Light-regulated activation of cellular signaling by gold nanoparticles that capture and release amines

A photoresponsive nanocarrier for amines based on gold nanoparticles (GNPs) having a photocleavable succinimidyl ester has been developed. It offers a useful platform for the synthesis of caged compounds. Using the GNPs, we have developed caged histamine for the first time and applied it to evoke intracellular signaling by controlled near-UV irradiation. The present work will allow for new possibilities in studies of inter- and intracellular signaling networks.

Arraying heterotypic single cells on photoactivatable cell-culturing substrates

This article describes a photochemical method for the site-selective assembly of heterotypic cells on a glass substrate modified with a silane coupling agent having a caged functional group. Silane coupling agents having a carboxyl (COOH), amino (NH 2), hydroxyl (OH), or thiol (SH) group protected by a photocleavable 2-nitrobenzyl group were synthesized to modify the surfaces of glass coverslips. The caged substrates were first coated by the adsorption of a blocking agent, bovine serum albumin (BSA), to make the entire surface non-cell-adhesive and then irradiated at 365 nm under a standard fluorescence microscope. The photocleavage reaction on the surface was followed by contact angle measurements and X-ray photoelectron spectroscopy. When COS7, NIH3T3, and HEK293 cells were seeded onto these substrates in a serum-free medium, the cells adhered selectively and efficiently to the irradiated regions on the caged NH 2 substrate, whereas the other caged COOH, SH, and OH substrates were nonphotoactivatable for cell adhesion. Qualitative and quantitative analysis of BSA adsorbed to the uncaged substrates revealed that this highly efficient photoactivation on the caged NH 2 substrate arose because of the following reasons: (i) upon photoactivation, BSA adsorbed in advance on the 2-nitrobenzyl groups was readsorbed onto the uncaged functional groups and (ii) BSA readsorbed onto the NH 2 groups became unable to passivate the surface against cell adhesion whereas BSA on the other groups still had normal passivating activity. It was also demonstrated that heterotypic single COS7, NIH3T3, and HEK293 cells were positioned at any desired arrangement on the caged NH 2 substrate by repeating the UV irradiation at optimized array spot sizes and cell seeding in optimized cell concentrations. The present method will be particularly useful in studying the dynamic processes of cell-cell interactions at a single-cell level.

Operational Space Control: A Theoretical and Empirical Comparison

Dexterous manipulation with a highly redundant movement system is one of the hallmarks of human motor skills. From numerous behavioral studies, there is strong evidence that humans employ compliant task space control, i.e. they focus control only on task variables while keeping redundant degrees-of-freedom as compliant as possible. This strategy is robust towards unknown disturbances and simultaneously safe for the operator and the environment. The theory of operational space control in robotics aims to achieve similar performance properties. However, despite various compelling theoretical lines of research, advanced operational space control is hardly found in actual robotics implementations, in particular new kinds of robots like humanoids and service robots, which would strongly profit from compliant dexterous manipulation. To analyze the pros and cons of different approaches to operational space control, this paper focuses on a theoretical and empirical evaluation of different methods that have been suggested in the literature, but also some new variants of operational space controllers. We address formulations at the velocity, acceleration, and force levels. First, we formulate all controllers in a common notational framework, including quaternion-based orientation control, and discuss some of their theoretical properties. Second, we present experimental comparisons of these approaches on a seven-degree-of-freedom anthropomorphic robot arm with several benchmark tasks. As an aside, we also introduce a novel parameter estimation algorithm for rigid body dynamics, which ensures physical consistency, as this issue was crucial for our successful robot implementations. Our extensive empirical results demonstrate that one of the simplified acceleration-based approaches can be advantageous in terms of task performance, ease of parameter tuning, and general robustness and compliance in the face of inevitable modeling errors.

Learning CPG-based Biped Locomotion with a Policy Gradient Method: Application to a Humanoid Robot

In this paper we describe a learning framework for a central pattern generator (CPG)-based biped locomotion controller using a policy gradient method. Our goals in this study are to achieve CPG-based biped walking with a 3D hardware humanoid and to develop an efficient learning algorithm with CPG by reducing the dimensionality of the state space used for learning. We demonstrate that an appropriate feedback controller can be acquired within a few thousand trials by numerical simulations and the controller obtained in numerical simulation achieves stable walking with a physical robot in the real world. Numerical simulations and hardware experiments evaluate the walking velocity and stability. The results suggest that the learning algorithm is capable of adapting to environmental changes. Furthermore, we present an online learning scheme with an initial policy for a hardware robot to improve the controller within 200 iterations.

Photografting and patterning of oligonucleotides on benzophenone-modified boron-doped diamond

Irradiation of a patterned benzophenone-terminated boron-doped diamond (BDD) surface with UV light (lambda = 350 nm) in the presence of a 15(mer) oligonucleotide resulted in the covalent linking of the DNA strand to the BDD interface.

Rh(I)-Catalyzed Carbonylative Cyclization Reactions of Alkynes with 2-Bromophenylboronic Acids Leading to Indenones

The Rh-catalyzed reaction of alkynes with 2-bromophenylboronic acids involves carbonylative cyclization to give indenones. The key steps in the reaction involve the addition of an arylrhodium(I) species to an alkyne and the oxidative addition of C-Br bonds on the adjacent phenyl ring to give vinylrhodium(I) species II. The regioselectivity depends on both the electronic and the steric nature of the substituents on the alkynes. A bulky group and an electron-withdrawing group favor the -position of indenones. In the case of silyl- or ester-substituted alkynes, the regioselectivity is extremely high. The selectivity increases in the order SiMe3 > COOR >> aryl >> alkyl. The reaction of norbornene with 2-bromophenylboronic acids under 1 atm of CO gives the corresponding indanone derivative. The reaction of alkynes with 2-bromophenylboronic acids under nitrogen gives naphthalene derivatives, in which two molecules of alkynes are incorporated. A vinylrhodium complex similar to II can also be generated by a different route by employing 2-bromophenyl(trimethylsilyl)acetylene and arylboronic acids in the presence of Rh(I) complex as the catalyst, resulting in the formation of indenones. The reaction of 1-(2-bromophenyl)-hept-2-yn-1-one with PhB(OH)2 in the presence of Rh(I) complex also resulted in carbonylative cyclization to give an indan-1,3-dione derivative.

Spatiotemporal control of cell adhesion on a self-assembled monolayer having a photocleavable protecting group

Control of cell adhesion is a key technology for cell-based drug screening and for analyses of cellular processes. We developed a method to spatiotemporally control cell adhesion using a photochemical reaction. We prepared a cell-culturing substrate by modifying the surface of a glass coverslip with a self-assembled monolayer of an alkylsiloxane having a photocleavable 2-nitrobenzyl group. Bovine serum albumin (BSA) was adsorbed onto the substrate to make the surface inert to cell adhesion. When exposed to UV light, the alkylsiloxane underwent a photocleavage reaction, leading to the release of BSA from the surface. Fibronectin, a protein promoting cell adhesion, was added to cover the irradiated regions and made them cell-adhesive. Seeding of cells on this substrate resulted in their selective adhesion to the illuminated regions. By controlling the sizes of the illuminated regions, we formed cell-adhesive spots smaller than single cells and located focal adhesions of the cells. Moreover, by subsequently illuminating the region alongside the cells patterned on the substrate in advance, we released their geometrical confinements and induced migration and proliferation. These manipulations were conducted under a conventional fluorescence microscope without any additional instruments. The present method of cell manipulation will be useful for cell biological studies as well as for the formation of cell arrays.

FRET-based monitoring of conformational change of the β2 adrenergic receptor in living cells

The beta(2) adrenergic receptor (beta(2)AR) is a G protein-coupled receptor that is selective to epinephrine. We demonstrate herein monitoring of an agonist-induced conformational change of beta(2)AR in living cells. The monitoring method is based on fluorescence resonance energy transfer from a cyan fluorescent protein (CFP) to a biarsenical fluorophore, FlAsH, attached to the C-terminus, and the third intracellular loop (ICL3), respectively. Recombinant beta(2)ARs exhibited agonist-induced increases in the FlAsH/CFP emission ratio, indicating that the ICL3 approached the C-terminus upon activation. Since the emission ratio changes were on a time scale of seconds, the conformational change of beta(2)AR in living cells was more rapid than that of purified beta(2)AR measured in vitro. Interestingly, the direction of the emission ratio change of beta(2)AR was opposite to that of the norepinephrine-responsive alpha(2A) adrenergic receptor reported recently. It was suggested that this discrepancy corresponds directly to the diametric biological functions, i.e., the activation or inactivation of adenylyl cyclase.

A new protein conformation indicator based on biarsenical fluorescein with an extended benzoic acid moiety

We demonstrate herein a new protein conformation indicator based on biarsenical fluorescein with an extended benzoic acid moiety. The present indicator is reactive to a genetically introduced tetracysteine motif (Cys-Cys-Xaa-Xaa-Cys-Cys, where Xaa is a noncysteine amino acid) of proteins. Compared to the original biarsenical fluorescein (FlAsH) and the biarsenical Nile red analogue (BArNile), the present indicator exhibited larger fluorescence intensity changes in response to Ca(2+)-induced conformational rearrangements of calmodulin. A calculation of the highest occupied molecular orbital (HOMO) level of the benzoic acid moiety of the indicator molecule supports possible involvement of a photoinduced electron transfer (PET) process. These results indicate that the present indicator is useful for sensitive detection of protein conformational changes.

Composite adaptive control with locally weighted statistical learning

This paper introduces a probably stable learning adaptive control framework with statistical learning. The proposed algorithm employs nonlinear function approximation with automatic growth of the learning network according to the nonlinearities and the working domain of the control system. The unknown function in the dynamical system is approximated by piecewise linear models using a nonparametric regression technique. Local models are allocated as necessary and their parameters are optimized on-line. Inspired by composite adaptive control methods, the proposed learning adaptive control algorithm uses both the tracking error and the estimation error to update the parameters. We first discuss statistical learning of nonlinear functions, and motivate our choice of the locally weighted learning framework. Second, we begin with a class of first order SISO systems for theoretical development of our learning adaptive control framework, and present a stability proof including a parameter projection method that is needed to avoid potential singularities during adaptation. Then, we generalize our adaptive controller to higher order SISO systems, and discuss further extension to MIMO problems. Finally, we evaluate our theoretical control framework in numerical simulations to illustrate the effectiveness of the proposed learning adaptive controller for rapid convergence and high accuracy of control.

Feedback error learning and nonlinear adaptive control

In this paper, we present our theoretical investigations of the technique of feedback error learning (FEL) from the viewpoint of adaptive control. We first discuss the relationship between FEL and nonlinear adaptive control with adaptive feedback linearization, and show that FEL can be interpreted as a form of nonlinear adaptive control. Second, we present a Lyapunov analysis suggesting that the condition of strictly positive realness (SPR) associated with the tracking error dynamics is a sufficient condition for asymptotic stability of the closed-loop dynamics. Specifically, for a class of second order SISO systems, we show that this condition reduces to K2D > K(P) where K(P) and K(D) are positive position and velocity feedback gains, respectively. Moreover, we provide a 'passivity'-based stability analysis which suggests that SPR of the tracking error dynamics is a necessary and sufficient condition for asymptotic hyperstability. Thus, the condition K2D > K(P) mentioned above is not only a sufficient but also necessary condition to guarantee asymptotic hyperstability of FEL, i.e. the tracking error is bounded and asymptotically converges to zero. As a further point, we explore the adaptive control and FEL framework for feedforward control formulations, and derive an additional sufficient condition for asymptotic stability in the sense of Lyapunov. Finally, we present numerical simulations to illustrate the stability properties of FEL obtained from our mathematical analysis.

Photoactivation of a Substrate for Cell Adhesion under Standard Fluorescence Microscopes

Cell-culturing substrates where cell adhesion can be switched on by external stimuli during cell cultivation are useful scaffolds for tissue engineering, cell-based drug screening, and fundamental cellular studies. Here, we show a new strategy for photoactivation of a substrate for cell adhesion under standard fluorescence microscopes. A glass substrate chemically modified with an alkylsiloxane having a photocleavable 2-nitrobenzyl group was coated with bovine serum albumin to prevent cell adhesion. Upon irradiation under a fluorescence microscope, the protein was replaced with fibronectin, which made the irradiated region cell-adhesive. Subsequent seeding of HEK293 or COS7 cells produced patterns corresponding to the irradiated patterns. We succeeded for the first time in positioning single cells in proximity to cultivating single cells. The present method provides a general strategy for positioning single cells of same or different types at any locations on the substrate and will be useful for studying cell-cell interactions.

Temporal trends of organochlorine pesticides in prawn (Macrobrachium nipponense) from Lake Kasumigaura, Japan, during 1978-2000

Temporal trends of organochlorine pesticides such as beta-hexachlorocyclohexane (beta-HCH), hexachlorobenzene (HCB), and 1,1-dichloro-2,2-bis(p-chlorophenyl)-ethylene (p,p'-DDE), were determined in freshwater prawn (Macrobrachium nipponense) collected from Lake Kasumigaura in 1978 to 2000. The organochlorine pesticides elucidated a 72.4% decrease in beta-HCH, from 42 (1978) to 11.6 ng/g fat (2000); an 89.6% decrease in HCB, from 1.64 (1978) to 0.17 ng/g fat (2000); and an 87.3% decrease in p,p'-DDE, from 97.5 (1978) to 12.4 ng/g fat (1992). After organochlorine pesticide prohibition in 1971, the declining trend of beta-HCH, HCB, and p,p'-DDE concentrations persisting in the prawns could be approximated by exponential equations.

Polychlorinated dibenzo-p-dioxins, dibenzofurans, and dioxin-like polychlorinated biphenyls in livers of birds from Japan

Concentrations of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and non- and mono-ortho-chlorine-substituted polychlorinated biphenyls (dioxin-like PCBs) were measured in livers of 17 species of birds collected from Japan. Birds were grouped according to their feeding habits as granivores, piscivores, omnivores, and predators for discussions. Livers of granivores contained relatively low concentrations of PCDD/DFs (80-660 pg/g) followed in increasing order by omnivores (2,300-8,000 pg/g), piscivores (61-12,000 pg/g) and predators (480-490,000 pg/g on a fat weight basis). Especially, one species of predatory bird (mountain hawk eagle) contained elevated concentrations of PCDDs, PCDFs, and dioxin-like PCBs, and the measured concentration is one of the highest reported to date. Homolog and congener patterns of PCDDs and PCDFs varied among species; hence, the results suggested that feeding habits, specific elimination, and metabolism influence contamination pattern. Concentrations of dioxin-like PCBs were in the order of granivores (32-83 ng/g) < predators [excluding mountain hawk eagle] (32-2,500 ng/g) < piscivore (61-12,000 ng/g) < omnivores (1,800-67,000 ng/g on a fat weight basis). Mountain hawk eagle contained the highest concentration of dioxin-like PCBs (55,000 ng/g fat weight). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) toxic equivalents (TEQs) ranged from 53-450,000 pg/g fat weight. 23478-PeCDF, 2378-TCDD/TCDF, and PCB congeners IUPAC 126 and 77 were major contributors to TEQs in birds. To our knowledge, this is the first study of PCDD/DFs and dioxin-like PCBs in livers of several species of Japanese birds.

Potentiometric selectivity coefficients of ion-selective electrodes. Part II. Inorganic anions (IUPAC Technical Report)

Potentiometric selectivity coefficients, KA,Bpot have been collected for ionophore-based ion-selective electrodes (ISEs) for inorganic anions reported during 1988-1998. In addition to the actual numerical values of KA,Bpot together with the methods and conditions for their determination, response slopes, linear concentration (activity) ranges, chemical compositions, and ionophore structures for the ISE membranes are tabulated.

Validation of modeling approach to evaluate congener-specific concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans in air and soil near a solid waste incinerator

A concise modeling approach using long-term averaged meteorological data was developed to estimate site-specific concentrations of congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) near a solid waste incinerator. This approach consists of calculation of atmospheric dispersion, dry and wet deposition of gaseous and particle-bound congeners, and non-steady-state concentrations in soil. The predictability of this approach was evaluated by comparison of calculated concentrations of congeners in soil with those measured at eight locations near a municipal solid waste incinerator (MSWI). The variation of these concentrations due to variability of meteorological parameters is small. A considerable number of mean values show good agreement with measured concentrations within a factor of three. The reasonable agreement between calculated and measured concentrations indicates that algorithms for the calculation of vapor-phase deposition and non-steady-state concentrations in soil must be included in the modeling approach for an accurate estimation of the concentrations of congeners of PCDD/Fs emitted from MSWIs to the atmosphere. For a detailed estimation of site-specific concentrations, it is important to specify the bulk density of soil in the evaluated area, together with meteorological parameters.