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Although the equivalence of heat and work has been unveiled since Joule's ingenious experiment in 1845, they rarely originate from the same source in experiments. In this study, we theoretically and experimentally demonstrated how to use a high-precision optical feedback trap to combine the generation of virtual temperature and potential to simultaneously manipulate the heat and work of a small system. This idea was applied to a microscopic Stirling engine consisting of a Brownian particle under a time-varying confining potential and temperature. The experimental results justified the position and the velocity equipartition theorem, confirmed several theoretically predicted energetics, and revealed the engine efficiency as well as its trade-off relation with the output power. The small theory-experiment discrepancy and high flexibility of the swift change of the particle condition highlight the advantage of this optical technique and prove it to be an efficient way for exploring heat and work-related issues in the modern thermodynamics for small systems.
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The legality of using simple kinetic schemes to determine the stochastic properties of a complex system depends on whether the fluctuations generated from hierarchical equivalent schemes are consistent with one another. To analyze this consistency, we perform lumping processes on the stochastic differential equations and the generalized fluctuation-dissipation theorem and apply them to networks with the frequently encountered Arrhenius-type transition rates. The explicit Langevin force derived from those networks enables us to calculate the state fluctuations caused by the intrinsic and extrinsic noises on the free energy surface and deduce their relations between kinetically equivalent networks. In addition to its applicability to wide classes of network related systems, such as those in structural and systems biology, the result sheds light on the fluctuation relations for general physical variables in Keizer's canonical theory.
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Modelos Biológicos , Simulación por Computador , Cinética , Procesos Estocásticos , Teoría de SistemasRESUMEN
The effect of chemical composition and morphology of the surface layers of new polyaramide-containing sorbents on the mechanism of selective sorption of nucleic acids and proteins was investigated as compared to the previously studied sorbents modified with fluoropolymers and polyaniline (high-throughput materials providing one-step isolation of DNA from biological mixtures). A series of silica-based sorbents modified with polyaramides having consistently varying structure and containing the set of "key" structural elements (aromatic units and nitrogen atoms in the backbone, fluorinated groups), and various donor and acceptor moieties was prepared. The chemical composition of the polymer coatings was evaluated by X-ray photoelectron spectroscopy. The surface morphology was studied by scanning probe microscopy. The sorption properties were investigated by passing the mixtures containing DNA, RNA and proteins of different nature through the cartridges containing the obtained sorbents. All the investigated materials weakly retain double-stranded DNA but effectively retain RNA and proteins. The sorption capacity of the sorbents depends on the protein nature. The observed sorption behavior was shown to be determined by the chemical structure and not by the morphology of the polymer coating. It was proposed that similarity of the sorption properties of the series of chemically different polymers could be determined by similar total input of different sorption mechanisms.
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Nylons/química , Proteínas/química , Adsorción , Ácidos Nucleicos/química , Espectroscopía de FotoelectronesRESUMEN
Conventional studies of biomolecular behaviors rely largely on the construction of kinetic schemes. Since the selection of these networks is not unique, a concern is raised whether and under which conditions hierarchical schemes can reveal the same experimentally measured fluctuating behaviors and unique fluctuation related physical properties. To clarify these questions, we introduce stochasticity into the traditional lumping analysis, generalize it from rate equations to chemical master equations and stochastic differential equations, and extract the fluctuation relations between kinetically and thermodynamically equivalent networks under intrinsic and extrinsic noises. The results provide a theoretical basis for the legitimate use of low-dimensional models in the studies of macromolecular fluctuations and, more generally, for exploring stochastic features in different levels of contracted networks in chemical and biological kinetic systems.
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Active immunisation against gonadotropin releasing hormone (GnRH) is a potential alternative to surgical castration. This study focused on the development of a GnRH subunit lipopeptide vaccine. A library of vaccine candidates that contained one or more (up to eight) copies of monomeric or dimeric GnRH peptide antigen, an adjuvanting lipidic moiety based on lipoamino acids, and an additional T helper epitope, was synthesised by solid phase peptide synthesis. The candidates were evaluated in vivo in order to determine the minimal components of this vaccine necessary to induce a systemic immune response. BALB/c mice were immunised with GnRH lipopeptide conjugates, co-administered with or without Complete Freund's Adjuvant, followed by two additional immunisations. Significant GnRH-specific IgG titres were detected in sera obtained from mice immunised with four of the seven lipopeptides tested, with an increase in titres observed after successive immunisations. This study highlights the importance of for epitope optimisation and delivery system design when producing anti-hapten antibodies in vivo. The results of this study also contribute to the development of future clinical and veterinary immunocontraceptives.
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Epítopos/inmunología , Hormona Liberadora de Gonadotropina/inmunología , Lipopéptidos/inmunología , Linfocitos T Colaboradores-Inductores/inmunología , Vacunación , Vacunas/inmunología , Animales , Femenino , Ratones , Ratones Endogámicos BALB CRESUMEN
Despite the fact that the localization-delocalization transition (LDT) widely exists in wave systems, quantitative studies on its critical and multifractal properties are mainly focused on solids. In this work, these properties are investigated on the vibrational motions of liquid water. Simulations of up to 18000 molecules on the flexible extended simple point charge water model provide nearly 10(6) instantaneous normal modes. They are shown to undergo an LDT close to the translational transition and exhibit multifractal fluctuations while approaching the LDT. In combination with finite-size scaling, multifractal analysis predicts the critical frequency Im(ω(c))≈-131.6 cm(-1) for unstable modes at room temperature. The estimated critical exponent ν≈1.60 is close to those of other calculated systems in the same Wigner-Dyson class. At the LDT, the fractal spectrum f(α) and the most probable local vibrational intensity α(mc)≈4.04 coincide with those of the Anderson model, which might be additional universal properties of LDT in more general wave systems. The results extend the validity of the multifractal scaling approach beyond Andersonian systems to a Hessian system.
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In this study, the effect of coagulation pretreatment on membrane fouling and ultrasonic cleaning efficiency was investigated using a dead-end polytetrafluoroethylene (PTFE) microfiltration system. The extent of membrane fouling was examined under different coagulation mechanisms such as charge neutralization (CN), electrostatic patch effect (EPE) and sweep flocculation (SW). Fouling through EPE mechanism provided the greatest flux decline and least permeate flux recovery over CN and SW. EPE produces more stable, smaller and more compact flocs while CN and SW have large, easily degraded and highly-branched structured flocs. The predominant fouling mechanism of EPE, CN and SW is pore blocking, a combination of pore blocking and cake formation, and cake formation, respectively. Better permeate flux recovery is observed with SW over CN and EPE, which implies formation of less dense and more porous cake deposits. The morphology of fouled membranes was examined using scanning electron microscopy (SEM).
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Incrustaciones Biológicas , Membranas Artificiales , Politetrafluoroetileno , Sonido , Incrustaciones Biológicas/prevención & control , Cloruros , Compuestos Férricos , Floculación , Microscopía Electrónica de Rastreo , EsterilizaciónRESUMEN
We generalized the semiclassical path integral method originally used in the D'yakonov-Perel' mechanism to study the spin relaxation of the Elliott-Yafet mechanism in low-dimensional systems. In quantum wells, the spin properties calculated by this method confirmed the experimental results. In two-dimensional narrow wires, size and impurity effects on the Elliott-Yafet relaxation were predicted, including the wire-width-dependent relaxation time, the polarization evolution on the sample boundaries, and the relaxation behavior during the diffusive-ballistic transition. These properties were compared with those of the D'yakonov-Perel' relaxation calculated under similar conditions. For ballistic narrow wires, we derived an exact relation between the Elliott-Yafet relaxation time and the wire width, which confirmed the above simulations.
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The molecular machines in biological cells are made of proteins, DNAs and other classes of molecules. The structures of these molecules are characteristically "soft", highly flexible, and yet their interactions with other molecules or ions are specific and selective. This chapter discusses a prevalent form, the catalytic wheel, or the energy transducer of cells, examines its mechanism of action, and extracts from it a set of simple but general rules for understanding the energetics of the biomolecular devices. These rules should also benefit design of manmade nanometer scale machines such as rotary motors or track-guided linear transporters. We will focus on an electric work that, by matching system dynamics and then enhancing the conformational fluctuation of one or several driver proteins, converts stochastic input of energy into rotation or locomotion of a receptor protein. The spatial (or barrier) and temporal symmetry breakings required for selected driver/receptor combinations are examined. This electric ratchet consists of a core engine that follows the Markovian dynamic, alleviates difficulties encountered in rigid mechanical model, and tailors to the soft-matter characteristics of the biomolecules.
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Proteínas Motoras Moleculares/fisiología , Animales , Fenómenos Biofísicos , Biofisica , Catálisis , Transferencia de Energía , Enzimas/fisiología , Técnicas In Vitro , Cadenas de Markov , Modelos Biológicos , Proteínas Motoras Moleculares/química , Conformación Proteica , Procesos Estocásticos , Biología de SistemasRESUMEN
To deliver non-permeable molecules into cells, one can utilize protocols such as microinjection, electroporation, liposome-mediated transfection or virus-mediated transfection. However, each method has its own limitations. Here we have developed a new molecular delivery technique where live cells or tissues are bombarded with highly accelerated molecules directly and without the need to conjugate the molecules onto carrier particles, which is essential in conventional "gene gun" experiments. Gene bombardments can be applied to well-differentiated cells, primary cultured cells/neurons or tissue explants, all of which are notoriously difficult to transfect. Exogenously made proteins and even bacteria can be effectively introduced into cells where they can execute their function or replicate. Our experimental results and physical model support the notion that accelerated chemicals, proteins, or microorganisms carry enough momentum to penetrate the plasma membrane. The bombardment process is associated with a transient (approximately 10 min) increase in cell permeability, but such membrane leakage has a minimal adverse effect on cell survival.
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Bacterias , Biolística/métodos , Sistemas de Liberación de Medicamentos/métodos , Animales , Técnicas Bacteriológicas , Células CHO , Línea Celular , Permeabilidad de la Membrana Celular , Cricetinae , Cricetulus , Proteínas del Citoesqueleto/administración & dosificación , Proteínas del Citoesqueleto/química , ADN Recombinante/administración & dosificación , ADN Recombinante/genética , Escherichia coli , Células HeLa , Humanos , Modelos Biológicos , Peso Molecular , Proteínas Recombinantes/administración & dosificación , Proteínas Recombinantes/química , TransfecciónRESUMEN
Naturally occurring metallothionein (MT) is a metal binding protein, which binds to seven Zn2+ through 20 conserved cysteines and forms two metal binding clusters with a Zinc-Blende structure. We demonstrate that the MT, when substituting the Zn2+ ions by Mn2+ and Cd2+, exhibits magnetic hysteresis loop observable by SQUID from 10 to 330 K. The magnetic moment may have originated from the bridging effect of the sulfur atoms between the metal ions that leads to the alignment of the electron spins of the Mn2+ ions inside the clusters. The protein backbone may restrain the net spin moment of Mn2+ ions from thermal fluctuation. The modified magnetic-metallothionein is a novel approach to creating molecular magnets with operating temperatures up to 330 K.
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Hígado/química , Magnetismo , Metalotioneína/química , Metalotioneína/ultraestructura , Animales , Simulación por Computador , Campos Electromagnéticos , Metalotioneína/efectos de la radiación , Modelos Moleculares , Conformación Proteica/efectos de la radiación , Conejos , Relación Estructura-Actividad , TemperaturaRESUMEN
This study investigated alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths adsorbed upon novel Au-coated microelectrodes, of which the surface properties were quantitatively evaluated by surface characterization and 3T3 fibroblast cell adhesion, total impedance and cell detachment tests. Thin-film SAMs adsorbed upon Au/PI/Si provided a hydrophobic or passive surface with increased water contact angle and initial total impedance. From cell adhesion tests, we can observe that the film formed as a dense-packed spacer resulted in incomplete cell sealing of 3T3 cells upon the surface-modified microelectrode. Thus the decrease in cell coverage rate and in the slope in association with total impedance as a function of cell-surface reaction time can be found. To study the adhesion force of a comparable single cell attached upon varied modified surfaces, a cell detachment test using a triangular probe tip of a well defined cantilever was carried out in medium containing fibroblast cells. Overall, both the peak force and the work required to detach a comparable single cell from the anchoring domain corresponded well to the increased length of alkyl chains adsorbed upon Au/PI/Si. Both measurements on the SAM modified surfaces demonstrated much smaller values than those on the pristine Au/PI/Si surface. These results concluded that a cell-repulsive characteristic was clearly formed on the SAM modified microelectrode surface. The non-adhering properties of surface-modified microelectrodes should provide better sensitivity for neuromuscular stimulation as well as for the recording of infinitesimal neural signals in future applications of neural prostheses.
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It is demonstrated that the stochastic back-and-forth vibrations of uncorrelated dipoles may lead to rotation of their ambient dipoles. This peculiar phenomenon is clarified by considering spatial and temporal symmetry breakings. The former asymmetry is the result of the multiple biased Hamiltonian vector fields, which is a ratchet effect, and the latter, of the time sequence specified by a metastable state. Since this driving mechanism is simpler than that of F0F1ATPase, it could benefit the design of nanometer scale rotary devices.
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Electroquímica/métodos , Modelos Químicos , Modelos Moleculares , Proteínas Motoras Moleculares/química , Nanotecnología/métodos , Simulación por Computador , Campos Electromagnéticos , Modelos Estadísticos , Nanotecnología/instrumentación , Rotación , Procesos Estocásticos , Estrés MecánicoRESUMEN
Alkanethiolate self-assembled monolayers (SAMs) of varied chain lengths were adsorbed upon Au-coated nerve microelectrodes and employed as protein-resistant spacers. The microelectrode spiraled as a cuff type can be used for restoring motor function via electrical stimulation on the peripheral nerve system; however, an increase of electrode impedance might occur during implantation. In this work, a thin-film SAMs treatment upon Au/polyimide (PI) surface of the microelectrode provided a hydrophobic characteristic, which retarded protein adsorption at the initial stage and subsequent pileup (or thickening) process. The protein-resistant effect exhibited comparable SAMs of different chain lengths adsorbed upon Au/PI surfaces. The increase of electrode impedance as a function of protein deposition time was mainly correlated with the addition of reactance that was associated with the pileup thickness of the deposited protein. Particularly, the SAMs-modified surface was capable to detach a significant portion of the accumulated protein from the protein-deposited SAMs/Au/PI, whereas the protein-deposited layers exhibited firm adhesion upon Au/PI surface. It is therefore very promising to apply thin-film SAMs adsorbed upon Au-coated surface for bioinvasive devices that have the need of functional electrical stimulations or sensing nerve signals during chronic implantation.
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Alcanos/química , Proteínas Sanguíneas/química , Oro/química , Compuestos de Sulfhidrilo/química , Adsorción , Animales , Impedancia Eléctrica , Electrodos , Cinética , Masculino , Sistema Nervioso Periférico/fisiología , Conejos , Análisis Espectral , TemperaturaRESUMEN
Ding-Chuan-Tang (DCT), a traditional Chinese medicine, has been used in treatment of the bronchial asthma for several centuries. However, the therapeutic mechanism of these Chinese medicine are still far from clear. To understand the mechanism of antiasthmatic property of DCT. A guinea pig model of allergic asthma was used to investigate the effects of DCT on ovalbumin-induced early and late asthmatic responses and airway inflammation, particularly the extent of eosinophil infiltration, and examine it direct beta2-adrenoceptor agonist activity in guinea-pig isolated trachea. We had used three different protocals in ovalbumin sensitized guinea pigs by administrating 10 g/kg of DCT extracts to sensitized guinea pigs 30 min before antigen challenge (group I), 5 hr after antigen challenge (group II) and 2.5 g/kg once daily from the day of sensitization to the day of challenge. Our result showed that administration of DCT singificantly inhibited the antigen induced immediate asthmatic responses (IAR) in group I and inhibited both IRA and late asthmatic responses (LAR) in actively sensitized guinea pig in group III. DCT caused concentration-dependent relaxations in strips of guinea pig trachea contracted with carbachol, however ICI-118551, a selective beta2-adrenoceptor antagonist, didn't significantly competitively inhibit the relaxations caused by DCT. Furthermore, examination of bronchoalveolar lavage fluid (BALF) revealed that DCT significantly inhibited the increase in percent of eosinophils in the airway after antigen challenge in three group. Histopathologic examination showed DCT suppressed the eosinophil infiltration into lung tissue. These results suggest that the antiasthmatic effect of DCT is mainly due to its bronchodilatation effect and its ability to inhibit the eosinophil into the airway and there is prophylactic effect of DCT on allergen-induced airway inflammation.
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Broncoconstricción/efectos de los fármacos , Leucocitos/efectos de los fármacos , Extractos Vegetales/farmacología , Tráquea/efectos de los fármacos , Resistencia de las Vías Respiratorias/efectos de los fármacos , Animales , Antiasmáticos/farmacología , Antiasmáticos/uso terapéutico , Asma/inducido químicamente , Asma/inmunología , Asma/prevención & control , Líquido del Lavado Bronquioalveolar/citología , Broncoconstricción/inmunología , Carbacol/farmacología , Recuento de Células , Eosinófilos/citología , Cobayas , Inmunización , Leucocitos/citología , Leucocitos/inmunología , Pulmón/citología , Masculino , Neutrófilos/citología , Ovalbúmina/administración & dosificación , Ovalbúmina/inmunología , Ovalbúmina/farmacología , Extractos Vegetales/uso terapéutico , Tráquea/citologíaRESUMEN
The dynamics division approach proposed in this work enables us to handle dynamical equations with complex fluctuations. A Brownian motor with cyclic conformational changes is analyzed to understand effects of noise on its signal transduction, and on condition in which stochastic resonance may take place. The result reproduces several features of the experimental data on the electric activation of ion pumping by Na, K-ATPase.
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Transferencia de Energía/fisiología , Activación del Canal Iónico/fisiología , Potenciales de la Membrana/fisiología , Modelos Biológicos , Modelos Estadísticos , Proteínas Motoras Moleculares/fisiología , ATPasa Intercambiadora de Sodio-Potasio/fisiología , Procesos Estocásticos , Simulación por Computador , Cinética , Dinámicas no Lineales , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
This work demonstrates the application of Bogomolny's transfer operator method on three-dimensional dynamics. Motivated by experimental observations of lenslike metal clusters, the quantum billiards bounded by a flat bottom and an upper surface with SO(2) symmetry are studied. A precise determination of the energies with error less than 0.05% and exact predicted degeneracies in the special case of the half-sphere billiard confirm the efficiency of this method. Furthermore, the spectra and degeneracies of lens billiards with varying heights are explicitly determined.
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The counter-intuitive feature of Parrondo's games is illustrated on various dynamical systems combined from different deterministic and stochastic subsystems. The concept of truncation and reset process is introduced, which provides a transparent perspective to understand the underlying mechanism of this class of dynamics, including the transport of flashing ratchets, and clarifies the puzzlement why random switching between two games can generate reversal dynamics as periodical switching does.
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This study investigates how ratchets perform under driving forces generated by the circle, baker, and logistic maps with varying driving frequencies. The markedly different unidirectional net transports induced by distinct maps and frequencies are clarified by vector field analysis of the ratchet equations. Analysis results indicate that both the deterministic property of the driving forces and the asymmetric effect due to the ratchet potential impact the transport. Moreover, the driving frequency determines which factor suppresses the other one and dominates the ratchet transport.
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Bogomolny's transfer operator method plays a significant role in the study of quantum chaos, along with other well known methods like Gutzwiller's trace formula and the dynamical zeta function, which generalize the Einstein-Brillouin-Keller quantization rule from integrable systems to chaotic systems. According to the theory, the Fredholm determinant of the transfer operator, defined on a Poincaré section of a classical physical system, provides a quantization condition to the energy spectrum of the corresponding quantum system. This study presents two factorization formulas, which relate different quantization conditions defined on different classical trajectory segments. These explicit relations answer the question of why all these classical quantization conditions determine exactly the same energy spectrum of the corresponding quantum systems. As an example, these formulas are illustrated in the equilateral triangular billiard.