (pKa) of host-guest inclusion complex (2,4-DNP-?-CD) were studied. The binding constant of inclusion complex at 303 K was calculated using Benesi-Hildebrand plot and thermodynamic parameter (?G) was also calculated. The solid inclusion complex formation between ?-CD and 2,4-DNP was confirmed by 1H NMR, FT-IR, XRD and SEM analysis. A schematic representation of this inclusion process is proposed by molecular docking studies using PatchDock server.

Srinivasan, K.; Stalin, T.; Sivakumar, K.

35

Thermally induced reversible conformational changes in the host–guest adduct of meso-tetramethyltetrakis(ethyl)calix[4]pyrrole  

Microsoft Academic Search

The binding of methanol, ethanol, and N,N-dimethylformamide to meso-tetramethyltetrakis(ethyl)calix[4]pyrrole (1) was investigated in both solid and solution with the exhibition of multi-fashion hydrogen bonding as shown by X-ray crystallography. The thermodynamic stability of these host–guest inclusion complexes were determined by exploiting TGA and DTA. An unexpected conformational change in 1·2EtOH occurred by thermal induction.

Soumen Dey; Kuntal Pal; Sabyasachi Sarkar

2007-01-01

36

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

PubMed

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

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

2014-09-10

37

Host-Guest Interactions between Calixarenes and Cp(2)NbCl(2).  

PubMed

The possible inclusion complexes of Cp(2)NbCl(2) into calixarenes hosts have been investigated. The existence of a true inclusion complex in the solid state was confirmed by a combination of NMR, ab-initio calculations, thermogravimetric analysis, FTIR, Raman and PXRD. Ab-initio calculations, (1)H NMR solution and solid state (13)C CP MAS NMR results demonstrated that p-sulfonic calix[6]arene does form an inclusion complex with Cp(2)NbCl(2). Raman spectroscopy showed, for the inclusion compound of p-sulfonic calix[6]arene-Cp(2)NbCl(2), a band between 500-850 cm(-1) characteristic of Nb-O vibration. This result suggests that Nb(V) may engage in coordination with the oxygen of the sulfonate group, as part of the host-guest interaction. However, it is important to mention that the niobocene dichloride (Cp(2)NbCl(2)) dissolves in water and undergoes oxidation and hydrolysis processes to yield Cp(2)NbCl(2)(OH) species. For that reason this band does not exclude that the Nb-O band belongs to Cp(2)NbCl(2)(OH). Solid State (13)C CP MAS NMR and solution (1)H NMR spectroscopies together with ab-initio results showed that Cp(2)NbCl(2) is included in the p-sulfonic calix[6]arene cavity, with both Cp rings inside the cavity. In contrast, the solution (1)H NMR results demonstrated that calix[6]arene does not form inclusion complex with Cp(2)NbCl(2) in CDCl(3) solution. Cp(2)NbCl(2) is not included in the calix[6]arene cavity, possibly due to the lack of sulfonate heads which promote Nb-O interactions and assist the inclusion of Cp(2)NbCl(2) into the cavity. PMID:21709809

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

2011-07-01

38

Formation of host-guest complexes of ?-cyclodextrin and perfluorooctanoic acid.  

PubMed

Structural characterization and dynamic properties of solid-state inclusion complexes of ?-cyclodextrin (?-CD) with perfluorooctanoic acid (PFOA) were investigated by (19)F/(13)C solid-state and (19)F/(1)H solution NMR spectroscopy. The complexes in the solid state were prepared using dissolution and slow cool methods, where thermal analyses (DSC and TGA), PXRD, and FT-IR results provided complementary support that inclusion complexes were formed between ?-CD and PFOA with variable stoichiometry and inclusion geometry. (19)F DP (direct polarization) and (13)C CP (cross-polarization) with magic-angle spinning (MAS) solids NMR, along with (19)F/(1)H solution NMR were used to characterize the complexes in the solid and solution phases, respectively. The dynamics of the guest molecules in the inclusion complexes (ICs) were studied using variable temperature (VT) (19)F DP/MAS NMR experiments in the solid state. The guest molecules were observed to be in several different molecular environments, providing strong evidence of variable host-guest stoichiometry and inclusion geometry, in accordance with the preparation method of the complex and the conformational preference of PFOA. It was concluded from PXRD that ?-CD and PFOA form inclusion complexes with "channel-type" structures. Variable spin rate (VSR) (19)F DP/MAS NMR was used to assess the phase purity of the complexes, and it was revealed that slow cooling resulted in relatively pure phases. In the solution state, (1)H and (19)F NMR complexation-induced chemical shifts (CISs) of ?-CD and PFOA, respectively, provided strong support for the formation of 1:1 and 2:1 ?-CD/PFOA inclusion complexes. The dynamics of the guest molecule in the ?-CD/PFOA complexes in D(2)O solutions were probed using VT (19)F NMR and revealed some guest conformational and exchange dynamics as a function of temperature and the relative concentrations of the host and guest. PMID:21688796

Karoyo, Abdalla H; Borisov, Alex S; Wilson, Lee D; Hazendonk, Paul

2011-08-11

39

The synthesis and host-guest applications of synthetic receptor molecules  

NASA Astrophysics Data System (ADS)

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.

Osner, Zachary R.

40

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

PubMed

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

Muddana, Hari S; Gilson, Michael K

2012-05-01

41

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

PubMed

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

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

2009-02-01

42

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

PubMed

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

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

2014-01-01

43

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

PubMed Central

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

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

2013-01-01

44

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

PubMed

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

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

2013-07-15

45

Remote-Controlled Release of DNA in Living Cells via Simultaneous Light and Host-Guest Mediations.  

PubMed

Using photons as external triggers to realize remote-controlled release of oligonucleotide is superior to other intracellular or external stimulus. UV light is a valid photon-controlled manner due to high efficiency. However, further applications of these approaches in living cells are hampered by the large dose of UV-light irradiation. To address this issue, a simultaneous light and host/guest mediation was proposed in this paper. Gold nanoparticles (AuNPs) encoding with mercapto-?-cyclodextrin (?CD) served as a carried agent. Azobenzene (Azo), which was labeled on a releasing oligonucleotide, acted as a photochemically controlled switch. Ferrocene (Fc), an excellent guest for inclusion complexation by ?CD, serves as "enhancers" and shifts the equilibrium of the inclusion-exclusion process between trans-Azo and ?CD under UV-light irradiation, thus making the dose of UV-light irradiation reduced obviously. For further application, transfected green fluorescent protein (GFP)-expressing human lung cancer A549 cells were used to determine cellular uptake and gene silencing mediated by our constructed system in vivo. The results demonstrate that by employing Fc host-guest interaction, about 62.4% gene silencing was achieved within 30 min, which is significantly higher than that without Fc competition. Our strategy provides the potential for orthogonal DNA delivery and therapeutic activation that would be capable of achieving higher levels of site-specific activity and reduced amounts of side effects. PMID:25255368

Zheng, Jing; Nie, Yuhong; Yang, Sheng; Xiao, Yue; Li, Jishan; Li, Yinhui; Yang, Ronghua

2014-10-21

46

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

47

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

PubMed

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

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

2014-11-01

48

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

NASA Astrophysics Data System (ADS)

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

Chen, Lei; Yan, Bing

2014-10-01

49

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

PubMed

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

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

2014-11-12

50

Supramolecular polymeric micelles by the host-guest interaction of star-like calix[4]arene and chlorin e6 for photodynamic therapy.  

PubMed

A supramolecular drug delivery system has been developed via the self-assembly of a supramolecular amphiphilic polymer, which is constructed by the host-guest interaction of hydrophilic PEGylated calix[4]arene and hydrophobic photosensitizer chlorin e6. It provides a new strategy for the preparation of supramolecular polymeric micelles, and plays an important role in biological applications. PMID:21519601

Tu, Chunlai; Zhu, Lijuan; Li, Pingping; Chen, Yan; Su, Yue; Yan, Deyue; Zhu, Xinyuan; Zhou, Guoyu

2011-06-01

51

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

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…

Rood, Jeffrey A.; Henderson, Kenneth W.

2013-01-01

52

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

PubMed

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. PMID:22084029

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

2012-01-16

53

Long-lived charge separation in a rigid pentiptycene bis(crown ether)-Li(+)@C60 host-guest complex.  

PubMed

We report long-lived charge separation in a highly rigid host-guest complex of pentiptycene bis(crown ether) and Li(+)@C60, in which the pentiptycene framework is actively involved as an electron donor in a photoinduced electron-transfer process to the excited states of Li(+)@C60 through a rigid distance in the complex. PMID:25372926

Supur, Mustafa; Kawashima, Yuki; Ma, Ying-Xian; Ohkubo, Kei; Chen, Chuan-Feng; Fukuzumi, Shunichi

2014-12-25

54

Molecular simulation of hydroxypropyl-beta-cyclodextrin with hydrophobic selective Cox-II chemopreventive agent using host-guest phenomena.  

PubMed

The present investigation outlays the host-guest penetration of hydrophobic selective Cox-II chemopreventive agent, celecoxib (CXB), with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) using inclusion complexation phenomena. Phase solubility studies conducted at 37 degrees C and 25 degrees C revealed typical A(L)-type curve for the HP-beta-CD indicating the formation of soluble complexes. The inclusion complexes in the molar ratio of 1:1 and 2:1 (CXB-HP-beta-CD) were prepared by kneading technique. The formation of inclusion complexes and the molecular simulation of CXB protons with HP-beta-CD cavity in all samples were testified by 1H-NMR, DSC, powder-XRD, SEM and FTIR and UV/visible spectroscopy. The results of these studies indicated that complex (prepared by kneading method) in molar ratio of 1:1 exhibited better improvement in in vitro dissolution profiles as compared to 1:2 complex. Mean in vitro dissolution time indicated significant difference in the release profiles of CXB from complexes and physical mixtures as compared to pure CXB. PMID:21796941

Sinha, Vivek Ranjan; Nanda, Amita; Chadha, Renu; Goel, Honey

2011-01-01

55

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

PubMed Central

The synthetic host cucurbit[7]uril (CB[7]) binds aromatic guests or metal complexes with ultrahigh affinity compared with that typically displayed in protein–ligand binding. Due to its small size, CB[7] serves as an ideal receptor–ligand system for developing computational methods for molecular recognition. Here, we apply the recently developed variational implicit-solvent model (VISM), numerically evaluated by the level-set method, to study hydration effects in the high-affinity binding of the B2 bicyclo[2.2.2]octane derivative to CB[7]. For the unbound host, we find that the host cavity favors the hydrated state over the dry state due to electrostatic effects. For the guest binding, we find reasonable agreement to experimental binding affinities. Dissection of the individual VISM free-energy contributions shows that the major driving forces are water-mediated hydrophobic interactions and the intrinsic (vacuum) host–guest van der Waals interactions. These findings are in line with recent experiments and molecular dynamics simulations with explicit solvent. It is expected that the level-set VISM, with further refinement on the electrostatic descriptions, can efficiently predict molecular binding and recognition in a wide range of future applications. PMID:24039554

2013-01-01

56

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

PubMed

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

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

2014-02-01

57

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

PubMed

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

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

2009-11-01

58

Solvation energies of amino acid side chains and backbone in a family of host-guest pentapeptides.  

PubMed

Octanol-to-water solvation free energies of acetyl amino amides (Ac-X-amides) [Fauchère, J.L., & Pliska, V. (1983) Eur. J. Med. Chem. --Chim. Ther. 18,369] form the basis for computational comparisons of protein stabilities by means of the atomic solvation parameter formalism of Eisenberg and McLachlan [(1986) Nature 319, 199]. In order to explore this approach for more complex systems, we have determined by octanol-to-water partitioning the solvation energies of (1) the guest (X) side chains in the host-guest pentapeptides AcWL-X-LL, (2) the carboxy terminus of the pentapeptides, and (3) the peptide bonds of the homologous series of peptides AcWLm (m = 1-6). Solvation parameters were derived from the solvation energies using estimates of the solvent-accessible surface areas (ASA) obtained from hard-sphere Monte Carlo simulations. The measurements lead to a side chain solvation-energy scale for the pentapeptides and suggest the need for modifying the Asp, Glu, and Cys values of the "Fauchère-Pliska" solvation-energy scale fro the Ac-X-amides. We find that the unfavorable solvation energy of nonpolar residues can be calculated accurately by a solvation parameter of 22.8 +/- 0.8 cal/mol/A2, which agrees satisfactorily with the AC-X-amide data and thereby validates the Monte Carlo ASA results. Unlike the Ac-X-amide data, the apparent solvation energies of the uncharged polar residues are also largely unfavorable. This unexpected finding probably results, primarily, from differences in conformation and hydrogen bonding in octanol and buffer but may also be due to the additional flaking peptide bonds of the pentapeptides. The atomic solvation parameter (ASP) for the peptide bond is comparable to the ASP of the charged carboxy terminus which is an order of magnitude larger than the ASP of the uncharged polar side chains of the Ac-X-amides. The very large peptide bond ASP, -96 +/- 6 cal/mol/A2, profoundly affects the results of computational comparisons of protein stability which use ASPs derived from octanol-water partitioning data. PMID:8611495

Wimley, W C; Creamer, T P; White, S H

1996-04-23

59

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

SciTech Connect

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

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

2000-02-02

60

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

PubMed

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

Xing, Hao; Wei, Peifa; Yan, Xuzhou

2014-06-01

61

How to simulate affinities for host-guest systems lacking binding mode information: application to the liquid chromatographic separation of hexabromocyclododecane stereoisomers.  

PubMed

A novel approach for the simulation of host-guest systems by systematically scanning the host molecule's orientations within the guest cavity is presented along with a thermodynamic strategy for determining preferential binding modes and corresponding optimal interaction energies between host and guest molecules. By way of example, the elution order of hexabromocyclododecane stereoisomers from high performance liquid chromatography separation on a permethylated ?-cyclcodextrin stationary phase has been computed using classical molecular dynamics simulations with the explicit solvents water and acetonitrile. Comparison of estimated with experimental separation data reveals remarkable squared coefficients of correlation with R(2) = 0.87 and a very high correlation R(LOO2) = 0.72 using the leave-one-out cross-validation method and water as solvent. In particular, the approach presented shapes up as very robust in terms of the evaluated time range under consideration, reflecting well thermodynamic equilibria. These and further observations correlating with experimental results suggest the suitability of the underlying force fields and our multi-mode approach for the estimation of relative binding affinities for host-guest systems with unknown binding modes. PMID:21989956

Durmaz, Vedat; Weber, Marcus; Becker, Roland

2012-06-01

62

Femtosecond Optical Tweezers  

NASA Astrophysics Data System (ADS)

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).)

Peng, Jiahui; Wang, Lei; Sokolov, Alexei

2004-10-01

63

Optical tweezers: Theory and modelling  

NASA Astrophysics Data System (ADS)

Since their development in the 1980s, optical tweezers have become a widely used and versatile tool in many fields. Outstanding applications include the quantitative measurement of forces in cell biology and biophysics. Computational modelling of optical tweezers is a valuable tool in support of experimental work, especially quantitative applications. We discuss the theory, and the theoretical and computational modelling of optical tweezers.

Nieminen, Timo A.; du Preez-Wilkinson, Nathaniel; Stilgoe, Alexander B.; Loke, Vincent L. Y.; Bui, Ann A. M.; Rubinsztein-Dunlop, Halina

2014-10-01

64

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

PubMed

Two new metal pnictide halides, (Hg9.75 As5.5 )(GaCl4 )3 and (Hg13 Sb8 )(ZnBr4 )4 , have been prepared by solid-state reactions. Their structures feature 3D cationic host frameworks built of mercury pnictide polyhedra and form 1D tunnels filled with discrete guest halide polyanions; the guests and hosts are assembled by van der Waals interactions. Both complexes exhibit good single-crystal humidity sensitivity, with a humidity sensitivity factor as big as three orders of magnitude, a quick resistance response, fast recovery, and good reproducibility. This study provide a new way to design promising resistive humidity detectors by introducing van der Waals host-guest interactions into their structures. PMID:25110860

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

2014-10-01

65

Structure, vibrational analysis, and insights into host-guest interactions in as-synthesized pure silica ITQ-12 zeolite by periodic B3LYP calculations.  

PubMed

As-made and calcined ITQ-12 zeolites are structurally characterized by means of the analysis of their vibrational modes. The experimental IR spectra made on high crystalline samples are compared with accurate B3LYP periodic calculations performed with the CRYSTAL06 code. The fair agreement between both sets of data allows us to make a reliable assignment of the IR modes. Thanks to the detailed information provided by the theoretical calculations, the analysis of the IR intensities, the Born dynamic charges, and the whole set of vibrational frequencies at Gamma-point shed light on several aspects of the host-guest interaction, structure-direction issues, including the role of fluoride anions in allowing the crystallization of silica structures with strained double-four rings, and the role played by the framework flexibility. PMID:17718565

Zicovich-Wilson, Claudio Marcelo; San-Román, María Luisa; Camblor, Miguel Angel; Pascale, Fabien; Durand-Niconoff, José Sergio

2007-09-19

66

Self-assembled vehicle construction via boronic acid coupling and host-guest interaction for serum-tolerant DNA transport and pH-responsive drug delivery.  

PubMed

By exploiting boronic acid coupling and host-guest chemistry, a pH-responsive drug/gene co-delivery nanoplatform is designed for cancer treatments with the excellently serum-tolerant transfection activity and the capability to load and release hydrophobic drugs in an acidity-accelerated manner. Via boronate linkage, ?-CD is allowed to spontaneously attach onto phenylboronic-acid-modified oligoethylenimine (PEI1.8K-PB2.9 ) at neutral condition. The formed vehicle/DNA nanoformulation is thus surrounded densely by ?-CD moieties to biomimic the carbohydrate-rich cell surface, providing a novel approach to overcome serum-susceptible drawbacks frequently associated with synthetic gene carriers. PEI1.8K-PB2.9 -?-CD conjugates demonstrate significantly improved cell-biocompatibility and transfection activity over PEI1.8K-PB2.9 . Noticeably, serum-associated inhibition effect is negligible for PEI1.8K-PB2.9 -?-CD-mediated transfection whereas marked transfection reduction occurs for PEI25K and PEI1.8K-PB2.9 upon serum exposure. Consequently, PEI1.8K-PB2.9 -?-CDs afford much higher transfection efficiency, that is, 25-fold higher luciferase expression over PEI25K in presence of 30% serum. An anticancer drug of doxorubicin (DOX) is shown to be readily accommodated into the nanoformulation via host-guest chemistry and intracellularly co-delivered together with plasmid DNA. Due to the acidity-labile feature of boronate linkage, DOX/?-CD inclusion complexes would be mostly detached from the nanoformulation triggered by acidity, leading to faster drug release. Furthermore, drug inclusion does not alter the serum-compatible transfection efficiency of PEI1.8K-PB2.9 -?-CD. PMID:23983152

Yang, Bin; Jia, Huizhen; Wang, Xuli; Chen, Si; Zhang, Xianzheng; Zhuo, Renxi; Feng, Jun

2014-04-01

67

optical tweezers tractor beams  

E-print Network

tweezers (HOT) #12;setup (HOT) #12;griergroup @ nyu Dufresne group @ yale pre-calculated holograms find favourite setup... holograms. Why care? applications etc. Movies! #12;A. Ashkin, J. M. Dziedzic, J. E � flip holograms � move traps � correct for aberrations � 1D amplitude modulation #12;references A

68

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)

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

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

2013-05-01

69

Nanoscale Molecular Tweezers  

NSDL National Science Digital Library

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

70

Distinct host guest interaction and subdued fluorescence in a coordination network of 2,3,6,7,10,11-hexakis(phenylthio)triphenylene and silver(I) triflate  

NASA Astrophysics Data System (ADS)

This paper reports our recent efforts in using host-guest interactions to control the fluorescent properties of coordination networks containing polycyclic aromatic units. The polycyclic aromatic ligand 2,3,6,7,10,11-hexakis(phenylthio)triphenylene (HPhTT) coordinates with AgTf (Tf: trifluoromethanesulfonate) in nitrobenzene to form single crystals of a 2-D host network consisting of octameric (i.e., containing eight AgTf units) and dimeric AgTf moieties linked to the HPhTT molecules through the Ag-thioether coordination bonds. The HPhTT adopts a starburst and rather irregular conformation, which apparently contributes to the formation of empty space between the 2-D coordination networks. Such voids are occupied by the nitrobenzene guest molecules, resulting in distinct aromatic-aromatic stacking interactions with the triphenylene units (interplanar distances: 3.46 and 3.60 Å). In comparison to a previous Ag-HPhTT network with toluene as weaker-interacting guests, the current system shows a significantly suppressed fluorescent emission from the triphenylene core, apparently due to the quenching effect from the nitrobenzene guests.

Li, Kunhao; Huang, Guo; Xu, Zhengtao; Carroll, Patrick J.

2006-12-01

71

Spectral investigation and characterization of host-guest inclusion complex of 4,4'-methylene-bis(2-chloroaniline) with beta-cyclodextrin.  

PubMed

The host-guest inclusion complex of 4,4'-methylene-bis(2-chloroaniline) (MBCA) with beta-cyclodextrin (?-CD) was prepared by co-precipitation method and characterized using absorption, fluorescence, fourier transform infrared, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The spectral shifts revealed that the aniline ring of 4,4'-methylene-bis(2-chloroaniline) was entrapped in the beta-cyclodextrin cavity. Nano second time resolved fluorescence studies revealed that 4,4'-methylene-bis(2-chloroaniline) exhibits single exponential decay in aqueous medium and bi-exponential in beta-cyclodextrin medium confirmed the formation of 1:1 inclusion complex. The Gibbs free energy change of the complexation process was determined and the complexation process was spontaneous. The differential scanning calorimetry analysis showed that the thermal stability of 4,4'-methylene-bis(2-chloroaniline) was altered in the presence of beta-cyclodextrin. The implementation of molecular docking test confirmed that the complexation could reduce the energy of the system. A mechanism was proposed to explain the mode of inclusion in the inclusion process. PMID:25263927

Periasamy, R; Kothainayaki, S; Rajamohan, R; Sivakumar, K

2014-12-19

72

Physics in Action: Optical Tweezers  

NSDL National Science Digital Library

This website introduces the concept of an optical tweezer, a laser trap used to manipulate objects as small as single molecules. This site lists several applications of optical tweezers and explains their application in molecular biology. Diagrams and links provide further information.

2007-07-18

73

Interferometer Control of Optical Tweezers  

NASA Technical Reports Server (NTRS)

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.

Decker, Arthur J.

2002-01-01

74

Are electron tweezers possible?  

PubMed

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

Oleshko, Vladimir P; Howe, James M

2011-11-01

75

Gate-Opening Gas Adsorption and Host-Guest Interacting Gas Trapping Behavior of Porous Coordination Polymers under Applied AC Electric Fields.  

PubMed

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 (?'). 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 (??) 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. PMID:25120189

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

2014-09-01

76

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

PubMed

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

Ponce-Vargas, Miguel; Muñoz-Castro, Alvaro

2014-07-14

77

Magnetic Tweezers for the Measurement of Twist and Torque  

E-print Network

1 Magnetic Tweezers for the Measurement of Twist and Torque Authors: Jan n.h.dekker@tudelft.nl Corresponding author: Nynke H. Dekker Keywords: magnetic tweezers, magnetic torque tweezers, freely-orbiting magnetic tweezers, twist, torque

Dekker, Nynke

78

On chip shapeable optical tweezers  

PubMed Central

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

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

2013-01-01

79

Optical tweezers absolute calibration  

E-print Network

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 fifteen 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 spo...

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

2014-01-01

80

Distinct host-guest interaction and subdued fluorescence in a coordination network of 2,3,6,7,10,11-hexakis(phenylthio)triphenylene and silver(I) triflate  

SciTech Connect

This paper reports our recent efforts in using host-guest interactions to control the fluorescent properties of coordination networks containing polycyclic aromatic units. The polycyclic aromatic ligand 2,3,6,7,10,11-hexakis(phenylthio)triphenylene (HPhTT) coordinates with AgTf (Tf: trifluoromethanesulfonate) in nitrobenzene to form single crystals of a 2-D host network consisting of octameric (i.e., containing eight AgTf units) and dimeric AgTf moieties linked to the HPhTT molecules through the Ag-thioether coordination bonds. The HPhTT adopts a starburst and rather irregular conformation, which apparently contributes to the formation of empty space between the 2-D coordination networks. Such voids are occupied by the nitrobenzene guest molecules, resulting in distinct aromatic-aromatic stacking interactions with the triphenylene units (interplanar distances: 3.46 and 3.60 A). In comparison to a previous Ag-HPhTT network with toluene as weaker-interacting guests, the current system shows a significantly suppressed fluorescent emission from the triphenylene core, apparently due to the quenching effect from the nitrobenzene guests. - Graphical abstract: Well-defined host-guest interactions are observed and apparently lead to subdued fluorescence in a coordination network of 2,3,6,7,10,11-hexakis(phenylthio)triphenylene and silver(I) triflate.

Li Kunhao [Department of Chemistry, the George Washington University, 725 21st Street NW, Washington, DC 20052 (United States); Huang Guo [Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China); Xu Zhengtao [Department of Biology and Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong (China)]. E-mail: zhengtao@cityu.edu.hk; Carroll, Patrick J. [P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104-6323 (United States)

2006-12-15

81

Optical tweezers: 20 years on.  

PubMed

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. PMID:17090474

McGloin, David

2006-12-15

82

Optical tweezers for confocal microscopy  

NASA Astrophysics Data System (ADS)

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

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

2000-11-01

83

Magnetic Tweezers Instrumentation: We have used magnetic tweezers to study chromatin assembly and disassembly and RNA  

E-print Network

Magnetic Tweezers Instrumentation: We have used magnetic tweezers to study chromatin assembly and disassembly and RNA transcription. Magnetic tweezers surface magnetic bead F DNA external magnets F =kBT l/> l F x surface Instrumental set-up video camera beam condenser hollow bearing with magnet 90x oil

Leuba, Sanford

84

Nanoceria-triggered synergetic drug release based on CeO(2) -capped mesoporous silica host-guest interactions and switchable enzymatic activity and cellular effects of CeO(2).  

PubMed

Herein, a pH stimuli-responsive vehicle for intracellular drug delivery using CeO2 capped mesoporous silica nanoparticles (MSN) is reported. ?-Cyclodextrin-modified CeO2 nanoparticles could cap onto ferrocene-functionalized mesoporous silica through host-guest interactions. After internalization into A549 cells by a lysosomal pathway, the ferrocenyl moieties are oxidized to ferrocenium ions by CeO2 lids, which could trigger the uncapping of the CeO2 and cause the drugs release. Because of the pH-dependent toxicity, the CeO2 here behaves as a multi-purpose entity that not only acts as a lid but also exhibits a synergistic antitumor effect on cancer cells. Meanwhile, the cell protective effect of CeO2 nanoparticles alone is demonstrated, which ensures that the dissolved CeO2 nanoparticles can be non-toxic to normal cells. PMID:23630084

Xu, Can; Lin, Youhui; Wang, Jiasi; Wu, Li; Wei, Weili; Ren, Jinsong; Qu, Xiaogang

2013-12-01

85

Synthesis of a polyrotaxane-based macroporous polymer as stationary phase for capillary electrochromatography via host-guest complexation of N,N '-ethylenedianilinediacrylamide with statistically methylated beta-cyclodextrin.  

PubMed

A synthetic route to acrylamide-based monolithic stationary phases for CEC with rotaxane-type immobilized derivatized beta-CD was explored. N,N'-Ethylenedianilinediacrylamide was synthesized as the water-insoluble crosslinker forming water-soluble inclusion complexes with statistically methylated beta-CD. Mixed-mode stationary phases were synthesized by free radical copolymerization of the bisacrylamide-CD host-guest complex with water-soluble monomers and an additional water-soluble crosslinker in aqueous solution. Complex formation in solution and inclusion of the pseudorotaxane into the polymeric network (formation of a polyrotaxane architecture) were studied by means of (1)H-NMR chemical shift analysis, CD modified micellar EKC (CD-MEKC), 2D-NOESY spectroscopy, and solid state( 13)C-NMR spectroscopy. The presence of a mixed-mode selectivity of the stationary phase based on hydrophobic and hydrophilic interaction was confirmed by CEC with neutral polar and nonpolar solutes. PMID:18428178

Wahl, Annika; Al-Rimawi, Fuad; Schnell, Ingo; Kornysova, Olga; Maruska, Audrius; Pyell, Ute

2008-05-01

86

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

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 are discussed. PMID:18507446

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

2008-06-20

87

Characterising Conical Refraction Optical Tweezers  

E-print Network

Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focussing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focussing on the trap stiffness and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot but benefit from rotational control.

McDonald, Craig; Rafailov, Edik; McGloin, David

2014-01-01

88

Optical Tweezer as a Viscometer  

NASA Astrophysics Data System (ADS)

An optical tweezer (OT) has been widely used to study the mechanical properties of microscopic living biological systems like red blood cells. These studies are based on measurement of deformations caused by a force exerted directly or indirectly by an optical trap. The trap is usually pre-calibrated using Stokes viscous force of the suspension fluids for the biological system which is directly proportional to the viscosity of the fluids. Therefore, calibration of the trap depends on the viscosity of the fluid which depends on temperature. In this work, we have demonstrated that OT can be used to precisely measure the viscosity of biological fluids affected by temperature. Using a an infrared laser trap which is calibrated using silica sphere suspended in a distilled deionized water and measuring the power as function of escape velocity, we have measured the viscosities of a newborn and unborn bovine serum with a different concentration of antibodies.

Erenso, Daniel; Elrod, Samuel; Barns, Taylor; Farone, Anthony; Farone, Mary

2009-03-01

89

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

PubMed Central

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

Neuman, Keir C.; Nagy, Attila

2012-01-01

90

Micro magnetic tweezers for nanomanipulation inside live cells  

Microsoft Academic Search

This study reports the design, realization, and characterization of a multi-pole magnetic tweezers that enables us to maneuver small magnetic probes inside living cells. So far, magnetic tweezers can be divided into two categories: I), tweezers that allow the exertion of high forces but consist of only one or two poles and therefore are capable of only exerting forces in

Vries de A. H; G. E. Krenn; Driel van R; J. S. Kanger

2005-01-01

91

Micro Magnetic Tweezers for Nanomanipulation Inside Live Cells  

Microsoft Academic Search

This study reports the design, realization, and characterization of a multi-pole magnetic tweezers that enables us to maneuver small magnetic probes inside living cells. So far, magnetic tweezers can be divided into two categories: I), tweezers that allow the exertion of high forces but consist of only one or two poles and therefore are capable of only exerting forces in

Anthony H. B. de Vries; Bea E. Krenn; Roel van Driel; Johannes S. Kanger

2005-01-01

92

Designing single-beam multitrapping acoustical tweezers  

E-print Network

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

Silva, Glauber T

2014-01-01

93

Applications of optical tweezers to optofluidics  

NASA Astrophysics Data System (ADS)

We explore the possibility of using optical tweezers to enable all optical control of optofluidic circuits. Optically trapped microspheres can be used as microlenses for optical signal switching and steering. By using cantilevers instead of microspheres we provide a method for robust and stable placement of switching elements in the optofluidic circuits. Cantilevers made of tapered optical fiber and polydimethyl siloxane are demonstrated. We also show that it is possible to use transverse optical tweezer beams to load silica beads into the hollow core photonic crystal fibers for tuning their transmission properties.

Cronin-Golomb, M.; Domachuk, P.; Mägi, E. C.; Perry, H.; Omenetto, F.; Eggleton, B. J.

2006-08-01

94

Holographic optical tweezers in the Fresnel regime  

Microsoft Academic Search

We present a flexible setup for steering of laser tweezers using a high resolution spatial light modulator (SLM). Moving of e.g. trapped cells in the focal plane of the microscope objective is possible without the need for time consuming re-calculation of holograms. Numerous light spots or other modes like the so called \\

Alexander Jesacher; Severin Furhapter; Stefan Bernet; Monika Ritsch-Marte

2004-01-01

95

Independent trapping and manipulation of microparticles using dexterous acoustic tweezers  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

96

Simultaneous calibration of optical tweezers spring constant and position  

E-print Network

. Howard, F. S. Pavone, F. J¨ulicher, and H. Flyvbjerg,"Calibration of optical tweezers with positional using acousto-optic deflectors," Rev. Sci. Instrum. 77, 013704 (2006). 9. K. Berg-Sørensen, L. B for optical tweezers," J. Appl. Phys. 93, 3167­3176 (2003). 10. K. Berg-Sørensen, and H. Flyvbjerg, "Power

Paris-Sud XI, Université de

97

Optical Tweezers in Colloid and Interface Science David G. Grier  

E-print Network

Optical Tweezers in Colloid and Interface Science David G. Grier The James Franck Institute with radiation pressure, otherwise known as optical trapping, has emerged as a powerful experimental tool of a particular trapping technique known colloquially as ``optical tweezers.'' Even though the theory of optical

Grier, David

98

Investigating hydrodynamic synchronisation using holographic optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

99

Micro magnetic tweezers for nanomanipulation inside live cells.  

PubMed

This study reports the design, realization, and characterization of a multi-pole magnetic tweezers that enables us to maneuver small magnetic probes inside living cells. So far, magnetic tweezers can be divided into two categories: I), tweezers that allow the exertion of high forces but consist of only one or two poles and therefore are capable of only exerting forces in one direction; and II), tweezers that consist of multiple poles and allow exertion of forces in multiple directions but at very low forces. The magnetic tweezers described here combines both aspects in a single apparatus: high forces in a controllable direction. To this end, micron scale magnetic structures are fabricated using cleanroom technologies. With these tweezers, magnetic flux gradients of nablaB = 8 x 10(3) T m(-1) can be achieved over the dimensions of a single cell. This allows exertion of forces up to 12 pN on paramagnetic probes with a diameter of 350 nm, enabling us to maneuver them through the cytoplasm of a living cell. It is expected that with the current tweezers, picoNewton forces can be exerted on beads as small as 100 nm. PMID:15556976

de Vries, Anthony H B; Krenn, Bea E; van Driel, Roel; Kanger, Johannes S

2005-03-01

100

Micro Magnetic Tweezers for Nanomanipulation Inside Live Cells  

PubMed Central

This study reports the design, realization, and characterization of a multi-pole magnetic tweezers that enables us to maneuver small magnetic probes inside living cells. So far, magnetic tweezers can be divided into two categories: I), tweezers that allow the exertion of high forces but consist of only one or two poles and therefore are capable of only exerting forces in one direction; and II), tweezers that consist of multiple poles and allow exertion of forces in multiple directions but at very low forces. The magnetic tweezers described here combines both aspects in a single apparatus: high forces in a controllable direction. To this end, micron scale magnetic structures are fabricated using cleanroom technologies. With these tweezers, magnetic flux gradients of ?B = 8 × 103 T m?1 can be achieved over the dimensions of a single cell. This allows exertion of forces up to 12 pN on paramagnetic probes with a diameter of 350 nm, enabling us to maneuver them through the cytoplasm of a living cell. It is expected that with the current tweezers, picoNewton forces can be exerted on beads as small as 100 nm. PMID:15556976

de Vries, Anthony H. B.; Krenn, Bea E.; van Driel, Roel; Kanger, Johannes S.

2005-01-01

101

Quantitative modeling and optimization of magnetic tweezers.  

PubMed

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

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

2009-06-17

102

Quantitative modeling of forces in electromagnetic tweezers  

PubMed Central

This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet. PMID:21258580

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M.; Vezenov, Dmitri V.

2010-01-01

103

Quantitative Modeling and Optimization of Magnetic Tweezers  

PubMed Central

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

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

2009-01-01

104

Optical tweezers calibration with Bayesian inference  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

105

Quantitative modeling of forces in electromagnetic tweezers  

NASA Astrophysics Data System (ADS)

This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet.

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M.; Vezenov, Dmitri V.

2010-11-01

106

A compact holographic optical tweezers instrument  

NASA Astrophysics Data System (ADS)

Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 ?m silica bead. We also present a range of objects that have been successfully manipulated.

Gibson, G. M.; Bowman, R. W.; Linnenberger, A.; Dienerowitz, M.; Phillips, D. B.; Carberry, D. M.; Miles, M. J.; Padgett, M. J.

2012-11-01

107

Exploring the mechanome with optical tweezers and single molecule fluorescence  

E-print Network

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

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

2008-01-01

108

21 CFR 878.5360 - Tweezer-type epilator.  

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

2014-04-01

109

21 CFR 878.5360 - Tweezer-type epilator.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

110

21 CFR 878.5360 - Tweezer-type epilator.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

111

21 CFR 878.5360 - Tweezer-type epilator.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

112

Using molecular tweezers to move and image nanoparticles.  

PubMed

The ability to manipulate nanoparticles is significant in nanoscale science and technology. As sizes of the objects scale down to the sub-10 nm regime, it imposes a great challenge for the conventional optical tweezers. There has been much effort to explore alternative manipulation methods including using nanostructures, electron beams, scanning probes, etc. In this paper, an overview of the latest advances in trapping and manipulation of nanoparticles with a focus on the emergent electron tweezers is provided. PMID:23592008

Zheng, Haimei

2013-05-21

113

Multiplexed spectroscopy with holographic optical tweezers  

NASA Astrophysics Data System (ADS)

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.

Cibula, Matthew A.; McIntyre, David H.

2014-09-01

114

Optical tweezers for studying taxis in parasites  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

115

Exploring Threaded Intercalation Using Optical Tweezers  

NASA Astrophysics Data System (ADS)

Dumbbell-shaped binuclear ruthenium complexes are of interest due to their potential for use in selective chemotherapy. In bulk experiments, these complexes exhibit extremely slow binding kinetics. In contrast, single molecule studies use optical tweezers to stretch the DNA and induce much more rapid intercalation. The observed DNA force-extension curves clearly indicate an increase in DNA melting force and elongation of the DNA molecule upon drug binding, which is evidence of stabilization of the DNA and intercalation of the binuclear ruthenium complex. Hysteresis in the stretching-relaxation curves implies very slow dissociation of these molecules due to threaded intercalation. The concentration profile suggests unusually strong DNA binding affinity for the binuclear complexes compared to simple intercalators.

Paramanathan, Thayaparan; McCauley, Micah J.; Westerlund, Fredrik; Rouzina, Ioulia; Williams, Mark C.

2007-03-01

116

High-Resolution Optical Tweezers for Single-Molecule Manipulation  

PubMed Central

Forces hold everything together and determine its structure and dynamics. In particular, tiny forces of 1-100 piconewtons govern the structures and dynamics of biomacromolecules. These forces enable folding, assembly, conformational fluctuations, or directional movements of biomacromolecules over sub-nanometer to micron distances. Optical tweezers have become a revolutionary tool to probe the forces, structures, and dynamics associated with biomacromolecules at a single-molecule level with unprecedented resolution. In this review, we introduce the basic principles of optical tweezers and their latest applications in studies of protein folding and molecular motors. We describe the folding dynamics of two strong coiled coil proteins, the GCN4-derived protein pIL and the SNARE complex. Both complexes show multiple folding intermediates and pathways. ATP-dependent chromatin remodeling complexes translocate DNA to remodel chromatin structures. The detailed DNA translocation properties of such molecular motors have recently been characterized by optical tweezers, which are reviewed here. Finally, several future developments and applications of optical tweezers are discussed. These past and future applications demonstrate the unique advantages of high-resolution optical tweezers in quantitatively characterizing complex multi-scale dynamics of biomacromolecules. PMID:24058311

Zhang, Xinming; Ma, Lu; Zhang, Yongli

2013-01-01

117

Optical tweezers force measurements to study parasites chemotaxis  

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

118

Systems approach to identification of feedback enhanced optical tweezers  

NASA Astrophysics Data System (ADS)

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.

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

2008-08-01

119

Tunable optical tweezers for wavelength-dependent measurements  

PubMed Central

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

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

2012-01-01

120

Tunable optical tweezers for wavelength-dependent measurements  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

121

Assembly of 3-dimensional structures using programmable holographic optical tweezers  

Microsoft Academic Search

The micromanipulation of objects into 3-dimensional geometries within holographic optical tweezers is carried out using modified Gerchberg-Saxton (GS) and direct binary search (DBS) algorithms to produce the hologram designs. The algorithms calculate sequences of phase holograms, which are implemented using a spatial light modulator, to reconfigure the geometries of optical traps in many planes simultaneously. The GS algorithm is able

Gavin Sinclair; Pamela Jordan; Johannes Courtial; Miles Padgett; Jon Cooper; Zsolt John Laczik

2004-01-01

122

Quantum dot thermal spectroscopy for biological optical tweezer applications  

E-print Network

Quantum dot thermal spectroscopy for biological optical tweezer applications William T Ramsay1. Quantum dots can be fabricated to hold particular emission properties and can be labelled to target specific binding sites in biological samples to act as biomarkers [1]. Many quantum dots have been observed

Greenaway, Alan

123

Determination of motility forces on isolated chromosomes with laser tweezers.  

PubMed

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

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

2014-01-01

124

Determination of motility forces on isolated chromosomes with laser tweezers  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

125

Determination of motility forces on isolated chromosomes with laser tweezers  

PubMed Central

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

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

2014-01-01

126

Optical tweezers for vortex rings in Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We study generation and stabilization of vortex rings in atomic Bose-Einstein condensates. We suggest an approach for generating vortex rings by optical tweezers—two blue-detuned optical beams forming a toroidal void in a magnetically or optically confined condensate cloud. We demonstrate that matter-wave vortex rings trapped within the void are energetically and dynamically stable. Our theoretical findings suggest a possibility for the generation, stabilization, and nondestructive manipulation of quantized vortex rings in experimentally feasible trapping configurations.

Yakimenko, A. I.; Bidasyuk, Yu. M.; Prikhodko, O. O.; Vilchinskii, S. I.; Ostrovskaya, E. A.; Kivshar, Yu. S.

2013-10-01

127

Optical shield: measuring viscosity of turbid fluids using optical tweezers.  

PubMed

The viscosity of a fluid can be measured by tracking the motion of a suspended micron-sized particle trapped by optical tweezers. However, when the particle density is high, additional particles entering the trap compromise the tracking procedure and degrade the accuracy of the measurement. In this work we introduce an additional Laguerre-Gaussian, i.e. annular, beam surrounding the trap, acting as an optical shield to exclude contaminating particles. PMID:22714199

Lee, M P; Curran, A; Gibson, G M; Tassieri, M; Heckenberg, N R; Padgett, M J

2012-05-21

128

Host–guest chemistry of pyrene-based molecular receptors  

Microsoft Academic Search

The design and synthesis of molecular fluorescent sensors that are able to detect cations and anions via changes in fluorescence intensity either by a fluorescence “turn on”, e.g., excimer formation or by a “turn off”, i.e., excimer quenching, is an area of current interest. There has been a plethora of work dedicated to the development of fluorescent chemosensors in the

Erendra Manandhar; Karl J. Wallace

129

NMR method for simultaneous host-guest binding constant measurement.  

PubMed

An NMR-based relative binding affinity measurement method has been developed in which differences in the binding affinities of different hosts toward a particular guest (?logK(ass) values) are measured in the same solution. As an advancement, the method allows the simultaneous determination of several ?logK(ass) values in a single run. As a proof of principle, the method was used to measure binding affinity differences of a number of indolocarbazole- and urea-based synthetic receptors toward acetate ion in DMSO-d6/H2O (99.5%:0.5% m/m). As a result, a binding affinity scale containing 33 receptors and spanning 2.32 log units with excellent self-consistency (consistency standard deviation = 0.01 log unit) was created. Together with the very good agreement of the results with those obtained by UV-vis spectrophotometry, this demonstrates the high accuracy of the method and the fact that the NMR and UV-vis techniques can be used interchangeably (in spite of the very different concentrations used in these techniques). Additionally, it was found for symmetrical receptor molecules from the same compound family that there is a correlation between the acetate binding affinity of a receptor and the (15)N chemical shift of the nitrogen atoms of its binding centers. PMID:24533827

Kadam, Sandip A; Haav, Kristjan; Toom, Lauri; Haljasorg, Tõiv; Leito, Ivo

2014-03-21

130

Reversible Guest Exchange Mechanisms in Supramolecular Host-GuestAssemblies  

SciTech Connect

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.

Pluth, Michael D.; Raymond, Kenneth N.

2006-09-01

131

Host-Guest Self-assembly in Block Copolymer Blends  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

132

Host-Guest Self-assembly in Block Copolymer Blends  

E-print Network

Ultrafine, uniform nanostructures with excellent functionalities can be formed by self-assembly of block copolymer (BCP) thin films. However, extension of their geometric variability is not straightforward due to their ...

Park, Woon Ik

133

A GSO tweezers-type coincidence detector for tumor detection.  

PubMed

A Gd2SiO5 (GSO) tweezers-type coincidence detector was developed and tested for tumor detection in procedures such as (18)F-fluorodeoxyglucose (FDG)-guided surgery. The detector consists of a pair of GSO scintillators, a pair of metal-packaged small-sized photomultiplier tubes (PMTs), and a coincidence circuit. Because the GSO scintillators are located on the tips of tweezers, a target organ such as a lymph node or the colon can be easily positioned between them. The size of a single GSO was 8 × 14 × 14 mm. The results show that the energy resolution was 30 % full-width at half-maximum (FWHM) and the timing resolution was 6 ns FWHM for 511-keV gamma photons. The point-spread function perpendicular to the detector was 4.5 mm FWHM, and the point-spread function parallel to the detector was 7.5 mm FWHM. The absolute sensitivity of the coincidence detector was 0.6% at the center of the detector when the two GSOs were 5 mm apart. Background counts due to the accidental and scatter coincidence were 2 cps up to 48 MBq from the positron source contained in a 20-cm-diameter, 20-cm-high cylindrical phantom. From these results, we conclude that the proposed tweezers-type coincidence detector is useful for tumor detection by the use of FDG, such as that in radio-guided surgery. PMID:23283753

Yamamoto, Seiichi; Higashi, Tatsuya; Senda, Michio

2013-07-01

134

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

PubMed Central

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

Gosse, Charlie; Croquette, Vincent

2002-01-01

135

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne optical tweezers from a single laser beam using diffractive optical elements. As a demonstration of this technique, we have implemented a 4 \\Theta 4 square array of optical tweezers -- the hexadeca

Grier, David

136

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

E-print Network

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

Paris-Sud XI, Université de

137

Combined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for  

E-print Network

of colloidal spheres is used as a mask for a lithographic step such as illumination, deposition, or etchingCombined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for Nanolithography Dirk L. J through a mask of colloidal particles. The use of optical tweezers combined with critical point drying

Polman, Albert

138

MatLab program for precision calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

139

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology  

NASA Technical Reports Server (NTRS)

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.

Decker, Arthur J.

2002-01-01

140

Imaging microscopic viscosity with confocal scanning optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2002-02-01

141

Translation and manipulation of silicon nanomembranes using holographic optical tweezers  

PubMed Central

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

2011-01-01

142

Near-field single tractor-beam acoustical tweezers  

NASA Astrophysics Data System (ADS)

The possibility to trap a sphere in the near-field of a single-beam piston transducer is theoretically demonstrated. Conditions are found where a rigid, fluid, elastic, and viscoelastic sphere with arbitrary radius placed in the near-field and centered on the axis of a circular piezoelectric transducer vibrating uniformly, experiences a pulling force, so the acoustical waves act as a "tractor" beam. Numerical predictions illustrate the theory with particular emphasis on the distance from the source, the size of the transducer, and the elastic properties of the sphere. Those results can potentially suggest a simple and reliable method in designing acoustical tweezers.

Mitri, F. G.

2013-09-01

143

Multiplexed force measurements on live cells with holographic optical tweezers  

PubMed Central

We describe open-loop and closed-loop multiplexed force measurements using holographic optical tweezers. We quantify the performance of our novel video-based control system in a driven suspension of colloidal particles. We demonstrate our system's abilities with the measurement of the mechanical coupling between Aplysia bag cell growth cones and beads functionalized with the neuronal cell adhesion molecule, apCAM. We show that cells form linkages which couple beads to the underlying cytoskeleton. These linkages are intermittent, stochastic and heterogeneous across beads distributed near the leading edge of a single growth cone. PMID:19365444

Mejean, Cecile O.; Schaefer, Andrew W.; Millman, Eleanor A.; Forscher, Paul; Dufresne, Eric R.

2009-01-01

144

Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments  

SciTech Connect

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.

Amenitsch, H.; Rappolt, M.; Sartori, B.; Laggner, P. [Institute of Biophysics and X-ray Structure Research, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz (Austria); Cojoc, D.; Ferrari, E.; Garbin, V.; Di Fabrizio, E. [CNR-INFM, Lab TASC, Area di Ricerca, 34012 Basovizza (Italy); Burghammer, M.; Riekel, Ch. [ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)

2007-01-19

145

Invited Article: A review of haptic optical tweezers for an interactive microworld exploration  

NASA Astrophysics Data System (ADS)

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 1012 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.

Pacoret, Cécile; Régnier, Stéphane

2013-08-01

146

Optical tweezers for force measurements on DNA in nanopores  

NASA Astrophysics Data System (ADS)

We demonstrate the means to integrate two powerful and widely used single-molecule techniques, viz., optical tweezers and solid-state nanopores. This setup permits simultaneous spatial sampling and high-resolution force measurements of nucleic acids and proteins. First, we demonstrate the rapid spatial localization of nanopores using our custom-built inverted microscope and ionic current measurements. This is made possible by including a specialized flow cell for silicon-based nanopores with an optical window for a high-numerical aperture microscope. Subsequently, we can insert individual DNA molecules into a single nanopore and arrest the DNA during voltage-driven translocation. To detect the position of the trapped particle in the optical trap with high accuracy in the presence of the nanopore, the optical tweezers uses reflected light from the bead for detection. Consequently, we can use our setup to directly determine the force on a DNA molecule in a solid-state nanopore. Finally, we suggest a number of new experiments that become possible with this unique technique.

Keyser, U. F.; van der Does, J.; Dekker, C.; Dekker, N. H.

2006-10-01

147

Calibration of optical tweezers based on an autoregressive model.  

PubMed

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

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

2014-07-14

148

Use of optical tweezers to probe epithelial mechanosensation  

PubMed Central

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. PMID:20210445

Resnick, Andrew

2010-01-01

149

Use of optical tweezers to probe epithelial mechanosensation.  

PubMed

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. PMID:20210445

Resnick, Andrew

2010-01-01

150

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

E-print Network

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 ...

Thompson, J. D.

151

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

PubMed Central

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

Capitanio, Marco; Pavone, Francesco S.

2013-01-01

152

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

SciTech Connect

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.

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

2012-06-30

153

Holographic optical tweezers and their relevance to lab on chip devices.  

PubMed

During the last decade, optical tweezers have been transformed by the combined availability of spatial light modulators and the speed of low-cost computing to drive them. Holographic optical tweezers can trap and move many objects simultaneously and their compatibility with other optical techniques, particularly microscopy, means that they are highly appropriate to lab-on-chip systems to enable optical manipulation, actuation and sensing. PMID:21327211

Padgett, Miles; Di Leonardo, Roberto

2011-04-01

154

Probing multiscale mechanics of collagen with optical tweezers  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

155

Trapping particles using waveguide-coupled gold bowtie plasmonic tweezers.  

PubMed

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

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

2014-12-21

156

Skewed Brownian Fluctuations in Single-Molecule Magnetic Tweezers  

PubMed Central

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

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

2014-01-01

157

Dynamic properties of bacterial pili measured by optical tweezers  

E-print Network

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 quate...

Fallman, Erik; Schedin, Staffan; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

2014-01-01

158

Speckle Optical Tweezers: Micromanipulation with Random Light Fields  

E-print Network

Current optical manipulation techniques rely on carefully engineered setups and samples. Although similar conditions are routinely met in research laboratories, it is still a challenge to manipulate microparticles when the environment is not well controlled and known a priori, since optical imperfections and scattering limit the applicability of this technique to real-life situations, such as in biomedical or microfluidic applications. Nonetheless, scattering of coherent light by disordered structures gives rise to speckles, random diffraction patterns with well-defined statistical properties. Here, we experimentally demonstrate how speckle fields can become a versatile tool to efficiently perform fundamental optical manipulation tasks such as trapping, guiding and sorting. We anticipate that the simplicity of these "speckle optical tweezers" will greatly broaden the perspectives of optical manipulation for real-life applications.

Giorgio Volpe; Lisa Kurz; Agnese Callegari; Giovanni Volpe; Sylvain Gigan

2014-03-03

159

Using Optical Tweezers to Study Cell Mechanics during Airway Reopening  

NASA Astrophysics Data System (ADS)

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.

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

2006-03-01

160

Further Development of the Laser Tweezers Technique for Biomedical Applications  

NASA Astrophysics Data System (ADS)

The results of the experimental work aimed at a functional enhancement of the existing laser tweezers system by introducing a pixel-addressable liquid-crystal spatial light modulator (Holoeye HEO-1080P) are presented. The use of the modulator allows us to generate light fields of complicated structure including ones with the vortex component and control the objects positions in real time. The special software is developed to form an array of optical traps with the number of elements up to thirty two with the capability of individual or subgroup control. The method of a spatial separation of the modulator aperture is implemented. The ability to control the lateral power distribution of the light field as well as the value of its orbital moment brings new possibilities of a precise manipulation of microobjects including biological ones.

Afanasiev, K.; Korobtsov, A.; Kotova, S.; Losevsky, N.; Mayorova, A.; Patlan, V.; Volostnikov, V.

2013-02-01

161

Dynamic excitations in membranes induced by optical tweezers.  

PubMed Central

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

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

1998-01-01

162

Kinect the dots: 3D control of optical tweezers  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

163

Computer-automated program for calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

165

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne)) We describe a simple method for creating multiple optical tweezers from a single laser beam using diffractive optical elements. As a demonstration of this technique, we have implemented a 4 Ã? 4 square array

Grier, David

166

Optical Tweezer Arrays and Optical Substrates Created with Di#ractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Di#ractive Optics Eric R. Dufresne)) We describe a simple method for creating multiple optical tweezers from a single laser beam using di#ractive optical elements. As a demonstration of this technique, we have implemented a 4 Ã? 4 square array

Grier, David

167

Fiber-pigtailed optical tweezer for single-atom trapping and single-photon S. Garcia,1  

E-print Network

: the aspheric lens (AL) is glued to the end of a ceramic tube, the fiber inside a ferrule is glued insideFiber-pigtailed optical tweezer for single-atom trapping and single-photon generation S. Garcia,1 D demonstrate a miniature, fiber-coupled optical tweezer to trap a single atom. The same fiber is used to trap

Paris-Sud XI, Université de

168

Temperature Control Methods in a Laser Tweezers System  

PubMed Central

Two methods of temperature control of a dual-beam optical-tweezers system are compared. In the first method, we used a 975 nm infrared laser to raise the temperature 5.6°C/100mW in a nonheating (830 nm) optical trap. The temperature increment logarithmically decreases toward the periphery of the heating beam, causing a fluid convection of 8 ?m/s inside a 180 ?m thick microchamber. In the second method, heating or cooling fluid was pumped through copper jackets that were placed on the water immersion objectives on both sides of the microchamber to control its temperature from 4.5°C to 68°C. The temperature controlled by the second method was both stable and homogeneous, inducing little fluid convection that would disturb single-molecule applications. An analysis of the power spectrum of the thermal force on a trapped bead showed no detectable vibration due to the liquid circulation. In both methods, force was measured directly by sensors of the momentum flux of light, independent of environmental disturbances including refractive index changes that vary with temperature. The utility of the second method was demonstrated in single-molecule experiments by measuring the mechanical stretch of a 41 kbp ? double-stranded DNA at temperatures ranging from 8.4°C to 45.6°C. PMID:15923237

Mao, Hanbin; Arias-Gonzalez, J. Ricardo; Smith, Steven B.; Tinoco, Ignacio; Bustamante, Carlos

2005-01-01

169

Probing the bulk viscosity of particles using aerosol optical tweezers  

NASA Astrophysics Data System (ADS)

Holographic aerosol optical tweezers can be used to trap arrays of aerosol particles allowing detailed studies of particle properties and processes at the single particle level. Recent observations have suggested that secondary organic aerosol may exist as ultra-viscous liquids or glassy states at low relative humidity, potentially a significant factor in influencing their role in the atmosphere and their activation to form cloud droplets. A decrease in relative humidity surrounding a particle leads to an increased concentration of solute in the droplet as the droplet returns to equilibrium and, thus, an increase in the bulk viscosity. We demonstrate that the timescales for condensation and evaporation processes correlate with particle viscosity, showing significant inhibition in mass transfer kinetics using ternary sucrose/sodium chloride/water droplets as a proxy to atmospheric multi-component aerosol. We go on to study the fundamental process of aerosol coagulation in aerosol particle arrays, observing the relaxation of non-spherical composite particles formed on coalescence. We demonstrate the use of bright-field imaging and elastic light scattering to make measurements of the timescale for the process of binary coalescence contrasting the rheological properties of aqueous sucrose and sodium chloride aerosol over a range of relative humidities.

Power, Rory; Bones, David L.; Reid, Jonathan P.

2012-10-01

170

Detection and characterization of individual intermolecular bonds using optical tweezers.  

PubMed Central

The development of scanning probe techniques has made it possible to examine protein-protein interactions at the level of individual molecular pairs. A calibrated optical tweezers, along with immunoglobulin G (IgG)-coated polystyrene microspheres, has been used to detect individual surface-linked Staphylococcus protein A (SpA) molecules and to characterize the strength of the noncovalent IgG-SpA bond. Microspheres containing, on average, less than one IgG per contact area were held in the optical trap while an SpA-coated substrate was scanned beneath them at a distance of approximately 50 nm. This geometry allows the trapped bead to make contact with the surface, from bond formation to rupture, and results in an enhancement of the force applied to a bond due to leverage supplied by the bead itself. Experiments yielded median single-bond rupture forces from 25 to 44 pN for IgG from four mammalian species, in general agreement with predictions based on free energies of association obtained from solution equilibrium constants. PMID:11371470

Stout, A L

2001-01-01

171

Optically controlled manipulation of live cells using optoelectronic tweezers  

NASA Astrophysics Data System (ADS)

Optoelectronic tweezers (OET) provides a non-invasive, low-power, optical manipulation tool for trapping, transporting, and separating microparticles, cells, and other bioparticles. The OET device uses a photosensitive layer to form "virtual electrodes" upon exposure to light, creating non-uniformities in an applied electric field. The electric field gives rise to a force known as dielectrophoresis: microparticles move as a result of the non-uniformities in the electric field imparting unequal forces on the induced dipoles of the particles. These virtual electrodes can be actuated with low optical intensities, enabling the use of incoherent light sources and direct imaging techniques to create optical manipulation patterns in real-time. In this paper, we demonstrate OET operation on live cells, including the trapping and manipulation of red and white blood cells, and the automated collection of HeLa cells. Automated size-based sorting is performed on a mixture of 15- and 20-?m-diameter polystyrene beads, and dielectric property-based separation is used to differentiate between live and dead white blood cells.

Ohta, Aaron T.; Chiou, Pei-Yu; Wu, Ming C.

2006-08-01

172

Optical tweezers as manufacturing and characterization tool in microfluidics  

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

173

Particle interaction measurements using laser tweezers optical trapping.  

SciTech Connect

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.

Koehler, Timothy P.; Brinker, C. Jeffrey; Brotherton, Christopher M.; Grillet, Anne M.; Molecke, Ryan A. (University of New Mexico, Albuquerque, NM)

2008-08-01

174

Temperature-Dependent Conformations of a Membrane Supported ‘Zinc Porphyrin Tweezer’ by 2D Fluorescence Spectroscopy  

PubMed Central

We studied the equilibrium conformations of a ‘zinc porphyrin tweezer’ composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4 butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of ‘folded’ and ‘extended’ conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17 – 85 °C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes. PMID:23480874

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

2013-01-01

175

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

PubMed

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. PMID:24968938

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

176

Recent advances in laser tweezers Raman spectroscopy (LTRS) for label-free analysis of single cells.  

PubMed

Laser tweezers Raman spectroscopy (LTRS), a technique that integrates optical tweezers with confocal Raman spectroscopy, is a variation of micro-Raman spectroscopy that enables the manipulation and biochemical analysis of single biological particles in suspension. This article provides an overview of the LTRS method, with an emphasis on highlighting recent advances over the past several years in the development of the technology and several new biological and biomedical applications that have been demonstrated. A perspective on the future developments of this powerful cytometric technology will also be presented. PMID:23175434

Chan, James W

2013-01-01

177

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

E-print Network

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

Decombe, Jean-Baptiste; Fick, Jochen

2013-01-01

178

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

NASA Astrophysics Data System (ADS)

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

Decombe, Jean-Baptiste; Huant, Serge; Fick, Jochen

2013-12-01

179

Raman tweezers on bacteria: following the mechanisms of bacteriostatic versus bactericidal action  

NASA Astrophysics Data System (ADS)

Raman tweezers represents a unique method for identification of different microorganisms on the basis of Raman scattering. Raman tweezers allows us to fix and sterile manipulate with the trapped object and in the same time check the growth, viability, response to the external environment etc. by Raman signal evaluating. The investigations presented here include distinction of bacteria in general (staphylococcal cells), identification of bacteria strains (biofilm-positive and biofilm-negative) by using principal component analysis (PCA) and monitoring the influence of antibiotics.

Bernatova, Silvie; Samek, Ota; Pilat, Zdenek; Sery, Mojmir; Jezek, Jan; Jakl, Petr; Siler, Martin; Krzyzanek, Vladislav; Zemanek, Pavel; Hola, Veronika; Dvorackova, Milada; Ruzicka, Filip

2014-05-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

181

Raman Study of Mechanically Induced Oxygenation State Transition of Red Blood Cells Using Optical Tweezers  

PubMed Central

Abstract Raman spectroscopy was used to monitor changes in the oxygenation state of human red blood cells while they were placed under mechanical stress with the use of optical tweezers. The applied force is intended to simulate the stretching and compression that cells experience as they pass through vessels and smaller capillaries. In this work, spectroscopic evidence of a transition between the oxygenation and deoxygenation states, which is induced by stretching the cell with optical tweezers, is presented. The transition is due to enhanced hemoglobin-membrane and hemoglobin neighbor-neighbor interactions, and the latter was further studied by modeling the electrostatic binding of two of the protein structures. PMID:18931252

Rao, Satish; Balint, Stefan; Cossins, Benjamin; Guallar, Victor; Petrov, Dmitri

2009-01-01

182

Characterisation of coated aerosols using optical tweezers and neutron reflectometry  

NASA Astrophysics Data System (ADS)

Thin organic films are believed to form naturally on the surface of aerosols [1,2] and influence aerosol properties. Cloud condensation nuclei formation and chemical reactions such as aerosol oxidation are effected by the presence of thin films [3]. There is a requirement to characterise the physical properties of both the core aerosol and its organic film in order to fully understand the contribution of coated aerosols to the indirect effect. Two complementary techniques have been used to study the oxidation of thin organic films on the surface of aerosols; laser optical tweezers and neutron reflectometry. Micron sized polystyrene beads coated in oleic acid have been trapped in air using two counter propagating laser beams. Polystyrene beads are used as a proxy for solid aerosol. The trapped aerosol is illuminated with a white LED over a broadband wavelength range and the scattered light collected to produce a Mie spectrum [4]. Analysis of the Mie spectrum results in determination of the core polystyrene bead radius, the oleic acid film thickness and refractive index dispersion of the core and shell [5]. A flow of ozone gas can then be introduced into the aerosol environment to oxidise the thin film of oleic acid and the reaction followed by monitoring the changes in the Mie spectrum. The results demonstrate complete removal of the oleic acid film. We conclude that the use of a counter propagating optical trap combined with white light Mie spectroscopy can be used to study a range of organic films on different types of aerosols and their oxidation reactions. Neutron reflectometry has been used as a complementary technique to study the oxidation of monolayer films at the air-water interface in order to gain information on reaction kinetics. The oxidation of an oleic acid film at the air-water interface by the common tropospheric oxidant ozone has been studied using a Langmuir trough. Results indicate complete removal of the oleic acid film with ozone in agreement with the optical tweezers study, which confounds a previous study [6]. Findings also show complicated reaction kinetics that depend on the surface coverage of the film. Combining single particle studies using optical tweezing with macromolecular studies of thin films using neutron reflectometry provides a detailed atmospheric understanding of thin films on aerosols and their oxidation reactions. 1. Tervahattu H., Hartonen K., Kerminen V-H., Kupianen K., Aarnio P., Koskentalo T., Tuck A. and Vaida V., 2002, J. Geophys. Res. 107, 4053-4060. 2. Ellison G., Tuck A. and Vaida V., 1999, J. Geophys. Res. 104, 11633-11641. 3. King M.D., Thompson K.C., Ward A.D., 2004, JACS, 51, 16710-16711. 4. Ward A.D., Zhang M. and Hunt O., 2008, Opt. Express, 16, 16390-16403. 5. C.F. Bohren and D.R. Huffman, Absorption and Scattering of Light by Small Particles, (Wiley Scientific 1998). 6. King M.D., Rennie A.R., Thompson K.C., Fisher F.N., Dong C.C., Thomas R.K., Pfrang C., Hughes A.V., 2009, PCCP, 11, 7699-7707.

Jones, S. H.; Ward, A.; King, M. D.

2013-12-01

183

Mechanical properties of stored red blood cells using optical tweezers  

NASA Astrophysics Data System (ADS)

We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity ? by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

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

184

Dynamic properties of bacterial pili measured by optical tweezers  

NASA Astrophysics Data System (ADS)

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.

Fallman, Erik G.; Andersson, Magnus J.; Schedin, Staffan S.; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

2004-10-01

185

A versatile bis-porphyrin tweezer host for the assembly of noncovalent photoactive architectures: a photophysical characterization of the tweezers and their association with porphyrins and other guests.  

PubMed

A bis(Zn(II)-porphyrin) tweezer host with anthracene components as apex and side-arms has been synthesized. Mono- (pyridine) and bidentate (4,4'-bipyridine) guests were used as models for single and double axial coordination inside the cavity, respectively. A series of dipyridylporphyrin guests with different substitution patterns and excited-state energy levels have association constants with the tweezers that are of the order of 10(6) M(-1), which is indicative of complexation with the inside of the cavity. This complexation can only occur upon an important distortion of the cavity that opens the bite by about 30 %. This characteristic, in conjunction with their ability to reduce the bite distance by rotation around single bonds, makes these porphyrin tweezers amongst the most versatile so far reported, with tuning of the bite distance in the range of approximately 5-20 Angstroms. Energy transfer to the free-base guest within the triporphyrin complex is nearly quantitative (95-98 %) and the rates of transfer are consistent with a Förster mechanism that is characterized by a reduced orientation factor. PMID:16224770

Flamigni, Lucia; Talarico, Anna Maria; Ventura, Barbara; Rein, Regis; Solladié, Nathalie

2006-01-11

186

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

PubMed Central

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

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

2002-01-01

187

TTFV-based molecular tweezers and macrocycles as receptors for fullerenes.  

PubMed

Hybrids of tetrathiafulvalene vinylogues (TTFVs) and planar arenes were synthesized via the click reaction to form tweezer-like and macrocyclic structures. These compounds were investigated as receptors for fullerenes (C60 and C70) by UV-vis absorption and fluorescence spectroscopy. PMID:23964798

Mulla, Karimulla; Shaik, Haseena; Thompson, David W; Zhao, Yuming

2013-09-01

188

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

E-print Network

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

Cicuta, Pietro

189

Characterization of bipolar and radial nematic liquid crystal droplets using laser-tweezers  

Microsoft Academic Search

Bipolar and radial droplets of 4-pentyl-4'-cyanobiphenyl were manipulated using circularly polarized laser-tweezers. Light-induced birefringence arising from orientational nonlinearity was observed and measured for the radial droplets. The highest laser trapping power used 0.5 W induced a birefringence of 0.02 and hence the spinning of the droplets was observed.

Naoki Murazawa; Saulius Juodkazis; Hiroaki Misawa

2005-01-01

190

Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers  

E-print Network

Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers Andreas R measured the viscoelastic properties of the cytoplasm of J774 macrophages with a recently developed circuit, we measured the shear elastic modulus, the effective viscosities, and the strain relaxation time

Bausch, Andreas

191

Semi-automated 3D assembly of multiple objects using holographic optical tweezers  

Microsoft Academic Search

The micromanipulation of objects into 2-dimensional and 3-dimensional geometries within holographic optical tweezers is carried out using a modified Gerchberg-Saxton algorithm. The modified algorithm calculates phase hologram sequences, used to reconfigure the geometries of optical traps in several planes simultaneously. The hologram sequences are calculated automatically from the initial, intermediate and final trap positions. Manipulation of multiple objects in this

Gavin S. Sinclair; Pamela Jordan; John Laczik; Johannes Courtial; Miles J. Padgett

2004-01-01

192

Parallel teleoperation of holographic optical tweezers using multi-touch user interface  

Microsoft Academic Search

Holographic optical tweezers (HOT) has ability to trap and manipulate a few hundred of small particles. Previously the manipulation speed is greatly limited to the calculation speed of holograms. But recent progress in parallel computing made it possible to generate the holograms in real-time. Therefore, HOT is thought to play an important role in dexterous micromanipulation. In practical application, the

Kazuhisa Onda; Fumihito Arai

2012-01-01

193

Construction and actuation of a microscopic gear assembly formed using optical tweezers  

NASA Astrophysics Data System (ADS)

The assembly of micrometer-sized parts is an important manufacturing process; any development in it could potentially change the current manufacturing practices for micrometer-scale devices. Due to the lack of reliable microassembly techniques, these devices are often manufactured using silicon, which includes etching and depositions with little use of assembly processes. The result is the requirement of specialized manufacturing conditions with hazardous byproducts and limited applications where only simple mechanisms are allowed. Optical tweezers are non-contact type manipulators that are very suitable for assembling microparts and solve one of the most difficult problems for microassembly, which is the sticking of the physical manipulator to the micropart. Although contact type manipulators can be surface modified to be non-sticky, this involves extra preprocessing—optical tweezers do not require such additional efforts. The weakness of using optical tweezers is that the permanent assembly of parts is not possible as only very small forces can be applied. We introduce an advanced microassembly environment with the combined use of optical tweezers and a motorized microtip, where the former is used to position two parts and the latter is used to introduce deformation in the parts so that they form a strongly fitted assembly.

Kim, Jung-Dae; Lee, Yong-Gu

2013-06-01

194

Raman Study of Mechanically Induced Oxygenation State Transition of Red Blood Cells Using Optical Tweezers  

Microsoft Academic Search

Raman spectroscopy was used to monitor changes in the oxygenation state of human red blood cells while they were placed under mechanical stress with the use of optical tweezers. The applied force is intended to simulate the stretching and compression that cells experience as they pass through vessels and smaller capillaries. In this work, spectroscopic evidence of a transition between

Satish Rao; Štefan Bálint; Benjamin Cossins; Victor Guallar; Dmitri Petrov

2009-01-01

195

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

E-print Network

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

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

2006-01-01

196

Optical tweezers for precise control of micro-bubble arrays: in situ temperature measurement  

NASA Astrophysics Data System (ADS)

We use highly a focused laser beam incident on a carbon coated coverslip to create microcavitation. Full optical control of the radii of the bubbles is attained. Multiple bubbles can also be created and their size changed independently. The dynamics of such multi-bubble systems are studied. These bubble systems generate strong flows such as Marangoni convection and also large thermal gradients. Since the size of the micro-bubbles is highly dependent on the temperature, we anticipate that these systems can be used for precise temperature control of samples. These methods are of use when the knowledge of exact and local temperature profiles are of importance. Furthermore, since bubble expansion can generate orders of magnitude more force than conventional optical tweezers, systems have application in manipulation of particles where large forces are required. We present methods based on optical tweezers for using the generated bubbles as thermal sensors and as opto-mechanical transducers.

Burns, Tristan M.; Preece, Daryl; Niemenen, Timo A.; Rubinsztein-Dunlop, Haliina

2013-09-01

197

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

E-print Network

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

Baresch, Diego; Marchiano, Régis

2014-01-01

198

Raman sorting and identification of single living micro-organisms with optical tweezers  

NASA Astrophysics Data System (ADS)

We report on a novel technique for sorting and identification of single biological cells and food-borne bacteria based on laser tweezers and Raman spectroscopy (LTRS). With this technique, biological cells of different physiological states in a sample chamber were identified by their Raman spectral signatures and then they were selectively manipulated into a clean collection chamber with optical tweezers through a microchannel. As an example, we sorted the live and dead yeast cells into the collection chamber and validated this with a standard staining technique. We also demonstrated that bacteria existing in spoiled foods could be discriminated from a variety of food particles based on their characteristic Raman spectra and then isolated with laser manipulation. This label-free LTRS sorting technique may find broad applications in microbiology and rapid examination of food-borne diseases.

Xie, Changan; Chen, De; Li, Yong-Qing

2005-07-01

199

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

PubMed

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

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

2004-06-28

200

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

201

Development of High-Resolution Magnetic Tweezers for Single-Molecule Measurements  

Microsoft Academic Search

Magnetic tweezers can sense single-molecule DNA-protein interactions through optical tracking of the motion of a colloidal particle. This is typically done by relating changes in the colloid's diffraction pattern to its position. While diffraction-tracking is relatively simple to implement, it is intrinsically limited in its resolution. To improve this, we have developed a tracking technique based on Reflection Interference Contrast

Kipom Kim; Omar A. Saleh

2007-01-01

202

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

Microsoft Academic Search

Recent studies have shown that the cell is mechanically differentiated both spatially and temporally, leading to a regional approach in cell behaviour essays. Most experiments are based on spatially-controlled contacts between microbeads and cells. We here propose an apparatus based on holographic optical tweezers to put on a target cell a two- or three-dimensional custom-built pattern of beads, with respect

Serge Monneret; Federico Belloni; Didier Marguet

2006-01-01

203

Statics and dynamics of radial nematic liquid-crystal droplets manipulated by laser tweezers  

Microsoft Academic Search

Laser manipulation of trapped radial 4' -n-pentyl-4-cyanobiphenyl (5CB) nematic liquid-crystal droplets induced by molecular reordering is presented. We show experimentally that optical tweezers having linear, elliptical, or circular polarization can break the radial symmetry of the initial molecular organization inside a radial nematic droplet. Static distorted or twisted deformation modes and steady or unsteady nonlinear rotational dynamics are observed. Statics

Etienne Brasselet; Naoki Murazawa; Saulius Juodkazis; Hiroaki Misawa

2008-01-01

204

Fast generation of holographic optical tweezers by random mask encoding of Fourier components.  

PubMed

The random mask encoding technique of multiplexing phase-only filters can be easily adapted to the generation of holographic optical tweezers. The result is a direct, non-iterative and extremely fast algorithm that can be used for computing arbitrary arrays of optical traps. Additional benefits include the possibility of modifying any existing hologram to quickly add more trapping sites and the inexistence of ghost traps or replicas. PMID:19503542

Montes-Usategui, Mario; Pleguezuelos, Encarnación; Andilla, Jordi; Martín-Badosa, Estela

2006-03-20

205

Axial and lateral trapping efficiency of Laguerre–Gaussian modes in inverted optical tweezers  

Microsoft Academic Search

Within inverted optical tweezers we measure both the lateral and axial trapping efficiency obtained with Gaussian and high-order Laguerre–Gaussian beams. Our results confirm that, for larger particles, the axial trapping is improved by using a Laguerre–Gaussian beam but, contrary to earlier suggestions, that the lateral efficiency is unchanged. We show that this latter observation is compatible with a ray-optical model

Anna T. O'Neil; Miles J. Padgett

2001-01-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

207

Scanning a DNA Molecule for Bound Proteins Using Hybrid Magnetic and Optical Tweezers  

PubMed Central

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 ?-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

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

208

Measurement of macrophage adhesion using optical tweezers with backward-scattered detection  

NASA Astrophysics Data System (ADS)

Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 ?m diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

2010-08-01

209

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

NASA Astrophysics Data System (ADS)

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

Monneret, Serge; Belloni, Federico; Marguet, Didier

2006-02-01

210

Optical nanofiber integrated into an optical tweezers for particle manipulation and in-situ fiber probing  

NASA Astrophysics Data System (ADS)

Precise control of particle positioning is desirable in many optical propulsion and sorting applications. Here, we develop an integrated platform for particle manipulation consisting of a combined optical nanofiber and optical tweezers system. Individual silica microspheres were introduced to the nanofiber at arbitrary points using the optical tweezers, thereby producing pronounced dips in the fiber transmission. We show that such consistent and reversible transmission modulations depend on both particle and fiber diameter, and may be used as a reference point for in-situ nanofiber or particle size measurement. Therefore we combine SEM size measurements with nanofiber transmission data to provide calibration for particle-based fiber assessment. We also demonstrate how the optical tweezers can be used to create a `particle jet' to feed a supply of microspheres to the nanofiber surface, forming a particle conveyor belt. This integrated optical platform provides a method for selective evanescent field manipulation of micron-sized particles and facilitates studies of optical binding and light-particle interaction dynamics.

Gusachenko, Ivan; Frawley, Mary C.; Truong, Viet. G.; Nic Chormaic, Síle

2014-09-01

211

Dielectrophoretic Tweezers as a Platform for Molecular Force Spectroscopy in a Highly Parallel Format  

PubMed Central

We demonstrated the application of a simple electrode geometry for dielectrophoresis (DEP) on colloidal probes as a form of molecular force spectroscopy in a highly parallel format. The electric field between parallel plates is perturbed with dielectric microstructures, generating uniform DEP forces on colloidal probes in the range of several hundred piconewtons across a macroscopic sample area. We determined the approximate crossover frequency between negative and positive DEP using electrodes without dielectric microstructures—a simplification over standard experimental methods involving quadrupoles or optical trapping. 2D and 3D simulations of the electric field distributions validated the experimental behavior of several of our DEP tweezers geometries and provided insight into potential improvements. We applied the DEP tweezers to the stretching of a short DNA oligomer and detected its extension using total-internal reflection fluorescence microscopy. The combination of a simple cell fabrication, a uniform distribution of high axial forces, and a facile optical detection of our DEP tweezers makes this form of molecular force spectroscopy ideal for highly parallel detection of stretching or unbinding kinetics of biomolecules. PMID:22051576

Cheng, Peng; Barrett, Michael J.; Oliver, Piercen M.; Cetin, Deniz; Vezenov, Dmitri

2012-01-01

212

Quantitation of malaria parasite-erythrocyte cell-cell interactions using optical tweezers.  

PubMed

Erythrocyte invasion by Plasmodium falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria. Invasion has been studied intensively, but our cellular understanding has been limited by the fact that it occurs very rapidly: invasion is generally complete within 1 min, and shortly thereafter the merozoites, at least in in vitro culture, lose their invasive capacity. The rapid nature of the process, and hence the narrow time window in which measurements can be taken, have limited the tools available to quantitate invasion. Here we employ optical tweezers to study individual invasion events for what we believe is the first time, showing that newly released P. falciparum merozoites, delivered via optical tweezers to a target erythrocyte, retain their ability to invade. Even spent merozoites, which had lost the ability to invade, retain the ability to adhere to erythrocytes, and furthermore can still induce transient local membrane deformations in the erythrocyte membrane. We use this technology to measure the strength of the adhesive force between merozoites and erythrocytes, and to probe the cellular mode of action of known invasion inhibitory treatments. These data add to our understanding of the erythrocyte-merozoite interactions that occur during invasion, and demonstrate the power of optical tweezers technologies in unraveling the blood-stage biology of malaria. PMID:25140419

Crick, Alex J; Theron, Michel; Tiffert, Teresa; Lew, Virgilio L; Cicuta, Pietro; Rayner, Julian C

2014-08-19

213

Single-cell optoporation and transfection using femtosecond laser and optical tweezers  

PubMed Central

In this paper, we demonstrate a new single-cell optoporation and transfection technique using a femtosecond Gaussian laser beam and optical tweezers. Tightly focused near-infrared (NIR) femtosecond laser pulse was employed to transiently perforate the cellular membrane at a single point in MCF-7 cancer cells. A distinct technique was developed by trapping the microparticle using optical tweezers to focus the femtosecond laser precisely on the cell membrane to puncture it. Subsequently, an external gene was introduced in the cell by trapping and inserting the same plasmid-coated microparticle into the optoporated cell using optical tweezers. Various experimental parameters such as femtosecond laser exposure power, exposure time, puncture hole size, exact focusing of the femtosecond laser on the cell membrane, and cell healing time were closely analyzed to create the optimal conditions for cell viability. Following the insertion of plasmid-coated microparticles in the cell, the targeted cells exhibited green fluorescent protein (GFP) under the fluorescent microscope, hence confirming successful transfection into the cell. This new optoporation and transfection technique maximizes the level of selectivity and control over the targeted cell, and this may be a breakthrough method through which to induce controllable genetic changes in the cell. PMID:24049675

Waleed, Muhammad; Hwang, Sun-Uk; Kim, Jung-Dae; Shabbir, Irfan; Shin, Sang-Mo; Lee, Yong-Gu

2013-01-01

214

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

NASA Astrophysics Data System (ADS)

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.

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

2014-09-01

215

High-refractive index particles in counter-propagating optical tweezers - manipulation and forces  

NASA Astrophysics Data System (ADS)

With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the trap. A higher refractive-index difference between a particle and the surrounding medium will increase the forces. The destabilizing scattering force, however, pushing the particle in the direction of the beam, increases more than the gradient force, directed towards the focus. As a consequence, particles with a certain refractive index cannot be trapped in a single-beam gradient trap, and a limit is set to the force that can be exerted. We developed an experimental setup with two opposing high-numerical objectives. By splitting the laser beam, we created counter-propagating tweezers in which the scattering forces were canceled in the axial direction and high-refractive index and metallic particles could also be trapped. With the use of a separate laser beam combined with a quadrant photodiode, accurate position detection on a trapped particle in the counter-propagating tweezers is possible. We used this to determine trap stiffnesses, and show, with measurements and calculations, an enhancement in trap stiffness of at least 3 times for high-index 1.1-micrometer-diameter titania particles as compared to 1.4-micrometer-diameter silica particles under the same conditions. The ability to exert higher forces with lower laser power finds application in biophysical experiments, where laser damage and heating play a role. The manipulation of high-index and metallic particles also has applications in materials and colloid science, for example to incorporate high-index defects in colloidal photonic crystals. We demonstrate the patterning of high-index particles onto a glass substrate. The sample cell was mounted on a high-accuracy piezo stage combined with a long-range stage with motorized actuators. Because we used image analysis of the patterned structure to accurately find back the starting position and compensate for drift of the sample, we could move far away from the patterning region. This enabled us to select particles from a separate reservoir of a mixture of particles, and, one-by-one, position them at chosen locations. By time-sharing the laser beam using acousto-optic deflectors, we created multiple counter-propagating tweezers. We trapped an array of high-refractive index particles, and were able to move those particles individually. We used such a dynamic array of counter-propagating tweezers to create line-optical tweezers in which we trapped semi-conducting high-refractive index nanorods in three dimensions. We demonstrate full 3D translational and in-plane rotational control over the rods, which could not be held in single-beam line-tweezers. The configuration of two opposing objectives was also used for simultaneous trapping with one objective and confocal imaging of the fluorescently labeled particles using the other objective. By trapping particles with a refractive index contrast in a dispersion of index-matched particles, crystallization could be induced, which was imaged in three dimensions using confocal microscopy.

van der Horst, Astrid

2006-09-01

216

NanoTracker: force-sensing optical tweezers for quantitative single-molecule nanomanipulation  

NASA Astrophysics Data System (ADS)

In the past decade, experiments involving the manipulation and observation of nanostructures with light using optical tweezers methodology have developed from proof-of-principle experiments to an established quantitative technique in fields ranging from (bio)physics to cell biology. With optical tweezers, microscopically small objects can be held and manipulated. At the same time, the forces exerted on the trapped objects can be accurately measured. With the Prism-Award winning NanoTracker a platform for performing experiments using specimen from single molecules to whole cells is available. With two time-continuous traps, it allows the controlled trapping and accurate tracking of nanoparticles, suspended either in a microfluidic multichannel flow chamber or even in a temperaturecontrolled open Petri dish. With its 3D detection system, particle displacements in the trap can be recorded with nanometer precision. Moreover, dynamic forces acting on the particle can be measured with better than picoNewton resolution on a microsecond time-scale. Here, we discuss design features of and measurements done with the NanoTracker platform. In particular, we show how one of the hallmarks of single-molecule biophysics, the overstretching transition of DNA, can be studied in a versatile manner and used for protein-DNA interaction mechanics. Moreover, on the lower side of the force range the other benchmark single-molecule biophysics, kinesin's 8-nm steps and stall forces, are shown to be measurable. With the NanoTracker, optical tweezers finally transcend from the labs of self-building scientists who helped the technique mature, to a turn-key system able to serve a much wider community of researchers in the life sciences.

Eggert, Helge A.; van Mameren, Joost; Wozniak, Anna; Jaehnke, Torsten

2010-02-01

217

A new determination of the shear modulus of the human erythrocyte membrane using optical tweezers.  

PubMed Central

Optical tweezers are used to apply calibrated forces to human erythrocytes, via small silica beads bound to their membrane. The shear modulus mu of the membrane is inferred from measurements of the cell deformation in the small strain linear regime. We find the same result mu = 2.5 +/- 0.4 microN/m for both discotic and nearly spherical swollen cells. This value is smaller than the one deduced from micropipettes experiments. However the two methods do not operate in the same deformation regime and are not expected to lead to the same result. PMID:9916046

Henon, S; Lenormand, G; Richert, A; Gallet, F

1999-01-01

218

Fast acoustic tweezers for the two-dimensional manipulation of individual particles in microfluidic channels  

NASA Astrophysics Data System (ADS)

This paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very controlled manner by the two-dimensional drifting of a standing wave array, using a slight frequency modulation of two ultrasound emitters around their resonance. These acoustic tweezers allow any type of motion at velocities up to few ×10 mm/s, while the device transparency is adapted for optical studies. The possibility of automation provides a critical step in the development of lab-on-a-chip cell sorters and it should find applications in biology, chemistry, and engineering domains.

Tran, S. B. Q.; Marmottant, P.; Thibault, P.

2012-09-01

219

Optoelectronic tweezers under arbitrary illumination patterns: theoretical simulations and comparison to experiment.  

PubMed

Photovoltaic tweezers are a promising tool to place and move particles on the surface of a photovoltaic material in a controlled way. To exploit this new technique it is necessary to accurately know the electric field created by a specific illumination on the surface of the crystal and above it. This paper describes a numerical algorithm to obtain this electric field generated by several relevant light patterns, and uses them to calculate the dielectrophoretic potential acting over neutral, polarizable particles in the proximity of the crystal. The results are compared to experiments carried out in LiNbO3 with good overall agreement. PMID:25402148

Arregui, Cándido; Ramiro, José Bruno; Alcázar, Angel; Méndez, Angel; Burgos, Héctor; García-Cabañes, Angel; Carrascosa, Mercedes

2014-11-17

220

Temporal response of biological cells to high-frequency optical jumping and vibrating tweezers  

NASA Astrophysics Data System (ADS)

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.

Yu, Lingyao; Sheng, Yunlong

2014-09-01

221

Template stripped double nanohole in a gold film for nano-optical tweezers.  

PubMed

Double nanohole (DNH) laser tweezers can optically trap and manipulate objects such as proteins, nanospheres, and other nanoparticles; however, precise fabrication of those DNHs has been expensive with low throughput. In this work, template stripping was used to pattern DNHs with gaps as small as 7 nm, in optically thick Au films. These DNHs were used to trap streptavidin as proof of operation. The structures were processed multiple times from the same template to demonstrate reusability. Template stripping is a promising method for high-throughput, reproducible, and cost efficient fabrication of DNH apertures for optical trapping. PMID:25407447

Zehtabi-Oskuie, Ana; Zinck, Aurora A; Gelfand, Ryan M; Gordon, Reuven

2014-12-12

222

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

NASA Astrophysics Data System (ADS)

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.

Chen, Shuxun; Cheng, Jinping; Kong, Chi-Wing; Wang, Xiaolin; Han Cheng, Shuk; Li, Ronald A.; Sun, Dong

2013-07-01

223

Application of laser tweezers Raman spectroscopy techniques to the monitoring of single cell response to stimuli  

NASA Astrophysics Data System (ADS)

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.

Chan, James W.; Liu, Rui; Matthews, Dennis L.

2012-06-01

224

A modular assembling platform for manufacturing of microsystems by optical tweezers  

NASA Astrophysics Data System (ADS)

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.

Ksouri, Sarah Isabelle; Aumann, Andreas; Ghadiri, Reza; Prüfer, Michael; Baer, Sebastian; Ostendorf, Andreas

2013-09-01

225

Design of hybrid optical tweezers system for controlled three-dimensional micromanipulation  

NASA Astrophysics Data System (ADS)

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.

Tanaka, Yoshio; Tsutsui, Shogo; Kitajima, Hiroyuki

2013-04-01

226

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

NASA Astrophysics Data System (ADS)

Based on an ongoing trend in miniaturization and due to the increased complexity in MEMS-technology new methods of assembly need to be developed. Recent developments show that particularly optical forces are suitable to meet the requirements. The unique advantages of optical tweezers (OT) are attractive due to their contactless and precise manipulation forces. Spherical as well as non-spherical shaped pre-forms can already be assembled arbitrarily by using appropriate beam profiles generated by a spatial light modulator (SLM), resulting in a so called holographic optical tweezer (HOT) setup. For the fabrication of shape-complementary pre-forms, a two-photon-polymerization (2PP) process is implemented. The purpose of the process combination of 2PP and HOT is the development of an optical microprocessing platform for assembling arbitrary building blocks. Here, the optimization of the 2PP and HOT processes is described in order to allow the fabrication and 3D assembling of interlocking components. Results include the analysis of the dependence of low and high qualities of 2PP microstructures and their manufacturing accuracy for further HOT assembling processes. Besides, the applied detachable interlocking connections of the 2PP building blocks are visualized by an application example. In the long-term a full optical assembly method without applying any mechanical forces can thus be realized.

Ksouri, Sarah Isabelle; Mattern, Manuel; Köhler, Jannis; Aumann, Andreas; Zyla, Gordon; Ostendorf, Andreas

2014-09-01

227

Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis  

NASA Astrophysics Data System (ADS)

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.

Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

2006-08-01

228

Molecular tweezers and clips as synthetic receptors. Molecular recognition and dynamics in receptor-substrate complexes.  

PubMed

The molecular tweezers (1, 2) and clips (3-7) containing naphthalene and benzene spacer units can be synthesized via repetitive Diels-Alder reactions by the use of a molecular "Lego" set consisting of bisdienophiles (8, 9, 14) and dienes (10, 13). The new receptors selectively bind electron-deficient neutral and cationic substrates in solution. Only the benzene-spaced tweezers form complexes with aliphatic substrates, whereas the other receptors bind aromatic substrates preferentially. HPLC studies with 1 and 2 chemically bonded to stationary phases give similar results for the heterogeneous systems. The formation of stable complexes between the water-soluble clip 5g and N-alkylpyridinium cations, such as N-methylnicotinamide and NAD(+), in aqueous solution illustrates the importance of the hydrophobic effect for arene-arene interactions. The dynamics of the complex formation and substrate mobility were investigated by the use of temperature-dependent liquid- and solid-state NMR spectroscopy. The electrostatic potential surface (EPS) of 1-7 is calculated to be surprisingly negative on the concave side of each molecule and, hence, complementary to the EPS of the electron-deficient substrates, suggesting that the attractive receptor-substrate interaction is here of predominantly electrostatic nature. PMID:14674783

Klärner, Frank-Gerrit; Kahlert, Björn

2003-12-01

229

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

PubMed

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. PMID:24880354

Ott, Dino; Reihani, S Nader S; Oddershede, Lene B

2014-05-01

230

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

NASA Astrophysics Data System (ADS)

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.

Ott, Dino; Reihani, S. Nader S.; Oddershede, Lene B.

2014-05-01

231

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

PubMed

Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level. PMID:23020384

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

2012-09-01

232

Quantifying heat transfer in DMD-based optoelectronic tweezers with infrared thermography  

NASA Astrophysics Data System (ADS)

Optoelectronic tweezers (OET) have emerged in recent years as a powerful form of optically-induced dielectrophoresis for addressing single cells and trapping individual nanostructures with DMD-based virtual-electrodes. In this technique an alternating electric field is used to induce a dipole within structures of interest while very low-intensity optical images are used to produce local electric field gradients that create dynamic trapping potentials. Addressing living cells, particularly for heat-sensitive cell lines, with OET's optical virtual-electrodes requires an in-depth understanding of heating profiles within OET devices. In this work we present quantitative measurements of the thermal characteristics of single-crystalline-silicon phototransistor based optoelectronic tweezers (PhOET). Midwave infrared (3 - 5 micron) thermographic imaging is used to determine relative heating in PhOET devices both with and without DMD-based optical actuation. Temperature increases of approximately 2°C from electrolyte Joule-heating are observable in the absence of DMD-illumination when glass is used as a support for PhOET devices. An additional temperature increase of no more than 0.2°C is observed when DMD-illumination is used. Furthermore, significantly reduced heating can be achieved when devices are fabricated in direct contact with a metallic heat-sink.

Pauzauskie, Peter J.; Hsu, Hsan-Yin; Jamshidi, Arash; Valley, Justin K.; Pei, Shao Ning; Wu, Ming C.

2010-02-01

233

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

PubMed

Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy. PMID:25140010

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

2015-02-01

234

Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria  

NASA Astrophysics Data System (ADS)

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.

Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

2011-04-01

235

Natural user interface as a supplement of the holographic Raman tweezers  

NASA Astrophysics Data System (ADS)

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.

Tomori, Zoltan; Kanka, Jan; Kesa, Peter; Jakl, Petr; Sery, Mojmir; Bernatova, Silvie; Antalik, Marian; Zemánek, Pavel

2014-09-01

236

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

E-print Network

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

Diego Baresch; Jean-Louis Thomas; Régis Marchiano

2014-11-07

237

Laser scanning confocal microscopy and laser tweezers based experiments to understand dentine-bacteria interactions  

NASA Astrophysics Data System (ADS)

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.

Peng, Sum Chee; Mohanty, Samarendra; Gupta, P. K.; Kishen, Anil

2007-02-01

238

Optical tweezers and cell biomechanics in macro- and nano-scale  

NASA Astrophysics Data System (ADS)

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.

Serafetinides, Alexander A.; Makropoulou, Mersini; Spyratou, Ellas

2013-03-01

239

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

SciTech Connect

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.

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

2013-04-15

240

Host-Guest Complexes with Protein-Ligand-Like Affinities: Computational Analysis and Design  

PubMed Central

It has recently been discovered that guests combining a nonpolar core with cationic substituents bind cucurbit[7]uril (CB[7]) in water with ultra-high affinities. The present study uses the Mining Minima algorithm to study the physics of these extraordinary associations and to computationally test a new series of CB[7] ligands designed to bind with similarly high affinity. The calculations reproduce key experimental observations regarding the affinities of ferrocene-based guests with CB[7] and ?-cyclodextrin and provide a coherent view of the roles of electrostatics and configurational entropy as determinants of affinity in these systems. The newly designed series of compounds is based on a bicyclo[2.2.2]octane core, which is similar in size and polarity to the ferrocene core of the existing series. Mining Minima predicts that these new compounds will, like the ferrocenes, bind CB[7] with extremely high affinities. PMID:19133781

Moghaddam, Sarvin; Inoue, Yoshihisa

2009-01-01

241

Host-guest inclusion system of mangiferin with ?-cyclodextrin and its derivatives.  

PubMed

The characterization, inclusion complexation behavior and binding ability of the inclusion complexes of mangiferin (MGF) with ?-cyclodextrin and its derivatives (hydroxypropyl-?-cyclodextrin (HP?CD), sulfobutyl ether ?-cyclodextrin (SBE?CD) and mono (6-ethylene-diamino-6-deoxy)-?-cyclodextrin (EN?CD)) were investigated in both solution and solid state by means of PL spectroscopy, (1)H and 2D NMR, XRD, TG and DSC. The results showed that the water solubility and thermal stability of MGF were significantly increased in the inclusion complex with cyclodextrins. The MGF/CDs complexes will be potentially useful for the design of a novel formulation of mangiferin for herbal medicine. PMID:23498273

Yang, Xuemin; Zhao, Yulin; Chen, Yunjian; Liao, Xiali; Gao, Chuanzhu; Xiao, Dan; Qin, Qixue; Yi, Dong; Yang, Bo

2013-05-01

242

Host-Guest Interaction between Herbicide Oxadiargyl and Hydroxypropyl-?-Cyclodextrin  

PubMed Central

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)-?-cyclodextrin (HP-?-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-?-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-?-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

Benfeito, Sofia; Borges, Fernanda; Garrido, E. Manuela

2013-01-01

243

Host-guest interactions in Fe(III)-trimesate MOF nanoparticles loaded with doxorubicin.  

PubMed

Doxorubicin (DOX) entrapment in porous Fe(III)-trimesate metal organic frameworks (MIL-100(Fe)) nanoparticles was investigated in neutral Tris buffer via UV-vis absorption, circular dichroism (CD), and fluorescence. The binding constants and the absolute spectra of the DOX-MIL-100(Fe) complexes were determined via absorption and fluorescence titrations. A binding model where DOX associates as monomer to the dehydrated Fe3O (OH)(H2O)2 [(C6H3)(CO2)3]2 structural unit in 1:1 stoichiometry, with apparent association constant of (1.1 to 1.8) × 10(4) M(-1), was found to reasonably fit the experimental data. Spectroscopic data indicate that DOX binding occurs via the formation of highly stable coordination bonds between one or both deprotonated hydroxyl groups of the aglycone moiety and coordinatively unsaturated Fe(III) centers. Complete quenching of the DOX fluorescence and remarkable thermal and photochemical stability were observed for DOX incorporated in the MIL-100(Fe) framework. PMID:24960194

Anand, Resmi; Borghi, Francesco; Manoli, Francesco; Manet, Ilse; Agostoni, Valentina; Reschiglian, Pierluigi; Gref, Ruxandra; Monti, Sandra

2014-07-24

244

Host-guest Interaction Mediated Polymeric Assemblies: Multifunctional Nanoparticles for Drug and Gene Delivery  

PubMed Central

Novel core-shell structured nano-assemblies are assembled by a ?-cyclodextrin containing positively charged host polymer and a hydrophobic guest polymer. The hydrophobic core of this type of assemblies serves as a nano-container to load and release the hydrophobic drugs, while the positively charged hydrophilic shell is able to condense the plasmid DNA and achieve its transfection/expression in osteoblast cells. These assemblies may be used as a new generation of multi-functional nano-carriers for simultaneous drug delivery and gene therapy. PMID:20112968

Zhang, Jianxiang; Sun, Hongli; Ma, Peter X

2010-01-01

245

Functionalization in flexible porous solids: effects on the pore opening and the host-guest interactions.  

PubMed

The synthesis on the gram scale and characterization of a series of flexible functionalized iron terephthalate MIL-53(Fe) type solids are reported. Chemical groups of various polarities, hydrophilicities, and acidities (-Cl, -Br, -CF(3), -CH(3), -NH(2), -OH, -CO(2)H) were introduced through the aromatic linker, to systematically modify the pore surface. X-ray powder diffraction (XRPD), molecular simulations, thermogravimetric analyses, and in situ IR and (57)Fe Mössbauer spectrometries indicate some similarities with the pristine MIL-53(Fe) solid, with the adoption of the narrow pore form for all solids in both the hydrated and dry forms. Combined XRPD and computational structure determinations allow concluding that the geometry of the pore opening is predominantly correlated with the intraframework interactions rather than the steric hindrance of the substituent. Only (MIL-53(Fe)-(CF(3))(2)) exhibits a nitrogen accessible porosity (S(BET) approximately 100 m(2) g(-1)). The adsorption of some liquids leads to pore openings showing some very specific behaviors depending on the guest-MIL-53(Fe) framework interactions, which can be related to the energy difference between the narrow and large pore forms evaluated by molecular simulation. PMID:20038143

Devic, Thomas; Horcajada, Patricia; Serre, Christian; Salles, Fabrice; Maurin, Guillaume; Moulin, Béatrice; Heurtaux, Daniela; Clet, Guillaume; Vimont, Alexandre; Grenèche, Jean-Marc; Le Ouay, Benjamin; Moreau, Florian; Magnier, Emmanuel; Filinchuk, Yaroslav; Marrot, Jerôme; Lavalley, Jean-Claude; Daturi, Marco; Férey, Gérard

2010-01-27

246

Toehold-mediated DNA logic gates based on host-guest DNA-GNPs.  

PubMed

A simple, toehold-mediated two-way input DNA machine has been developed. Utilizing symmetric and asymmetric protector sequences, INH, XOR logic gates and a half-subtractor are designed based on this two-way structure. PMID:24865223

Liu, Yizhen; Dong, Boran; Wu, Zitong; Fang, Wei; Zhou, Guohua; Shen, Aiguo; Zhou, Xiaodong; Hu, Jiming

2014-10-18

247

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

NASA Astrophysics Data System (ADS)

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.

Sun, Shiguo; Li, Fusheng; Liu, Fengyu; Wang, Jitao; Peng, Xiaojun

2014-01-01

248

Light-harvesting host-guest antenna materials for solar energy conversion devices  

Microsoft Academic Search

In natural photosynthesis, light is absorbed by photonic antenna systems consisting of a few hundred chlorophyll molecules. These devices allow fast energy transfer from an electronically excited molecule to an unexcited neighbour molecule in such a way that the excitation energy reaches the reaction centre with high probability. Trapping occurs there. The anisotropic arrangement of the chlorophyll molecules is important

Stefan Huber; Gion Calzaferri

2006-01-01

249

Reactions in HostGuest Complexes Molecular Mousetraps: Gas-Phase Studies of the  

E-print Network

Reactions in Host­Guest Complexes Molecular Mousetraps: Gas-Phase Studies of the Covalent Coupling of purposes.[1,2] These noncovalent complexes are easily transferred to the gas phase by electrospray. May The Arnold and Mabel Beckman Laboratories of Chemical Syn- thesis, Division of Chemistry

Stoltz, Brian M.

250

A Novel Approach to Molecular Recognition Surface of Magnetic Nanoparticles Based on Host-Guest Effect  

NASA Astrophysics Data System (ADS)

A novel route has been developed to prepared ?-cyclodextrin (?-CD) functionalized magnetic nanoparticles (MNPs). The MNPs were first modified with monotosyl-poly(ethylene glycol) (PEG) silane and then tosyl units were displaced by amino-?-CD through the nucleophilic substitution reaction. The monotosyl-PEG silane was synthesized by modifying a PEG diol to form the corresponding monotosyl-PEG, followed by a reaction with 3-isocyanatopropyltriethoxysilane (IPTS). The success of the synthesis of the monotosyl-PEG silane was confirmed with 1H NMR and Fourier transform infrared (FTIR) spectroscopy. The analysis of FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed the immobilization of ?-CD onto MNPs. Transmission electron microscopy (TEM) indicated that the ?-CD functionalized MNPs were mostly present as individual nonclustered units in water. The number of ?-CD molecules immobilized on each MNP was about 240 according to the thermogravimetric analysis (TGA) results. The as-prepared ?-CD functionalized MNPs were used to detect dopamine with the assistance of a magnet.

Wu, Yuanpeng; Zuo, Fang; Zheng, Zhaohui; Ding, Xiaobin; Peng, Yuxing

2009-07-01

251

Light-harvesting host-guest antenna materials for solar energy conversion devices  

NASA Astrophysics Data System (ADS)

In natural photosynthesis, light is absorbed by photonic antenna systems consisting of a few hundred chlorophyll molecules. These devices allow fast energy transfer from an electronically excited molecule to an unexcited neighbour molecule in such a way that the excitation energy reaches the reaction centre with high probability. Trapping occurs there. The anisotropic arrangement of the chlorophyll molecules is important for efficient energy migration. In natural antennae the formation of aggregates is prevented by fencing the chlorophyll molecules in polypeptide cages. A similar approach is possible by enclosing dyes inside a microporous material and by choosing conditions such that the cavities are able to uptake only monomers but not aggregates. In most of our experiments we have been using zeolite L as a host because it was found to be very versatile. Its crystals are of cylindrical shape and consist of an extended one-dimensional tube system. They can be prepared in wide size range. We have filled the individual tubes with successive chains of different dye molecules and we have shown that photonic antenna materials can be prepared. Moreover, fluorescent dye molecules can be bound covalently to the channel entrances. Dependent on the spectral properties of these stopcock molecules, the electronic excitation energy is transported radiationless to the stopcock fixed at the ends of the nanochannels or injected from the stopcock to the dyes inside the zeolite. The radiationless energy migration is in competition with spontaneous emission, thermal deactivation, quenching, and photochemically induced degradation. Fast energy migration is therefore crucial for an efficient antenna material. - The supramolecular organization of the dyes inside the channels is a first stage of organization. It allows light harvesting within the volume of a dye-loaded zeolite L crystal and radiationless transport to both ends of the cylinder or from the ends to the centre. The second stage of organization is the coupling to an external acceptor or donor stopcock fluorophore at the ends of the zeolite L channels, which can trap or inject electronic excitation energy. The third stage of organization is the coupling to an external device via a stopcock intermediate. The wide-ranging tunability of these highly organized materials offers fascinating new possibilities for exploring excitation energy transfer phenomena, and challenges for developing new photonic devices for solar energy conversion and storage.

Huber, Stefan; Calzaferri, Gion

2006-04-01

252

Host-guest encapsulation of materials by assembled virus protein cages  

NASA Astrophysics Data System (ADS)

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.

Douglas, Trevor; Young, Mark

1998-05-01

253

Elongation flow-triggered morphology transitions of dendritic polyethylene amphiphilic assemblies: host-guest implications.  

PubMed

The assemblies and transformations of dendritic polyethylene (DPE)-poly(oligo(ethyleneglycol) methacrylate) (POEGMA) amphiphilic micelles have been demonstrated by cryo-TEM and DLS techniques under elongation flow stimuli. The flow rate-dependence of the dissymmetry ratio suggests the possibility that a combination of shear and elongation could also be responsible for the transitions of DPE-POEGMAs, but it is obvious that the exposure of elongation flow is essential and plays a key role in the assembly and fusion of the DPE-POEGMA micelles. Fluorescence resonance energy transfer (FRET) is used to provide insight into the assembly and fusion of DPE-POEGMA under elongation flow. The FRET results show that a shorter separation distance of DiO-DiI with higher elongation rate can result in higher FRET efficiency. Furthermore, DPE-POEGMAs can display the responsive switching ability of the elongation flow-triggered FRET. PMID:25046698

Zhu, Jieqing; Tan, Minghao; Zhang, Ling; Yin, Qihe

2014-09-14

254

Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability  

NASA Astrophysics Data System (ADS)

The inclusion complexation behavior, characterization and binding ability of pinocembrin with ?-cyclodextrin (?-CD) and its derivative 2-hydroxypropyl-?-cyclodextrin (HP?CD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

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

255

Responsive supramolecular polymers based on the bis[alkynylplatinum(II)] terpyridine molecular tweezer/arene recognition motif.  

PubMed

Supramolecular polymers are constructed based on the novel bis[alkynylplatinum(II)] terpyridine molecular tweezer/pyrene recognition motif. Successive addition of anthracene as the diene and cyano-functionalized dienophile triggers the reversible supramolecular polymerization process, thus advancing the concept of utilizing Diels-Alder chemistry to access stimuli-responsive materials in compartmentalized systems. PMID:24810864

Tian, Yu-Kui; Shi, Yong-Gang; Yang, Zhi-Shuai; Wang, Feng

2014-06-10

256

Direct integration of micromachined pipettes in a flow channel for single DNA molecule study by optical tweezers  

Microsoft Academic Search

We have developed a micromachined flow cell consisting of a flow channel integrated with micropipettes. The flow cell is used in combination with an optical trap setup (optical tweezers) to study mechanical and structural properties of ?-DNA molecules. The flow cell was realized using silicon micromachining including the so-called buried channel technology to fabricate the micropipettes, the wet etching of

Cristina Rusu; Oever van't Ronny; M. J. de Boer; Henri V. Jansen; J. W. Berenschot; Martin L. Bennink; Johannes S. Kanger; B. G. de Grooth; Miko Elwenspoek; Jan Greve; Jürgen Brugger; Berg van den Albert

2001-01-01

257

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

NASA Astrophysics Data System (ADS)

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

Ingle, Ninad; Mohanty, Samarendra K.

2011-03-01

258

Stable trapping and manually controlled rotation of an asymmetric or birefringent microparticle using dual-mode split-beam optical tweezers.  

PubMed

Inserting a coverslip into half of a Gaussian laser beam at a suitable tilting angle can make the single-mode laser beam become closely spaced dual light spots at the laser focus. In this way, we can reform the conventional single-beam optical tweezers easily and construct a set of dual-mode split-beam optical tweezers, which can be used to manually rotate a trapped and twisted red blood cell around the optical axis. Furthermore, we demonstrate that the split-beam optical tweezers can also stably trap and orient a birefringent polystyrene micro strip particle, which otherwise will self rotate at a varying speed along the structural principal axes, fast spin about the optical axis in a tilting pose, or precess like a gyroscope, in the original linearly polarized single-beam optical tweezers. PMID:20639958

Sheu, Fang-Wen; Lan, Tzu-Kai; Lin, Yu-Chung; Chen, Shiung; Ay, Chyung

2010-07-01

259

A bisphosphonate tweezers and clickable PEGylated PAMAM dendrons for the preparation of functional iron oxide nanoparticles displaying renal and hepatobiliary elimination.  

PubMed

The functionalization of superparamagnetic iron oxide nanoparticles (SPION) with PEGylated PAMAM dendrons through a bisphosphonate tweezers yielded 15 and 30 nm dendritic nano-objects stable in physiological media and showing both renal and hepatobiliary elimination. PMID:23991429

Ghobril, Cynthia; Popa, Gabriela; Parat, Audrey; Billotey, Claire; Taleb, Jacqueline; Bonazza, Pauline; Begin-Colin, Sylvie; Felder-Flesch, Delphine

2013-10-14

260

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

Microsoft Academic Search

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

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

1999-01-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

262

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

PubMed

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

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

2006-02-10

263

Trehalose facilitates DNA melting: a single-molecule optical tweezers study.  

PubMed

Using optical tweezers, here we show that the overstretching transition force of double-stranded DNA (dsDNA) is lowered significantly by the addition of the disaccharide trehalose as well as certain polyol osmolytes. This effect is found to depend linearly on the logarithm of the trehalose concentration. We propose an entropic driving mechanism for the experimentally observed destabilization of dsDNA that is rooted in the higher affinity of the DNA bases for trehalose than for water, which promotes base exposure and DNA melting. Molecular dynamics simulation reveals the direct interaction of trehalose with nucleobases. Experiments with other osmolytes confirm that the extent of dsDNA destabilization is governed by the ratio between polar and apolar fractions of an osmolyte. PMID:25096217

Bezrukavnikov, Sergey; Mashaghi, Alireza; van Wijk, Roeland J; Gu, Chan; Yang, Li Jiang; Gao, Yi Qin; Tans, Sander J

2014-10-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2002-05-01

265

Accurate measurement of force and displacement with optical tweezers using DNA molecules as metrology standards  

NASA Astrophysics Data System (ADS)

Optical tweezers facilitate measurement of piconewton-level forces and nanometer-level displacements and have broad applications in biophysics and soft matter physics research. We have shown previously that DNA molecules can be used as metrology standards to define such measurements. Force-extension measurements on two DNA molecules of different lengths can be used to determine four necessary measurement parameters. Here, we show that the accuracy of determining these parameters can be improved by more than 7-fold by incorporating measurements of the DNA overstretching transition and using a multi-step data analysis procedure. This method results in very robust and precise fitting of DNA force-extension measurements to the worm-like chain model. We verify the accuracy through independent measurements of DNA stretching, DNA unzipping, and microsphere contact forces.

delToro, Damian; Smith, Douglas E.

2014-04-01

266

Optical levitation and manipulation of stuck particles with pulsed optical tweezers  

NASA Astrophysics Data System (ADS)

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 ?m was used to generate a large gradient force (up to 10^-9 N) within a short duration (~45 ?s) 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 ?m 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%.

Ashok Ambardekar, Amol; Li, Yong-Qing

2005-07-01

267

Optical tweezers assisted imaging of the Z-ring in Escherichia coli: measuring its radial width  

NASA Astrophysics Data System (ADS)

Using single-beam, oscillating optical tweezers we can trap and rotate rod-shaped bacterial cells with respect to the optical axis. This technique allows imaging fluorescently labeled three-dimensional sub-cellular structures from different, optimized viewpoints. To illustrate our method we measure D, the radial width of the Z-ring in unconstricted Escherichia coli. We use cells that express FtsZ-GFP and have their cytoplasmic membrane stained with FM4-64. In a vertically oriented cell, both the Z-ring and the cytoplasmic membrane images appear as symmetric circular structures that lend themselves to quantitative analysis. We found that D ? 100 nm, much larger than expected.

Carmon, G.; Kumar, P.; Feingold, M.

2014-01-01

268

Optical tweezers study of viscoelastic properties in the outer hair cell plasma membrane  

NASA Astrophysics Data System (ADS)

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 (?), stiffness values (?), and coefficients of friction (?). 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.

Murdock, David R.; Ermilov, Sergey A.; Qian, Feng; Brownell, William E.; Anvari, Bahman

2004-06-01

269

Studies of cochlear outer hair cell membrane mechanics using optical tweezers  

NASA Astrophysics Data System (ADS)

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,(?) and effective membrane viscosity (?eff) was measured. The Feq for the OHC lateral wall plasma membrane was ~60 pN and was unchanged by addition of CPZ. A significantly greater ? value was observed in CPZ-treated OHCs (30.5 +/- 12.6 s) than in control OHCs (19.0 +/- 13.2 s). The Feq and ? 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/?m for CPZ-treated OHCs. This represents a decrease from reported control OHC membrane viscosities.

Murdock, David R.; Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

2003-06-01

270

Engineered Tumor Cell Apoptosis Monitoring Method Based on Dynamic Laser Tweezers  

PubMed Central

Monitoring the cells' apoptosis progression could provide a valuable insight into the temporal events that initiate cell death as well as the potential for rescue of apoptotic cells. In this paper, we engineered a novel and robust method for monitoring apoptosis of tumor cells based on dynamic laser tweezers, using A549 and HeLa cell line as typical samples. The entire experiment can be completed in a few hours with small amount of fluid sample, presenting great advantages of celerity, microscaled measurement, and label-free explorations without perturbing experimental conditions in combination with other probes. Validity and stability of this method are verified experimentally in terms of physical parameters of the system. The proposed technique has great potential in improving cancer treatment by monitoring the objective efficacy of tumor cell killing. PMID:24800217

Zhang, Yuquan; Wu, Xiaojing; Min, Changjun; Zhu, Siwei; Urbach, H. Paul; Yuan, Xiaocong

2014-01-01

271

Engineered tumor cell apoptosis monitoring method based on dynamic laser tweezers.  

PubMed

Monitoring the cells' apoptosis progression could provide a valuable insight into the temporal events that initiate cell death as well as the potential for rescue of apoptotic cells. In this paper, we engineered a novel and robust method for monitoring apoptosis of tumor cells based on dynamic laser tweezers, using A549 and HeLa cell line as typical samples. The entire experiment can be completed in a few hours with small amount of fluid sample, presenting great advantages of celerity, microscaled measurement, and label-free explorations without perturbing experimental conditions in combination with other probes. Validity and stability of this method are verified experimentally in terms of physical parameters of the system. The proposed technique has great potential in improving cancer treatment by monitoring the objective efficacy of tumor cell killing. PMID:24800217

Zhang, Yuquan; Wu, Xiaojing; Min, Changjun; Zhu, Siwei; Urbach, H Paul; Yuan, Xiaocong

2014-01-01

272

Micro-rheology on (polymer-grafted) colloids using optical tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it—without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

Gutsche, C.; Elmahdy, M. M.; Kegler, K.; Semenov, I.; Stangner, T.; Otto, O.; Ueberschär, O.; Keyser, U. F.; Krueger, M.; Rauscher, M.; Weeber, R.; Harting, J.; Kim, Y. W.; Lobaskin, V.; Netz, R. R.; Kremer, F.

2011-05-01

273

Micro-rheology on (polymer-grafted) colloids using optical tweezers.  

PubMed

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed. PMID:21508470

Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschär, O; Keyser, U F; Krueger, M; Rauscher, M; Weeber, R; Harting, J; Kim, Y W; Lobaskin, V; Netz, R R; Kremer, F

2011-05-11

274

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers.  

PubMed

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 microm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures. PMID:18711539

Benito, D C; Carberry, D M; Simpson, S H; Gibson, G M; Padgett, M J; Rarity, J G; Miles, M J; Hanna, S

2008-08-18

275

Mechanism of termination of bacteriophage DNA packaging investigated with optical tweezers  

NASA Astrophysics Data System (ADS)

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.

delToro, Damian J.; Smith, Douglas E.

2012-10-01

276

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

PubMed Central

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

Frusawa, Hiroshi; Matsumoto, Youei

2014-01-01

277

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

PubMed

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

Frusawa, Hiroshi; Matsumoto, Youei

2014-01-01

278

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

NASA Astrophysics Data System (ADS)

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

Frusawa, Hiroshi; Matsumoto, Youei

2014-02-01

279

Haptic guidance for improved task performance in steering microparticles with optical tweezers.  

PubMed

We report the manipulation of 4-5 mum diameter polymer microspheres floating in water using optical tweezers (OT) and a haptic device (i.e. force-reflecting robotic arm). Trapped microspheres are steered using the end-effector of a haptic device that is virtually coupled to an XYZ piezo-scanner controlling the movements of the fluid bed. To help with the manipulations, we first calculate a collision-free path for the particle and then display artificial guidance forces to the user through the haptic device to keep him/her on this path during steering. Experiments conducted with 8 subjects show almost two-fold improvements in the average path error and average speed under the guidance of haptic feedback. PMID:19547521

Basdogan, Cagatay; Kiraz, Alper; Bukusoglu, Ibrahim; Varol, Ayd?n; Do?anay, Sultan

2007-09-01

280

Nanoplasmonic Tweezers Visualize Protein p53 Suppressing Unzipping of Single DNA-Hairpins  

E-print Network

Here we report on the use of double-nanohole (DNH) optical tweezers as a label-free and free-solution single-molecule probe for protein-DNA interactions. Using this approach, we demonstrate the unzipping of individual 10 base pair DNA-hairpins, and quantify how tumor suppressor p53 protein delays the unzipping. From the Arrhenius behavior, we find the energy barrier to unzipping introduced by p53 to be $2\\times 10^{-20}$ J, whereas cys135ser mutant p53 does not show suppression of unzipping, which gives clues to its functional inability to suppress tumor growth. This transformative approach to single molecule analysis allows for ultra-sensitive detection and quantification of protein-DNA interactions to revolutionize the fight against genetic diseases.

Kotnala, Abhay

2014-01-01

281

Extended linear detection range for optical tweezers using image-plane detection scheme  

NASA Astrophysics Data System (ADS)

Ability to measure pico- and femto-Newton range forces using optical tweezers (OT) strongly relies on the sensitivity of its detection system. We show that the commonly used back-focal-plane detection method provides a linear response range which is shorter than that of the restoring force of OT for large beads. This limits measurable force range of OT. We show, both theoretically and experimentally, that utilizing a second laser beam for tracking could solve the problem. We also propose a new detection scheme in which the quadrant photodiode is positioned at the plane optically conjugate to the object plane (image plane). This method solves the problem without need for a second laser beam for the bead sizes that are commonly used in force spectroscopy applications of OT, such as biopolymer stretching.

Hajizadeh, Faegheh; Masoumeh Mousavi, S.; Khaksar, Zeinab S.; Reihani, S. Nader S.

2014-10-01

282

DNA interaction with diaminobenzidine studied with optical tweezers and dynamic light scattering.  

PubMed

We have studied the interaction of the DNA molecule with the ligand 3,3'-diaminobenzidine (DAB) by performing single molecule stretching experiments with optical tweezers and dynamic light scattering (DLS) on the DNA-DAB complexes. In the stretching experiments, the persistence and contour lengths of the complexes were measured as a function of DAB concentration, allowing one to infer the main binding mechanism and also to determine the physicochemical parameters of the interaction. In the DLS experiments, the effective size of the complexes, measured as the hydrodynamic radius, was monitored as a function of DAB concentration. We found a qualitative agreement between the results obtained from the two techniques by comparing the behaviors of the hydrodynamics radius and the radius of gyration, since this last one can be expressed as a function of the persistence and contour lengths. PMID:24164302

Reis, L A; Ramos, E B; Rocha, M S

2013-11-21

283

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

E-print Network

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

Hiroshi Frusawa; Youei Matsumoto

2014-03-05

284

An active one-particle microrheometer: Incorporating magnetic tweezers to total internal reflection microscopy  

NASA Astrophysics Data System (ADS)

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.

Gong, Xiangjun; Hua, Li; Wu, Chi; Ngai, To

2013-03-01

285

Optoelectronic tweezers for the measurement of the relative stiffness of erythrocytes  

NASA Astrophysics Data System (ADS)

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.

Neale, Steven L.; Mody, Nimesh; Selman, Colin; Cooper, Jonathan M.

2012-10-01

286

Protection of primary neurons and mouse brain from Alzheimer's pathology by molecular tweezers  

PubMed Central

Alzheimer’s disease is a devastating cureless neurodegenerative disorder affecting >35 million people worldwide. The disease is caused by toxic oligomers and aggregates of amyloid ? protein and the microtubule-associated protein tau. Recently, the Lys-specific molecular tweezer CLR01 has been shown to inhibit aggregation and toxicity of multiple amyloidogenic proteins, including amyloid ? protein and tau, by disrupting key interactions involved in the assembly process. Following up on these encouraging findings, here, we asked whether CLR01 could protect primary neurons from Alzheimer’s disease-associated synaptotoxicity and reduce Alzheimer’s disease–like pathology in vivo. Using cell culture and brain slices, we found that CLR01 effectively inhibited synaptotoxicity induced by the 42-residue isoform of amyloid ? protein, including ?80% inhibition of changes in dendritic spines density and long-term potentiation and complete inhibition of changes in basal synaptic activity. Using a radiolabelled version of the compound, we found that CLR01 crossed the mouse blood–brain barrier at ?2% of blood levels. Treatment of 15-month-old triple-transgenic mice for 1 month with CLR01 resulted in a decrease in brain amyloid ? protein aggregates, hyperphosphorylated tau and microglia load as observed by immunohistochemistry. Importantly, no signs of toxicity were observed in the treated mice, and CLR01 treatment did not affect the amyloidogenic processing of amyloid ? protein precursor. Examining induction or inhibition of the cytochrome P450 metabolism system by CLR01 revealed minimal interaction. Together, these data suggest that CLR01 is safe for use at concentrations well above those showing efficacy in mice. The efficacy and toxicity results support a process-specific mechanism of action of molecular tweezers and suggest that these are promising compounds for developing disease-modifying therapy for Alzheimer’s disease and related disorders. PMID:23183235

Attar, Aida; Ripoli, Cristian; Riccardi, Elisa; Maiti, Panchanan; Li Puma, Domenica D.; Liu, Tingyu; Hayes, Jane; Jones, Mychica R.; Lichti-Kaiser, Kristin; Yang, Fusheng; Gale, Greg D.; Tseng, Chi-hong; Tan, Miao; Xie, Cui-Wei; Straudinger, Jeffrey L.; Klarner, Frank-Gerrit; Schrader, Thomas; Frautschy, Sally A.; Grassi, Claudio

2012-01-01

287

Surface charge measurements and (dis)charging dynamics of organic semiconductors in various media using optical tweezers  

NASA Astrophysics Data System (ADS)

An exciting application of optical tweezers is the measurement of the surface charge on a trapped particle, as well as its time evolution with a single charge resolution. We report on an optical tweezer-based method to measure the effective surface charge on an organic semiconductor film at microscopic scales, which offers opportunities for investigations of ion and electron transfer between organic molecules and surrounding medium. Effective charge densities of 13+/-5 elementary charges per ?m2 were observed in anthradithiophene-coated silica microspheres suspended in water, with a more than an order of magnitude reduction in charge densities upon replacing water with the 50% wt/wt glycerol/water mixture.

Grollman, Rebecca R.; Peters, Kyle; Ostroverkhova, Oksana

2014-03-01

288

Isolation of genomic DNA molecule from a single cell and control its higher order structure using optical tweezers  

NASA Astrophysics Data System (ADS)

In this report, we describe a noninvasive methodology for manipulating single Mb-size whole-genome DNA molecules. Cells were subjected to osmotic shock and the genome DNA released from the burst cells was transferred to a region of higher salt concentration between cover slips using optical tweezers. The transferred genome DNA exhibits a conformational transition from a compact state into an elongated state, accompanied by the change in its environment. Here, the applicability of optical tweezers to the on-site manipulation of giant genomic DNA is suggested. Next, to control the field environment more precisely, a flow chamber was made and similar investigations were carried out. In the flow chamber, the higher-order structure of individual chromosomal DNA molecules from a fission yeast that were folded by polyamine was changed to a partially unfolded form by transporting into a higher salt condition using optical tweezers. These promising methodologies demonstrated here may make it possible to recover an intact single whole-genome DNA from a cell and carry out further sequential investigations under a microscope.

Oana, Hidehiro; Hagiya, Isao; Washizu, Masao; Kubo, Koji; Yoshikawa, Kenichi; Atomi, Haruyuki; Imanaka, Tadayuki

2005-08-01

289

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

NASA Astrophysics Data System (ADS)

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

Paramanathan, Thayaparan

290

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

PubMed

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

Power, Rory M; Reid, Jonathan P

2014-07-01

291

Manipulating cell adhesions with optical tweezers for study of cell-to-cell interactions.  

PubMed

This paper presents an approach to manipulating cell adhesions using optical tweezers for cell-to-cell interactions at single cell level. A case study of investigating the adhesions between leukemia cells and bone marrow stromal cells is reported. First, the trapping force imposed on the cell is calibrated and the viability of leukemia cells after optical trapping is tested and verified. This is for demonstrating the feasibility of the proposed optical manipulation method. Second, properties of adhesions of leukemia cells K562 on stromal cells M210B4 from mouse and HS5 from human are characterized. Based on characterization results, we classify adhesions into three categories namely tightly adherent, loosely adherent or free suspending. Finally, the adhesion abilities of K562 on M210B4 and HS5 are changed by adding heparin into culture medium, which demonstrates the specificity of the adhesion. The important contribution of this paper lies in development of a dexterous cell manipulation method to characterize cell adhesion properties, which helps create a new opportunity to investigate cell-to-cell interactions at single cell level. PMID:23627055

Hu, Songyu; Gou, Xue; Han, Hochun; Leung, Anskar Y H; Sun, Dong

2013-02-01

292

DNA condensation by TmHU studied by optical tweezers, AFM and molecular dynamics simulations  

PubMed Central

The compaction of DNA by the HU protein from Thermotoga maritima (TmHU) is analysed on a single-molecule level by the usage of an optical tweezers-assisted force clamp. The condensation reaction is investigated at forces between 2 and 40 pN applied to the ends of the DNA as well as in dependence on the TmHU concentration. At 2 and 5 pN, the DNA compaction down to 30% of the initial end-to-end distance takes place in two regimes. Increasing the force changes the progression of the reaction until almost nothing is observed at 40 pN. Based on the results of steered molecular dynamics simulations, the first regime of the length reduction is assigned to a primary level of DNA compaction by TmHU. The second one is supposed to correspond to the formation of higher levels of structural organisation. These findings are supported by results obtained by atomic force microscopy. PMID:22210966

Olbrich, Carsten; Brutzer, Hergen; Salomo, Mathias; Kleinekathofer, Ulrich; Keyser, Ulrich F.; Kremer, Friedrich

2010-01-01

293

Optical force sensor array in a microfluidic device based on holographic optical tweezers.  

PubMed

Holographic optical tweezers (HOT) are a versatile technology, with which complex arrays and movements of optical traps can be realized to manipulate multiple microparticles in parallel and to measure the forces affecting them in the piconewton range. We report on the combination of HOT with a fluorescence microscope and a stop-flow, multi-channel microfluidic device. The integration of a high-speed camera into the setup allows for the calibration of all the traps simultaneously both using Boltzmann statistics or the power spectrum density of the particle diffusion within the optical traps. This setup permits complete spatial, chemical and visual control of the microenvironment applicable to probing chemo-mechanical properties of cellular or subcellular structures. As an example we constructed a biomimetic, quasi-two-dimensional actin network on an array of trapped polystyrene microspheres inside the microfluidic chamber. During crosslinking of the actin filaments by Mg(2+) ions, we observe the build up of mechanical tension throughout the actin network. Thus, we demonstrate how our integrated HOT-microfluidics platform can be used as a reconfigurable force sensor array with piconewton resolution to investigate chemo-mechanical processes. PMID:19224015

Uhrig, Kai; Kurre, Rainer; Schmitz, Christian; Curtis, Jennifer E; Haraszti, Tamás; Clemen, Anabel E-M; Spatz, Joachim P

2009-03-01

294

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

PubMed

A novel instrument to manipulate and characterize the mechanical environment in and around microscale objects in a fluidic environment has been developed by integrating two laser-based techniques: micron-resolution particle image velocimetry (?PIV) and optical tweezers (OT). This instrument, the ?PIVOT, enables a new realm of microscale studies, yet still maintains the individual capabilities of each optical technique. This was demonstrated with individual measurements of optical trap stiffness (?70 pN ?m(-1) for a 20 ?m polystyrene sphere and a linear relationship between trap stiffness and laser power) and fluid velocities within 436 nm of a microchannel wall. The integrated device was validated by comparing computational flow predictions to the measured velocity profile around a trapped particle in either a uniform flow or an imposed, gravity-driven microchannel flow (R(2) = 0.988, RMS error = 13.04 ?m s(-1)). Interaction between both techniques is shown to be negligible for 15 ?m to 35 ?m diameter trapped particles subjected to fluid velocities from 50 ?m s(-1) to 500 ?m s(-1) even at the highest laser power (1.45 W). The integrated techniques will provide a unique perspective toward understanding microscale phenomena including single-cell biomechanics, non-Newtonian fluid mechanics and single particle or particle-particle hydrodynamics. PMID:18953424

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

2008-01-01

295

Computations of radiation force using the translational addition theorem: Applications to acoustical tweezers  

E-print Network

This work proposes a method to compute both axial and transverse radiation forces produced by an ultrasound beam of arbitrary wavefront based on the partial-wave expansion (PWE) and the translational addition theorem for spherical wave functions. The major advantage of using the addition theorem is the computation of acoustic radiation force for a wide variety of beams which satisfy the Helmholtz equation without the need of numerical quadrature schemes. The PWE method is applied to calculate the radiation force exerted on a silicone-oil droplet suspended in water. The force is produced by a single-beam acoustical tweezer composed by a spherically focused transducer with driving frequency of 3.1 MHz and F-number of 1.6. The droplet can be positioned anywhere in the host medium. The radiation force is analyzed in the Rayleigh and resonant scattering regimes. The obtained results in the Rayleigh scattering regime are compared to those calculated with Gor'kov's radiation force theory. It turns out to be that bot...

Baggio, André L; Silva, Glauber T

2012-01-01

296

New magnetic tweezers for investigation of the mechanical properties of single DNA molecules  

NASA Astrophysics Data System (ADS)

This study reports new three-dimensional (3D) micromachined magnetic tweezers consisting of micro-electromagnets and a ring-trap structure, fabricated using MEMS (micro-electro-mechanical systems) technology, for manipulating a single 2 nm diameter DNA molecule. The new apparatus uses magnetic forces to exert over 20 pN with less heating, allowing the extension of the DNA molecule over its whole contour length to investigate its entropic and elastic regions. To improve the localized DNA immobilization efficiency, a novel ring-trapper structure was used to handle the vertical movement of magnetic beads which were adhered to the DNA molecules. One extremity of the DNA molecule, which was bound to the thiol-modified magnetic bead, could be immobilized covalently on a gold surface. The other extremity, which was bound to another unmodified magnetic bead, could be manipulated under a magnetic field generated by micro-electromagnets. The important elastic modulus of DNA has been explored to be 453 pN at a low ionic strength. This result reveals that DNA becomes more susceptible to elastic elongation at a low ionic strength due to electrostatic repulsion. The force-extension curve for DNA molecules is found to be consistent with theoretical models. In addition to a single DNA stretching, this study also successfully demonstrates the stretching of two parallel DNA molecules.

Chiou, Chi-Han; Huang, Yu-Yen; Chiang, Meng-Han; Lee, Huei-Huang; Lee, Gwo-Bin

2006-03-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

298

Induction of sustained glycolytic oscillations in single yeast cells using microfluidics and optical tweezers  

NASA Astrophysics Data System (ADS)

Yeast glycolytic oscillations have been studied since the 1950s in cell free extracts and in intact cells. Until recently, sustained oscillations have only been observed in intact cells at the population level. The aim of this study was to investigate sustained glycolytic oscillations in single cells. Optical tweezers were used to position yeast cells in arrays with variable cell density in the junction of a microfluidic flow chamber. The microfluidic flow chambers were fabricated using soft lithography and the flow rates in the different inlet channels were individually controlled by syringe pumps. Due to the low Reynolds number, the solutions mixed by diffusion only. The environment in the junction of the chamber could thus be controlled by changing the flow rates in the inlet channels, with a complete change of environment within 2 s. The optimum position of the cell array was determined by simulations, to ensure complete coverage of the intended solution without any concentration gradients over the cell array. Using a DAPI filter set, the NADH auto fluorescence could be monitored in up to 100 cells simultaneously. Sustained oscillations were successfully induced in individual, isolated cells within specific flow rates and concentrations of glucose and cyanide. By changing the flow rates without changing the surrounding solution, it was found that the cell behavior was dependent on the concentration of chemicals in the medium rather than the flow rates in the range tested. Furthermore, by packing cells tightly, cell-to-cell interaction and synchronization could be studied.

Gustavsson, Anna-Karin; Adiels, Caroline B.; Goksör, Mattias

2012-10-01

299

Optical tweezers and multiphoton microscopies integrated photonic tool for mechanical and biochemical cell processes studies  

NASA Astrophysics Data System (ADS)

The research in biomedical photonics is clearly evolving in the direction of the understanding of biological processes at the cell level. The spatial resolution to accomplish this task practically requires photonics tools. However, an integration of different photonic tools and a multimodal and functional approach will be necessary to access the mechanical and biochemical cell processes. This way we can observe mechanicaly triggered biochemical events or biochemicaly triggered mechanical events, or even observe simultaneously mechanical and biochemical events triggered by other means, e.g. electricaly. One great advantage of the photonic tools is its easiness for integration. Therefore, we developed such integrated tool by incorporating single and double Optical Tweezers with Confocal Single and Multiphoton Microscopies. This system can perform 2-photon excited fluorescence and Second Harmonic Generation microscopies together with optical manipulations. It also can acquire Fluorescence and SHG spectra of specific spots. Force, elasticity and viscosity measurements of stretched membranes can be followed by real time confocal microscopies. Also opticaly trapped living protozoas, such as leishmania amazonensis. Integration with CARS microscopy is under way. We will show several examples of the use of such integrated instrument and its potential to observe mechanical and biochemical processes at cell level.

de Thomaz, A. A.; Faustino, W. M.; Fontes, A.; Fernandes, H. P.; Barjas-Castro, M. d. L.; Metze, K.; Giorgio, S.; Barbosa, L. C.; Cesar, C. L.

2007-09-01

300

Determination of femto Newton forces and fluid viscosity using optical tweezers: application to Leishmania amazonensis  

NASA Astrophysics Data System (ADS)

The objective of this research is to use the displacements of a polystyrene microsphere trapped by an optical tweezers (OT) as a force transducer in mechanical measurements in life sciences. To do this we compared the theoretical optical and hydrodynamic models with experimental data under a broad variation of parameters such as fluid viscosity, refractive index, drag velocity and wall proximities. The laser power was measured after the objective with an integration sphere because normal power meters do not provide an accurate measurement for beam with high numerical apertures. With this careful laser power determination the plot of the optical force (calculated by the particle displacement) versus hydrodynamic force (calculated by the drag velocity) under very different conditions shows an almost 45 degrees straight line. This means that hydrodynamic models can be used to calibrate optical forces and vice-versa. With this calibration we observed the forces of polystyrene bead attached to the protozoa Leishmania amazonensis, responsible for a serious tropical disease. The force range is from 200 femto Newtons to 4 pico Newtons and these experiments shows that OT can be used for infection mechanism and chemotaxis studies in parasites. The other application was to use the optical force to measure viscosities of few microliters sample. Our result shows 5% accuracy measurements.

Fontes, Adriana; Giorgio, Selma; de Castro, Archimedes B., Jr.; Neto, Vivaldo M.; Pozzo, Liliana d. Y.; Marques, Gustavo P.; Barbosa, Luiz C.; Cesar, Carlos L.

2005-03-01

301

Spatially-sculpted aberrated optical tweezers for delivery of nanoparticles onto cells  

NASA Astrophysics Data System (ADS)

Nanoparticles (NP) are emerging as photochemical and photothermal agents for delivery of drugs and heat onto the targeted cells. Here, we report spatially-sculpting of transverse potential landscape by introducing aberration in the optical tweezers beam for delivery of therapeutic NP on to the prostate cancer PC3 cells. A tunable Ti-Sapphire laser beam was focused to a diffraction limited spot by use of a high numerical aperture microscope objective for optical trapping. A cylindrical lens was used to create the beam profile astigmatic, which led to spatially extended potential landscape. In order to facilitate transport of NP, Comatic potential was created by tilting of the astigmatic beam with respect to the optic axis. NPs were attracted towards the potential minima, transported along the major axis of the elliptic spot and ejected out along the direction having lower stiffness. The Carbon NPs as well as Poly Lactic-co-Glycolic Acid NPs were efficiently transported and concentrated near the PC3 cells in-vitro. The direction and the speed of transport of nano-particles could be reversed by change in tilt direction and angle. Further, by utilizing the scattering force with the asymmetric gradient force, three-dimensional transport of nanoparticles was achieved. The effect of laser beam power and size / refractive index of the nano-particles on the speed of transport will be presented.

Shivalingaiah, Shivaranjani; Chhajed, Suyash; Mohanty, Samarendra

2011-03-01

302

The history and evolution of surgical instruments. VII. Spring forceps (tweezers), hooks and simple retractors.  

PubMed Central

Instruments manufactured by bending a basic metal strip or rod, either about its middle to create spring forceps (tweezers), or towards one extremity to create hooks and retractors are related structures. Spring forceps depend on tension mediated at the bend (hoop) or fixed end which is transmitted as dynamic 'spring' to the jaws, whereas the bend of hooks and retractors remains fixed and static. If such instruments refine the digital postures of pinch, pincer and retraction during surgery, they have not supplanted these manual actions entirely. After a brief historical introduction, the structure, modifications, functions and controls of spring forceps are analysed. Importantly, this instrument enjoys both right and left-handed functions, some of which are ancient, some transient as haemostats and needle-holders, and some, including left-handed dissection, surprisingly recent. Hooks are sharp or blunt and, among other functions, pre-date the left-handed spring forceps for dissection; in general hooks function as retractors. Hand-held retractors are enlarged blunt hooks, the wide retracting contact surface reducing trauma to wound margins and viscera. The physical effort of employing these retractors deep in body cavities is abated by applying them autostatically around a square or circular frame. Images Figure 1 PMID:8943642

Kirkup, J.

1996-01-01

303

Single-molecule kinetics under force: probing protein folding and enzymatic activity with optical tweezers  

NASA Astrophysics Data System (ADS)

Weak non-covalent bonds between and within single molecules govern many aspects of biological structure and function (e.g. DNA base-paring, receptor-ligand binding, protein folding, etc.) In living systems, these interactions are often subject to mechanical forces, which can greatly alter their kinetics and activity. My group develops and applies novel single-molecule manipulation techniques to explore and quantify these force-dependent kinetics. Using optical tweezers, we have quantified the force-dependent unfolding and refolding kinetics of different proteins, including the cytoskeletal protein spectrin in collaboration with E. Evans's group [1], and the A2 domain of the von Willebrand factor blood clotting protein in collaboration with T. Springer's group [2]. Furthermore, we have studied the kinetics of the ADAMTS13 enzyme acting on a single A2 domain, and have shown that physiolgical forces in the circulation can act as a cofactor for enzymatic cleavage, regulating hemostatic activity [2]. References: 1. E. Evans, K. Halvorsen, K. Kinoshita, and W.P. Wong, Handbook of Single Molecule Biophysics, P. Hinterdorfer, ed., Springer (2009). 2. X. Zhang, K. Halvorsen, C.-Z. Zhang, W.P. Wong, and T.A. Springer, Science 324 (5932), 1330-1334 (2009).

Wong, Wesley

2010-03-01

304

A survey of DNA looping and cleavage properties of different restriction enzymes using optical tweezers  

NASA Astrophysics Data System (ADS)

Of the more than 3500 known Type II REases, a small but growing number have been identified that require two copies of the enzyme's recognition site for activity. Each site is bound to one enzyme subunit, and the two subunits come together by thermodynamic DNA looping to form an active multimer that cleaves the DNA. When Ca^++ is replaced with Mg^++ however, the multimers usually ``staple'' the recognition sites together trapping the DNA loops. Using force measuring optical tweezers, we investigate the behavior of 16 different two-site REases from the Type IIe, Type IIf, and Type IIs subsets on single DNA molecules in the presence of Mg^++, Ca^++, and EDTA. We show that one-site and two-site REases may be rapidly discerned. By measuring the force needed to disrupt the loops in the presence of Ca^++, we elucidate various binding behaviors amongst the two-site REases, probing DNA-enzyme and/or enzymatic subunit-subunit affinity. For one enzyme, HpaII, the effect of [Ca^++] on activity is studied in detail.

Millin, Rachel

2005-03-01

305

Thermodynamic DNA Looping by a Two-Site Restriction Endonuclease Studied using Optical Tweezers  

NASA Astrophysics Data System (ADS)

Many enzyme-DNA interactions involve multimeric protein complexes that bind at two distant sites such that the DNA is looped. An example is the type IIe restriction enzyme Sau3AI, which requires two recognition sites to cleave the DNA. Here we study this process at the single DNA level using force measuring optical tweezers. We characterize cleavage rates of single DNA molecules in the presence of Sau3AI as a function of enzyme concentration, incubation time, and the fractional extension of the DNA molecule. Activity is completely inhibited by tensions of a few picoNewtons. By replacing Mg^2+ with Ca^2+, the Sau3AI dimers form but do not cleave the DNA, thus trapping DNA loops. We are able to pull apart these loops, measuring the force needed and the length of DNA released for each. We also characterize the number and length distributions of these loops as a function of incubation time and DNA fractional extension. The results of these studies are discussed in the context of a Brownian dynamics model of DNA looping.

Gemmen, Gregory J.

2005-03-01

306

The elasticity of single titin molecules using a two-bead optical tweezers assay.  

PubMed

Titin is responsible for the passive elasticity of the muscle sarcomere. The mechanical properties of skeletal and cardiac muscle titin were characterized in single molecules using a novel dual optical tweezers assay. Antibody pairs were attached to beads and used to select the whole molecule, I-band, A-band, a tandem-immunoglobulin (Ig) segment, and the PEVK region. A construct from the PEVK region expressing >25% of the full-length skeletal muscle isoform was chemically conjugated to beads and similarly characterized. By elucidating the elasticity of the different regions, we showed directly for the first time, to our knowledge, that two entropic components act in series in the skeletal muscle titin I-band (confirming previous speculations), one associated with tandem-immunoglobulin domains and the other with the PEVK region, with persistence lengths of 2.9 nm and 0.76 nm, respectively (150 mM ionic strength, 22 degrees C). Novel findings were: the persistence length of the PEVK component rose (0.4-2.7 nm) with an increase in ionic strength (15-300 mM) and fell (3.0-0.3 nm) with a temperature increase (10-60 degrees C); stress-relaxation in 10-12-nm steps was observed in the PEVK construct and hysteresis in the native PEVK region. The region may not be a pure random coil, as previously thought, but contains structured elements, possibly with hydrophobic interactions. PMID:15298915

Leake, Mark C; Wilson, David; Gautel, Mathias; Simmons, Robert M

2004-08-01

307

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

PubMed

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

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

2014-07-01

308

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

309

The Elasticity of Single Titin Molecules Using a Two-Bead Optical Tweezers Assay  

PubMed Central

Titin is responsible for the passive elasticity of the muscle sarcomere. The mechanical properties of skeletal and cardiac muscle titin were characterized in single molecules using a novel dual optical tweezers assay. Antibody pairs were attached to beads and used to select the whole molecule, I-band, A-band, a tandem-immunoglobulin (Ig) segment, and the PEVK region. A construct from the PEVK region expressing >25% of the full-length skeletal muscle isoform was chemically conjugated to beads and similarly characterized. By elucidating the elasticity of the different regions, we showed directly for the first time, to our knowledge, that two entropic components act in series in the skeletal muscle titin I-band (confirming previous speculations), one associated with tandem-immunoglobulin domains and the other with the PEVK region, with persistence lengths of 2.9 nm and 0.76 nm, respectively (150 mM ionic strength, 22°C). Novel findings were: the persistence length of the PEVK component rose (0.4–2.7 nm) with an increase in ionic strength (15–300 mM) and fell (3.0–0.3 nm) with a temperature increase (10–60°C); stress-relaxation in 10–12-nm steps was observed in the PEVK construct and hysteresis in the native PEVK region. The region may not be a pure random coil, as previously thought, but contains structured elements, possibly with hydrophobic interactions. PMID:15298915

Leake, Mark C.; Wilson, David; Gautel, Mathias; Simmons, Robert M.

2004-01-01

310

High-resolution detection of Brownian motion for quantitative optical tweezers experiments.  

PubMed

We have developed an in situ method to calibrate optical tweezers experiments and simultaneously measure the size of the trapped particle or the viscosity of the surrounding fluid. The positional fluctuations of the trapped particle are recorded with a high-bandwidth photodetector. We compute the mean-square displacement, as well as the velocity autocorrelation function of the sphere, and compare it to the theory of Brownian motion including hydrodynamic memory effects. A careful measurement and analysis of the time scales characterizing the dynamics of the harmonically bound sphere fluctuating in a viscous medium directly yields all relevant parameters. Finally, we test the method for different optical trap strengths, with different bead sizes and in different fluids, and we find excellent agreement with the values provided by the manufacturers. The proposed approach overcomes the most commonly encountered limitations in precision when analyzing the power spectrum of position fluctuations in the region around the corner frequency. These low frequencies are usually prone to errors due to drift, limitations in the detection, and trap linearity as well as short acquisition times resulting in poor statistics. Furthermore, the strategy can be generalized to Brownian motion in more complex environments, provided the adequate theories are available. PMID:23005790

Grimm, Matthias; Franosch, Thomas; Jeney, Sylvia

2012-08-01

311

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

SciTech Connect

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

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

2006-10-15

312

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

PubMed Central

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

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

2012-01-01

313

Effect of Low-Pass Filtering in Force Calibration of Magnetic Tweezers  

NASA Astrophysics Data System (ADS)

In typical experiments where magnetic tweezers are involved, precise measurement of the magnetic forces is of crucial importance. To achieve this, a widely applied method is to track the bead's Brownian motion trajectory and to calculate the force from its mean-squared-displacement. However, this method does not take into account the fact that the bead-tracking device always has a finite bandwidth, acting effectively as a low-pass filter. The result could be subjected to significant system errors, which overestimates the magnetic force. We analyze the power spectrum of the bead's Brownian motion, and provide a corrected formula to calculate the magnetic force, which is free of system errors induced by limited detection bandwidth. A dsDNA force-extension curve is experimentally measured. The curve is consistent with the WLC model, exhibiting correctness of the new formula. On the other hand, the force given by the traditional method shows significant deviation from the WLC model, which is 3 times larger at most.

Zheng, Hai-Zi; Nong, Da-Guan; Li, Ming

2013-11-01

314

On chip single-cell separation and immobilization using optical tweezers and thermosensitive hydrogel.  

PubMed

A novel approach appropriate for rapid separation and immobilization of a single cell by concomitantly utilizing laser manipulation and locally thermosensitive hydrogelation is proposed in this paper. We employed a single laser beam as optical tweezers for separating a target cell and locating it adjacent to a fabricated, transparent micro heater. Simultaneously, the target cell is immobilized or partially entrapped by heating the thermosensitive hydrogel with the micro heater. The state of the thermosensitive hydrogel can be switched from sol to gel and gel to sol by controlling the temperature through heating and cooling by the micro heater. After other unwanted cells are removed by the high-speed cleaning flow in the microchannel, the entrapped cell is successfully isolated. It is possible to collect the immobilized target cell for analysis or culture by switching off the micro heater and releasing the cell from the entrapment. We demonstrated that the proposed approach is feasible for rapid manipulation, immobilization, cleaning, isolation and extraction of a single cell. The experimental results are shown here. PMID:16286972

Arai, Fumihito; Ng, Chinaik; Maruyama, Hisataka; Ichikawa, Akihiko; El-Shimy, Haitham; Fukuda, Toshio

2005-12-01

315

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

NSDL National Science Digital Library

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

Bhavaraju, Krishna; Choudhury, Alamgir A.; Dwivedi, Suren; Ikonomove, Pavel

2009-10-02

316

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

PubMed Central

Mechanical manipulation of single DNA molecules can provide novel information about DNA properties and protein–DNA interactions. Here we describe and characterize a useful method for manipulating desired DNA sequences from any organism with optical tweezers. Molecules are produced from either genomic or cloned DNA by PCR using labeled primers and are tethered between two optically trapped microspheres. We demonstrate that human, insect, plant, bacterial and viral sequences ranging from ?10 to 40 kilobasepairs can be manipulated. Force-extension measurements show that these constructs exhibit uniform elastic properties in accord with the expected contour lengths for the targeted sequences. Detailed protocols for preparing and manipulating these molecules are presented, and tethering efficiency is characterized as a function of DNA concentration, ionic strength and pH. Attachment strength is characterized by measuring the unbinding time as a function of applied force. An alternative stronger attachment method using an amino–carboxyl linkage, which allows for reliable DNA overstretching, is also described. PMID:16452295

Fuller, Derek N.; Gemmen, Gregory J.; Rickgauer, John Peter; Dupont, Aurelie; Millin, Rachel; Recouvreux, Pierre; Smith, Douglas E.

2006-01-01

317

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

PubMed

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

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

2014-03-01

318

Simultaneous three-dimensional tracking of individual signals from multi-trap optical tweezers using fast and accurate photodiode detection.  

PubMed

Multiple-beam optical traps facilitate advanced trapping geometries and exciting discoveries. However, the increased manipulation capabilities come at the price of more challenging position and force detection. Due to unrivaled bandwidth and resolution, photodiode based detection is preferred over camera based detection in most single/dual-beam optical traps assays. However, it has not been trivial to implement photodiode based detection for multiple-beam optical traps. Here, we present a simple and efficient method based on spatial filtering for parallel photodiode detection of multiple traps. The technique enables fast and accurate 3D force and distance detection of multiple objects simultaneously manipulated by multiple-beam optical tweezers. PMID:25321832

Ott, Dino; Nader, S; Reihani, S; Oddershede, Lene B

2014-09-22

319

EWOD-driven droplet microfluidic device integrated with optoelectronic tweezers as an automated platform for cellular isolation and analysis.  

PubMed

We report the integration of two technologies: droplet microfluidics using electrowetting-on-dielectric (EWOD) and individual particle manipulation using optoelectronic tweezers (OET)-in one microfluidic device. The integrated device successfully demonstrates a sequence involving both EWOD and OET operations. We encountered various challenges during integration of the two different technologies and present how they are addressed. To show the applicability of the device in cellular biology, live HeLa cells are used in the experiments. The unique advantages of EWOD and OET make their integration a significant step towards a powerful tool for many applications, such as single cell studies involving multiplexed environmental stimuli. PMID:19495457

Shah, Gaurav J; Ohta, Aaron T; Chiou, Eric P-Y; Wu, Ming C; Kim, Chang-Jin C J

2009-06-21

320

Direct measurement of the dielectrophoresis forces acting on micro-objects using optical tweezers and a simple microfluidic chip  

NASA Astrophysics Data System (ADS)

We constructed a reliable frequency-dependent dielectrophoretic (DEP) force measurement system based on optical tweezers and a microfluidic chip. Using this system, we directly measured the frequency-dependent DEP forces acting on polystyrene beads while varying various parameters, which were all verified by theoretical simulations. We also investigated the DEP characteristics of non-functionalized and carboxyl-functionalized polystyrene beads in solutions with different conductivities by associating the measured crossover frequencies with a theoretical DEP model. This system can be used as a quantifying tool for surface conductance assays by characterizing the DEP forces acting on micro-objects in various experimental conditions.

Park, In Soo; Park, Se Hee; Yoon, Dae Sung; Lee, Sang Woo; Kim, Beop-Min

2014-09-01

321

Multiple-trap laser tweezers Raman spectroscopy for simultaneous monitoring of the biological dynamics of multiple individual cells.  

PubMed

We report the development of a multiple-trap laser tweezers Raman spectroscopy (LTRS) array for simultaneously acquiring Raman spectra of individual cells in physiological environments. This LTRS-array technique was also combined with phase contrast and fluorescence microscopy, allowing measurement of Raman spectra, refractility, and fluorescence images of individual cells with a temporal resolution of ~5 s. As a demonstration, we used this technique to monitor multiple Bacillus cereus spores germinating in a nutrient medium for up to 90min and observed the kinetics of dipicolinic acid release and uptake of nucleic acid-binding stain molecules during spore germination. PMID:20967053

Zhang, Pengfei; Kong, Lingbo; Setlow, Peter; Li, Yong-Qing

2010-10-15

322

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers  

PubMed Central

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

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

2011-01-01

323

Quantitative high-resolution sensing of DNA hybridization using magnetic tweezers with evanescent illumination  

NASA Astrophysics Data System (ADS)

We applied the combined approach of evanescent nanometry and force spectroscopy using magnetic tweezers to quantify the degree of hybridization of a single synthetic single-stranded DNA oligomer to a resolution approaching a single-base. In this setup, the 200 nucleotide long DNA was covalently attached to the surface of an optically transparent solid support at one end and to the surface of a superparamagnetic fluorescent microsphere (force probe) at the other end. The force was applied to the probes using an electromagnet. The end-to-end molecular distance (i.e. out-of-image-plane position of the force probe) was determined from the intensity of the probe fluorescence image observed with total-internal reflectance microscopy. An equation of state for single stranded DNA molecules under tension (extensible freely jointed chain) was used to derive the penetration depth of the evanescent field and to calibrate the magnetic properties of the force probes. The parameters of the magnetic response of the force probes obtained from the equation of state remained constant when changing the penetration depth, indicating a robust calibration procedure. The results of such a calibration were also confirmed using independently measured probe-surface distances for probes mounted onto cantilevers of an atomic force microscope. Upon hybridization of the complementary 50 nucleotide-long oligomer to the surface-bound 200-mer, the changes in the force-distance curves were consistent with the quantitative conversion of 25% of the original single-stranded DNA to its double-stranded form, which was modeled as an elastic rod. The method presented here for quantifying the hybridization state of the single DNA molecules has potential for determining the degree of hybridization of individual molecules in a single molecule array with high accuracy.We applied the combined approach of evanescent nanometry and force spectroscopy using magnetic tweezers to quantify the degree of hybridization of a single synthetic single-stranded DNA oligomer to a resolution approaching a single-base. In this setup, the 200 nucleotide long DNA was covalently attached to the surface of an optically transparent solid support at one end and to the surface of a superparamagnetic fluorescent microsphere (force probe) at the other end. The force was applied to the probes using an electromagnet. The end-to-end molecular distance (i.e. out-of-image-plane position of the force probe) was determined from the intensity of the probe fluorescence image observed with total-internal reflectance microscopy. An equation of state for single stranded DNA molecules under tension (extensible freely jointed chain) was used to derive the penetration depth of the evanescent field and to calibrate the magnetic properties of the force probes. The parameters of the magnetic response of the force probes obtained from the equation of state remained constant when changing the penetration depth, indicating a robust calibration procedure. The results of such a calibration were also confirmed using independently measured probe-surface distances for probes mounted onto cantilevers of an atomic force microscope. Upon hybridization of the complementary 50 nucleotide-long oligomer to the surface-bound 200-mer, the changes in the force-distance curves were consistent with the quantitative conversion of 25% of the original single-stranded DNA to its double-stranded form, which was modeled as an elastic rod. The method presented here for quantifying the hybridization state of the single DNA molecules has potential for determining the degree of hybridization of individual molecules in a single molecule array with high accuracy. Electronic supplementary information (ESI) available: SEM images, magnetic properties, and force versus field estimates for magnetic-fluorescent probes. Evanescent field penetration depth from simultaneous AFM/TIRF measurement. Noise estimate from immobilized probes. Sample raw intensity-current data. Conversion of intensity fluctuations to force. See DOI: 10.1039/c0nr00479k

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

2011-02-01

324

Optical tweezers for single molecule force spectroscopy on bacterial adhesion organelles  

NASA Astrophysics Data System (ADS)

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

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

2006-08-01

325

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

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2004-06-01

327

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

PubMed Central

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

Schwingel, Melanie; Bastmeyer, Martin

2013-01-01

328

Femtosecond single optical fiber tweezers enabled two-photon fluorescence excitation of trapped microscopic objects  

NASA Astrophysics Data System (ADS)

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber femto second optical tweezers and its use in two-photon fluorescence (TPF) excitation of trapped fluorescent particles. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Trapping depth of few cm was achieved inside colloidal sample with TPF from the trapped particle being visible to the naked eye. Furthermore, the fiber optic trapping was so stable that the trapped particle could be moved in 3D even by holding the fiber in hand and slow maneuvering of the same. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. The theoretical simulation of fiber optical microbeam profiles emerging from the axicon tip and trapping force estimations was found to be in good agreement with the experimentally observed stiffness and TPF patterns. Apart from miniaturization capability into lab-on- a-chip micro-fluidic devices, the proposed non-invasive micro axicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting and ablation as well as for two-photon fluorescence excitation of motile sample which will revolutionize biophysics and research in material science.

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

2011-03-01

329

Optoacoustic tweezers: a programmable, localized cell concentrator based on opto-thermally generated, acoustically activated, surface bubbles  

PubMed Central

We present a programmable, biocompatible technique for dynamically concentrating and patterning particles and cells in a microfluidic device. Since our technique utilizes opto-thermally generated, acoustically activated, surface bubbles, we name it “optoacoustic tweezers.” The optoacoustic tweezers are capable of concentrating particles/cells at any prescribed locations in a microfluidic chamber without the use of permanent structures, rendering it particularly useful for the formation of flexible, complex cell patterns. Additionally, this technique has demonstrated excellent biocompatibility and can be conveniently integrated with other microfluidic units. In our experiments, micro-bubbles were generated by focusing a 405 nm diode laser onto a gold-coated glass chamber. By properly tuning the laser, we demonstrate precise control over the position and size of the generated bubbles. Acoustic waves were then applied to activate the surface bubbles, causing them to oscillate at an optimized frequency. The resulting acoustic radiation force allowed us to locally trap particles/cells, including 15 ?m polystyrene beads and HeLa cells, around each bubble. Cell-adhesion tests were also conducted after cell concentrating to confirm the biocompatibility of this technique. PMID:23511348

Zhao, Yanhui; Li, Sixing; Rufo, Joseph; Yang, Shikuan; Guo, Feng; Huang, Tony Jun

2014-01-01

330

Microfluidic growth chambers with optical tweezers for full spatial single-cell control and analysis of evolving microbes.  

PubMed

Single-cell analysis in microfluidic systems has opened up new possibilities in biotechnological research enabling us to deal with large eukaryotic cells and even small bacteria. In particular, transient investigations in laminar flow or diffusive environments can be performed to unravel single cell behaviour. Up to now, most systems have been limited with respect to precise cell inoculation and sampling methods. Individual cell selection and manipulations have now been made possible by combining laser tweezers with microfluidic cell cultivation environments specifically tailored for micrometre-sized bacteria. Single cells were optically seeded into various micrometre-sized growth sites arranged in parallel. During cultivation, single-cell elongation, morphology and growth rates were derived from single cells and microcolonies of up to 500 cells. Growth of irradiated bacteria was not impaired by minimizing the exposed laser dosage as confirmed by exceptional growth rates. In fact, Escherichia coli exhibited doubling times of less than 20min. For the first time, a filamentous Escherichia coli WT (MG1655) was safely relocated from its growing microcolony by laser manipulations. The cell was transferred to an empty cultivation spot allowing single-cell growth and morphology investigations. Contrary to previous discussions, the filamentous E. coli exhibited normal cell morphology and division after a few generations. This combination of optical tweezers and single-cell analysis in microfluidics adds a new degree of freedom to microbial single-cell analysis. PMID:24041615

Probst, Christopher; Grünberger, Alexander; Wiechert, Wolfgang; Kohlheyer, Dietrich

2013-12-01

331

Real-time detection of single-living pancreatic beta-cell by laser tweezers Raman spectroscopy: high glucose stimulation.  

PubMed

Glucose acts as a beta-cell stimulus factor and leads to cellular responses that involve a large amount of biomolecule formation, relocation, and transformation. We hypothesize that information about these changes can be obtained in real-time by laser tweezers Raman spectroscopy. To test this hypothesis, repeated measurements designs in accordance with the application of Raman spectroscopy detection were used in the current experiment. Single rat beta-cells were measured by Raman spectroscopy in 2.8 mmol/l glucose culture medium as a basal condition. After stimulation with high glucose (20 mmol/l), the same cells were measured continuously. Each cell was monitored over a total time span of 25 min, in 5 min intervals. During this period of time, cells were maintained at an appropriate temperature controlled by an automatic heater, to provide near-physiological conditions. It was found that some significant spectral changes induced by glucose were taking place during the stimulation time course. The most noticeable changes were the increase of spectral intensity at the 1002, 1085, 1445, and 1655 cm(-1) peaks, mainly corresponding to protein and lipid. We speculate that these changes might have to do with beta-cell protein and lipid synthesis. Using laser tweezers Raman spectroscopy in combination with glucose stimulation, optical spectral information from rat beta-cells was received and analyzed. PMID:20091674

Rong, Xi; Huang, Shu-Shi; Kuang, Xiao-Cong; Liu, Hong

2010-07-01

332

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

333

A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells  

Microsoft Academic Search

The dynamics of cell surface membrane proteins plays an important role in cell-cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where optical tweezers are used to trap cells and precisely control in space and time the initiation of interactions

M. I. Snijder-Van As; B. Rieger; B. H. G. M. Joosten; V. Subramaniam; C. G. Figdor; J. S. Kanger

2009-01-01

334

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

SciTech Connect

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

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

2007-01-09

335

Applying combined optical tweezers and fluorescence microscopy technologies to manipulate cell adhesions for cell-to-cell interaction study.  

PubMed

Cell-to-cell interactions are important for the regulation of various cell activities, such as proliferation, differentiation, and apoptosis. This paper presents an approach to studying cell-to-cell interactions at a single-cell level through manipulating cell adhesions with optical tweezers. Experiments are performed on leukemia cancer cells and stromal cells to demonstrate the feasibility of this method. After the adhesion properties of leukemia cells on stromal cells are characterized, fluorescence intensity is used as a label to study the Wnt signaling pathway of leukemia cells. The activities of the Wnt signaling pathway of K562 cells on M210B4 and HS5 cells are examined based on fluorescence analysis. The reliability of the fluorescence imaging is confirmed through comparison with traditional flow cytometry analysis. The proposed approach will offer new avenues to investigate otherwise inaccessible mechanisms in cell-to-cell interactions. PMID:23549881

Gou, Xue; Han, Ho Chun; Hu, Songyu; Leung, Anskar Y H; Sun, Dong

2013-08-01

336

The interaction of lipopolysaccharide-coated polystyrene particle with membrane receptor proteins on macrophage measured by optical tweezers  

NASA Astrophysics Data System (ADS)

Lipopolysaccharide (LPS) is one of the cell wall components of Gram-positive bacteria recognized by and interacted with receptor proteins such as CD14 on macrophage cells. Such a process plays an important role in our innate immune system. In this paper, we report the application of optical tweezers (? = 1064nm Gaussian beam focused by a water-immersed objective lens with N.A. = 1.0) to the study of the dynamics of the binding of a LPS-coated polystyrene particle (diameter = 1.5?m) onto the plasma membrane of a macrophage cell. We demonstrated that the binding rate increased significantly when the macrophage cell was pre-treated with the extract of Reishi polysaccharides (EORP) which has been shown to enhance the cell surface expression of CD14 (receptor of LPS) on macrophage cells.

Wei, Ming-Tzo; Hua, Kuo-Feng; Hsu, Jowey; Karmenyan, Artashes; Hsu, Hsien-Yeh; Chiou, Arthur

2006-08-01

337

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

NASA Astrophysics Data System (ADS)

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

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

2007-07-01

338

Predicting the properties of a new class of host-guest complexes: C60 fullerene and CB[9] cucurbituril.  

PubMed

DFT, semi-empirical and classical molecular dynamics methods were used to describe the structure and stability of the inclusion complex formed by the fullerene C60 and the cucurbituril CB[9]. Our results indicate a high structural compatibility between the two monomers, which is evident from the potential energy curve for the inclusion process of the C60 into the CB[9] cavity. The interaction between the two monomers is mainly of the van der Waals type and leads to a highly stable complex. Thermal contributions and environmental interaction are taken into account by the free energy of binding of -224 kJ mol(-1), indicating that even in aqueous medium the complex remains very stable. PMID:25241778

Fileti, Eudes; Colherinhas, Guilherme; Malaspina, Thaciana

2014-10-01

339

Host-guest system of nimbin and beta-cyclodextrin or its derivatives: preparation, characterization, inclusion mode, and solubilization.  

PubMed

The inclusion complexation behavior, characterization, and binding ability of nimbin with beta-cyclodextrin (beta-CD) and its derivatives were investigated in both solution and the solid state by means of XRD, DSC, (1)H and 2D NMR, and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of nimbin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high thermal stability of the nimbin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products. PMID:20681641

Yang, Li-Juan; Yang, Bo; Chen, Wen; Huang, Rong; Yan, Sheng-Jiao; Lin, Jun

2010-08-11

340

Host-guest interaction between new nitrooxoisoaporphine and ?-cyclodextrins: synthesis, electrochemical, electron spin resonance and molecular modeling studies.  

PubMed

A new nitrooxoisoaporphine derivative was synthetized and characterized by cyclic voltammetry and electron spin resonance. Its aqueous solubility was improved by complexes formation with ?-cyclodextrin, heptakis(2,6-di-O-methyl)-?-cyclodextrin and (2-hydroxypropyl)-?-cyclodextrin. In order to assess the inclusion degree reached by nitrooxoisoaporphine in cyclodextris cavity, the stability constants of formation of the complexes were determined by phase-solubility measurements obtaining in all cases a type-A(L) diagram. Moreover, electrochemical studies were carried out, where the observed change in the EPC value indicated a lower feasibility of the nitro group reduction. Additionally, a detailed spatial configuration is proposed for inclusion of derivate within the cyclodextrins cavity by 2D NMR techniques. Finally, these results are further interpreted by means of molecular modeling studies. Thus, theoretical results are in complete agreement with the experimental data. PMID:23220661

Pérez-Cruz, Fernanda; Aguilera-Venegas, Benjamín; Lapier, Michel; Sobarzo-Sánchez, Eduardo; Uriarte Villares, Eugenio; Olea-Azar, Claudio

2013-02-01

341

Host-guest interaction between new nitrooxoisoaporphine and ?-cyclodextrins: Synthesis, electrochemical, electron spin resonance and molecular modeling studies  

NASA Astrophysics Data System (ADS)

A new nitrooxoisoaporphine derivative was synthetized and characterized by cyclic voltammetry and electron spin resonance. Its aqueous solubility was improved by complexes formation with ?-cyclodextrin, heptakis(2,6-di-O-methyl)-?-cyclodextrin and (2-hydroxypropyl)-?-cyclodextrin. In order to assess the inclusion degree reached by nitrooxoisoaporphine in cyclodextris cavity, the stability constants of formation of the complexes were determined by phase-solubility measurements obtaining in all cases a type-AL diagram. Moreover, electrochemical studies were carried out, where the observed change in the EPC value indicated a lower feasibility of the nitro group reduction. Additionally, a detailed spatial configuration is proposed for inclusion of derivate within the cyclodextrins cavity by 2D NMR techniques. Finally, these results are further interpreted by means of molecular modeling studies. Thus, theoretical results are in complete agreement with the experimental data.

Pérez-Cruz, Fernanda; Aguilera-Venegas, Benjamín; Lapier, Michel; Sobarzo-Sánchez, Eduardo; Uriarte Villares, Eugenio; Olea-Azar, Claudio

2013-02-01

342

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

E-print Network

and the high energy for per water molecule induced by the incapability to form stable H-bonds network due of California, San Diego, La Jolla, California 92093-0112, United States 6 Soft Matter and Functional Materials cucurbit[7]uril (CB[7]) host molecule1,2 has recently attracted experimental and theoretical attention due

Li, Bo

343

Copper(I) and silver(I) 2-methylimidazolates: extended isomerism, isomerization, and host-guest properties.  

PubMed

Syntheses, structures, and properties of univalent coinage metal 2-methylimidazolate supramolecular isomers [M(mim)] (1, M = Cu; 2, M = Ag) were investigated in detail. In addition to the known isomers, namely, zigzag chains [Cu(mim)] (1a) and [Ag(mim)] (2a), molecular octagon [Cu(8)(mim)(8)]·C(6)H(6) (1b), decagon [Cu(10)(mim)(10)]·C(8)H(10) (1c), helical chain [Ag(4)(mim)(4)]·C(6)H(6) (2b), and S-shaped chain [Ag(4)(mim)(4)]·C(8)H(10) (2c), two new structures including a polyrotaxane [Cu(10)(mim)(10)]·[Cu(mim)] (1d, C2/m, a = 14.452(4) Å, b = 27.712(7) Å, c = 11.427(3) Å, ? = 125.899(4)°, V = 3707(2) Å(3)) and a new octagon [Ag(8)(mim)(8)]·Me(2)CO (2d, C2/c, a = 21.852(3) Å, b = 12.101(2) Å, c = 20.907(3) Å, ? = 90.875(2)°, V = 5528(2) Å(3)) were discovered. The potential porous properties of guest-containing [M(mim)] isomers were studied by thermogravimetry, X-ray powder diffraction, vacuum thermal desorption, and CO(2) sorption experiments. The isomers show distinctly different guest removal behaviors depending on their pore structures. By heating, the guest-containing isomers, 1b-1c and 2b-2d, undergo irreversible, two-step, crystal-to-crystal structural transformations to form the guest-free isomers 1a or 2a, respectively. Except 1b, other guest-containing isomers can retain their porous structures after removal of the template molecules, which were confirmed by CO(2) sorption experiments. PMID:22468792

Wang, Yu; He, Chun-Ting; Liu, Yi-Jiang; Zhao, Tian-Qi; Lu, Xiao-Min; Zhang, Wei-Xiong; Zhang, Jie-Peng; Chen, Xiao-Ming

2012-04-16

344

Ultrafast 2DIR probe of a host-guest inclusion complex: Structural and dynamical constraints of nanoconfinement  

NASA Astrophysics Data System (ADS)

Two-dimensional infrared (2DIR) spectroscopy is used to study the influence of nanoconfinement on the spectral diffusion dynamics of cyclopentadienyl manganese tricarbonyl (CpMn(CO)3, CMT) free in solution and confined in the cavity of ?-cyclodextrin. Contrary to the reorientation correlation function of the solvent molecules, determined through molecular dynamics simulations, measurements in three different solvents indicate that CMT confined in ?-cyclodextrin undergoes spectral diffusion that is faster than free CMT. To account for this discrepancy, we propose that spectral diffusion time scales contain a dynamical contribution that is dependent on the effective size of the conformational space presented by the solvation environment. This solvation state space size is related to the number of participating solvent molecules, which in turn is proportional to the solvent accessible surface area (SASA). We test the role of the number of participating solvent molecules using a simple Gaussian-Markov simulation and find that an increase in the number of participating solvent molecules indeed slows the time required to search the available conformational space. Finally, we test this dependence by comparing the spectral diffusion of a previously studied manganese carbonyl, dimanganese decacarbonyl (Mn2(CO)10, DMDC), to CMT and find that DMDC, which has a larger SASA, exhibits slower spectral diffusion. The experimental observations and the supporting simplistic solvation model suggest that vibrational probe molecules, such as CMT, might be able to function as sensors of conformational entropy.

Osborne, Derek G.; King, John T.; Dunbar, Josef A.; White, Aaron M.; Kubarych, Kevin J.

2013-04-01

345

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

E-print Network

. The product was isolated at 86% yield by vacuum filtration, washed with hexanes, and dried in Vacuo. 1H NMR by adding a large volume of methanol/water mixture. The product was isolated by vacuum-filtration, washed of electron density from the porphyrin system upon rhenium-pyridine bond formation. Near-UV fluorescence

346

Microfluidic Assembly of Cationic-?-Cyclodextrin:Hyaluronic Acid-Adamantane Host:Guest pDNA Nanoparticles  

PubMed Central

Traditionally, transfection complexes are typically formed by bulk mixing, producing particles with high polydispersity and limited control over vector size. Herein, we demonstrate the use of a commercial micro-reactor to assemble pDNA:cationic cyclodextrin:pendant polymer nanoparticles using a layer-by-layer approach. Our studies reveal that the particles formulated via microfluidic assembly have much smaller sizes, lower polydispersity, lower ?-potentials, and comparable cell viability and transfection profiles in HeLa cells than bulk mixed particles. The complexes also show a flow rate-dependent stability, with particles formed at slower flow rates giving rise to more stable complexes as determined by heparin challenge. Our findings suggest that microfluidic reactors offer an attractive method for assembling reproducible, size-controlled complexes from multi-component transfection complex assemblies. PMID:24349706

Kulkarni, Aditya; VerHeul, Ross; DeFrees, Kyle; Collins, Christopher J.; Schuldt, Ryan A.; Vlahu, Alexander; Thompson, David H.

2013-01-01

347

Push and Pull of Tropomyosin's Opposite Effects on Myosin Attachment to Actin. A Chimeric Tropomyosin Host-guest Study†  

PubMed Central

Tropomyosin is a ubiquitous actin-binding protein with an extended coiled-coil structure. Tropomyosin-actin interactions are weak and loosely specific, but they potently influence myosin. One such influence is inhibitory, and is due to tropomyosin’s statistically preferred positions on actin that sterically interfere with actin’s strong attachment site for myosin. Contrastingly, tropomyosin’s other influence is activating. It increases myosin’s overall actin affinity ~4-fold. Stoichiometric considerations cause this activating effect to equate to a ~ 47- fold effect of myosin on the actin-affinity of tropomyosin. These positive, mutual, myosin-tropomyosin effects are absent if S. cerevisiae tropomyosin replaces mammalian tropomyosin. To investigate these phenomena, chimeric tropomyosins were generated in which 38 residue muscle tropomyosin segments replaced a natural duplication within S. cerevisiae tropomyosin TPM1. Two such chimeric tropomyosins were sufficiently folded coiled-coils to allow functional study. The two chimeras differed from TPM1, but in opposite ways. Consistent with steric interference, myosin greatly decreased the actin-affinity of chimera 7, which contained muscle tropomyosin residues 228–265. On the other hand, myosin S1 increased by an order of magnitude the actin-affinity of chimera 3, which contained muscle tropomyosin residues 74–111. Similarly, myosin S1-ADP binding to actin was strengthened 2-fold by substitution of chimera 3 tropomyosin for wild type TPM1. Thus, a yeast tropomyosin was induced to mimic the activating behavior of mammalian tropomyosin by inserting a mammalian tropomyosin sequence. The data were not consistent with direct tropomyosin-myosin binding. Rather they suggest an allosteric mechanism, in which myosin and tropomyosin share an effect on the actin filament. PMID:21114337

Ali, Laith F.; Cohen, Joshua M.; Tobacman, Larry S.

2013-01-01

348

Push and pull of tropomyosin's opposite effects on myosin attachment to actin. A chimeric tropomyosin host-guest study.  

PubMed

Tropomyosin is a ubiquitous actin-binding protein with an extended coiled-coil structure. Tropomyosin-actin interactions are weak and loosely specific, but they potently influence myosin. One such influence is inhibitory and is due to tropomyosin's statistically preferred positions on actin that sterically interfere with actin's strong attachment site for myosin. Contrastingly, tropomyosin's other influence is activating. It increases myosin's overall actin affinity ?4-fold. Stoichiometric considerations cause this activating effect to equate to an ?4(7)-fold effect of myosin on the actin affinity of tropomyosin. These positive, mutual, myosin-tropomyosin effects are absent if Saccharomyces cerevisiae tropomyosin replaces mammalian tropomyosin. To investigate these phenomena, chimeric tropomyosins were generated in which 38-residue muscle tropomyosin segments replaced a natural duplication within S. cerevisiae tropomyosin TPM1. Two such chimeric tropomyosins were sufficiently folded coiled coils to allow functional study. The two chimeras differed from TPM1 but in opposite ways. Consistent with steric interference, myosin greatly decreased the actin affinity of chimera 7, which contained muscle tropomyosin residues 228-265. On the other hand, myosin S1 increased by an order of magnitude the actin affinity of chimera 3, which contained muscle tropomyosin residues 74-111. Similarly, myosin S1-ADP binding to actin was strengthened 2-fold by substitution of chimera 3 tropomyosin for wild-type TPM1. Thus, a yeast tropomyosin was induced to mimic the activating behavior of mammalian tropomyosin by inserting a mammalian tropomyosin sequence. The data were not consistent with direct tropomyosin-myosin binding. Rather, they suggest an allosteric mechanism, in which myosin and tropomyosin share an effect on the actin filament. PMID:21114337

Ali, Laith F; Cohen, Joshua M; Tobacman, Larry S

2010-12-28

349

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

PubMed

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

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

2003-05-01

350

Simple Host-Guest Chemistry To Modulate the Process of Concentration and Crystallization of Membrane Proteins by  

E-print Network

of Membrane Proteins by Detergent Capture in a Microfluidic Device Liang Li, Sigrid Nachtergaele, Annela M the crystallization of membrane proteins and the process of concentration of membrane protein samples. Methyl of membrane proteins by sequestering detergent monomers. Reaction Center (RC) from Blastochloris viridis

Ismagilov, Rustem F.

351

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V  

PubMed Central

Summary The selectivity of the cryptands [2.2.bpy] and [2.bpy.bpy] for the endohedral complexation of alkali, alkaline-earth and earth metal ions was predicted on the basis of the DFT (B3LYP/LANL2DZp) calculated structures and complex-formation energies. The cavity size in both cryptands lay between that for [2.2.2] and [bpy.bpy.bpy], such that the complexation of K+, Sr2+ and Tl3+ is most favorable. While the [2.2.bpy] is moderately larger, preferring Rb+ complexation and demonstrating equal priority for Sr2+ and Ba2+, the slightly smaller [2.bpy.bpy] yields more stable cryptates with Na+ and Ca2+. Although the CH2-units containing molecular bars fixed at the bridgehead nitrogen atoms determine the flexibility of the cryptands, the twist angles associated with the bipyridine and glycol building blocks also contribute considerably. PMID:23843921

Begel, Svetlana; van Eldik, Rudi

2013-01-01

352

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

Microsoft Academic Search

The structure of the complex [Cs(tetrabenzo-24-crown-8)(1,2-dichloroethane)â](NOâ){sm{underscore}bullet}HâO was shown by X-ray crystallography to involve an unprecedented bidentate coordination of two 1,2-dichloroethane solvent molecules to the Cs{sup +} cation via the four chlorine atoms. The coordination of the solvent molecules occurs within two clefts between facing benzo groups, one pair of benzo groups related to the other pair by an improper noncrystallographic

Tatiana G. Levitskaia; Jeffrey C. Bryan; Richard A. Sachleben; John D. Lamb; Bruce A. Moyer

2000-01-01

353

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

SciTech Connect

This paper reports a study of the location of Methyl Tertiary Butyl Ether (MTBE) and toluene molecules adsorbed in the pores of the organophylic zeolite mordenite from an aqueous solution. The presence of these organic molecules in the zeolite channels was revealed by structure refinement performed by the Rietveld method. About 3 molecules of MTBE and 3.6 molecules of toluene per unit cell were incorporated into the cavities of mordenite, representing 75% and 80% of the total absorption capacity of this zeolite. In both cases a water molecule was localized inside the side pocket of mordenite. The saturation capacity determined by the adsorption isotherms, obtained by batch experiments, and the weight loss given by thermogravimetric (TG) analyses were in very good agreement with these values. The interatomic distances obtained after the structural refinements suggest MTBE could be connected to the framework through a water molecule, while toluene could be bonded to framework oxygen atoms. The rapid and high adsorption of these hydrocarbons into the organophylic mordenite zeolite makes this cheap and environmental friendly material a suitable candidate for the removal of these pollutants from water. - graphical abstract: Location of MTBE (a) and toluene (b) in mordenite channels (projection along the [001] direction). Highlights: Black-Right-Pointing-Pointer We investigated the MTBE and toluene adsorption process into an organophilic zeolite mordenite. Black-Right-Pointing-Pointer The presence of MTBE and toluene in mordenite was determined by X-ray diffraction studies. Black-Right-Pointing-Pointer About 3 molecules of MTBE and 3.6 molecules of toluene per unit cell were incorporated into the zeolite cavities. Black-Right-Pointing-Pointer MTBE is connected to the framework through a water molecule. Black-Right-Pointing-Pointer Toluene is directly bonded to framework oxygen atoms.

Arletti, Rossella, E-mail: rossella.arletti@unito.it [Department of Earth Sciences, University of Torino Via Valperga Caluso 35, I-10125, Torino (Italy)] [Department of Earth Sciences, University of Torino Via Valperga Caluso 35, I-10125, Torino (Italy); Martucci, Annalisa; Alberti, Alberto [Department of Earth Sciences, University of Ferrara, Via G. Saragat 1, I-44100, Ferrara (Italy)] [Department of Earth Sciences, University of Ferrara, Via G. Saragat 1, I-44100, Ferrara (Italy); Pasti, Luisa; Nassi, Marianna [Department of Chemistry, University of Ferrara, Via L. Borsari 26, I-44100 Ferrara (Italy)] [Department of Chemistry, University of Ferrara, Via L. Borsari 26, I-44100 Ferrara (Italy); Bagatin, Roberto [Research Centre for Non-Conventional Energy-Istituto ENI Donegani, Environmental Technologies, Via Fauser 4, I-28100 Novara (Italy)] [Research Centre for Non-Conventional Energy-Istituto ENI Donegani, Environmental Technologies, Via Fauser 4, I-28100 Novara (Italy)

2012-10-15

354

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

SciTech Connect

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

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

2008-07-15

355

Optoelectronic tweezers integrated with lensfree holographic microscopy for wide-field interactive cell and particle manipulation on a chip.  

PubMed

We demonstrate an optoelectronic tweezer (OET) coupled to a lensfree holographic microscope for real-time interactive manipulation of cells and micro-particles over a large field-of-view (FOV). This integrated platform can record the holographic images of cells and particles over the entire active area of a CCD sensor array, perform digital image reconstruction to identify target cells, dynamically track the positions of cells and particles, and project light beams to trigger light-induced dielectrophoretic forces to pattern and sort cells on a chip. OET technology has been previously shown to be capable of performing parallel single cell manipulation over a large area. However, its throughput has been bottlenecked by the number of cells that can be imaged within the limited FOV of a conventional microscope objective lens. Integrating lensfree holographic imaging with OET solves this fundamental FOV barrier, while also creating a compact on-chip cell/particle manipulation platform. Using this unique platform, we have successfully demonstrated real-time interactive manipulation of thousands of single cells and micro-particles over an ultra-large area of e.g., 240 mm(2) (i.e. 17.96 mm × 13.52 mm). PMID:23661233

Huang, Kuo-Wei; Su, Ting-Wei; Ozcan, Aydogan; Chiou, Pei-Yu

2013-06-21

356

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

PubMed Central

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

Tatischeff, Irene; Larquet, Eric; Falcon-Perez, Juan M.; Turpin, Pierre-Yves; Kruglik, Sergei G.

2012-01-01

357

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

358

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

359

Studies of viral DNA packaging motors with optical tweezers: a comparison of motor function in bacteriophages ?29, ?, and T4  

NASA Astrophysics Data System (ADS)

A key step in the assembly of many viruses is the packaging of double-stranded DNA into a viral procapsid (an empty protein shell) by the action of an ATP-powered portal motor complex. We have developed methods to measure the packaging of single DNA molecules into single viral proheads in real time using optical tweezers. We can measure DNA binding and initiation of translocation, the DNA translocation dynamics, and the filling of the capsid against resisting forces. In addition to studying bacteriophage ?29, we have recently extended these methods to study the E. coli bacteriophages ? and T4, two important model systems in molecular biology. The three systems have different capsid sizes/shapes, genome lengths, and biochemical and structural differences in their packaging motors. Here, we compare and contrast these three systems. We find that all three motors translocate DNA processively and generate very large forces, each exceeding 50 piconewtons, ~20x higher force than generated by the skeletal muscle myosin 2 motor. This high force generation is required to overcome the forces resisting the confinement of the stiff, highly charged DNA at high density within the viral capsids. However, there are also striking differences between the three motors: they exhibit different DNA translocation rates, degrees of static and dynamic disorder, responses to load, and pausing and slipping dynamics.

Smith, Douglas E.; Fuller, Derek N.; Raymer, Dorian M.; Rickgauer, Peter; Grimes, Shelley; Jardine, Paul J.; Anderson, Dwight L.; Catalano, Carlos E.; Kottadiel, Vishal; Rao, Venigalla B.

2007-09-01

360

DNA looping and cleavage by restriction enzymes studied by manipulation of single DNA molecules with optical tweezers  

NASA Astrophysics Data System (ADS)

Looping and cleavage of single DNA molecules by the two-site restriction endonuclease Sau3AI were measured with optical tweezers. A DNA template containing many recognition sites was used, permitting loop sizes from ~10 to 10,000 basepairs. At high enzyme concentration cleavage events were detected within 5 seconds and nearly all molecules were cleaved within 5 minutes. Activity decreased ~10-fold as the DNA tension was increased from 0.03 to 0.7 pN. Substituting Ca 2+ for Mg 2+ blocked cleavage, permitting measurement of stable loops. At low tension, the initial rates of cleavage and looping were similar (~0.025 s -1 at 0.1 pN), suggesting that looping is rate limiting. Short loops formed more rapidly than long loops. The optimum size decreased from ~250 to 45 bp and the average number of loops (in 1 minute) from 4.2 to 0.75 as tension was increased from 0.03 to 0.7 pN. No looping was detected at 5 pN. These findings are in qualitative agreement with recent theoretical predictions considering only DNA mechanics, but we observed weaker suppression with tension and smaller loop sizes. Our results suggest that the span and elasticity of the protein complex and protein-induced DNA bending and wrapping play an important role.

Smith, Douglas E.; Gemmen, Gregory J.; Millin, Rachel

2006-08-01

361

Mechanism of a viral DNA packaging motor studied by characterization of biochemical mutants via optical tweezers measurements  

NASA Astrophysics Data System (ADS)

Optical tweezers measurements were employed to directly observe viral DNA packaging in wild type and packaging mutants of bacteriophage lambda. Several key findings are reported here: DNA packaging by purified wild type lambda motors was measured for the first time, showing nearly identical behavior in packaging DNA to crude extracts of terminase components. A slow packaging lambda mutant, T194M, was found to package DNA at ~10× slower velocity than wild type. Meanwhile another packaging mutant Y46F was found to package DNA slower than the wild type (60-70% the velocity of the wild type velocity) as well as slipping >10x more frequently (per length of DNA) than wild type. Another mutant (K84A) showed slower packaging (60-70% the velocity of wildtype), but displayed slipping and pausing behavior similar to wild type. Finally the pausing and slipping dependence on length of DNA packaged of the various terminases studied was discovered, suggesting further structural defects of the mutants that are detrimental to translocation. These studies confirm the location of an ATPase center in the N-terminal portion of gpA which is responsible for translocation of dsDNA.

Tsay, James M.; Sippy, Jean; Feiss, Michael; Smith, Douglas E.

2008-08-01

362

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

363

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

PubMed

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample. PMID:22029347

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

2011-10-01

364

A Polypeptide-DNA Hybrid with Selective Linking Capability Applied to Single Molecule Nano-Mechanical Measurements Using Optical Tweezers  

PubMed Central

Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN) and the peptide StrepTag II (ST). We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST). In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP) using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV) linkage. It can be used in conjunction with Neutravidin (NTV)-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications. PMID:23336001

Tans, Sander J.

2013-01-01

365

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

PubMed

By using optical tweezers and a specially designed flow cell with an integrated glass micropipette, we constructed a setup similar to that of Smith et al. (Science 271:795-799, 1996) in which an individual double-stranded DNA (dsDNA) molecule can be captured between two polystyrene beads. The first bead is immobilized by the optical tweezers and the second by the micropipette. Movement of the micropipette allows manipulation and stretching of the DNA molecule, and the force exerted on it can be monitored simultaneously with the optical tweezers. We used this setup to study elongation of dsDNA by RecA protein and YOYO-1 dye molecules. We found that the stability of the different DNA-ligand complexes and their binding kinetics were quite different. The length of the DNA molecule was extended by 45% when RecA protein was added. Interestingly, the speed of elongation was dependent on the external force applied to the DNA molecule. In experiments in which YOYO-1 was added, a 10-20% extension of the DNA molecule length was observed. Moreover, these experiments showed that a change in the applied external force results in a time-dependent structural change of the DNA-YOYO-1 complex, with a time constant of approximately 35 s (1/e2). Because the setup provides an oriented DNA molecule, we determined the orientation of the transition dipole moment of YOYO-1 within DNA by using fluorescence polarization. The angle of the transition dipole moment with respect to the helical axis of the DNA molecule was 69 degrees +/- 3. PMID:10404969

Bennink, M L; Schärer, O D; Kanaar, R; Sakata-Sogawa, K; Schins, J M; Kanger, J S; de Grooth, B G; Greve, J

1999-07-01

366

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

NASA Astrophysics Data System (ADS)

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

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

2007-02-01

367

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

SciTech Connect

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

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

2011-01-07

368

tweezercalib 2.1: Faster version of MatLab package for precise calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

New version program summaryTitle of program: tweezercalib Catalogue identifier:ADTV_v2_1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV_v2_1 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:no No. of lines in distributed program, including test data, etc.: 134 188 No. of bytes in distributed program, including test data, etc.: 1 050 368 Distribution format: tar.gz Programming language: MatLab (Mathworks Inc.), standard license Computer:General computer running MatLab (Mathworks Inc.) Operating system:Windows2000, Windows-XP, Linux RAM:Of order four times the size of the data file Classification:3, 4.14, 18, 23 Catalogue identifier of previous version: ADTV_v2_0 Journal reference of previous version: Comput. Phys. Comm. 174 (2006) 518 Does the new version supersede the previous version?: yes Nature of problem:Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system. The theoretical underpinnings of the procedure may be found in Ref. [3]. Solution method:Elimination of cross-talk between quadrant photo-diodes, output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects; Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for "virtual filtering" caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting with custom written routines based on Refs. [1,2]. Statistical support for fit is given, with several plots facilitating inspection of consistency and quality of data and fit. Reasons for the new version:Recent progress in the field has demonstrated a better approximation of the formula for the theoretical power spectrum with corrections due to frequency dependence of motion and distance to a surface nearby. Summary of revisions:The expression for the theoretical power spectrum when accounting for corrections to Stokes law, P(f), has been updated to agree with a better approximation of the theoretical spectrum, as discussed in Ref. [4] The units of the kinematic viscosity applied in the program is now stated in the input window. Greek letters and exponents are inserted in the input window. The graphical output has improved: The figures now bear a meaningful title and four figures that test the quality of the fit are now combined in one figure with four parts. Restrictions: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate; The sampling rate should be well above the characteristic frequency of the trap, the so-called corner frequency. Thus, the sampling frequency should typically be larger than 10 kHz. The Fast Fourier Transform used works optimally when the time series contain 2 data points, and long measurement time is obtained with n>12-15. Finally, the optics should be set to ensure a harmonic trapping potential in the range of positions visited by the bead. The fitting procedure checks for harmonic potential. Running time:seconds ReferencesJ. Nocedal, Y.x. Yuan, Combining trust region and line search techniques, Technical Report OTC 98/04, Optimization Technology Center, 1998. W.H. Press, B.P. Flannery, S.A. Teukolsky, W.T. Vetterling, Numerical Recipes. The Art of Scientific Computing, Cambridge University Press, Cambridge, 1986. (The theoretical underpinnings for the procedure) K. Berg

Hansen, Poul Martin; Tolic-Nørrelykke, Iva Marija; Flyvbjerg, Henrik; Berg-Sørensen, Kirstine

2006-10-01

369

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

NASA Astrophysics Data System (ADS)

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

Chen, Ying-chun; Wu, Chien-ming

2012-12-01

370

Safety and pharmacological characterization of the molecular tweezer CLR01 - a broad-spectrum inhibitor of amyloid proteins' toxicity  

PubMed Central

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

2014-01-01

371

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

PubMed

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

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

2014-07-01

372

Fiber-integrated optical nano-tweezer based on a bowtie-aperture nano-antenna at the apex of a SNOM tip.  

PubMed

We propose a new concept of fiber-integrated optical nano-tweezer on the basis of a single bowtie-aperture nano-antenna (BNA) fabricated at the apex of a metal-coated SNOM tip. We demonstrate 3D optical trapping of 0.5 micrometer latex beads with input power which does not exceed 1 mW. Optical forces induced by the BNA on tip are then analyzed numerically. They are found to be 10(3) times larger than the optical forces of a circular aperture of the same area. Such a fiber nanostructure provides a new path for manipulating nano-objects in a compact, flexible and versatile architecture and should thus open promising perspectives in physical, chemical and biomedical domains. PMID:24787888

El Eter, Ali; Hameed, Nyha M; Baida, Fadi I; Salut, Roland; Filiatre, Claudine; Nedeljkovic, Dusan; Atie, Elie; Bole, Samuel; Grosjean, Thierry

2014-04-21

373

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

PubMed

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

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

2014-12-01

374

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

NASA Astrophysics Data System (ADS)

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

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

2004-10-01

375

Host-Guest Chemistry of a Water-Soluble Pillar[5]arene: Evidence for an Ionic-Exchange Recognition Process and Different Complexation Modes.  

PubMed

The complexation of an anionic guest by a cationic water-soluble pillararene is reported. Isothermal titration calorimetry (ITC), (1) H?NMR, (1) H and (19) F DOSY, and STD NMR experiments were performed to characterize the complex formed under aqueous neutral conditions. The results of ITC and (1) H?NMR analyses showed the inclusion of the guest inside the cavity of the pillar[5]arene, with the binding constant and thermodynamic parameters influenced by the counter ion of the macrocycle. NMR diffusion experiments showed that although a fraction of the counter ions are expelled from the host cavity by exchange with the guest, a complex with both counter ions and the guest inside the pillararene is formed. The results also showed that at higher concentrations of guest in solution, in addition to the inclusion of one guest molecule in the cavity, the pillararene can also form an external complex with a second guest molecule. PMID:25110897

Gómez, Borja; Francisco, Vitor; Fernández-Nieto, Fernando; Garcia-Rio, Luis; Martín-Pastor, M; Paleo, M Rita; Sardina, F Javier

2014-09-15

376

Host-guest chemistry of aromatic-amide-linked bis- and tris-calix[4]pyrroles with bis-carboxylates and citrate anion.  

PubMed

A small library of polytopic receptors has been synthesized from meso-p- and meso-m-aminophenylcalix[4]pyrroles and p- or m-phthaloyl or trimesic chloride. Selected bis-carboxylates and the citrate anion, which either exhibit altered distribution profiles in cancerous tissues in comparison with healthy tissues or are metabolites of carcinogenic substances (for example, trans,trans-muconic acid from benzene exposure in humans) were tested as ligands. Varied affinities and binding modes were observed as a function of the number of calix[4]pyrroles and the topology of amide units present in each of the polytopic receptors. The structures of the 1:1 complexes derived by molecular modeling are in excellent agreement with the results of (1)H?NMR complexation studies. PMID:24402826

Cafeo, Grazia; Gattuso, Giuseppe; Kohnke, Franz H; Papanikolaou, Georgia; Profumo, Aldo; Rosano, Camillo

2014-02-01

377

Ternary europium mesoporous polymeric hybrid materials Eu({beta}-diketonate){sub 3}pvpd-SBA-15(16): host-guest construction, characterization and photoluminescence  

SciTech Connect

Novel organic-inorganic mesoporous luminescent polymeric hybrid materials containing europium(III) complexes incorporated to mesoporous silica SBA-15/SBA-16 have been prepared by simple physical doping (impregnation) methods, followed by the addition polymerization reaction of the monomer 4-vinylpyridine (vpd) extending along the mesoporous channels. The precursor europium(III) complexes are synthesized by {beta}-diketonate ({beta}-diketonate=2-thenoyltrifluoroacetonate (tta), hexafluoroacetylacetonate (hfac), trifluoroacetylacetonate (taa)) and monomer 4-vinylpyridine (vpd) coordinated to Eu{sup 3+}, and SBA-15/SBA-16 are obtained via a sol-gel process. After the physical doping and the polymerization reaction, the final ternary materials Eu({beta}-diketonate){sub 3}pvpd-SBA-15/Eu({beta}-diketonate){sub 3}pvpd-SBA-16 ({beta}-diketonate=tta, hfac, taa) are received. The physical properties and espeically the photoluminescence of these hybrids are characterized, and the XRD and BET results reveal that all of these hybrid materials have uniformity in the mesostructure. The detailed luminescence investigation on all the materials show that Eu(tta){sub 3}pvpd-SBA-16 have the highest luminescence intensity and the materials with taa ligands have longer lifetimes. - Grapical abstract: Luminescent mesoporous polymeric hybrid materials containing europium complexes hydrogen bonding to silica SBA-15/SBA-16 followed by the addition polymerization reaction of 4-vinylpyridine (vpd) extending along the mesoporous channels. Highlights: Black-Right-Pointing-Pointer Functional mesoporous with simple impregnation method. Black-Right-Pointing-Pointer New lanthanide mesoporous hybrids with polymer ligands. Black-Right-Pointing-Pointer Luminescence in visible region.

Gu Yanjing [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China); Yan Bing, E-mail: byan@tongji.edu.cn [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China); Li Yanyan [Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092 (China)

2012-06-15

378

Ternary europium mesoporous polymeric hybrid materials Eu(?-diketonate)3pvpd-SBA-15(16): host-guest construction, characterization and photoluminescence  

NASA Astrophysics Data System (ADS)

Novel organic-inorganic mesoporous luminescent polymeric hybrid materials containing europium(III) complexes incorporated to mesoporous silica SBA-15/SBA-16 have been prepared by simple physical doping (impregnation) methods, followed by the addition polymerization reaction of the monomer 4-vinylpyridine (vpd) extending along the mesoporous channels. The precursor europium(III) complexes are synthesized by ?-diketonate (?-diketonate=2-thenoyltrifluoroacetonate (tta), hexafluoroacetylacetonate (hfac), trifluoroacetylacetonate (taa)) and monomer 4-vinylpyridine (vpd) coordinated to Eu3+, and SBA-15/SBA-16 are obtained via a sol-gel process. After the physical doping and the polymerization reaction, the final ternary materials Eu(?-diketonate)3pvpd-SBA-15/Eu(?-diketonate)3pvpd-SBA-16 (?-diketonate=tta, hfac, taa) are received. The physical properties and espeically the photoluminescence of these hybrids are characterized, and the XRD and BET results reveal that all of these hybrid materials have uniformity in the mesostructure. The detailed luminescence investigation on all the materials show that Eu(tta)3pvpd-SBA-16 have the highest luminescence intensity and the materials with taa ligands have longer lifetimes.

Gu, Yan-Jing; Yan, Bing; Li, Yan-Yan

2012-06-01

379

A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells.  

PubMed

The dynamics of cell surface membrane proteins plays an important role in cell-cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where optical tweezers are used to trap cells and precisely control in space and time the initiation of interactions between a cell and a functionalized surface. This approach is combined with total internal reflection fluorescence microscopy to monitor dynamics of membrane bound proteins. We demonstrate an accuracy of approximately 2 s in determining the onset of the interaction. Furthermore, we developed a data analysis method to determine the dynamics of cell adhesion and the organization of membrane molecules at the contact area. We demonstrate and validate this approach by studying the dynamics of the green fluorescent protein tagged membrane protein activated leukocyte cell adhesion molecule expressed in K562 cells upon interaction with its ligand CD6 immobilized on a coated substrate. The measured cell spreading is in excellent agreement with existing theoretical models. Active redistribution of activated leukocyte cell adhesion molecule is observed from a clustered to a more homogenous distribution upon contact initiation. This redistribution follows exponential decay behaviour with a characteristic time of 35 s. PMID:19196415

Snijder-Van As, M I; Rieger, B; Joosten, B; Subramaniam, V; Figdor, C G; Kanger, J S

2009-01-01

380

Combination of Raman tweezers and quantitative differential interference contrast microscopy for measurement of dynamics and heterogeneity during the germination of individual bacterial spores  

NASA Astrophysics Data System (ADS)

Raman tweezers and quantitative differential interference contrast (DIC) microscopy are combined to monitor the dynamic germination of individual bacterial spores of Bacillus species, as well as the heterogeneity in this process. The DIC bias phase is set properly such that the brightness of DIC images of individual spores is proportional to the dipicolinic acid (DPA) level of the spores, and an algorithm is developed to retrieve the phase image of an individual spore from its DIC image. We find that during germination, the rapid drop in both the intensity of the original DIC image and the intensity of the reconstructed phase image precisely corresponds to the release of all DPA from that spore. The summed pixel intensity of the DIC image of individual spores adhered on a microscope coverslip is not sensitive to the drift of the slide in both horizontal and vertical directions, which facilitates observation of the germination of thousands of individual spores for long periods of time. A motorized stage and synchronized image acquisition system is further developed to effectively expand the field of view of the DIC imaging. This quantitative DIC technique is used to track the germination of hundreds or thousands of individual spores simultaneously.

Zhang, Pengfei; Kong, Lingbo; Wang, Guiwen; Setlow, Peter; Li, Yong-Qing

2010-09-01

381

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

PubMed

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

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

2009-09-01

382

Recent Advances in Optical Tweezers  

E-print Network

. Biochem. 2008. 77:205­28 First published online as a Review in Advance on February 28, 2008 The Annual Review of Biochemistry is online at biochem.annualreviews.org This article's doi: 10.1146/annurev.biochem.77.043007.090225 Copyright c 2008 by Annual Reviews. All rights reserved 0066

Ritort, Felix

383

Kinect 4 … holographic optical tweezers  

NASA Astrophysics Data System (ADS)

The 3D position and orientation of a microtool confined in multiple optical traps needs to be controlled in order for one to perform modern, challenging experiments; for example, in order to utilize it as a scanning probe and investigate the surface of optically sensitive cells. The control interface has traditionally used the keyboard/mouse combination—limiting manipulations to a series of 1D/2D transforms. In this paper we demonstrate how the Kinect can be utilized to control the position and orientation of a microtool utilizing macroscopic models.

Muhiddin, C.; Phillips, D. B.; Miles, M. J.; Picco, L.; Carberry, D. M.

2013-07-01

384

Host-guest-driven color change in water: influence of cyclodextrin on the structure of a copper complex of poly((4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl)methacrylamide-co-dimethylacrylamide)  

PubMed Central

Summary In the present work we report the synthesis of poly((4-hydroxy-3-(pyridin-3-yldiazenyl)phenethyl)methacrylamide-co-dimethylacrylamide) and its reversible optical and complex-forming properties due to copper and cyclodextrin (CD) interactions. Color changing effects are characterized by UV–vis spectroscopy and the supramolecular behavior is investigated by dynamic light scattering experiments. PMID:25383119

Retzmann, Nils; Maatz, Gero

2014-01-01

385

Host-guest chemistry. 2. Amine inclusion compounds of 2-[ o -(triphenylphosphoranylidenamino)benzyliden]amino-1 H -2,3-dihydroindazol-3-one. X-ray structure of its 1?1?1 inclusion complex with isopropylamine and water  

Microsoft Academic Search

The crystal and molecular structure is reported for the inclusion compound 2-[o-(triphenylphosphoranylidenamino)benzyliden]amino-1H-2,3-dihydroindazol-3-one\\/isopropylamine\\/water3b. The crystal structure consists of discrete dimeric salt-like aggregates joined together by strong N+-H...-O-C hydrogen bonds between pairs of centrosymmetrically-related indazolonate anions and isopropylammonium cations. Six other inclusion compounds have been prepared and characterized by NMR [with propylamine (3a), withtert-butylamine (3c), withsec-butylamine (3d), withtert-pentylamine (3e), with 1-methylbutylamine (3f)

Concepcion Foces-Foces; Antonio L. Llamas-Saiz; Rosa M. Claramunt; Jose Elguero; Pedro Molina; Antonio Arques; Rosario Obon

1993-01-01

386

Argentophilicity as Essential Driving Force for a Dynamic Cation-Cation Host-Guest System: [Ag(acetonitrile)2](+)?[Ag2(bis-NHC)2](2+) (NHC = N-Heterocyclic Carbene).  

PubMed

A cationic [Ag2(bis-NHC)2](2+) system behaves as an excellent host for Ag(+). In the solid-state variation, Ag···Ag are the only bonding interactions between host and guest, overcoming their inherent electrostatic repulsion. It represents a clear example of ligand-unsupported ("pure") argentophilicity. In solution, we also found evidence for this kind of Ag···Ag approximation, which might be recognized as an initial step of transmetalation mechanisms involving formally closed-shell metal centers as transferring agents. PMID:25226368

Vellé, Alba; Cebollada, Andrea; Iglesias, Manuel; Sanz Miguel, Pablo J

2014-10-01

387

Angular Orientation of Nanorods using Nanophotonic Tweezers  

E-print Network

Experiments For a light source a 1064 nm fiber coupled high power diode laser (LU1064M400 Lumics, EL Segundo resonance wavelength of resonators resulted from fabrication is compensated. The Laser light was coupled into silicon nitride waveguides through a lensed fiber. The power coupled to the resonator was measured

Erickson, David

388

Vortical laser tweezers with predetermined intensity structure  

NASA Astrophysics Data System (ADS)

The intensity of spiral beams remains unchanged under propagation and focusing neglecting scaling and rotation. The spiral beam with predetermined intensity in the shape of any planar curve can be generated by use of amplitude and phase elements concurrently. We introduce the new method of singular laser fields formation, close to spiral type, by means of pure phase modulation. Our algorithm is based on the well-known Gerchberg-Saxton phase retrieval algorithm and spiral beams optics. It demonstrates fast convergence and some other advantages: phase distributions obtained are stable to spatial resolution changing (it is enough 128 x 128 pixels for some patterns), theoretical energy efficiency is about 85 % with acceptable intensity homogeneity. We demonstrate theoretical results on fields formation in the shape of closed-curves (triangular, square, "snowflake") and open-ended curve (Archimedes spiral) by means of elements on dichromate gelatin. Besides, the example of experiment on micromanipulation with the use of the square-shaped field is presented.

Afanasiev, Kirill N.; Abramochkin, Eugeny G.; Korobtsov, Alexander V.; Kotova, Svetlana P.; Losevsky, Nikolay N.; Razueva, Eugenia V.; Volostnikov, Vladimir G.

2007-09-01

389

Holographic optical tweezers Gabriel C. Spalding  

E-print Network

: entirely new techniques are needed. Luckily, Newton's second law dictates that as the mass of the object simple static structures ­ the same approaches that we would naturally use on the macroscopic scale taken to preclude any possibility of extracting such equilibrium information from experimental data

Spalding, Gabriel Cooper

390

Iptycene-derived crown ether hosts for molecular recognition and self-assembly.  

PubMed

CONSPECTUS: Synthetic macrocyclic hosts have played key roles in the development of host-guest chemistry. Crown ethers are a class of macrocyclic molecules with unique flexible structures. They have served as the first generation of synthetic hosts, and researchers have extensively studied them in molecular recognition. However, the flexible structures of simple crown ethers and their relatively limited modes of complexation with guests have limited the further applications of these molecules. In recent years, researchers have moved toward fabricating interlocking molecules, supramolecular polymers, and other assemblies with specific structures and properties. Therefore, researchers have developed more complex crown ether-based macrocyclic hosts with multicavity structures and multicomplexation modes that provide more diverse and sophisticated host-guest systems. In this Account, we summarize our research on the synthesis and characterization of iptycene-derived crown ether hosts, their use as host molecules, and their applications in self-assembled complexes. Iptycenes including triptycenes and pentiptycenes are a class of aromatic compounds with unique rigid three-dimensional structures. As a result, they are promising building blocks for the synthesis of novel macrocyclic hosts and the construction of novel self-assembled complexes with specific structures and properties. During the last several years, we have designed and synthesized a new class of iptycene-derived crown ether hosts including macrotricyclic polyethers, molecular tweezer-like hosts, and tritopic tris(crown ether) hosts, which are all composed of rigid iptycene building blocks linked by flexible crown ether chains. We have examined the complexation behavior of these hosts with different types of organic guest molecules. Unlike with conventional crown ethers, the combination of iptycene moieties and crown ether chains provides the iptycene-derived crown ether hosts with complexation properties that differ based on the structure of the guests. The rigid iptycene moieties within these synthetic host molecules both maintain their inherent three-dimensional cavities and generate multicavity structures. The flexible crown ether chains allow the iptycene-derived hosts to adjust their conformations as they encapsulate guest molecules. Moreover, the expanded complexation properties also allow the host-guest systems based on the iptycene-derived crown ethers to respond to multiple external stimuli, resulting in a variety of supramolecular assemblies. Finally, we also describe the construction of mechanically interlocked self-assemblies, molecular switches/molecular machines, and supramolecular polymers using these new host molecules. We expect that the unique structural features and diverse complexation properties of these iptycene-derived crown ether hosts will lead to increasing interest in this field and in supramolecular chemistry overall. PMID:24877894

Han, Ying; Meng, Zheng; Ma, Ying-Xian; Chen, Chuan-Feng

2014-07-15

391

Synthesis and characterization of transition metal clusters: From the isolation of ligand-stabilized solid fragments to the tuning of magnetic anisotropy and host-guest selectivity, and, Approaches to science teaching: Development of an observation instrument with a measurement model based on item response theory  

NASA Astrophysics Data System (ADS)

Part I. The work presented herein describes efforts to develop general techniques for the synthesis of transition metal clusters and the manipulation of their properties. In Chapter 2, it is demonstrated that a modified metal atom reactor allows for the vaporization, passivation, and isolation of metal-chalcogenide clusters from their parent binary solids. Among the clusters produced by this method were Cr6S8(PEt3)6, Fe4S 4(PEt3)4, Co6S8(PEt 3)6, Cu6S4(PEt3)6, Cu12S6(PEt3)8, and Cu26Se 13(PEt3)14. To create single-molecule magnets with higher demagnetization barriers, we are developing metal-cyanide systems which exhibit highly adjustable magnetic behavior. Chapter 3 reports an attempt to introduce magnetic anisotropy into a MnCr6 cluster. Replacement of CrIII with Mo III resulted in the assembly of K[(Me3tacn)6MnMo 6(CN)18](ClO4)3 (Me3tacn = N,N',N? -trimethyl-1,4,7-triazacyclononane)---the first well-documented example of a cyano-bridged single-molecule magnet. Recently, it was demonstrated that replacing Me3tacn with the less sterically hindering tach (tach = cis,cis-1,3,5-triaminocyclohexane) in the face-centered cubic cluster [(tach)8Cr8Ni 6(CN)24]Br12 provides greater access to the cluster cavity. Chapter 4 describes my efforts to probe the selectivity of this cluster toward inclusion of various guests. Part II. Successful implementation of student-centered curricula reforms requires the creation of a measurement instrument for monitoring whether the curricula are being used as intended. The creation and development of an observation instrument would greatly contribute to this effort. To develop a theoretically sound construct map, it is necessary to review the literature and conduct our own investigations of approaches to science teaching. Chapter 2 presents the findings of these investigations and their contributions to our understanding of the construct. Using these findings, the Science Teaching Observation Protocol (STOP) was created and designed to measure two subconstructs: intentions and strategies. Chapter 3 details the first pilot test of STOP and analysis of the collected data. In Chapter 4, the theoretical shortcomings of the instrument are analyzed and discussed. Modified versions of the intention and strategy subconstruct maps are presented.

Hee, Allan George

392

Two-photon fluorescence diagnostics of femtosecond laser tweezers  

PubMed Central

We show how two-photon fluorescence signal can be used as an effective detection scheme for trapping particles of any size in comparison to methods using back-scattered light. Development of such a diagnostic scheme allows us a direct observation of trapping a single nanoparticle, which shows new directions to spectroscopy at the single-molecule level in solution. PMID:23814313

Kumar De, Arijit; Roy, Debjit; Goswami, Debabrata

2013-01-01

393

Multiplying optical tweezers force using a micro-lever  

E-print Network

. The relationship between the optical force and the spring constant can be determined by using the principle-beam gradient force optical trap for dielectric particles," Opt. Lett. 11, 288-290 (1986). 2. P. Galadja and P

Boyer, Edmond

394

Effects of viscosity on sperm motility studied with optical tweezers  

NASA Astrophysics Data System (ADS)

The purpose of this study is to analyze human sperm motility and energetics in media with different viscosities. Multiple experiments were performed to collect motility parameters using customized computer tracking software that measures the curvilinear velocity (VCL) and the minimum laser power (Pesc) necessary to hold an individual sperm in an optical trap. The Pesc was measured by using a 1064 nm Nd:YVO4 continuous wave laser that optically traps motile sperm at a power of 450 mW in the focused trap spot. The VCL was measured frame by frame before trapping. In order to study sperm energetics under different viscous conditions sperm were labeled with the fluorescent dye DiOC6(3) to measure membrane potentials of mitochondria in the sperm midpiece. Fluorescence intensity was measured before and during trapping. The results demonstrate a decrease in VCL but an increase in Pesc with increasing viscosity. Fluorescent intensity is the same regardless of the viscosity level indicating no change in sperm energetics. The results suggest that, under the conditions tested, viscosity physically affects the mechanical properties of sperm motility rather than the chemical pathways associated with energetics.

Hyun, Nicholas; Chandsawangbhuwana, Charlie; Zhu, Qingyuan; Shi, Linda Z.; Yang-Wong, Collin; Berns, Michael W.

2012-02-01

395

Tools to study the kinesin mechanome using optical tweezers  

E-print Network

Molecular motors play an important role in driving some of the most complex and important tasks in biological systems, ranging from transcribing RNA from a DNA template (Polymerases) to muscle contraction (Myosin) and ...

González Rubio, Ricardo, S.M. Massachusetts Institute of Technology

2009-01-01

396

Iron under pressure: "Kohn tweezers" and remnant magnetism.  

PubMed

In this work we investigate the magnetic and structural properties of bulk Fe and Fe nanoparticles under pressure with x-ray absorption and emission spectroscopies providing answers to two fundamental questions: (a) the chicken-or-egg problem for the magnetic and structural transitions and (b) magnetism in the high pressure hcp phase. The two transitions, inextricably linked in the bulk, are clearly decoupled in the nanoparticles, with the magnetic collapse preceding the structural transition. Ultrafast x-ray emission spectroscopy detects remnant magnetism, probably antiferromagnetic fluctuations, up to pressures of about 40 GPa in the hcp phase. This could be of direct relevance to the superconductivity in ?-Fe [K. Shimizu et al., Nature (London) 412, 316 (2001)] through the existence of a quantum critical point and associated magnetic fluctuations. PMID:21770592

Monza, A; Meffre, A; Baudelet, F; Rueff, J-P; d'Astuto, M; Munsch, P; Huotari, S; Lachaize, S; Chaudret, B; Shukla, Abhay

2011-06-17

397

Force measurement in colloidal glasses using optical tweezers  

NASA Astrophysics Data System (ADS)

Colloidal systems form the basis of many complex areas of academic and industrial research efforts. As well as contributing to the understanding of many industrially-produced substances such as paints and glues, they have also proved an excellent model thermodynamic system. Changing the properties of an ensemble of colloidal particles, chemically or otherwise, and observing the evolution of the many-body system gives insight into thermodynamic phenomena such as condensation and crystallisation. Some colloidal systems with a particle density that would place them around the dense end of the liquid-crystal coexistence region show a transition into an amorphous glassy state. Long range particle movement is prevented, while local diffusion is still allowed. Such systems are ideal candidates for exploration with optical force measurements, which allow the relatively non-intrusive manipulation of particles deep within colloidal suspensions. Careful use of refractive index matching has allowed an invisible colloidal suspension to be examined with probe particles of a similar size, but higher refractive index. The environment of particles in colloidal cages has been measured by studying the forces acting on a localised particle, as well as the forces needed to break one or more cages.

Wilson, Laurence; Besseling, Rut; Arlt, Jochen; Poon, Wilson C. K.

2005-08-01

398

Single beam optical vortex tweezers with tunable orbital angular momentum  

NASA Astrophysics Data System (ADS)

We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.

Gecevi?ius, Mindaugas; Drevinskas, Rokas; Beresna, Martynas; Kazansky, Peter G.

2014-06-01

399

Compact microscope-based optical tweezers system for molecular manipulation  

E-print Network

. Comparison of YOYO-1-, ethidium bromide intercalated DNA, and distamycin-A complexed DNA revealed accurate of individual double-stranded deoxyribonucleic acid DNA molecules was integrated into a commercial inverted was tested with individual -DNA molecules and renders new aspects of dynamic forces phenomena with higher

Bielefeld, Universität

400

Torsional sensing of small-molecule binding using magnetic tweezers  

E-print Network

intercalation lengthens DNA $1.5-fold and decreases the persist- ence length, from which we extract binding con- stants. Using our control of supercoiling, we measure the decrease in DNA twist per intercalation of different DNA binding modes such as intercalation (1), minor groove binding and major groove binding (2

Dekker, Nynke

401

A Theoretical Light Scattering Model of Nanoparticle Laser Tweezers  

NASA Technical Reports Server (NTRS)

Accomplishments this reporting period include: 1. derived, programmed, checked, and tested the Mie light scattering theory formulas for the radiation trapping force for both the on-axis and off-axis geometry of the trapping beam plus trapped spherical particle; 2. verified that the computed radiation trapping force for a freely propagating focused Gaussian laser beam incident on a spherical particle agrees with previous published calculations; 3. compared the small particle size and large particle size limits of the Mie calculation with the results of Rayleigh scattering theory and ray scattering theory, respectively and verified that the comparison is correct for Rayleigh scattering theory but found that ray theory omits an important light scattering effect included in the Mie theory treatment; 4. generalized the calculation of the radiation trapping force on a spherical particle in the on-axis geometry from a freely propagating focused Gaussian laser beam to the realistic situation of a Gaussian beam truncated and focused by a high numerical aperture oil-immersion microscope objective lens and aberrated by the interface between the microscope cover slip and the liquid-filled sample volume; and 5. compared the calculated radiation trapping force for this geometry with the results of previously published experiments and found that the agreement is better than when using previously developed theories.

Lock, James A.

2003-01-01

402

Solar sails, optical tweezers, and other light-driven machines  

NASA Astrophysics Data System (ADS)

Electromagnetic waves carry energy, linear momentum, and angular momentum. When light (or other electromagnetic radiation) interacts with material media, both energy and momentum are usually exchanged. The force and torque experienced by material bodies in their interactions with the electromagnetic field are such that the energy as well as the linear and angular momenta of the overall system (i.e., the system of field plus matter) are conserved. Radiation forces are now used routinely to trap and manipulate small objects such as glass or plastic micro-beads and biological cells, to drive micro- and nanomachines, and to contemplate interstellar travel with the aid of solar sails. We discuss the properties of the electromagnetic field that enable such wide-ranging applications.

Mansuripur, Masud

2011-10-01

403

Multispectral optical tweezers for molecular diagnostics of single biological cells  

E-print Network

on yeast cells #12;Motivation #12;Need for single cell manipulation Avoid (control) many-body effects Stable control of the cell/particle over more than 50 m 1 m polystyrene beads #12;Spectral detection Aldrich LB30-1ML 3µm PS beads (Raman) Sigma Aldrich L3030-1ML 2µm dyed fluorescent PS beads #12

Wu, Shin-Tson

404

The Rich Chemistry of Cyclotriveratrylene (CTV) And CT-Inspired Reactions: Anthracenes with Organic Light-Emitting Diode (OLED) Applications and the Discovery of Cascade Reactions.  

E-print Network

?? Cyclotriveratrylene (CTV) is a supramolecular scaffold with applications in host-guest chemistry, analytical detection, drug delivery and liquid crystals. We have discovered that CTV rearranges… (more)

Sarsah, Samuel

2013-01-01

405

Selectivity Control in Synergistic Liquid-Liquid Anion Exchange of Univalent Anions via Structure-Specific Cooperativity between Quaternary Ammonium Cations and Anion Receptors  

SciTech Connect

Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence upon the structure of the alkylammonium cation. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). C4P has the unique ability in its cone anion-binding conformation to accept an appropriately sized electropositive species in the resulting cup formed by its four electron-rich pyrrole groups, while BTU is not expected to be predisposed for a specific host-guest interaction with the quaternary ammonium cations. It was therefore hypothesized that synergism between C4P and methyltri(C8,10)alkylammonium chloride (Aliquat 336) would be uniquely pronounced owing to insertion of the methyl group of the Aliquat cation into the C4P cup, and we present herein data supporting this expectation. While synergism is comparatively weak for both exchangers with the BTU receptor, synergism between C4P and Aliquat 336 is indeed so strong that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, unraveling the observed selectivity behavior and resulting in the estimation of binding constants for C4P with the ion pairs of A336+ with Cl , Br , OAcF3 , NO3 , and I . The uniquely strong positive cooperativity between A336 and C4P underscores the advantage of a supramolecular approach in the design of synergistic anion exchange systems.

Borman, Christopher J [ORNL; Bonnesen, Peter V [ORNL; Moyer, Bruce A [ORNL

2012-01-01

406

Molecular recognition of curcumin (Indian Ayurvedic medicine) by the supramolecular probe, p-t-butyl calix(8)arene.  

PubMed

The thermodynamic property of the host-guest complexes formed between the curcumin, component of Indian Ayurvedic medicine turmeric, a drug molecule, with the supra molecule, p-t-butyl calix(8)arene was studied. p-t-Butyl calix(8)arene has been used as a host molecule and curcumin as a guest molecule. Optical absorption spectral studies were carried out to investigate the molecular recognition properties of p-t-butyl calix(8)arene with curcumin. The stochiometry of the host-guest complexes formed and the binding constant were determined. An interesting 1:1 and 4:1 stochiometric host-guest complexes were formed. Job's continuous method of variation and Benesi-Hildebrand expression were used for the determination of binding constant and the stochiometry of the host-guest complex formed. PMID:24632170

Meenakshi, C; Jayabal, P; Ramakrishnan, V

2014-06-01

407

Assessment of molecular interaction in a cycluron-cyclodextrin inclusion complex  

NASA Astrophysics Data System (ADS)

Thermodynamic parameters and the host-guest stoichiometry of inclusion complex cycluron with ?-cyclodextrin in aqueous solution have been determined. The supramolecular structure has been investigated by isothermal titration nanocalorimetry and 1H NMR spectroscopy at 298.15 K.

Mic, Mihaela; Cruickshank, Dyanne; Turcu, Ioan

2009-08-01

408

Imidazole Metalloporphyrins as Photosensitizers for Photodynamic Therapy: Role of Molecular Charge, Central Metal and Hydroxyl Radical Production  

PubMed Central

SUMMARY The in vitro photodynamic therapy activity of four imidazole-substituted metalloporphyrins has been studied using human (HeLa) and mouse (CT26) cancer cell lines: an anionic Zn porphyrin and a homologous series of three cationic Zn, Pd or InCl porphyrins. A dramatic difference in phototoxicity was found: Pd cationic > InCl cationic > Zn cationic > Zn anionic. HeLa cells were more susceptible than CT26 cells. Induction of apoptosis was demonstrated using a fluorescent caspase assay. The anionic Zn porphyrin localized in lysosomes while the cationic Zn porphyrin localized in lysosomes and mitochondria, as assessed by fluorescence microscopy. Studies using fluorescent probes suggested that the cationic Pd porphyrin produced more hydroxyl radicals as the reactive oxygen species. Thus, the cationic Pd porphyrin has high potential as a photosensitizer and gives insights into characteristics for improved molecular designs. PMID:19346065

Mroz, Pawel; Bhaumik, Jayeeta; Dogutan, Dilek K.; Aly, Zarmeneh; Kamal, Zahra; Khalid, Laiqua; Kee, Hooi Ling; Bocian, David F.; Holten, Dewey; Lindsey, Jonathan S.; Hamblin, Michael R.

2009-01-01

409

Spectrin-Level Modeling of the Cytoskeleton and Optical Tweezers Stretching of the Erythrocyte  

E-print Network

is used in defining the in-plane energy, then the bending modulus k needs to be at least a decade larger investigation for many decades. Interest in the mechanics of RBC can be attributed to several factors. Firstly

Dao, Ming

410

Dielectrophoretic Tweezers as a Platform for Single Molecular Force Spectroscopy in a Highly Parallel Format  

NASA Astrophysics Data System (ADS)

Miniaturization has driven down the cost of tools used in bioanalysis and diagnostics, with single molecules becoming the ultimate detection limit. I will describe how one can exploit mechanical properties of individual biomolecules to determine changes in their state or structure. Our aim is to build a force-spectroscopy-on-a-chip device that can detect and manipulate many (millions) single molecules in parallel. A critical element of this approach is the design of materials properties of molecular handles or probes. By tuning interactions of these probes with electric fields which generate by a simple electrode geometry, we are able to apply piconewton forces to individual DNA molecules and record their response with a single base sensitivity. I will present how we determined the approximate crossover frequency between negative and positive DEP using plain electrodes instead of conventional micro-structures. The technique is attractive not only for conducting single molecule force spectroscopy but also for label-free single cell detection. I will discuss potential applications of this approach to high throughput analyses such as genome sequencing and HIV detection.

Cheng, Peng; Barrett, Michael; Oliver, Piercen; Vezenov, Dmitri

2012-02-01

411

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

Microsoft Academic Search

Computer-generated holograms in conjunction with spatial light modulators (SLMs) offer a way to dynamically generate holograms that are adapted to specific tasks. To use the full dynamic capability of the SLM, the hologram computation should be very fast. We present a method that uses the highly parallel architecture of a consumer graphics board to compute analytical holograms in video real

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

2006-01-01

412

Unzipping DNA with Optical Tweezers: High Sequence Sensitivity and Force Flips  

E-print Network

and consider fluctuations in the force signal. With respect to earlier work performed with soft microneedles with a soft glass microneedle (Bockelmann et al., 1997, 1998; Essevaz-Roulet et al., 1997). Force signals have

Croquette, Vincent

413

Active Microrheology of Networks Composed of Semiflexible Polymers I. Computer Simulation of Magnetic Tweezers  

E-print Network

We have simulated the motion of a bead subjected to a constant force while embedded in a network of semiflexible polymers which can represent actin filaments. We find that the bead displacement obeys the power law x ~ t^alfa. After the initial stage characterized by the exponent alfa=0.75 we find a new regime with alfa=0.5. The response in this regime is linear in force and scales with the polymer concentration as c^(-1.4). We find that the polymers pile up ahead of the moving bead, while behind it the polymer density is reduced. We show that the force resisting the bead motion is due to steric repulsion exerted by the polymers on the front hemisphere of the bead.

N. Ter-Oganessian; D. A. Pink; B. Quinn; A. Boulbitch

2005-03-23

414

Colliding and moving Bose-Einstein condensates : studies of superfluidity and optical tweezers for condensate transport  

E-print Network

In this thesis, two different sets of experiments are described. The first is an exploration of the microscopic superfluidity of dilute gaseous Bose-Einstein condensates. The second set of experiments were performed using ...

Chikkatur, Ananth P., 1975-

2003-01-01

415

Keratin contribution to cellular mechanical stress response at focal adhesions as assayed by laser tweezers  

Microsoft Academic Search

The ability of adherent cells to sense and adapt to a mechanical stress generated at focal adhesions (FAs) largely occurs through the integrin-mediated interaction between the cytoskeleton, namely actin microfilaments, and extra- cellular matrix elements, like fibronectin. Here we assessed the contribution of keratin 8 and 18 (K8\\/K18) intermediate fil- aments (IFs) in simple epithelial cells in response to a

François Bordeleau; Judicael Bessard; Yunlong Sheng; Normand Marceau

2008-01-01

416

Measurements of forces produced by the mitotic spindle using optical tweezers  

PubMed Central

We used a trapping laser to stop chromosome movements in Mesostoma and crane-fly spermatocytes and inward movements of spindle poles after laser cuts across Potorous tridactylus (rat kangaroo) kidney (PtK2) cell half-spindles. Mesostoma spermatocyte kinetochores execute oscillatory movements to and away from the spindle pole for 1–2 h, so we could trap kinetochores multiple times in the same spermatocyte. The trap was focused to a single point using a 63× oil immersion objective. Trap powers of 15–23 mW caused kinetochore oscillations to stop or decrease. Kinetochore oscillations resumed when the trap was released. In crane-fly spermatocytes trap powers of 56–85 mW stopped or slowed poleward chromosome movement. In PtK2 cells 8-mW trap power stopped the spindle pole from moving toward the equator. Forces in the traps were calculated using the equation F = Q?P/c, where P is the laser power and c is the speed of light. Use of appropriate Q? coefficients gave the forces for stopping pole movements as 0.3–2.3 pN and for stopping chromosome movements in Mesostoma spermatocytes and crane-fly spermatocytes as 2–3 and 6–10 pN, respectively. These forces are close to theoretical calculations of forces causing chromosome movements but 100 times lower than the 700 pN measured previously in grasshopper spermatocytes. PMID:23485565

Ferraro-Gideon, Jessica; Sheykhani, Rozhan; Zhu, Qingyuan; Duquette, Michelle L.; Berns, Michael W.; Forer, Arthur

2013-01-01

417

Computer-Generated Holographic Optical Tweezer Arrays Eric R. Dufresne and David G. Grier  

E-print Network

. Dielectric particles polarized by the light's electric field are drawn up the gradients to the brightest aperture lens. Microscope objective lenses of- fer an ideal combination of minimal aberration and large is to direct a laser beam into the objective lens' back aperture so that the beam fills the aperture and so

Grier, David

418

ComputerGenerated Holographic Optical Tweezer Arrays Eric R. Dufresne and David G. Grier  

E-print Network

. Dielectric particles polarized by the light's electric field are drawn up the gradients to the brightest aperture lens. Microscope objective lenses of­ fer an ideal combination of minimal aberration and large is to direct a laser beam into the objective lens' back aperture so that the beam fills the aperture and so

Grier, David

419

Computer-Generated Holographic Optical Tweezer Arrays Eric R. Dufresne(1)  

E-print Network

by optical intensity gradients. Dielectric particles polarized by the light's electric field are drawn up to a tight focus with a high numerical aperture lens. Microscope objective lenses of- fer an ideal to an objective lens' back aperture (B) by lenses L1 and L2 and focused into a trapping array. OP denotes

Grier, David