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1.
Abstract— The technique of forming bilayer lipid membranes (BLM) has made it possible to study photoreactions of pigments in an environment that is much closer to those in photosynthetic and visual membranes. A pigmented BLM system with Mg2+ -porphyrins as membrane-bound pigments and with ferricyanide and ferrocyanide as the aqueous electron acceptor and donor, respectively, was used to illustrate the photoelectric effects due to coupled interfacial charge transfer reactions.
The steady-state continuous photoresponse was studied by means of the voltage clamp method and a null current method. The independence of the pigment conductance channel and the ionic conductance channel was demonstrated. A tunable voltage clamp method was used to study the transient pulsed photoresponses. Such a measurement permits us to characterize the photosystem in terms of an equivalent circuit model which contains a novel chemical capacitance. Molecular interpretation of this equivalent circuit model was given.
A microscopic model based on the Gouy–Chapman theory and chemical kinetics calculation leads to an equivalent circuit which is also equivalent to the previous one. Generalization of this microscopic model further leads to a physical mechanism of the generation of the early receptor potential (ERP) in visual membranes. Relevance of pigmented BLM research to photosynthesis and other disciplines was also discussed. 相似文献
The steady-state continuous photoresponse was studied by means of the voltage clamp method and a null current method. The independence of the pigment conductance channel and the ionic conductance channel was demonstrated. A tunable voltage clamp method was used to study the transient pulsed photoresponses. Such a measurement permits us to characterize the photosystem in terms of an equivalent circuit model which contains a novel chemical capacitance. Molecular interpretation of this equivalent circuit model was given.
A microscopic model based on the Gouy–Chapman theory and chemical kinetics calculation leads to an equivalent circuit which is also equivalent to the previous one. Generalization of this microscopic model further leads to a physical mechanism of the generation of the early receptor potential (ERP) in visual membranes. Relevance of pigmented BLM research to photosynthesis and other disciplines was also discussed. 相似文献
2.
6-Thiopurine and its N- or C-alkyl derivatives all form an [M – 1]-ion upon fragmentation. In the 7-alkyl derivatives, this ion represents the major component of the spectrum. This is ascribed to formation of a five-membered thiazoline-like ring. Similar ring formation stabilises the [M – 1]-ion in the 7-methyl derivatives of hypoxanthine, adenine and 6-selenopurine. 相似文献
3.
4.
Haiwen Zhang David W. Norman Tracey M. Wentzell Alison M. Irving Janet P. Edwards Susan L. Wheaton Christopher M. Vogels Stephen A. Westcott Felix J. Baerlocher Andreas Decken 《Transition Metal Chemistry》2005,30(1):63-68
Reactions of salicylaldehydes with boronate ester derivatives of aniline have been examined. Addition of these Schiff base ligands to palladium acetate or Na2PdCl4 afforded novel boron-containing trans-bis(N-arylsalicylaldiminato) palladium complexes.Condensation of salicylaldehyde (2-HOC6H4C(O)H) with H2NC6H4Bpin (pin=1,2-O2C2Me4) afforded the boron-containing Schiff bases, 2-HOC6H4C(H)=NC6H4Bpin (1–3a). Similar reactivity with 2-hydroxy-5-nitrobenzaldehyde and 2-hydroxy-1-naphthaldehyde gave the corresponding Schiff bases (1-3b) and (1-3c), respectively. Reaction of Schiff bases (2) and (3) with palladium acetate or Na2PdCl4 afforded complexes of the type PdL2
(4,5), where L=deprotonated Schiff base. The molecular structure of the nitro-salicylaldehyde 4-Bpin palladium complex (5b) was characterized by an X-ray diffraction study. All new palladium compounds have been characterized fully and tested for their antifungal activity against Aspergillus niger and Aspergillus flavus. 相似文献
5.
Background
In the barley malting process, partial hydrolysis of β-glucans begins with seed germination. However, the endogenous 1,3-1,4-β-glucanases are heat inactivated, and the remaining high molecular weight β-glucans may cause severe problems such as increased brewer mash viscosity and turbidity. Increased viscosity impairs pumping and filtration, resulting in lower efficiency, reduced yields of extracts, and lower filtration rates, as well as the appearance of gelatinous precipitates in the finished beer. Therefore, the use of exogenous β-glucanases to reduce the β-glucans already present in the malt barley is highly desirable. 相似文献6.
Jaime Aspas-Caceres Marc Rico-Pasto Isabel Pastor Felix Ritort 《Entropy (Basel, Switzerland)》2022,24(7)
Nonequilibrium work relations and fluctuation theorems permit us to extract equilibrium information from nonequilibrium measurements. They find application in single-molecule pulling experiments where molecular free energies can be determined from irreversible work measurements by using unidirectional (e.g., Jarzynski’s equality) and bidirectional (e.g., Crooks fluctuation theorem and Bennet’s acceptance ratio (BAR)) methods. However, irreversibility and the finite number of pulls limit their applicability: the higher the dissipation, the larger the number of pulls necessary to estimate G within a few . Here, we revisit pulling experiments on an RNA three-way junction (3WJ) that exhibits significant dissipation and work-distribution long tails upon mechanical unfolding. While bidirectional methods are more predictive, unidirectional methods are strongly biased. We also consider a cyclic protocol that combines the forward and reverse work values to increase the statistics of the measurements. For a fixed total experimental time, faster pulling rates permit us to efficiently sample rare events and reduce the bias, compensating for the increased dissipation. This analysis provides a more stringent test of the fluctuation theorem in the large irreversibility regime. 相似文献
7.
M. Zeeman C. M. Auer R. G. Clements J. V. Nabholz R. S. Boethling 《SAR and QSAR in environmental research》2013,24(3):179-201
Abstract As testing is not required, ecotoxicity or fate data are available for ≈ 5% of the approximately 2,300 new chemicals/year (26,000 + total) submitted to the US-EPA. The EPA's Office of Pollution Prevention and Toxics (OPPT) regulatory program was forced to develop and rely upon QSARs to estimate the ecotoxicity and fate of most of the new chemicals evaluated for hazard and risk assessment. QSAR methods routinely result in ecotoxicity estimations of acute and chronic toxicity to fish, aquatic invertebrates, and algae, and in fate estimations of physical/chemical properties, degradation, and bioconcentration. The EPA's Toxic Substances Control Act (TSCA) Inventory of existing chemicals currently lists over 72,000 chemicals. Most existing chemicals also appear to have little or no ecotoxicity or fate data available and the OPPT new chemical QSAR methods now provide predictions and cross-checks of test data for the regulation of existing chemicals. Examples include the Toxics Release Inventory (TRI), the Design for the Environment (DfE), and the OECD/SIDS/HPV Programs. QSAR screening of the TSCA Inventory has prioritized thousands of existing chemicals for possible regulatory testing of: 1) persistent bioaccumulative chemicals, and 2) the high ecotoxicity of specific discrete organic chemicals. 相似文献
8.
The long-time behavior of transport coefficients in a model for spatially heterogeneous media in two and three dimensions is investigated by molecular dynamics simulations. The behavior of the velocity autocorrelation function is rationalized in terms of a competition of the critical relaxation due to the underlying percolation transition and the hydrodynamic power-law anomalies. In two dimensions and in the absence of a diffusive mode, another power-law anomaly due to trapping is found with an exponent -3 instead of -2. Further, the logarithmic divergence of the Burnett coefficient is corroborated in the dilute limit; at finite density, however, it is dominated by stronger divergences. 相似文献
9.
Bhuvanesh Gupta Felix N. Büchi Markus Staub D. Grman Günther G. Scherer 《Journal of polymer science. Part A, Polymer chemistry》1996,34(10):1873-1880
The structure and some physico-chemical properties of radiation grafted FEP-g-polystyrenesulfonic acid proton exchange membranes were studied as a function of the degree of grafting. The distribution of grafted polymer across the membrane thickness was obtained from microprobe measurements. It was found that for low levels of grafting (ca. 3%), polystyrene chains are located near the membrane surface only, and the interior of the membrane remains ungrafted. With the increasing degree of grafting, polystyrene chains were incorporated into the interior of the membrane as well. An almost homogeneous distribution of grafts in the membrane was obtained at a graft level of > 13%. The influence of the degree of grafting on membrane properties, such as ion exchange capacity, swelling, and specific resistivity was studied. Three different states of water, viz., freezing free, freezing bound, and nonfreezing water have been identified in noncrosslinked membranes. However, the nature and the amount of crosslinker had a profound influence on the states of water in a membrane. © 1996 John Wiley & Sons, Inc. 相似文献
10.