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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Adaptive behaviors and dynamic activities within living cells are organized by the cytoskeleton: intracellular networks of interconnected protein polymers which include microtubules (MTs), actin, intermediate filaments, microtubule associated proteins (MAPs) and other protein structures. Cooperative interactions among cytoskeletal protein subunit conformational states have been used to model signal transmission and information processing. In the present work we present a theoretical model for molecular computing in which Boolean logic is implemented in parallel networks of individual MTs interconnected by MAPs. Conformational signals propagate on MTs as in data buses and in the model MAPs are considered as Boolean operators, either as bit-lines (like MTs) where a signal can be transported unchanged between MTs ('BUS-MAP'), or as bit-lines where a Boolean operation is performed in one of the two MAP-MT attachments ('LOGIC-MAP'). Three logic MAPs have been defined ('NOT-MAP, 'AND-MAP', 'XOR-MAP') and used to demonstrate addition, subtraction and other arithmetic operations. Although our choice of Boolean logic is arbitrary, the simulations demonstrate symbolic manipulation in a connectionist system and suggest that MT-MAP networks can perform computation in living cells and are candidates for future molecular computing devices.
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PMID:Cytoskeletal logic: a model for molecular computation via Boolean operations in microtubules and microtubule-associated proteins. 831 77

We report herein a set of deoxyribozyme-based logic gates capable of generating any Boolean function. We construct basic NOT and AND gates, followed by the more complex XOR gate. These gates were constructed through a modular design that combines molecular beacon stem-loops with hammerhead-type deoxyribozymes. Importantly, as the gates have oligonucleotides as both inputs and output, they open the possibility of communication between various computation elements in solution. The operation of these gates is conveniently connected to a fluorescent readout.
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PMID:Deoxyribozyme-based logic gates. 1192 43

Integrated "ICT chromophore-receptor" systems show ion-induced shifts in their electronic absorption spectra. The wavelength of observation can be used to reversibly configure the system to any of the four logic operations permissible with a single input (YES, NOT, PASS 1, PASS 0), under conditions of ion input and transmittance output. We demonstrate these with dyes integrated into Tsien's calcium receptor, 1-2. Applying multiple ion inputs to 1-2 also allows us to perform two- or three-input OR or NOR operations. The weak fluorescence output of 1 also shows YES or NOT logic depending on how it is configured by excitation and emission wavelengths. Integrated "receptor(1)-ICT chromophore-receptor(2)" systems 3-5 selectively target two ions into the receptor terminals. The ion-induced transmittance output of 3-5 can also be configured via wavelength to illustrate several logic types including, most importantly, XOR. The opposite effects of the two ions on the energy of the chromophore excited state is responsible for this behaviour. INHIBIT and REVERSE IMPLICATION are two of the other logic types seen here. Integration of XOR logic with a preceding OR operation can be arranged by using three ion inputs. The fluorescence output of these systems can be configured via wavelength to display INHIBIT or NOR logic under two-input conditions. The superposition or multiplicity of logic gate configurations is an unusual consequence of the ability to simultaneously observe multiple wavelengths.
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PMID:Simultaneously multiply-configurable or superposed molecular logic systems composed of ICT (internal charge transfer) chromophores and fluorophores integrated with one- or two-ion receptors. 1239 95

Readily formed at nanoscale break junctions, arrays of individual spatially isolated, strongly electroluminescent Ag(2)-Ag(8) nanoclusters perform complex logic operations within individual two-terminal nanoscale optoelectronics devices. Simultaneous electrical excitation of discrete room-temperature nanocluster energy levels directly yields AND, OR, NOT, XOR, and even full addition logic operations with either individual nanoclusters or nanocluster pairs as the active medium between only two electrodes. Imaged in parallel, noncontact electroluminescent readout obviates the need for electrically isolating individual features. This gated, pulsed, two-terminal device operation will likely drive future nano and molecular electronics advances without complicated nanofabrication.
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PMID:Discrete two-terminal single nanocluster quantum optoelectronic logic operations at room temperature. 1262 Nov 54

Quantum computers have the potential to perform certain computational tasks more efficiently than their classical counterparts. The Cirac-Zoller proposal for a scalable quantum computer is based on a string of trapped ions whose electronic states represent the quantum bits of information (or qubits). In this scheme, quantum logical gates involving any subset of ions are realized by coupling the ions through their collective quantized motion. The main experimental step towards realizing the scheme is to implement the controlled-NOT (CNOT) gate operation between two individual ions. The CNOT quantum logical gate corresponds to the XOR gate operation of classical logic that flips the state of a target bit conditioned on the state of a control bit. Here we implement a CNOT quantum gate according to the Cirac-Zoller proposal. In our experiment, two 40Ca+ ions are held in a linear Paul trap and are individually addressed using focused laser beams; the qubits are represented by superpositions of two long-lived electronic states. Our work relies on recently developed precise control of atomic phases and the application of composite pulse sequences adapted from nuclear magnetic resonance techniques.
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PMID:Realization of the Cirac-Zoller controlled-NOT quantum gate. 1266 Jul 65

One of the fundamental goals of molecular computing is to reproduce the tenets of digital logic, such as component modularity and hierarchical circuit design. An important step toward this goal is the creation of molecular logic gates that can be rationally wired into multi-level circuits. Here we report the design and functional characterization of a complete set of modular DNA-based Boolean logic gates (AND, OR, and AND-NOT) and further demonstrate their wiring into a three-level circuit that exhibits Boolean XOR (exclusive OR) function. The approach is based on solid-supported DNA logic gates that are designed to operate with single-stranded DNA inputs and outputs. Since the solution-phase serves as the communication medium between gates, circuit wiring can be achieved by designating the DNA output of one gate as the input to another. Solid-supported logic gates provide enhanced gate modularity versus solution-phase systems by significantly simplifying the task of choosing appropriate DNA input and output sequences used in the construction of multi-level circuits. The molecular logic gates and circuits reported here were characterized by coupling DNA outputs to a single-input REPORT gate and monitoring the resulting fluorescent output signals.
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PMID:Modular multi-level circuits from immobilized DNA-based logic gates. 1799 34

The vector-matrix multiplier is the engine of many artificial neural network implementations because it can simulate the way in which neurons collect weighted input signals from a dendritic arbor. A new technology for building analog weighting elements that is theoretically capable of densities and speeds far beyond anything that conventional VLSI in silicon could ever offer is presented. To illustrate the feasibility of such a technology, a small three-layer feedforward prototype network with five binary neurons and six tri-state synapses was built and used to perform all of the fundamental logic functions: XOR, AND, OR, and NOT.
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PMID:A feedforward artificial neural network based on quantum effect vector-matrix multipliers. 1826 45

All-optical XOR-, OR-, NOT-, and AND-gate were demonstrated for 10 Gb/s return-to-zero on-off keying (RZ-OOK) signals using a single experimental setup. This setup can be set to output different logic by altering input power, state-of-polarization, center frequencies of input optical signals, and/or input bitstreams. Full-width at half-maximum pulsewidth of the input and the output signals were less than 5.1 ps in all cases showing a possibility of higher data rate operation at 80Gb/s or beyond.
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PMID:All-optical picoseconds logic gates based on a fiber optical parametric amplifier. 1895 14

The first demonstration to our knowledge of new all-optical logic gates and modulators that use nonlinear refraction and absorption to modify fiber-to-fiber coupling is reported. Results are presented for the AND, NOR, NOT, and XOR functions with better than 20-dB contrast ratio. Silicon (at lambda = 1.06 microm) is used as the nonlinear material for this proof-of-concept experiment. No resonators, feedback, or stringent wavelength controls are needed. The feasibility of picosecond operation is discussed.
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PMID:All-optical, fiber-optic modulator and logic gate using nonlinear refraction and absorption. 1973 49

We describe parallel optical XOR and XNOR logic gates implemented with ferroelectric liquid-crystal (FLC) electro-optic elements to yield naturally a logic in which the binary gate outputs are indicated by two orthogonal polarizations of transmitted light. These gates absorb no power from the incident light beam and hence can be cascaded without the need to regenerate NOT inputs. The FLC elements also confer the advantages of low-voltage, low-power, submicrosecond switching and intrinsic two-state memory. Experimental results demonstrating the XOR and XNOR function are presented, along with measurements of the percentage of polarized light rotated into the two binary states.
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PMID:Polarization-based optical parallel logic gate utilizing ferroelectric liquid crystals. 1974 15


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