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Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Zhao J, Szczesna-Cordary D, Borejdo J. Cross-bridge kinetics in myofibrils containing familial hypertrophic cardiomyopathy R58Q mutation in the regulatory light chain of myosin. J Theor Biol 2011; 284:71-81. [PMID: 21723297 PMCID: PMC3152379 DOI: 10.1016/j.jtbi.2011.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 06/09/2011] [Accepted: 06/14/2011] [Indexed: 12/16/2022]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a heritable form of cardiac hypertrophy caused by single-point mutations in genes encoding sarcomeric proteins including ventricular myosin regulatory light chain (RLC). FHC often leads to malignant outcomes and sudden cardiac death. The FHC mutations are believed to alter the kinetics of the interaction between actin and myosin resulting in inefficient energy utilization and compromised function of the heart. We studied the effect of the FHC-linked R58Q-RLC mutation on the kinetics of transgenic (Tg)-R58Q cardiac myofibrils. Kinetics was determined from the rate of change of orientation of actin monomers during muscle contraction. Actin monomers change orientation because myosin cross-bridges deliver periodic force impulses to it. An individual impulse (but not time average of impulses) carries the information about the kinetics of actomyosin interaction. To observe individual impulses it was necessary to scale down the experiments to the level of a few molecules. A small population (∼4 molecules) was selected by using (deliberately) inefficient fluorescence labeling and observing fluorescent molecules by a confocal microscope. We show that the kinetic rates are significantly smaller in the contracting cardiac myofibrils from Tg-R58Q mice then in control Tg-wild type (WT). We also demonstrate a lower force per cross-section of muscle fiber in Tg-R58Q versus Tg-WT mice. We conclude that the R58Q mutation-induced decrease in cross-bridge kinetics underlines the mechanism by which Tg-R58Q fibers develop low force and thus compromise the ability of the mutated heart to efficiently pump blood.
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Lee KM, Neogi A, Basu Neogi P, Kim M, Kim B, Luchowski R, Gryczynski Z, Calander N, Choi TY. Silver nanostructure sensing platform for maximum-contrast fluorescence cell imaging. JOURNAL OF BIOMEDICAL OPTICS 2011; 16:056008. [PMID: 21639576 DOI: 10.1117/1.3579157] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We present herein a silver nanostructure-assisted sensing platform which consists of a combined structure of Ag nanowire (NW) and nanodot (ND) array. Highly enhanced fluorescence from fluorophore is attributed to a strongly coupled optical near-field interaction between proximately located Ag NW and NDs. We obtained enhanced fluorescence intensity with up to 140 folds, as contrasted from background intensity, reaching a theoretical maximum value. On the other hand, fluorescence lifetime was greatly reduced to 0.27 ns (from 2.17 ns for the same fluorophores without nanostructure). This novel platform can be a promising utility for optical imaging and labeling of biological systems with a great sensitivity.
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Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Borejdo J. Observing cycling of a few cross-bridges during isometric contraction of skeletal muscle. Cytoskeleton (Hoboken) 2010; 67:400-11. [PMID: 20517927 DOI: 10.1002/cm.20453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
During muscle contraction a myosin cross-bridge imparts periodic force impulses to actin. It is possible to visualize those impulses by observing a few molecules of actin or myosin. We have followed the time course of orientation change of a few actin molecules during isometric contraction by measuring parallel polarized intensity of its fluorescence. The orientation of actin reflects local bending of a thin filament and is different when a cross-bridge binds to, or is detached from, F-actin. The changes in orientation were characterized by periods of activity during which myosin cross-bridges interacted normally with actin, interspersed with periods of inactivity during which actin and myosin were unable to interact. The periods of activity lasted on average 1.2 +/- 0.4 s and were separated on average by 2.3 +/- 1.0 s. During active period, actin orientation oscillated between the two extreme values with the ON and OFF times of 0.4 +/- 0.2 and 0.7 +/- 0.4 s, respectively. When the contraction was induced by a low concentration of ATP both active and inactive times were longer and approximately equal. These results imply that cross-bridges interact with actin in bursts and suggest that during active period, on average 36% of cross-bridges are involved in force generation.
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Luchowski R, Calander N, Shtoyko T, Apicella E, Borejdo J, Gryczynski Z, Gryczynski I. Plasmonic platforms of self-assembled silver nanostructures in application to fluorescence. JOURNAL OF NANOPHOTONICS 2010; 4:043516. [PMID: 21403765 PMCID: PMC3053531 DOI: 10.1117/1.3500463] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Fluorescence intensity changes were investigated theoretically and experimentally using self-assembled colloidal structures on silver semitransparent mirrors. Using a simplified quasi-static model and finite element method, we demonstrate that near-field interactions of metallic nanostructures with a continuous metallic surface create conditions that produce enormously enhanced surface plasmon resonances. The results were used to explain the observed enhancements and determine the optimal conditions for the experiment. The theoretical parts of the studies are supported with reports on detailed emission intensity changes which provided multiple fluorescence hot spots with 2-3 orders of enhancements. We study two kinds of the fluorophores: dye molecules and fluorescent nanospheres characterized with similar spectral emission regions. Using a lifetime-resolved fluorescence/reflection confocal microscopy technique, we find that the largest rate for enhancement (~1000-fold) comes from localized areas of silver nanostructures.
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Borejdo J, Szczesna-Cordary D, Muthu P, Calander N. Familial hypertrophic cardiomyopathy can be characterized by a specific pattern of orientation fluctuations of actin molecules . Biochemistry 2010; 49:5269-77. [PMID: 20509708 DOI: 10.1021/bi1006749] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A single-point mutation in the gene encoding the ventricular myosin regulatory light chain (RLC) is sufficient to cause familial hypertrophic cardiomyopathy (FHC). Most likely, the underlying cause of this disease is an inefficient energy utilization by the mutated cardiac muscle. We set out to devise a simple method to characterize two FHC phenotypes caused by the R58Q and D166V mutations in RLC. The method is based on the ability to observe a few molecules of actin in working ex vivo heart myofibril. Actin is labeled with extremely diluted fluorescent dye, and a small volume within the I-band ( approximately 10(-16) L), containing on average three actin molecules, is observed by confocal microscopy. During muscle contraction, myosin cross-bridges deliver cyclic impulses to actin. As a result, actin molecules undergo periodic fluctuations of orientation. We measured these fluctuations by recording the parallel and perpendicular components of fluorescent light emitted by an actin-bound fluorophore. The histograms of fluctuations of fluorescent actin molecules in wild-type (WT) hearts in rigor were represented by perfect Gaussian curves. In contrast, histograms of contracting heart muscle were peaked and asymmetric, suggesting that contraction occurred in at least two steps. Furthermore, the differences between histograms of contracting FHC R58Q and D166V hearts versus corresponding contracting WT hearts were statistically significant. On the basis of our results, we suggest a simple new method of distinguishing between healthy and FHC R58Q and D166V hearts by analyzing the probability distribution of polarized fluorescence intensity fluctuations of sparsely labeled actin molecules.
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Abstract
Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst-Planck, Poisson, and Navier-Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures and is shown to be crucial for the behavior at the tip. It is demonstrated that the concentration of molecules is a consequence of ionic charge accumulation at the tip screening the electric field, thereby slowing down the electrophoretic motion of the molecules, which is further slowed down or stopped by the oppositely directed electro-osmosis. It is also shown that the trapping is very sensitive to the properties of the molecule, that is, its electrophoretic mobility and diffusion coefficient, the properties of the pipette, the ionic strength of the solution, and the applied electric field.
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Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Borejdo J. Kinetics of a single cross-bridge in familial hypertrophic cardiomyopathy heart muscle measured by reverse Kretschmann fluorescence. JOURNAL OF BIOMEDICAL OPTICS 2010; 15:017011. [PMID: 20210485 PMCID: PMC2847936 DOI: 10.1117/1.3324871] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2009] [Revised: 01/04/2010] [Accepted: 01/06/2010] [Indexed: 05/28/2023]
Abstract
Familial hypertrophic cardiomyopathy (FHC) is a serious heart disease that often leads to a sudden cardiac death of young athletes. It is believed that the alteration of the kinetics of interaction between actin and myosin causes FHC by making the heart to pump blood inefficiently. We set out to check this hypothesis ex vivo. During contraction of heart muscle, a myosin cross-bridge imparts periodic force impulses to actin. The impulses are analyzed by fluorescence correlation spectroscopy (FCS) of fluorescently labeled actin. To minimize observation volume and background fluorescence, we carry out FCS measurements in surface plasmon coupled emission mode in a reverse Kretschmann configuration. Fluorescence is a result of near-field coupling of fluorophores excited in the vicinity of the metal-coated surface of a coverslip with the surface plasmons propagating in the metal. Surface plasmons decouple on opposite sides of the metal film and emit in a directional manner as far-field p-polarized radiation. We show that the rate of changes of orientation is significantly faster in contracting cardiac myofibrils of transgenic mice than wild type. These results are consistent with the fact that mutated heart muscle myosin translates actin faster in in vitro motility assays.
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Muthu P, Mettikolla P, Calander N, Luchowski R, Gryczynski I, Gryczynski Z, Szczesna-Cordary D, Borejdo J. Single molecule kinetics in the familial hypertrophic cardiomyopathy D166V mutant mouse heart. J Mol Cell Cardiol 2009; 48:989-98. [PMID: 19914255 DOI: 10.1016/j.yjmcc.2009.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/21/2009] [Accepted: 11/06/2009] [Indexed: 11/26/2022]
Abstract
One of the sarcomeric mutations associated with a malignant phenotype of familial hypertrophic cardiomyopathy (FHC) is the D166V point mutation in the ventricular myosin regulatory light chain (RLC) encoded by the MYL2 gene. In this report we show that the rates of myosin cross-bridge attachment and dissociation are significantly different in isometrically contracting cardiac myofibrils from right ventricles of transgenic (Tg)-D166V and Tg-WT mice. We have derived the myosin cross-bridge kinetic rates by tracking the orientation of a fluorescently labeled single actin molecule. Orientation (measured by polarized fluorescence) oscillated between two states, corresponding to the actin-bound and actin-free states of the myosin cross-bridge. The rate of cross-bridge attachment during isometric contraction decreased from 3 s(-1) in myofibrils from Tg-WT to 1.4 s(-1) in myofibrils from Tg-D166V. The rate of detachment decreased from 1.3 s(-1) (Tg-WT) to 1.2 s(-1) (Tg-D166V). We also showed that the level of RLC phosphorylation was largely decreased in Tg-D166V myofibrils compared to Tg-WT. Our findings suggest that alterations in the myosin cross-bridge kinetics brought about by the D166V mutation in RLC might be responsible for the compromised function of the mutated hearts and lead to their inability to efficiently pump blood.
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Mettikolla P, Luchowski R, Gryczynski I, Gryczynski Z, Calander N, Borejdo J. The Fluorescence Lifetime of a Single Actin-bound Fluorophore During Contraction of Skeletal Muscle. Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.3254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Muthu P, Calander N, Gryczynski I, Gryczynski Z, Talent JM, Shtoyko T, Akopova I, Borejdo J. Monolayers of silver nanoparticles decrease photobleaching: application to muscle myofibrils. Biophys J 2008; 95:3429-38. [PMID: 18556759 PMCID: PMC2547432 DOI: 10.1529/biophysj.108.130799] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2008] [Accepted: 04/07/2008] [Indexed: 11/18/2022] Open
Abstract
Studying single molecules in a cell has the essential advantage that kinetic information is not averaged out. However, since fluorescence is faint, such studies require that the sample be illuminated with the intense light beam. This causes photodamage of labeled proteins and rapid photobleaching of the fluorophores. Here, we show that a substantial reduction of these types of photodamage can be achieved by imaging samples on coverslips coated with monolayers of silver nanoparticles. The mechanism responsible for this effect is the interaction of localized surface plasmon polaritons excited in the metallic nanoparticles with the transition dipoles of fluorophores of a sample. This leads to a significant enhancement of fluorescence and a decrease of fluorescence lifetime of a fluorophore. Enhancement of fluorescence leads to the reduction of photodamage, because the sample can be illuminated with a dim light, and decrease of fluorescence lifetime leads to reduction of photobleaching because the fluorophore spends less time in the excited state, where it is susceptible to oxygen attack. Fluorescence enhancement and reduction of photobleaching on rough metallic surfaces are usually accompanied by a loss of optical resolution due to refraction of light by particles. In the case of monolayers of silver nanoparticles, however, the surface is smooth and glossy. The fluorescence enhancement and the reduction of photobleaching are achieved without sacrificing the optical resolution of a microscope. Skeletal muscle myofibrils were used as an example, because they contain submicron structures conveniently used to define optical resolution. Small nanoparticles (diameter approximately 60 nm) did not cause loss of optical resolution, and they enhanced fluorescence approximately 500-fold and caused the appearance of a major picosecond component of lifetime decay. As a result, the sample photobleached approximately 20-fold more slowly than the sample on glass coverslips.
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Calander N, Muthu P, Gryczynski Z, Gryczynski I, Borejdo J. Fluorescence correlation spectroscopy in a reverse Kretchmann surface plasmon assisted microscope. OPTICS EXPRESS 2008; 16:13381-13390. [PMID: 18711576 DOI: 10.1364/oe.16.013381] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Fluorescence Correlation Spectroscopy (FCS) demands a high rate of photon detection per molecule, low background, and large fluctuations of fluorescence associated with translational motion. The new approach presented here, Surface Plasmon Assisted Microscope (SPAM), meets these requirements by drastically limiting the observation volume. In this method, the observational layer is made so thin that fluctuations are mostly due to the axial motion of molecules. This is conveniently realized by placing a sample on a thin metal film and illuminating it with a laser beam through an aqueous medium. The excited fluorophores close to the surface couple (via near-field interactions) to surface plasmons in the metal. Propagated surface plasmons decouple on opposite side of the metal film as a far-field radiation and emit in directional manner. Fluorescence is collected with a high Numerical Aperture objective. A confocal aperture inserted in its conjugate image plane reduces lateral dimensions of the detection volume to a diffraction limit. The thickness of the detection layer is reduced further by metal quenching of excited fluorophores at a close proximity (about 30 nm) to the surface. We used a suspension of fluorescent microspheres to show that FCS-SPAM is an efficient method to measure molecular diffusion.
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Borejdo J, Muthu P, Talent J, Gryczynski Z, Calander N, Akopova I, Shtoyko T, Gryczynski I. Reduction of photobleaching and photodamage in single molecule detection: observing single actin monomer in skeletal myofibrils. JOURNAL OF BIOMEDICAL OPTICS 2008; 13:034021. [PMID: 18601566 DOI: 10.1117/1.2938689] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Recent advances in detector technology make it possible to achieve single molecule detection (SMD) in a cell. SMD avoids complications associated with averaging signals from large assemblies and with diluting and disorganizing proteins. However, it requires that cells be illuminated with an intense laser beam, which causes photobleaching and cell damage. To reduce these effects, we study cells on coverslips coated with silver nanoparticle monolayers (NML). Muscle is used as an example. Actin is labeled with a low concentration of fluorescent phalloidin to assure that less than a single molecule in a sarcomere is fluorescent. On a glass substrate, the fluorescence of actin decays in a step-wise fashion, establishing a single molecule detection regime. Single molecules of actin in living muscle are visualized for the first time. NML coating decreases the fluorescence lifetime 17 times and enhances intensity ten times. As a result, fluorescence of muscle bleaches four to five times slower than on glass. Monolayers decrease photobleaching because they shorten the fluorescence lifetime, thus decreasing the time that a fluorophore spends in the excited state when it is vulnerable to oxygen attack. They decrease damage to cells because they enhance the electric field near the fluorophore, making it possible to illuminate samples with weaker light.
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Calander N. Focused optical beams obtained at planar structures by an imaginary shift in position. JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. A, OPTICS, IMAGE SCIENCE, AND VISION 2007; 24:2513-5. [PMID: 17767222 DOI: 10.1364/josaa.24.002513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
A theory for focused optical beams at planar structures is described. It is an extension of a previous theory based on summation of plane waves. The focused beam is obtained by an imaginary shift in the position vector of the plane waves. It is well suited for calculations of electromagnetic fields at planar surface plasmon resonance structures excited by a focused optical beam.
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Matveeva EG, Gryczynski I, Barnett A, Calander N, Gryczynski Z. Red blood cells do not attenuate the SPCE fluorescence in surface assays. Anal Bioanal Chem 2007; 388:1127-35. [PMID: 17534609 DOI: 10.1007/s00216-007-1322-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 04/11/2007] [Accepted: 04/24/2007] [Indexed: 12/19/2022]
Abstract
We describe the positive effect of surface plasmon-coupled fluorescence emission (SPCE) on the detection of a signal from a surface immunoassay in highly absorbing or/and scattering samples. A model immunoassay using fluorescently labeled anti-rabbit antibodies that bind to rabbit immunoglobulin on a silver surface was performed, and the signal was detected in the presence of various highly absorbing and/or scattering solutions or suspensions, such as hemoglobin solution, plastic beads, and red blood cells. The results showed that a highly absorbing solution consisting of small molecules (dye, hemoglobin) attenuates the SPCE signal approximately 2-3-fold. In contrast, suspensions with the same absorption containing large particles (large beads, red blood cell suspension) attenuate the SPCE signal only slightly, approximately 5-10%. Also, a suspension of large undyed, highly scattering beads does not reduce the SPCE signal. The effects on the immunoassay signal of the sample background absorption and scattering, the size of the background particles, and the geometry of the experimental set-up are discussed. We believe that SPCE is a promising technique in the development of biosensors utilized for surface-based assays, as well as any assays performed directly in highly absorbing and/or scattering solutions without washing or separation procedures. Figure Red blood cells (unlike hemoglobin) do not attenuate the SPCE fluorescence in surface assays.
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Risveden K, Pontén JF, Calander N, Willander M, Danielsson B. The region ion sensitive field effect transistor, a novel bioelectronic nanosensor. Biosens Bioelectron 2007; 22:3105-12. [PMID: 17400440 DOI: 10.1016/j.bios.2007.01.019] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2006] [Revised: 12/22/2006] [Accepted: 01/23/2007] [Indexed: 10/23/2022]
Abstract
A novel type of bioelectronic region ion sensitive field effect transistor (RISFET) nanosensor was constructed and demonstrated on two different sensor chips that could measure glucose with good linearity in the range of 0-0.6mM and 0-0.3mM with a limit of detection of 0.1 and 0.04 mM, respectively. The sensor is based on the principle of focusing charged reaction products with an electrical field in a region between the sensing electrodes. For glucose measurements, negatively charged gluconate ions were gathered between the sensing electrodes. The signal current response was measured using a low-noise pico ammeter (pA). Two different sizes of the RISFET sensor chips were constructed using conventional electron beam lithography. The measurements are done in partial volumes mainly restricted by the working distance between the sensing electrodes (790 and 2500 nm, respectively) and the influence of electrical fields that are concentrating the ions. The sensitivity was 28 pA/mM (2500 nm) and 830 pA/mM (790 nm), respectively. That is an increase in field strength by five times between the sensing electrodes increased the sensitivity by 30 times. The volumes expressed in this way are in low or sub femtoliter range. Preliminary studies revealed that with suitable modification and control of parameters such as the electric control signals and the chip electrode dimensions this sensor could also be used as a nanobiosensor by applying single enzyme molecule trapping. Hypotheses are given for impedance factors of the RISFET conducting channel.
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Calander N, Gryczynski I, Gryczynski Z. Interference of surface plasmon resonances causes enhanced depolarized light scattering from metal nanoparticles. Chem Phys Lett 2007; 434:326-330. [PMID: 18516244 PMCID: PMC2404116 DOI: 10.1016/j.cplett.2006.12.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We show that the strongly depolarized light scattering from noble metal particles is a result of interference of two surface plasmon resonances on the same particle. The maximum depolarization occurs between two resonances. Under favorable conditions the anisotropy of the scattering light can be much lower than what is possible for dielectric particles. This explanation is discussed in relation to earlier published experimental measurements. Comparison of experimental results with theoretical calculations provides information on the shape distribution of metallic particles in the suspension.
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Borejdo J, Gryczynski Z, Calander N, Muthu P, Gryczynski I. Application of surface plasmon coupled emission to study of muscle. Biophys J 2006; 91:2626-35. [PMID: 16844757 PMCID: PMC1562373 DOI: 10.1529/biophysj.106.088369] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 06/09/2006] [Indexed: 11/18/2022] Open
Abstract
Muscle contraction results from interactions between actin and myosin cross-bridges. Dynamics of this interaction may be quite different in contracting muscle than in vitro because of the molecular crowding. In addition, each cross-bridge of contracting muscle is in a different stage of its mechanochemical cycle, and so temporal measurements are time averages. To avoid complications related to crowding and averaging, it is necessary to follow time behavior of a single cross-bridge in muscle. To be able to do so, it is necessary to collect data from an extremely small volume (an attoliter, 10(-18) liter). We report here on a novel microscopic application of surface plasmon-coupled emission (SPCE), which provides such a volume in a live sample. Muscle is fluorescently labeled and placed on a coverslip coated with a thin layer of noble metal. The laser beam is incident at a surface plasmon resonance (SPR) angle, at which it penetrates the metal layer and illuminates muscle by evanescent wave. The volume from which fluorescence emanates is a product of two near-field factors: the depth of evanescent wave excitation and a distance-dependent coupling of excited fluorophores to the surface plasmons. The fluorescence is quenched at the metal interface (up to approximately 10 nm), which further limits the thickness of the fluorescent volume to approximately 50 nm. The fluorescence is detected through a confocal aperture, which limits the lateral dimensions of the detection volume to approximately 200 nm. The resulting volume is approximately 2 x 10(-18) liter. The method is particularly sensitive to rotational motions because of the strong dependence of the plasmon coupling on the orientation of excited transition dipole. We show that by using a high-numerical-aperture objective (1.65) and high-refractive-index coverslips coated with gold, it is possible to follow rotational motion of 12 actin molecules in muscle with millisecond time resolution.
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Borejdo J, Calander N, Gryczynski Z, Gryczynski I. Fluorescence correlation spectroscopy in surface plasmon coupled emission microscope. OPTICS EXPRESS 2006; 14:7878-7888. [PMID: 19529155 DOI: 10.1364/oe.14.007878] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Study of dynamics of single molecules by Fluorescence Correlation Spectroscopy (FCS) requires that the rate of photon detection per molecule be high, that the background be low, and that there be a large change in fluorescent signal associated with change in a position of a molecule. FCS applied to microscopic Surface Plasmon Coupled Emission (SPCE) suggests a powerful method to meet those requirements. In this method, the observational volume is made shallow by placing a sample on a thin metal film and illuminating it with the laser beam at Surface Plasmon Resonance (SPR) angle through high numerical aperture objective. The illuminating light excites surface plasmons in the metal film that produce an evanescent wave on the aqueous side of the interface. The thickness of the detection volume is a product of evanescent wave penetration depth and distance-dependent fluorescence coupling to surface plasmons. It is further reduced by a metal quenching of excited fluorophores at a close proximity (below 10 nm) to a surface. The fluorescent light is emitted through the metal film only at an SPCE angle. Objective collects emitted light, and a confocal aperture inserted in its conjugate image plane reduces lateral dimensions of the detection volume to a fraction of a micrometer. By using diffusion of fluorescent microspheres, we show that SPCE-FCS is an efficient method to measure molecular diffusion and that on gold surface the height of the detection volume is ~35 nm.
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Calander N. Propensity of a circadian clock to adjust to the 24h day-night light cycle and its sensitivity to molecular noise. J Theor Biol 2006; 241:716-24. [PMID: 16487978 DOI: 10.1016/j.jtbi.2006.01.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2005] [Revised: 01/05/2006] [Accepted: 01/07/2006] [Indexed: 10/25/2022]
Abstract
The circadian clock of Drosophila melanogaster and its tendency to adjust to the day-night light cycle is simulated by deterministic and stochastic methods. The robustness of the locking to the light-cycle with respect to molecular noise is studied. It is found that within the model studied, the molecular noise in the stochastic simulation erases the finer injection-locking structures, stronger injection signals are needed and the locking has the character of prolonged locked time intervals with cycle slips in between. The simulations are compared to a simple injection-locking model with noise that seems to describe the overall behavior well.
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Gryczynski Z, Borejdo J, Calander N, Matveeva EG, Gryczynski I. Minimization of detection volume by surface-plasmon-coupled emission. Anal Biochem 2006; 356:125-31. [PMID: 16764813 DOI: 10.1016/j.ab.2006.05.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2006] [Revised: 05/03/2006] [Accepted: 05/05/2006] [Indexed: 10/24/2022]
Abstract
We report theoretical predictions and experimental observations of the reduced detection volume with the use of surface-plasmon-coupled emission (SPCE). The effective fluorescence volume (detection volume) in SPCE experiments depends on two near-field factors: the depth of evanescent wave excitation and a distance-dependent coupling of excited fluorophores to the surface plasmons. With direct excitation of the sample (reverse Kretschmann excitation) the detection volume is restricted only by the distance-dependent coupling of the excitation to the surface plasmons. However, with the excitation through the glass prism at surface plasmon resonance angle (Kretschmann configuration), the detection volume is a product of evanescent wave penetration depth and distance-dependent coupling. In addition, the detection volume is further reduced by a metal quenching of excited fluorophores at a close proximity (below 10nm). The height of the detected volume size is 40-70nm, depending on the orientation of the excited dipoles. We show that, by using the Kretschmann configuration in a microscope with a high-numerical-aperture objective (1.45) together with confocal detection, the detection volume can be reduced to 1-2attoL. The strong dependence of the coupling to the surface plasmons on the orientation of excited dipoles can be used to study the small conformational changes of macromolecules.
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Gryczynski I, Malicka J, Lakowicz JR, Goldys EM, Calander N, Gryczynski Z. Directional two-photon induced surface plasmon-coupled emission. THIN SOLID FILMS 2005; 491:173-176. [PMID: 33828343 PMCID: PMC8022891 DOI: 10.1016/j.tsf.2005.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
We measured a directional surface plasmon-coupled emission (SPCE) induced by a two-photon absorption. A 60 nm thick layer of poly(vinyl alcohol) film doped with rhodamine 123 was deposited on a silvered (50 nm Ag) glass slide, which was attached to a hemicylindrical glass prism. The 820 nm excitation from a femtosecond Ti:Sapphire laser was used either in reverse Kretschmann or Kretschmann configuration. The angular distribution of two-photon induced SPCE does not depend on the used configuration. The two-photon induced SPCE can be applied to improve immunoassays and deoxyribonucleic acid detection.
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Hölzel R, Calander N, Chiragwandi Z, Willander M, Bier FF. Trapping single molecules by dielectrophoresis. PHYSICAL REVIEW LETTERS 2005; 95:128102. [PMID: 16197115 DOI: 10.1103/physrevlett.95.128102] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2005] [Indexed: 05/04/2023]
Abstract
We have trapped single protein molecules of R-phycoerythrin in an aqueous solution by an alternating electric field. A radio frequency voltage is applied to sharp nanoelectrodes and hence produces a strong electric field gradient. The resulting dielectrophoretic forces attract freely diffusing protein molecules. Trapping takes place at the electrode tips. Switching off the field immediately releases the molecules. The electric field distribution is computed, and from this the dielectrophoretic response of the molecules is calculated using a standard polarization model. The resulting forces are compared to the impact of Brownian motion. Finally, we discuss the experimental observations on the basis of the model calculations.
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Calander N. Surface Plasmon-Coupled Emission and Fabry−Perot Resonance in the Sample Layer: A Theoretical Approach. J Phys Chem B 2005; 109:13957-63. [PMID: 16852751 DOI: 10.1021/jp0510544] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A theoretical approach is used to investigate the coupling of surface plasmon-coupled emission to Fabry-Perot resonance in the sample layer. Quantities investigated are emission angles, polarization, power levels, and fluorescence lifetimes. The results are compared to experimental findings. For comparison a layered structure without surface plasmons, possessing only dielectric Fabry-Perot resonances, is explored. This structure seems to be amenable to s-polarization only but is in principle loss-less and has more degrees of freedom for design and optimization.
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Calander N. Theory and simulation of surface plasmon-coupled directional emission from fluorophores at planar structures. Anal Chem 2005; 76:2168-73. [PMID: 15080724 DOI: 10.1021/ac049925d] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A theoretical approach to surface plasmon-coupled emission (SPCE) from planar structures is developed. It is used for simulations. The results are compared to experimental findings. The match is almost perfect concerning emission angles. Power relations and decay times are reproduced qualitatively. The theory is based on Fresnel plane wave refraction at planar multilayered structures and the Weyl identity for expressing the dipolar radiation in terms of plane waves. One-dimensional integrals, used for the numerical computations, are derived for the fields, powers, and decay enhancements. This theoretical approach is shown to be well suited for design of SPCE setups and for prediction and explanation of experimental results. It also shows promise for refinement and optimization of SPCE, concerning enhancement of weak fluorophores, and usage of decay times.
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